SELECTIVE SELF-ALIGNED PATTERNING OF SILICON GERMANIUM, GERMANIUM AND Group III

Abstract

The invention relates to selective self-aligned patterning of SiGe, Germanium and Group III / V materials using a sulfur-containing mask. A method of patterning a substrate comprising a plurality of layers using a sulfur-based mask includes providing a substrate comprising a first layer and a second layer disposed on the first layer. The first layer includes a material selected from the group consisting of germanium, silicon germanium, and a Group III / V material. The method includes depositing a mask layer comprising a sulfur species on sidewalls of the first layer and the second layer by exposing the substrate to a first wet chemistry. The method includes removing the mask layer on the sidewalls of the second layer without completely removing the mask layer on the sidewalls of the first layer by exposing the substrate to a second wet chemistry. The method includes selectively etching the second layer relative to the first layer and the mask layer on the sidewalls of the first layer by exposing the substrate to a third wet chemistry.

Description

This application is a divisional application of the invention patent application with application number 201710197507.4, application date March 29, 2017, applicant is Rum Research Corporation, and invention name is "Selective self-aligned patterning of germanium silicon, germanium and III / V materials using sulfur-containing masks". CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 314,685, filed on March 29, 2016. The entire disclosure of that application is incorporated herein by reference. Technical Field

[0002] The present disclosure relates to substrate processing systems, and more particularly to patterning films in substrate processing systems. Background Art

[0003] The background description provided here is for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors is neither explicitly nor implicitly admitted to be prior art against the present invention to the extent it is described in this background section and aspects of the specification that may not otherwise be considered prior art at the time of filing.

[0004] Further scaling of transistors will require materials to replace silicon (Si) in the transistor channel. For example, films of germanium (Ge) and silicon germanium (SiGe) and films including III / V materials such as gallium (Ga), arsenic (As), and indium (In) have been proposed for future transistors. Material selective patterning of these advanced materials beyond the 7nm node is challenging. These materials have very low chemical resistance, especially to oxidation. The oxides of these materials are typically water soluble, which presents additional challenges for wet chemical methods.

[0005] For example, Ge / SiGe nanowires can be used in some applications. SiGe films (usually with 50-75% Ge) need to be selectively etched relative to Ge films. However, Ge films have much lower chemical resistance to oxidizing solutions than SiGe films. Traditional wet chemical methods are based on oxidation and dissolution steps. Therefore, since Ge films are etched significantly faster than SiGe films, the oxidation step is greatly limited. Summary of the invention

[0006] A method of patterning a substrate comprising a plurality of layers using a sulfur-based mask comprises: a) providing a substrate comprising a first layer and a second layer disposed on the first layer. The first layer comprises a material selected from the group consisting of germanium, silicon germanium, and a III / V material. The method comprises: b) depositing a mask layer comprising a sulfur material on sidewalls of the first layer and the second layer by exposing the substrate to a first wet chemistry; c) removing the mask layer on the sidewalls of the second layer without removing the mask layer on the sidewalls of the first layer by exposing the substrate to a second wet chemistry; and d) selectively etching the second layer relative to the first layer and the mask layer on the sidewalls of the first layer by exposing the substrate to a third wet chemistry.

[0007] In other features, the method includes repeating b), c) and d) one or more times. The method includes e) performing a cleaning process before b). The cleaning process includes exposing the substrate to a solution containing deionized water (DIW), hydrochloric acid (HCl) and hydrogen peroxide (H 2 O 2 ) aqueous solution for a predetermined period of time. The cleaning process includes exposing the substrate to dilute hydrofluoric acid (HF).

[0008] In other features, the method includes: f) before b) modifying the surface of the substrate by exposing the substrate to a fourth wet chemistry to enhance bonding of the mask layer. The method includes repeating f), b), c) and d) one or more times.

[0009] In other features, exposing the substrate to the fourth wet chemistry includes exposing the substrate to a chemistry selected from the group consisting of dilute hydrogen chloride (HCl), dilute hydrogen bromide (HBr), dilute hydrogen iodide (HI), and combinations thereof.

[0010] In other features, exposing the substrate to the first wet chemistry comprises exposing the substrate to a chemistry selected from the group consisting of ammonium sulfide (NH 4 ) 2 S, elemental sulfur (S), alkanes-thiols and combinations thereof.

