Methods for removing particle contamination in trenches after wafer CMP

Abstract

This invention provides a method for removing particle contamination in trenches after CMP (Chemical Mechanical Polishing) of a wafer, comprising the following steps: S1, depositing a thin layer of silicon dioxide on the wafer surface; S2, etching the silicon dioxide outside the sidewalls of the wafer trench using a dry etching process followed by CMP treatment; S3, etching the silicon dioxide in the wafer trench using an acidic cleaning solution to loosen large particle contamination embedded in the trench; S4, cleaning the wafer using a first mixed cleaning solution; S5, cleaning the wafer using ultrasound; S6, removing small particles from the wafer using megasonic waves in conjunction with a second mixed cleaning solution. This invention solves the problem of difficult particle contamination removal from trench-structured wafers after CMP by depositing a thin layer of silicon dioxide before CMP, loosening particles in the trench by etching silicon dioxide after CMP, and combining ultrasound, megasonic waves, and cleaning solution cleaning.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for removing particle contamination in trenches after wafer CMP. Background Technology

[0002] In the semiconductor manufacturing industry, CMP (Chemical Mechanical Polishing) is a common processing technique used to planarize the wafer surface. It combines surface chemical action with mechanical polishing techniques to remove micron / nanoscale materials from the wafer surface, achieving nanometer-level planarization and enabling subsequent processes. Due to the diverse structures of chip designs, many wafer surfaces have trench structures before CMP. During CMP, under certain pressure, the wafer being polished moves relative to the polishing pad. The pressure during polishing generates relatively large particles that become embedded within the trenches. Because these particles are tightly embedded in the wafer trenches, subsequent conventional cleaning processes are difficult to remove them. Summary of the Invention

[0003] In view of the above problems, the purpose of this invention is to propose a method for removing particle contamination in trenches after wafer CMP. By depositing a thin layer of silicon dioxide before CMP, and then using etching of silicon dioxide after CMP to loosen the particles in the trenches, combined with ultrasonic and megasonic cleaning with cleaning fluid, this method solves the problem of difficult particle contamination removal generated after CMP processing of trench structure wafers. This improves the feasibility of using CMP for trench structure wafers in the semiconductor manufacturing industry and increases the feasibility of diverse chip structure designs.

[0004] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0005] This invention provides a method for removing particle contamination in trenches after wafer CMP, comprising the following steps:

[0006] S1. A thin layer of silicon dioxide is deposited on the wafer surface using a chemical vapor deposition method;

[0007] S2. After etching the silicon dioxide outside the inner trench sidewalls of the wafer using a dry etching process, CMP process is performed.

[0008] S3. After etching the silicon dioxide in the wafer trench with an acidic cleaning solution, the large particles of contaminant embedded in the trench become loose.

[0009] S4. Use the first mixed cleaning solution to clean the wafer to remove organic contaminants and metal contaminants;

[0010] S5. Use ultrasonic waves to clean the wafer, causing large particles of contaminant to detach from the wafer trenches.

[0011] S6. The wafer is cleaned again using megasonic waves and a second mixed cleaning solution to remove tiny particles from the wafer.

[0012] Preferably, the thickness of the silica thin layer is greater than 0.1 μm.

[0013] Preferably, the acidic cleaning solution is hydrofluoric acid; the concentration of hydrofluoric acid is 0.5% to 2%.

[0014] Preferably, the first mixed cleaning solution includes sulfuric acid and hydrogen peroxide, with the ratio of sulfuric acid to hydrogen peroxide being 5:1 to 20:1, and the cleaning temperature being 100℃ to 130℃.

[0015] Preferably, the second mixed cleaning solution includes ammonia, hydrogen peroxide, and water, with the ratio of ammonia, hydrogen peroxide, and water being 1:4:20 to 1:2:7; and the cleaning temperature being 50℃ to 70℃.

[0016] Preferably, after the wafer is cleaned with hydrogen peroxide, a natural oxide film is formed on the wafer surface; when the natural oxide film is corroded by ammonia, the tiny particles attached to the wafer surface begin to detach and fall into the cleaning solution.

[0017] Preferably, the microparticles are particles with a diameter of less than 0.1 micrometers.

[0018] Preferably, CF4, CHF3, or C4F8 gases are used to anisotropically etch the silicon dioxide thin layer on the wafer surface.

