CN106495087B

CN106495087B - Etching method of silicon dioxide substrate

Info

Publication number: CN106495087B
Application number: CN201510566883.7A
Authority: CN
Inventors: 李成强
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing Naura Microelectronics Equipment Co Ltd
Priority date: 2015-09-08
Filing date: 2015-09-08
Publication date: 2020-04-28
Anticipated expiration: 2035-09-08
Also published as: CN106495087A

Abstract

The invention provides an etching method of a silicon dioxide substrate, which comprises the following steps: a pretreatment step, introducing oxygen into the reaction chamber, and starting an upper electrode power supply and a lower electrode power supply to modify the side wall of the mask; and an etching step, wherein etching gas is introduced into the reaction chamber, and the upper electrode power supply and the lower electrode power supply are started to etch a pattern on the surface of the silicon dioxide substrate. The etching method of the silicon dioxide substrate provided by the invention can enable the side wall and the bottom of the obtained etched pattern to be straighter and smoother, thereby improving the performance and the overall reliability of a device.

Description

Etching method of silicon dioxide substrate

Technical Field

The invention relates to the technical field of microelectronics, in particular to an etching method of a silicon dioxide substrate.

Background

With the rapid development of optical communication, SiO₂The optical waveguide becomes an ideal waveguide element due to its own characteristics, and also becomes a hot spot for research in the field of optical communication. With the development of etching technology, especially dry etching technology, the advantages of high etching precision, small surface damage and the like are gradually introduced into the development of optical waveguide devices.

The existing etching method of the silicon dioxide substrate adopts C₄F₈Ar and H₂And etching the silicon dioxide substrate by using the photoresist as a mask. The etching method is mainly characterized in that: higher upper and lower electrode powers are used, and C₄F₈Ar and H₂The gas flow ratio of (2) is 5: 5: 1. typical process parameters are: the chamber pressure is 4 mT; the power of the upper electrode is 2000W; the lower electrode power is 600W; c₄F₈The gas flow of (2) is 50 sccm; the gas flow of Ar is 50 sccm; h₂The gas flow of (2) is 10 sccm; the temperature of the chamber is 20 ℃; the process time was 230 s.

FIG. 1 is an electron microscope scanning image of a substrate obtained by a conventional silicon dioxide substrate etching method. As can be seen from fig. 1, the etched pattern obtained by the above etching method has a minute trench formed at the bottom (as shown in region I in fig. 1) and a discontinuous corner (as shown in region II in fig. 1) at the sidewall, resulting in etching of the top of the substrate. The reasons for these problems are:

FIG. 2 is a scanning electron microscope image of a photoresist mask after photolithography. As shown in fig. 2, since the exposure intensity received by the bottom of the mask 2 is weak after the photoresist mask 2 is subjected to photolithography, small protruding feet (foot) are formed at the bottom of the mask (as shown in the region III in fig. 2), the roughness of the sidewall of the mask 2 is uneven, which may cause the roughness of the bottom and sidewall of the substrate 1 to be uneven, and a tiny trench is formed at the bottom, thereby reducing the performance of the device and impairing the overall reliability of the device.

Disclosure of Invention

The invention aims to solve at least one technical problem in the prior art, and provides an etching method of a silicon dioxide substrate, which can enable the side wall and the bottom of an obtained etched pattern to be straighter and smoother, so that the performance and the overall reliability of a device can be improved.

In order to achieve the object of the present invention, there is provided a method for etching a silicon dioxide substrate, comprising:

a pretreatment step, introducing oxygen into the reaction chamber, and starting an upper electrode power supply and a lower electrode power supply to modify the side wall of the mask;

and an etching step, wherein etching gas is introduced into the reaction chamber, and the upper electrode power supply and the lower electrode power supply are started to etch a pattern on the surface of the silicon dioxide substrate.

Preferably, in the etching step, the etching gas includes Ar, He and N₂And a fluorocarbon-based gas.

Preferably, the fluorocarbon-based gas includes C₄F₈、CF₄Or CHF₃。

Preferably, the flow rate of the fluorocarbon gas ranges from 10sccm to 40 sccm.

Preferably, Ar, He or N is₂The flow rate of the gas is 70-100 sccm.

