Etching solution, substrate processing method, and silicon device manufacturing method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOKUYAMA CORP
- Filing Date
- 2023-02-27
- Publication Date
- 2026-06-05
Smart Images
Figure 0007870738000001 
Figure 0007870738000002
Abstract
Description
[Technical Field]
[0001] This invention relates to an etching solution, a substrate processing method, and a silicon device manufacturing method. More specifically, it relates to an etching solution used when etching silicon-germanium (SiGe) for microfabrication during the manufacturing of silicon devices. In particular, it relates to an etching solution for selectively removing silicon-germanium from silicon and silicon oxide, respectively. [Background technology]
[0002] In recent years, silicon-germanium has been used as a material for forming transistors with a structure called GAA (Gate All Around). In GAA transistors, nanosheets stacked by epitaxial growth are used as the channel, making it easy to control the channel thickness with high precision. Furthermore, because the gate is positioned to surround the channel, leakage current due to short-channel effects is less likely to occur, making it an indispensable material for improving the performance of logic devices. In the fabrication process of GAA structure transistors, it is necessary to etch only the silicon-germanium layer from the alternating layered structure of silicon and silicon-germanium. Therefore, an etching solution that can selectively etch silicon-germanium relative to silicon is required. Furthermore, in the silicon-germanium etching process during the fabrication of GAA structure transistors, there are cases where not only silicon but also silicon oxide and other materials come into contact with the etching solution as non-etchable materials. In such cases, a high etching selectivity ratio of silicon-germanium relative to silicon oxide and other materials is required.
[0003] Patent Document 1 proposes an etching solution that can selectively etch silicon-germanium with respect to silicon, comprising water, an oxidizing agent, a water-miscible organic solvent, and a fluoride ion source. Patent Document 2 proposes an etching composition comprising an oxidizing agent, an organic acid, and a fluorine-containing compound.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0005] According to the etching solution of Patent Document 1 and the etching composition of Patent Document 2 (hereinafter referred to as the etching solution), it is possible to selectively etch silicon-germanium with respect to silicon. However, since these etching solutions do not contain an alkali source and from their composition, these etching solutions are considered to have an acidic liquor property. Furthermore, these etching solutions contain both an oxidizing agent and fluoride ions. As a result, it is presumed that the etching solutions of Patent Document 1 and Patent Document 2 cannot sufficiently reduce the etching rate of silicon oxide. Therefore, in the above-described silicon-germanium etching process, when these etching solutions are used in applications where not only silicon but also silicon oxide comes into contact with the etching solution as an object not to be etched, there remains a problem in the etching selectivity of silicon-germanium with respect to silicon oxide.
[0006] Therefore, an object of the present invention is to provide an etching solution, a method for treating a substrate, and a method for manufacturing a silicon device for selectively removing silicon-germanium with respect to each of silicon and silicon oxide.
Means for Solving the Problems
Means for Solving the Problems
[0007] In view of the above problems, the inventors of the present invention have conducted intensive studies. As a result, by using an etching solution containing an organic alkali, an oxidizing agent, and water, and having a pH and a hydroxide ion concentration within a predetermined range, it is possible to suppress the etching of silicon and silicon oxide while etching silicon-germanium, and to increase the etching selectivity of silicon-germanium with respect to each of silicon and silicon oxide. Thus, the present invention has been completed.
[0008] That is, the configuration of the present invention is as follows. Item 1: An etching solution containing an organic alkali, an oxidizing agent, and water, at 24 °C, the pH of the etching solution is 10.00 or more and 13.27 or less, and at 24 °C, the hydroxide ion concentration in the etching solution is 1.0×10 -4 mol / L or more and 1.9×10 -1 mol / L or less, which is characterized by being an etching solution for selectively removing silicon-germanium with respect to each of silicon and silicon oxide. Item 2: The etching solution according to Item 1, wherein in the etching solution, the value of the ratio of the oxidizing agent concentration (mol / L) to the hydroxide ion concentration (mol / L) is 0.50 or more. Item 3: The etching solution according to Item 1 or 2, wherein the oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, m-chloroperbenzoic acid, 9-azabicyclo[3.3.1]nonane-N-oxyl, hypochlorite, and hypobromite. Item 4: The etching solution according to any one of Items 1 to 3, further containing an inhibitor for suppressing silicon etching. Item 5: The etching solution according to Item 4, wherein the inhibitor for suppressing silicon etching is at least one selected from the group consisting of a halogen salt of a quaternary ammonium, a BF4 salt of a quaternary ammonium, and a carboxylic acid compound. Item 6: The etching solution according to Item 4 or 5, wherein the inhibitor for suppressing silicon etching is a compound having a dication structure. Item 7 The etching solution according to any one of items 1 to 6, wherein the organic alkali is a quaternary ammonium hydroxide. Item 8 A method for processing a substrate containing silicon, silicon oxide, and silicon-germanium, A method for processing a substrate, comprising an etching step of selectively etching silicon and silicon oxide with silicon-germanium using an etching solution described in any one of items 1 to 7. Item 9 The substrate further comprises silicon nitride, The substrate processing method according to item 8, wherein the etching step is a step of selectively etching silicon-germanium with respect to silicon nitride. Item 10 A method for manufacturing a silicon device using a substrate containing silicon, silicon oxide, and silicon-germanium, A method for manufacturing a silicon device, comprising an etching step of selectively etching silicon and silicon oxide with silicon-germanium using an etching solution described in any one of items 1 to 7. Item 11 The substrate further comprises silicon nitride, The method for manufacturing a silicon device according to item 10, wherein the etching step is a step of selectively etching silicon-germanium with respect to a silicon nitride. [Effects of the Invention]
[0009] According to the present invention, an etching solution with a high silicon-germanium etching selectivity ratio for silicon and silicon oxide, respectively, a substrate processing method, and a method for manufacturing a silicon device can be provided. [Modes for carrying out the invention]
[0010] Embodiments of the present invention will be described in detail below, but the present invention is not limited to these contents unless it exceeds the spirit of the invention. Furthermore, the present invention can be modified and implemented as desired without departing from its spirit.
[0011] In this specification, a numerical range indicated by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively, and "A~B" means that it is greater than or equal to A and less than or equal to B. Furthermore, when a numerical range is described in steps, the upper and lower limits of each numerical range can be combined in any way.
