ACKERMANN STEFANIE (DE)
LUCKS SANDRA (DE)
WU JUN (DE)
ADOLF JAMES (DE)
| WO2007147604A2 | 2007-12-27 | |||
| WO2017004424A1 | 2017-01-05 | |||
| WO2017004424A1 | 2017-01-05 |
| US20160273117A1 | 2016-09-22 | |||
| US20090188805A1 | 2009-07-30 | |||
| CA1086679A | 1980-09-30 | |||
| US6923897B1 | 2005-08-02 | |||
| US3432509A | 1969-03-11 |
| C L A I M S 1. An aqueous composition for depositing a cobalt deposit, the composition comprising (a) a total amount of cobalt (II) ions, (b) at least one first compound of formula (I) wherein independently R denotes H, -NR3R4, -OR5, or -CR6R6'R7, R2 denotes H, C1 to C4 alkyl, halogen, or OH, n is 1 , 2, or 3 wherein independently R3 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the nitrogen atom in R via R4, R4 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the nitrogen atom in R via R3, R5 denotes H or a pair of electrons, or C1 to C4 alkyl, R6 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the carbon atom in R via R7, R6' denotes H or C1 to C4 alkyl, R7 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the carbon atom in R via R6, with the proviso that the total amount of said cobalt (II) ions in the composition represents 51 wt.-% to 100 wt.-% of all transition metal cations in the composition, based on the total weight of all transition metal cations in the composition. The composition of claim 1 , wherein the total amount of said cobalt (II) ions in the composition represents 80 wt.-% to 100 wt.-% of all transition metal cations in the composition, based on the total weight of all transition metal cations in the composition, preferably at least 90 wt.-%, more preferably at least 95 wt.-%, even more preferably at least 98 wt.-%, most preferably at least 99 wt.-%. The composition of claim 1 or 2, wherein the composition additionally comprises (c) at least one polymer comprising a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen. The composition of any of the aforementioned claims, wherein in formula (I) R2 is H and/or n is 1. The composition of any of the aforementioned claims, wherein C1 to C4 alkyl in R2 to R7 of formula (I) is independently methyl or ethyl. The composition of any of the aforementioned claims, wherein in formula (I) the - (CO)-R1 moiety is in meta position. The composition of any of the aforementioned claims, wherein the at least one first compound of formula (I) is selected from the group consisting of (la) (lb) (lc) (Id) (le) (If) (Ig). 8. The composition of any of the aforementioned claims, wherein the total concentration of the at least one first compound in the composition is in the range from 5 mg/L to 250 mg/L, based on the total volume of the composition, preferably in the range from 7 mg/L to 150 mg/L, more preferably in the range from 9 mg/L to 90 mg/L, even more preferably in the range from 12 mg/L to 70 mg/L. 9. The composition of any of the aforementioned claims, wherein each of the at least one polymer has a weight average molecular weight Mw in the range from 1 200 g/mol to 50 000 000 g/mol, preferably in the range from 2 000 g/mol to 20 000 000 g/mol, more preferably in the range from 3 000 g/mol to 8 000 000 g/mol, even more preferably in the range from 4 000 g/mol to 6 000 000 g/mol, most preferably in the range from 5 000 g/mol to 5 000 000 g/mol. 10. The composition of any of the aforementioned claims, wherein the carboxamide moieties are independently represented by formula (II) (ll), wherein R8 denotes C1 to C3 alkyl, an alkylene moiety connected via R9 to the amine nitrogen atom of the carboxamide moiety in formula (II), R9 denotes hydrogen, C1 to C3 alkyl, a carbon atom of the backbone chain of the polymer, or an alkylene moiety connected via R8 to the carbonyl carbon atom of the carboxamide moiety in formula (II), and R 0 denotes a carbon atom of the backbone chain of the polymer. 11. The composition of any of the aforementioned claims, wherein the at least one polymer is selected from the group consisting of (I la) Polyvinylpyrrolidone; (lib) Polyvinylcaprolactam; (lie) Poly(2-methyl-2-oxazoline); (lid) Poly(2-ethyl-2-oxazoline); (lie) Poly(N-vinyl-acetamide); and (I If) Poly(N-methyl-N-vinyl-acetamide) 12. The composition of any of the aforementioned claims, wherein the total concentration of the at least one polymer in the composition is in the range from 60 mg/L to 1000 mg/L, based on the total volume of the composition, preferably in the range from 80 mg/L to 800 mg/L, more preferably in the range from 100 mg/L to 600 mg/L, even more preferably in the range from 150 mg/L to 500 mg/L, most preferably in the range from 200 mg/L to 400 mg/L. 13. A method for electrolytically depositing a cobalt deposit onto a substrate, the method comprising the steps (A) providing the substrate, (B) providing an aqueous composition according to any of claims 1 to 12, (C) contacting the substrate with the aqueous composition and supplying an electrical current such that cobalt is deposited onto the substrate to form the cobalt deposit. 14. The method of claim 13, wherein the substrate comprises on at least one of its surfaces a plurality of vias and/or trenches. 15. The method of claim 14, wherein in step (C) the cobalt deposit fills said vias and/or trenches. 16. Use of a composition as defined in any of claims 1 to 12 for depositing a cobalt deposit, preferably for filling vias and/or trenches. |
Field of the Invention
The present invention relates to an aqueous composition for depositing a cobalt deposit and a method for electrolytically depositing such a cobalt deposit onto a substrate, in particular to a method for electrolytically depositing such a cobalt deposit into a plurality of vias and/or trenches.
Background of the Invention
Trenches and vias are typical features on semiconductor substrates of modern electronic devices. Since copper is an excellent conducting material with basically low resistivity and high reliability, for decades and still until today, it is deposited into such features in order to fill respective vias and trenches and to form a pattern of conductive lines and interconnects. However, copper as filling metal also bears some drawbacks.
It is well known that copper has a high migration and diffusion tendency. Depending on the substrate (for example silicon oxide containing substrates), copper easily diffuses into the substrate thereby causing voids, an interrupted electrical flow and even electrical shorts. In order to address such critical problems, typically a barrier layer is applied on the surface of the substrate to block or at least significantly suppress said migration and diffusion. In many applications, barrier layers contain cobalt.
The application of such barrier layers becomes more and more demanding because during recent years the size of said features is getting smaller and smaller, demanding also thinner und more uniform barrier layers. At present, a common feature size is in the range from 50 nm to even less than 10 nm. Furthermore, in order to deposit copper electrolytically onto a barrier layer, a conductive and thin seed layer needs to be additionally deposited onto the barrier layer.
