Method of manufacturing semiconductor device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a resist pattern of a semiconductor device.

【0002】

[Conventional technology]

With the increasing integration and miniaturization of semiconductor devices, the problem of element reduction is becoming more important. In particular, the ability to form patterns in the lithography process has become important.

【0003】

In order to achieve high integration of semiconductor devices, it is desired to form fine patterns up to the processing limit by lithography and etching for miniaturization of elements and wiring.

【0004】

A lithography process widely used in the manufacture of semiconductor devices will be described with reference to FIG.

【0005】

As shown in FIG. 4, a silicon oxide film 2 and a silicon nitride film 3 as pad oxide films are sequentially formed on a single crystal silicon substrate 1, and then a photoresist is applied, exposed, and developed to obtain a photoresist pattern. Form 5. The silicon oxide film 2 and the silicon nitride film 3 are patterned using this photoresist pattern 5.

【0006】

[Problems to be Solved by the Invention]

However, in the above-mentioned lithography process, there is a problem that the pattern forming ability is lowered due to the tailing of the photoresist due to the interaction between the resist material and the base film depending on the base film. For example, even if an attempt is made to form a resist pattern 5 having a width of 0.3 micron, there is a problem that the width becomes 0.33 micron due to the tailing of the photoresist, and it is necessary to take a large process margin.

【0007】

An object of the present invention is to provide a method for manufacturing a semiconductor, which is made to solve the above-mentioned conventional problems, eliminates the occurrence of tailing of a photoresist, and improves the lithography technique.

【0008】

[Means for solving problems]

The present invention includes a step of laminating a first substance layer and a second substance layer on a substrate, a step of introducing oxygen into the surface of the second substance layer, and a step of forming an oxide layer on the surface of the second substance layer, and a second. It is characterized by including a step of forming a pattern on a material layer by lithography.

【0009】

The first substance layer can be composed of a silicon oxide film, and the second substance layer can be composed of a silicon nitride film.

【0010】

Further, thermal oxidation or oxygen plasma treatment can be used as the means for introducing the oxygen.

【0011】

As described above, the present invention reduces the interaction with the resist material by introducing oxygen into the second substance layer by, for example, thermal oxidation treatment. As a result, it is possible to reduce the tailing of the resist and improve the pattern forming ability.

【0012】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings. The same parts as those in the conventional example are designated by the same reference numerals.

【0013】

A silicon oxide film 2 (thickness 10 to 20 nm) is formed as a first substance layer on a p-type single crystal silicon substrate 1 by, for example, a thermal oxidation method using 950 ° C dry oxygen, and then CVD is performed on the silicon oxide film 2 (thickness 10 to 20 nm). A silicon nitride film 3 (100 to 300 nm) is formed as the second material layer by the method (decompression CVD method, plasma CVD method, high density plasma CVD method or atmospheric pressure CVD method) (see Fig. 1 (a)). ..

【0014】

The silicon oxide film 2 plays a role of protecting the stress buffer and the active region in the subsequent step, and the silicon nitride film 3 plays a role of a stopper in the subsequent flattening step.

【0015】

Next, thermal oxidation is performed at a temperature of about 900 to 1200 ° C. to modify the surface of the silicon nitride film 3 to form an oxide nitride film 4 having a thickness of about 0.3 to 5 nm (see FIG. 1 (b)). ).

【0016】

Then, the photoresist 5 is applied onto the oxide film 4, exposed and developed to form the photoresist pattern 5 (see FIGS. 1 (c) and 1 (d)).

【0017】

According to the present invention, the interaction with the resist material can be reduced by thermally oxidizing the surface of the silicon nitride film 3 to provide the modified oxide nitride film 4. As a result, it is possible to reduce the tailing of the resist and improve the pattern forming ability as shown in FIG. 1 (d).

【0018】

In addition, as a method of treating the surface of the silicon nitride film 3 in order to reduce the interaction of the resist material, the method of performing thermal oxidation has been described in the above-described embodiment, but oxygen is applied to the surface by another method. The same effect can be obtained by forming the introduced layer. For example, ozone may be plasma-treated to introduce oxygen to the surface, oxygen may be ion-implanted to be introduced, or treated with a chemical solution.