Preferably, in the etching step, the value range of the upper electrode power output by the upper electrode power supply is 800-1500W.

Preferably, in the etching step, the value range of the lower electrode power output by the lower electrode power supply is 300-500W.

Preferably, in the etching step, the etching temperature is in a range of-10 to 10 ℃.

Preferably, in the pretreatment step, the flow rate of the oxygen gas ranges from 50sccm to 200 sccm.

Preferably, in the preprocessing step, the value range of the upper electrode power output by the upper electrode power supply is 500-1500W.

The invention has the following beneficial effects:

according to the etching method of the silicon dioxide substrate, provided by the invention, the pretreatment step is carried out before the etching step of etching the silicon dioxide substrate, namely, oxygen is introduced into the reaction chamber, and the upper electrode power supply and the lower electrode power supply are started, so that the effect of modifying the side wall of the mask can be achieved, the mask becomes vertical and smooth, the side wall and the bottom of the obtained etched pattern can be flatter and smoother, and the performance and the overall reliability of a device can be further improved.

Drawings

FIG. 1 is an electron microscope scanning image of a substrate obtained by a conventional silicon dioxide substrate etching method;

FIG. 2 is an electron microscope scan of a photoresist mask after photolithography;

FIG. 3 is a flow chart of a method for etching a silicon dioxide substrate according to the present invention; and

FIG. 4 is an electron microscope scanning image of the substrate obtained by the etching method of the silicon dioxide substrate provided by the invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the following describes the etching method of the silicon dioxide substrate provided by the present invention in detail with reference to the accompanying drawings.

FIG. 3 is a flow chart of a method for etching a silicon dioxide substrate according to the present invention. As shown in fig. 3, the method for etching a silicon dioxide substrate includes:

In the pretreatment step, the flow rate of oxygen is in a range of 50-200 sccm; the value range of the upper electrode power output by the upper electrode power supply is 500-1500W; the value range of the lower electrode power output by the lower electrode power supply is 50-150W. Typical process parameters are: the chamber pressure is 20 mT; the power of the upper electrode is 1000W; the lower electrode power is 100W; o is₂The gas flow of (2) is 100 sccm; the temperature of the chamber is 0 ℃; the process time was 20 s.

By performing the pretreatment step before the etching step of etching the silicon dioxide substrate, the side wall of the mask can be modified to be vertical and smooth, so that the side wall and the bottom of the obtained etched pattern are straighter and smoother, and the performance and the overall reliability of the device can be improved.

In order to eliminate the tiny trenches formed at the bottom of the etched pattern and to obtain a straight and smooth profile of the sidewalls and bottom, the following process parameters may also be adjusted during the etching step relative to the prior art.

Specifically, in the etching step, the etching gas includes Ar, He and N₂And a fluorocarbon-based gas. The fluorocarbon gas includes C₄F₈、CF₄Or CHF₃. During etching, charged byproducts tend to deposit on the sidewalls, which can affect the deflection of ions in the plasma toward the bottom of the sidewalls, thereby enhancing the etching of the bottom of the sidewalls where minute trenches are formed. For this purpose, the invention provides a method for etching a silicon dioxide substrate by using a gas with a strong physical bombardment effect, such as Ar, He or N, in the etching step₂The Si-O bond can be broken, and the charged by-product generated by the chemical reaction at the bottom can be removed, so that the formation of a tiny groove at the bottom of the graph can be avoided, and the appearance with a straight and smooth bottom can be obtained. Preferably, the flow rate of the fluorocarbon gas is in the range of 10 to 40sccm, and more preferably 30 sccm. Ar, He or N₂The flow rate of the gas is 70-100 sccm. In addition, in the etching stepIn the etching step, H is not introduced into the reaction chamber₂Due to H₂Will react with the photoresist mask to form more polymer, so no H is introduced₂There is further less by-product, so that formation of minute trenches at the bottom of the pattern can be avoided.