But besides such a layer arrangement, void-free filling of such small features with copper becomes increasingly demanding and difficult. In addition to decreasing feature sizes and the application of thin barrier and seed layers, feature geometry calls for additional attention because of feature's high aspect ratios. Features with an opening dimension of for example 10 nm and a feature depth of for example 100 nm exhibit an aspect ratio of 10: 1. This and similar aspect ratios become more important today and it is expected that aspect ratios will further increase in the near future. Features with such high aspect ratios require sophisticated filling methods and specifically designed copper deposition baths to avoid incomplete feature filling, causing defects widely known as voids.
Another drawback of a decreasing feature size is the resulting copper resistivity, which exponentially increases, in particular with feature dimensions below 10 nm. Although resistivity is a metal intrinsic characteristic, overall resistivity of a copper filled feature is largely affected by the metallic and non-metallic materials surrounding the copper and the way how electrons interact with these materials. For example, the flow of electrons is largely affected by coming across interfaces such as between (i) copper and embedded impurities in the copper, (ii) grain boundaries, (ii) copper and other layers such as seed and barrier layers. Recent investigations have revealed that other metals, such as cobalt, are less susceptible to such an exponential resistivity increase and it has been therefore suggested to replace copper by cobalt. This appears reasonable also for another reason. Using metals that can serve dual or even multiple purposes (as filling metal as well as barrier and/or seed layer) may allow more volume for the conducting metal and thus a lower overall resistivity. Since cobalt often serves as metal in barrier layers for copper deposits, cobalt filled features do not necessarily require an additional barrier layer. Furthermore, a cobalt layer may also serve as conductive seed layer. As a result, a very homogeneous cobalt deposit can be achieved with cobalt as copper replacement.
US 2009/0188805 A1 relates to using electrodeposition to fill recessed surface features of a substrate with metals and alloys in a substantially void free manner and discloses a cobalt deposition bath for void-free cobalt filling comprising 2-mercapto-5- benzimidazolesulfonic acid (MBIS) as filling additive.
CA 1086679 A relates to a process and composition for the preparation of an electro- deposit which contains cobalt. A composition may comprise an unsaturated cyclosulfone in combination with propargyl alcohol.
US 6,923,897 B1 relates to a cold rolled strip which is provided with a cobalt or a cobalt alloy layer by an electrolytic method. An electrolyte bath may comprise butynediol and saccharine.
WO 2017/004424 A1 relates to electrolytic deposition chemistry and a method for depositing cobalt and cobalt alloys; and more specifically to additives and overall compositions for use in an electrolytic plating solution and a method for cobalt-based metallization of interconnect features in semiconductor substrates. A composition may comprise propargyl alcohol in combination with bis-(sodium sulfopropyl) disulphide (SPS). US 3,432,509 A relates to novel pyridinium compounds and their use as primary bright- eners in the electrodeposition of nickel.
Organic additives, such as linear propargylic compounds (e.g. propargyl alcohol), are already utilized for filling features with cobalt. Furthermore, such compounds show in some cases an acceptable bottom-up filling performance, in particular for features with moderate aspect ratios.
An excellent bottom-up filling performance is even more required the higher the aspect ratios of features are. If the total concentration of said organic additives is too low, the bottom-up filling performance is insufficient too and voids are often observed. As a result, in many cases the total concentration of organic additives is increased in order to adequately fill features with high aspect ratios. However, if the total concentration exceeds a certain limit, inacceptable deposition defects (e.g. skip plating) frequently occur on the substrate's surface. In such a case the coverage with cobalt on the substrate's surface is insufficient. Ideally the entire surface of a substrate is completely and homogeneously covered with cobalt while all features on the substrate are void free filled with cobalt.
A drawback of said linear propargylic compounds (in particular of propargylic alcohol) is its toxicity. Therefore, it is desired to identify alternative, less toxic organic additives and less toxic compositions, respectively.
Furthermore, compositions comprising said linear propargylic compounds are not highly effective. Therefore, there is an ongoing demand to identify more effective compositions for depositing a cobalt deposit, preferably more effective compositions with additionally an improved bottom-up filling performance.
Furthermore, it is vital to establish a robust and well operating method for electrolytically depositing a cobalt deposit. This primarily includes reliably monitoring the total concentration of such linear propargylic compounds in a respective composition. Typically, the total concentration of such compounds in a composition is usually very low and practically ranges between 10 mg/L and 50 mg/L, based on the total volume of the composition. Thus, a reliable monitoring is demanding, in particular for said linear propargylic compounds, which exhibit comparatively low extinction coefficients.
Objective of the present Invention
It is an objective of the present invention to provide an aqueous composition for depositing a cobalt deposit, which overcomes the above mentioned problems. It is in particular the objective, to identify and provide compositions that are preferably simultaneously (i) more effective, (ii) less toxic, and (iii) allow an easy and reliable monitoring of the utilized organic filling additives in particular by UV/VIS measurements.
It is desired that these compositions additionally provide an excellent skip plating performance, in particular in the presence of a comparatively high total concentration of said organic additives.
Preferably, these compositions additionally provide excellent bottom-up filling performance in features with very small opening dimensions, preferably with comparatively high aspect ratios.
It is an additional objective of the present invention to provide also a method for electro- lytically depositing a cobalt deposit with above mentioned advantages.
Summary of the Invention
These objectives are solved by an aqueous composition for depositing a cobalt deposit, the composition comprising
(a) a total amount of cobalt (II) ions,
(b) at least one first compound of formula (I)
wherein independently
R denotes H, -NR 3 R 4 , -OR 5 , or -CR 6 R 6' R 7 ,
R 2 denotes H, C1 to C4 alkyl, halogen, or OH,
n is 1 , 2, or 3
wherein independently
R 3 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the nitrogen atom in R via R 4 ,
R 4 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the nitrogen atom in R via R 3 , R 5 denotes H or a pair of electrons, or C1 to C4 alkyl,
R 6 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the carbon atom in R via R 7 ,
R 6' denotes H or C1 to C4 alkyl,
R 7 denotes H, C1 to C4 alkyl, or an alkylene moiety connected to the carbon atom in R via R 6 ,
with the proviso that the total amount of said cobalt (II) ions in the composition represents 51 wt.-% to 100 wt.-% of all transition metal cations in the composition, based on the total weight of all transition metal cations in the composition.
Furthermore, the additional objective is solved by a method for electrolytically depositing a cobalt deposit onto a substrate, the method comprising the steps
(A) providing the substrate,
(B) providing an aqueous composition according to the present invention (as described above and below in the present text),
(C) contacting the substrate with the aqueous composition and supplying an electrical current such that cobalt is deposited onto the substrate to obtain the cobalt deposit.
