JPH02237019A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To secure the accuracy of pattern by focussing the light of exposure by a method wherein a first film and a second film are patternized almost same as the pattern of a resist film using a patternized resist film as a radical, and the patternized first and the second films are formed into the mask for processing of the substrate. CONSTITUTION:A photoresist is coated on the whole surface of a wiring layer 3, and a first film 21 consisting of a resist is formed by patterning in such a manner that the resist will be left only on the lower step region of the step of the wiring 3 by conducting exposing and developing operations. Then, a second film 22 consisting of resist is formed by coating the same resist as the first film 21 on the whole surface. Subsequently, a third film 23 consisting of SOG is formed by spin-coating spin-on-glass(SOG) on the whole surface, and besides, a resist film for exposure is formed by spin-coating a photoresist on the whole surface. As the surface of the second film 22 is almost plane, the resist film for exposure 24 has the almost plane surface, a focussing can be conducted on the whole area when a patterning exposure is performed, and the accuracy of pattern of the mask for substrate processing can be secured.

Description

[Detailed Description of the Invention] [Summary] A method of manufacturing a semiconductor device, particularly a method of forming a patterned mask for processing a substrate on the surface of a substrate having a step on the surface. The purpose of this is to ensure the pattern accuracy of the substrate processing mask by making it possible to focus the exposure over the entire area despite the presence of the steps in the exposure resist film used in photolithography. After forming a first film on the lower step region of the substrate surface with a surface height approximately equal to the upper step region of the substrate surface using a material that can serve as an anti-processing mask and can be selectively removed from the substrate, A process of forming a second film with a substantially flat surface over the entire surface of the substrate using a material that can be used as a mask for substrate processing and can be selectively removed from the substrate; A process of forming a resist film for exposure and patterning the resist film by exposure and development, and forming a second film and a first film approximately in the pattern of the resist film based on the patterned resist film. The patterned first film and second film are configured to be used as a mask for processing the substrate.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a patterned substrate processing mask on the surface of a substrate having a step on the surface.

2. Description of the Related Art As semiconductor devices become more highly integrated, the pattern to be processed becomes finer, and the level difference formed on the surface of a substrate being processed becomes larger, as seen in, for example, a DRAM.

Therefore, it is necessary for the above-mentioned substrate processing mask to ensure pattern accuracy even when the substrate surface has this step difference.

[Prior Art] In the manufacture of semiconductor devices, substrate processing is performed by forming a mask for substrate processing on the surface of the substrate, for example, ion implantation to form a diffusion region in the semiconductor portion, deposition on the substrate, etc. This includes etching to form electrode windows or ion implantation windows in the insulating film, and etching to pattern a wiring layer deposited on the insulating film. The substrate surface herein refers to the surface of the semiconductor portion, the insulating film, the wiring layer, or the like.

In this case, the blank area of the substrate processing mask becomes the processing area of the substrate, and the pattern of the processing area is fine, so the mask is formed using photolithography.

That is, a resist film for exposure is formed on the surface of a substrate by, for example, spin coating, and the resist film is focused by light irradiation to transfer a photomask pattern. The resist film is exposed to the same light, and the resist film is patterned by development to form the mask for processing the substrate.

Alternatively, in the so-called tri-level method (31 resist method), a resist film and a Sin2 film are sequentially formed on the substrate surface, and then a resist film for exposure is formed and patterned as described above. The SiO film is patterned by etching using the resist film as a mask, and then this S
in. The lower resist film is patterned by etching using the film as a mask, and this resist film is used as a mask for substrate processing. This method allows the lower resist film to be made thicker than the exposure resist film, and even if there is a narrow recess on the substrate surface, the recess is filled and the surface of the lower resist film is almost flat. It has the advantage of being able to become.

, [Problem to be Solved by the Invention] However, the above-mentioned conventional method for forming a mask for processing a substrate does not require wide steps on the surface of the substrate, as shown in the side cross-sectional view of FIG. 2, for example. If you have one, you will have the following problem.

