METHOD FOR FORMING WIRING ON SEMICONDUCTOR DEVICE

A method for forming electroconductive elements into a pattern on a substrate, in which: recesses (3) in a printing plate (2) are filled with an electroconductive paste (4) containing a resin that is curable by active light rays, the active-light-curable-resin-containing electroconductive paste (4) including an active-light-curable resin for which the average particle diameter is set to 0.1-20 μm; the printing plate (2) is superposed on a substrate (1); at least a contact interface portion at which the active-light-curable-resin-containing electroconductive paste (4) contacts the recesses (3) is cured by being irradiated with active light rays from the printing plate (2) side; and then the printing plate (2) is separated from the substrate (1), the active-light-curable-resin-containing electroconductive paste (4) is transferred to the substrate (1), and electroconductive elements (5) having a prescribed pattern are formed on the substrate (1).

TECHNICAL FIELD

The present invention relates to a method for forming electroconductive elements into a pattern on a substrate.

BACKGROUND ART

Semiconductor chips are proceeding to decrease in size as chip wiring rules allow for increases in fineness. However, in substrates on which chips are mounted (i.e., semiconductor package substrates), it has become difficult to reduce the substrate surface area using the same proportions as those for the chip size because limitations are imposed in regard to increasing the fineness of bump pitch.

In view of the foregoing, the applicant furthered the development of a feature for reducing the pitch of substrate wiring using grayscale lithography and imprinting techniques, and proposed the method for manufacturing a substrate having electroconductive elements that is disclosed in Japanese Laid-open Patent Application No. 2016-58664 (referred to below as a prior-art example).

In the prior-art example: recesses provided to a printing plate are filled with an electroconductive paste, the recesses being formed in the same pattern as a wiring pattern to be formed on a substrate; and the printing plate, in which the recesses are filled with the electroconductive paste, is superposed and pressure-bonded onto the substrate, whereby the electroconductive paste with which the recesses in the printing plate are filled is transferred to the substrate, and wiring having a prescribed pattern is formed on the substrate.

PRIOR ART DOCUMENTS

Patent Documents

DISCLOSURE OF THE INVENTION

Problem the Invention is Intended to Solve

In the prior-art example described above, the applicant used a thermoset-resin-containing electroconductive paste in which a thermoset resin was incorporated into an electroconductive paste. When the electroconductive paste with which the recesses in the printing plate are filled is transferred to the substrate, the resin in sites where the electroconductive paste contacts the printing plate is cured through a heat treatment, so that the release properties of the electroconductive paste relative to the printing plate are improved.

However, in the prior-art example, although using thermoset-resin-containing electroconductive paste improves the release properties, other problems may arise; i.e., thermal expansion or thermal shrinkage may occur due to the heat treatment, the pattern may deform as a consequence thereof or stress may arise between the electroconductive paste and the printing plate due to the pattern deforming, there will be a greater likelihood of incomplete transferring due to the resulting stress, and it will be necessary to maintain a heated state for a given time in the heat treatment, increasing the processing time and reducing throughput.

The present invention was contrived in view of such circumstances, it being an object of the present invention to provide an exceptionally practical method for forming electroconductive elements into a pattern on a substrate, the method being such that pattern deformation occurring during curing of an electroconductive paste is suppressed when a prescribed wiring pattern is formed by transfer on a substrate, complete transfer of the electroconductive paste can be realized, a curing process can be performed in a short time, and throughput is improved.

