DHINDSA, Rajinder (4650 Cushing ParkwayFremont, California, 94538, US)
CLAIMS
What is claimed is'
i In a plasma processing chamber, a method for processing a substrate, said substrate being disposed above a chuck and surrounded by an edge ring, said edge ring being electrically isolated from said chuck, comprising- providing RF power to said chuck, providing an edge ring DC voltage control arrangement, said edge ring OC voltage control arrangement being coupled to said edge ring to provide first voltage to said edge ring, resulting in said edge ring having an edge ring potential, generating a plasma within said plasma processing chamber to process said substrate, said substrate being processed while said edge ring DC voltage control, arrangement is configured to cause said edge ring potential to be substantially equal to a DC potential of said substrate while processing said substrate.
2. The method of claim 1 wherein said edge ring DC voltage control arrangement includes an RF filter arrangement and a DC power source., said RF filter arrangement being disposed between said edge ring and said DC power source.
3. The method of claim 2 wherein said RF filter arrangement is configured to attenuate unwanted harmonic RF energy from reaching said DC power source.
4 The method of claim \ wherein said RF power has an RF frequency in a range from about 20 KHz to about SOO KHz.
5. The method of claim I wherein said RF power has a set of Rf frequencies that includes at least one of 2 MHz, 27 MHz, and 60 MHz.
6 The method of claim I wherein said plasma processing chamber represents a capacitϊveiy coupled plasma processing chamber,
7. The method of claim I wherein said plasma processing chamber represents an inductively coupled plasma processing chamber 8 The method of claim i wherein said edge ring DC \ oltage coniiol arrangement includes an RF power supply
9 The method of claim 1 wherein said edge ring DC voltage control aπangεment includes an DC power supply
10 The method of claim 1 further including a feedback circuit configured to monitor said DC potential of said substrate, whereby said DC potential of said substrate is employed as a feedback signal to varv said first voltage when said DC potential of said substrate changes
1 1 hi a plasma processing chamber, a method for reducing polymer deposition around an edge of a substrate, said substrate being disposed above a chuck and surrounded by an edge ling, said edge ring being electrically isolated from said chuck, comprising providing RF power to said chuck, providing a edge ring DC voltage control arrangement, said edge ring DC voltage control arrangement being coupled to said edge ring to provide first voltage to said edge ring, resulting in said edge ring having an edge ring potential, generating a plasma within said plasma processing chamber to process said substrate, said substrate being processed while said edge ring DC voltage control arrangement is configured to cause said edge ring potential to be different from a DC potential of ^aid substrate while processing said substrate so as to cause an ion incident angle of ions disposed in a viciπitv of said edge of said substrate to be biased tow aid said edge of said substiate and away from said edge ring
12 (lie method of claim 11 wherein sasd edge ring Di ' voltage control arrangement includes an RF filter arrangement and a DC power source, said RF filter arrangement being disposed between said edge ring and said DC" power source
13 The method of claim 12 wherein &aid RF filter arrangement is configured to attenuate unwanted harmonic RF energy
U
14. The method of claim 1 1 wherein said plasma processing chamber represents a capacitively coupled plasma processing chamber.
15. The method of claim 11 wherein said RF power has an RF frequency in a range from about 20 KI Iz to about 800 KHz.
16. The method of claim 1 1 wherein said RF power has a set of KF frequencies that includes at least one of 2 MHz, 27 MHz, and 60 MHz
17. The method of claim 1 1 wherein said plasma processing chamber represents an inductively coupled plasma processing chamber.
18. The method of claim 11 wherein said edge ring DC voltage control arrangement includes a.n RF power supply
1*5. The method of claim 1 1 wherein said edge ring DC voltage control arrangement ' includes an DC power supply.
20. The method of claim 1 1 further including a feedback circuit configured to monitor said DC potential of said substrate, whereby said DC potential of said substrate is employed as a feedback signal to vary said first voltage when said DC potential of said substrate changes
21. In a plasma processing chamber, a method for processing a substrate, said substrate being disposed above a chuck and surrounded by an edge ring, said edge ring being electrically isolated from said chuck, comprising. providing RF power to said chuck; providing a edge ring DC voltage control arrangement, said edge ring DC voltage control arrangement being coupled to said edge ring to provide first voltage to said edge ring, resulting in said edge ring basing an edge ring potential; generating a plasma within said plasma processing chamber to process said substrate, said substrate being processed while said edge ring DC voltage control arrangement is configured to cause said edge ring potential to be less than a DC potential of said substrate while processing said substrate.
