JP3563709B2 - Thin film formation method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin film forming method for forming a flat thin film by reducing unevenness of a lower layer in manufacturing a semiconductor device, a mounting substrate, and a liquid crystal substrate.
[0002]
[Prior art]
2. Description of the Related Art With the increase in the density of semiconductor integrated circuits, multilayer wiring technology has become essential. In order to realize the multilayer wiring technology, a flattening technology of an insulating film or a metal wiring layer for separating the wiring layers has been developed. Heretofore, SOG (Spin-On-Glass) method and PIQ method (K. Sato, S. Harada, A. Saiki, T. Kitamura, T. Okubo, and K. K.) Mukai, "A Novel Planar Multilevel Interconnection Technology Utilizing Polymer", IEEE Trans. Part Hybrid Package., PHP-9, 176 (1973).
[0003]
In addition, the etch-back method (P. Elkins, K. Reinhardt, and R. Layer, "A planarization process for double metal CMOS using Spin-on Glass as a sacrifice, 100 ed. )) And the lift-off method (K. Ehara, T. Morimoto, S. Muramoto, and S. Matsuo, "Planar Interconnection Technology for LSI Fabrication Lifting proofing proofing. 1, No.2,419 (1984).) Was also examined, such as.
[0004]
In the 1990s, a polishing method has been proposed as a method for planarizing the surface of an interlayer film (WJ Patrick, WL Guthrie, CL Standley, PM Schiable, "Application"). of Chemical Mechanical Polishing to the Fabrication of VLSI Circuit Interconnections ", J. Electrochem. Soc., Vol. 138, No. 6, June, 1778 (1991). This is a technique generally called a chemical mechanical polishing (CMP) method.
[0005]
Of the various flattening methods described above, generally, an etch-back method and a CMP method are mainly used. In these methods, after an insulating film is formed on a wiring electrode, a convex portion on the surface of the insulating film is shaved and flattened, which is a widely used technique. In particular, the CMP method is a technique that has been actively developed in recent years. The planarization by the CMP method will be briefly described. First, as shown in FIG. 4A, a pattern 402 such as a wiring is formed on a substrate 401, and then an insulating film 403 is formed on the substrate 401 so as to cover the pattern 402. To form
[0006]
At the time when the insulating film 403 is formed, as shown in FIG. 4A, the insulating film 403 above the pattern 402 is raised in a convex shape. Thereafter, the convex portion is ground by the CMP method, and the surface of the insulating film 403 is made flat as shown in FIG. However, the CMP method has a lack of stability and simplicity in some cases, such as a strong pattern dependency and a need to prepare a dummy pattern in some cases.
[0007]
In addition to the above-described flattening technique, a flattening method using transfer has been proposed as a new technique (K. Machida et al., "Novell Global Planarization Technology for Interlayer Diertrics Uses, Spin on Glass, Pharmaceuticals, J.P. Sci.Technol.B16 (3), May / June, 1093 (1998)). In this method, a thin film to be formed is previously formed on a base material, dried in the air, and then heated and pressed in a vacuum to transfer the thin film onto a semiconductor substrate.
[0008]
[Problems to be solved by the invention]
However, in the above-described flattening method by transfer, since a thin film to be transferred flows during heating and pressurization to achieve flattening, there is a problem that it can be applied only to a special material such as a thermoplastic material. there were.
The present invention has been made in order to solve the above problems, and has as its object to realize a planarization method by transfer using a wider variety of materials.
[0009]
[Means for Solving the Problems]
The thin film forming method of the present invention includes a first step of forming a thin film in a first state by applying a coating solution in which a desired material is dissolved or dispersed in a medium on a substrate, and forming the substrate in a vacuum. The medium in the thin film was volatilized by heating at a temperature of about 50 ° C. in an atmosphere evacuated to a degree of 330 to 1920 Pa by 50 to 80%, and the thin film was held on the base without flowing out from the base. A second step of bringing a second state having fluidity within a range in which the state can be maintained, a third step of bringing the thin film forming surface of the base into contact with the substrate surface, and a pressure between the base and the substrate And a fifth step of separating the base material from the thin film to form a thin film in the second state on the substrate.