[0011] In other features, exposing the substrate to the second wet chemistry comprises exposing the substrate to a chemistry selected from the group consisting of hydrofluoric acid (HF) and hydrogen peroxide (H 2 O 2 ) mixture; ammonia (NH 3 ); potassium hydroxide (KOH); tetramethylammonium hydroxide (TMAH); tetraethylammonium hydroxide (TEAH); chlorine; sodium peroxide (Na2 O 2 ); sodium hypochlorite (NaClO); ozone (O 3 ); potassium cyanide (KCN); potassium hydroxide (KOH), potassium ferrocyanide K 3 Fe(CN) 6 and water (H 2 O) mixture; mixture of hydrofluoric acid and nitric acid (HF / HNO 3 ); citric acid and H 2 O 2 mixture; HF / HNO 3 / acetic acid (HAc) and silver nitrate (AgNO 3 ) mixture; HNO 3 A mixture of tartaric acid; ammonium persulfate and combinations thereof.

[0012] In other features, exposing the substrate to the third wet chemistry comprises exposing the substrate to a chemistry selected from hydrogen peroxide (H 2 O 2 ); hydrochloric acid (HCl) and hydrogen peroxide (H 2 O 2 ) mixture; HCl and nitric acid (HNO 3 ) mixture; HNO 3 ; a mixture of hydrofluoric acid, nitric acid and tartaric acid; a mixture of hydrofluoric acid, nitric acid and acetic acid; and a chemical substance in the group consisting of combinations thereof.

[0013] In other features, the second layer comprises the material and one or more other materials, and wherein the weight of the material is greater than or equal to 50% of the weight of the second layer. The first layer comprises germanium, and the second layer comprises silicon germanium. The weight of germanium in the second layer is greater than or equal to 50% of the weight of the second layer. The first layer comprises silicon germanium, and the second layer comprises silicon.

[0014] A method of patterning a substrate comprising a plurality of layers using a sulfur-based mask, comprising: a) providing a substrate comprising a first layer and a second layer disposed on the first layer. The first layer comprises a material selected from the group consisting of germanium, silicon germanium, and III / V materials. The second layer comprises the material and one or more other materials. The weight of the material is greater than or equal to 50% of the weight of the second layer. The method comprises: b) cleaning the substrate; c) improving the surface of the substrate to enhance bonding of the mask layer; d) depositing the mask layer comprising a sulfur material onto the sidewalls of the first layer and the second layer by exposing the substrate to a first wet chemistry; e) removing the mask layer on the sidewalls of the second layer without completely removing the mask layer on the sidewalls of the first layer by exposing the substrate to a second wet chemistry; f) selectively etching the second layer relative to the first layer by exposing the substrate to a third wet chemistry; and g) repeating d), e), and f) one or more times.

[0015] In other features, b) includes exposing the substrate to an aqueous solution comprising deionized water (DIW), hydrochloric acid (HCl) and hydrogen peroxide (H 2 O 2 ) aqueous solution for a predetermined period of time.

[0016] In other features, b) includes exposing the substrate to dilute hydrofluoric acid (HF).

[0017] In other features, c) includes exposing the substrate to a chemical selected from the group consisting of dilute hydrogen chloride (HCl), dilute hydrogen bromide (HBr), dilute hydrogen iodide (HI), and combinations thereof. The first wet chemical is selected from the group consisting of ammonium sulfide (NH 4 ) 2 S, elemental sulfur (S), alkane-thiols and combinations thereof. The second wet chemistry is selected from the group consisting of hydrofluoric acid (HF) and hydrogen peroxide (H 2 O 2 ) mixture; ammonia (NH 3 ); potassium hydroxide (KOH); tetramethylammonium hydroxide (TMAH); tetraethylammonium hydroxide (TEAH); chlorine; sodium peroxide (Na 2 O 2 ); sodium hypochlorite (NaClO); ozone (O 3 ); potassium cyanide (KCN); potassium hydroxide (KOH), potassium ferrocyanide K 3 Fe(CN) 6 and water (H 2 O) mixture; mixture of hydrofluoric acid and nitric acid (HF / HNO 3 ); citric acid and H 2O 2 mixture; HF / HNO 3 / acetic acid (HAc) and silver nitrate (AgNO 3 ) mixture; HNO 3 and tartaric acid; ammonium persulfate and a combination thereof.

