Cleaning solution for low-stress silicon nitride and cleaning method for low-stress silicon nitride furnace tube component

Abstract

The invention provides a cleaning solution for low-stress silicon nitride, the cleaning solution comprises nitric acid, hydrofluoric acid and water, the volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%; the invention further provides application of the cleaning solution to cleaning of a low-stress silicon nitride film. The invention further provides a cleaning method of the low-stress silicon nitride furnace tube component, the cleaning method comprises the steps that the component to be cleaned is soaked in the cleaning liquid for cleaning, the cleaning liquid comprises nitric acid, hydrofluoric acid and water, the volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%. According to the cleaning solution, the etching rate of a low-stress silicon nitride film can be remarkably increased, and the cleaning time of a low-stress silicon nitride furnace tube component is effectively shortened.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a cleaning liquid for low-stress silicon nitride and a cleaning method for low-stress silicon nitride furnace tube components. Background Art

[0002] Silicon nitride films are widely used in semiconductor wafer manufacturing processes. However, ordinary silicon nitride films have large stress, which may affect the performance of the device. With the research and application of low-stress silicon nitride processes, more uniform and low-stress silicon nitride films can be obtained. Low-stress silicon nitride can reduce the bending and deformation of devices and improve the mechanical properties and reliability of devices.

[0003] LPCVD (low pressure chemical vapor deposition) silicon nitride furnace tube is a common device for preparing low stress silicon nitride film. When low stress silicon nitride is deposited, a layer of low stress silicon nitride film will inevitably be formed on the internal parts of the furnace tube. After the equipment has been used for a certain period of time, it is necessary to carry out maintenance (Prevention Maintenance, PM) for process stability. Due to the high cost of the components of the LPCVD silicon nitride furnace tube, the deposits on the surface of the components need to be cleaned and recycled each time. However, due to the particularity of the low stress silicon nitride process conditions, a small amount of single crystal silicon film is generated in the film layer on the surface of the component in addition to the original silicon nitride film. The existing cleaning method has extremely low cleaning efficiency for this kind of deposit, resulting in a small amount of single crystal silicon film remaining after the low stress silicon nitride film on the surface of the component is cleaned, and the cleaning time is seriously prolonged, which greatly affects the recovery time of the equipment.

[0004] Therefore, it is necessary to provide a new cleaning method to speed up the cleaning speed of low stress silicon nitride furnace tube components and improve efficiency. Summary of the invention

[0005] The present invention aims to solve all or part of the problems of the above-mentioned prior art. In a first aspect, the present invention provides a cleaning solution for low-stress silicon nitride, wherein the cleaning solution comprises nitric acid, hydrofluoric acid and water, wherein the volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%. Compared with the commonly used DHF solution, the cleaning solution provided by the present invention has a significantly increased etching rate for low-stress silicon nitride.

[0006] The cleaning solution comprises nitric acid, hydrofluoric acid with a mass concentration of 49% and water, and the volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1: (2-7): (2-7).

[0007] The volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1:7:7. Compared with the commonly used DHF solution, the cleaning solution with this ratio significantly increases the etching rate of low-stress silicon nitride, which can reach more than 4 times.

[0008] In a second aspect, the present invention further provides a use of a cleaning liquid for low stress silicon nitride according to the first aspect in cleaning a low stress silicon nitride film.

[0009] In a third aspect, the present invention also provides a method for cleaning low-stress silicon nitride furnace tube components, comprising: immersing the components to be cleaned in a cleaning liquid for cleaning, wherein the cleaning liquid comprises nitric acid, hydrofluoric acid and water, the volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%.

[0010] The cleaning solution comprises nitric acid, hydrofluoric acid with a mass concentration of 49% and water, and the volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1: (2-7): (2-7).

[0011] The volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1:7:7. Compared with the commonly used DHF solution, the cleaning solution with this ratio significantly increases the etching rate of low-stress silicon nitride, which can reach more than 4 times.