[0010]
In the above invention, in the first step, a coating liquid in which a desired material is dissolved in a medium is applied to the base material to form a thin film in the first state on the base material, and the second step Then, the medium in the thin film in the first state is volatilized to form the thin film in the second state. Further, in the first step, a coating liquid in which a desired material is dispersed in a medium is applied on the substrate to form a thin film in the first state on the substrate, and in the second step, The medium in the first state thin film is volatilized to form the second state thin film.
In the above invention, the material constituting the thin film is an organic material. In the fourth step, the substrate is heated.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the method of forming a thin film according to the present embodiment, first, as shown in FIG. 1A, a positive photosensitive resin is coated on a sheet film (substrate) 101 made of a thermoplastic resin film by a solvent (medium). ) Is applied to form a coating film (first state thin film) 102. As the resin, a resin obtained by adding a positive photosensitive agent to a base resin such as polyimide, polyamic acid, or polybenzoxazole is used.
[0012]
In the case of using polybenzaxazole as a base resin, for example, CRC8304 (trade name) manufactured by Sumitomo Bakelite Co., Ltd. may be used. In this embodiment mode, a coating liquid using this material is applied by about 7 μm to form the coating film 102. The coating liquid to be applied is not limited to a solution in which the components remaining as a film are dissolved in a medium, and the components remaining as a film are dispersed in a medium by using, for example, a surfactant. There may be.
[0013]
Next, as shown in FIG. 1 (b), in the thin film forming apparatus 110, the sheet film 101 is fixed on the transfer plate 114, and the fixed sheet is fixed in a state where the degree of vacuum in the thin film forming chamber 111 is set to about 2000 Pa. The film 101 is heated to about 50 ° C. for 2 minutes. As a result, the medium in the coating film 102 formed on the sheet film 101 is volatilized to obtain a dried film (a thin film in the second state) 102a in which a predetermined fluidity is obtained. Further, by volatilizing the medium in a state of being evacuated, it is possible to prevent the volatilized medium from flowing on the dry film 102a. Here, the volatilization amount of the medium is set to about 50%.
[0014]
Here, the thin film forming apparatus 110 shown in FIG. 1B will be described. In a thin film forming chamber 111 which can be evacuated, a sample stage 112 for fixing a substrate to be processed downward, and a sample stage 112 are arranged opposite to the sample stage 112. The transfer plate 114 and a transfer plate support plate 115 for moving the transfer plate 114 are arranged. Note that the sample table 112 is fixed to the thin film formation chamber 111 by support rods 118.
[0015]
Further, the thin film forming chamber 111 is evacuated by a vacuum exhaust unit (not shown) communicating with the exhaust port 113. As described above, the degree of vacuum in the thin film forming chamber 111 is set to about 2000 Pa by this vacuum exhaust means. Further, the sample stage 112 and the transfer plate 114 are provided with heaters 116 and 116a as a heating mechanism inside, and the heaters 116 and 116a are controlled by heater control units 117 and 117a, and the heating is controlled between 0 and 300 ° C. . The above-described heating of the sheet film 101 is performed by the heater 116 controlled by the heater control unit 117.
[0016]
The transfer plate 114 is connected to the transfer plate support plate 115 by a spring 119 so that the transfer plate 114 can be uniformly loaded. The transfer plate support plate 115 is intended to move the transfer plate 114 in the direction of the sample table 112, that is, upward. The transfer plate support plate 115 is held by a support 120 for moving the transfer plate 114 in parallel. By pushing up the transfer plate 114, that is, the transfer plate support plate 115, the sheet film 101 on the transfer plate 114 can be brought into contact with a later-described substrate 103 fixed to the sample table 112.
