A silicon dioxide deposition process for a vertical LPCVD apparatus

Abstract

The application discloses a silicon dioxide deposition coating process of a vertical LPCVD device, and comprises the following steps: S1, checking whether the process pipe leaks; S2, blowing the process pipe with nitrogen gas under low pressure; S3, after the leakage rate detection is qualified, nitrogen gas is blown into the gas path pipeline, so that the pressure and the gas flow of the process pipe are stabilized under the pressure and the gas flow conditions set during film deposition; S4, under the set pressure condition, a reaction gas source is introduced, and a silicon dioxide film is deposited on the surface of a semiconductor substrate; and S5, after the silicon dioxide film deposition is completed, nitrogen gas is blown into the process pipe and the exhaust pipeline, nitrogen gas is introduced to increase the pressure to normal pressure, and the boat is discharged. The application has the advantages of simple operation, good stability, high film uniformity and the like, solves the problems of poor film thickness uniformity, high process granularity, poor repeat stability and extremely harsh requirements on process pressure of the existing LPCVD when depositing a SiO2 film, and realizes high-quality wafer coating.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing technology, specifically relating to a silicon dioxide (SiO2) coating process for a vertical LPCVD equipment. Background Technology

[0002] There are four main methods for forming silicon dioxide layers in semiconductor processes: thermal oxidation, plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD), and low-pressure chemical vapor deposition (LPCVD). Thermal oxidation relies on silicon atoms provided by the wafer to form silicon dioxide through high-temperature thermal growth, but it requires a high-temperature environment, and the film thickness and deposition rate are significantly limited. PECVD has a low process temperature, typically around 400°C, making it suitable for processing high-temperature volatile compound semiconductor materials such as GaAs and GaN. However, the dielectric film is porous, and its resistance to high temperatures and contamination is lower than that of LPCVD. APCVD requires a large gas flow rate and generates a relatively large number of particles during the process; therefore, it is rarely used in most semiconductor processes now.

[0003] SiO2 films prepared by LPCVD using TEOS as a liquid source have many advantages, such as good uniformity, good step coverage, high controllability and repeatability, low cost, and suitability for large-scale production. As a result, LPCVD using TEOS as a liquid source has gradually become the mainstream process for depositing SiO2 films.

[0004] However, currently, domestically produced LPCVD equipment for depositing SiO2 thin films generally suffers from problems such as poor film thickness uniformity, high process particle size, and poor repeatability. Moreover, it has extremely stringent requirements for process pressure. Lower process pressure poses a significant challenge to the stability of the equipment's airflow field, making it difficult to meet users' batch production requirements. This exacerbates the obstacles to the industrialization and promotion of domestically produced equipment.

[0005] Therefore, based on these shortcomings of vertical LPCVD equipment, a coating process for vertical LPCVD equipment to improve the SiO2 coating effect has been developed to make up for the deficiencies of domestic vertical LPCVD equipment, so that its thin film deposition effect can meet the batch production requirements of users. This is of great significance for the industrialization and application of domestic equipment. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that existing LPCVD methods for depositing SiO2 thin films generally suffer from poor film thickness uniformity, high process particle size, poor repeatability and stability, and extremely stringent requirements for process pressure. The invention provides a silicon dioxide deposition process for vertical LPCVD equipment that is simple to operate, has good stability and high film uniformity.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A silica deposition process using a vertical LPCVD equipment includes the following steps:

[0009] Step S1: Check if the process pipe is leaking air;

[0010] Step S2: Purge the process pipe with nitrogen under low pressure;

[0011] Step S3: After the leak rate test is qualified, nitrogen gas is introduced to purge the gas pipeline, so that the pressure and gas flow rate of the process pipe are stabilized under the pressure and gas flow rate conditions set during thin film deposition.

[0012] Step S4: Under the set pressure conditions, a reaction gas source is introduced to deposit a silicon dioxide thin film on the surface of the semiconductor substrate.

[0013] Step S5: After completing the silicon dioxide thin film deposition, nitrogen gas is introduced to purge the process pipe and exhaust pipe, and nitrogen gas is introduced to pressurize to atmospheric pressure before unloading the boat.

[0014] As a further improvement of the present invention, in step S4, the reaction gas source is tetraethyl orthosilicate.

[0015] As a further improvement of the present invention, the gas inlet end of the process tube is provided with a first interface, a second interface and a third interface; the first interface and the second interface are both located at the bottom of the process tube, the first interface is used to introduce nitrogen gas, and the second interface is used to introduce tetraethyl orthosilicate; the third interface is located at 3 / 4 of the height of the process tube, and the third interface is used to introduce tetraethyl orthosilicate.

