A selective etching solution for si ge relative to si o and si

Abstract

A SiGe selective etching solution relative to SiO and Si is described. The etching solution includes the following components by mass fraction: fluoride 0.001-10 wt%; oxidizer 0.001-60 wt%; buffer composition 0.01-50 wt%; silica inhibitor 0.0001-10 wt%; silicon inhibitor 0.0001-10 wt%; stabilizer 0.0001-20 wt%; with the balance being water. The composition of the present invention can be used to selectively remove SiGe from a microelectronic device having a stack of Si, SiO, and SiGe thereon relative to Si and SiO in the process of manufacturing microelectronic devices.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electronic chemicals, and particularly relates to a SiGe selective etching solution relative to SiO and Si. BACKGROUND

[0002] In the structure of 3D DRAM, the fabrication starts with a stack of alternating SiGe / Si layers, isolation pillars are formed by etching and filled with dielectric material, then holes are etched in the grid avoiding the isolation pillars, the sacrificial SiGe layers are removed through these openings, leaving horizontal Si layers supported by the isolation pillars. These Si layers provide support for subsequent processes. The removal of SiGe sacrificial layers is crucial in the process of GAA, by selectively etching the SiGe layer, so that the high dielectric constant metal gate process can be prepared on the Si nanowire, which requires to ensure the cleanliness of the Si nanowire surface, and the SiGe is completely etched.

[0003] Therefore, there is a need in the art for an etching composition, aiming to provide a better etching process control for etching the sacrificial layer SiGe, while improving the selectivity and uniformity of SiGe nanolayer etching. SUMMARY

[0004] Due to the fact that silicon and germanium are in the same main group, and the chemical properties of Si and SiGe are similar, it is difficult to precisely control the etching of both by chemical reagents. The general design idea of the formula is to oxidize SiGe by oxidizing agent, and a small amount of Si will also be oxidized, and the oxidizing property of the liquid is adjusted to oxidize Si as little as possible; the oxidized SiGe product is etched by fluorine source, and since fluorine source is introduced, SiO will also be etched, so it is difficult to make a selection ratio for SiO; in order to selectively etch SiGe without etching Si and SiO, an inhibitor is needed to inhibit the etching of Si and SiO.

[0005] To solve the above-mentioned etching problem of Si and SiO, the present application provides a SiGe selective etching solution relative to SiO and Si. A specific composition is used for etching, which comprises: fluoride, oxidizing agent, buffer composition, silicon dioxide inhibitor, silicon inhibitor, stabilizer and water. This composition can achieve high selective etching of silicon germanium, and the etching selectivity ratio of silicon germanium to silicon can reach more than 200. The silicon dioxide inhibitor can reduce the etching of SiO, the silicon inhibitor can reduce the etching of Si, and the stabilizer alcohol can effectively prevent the polymerization of silane to produce precipitation.

[0006] A SiGe selective etching solution relative to SiO and Si, comprising: fluoride, oxidizing agent, buffer composition, silicon dioxide inhibitor, silicon inhibitor, stabilizer, water.

[0007] The SiGe selective etching solution with respect to SiO and Si as described in the above solution, wherein the fluoride ion source is selected from at least one of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluoroboric acid, tetramethylammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, and fluorosilicate, the component accounts for 0.001-10 wt% of the composition, preferably 0.002-5 wt%, more preferably 0.005-2 wt%.

[0008] The SiGe selective etching solution with respect to SiO and Si as described in the above solution, wherein the oxidizing agent is any one or more of potassium permanganate, potassium dichromate, periodic acid, sodium periodic acid, sodium perbromate, potassium persulfate, hydrogen peroxide, peroxyacetic acid, calcium peroxide, barium peroxide, sodium percarbonate, sodium perborate, ozone, potassium bromate, potassium chlorate, calcium hypochlorite, potassium ferrate, permanganic acid, and ammonium ceric nitrate. Preferably, the oxidizing agent is hydrogen peroxide. The component accounts for 0.001-60 wt% of the composition, preferably 10-30 wt%.