[0017]
Here, for example, if a weighting motor is provided outside the transfer plate support plate 115 via a weighting drive unit, the sheet film held between the sample table 112 and the substrate 103 on the transfer plate 114 is in contact with the substrate 103. 101 can be weighted from the back. If a weight sensor or the like is provided on the rear surface (upper portion) of the sample table 112 to measure the weight that the sample table 112 receives from below, overload can be prevented.
[0018]
In the thin film forming apparatus 110 described above, the coating film 102 applied on the sheet film 101 is dried to a certain extent as a dried film 102a as described above, while the wiring pattern is formed as shown in FIG. A substrate 103 on which 104 is formed is prepared. The substrate 103 is, for example, a semiconductor substrate, and the wiring pattern 104 is a wiring made of aluminum having a thickness of about 0.5 μm. This wiring can be formed by, for example, forming an aluminum film by a sputtering method, and then processing the formed aluminum film by a known photolithography technique and etching technique.
[0019]
The sheet film 101 is brought into contact with the substrate 103 prepared in this manner so that the dry film 102a and the surface on which the wiring pattern 104 is formed face each other. In this contact, the substrate 103 is fixed to the sample stage 112 of the thin film forming apparatus 110 shown in FIG. 1B, the transfer plate support plate 115 is moved upward, and the transfer plate 114 is pressed against the sample stage 112. do it. By this pressing, the substrate 103 fixed to the sample table 112 comes into contact with the dry film 102a applied to the sheet film 101 fixed on the transfer plate 114.
[0020]
In this state, the transfer plate support plate 115 is moved further upward, so that the transfer plate 114 is loaded from below to above, and a force of 98 N is applied between the sheet film 101 and the substrate 103. In addition, the heater 116a is caused to generate heat by controlling the heater control unit 117a, whereby the substrate 103 fixed on the sample stage 112 is heated to about 120 ° C. The heating and pressurizing are performed for about 15 minutes.
As a result, as shown in FIG. 1D, the dry film 102a on the sheet film 101 is brought into close contact with the surface of the substrate 103 so as to embed the wiring pattern 104 on the substrate 103.
[0021]
As described above, the dried film 102a on the sheet film 101 is heated and dried in a vacuum-evacuated and reduced-pressure atmosphere, so that the dried film 102a does not flow out of the sheet film 101 and is maintained on the sheet film 101. It is in a state having fluidity within the range that can be achieved. In the above-mentioned conventional technology, the film formed on the sheet film is made to have fluidity by heating or the like. was there.
[0022]
On the other hand, in the present embodiment, a material to be a film is dissolved or dispersed in a medium to form a coating film, and by adjusting the mass of the medium in the coating film, the coating film has fluidity. The fluidity was controlled. For example, in the above description, the medium is volatilized by 50% from the coating film 102 immediately after the coating, so that the dried film 102a has a predetermined fluidity. As a result, the dried film 102 a on the sheet film 101 absorbs the step of the wiring pattern 104 formed on the substrate 103 and comes into close contact with the substrate 103 by being pressed against the substrate 103.
[0023]
Next, as shown in FIG. 2A, when the sheet film 101 is peeled off from the dry film 102a adhered to the substrate 103, the step of the wiring pattern 104 is absorbed and the surface is flattened. A state in which the film 102a is formed is obtained. Thereafter, the substrate 103 is heated to about 310 ° C. for 60 minutes in a nitrogen atmosphere to thermally cure the dried film 102a. As a result, as shown in FIG. 2B, a state is obtained in which the insulating film 105 covering the wiring pattern 104 and having a flat surface is formed on the substrate 103. Note that the insulating film 105 is formed to have a thickness of about 6.0 μm.
