JP2001308177A - Flattening method of semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method wherein a step-difference of an underlying layer formed on a semiconductor substrate is easily and uniformly flattened without contaminating the semiconductor substrate. SOLUTION: In this flattening method of a semiconductor substrate, the underlying layer 2 having the step-difference 10 is formed on the semiconductor substrate 1. A film 3 for flattening the step-difference 10 is arranged on the underlying layer 2, an adhesive sheet 4 or the like is stuck on the film 3, and the film 3 is subjected to flattening work by peeling operation of the sheet 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for flattening a step on a semiconductor substrate, and more particularly to a method for flattening a step having an underlayer having a step on a semiconductor substrate.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, an underlayer such as an oxide film layer or a metal layer is provided on a semiconductor substrate (silicon wafer), and an etching process is performed using a resist film, which is a resist pattern, as a mask. To form In recent years, the number of metal wirings has increased with the increase in the degree of integration and functionality of semiconductor devices, and the steps in the substrate have increased. Have been used.

A resist pattern is formed by applying a resist material directly on an underlying layer such as an oxide film layer or a metal layer and patterning the resist material. Uneven thickness occurs, and good pattern formation and etching cannot be performed. Therefore, a film for flattening the step, that is, a flattening film is formed on the underlayer, and this film is formed by a CMP (Chemical Mechanical) method.
Attempts have been made to flatten the steps by processing by L polishing or etching back, then apply a resist material and pattern.

[0004]

However, the above CM
In the P method, there is a problem of contamination due to polishing residue on the substrate.
There are also problems such as low productivity and high cost, and furthermore, a flattening film cannot be applied to an organic film. In addition, in the etching method, there is still a problem of contamination due to reaction deposits at the time of etching of the flattening film, and there is a problem that the degree of etching becomes nonuniform on the film surface, making it impossible to evenly flatten the underlying layer. .

According to the present invention, in view of such circumstances, a step of a semiconductor substrate, particularly a step of an underlayer formed on the semiconductor substrate, is easily and uniformly planarized without contaminating the semiconductor substrate. It is intended to provide a way.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above object, and as a result, after forming a flattening film on a stepped underlayer on a semiconductor substrate, the flattening film has been formed. Paste the adhesive sheet on the top and peel it off,
The film portion filled in the step remains on the substrate, and the excess film portion on the underlayer is peeled off and removed integrally with the adhesive sheet, so that the film is uniformly flattened. It has been found that the step can be easily and uniformly flattened without contaminating the substrate, and that this method is particularly effective when the flattening film is an organic coating film. The present invention has been found as a result of further study based on such findings.

That is, the present invention provides a method for flattening a semiconductor substrate, which comprises flattening a step on a semiconductor substrate by using an adhesive sheet, and in particular, has an underlayer having a step on the semiconductor substrate. A step of flattening the step; a step of flattening the underlayer comprising an oxide film layer or a metal layer; and forming a film on the underlayer to flatten the step. Paste adhesive sheets on the film,
By performing a peeling operation, the flattening method of flattening the film, the flattening method in which the film for flattening the step of the underlayer is an organic coating film, and the adhesive sheet are used. The present invention relates to the above-mentioned flattening method, wherein the sheets are UV-curable adhesive sheets.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as an embodiment of the present invention, a method of flattening a step having an underlayer having a step on a semiconductor substrate will be described with reference to FIGS. .

In FIG. 1, an underlayer 2 made of an oxide film layer or a metal layer is provided on a semiconductor substrate 1 by a conventional method, and a resist pattern is formed thereon by a conventional method. By etching the base layer 2 as a mask, circuit elements and wirings are formed. By this processing step, the base layer 2 is provided on the semiconductor substrate 1 so that the portion subjected to the etching processing becomes a step 10.

Next, in FIG. 2, a flattening film 3 made of an organic coating film is formed on the entire surface of the underlayer 2 in order to flatten the step 10. The flattening film 3 is formed by applying and drying an organic coating solution, filling the coating film in the step 10, and flattening the step at the filling portion 3a. However, at the time of the above-mentioned coating and drying, an excessive coating liquid is inevitably formed on the underlayer 2 unevenly, and an excessive portion 3b having poor surface smoothness is formed.
The step 10 cannot be flattened only by forming the flattening film 3. In addition, in addition to the general resist material used for pattern formation, various synthetic resins such as acrylic resins, vinyl chloride resins, and polyester resins, and natural rubber, A coating solution obtained by dissolving synthetic rubber or the like in an appropriate organic solvent is used.

