JPH04290230A - Etching method of silicon oxide film - Google Patents

Abstract

PURPOSE:To enhance the uniformity of an etching operation by a method wherein a rinsing operation is performed in the halfway part of the etching operation and the etching operation is performed after it has been divided into a plurality of operations at the etching method of a silicon oxide film by using buffer hydrofluoric acid. CONSTITUTION:A silicon oxide film 102 is coated with a resist 103; many holes having a diameter of, e.g. 0.8mum are formed; the silicon oxide film 102 is etched by using buffer hydrofluoric acid. At this time, a rinsing operation is performed in the halfway part of the etching operation, and the etching operation is performed after it has been divided into a plurality of operations. When the rinsing operation is performed during the process of the etching operation by using the buffer hydrofluoric acid, a reaction product, with the buffer hydrofluoric acid, which has adhered to a substrate 101 is washed off. As a result, it is possible to restrain that an oxide by the precipitation of the reaction product is etched, and the etching operation is performed uniformly.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of etching a silicon oxide film in a semiconductor integrated circuit manufacturing process.

0002

[Prior Art] In the semiconductor integrated circuit manufacturing process, wet etching of silicon oxide films is generally performed using dilute hydrofluoric acid (HF) or buffered hydrofluoric acid (NH4F/HF/H2O).
) is used. The etching rate of dilute hydrofluoric acid is
The etching rate of buffered hydrofluoric acid is approximately 100 Å/min (at 3%), and is mainly used for etching thin oxide films, whereas the etching rate of buffered hydrofluoric acid is approximately 1000 Å/min, and is mainly used for etching thick oxide films. It is being

0003

[Problem to be Solved by the Invention] When a silicon oxide film in a contact hole portion is etched using buffered hydrofluoric acid, (NH4)2SiF6 is formed as a reaction product, precipitates on the silicon oxide film, and etches. The reaction is suppressed and etching does not proceed uniformly (Figure 2). An object of the present invention is to provide a method for improving etching uniformity when etching a silicon oxide film in a microscopic hole such as a contact hole using buffered hydrofluoric acid.

0004

[Means for Solving the Problems] The method of the present invention for solving the above-mentioned problems involves washing a silicon oxide film in the middle of etching when etching a silicon oxide film with buffered hydrofluoric acid, and performing etching multiple times. It is characterized by being divided into parts.

[0005]

[Effect] By washing with water during etching with buffered hydrofluoric acid, reaction products with buffered hydrofluoric acid adhering to the substrate are washed away, so suppression of oxide film etching due to precipitation of reaction products can be prevented. , the etching is uniform.

[0006]

[Example] A resist is applied on a silicon oxide film, many holes with a diameter of 0.8 μm are formed, and buffered hydrofluoric acid (N
The oxide film was etched using the following two methods using H4F 37%, HF 5%).

(a) Immersion in buffered hydrofluoric acid for 1 minute → washing with water → drying
(b) Dip in buffered hydrofluoric acid for 30 seconds → Wash with water → Dip in buffered hydrofluoric acid for 30 seconds
→ Water washing → Drying After this, the resist was removed with a mixture of sulfuric acid and hydrogen peroxide, and the silicon oxide film surface was measured using an atomic force microscope (AFM) to determine the percentage of oxide film etching that stopped midway. According to research, 17% for (a) and 7% for (b)
It was confirmed that the uniformity was improved by dividing the etching with buffered hydrofluoric acid (Fig. 1).
).

[0008] It goes without saying that the number of times the etching is divided is not limited to two.

[0009]

According to the silicon oxide film etching method of the present invention, it is possible to improve the uniformity of oxide film etching using buffered hydrofluoric acid.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a comparison between a conventional method of etching uniformity and a method of the present invention.

FIG. 2 is a diagram showing how an oxide film is etched in a contact hole portion using a resist as a mask.

[Explanation of symbols]

101 Silicon substrate 102 Silicon oxide film 103 Resist 104 Normal etched part

Claims (1)

[Claims] 1. A method for etching a silicon oxide film using buffered hydrofluoric acid, the method comprising: washing with water during etching, and performing the etching in multiple steps.