# US 12,765,289 B2 · Method for etching silicon wafer

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- Number: US 12,765,289 B2
- Document ID: US12765289B2
- Status: Granted
- Kind: B2
- Application number: 18/252,705
- Filed: 2021-11-15
- Published: 2024-01-04
- Granted: 2026-10-13
- Earliest claimed: 2020-11-16
- Assignees: Beijing Naura Microelectronics Equipment Co., Ltd.
- Applicants: Beijing Naura Microelectronics Equipment Co., Ltd.
- Inventors: Haiyun Zhu; Zhongwei Jiang; Jing Wang
- Web page: https://patentgrep.com/patent/US12765289B2

## CPC

- H10P 50/242: {of Group IV materials}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A method for etching a silicon wafer includes: a main etching process using a first mixed gas to perform a plasma etching process to etch the silicon wafer until a pattern on the silicon wafer reaches a specified aspect ratio, the first mixed gas being configured to etch silicon and react with silicon to form non-volatile reaction products; and an auxiliary etching process using a second mixed gas to perform another plasma etching process, the second mixed gas being configured to react with silicon to generate the non-volatile reaction products, and a formation rate of the non-volatile reaction products in the auxiliary etching process being greater than a formation rate of the non-volatile reaction products in the main etching process. The main etching process and the auxiliary etching process are alternately performed at least once until the pattern on the silicon wafer reaches a specified etching depth.

## Claims

### Claim 1

A method for etching a silicon wafer, comprising:
a main etching process using a first mixed gas to perform a plasma etching process to etch the silicon wafer until a pattern on the silicon wafer reaches a specified aspect ratio, the first mixed gas being configured to etch silicon and react with silicon to form non-volatile reaction products; and
an auxiliary etching process using a second mixed gas to perform another plasma etching process, the second mixed gas being configured to react with silicon to generate the non-volatile reaction products, and a formation rate of the non-volatile reaction products in the auxiliary etching process being greater than a formation rate of the non-volatile reaction products in the main etching process;
wherein:
the main etching process and the auxiliary etching process are alternately performed at least once until the pattern on the silicon wafer reaches a specified etching depth;
the specified etching depth is smaller than a target etching depth;
after the pattern on the silicon wafer reaches the specified etching depth, the main etching process is performed until the pattern on the silicon wafer reaches the target etching depth;
the first mixed gas includes sulfur hexafluoride, and one or more of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride;
the second mixed gas includes one or more of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride;
if the first mixed gas and the second mixed gas contain exactly the same gas types in the four gases of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride, a flow rate of each gas included in the four gases in the first mixed gas is smaller than the flow rate of the same gas included in the four gases in the second mixed gas; and
if the gas types contained in the first mixed gas and the second mixed gas are at least partially different in the four gases of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride, a total flow rate of these four gases in the first mixed gas is less than a total flow rate of these four gases in the second mixed gas.

### Claim 2 (depends on 1)

The method according to claim 1, wherein:
after the main etching process and the auxiliary etching process are alternately performed, the main etching process is performed at least once until the pattern on the silicon wafer reaches the specified etching depth.

### Claim 3 (depends on 1)

The method according to claim 1, wherein:
the specified aspect ratio achieved after each main etching process is greater than or equal to N−1:1 and less than or equal to N:1, wherein N is a sequence number of the main etching processes.

### Claim 4 (depends on 3)

The method according to claim 3, wherein:
the specified aspect ratio is greater than or equal to 3:1 and less than or equal to 5:1.

### Claim 5 (depends on 1)

The method according to claim 1, wherein:
a duration of the auxiliary process is greater than or equal to 2 seconds and smaller than or equal to 3 seconds.

### Claim 6 (depends on 1)

The method according to claim 1, wherein:
the second mixed gas further includes sulfur hexafluoride.