[0016] As a further improvement of the present invention, in step S1, all air intake valves of the vertical LPCVD equipment are closed. If the process pipe pressure drops to ≤5Pa, the angle valve in the exhaust pipe is closed. If the vacuum leakage rate of the process pipe is ≤1.5Pa / min after 5 minutes of closure, it indicates that the leakage rate test is qualified.

[0017] As a further improvement of the present invention, in step S2, the pressure is set to 0 Pa during nitrogen purging, and the nitrogen flow rate of the first interface is adjusted within the range of 100 sccm to 5000 sccm.

[0018] As a further improvement of the present invention, in step S3, the pressure range is set to 60Pa~90Pa, and after the pressure stabilizes, the pressure fluctuation is ≤±2Pa.

[0019] As a further improvement of the present invention, in step S4, the pressure of the process tube is set to 60Pa to 90Pa, the tetraethyl orthosilicate flow rate of the second interface is 80sccm to 120sccm, and the tetraethyl orthosilicate flow rate of the third interface is 10sccm to 20sccm.

[0020] As a further improvement of the present invention, in step S4, the semiconductor substrate is an 8-inch silicon-based wafer, a silicon carbide wafer, or a gallium nitride wafer.

[0021] As a further improvement of the present invention, in step S5, during the nitrogen purging process, the main extraction valve is in the normally open state, and nitrogen is intermittently introduced for purging. The nitrogen introduction time and interval time are 5 min to 15 min each time, and the cycle is repeated 3 to 5 times.

[0022] As a further improvement of the present invention, in step S5, after the nitrogen purging is completed, all pneumatic valves at the inlet and outlet ends connected to the process pipe are closed, and the process pipe is left to stand for 10 min to 15 min under extreme low pressure. Then, the nitrogen gas path valve at the inlet end is opened to increase the pressure, and the nitrogen flow rate is 50 sccm to 2000 sccm.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. The silica deposition process of the vertical LPCVD equipment of the present invention divides the deposition process into five steps: vacuum leak detection, nitrogen purging, process pressure control, thin film deposition, and purging pressure boosting. This not only improves the thickness uniformity and particle size of the deposited film, but also significantly increases the PM cycle length. Therefore, the present invention can greatly improve the performance of the vertical LPCVD equipment and meet the user's hard requirements for mass production equipment such as good process effect, strong stability, and long PM cycle.

[0025] 2. The silica deposition process of the vertical LPCVD equipment of this invention involves first modifying the inlet gas path structure, and then using this as a basis for debugging and verification of the thin film deposition process. Through structural improvement and process development, the process effect of SiO2 thin film deposition is improved, and the maintenance cycle and output are significantly increased. Furthermore, the gaseous source tetraethyl orthosilicate (TEOS) adopts a dual-inlet method, with one inlet at the bottom of the process tube and the other at three-quarters of the height of the process tube. Based on this, process debugging and verification were carried out for the inlet flow rate of different inlets, and the optimal process parameter ratio was explored. Under these conditions, the process tube pressure can be maintained at a high level (60Pa~90Pa), which reduces the requirements for equipment leakage rate and gas flow field stability to a certain extent. During batch production, not only is the uniformity of film thickness (intra-wafer and inter-wafer) greatly improved, but the process particle size is also usually maintained at a low level, improving stability and reliability, and significantly increasing the equipment maintenance cycle. This invention significantly improves the process debugging window of the vertical LPCVD equipment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process tube structure of a vertical LPCVD equipment in a specific embodiment of the present invention.

[0027] Figure 2 This is a flowchart of the silicon dioxide deposition process of a vertical LPCVD equipment in a specific embodiment of the present invention.

[0028] Legend: 1. Process tube; 2. First interface; 3. Second interface; 4. Third interface. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0030] Example

[0031] like Figure 2 As shown, the silicon dioxide deposition process of the vertical LPCVD equipment of the present invention includes the following steps:

[0032] Step S1, Vacuum leak detection: Check if process tube 1 is leaking air;

[0033] Step S2: Purge process pipe 1 with nitrogen under low pressure;

[0034] Step S3: After the leak rate test is qualified, nitrogen gas is introduced to purge the gas pipeline, so that the pressure and gas flow rate of process pipe 1 are stabilized under the pressure and gas flow rate conditions set during thin film deposition.

[0035] Step S4: Under the set pressure conditions, a reaction gas source is introduced to deposit a silicon dioxide thin film on the surface of the semiconductor substrate.

[0036] Step S5: After completing the deposition of the silicon dioxide thin film, nitrogen gas is introduced to purge the process pipe 1 and the exhaust pipe, and nitrogen gas is introduced to pressurize to atmospheric pressure before unloading the boat.

[0037] In step S4 of this embodiment, the reaction gas source is tetraethyl orthosilicate (TEOS).