[0019] Compared with existing technologies, this invention solves the problem of difficult removal of contaminants embedded in trenches after CMP processing by sequentially cleaning the wafer with ultrasonic waves and mixed cleaning fluid. This improves the feasibility of using CMP process on trench structure wafers in the semiconductor manufacturing industry and increases the feasibility of diverse chip structure designs. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for removing particle contamination in trenches after wafer CMP according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the wafer cross-sectional structure of a method for removing particle contamination in trenches after wafer CMP provided in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the cross-sectional structure of the wafer surface after silicon dioxide deposition, according to the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the wafer cross-sectional structure after etching silicon dioxide (excluding the trench sidewalls) using a dry etching process according to an embodiment of the present invention, which is a method for removing particle contamination in the trench after wafer CMP.

[0024] Figure 5 This is a schematic cross-sectional view of the large particle contamination in the wafer trench of the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention.

[0025] Figure 6 This is a top view of the wafer trench containing large particle contamination, according to the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram of the cross-sectional structure of the wafer trench after hydrofluoric acid etching, based on the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention.

[0027] Figure 8 This is a schematic diagram of the cross-sectional structure of the wafer trench after ultrasonic cleaning, based on the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention. Detailed Implementation

[0028] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0030] Figure 1 A schematic flowchart of a method for removing particle contamination in trenches after wafer CMP according to an embodiment of the present invention is shown.

[0031] like Figure 1 As shown, the method for removing particle contamination in the trench after wafer CMP provided in this embodiment of the invention includes the following steps:

[0032] Figure 2 The wafer cross-sectional structure of the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention is shown.

[0033] Figure 3 The cross-sectional structure of the wafer surface after silicon dioxide deposition is shown in the method for removing particle contamination in trenches after wafer CMP provided in an embodiment of the present invention.

[0034] Figure 4 The diagram illustrates a cross-sectional structure of a wafer after etching silicon dioxide (excluding the trench sidewalls) using a dry etching process, according to an embodiment of the present invention, for a method of removing particle contamination in trenches after wafer CMP.

[0035] Figure 5 The cross-sectional structure of large particle contamination in the wafer trench is shown in the method for removing particle contamination in the trench after wafer CMP provided according to an embodiment of the present invention.

[0036] Figure 6 A top view of a wafer trench showing a method for removing particle contamination in a wafer post-CMP trench according to an embodiment of the present invention is shown.

[0037] like Figure 2-6 As shown, the wafer has several trench structures. When the wafer is subjected to CMP treatment, many contaminant particles will adhere to the inside of the trenches.

[0038] S1. A thin layer of silicon dioxide is deposited on the wafer surface using a chemical vapor deposition method;

[0039] S2. After etching the silicon dioxide outside the sidewalls of the wafer trench using a dry etching process, CMP process is performed.

[0040] The thickness of the silicon dioxide is greater than 0.1 μm.

[0041] Anisotropic etching of silicon dioxide on the wafer surface is performed using gases such as CF4 / CHF3 / C4F8.

[0042] S3. After etching the silicon dioxide in the wafer trench with an acidic cleaning solution, the large particles of contaminant embedded in the trench become loose.

[0043] The acidic cleaning solution is hydrofluoric acid. The concentration of hydrofluoric acid is 0.5% to 2%.

[0044] Figure 7 The cross-sectional structure of the wafer trench after hydrofluoric acid etching is shown in the method for removing particle contamination in the trench after wafer CMP provided in an embodiment of the present invention.

[0045] like Figure 7 As shown, after using hydrofluoric acid to etch the thin layer of silicon dioxide in the wafer trench, the large particles inside the trench begin to "loosen".

[0046] S4. Use the first mixed cleaning solution to clean the wafer and remove organic contaminants and metal contaminants.

[0047] The first mixed cleaning solution consists of sulfuric acid and hydrogen peroxide. The ratio of sulfuric acid to hydrogen peroxide is 5:1 to 20:1, and the cleaning temperature is 100℃ to 130℃. The purpose of this step is to remove organic contaminants and some metal contaminants from the wafer surface.

[0048] S5. Use ultrasonic waves to clean the wafer, causing large particles of contaminant to detach from the wafer trenches.

[0049] Figure 8 The cross-sectional structure of the wafer trench after ultrasonic cleaning is shown, illustrating the method for removing particle contamination in the trench after wafer CMP according to an embodiment of the present invention.

