JPH0473290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for forming a fine groove pattern in an oxide film on a substrate.

(2) Background of the technology Conventionally, for example, lithography has been used to form a desired groove pattern in an oxide film (silicon dioxide film) on a semiconductor substrate. That is, ultraviolet rays are irradiated through a mask with a desired pattern drawn on it, the pattern is baked onto a photoresist film coated on the oxide film, and after the photoresist film is developed, the oxide film layer is etched using the photoresist film as a mask. , to form the desired groove pattern.

(3) Prior art and problems The above process uses ultraviolet light to bake the photoresist film, and is therefore limited by the wavelength of the light, and the width of the groove pattern is limited to about 1 μm. The wavelength of the ultraviolet light used to form this width is approximately
It is 0.4 μm. To achieve groove widths smaller than 1 μm, X-rays or electron beams must be used. However, equipment for generating X-rays or electron beams is expensive and has a complicated structure, and a method of forming fine groove patterns in an oxide film using conventional techniques is desired.

(4) Object of the Invention In view of the above-mentioned conventional problems, the present invention provides a method of forming an accurate microgroove pattern using a commonly practiced technique.

(5) Structure of the Invention According to the present invention, this object includes a step of forming a first film pattern on the surface of a first layer, and a step of forming the first layer so as to cover the first film pattern. a step of depositing a second film on the surface of the second film, and etching the entire surface of the second film to selectively remove a stepped portion of the second film corresponding to an edge of the first film pattern; and a step of selectively etching the exposed first layer using the second film provided with an opening and the first film as a mask. This is achieved by providing a method for forming fine patterns.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 and below show cross-sectional views of the main parts of a semiconductor substrate in the process of carrying out the method of the present invention. Referring to FIG. 1, an oxide film (silicon dioxide film) is )2
A nitride film (nitride film) 3 that can be removed by etching is deposited on top of the film to a thickness of 1000 Å.
A polycrystalline silicon film (polysilicon film) 4 is sequentially grown as a first film thereon to a thickness of about 5000 Å by chemical vapor deposition (CVD). The oxide film 2 may be grown by a thermal oxidation method.

Next, as shown in FIG. 2, the polysilicon film 4 is patterned into an arbitrary first film pattern 4a (for example, if a normal transistor is to be formed on the silicon substrate 1, a pattern with a width covering the entire base or emitter of the transistor) is formed. Eggplant. This patterning is done using conventional lithography methods.

Next, as shown in FIG. 3, a second film, ie, a phosphorous silicate glass (PSG) film 5, which can be removed by etching by low pressure CVD, is grown to a thickness greater than that of the polysilicon film 4 described above. . or
Instead of PSG growth, a silicon dioxide film may be grown to the same thickness by plasma CVD. In the CVD method, film growth proceeds vertically on horizontal surfaces and horizontally on vertical surfaces. As shown in Figure 3, when a step exists and chemical vapor deposition proceeds in the vertical and horizontal directions, PSG growing vertically and PSG growing horizontally are separated along the plane 5a in the figure. This forms a discontinuous surface, and the PSG is rough on this discontinuous surface, and when observed microscopically, the PSG is discontinuous there.

Next, the entire surface is etched using an HF-based etching solution. Along the aforementioned discontinuous surface 5a
Since the PSG is rough (discontinuous), the etching solution penetrates into it, and when etching is allowed to proceed for a certain period of time, the structure shown in FIG. 4 is obtained, and the PSG is removed along the part where the discontinuous surface 5a existed. First groove 6
is formed. For HF-based etching solutions
The etching rate of PSG is fast, and the PSG film with a thickness of about 5000 Å shown in FIG. 3 is completely removed in about 40 seconds. Therefore, etching for about 5 to 10 seconds is sufficient to obtain the first groove 6 shown in FIG. In addition, in the state shown in Figure 4, the PSG
The film 5 is etched to about half the thickness of that shown in FIG. The formation of The etching time to obtain the desired groove width is determined in advance by experiment.

Next, PSG film 5 and polysilicon pattern 4a
Using phosphoric acid as a mask, the nitride film 3 is etched through the first groove 6 to form a second groove 7. At this time, the oxide film 2 below the second groove 7
It is also etched, albeit in a small amount. Continued
When the PSG film 5 is removed by dry etching or wet etching (washout),
The structure shown in FIG. 5 is obtained. For this washout, wet etching is preferable when the PSG film is used, and dry etching is preferable when it is a silicon dioxide film.

Finally, the polysilicon pattern 4a is washed out, and the second groove 7 is partially etched.
When the oxide film 2 is etched through the second groove 7 using the nitride film 3 formed thereon as a mask (FIG. 6), a desired groove pattern is formed in the oxide film 2. According to the measurements of the inventor, 0.1 to 0.15μm
It became possible to form fine grooves 8 with a width of .

As explained above, the PSG film 5 may be replaced with a silicon dioxide film, so the scope of application of the present invention is broadened, and the method of the present invention is not limited to the manufacture of semiconductor devices. , covering all cases of fine pattern formation. Further, the scope of application of the present invention is not limited to the case where the above-described nitride film or PSG film is used.

(7) Effects of the invention As explained in detail above, according to the method of the present invention, using the technology that has been generally practiced in the past,
It is possible to form groove patterns with extremely fine widths on the order of 0.1 to 0.2 μm, which is highly effective in making patterns finer and increasing the degree of integration.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views of essential parts of a semiconductor substrate in the process of carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Oxide film (silicon dioxide film), 3... Nitride film (nitride film), 4... Polysilicon film, 4a... Polysilicon pattern, 5...
PSG film (or silicon dioxide film), 5a...PSG
film or discontinuous surface of silicon dioxide film, 6...first
groove, 7... second groove, 8... groove formed in the oxide film.

Claims (1)

[Claims] 1. A step of forming a first film pattern on the surface of the first layer, and forming a second film on the surface of the first layer so as to cover the first film pattern. a step of depositing the second film, and etching the entire surface of the second film to selectively remove the stepped portion of the second film corresponding to the end of the first film pattern to expose the first layer. and a step of selectively etching the exposed first layer using the second film provided with an opening and the first film as a mask. 2. The fine pattern forming method according to claim 1, wherein the second film is a vapor-phase growth insulating film. 3. The fine pattern forming method according to claim 1, wherein the first film is a polycrystalline silicon film. 4. The fine pattern forming method according to claim 1, wherein the base is a silicon nitride film.