[0012] 1. Etching solution The etching solution of the present invention is an etching solution for selectively removing silicon-germanium from silicon and silicon oxide, respectively. Therefore, it can be used for etching silicon-germanium in the manufacture of silicon devices, etc. (i.e., it is a silicon-germanium etching solution).
[0013] In the manufacturing of the aforementioned silicon devices, if the processing solution, such as the etching solution, contains metal, it often affects the workpiece (not limited to the silicon surface being etched), resulting in a decrease in the quality of the silicon device.
[0014] Therefore, it is preferable that the etching solution of the present invention does not contain metal. It is more preferable that the metal content in the etching solution is below the impurity level, and it is even more preferable that the etching solution is substantially free of metal. However, the etching solution may contain metal. The metal referred to here includes nonionic metals (particulate metals) such as elemental metals, and metal ions (ionic metals). For example, the total metal content is preferably 1 ppm or less by weight, and more preferably 1 ppb or less. The lower limit is not particularly limited, and the total metal content may be, for example, 0 ppm or more and 1 ppm or 0 ppb or more and 1 ppb or less. The content of Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, and Zn is preferably 1 ppm or less by weight, and more preferably 1 ppb or less. The lower limit is not particularly limited, and the content of each of the above metals may be, for example, 0 ppm to 1 ppm or 0 ppb to 1 ppb by weight. The metals listed here are those that are considered to potentially affect the quality of chemicals used in semiconductor manufacturing. In other words, the quality of the etching solution can be improved by ensuring that the content of each metal is within the above-mentioned range.
[0015] Furthermore, it is preferable that one of the above metals selected from Fe, Cu, Mn, Cr, and Zn is present in an amount of 0.01 ppt or more and 1.00 ppb or less by weight, more preferably 0.01 ppt or more and 0.50 ppb or less, even more preferably 0.01 ppt or more and 0.20 ppb or less, and particularly preferably 0.01 ppt or more and 0.1 ppb or less.
[0016] The etching solution contains an organic alkali. The presence of the organic alkali generates hydroxide ions, which suppress the metal content in the etching solution while affecting the pH and hydroxide ions of the etching solution. The ion concentration can be adjusted.
[0017] The organic alkali is not particularly limited, but examples include onium hydroxide and organic amines. Examples of onium hydroxide include ammonium hydroxide such as primary ammonium hydroxide, secondary ammonium hydroxide, tertiary ammonium hydroxide, and quaternary ammonium hydroxide, as well as phosphonium hydroxide, sulfonium hydroxide, iminium hydroxide containing multiple bonds, and diazenium hydroxide. Among these, ammonium hydroxide is preferred, and quaternary ammonium hydroxide is more preferred from the viewpoint of having good stability against oxidizing agents and being able to improve the stability of the etching solution over time. As the quaternary ammonium hydroxide, one or more selected from the group consisting of tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, propyltrimethylammonium hydroxide, butyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethyl-2-hydroxyethylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide, methyltris(2-hydroxyethyl)ammonium hydroxide, phenyltrimethylammonium hydroxide, and benzyltrimethylammonium hydroxide can be used.
[0018] Furthermore, one or more organic amines selected from the group consisting of primary amines, secondary amines, and tertiary amines can be used. Examples of primary or secondary amines include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,1,3,3-tetramethylguanidine, diethylenetriamine, dipropylenetriamine, bis(hexamethylene)triamine, N,N,N-trimethyldiethylenetriamine, and N,N-bis(3-aminopropyl)ethylene One or more substances selected from the group consisting of diamine, 2-(2-aminoethoxy)ethanol, 2-amino-2-methyl-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol, 6-amino-1-hexanol, N-(2-aminoethyl)propanolamine, N-(2-hydroxypropyl)ethylenediamine, azetidine, pyrrolidine, piperidine, hexamethyleneimine, pentamethyleneimine, and octamethyleneimine can be used.
[0019] Furthermore, specific examples of tertiary amines include one or more selected from the group consisting of 2-(dimethylamino)ethanol, 3-(dimethylamino)-1-propanol, 4-dimethylamino-1-butanol, 2-(diethylamino)ethanol, triethylamine, methylpyrrolidine, methylpiperidine, 1,8-diazabicyclo[5.4.0]undeca-7-ene, and 1,5-diazabicyclo[4.3.0]non-5-ene.
[0020] More preferably, the organic amine can be one or more selected from the group consisting of ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,1,3,3-tetramethylguanidine, diethylenetriamine, dipropylenetriamine, bis(hexamethylene)triamine, 2-(2-aminoethoxy)ethanol, 2-amino-2-methyl-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol, 6-amino-1-hexanol, N-(2-aminoethyl)propanolamine, pyrrolidine, piperidine, hexamethyleneimine, and pentamethyleneimine. More preferably, one or more substances selected from the group consisting of ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,1,3,3-tetramethylguanidine, diethylenetriamine, dipropylenetriamine, bis(hexamethylene)triamine, 2-(2-aminoethoxy)ethanol, 2-amino-2-methyl-1-propanol, pyrrolidine, and piperidine can be listed.
[0021] Such organic alkalis should be selected and used according to their known characteristics, depending on the target and purpose of silicon etching. From the viewpoint of stability against oxidizing agents, quaternary ammonium hydroxides that do not have a hydroxyl group in the cation are more preferred among the above. Examples of quaternary ammonium hydroxides include one or more selected from the group consisting of tetramethylammonium hydroxide ion, ethyltrimethylammonium hydroxide, propyltrimethylammonium hydroxide, butyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Among these, one or more selected from the group consisting of tetramethylammonium hydroxide ion, ethyltrimethylammonium hydroxide, propyltrimethylammonium hydroxide, butyltrimethylammonium hydroxide, and tetraethylammonium hydroxide are particularly preferred in that they exhibit a high etching rate.
[0022] In the etching solution of the present invention, the compound used as the organic alkali may be used alone or as a mixture of several different compounds. Furthermore, in order to reduce the metal content in the etching solution, it is preferable to use an organic alkali that contains as few metal impurities and insoluble impurities as possible. If necessary, commercially available products can be purified by recrystallization, column purification, ion exchange purification, filtration, etc., before use. When using quaternary ammonium hydroxide as the alkali compound, depending on the type, extremely high-purity versions are manufactured and sold for semiconductor manufacturing, and it is preferable to use such a product. High-purity quaternary ammonium hydroxide for semiconductor manufacturing is generally sold as an aqueous solution. In manufacturing the etching solution of the present invention, this solution can be mixed directly with water and other components.