### Claim 7 (depends on 1)

The method according to claim 1, wherein:
the first mixed gas includes four gases: sulfur hexafluoride, oxygen, hydrogen bromide, and silicon tetrafluoride; and
a flow ratio of sulfur hexafluoride, oxygen, hydrogen bromide, and silicon tetrafluoride is (1.7-2.3):(1.3-1.7):(13-17):1.

### Claim 8 (depends on 7)

The method according to claim 7, wherein:
the flow ratio of sulfur hexafluoride, oxygen, hydrogen bromide, and silicon tetrafluoride is 2:1.5:15:1.

### Claim 9 (depends on 1)

The method according to claim 1, wherein:
when performing the main etching process, a value range of an upper radio frequency (RF) power is greater than or equal to 300 W and less than or equal to 2,500 W, a value range of the lower RF power is greater than or equal to 15 W and less than or equal to 800 W, and a pressure in a process chamber ranges between 10 mT and 90 mT; and
when performing the auxiliary etching process, a value range of an upper RF power is greater than or equal to 500 W and less than or equal to 2,000 W, a value range of the lower RF power is greater than or equal to 50 W and less than or equal to 500 W, and the pressure in the process chamber ranges between 10 mT and 100 mT.

### Claim 10 (depends on 9)

The method according to claim 9, wherein:
frequencies of the upper and lower RF powers are 13.56 MHz in both the main etching process and the auxiliary etching process.

### Claim 11 (depends on 9)

The method according to claim 9, wherein:
when performing the main etching process, a temperature range of a base in the process chamber is less than or equal to 100° C., and a temperature range of the process chamber is greater than or equal to 10° C. and less than or equal to 40° C.; and
when performing the auxiliary etching process, the temperature range of the process chamber is greater than or equal to 10° C. and less than or equal to 40° C.

### Claim 12 (depends on 11)

The method according to claim 11, wherein:
when performing the main etching process, the temperature range of the base in the process chamber is greater than or equal to 20° C. and less than or equal to 80° C.

### Claim 13 (depends on 1)

The method according to claim 1, further comprising before the main etching process is performed for the first time:
a pre-etching process using a pre-etching gas to perform the plasma etching process to etch the silicon wafer and remove an oxide layer on the surface of the silicon wafer.

### Claim 14 (depends on 13)

The method according to claim 13, wherein:
the pre-etching gas includes one or more combinations of carbon tetrafluoride or other fluorine-containing hydrocarbon organic gases.

### Claim 15

A method for etching a silicon wafer, comprising:
a main etching process using a first mixed gas to perform a plasma etching process to etch the silicon wafer until a pattern on the silicon wafer reaches a specified aspect ratio; and
an auxiliary etching process using a second mixed gas to perform another plasma etching process, the second mixed gas being configured to react with silicon to generate the non-volatile reaction products, and an etching rate of the second mixed gas on the silicon wafer being smaller than an etching rate of the first mixed gas on the silicon wafer;
wherein:
in different main etching processes, the specified aspect ratio is different;
the first mixed gas includes at least one gas being able to react with silicon to form non-volatile reaction products, and a formation rate of the non-volatile reaction products in the auxiliary etching process being greater than a formation rate of the non-volatile reaction products in the main etching process;
the second mixed gas includes one or more of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride;
the first mixed gas includes sulfur hexafluoride, oxygen, hydrogen bromide, and silicon tetrafluoride, and a flow ratio of sulfur hexafluoride, oxygen, hydrogen bromide, and silicon tetrafluoride is (1.7-2.3):(1.3-1.7):(13-17):1; and
the first mixed gas and the second mixed gas satisfy at least one of:
a flow rate of the oxygen in the first mixed gas is smaller than a flow rate of the oxygen in the second mixed gas;
a flow rate of the hydrogen bromide in the first mixed gas is smaller than a flow rate of the hydrogen bromide in the second mixed gas; or
a flow rate of the silicon tetrafluoride in the first mixed gas is smaller than a flow rate of the silicon tetrafluoride in the second mixed gas.