22. The method of claim 21 wherein said edge ring DC voltage control arrangement includes a.n RF filter arrangement and a DC power source, said RP filter arrangement being disposed between said edge ring and said DC power source.
23 The method of claim 22 wherein said RF filter arrangement is configured to attenuate unwanted harmonic RF energy
24. The method of claim 21 wherein said RF power has an RF frequency in a range from about 20 KHz Io about 800 KHz.
25. The method of claim 21 wherein said RF power has a set of RF frequencies that includes at least one of 2 MHz, 27 MHz, and 60 MHz.
26. The method of claim 21 wherein said plasma processing chamber represents a capacitiveiy coupled plasma processing chamber.
27. The method of claim 21 wherein said plasma processing chamber represents an inductively coupled plasma processing chamber,
28 The method of claim 21 wherein said edge ring DC voltage control arrangement includes an RF power supply.
29. The method of claim 21 wherein said edge ring DC voltage control arrangement includes an DC power supply.
30. The method of claim 31 further including a feedback circuit configured to monitor said DC potential of said substrate, whereby said DC potential of said substrate is employed as a feedback signal to vary said first voltage when said DC potential of said substrate changes. |
APPARATUS FOR SUBSTRATE PROCESSING AND METHODS THEREFOR
BACKGROUND OF THE INVEN TION
JOOOl \ The present invention relates in general to substrate manufacturing technologies and in particular to an apparatus for ion incident angle control and/or for polymer control and methods therefor, j0002| In the processing of a substrate, e.g , a semiconductor substrate or a glass panel such as one used in flat panel display manufacturing, plasma is often employed. As part of the processing of a substrate for example, the substrate is divided into a plurality of dies, or rectangular areas, each of which will become an integrated circuit. The substrate is then processed in a series of steps in which materials are selectively removed (etching) and deposited. Control of the transistor gate critical dimension (CD) on the order of a few nanometers is a top priority, as each nanometer deviation from the target gate length may translate directly into the operational speed of these devices
(0003] Areas of the hardened emulsion are then selectively removed, causing components of the underlying layer to become exposed. The substrate is then placed in a plasma processing chamber on a substrate support structure comprising a mono-polar or bipolar electrode, called a chuck or pedestal. Appropriate etchant gases are then flowed into the chamber and struck to form a plasma to etch exposed areas of the substrate. {0004] A common etching method is RIE or reactive ion etch. RlE combines both chemical and ion processes in order to remove material from the substrate (e g., photoresist, BARC, TiN 5 Oxide, etc ). However, the pressure to further reduce substrate feature sizes, as well as the implementation of newer optimized substrate materials, has challenged current fabrication technologies. For example., it is becoming increasing difficult to maintain the uniformity or process results from the center to the edge of larger substrates (e.g., > 300 ramj. Jn general, for a given feature size, the larger the size of the substrate, the greater the number of devices on the substrate near the edge. Likewise, for a given substrate size, the smaller the feature size, the greater the number of devices on the substrate near the edge For example, often over 20% the total number of devices on a substrate is located near the perimeter the substrate.
J0005J Due to substrate edge effects, such as electric field, plasma temperature, and the loading effects from process chemistry, the process results near the substrate edge may
differ from the remaining (center) area of the substrate. For example, the equi potential lines of the plasma sheath may become disrupted, causing non-uniform ion angular distribution around the substrate edge. j0006| Referring now to FIG. I , a simplified diagram of a capacitively coupled plasma processing system is shown. In general, a source RF generated by source RF generator 1 I O is commonly used to generate the plasma as well as control the plasma density via capacitively coupling, in other configurations, multiple RF generators may be used. jOGO?! Generally, an appropriate set of gases is flowed through an inlet in upper electrode 102, and subsequently ionized to form a plasma 104, in order to process (e.g., etch or deposit) exposed areas of substrate 106, such as a semiconductor substrate or a glass pane, positioned with an edge ring 1 12 (e g., Ss, etc ) on an electrostatic chuck 108, which also serv es as a powered electrode. Certain etch applications may require the upper electrode to be grounded with respect to a Sower electrode frequency RF signal within -20 KHz thru 800 KHz. Other etch applications may require the upper electrode to be grounded with respect to a lower electrode RF signal that is at least one of 2MHz, 27 MHz, and 60 MHz. Still other etch application may require the upper electrode to be grounded with respect to all of the RF signal frequencies previously mentioned.
