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Title:
STABILIZING STRESS IN A LAYER WITH RESPECT TO THERMAL LOADING
Document Type and Number:
WIPO Patent Application WO/2019/162041
Kind Code:
A1
Abstract:
The stress in a layer deposited on a substrate is stabilized with respect to thermal loading by performing sputter deposition of the layer, maintaining all the elements of the material of the layer throughout the thickness of the layer and abruptly changing at least one of the sputter deposition process parameters.

Inventors:
ELGHAZZALI, Mohamed (Wolfgangstrasse 28b, 6800 Feldkirch, 6800, AT)
HOFFMANN, Mike (Heuwiesenweg 9, 9476 Weite, 9476, CH)
CURTIS, Ben (Reschustrasse 21, 8888 Heiligkreuz, 8888, CH)
Application Number:
EP2019/051895
Publication Date:
August 29, 2019
Filing Date:
January 25, 2019
Export Citation:
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Assignee:
EVATEC AG (Hauptstrasse 1a, 9477 Trübbach, 9477, CH)
International Classes:
C23C14/00; C23C14/06; C23C14/34; H01J37/34
Foreign References:
US20150132551A12015-05-14
US20050211545A12005-09-29
US20160130694A12016-05-12
US20020064359A12002-05-30
US6139699A2000-10-31
US20160168686A12016-06-16
US20040214417A12004-10-28
US20150340225A12015-11-26
Attorney, Agent or Firm:
TROESCH SCHEIDEGGER WERNER AG (Schwäntenmos 14, 8126 Zumikon, 8126, CH)
Download PDF:
Claims:
Claims

1) A method of stabilizing stress in a layer with respect to thermal loading, or a method of manufacturing a layer with stabilized stress with respect to thermal loading or a method of manufacturing a substrate with a layer which layer is stabilized with respect to thermal loading, comprising:

• Providing a substrate;

• Depositing a layer on said substrate, said

depositing consisting of:

•Sputtering a material consisting of one or more than one first chemical elements from at least one target;

• Depositing a material consisting of one or more than one second chemical elements, including said first one or more than one chemical elements, on said substrate, thereby abruptly changing at least one of the sputter-deposition- process parameters after depositing a predetermined thickness of the layer and ongoingly depositing said second chemical elements .

2) The methods of claim 1 wherein said second chemical elements comprise at least one chemical element fed into the sputter atmosphere as a gas or gas mixture.

3) The methods of one of claims 1 or 2 wherein abruptly changing said sputter-deposition-process parameter comprises or consists of abruptly changing the partial pressure of a gas in said sputter atmosphere.

4) The methods of claim 3 wherein abruptly changing said partial pressure comprises or consisting of abruptly changing the partial pressure of a noble gas in said sputter atmosphere.

5) The methods of claim 4 wherein said noble gas is at

least one of Ar, He, Kr, Xe and Ne .

6) The methods of one of claims 1 to 5 wherein said

abruptly changing said sputter-deposition -process parameter comprises or consists of switching a flow of a noble gas into said sputter atmosphere ON and/or OFF.

7) The methods of one of claims 1 to 6 wherein abruptly changing said sputter-deposition-process parameter comprises or consists of abruptly changing a noble gas type fed to said sputter atmosphere.

8) The methods of claim 7 thereby changing said noble gas type between at least two of Ar, He, Kr, Xe and Ne.

9) The method of at least one of claims 1 to 8 comprising performing said abruptly changing more than once, staggered in time. 10) The method of at least one of claims 1 to 9 comprising performing said abrupt changing more than once and between two or between more than two states of said sputter-deposition- process parameters.

11) The methods of at least one of claims 1 to 10 wherein said first elements are selected out of the group

- Si,

- Si and N,

- Si and 0,

- Si and C,

- Al,

- Al and 0,

- Al and N,

- Al and Ti,

- Ti,

- Ta,

- Cr,

- W,

- W and Ti,

Zr . 12) The methods of at least one of claims 1 to 11 wherein said second elements are selected to comprise or to consist of nitrogen and/or of oxygen, fed to the sputter atmosphere as a gas or a gas mixture.

13) The methods of at least one of claims 1 to 12

comprising depositing upon said substrate before depositing said layer, at least one further layer and compensating a bow of the combination of said substrate and of said further layer by said layer.

