JPH06275576A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a silicon substrate from being etched by oxidizing part of a polycrystalline silicon layer and etching the oxide film. CONSTITUTION:A photoresist 4 is formed in a prescribed shape on polycrystalline silicon film 3. Then, after implanting oxygen ions into the film 3 by using the photoresist 4 as a mask and removing the photoresist 4, the polycrystalline silicon is changed to an oxide film 6 by performing heat treatment. Thereafter, the silicon film 3 is patterned by etching the oxide film 6. Therefore, the etching of a silicon substrate 1 can be prevented, because the etching method used for the oxide film 6 can be increased in etching ratio against silicon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for patterning a polycrystalline silicon layer.

[0002]

2. Description of the Related Art Conventionally, a method of patterning a polycrystalline silicon layer has been described after forming a polycrystalline silicon layer on a semiconductor substrate.
After patterning the font resist on the polycrystalline silicon layer into a prescribed shape, the polycrystalline silicon layer is etched (wet etching or dry etching) using the photoresist as a mask to pattern the polycrystalline silicon layer into a prescribed shape. Was.

4A to 4C are sectional views showing a conventional method of patterning a polycrystalline silicon layer in the order of steps.

First, as shown in FIG. 4a, an oxide film 2 is formed on a silicon substrate 1, and then polycrystalline silicon 3 is formed.

Next, as shown in FIG. 4b, a photoresist 4 is formed and patterned into a predetermined shape.

Next, as shown in FIG. 4c, the polycrystalline silicon 3 is anisotropically etched by plasma ion etching using the photoresist 4 patterned into a predetermined shape as a mask, and then the photoresist 4 is removed.

[0007]

In the above-mentioned conventional polycrystalline silicon patterning method, anisotropic etching by plasma etching is performed using a photoresist as a mask. When anisotropically etching polycrystalline silicon,
In order to cover the variation in the etching rate and the thickness of the in-plane polycrystalline silicon layer, it is necessary to overetch. Then, the etching rate ratio between the polycrystalline silicon and the oxide film is not so large that the underlying oxide film is etched and the silicon substrate is also etched. Further, in isotropic etching such as wet etching, the etching ratio between polycrystalline silicon and an oxide film is increased, but there is a drawback that the patterning dimension accuracy is deteriorated.

[0008]

A method of patterning polycrystalline silicon according to the present invention comprises a step of forming a polycrystalline silicon layer on a semiconductor substrate and a mask material for oxygen ion implantation on the polycrystalline silicon layer. Forming step, patterning the mask material into a predetermined shape, injecting oxygen ions into the polycrystalline silicon layer as a mask having a predetermined shape, and implanting oxygen ion into the polycrystalline silicon layer Is formed into an oxide film, and the polycrystalline silicon layer formed into an oxide film is removed by etching.

[0009]

According to the above structure, the polycrystalline silicon layer is converted into an oxide film by oxygen ion implantation and heat treatment, and the polycrystalline silicon layer is patterned by etching (dry etching or wet etching) the oxide film. . In the method of etching the oxide film, the etching ratio with respect to silicon and polycrystalline silicon can be increased, so that the silicon substrate can be prevented from being etched.
Further, the isotropic etching such as wet etching does not etch the polycrystalline silicon layer, so that the patterning dimension accuracy does not deteriorate.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1A to 1D are cross-sectional views showing the steps in order to explain one embodiment of the present invention.

First, as shown in FIG. 1a, an oxide film 2 is grown on a silicon substrate 1, and polycrystalline silicon 3 is formed thereon.
To grow. Next, as shown in FIG. 2B, a photoresist 4 is formed on the polycrystalline silicon 3 and patterned into a predetermined shape, and then oxygen ions 5 are implanted so that the polycrystalline silicon in the portion where the photoresist 4 is not present is formed. Oxygen ions 5 are implanted into 3.

Next, as shown in FIG. 1c, the photoresist 4 is removed, and a heat treatment is carried out, for example, at 1000 ° C. · N ₂ to make the polycrystalline silicon 3 implanted with oxygen ions 5 into an oxide film 6. (For the above processing, for example, the method disclosed in JP-A-59-155126 may be used).

Next, as shown in FIG. 1d, the oxide film 6 is etched (dry etching or wet etching).
Then, the polycrystalline silicon 3 is patterned. According to this embodiment, even if the oxide film 2 is thin, such as a gate oxide film of a MOS transistor, the polycrystalline silicon (for example, gate) 3 can be accurately patterned without etching the silicon substrate 1.