J0008J Edge ring 1 12 generally performs many functions, including positioning substrate 106 on chuck 108 and shielding the underlying components not protected by the substrate itself from being damaged by the ions of the plasma edge ring 1 12 may further sit on coupling ring 120 Ce g., quartz, etc.), which is generally configured to provide a current path from chuck 108 to an edge ring 1 12
|0009| in general, it is desirable for the electric field to remain substantially constant over the entire surface of the substrate in order to maintain process uniformity and vertical etch profiles. However, because of plasma chamber conditions and/or configuration, a potential difference may exist between chuck 108 and the edge ring 1 12. Consequently, this potential difference may create a non-uniformity 122 in the plasma sheath shape, and hence adversely affect the etch profile
[0010} In addition, during the etch process, it is not uncommon for polymer byproducts (e.g , fiuorinated polymers, etc.) to form on the substrate backside and/or around the substrate edge. Fiuorinated polymers generally comprise photoresist material previously
exposed to an etch chemistry, 01 polymer b\ products deposited during a fluoraearbcn etch pi Gees: * In geneial, a fluorinated polyme? is a substance with a chemical equation Of CJI x F / , where x, /. are integers greater than 0. and y h an integer greater than or equal to 0 (e g 5 CF 4 , C 2 F^ CH 2 I 2 . OK. Ch 8 , etc )
[001 11 5 (owever, as successisε polymer layers are deposited on the edge area as the result of several different etch processes, organic bonds that are normali\ strong and adhesive \\ ill eventually weaken and pee! ot flake off, often onto another substrate during transport For substrates are commonly moved in sets between plasma processing sy stems
J0G12J Referring now to FIG 2, a simplified diagram of a subsuate in which a set of edge poh mers have been deposited on the planar backside is shown λs previously stated, during the etch process, it is not uncommon for polymer byproducts (edge polymers) to form on the substrate In this example, the polymer byproducts have been deposited on the planar backside, that is, the side of the substrate awa\ from the plasma For example, the polymer thickness may be about 250 nm at about 70° 202, 270 nrø at about 45° 204, and about 120 nrn at 0° 206 In general, the greater the thickness of the polymer, the higher the likeliness that a portion of the polymer may become dislodged and fall onto another substrate or the chuck, potentially affecting manufacturing yield
SUMMARY OF THE INVENTION
|0013| The im entioπ lelates. in an embodiment, to a method foi processing a substrate in a plasma processing chamber The substrate is disposed above a chuck and surrounded b> an edge ring while the edge ring being electrically isolated from the chuck 1 he method includes providing RF power to the chuck and providing a edge ring DC
be substantially equal to the I)C potential of the substrate in anothei embodiment, or to be less than the DC potential of the substrate in yet anothei embodiment to control the ion ά\ recti onality at the substrate edge
|00l4| These and othei features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures
BRIEF DESCRIPTION OF THE DRAWINGS
J00ϊ5] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompam ing drawings and in which like reference numerals refer to similar elements and in which'
[0016} FiG 1 shows a simplified diagram of a capacitively coupled plasma processing system,
J00I7} FlG 2 shows a simplified diagram of a substrate in which a set of edge polymers ha\ e been deposited on the planar backside, and
J0018J ItKiS Jλ-B show a set of simplified diagrams showing a capaeuiveK coupled plasma processing system with optimized ion angular distribution, according to an embodiment of the im enti on
DE TAILED DhSCRIP TlON Ot 1ηE PREFLRiIBD LMBODIMHM S J0G19J The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings In the follow ing description, numerous specific details are set forth in oidei to provide a thorough understanding of the present invention It will be apparent,
[0020} While not wishing to be bound b> theory, the im enter believes that the ion angular distribution mav be controlled by altering the DC potential between the substrate and the edge ring, thus optimizing the equipotential lines of the plasma sheath for a given plasma process in an advantageous niannei, changes be made to the electric field around the
subsUate edge by changing an Rb coupling of an edge ring In an embodiment, the chuck is substantially electrical!) isolated from the edge ring