14) The methods of at least one of claims 1 to 13

comprising depositing upon said substrate after

depositing said layer, at least one further layer and compensating an anticipatedly bow of said substrate with said further layer, by said layer.

15) The method of claim 14 depositing said further layer causing a temperature of said layer which is higher than the temperature of said layer before depositing said further layer.

16) The methods of at least one of claims 13 to 15

comprising applying said layer on the same side of said substrate with respect to the side of the substrate whereupon said further layer is applied.

17) The methods of at least one of claims 13 to 15

comprising applying said layer on the opposite side of said substrate with respect to the side of the

substrate, whereupon said further layer is applied.

18) The methods of claim 17 comprising depositing at least a part of said layer and at least apart of said further layer simultaneously.

19) The methods of at least one of claims 1 to 18

comprising depositing on said substrate more than one of said layer.

20) The method of at least one of claims 1 to 19 wherein said one or more than one target is/are kept stationary with respect to said substrate during said depositing.

21) The methods of at least one of claims 1 to 20 wherein said second elements consist of Si and N.

22) The methods of at least one of claims 1 to 21

comprising performing said abrupt changing more than once and between two or between more than two states of said sputter-deposition- process parameters and wherein said layer is grown between subsequent of said abrupt

changings with a thickness of between 3nm and lOOnm, both limits included.

23) The methods of at least one of claims 1 to 22 wherein said layer is deposited with a thickness of between 50mm and 500nm, both limits included. 24) The methods of at least one of claims 1 to 23 wherein said substrate is a silicon wafer.

25) A substrate with a layer, deposited by a method

according to at least one of claims 1 to 24.

26) A substrate with a layer, said layer consisting over its entire thickness of same elements and comprising one or more than one material and/or morphologic unsteadiness- interface.

27) A sputter deposition apparatus comprising

• A target arrangement comprising at least one target;

• A substrate holder for at least one substrate;

• A timing unit adapted to control at least one

sputter-deposition-process parameter to abruptly change during sputter deposition of a layer on a substrate in a predetermined rhythm, thereby

ongoingly depositing same chemical elements on said substrate .

28) The sputter deposition apparatus of claim 27 adapted to perform the layer deposition methods according to at least one of claims 1 to 24.

Description:
Stabilizing stress in a layer with respect to thermal loading

The present invention is generically directed on

stabilizing stress in a layer with respect to thermal loading. In other words, the stress in a layer shall change as few as possible upon thermal loading of the layer by increased temperatures.

The need for stabilizing stress in a deposited layer with respect to thermal loading arises for instance as follows: Stress, tensile- or compressive, in a layer or multiple layers deposited on a substrate may greatly affect the overall characteristics of the system substrate/layer.

As such system may be present as a middling product it is often further treated by one or more than one additional process by which the system is heated, i.e. loaded

thermally. It is often desired, that those characteristics of the middling product, which depend from the stress in the addressed layer or layers are maintained in the

finished product and do not alter due to such additional processes .

Even if a finished product has characteristics which depend from the stress in one or more than one of the layers deposited on a respective substrate, it might be desirable to maintain such stress and the respective characteristics dependent therefrom even if the finished product is

subjected to thermal loading, e.g. to intense sun-exposure. E.g. whenever one or more than one layers -a layer system- is deposited upon a substrate, especially by a vacuum process, being a CVD or PVD process, and such deposited layer system, as deposited, shows up to have an overall tensile- or compressive stress, the substrate is loaded with a bending stress which results in bowing or warping the system substrate/layer- system, if the system is not stiff enough to stand the bending stress. Such bowing may be avoided if more than one respective layer systems are deposited on the substrate with respective stresses which lead to a resulting vanishing overall bending stress.

Nevertheless, and even if the overall layers or layer system, which may be of different material layers, is bow compensated, different changes of their respective stress, as thermally loaded, result in a hardly predictable "after thermal load"-bow of the overall system.

Providing an overall substrate/layer system which is bow compensated by providing functional layers, from which the characteristics of the overall system depends, as well as so called "stress-compensating layers" for compensating a bow caused by the functional layers, is known from

US2015/0340225.

Thus, there is a need to provide a layer, the stress of which being influenced only to a minimum by thermal loading. Such layer may be a functional layer e.g. with optical function and/or with electrical function or with a function in the frame of photolithography etc. This additionally to its object, namely, to compensate for unwanted effects of stress in the overall system as of a bow as addressed above.

