Analysis Method of Silicon Concentration in Phosphoric Acid Solution

Abstract

The present invention relates to a method for analyzing silicon concentration by using silicon solubility in a phosphoric acid solution in order to analyze the silicon concentration generated in a process of etching silicon nitride. The silicon concentration analysis method of the present invention has the effect of being able to analyze not only the silicon concentration generated in the phosphoric acid process of etching silicon nitride, but also the concentration of a silicon compound added to increase the selectivity of silicon nitride and silicon oxide.

Description

Technical Field

[0001] The present invention relates to a method for analyzing the concentration of silicon in a phosphoric acid solution, and more particularly, to a method for analyzing the concentration of silicon in a phosphoric acid solution used for etching silicon nitride (Si3N4). Background Art

[0002] The present invention relates to a method for analyzing the silicon concentration in a phosphoric acid solution used for etching silicon nitride (Si3N4).

[0003] Conventionally, only phosphoric acid solution was used to etch the silicon nitride, so the concentration of silicon in the solution was not important. However, as the 3D NAND process progresses, the selectivity of silicon nitride and silicon oxide (SiO2) becomes important.

[0004] Since the selectivity of silicon nitride and silicon oxide is affected by the concentration of silicon in the solution, the silicon concentration becomes very important. By measuring and analyzing the silicon concentration, not only can the selectivity be determined, but also the point at which silicon oxide is not etched can be known, so it is more important.

[0005] As a method for analyzing the silicon concentration in a pure phosphoric acid solution, US Pat. No. 7,351,349, European Patent No. 1,724,824 A2, and US Pat. No. 8,008,087 disclose a method utilizing fluorine concentration.

[0006] However, this method is suitable only as an analysis method for a phosphoric acid solution which does not require a selective ratio of silicon nitride to silicon oxide.

[0007] In contrast, in the 3D NAND process, in order to increase the selectivity of silicon nitride and silicon oxide, a silicon compound that can exist in a solution state in phosphoric acid is added and used. However, the above analysis method cannot distinguish between the silicon compound that exists in a dissolved state in phosphoric acid and the silicon concentration generated by etching silicon nitride.

[0008] Furthermore, the amount of silicon added to increase the selectivity is very large compared to the concentration of silicon generated by etching, so the reliability of analyzing the concentration of silicon generated by etching becomes very low.

[0009] As a prior art document, there is European Patent 1724824A2. Summary of the invention

[0010] Problem to be solved

[0011] The present invention relates to a method for increasing the selectivity ratio of silicon nitride (Si3N4) and silicon oxide (SiO2) by analyzing the concentration of silicon generated after etching in a phosphoric acid solution containing a silicon compound.

[0012] In addition, the present invention also relates to a method for analyzing the concentration of silicon generated after etching silicon nitride using pure phosphoric acid.

[0013] Solutions to the problem

[0014] In order to solve the above-mentioned problems, the present invention provides a silicon concentration analysis method, which includes: diluting a pure phosphoric acid solution for etching silicon nitride and phosphoric acid to which a silicon compound is added in order to increase the selectivity in a solvent respectively, cooling the solution at a temperature in the range of 1 to 35°C to precipitate only the silicon compound generated in the silicon nitride etching process; analyzing the precipitate with a particle analyzer or dissolving the precipitate with hydrofluoric acid to analyze the silicon concentration generated in the silicon nitride etching process.

[0015] Conventionally, only phosphoric acid solution was used to etch the silicon nitride, so the concentration of silicon in the solution was not important. However, as the 3D NAND process progresses, the selectivity of silicon nitride and silicon oxide (SiO2) becomes important.

[0016] Since the selectivity of silicon nitride and silicon oxide is affected by the concentration of silicon in the solution, the silicon concentration becomes very important. By measuring and analyzing the silicon concentration, not only can the selectivity be determined, but also the point at which silicon oxide is not etched can be known, so it is more important.

[0017] Effects of the Invention

[0018] The silicon concentration analysis method of the present invention has the effect of not only being able to analyze the silicon concentration generated in the phosphoric acid process of etching silicon nitride, but also optionally providing a method for analyzing the concentration of silicon compounds added to increase the selectivity of silicon nitride and silicon oxide.

[0019] Best Mode for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail.

[0021] The present invention relates to a method for analyzing silicon concentration in a phosphoric acid solution, which is specifically described using an embodiment.

[0022] The embodiments are merely illustrative with specific numerical values ​​to help understand the present invention. The specific numerical values ​​shown for illustration are numerical values ​​required for illustration within the critical technical scope of the present invention and are not to be construed as limiting the technical scope of the present invention.

[0023] Table 1 below shows silicon concentration values ​​according to temperature in the present invention.

[0024]

Table 1

[0025] Temperature(℃) Si concentration (ppm) 25 50 50 60 70 70 100 90 150 120

[0026] As shown in the silicon solubility graph in Table 1, with respect to silicon generated in the process of etching silicon nitride, only a predetermined amount of silicon is dissolved at a certain temperature in a phosphoric acid solution.

[0027] The supersaturated silicon compound precipitates as particles, which can be analyzed using a particle analyzer.