[0012] The cleaning process is divided into multiple times and the residual cleaning liquid is removed with deionized water after each cleaning, which can effectively avoid possible damage to the furnace tube components by the cleaning liquid and acid residue on the furnace tube components.

[0013] Compared with the prior art, the beneficial effects of the present invention mainly include the following: providing a new cleaning liquid and a cleaning method for low-stress silicon nitride furnace tube components, which can significantly improve the etching rate of low-stress silicon nitride film and shorten the cleaning time of low-stress silicon nitride furnace tube components. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 The present invention provides a prior art method for cleaning the residues of deposits. DETAILED DESCRIPTION

[0016] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0017] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0018] The low stress silicon nitride process is an important process in the semiconductor wafer manufacturing process, and is usually prepared by low pressure chemical vapor deposition (LPCVD). Deposition under low pressure conditions can obtain a more uniform and low stress silicon nitride film, which is usually used in the preparation of integrated circuits and MEMS devices. Due to the particularity of the low stress silicon nitride process conditions, the deposited film layer contains a small amount of single crystal silicon film in addition to the silicon nitride film. During PM, in order to remove the low stress silicon nitride film layer deposited on the LPCVD silicon nitride furnace tube components (mainly the inner and outer tubes, crystal boats and bases, etc.), the commonly used cleaning method is to use a DHF solution with a mass concentration of 49% hydrofluoric acid (HF) and water in a 1:1 ratio. The cleaning rate of this method for conventional silicon nitride films is about 5-10nm / min, and a single cleaning takes 12 hours to clean; however, its cleaning rate for low stress silicon nitride films is only 1-2nm / min. Taking a single cleaning of 12 hours as an example, there are still deposits left after cleaning, such as Figure 1 As shown, it usually takes 4-5 times of cleaning to be completely clean, which greatly increases the cleaning time, leads to low PM efficiency, and greatly affects the recovery time of the equipment.

[0019] Due to the particularity of the low stress silicon nitride process conditions, the film layer deposited on the furnace tube components is not a pure silicon nitride material, but is mixed with single crystal silicon in the film layer. Therefore, when the above-mentioned DHF solution is used, the hydrofluoric acid therein has a higher etching rate for silicon nitride materials but a lower etching rate for single crystal silicon. When the cleaning solution etches away the silicon nitride material and contacts the single crystal silicon mixed therein, its etching rate is lower. The single crystal silicon is equivalent to the protective layer of the silicon nitride below it. Only when the single crystal silicon is etched away can the subsequent silicon nitride be etched, thereby greatly reducing the etching rate.

[0020] Based on the above research, we found that the key to improving the etching rate of low-stress silicon nitride film is to increase the etching rate of the cleaning solution for single-crystal silicon. To this end, we added nitric acid (HNO3) to the original solution base, and used the strong oxidizing property of nitric acid to oxidize the single-crystal silicon film on the surface of the furnace tube components to generate silicon dioxide (SiO2), and then the hydrofluoric acid in the solution reacted with it, thereby achieving the purpose of improving the cleaning efficiency.

[0021] Embodiment 1:

[0022] The present invention provides a cleaning solution for low-stress silicon nitride, the cleaning solution comprising nitric acid (HNO3), hydrofluoric acid (HF) and water (H2O); wherein the hydrofluoric acid (HF) is HF with a concentration (mass concentration) of 49%. In this embodiment, the specific ratio is HNO3:49% HF:H2O ratio (volume ratio) of 1:7:7. When the cleaning solution with this ratio is used to clean the low-stress silicon nitride film under the same conditions, the etching rate is 4-8nm / min, which is more than 4 times the efficiency of the DHF solution (rate of about 1-2nm / min) in the prior art.

[0023] It should be noted that, in this embodiment, HF with a mass concentration of 49% is used, but the present application does not limit the concentrations of the nitric acid and hydrofluoric acid used. The actual ratio can be converted according to the volume ratio of the three components in the cleaning solution. For example, HF with a mass concentration of 49% is converted to a volume ratio of about 54%, that is, the ratio (volume ratio) of HNO3:HF:H2O in this embodiment is about 1:3.78:10.22, that is, HNO3 accounts for about 6.67% by volume, HF accounts for about 25.2%, and the remainder is H2O.