In the present invention, an adhesive sheet 4 is attached on the flattening film 3 as shown in FIG.
At this time, it is preferable that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet 4 is sufficiently adhered to the flattening film 3 by heating and pressing as necessary. As shown in FIG. 5, the pressure-sensitive adhesive sheets 4 are provided with a pressure-sensitive adhesive layer 42 having a thickness of usually 20 to 150 μm on a film substrate 41, and are formed in a sheet shape or a tape shape. Things.

The film base material 41 is made of a plastic such as polyester, polycarbonate, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like. Consisting of, usually 10 to 10
A plastic film of 0 μm is used. The pressure-sensitive adhesive layer 42 may be a non-curable type, but is preferably a curable type which is cured by active energy such as heat or ultraviolet rays. Curable ones are particularly preferably used.

As the UV-curable pressure-sensitive adhesive, an acrylic polymer is used as a pressure-sensitive adhesive, which has at least one polymerizable carbon-carbon double bond in the molecule and usually has a molecular weight of 1%.
Up to 10,000 non-volatile low molecular weight compounds (hereinafter referred to as curable compounds) and a photopolymerization initiator, and if necessary, as a crosslinking agent, polyfunctional such as polyisocyanate, polyepoxy, various metal salts, and chelate compounds. Compounds, fillers such as finely divided silica, tackifying resins, coloring agents, antioxidants,
What mix | blends various additives, such as a polymerization inhibitor, is preferably used. As the adhesive strength, as a 180-degree peel adhesive strength to a semiconductor substrate, 150 g after ultraviolet curing.
It is preferably less than / 10 mm width (usually 10 to 100 g / 10 mm width).

The acrylic polymer may be a homopolymer or a copolymer of an alkyl (meth) acrylate, or a copolymer of the above monomer with a monomer containing a carboxyl group or a hydroxyl group or other monomers requiring modification. A compound having a weight average molecular weight of usually 300,000 to 2,000,000 is preferred. Examples of the curable compound include polyethylene glycol di (meth) acrylate, trimethylolpropanetri (meth) acrylate, tetramethylolmethanetri (meth) acrylate, and oligoester (meth) acrylate.
Acrylate and urethane (meth) acrylate oligomers are used. Examples of the photopolymerization initiator include, for example, benzoin, benzoin ethyl ether, isopropyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, acetophenone diethylketal, and benzyldimethylkether. And α-hydroxycyclohexylphenyl ketone.

After the adhesive sheet 4 is attached as described above, if the adhesive sheet 4 is a curable type such as an ultraviolet curable type, a curing treatment is performed by irradiating ultraviolet rays or the like. The sheets 4 are peeled off. This allows
As shown in FIG. 4, only a portion 3a of the flattening film 3 filling the step 10 remains on the substrate, and a surplus portion 3b on the base layer 2 is peeled off and removed integrally with the adhesive sheet 4, and The film 3 is flattened, so that the step 10 of the underlayer 2 is flattened. In this case, unlike the conventional CMP method or etch back method, there is no fear of contaminating the substrate 1 and moreover, it can be evenly and easily planarized over the entire underlayer, and furthermore, the organic coating film cannot be formed by the CMP method. The above-described effects can be exhibited by applying to the flattening film 3 made of.

The semiconductor substrate 1 having the flattened underlayer 2 can stably perform the pattern formation on the underlayer 2 again and the etching process using the same as a mask. The size of the circuit formed on the semiconductor substrate 1 can be stabilized, the characteristics and reliability of the semiconductor can be improved, the yield of the semiconductor substrate can be improved, and favorable results can be obtained for the productivity of the semiconductor. be able to.

In the flattening method of the present invention,
The planarizing film 3 may have a film configuration other than the organic coating film. Further, the present invention can be applied to a case where the semiconductor substrate has a step other than the base layer. That is, the present invention includes all aspects of flattening a step of a semiconductor substrate using adhesive sheets.