Brief description of the figure
Figure 1a is an image of a cross-section showing trenches obtained from filling experiment C1 after 30 seconds (comparative example).
Figure 1 b is an image of a cross-section showing trenches obtained from filling experiment C2 after 20 seconds (comparative example).
Figure 2a is an image of a cross-section showing trenches obtained from filling experiment E1 after 30 seconds (according to the invention).
Figure 2b is an image of a cross-section showing trenches obtained from filling experiment E2 after 20 seconds (according to the invention).
Figure 3 is an image of a cross-section showing trenches obtained from filling experiment E10 after 15 seconds (according to the invention).
Figure 4 is an image of a cross-section showing trenches obtained from filling experiment E14 after 15 seconds (according to the invention). Detailed Description of the Invention
The composition of the present invention is an aqueous composition, which means that water is the primary component. Thus, more than 50 wt.-% of the composition is water, based on the total weight of the aqueous composition, preferably at least 70 wt.-%, even more preferably at least 90 wt.-%, most preferably 95 wt.-% or more. It is preferred that the aqueous composition is substantially free of organic solvents; more preferably does not contain organic solvents at all. Furthermore, the composition is preferably a homogeneous aqueous solution and thus preferably does not contain any particles.
The composition is for depositing a cobalt deposit, preferably a sulfur-free cobalt deposit.
Preferred is a composition of the present invention, wherein the composition is acidic, preferably has a pH in the range from 0.5 to 6.8, more preferably in the range from 1 to 6, even more preferably in the range from 1.5 to 5, most preferably in the range from 2.5 to 4.6, even most preferably in the range from 3.5 to 4.6. A basic pH is undesired because cobalt hydroxide precipitation is typically observed at a basic pH, which usually results in an undesired increased surface roughness of the cobalt deposit.
The aqueous composition of the present invention comprises, besides (a) the total amount of cobalt (II) ions, (b) at least one (preferably one) first compound of formula (I) and preferably additionally (c) at least one (preferably one) polymer comprising a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen.
Such compositions of the present invention are usually less toxic compared to compositions comprising linear propargylic compounds, for example compositions comprising propargyl alcohol.
Furthermore, compounds of formula (I) contain a pyridine moiety, which is sensitive to UV detection and excellently detectable by means of respective analytical tools. This allows a reliable monitoring of the total concentration of compounds of formula (I) in the composition of the present invention. Typical organic compounds such as propargyl alcohol and propargyl alcohol ethoxylate maintain a significantly low profile over the typical UV/VIS spectrum, in particular between 250 nm and 280 nm (absorption remains almost zero between 210 nm and 400 nm; concentration 0.2 mmol/L). In contrast, compounds of formula (I) typically have a strong absorption between 250 nm and 280 nm, which can be utilized for monitoring and even quantification. For example, compound of formula (la) (concentration 0.2 mmol/L) shows an absorption maximum of more than 0.9 at 266 nm. Own experiments have shown that the composition of the present invention is more effective compared to compositions comprising linear propargylic compounds (see examples below). This means that a lower working concentration can be utilized in the composition of the present invention to achieve identical results, compared to compositions comprising linear propargylic compounds instead (see examples below).
Preferred is a composition of the present invention, wherein the total concentration of the cobalt (II) ions in the composition is in the range from 0.5 g/L to 50 g/L, based on the total volume of the composition, preferably in the range from 0.7 g/L to 25 g/L, more preferably in the range from 0.9 g/L to 15 g/L, even more preferably in the range from 1.2 g/L to 1 1 g/L, most preferably in the range from 1.4 g/L to 7 g/L. A concentration below 0.5 g/L often results in an incomplete cobalt deposit and surface defects. If the concentration significantly exceeds 50 g/L undesired precipitation is observed in some cases in the composition, also frequently leading to an undesired increased surface roughness of the cobalt deposit.
The cobalt source of said cobalt (II) ions is preferably at least one cobalt salt, more preferably at least one inorganic cobalt salt and/or at least one organic cobalt salt. Preferred inorganic cobalt salts are selected from the group consisting of cobalt nitrate, cobalt sulfate and cobalt halides. Preferred cobalt halides are selected from the group consisting of cobalt fluoride, cobalt chloride and cobalt bromide. A preferred organic cobalt salt is cobalt acetate. The most preferred at least one cobalt salt is cobalt sulfate, preferably cobalt sulfate heptahydrate.
By means of the composition of the present invention a cobalt deposits is preferably obtained which primarily contains cobalt. This means that a composition of the present invention is preferred, wherein said cobalt (II) ions are the major metal ion species for metal deposition. Preferred is a composition of the present invention, wherein the total amount of said cobalt (II) ions in the composition represents 80 wt.-% to 100 wt.-% of all transition metal cations in the composition, based on the total weight of all transition metal cations in the composition, preferably at least 90 wt.-%, more preferably at least 95 wt.-%, even more preferably at least 98 wt.-%, most preferably at least 99 wt.-%.
Preferred is a composition of the present invention, wherein in the composition the molar ratio of the total molar amount of transition metal cations other than cobalt (II) ions (i.e. excluding the total amount of cobalt (II) ions) to the total molar amount of cobalt (II) ions is in the range from 0 to 0.4, based on the total volume of the composition, preferably in the range from 0 to 0.2, more preferably in the range from 0 to 0.1 , even more preferably in the range from 0 to 0.1 , most preferably in the range from 0 to 0.01.
In particular, if nickel ions are present in the composition of the present invention, the total molar amount of said cobalt (II) ions is at least 5 times the total molar amount of nickel cations, preferably at least 10 times. Most preferably, the composition of the present invention is substantially free of nickel.
In the context of the present invention, transition metals are elements of groups 3 to 12 on the periodic table.
In most of all cases the composition of the present invention is most preferably substantially free of (preferably does not contain) alloying metal cations. Thus, by means of the composition of the present invention most preferably a pure cobalt deposit is obtained.
In the context of the present invention, the term "substantially free" of a subject-matter (e.g. a compound, a material, etc.) denotes that said subject-matter is not present at all or is present only in (to) a very little and undisturbing amount (extent) without affecting the intended purpose of the invention. For example, such a subject-matter might be added or utilized unintentionally, e.g. as unavoidable impurity. "Substantially free" preferably denotes 0 (zero) ppm to 50 ppm, based on the total weight of the composition of the present invention, if defined for said composition, or based on the total weight of the cobalt deposit obtained in the method of the present invention, if defined for said deposit; preferably 0 ppm to 25 ppm, more preferably 0 ppm to 10 ppm, even more preferably 0 ppm to 5 ppm, most preferably 0 ppm to 1 ppm.