[0038] like Figure 1 As shown, in this embodiment, the inlet end of the process tube 1 is provided with a first interface 2, a second interface 3, and a third interface 4. Both the first interface 2 and the second interface 3 are located at the bottom of the process tube 1. The first interface 2 is used to introduce nitrogen gas, and the second interface 3 is used to introduce tetraethyl orthosilicate. The third interface 4 is located at 3 / 4 of the height of the process tube 1 and is used to introduce tetraethyl orthosilicate.

[0039] In step S1 of this embodiment, the specific operation of vacuum leak detection is as follows: close all inlet valves of the vertical LPCVD equipment; if the pressure of process pipe 1 drops to ≤5Pa, close the angle valve in the exhaust pipe; if the vacuum leak rate of process pipe 1 is ≤1.5Pa / min after 5 minutes of closure, it indicates that the leak rate test is qualified. Table 1 shows the relevant parameters for checking whether the leak rate of process pipe 1 is qualified.

[0040] Table 1. Process parameters for vacuum leak detection and pressure control.

[0041]

[0042] In step S2 of this embodiment, during nitrogen purging, the pressure is set to 0 Pa, and the nitrogen flow rate of the first interface 2 is adjusted within the range of 100 sccm to 5000 sccm. Specifically, after the leak rate test is qualified, nitrogen purging process pipe 1 is introduced, the main extraction valve of the exhaust pipe is in the normally open state, and nitrogen is introduced intermittently for purging. The nitrogen flow rate is 5 slm, and the interval and nitrogen introduction time are both 10 min, repeated twice.

[0043] In step S3 of this embodiment, the pressure range is set to 60Pa~90Pa, and after the pressure stabilizes, the pressure fluctuation is ≤±2Pa. Specifically, after nitrogen is introduced into the purging gas pipeline, the process pressure is set to 60Pa, and the nitrogen flow rates of the second interface 3 and the third interface 4 are set to 1000sccm and 100sccm, respectively, and the pressure is maintained for 5 minutes after stabilization.

[0044] In step S4 of this embodiment, the pressure of process tube 1 is set to 60 Pa to 90 Pa, the tetraethyl orthosilicate flow rate of the second interface 3 is set to 80 sccm to 120 sccm, and the tetraethyl orthosilicate flow rate of the third interface 4 is set to 10 sccm to 20 sccm. Specifically, the pressure of process tube 1 is set to 60 Pa, and the gaseous TEOS flow rates of the second interface 3 and the third interface 4 are set to 100 sccm and 10 sccm, respectively. In other embodiments, the process temperature and deposition time can be adjusted according to the film thickness requirements.

[0045] In step S4 of this embodiment, the semiconductor substrate is an 8-inch silicon-based wafer, a silicon carbide wafer, or a gallium nitride wafer.

[0046] In step S5 of this embodiment, during the nitrogen purging process, the main extraction valve is in the normally open state, and nitrogen is intermittently introduced for purging. The nitrogen introduction time and interval for each cycle are 5 min to 15 min, and the cycle is repeated 3 to 5 times. Specifically, during the purging process, the main extraction valve is in the normally open state, and nitrogen is intermittently introduced for purging. The nitrogen flow rate is 5 slm, and the introduction time and interval are both 5 min, which is repeated 3 times.

[0047] In step S5 of this embodiment, after nitrogen purging, all pneumatic valves at the inlet and outlet ends connected to process pipe 1 are closed. Process pipe 1 is left to stand under extreme low pressure for 10 to 15 minutes. Then, the nitrogen gas path valve at the inlet end is opened to increase the pressure, with a nitrogen flow rate of 50 sccm to 2000 sccm. Specifically, all valves at the inlet and outlet ends connected to process pipe 1 are closed, and the vacuum standing time is 5 minutes. Then, the nitrogen inlet valve at the first interface 2 is opened to slowly increase the pressure, with a nitrogen flow rate of 100 sccm and a ventilation time of 15 minutes. Then, the nitrogen flow rate is increased to 1000 sccm, and the pressure in process pipe 1 slowly increases until it reaches atmospheric pressure.

[0048] In this embodiment, the thickness uniformity (intra-wafer and inter-wafer), process particle size, and maintenance cycle (cumulative film thickness at low PM) of the deposited SiO2 film are shown in Table 2.

[0049] Table 2 Statistical results of SiO2 film thickness uniformity, process particle size, and maintenance cycle

[0050]

[0051] Currently, vertical LPCVD systems have only one TEOS inlet path, with the inlet located at the bottom of the process tube. The extraction port is positioned symmetrically at the bottom of the process tube, creating an airflow field from the bottom to the top of the process tube under low-pressure conditions. Under high-temperature conditions, gaseous TEOS decomposes and deposits at any diffuseable and accessible location; the higher the temperature, the greater the decomposition and deposition rate.

