SiGe selective etching solution relative to SiO and Si

Abstract

The invention relates to a SiGe selective etching solution with respect to SiO and Si. The etching liquid comprises the following components in percentage by mass: 0.001-10wt% of fluoride, 0.001-10wt% of a solvent and the balance of a solvent. 0.001 to 60 wt% of an oxidizing agent; 0.01 to 50 wt% of a buffer composition; 0.0001 to 10 wt% of a silicon dioxide inhibitor; 0.0001 to 10 wt% of a silicon inhibitor; 0.0001 to 20 wt% of a stabilizer; and the balance of water. The composition of the invention can be used to selectively remove SiGe relative to Si and SiO from a microelectronic device having a stack of Si, SiO, and SiGe thereon during the manufacture of the microelectronic device.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals, and in particular relates to a SiGe selective etching solution relative to SiO and Si. Background Art

[0002] In the structure of 3D DRAM, the manufacturing starts with a set of alternating SiGe / Si layer stacks. The isolation columns formed by etching are filled with dielectric materials, and then holes are etched in the grid avoiding the isolation columns. The sacrificial SiGe layer is removed through these openings, leaving a horizontal Si layer supported by the isolation columns. These Si layers provide support for subsequent processes. The removal of the SiGe sacrificial layer is crucial in the GAA process. By selectively etching away the SiGe layer, preparations can be made for the high dielectric constant metal gate process on the Si nanowires. This step requires ensuring that the surface of the Si nanowire is clean and the SiGe is completely etched away.

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

[0004] Since silicon and germanium are in the same main group, and Si and SiGe have similar chemical properties, it is difficult to precisely control the etching of the two through chemical reagents. The general idea of ​​formula design is to oxidize SiGe through an oxidant, and a small amount of Si will also be oxidized, so the oxidizing property of the solution is adjusted to minimize the oxidation of Si; the oxidation product of SiGe after oxidation is etched away through a fluorine source, but SiO will also be etched due to the introduction of a fluorine source, so it is difficult to make a selective ratio for SiO; the etching of Si and SiO needs to be suppressed by an inhibitor in order to selectively etch SiGe without etching Si and SiO.

[0005] In order to solve the above-mentioned corrosion problem of Si and SiO, the present invention provides a SiGe selective etching solution relative to SiO and Si. A specific composition is used for etching, and the composition comprises: fluoride, oxidant, buffer composition, silicon dioxide inhibitor, silicon inhibitor, stabilizer and water. This composition can achieve high selective etching of silicon germanium, wherein the etching selectivity ratio of silicon germanium relative 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 substance can effectively prevent the polymerization of silanes and produce precipitation.

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

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

[0008] The SiGe selective etching solution relative to SiO and Si described in the above scheme, wherein the oxidant is any one or more of potassium permanganate, potassium dichromate, periodic acid, sodium periodate, sodium perbromate, potassium persulfate, hydrogen peroxide, peracetic acid, calcium peroxide, barium peroxide, sodium percarbonate, sodium perborate, ozone, potassium bromate, potassium chlorate, calcium hypochlorite, potassium ferrate, permanganate, and cerium ammonium nitrate. The preferred oxidant is hydrogen peroxide. This component accounts for 0.001-60 wt% of the composition, preferably 10-30 wt%.

[0009] The SiGe selective etching solution relative to SiO and Si described in the above scheme, wherein the buffer composition is an optional amine-containing compound and a multifunctional organic acid. The buffer composition may 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, and most preferably in the range of 3 to 5. This component accounts for 0.01-50wt% of the composition, preferably 0.05-10wt%, more preferably 0.1-20wt%, and most preferably 0.5-10wt%.

[0010] In the above-mentioned scheme, the SiGe selective etching solution relative to SiO and Si, the Si inhibitor is a polyethylene polyamine-amide type cationic polymer, which is obtained by reacting polyethylene polyamine with a urea compound and epichlorohydrin. The synthesis method of the Si inhibitor is divided into two steps: S1 polyethylene polyamine, formaldehyde, and urea are stirred and reacted, and the molar ratio of polyethylene polyamine, formaldehyde, and urea in step S1 is 1: (1-2): (1-2), preferably 1: 1: 1, and the reaction is stirred at 50-70 ° C for 4-7 hours; S2 epichlorohydrin is added, and the mass ratio of epichlorohydrin to S1 mixture is 1: (1-2), preferably 1: 1.5, and the reaction is stirred at 50-70 ° C for 5-8 hours to obtain the Si inhibitor. 。

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

[0012] In the above-mentioned scheme, the SiGe selective etching solution relative to SiO and Si, wherein the SiO inhibitor is a silane, which can be one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, etc. The component accounts for 0.001-5wt% of the composition, preferably 0.1-2wt%.