J0G21J For example, if the DC potential of the substrate edge is substantially the same as the DC potential of the edge ring, the ton angular distribution is general !\ uniform Consequently, in an area of the plasma sheath above both the substrate and the edge ring, a set of ion sectors are fotmed that ate substantially perpendicuiat to the substrate
|0022| H oxs ever, if the DC potential of the substrate edge is substantially different to the DC potential of the edge ring, the ion angular distribution is generally non-uniform. Consequently, in an area of the plasma sheath abo\e both the substrate and the edge ring, a set of ion vectors arc formed that tend to point cither toward or away from the substrate
[0023} In an advantageous fashion, the DC potential on the edge ring max be independent!) controlled from that of the substrate Consequent!}', the difference between the DC potential of the substrate to the DC potential of the edge ring may be optimized in order to control the angular distribution of the positively charged ions in the plasma around the edge of the substrate
[0024} I-Or example, if the DC soltage of the edge ring is negative and substantial!) similar to that of the substrate {e g ,
{0025} in addition, certain dex ices require the etch features (e g , high aspect ratio contacts, vias oi trenches) to assume a particular directionality in order to. for example, enable a particular etch feature to make contact with another underlying feature for example, if a vertical via etch is required to allow the via to make contact with an underlying feature, a deviation from etch vertical uy may cause the x ia to miss the intended underlying feature, thereby resulting in a defcctix * e device and affecting yield For these applications, precise control of ion directionality at the substrate edge to achiex e piopcr etch directionality is a critical requirement
{(1026) in contrast, if the DC vυltage of the edge ri ng is more poshiv e (less negath e) than that of the substrate {e g , V., U h. 1H!c -\' C dg . c«n § ^ 0), the angulai iυn distribution profile is substantially non-uniform, with a set of that tend to point toward the substrate edge. This angular profile may be useful for edge polymer remo\ al Lnlike wet cleaning processes, the current ention allows edge polymer removal in an all-dry fe g , process, etc ) with minimal effluent across a wide variety of vacuum-compatible materials (e g , silicon, metals, glass ceramics, etc ) For example, a common dry etch process involves ion-assisted etching, or sputtering, in which ions are used to dislodge material from the substrate (e g , oxide, etc ) Generally ions in the plasma enhance a chemical process by striking the surface of the substrate, and subsequently breaking the chemical bonds of the atoms on the surface in order to make them more susceptible to reacting with the molecules of the chemical process j002?| Referring now to FIGS 3A-B, a set of Mrnpliiled diagrams showing a eapacithely coupled plasma processing system with optimized ion angular distribution is shown, according to an embodiment of the inv ention FlG 3 A shows a simplified diagram of a eapaάtiveh coupled plasma processing system in which the DC potential of the edge ring is substantially greater than that of the substrate In general, a source RF generated by source RF generator 1 10 is commonly used to generate the plasma as well as control the plasma density via eapacithely coupling As previously mentioned, certain etch applications ma\ require the upper electrode to be grounded with respect to a lower electrode frequency KV signal within -20 KHz thai 800 KHz Other etch applications may require the upper electrode to be grounded λvith respect to an RF signal that is at least one of 2Ml iz, 27 VlHz, and 60 Mi L? Still other etch applications may lequire the upper electtode to be grounded with respect to all of the RF signal frequencies previously mentioned
(0028) Generally, an appropriate set of gases is flowed through an inlet in upper electrode 102. and subsequently ionized to form a plasma 104. in order to process (e g , etch or deposit) exposed areas of sυbsttate 106. Mich as a semiconductor substrate oi a glass pane, positioned with an edge ring 1 12 (e g , Si, etc ) on an electrostatic chuck 108, which also serves as a powered electrode
|0029| Cdge ling 1 12 generally performs many functions, including positioning substrate 106 on chuck 108 and shielding the underlying components not protected by the substrate itself from being damaged by the ions of the plasma, edge ring 1 12 may further sit
on coupling ring 120 (e g , quart/, etc ), which Ls generally configured io