[0018] In other features, the third wet chemical is selected from hydrogen peroxide (H 2 O 2 ), hydrochloric acid (HCl) and hydrogen peroxide (H 2 O 2 ) mixture; HCl and nitric acid (HNO 3 ) mixture; HNO 3 ; a mixture of hydrofluoric acid, nitric acid and tartaric acid; a mixture of hydrofluoric acid, nitric acid and acetic acid; and a group consisting of combinations thereof.

[0019] In other features, the first layer comprises germanium and the second layer comprises silicon germanium. The first layer comprises silicon germanium and the second layer comprises silicon.

[0020] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the accompanying drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0022] Figure 1-2 showing cross-sectional views of examples of a substrate including a first layer and a second layer during native oxide removal and cleaning, respectively;

[0023] Figure 3 Shows Figure 1 and Figure 2 a cross-sectional view of a substrate of during surface modification for subsequent bonding with a sulfur species;

[0024] Figure 4 Shows Figure 3 A cross-sectional view of a substrate after depositing a sulfur mask layer;

[0025] Figure 5 Shows Figure 4 A cross-sectional view of a substrate in which a portion of a mask layer on a second layer is removed while other portions on the first layer for passivating the first layer are retained;

[0026] Figure 6 Shows Figure 5 a cross-sectional view of a substrate of during selective etching of a first layer; and

[0027] Figure 7 A method for selectively etching a first layer of a substrate relative to a second layer of the substrate is shown.

[0028] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0029] The present disclosure relates to a masking method using a sulfur (S) film to protect a first layer (e.g., Ge or SiGe) to enable patterning of a second film (e.g., SiGe or Si film, respectively). The method for selective patterning according to the present invention is based on a process including surface modification, masking, partial mask removal, and selective etching. Wet chemicals for surface modification, masking, partial mask removal, and selective etching are disclosed. Multiple cycles can be performed to increase the effect of passivation of the first film and etching of the second film.

[0030] The method according to the present invention enables selective patterning of materials using a cyclic wet chemical process. Although the specific example of using a Ge film for the first layer and a SiGe film for the second layer is described above, the first layer may include materials such as SiGe, gallium (Ga), arsenic (As), indium (In) and other III / V materials. The second layer may include a combination of the material in the first layer and one or more other materials. For example, one or more other materials may include silicon (Si). Alternatively, the second layer may include a Si film.

[0031] In some examples, the weight of the material is greater than or equal to 50% of the weight of the second layer. In some examples, the first layer includes a Ge film and the second layer includes a SiGe film (the SiGe film has a Ge concentration that is the same as or higher than the Si concentration). In some examples, the concentration of Ge in the SiGe film is in a range between 50% and 75%. In other examples, the second layer does not include a III / V material. For example, the second layer can include a Si film or other materials.

[0032] As mentioned above, it is relatively difficult to pattern SiGe films (with high Ge content) with high selectivity relative to Ge films because the two materials have very little contrast in chemistry and etch rate. In general, the etch rate is proportional to the percentage of Ge.

[0033] Reference now Figure 1 and Figure 2, substrate 10 includes a first layer 12 and a second layer 14 disposed on first layer 12. In some examples, first layer 12 includes a Ge film and second layer 14 includes a SiGe film. In some examples, first layer 12 includes a SiGe film and second layer 14 includes a Si film. Sidewall oxide 18 may be located on sidewalls of first layer 12 and second layer 14. In some examples, sidewall oxide 18 includes a fin. Figure 1 In some examples, the sidewall oxide 18 can be etched or otherwise removed. In some examples, the mask layer 19 is disposed on the top surface of the second layer 14 to protect the top surface of the substrate. In some examples, the mask layer 19 can be made of nitride, oxide, or carbon-based oxide.

[0034] like Figure 2 As shown, a cleaning process may be performed on substrate 10 to remove etching byproducts, passivation layers, and / or encapsulation layers. In some examples, the substrate is exposed to the cleaning process using diluted hydrofluoric acid (HF), or a standard clean 2 (SC2) may be performed to remove etching byproducts without attacking the Ge / SiGe bulk material. In some examples, a cleaning process including deionized water (DIW), hydrochloric acid (HCl) aqueous solution, and hydrogen peroxide (H 2 O 2 ) aqueous solution and performing SC2 at a predetermined substrate temperature for a predetermined period of time. In some examples, the temperature is in a range of 20° C. to 50° C., and the predetermined period of time is in a range of 60 seconds to 300 seconds. In some examples, the HCl aqueous solution is 30 wt % to 50 wt %, HCl 2 O 2 The aqueous solution is 20 wt % to 40 wt %, but other values ​​may be used. In some examples, the SC2 treatment includes 4000-6000 parts DIW, 1 part HCl aqueous solution, and 5-20 parts HCl. 2 O 2 Aqueous solution.