[0009] The SiGe selective etching solution with respect to SiO and Si as described in the above solution, wherein the buffer composition is an optional amine-containing compound and a multifunctional organic acid. The buffer composition can be an acetic acid-ammonium acetate buffer system or a citric acid-ammonium citrate buffer system, and the buffer pH is preferably in the range of 1 to 7, most preferably in the range of 3 to 5. The component accounts for 0.01-50 wt% of the composition, preferably 0.05-10 wt%, more preferably 0.1-20 wt%, most preferably 0.5-10 wt%.

[0010] The SiGe selective etching solution with respect to SiO and Si as described in the above solution, wherein the Si inhibitor is a polyethylene polyamine-amide type cationic polymer obtained by reacting a polyethylene polyamine and an oxirane compound. The synthesis method of the Si inhibitor is in two steps: S1 stirring reaction of polyethylene polyamine, formaldehyde, and urea, wherein the molar ratio of polyethylene polyamine, formaldehyde, and urea in the step S1 is 1: (1-2): (1-2), preferably 1:1:1, and the stirring reaction is carried out at 50-70°C for 4-7 hours; S2 adding epichlorohydrin, wherein the mass ratio of epichlorohydrin to the S1 mixture is 1: (1-2), preferably 1:1.5, and the stirring reaction is carried out at 50-70°C for 5-8 hours to obtain the Si inhibitor.

[0011] Further, the amount of the Si inhibitor is 0.0001-10 wt%, preferably 0.0005-5 wt%, more preferably 0.001-2 wt%, most preferably 0.01-1 wt%.

[0012] The SiGe selective etching solution with respect to SiO and Si described in the above solution, wherein the SiO inhibitor is silane, can be one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, and the like. The component is present in the composition in an amount of 0.001 to 5 wt%, preferably 0.1 to 2 wt%.

[0013] The SiGe selective etching solution with respect to SiO and Si described in the above solution, wherein the SiO inhibitor is silane, can be one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, and the like. The component is present in the composition in an amount of 0.001 to 5 wt%, preferably 0.1 to 2 wt%.

[0014] Further, the stabilizer is present in an amount of 0.0001 to 20 wt%, preferably 0.001 to 15 wt%.

[0015] The SiGe selective etching solution with respect to SiO and Si described in the above solution, wherein the SiO inhibitor is silane, can be one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, and the like. The component is present in the composition in an amount of 0.001 to 5 wt%, preferably 0.1 to 2 wt%.

[0016] Further, the rate of removal of SiGe can be adjusted by increasing or decreasing the etching conditions, such as component concentration, temperature.

[0017] Further, prior to etching, the entire device structure can be cleaned with an aqueous solution containing 0.5 wt% HF at room temperature for about 30 s to 240 s, preferably 60 s, more preferably 30 s. After etching is complete, the etching solution can be easily removed from the microelectronic device by rinsing, washing, or other removal steps. For example, the etching solution can be removed by rinsing with a rinsing solution such as deionized water or an organic solvent, and / or drying (e.g., spin-drying, N2, vapor drying, etc.).

[0018] The etching composition of the present application is suitable for use with microelectronic devices comprising silicon and silicon germanium, including layers comprising or consisting of SiGe alloys.

[0019] It should be understood that the term "silicon" as used in reference to material deposition on a microelectronic device includes, but is not limited to, amorphous silicon, crystalline silicon, polysilicon, p-type doped silicon, n-type doped silicon, and the like.

[0020] As used herein, "silicon germanium containing layer" or "SiGe layer" corresponds to a layer comprising or consisting of a silicon germanium alloy as known in the art and represented by the formula Si x Ge y wherein x + y = 1.00. SiGe25 refers herein to a layer comprising or consisting of a silicon germanium alloy where y is 0.25.

[0021] The present application has the following advantages:

[0022] (1) High selectivity: The present application adopts a specific composition of fluoride, oxidizing agent, buffer composition, Si inhibitor, SiO inhibitor, stabilizer and water, which can accurately control the removal rate of SiGe, with a selectivity of up to 200 for Si, and slight etching for Si and SiGe, much higher than the selectivity of the prior art.

[0023] (2) Improved etching uniformity: The composition of the present application can uniformly etch SiGe during use, avoiding the problem of uneven etching caused by uneven distribution of chemical reagents in the prior art, thereby improving the quality of microelectronic devices.