Means for Solving the Problem

The present invention relates to a method for forming electroconductive elements into a pattern on a substrate, the method being characterized by having: a step for filling recesses3that are formed in a printing plate2and that exhibit a prescribed pattern with an electroconductive paste4containing a resin that is curable by active light rays, the active-light-curable-resin-containing electroconductive paste4being obtained by incorporating an active-light-curable resin into an electroconductive paste for which the average particle diameter of an electroconductive material is set to 0.1-20 μm; a step for superposing the printing plate2filled with the active-light-curable-resin-containing electroconductive paste4onto a substrate1; a step for irradiating the active-light-curable-resin-containing electroconductive paste4, with which the recesses3in the printing plate2are filled, with active light rays and curing the active-light-curable-resin-containing electroconductive paste4; and a step for separating the printing plate2from the substrate1, transferring the active-light-curable-resin-containing electroconductive paste4to the substrate1, and forming electroconductive elements5having the prescribed pattern on the substrate1.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the first aspect, the method being characterized in that the active-light-curable-resin-containing electroconductive paste4is irradiated with the active light rays from the bottom side of the recesses3in the printing plate2during curing.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the first aspect, the method being characterized in that the volumetric content ratio for the active-light-curable resin in the active-light-curable-resin-containing electroconductive paste4is 70% or less.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the second aspect, the method being characterized in that the volumetric content ratio for the active-light-curable resin in the active-light-curable-resin-containing electroconductive paste4is 70% or less.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to any of the first to fourth aspects, the method being characterized in that an intermediate layer6that deforms under application of pressure is provided to the substrate1, the printing plate2filled with the active-light-curable-resin-containing electroconductive paste4is superposed on the intermediate layer6, and the active-light-curable-resin-containing electroconductive paste4is transferred to the substrate1with the intermediate layer6interposed therebetween.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the fifth aspect, the method being characterized in that the intermediate layer6is formed from an active-light-curable resin or a thermoset resin.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to any of the first to fourth aspects, the method being characterized in that the active-light-curable resin is an ultraviolet-ray-curable resin that is cured by being irradiated with ultraviolet rays.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the fifth aspect, the method being characterized in that the active-light-curable resin is an ultraviolet-ray-curable resin that is cured by being irradiated with ultraviolet rays.

The present invention also relates to the method for forming electroconductive elements into a pattern on a substrate according to the sixth aspect, the method being characterized in that the active-light-curable resin is an ultraviolet-ray-curable resin that is cured by being irradiated with ultraviolet rays.

Effect of the Invention

Due to being configured as described above, the present invention provides an unprecedented and innovative method for forming electroconductive elements into a pattern on a substrate, the method being such that pattern deformation occurring during curing of an electroconductive paste is suppressed when a prescribed wiring pattern is formed by transfer on a substrate, complete transfer of the electroconductive paste can be realized, and furthermore, curing advances in a short time (instantaneously) provided that an active-light-curable resin is irradiated with active light rays required for the effect, therefore making it possible to shorten the time required for a curing process and to improve throughput. Moreover, in the method according to the present invention, because there is used an active-light-curable-resin-containing electroconductive paste obtained by incorporating an active-light-curable resin into an electroconductive paste for which the average particle diameter of an electroconductive material is set to 0.1-20 μm, the wiring pattern formed by transfer on the substrate becomes smoother (assumes a smooth form having few recesses and protrusions), whereby localized concentration of electrical fields between wirings is mitigated and the long-term reliability of the wirings is improved.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are briefly described below with reference to the diagrams while indicating the effects of the present invention.

Recesses3formed in a printing plate2are filled with an electroconductive paste4containing a resin that is curable by active light rays, the printing plate2filled with the active-light-curable-resin-containing electroconductive paste4is superposed on a substrate1(or the substrate1may be superposed on the printing plate2), and, for example, at least a contact interface portion at which the active-light-curable-resin-containing electroconductive paste4with which the recesses3are filled contacts the recesses3is cured by being irradiated with active light rays from the printing plate2side, after which the printing plate2is separated from the substrate1.

The active-light-curable-resin-containing electroconductive paste4, with which the recesses3in the printing plate2are filled, is thereby transferred to the substrate1, and electroconductive elements5having a prescribed pattern are formed on the substrate1. The printing plate2may be superposed on the substrate1after at least the contact interface portion at which the active-light-curable-resin-containing electroconductive paste4with which the recesses3are filled contacts the recesses3is cured by being irradiated with active light rays in advance.

In the present invention, as described above, the active-light-curable-resin-containing electroconductive paste4is used as an electroconductive paste for forming the electroconductive elements5, and the active-light-curable-resin-containing electroconductive paste4is cured by being irradiated with active light rays. Therefore, the release properties of the active-light-curable-resin-containing electroconductive paste4with respect to the printing plate2are improved, the occurrence of defects such as pattern deformation or incomplete transfer occurring upon curing with heat is prevented, and furthermore, the time required for a curing process is shorter than is the case when curing with heat (i.e., curing advances instantaneously) and throughput is also improved.