[0035] Reference now Figure 3 , the first layer 12 and the second layer 14 are treated with a surface improvement chemical to improve the exposed sidewall surface so that a sulfur masking material can be subsequently bonded. For example, the chemical and process conditions are selected to remove oxides. For example, the chemical and process conditions are selected to remove Ge oxides without attacking Ge. In some examples, the wet chemical is selected from dilute hydrogen chloride (HCl), dilute hydrogen bromide (HBr), and dilute hydrogen iodide (HI). In some examples, the dilute HCl has a concentration of 0.01 wt%-10 wt%, but other concentrations can be used.

[0036] Reference now Figure 4, a mask layer 30 is deposited on the sidewalls of the first layer 12 and the second layer 14. In some examples, the mask layer 30 contains sulfur and is deposited using a wet chemistry. The strength and thickness of the sulfur bonds are a function of the concentration of Ge or other III / V materials in the corresponding layers and the concentration of the chemistry of the solution. Thus, the sulfur bonds are stronger and thicker on the first layer than on the second layer because the concentration of Ge is higher in the first layer relative to the second layer.

[0037] The mask layer 30 is adjusted to bond to a greater extent (as shown in portion 30B) with the first layer 12 (e.g., Ge film) and to a lesser extent (as shown in portion 30A) with the second layer 14 (e.g., SiGe film). The wet chemistry and process conditions effectively passivate the first layer 12 during etching performed in subsequent steps. In some examples, the wet chemistry is selected from a material containing ammonium sulfide (NH 4 ) 2 S, elemental sulfur (S), alkane thiols, and combinations thereof.

[0038] Reference now Figure 5 , the substrate 10 is exposed to a wet chemical to remove a portion 30A of the mask layer 30 on the second layer 14. More specifically, the wet chemical removes the portion 30A of the mask layer 30 on the second layer 14 (e.g., SiGe), while retaining a portion of the mask layer 30 on the first layer 12 (e.g., Ge) to enable passivation during a subsequent step. In other words, the wet chemical applied to the mask layer 30 (disposed on both the first layer 12 and the second layer 14) performs mask removal of the portion 30A of the mask layer 30 disposed on the second layer 14, while the portion 30B of the mask layer 30 is not completely removed due to its thicker thickness. In other words, the mask removal of the portion 30A may be caused by the lower bonding strength and thickness of the portion 30A relative to the portion 30B.

[0039] In some examples, the substrate is exposed to a wet chemistry selected from the group consisting of dilute hydrofluoric acid (dHF) and dilute hydrogen peroxide (dH 2 O 2 ); dilute ammonia (dNH 3 ); dilute potassium hydroxide (dKOH); dilute tetramethylammonium hydroxide (TMAH); dilute tetraethylammonium hydroxide (dTEAH); dilute chlorine; sodium peroxide (Na 2 O 2 ); sodium hypochlorite (NaClO); ozone (O 3 ); potassium cyanide (KCN); potassium hydroxide (KOH), potassium ferrocyanide K 3 (FeCN) 6 and water (H 2 O) mixture; mixture of hydrofluoric acid and nitric acid (HF / HNO 3 ); citric acid and H2 O 2 mixture of HF, HNO 3 , acetic acid and silver nitrate (AgNO 3 ) mixture; HNO 3 and tartaric acid; persulfate; and combinations thereof.

[0040] Reference now Figure 6 , the substrate is exposed to a wet chemical to selectively etch the second layer 14 (e.g., SiGe film) without attacking the mask layer 30 remaining on the first layer 12. As a result, the second layer 14 is etched at a higher rate than the first layer 12 (e.g., Ge film). In some examples, the chemical is selected from dH 2 O 2 HCl and H 2 O 2 A mixture of HCl and HNO 3 mixture; dHNO 3 ; HF, HNO 3 and tartaric acid mixture; HF, HNO 3 and HAc; and a group consisting of a mixture thereof. In some examples, the etching ratio of the second layer 14 relative to the first layer 12 is greater than or equal to 5:1. In some examples, the etching ratio of the second layer 14 relative to the first layer 12 is greater than or equal to 10:1.