[0024] (3) Wide applicability: The composition of the present application is not only suitable for SiGe etching of planar structure, but also suitable for SiGe etching of complex three-dimensional structure, with wide adaptability, which can meet the needs of different device manufacturing.

[0025] (4) Environmental friendliness and safety: The composition of the present application does not contain harmful chemical reagents to the environment, such as hydrofluoric acid, etc., has good environmental friendliness and safety, and meets the requirements of modern green manufacturing.

[0026] (5) Simplified process flow: The composition of the present application is easy to use and simple to operate, which can simplify the manufacturing process flow of microelectronic devices, improve production efficiency and reduce production cost.

[0027] In summary, the present application has higher selectivity, improved etching uniformity, wide applicability, environmental friendliness and safety, and simplified process flow, etc. compared with the prior art, and is a SiGe etching technology with significant advantages. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of Si / SiGe25 structure of Example 1;

[0029] Figure 2 SEM image of Si / SiGe25 structure of Comparative Example 1;

[0030] Figure 3 SEM image of Si / SiGe25 structure of Comparative Example 2. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below with reference to the examples, which are only used to illustrate the present application and should not be regarded as limiting the scope of the present application.

[0032] 1) Preparation: According to the components and contents in the following table, the corresponding mass of each raw material is calculated by percentage, and different selective etching liquids are prepared, with water as the balance.

[0033] 2) Etching condition: 30℃, 300r / min stirring soak 1-30min.

[0034] 3) Etching coupon: Si / SiGe stack, where Si(110), SiGe 25.

[0035] Si inhibitor preparation method in examples and comparative examples:

[0036] S1 Stirring reaction of polyethylene polyamine, formaldehyde, urea, the molar ratio of polyethylene polyamine, formaldehyde, urea is 1:1:1, stirring reaction at 70℃ for 6 hours;

[0037] S2 Add epichlorohydrin, the part ratio of epichlorohydrin and S1 mixture is 1:1.5, stirring reaction at 70℃ for 4 hours, continue to react for 6 hours to obtain Si inhibitor.

[0038] Citric acid-ammonium citrate buffer system, buffer pH is 5.

[0039] The formula and test data of each example and comparative example are shown in tables 1-5.

[0040] Table 1 Different Si inhibitor formula ratio and test data

[0041]

[0042] From table 1, comparative example 1 and example 1, it can be seen that the selectivity ratio of the combination without adding Si inhibitor to Si is only 10.5, and the selectivity ratio to SiO is only 28.6. After adding Si inhibitor, the etching rates of SiGe, Si and SiO are inhibited to a certain extent, but the inhibition to Si and SiO is stronger, greatly improving the selectivity ratio to Si and SiO. Si inhibitor is a cationic surfactant, and the dissociated cationic surfactant containing amine is easy to form electrostatic adsorption with O element with strong electronegativity, and generate protective film on the surface. This surface active substance has stronger adsorption to Si oxide than Ge oxide, so it can increase the selectivity ratio.

[0043] Table 2 Etching rate and selectivity ratio at different etching temperatures

[0044]

[0045] From the comparative examples and examples of Table 2, it can be seen that the etching rates of SiO and Si are already very slow at low and high temperatures, and the etching rates of both do not change much with increasing temperature, but the etching rate of SiGe increases greatly, so the selectivity ratio increases. The etching rates of Si and SiO at high temperature are also very small, which is sufficient to show that the adsorption of the Si corrosion inhibitor is very strong, and the effect is excellent. It should be noted that although the etching at high temperature increases the selectivity ratio greatly, the high-temperature decomposition of hydrogen peroxide also greatly reduces the life of the chemical solution.

[0046] From the SEM pictures, it can be seen that in Comparative Example 1, the Si and SiO layers are obviously corroded without the addition of the inhibitor, and the corrosion position of the Si layer is relatively rough, which can destroy the performance of the device. The etching condition of Comparative Example 2 is relatively good, and the corrosion of Si and SiO is relatively slight, that is, the etching rate is relatively slow. From the picture of Example 1, it can be seen that the SiGe layer is etched, and the uniformity is good, and the Si layer and the SiO layer are almost not etched.