It is an object of the present invention to provide a method of stabilizing stress in a layer with respect to thermal loading, a method of manufacturing a layer with stabilized stress with respect to thermal loading and a method of manufacturing a substrate with a deposited layer which layer is stabilized with respect to thermal loading as well as a substrate with a layer, which layer has a stress which is stabilized with respect to thermal loading, and an apparatus to perform the addressed methods and to manufacture the addressed layer and substrate.

This is achieved according to the present invention

a) by a method of stabilizing stress in a layer with respect to thermal loading,

b) by a method of manufacturing a layer with stabilized stress with respect to thermal loading,

c) by a method of manufacturing a substrate with a layer which layer is stabilized with respect to thermal loading. These methods comprise:

• Providing a substrate;

Depositing a layer on said substrate, said depositing consisting of: • Sputtering a material consisting of one or more than one first chemical element from at least one target. Thus, the layer is sputter deposited, normally by magnetron sputtering.

The deposition further consists of:

• Depositing a material consisting of one or more than one second chemical elements, including the first one or more than one chemical elements, on the substrate, thereby abruptly changing at least one of the sputter- deposition- process parameters after depositing a predetermined thickness of the layer and maintaining depositing of said second chemical-elements i.e.

ongoingly depositing the second chemical elements.

Because the abrupt change is performed after a

predetermined thickness of the layer has been deposited, pulsed- or AC type- operation per se of a respective parameter is not to be considered as "abruptly changing" .

When we address throughout the description and claims

"elements" we always mean "chemical elements".

The material, which is sputtered, may consist of one single first element or of more than one first elements, may be a compound. The material, which is deposited on the substrate may consist of one or more than one second elements. The second elements do in any case include the one or more than one first elements. The second elements may nevertheless include one or more than one element which are different from the first elements and which are fed to the sputter atmosphere by reactive gas or by reactive gas mixture. The sputter atmosphere may or may not comprise a noble gas, which is not one of the second elements, as such noble gas is not or only in a neglectable amount, an element of the material which is deposited on the substrate.

It must be noted, that the second elements may comprise one or more than one element which are first elements, but which are additionally also fed to the sputter atmosphere by a reactive gas or gas mixture. E.g. an oxide may be sputtered and additionally oxygen may be fed to the sputter atmosphere as gas or in a gas mixture.

During depositing the material consisting of the one or more than one second elements as addressed on the

substrate, there is abruptly changed at least one of the sputter-deposition- process parameters. Thereby depositing the addressed second elements is ongoingly maintained, the deposited material ongoingly consists of the second elements .

The target material is not changed, as first elements are ongoingly deposited at least as a part of the second elements. If two or more targets are used, different or at least some different first elements may be co-sputtered from respective targets or the same elements may be sputtered from all targets as provided. Because, ongoingly, material consisting of the second elements is deposited, the generic characteristics of the deposited material are mostly kept substantially unchanged within a relatively narrow range. Such characteristics of the deposited layer may be optical, electrical etc.

Definition

We understand under the term "abruptly changing" a change of at least one of the sputter- deposition- process

parameters which is incurred by a switching action. The slope of change of the addressed sputter- deposition- process parameter itself results dependent from the

respective system inertia. As an example, if the

composition of gas in the sputtering atmosphere is

"abruptly "changed by a switching action upon a gas flow, the respective change in the sputter atmosphere will have a slope, which is less steep than the switching slope.

Nevertheless, the step response of the system is named "abrupt change".

We define the term "comprising something", throughout the description and claims as "having something not

exclusively". E.g. "comprising A" means "having A and possibly additional members".

We define the term "consisting of something" throughout the description and claims as "having exclusively something" . E.g. "consisting of A" means "having A and nothing else". Astonishingly, by performing the addressed methods, the tensile or compressive stress in the layer becomes

significantly less affected by subsequent thermal loading. Today, it is believed that the addressed abrupt change of the at least one sputter- deposition- process parameter leads in the layer being built up to a discontinuity, which stabilizes the overall layer with respect to a change of compressive or tensile stress.