A composition according to the present invention is preferred, wherein the composition is substantially free of (preferably does not contain) nickel ions, preferably is substantially free of (preferably does not contain) nickel ions, iron ions, and copper ions, more preferably is substantially free of (preferably does not contain) nickel ions, iron ions, copper ions, aluminium ions, lead ions, and tin ions.
Preferably, the composition of the present invention is substantially free of (preferably does not contain) compounds comprising divalent sulfur and/or compounds comprising a mercapto group, more preferably MBIS.
More preferably, the composition is substantially free of sulfur containing compounds with a sulfur atom having an oxidation number below +5. Most preferably the composition does not comprise such sulfur containing compounds. This means that the composition is substantially free of (preferably does not contain) sulfur containing compounds widely used as brighteners in other metal deposition baths such as nickel plating baths. However, this does not exclude the presence of sulfate ions in the composition of the present invention because a sulfate ion contains a sulfur atom having an oxidation number of +6 (but not below +6). This does also not exclude the presence of anions with a sulfonic acid moiety, preferably as described in the text below, which typically comprise a sulfur atom having an oxidation number of +5. If the composition contains sulfur containing compounds with a sulfur atom having an oxidation number particularly below +5 or lower (e.g. divalent sulfur) in many cases sulfur is incorporated into the cobalt deposit. This is undesired because sulfur negatively affects resistivity in the cobalt deposit. Similar observations have been made for other alloying metals or elements. Furthermore, cobalt deposits comprising significant amounts of sulfur negatively affect further processing steps carried out after cobalt deposition, e.g. chemical mechanical polishing (CMP).
Even more preferably, the composition is substantially free of sulfur containing compounds with a sulfur atom having an oxidation number below +6. Most preferably the composition does not comprise such sulfur containing compounds. However, this does not exclude the presence of sulfate ions in the composition of the present invention.
Very preferred is an aqueous composition according to the present invention with the proviso that, if the aqueous composition contains sulfur containing compounds, the only sulfur containing compounds are sulfate ions (S0 4 2" ) or anions with a sulfonic acid moiety (preferably as described below in the text).
Preferably, the composition of the present invention is for electrolytic deposition in order to obtain the cobalt deposit. Thus, the composition is preferably not for electroless cobalt deposition. Therefore, a composition of the present invention is preferred, wherein the composition does not contain effective amounts of reducing agents being capable of reducing the cobalt (II) ions to metallic cobalt. This may include that tiny amounts of such reducing agents are present in the composition. Preferably these tiny amounts are either not detectable by means of standard analytical tools or at least not detrimental to the intended utilization as an electrolyte. Preferred is a composition of the present invention, wherein the composition comprises a reducing agent being capable of reducing the cobalt (II) ions to metallic cobalt in a total concentration of 0 mg/L to 200 mg/L, based on the total volume of the composition, preferably the composition is substantially free of reducing agents being capable of reducing the cobalt (II) ions to metallic cobalt. Most preferred, the composition of the present invention does not contain a reducing agent being capable of reducing the cobalt (II) ions to metallic cobalt.
A composition of the present invention is preferred, wherein the composition is substantially free of (preferably does not contain) reducing agents being capable of reducing the cobalt (II) ions to metallic cobalt containing phosphorous, even more preferably the composition is substantially free of (preferably does not contain) phosphorous containing compounds.
In the most cases an aqueous composition according to the present invention is preferred, wherein the composition is substantially free of (preferably does not contain) an unsaturated cyclosulfone compound, preferably is substantially free of (preferably does not contain) unsaturated cyclic compounds comprising a sulfur atom.
A composition according to the present invention is preferred, wherein the composition is substantially free of (preferably does not contain) compounds comprising an acetylenic moiety but not being a compound of formula (I). Preferably, the total concentration of such compounds is in the range from 0 mg/L to 10 mg/L, more preferably in the range from 0 mg/L to 2 mg/L, most preferably in the range from 0 mg/L to 0.5 mg/L. In other words, in the composition of the present invention, compounds of formula (I) are preferably the only compounds with an acetylenic moiety.
The aqueous composition of the present invention comprises (b) at last one (preferably one) first compound of formula (I) (see above), which does not contain sulfur.
In the context of the present invention, the term "at least one" generally denotes (and is exchangeable with) "one, two, three or more than three". The term "at least [... ]" includes "or more than [... ]".
Without wishing to be bound by theory, it is assumed that the first compound acts as suppressor if the composition is utilized in the method of the present invention, such that cobalt deposition is inhibited on areas where a reduced deposition rate is desired, e.g. at the side walls inside a via or trench.
In the composition of the present invention the at least one first compound contains an acyl moiety with a carbonyl oxygen atom which is connected to a carbonyl carbon atom. Furthermore, the compound of formula (I) comprises an acetylenic moiety covalently connected to the ring nitrogen. As a result, the at least first compound is positively charged. Preferably, the acetylenic moiety is a propargyl moiety (HC≡C-CH 2 -). Thus, most preferred is a composition according to the present invention, wherein R 2 is hydro- gen. Even more preferred is a composition according to the present invention, wherein in formula (I) R 2 is H and/or n is 1.
Preferred counter anions in the composition of the present invention are selected from the group consisting of halogen, carboxylic acid residue anions, and anions with a sulfonic acid moiety. Halogen preferably refers to chloride and bromide. Preferred carboxylic acid residue anions are formiate and acetate. Preferred anions with a sulfonic acid moiety are selected from the group consisting of tosylate, mesylate, triflate, and no- naflate. Such anions comprise a covalent bond between carbon and sulfur. Preferred is a composition of the present invention, wherein the composition comprises at least one of the aforementioned counter anions, preferably at least bromide or at least one anion with a sulfonic acid moiety.
Preferred is a composition of the present invention, wherein in formula (I) R denotes - NR 3 R 4 , -OR 5 , or -CR 6 R 6' R 7 , more preferably denotes -NR 3 R 4 or -OR 5 , most preferably denotes -NR 3 R 4 .
In the composition of the present invention, said at least one first compound is a monomer, i.e. is not a polymer. Preferably, said first compound consists of carbon atoms, hydrogen atoms, nitrogen atoms and oxygen atoms (i.e. in these cases in R 2 halogen is not included). Thus, preferred is a composition of the present invention, wherein in formula (I) R 2 denotes H, halogen, or OH, preferably in some cases denotes H or halogen, or in other cases preferably denotes H or OH.
Preferred is a composition of the present invention, wherein in formula (I) n is 1 or 2, preferably 1.