[0018]

Next, an embodiment of the present invention will be described in more detail.

Reference Example 1 CVD (Chemical Vapor Depos)
a resist material comprising PHS (polyhydroxystyrene) and an acid generator is applied to the surface of a silicon wafer (8-inch semiconductor substrate) provided with an underlayer made of an oxide film on the surface, and heated, exposed, Development was performed to form a resist film image (resist pattern).
Using this as a mask, the oxide film of the underlying layer was removed by dry etching, and then the resist mask was removed. Thus, a silicon wafer having a step in the underlayer was formed. Next, on this silicon wafer,
An organic coating solution (resist material comprising the same PHS and acid generator as described above) was applied and dried to form a flattened film so that the steps of the underlayer were flattened as much as possible. .

Example 1 As an acrylic polymer, 2-ethylhexyl acrylate / methyl acrylate / acrylic acid = 30/70/1
0 (weight ratio) of a copolymer, and 100 g of a toluene solution having a concentration of 27% by weight of this polymer was added to a diacrylate of polyethylene glycol 600 as a curable compound (“NK ester manufactured by Shin-Nakamura Chemical Co. A-600 ") 10
0 g, polyethylene glycol 200 dimethacrylate
G (“NK ester 4G” manufactured by Shin-Nakamura Chemical Co., Ltd.) 100
g, polyisocyanate compound 3 as polyfunctional compound
g, 3 g of benzyldimethyl ketal as a photopolymerization initiator
Was uniformly mixed to obtain a UV-curable pressure-sensitive adhesive solution.

This adhesive solution was applied on a polyester film having a thickness of 50 μm, and dried by a drying oven.
3 minutes each at 30 ° C. and 130 ° C.
A μm pressure-sensitive adhesive layer was formed to obtain a UV-curable pressure-sensitive adhesive sheet. The peel strength of the adhesive sheet at 180 ° C. to the silicon wafer before UV curing was 12 g / 10 mm width, and the peel strength after UV curing was 10 g / 10 mm width.

Next, on the silicon wafer having a flattened film for flattening the step formed on the underlying layer having the step by the method of Reference Example 1, the above-mentioned ultraviolet-curable adhesive sheet is applied.
In a reduced pressure atmosphere of about 10 mmTorr, the substrate was pressed and attached on a heating plate at 40 ° C. Thereafter, ultraviolet rays were irradiated from a high-pressure mercury lamp at a dose of 1 J / cm ² to perform a curing treatment. After this curing treatment, the adhesive sheet was peeled off from the silicon wafer. After this operation, when the cross section of the silicon wafer was observed with a scanning electron microscope (SEM), only the portion of the flattened film filling the step remained on the wafer, and the excess portion on the underlayer was an adhesive sheet. The underlying layer was uniformly planarized by selective planarization of the planarizing film. At that time,
No contamination of the silicon wafer by the adhesive sheet was observed at all.

When a resist pattern was formed again on the silicon wafer in which the steps of the underlayer were flattened, no variation in the thickness of the resist film was observed and the etching shape of the underlayer by dry etching was good. Was. As a result, the size of the circuit formed on the silicon wafer was stabilized, and the characteristics and reliability of the semiconductor were improved. It has also been found that the yield of silicon wafers can be improved, and good results can be obtained in terms of semiconductor productivity.

Example 2 Toluene solution 10 of the acrylic polymer obtained in Example 1
0 g of polyethylene glycol 6 as a curable compound.
100 g of diacrylate (“NK ester A-600” manufactured by Shin-Nakamura Chemical Co., Ltd.), 100 g of urethane acrylate (“UN-01” manufactured by Shin-Nakamura Chemical Co., Ltd.), and polyisocyanate as a polyfunctional compound 3 g of a toluene compound and 3 g of benzyldimethylketal as a photopolymerization initiator were uniformly mixed to prepare a UV-curable pressure-sensitive adhesive solution.