FIG. 2 shows a case where wiring N3 deposited on an insulating film 2 on a substrate 1 in a DRAM is patterned, and a resist film 11 for exposure used as a mask for processing the substrate is formed on the wiring layer 3. Show what you did.

This DRAM has a memory cell area 4 and a peripheral circuit head area 5, and uses a stacked storage capacitor 6 with a laminated structure in the memory cell, so that the memory cell area 4 is raised high, so that the surface of the wiring layer 3 is There is a large step difference between the memory cell region 4 and the peripheral circuit region 5.

From this, the exposure resist film 11 has a step on its surface that follows the wiring layer 3, and during patterning exposure, the focus is focused on one side between the memory cell area 4 and the peripheral circuit head area 5. When one focuses, the other becomes out of focus.

For this reason, the patterning of the resist film 11 becomes inaccurate, and a mask for substrate processing using the resist film 11 is
It is difficult to make it suitable for the micro-machining described in No. 3. This becomes more noticeable as the processing pattern becomes finer because the depth of focus of exposure becomes shallower.

The same holds true even if the tri-level method is adopted. This is because the lower step area (peripheral circuit head area 5) corresponding to the above-mentioned concave portion on the substrate surface is wide, so a step similar to the wiring layer 3 is formed on the surface of the lower resist film, and the exposure resist film is the same as above.

Therefore, the present invention provides a method for manufacturing a semiconductor device, in particular, a method for forming a patterned substrate processing mask on the surface of a substrate having a step on the surface, in which exposure light used in photolithography for patterning is provided. It is an object of the present invention to ensure pattern accuracy of the substrate processing mask by making it possible to focus exposure over the entire area of the resist film despite the presence of the steps.

[Means to solve the problem]

The above purpose is to form a first film on the lower step area of the substrate surface with a surface height approximately equal to the upper step area of the substrate surface using a material that can be used as a mask for substrate processing and can be selectively removed from the substrate. After the formation, there is a step of forming a second film with a substantially flat surface over the entire surface of the substrate using a material that can be used as a mask for substrate processing and can be selectively removed from the substrate, and a step of forming a second film on the second film with a substantially flat surface. A process of forming an exposure resist film with a substantially uniform thickness and patterning the resist film by exposure and development, and forming a second film and a first film on the resist film based on the patterned resist film. This problem is solved by the manufacturing method of the present invention, which includes the step of patterning the I film almost identically to the pattern of the film, and uses the patterned first film and second film as masks for processing the substrate.

[For production]

Due to the presence of the first film, the surface of the second film can easily become substantially flat, so that the surface of the resist film for exposure becomes almost flat regardless of the level difference on the substrate surface, and the focus of exposure can be maintained over the entire area. It becomes something that can be matched.

From this, the resist film for exposure can be patterned with high accuracy, and a mask for substrate processing with guaranteed pattern accuracy can be formed.

〔Example〕

An example of forming a substrate processing mask according to the present invention will be described below with reference to the side sectional view of FIG.

The same reference numerals indicate the same objects throughout the figures.

This embodiment is for patterning the wiring layer 3 on the surface of the DRAM substrate 1 described in FIG. 2.

In FIG. 1, a photoresist (for example, OF
PR800) is applied to the entire surface of the wiring layer 3, and patterned by exposure and development so as to remain only on the lower step area (peripheral circuit head area 5) of the wiring layer 3, thereby forming the first film 21 made of resist. .

The coating is performed, for example, by spin coating, and the thickness is adjusted according to the height of the step on the surface of the wiring layer 3 (difference in height between the memory cell region 4 and the peripheral circuit region 5), for example. It is 0.6 μm. By doing this, the exposed upper part of the memory cell region 4 on the surface of the wiring layer 3 and the surface of the first film 21 are aligned on approximately 1,000 planes, and a narrow recess exists between them. .

