JPH0496222A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To perform etching of an Si oxide film and an Si nitride film by a dry method without damaging a substrate by etching the Si oxide film and the Si nitride film by exposing these to F-group gas containing specific atoms, and mixed gas of aforesaid F-group gas and H2O, H2. CONSTITUTION:Etching of an Si oxide film 3 and an Si nitride film 4 is performed by exposing these to F-group gas containing F-atoms of HF, F2, XeF2 and to mixed gas of aforesaid F-group gas and H2O, H2. Etching of a nitride film, an oxide film is performed according to an etching property, thickness of semiconductor constitution materials such as single Si, polySi, a nitride film, an oxide film and the kinds of F-group gas, and the materials around them are made to remain. During an etching process, ultraviolet light is directly applied to F-group gas or a substrate 1. After the etching process, annealing is performed. After etching or annealing processes, again a film 6 is formed. Directly before finishing the etching process, F-group gas is changed to F-group gas having low etching speed of the semiconductor substrate.

Description

[Detailed Description of the Invention] [Summary] This article relates to an etching method for Si oxide films and Si nitride films and a method for manufacturing semiconductor devices using the same. Regarding the manufacturing method, it is a dry method that does not damage the substrate (for the purpose of etching Si oxide films and Si nitride films, it uses F-based gases containing F atoms such as HF + F 2 and X e F 2, and The structure is such that the Si oxide film and the Si nitride film are etched by exposing the F-based gas to a mixed gas such as F20 or F2.

[Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and more specifically, it relates to a method for etching Si oxide films and Si nitride films, and a method for manufacturing a semiconductor device using the same. .

[Prior art] In the manufacturing process of semiconductor devices, Si oxide film and S
The process of etching the i-nitride film is performed to remove the mask for forming the thick oxide film of LOGO8.

Conventionally, for etching Si oxide films and Si nitride films, wet methods using dilute HF solutions, phosphoric acid solutions, etc., and methods using high-energy particles such as RIE have been used.

In LSI manufacturing technology, which is becoming more precise and miniaturized,
It has become essential to transition from wet processes to dry processes suitable for microfabrication. As dry etching methods, plasma etching, microwave etching, reactive sputter etching, etc. are known. CHF3, CF is used as a plasma etching gas for the oxide film.
Carbon fluorides such as 4+H2 and CF2 are used, and CF4 and CF4+8 are used as plasma etching gas for nitride films.
2 etc. are known.

[Problem to be solved by the invention]

With the adoption of dry processes, it has become a problem that damage caused by high-energy particles used in dry processes can adversely affect device characteristics (for example, rVL
SI Manufacturing Technology” Nikkei BP, 1989, No. 261~
262 pages).

An object of the present invention is to etch a Si oxide film and a Si nitride film using a dry method without damaging the substrate.

[Means for Solving the Problems] The present invention provides a method for solving the problems of the prior art, as follows:
This is a method of etching a Si oxide film and a Si nitride film, which is characterized by taking the following technical steps.

1. The Si oxide film and Si nitride film are etched by exposure to an F-based gas containing F atoms such as HF, Fz, XeF2, etc., and a mixed gas of the F-based gas and H2O, H, etc.

(2) Directly irradiating the F-based gas or the substrate with ultraviolet light during the etching process.

(2) Annealing is performed after the etching process.

After IV, etching or annealing process, a new film is formed.

(2) Immediately before the end of the etching process, the F-based gas is switched to an F-based gas that has a lower etching rate for the semiconductor substrate.

Hereinafter, the configuration of the present invention will be explained in detail.

As the F-based gas, an F-based gas containing HF, Fz, and XeFi atoms, and a mixed gas of the F-based gas and H, 01H2, etc. can be used. These gases are Ar, N
Gases diluted with t etc. can also be used.

Although the reaction between the F-based gas and the Si oxide film and the Si nitride film occurs at room temperature and even at a certain high temperature, there is no need to ionize or turn these gases into plasma.

As a mask for selectively removing a nitride film and an oxide film, it is not preferable because the resist contains moisture and the reaction product of H2O and F-based gas etches the Si underneath the resist.

Therefore, depending on the etching properties and thickness of semiconductor constituent materials such as single Si, poly-Si, nitride film, and oxide film, as well as the type of F-based gas, the nitride film and oxide film are etched so that the surrounding materials remain. There is a need. For example, HF does not etch Si comparatively, but F2 does not etch Si.
Since the etching rate of is high, it is preferable to use HF as an etching gas when etching a material with a Si base. Note that etching is possible regardless of which of the oxide film and nitride film is on top. . In addition, it is highly efficient and preferable to remove the entire thickness of the oxide film and nitride film using F-based gas, but normal dry etching is performed halfway through these films, and immediately before the end of etching,
Damage-free etching can also be performed by etching using a system gas. The reaction products of etching are removed from the substrate surface by washing with water or processing in a vacuum. Removal speed of 100-100
0x height of about 100 is created. A practical etching rate can be obtained by using F as the ultraviolet light and using a wavelength of 200 to 400 nm in the case of gas.

skin and blood plate soil and yu Annealing is performed after the step [I] [11] above.