In the composition of the present invention, in formula (I) R 3 and R 4 include an alkylene moiety connected to the nitrogen atom in R via R 4 and R 3 , respectively. Such an alkylene moiety forms a saturated, intramolecular ring structure including the nitrogen atom of R 1 . Preferred alkylene moieties comprise 4 to 6 carbon atoms (i.e. a butylene bridge, a pentylene bridge or a hexylene bridge), preferably 4 to 5 carbon atoms.
Preferred is a composition of the present invention, wherein in formula (I) R 3 denotes H or C1 to 04 alkyl, preferably denotes H, methyl or ethyl. In these cases R 3 does not comprise the above mentioned cyclization.
Preferred is a composition of the present invention, wherein in formula (I) R 4 denotes H or 01 to 04 alkyl, preferably denotes H, methyl or ethyl. In these cases R 4 does not comprise the above mentioned cyclization. In some cases it is very preferred that in formula (I) R 3 and R 4 are identical, most preferably if R 3 and R 4 do not denote said alkylene moiety. Most preferably both are H, methyl or ethyl.
In the composition of the present invention, in formula (I) R 5 denotes H or a pair of electrons, or C1 to C4 alkyl. A pair of electrons means that the oxygen atom in R is present in a dissociated/deprotonated form, carrying a negative charge distributed over the entire carboxylic group in the compound of formula (I) and leading to a carboxylate anion (- COO-). In other words, R denotes H, -NR 3 R 4 , -OR 5 , -Or, or -CR 6 R 6' R 7 , wherein R 5 denotes H or C1 to C4 alkyl. Regarding the definition of R 2 , R 3 , R 4 , R 6 , R 6' , R 7 see the text above and below, respectively.
Preferred is a composition of the present invention, wherein in formula (I) R 5 denotes C1 to C4 alkyl, more preferably denotes methyl or ethyl.
In the composition of the present invention, in formula (I) R 6 and R 7 include an alkylene moiety connected to the carbon atom in R via R 7 and R 6 , respectively. Such an alkylene moiety forms a saturated, intramolecular ring structure including the carbon atom of R 1 . Preferred alkylene moieties comprise 4 to 6 carbon atoms (i.e. a butylene bridge, a pen- tylene bridge or a hexylene bridge), preferably 4 to 5 carbon atoms.
Preferred is a composition of the present invention, wherein in formula (I) R 6 denotes H or C1 to C4 alkyl, preferably denotes H, methyl or ethyl. In these cases R 6 does not comprise the above mentioned cyclization.
Preferred is a composition of the present invention, wherein in formula (I) R 6' denotes H, methyl or ethyl, preferably denotes H.
Preferred is a composition of the present invention, wherein in formula (I) R 7 denotes H or C1 to C4 alkyl, preferably denotes H, methyl or ethyl. In these cases R 7 does not comprise the above mentioned cyclization.
In some cases it is very preferred that in formula (I) R 6' is H and one of R 6 and R 7 is H and the other is H, methyl or ethyl.
In the context of the present invention, C1 to C4 alkyl preferably denotes methyl, ethyl, n- propy, iso-propyl, n-butyl, iso-butyl, sec-butyl, or tert-butyl, more preferably denotes methyl or ethyl. Preferred is a composition of the present invention, wherein C1 to C4 alkyl in R 2 to R 7 (including R 6' ) of formula (I) is independently methyl or ethyl. In the compound of formula (I) the -(CO)-R 1 moiety is in ortho, metha or para position. Preferred is a composition of the present invention, wherein in formula (I) the -(CO)-R 1 moiety is in meta position.
Most preferred is a composition of the present invention, wherein the at least one first compound of formula (I) is selected from the group consisting of
(la) (lb) (lc)
(Id) (le) (If) (Ig).
The term "independently" denotes that R to R 7 of a first compound of formula (I) are selected independently from R to R 7 in further compounds of formula (I) in the same composition of the present invention.
Preferred is a composition of the present invention, wherein the total concentration of the at least one first compound in the composition is in the range from 5 mg/L to 250 mg/L, based on the total volume of the composition, preferably in the range from 7 mg/L to 150 mg/L, more preferably in the range from 9 mg/L to 90 mg/L, even more preferably in the range from 12 mg/L to 70 mg/L. If the concentration is significantly below 5 mg/L typically no suppressing effect is observed if a respective composition is utilized in a cobalt deposition method to fill features, usually resulting in a plurality of voids. If the concentration significantly exceeds 250 mg/L usually heavy and uncontrollable skip plating occurs in a cobalt deposition method. The aqueous composition of the present invention preferably additionally comprises (c) at least one (preferably one) polymer comprising a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen. Preferably, said at least one polymer does not contain a primary amine nitrogen. A polymer typically consists of monomeric building units.
Preferred is a composition of the present invention, wherein more than 50% of all monomeric building units in the at least one polymer comprise at least one (preferably one) of said carboxamide moiety with a secondary or tertiary amine nitrogen, preferably more than 70%, even more preferably more than 85%, most preferably more than 95%. The carboxamide moieties in the monomeric building units are identical or different (for example, one species of monomeric building units comprises a carboxamide moiety with a secondary amine nitrogen and another species comprises a carboxamide moiety with a tertiary amine nitrogen). Most preferred is a composition of the present invention, wherein the at least one polymer is a homopolymer. This means that every monomeric building unit comprises identically at least one (preferably one) of said carboxamide moiety with a secondary or tertiary amine nitrogen.
Said polymers positively affect the skip plating performance on a substrate's surface despite a comparatively high total concentration of the at least one first compound. This positive effect occurs over a broad range of molecular weights. Thus, preferred is a composition of the present invention, wherein each of the at least one polymer has a weight average molecular weight Mw in the range from 1 200 g/mol to 50 000 000 g/mol, preferably in the range from 2 000 g/mol to 20 000 000 g/mol, more preferably in the range from 3 000 g/mol to 8 000 000 g/mol, even more preferably in the range from 4 000 g/mol to 6 000 000 g/mol, most preferably in the range from 5 000 g/mol to 5 000 000 g/mol (see examples below).
Said polymers but with a comparatively high molecular weight additionally improve the bottom-up filling performance in respective filling experiments (see examples below). Although the molecular weight is not in particular limited, it appears that this effect is primarily restricted by a lower molecular weight limit. Thus, preferred is, either for at least one or preferably for all of said at least one polymer, a weight average molecular weight Mw of at least 100 000 g/mol. Preferred is a composition of the present invention, wherein either at least one or preferably all of said at least one polymer have a weight average molecular weight Mw in the range from 100 000 g/mol to 50 000 000 g/mol, preferably in the range from 200 000 g/mol to 10 000 000 g/mol, most preferably in the range from 500 000 g/mol to 5 000 000 g/mol. Utilizing such polymers usually results in an improved skip plating performance as well as (i.e. additionally) an improved bottom-up filling performance (see examples below). Therefore, such polymers are most preferred in the composition of the present invention.