[0052] In this embodiment, during the SiO2 thin film deposition process, vacuum leak detection, nitrogen purging, process pressure control, thin film deposition, and process tube purging and pressurization are performed sequentially. After the TEOS source is introduced through the inlet, the gaseous source forms a concentration gradient from the bottom to the top of the process tube at high temperature. The lower the process pressure, the smaller the concentration gradient. To ensure the consistency of the deposition rate inside the tube, the temperature of the top temperature zone is usually gradually increased, or the process tube pressure is reduced as much as possible. However, in actual batch production applications, the process pressure is usually below 20 Pa, and the top temperature zone is usually more than 25°C higher than the bottom temperature zone. If the temperature deviation is too large, it can easily affect the consistency of product performance. Therefore, the process pressure must be reduced. If the pressure is lower, the requirements for the sealing of the process tube and the stability of the airflow field are more stringent, and vacuum leakage and airflow field fluctuations are more likely to occur during batch production. Regarding the impact on process performance, it not only leads to significant fluctuations in the uniformity of deposited film thickness (mainly referring to intra-wafer and inter-wafer areas), but also affects the stability of process particle size. In terms of its impact on batch production efficiency, it not only severely shortens equipment maintenance cycles but also significantly reduces product output efficiency. In actual batch production, film thickness uniformity (intra-wafer and inter-wafer areas) easily exceeds 2.5%, and process particle size easily exceeds 100 (diameter ≥ 100 μm), with equipment maintenance cycles typically within 9 μm (usually requiring 10–15 μm).

[0053] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A silica deposition process for a vertical LPCVD equipment, characterized in that, Includes the following steps: Step S1: Check if the process pipe (1) is leaking air; Step S2: Purge the process pipe (1) with nitrogen under low pressure; Step S3: After the leak rate test is qualified, nitrogen gas is introduced to purge the gas pipeline so that the pressure and gas flow rate of the process pipe (1) are stabilized under the pressure and gas flow rate conditions set during thin film deposition; wherein, the set pressure range is 60Pa~90Pa. Step S4: Under the set pressure conditions, tetraethyl orthosilicate is introduced as a reaction gas source to deposit a silicon dioxide thin film on the surface of the semiconductor substrate; wherein, the gas inlet end of the process tube (1) is provided with a first interface (2), a second interface (3) and a third interface (4); the first interface (2) and the second interface (3) are both located at the bottom of the process tube (1), the first interface (2) is used to introduce nitrogen gas, and the second interface (3) is used to introduce tetraethyl orthosilicate; the third interface (4) is located at 3 / 4 of the height of the process tube (1), and the third interface (4) is used to introduce tetraethyl orthosilicate; the pressure of the process tube (1) is set to 60Pa~90Pa, the tetraethyl orthosilicate flow rate of the second interface (3) is 80sccm~120sccm, and the tetraethyl orthosilicate flow rate of the third interface (4) is 10sccm~20sccm; Step S5: After completing the deposition of the silicon dioxide thin film, nitrogen gas is introduced to purge the process pipe (1) and the exhaust pipe, and nitrogen gas is introduced to pressurize to atmospheric pressure before exiting the boat.

2. The silica deposition process of the vertical LPCVD equipment according to claim 1, characterized in that, In step S1, all air intake valves of the vertical LPCVD equipment are closed. If the pressure of the process pipe (1) drops to ≤5Pa, the angle valve in the exhaust pipe is closed. If the vacuum leakage rate of the process pipe (1) is ≤1.5Pa / min after 5 minutes of closure, the leakage rate test is qualified.

3. The silica deposition process of the vertical LPCVD equipment according to claim 1, characterized in that, In step S2, the pressure is set to 0 Pa during nitrogen purging, and the nitrogen flow rate of the first interface (2) is adjusted from 100 sccm to 5000 sccm.

4. The silica deposition process of the vertical LPCVD equipment according to claim 1, characterized in that, In step S3, after the pressure stabilizes, the pressure fluctuation is ≤ ±2Pa.

5. The silica deposition process of the vertical LPCVD equipment according to claim 1, characterized in that, In step S4, the semiconductor substrate is an 8-inch silicon-based wafer, a silicon carbide wafer, or a gallium nitride wafer.

6. The silica deposition process for a vertical LPCVD equipment according to claim 1, characterized in that, In step S5, during the nitrogen purging process, the main extraction valve is in the normally open state, and nitrogen is intermittently introduced for purging. The nitrogen introduction time and interval for each time are 5 min to 15 min, and the cycle is repeated 3 to 5 times.

7. The silicon dioxide deposition process of the vertical LPCVD equipment according to claim 1, characterized in that, In step S5, after the nitrogen purging is completed, all pneumatic valves at the inlet and outlet ends connected to the process pipe (1) are closed. The process pipe (1) is left to stand for 10 min to 15 min under extreme low pressure. Then, the nitrogen gas path valve at the inlet end is opened to increase the pressure. The nitrogen flow rate is 50 sccm to 2000 sccm.

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