Moreover, in the present invention, because the electroconductive elements5are formed from the active-light-curable-resin-containing electroconductive paste4, which is obtained by incorporating an active-light-curable resin into an electroconductive paste for which the average particle diameter of an electroconductive material is set to 0.1-20 μm, the electroconductive elements5formed on the substrate1becomes smoother (assumes a smooth form having few recesses and protrusions), whereby localized concentration of electrical fields between wirings is mitigated and the long-term reliability of the wirings is improved.

Thus, the present invention relates to an unprecedented and innovative method for forming electroconductive elements into a pattern on a substrate.

EXAMPLES

A specific example of the present invention is described below with reference to the drawings.

The present example relates to a method for manufacturing a semiconductor device (method for forming wiring in a semiconductor device).

Specifically, the present invention relates to a method for forming electroconductive elements5(wiring) having a prescribed pattern on a substrate1using an imprinting technique, the method having: a step (electroconductive paste filling process step) for filling recesses3that are formed in a printing plate2and that exhibit a prescribed pattern with an electroconductive paste4containing a resin that is curable by active light rays, the active-light-curable-resin-containing electroconductive paste4being obtained by incorporating an active-light-curable resin into an electroconductive paste for which the average particle diameter of an electroconductive material is set to 0.1-20 μm; a step (printing plate superposition process step) for superposing the printing plate2filled with the active-light-curable-resin-containing electroconductive paste4onto the substrate1; a step (electroconductive paste curing process step) for irradiating the active-light-curable-resin-containing electroconductive paste4, with which the recesses3in the printing plate2are filled, with active light rays and curing the active-light-curable-resin-containing electroconductive paste4; and a step (electroconductive paste transfer process step) for separating the printing plate2from the substrate1, transferring the active-light-curable-resin-containing electroconductive paste4to the substrate1, and forming the electroconductive elements5having the prescribed pattern on the substrate1.

First to be described are, inter alia, the members that are used in the present example.

In the substrate1, an intermediate layer6is provided to an electroconductive element formation surface at which the electroconductive elements5are to be formed. The intermediate layer6is used for bringing the active-light-curable-resin-containing electroconductive paste4uniformly into contact with the electroconductive element formation surface of the substrate1. The intermediate layer6is formed from an adhesive material that deforms under application of pressure, specifically an active-light-curable resin or a thermoset resin, and is provided at least to a position at which the electroconductive elements5are to be formed.

The recesses3, which exhibit the same pattern as the electroconductive elements5having the prescribed pattern to be formed by transfer on the substrate1, are formed in the printing plate2.

Specifically, the printing plate2of the present example is a replica mold obtained by: adding a resin material such as a cycloolefin polymer (COC), polyethylene terephthalate (PET), a liquid crystal polymer (LCP), polymethyl methacrylate (PMMA), polydimethyl siloxane (PDMS), or a polyimide (PI) dropwise into a master mold produced in advance; applying pressure to the resin material using a support substrate; and curing the resin material.

The recesses3are formed in shapes having differing depths such that electroconductive elements5that serve as wiring and electroconductive elements5that serve as bumps can be formed by transfer at the same time.

Specifically, the recesses3are formed in shapes such that the electroconductive elements5formed by transfer on the substrate1have an aspect ratio of 0.5 or higher, specifically such that the aspect ratio of the electroconductive elements5that serve as bumps is 2-3.

Furthermore, the recesses3are formed as tapered (forward-tapered) recesses such that the electroconductive elements5attain a forward-tapered shape. Forming the recesses3in such a tapered shape allows an ultraviolet-ray-curable-resin-containing electroconductive paste4to be readily released and smoothly transferred, and also improves the yield.

