JPH0567597A - Etching of silicon - Google Patents

Abstract

PURPOSE:To provide an etching method, in a dry etching used for a semiconductor device manufacturing process, for setting an etching rate ratio of silicon for silicon oxide film to 20 or higher and prescribing an etching rate of silicon to 200nm/min or higher. CONSTITUTION:As an etching gas of silicon, a mixed gas of hydrogen bromide (HBr) and oxygen is used and content of oxygen is prescribed to 15% to 30% (Vol%).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method used for manufacturing semiconductor devices, and more particularly to a dry etching method for silicon (amorphous, polycrystalline and single crystal).
In particular, it relates to a method of increasing the etching rate ratio of silicon to a silicon oxide film.

[0002]

[Prior art and its problems] Higher density of semiconductor devices
Along with the miniaturization, pattern formation is currently performed by dry etching. The advantage of dry etching is that it is etched in a direction perpendicular to the silicon wafer, which allows a pattern of 2 μm or less to be accurately formed. However, in such dry etching, the film to be etched and the mask,
Also, the etching selectivity between the film to be etched and the material immediately below the film to be etched is a problem.

1 (a), 1 (b) and 2 (a),
FIG. 2B is an explanatory view of the silicon etching method. In the etching of polycrystalline silicon, as shown in FIGS. 1A to 1B, the polycrystalline silicon 3 is formed in the same manner as the resist pattern 4. Ideally, etching will stop when the silicon oxide film 2 appears as the etching progresses. However, conventional CCl ₂ F ₂ or SF used for etching polycrystalline silicon is used.
_The silicon oxide film 2 is also etched to some extent by an etching gas such as ₆ , Cl ₂ or a mixture thereof.
Recently, the silicon oxide film 2 is very thin (50 nm
Since the following) is formed, the silicon oxide film 2 may also be etched during the over-etching considering the uniformity of the etching in the silicon substrate, and the underlying silicon substrate 1 may be exposed. As a result, the silicon substrate is also etched and the device characteristics are adversely affected.

Further, as shown in FIGS. 2 (a) to 2 (b), when the silicon substrate 1 is etched according to the pattern using the above-mentioned etching gas with the silicon oxide film 2 as a mask, a deep groove is formed. When forming the mask, the silicon oxide film 2 of the mask must be made thick in consideration of the desired dimensions. Therefore, at present, as is clear from the above two examples, an etching gas is desired that maximizes the etching rate ratio between the silicon oxide film and silicon. The selectivity of the dry etching currently put into practical use is about 10 to 20.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and provides a method of increasing the etching rate ratio of silicon to a silicon oxide film to 20 or more and the etching rate of silicon to 200 nm / min or more. With the goal.

In the present invention, a mixed gas of HBr and oxygen is used as an etching gas for silicon, and when the oxygen content is 15% or more and less than 30%, the etching rate ratio of silicon to the silicon oxide film is 20 or more. And the silicon etching rate is 200 nm
/ Min or more. 3 (a) and 3 (b) show an HB using a predetermined etching apparatus in order to explain the present invention.
FIG. 3 (a) is a measurement diagram in which the etching rate of silicon and the silicon oxide film when oxygen is added to r is measured. As shown in FIG.
An etching rate of 200 nm / min or more could be secured at -25%, and if the oxygen concentration was increased further, the etching rate of silicon decreased to 20 nm / min or less.
Further, the etching rate of the silicon oxide film is 0 when the oxygen concentration is 0.
At ~ 12.5%, it is constant at about 25 nm / min,
Then, it was gradually reduced to 23%, and it was found that etching was hardly performed at 25% or more. The etching rate ratio of silicon to the silicon oxide film is plotted in FIG. 3B. The oxygen concentration is 20% or more, and the etching rate ratio of 20 or more is secured. Therefore, when considering the etching rate of silicon and the etching rate ratio, optimum silicon etching can be expected when the oxygen concentration is 15% or more and less than 30%.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for etching polycrystalline silicon is shown in FIG.
This will be described with reference to (a) and (b). First, a dry oxide film 2 of 50 nm is formed on a silicon wafer by using a predetermined oxidation furnace. Next, CVD is performed on the dry oxide film 2.
A polycrystalline silicon film 3 having a thickness of 500 nm is deposited in a furnace, and then POCl ₃ is heated in a gas at 950 ° C. to dope phosphorus into the polycrystalline silicon film 3 so that the polycrystalline silicon film has conductivity. Let At this time, since the surface of the polycrystalline silicon is slightly oxidized, the oxide film is removed with a mixed solution of HF and NH ₄ F. Finally, a positive resist 4 having a thickness of 1 μm is applied, and the resist is patterned using a stepper. As a result, the shape shown in FIG. 1 (a) was completed. Next, the polycrystalline silicon is etched. In a predetermined etching apparatus, first, CF
_Four gases were introduced into the apparatus and etching was performed for 30 seconds. This was done in order to remove the oxide film on the polycrystalline silicon film which was slightly oxidized during the resist application. Then, H
The polycrystalline silicon was etched for 2 minutes and 30 seconds using an etching gas containing Br and oxygen gas at a flow rate ratio (HBr gas: oxygen gas = 1: 0.2). Although the etching of the polycrystalline silicon film is completed in about 2 minutes, over-etching was performed for 30 seconds in consideration of the etching uniformity in the wafer substrate. As can be seen from FIG. 3 (a), the resist used as the mask is etched by about 250 nm in the etching for 2 minutes and 30 seconds, but since the resist was first coated by 1 μm, the shape of the polycrystalline silicon was The desired product shown in Fig. 1 (b) was produced.

[0008]

EXAMPLES Next, a method for etching single crystal silicon will be described with reference to FIGS. An oxide film of about 100 nm is formed on a silicon substrate, a resist pattern is formed on the oxide film, and CHF ₃ is formed in a predetermined etching apparatus.
The gas was introduced and the oxide film was etched in about 1 minute. Further, the resist was removed with fuming nitric acid to obtain the shape shown in FIG. 2 (a). Then, in a predetermined etching apparatus, CF ₄ gas is introduced into the apparatus and etching is performed for 30 seconds, and then, for example, a flow rate ratio (HBr gas: oxygen gas = 1: 0.25) in which HBr and oxygen gas are mixed. Etching gas was used to etch silicon.
As a result, the shape shown in FIG. 2 (b) was obtained.

[0009]

As described above, according to the method of the present invention, HBr and oxygen are used as the etching gas, and the oxygen content is set to 15% or more and less than 30%, and the etching rate ratio of silicon to the silicon oxide film is increased. It is 20 or more, and the etching rate of silicon is 200 nm / min or more. It can be applied to all uses of silicon etching, has good controllability, and greatly contributes to the production of fine semiconductor devices and the like.

[Brief description of drawings]

1A and 1B are explanatory views of a method for etching polycrystalline silicon.

2A and 2B are explanatory views of a method for etching single crystal silicon.

3A and 3B are measurement diagrams for explaining the present invention. 1 silicon substrate 2 silicon oxide film 3 polycrystalline silicon film 4 photoresist

Claims (2)

[Claims] 1. A silicon etching method using a mixed gas of hydrogen bromide gas (HBr) and oxygen gas, wherein oxygen gas is contained in an amount of 15% to 30% (volume%) with respect to the hydrogen bromide gas. A method for etching silicon, comprising: 2. A method of etching silicon, characterized in that the silicon is an amorphous, polycrystalline or single crystal silicon substrate, or a silicon film or an oxide thereof.