More preferred is a composition of the present invention, wherein the carboxamide moieties are independently represented by formula (II)
(II),
wherein
R 8 denotes C1 to C3 alkyl, an alkylene moiety connected via R 9 to the amine nitrogen atom of the carboxamide moiety in formula (II),
R 9 denotes hydrogen, C1 to C3 alkyl, a carbon atom of the backbone chain of the polymer, or an alkylene moiety connected via R 8 to the carbonyl carbon atom of the carboxamide moiety in formula (II), and
R 0 denotes a carbon atom of the backbone chain of the polymer.
The moiety represented by formula (II) comprises an amine nitrogen atom, which is connected to R 9 and R 0 , as well as a carbonyl carbon atom, which is connected to R 8 .
The term "a carbon atom of the backbone chain of the polymer" includes that the amine nitrogen atom of the carboxamide moiety in Formula (II) is either included in the backbone chain of the polymer (e.g. such as in PEOX or PMOX, see text below) or is included in the side chain of the polymer (e.g. such as in PNVA or PMVA, see text below).
In R 8 and R 9 , respectively, the term "an alkylene moiety connected via [... ]" denotes a bridging alkylene moiety leading to an intramolecular ring structure including the amine nitrogen atom and the carbonyl carbon atom (e.g. such as in PVP or PVCL, see text below). Preferred alkylene moieties comprise 3 to 5 carbon atoms (i.e. a propylene bridge, a butylene bridge or a pentylene bridge), preferably 3 carbon atoms.
Preferably, in R 8 and R 9 said C1-C3 alkyl is independently selected from the group consisting of methyl, ethyl, n-propy, and iso-propyl, preferably independently selected from the group consisting of methyl and ethyl. Preferred is a composition of the present invention, wherein the at least one polymer does not contain a sulfur atom.
More preferred is a composition of the present invention, wherein each of the at least one polymer consists of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms.
Preferred is a composition of the present invention, wherein the at least one polymer does not contain a hydroxyl group.
Preferred is a composition of the present invention, wherein the at least one polymer does not contain an acetylenic moiety.
Preferred is a composition of the present invention, wherein the at least one polymer does not contain an ether oxygen atom.
Most preferred is a composition of the present invention, wherein the at least one polymer is selected from the group consisting of
Label Chemical name Structural formula Common
abbreviation
(lla) Polyvinylpyrrolidone PVP
n
(lib) Polyvinylcaprolactam PVCL
n
(lie) Poly(2-methyl-2-oxazoline) PMOX
n (lid) Poly(2-ethyl-2-oxazoline) PEOX
n
(lie) Poly(N-vinyl-acetamide) PNVA
(I if) Poly(N-methyl-N-vinyl-acetamide) PMVA
n
Most preferred is a composition, wherein the at least one polymer is selected from the group consisting of PVP, PEOX, and PNVA.
Preferred is a composition of the present invention, wherein the total concentration of the at least one polymer in the composition is in the range from 60 mg/L to 1000 mg/L, based on the total volume of the composition, preferably in the range from 80 mg/L to 800 mg/L, more preferably in the range from 100 mg/L to 600 mg/L, even more preferably in the range from 150 mg/L to 500 mg/L, most preferably in the range from 200 mg/L to 400 mg/L. If the concentration is significantly below 60 mg/L usually undesired skip plating in the presence of comparatively high concentrations of the first compound cannot longer adequately suppressed. If the concentration significantly exceeds 1000 mg/L the deposition process is undesirably disturbed.
The composition of the present invention optionally contains a buffering agent for pH stabilization, preferably selected from the group consisting of boric acid and acetic acid/acetic salt. Most preferred is boric acid. Preferably the total concentration of the buffering agent (preferably of boric acid) in the composition is in the range from 5 g/L to 60 g/L, based on the total volume of the composition, preferably in the range from 10 g/L to 40 g/L, most preferably in the range from 20 g/L to 30 g/L. As mentioned above, the present invention also refers to a method for electrolytically depositing a cobalt deposit onto a substrate, utilizing the composition of the present invention.
In step (A) of the method of the present invention, the substrate is provided. Preferred is a method of the present invention, wherein the substrate is a semiconductor base substrate. This means that the substrate preferably comprises at least one metalloid and/or gallium, more preferably selected from the group consisting of silicon, germanium and gallium, most preferably silicon.
Substrates for modern technical devices typically comprise features of small dimensions. Preferred is a method of the present invention, wherein the substrate comprises on at least one of its surfaces a plurality of vias and/or trenches.
More preferred is a method of the present invention, wherein the substrate is a wafer, more preferably a wafer with a plurality of vias and/or trenches on at least one of its surfaces.
A method of the present invention is preferred, wherein in step (C) the cobalt deposit fills said vias and/or trenches. More preferred is a method of the present invention, wherein in step (C) the cobalt deposit
- fills said vias and/or trenches and additionally
- at least covers the entire substrate on the side comprising said filled vias and/or trenches.
Subsequent to the deposition of the cobalt deposit, a method of the present invention is preferred, wherein in a further step the cobalt deposit is partly, horizontally removed, preferably by mechanical and/or chemical removal. As a result, a very smooth and uniform surface of the cobalt deposit is obtained.
Preferred is a method of the present invention, wherein the smallest opening dimension of said vias and trenches is 100 nm or less than 100 nm, preferably 50 nm or less than 50 nm, more preferably 30 nm or less than 30 nm, even more preferably 20 nm or less than 20 nm, most preferably 10 nm or less than 10 nm.
Preferred is a method of the present invention, wherein said vias and trenches have an aspect ratio in the range from 2:1 to 50: 1 , preferably 3: 1 to 40: 1 , more preferably 3: 1 to 30: 1 , even more preferably 3: 1 to 20: 1 , most preferably 3: 1 to 15: 1. Typically said substrate comprises a conductive seed layer for electrolytic deposition of cobalt. Preferred is a method of the present invention, wherein the substrate comprises a cobalt seed layer. Thus, in step (C) the cobalt deposit is preferably deposited onto a cobalt seed layer. This results in a very preferred homogeneous layer arrangement of seed layer and cobalt deposit. Usually such a homogeneous arrangement exhibits a very desirable resistivity. Furthermore, no additional barrier layer is preferably required.