The etching step uses a lower upper electrode power than the prior art. The prior art upper electrode power is usually 2000W, which increases the ion recombination reaction in the plasma and the radical ratio, resulting in increased isotropic etching and thus uneven sidewall and bottom roughness. In the technical scheme of the invention, the value range of the upper electrode power output by the upper electrode power supply is 800-1500W. The upper electrode power in the range can not only obtain the appearance that the side wall and the bottom are smooth and straight, but also avoid the lower etching rate caused by the fact that the fluorocarbon gas can not be effectively ionized due to the lower upper electrode power.

The etching step uses a lower bottom electrode power than the prior art. In the prior art, the power of the lower electrode is usually 600W, which easily causes the bombardment effect in the etching process to be too strong, and further causes the formation of a tiny trench at the bottom of the pattern. In the technical scheme of the invention, the value range of the lower electrode power output by the lower electrode power supply is 300-500W, and further 400W. The lower electrode power in the range can avoid the bombardment effect in the etching process from being too strong, thereby avoiding the formation of a tiny groove at the bottom of the pattern.

The etching step uses a lower etching temperature than the prior art. The etching temperature refers to the temperature of the silicon dioxide substrate during etching. This temperature is typically controlled by a chiller (chiller). In the technical scheme of the invention, the etching temperature adopted in the etching step is in the range of-10 ℃, and is further preferably 0 ℃, and the etching temperature in the prior art is usually 20 ℃. By adopting lower etching temperature in the etching step, the phenomenon of glue pasting caused by overhigh mask temperature can be avoided, the lower etching temperature is more favorable for keeping the appearance of the mask, and the mask is prevented from shrinking caused by overhigh temperature, so that the straight and smooth appearance of the side wall can be favorably obtained.

The following is a test of the etching method of the silicon dioxide substrate provided by the present invention. The process parameters used in this test were: in the pretreatment step, the chamber pressure was 20 mT; the power of the upper electrode is 1000W; the lower electrode power is 100W; o is₂The gas flow of (2) is 100 sccm; the temperature of the chamber is 0 ℃; the process time was 20 s. In the etching step, the pressure of the chamber is 4 mT; the power of the upper electrode is 1500W; the lower electrode power is 400W; c₄F₈The gas flow of (2) is 30 sccm; the gas flow of Ar is 70 sccm; the temperature of the chamber is 0 ℃; the process time was 240 s.

FIG. 4 is an electron microscope scanning image of the substrate obtained by the method for etching the silicon dioxide substrate provided by the invention. As can be seen from fig. 4, by using the etching method of the silicon dioxide substrate provided by the present invention, a straight and smooth profile of the sidewall and the bottom can be obtained, so that the performance and the overall reliability of the device can be improved.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. A method for etching a silicon dioxide substrate is characterized by comprising the following steps:

a pretreatment step, introducing oxygen into the reaction chamber, and starting an upper electrode power supply and a lower electrode power supply to modify the side wall of the mask so as to ensure that the side wall is vertical and smooth;

2. The method of etching a silicon dioxide substrate according to claim 1, wherein in the etching step, the etching gas includes Ar, He and N₂And a fluorocarbon-based gas.

3. The method of etching a silicon dioxide substrate according to claim 2, wherein the fluorocarbon-based gas comprises C₄F₈、CF₄Or CHF₃。

4. The method for etching a silicon dioxide substrate according to claim 2 or 3, wherein the flow rate of the fluorocarbon gas ranges from 10 to 40 sccm.

5. The method of etching a silicon dioxide substrate according to claim 2, wherein the Ar, He or N is₂The flow rate of the gas is 70-100 sccm.

6. The method for etching a silicon dioxide substrate according to claim 1, wherein in the etching step, the upper electrode power output by the upper electrode power supply has a value ranging from 800W to 1500W.

7. The method for etching a silicon dioxide substrate according to claim 1, wherein in the etching step, the value of the lower electrode power output by the lower electrode power supply ranges from 300W to 500W.

8. The method for etching a silicon dioxide substrate according to claim 1, wherein in the etching step, the etching temperature is in a range of-10 to 10 ℃.

9. The method for etching a silicon dioxide substrate according to claim 1, wherein in the pretreatment step, the flow rate of the oxygen gas is in a range of 50 to 200 sccm.

10. The method for etching a silicon dioxide substrate according to claim 1, wherein in the pretreatment step, the upper electrode power output by the upper electrode power supply has a value in a range of 500 to 1500W.