[0024] This embodiment also provides an application of the above-mentioned cleaning solution for low-stress silicon nitride in cleaning a low-stress silicon nitride film.

[0025] This embodiment also provides a method for cleaning low-stress silicon nitride furnace tube components, immersing the furnace tube components to be cleaned in a cleaning solution, and the cleaning process is divided into two alternating processes of cleaning with the cleaning solution and rinsing with deionized water. The cleaning process with the cleaning solution includes at least one time, and the cleaning time can be set according to the needs. After each cleaning with the cleaning solution, a long-term rinsing treatment with deionized water is performed to ensure that there is no residue of the cleaning solution on the surface of the component. The cleaning process with the cleaning solution and the rinsing with deionized water can be repeated multiple times until the deposits on the surface of the component are completely removed.

[0026] In this embodiment, the volume ratio of HNO3:49% HF:H2O in the cleaning liquid is 1:7:7. First, the furnace tube components are cleaned with the cleaning liquid, and the cleaning time is 8 hours at a time; then, the residual cleaning liquid on the furnace tube components is rinsed clean with deionized water; then, the furnace tube components are cleaned with the cleaning liquid again, and the cleaning time is 8 hours. Then, the furnace tube components are taken out and the residual cleaning liquid is rinsed clean with deionized water. In this embodiment, after changing the cleaning liquid, the furnace tube components are cleaned for 8 hours at a time, and can be cleaned twice. Compared with the prior art, this technology can reduce the cleaning time of the furnace tube components by about 32 hours, greatly shorten the PM time of the equipment, and speed up the recovery speed of the equipment.

[0027] In the present embodiment, the cleaning of the furnace tube components is divided into multiple times, considering the possible erosion of the rest of the furnace tube components (referring to the area outside the low stress silicon nitride film layer) by the cleaning liquid. Although the cleaning liquid provided in the present embodiment has good etching selectivity and the etching rate of the furnace tube components is extremely low, there may still be certain damage due to long-term contact, and the cleaning liquid may also remain in some gaps, volatilize when the furnace tube is heated and used, and cause corrosion to the equipment. Therefore, in order to reduce the possible related adverse effects, the cleaning process of the furnace tube components is divided into multiple times, and the duration of each cleaning is generally not more than 12 hours, and deionized water is used to rinse in time after each cleaning liquid cleaning. In other embodiments, the number of cleaning liquid cleanings and the time of a single cleaning liquid cleaning can be reasonably allocated according to the thickness of the film layer on the furnace tube components.

[0028] Embodiment 2:

[0029] The content of the second embodiment is basically the same as that of the first embodiment, except for the specific ratio of the cleaning solution. This embodiment provides a cleaning solution for low stress silicon nitride, which includes nitric acid (HNO3), hydrofluoric acid (HF) and water (H2O); wherein the hydrofluoric acid (HF) is HF with a mass concentration of 49%. In this embodiment, the specific ratio is HNO3:49% HF:H2O, and the volume ratio is 2:6:7. The mass concentration of HF is about 54% by volume, that is, the volume ratio of HNO3:HF:H2O in this embodiment is about 1:1.62:4.88, that is, HNO3 accounts for about 13.3% by volume, HF accounts for about 21.5%, and the remainder is H2O. The cleaning solution using this ratio has an etching rate of about 3-6nm / min for low stress silicon nitride film under the same conditions, which is significantly improved compared with the efficiency of the DHF solution (rate of about 1-2nm / min) of the prior art.