【0019】

Further, in the above embodiment, the silicon nitride film 3 was used as the second substance layer, and the surface thereof was subjected to oxidation treatment. However, as the second substance layer, an amorphous silicon film, a polysilicon film, a Ti film, and a TiN film were used. By using and performing the same surface treatment, the interaction of the resist material can be reduced.

【0020】

Next, an embodiment in which the present invention is used in the trench element separation method (Shallow Trench Isolation method: hereinafter referred to as the STI method) will be described with reference to FIGS. 2 (a) to 3 (h).

【0021】

Step 1 (see Fig. 2 (a)): A silicon oxide film 2 (thickness 10 to 20 nm) was formed on a p-type single crystal silicon substrate 1 by using, for example, a thermal oxidation method using 950 ° C dry oxygen. After that, a silicon nitride film 3 (100 to 300 nm) is formed on the silicon nitride film 3 (100 to 300 nm) by using the CVD method. Thermal oxidation is performed at a temperature of about 900 to 1200 ° C. to form an oxide nitride film 4 having a thickness of about 0.3 to 5 nm on the surface of the silicon nitride film 4. Then, the photoresist 5 is applied onto the oxide nitride film 4, exposed and developed to form the photoresist pattern 5. By thermally oxidizing the surface of the silicon nitride film 3 to form the oxide nitride film 4, the interaction with the resist material is reduced. As a result, the hemming of the resist is reduced.

【0022】

Step 2 (see Fig. 2 (b)): The oxide nitride film 4, the silicon nitride film 3, and the silicon oxide film 2 are etched using the resist 5 formed by the photolithography technique as a mask corresponding to the element separation region. To form a hard mask for forming a trench. This etching is, for example, Cl₂This is done by RIE using a gas mainly composed of. After the etching is completed, the resist is removed (see Fig. 1 (c)).

【0023】

Step 3 (see Fig. 2 (d)): In the STI forming region opened with the oxide nitride film 4 and the silicon nitride film 3 as masks, for example, HBr and oxygen (0).₂A groove 6 having a depth of about 350 nm is formed on the silicon substrate 1 by RIE using a gas such as).

【0024】

Step 5 (see FIG. 3 (e)): The silicon substrate 1 after groove formation is oxidized by, for example, 950 ° C dry oxygen by about 15 nm to form an oxide film 7. At this time, the corner portion of STI shown in FIG. 8 is oxidized so that the corner is rounded.

【0025】

Step 6 (see Figure 3 (f)): Groove 6 is silicon dioxide (SiO) by, for example, HDP-CVD method.₂Membrane) 9 is deposited at about 200 nm and backfilled.

【0026】

Step 7 (see FIG. 3 (g)): The insulating film 9 deposited on the oxide nitride film 4 and the silicon nitride film 3 is removed by using the CMP method, and the entire upper surface of the oxide nitride film 4 is exposed. At this time, the film thickness of the insulating film 9 is reduced by CMP. In addition, instead of the CMP method, anisotropic whole surface etch back may be performed to flatten the surface. When this etchback is used, the oxide nitride film 4 serves as an etching stopper due to the difference in etching rate between the silicon oxide film 9 and the oxide nitride film 4, and the etchback ends when the oxide nitride film 4 is exposed.

【0027】

Step 8 (see Fig. 3 (h)): Selectively remove the oxide nitride film 4 and the silicon nitride film 3 using phosphoric acid heated to 160 ° C. With the insulating film 2 and the element separation film 10 exposed, the insulating film 2 is removed. In this way, the element separation region by the STI method can be created with a fine pattern.

【0028】

In the above embodiment, the present invention is used in the STI method, but the present invention is not limited to this, and it goes without saying that the present invention can be applied to other patterning.

【0029】

[Effect of the invention]

As described above, according to the method for manufacturing a semiconductor device according to the present invention, the pattern forming ability of the lithography process can be improved by forming the oxide nitride film on the surface by thermally oxidizing the silicon nitride film. Can be done.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing which shows the manufacturing method of the semiconductor device of this invention by a process.

[Figure 2]

It is sectional drawing which shows the embodiment which used this invention in the STI method for each process.

[Fig. 3]

It is sectional drawing which shows the embodiment which used this invention in the STI method for each process.

[Fig. 4]

It is sectional drawing which shows the manufacturing method of the conventional semiconductor device by process.

[Explanation of symbols]

1 Silicon substrate, 2 Silicon oxide film 3 Silicon nitride film 4 Oxidation nitride film 5 resist pattern