[0023] In the highly selective etching of silicon-germanium with respect to silicon, the first acid dissociation constants (pKa1) of silicon hydroxide and germanium hydroxide, which are the products of etching, are 9.86 and 8.68, respectively. Therefore, as the alkalinity of the etching solution decreases, silicon hydroxide becomes less ionizable than germanium hydroxide, and its solubility in the etching solution decreases. For this reason, the lower the pH and hydroxide ion concentration of the etching solution (and thus the lower the alkalinity), the more the etching rate of silicon relatively decreases with respect to the etching rate of silicon-germanium, and the etching selectivity ratio of silicon with respect to silicon-germanium tends to increase. On the other hand, if the alkalinity of the etching solution is too low, the etching rate of silicon-germanium tends to be slow and the productivity decreases. Furthermore, when the etching solution contains fluoride ions, the concentration of free hydrogen fluoride and bifluoride ions in the etching solution increases, and the etching rate of silicon oxide increases.
[0024] For this reason, at 24°C, the pH of the etching solution is 10.00 or more and 13.27 or less. More preferably, the pH is 11.00 or more and 13.27 or less, and even more preferably, the pH is 11.50 or more and 13.27 or less. The pH refers to the value measured by the glass electrode method described below. Also, at 24°C, the hydroxide ion concentration in the etching solution is 1.0×10 -4 mol / L or more and 1.9×10 -1 mol / L or less. More preferably, it is 1.0×10 -3 mol / L or more and 1.9×10 -1 mol / L or less, and even more preferably, it is 3.1×10 -3 or more and 1.9×10 -1 mol / L or less. The hydroxide ion concentration in the etching solution is calculated using the measured pH up to the second decimal place and the following formula (1). In the following formula (1), the ion product of water at 24°C is 1.000×10 -14 mol 2 / L 2 is. Hydroxide ion concentration (mol / L) = Ion product of water at 24°C / 10 -pH (1 )
[0025] As described above, by keeping the pH of the etching solution and the hydroxide ion concentration within the etching solution within the above range, the etching selectivity ratio of silicon-germanium to silicon is increased, and etching of silicon oxide is also suppressed. Therefore, the etching selectivity ratio of silicon-germanium to both silicon and silicon oxide can be increased. Furthermore, even when the etching solution contains fluoride ions, etching of silicon oxide can be significantly suppressed. This is because, when the pH of the etching solution and the hydroxide ion concentration in the etching solution are within the above range, the equilibrium between fluoride ions and free hydrogen fluoride shifts towards the fluoride ion side, resulting in a sufficiently low concentration of free hydrogen fluoride and dihydrogen fluoride ions in the etching solution, which contribute to the etching of silicon oxide. Furthermore, if the pH of the etching solution and the hydroxide ion concentration in the etching solution are within the above range, etching of silicon nitride can also be suppressed, thereby increasing the etching selectivity ratio of silicon-germanium to silicon nitride. Additionally, even when the etching solution contains fluoride ions, the etching rate of silicon nitride can be significantly suppressed. This is for the same reason as the significant suppression of silicon oxide etching described above. On the other hand, it is presumed that the etching solutions described in Patent Documents 1 and 2 cannot sufficiently reduce the etching rate of silicon nitrides because their acidic properties make them ineffective.
[0026] Furthermore, as described above, the etching solution of the present invention is alkaline. Because the etching solution is alkaline, both the surface charge of the fine particles (particles) such as silicon oxide and the surface charge of the etched surface become negative, so the re-adhesion of particles to the etched surface can be prevented by electrostatic repulsion. As a result, the cleaning step after etching can be omitted. Therefore, by using the etching solution of the present invention, it is possible to manufacture silicon devices and the like with high productivity.
[0027] The etching solution contains the above-mentioned organic alkali, oxidizing agent, and water. Preferably, the ratio of the oxidizing agent concentration (mol / L) to the hydroxide ion concentration (mol / L) in the etching solution is 0.50 or higher. When the ratio of the oxidizing agent concentration to the hydroxide ion concentration is 0.50 or higher, the etching rate of silicon is significantly reduced compared to the etching rate of silicon-germanium, and the etching selectivity ratio of silicon-germanium to silicon is improved.
[0028] The reason for this is not entirely clear, but I speculate the following: In an etching solution containing an oxidizing agent, increasing the oxidizing agent content increased the oxidation rate of the silicon surface, which in turn increased the proportion of silicon oxide on the silicon surface and decreased the etching rate. This is thought to be because the alkaline aqueous solution hardly etches silicon oxide. Furthermore, as oxidation reactions by oxidizing agents occur, etching by hydroxide ions progresses on the unoxidized silicon surface simultaneously. Therefore, as the hydroxide ion concentration increases, the etching rate of silicon tends to increase. In other words, since the oxidation and etching reactions of silicon occur competitively, it is hypothesized that the etching rate of silicon has a negative correlation with the ratio of the oxidizing agent concentration to the hydroxide ion concentration (oxidizing agent concentration / hydroxide concentration). On the other hand, for silicon-germanium, increasing the ratio of the oxidizing agent concentration to the hydroxide ion concentration (oxidizing agent concentration / hydroxide ion concentration) suppresses etching starting from silicon atoms in silicon-germanium, but because germanium oxide is soluble in water, etching starting from germanium atoms is not easily suppressed. Therefore, by increasing the ratio of the oxidizing agent concentration to the hydroxide ion concentration, it is possible to control the etching rate of silicon-germanium. We hypothesize that this selectively suppresses the etching of silicon compared to that of germanium, thereby improving the silicon-germanium etching selectivity ratio relative to silicon.
[0029] In the etching solution, the ratio of the oxidizing agent concentration to the hydroxide ion concentration is preferably 0.50 or higher, more preferably 1.2 or higher, and even more preferably 10 or higher, in terms of the selectivity of silicon-germanium etching over silicon etching. The upper limit is not particularly limited, but may be 150 or lower, or 80 or lower. That is, preferably, for example, 0.50 to 150, 1.2 to 80, and 10 to 80. The oxidizing agent concentration in the etching solution can be measured by the iodine titration method described later.