In one variant of the methods according to the invention, the second elements comprise at least one element, which is fed into the sputter atmosphere as a gas or gas mixture. Thus, reactive sputtering is performed, or the

stoichiometry of the deposited material is changed with respect to the stoichiometry of the material sputtered from the at least one target.

In one variant of the methods according to the invention, abruptly changing the at least one sputter- deposition- process parameter comprises or consists of abruptly

changing the partial pressure of a gas in the sputter atmosphere .

In one variant of the just addressed variant of the methods according to the invention, abruptly changing the partial pressure comprises or consists of abruptly changing the partial pressure of a noble gas in the sputter atmosphere. In one variant of the just addressed variant of the invention the noble gas is at least one of Ar, He, Kr, Xe and Ne.

In one variant of the invention, abruptly changing the sputter-deposition process parameter comprises or consists of switching a flow of a noble gas into the sputter atmosphere ON and/or OFF.

Please note that it might suffice in some cases to just switch the flow of a noble gas ON after a certain, not vanishing time span of sputter deposition, or inversely to switch the flow of the noble gas OFF after a not vanishing time span of sputter deposition with the noble gas.

In one variant of the invention abruptly changing the sputter-deposition-process parameter comprises or consists of abruptly changing a noble gas type fed to said sputter atmosphere .

In one variant of the just addressed variant the noble gas type is changed between at least two of Ar, He, Kr, Xe and Ne.

One variant of the invention comprises performing abruptly changing more than once, staggered in time.

In spite of the fact, that it is absolutely possible to perform abruptly changing the addressed at least one parameter just once during deposition of the layer, in one variant abruptly changing is performed more than once. In one variant, in which abrupt changing is performed more than once, such abrupt changing is realized between two values or states or between more than two values or states of the addressed at least one sputter-deposition -process parameter .

If we address one parameter value or state with A, a second with B, a third with C etc., the abrupt changings may be (A to B to A) , or (A to C to A) or (A to B to C) or (A to C to B) etc.

In one variant of the methods according to the invention, the first elements are selected out of the following group:

- Si,

- Si and N,

- Si and 0,

- Si and C,

- Al,

- Al and 0,

- Al and N,

- Al and Ti,

- Ti,

- Ta,

- Cr,

- W,

- W and Ti,

- Zr.

In one variant of the methods according to the invention, the second elements are selected to comprise at least one of nitrogen and of oxygen, fed to the sputter atmosphere as a gas or as a gas mixture. Thereby and in one variant a reactive gas fed to the sputter atmosphere consists of at least one of oxygen and of nitrogen.

One variant of the methods according to the invention comprises depositing upon said substrate, before depositing said layer, at least one further layer and compensating a bow of the combination of substrate and further layer, by the layer acting as a bow compensating layer.

One variant of the methods according to the present

invention comprises depositing upon the substrate, after depositing the layer, at least one further layer and compensating an anticipated bow of the substrate with the further layer, by the layer, acting as bow compensating layer .

In one variant of the just addressed variant of the methods according to the invention, depositing said further layer causes a temperature of said layer which is higher than the temperature of said layer before depositing said further layer .

Because the layer as deposited according to the invention is stabilized with respect to thermal loading, the

subsequent deposition of the further layer at an increased temperature does not significantly change the tensile or compressive stress in the layer. Therefore, a bow or warpage of the substrate by the stress of the further layer may be compensated in advance by the layer according to the invention, although this layer will be thermally loaded by the deposition of the further layer.

One variant of the methods according to the invention comprises applying the layer on the same side of the substrate, with respect to the side of the substrate whereupon the further layer is applied.

Another variant comprises applying the layer on the

opposite side of the substrate, with respect to the side of the substrate whereupon the further layer is applied.

In one variant of the just addressed variant of the methods according to the invention at least a part of the layer and at least a part of the further layer are deposited

simultaneously.

In one variant of the methods according to the invention more than one of the addressed layers are deposited.

In one variant of the methods according to the invention the one or more than one target/s is/are kept stationary with respect to the substrate during depositing.

In one variant of the methods according to the invention the second elements consist of Si and N.

One variant of the methods according to the invention comprises performing the abrupt changing more than once and between two or between more than two values or states of the sputter-deposition- process parameters and wherein said layer is grown between subsequent of said abrupt changings with a thickness of between 3nm and lOOnm, both limits included.

In one variant of the methods according to the invention the layer is deposited with a thickness of between 50mm and 500nm, both limits included.