The active-light-curable-resin-containing electroconductive paste4that forms the electroconductive elements5is an ultraviolet-ray-curable-resin-containing electroconductive paste4, in which an ultraviolet-ray-curable resin that is cured by being irradiated with ultraviolet rays is incorporated into an electroconductive paste. For example, a silver (Ag) paste/nanopaste, a copper (Cu) paste/nanopaste, a gold (Au) paste/nanopaste, a platinum (Pt) paste/nanopaste, a palladium (Pd) paste/nanopaste, a ruthenium (Ru) paste/nanopaste, or a carbon (C) paste/nanopaste can be employed as the electroconductive paste serving as the electroconductive member.

The active-light-curable resin (ultraviolet-ray-curable resin) content of the ultraviolet-ray-curable-resin-containing electroconductive paste4is set to 70 vol % or less, specifically 20-40 vol %. Specifically, the volumetric ratio of the electroconductive paste and the ultraviolet-ray-curable resin in the ultraviolet-ray-curable-resin-containing electroconductive paste4used in the present example is set to 6:4-8:2.

The average grain diameter of the electroconductive material contained in the electroconductive paste in the ultraviolet-ray-curable-resin-containing electroconductive paste4is set to 0.1-20 μm. The average particle diameter of the electroconductive material is preferably ⅕ to 1/10 of the minimum line width of the electroconductive elements5(wiring) formed on the substrate1. Specifically, when forming a pattern of electroconductive elements5for which, e.g., the minimum ratio of lines and spaces (L/S) is 5 μm/5 μm, it is permissible to use an ultraviolet-ray-curable-resin-containing electroconductive paste4obtained by incorporating the ultraviolet-ray-curable resin into an electroconductive paste for which the average particle diameter of the electroconductive material is set to 0.5-1.0 μm.

The specific manufacturing method according to the present example is described next.

FIG.1is a step flow chart of the present example.FIG.2is a schematic cross-sectional view of a semiconductor device during the course of manufacture in the present example.

In the present example as shown inFIG.1, in the electroconductive paste filling process step, the recesses3in the printing plate2are first filled with the ultraviolet-ray-curable-resin-containing electroconductive paste4. Suitable means can be used for the filling method; in the present example, a squeegee is used as filling means as shown inFIG.2.

Next, in the printing plate superposition process step, the printing plate2filled with the ultraviolet-ray-curable-resin-containing electroconductive paste4is superposed on the substrate1.

Specifically, after the printing plate2is superposed on the substrate1, pressure is applied and the printing plate2is pressure-bonded to the substrate1. The printing plate2thereby presses the intermediate layer6of the substrate1, the intermediate layer6deforms, and the surface (surface exposed from the opening section of the recesses3) of the ultraviolet-ray-curable-resin-containing electroconductive paste4, with which the recesses3in the printing plate2are filled, uniformly achieves close contact (adhesion) with the surface of the substrate1with the intermediate layer6interposed therebetween.

Next, in the electroconductive paste curing process step, the printing plate2superposed on the substrate1is irradiated with ultraviolet rays from the printing plate2side, i.e., from the bottom side of the recesses3in the printing plate2, curing the contact interface portion at which the ultraviolet-ray-curable-resin-containing electroconductive paste4with which the recesses3in the printing plate2are filled contacts the recesses3. This improves the release properties of the active-light-curable-resin-containing electroconductive paste4with respect to the printing plate2.

Because curing of the ultraviolet-ray-curable resin advances instantaneously due to the irradiation with ultraviolet rays, the processing time is much shorter than with a heat treatment. Moreover, in the present example, because only the ultraviolet-ray-curable-resin-containing electroconductive paste4near the contact interface for contacting the recesses3is to be cured, the ultraviolet ray irradiation time can be set very short.

Finally, in the electroconductive paste transfer process step, the printing plate2is separated from the substrate1, the ultraviolet-ray-curable-resin-containing electroconductive paste4is transferred to the substrate1, and the electroconductive elements5having the prescribed pattern are formed on the substrate1.

The electroconductive paste curing process step may be carried out before the printing plate superposition process step. Specifically, a configuration may be adopted in which, after the recesses3in the printing plate2are filled with the ultraviolet-ray-curable-resin-containing electroconductive paste4, the portion of the ultraviolet-ray-curable-resin-containing electroconductive paste4within the recesses3that is near a recess interface is first cured by irradiation with ultraviolet rays, after which the printing plate2is superposed on the substrate1.