[0014]

[Embodiment 2] FIGS. 2A to 2C are sectional views showing the steps in order to explain the second embodiment of the invention. This example
After patterning the photoresist 4 of the first embodiment, the polycrystalline silicon 3 is used as a mask with the photoresist 4 as a mask.
Is anisotropically etched to leave a certain amount. Then, except that oxygen ions 5 are implanted into the remaining polycrystalline silicon 3 with the photoresist 4 as a mask, the same parts as those in the first embodiment are denoted by the same reference numerals. The description is omitted.

In this embodiment, since the thickness of the polycrystalline silicon which becomes an oxide film is thin, the etching time when the oxide film is isotropically etched can be shortened.
The amount of overetching is reduced, and polycrystalline silicon 3
There is an advantage that the side etching amount of the underlying oxide film 2 can be reduced.

[0016]

[Embodiment 3] FIGS. 3A to 3C are sectional views showing steps in order to explain the third embodiment of the present invention. This example
The refractory metal 7 is formed on the polycrystalline silicon 3 of the first embodiment.
Is formed, a photoresist 4 is formed thereon, and patterned into a predetermined shape. Then photoresist 4
The refractory metal 7 is etched by using as a mask to remove the photoresist 4.

Next, oxygen ions 5 are used with the refractory metal 7 as a mask.
Since it is the same as that of the first embodiment except that is implanted into the polycrystalline silicon 3, the same parts are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is applied to a polycide structure and has an advantage that the silicon substrate 1 is not etched as in the first embodiment.

[0019]

As described above, according to the present invention, when patterning a polycrystalline silicon layer, the polycrystalline silicon layer is converted into an oxide film by oxygen ion implantation and heat treatment. Since the etching ratio with silicon can be increased, it has the effect of preventing the silicon substrate from being etched, and isotropic etching such as wet etching also does not etch the polycrystalline silicon layer, which improves patterning dimension accuracy. effective.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention in the order of steps.

FIG. 2 is a sectional view showing a second embodiment of the present invention in the order of steps.

FIG. 3 is a sectional view showing a third embodiment of the present invention in the order of steps.

FIG. 4 is a sectional view showing a conventional method in order of steps.

[Explanation of symbols]

 1 Silicon Substrate 2 Oxide Film 3 Polycrystalline Silicon 4 Photoresist 5 Oxygen Ion 6 Oxide Film 7 Refractory Metal

Claims (5)

[Claims] 1. A step of forming a polycrystalline silicon layer on a semiconductor substrate, a step of forming a mask material at the time of ion implantation on the polycrystalline silicon layer and patterning it into a predetermined shape, and the mask material As a mask, a step of implanting oxygen ions into the polycrystalline silicon layer, a heat treatment step for converting the polycrystalline silicon layer into which the oxygen ions are injected into an oxide film, and etching the oxidized polysilicon layer. And a step of removing the semiconductor device. 2. A step of forming a polycrystalline silicon layer on a semiconductor substrate via an oxide film, a step of forming a mask material in a predetermined shape on the polycrystalline silicon layer, and using the mask material as a mask. The invention is characterized by a step of implanting oxygen ions into the crystalline silicon layer, a heat treatment step for forming an oxide film in the polycrystalline silicon layer into which the oxygen ions have been implanted, and a step of etching away the oxide film-formed portion. Manufacturing method of semiconductor device. 3. After the mask material is formed, the polycrystalline silicon layer is partially etched using the mask material as a mask,
The method of manufacturing a semiconductor device according to claim 2, wherein oxygen ions are implanted using the mask material as a mask. 4. A step of forming a polycrystalline silicon layer on a semiconductor substrate via an oxide film, a step of forming a refractory metal layer thereon, and a step of etching the refractory metal layer into a predetermined pattern. , A step of implanting oxygen ions into the polycrystalline silicon layer using the refractory metal layer as a mask, a step of performing a heat treatment to form an oxygen ion-implanted portion of the polycrystalline silicon layer, and the oxide film-formed portion Is removed by etching to pattern the polycrystalline silicon. 5. The etching for removing the portion of the polycrystalline silicon layer formed into an oxide film by etching is isotropic etching, claim 2, claim 3 or claim 4.
Of manufacturing a semiconductor device of.