JPH06151359A - Method and apparatus for etching of semiconductor wafer - Google Patents

Abstract

PURPOSE:To improve a method and an apparatus so as to prevent the surface of a wafer from being roughened in an etching treatment. CONSTITUTION:In an etching method in which an etching operation is executed by bringing an etching gas into contact with a surface film 6 formed on a semiconductor wafer 5, the concentration of the etching gas is changed according to the progress of the etching operation. For this purpose, means 9b, 9c which make the concentration of the etching gas variable are installed at an etching apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer etching method and an etching apparatus for etching a surface film formed on a semiconductor wafer in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In an etching process for forming a predetermined pattern on a surface film formed on a semiconductor wafer in a semiconductor manufacturing process, as shown in FIG.
For example, hydrofluoric acid vapor 2 generated by the etching gas supply device 1 is supplied to the etching processing chamber 4 together with an inert gas such as nitrogen gas 3 and, for example, dioxidation as an insulating layer formed in advance on the wafer 5 is performed. Etching treatment for pattern formation is performed by bringing hydrofluoric acid vapor into contact with the silicon film 6 in the etching treatment chamber 4.

[0003]

In the conventional etching process described above, since the concentration of the etching gas is constant throughout the process, the etching may proceed excessively in some cases, and the surface of the wafer after the treatment may be affected. Inconveniences such as surface roughness on the order of submicrons may occur.

The present invention has been devised to eliminate such disadvantages of the prior art, and its main purpose has been improved so as not to cause surface roughness in the etching process. An object of the present invention is to provide a method for etching a semiconductor wafer and an etching apparatus.

[0005]

According to the etching method of the present invention, such an object is to change the concentration of the etching gas for etching the surface film formed on the semiconductor wafer according to the progress of the etching. It is achieved by making Further, according to the etching apparatus of the present invention, it can be achieved by providing the etching gas concentration varying means for etching the surface film formed on the semiconductor wafer.

[0006]

According to this structure, the etching gas of a low concentration is brought into contact with the surface film on the wafer in the early stage of the etching process, so that the etching gas is uniformly adsorbed on the surface film and the surface is roughened. Occurrence of uneven etching is suppressed. After that, if the concentration of the etching gas is increased, normal etching can be performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to specific embodiments shown in the accompanying drawings.

FIG. 1 shows a schematic configuration of a semiconductor wafer etching apparatus according to the present invention. The same parts as those of the conventional configuration shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the etching gas supply device 1 is supplied with nitrogen gas 3, pure water 7 and hydrogen fluoride 8, respectively, and the flow rate is supplied to each of these supply pipelines. Control valves 9a to 9c are provided so that hydrofluoric acid 2 having an arbitrary composition can be generated.

In this embodiment, the hydrofluoric acid vapor 2 adjusted to a predetermined concentration by the etching gas supply device 1 is used.
Are supplied to the etching processing chamber 4 together with the nitrogen gas 3 through the flow rate control valve 9e. Pure water 7 for cleaning is supplied to the etching processing chamber 4 through a flow rate control valve 9d, and nitrogen gas 3 for scavenging is supplied to the flow rate control valve 9f.
It is designed to be supplied via.

A heater 10 is provided in the etching processing chamber 4.
Is provided. As a result, the wafer temperature can be maintained at the optimum temperature for activating the etching gas or the temperature at which the etching selectivity is the best (for example, in the range of room temperature to 120 degrees Celsius).

Next, a processing method by the apparatus of this embodiment will be described. First, by setting the flow rate control valves 9b and 9c,
By adjusting the mixing ratio of pure water 7 and hydrogen fluoride 8,
For example, about 0 to 5 percent hydrofluoric acid is generated.

Subsequently, the hydrofluoric acid vapor 2 and the pure water 7 are supplied into the etching processing chamber 4 and are brought into contact with the silicon dioxide film 6 on the wafer surface for a predetermined time, and a low concentration etching gas is applied to the surface film. Adsorb evenly on 6.

Next, the concentration of hydrofluoric acid is set to, for example, 5 to 40.
The percentage is adjusted, this is brought into contact with the surface film 6 in the same manner as described above, and predetermined etching is performed. At this time, in order to rapidly change the etching gas concentration, a plurality of sets of etching gas supply devices adjusted to have different concentrations in advance may be prepared, and these may be selectively switched and used.

At this time, the internal pressure of the etching processing chamber 4 may be normal pressure, but it is preferable to bring the etching gas and the wafer into contact with each other in a reduced pressure state in order to make the etching gas concentration more uniform. By the way, the room pressure may be, for example, 760 to 0.1 torr.

Further, the temperature in the etching processing chamber 4 is preferably heated from room temperature to about 120 degrees Celsius in order to enhance the activation of the etching gas and enhance the etching selectivity of the silicon dioxide film.

When the target etching is completed, the flow rate control valve 9e is closed to stop the supply of the hydrofluoric acid vapor 2,
Further, the flow rate control valve 9d is opened and only the pure water 7 is supplied to clean the wafer 5, thereby stopping the progress of etching due to the residual gas. Further, by opening the flow rate adjusting valve 9f and supplying only the scavenging nitrogen gas 3 into the etching processing chamber 4, the decomposed substances and foreign substances are discharged to the outside of the etching processing chamber 4 through the exhaust pipe 11. To do.

[0018]

As described above, according to the present invention, since the concentration of the etching gas brought into contact with the surface film of the wafer is changed stepwise according to the progress of the etching process, the non-uniformity of etching is prevented. Therefore, a great effect can be exerted in suppressing the occurrence of surface roughness of the processed wafer.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a device of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional device.

[Explanation of symbols]

 1 Etching Gas Supply Device 2 Hydrofluoric Acid Vapor 3 Nitrogen Gas 4 Etching Processing Chamber 5 Wafer 6 Surface Coating 7 Pure Water 8 Hydrogen Fluoride 9a-9f Flow Control Valve 10 Heating Heater 11 Exhaust Pipe

Claims (2)

[Claims] 1. An etching method for etching a surface film formed on a semiconductor wafer with an etching gas, wherein the concentration of the etching gas is changed according to the progress of etching. Method. 2. An etching apparatus for etching a surface film formed on a semiconductor wafer with an etching gas, comprising an etching gas concentration varying means.