[0013] The SiGe selective etching solution relative to SiO and Si described in the above scheme contains small molecule alcohols soluble in water, such as methanol, ethanol, propanol, isopropanol, propylene glycol, glycerol, etc.

[0014] Furthermore, the amount of the stabilizer is 0.0001-20wt%, preferably 0.001-15wt%.

[0015] The SiGe selective etching solution relative to SiO and Si described in the above scheme is used at a temperature of 25°C to 70°C, preferably 25-40°C.

[0016] Furthermore, the rate of removing silicon germanium can be adjusted by increasing or decreasing etching conditions, such as component content and temperature.

[0017] Further, before etching, the entire device structure is cleaned with an aqueous solution containing 0.5 wt% HF at room temperature for about 30s-240s, preferably 60s, and more preferably 30s. After etching is completed, 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 (such as spin drying, N2, steam drying, etc.).

[0018] The etching compositions of the present invention are suitable for use in microelectronic devices comprising silicon and silicon germanium, including layers comprising SiGe alloys or consisting thereof.

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

[0020] As used herein, a "silicon germanium-containing layer" or "SiGe layer" corresponds to a layer comprising a silicon germanium-containing layer known in the art and having the formula Si x Ge y denoted by SiGe25, wherein x+y=1.00. SiGe25 here means that y is 0.25.

[0021] The beneficial effects of the present invention are as follows: (1) High selectivity: The present invention uses a specific composition of fluoride, oxidant, buffer composition, Si inhibitor, SiO inhibitor, stabilizer and water to accurately control the removal rate of SiGe. The selectivity relative to Si is as high as 200, and the corrosion to Si and SiGe is slight, which is much higher than the selectivity of the prior art.

[0022] (2) Improved etching uniformity: During use, the composition of the present invention can evenly etch SiGe, avoiding the problem of uneven etching caused by uneven distribution of chemical reagents in the prior art, thereby improving the quality of microelectronic devices.

[0023] (3) Wide applicability: The composition of the present invention is not only suitable for SiGe etching of planar structures, but also for SiGe etching of complex three-dimensional structures. It has wide adaptability and can meet the needs of different device manufacturing.

[0024] (4) Environmental protection and safety: The composition of the present invention does not contain chemical reagents harmful to the environment, such as hydrofluoric acid, etc., has good environmental protection and safety, and meets the requirements of modern green manufacturing.

[0025] (5) Simplified process flow: The composition of the present invention is easy to use and simple to operate, and can simplify the manufacturing process flow of microelectronic devices, improve production efficiency, and reduce production costs.

[0026] In summary, compared with the prior art, the present invention has the advantages of higher selectivity, improved etching uniformity, wide applicability, environmental protection and safety, and simplified process flow, and is a SiGe etching technology with significant advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Example 1 Si / SiGe25 structure SEM image; Figure 2 SEM image of Si / SiGe25 structure of Comparative Example 1; Figure 3 SEM image of the Si / SiGe25 structure of Comparative Example 2. DETAILED DESCRIPTION

[0028] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0029] 1) Preparation: According to the components and contents in the table below, weigh the corresponding raw materials by percentage calculation to prepare different selective etching solutions, with water as the balance.

[0030] 2) Etching conditions: 30℃, 300r / min stirring and soaking for 1-30min.

[0031] 3) Etching test piece: Si / SiGe stack, including Si(110) and SiGe25.

[0032] Method for preparing Si inhibitor in the embodiments and comparative examples: S1: Polyethylene polyamine, formaldehyde and urea are stirred to react, the molar ratio of polyethylene polyamine, formaldehyde and urea is 1:1:1, and the reaction is stirred at 70°C for 6 hours; Add epichlorohydrin to S2, the ratio of epichlorohydrin to S1 is 1:1.5, stir and react at 70°C for 4 hours and continue to react for 6 hours to obtain Si inhibitor. Citric acid-ammonium citrate buffer system, buffer pH at 5.