In one variant of the methods according to the invention the substrate is a silicon wafer. Such wafer may have a diameter of 300 mm and even more.

The methods according to the invention may be combined with one or more than one of the variants as addressed, if not in contradiction.

The invention is further directed to a substrate with a layer which is deposited by a method according to the invention or at least one variant thereof.

The invention is further directed to a substrate with a layer, wherein the layer consists over its entire thickness of the same elements and comprises one or more than one material or morphologic unsteadiness- interface.

The present invention is further directed to a sputter deposition apparatus which comprises A target arrangement comprising at least one target;

• a substrate holder for at least one substrate;

• a gas feed into a sputter space between the substrate holder and the target arrangement;

• a timing unit adapted to control at least one sputter- deposition-process parameter to abruptly change in a predetermined rhythm during sputter deposition of a layer on a substrate, thereby ongoingly depositing same chemical elements on the substrate.

In one embodiment of the addressed apparatus it is adapted to perform the layer deposition methods as were addressed above .

The invention shall be further explained with the help of examples and figures. The figures show:

Fig.l: By means of a simplified diagrammatic

representation, a variant of the methods according to the invention and representing in a simplified block

diagrammatic manner an embodiment of the sputter apparatus according to the invention;

Fig.2: In a representation in analogy to that of fig.l a variant of the methods according to the invention and representing in a simplified block diagrammatic manner an embodiment of the sputter apparatus according to the invention; Fig.3: In a representation in analogy to that of fig.l or fig.2 a variant of the methods according to the invention and representing in a simplified block diagrammatic manner an embodiment of the sputter apparatus according to the invention;

Fig.4: In a representation in analogy to that of fig.l or fig.2 the variant of fig.3 as today practiced;

Fig.5: The structure of a layer on a substrate as

manufactured according to the variant of fig.4;

Fig.6: The stress characteristics of the layer according to fig.5 each, before and after thermal loading;

Fig.7: The stress characteristics of comparative layers before thermal loading;

Fig.8: The stress characteristics of the comparative layers of fig.7 after thermal loading;

Fig.9: schematically an effect of stress in a layer;

Fig.10: The bow of a wafer with the layer according to fig.5 before and after thermal loading;

Fig.11: The bow of a wafer with the comparative layer before thermal loading; Fig.12: The bow of the wafer according to fig. 11 with the comparative layer after thermal loading;

Fig.13: Schematically processing a substrate by first depositing a layer according to the invention and then depositing a further layer involving a thermally loading process .

As was addressed above, the layer according to the

invention is deposited exclusively by sputter deposition. During sputter deposition of the layer, at least one of the sputter- deposition- process parameters is abruptly changed once or more than once, whereby the material, which is deposited upon the substrate is kept unchanged with respect to the chemical elements contained therein.

Sputter deposition-process- parameters, which may be abruptly changed, may e.g. be selected out of the following group :

a) Gas composition in the sputter atmosphere :

al) Partial pressure of one or more than one reactive gases; a partial pressure of a reactive gas may not be changed to vanish unless the element introduced by such reactive gas is already present in the material sputtered from the target arrangement. a2) Overall pressure of the sputter atmosphere; a3) Partial pressure of noble gas; may be changed to vanish, if, additionally, a reactive gas is present in the sputter atmosphere; thereby the type of noble gas may be changed, i.e. by changing the partial pressure of one type of noble gas to vanish and changing the partial pressure of an other type of noble gas to appear.

Combinations of al) and/or a2) and/or a3) . b) Electric supply of plasma discharge : bl) DC power; b2) AC power including Rf power, frequency thereof; b3) Pulse power, duty cycle, repetition frequency;

Combination of bl) and/or b2) and/ or b3) . c) Electric bias of substrate:

cl) DC power; c2) AC power including Rf power, frequency thereof; c3) Pulse power, duty cycle, repetition frequency;

Combination of cl) and/or c2) and or c3) .

Combination of a) and/or b) and /or c) .

In Fig. 1 there is schematically shown a variant of the methods according to the invention, as well as an

embodiment of a sputter apparatus according to the

invention, also in simplified, schematic representation. From a target arrangement 1 comprising one or more than one targets, a material consisting of first elements En , E 12 ... is sputtered into the sputter atmosphere 3. These elements are simultaneously sputtered into the sputter atmosphere 3. Although normal, non-magnetically enhanced sputtering may be used, mostly magnetron sputtering is used.