[0030] The content of organic alkali in the etching solution is not particularly limited, but 0.001 mol / L or more is preferred. A higher content increases the alkalinity of the etching solution, which tends to increase the silicon-germanium etching rate and improves the productivity of silicon devices. Therefore, the content of organic alkali is more preferably 0.010 mol / L or more, even more preferably 0.050 mol / L or more, and particularly preferably 0.100 mol / L or more. Furthermore, there is no particular upper limit, but it may be 1.200 mol / L or less, 1.000 mol / L or less, or 0.800 mol / L or less. In other words, preferred values include, for example, 0.001 mol / L or more and 1.200 mol / L or less, 0.010 mol / L or more and 1.000 mol / L or less, 0.050 mol / L or more and 0.800 mol / L or less, and 0.100 mol / L or more and 0.800 mol / L or less. Having the organic alkali content within the above range makes it easier to adjust the pH of the etching solution and the hydroxide ion concentration in the etching solution to within that range.
[0031] The oxidizing agent in the etching solution is not particularly limited, but examples include one or more selected from the group consisting of peroxides such as hydrogen peroxide and m-chloroperbenzoic acid; N-oxide compounds such as 9-azanoradamantane-N-oxyl (nor-AZADO) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL); and hypohalite salts such as hypochlorite and hypobromite.
[0032] Among these, one or more selected from the group consisting of hydrogen peroxide, m-chloroperbenzoic acid, nor-AZADO, hypochlorite, and hypobromite are more preferred in terms of their effect in suppressing silicon etching, one or more selected from the group consisting of hydrogen peroxide, m-chloroperbenzoic acid, and nor-AZADO are even more preferred in terms of their effect in suppressing silicon etching, and one or more selected from the group consisting of hydrogen peroxide and m-chloroperbenzoic acid are particularly preferred in terms of ease of handling and availability. As the hypohalite salt, nonmetallic salts are preferred. Specifically, various ammonium salts such as primary ammonium salts, secondary ammonium salts, tertiary ammonium salts, and quaternary ammonium salts are more preferred, with quaternary ammonium salts being particularly preferred. More specifically, examples of quaternary ammonium salts include one or more selected from the group consisting of tetramethylammonium salt, ethyltrimethylammonium salt, propyltrimethylammonium salt, butyltrimethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, tetrabutylammonium salt, phenyltrimethylammonium salt, and benzyltrimethylammonium salt.
[0033] In the etching solution of the present invention, the oxidizing agent may be present in the form of an ion. The countercation is preferably a nonmetallic cation. Specifically, various ammonium cations such as primary ammonium cations, secondary ammonium cations, tertiary ammonium cations, and quaternary ammonium cations are more preferred, and among these, quaternary ammonium cations are particularly preferred. To give a more specific example of a quaternary ammonium cation, consider tetramethylammonium cation. One or more cations selected from the group consisting of thion, ethyltrimethylammonium cation, propyltrimethylammonium cation, butyltrimethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetrabutylammonium cation, phenyltrimethylammonium cation, and benzyltrimethylammonium cation can be used.
[0034] The content of the oxidizing agent in the etching solution is not particularly limited, but is preferably 0.003 mol / L or higher. A higher content improves the etching performance of the etching solution, which tends to increase the silicon-germanium etching rate and thus improves the productivity of silicon devices. For this reason, the content of the oxidizing agent is more preferably 0.010 mol / L or higher, even more preferably 0.029 mol / L or higher, particularly preferably 0.050 mol / L or higher, and especially preferably 0.150 mol / L or higher. Furthermore, there is no particular upper limit, but it may be 1.200 mol / L or lower, 1.000 mol / L or lower, or 0.800 mol / L or lower. In other words, preferably, for example, concentrations of 0.003 mol / L or more and 1.200 mol / L or less, 0.010 mol / L or more and 1.000 mol / L or less, 0.029 mol / L or more and 0.800 mol / L or less, 0.050 mol / L or more and 0.800 mol / L or less, and 0.150 mol / L or more and 0.800 mol / L or less are included. By keeping the oxidizing agent content within the above range, it becomes easier to adjust the ratio of the oxidizing agent concentration to the hydroxide ion concentration within that range.
[0035] As stated above, the etching solution contains water. If water is not present, etching will not proceed. Depending on the type and amount of other components, the water content in the etching solution is preferably 30.0% by mass or more and less than 100.0% by mass, more preferably 50.0% by mass or more and less than 100.0% by mass, even more preferably 60.0% by mass or more and less than 100.0% by mass, and particularly preferably 75.0% by mass or more and less than 100.0% by mass. Furthermore, there is no particular upper limit as long as the necessary amount of other components can be contained, but usually 99.5% by mass or less is sufficient, and 99.0% by mass is also sufficient. That is, for example, 50.0% by mass or more and 99.5% by mass or less, and 60.0% by mass or more and 99.0% by mass or less. Also, for example, the remainder of the etching solution other than the organic alkali and oxidizing agent may be water. Furthermore, if the etching solution contains components such as silicon etching inhibitors or fluorine-containing compounds, the remainder of the organic alkali, oxidizing agent and other components may be water. While the water used is not particularly limited, it is preferable to use high-purity water with few impurities. The amount of impurities can be evaluated by its electrical resistivity. Specifically, the electrical resistivity is preferably 0.10 MΩ·cm or higher, more preferably 15.00 MΩ·cm or higher, and even more preferably 18.00 MΩ·cm or higher. The upper limit is not particularly limited, but it may be 18.25 MΩ·cm or lower. That is, preferably, for example, 0.10 MΩ·cm to 18.25 MΩ·cm, 15.00 MΩ·cm to 18.25 MΩ·cm, and 18.00 MΩ·cm to 18.25 MΩ·cm. Such water with few impurities can be easily manufactured and obtained as ultrapure water for semiconductor manufacturing. Furthermore, ultrapure water has significantly fewer impurities that do not affect (or have little effect on) electrical resistivity, making it highly suitable as a raw material for etching solutions.
[0036] The silicon-germanium etching solution of the present invention may further contain a silicon etching inhibitor. Even when a silicon etching inhibitor is included, the etching selectivity of silicon-germanium to silicon can be improved by changing the concentration of the oxidizing agent as described above. In other words, the effect of the inhibitor on the reduction of the etching selectivity of silicon-germanium to silicon can be reduced. However, compounds with strong reducing properties may not only react with the oxidizing agent contained in the etching solution of the present invention, but may also have the effect of significantly reducing the etching rate of silicon-germanium. The impact on selectivity can be significant, and even if the concentration of the oxidizing agent is changed, it may not be possible to completely reduce the impact of the decrease in selectivity. Therefore, it is preferable that compounds with strong reducing properties are not included.
