JPH0831437B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention forms an aluminum (Al) film or an Al alloy film on a semiconductor substrate, and forms a desired pattern with a photoresist using a photolithography technique. After that, the present invention relates to an improvement in a method for manufacturing a semiconductor device in which this film is etched using it as a mask.

[Conventional technology]

As a conventional method for manufacturing a semiconductor device of this type, as shown in FIG. 4, a photoresist 4 is coated on an Al film 3 formed on a semiconductor substrate and baked using a mask having a desired pattern and a projection exposure apparatus. After the development and development, the photoresist is used as a mask to immerse in a phosphoric acid (H ₃ PO ₄ ) -based etching solution, for example, a mixed solution of phosphoric acid, acetic acid, and nitric acid, or to spray the etching solution by exposing A method of etching an Al film has been performed.

[Problems to be solved by the invention]

However, in the above-described conventional liquid etching (hereinafter referred to as wet etching), as shown in FIG. 4, when the etching from the surface to the inside, that is, the so-called vertical etching is attempted, the horizontal etching also progresses at the same time. (It is called side etch below). Therefore, when performing this kind of etching, it is necessary to perform patterning in which a desired pattern has this side-etching amount taken into consideration, that is, it has been a major obstacle to pattern miniaturization. Incidentally, 1 is a semiconductor substrate including a surface insulating film. On the other hand, high pressure voltage (mostly 13.56MHz is used) such as reactive ion etching developed in recent years and reactive gas (freon gas or halogen gas is used) causes low pressure ( 1-50P
In a), a glow discharge is generated, and a physical and chemical etching technique utilizing gas reaction in plasma discharge is used to obtain an etching shape without side etching as shown in FIG. ing. However, this reactive ion etching also utilizes the impact effect of active ions of plasma discharge, and it is known that the inner wall of the reaction vessel is sputtered and heavy metal contamination and damage of the device are induced (Autumn Society of Applied Physics). Joint Lecture Proceedings 7a
-H-10 1981). Further, since it is directly exposed to plasma discharge, there is a serious drawback that it is damaged by irradiation with ultraviolet rays, electrons and X-rays. Particularly, in a charge-coupled device such as an image pickup device, it has an influence on the surface charge and has been a cause of remarkably reducing the yield. Incidentally, in FIG.
The same functions as those in the figure are denoted by the same reference numerals.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and to promote further miniaturization of patterns to provide high integration of semiconductor devices.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention is
After forming a film or Al alloy film and using photoresist to form a desired pattern with photoresist, using this as a mask, part of this film in the thickness direction is formed by reactive ion etching. The first step of etching and then the organic deposits generated during this reactive ion etching (Anisotropic Etching of Al-Si Films).
1983 Dry Process Symposium, II-1, P14 and Jpn.J.App
l.Phys.19: 1405,1980) to remove oxygen (O ₂ ) gas plasma in the second step, and then the remaining film is etched by wet etching using the photoresist as a mask. Have a process.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 to 3 are vertical joint views of an embodiment of the present invention.

A protective film 2 which is a silicon oxide film is formed on the surface of the silicon substrate 1 by, for example, high temperature oxidation (about 1000 ° C.) in a water vapor atmosphere to a thickness of about 1 μm. This protective film 2
The surface of the Al film 3 is formed by the sputtering method (about 300 ° C), etc.
For example, it is formed with a thickness of about 1 μm. Next, the photoresist 4 is applied so as to have a thickness of, for example, about 1.5 μm. Then, as shown in FIG. 2, the photoresist 4 is patterned by exposure and development using a photomask on which a predetermined pattern is formed. Using this resist pattern as a mask, carbon tetrachloride (CCl ₄ ) or trichloride is formed. Boron (BCl ₃ )
Reactive ion etching is performed in a low-pressure (1 to 50 Pa) closed container with a reactive gas such as the above and a high-frequency voltage, for example, 13.56 MHz. If the Al film thickness removed by this reactive ion etching is, for example, 0.7 μm, the remaining Al film thickness is
It becomes 0.3 μm. This residual film is preferably as small as possible, but should be determined in consideration of variations in the etching rate within the same substrate and between substrates during reactive ion etching.