[0033] The formulations and test data of the embodiments and comparative examples are shown in Tables 1-5. Table 1 Ratios of different Si inhibitor formulations and test data

[0034] It can be seen from Comparative Example 1 and Example 1 in Table 1 that the combination without adding Si inhibitor has a selectivity of only 10.5 for Si and a selectivity of only 28.6 for SiO. After adding Si inhibitor, the etching rates of SiGe, Si, and SiO are all inhibited to a certain extent, but the inhibitory effect on Si and SiO is stronger, which greatly improves the selectivity of Si and SiO. Si inhibitor is a cationic surfactant, and the dissociated amine-containing cationic surfactant is easy to form electrostatic adsorption with the electronegative O element, and form a protective film on the surface. This surfactant has a stronger adsorption to Si oxide than Ge oxide, so it can increase the selectivity. Table 2 Etching rate and selectivity at different etching temperatures

[0035] It can be seen from the comparative examples and embodiments in Table 2 that the etching rates of SiO and Si are already very slow at low and high temperatures. As the temperature rises, the etching rates of the two do not change much, but the etching rate of SiGe increases greatly, so the selectivity will increase. The etching rates of Si and SiO at high temperatures are also very small, which is enough to show that the adsorption of this Si corrosion inhibitor is very strong and the effect is excellent. It should be noted that although etching at high temperatures will increase the selectivity a lot, the high-temperature decomposition of hydrogen peroxide will also greatly reduce the life of the solution.

[0036] From the SEM images, it can be seen that in Comparative Example 1, without adding an inhibitor, the Si and SiO layers are obviously corroded, and the corrosion position of the Si layer is relatively rough, which will damage 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 corrosion rate is relatively slow. From the images of Example 1, it can be seen that the silicon germanium layer is etched, and the uniformity is good, and the silicon layer and silicon dioxide layer are almost not etched.

[0037] The foregoing description is primarily for illustrative purposes. Although the present invention has been shown and described with respect to exemplary embodiments thereof, it will be appreciated by those skilled in the art that the foregoing and various other changes, omissions and additions may be made in its form and details without departing from the spirit and scope of the present invention.

Claims

1. A SiGe selective etching solution relative to SiO and Si, characterized in that: The etching solution comprises the following components by mass fraction: Fluoride 0.001-10 wt%; Oxidant 0.001-60wt%; Buffer composition 0.01-50wt%; Silica inhibitor 0.0001-10 wt%; Silicon inhibitor 0.0001-10 wt%; Stabilizer 0.0001-20wt%; The balance is water.

2. The SiGe selective etching solution relative to SiO and Si according to claim 1, characterized in that: The fluoride is selected from 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 relative to SiO and Si according to claim 1, characterized in that: The oxidant is any one or more of potassium permanganate, potassium dichromate, periodic acid, sodium periodate, sodium perbromate, potassium persulfate, hydrogen peroxide, peracetic acid, calcium peroxide, barium peroxide, sodium percarbonate, sodium perborate, ozone, potassium bromate, potassium chlorate, calcium hypochlorite, potassium ferrate, permanganic acid, and ceric ammonium nitrate, wherein the preferred oxidant is hydrogen peroxide.

4. The SiGe selective etching solution relative to SiO and Si according to claim 1, characterized in that: The buffer composition contains an amine compound and a multifunctional organic acid, and can be an acetic acid-ammonium acetate buffer system or a citric acid-ammonium citrate buffer system, and the buffer pH is in the range of 1-7, preferably in the range of pH 3-5.

5. The SiGe selective etching solution relative to SiO and Si according to claim 4, characterized in that: The Si inhibitor is a polyethylene polyamine-amide type cationic polymer obtained by reacting polyethylene polyamine with a urea compound and epichlorohydrin.

6. The SiGe selective etching solution relative to SiO and Si according to claim 5, characterized in that: The synthesis method of the Si inhibitor comprises the following steps: S1. Stirring and reacting polyethylene polyamine, formaldehyde and urea. In step S1, the molar ratio of polyethylene polyamine, formaldehyde and urea is 1:(1-2):(1-2), preferably 1:1:1, and stirring and reacting at 50-70° C. for 4-7 hours; S2 is added with epichlorohydrin, the mass ratio of epichlorohydrin to S1 mixture is 1:(1-2), preferably 1:1.5, and the reaction is stirred at 50-70°C for 5-8 hours to obtain the Si inhibitor.

7. The SiGe selective etching solution relative to SiO and Si according to claim 1, characterized in that: The silicon dioxide inhibitor is silane, and the silane is one or more of methyltrimethoxysilane, methyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, cyanoethyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and vinyltrimethoxysilane.

8. The SiGe selective etching solution relative to SiO and Si according to claim 1, characterized in that: The alcohol is methanol, ethanol, propanol, isopropanol, propylene glycol or glycerol.

9. The SiGe selective etching solution with respect to SiO and Si according to claim 1, characterized in that: The etching solution is used at a temperature of 25°C to 70°C, preferably 25-40°C.

10. The SiGe selective etching solution with respect to SiO and Si according to claim 1, characterized in that: Before etching, the etching solution is used to clean the entire device structure with an aqueous solution containing 0.4-0.7wt% HF at room temperature for about 30s-240s, preferably 60s, and more preferably 30s; after etching, the etching solution can be easily removed from the microelectronic device by rinsing, washing or other removal steps.

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