[0050] like Figure 8 As shown, large particles of contaminant in the trenches have been removed after ultrasonic rinsing. Ultrasonic waves rely on an elastic medium for propagation. During propagation, particles within the elastic medium vibrate, and energy is transferred through the medium in the direction of propagation. This ultrasonic energy can effectively clean large particles of contaminant from the wafer trenches after hydrofluoric acid etching.

[0051] S6. The wafer is cleaned again using megasonic waves and a second mixed cleaning solution to remove tiny particles from the wafer.

[0052] The second mixed cleaning solution includes ammonia, hydrogen peroxide, and water. The ratio of ammonia, hydrogen peroxide, and water is between 1:4:20 and 1:2:7; the cleaning temperature is between 50℃ and 70℃.

[0053] Due to the action of hydrogen peroxide, a natural oxide film forms on the wafer surface, which is hydrophilic. The wafer surface and the tiny particles can be penetrated by the second mixed cleaning solution. Because the natural oxide layer on the wafer surface is corroded by ammonia, the tiny particles attached to the silicon dioxide thin layer fall into the cleaning solution, thereby achieving the purpose of removing the tiny particles.

[0054] The use of mega-sonic waves enhances the removal of microparticles in this step. The principle is that the silicon wafer is cleaned by the high-energy frequency vibration effect combined with the chemical reaction of the second mixed cleaning solution. During cleaning, a transducer emits high-energy sound waves with wavelengths in the megahertz range. Driven by these sound waves, solution molecules accelerate, and the high-speed hydrodynamic layer generated by the strong sound pressure gradient and acoustic flow continuously impacts the wafer surface, forcibly removing particles adhering to the wafer surface and drawing them into the cleaning solution. Mega-sonic cleaning can remove particles smaller than 0.1 micrometers from the wafer surface.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that these embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention. The specific embodiments described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for removing particle contamination from trenches after wafer CMP, characterized in that, Includes the following steps: S1. A thin layer of silicon dioxide is deposited on the wafer surface using a chemical vapor deposition method; S2. After etching the silicon dioxide outside the inner trench sidewall of the wafer using a dry etching process, CMP process is performed. S3. After etching the silicon dioxide in the wafer trench with an acidic cleaning solution, the large particles of contaminant embedded in the trench become loose. S4. The wafer is cleaned using the first mixed cleaning solution to remove organic contaminants and metal contaminants; S5. Use ultrasonic waves to clean the wafer, causing the large particles of contaminant to detach from the inside of the wafer trench. S6. The wafer is cleaned again using megasonic waves and a second mixed cleaning solution to remove tiny particles from the wafer.

2. The method for removing particle contamination in the trench after wafer CMP according to claim 1, characterized in that, The thickness of the silicon dioxide thin layer is greater than 0.1 μm.

3. The method for removing particle contamination in the trench after wafer CMP according to claim 2, characterized in that, The acidic cleaning solution is hydrofluoric acid; the concentration of the hydrofluoric acid is 0.5%~2%.

4. The method for removing particle contamination in the trench after wafer CMP according to claim 3, characterized in that, The first mixed cleaning solution includes sulfuric acid and hydrogen peroxide, wherein the ratio of sulfuric acid to hydrogen peroxide is 5:1 to 20:1, and the cleaning temperature is 100℃ to 130℃.

5. The method for removing particle contamination in the trench after wafer CMP according to claim 4, characterized in that, The second mixed cleaning solution includes ammonia, hydrogen peroxide, and water, with the ratio of ammonia, hydrogen peroxide, and water being 1:4:20 to 1:2:7; the cleaning temperature is 50℃ to 70℃.

6. The method for removing particle contamination in the trench after wafer CMP according to claim 5, characterized in that, After the wafer is cleaned with hydrogen peroxide, a natural oxide film is formed on the surface of the wafer. When the natural oxide film is corroded by the ammonia water, the tiny particles attached to the surface of the wafer begin to detach and fall into the cleaning solution.

7. The method for removing particle contamination in the trench after wafer CMP according to claim 6, characterized in that, The microparticles are particles with a diameter of less than 0.1 micrometers.

8. The method for removing particle contamination in the trench after wafer CMP according to claim 6, characterized in that, use , or The gas anisotropically etches the silicon dioxide thin layer on the surface of the wafer.

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