The sputtered-off material may consist of only one of the first elements En , E 12 ... .

We may write:

Ei= (En, E 12 ...) , wherein Ei are the first elements.

In this example exclusively at least one noble gas selected e.g. from the group Ar, He, Kr, Xe, Ne often just argon, is fed from a noble gas source 5 into the sputter atmosphere 3. Thus, the elements E21 , E2 2 , E23... are equal to the first elements En , E12 .... The elements E21 , E 22 , E 23 ... namely the elements of the material deposited on the substrate 7, are called "second elements", E 2 .

Thus, in this example we may write:

E 2 = ( E21 , E22 , E23 · · · ) = Ei .

When we address that a layer or a material or an element is deposited on or upon a substrate or on or upon a side of a substrate, this includes direct deposition thereupon as well as deposition on a layer or multilayer pre-applied on the substrate.

Controlled by means of a timing unit 9 specifically adapted and during sputter deposition of the layer, at least one of the following sputter-deposition parameters is abruptly changed (see above) : a2) pressure in the sputter atmosphere according, according to control block 11; b) Electric supply of plasma discharge, according to

control block 13; c) Electric bias of substrate, according to control block 15.

Combinations of a2) and/or b) and/or c) .

Abrupt changing at least one of the addressed sputter- deposition-process parameters is performed once or more than once and, in latter case, between two or more than two parameter values or states, a schematically shown in the block of the timer unit 9.

The material deposited on the substrate 7 consists

ongoingly of the elements of Ei as, in this case no

reactive gas is applied.

Fig. 2 is a representation in analogy to that of Fig. 1 of a further variant of the methods according to invention and of an embodiment of the sputter apparatus according to the invention. The difference with respect to the variant and embodiment of fig. 1 is, that no noble gas is fed to the sputter atmosphere 3. Instead and from one or more than one gas sources 5a, one or more than one reactive gas is fed to the sputter atmosphere 3. By these one or more than one reactive gases one or more elements E gi , E g2 .. are fed to the sputter atmosphere and are reacted with one or more than one of the first elements Ei. Elements fed to the sputter atmosphere by reactive gas are addressed by E g .

The second elements thus become:

E2= (E21, E22, E23 · · · ) = ( Ei , E g i, Eg2. . ) = (Ei , Eg)

The material deposited on the substrate 7 consists

ongoingly of these second elements E2.

Thereby it must by pointed out, that if one or more than one of the first elements Eu, E l2 ... is an element which exists in or as a gas, e.g. nitrogen or oxygen, then some or all of the elements E gi , E g 2 ... may be the same elements as one or more than one of the first elements Eu, E12 .... The group of sputter-deposition-process parameters out of which at least one may abruptly be changed is:

al), a2), b) and/or c) and combinations thereof.

Fig. 3 shows in a representation in analogy to those of the Figs . 1 and 2 a further variant of the methods according to the invention and an embodiment of a sputter apparatus according to the invention. The difference to the variant according to Fig. 2 is that additionally to one or more elements E gi , E g 2 introduced by reactive gas to the sputter atmosphere 3, a noble gas is fed to the sputter atmosphere by the noble gas source 5.

The group of sputter-deposition-process parameters out of which at least one may abruptly be changed are:

a), b) , c) and combinations thereof. As first elements En , E12 ... it is proposed to use elements out of the following group:

- Si,

- Si and N,

- Si and 0,

- Si and C,

- Al,

- Al and 0,

- Al and N,

- Al and Ti,

- Ti,

- Ta,

- Cr,

- W ,

- W and Ti,

- Zr.

As elements E g introduced by feeding at least one reactive gas to the sputter atmosphere i.e. into the reaction space of the sputter apparatus, there is proposed at least one of nitrogen and of oxygen, in a variant, exclusively one of nitrogen and of oxygen.

Today it is further proposed to feed to the sputter

atmosphere at least one reactive gas resulting in at least one element E g as well as a noble gas, thus according to fig.3, and thereby to select as that sputter-deposition- process parameter abruptly changed, only the partial pressure and/or the type of the noble gas. The partial pressure of at least one noble gas may even be changed by switching the flow of that at least one noble gas to the sputter atmosphere ON and OFF.