When etching a Si nitride film using F-based gas, reaction products may remain on the substrate surface. For example, N
An ionic film of H4"" and 5iFe"- can be considered. Since such reaction products remain on the substrate surface after the reaction,
To remove this, annealing is performed at a temperature of 100° C. or higher after etching.

After removing the oxide film and nitride film by the above process, the electrode,
Wires and other thin films are grown by conventional methods.

Since the skin, blood, and NF gases have etching properties for various substances, although there are some differences in etching rate, the underlying Si substrate is also etched to some extent. Therefore, during etching, the material to be processed (S iO 21 S I N) is first etched with a material having a high etching rate, and just before the end of etching, etching is performed with a material having a low etching rate of Si.

[Function] HF and F2 gases have the ability to etch Si oxide films and Si nitride films. Moreover, since it is a dry method using gas and etching proceeds only by chemical reactions, it does not damage the substrate.

2 F 2+ S iO□→S I F4 + O□↑
(1) 2 F 2 + S 1N-IS s F
4 + 1/2 N x T (2) F2 is SiN
and directly reacts with 5in2.

The reaction product, SiF, is a gas at room temperature.

2HF+2H20→HF2-+8.0' (3) HF reacts with H2O to generate HF,-.

Trace amounts of 820 or gaseous H naturally present on the substrate surface
, O reacts with HF according to equation (3) to produce HF2-. It is thought that this reacts with oxides and nitrides as follows.

4 HF + Si O2→SiF4↑+2H,0T
4HF+5iN-3iF4 ↑+NH4(5)S i
Ox +2Hs O" +2HF2--3
i F4+4Hz O(6)S i F4
+8m O" +HF*-+Hi O→2Hs
O'+5iFs"-(7) SiF4- and NH,' are ionic compounds, so they are adsorbed to the substrate due to electric charge. Therefore, they must be removed by washing with water or annealing. If you wash it with water when removing it, S
Since the i-substrate is extremely thin (oxidized), a clean Si surface can be obtained by performing annealing in vacuum or in an inert gas.

Ultraviolet light irradiation increases the reaction rate of the above reaction formula to 10 to 1100 n/hr by exciting compounds such as F, HF, etc. (Method of Claim 3) 6. Removal of oxide films and nitride films in the above method causes damage. No clean side is exposed. By depositing electrodes and the like here, a high-performance device can be made (claim 4).

F-based gas can form the resist in a reverse pattern, but
Since it cannot be used as a mask, the structure of the etching material must be devised, but by switching the F-based gas, highly accurate etching with a high selectivity can be achieved.

The present invention will be explained in detail below.

[Example] An example in which the present invention is applied to the removal of a Si nitride film and a pad oxide film after LOCOS formation will be described with reference to FIGS. 1 to 4.

The cross-sectional structure after forming LOGO3 is as shown in Figure 1 (A), which includes a thin Si oxide film (approximately 10 nm) 3 and a Si nitride film (100 nm).
It has a multilayer structure of 4 m) and 2 pad oxide films (50 nm). After forming LOGO8, the wafer was exposed to ultraviolet light using a low-pressure mercury lamp.
When the Si substrate 1 was exposed to a two-gas atmosphere (1%, diluted with Ar) for 15 ml (FIG. 1(B)), a porous film 5 was formed on the Si substrate 1 exposed on the second floor of the pad acid film. As a result of analysis, the porous film 5 remaining on the surface was found to be NH4'' and S.
It was found to be an ionic membrane of iF,'. This was annealed at 150° C. in a hydrogen atmosphere to remove the ionic film 5 (FIG. 1(C)). After this treatment, the gate oxide film 6 was formed by normal thermal oxidation (Fig. 1(D)).
.

When the surface of the Si substrate was analyzed by XPS after annealing in a hydrogen atmosphere, elements such as N, F, and O were not detected. Further, when damage was measured using a thermal wave method, no damage was found, and it was confirmed that the lattice of the Si crystal was exposed.

[Effects of the Invention] According to the present invention, Si oxide films and nitride films can be etched using a dry method that solves various problems associated with wet etching (trench, contamination, etc.) and without damaging the substrate.

[Brief Description of the Drawings] Figure 1 (A) is a diagram showing the intermediate process of LOGO3, Figure 1 (B) is a diagram showing the process of removing the oxide film and nitride film with F-based gas, Figure 1 ( C) is a diagram showing an annealing process, and FIG. 1(D) is a diagram showing a gate oxide film. 1-3i substrate, 2-pad oxide film, 3-8i nitride film, 4
- Pad oxide film, 5- ionic reaction product

Claims (1)

[Claims] 1. Etching a Si oxide film and a Si nitride film by exposing to an F-based gas containing F atoms such as HF, F_2, and XeF_2, and a mixed gas of the F-based gas and H_2O, H_2, etc. 1. A method for manufacturing a semiconductor device, comprising the step of: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the F-based gas or the substrate is directly irradiated with ultraviolet light during the etching step. 3. The method of manufacturing a semiconductor device according to claim 1 or 2, wherein annealing is performed after the etching step. 4. The method of manufacturing a semiconductor device according to claim 1, wherein a new film is formed after the etching or annealing step. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the F-based gas is switched to an F-based gas having a low etching rate of the semiconductor substrate immediately before the end of the etching step.