JP2005153054A - Manufacturing method for fine metal member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a fine metal member to form a desired resist pattern on a substrate by lithography and remove the substrate and a resist film after filling a recessed part of this resist pattern with a metal layer, preventing occurrence of a problem that the resist film is peeled from the substrate in polishing an upper surface of the metal layer. <P>SOLUTION: This manufacturing method of the fine metal member has a patterning process to form the desired resist pattern on the substrate by exposing the resist film radial to rays followed by development a process for forming a metal layer to fill in the recess of the resist pattern and a polishing process to polish the resist pattern and the surface part of the metal layer, and removes the substrate and the resist pattern after the polishing process. The method also has a post-cure process to make Vickers hardness of the resist pattern more than 15 before the polishing process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a fine metal member using lithography. More specifically, it includes a step of forming a fine mold having a shape corresponding to a target member by lithography using a resist, and filling a metal constituting the target member into the mold by plating or the like. The present invention relates to a method for producing a fine metal member such as a fine spring.

  A fine metal member may be used for manufacture and inspection of electronic equipment. For example, in a contact probe used for electrical inspection of a semiconductor substrate or a liquid crystal display device, a fine spring having a total length of about 5 mm or less is used to elastically support the stylus.

  As a method for manufacturing such a fine metal member, a method using lithography is known. For example, Japanese Patent Laid-Open No. 2002-202770 (Patent Document 1) discloses a method in which a desired resist pattern is formed on a substrate by lithography using X-rays, and a concave portion of the resist pattern is filled with a metal layer by electroplating. Discloses a method of manufacturing a fine spring by removing a substrate and a resist (paragraphs 0003 to 0006).

The method for manufacturing the fine spring will be described more specifically with reference to FIGS.
First, as shown in FIG. 5A, a resist film 2 is formed on the surface of a conductive substrate 1. As the substrate 1, a Si substrate obtained by sputtering titanium, copper, chromium or the like, or a conductive substrate such as stainless steel or copper is used. Thereafter, as shown in FIG. 5B, the mask 7 is used to irradiate the surface of the resist film 2 with X-rays 3 (or ultraviolet rays), and the resist in the exposed portion 4 is removed by development. As shown in c), the recess 5 is formed.

  Next, plating is performed as shown in FIG. 6A, and the recess 5 is filled with a plated metal layer 6 such as nickel or a nickel-based alloy. Thereafter, when the resist film 2 remaining on the substrate 1 is removed by ashing with oxygen plasma or development after re-irradiation, the structure shown in FIG. 6B is obtained. Finally, when the portion of the substrate 1 is melted with potassium hydroxide (KOH) or the like and only the portion of the plated metal layer 6 is taken out, a fine spring is obtained as shown in FIG.

  In such a manufacturing method of a fine metal member using lithography, after filling the concave portion of the resist pattern with the metal layer, in order to align the thickness of the metal layer with a desired thickness, the upper surface of the metal layer is usually ground or Polishing (hereinafter simply referred to as polishing including grinding) is performed (Patent Document 1, Paragraph 0022, FIG. 10). This polishing is performed before the resist is removed. That is, in the above example, when the polishing is performed after the resist film 2 is removed, that is, at the stage shown in FIG. 6B, a lateral protrusion (so-called burr) is generated on the plated metal layer 6 by polishing. Since the plated metal layer 6 is pulled down, this polishing needs to be performed before the resist film 2 is removed, that is, at the stage shown in FIG.

However, it has been found that when the upper surface of the plated metal layer 6 (and the resist 2) is polished at the stage of FIG. 6A, the problem that the resist film 2 is peeled off from the substrate is likely to occur. If only the resist film 2 is peeled off from the substrate, it will be difficult to achieve good polishing.
JP 2002-202770 A (paragraphs 0003 to 0006)

  The present invention is a method for producing a fine metal member by forming a desired resist pattern on a substrate by lithography, filling a concave portion of the resist pattern with a metal layer, and then removing the substrate and the resist film, It is an object of the present invention to provide a method for manufacturing a fine metal member that does not cause a problem that the resist film is peeled off from the substrate when the upper surface of the metal layer is polished.

  As a result of intensive studies, the inventor did not cause the resist film to be peeled off from the substrate due to insufficient adhesion between the resist film and the substrate (actually, the adhesion between the resist film and the substrate and the metal layer). The adhesive strength between the resist film and the substrate is usually equivalent.), Because the resist film has a low hardness, the resist film bites part of the abrasive material, and the resist film has a high hardness. The present inventors have found that the above problems can be solved, and have completed the present invention based on this finding.