J0030J RF filter 314 is genera! Iv used to prcn ide attenuation of unwanted harmonic
RF cnoTgy without introducing losses to DC power source 3 16 In an embodiment, RF filter 314 includes a snitch module that allows a posiϋse or negative cuπent poiaaty to be selected, as well as a path to ground In an embodiment, the RF filter 314 includes vacuum relays Harmonics arc generated in the plasma discharge and may be kept from being returned to the DC power source by the RF filter in this case, since DC power source 3 Ib sources a positive voltage, the DC potential of the edge ring is substantially higher than that of the substrate in a typical plasma process I bus, the angular ion distribution profile is thus substantially non-uniform, with a set of vectors that tend to point toward aicas of lower potential, such as the substrate edge This application is highly useful for polymer removal from the substrate edge, as mentioned eatlicr
J003I I Referring now to FIG 3B, a simplified diagram is shown of a capacithely coupled plasma processing svstem in which the DC potential of the edge ring is substantially si milar to that of the substrate {e g , Y slJ
h tr.«c -V 0
^ ,w a
- Oj Generally speaking, the DC potential on the substtate during processing tends to be negative with respect to ground, and thus when, the edge ring is coupled to receive a negative potential (with respect to ground), the DC potential of the edge ring and the DC potential of the substrate are substantially equal Consequently, angular ion distribution is substantially uniform, with a set of vectors that are substantially perpendiculai to the substrate in an area of the plasma sheath
|0032J It i& also possible to, for example, couple the ground terminal of the DC power source, in which case the edge ring may base a higher potential (being at ground) than the DC potential of the substrate (being generally negative during processing, in an embodiment) In this case, the angular ion distribution will also tend toward the substiate edge, albeit to a lesser degree than when the edge ring is coupled to receive voltage from the positive terminal of the DC power source (as in the case of Fig 3Aj
{(1033) in an embodiment, a feedback circuit may be provided to monitor the DC voltage of the substrate (which may vary during the various process steps and process suhsteps). The monitored DC voltage of the substrate may be employed as a feedback signal in an appropriate control circuit to control the DC voltage delivered to the edge ring, thereby allowing the appropriate ion directionality to be maintained even if the DC voltage of the substrate changes. j0034| In an embodiment, the DC voltage of the edge ring may be provided by a RF power source (e.g., a RF power source that may be different from the R.F power source delivering RF power to the lower electrode). Thus, DC voltage control of the edge ring relative to the DC potential of the substrate is the thrust of the techniques of various embodiments disclosed herein, and the actual edge ring DC voltage control arrangement to provide/maintain the DC voltage to the edge ring may differ depending on implementations. jj0035j While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. Although various examples are provided herein, it is intended that these examples be illustrative and not limiting with respect to the invention. Further, the abstract is provided herein for convenience and should not be employed to construe or limit the overall invention, which is expressed in the claims. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention. For example, although the present invention has been described in connection with Lam Research plasma processing systems (e.g., Ex el an™, Exelan™ MP, Exelan™ HPT, 2300 7λS , Versys™ Star, etc.), other plasma processing systems may be used (e.g., capacitiveiy coupled, inductively coupled, etc. ). This invention may also be used with substrates of various diameters (e.g., 200 mm, 300 mm, LCD, etc.). Furthermore, the term set as used herein includes one or more of the named element of the set. For example, a set of "X " refers to one or more "X."
|0036| Advantages of the invention Include substantial control of ion angular distribution around the substrate edge. Additional advantages Include cleaning a bevel
polymer during an in situ strip process, optimizing the plasma process, and improving substrate yield.
|0037| Having disclosed exemplary embodiments and the best mode, modifications and variations may be made to the disclosed embodiments whϋe remaining within the subject and spirit of the invention as defined by the following claims.
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