Next, the same photoresist as the first film 21 is coated on the entire surface by spin coating to a thickness of about 1 μm to form a second film made of resist.
A film 22 is formed. The above recess is filled with the second film 22.
The surface of is almost flat.

Next, Subin-on-glass (SOG: the main component is SiO)
) is coated on the entire surface by spin coating to a thickness of about 0.2 μm to form the third film 23 made of SOC, and then a photoresist (for example, TSMR8800) is coated on the entire surface by spin coating to a thickness of about 0.2 μm. Resist film 2 for exposure
form 4. Since the surface of the second film 22 is substantially flat, the surface of the exposure resist film 24 is substantially flat, and can be focused over the entire area during patterning exposure.

FIG. 1 shows the situation.

Next, the exposure resist film 24 is patterned in accordance with the pattern of the wiring layer 3 by exposure and development. Because the focus of exposure can be adjusted over the entire area,
This Bakunization can be performed with high precision.

Next, the third SOG film 23 is patterned by RIB (reactive ion etching) using CHFI +Hz plasma using the patterned exposure resist film 24 as a mask, and further, using the patterned third film 23 as a mask. The second resist film 22 and the first resist film 21 are patterned by RIE using 02 plasma, thereby completing a mask for processing the required substrate. Since the above RIE is anisotropic, the pattern of the exposure resist film 24 is faithfully transferred to the formed substrate processing mask, ensuring desired pattern accuracy.

This substrate processing mask is removed after being used as an etching mask for patterning the wiring N3. Its removal can be easily accomplished using well-known methods.

Note that the method for forming the mask for substrate processing described in this embodiment is applicable to a DRA being manufactured that has a step in the wiring N3 on the surface of the substrate.
It goes without saying that this method is also effective when dealing with other semiconductor devices under manufacture that have steps on the substrate surface.

Furthermore, as can be easily understood from the above explanation, the materials of the first film 21 and the second film 22 serve as a mask for processing the object to be processed on the surface of the substrate, and can be selectively removed. It is not limited to the resist of the embodiment, and it is not necessary that the resists are the same.

Furthermore, when the exposure resist film 24 can serve as an etching mask for the materials of the first film 21 and the second film 22,
The third film 23 can be omitted.

[Effects of the Invention] As explained above, according to the configuration of the present invention, a method for manufacturing a semiconductor device, particularly for a substrate having a step on the surface, can be applied.
In a method of forming a patterned mask for processing a substrate on the surface of a substrate, the exposure resist film used for photolithography for patterning can be focused over the entire area despite the presence of the steps. This makes it possible to ensure the pattern accuracy of the substrate processing mask, and has the effect of facilitating microfabrication of a substrate having a step on its surface.

[Brief explanation of drawings]

FIG. 1 is a side sectional view explaining the embodiment; FIG. 2 is a side sectional view illustrating the problems of the conventional method. 23 is the third membrane; 11 and 24 are resist films for exposure; It is. In the figure, 1 is the board, 2 is an insulating film, 3 is the wiring layer, 4 is a memory cell area, 5 is the peripheral circuit area; 6 is a storage capacitor, 21 is the first film; 22 is a second film;

Claims (1)

[Claims] A method for forming a patterned substrate processing mask on the surface of a substrate having a step in the manufacturing of semiconductor devices, the method comprising: forming a patterned substrate processing mask on the substrate surface; On the other hand, after forming a first film using a selectively removable material on the lower step area of the substrate surface, the surface height of which is approximately equal to the upper step area of the substrate surface, the first film can be used as a mask for substrate processing. On the other hand, a process of forming a second film with a substantially flat surface on the entire surface of the substrate using a selectively removable material, and forming a resist film for exposure with a substantially uniform thickness on the second film, A step of patterning the resist film by exposure and development; and a step of patterning a second film and a first film substantially equal to the pattern of the resist film based on the patterned resist film. . A method of manufacturing a semiconductor device, characterized in that the patterned first film and second film are used as masks for processing the substrate.