[0041] Figure 3-6 The process shown can be performed one or more times or cycles as needed. It is expected that the above process will also be used for other semiconductor materials that can form metal-sulfur (MS) bonds, such as Ga, As, and In. For SiGe / Ge, each cycle etches 5 angstroms to 30 angstroms. A SiGe film, wherein the selectivity ratio of the SiGe film to the Ge film is 10:1.

[0042] Reference now Figure 7 , a method 100 for selective self-aligned patterning of a material using a sulfur-containing mask is shown. At 104, a substrate comprising a first and a second layer is provided. In some examples, the first layer comprises a material selected from the group consisting of germanium (Ge), silicon germanium (SiGe), and a III / V material. In some examples, the second layer comprises the material and one or more other materials. In other examples, the second layer does not comprise the material. In other examples, the second layer comprises Si.

[0043] At 108, the native oxide layer is removed. At 110, a cleaning process is performed. At 112, a surface modification process is performed to improve bonding of the sulfur mask. At 114, a sulfur mask layer is deposited. At 118, portions of the mask layer are removed from the second layer while allowing other portions of the mask layer to remain (sufficiently passivated) on the first layer. In some examples, the etch rate of the portion on the first layer is similar to the etch rate of the portion on the second layer. However, the mask portion on the second layer is thinner and is removed before the entire mask portion on the first layer is removed.

[0044] At 122, a selective etch of the second layer relative to the first layer is performed. At 126, the method determines whether additional cycles should be performed. If 126 is true, the method continues with 110, 112, or 114. Otherwise, the method ends.

[0045] The foregoing description is merely illustrative in nature and is by no means intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because other modifications will become apparent when studying the drawings, descriptions and appended claims. It should be understood that one or more steps in the method can be performed in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the exchange of one or more embodiments with each other remains within the scope of the present disclosure.

[0046] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms including "connected," "engaged," "coupled," "adjacent," "near," "on," "above," "below," and "disposed." When describing the relationship between a first and a second element in the above disclosure, unless explicitly described as "directly," such relationship may be a direct relationship in which no other intervening elements exist between the first and second elements, but may also be an indirect relationship in which one or more intervening elements (either spatially or functionally) exist between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR, and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

Claims

1. A method of patterning a substrate comprising a plurality of layers using a sulfur-based mask, comprising: a) providing a substrate comprising a first layer and a second layer disposed on the first layer, wherein the first layer comprises a material selected from the group consisting of germanium, silicon germanium, and III / V materials; b) depositing a mask layer comprising a sulfur species on sidewalls of the first layer and the second layer by exposing the substrate to a first wet chemistry; as well as c) completely removing the mask layer on the sidewalls of the second layer without completely removing the mask layer on the sidewalls of the first layer by exposing the substrate to a second wet chemistry.

2. The method according to claim 1, further comprising: d) etching the second layer relative to the first layer and the mask layer on the sidewalls of the first layer by exposing the substrate to a third wet chemistry.

3. The method according to claim 2, further comprising repeating b), c) and d) one or more times.

4. The method according to claim 2, further comprising: e) Performing a cleaning process before b).

5. The method of claim 4, wherein the cleaning process comprises exposing the substrate to a mixture comprising deionized water (DIW), an aqueous hydrochloric acid (HCl) solution, and an aqueous hydrogen peroxide (H2O2) solution at a predetermined temperature for a predetermined period of time. The method of claim 4 , wherein the cleaning process comprises exposing the substrate to dilute hydrofluoric acid (HF).

7. The method according to claim 4, further comprising: f) modifying the surface of the substrate by exposing the substrate to a fourth wet chemistry prior to b) to enhance bonding of the mask layer.

8. The method of claim 7, further comprising repeating f), b), c) and d) one or more times.

9. The method of claim 7, wherein exposing the substrate to the fourth wet chemistry comprises exposing the substrate to a chemistry selected from the group consisting of dilute hydrogen chloride (HCl), dilute hydrogen bromide (HBr), dilute hydrogen iodide (HI), and combinations thereof.

10. The method of claim 1, wherein exposing the substrate to the first wet chemistry comprises exposing the substrate to a chemistry selected from the group consisting of ammonium sulfide (NH4)2S, elemental sulfur (S), alkanes-thiols, and combinations thereof.