[0037] In etching solutions containing an oxidizing agent, the silicon surface becomes hydrophilic due to the oxidizing agent, so the adsorption of compounds to the silicon surface due to hydrophobic interactions hardly occurs. Therefore, it is presumed that the inhibitor is adsorbed to the δ+ or δ- sites on the silicon surface by electrostatic interactions. By adsorbing to the silicon surface through such electrostatic interactions, the inhibitor can suppress the etching of silicon. Therefore, compounds that can act as inhibitors include nonionic compounds, anionic compounds, and cationic compounds that have strongly polarized sites. Specifically, examples include carboxylic acid compounds such as propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, isopropanoic acid, isobutanoic acid, isopentanoic acid, isohexanoic acid, isoheptanoic acid, isooctanoic acid, 2-cyclobutylacetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, tridecanediic acid, methylsuccinic acid, tetramethylsuccinic acid, benzoic acid, phthalic acid, terephthalic acid, gluconic acid, glycine, methylglycine, ethylglycine, alanine, β-alanine, leucine, isoleucine, proline, hydroxyproline, N-methylproline, α-methylproline, and tyrosine; Phosphoric acid and phosphorus compounds such as phosphonic acid compounds including ethylphosphonic acid, propylphosphonic acid, butylphosphonic acid, pentylphosphonic acid, heptylphosphonic acid, octylphosphonic acid, isopropylphosphonic acid, isobutylphosphonic acid, isopentylphosphonic acid, isoheptylphosphonic acid, and isooctylphosphonic acid; Glycols such as ethylene glycol, propylene glycol, and dipropylene glycol, and polyol compounds having multiple hydroxyl groups such as glycerin; Glycol ether compounds such as alkylene glycol monoalkyl esters including ethylene glycol monopropyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and diethylene glycol n-butyl ether, and alkylene glycol dialkyl esters including diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether; Halogenated salts of quaternary ammonium and BF4 salts of quaternary ammonium, such as tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, decyltrimethylammonium chloride, decyltrimethylammonium bromide, decametonium chloride, decametonium bromide, 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dibromide, and 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dichloride; One or more items selected from the group consisting of these can be listed.
[0038] Among these, compounds having a dication structure with two cations in the molecule, such as 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dibromide and 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dichloride, are preferred. In other words, silicon etching inhibitors are preferably those having a dication structure. The reason why having a dication structure is preferred is speculated as follows. If the inhibitor has a dication structure, it will have two cation sites, and therefore it can be strongly adsorbed by the electrostatic interaction between the two cation sites and the silicon surface, even on a silicon surface that has become hydrophilic due to the action of an oxidizing agent, i.e., a silicon surface where adsorption due to hydrophobic interactions hardly occurs. Furthermore, when the inhibitor has a monocation structure with one cation within the molecule, crystal plane anisotropy may occur in the adsorption due to differences in the magnitude of steric hindrance for each crystal plane orientation on the silicon surface. In particular, it is difficult to suppress etching of the Si(100) plane. In this respect, when the inhibitor has a dication structure, even in areas where steric hindrance makes it difficult for cation sites to adsorb, the approach of reactive species can be suppressed by the linking group between the two cation sites, so the difference in etching suppression effect between each crystal plane orientation tends to be smaller. In addition, etching of the Si(100) plane can also be suppressed efficiently.
[0039] The amount of inhibitor in the etching solution is not particularly limited, but examples include 0.0001 mol / L to 0.2000 mol / L and 0.0010 mol / L to 0.1000 mol / L.
[0040] In the manufacturing of silicon devices, when etching silicon-germanium, silicon oxide parts (surfaces) such as silicon dioxide and silicon nitride parts (surfaces) such as silicon nitride are often non-etchable. However, if the etching solution contains fluoride ions, it may etch the silicon oxide and silicon nitride parts that are not etchable. Therefore, it is preferable that the etching solution does not contain fluoride ions. However, since the etching solution of the present invention is alkaline, silicon dioxide and silicon nitride are not easily etched even if fluoride ions are included as other components. Therefore, the etching solution may contain fluoride ions. Including fluoride ions can sometimes increase the silicon-germanium etching rate. The reason is not entirely clear, but it is presumed that the etching reaction is promoted because the fluoride ions adsorb onto the surface of silicon-germanium, and the polarization between the atoms to which the fluoride ions are adsorbed and the other atoms increases. On the other hand, as the pH decreases (the hydroxide ion concentration decreases), etching of silicon oxides and silicon nitrides tends to proceed more easily. Therefore, by adjusting the pH of the etching solution to the above range, sufficient etching selectivity of silicon-germanium for silicon oxides and silicon nitrides can be obtained, even if the etching solution of the present invention contains fluoride ions. For this purpose, it is preferable to appropriately adjust the concentration of fluoride ions according to the pH of the etching solution.
[0041] The concentration of fluoride ions in the etching solution can be adjusted, for example, by changing the content of the fluorine-containing compound that supplies the fluoride ions. In other words, the etching solution may contain a fluorine-containing compound. The content of fluorine-containing compounds is not particularly limited, but examples include 0.01 mol / L to 1.00 mol / L and 0.05 mol / L to 0.20 mol / L.
[0042] Examples of fluorine-containing compounds include one or more selected from the group consisting of hydrogen fluoride, ammonium fluoride, tetramethylammonium fluoride, tetrabutylammonium fluoride, tetrafluoroboric acid, hexafluorophosphate, hexafluorosilicic acid, ammonium tetrafluoroborate, ammonium hexafluorophosphate, and ammonium hexafluorosilicate, with tetramethylammonium fluoride being preferred among them.
[0043] The etching solution is preferably a homogeneous solution in which all the components to be blended are dissolved. Furthermore, in order to prevent contamination during etching, it is preferable that the number of particles 200 nm or larger in the etching solution be 100 particles / mL or less, and more preferably 50 particles / mL or less. The lower limit is not particularly limited, but may be 0 particles / mL or more. For example, it may be preferably 0 particles / mL or more and 100 particles / mL or less, or 0 particles / mL or more and 50 particles / mL or less. Furthermore, the silicon etching solution of the present invention may contain gases such as hydrogen and oxygen, depending on manufacturing considerations.