Fig. 4 shows in a representation in analogy to those of the Figs. 1 to 3 a variant of the methods of the invention and an embodiment of the sputter apparatus according to the invention as realized today. There is valid:

Ei= En= Si

E g E gl — N

E2= Si and N.

Noble as: Ar.

The partial pressure of argon is abruptly changed by switching argon flow into the putter atmosphere ON and OFF.

Example

As schematically shown in Fig. 5, a layer 17 was deposited according to the variant of the methods according to the invention as schematically represented in Fig. 4. Upon a silicon wafer 11 of 150 m diameter, a layer 17 of SiN was deposited by sputtering a silicon target in a nitrogen atmosphere .

The following deposition sequence was realized:

12: up to a thickness of lOnm, argon flow to sputter

atmosphere switched OFF,

13: subsequently, up to an overall thickness of 26 nm i.e. for the following 16 nm, argon flow switched ON, 14: subsequently, up to an overall thickness of 52 nm, l . e . for the following 26 nm, argon flow to sputter

atmosphere switched OFF,

15: subsequently, up to an overall thickness of 84 nm, i.e. for the following 32 nm, argon flow to sputter

atmosphere switched ON,

Subsequently, the sequences 14 and 15 were repeated for additional 4 times, leading to an overall thickness of the layer 17 on substrate 11 of approximately 316 n .

The local stress along the diameter of two equal wafers, provided equally with the layer 17, was measured.

The results are shown in Fig. 6 by the stress- profile ai for one wafer, and a 2 for the second wafer.

Thereafter, both wafers with the layer applied thereon were subjected to a temperature of 1000C° for 20 sec. After cooling down, the remaining local stress is shown in Fig. 6 by the characteristic bi for the one wafer, and by the characteristic b 2 for the second wafer.

The average stress prior to subjecting to the high

temperature was -1'800 MPa for the first wafer, -1'743 MPa for the second wafer, and after subjecting to the high temperature -1'829 MPa for the first wafer and -1'749 MPa for the second wafer.

It may be seen that subjecting the wafers with the layer according to the invention deposited thereon to thermal loading, according to 1000° C, influences the stress in the layer only to a neglectable amount . Comparative Example

Two 150mm diameter silicon wafers as of wafers 11 of Fig. 5 were coated with a SiN layer from a silicon target as in the experiment in a nitrogen atmosphere but with ongoingly open argon flow to the sputter atmosphere, i.e. without any abrupt change of sputter-deposition -process parameter.

The resulting local stress is shown in Fig. 7 again for two wafers. The average stress in the comparative layers SiN layer was -1'969 MPa.

Subsequently, these comparative layers of approx. 290nm thickness, were subjected to a temperature of 1'035C° for 10 sec. After cooling down, there resulted in the

comparative layers a local stress as shown in Fig. 8. The average stress was -796 MPa.

It may be seen that the influence of thermal loading on the local stress of the layer deposited according to the present invention was substantially lower than the

influence of a very similar thermal loading, even during a shorter time span, on the local stress in the layer deposited without exploiting the abrupt change of sputter- deposition-process parameter according to the invention. Whereas, in the comparative example, the average stress in the layer alters by 1'173 MPa, it alters in the layer deposited according to the present invention by at most 29 MPa, which accords to a factor of approx. 4 decades.

Fig.9 shows the effect of the tensile stress T in a layer or multilayer 30 applied on a substrate as of a circular wafer-substrate 32.

As the layer or layer system is applied on the one of the extended surfaces of the substrate 32, the tensile stress T leads to warping or bending of the overall system of layer 30 and substrate 32 according to a bow B as schematically shown in Fig. 9. The bow is thereby measured by the maximum deviation d of the substrate 32 from a plane E. As

perfectly clear to the skilled artisan, if the stress in the one-side deposited layer or layer system 30 is

compressive, then bowing according to B is inversed to -d.

Bowing of a circular substrate or, more generically warping of a substrate of any shape, becomes larger with increasing thickness of the layer or of the multilayer 30 due to the respective bending momentum-distribution from the layer- stress on the substrate.

The present invention as described up to now provides for a layer, the stress of which being practically not affected by a thermal loading of the substrate with the layer. Thus, this layer provides, applied on a substrate a warpage or, on a circular substrate as of a wafer, a bow B, which is stabilized or largely not affected by a thermal loading which the substrate and the layer are subjected to.