  That is, the present invention relates to a patterning step in which a resist film formed on a substrate is exposed to radiation and then a desired resist pattern is formed on the substrate by development, and a metal layer filling the concave portions of the resist pattern is formed on the substrate. A method of manufacturing a fine metal member, comprising: a step of forming a surface layer portion of the resist pattern and the metal layer, and a step of removing the substrate and the resist pattern after the polishing step. The present invention provides a method for producing a fine metal member, further comprising a post-cure step for setting the Vickers hardness of the resist pattern to 15 or more after the patterning step and before the polishing step. .

  Examples of the method for forming the metal layer filling the recesses of the resist pattern on the substrate include electroplating and vapor deposition. Even when the aspect ratio of the recesses of the resist pattern is large, the recesses can be easily and reliably formed. Electroplating is preferably used because it can be filled with a metal layer. However, when electroplating is performed on the substrate, the surface of the substrate needs to have conductivity. Therefore, in the case of a nonconductive substrate such as a Si substrate, it is necessary to form a metal layer such as titanium on the surface thereof by sputtering or the like to impart conductivity to the surface.

  Claim 2 of the present invention corresponds to this preferred embodiment, and is a method of manufacturing the fine metal member, wherein the surface of the substrate is conductive, and the metal layer is electroplated. The manufacturing method of the fine metal member characterized by being formed by these is provided.

  Examples of radiation used for exposure in the patterning process include X-rays and electron beams, but the apparatus is relatively inexpensive, the operation is relatively easy, and the productivity in the patterning process is high. From the viewpoint of many types of resists to be used, ultraviolet rays or visible rays are preferably used.

  Claim 3 of the present invention corresponds to this preferred embodiment, and is the method for producing a fine metal member, wherein the radiation used for exposure in the patterning step is ultraviolet light or visible light. The manufacturing method of the fine metal member characterized by these is provided. The ultraviolet rays or visible rays used include far ultraviolet rays such as F2 excimer laser, ArF excimer laser, and KrF excimer laser, near ultraviolet rays such as I rays and G rays, visible rays, and the like.

  The resist is selected according to the type of radiation used in the patterning step, and both positive and negative types can be used. Even when the radiation used for exposure is ultraviolet light or visible light, either a positive type or a negative type can be used, but in the case of a positive type, it is cured by heat or radiation irradiation in the post-cure process to improve the hardness. In the case of the negative type, the post-cure described later is easily performed using ultraviolet rays or visible rays of the same type as the ultraviolet rays or visible rays used for exposure. This is preferable because it can be performed.

  Claim 4 of the present invention corresponds to this preferred embodiment, and is a method for producing the fine metal member using ultraviolet light or visible light for exposure, and further for forming a resist pattern, a negative photoresist. The method for producing a fine metal member according to claim 3 is provided.

  A Vickers hardness of a resist pattern formed by a normal resist, particularly a resist used when ultraviolet rays or visible rays are used for exposure is about 5 to 10. The method for producing a fine metal member according to the present invention further includes a post-cure process for setting the Vickers hardness to 15 or more before the polishing process. Here, the Vickers hardness is an area of a pyramid-shaped portion of the indentation generated by pushing a square pyramid-shaped indenter with an apex angle of 136 ° into the surface of a test piece using a diamond pyramid hardness meter. The value obtained by dividing by.

  By setting the Vickers hardness to 15 or more before the polishing step, it is possible to prevent a problem that the resist film is peeled off from the substrate in the polishing step. On the other hand, if it is less than 15, this problem cannot be prevented sufficiently. Examples of the method for setting the Vickers hardness to 15 or more include heating the resist pattern and irradiating the resist pattern with radiation.

Among these, post-curing by radiation irradiation is preferably employed because it can make the Vickers hardness 15 or more by irradiating the same type of radiation as that used in the patterning step.
Claim 5 of the present invention corresponds to this preferred embodiment, and is the method for producing a fine metal member, wherein the post-cure step is performed by irradiating the resist pattern with radiation. The manufacturing method of the fine metal member characterized by these is provided.