In the method of the present invention, the substrate is operated as a cathode in order to obtain the cobalt deposit in step (C).
Preferred is a method of the present invention, wherein the electrical current is a direct current, preferably with a cathodic current density in the range from 0.01 A/dm 2 to 2 A/dm 2 , more preferably with a cathodic current density in the range from 0.03 A/dm 2 to 1.5 A/dm 2 , most preferably with a cathodic current density in the range from 0.05 A/dm 2 to 1.0 A/dm 2 . In some cases it is preferred that the direct current in step (C) is not supplemented by current pulses. This means that preferably in step (C) the direct current is the only electrical current.
A method of the present invention is preferred, wherein in step (C) the contacting and supplying of electrical current is carried out for 3 seconds to 600 seconds, preferably for 5 seconds to 300 seconds, most preferably for 10 seconds to 150 seconds. If the contacting is carried out for significantly less than 3 seconds typically an incomplete cobalt deposit is obtained and often the plurality of vias and/or trenches is not or at least not sufficiently filled. If the contacting is carried out for significantly more than 600 seconds in most cases a too thick cobalt layer is deposited over the entire substrate, which is unde- sired for subsequent processing steps, such as CMP, which are unnecessarily prolonged.
Preferably, a deposition sequence is carried out if direct current is applied. Therefore, a method of the present invention is preferred, wherein the contacting in step (C) comprises a first contacting time with a first cathodic current density, followed by a second contacting time with a second cathodic current density, wherein the first contacting time is shorter than the second contacting time and the first cathodic current density is lower than the second cathodic current density.
Preferably, the first contacting time is in the range from 3 seconds to 90 seconds, more preferably from 5 seconds to 40 seconds. Independently from that, a preferred first cathodic current density is in the range from 0.01 A/dm 2 to 0.5 A/dm 2 , more preferred in the range from 0.1 A/dm 2 to 0.4 A/dm 2 . Preferably, the second contacting time is in the range from 50 seconds to 510 seconds, more preferably from 70 seconds to 150 seconds. Independently from that, a preferred second cathodic current density is in the range from 0.1 A/dm 2 to 2.0 A/dm 2 , more preferred in the range from 0.2 A/dm 2 to 1.0 A/dm 2 .
By means of the electrical current the cobalt deposit is deposited on the substrate (preferably first into said vias and/or trenches and subsequently ono the entire substrate) in step (C) of the method of the present invention. Preferred is a method of the present invention, wherein the cobalt deposit comprises 60 wt.-% or more cobalt, based on the total weight of the cobalt deposit, preferably 75 wt.-% or more, more preferably 90 wt.-% or more, even more preferably 95 wt.-% or more, very much preferably 98 wt.-% or more, most preferably 99.9 wt.-% or more. A cobalt deposit comprising at least 99.9 wt.-% cobalt is usually considered as a pure cobalt deposit. Such a cobalt deposit is very much desired in modern electronic devices.
Preferably, the cobalt deposit is substantially free of (preferably does not comprise) one, more than one or all elements of the group consisting of nickel, iron, copper, aluminium, lead, and tin. More preferably, the cobalt deposit is not a nickel cobalt alloy.
Very preferred is a method of the present invention, wherein the cobalt deposit is substantially free of (preferably does not contain) phosphorous and/or sulfur, preferably substantially free of (preferably does not contain) phosphorous and sulfur. Thus, the cobalt deposit is preferably a sulfur-free and/or phosphorous-free cobalt deposit. Furthermore, the cobalt deposit is preferably substantially free of (preferably does not contain) boron.
Preferred is a method of the present invention, wherein in step (C) the aqueous composition has a temperature in the range from 5°C to 90°C, preferably in the range from 15°C to 60°C, more preferably in the range from 20°C to 50°C, most preferably in the range from 22 °C to 30°C.
The present invention also refers to a use of the composition of the present invention for depositing a cobalt deposit, preferably for filling vias and/or trenches. The aforementioned regarding the composition of the present invention and the method of the present invention, respectively, applies likewise to the aforementioned use.
The present invention is described in more detail by the following non limiting examples.
Examples
1. Synthesis of compounds of formula (I): Compounds of formula (I), in particular compounds (la), to (Ig) (as described above in the text), are synthesized as disclosed in US 3,432,509 A, column 5, line 68 to column 8, line 5. Synthesis of above mentioned compounds is in particular based on examples 19 to 21 of US'509.
2-A. Aqueous compositions for depositing the cobalt deposit:
In a first step several aqueous compositions (No. C1 to C4 and E1 to E14) are prepared. Each composition contains at least 90 wt.-% Dl water (based on the total weight of the composition), approximately 30 g/L boric acid and cobalt sulfate in such an amount that the total concentration of cobalt (II) ions in each composition was approximately 3 g/L (each based on the total volume of the composition). Table 1 summarizes the presence and concentration of further compounds. Each composition has a pH in the range between 4.0 and 4.5 and cobalt is the only transition metal in the compositions.
Table 1
First Compound Polymer
No. Label c [mg/L]* MW [g/mol] c [mmol/L] Label Mw [g/mol] c [mg/L]*
Comparative examples
C1 X1 30 100 0.300
C2 X1 50 100 0.500
C3 X1 50 100 0.500 X2 354 5
C4 X1 50 100 0.500 X2 354 25
Examples according to the invention
E1 (la) 30 161 0.186
E2 (la) 50 161 0.311
E3 (lb) 30 217 0.138
E4 (lb) 50 217 0.230
E5 (lc) 30 189 0.159
E6 (lc) 50 189 0.265
E7 (Id) 30 160 0.188
E8 (Id) 50 160 0.313 E9 (la) 30 161 0.186 (Ma) 1 300 000 200
E10 (la) 50 161 0.311 (Ma) 1 300 000 200
E1 1 (la) 30 161 0.186 (lid) 5 000 200
E12 (la) 50 161 0.311 (lid) 5 000 200
E13 (la) 30 161 0.186 (lid) 500 000 200
E14 (la) 50 161 0.311 (lid) 500 000 200
* based on the total volume of the composition
# abbreviates "molecular weight" in general and refers to the specific molecular weight of compounds of formula (I)
In Table 1 , X1 and X2 have the following meaning:
X1 denotes HC≡C-CH2-0-(CH2)2-OH (propargyl alcohol ethoxylate), purchased from BASF
X2 denotes Bis-(sodium sulfopropyl)-disulfide (SPS), which is not a polymer; these experiments are for comparison reasons and are based on WO 2017/004424 A1. The specific molecular weight is 354 g/mol.