[0030] Embodiment three:

[0031] The content of Example 3 is basically the same as that of Example 1, except for the specific ratio of the cleaning solution. This embodiment provides a cleaning solution for low-stress silicon nitride, the cleaning solution comprising nitric acid (HNO3), hydrofluoric acid (HF) and water (H2O); wherein the hydrofluoric acid (HF) is HF with a mass concentration of 49%. In this embodiment, the specific ratio is HNO3:49% HF:H2O, and the volume ratio is 1:2:2. The mass concentration of 49% HF is converted to a volume ratio of approximately 54%, that is, the volume ratio of HNO3:HF:H2O in this embodiment is 1:1.08:

[0032] 2.92, that is, HNO3 accounts for about 20% by volume, HF accounts for about 21.6% by volume, and the balance is H2O. The cleaning solution using this ratio has an etching rate of about 4-7nm / min for low-stress silicon nitride film under the same conditions, which is significantly higher than the efficiency of the DHF solution (rate of about 1-2nm / min) in the prior art. However, due to the high acid concentration in this ratio, it may cause certain corrosion to the equipment components, resulting in a shortened component life, so the balance between the etching rate and the component life should be considered.

[0033] It should be noted that, generally speaking, as the proportion of HNO3 in the cleaning solution increases and the proportion of HF decreases, the etching ability of the cleaning solution for single crystal silicon increases; however, considering that the amount of single crystal silicon film generated in the low stress silicon nitride film layer is small and the amount of silicon nitride film is relatively large, as the HNO3 content in the cleaning solution increases, it may cause excessive HNO3 and cannot be completely consumed, resulting in waste; excessive HNO3 content and low HF proportion will also reduce the etching rate of HF on silicon nitride and silicon dioxide films, and the cleaning efficiency will decrease. In addition, as the total proportion of the two acids in the cleaning solution increases, the etching rate will increase, but it will also increase the possibility of corrosion to equipment components and reduce the service life of the components. Therefore, it is necessary to make comprehensive considerations and appropriately control the proportion of HNO3 and HF in the cleaning solution. Normally, the volume ratio of nitric acid in the cleaning solution is between 5% and 20%, and the volume ratio of hydrofluoric acid is between 20% and 26%.

[0034] In order to facilitate the description, some common English nouns or letters used in the present invention are only used for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0035] It should also be noted that, in this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

Claims

1. A cleaning solution for low stress silicon nitride, characterized in that: The cleaning solution comprises nitric acid, hydrofluoric acid and water, the volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%.

2. A cleaning solution for low stress silicon nitride according to claim 1, characterized in that: The cleaning solution comprises nitric acid, hydrofluoric acid with a mass concentration of 49% and water, and the volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1: (2-7): (2-7).

3. A cleaning solution for low stress silicon nitride according to claim 2, characterized in that: The volume ratio of the nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1:7:

7.

4. Use of the cleaning solution for low stress silicon nitride according to any one of claims 1 to 3 in cleaning low stress silicon nitride films.

5. A method for cleaning low stress silicon nitride furnace tube components, characterized in that: include: The parts to be cleaned are immersed in a cleaning solution for cleaning. The cleaning solution comprises nitric acid, hydrofluoric acid and water. The volume ratio of the nitric acid is 5%-20%, and the volume ratio of the hydrofluoric acid is 20%-26%.

6. A method for cleaning low stress silicon nitride furnace tube components according to claim 5, characterized in that: The cleaning solution comprises nitric acid, hydrofluoric acid with a mass concentration of 49% and water, and the volume ratio of nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1: (2-7): (2-7).

7. A method for cleaning low stress silicon nitride furnace tube components according to claim 6, characterized in that: The volume ratio of the nitric acid: hydrofluoric acid with a mass concentration of 49%: water is 1:7:

7.

8. The method for cleaning low stress silicon nitride furnace tube components according to claim 5, characterized in that: It also includes deionized water rinsing, the cleaning solution cleaning and the deionized water rinsing are performed alternately, and the cleaning solution cleaning process includes at least one time.

9. A method for cleaning low stress silicon nitride furnace tube components according to claim 8, characterized in that: The cleaning time of each cleaning solution shall not exceed 12 hours.

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