After interrupting the reactive ion etching in this way, the etching gas such as unreacted carbon tetrachloride (CCl ₄ ) and boron trichloride (BCl ₃ ) in the sealed container and aluminum trichloride (AICI
₃ ) Evacuate the reaction product with a vacuum pump. At this time, it is important to sufficiently exhaust the pressure in the closed container so that the pressure is 5 × 10 ^-1 Pa or less.

Next, low pressure (1 to 50 Pa) is applied to the inside of the same closed container, and oxygen (O ₂ ) gas and high frequency voltage, for example, 13.56 MHz, is used to incinerate organic deposits mainly composed of the resist generated during the reactive ion etching. Remove. Although this organic deposit is a very thin film, it has a great masking property against a phosphoric acid (H ₃ PO ₄ ) -based etching solution, so if it is neglected to be removed by this oxygen (O ₂ ) gas plasma. Therefore, insufficient etching or uneven etching occurs. This oxygen (O ₂ ) gas plasma also etches the photoresist at the same time, but RF, Power 200-300W
Etching rate of resist is 0.1μm in 5-10 minutes
It is needless to say that the amount is negligible considering the following and the initial photoresist film thickness of 1.5 μm, and sufficient masking property for an etching solution used thereafter can be secured.

As described above, the two steps of reactive ion etching of Al and removal of organic deposits are continuously processed in the same closed container, and then taken out from the etching apparatus and washed with water.
This is to prevent Al wiring from being corroded by hydrochloric acid (HCl) formed by the reaction of the chloride adhering to the resist with the moisture in the atmosphere). Then, a phosphoric acid (H ₃ PO ₄ ) based etching solution, for example, a mixed solution of phosphoric acid, acetic acid and nitric acid is heated (about 50
C.), atomize and spray it to etch the remaining Al film (FIG. 3).

In this embodiment, by adding a step of oxygen (O ₂ ) gas plasma to the reactive ion etching and the wet etching, the advantages of both can be sufficiently exhibited and etching having a good shape and without damage can be performed.

〔The invention's effect〕

In the present invention, by removing a part of the film such as Al by reactive ion etching, by removing the rest by wet etching, while maintaining the good etching shape of reactive ion etching, at the end By performing wet etching, there is an effect that etching without damage to the substrate becomes possible.

Further, in the present invention, the reactive ion etching for removing the Al film and the subsequent oxygen gas plasma can be continuously performed in the same apparatus, so that it is not necessary to purchase a new apparatus in order to carry out the present invention. Absent.

Furthermore, by suppressing variations in the etch rate within the same substrate and between substrates during reactive ion etching, the ratio of the final wet etch can be reduced, and the same pattern size can be obtained when etching is performed only by reactive ion etching. You can do it. As a result, a semiconductor device capable of achieving high integration and high speed can be manufactured.

[Brief description of drawings]

1 to 3 are sectional views showing an embodiment of the present invention in the order of steps. FIG. 4 is a cross-sectional view when conventional wet etching is performed. FIG. 5 is a cross-sectional view when conventional reactive ion etching is performed. 1 ... Silicon substrate, 2 ... Field oxide film, 3 ...
Al film, 4 ... Photoresist.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/88 D

Claims (1)

[Claims] 1. An aluminum film or an aluminum alloy film is formed on a semiconductor substrate, and a photoresist is used as a mask to selectively carry out reactive ion etching from the surface to the inside of the film to form a film in the thickness direction of the film. Part, a step of ashing and removing organic deposits generated by the reactive ion etching by gas plasma while leaving the photoresist with RF output of 200 to 300 W, and masking the remaining photoresist. And a step of patterning by removing the remaining film with an acid-based etching solution.