[0028] In the process of etching silicon nitride, when the temperature of the phosphoric acid solution is lowered to analyze the silicon concentration and silicon particles are analyzed, silicon particles remain on the wall of the vessel where the phosphoric acid flows, and the correct silicon concentration cannot be analyzed.

[0029] In order to solve these problems, the phosphoric acid solution is diluted with a solvent so that the precipitated particles can be well dispersed in the solvent. Since the dilution ratio of the solvent may vary with the sensitivity of the particle analyzer, the present invention does not limit the dilution ratio, but it can be confirmed that the solvent is preferably 50 to 100 parts by weight relative to 100 parts by weight of the phosphoric acid solution.

[0030] In order to improve the selective etching ratio of silicon nitride and silicon oxide, for a phosphoric acid solution containing a silicon compound stably dissolved in a phosphoric acid solution, even if the temperature is lowered after etching silicon nitride, the silicon compound stably dissolved in phosphoric acid will not precipitate, and only the silicon generated in the process will precipitate. Therefore, regardless of the concentration of the silicon compound added to improve the selectivity of silicon nitride and silicon oxide (SiO2), only the concentration of silicon generated in the process is analyzed.

[0031] In addition, if necessary, when confirming the concentration of the silicon compound added to increase the selectivity of silicon nitride and silicon oxide (SiO2), the concentration can also be analyzed using the method of the present invention. When diluting the phosphoric acid solution to which the stably existing silicon compound is added in order to increase the selectivity of the silicon nitride and silicon oxide (SiO2), distilled water is added to the solvent to dilute the phosphoric acid solution for use. When distilled water is added to the solvent, preferably, 50 to 100 parts by weight of distilled water are mixed with 100 parts by weight of the solvent.

[0032] In addition, as a method for analyzing the concentration of the precipitated silicon compound, the precipitated silicon compound can be dissolved in a fluorine-containing compound for analysis. At this time, when the silicon compound is dissolved in the fluorine compound solution, preferably, 50 to 100 parts by weight of the silicon compound are mixed relative to 100 parts by weight of the fluorine compound solution.

[0033] The silicon compound that is stably present in the phosphoric acid solution will precipitate when it comes into contact with distilled water, and therefore can be analyzed by the same method as above.

[0034] After etching the silicon nitride wafer with phosphoric acid solution, ICP-OES was used to determine the exact silicon concentration.

[0035] At 20-180°C, use phosphoric acid solution to 1000-5000 angstroms A 300 mm wafer with a thickness of 1 / 2 deposited with silicon nitride was etched. At this time, the silicon concentration measured by ICP-OES was 50 to 150 ppm. The phosphoric acid solution was diluted with ethanol at a ratio of 1:0.5 to 1, and the silicon concentration measured by ICP-OES was measured at a temperature of 20 to 30°C. The silicon etched in the phosphoric acid solution was precipitated and was not shown in the result measured after dilution with ethanol.

[0036] As shown in Table 1, the silicon concentration of the phosphoric acid solution for etching silicon nitride at different temperatures was measured. The results showed that the silicon concentration was 50 ppm at 25°C, 60 ppm at 50°C, 70 ppm at 70°C, 90 ppm at 100°C, and 120 ppm at 150°C.

[0037] In the same way as above, phosphoric acid solution for etching silicon nitride at concentrations of 0ppm, 50ppm, 100ppm, 150ppm, and 200ppm was diluted with ethanol at a ratio of 50:0.5 to 30, and then a liquid particle counter (LPC) was used to measure LPC of 0.5μm in size. The LPC used was RION's KE-40. DETAILED DESCRIPTION

[0038] [Example]

[0039] After etching the silicon nitride wafer with phosphoric acid solution, ICP-OES was used to determine the exact silicon concentration.

[0040] At 160°C, 4000 angstroms of A 1 / 2 sheet of a 300 mm wafer with silicon nitride deposited thereon was etched. At this time, the silicon concentration measured by ICP-OES was 100 ppm, and the phosphoric acid solution was diluted with ethanol at a ratio of 1:1, and the silicon concentration measured by ICP-OES at 25°C was 25 ppm. The 50 ppm of silicon etched in the phosphoric acid solution was precipitated, but was not shown in the result measured after dilution with ethanol.

Claims

1. An analysis method for analyzing only the concentration of silicon generated by etching silicon nitride, wherein the concentration of silicon generated by etching is analyzed in a process of etching using a phosphoric acid solution containing a silicon compound to increase the selectivity ratio between silicon nitride and silicon oxide, wherein the concentration of silicon generated by etching is distinguished from the concentration of the silicon compound in the phosphoric acid solution, As a method utilizing the solubility of silicon contained in a phosphoric acid solution at a temperature of 20 to 180° C., the method is as follows: The phosphoric acid solution is diluted with a solvent, wherein the solvent is 33.3 to 50% by weight of ethanol, and the phosphoric acid solution and ethanol are diluted in a ratio of 1:0.5 to 1. Cooling the phosphoric acid solution to a temperature of 1 to 35° C. to precipitate silicon; 100 parts by weight of a fluorine compound solution was mixed and dissolved in 50 to 100 parts by weight of the precipitated silicon compound particles, and the mixture was analyzed.