[0044] The etching solution of the present invention can be suitably used as an etching solution in the manufacture of silicon devices, which includes an etching step for etching silicon-germanium, such as a silicon-germanium single crystal film. Note that the silicon-germanium single crystal film includes those produced by epitaxial growth.
[0045] 2. Method for manufacturing etching solution The method for producing the etching solution of the present invention is not particularly limited and may include, for example, a mixing step of mixing an organic alkali and an oxidizing agent with water to a predetermined concentration to obtain a mixture, and a dissolving step of dissolving the obtained mixture uniformly. Alternatively, these steps may be combined into a single step. For the raw materials of the etching solution, such as organic alkalis, oxidizing agents, and water, those listed in the etching solution section may be used.
[0046] In the manufacturing of the etching solution of the present invention, it is also preferable to include a step of removing particles by passing the mixture of raw materials through a filter of several nanometers to several tens of nanometers after mixing and dissolving them. If necessary, the particle removal step may be performed multiple times.
[0047] Furthermore, various known treatments can be applied to obtain the necessary physical properties in the manufacturing of semiconductor manufacturing chemicals, such as reducing dissolved oxygen in the etching solution by bubbling with an inert gas like high-purity nitrogen gas.
[0048] For the mixing and dissolving processes described above, and for storing the etching solution, it is preferable to use containers or equipment formed or coated with materials known as the inner walls of semiconductor manufacturing chemicals, specifically polyfluoroethylene or high-purity polypropylene, which are materials that do not easily leach contaminants into the etching solution. It is also preferable to clean these containers and equipment beforehand.
[0049] 3. Method for manufacturing silicon devices A second embodiment of the present invention is a method for manufacturing a silicon device using a substrate containing silicon, silicon oxide, and silicon-germanium, This invention relates to a method for manufacturing a silicon device, which includes an etching step in which silicon and silicon oxide are selectively etched with silicon-germanium using the etching solution of the first embodiment. The second embodiment will be described below.
[0050] The method for manufacturing a silicon device according to the second embodiment can use known methods for manufacturing silicon devices, except that it includes an etching step in which silicon and silicon oxide are selectively etched with silicon-germanium using the etching solution of the first embodiment. For example, it may include one or more steps selected from the group consisting of a wafer fabrication step, an oxide film formation step, a transistor formation step, a wiring formation step, and a CMP step, and may also include other known steps used in semiconductor manufacturing methods.
[0051] Using the etching solution of the first embodiment, silicon and silicon oxide are treated respectively. The etching process for selectively etching silicon-germanium is not particularly limited, but examples include a contact process in which an etching solution is brought into contact with a substrate containing silicon, silicon oxide, and silicon-germanium. By including such a process, it is possible to selectively remove only silicon from a device structure in which silicon oxide is used as an insulating film and silicon and silicon-germanium are alternately stacked, by contacting the etching solution with the device structure. Furthermore, it is possible to fabricate a GAA structure using silicon nanowires as channels while leaving the silicon oxide insulating film intact.
[0052] Furthermore, the etching process is not particularly limited as long as it is possible to selectively etch silicon and silicon oxide with respect to silicon-germanium, and may include a substrate holding step of holding the substrate in a horizontal position and a processing liquid supply step of supplying an etching solution to the main surface of the substrate while rotating the substrate around a vertical axis of rotation passing through the center of the substrate, or it may include a substrate holding step of holding a plurality of substrates in an upright position and a step of immersing the substrates in an upright position in an etching solution stored in a processing tank.
[0053] The conditions for the etching process are not particularly limited. For example, the temperature of the etching solution in the etching process can be appropriately determined considering the desired etching rate, the shape and surface condition of the silicon-germanium after etching, productivity, etc. For example, it can be 20 to 95°C, and is preferably in the range of 35 to 90°C.
[0054] In the etching process, etching can also be performed under vacuum or reduced pressure while degassing or bubbling with an inert gas. Such operations can suppress or reduce the increase in dissolved oxygen during etching. Alternatively, etching can be performed without bubbling with an inert gas. By not bubbling with an inert gas, the amount of dissolved oxygen in the etching solution increases. Since dissolved oxygen in the etching solution contributes to the oxidation of silicon-germanium, it may be possible to increase the etching rate of silicon-germanium. On the other hand, for silicon, the decrease in etching rate due to the effect of dissolved oxygen is small, or it may even increase. Therefore, if the etching rate of silicon increases due to the effect of dissolved oxygen, that is, if the etching rate of silicon-germanium relative to silicon may decrease, bubbling with an inert gas should be performed. If the etching rate of silicon is maintained or decreases due to the effect of dissolved oxygen, bubbling with an inert gas should not be performed.
[0055] In the etching process, it is sufficient to simply bring the substrate into contact with the etching solution, such as by immersing it in the solution. However, an electrochemical etching method, which involves applying a constant potential to the substrate, can also be employed.
[0056] As mentioned above, the materials to be etched in the etching process are substrates containing silicon, silicon oxide, and silicon-germanium. Here, silicon and silicon oxide are non-etchable materials and are not subject to the etching process. The forms of silicon, silicon oxide, and silicon-germanium are not particularly limited, but may include, for example, a silicon film, a silicon oxide film, or a silicon-germanium film, and a silicon-containing silicon-germanium single crystal film is an example. The substrate may also include silicon nitride films, various metal films, etc., as non-etchable objects. Examples include alternating stacks of silicon and silicon-germanium, silicon-germanium films, silicon oxide films, silicon nitride films, and even silicon, polysilicon, and silicon-germanium films deposited on a silicon single crystal, and structures with patterns formed using these films.
[0057] In a method for manufacturing silicon devices, it is preferable that the substrate further contains silicon nitride, and that the etching step is a step in which silicon-germanium is selectively etched from the silicon nitride. By having such an etching step, silicon-germanium can be selectively removed not only from silicon and silicon oxide, but also from the silicon nitride. The step in which silicon-germanium is selectively etched from the silicon nitride is not particularly limited, but examples include a contact step in which an etching solution is brought into contact with a substrate containing silicon nitride and silicon-germanium, and a contact step in which an etching solution is brought into contact with a substrate containing silicon, silicon oxide, silicon nitride, and silicon-germanium. By including such a process, it is possible to selectively remove only silicon from a device structure in which silicon nitride is used as an insulating film and silicon and silicon-germanium are alternately stacked, by contacting the etching solution with the device structure. Furthermore, it is possible to fabricate a GAA structure using silicon nanowires as channels while leaving the silicon nitride insulating film intact.