The following figures show, departing from the Example given above, the bow B of the respectively coated 150mm silicon wafers before and after the addressed thermal loading and the respective bowing of the system according to the comparative Example as addressed above. Fig. 10 shows the bow of the two 150min wafer-substrates plus layer according to fig.5 as described above,

respectively before and after loading to the temperature of 1'000C° for 20 sec. The bow-extent d of the coated wafers prior to thermal loading was 0.089 m and 0.088 mm. After the addressed thermal loading the bow-extent was

unchanged, 0.089mm and 0.088mm. One may see that the resulting bows prior and after thermal loading and for both wafers of the example are identical. Thus, the resulting bow is stable with respect to temperature loading up to l'OOOC 0 for 20 sec.

Fig. 11 shows the bow of the wafers of the comparative example before being subjected to the 1'035C° thermal loading for 10 sec. The bow d is 271pm.

Fig. 12 shows the bow of the wafers according to the comparative Example after having been subjected to the 1'035C° thermal load for 10 sec. The bow d is 114 pm.

It has to be noted that the layer deposited according to the invention on a substrate may have additional function, additional to the function of being stabilized to thermal loading with respect to its stress. It may be e.g. a layer with optical function and/or with electrical function and/or with a function in context with photolithography etc. Keeping this in mind multiple variants of the methods according to the present invention become apparent and respective substrate/layer systems incorporating the layer as realized by the present invention.

Some examples shall now be described: In one variant layers may be deposited on a substrate which layers, if providing a non-neglectable stress, are all stabilized with respect to thermal loading according to the present invention. The overall substrate- layer-system is stabilized with respect to bow or warpage and with respect to thermal loading.

In one variant of the methods according to the present invention there is applied upon the substrate a further or additional layer or layer system to perform a desired function, e.g. an optical and/or an electrical function, or in the frame of photolithography as addressed in US

2015/0340225 mentioned above. We call such additional layer or layer system a "functional layer" if it is not a layer or layer system which is stabilized with respect to

stress/thermal-loading according to the present invention.

Most generically, such additional functional layer may be deposited on the substrate before and/or during and/or after depositing the layer according to the present

invention. Such functional layer will customarily have an overall tensile or compressive stress and will lead to bowing of the entire system of substrate/functional layer.

In one variant of the present invention this functional layer induced bow or warpage is compensated by applying the stabilized layer according to the invention. Because the layer according to the invention is stress-stabilized with respect to thermal loading as was addressed above, this layer provides on the substrate a bow, which is

substantially unaffected by thermal loading. This leads to the fact that, if the bow of the system

substrate/functional-layer is approximately known, applying the layer stabilized with respect to stress/thermal

loading, according to the present invention, may accurately compensate for that bow induced by the functional layer.

The stress/thermal loading stabilized layer according to the present invention may especially be applied if

subsequent to the deposition thereof, thermal loading occurs. Such high thermal loading may be necessary because of a subsequent respective treatment process e.g. for layer deposition, for etching etc. The applied stress/thermal- loading stabilized layer according to the invention allows that an anticipated bow may be advance compensated by applying a layer according to the invention. The finally resulting bow is only caused by the stress in layers applied subsequent to applying the stress/thermal-load stabilized layer on one hand and the stress/thermal- load stabilized layer on the other hand, even if subsequently applying such layer causes high thermal loading.

Fig.13 schematically shows such processing example.

The substrate 40, as of a wafer, is subjected to deposition of a layer 42 according to the invention with compressive stress, C. The substrate 40/layer 42 is subjected to a bow. This bow is controllable by the material and thickness of the layer 42 and is set on a predetermined amount +d.

Subsequently the substrate 40/layer42 is subjected to a further layer - 44- deposition process which may be PVD or CVD. This process causes thermal loading of the substrate 40/layer 42 but does not affect the +d bow. As applied on the opposite side of the substrate 40, with respect to the side whereupon the layer 42 was applied, and with

compressive stress C as well, the layer 44 causes the predicted -d bow of the substrate 40/layer42 /layer 44- system.

Both layers 44 and 42 may be applied on the same side of the substrate 40, in this case with compressive and with tensile stress.