JPS61285721A - Etching method for silicon oxide - Google Patents

Abstract

PURPOSE:To enable the complete etching of SiO2 by placing the etching auxiliary material consisting of Si atoms adjacently to the object to be etched before etching the SiO2 formed on a substrate not including Si atoms. CONSTITUTION:Before etching the SiO2 thin film 2 formed on a GaAs substrate 1, the whole substrate 1 is placed on a crystal (SiO2) plate 3 for etching. A plenty of SiFx ions produced by etching the crystal plate 3 exist even right before the SiO2 2 on the substrate 1 is eliminated, so that those are accelerated by self-bias voltage and bump against the wafer surface, thereby preventing the formation of polymer. At this time, an etching rate of SiO2 is always constant and does not change before the quantity of remaining SiO2 2 becomes zero. Thus, the complete removal is done.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for etching silicon oxide, which is widely used in the manufacture of semiconductor devices.

, Conventional Technology Silicon oxide has excellent insulating properties and is easy to form, so it is widely used as a glabellar insulating film for semiconductor devices. As semiconductor devices become more highly integrated, the etching of silicon oxide has shifted from the conventional wet etching using hydrofluoric acid to dry etching, which allows finer shape processing.

Dry etching of 5102 is performed using gas plasma, especially RI.
It is often carried out using a reactive gas called C3F8. CF4. CHF3 and other various substances have been reported. (For example, Proceedings on the First Symposium Ondry Bromo x (1
979) (Proceeding of the f.
irst symposium on dry-pro
Especially in etching with CHF3 gas, S1
It is widely used because it has a high etching selectivity between 02 and other materials (GaAs+, SL, etc.) and allows anisotropic etching. C in Table 1
S io2. in RIE with HF3 gas. GaAs,
S i , the etching characteristics of photoresists are compared.

The following margin shows the etching selection ratio of SiO3 (
The etching rate ratio) is 4.0 or more, which is large compared to other materials. However, the etching rate of SlO□ is not always constant during etching.

Problems to be Solved by the Invention FIG. 2 shows the relationship between the remaining etching amount of 5 lO2 and the etching rate. The broken line shows 5lo2 deposited on Si, and the solid line shows 5lo2 deposited on GaAs. For those deposited on Si, there is almost no change in the etching rate, but for those deposited on GaAs, etching of S102 progresses, and when the remaining amount is less than 500 Å, the etching rate decreases rapidly, and further etching is difficult. will stop progressing. Conversely, C-H-polymer produced by decomposition of CHF3 accumulates on the wafer. That is, CHF
3 In plasma etching, polymer accumulation and 5102 etching proceed simultaneously, but 5lo2
There is a large amount of 5iFx (x
=1.2.3.4), the formation of the polymer is inhibited by the 5iFx. However, if the remaining amount of 5102 decreases and 5iFx decreases, the C
F! , CHFx (x=1, 2.3), etc., cannot remove the polymer, and etching does not proceed. In the case where 5102 is attached to 81, even if the remaining amount of SiO2 becomes small, 5iFx is created by etching the Sl substrate, so the etching rate does not decrease. As mentioned above, in the conventional method, 510
Etching differs depending on the type of substrate on which No. 2 is placed, and in particular, when the substrate does not contain Si atoms, complete S102
etching was impossible.

Means for Solving the Problems In order to solve the above problems, the etching method of the present invention includes placing a material containing Si atoms as an etching auxiliary material adjacent to the object to be etched, and performing etching at the same time. Features.

By installing this etching auxiliary material, even just before the end of 5lo2 etching, the etching auxiliary material
iFz ions are supplied to prevent polymer formation and allow complete 5i02 etching.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

The etching gas consisting of CHF3 was kept at α02toxr and 13.56 MHz RF was applied by cathode coupling.
generates plasma. At this time, a self-bias voltage is applied between the anode and the electrode, and o, 1swA
-1! □ G
When etching 3000 pieces of 51022 formed on aAs I, the entire substrate 1 is placed on a quartz (SiO2) plate 3 as shown in FIG.

5iFx (x=1
, 2.3.4) Ions are S z022 on GaAs
Since it exists in a large amount even just before it disappears, it is accelerated by the self-bias voltage, collides with the wafer surface, and prevents polymer formation. At this time, the etching rate of 51o2 is always constant at 320A/mln, and the etching rate of 5ooO2 is always constant at 320A/mln.
The etching rate does not change until the remaining amount of O□2 becomes 0, and complete removal is performed.

As described above, according to this embodiment, complete etching of Sio2 becomes possible by placing an etching auxiliary material containing St atoms as a constituent element adjacent to the object to be etched.

In this example, 5102 was used as the etching auxiliary material.
However, it is not limited to this, and any material containing St atoms may be used, such as Si3N4.81 alone.

Effects of the Invention As described above, the present invention enables complete etching of 8102 by placing an etching auxiliary material containing SL atoms as a constituent element adjacent to the object to be etched during etching of 9102 in a plasma containing CHF3 gas. It enables highly effective etching and has great effects in applications to highly integrated semiconductor processes.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the positional relationship between the material to be etched and the etching auxiliary material according to an embodiment of the present invention, and FIG.
FIG. 2 is a diagram showing the relationship between the remaining amount of etching and the etching rate of No. 02. 1...GaAs substrate, 2...S 10
2.3...Quartz plate (S 102) 0 Name of agent Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] When etching silicon oxide formed on a substrate that does not contain Si atoms, a material containing Si atoms is placed adjacent to the substrate and etching is performed in a plasma gas containing CHF_3 gas. Silicon etching method.