[0058] 4. Processing method for circuit boards A third embodiment of the present invention is a method for processing a substrate containing silicon, silicon oxide, and silicon-germanium, The present invention relates to a substrate processing method that includes an etching step in which silicon and silicon oxide are selectively etched with silicon-germanium using the etching solution of the first embodiment. The third embodiment will be described below.
[0059] As an etching process for selectively etching silicon and silicon oxide with silicon-germanium using an etching solution, the etching process described in the section on the method of manufacturing silicon devices can be used. In other words, in the substrate processing method, it is preferable that the substrate further contains silicon nitride, and the etching step is a step in which silicon germanium is selectively etched from the silicon nitride. Furthermore, examples of methods include a step of holding a substrate in a horizontal position and a step of supplying an etching solution to the main surface of the substrate while rotating the substrate around a vertical axis of rotation passing through the center of the substrate, and a step of holding a plurality of substrates in an upright position and immersing the substrates in an upright position in the etching solution of the first embodiment stored in a processing tank. Furthermore, the substrate described in the section on the manufacturing method of silicon devices can be used as the substrate. [Examples]
[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
[0061] The evaluation methods in the examples and comparative examples are as follows.
[0062] (Method for measuring the pH of etching solution) The pH of the etching solution was measured at a temperature of 24°C using a Horiba F-73 benchtop pH meter and a Horiba 9632-10D pH electrode for strong alkaline samples.
[0063] (Hydroxide ion concentration in etching solution) The hydroxide ion concentration was calculated from the pH value measured by the above measurement method using the following formula (1). In formula (1), the ion product of water at 24°C is 1.000 × 10⁻⁶. -14 mol 2 / L 2 That is the case. Hydroxide ion concentration (mol / L) = Ion product of water at 24°C / 10 -pH (1)
[0064] (Oxidizing agent concentration in etching solution) The concentration was determined by iodine titration. Specifically, first, 1 g of etching solution was weighed into a container, and 10 g of 1% by mass acetic acid aqueous solution was added. Next, 1 g of potassium iodide was added, and the oxidizing agent reacted with potassium iodide. When using an oxidizing agent that reacts slowly with potassium iodide, such as hydrogen peroxide or m-chloroperbenzoic acid, 3 drops (catalytic amount) of 3% by mass molybdic(VI) acid aqueous solution were added as a catalyst to accelerate the reaction. While stirring the resulting solution, 0.01 mol / L sodium thiosulfate aqueous solution was added dropwise until the solution turned pale yellow. Next, 10 drops of 1% by mass starch aqueous solution were added to color the solution by the iodine-starch reaction, and then 0.01 mol / L sodium thiosulfate aqueous solution was added dropwise until the solution became colorless. The concentration of the oxidizing agent was calculated from the amount of sodium thiosulfate added.
[0065] (Method for calculating the etching rate of SiGe) 100 mL of etching solution heated to 70°C was prepared, and a silicon substrate (manufactured by GlobalNet Co., Ltd.) with a silicon-germanium film (germanium content 25% by mass) epitaxially grown on a 2 cm x 1 cm silicon substrate was immersed in it for 10 minutes. The etching solution was stirred at 1200 rpm during etching. Etching rate of silicon-germanium (R SiGe The film thickness (nm / min) was calculated by measuring the film thickness of each substrate before and after etching using a spectroscopic ellipsometer, determining the amount of silicon-germanium etching from the difference in film thickness before and after treatment, and dividing by the etching time (10 minutes).
[0066] (Etching selectivity ratios of Si(100), SiO2, and SiN, and SiGe) Except for using a silicon-germanium (SiGe) substrate with silicon (Si) epitaxially grown on a 2cm x 1cm silicon-germanium (SiGe) substrate (silicon (100-plane) film, manufactured by GlobalNet Co., Ltd.), the etching rate of silicon (R') was calculated using the same method as described above for calculating the etching rate of SiGe. 100 The value (nm / min) was calculated. Furthermore, using a silicon substrate (manufactured by GlobalNet Co., Ltd.) on which a silicon oxide film was epitaxially grown on a 2cm x 1cm silicon substrate, and with an immersion time of 60 minutes, the etching rate of silicon oxide (R) was calculated in the same manner as the method for calculating the etching rate of SiGe described above. SiO2 The value (nm / min) was calculated. Furthermore, except for using a substrate (manufactured by GlobalNet Co., Ltd.) on which a silicon nitride film was epitaxially grown on a 2cm x 1cm silicon substrate, the etching rate of the silicon nitride (R) was calculated in the same manner as the above-mentioned method for calculating the etching rate of silicon oxide. SiN The value (nm / min) was calculated.
[0067] From these measurement results, the etching selectivity ratio (R) between silicon-germanium film and silicon (100), SiO2, and SiN can be determined. SiGe / R' 100、 R SiGe / R SiO2、 R SiGe / R SiN ) was sought.
[0068] The lower limit of measurement for film thickness change using the spectroscopic ellipsometer used is 0.01 nm. Therefore, the lower limit of the etching rate of the silicon-germanium film that can be determined by the above method is 0.001 nm / min.
[0069] <Example 1> (Method for preparing etching solution) As an organic alkali, an aqueous solution of tetramethylammonium hydroxide (TMAH) (2.73 mol / L) is diluted with ultrapure water and mixed until the chemical solution is homogeneous, and then as an oxidizing agent, An etching solution was prepared by adding hydrogen peroxide to achieve a TMAH concentration of 0.110 mol / L and an oxidizing agent (hydrogen peroxide) concentration of 0.073 mol / L. The solution was then heated at 70°C for 1 hour. The resulting etching solution had a pH of 12.64 at 24°C, and the hydroxide ion concentration calculated using the pH value was 0.044 mol / L. The ratio of the oxidizing agent concentration to the hydroxide ion concentration (oxidizing agent concentration / hydroxide concentration) was 1.7. The results are shown in Table 1. The etching rates of silicon and silicon-germanium were evaluated using the obtained etching solution. The evaluation results are shown in Table 2. During etching, nitrogen bubbling was performed with a nitrogen supply rate of 0.2 L / min. In this experimental example, the etching selectivity ratio (R) between the silicon-germanium film and the silicon(100) film was determined. SiGe / R' 100 The ratio was 5.1, and the silicon-germanium film could be selectively etched against the silicon(100) film.