Polymer (I la) was purchased from Alfa Aesar; polymers (lid), Mw 5 000 and 500 000 from Polyscience and Sigma Aldrich, respectively.
2-B. Method for electrolytically depositing a cobalt deposit onto a substrate (deposition and filling experiments):
In a second step the method of the present invention is carried out and sulfur-free cobalt is deposited and filled, respectively.
In each experiment, 500 ml of a respective aqueous composition prepared in the first step is used. For the sake of comparison, each number given in Table 1 (No.) refers to the corresponding experiment.
Prior to the experiments, each aqueous composition is purged for 15 minutes with inert nitrogen gas and is subsequently tested in view of (I) skip plating performance in respective deposition experiments and (II) filling performance in respective filling experiments.
2.1 (I) skip plating performance (deposition experiments): In order to evaluate (I) skip plating performance, a blanket wafer (without features) is used as substrate and provided for each deposition experiment. On its active side, each substrate is equipped with a 3 nm TaN layer (deposited by PVD) and thereon a 10 nm cobalt layer (deposited by CVD) as conductive seed layer.
In each deposition experiment an electrical current with a current density of 0.6 A/dm 2 is supplied in order to electrolytically deposit the cobalt deposit, which is a layer having a thickness in the range from 220 nm to 280 nm. In each experiment, the substrate is contacted with the respective aqueous composition for approximately 100 seconds while said electrical current is supplied. During the experiments, the temperature of each composition is about 22°C.
Afterwards each substrate is rinsed with Dl water and dried by nitrogen gas flow such that a dried substrate is obtained.
Skip plating performance is evaluated for each dried substrate by visually inspecting images of each dried substrate. Imaging is carried out using a Laser Scanning Confocal Microscope (Olympus Lext OLS4100). The visual inspection is carried out by trained experts.
Skip plating performance of Examples E1 to E8 is identical to the performance obtained with Comparative Examples C1 and C2. Only very few surface defects (i.e. little spots without sufficient cobalt deposit) are observed in C1 , E1 , E3, E5, and E7. In Comparative Example C2 as well as in Examples E2, E4, E6, and E8 the number of surface defects is slightly increased compared to C1 , E1 , E3, E5, and E7. These examples show that the skip plating performance decreases upon a significantly increased total concentration of compound X1 and the first compound of formula (I), respectively. In Comparative Examples C3 and C4 the skip plating performance is worst; a significant higher number of surface defects is observed compared to C2, E2, E4, E6, and E8.
However, the results in Examples E1 to E8 are obtained by utilizing a significantly lower working concentration (mmol/L) compared to Comparative Examples C1 and C2, respectively, although the total concentration in mg/L is identical. In each respective example according to the present invention, the effective working concentration of the first compound is reduced by 30 mol-% to 50 mol-%. This effect is even more dramatic if propar- gyl alcohol (M=56 g/mol) is used instead of compound X1 (data not shown). Thus, above mentioned compositions of the present invention comprising a compound of formula (I) are more effective than compositions according to Comparative Examples C1 and C2 in order to achieve identical results. In Examples E9 to E14 a polymer comprising a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen is additionally utilized. In Examples E9, E11 , and E13 skip plating performance is slightly improved compared to Comparative Example C1 and Example E1 (as well as compared to Examples E3, E5, and E7). Improved means that skip plating performance is excellent and no significant surface defects are observable. In Examples E10, E12, and E14 skip plating performance is identically good as obtained for Examples E9, E1 1 , and E13. Thus, the presence of the polymer improves skip plating performance, in particular if the first compound is present in a higher total concentration, for example 50 mg/L.
2.2 (II) filling performance (filling experiments):
In order to evaluate the filling performance, wafers (Empire 1 M1 , SUNY Polytechnic Institute) are used as substrates and provided for each filling experiment, each substrate with a 3 nm TaN layer (deposited by PVD) and thereon a 4 nm cobalt seed layer (deposited by CVD). Each substrate is equipped with a plurality of trenches on its active surface with opening dimensions of approximately 100 nm and a depth of approximately 200 nm.
In each filling experiment an electrical current with a current density of 0.3 A/dm 2 is supplied in order to fill said trenches. Each substrate is contacted with the respective aqueous composition for approximately 30 seconds while said electrical current is supplied. During the experiments, the temperature of each composition is about 22°C.
Afterwards each substrate is also rinsed with Dl water and dried by nitrogen gas flow such that again dried substrates are obtained.
Filling performance is evaluated for each dried substrate by visually inspecting vertical cross-sections of said filled trenches obtained after 5 second time intervals during said approximately 30 seconds (in particular after 10, 15, 20, 25, and 30 seconds). For this purpose FIB-SEM (FEI Helios Nanolab 450S) is carried out (see Figures).
Filling performance of Examples E1 to E8 is identical to the performance obtained with Comparative Examples C1 and C2. Figures 1 a and 1 b show completely filled trenches after 30 seconds (Comparative Example C1) and 20 seconds (Comparative Example C2). In Examples E1 and E2 an identical filling performance is obtained (Example E1 after 30 seconds see Fig. 2a; Example E2 after 20 seconds see Fig. 2b).
However, in addition to an identical filling performance the advantages as described above in item 2.1 are obtained utilizing compounds of formula (I). Again, compositions of the present invention comprising a compound of formula (I) are more effective than com- positions according to Comparative Examples C1 and C2 in terms of working concentration.
In the presence of a polymer comprising a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen filling performance is further improved. In Examples E9, E10, E13, and E14 trenches are not only filled but in addition a significant bottom-up filling is observable within the trenches. This means that a clear horizontal deposition level can be observed. In these experiments filling of the trenches starts at the bottom and continues to the openings of the trenches, thereby avoiding the formation of unde- sired voids. Fig. 3 shows partly filled trenches as obtained after 15 seconds in Example E10. Said horizontal deposition level can be clearly seen in the trenches. This applies likewise to Fig. 4, representing the filling according to Example E14 (after 15 seconds too). Such a bottom-up filling is beneficial and highly desired in order to fill trenches with high aspect ratios without voids. Thus, compositions according to the present invention comprising a first compound of formula (I) and furthermore a polymer with (i) comparatively high molecular weight and (ii) a plurality of carboxamide moieties each with a secondary or tertiary amine nitrogen, have a significantly improved bottom-up filling performance. Furthermore, the presence of SPS in Comparative Examples C3 and C4 does not facilitate bottom-up filling.
Results of deposition and filling experiments obtained from compounds of formula (I) with n = 2 and/or R 2 = methyl and hydroxyl, respectively, are not shown.