Using this pressure-sensitive adhesive solution, a UV-curable pressure-sensitive adhesive sheet was produced in the same manner as in Example 1. 18 with respect to the silicon wafer of this adhesive sheet before ultraviolet curing.
The peel adhesion at 0 ° C. was 84 g / 10 mm width, and the peel adhesion after ultraviolet curing was 11 g / 10 mm width. Next, a flattening film for flattening the step was formed on the stepped underlayer by the method of Reference Example 1 in the same manner as in Example 1 by using this UV-curable pressure-sensitive adhesive sheet. Attachment, curing treatment by ultraviolet irradiation, and peeling operation were attempted on the silicon wafer.

As a result, in the same cross-sectional SEM observation as in the first embodiment, the flattening film is selectively flattened as in the first embodiment, and the underlying layer is uniformly flattened. ,
No contamination by the adhesive sheet on the silicon wafer was observed. When a resist pattern was formed again on the silicon wafer in which the step of the underlayer was flattened, the thickness of the resist film did not vary as in the case of the first embodiment. It has been found that the etching shape of the underlayer is good, that the dimensions of the circuit formed on the silicon wafer can be stabilized, and that the characteristics and reliability of the semiconductor and the productivity can be greatly improved.

COMPARATIVE EXAMPLE 1 A flattening film was processed by etching back on a silicon wafer having a flattening film for flattening the step formed on the underlying layer having the step according to the method of Reference Example 1. I got it. As a result, according to the same cross-sectional SEM observation as in Example 1, the planarization film on the underlayer was not clearly planarized as compared with Example 1, and the steps of the underlayer could be evenly planarized. I couldn't. For this reason, when the resist pattern was formed again thereafter, the thickness of the resist film was varied or the etching shape of the underlying layer due to dry etching became poor as compared with the first embodiment, so that the resist pattern was formed on the silicon wafer. Variations have occurred in the dimensions of the circuit, and good results have not been obtained in the characteristics and reliability of the semiconductor, and further in the productivity.

[0028]

As described above, according to the present invention, the step of the semiconductor substrate, particularly, the step of the underlayer formed on the semiconductor substrate is flattened by using an adhesive sheet. A film for flattening the step is provided on the base layer of the above, an adhesive sheet is attached on this film, and the semiconductor substrate is not contaminated by performing a peeling operation.
Flattening can be performed easily and uniformly, and as a result, the dimensional stability of the circuit on the semiconductor substrate, the characteristics and reliability of the semiconductor, and the yield (productivity) can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which an underlayer having a step is formed on a semiconductor substrate.

FIG. 2 is a cross-sectional view showing a state where a flattening film is formed on the underlayer.

FIG. 3 is a cross-sectional view showing a state where an adhesive sheet is attached on the flattening film.

FIG. 4 is a cross-sectional view showing a state where the above-mentioned adhesive sheets are peeled off.

FIG. 5 is a cross-sectional view showing a configuration of the above-mentioned adhesive sheets.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Underlayer 3 Flattening film 4 Adhesive sheet 10 Step 41 Film base material 42 Adhesive layer

Continued on the front page (72) Inventor Yoshio Terada 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Ryo Namiwa 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko stock In-house (72) Inventor Eiji Toyoda 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Naofumi Tokunaga 6-16 Shinmachi, Ome-shi, Tokyo 3 Hitachi, Ltd. Device development Inside the center (72) Inventor Atsushi Maekawa 5-2-2-1, Kamimizuhoncho, Kodaira-shi, Tokyo F-term in Hitachi Super LSI Systems Co., Ltd. 5F033 RR21 SS21 XX01

Claims (6)

[Claims] 1. A method of flattening a semiconductor substrate, wherein the step of the semiconductor substrate is flattened by using an adhesive sheet. 2. The method according to claim 1, further comprising a stepped base layer on the semiconductor substrate, wherein the step is flattened. 3. The method according to claim 2, wherein the underlayer comprises an oxide film layer or a metal layer. 4. A method for flattening said film by providing a film for flattening the step on the underlayer, sticking an adhesive sheet on the film, and peeling off the film. Item 4. The method for planarizing a semiconductor substrate according to item 2 or 3. 5. A film for flattening a step of an underlayer,
The method for planarizing a semiconductor substrate according to claim 4, wherein the method is an organic coating film. 6. The method for flattening a semiconductor substrate according to claim 1, wherein the adhesive sheets are ultraviolet-curable adhesive sheets.