The present example was described with reference to a case in which the intermediate layer6is present, and although the intermediate layer6may be omitted from the substrate or not illustrated in the drawings, as shown inFIG.3, the method for forming electroconductive elements into a pattern on a substrate according to the present invention can also be employed when electroconductive elements such as wiring or bumps are formed on a substrate on which wiring (a wiring layer) is already formed.

Because the present example is configured as described above, there is achieved an exceptionally practical method for forming electroconductive elements into a pattern on a substrate, the method being such that pattern deformation occurring during curing of the ultraviolet-ray-curable-resin-containing electroconductive paste4is suppressed when the electroconductive elements5having the prescribed pattern are formed by transfer on the substrate1, complete transfer of the ultraviolet-ray-curable-resin-containing electroconductive paste4can be realized, the curing process can be performed in a short time, and throughput is improved.

Specifically, when a thermoset-resin-containing electroconductive paste that is cured through a heat treatment is used, there is a greater likelihood that a post-curing pattern could deform depending on the curing temperature due to a difference in the coefficients of thermal expansion between the electroconductive paste and a printing plate having recesses, or that defects could occur such that stress is generated between the electroconductive paste and the printing plate due to the deformation of the pattern and transfer cannot readily be completed. However, in the present example, the ultraviolet-ray-curable-resin-containing electroconductive paste4is used as the electroconductive paste for forming the electroconductive elements5, and the ultraviolet-ray-curable-resin-containing electroconductive paste4is cured by being irradiated with ultraviolet rays. Therefore, pattern deformation is reduced to a greater extent than when a thermoset-resin-containing electroconductive paste is used and cured through a heat treatment, the generation of stress is also suppressed, and a 100% complete transfer can be achieved; moreover, the curing time is greatly shortened and throughput is improved.

Additionally, in the present example, there is used an ultraviolet-ray-curable-resin-containing electroconductive paste4in which the average particle diameter of an electroconductive material contained in an electroconductive paste is set to 0.1-20 μm. Therefore, the shape of the electroconductive elements5(wiring and bumps) formed on the substrate1becomes smoother (assumes a smooth form having few recesses and protrusions), whereby localized concentration of electrical fields between the electroconductive elements5is mitigated and the long-term reliability of the electroconductive elements5is improved. Furthermore, in the present example, because only the ultraviolet-ray-curable-resin-containing electroconductive paste4near the contact interface for contacting the recesses3in the printing plate2is to be cured, there are no design restrictions placed on the particle diameter of the electroconductive material.

Moreover, in the present example, there is used an ultraviolet-ray-curable-resin-containing electroconductive paste4in which the volume ratio of the electroconductive paste and the ultraviolet-ray-curable resin is set to 6:4 to 8:2. Therefore, the final resistance value of the electroconductive elements5(wiring) formed from the ultraviolet-ray-curable-resin-containing electroconductive paste4can be lowered.

Additionally, in the present example, the intermediate layer6that deforms under application of pressure is provided to the substrate1, and the ultraviolet-ray-curable-resin-containing electroconductive paste4is transferred to the substrate1with the intermediate layer6interposed therebetween. Therefore, the intermediate layer6deforms when the printing plate2is superposed on the substrate1and pressure is applied, and the printing plate2uniformly adheres to a transfer surface of the substrate1, therefore making it possible for the ultraviolet-ray-curable-resin-containing electroconductive paste4to be completely transferred in an even more reliable manner.

Moreover, in the present example, the recesses3in the printing plate2are formed in tapered (forward-tapered) shapes. Therefore, the electroconductive elements5attain a forward-tapered shape, the release properties of the ultraviolet-ray-curable-resin-containing electroconductive paste4with respect to the recesses3in the printing plate2during transfer are improved, separation is carried out smoothly, and the yield in the electroconductive paste transfer process step is improved.

Thus, the present example exhibits the innovative effects described above, and furthermore, there is achieved an unprecedented and innovative method for forming electroconductive elements into a pattern on a substrate, the method being such that wiring and bumps having a high aspect ratio can be formed easily and in a satisfactory manner.

The present invention is not limited to the present example; the various configuring matters can be designed in specific configurations, as appropriate.