[0070] <Examples 2-3> Etching solutions were prepared and evaluated in the same manner as in Example 1, except that the TMAH concentration and hydrogen peroxide concentration were changed as shown in Table 1. The evaluation results are shown in Table 2.
[0071] <Comparative Examples 1-3> Etching solutions were prepared and evaluated in the same manner as in Example 1, except that the TMAH concentration and hydrogen peroxide concentration were changed as shown in Table 1. The evaluation results are shown in Table 2. In Comparative Examples 1 to 3, the pH of the etching solution was 13.40 for Comparative Example 1, 13.36 for Comparative Example 2, and 13.30 for Comparative Example 3, respectively. In all comparative examples, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon(100) film was SiGe / R' 100 The value was less than 1.0, indicating that the silicon-germanium film could not be selectively etched against the silicon(100) film.
[0072] <Example 4> An etching solution was prepared in the same manner as in Example 1, except that the TMAH concentration and hydrogen peroxide concentration were changed as shown in Table 1. Furthermore, the etching solution was evaluated in the same manner as in Example 1, except that nitrogen bubbling was not performed during etching. The evaluation results are shown in Table 2. In Example 4, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon (100) film was SiGe / R' 100 The ratio was 4.1, and the silicon-germanium film could be selectively etched against the silicon(100) film.
[0073] <Example 5> An etching solution was prepared and evaluated in the same manner as in Example 4, except that hexanoic acid was added to the etching solution as additive-1 in the proportions shown in Table 1. In addition to silicon and silicon-germanium, the etching rates of silicon oxide films and silicon nitride films were also evaluated. The evaluation results are shown in Table 2. In Example 5, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon (100) film was SiGe / R' 100 ) is 4.0, and the etching selectivity ratio of the silicon-germanium film to the silicon oxide film (R SiGe / R SiO2 ) is 19, the etching selectivity ratio of silicon-germanium film to silicon nitride film (R SiGe / R SiN ) was 79, which was excellent.
[0074] <Example 6> An etching solution was prepared and evaluated in the same manner as in Example 4, except that 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dibromide (Additive-A) was added to the etching solution as Additive-1 in the proportions shown in Table 1. The evaluation results are shown in Table 2. In Example 6, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon (100) film was SiGe / R' 100The etching selectivity ratio (R) of the silicon-germanium film to the silicon oxide film was 7.3, which was even better than that of Example 5. SiGe / R SiO2 ) is 41, the etching selectivity ratio of silicon-germanium film to silicon nitride film (R SiGe / R SiN ) was 185, which was excellent.
[0075] <Examples 7-8> An etching solution was prepared and evaluated in the same manner as in Example 4, except that the additive listed in Table 1 was added as additive-1, and TMAF (tetramethylammonium fluoride), a fluorine-containing compound, was added as additive-2, in the proportions listed in Table 1. The evaluation results are shown in Table 2. In Example 7, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon (100) film was SiGe / R' 100 The etching selectivity ratio (R) of the silicon-germanium film to the silicon oxide film was 9.1, which was even better than that of Example 6. SiGe / R SiO2 ) is 56, the etching selectivity ratio of silicon-germanium film to silicon nitride film (R SiGe / R SiN The result was 134, which was excellent, similar to Experimental Example 6 where the etching solution did not contain fluoride ions. Furthermore, in Example 8, the etching selectivity ratio (R) of the silicon-germanium film relative to the silicon (100) film was SiGe / R' 100 The etching selectivity ratio (R) of the silicon-germanium film relative to the silicon oxide film was 7.9, which was even better than that of Example 5. SiGe / R SiO2 ) is 29, the etching selectivity ratio of silicon-germanium film to silicon nitride film (R SiGe / R SiN The value was 100, which was excellent, similar to Experimental Example 5 where the etching solution did not contain fluoride ions.
[0076] [Table 1] In the table, Additive-A represents 1,1'-(decane-1,10-diyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane]dibromide.
[0077] [Table 2]
Claims
1. An etching solution comprising an organic alkali, an oxidizing agent, and water, At 24°C, the pH of the etching solution is 10.00 or higher and 13.27 or lower, and At 24°C, the hydroxide ion concentration in the etching solution is 1.0 × 10⁻⁶ －４ mol / L or more 1.9×10 －１ An etching solution characterized by having a concentration of mol / L or less, for selectively removing silicon-germanium from silicon and silicon oxide, respectively.
2. The etching solution according to claim 1, wherein the ratio of the oxidizing agent concentration (mol / L) to the hydroxide ion concentration (mol / L) in the etching solution is 0.50 or more.
3. The etching solution according to claim 1 or 2, wherein the oxidizing agent is one or more selected from the group consisting of hydrogen peroxide, m-chloroperbenzoic acid, 9-azanoradamantan-N-oxyl, hypochlorite, and hypobromite.
4. The etching solution according to claim 1 or 2, further comprising a silicon etching inhibitor.
5. The silicon etching inhibitor is a halogen salt of quaternary ammonium, or BF of quaternary ammonium. ４ The etching solution according to claim 4, which is one or more selected from the group consisting of salts and carboxylic acid compounds.
6. The etching solution according to claim 4, wherein the silicon etching inhibitor is a compound having a dication structure.
7. The etching solution according to claim 1 or 2, wherein the organic alkali is a quaternary ammonium hydroxide.
8. A method for processing a substrate containing silicon, silicon oxide, and silicon-germanium, A method for processing a substrate, comprising an etching step of selectively etching silicon and silicon oxide with silicon-germanium using the etching solution described in claim 1 or 2.
9. The substrate further comprises silicon nitride, The substrate processing method according to claim 8, wherein the etching step is a step of selectively etching silicon-germanium with respect to silicon nitride.
10. A method for manufacturing a silicon device using a substrate containing silicon, silicon oxide, and silicon-germanium, A method for manufacturing a silicon device, comprising an etching step of selectively etching silicon and silicon oxide with silicon-germanium using the etching solution described in claim 1 or 2.
11. The substrate further comprises silicon nitride, The method for manufacturing a silicon device according to claim 10, wherein the etching step is a step of selectively etching silicon-germanium with respect to a silicon nitride.