[0047] The foregoing description is mainly for the purpose of illustration. Although the present application has been shown and described with respect to exemplary embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof can be made therein without departing from the spirit and scope of the application.

Claims

1. A SiGe selective etching liquid with respect to SiO and Si, characterized by, The etching solution comprises the following components by mass fraction: Fluoride 0.001-10 wt%; Oxidizing agent 0.001-60 wt%; Buffering composition 0.01-50 wt%; Silica inhibitor 0.0001-10 wt%; Silicon inhibitor 0.0001-10 wt%; Stabilizer 0.0001-20 wt%; The balance is water; The buffering composition is an amine-containing compound and a multifunctional organic acid, the buffering composition is an acetic acid-ammonium acetate buffer system or a citric acid-ammonium citrate buffer system, and the buffering pH is 1-7; The silicon inhibitor is a polyethylene polyamine-amide type cationic polymer, which is obtained by reacting a polyethylene polyamine and a urea-based compound with epichlorohydrin; The silica inhibitor is a silane, and the silane is one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and vinyltrimethoxysilane; The stabilizer is methanol, ethanol, propanol, isopropanol, propylene glycol, or glycerol.

2. The SiGe selective etching solution with respect to SiO and Si according to claim 1, wherein The fluoride is at least one or more of hydrofluoric acid, ammonium fluoride, ammonium bifluoride, fluoroboric acid, tetramethylammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, and fluorosilicate.

3. The SiGe selective etching solution with respect to SiO and Si of claim 1, wherein The oxidizing agent is any one or more of potassium permanganate, potassium dichromate, periodic acid, sodium periodic acid, sodium bromic acid, potassium persulfate, hydrogen peroxide, peroxyacetic acid, calcium peroxide, barium peroxide, sodium percarbonate, sodium perborate, ozone, potassium bromate, potassium chlorate, calcium hypochlorite, potassium ferrate, permanganic acid, and cerium ammonium nitrate.

4. The SiGe selective etching solution with respect to SiO and Si according to claim 3, wherein The oxidizing agent is hydrogen peroxide.

5. The SiGe selective etching solution with respect to SiO and Si of claim 1, wherein, The buffering pH of the buffering composition is 3-5. ​ 6. The SiGe selective etching solution with respect to SiO and Si according to claim 1, wherein The method for synthesizing the silicon inhibitor comprises the following steps: S1: stirring and reacting polyethylene polyamine, formaldehyde, and urea, wherein the molar ratio of polyethylene polyamine, formaldehyde, and urea in step S1 is 1: (1-2): (1-2), and the stirring and reaction are performed at 50-70°C for 4-7 hours; S2: adding epichlorohydrin, wherein the mass ratio of epichlorohydrin to the mixture of step S1 is 1: (1-2), and the stirring and reaction are performed at 50-70°C for 5-8 hours to obtain the silicon inhibitor.

7. The SiGe selective etching liquid with respect to SiO and Si according to claim 6, wherein The molar ratio of polyethylene polyamine, formaldehyde, and urea in step S1 is 1:1:

1. The mass ratio of epichlorohydrin to the mixture of step S1 in step S2 is 1:1.

5.

8. The SiGe selective etching solution with respect to SiO and Si according to claim 1, wherein The etching solution is used at a temperature of 25°C to 70°C.

9. The SiGe selective etching solution with respect to SiO and Si according to claim 8, wherein The etching solution is used at a temperature of 25-40°C.

10. The SiGe selective etching solution with respect to SiO and Si according to claim 1, wherein Before etching, the entire device structure is cleaned with an aqueous solution containing 0.4-0.7 wt% HF at room temperature for 30s-240s; after etching is completed, the etching solution is removed from the microelectronic device through rinsing, washing, or other removal steps.

11. The SiGe selective etching solution with respect to SiO and Si according to claim 10, wherein Before etching, the entire device structure is cleaned with an aqueous solution containing 0.4-0.7 wt% HF at room temperature for 60s.

12. The SiGe selective etching solution with respect to SiO and Si according to claim 11, wherein Before etching, the entire device structure is cleaned with an aqueous solution containing 0.4-0.7 wt% HF at room temperature for 30s.

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