11. The method of claim 1 , wherein exposing the substrate to the second wet chemistry comprises exposing the substrate to a chemistry selected from the group consisting of a mixture of hydrofluoric acid (HF) and hydrogen peroxide (H2O2), ammonia (NH3), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), chlorine, sodium peroxide (Na2O2), sodium hypochlorite (NaClO), ozone (O3), potassium cyanide (KCN), a mixture of potassium hydroxide (KOH), potassium ferrocyanide K3Fe(CN)6 and water (H2O), a mixture of hydrofluoric acid and nitric acid (HF / HNO3), a mixture of citric acid and H2O2, a mixture of HF / HNO3 / acetic acid (HAc) and silver nitrate (AgNO3), a mixture of HNO3 and tartaric acid, ammonium persulfate, and combinations thereof.

12. The method of claim 2, wherein exposing the substrate to the third wet chemical comprises exposing the substrate to a chemical selected from the group consisting of hydrogen peroxide (H2O2), a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2), a mixture of HCl and nitric acid (HNO3), HNO3, a mixture of hydrofluoric acid, nitric acid, and tartaric acid, a mixture of hydrofluoric acid, nitric acid, and acetic acid, and combinations thereof.

13. The method of claim 1, wherein the second layer comprises the material and one or more other materials, and wherein the material is greater than or equal to 50 weight percent of the second layer.

14. The method of claim 1 wherein the first layer comprises germanium and the second layer comprises silicon germanium.

15. The method of claim 14, wherein the germanium in the second layer is greater than or equal to 50 weight percent of the second layer.

16. The method of claim 1 wherein the first layer comprises silicon germanium and the second layer comprises silicon.

17. A method of patterning a substrate comprising a plurality of layers using a sulfur-based mask, comprising: a) providing a substrate comprising a first layer and a second layer disposed on the first layer, the first layer comprising a material selected from the group consisting of germanium, silicon germanium, and a III / V material, the second layer comprising the material and one or more other materials, and wherein the material is greater than or equal to 50 weight percent of the second layer; b) cleaning the substrate; c) improving the surface of the substrate to enhance bonding of the mask layer; d) depositing the mask layer comprising a sulfur species onto sidewalls of the first layer and the second layer by exposing the substrate to a first wet chemistry; as well as e) completely removing the mask layer on the sidewalls of the second layer without completely removing the mask layer on the sidewalls of the first layer by exposing the substrate to a second wet chemistry.

18. The method according to claim 17, further comprising f) etching the second layer relative to the first layer by exposing the substrate to a third wet chemistry; and g) Repeat d), e) and f) one or more times.

19. The method of claim 17, wherein b) comprises exposing the substrate to a mixture comprising deionized water (DIW), aqueous hydrochloric acid (HCl) and aqueous hydrogen peroxide (H2O2) at a predetermined temperature for a predetermined period of time.

20. The method of claim 19, wherein b) comprises exposing the substrate to dilute hydrofluoric acid (HF).

21. The method of claim 19, wherein c) comprises exposing the substrate to a chemical selected from the group consisting of dilute hydrogen chloride (HCl), dilute hydrogen bromide (HBr), dilute hydrogen iodide (HI), and combinations thereof.

22. The method of claim 19, wherein the first wet chemistry is selected from the group consisting of ammonium sulfide (NH4)2S, elemental sulfur (S), alkanes-thiols, and combinations thereof.

23. The method of claim 19, wherein the second wet chemistry is selected from the group consisting of a mixture of hydrofluoric acid (HF) and hydrogen peroxide (H2O2), ammonia (NH3), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), chlorine, sodium peroxide (Na2O2), sodium hypochlorite (NaClO), ozone (O3), potassium cyanide (KCN), a mixture of potassium hydroxide (KOH), potassium ferrocyanide K3Fe(CN)6 and water (H2O), a mixture of hydrofluoric acid and nitric acid (HF / HNO3), a mixture of citric acid and H2O2, a mixture of HF / HNO3 / acetic acid (HAc) and silver nitrate (AgNO3), a mixture of HNO3 and tartaric acid, ammonium persulfate and combinations thereof.

24. The method of claim 18, wherein the third wet chemical is selected from the group consisting of hydrogen peroxide (H2O2), a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2), a mixture of HCl and nitric acid (HNO3), HNO3, a mixture of hydrofluoric acid, nitric acid, and tartaric acid, a mixture of hydrofluoric acid, nitric acid, and acetic acid, and combinations thereof.

25. The method of claim 19, wherein the first layer comprises germanium and the second layer comprises silicon germanium.

26. The method of claim 19, wherein the first layer comprises silicon germanium and the second layer comprises silicon.

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