[0024]
Here, FIG. 3 shows the relationship between the degree of vacuum in the atmosphere and the amount of volatilization when the medium of the coating film 102 is volatilized. As is clear from FIG. 3, the higher the degree of vacuum, that is, the lower the pressure of the atmosphere, the greater the amount of medium volatilized in the coating film 102. In the above embodiment, by setting the medium volatilization amount to 50%, the dry film 102a does not flow out of the sheet film 101 and has a fluidity in a range that can be maintained on the sheet film 101. And Thus, the step is absorbed to form the flat insulating film 105.
[0025]
However, the present invention is not limited to this. For example, the medium volatilization amount may be set to 80%, the fluidity of the coating film applied on the sheet film may be reduced, and the coating film may not enter between the wirings on the substrate to be transferred. In this case, when the coating film is transferred from the sheet film to the substrate and the coating film is formed on the substrate, a cavity is formed between the wirings. For example, in the case of LSI wiring, the problem of crosstalk can be suppressed by lowering the dielectric constant between wirings. However, as described above, by forming a cavity between wirings, the dielectric between the wirings becomes more dielectric than a state in which an insulator is filled. The rate can be reduced.
[0026]
【The invention's effect】
As described above, in the present invention, the state of the thin film in the first state formed on the base material by coating or the like is changed, and the volatile components constituting the thin film are reduced from 50 to 80 from the thin film in the first state. % Volatilization to control the fluidity of the thin film on the substrate and transfer the thin film onto the substrate. Therefore, according to the present invention, even if the material constituting the film itself does not have fluidity, flattening by transfer becomes possible, so that a flattening method by transfer can be realized using a wider variety of materials. An excellent effect is obtained.
[Brief description of the drawings]
FIG. 1 is a process chart for explaining a thin film forming method according to an embodiment of the present invention.
FIG. 2 is a process chart for explaining a thin film forming method following FIG. 2;
FIG. 3 is a correlation diagram showing the relationship between the degree of vacuum in the atmosphere and the amount of volatilization when the medium of the coating film 102 is volatilized.
FIG. 4 is a process chart for explaining a conventional planarization technique.
[Explanation of symbols]
101: sheet film (substrate), 102: coating film (first state thin film), 102a: dry film (second state thin film), 103: substrate, 104: wiring pattern, 105: insulating film, 110 ... thin film forming apparatus, 111 ... thin film forming chamber, 112 ... sample stage, 113 ... exhaust port, 114 ... transfer plate, 115 ... transfer plate support plate, 116, 116a ... heater, 117, 117a ... heater control unit, 118 ... support Rods, 119 ... springs, 120 ... posts.

Claims (4)

A first step of forming a thin film in a first state by applying a coating solution in which a desired material is dissolved in a medium on a base material;
The medium in the thin film in the first state is volatilized by heating the base material to a temperature of about 50 ° C. in an atmosphere evacuated to a degree of vacuum of 330 to 1920 Pa by 50 to 80%. A second step of forming a second state having a fluidity in a range that can maintain a state held on the base material without flowing out from the base material,
A third step of bringing the thin film forming surface of the base material into contact with the substrate surface;
A fourth step of applying pressure between the substrate and the substrate;
A fifth step of peeling the base material from the thin film so that the thin film in the second state is formed on the substrate. A first step of forming a thin film in a first state by applying a coating liquid in which a desired material is dispersed in a medium on a base material;
The medium in the thin film in the first state is volatilized by heating the base material to a temperature of about 50 ° C. in an atmosphere evacuated to a degree of vacuum of 330 to 1920 Pa by 50 to 80%. A second step of forming a second state having a fluidity in a range that can maintain a state held on the base material without flowing out from the base material,
A third step of bringing the thin film forming surface of the base material into contact with the substrate surface;
A fourth step of applying pressure between the substrate and the substrate;
A fifth step of peeling the base material from the thin film so that the thin film in the second state is formed on the substrate. The method for forming a thin film according to claim 1 or 2,
The method for forming a thin film, wherein the material is an organic material. The thin film forming method according to any one of claims 1 to 3,
In the fourth step, the substrate is heated.

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