The radiation used for post-cure by irradiation with radiation is preferably ultraviolet rays or visible rays for the same reason as the radiation used for patterning, that is, from the viewpoint of cost and the like.
Claim 6 of the present invention corresponds to this preferred embodiment, and is the method for producing a fine metal member according to claim 5, further comprising using ultraviolet rays or visible rays as the radiation. The manufacturing method of a metal member is provided.

When a negative photoresist is used, the radiation exposure amount in the post cure process is preferably 1.5 to 6 times the radiation exposure amount in the patterning process. If the amount is less than 1.5 times, the increase in hardness may be insufficient and a Vickers hardness of 15 or more may not be achieved. On the other hand, if the amount exceeds 6 times, the resist pattern profile becomes poor, that is, the convex pattern wall of the resist pattern does not have a shape rising vertically from the substrate, but tends to have a shape in which the convex skirt is widened. There is a case. Here, the exposure amount refers to the amount of light energy per unit area of the exposed portion, and is usually expressed in units of mJ / cm ² .

  Claim 7 of the present invention corresponds to this preferred embodiment, and is the method for producing a fine metal member using a negative photoresist, wherein the post-cure process is a radiation exposure in the patterning process. The present invention provides a method for producing a fine metal member, which is performed by irradiating the resist pattern with radiation having an exposure amount 1.5 to 6 times the amount.

  Note that post-cure (post-bake) in which heating and radiation irradiation are performed after the formation of the resist pattern is generally performed in lithography. For example, Japanese Patent Application Laid-Open No. 2002-241615 discloses an improvement in acid resistance of a resist pattern. Post bake for the purpose is disclosed (paragraph 0005). However, the conventional post-cure is performed with an exposure amount equal to or less than the exposure amount in the patterning step even in the case of radiation irradiation. With respect to the exposure amount in the patterning step, the optimum light energy is determined in order to form a highly accurate pattern shape with a high aspect ratio. However, in order to increase the hardness of the resist pattern, high light energy is required, and the hardness of the resist pattern cannot be increased even if post-cure is performed with an exposure amount equal to or less than the optimal light energy for the patterning process. Therefore, the conventional post-cure does not obtain the high hardness of the resist pattern as in the present invention.

  The irradiation of the radiation in the post cure process may be performed after the metal layer is formed on the substrate by electroplating or the like. However, there are cases where the upper surface of the resist pattern is covered with a plated metal due to the formation of the metal layer, and radiation of radiation is blocked by this metal. In this case, radiation of the resist pattern is insufficient. Therefore, it is preferable to perform radiation irradiation in the post-cure process before the metal layer is formed on the substrate by electroplating or the like.

  An eighth aspect of the present invention corresponds to this preferred embodiment, and is the method for manufacturing a fine metal member according to the seventh aspect, wherein the irradiation with radiation in the post-cure process is performed on a metal on the substrate. The present invention provides a method for producing a fine metal member, which is performed before the step of forming a layer.

  In the method for producing a fine metal member of the present invention, the hardness of the resist pattern is improved by post-cure. The problem of being peeled off does not occur, and as a result, a fine metal member can be reliably manufactured in a desired shape.

  Furthermore, according to the method for producing a fine metal member of the present invention, the effect of improving the hardness of the resist pattern, the difference in hardness between the resist pattern and the metal layer is reduced, and the height of the resist pattern upper surface and the metal layer upper surface during polishing is reduced. There is also an effect that the variation in thickness is reduced and the thickness distribution of the resist pattern and the metal layer becomes uniform.

  Next, the process of preferable one Embodiment (manufacture of a fine spring) of this invention is demonstrated using FIGS. 1-4.

  First, as shown in FIG. 1A, a resist film 12 is formed on the surface of a conductive substrate 11. The resist film 12 is formed by applying a resist solution on the substrate 11 and drying it by heating (prebaking) or the like. In order to improve the adhesion between the substrate 11 and the resist film 12, heating (pre-bake) may be performed.

  A method for applying the resist solution onto the substrate 11 is not particularly limited, but in the present embodiment, the resist solution is formed by a spin coating method that facilitates the formation of a uniform coating film. The thickness of the coating film varies depending on the size (thickness) of the member to be manufactured, and is usually in the range of about 30 to 100 μm as the thickness after drying. In the present embodiment, it is about 70 μm.

  As the resist solution, a negative photoresist containing a polymer, a monomer, and a photopolymerization initiator is used. Examples of the polymer used in such a negative photoresist include acrylic polymers such as PMA and PMMA, and copolymers thereof, and monomers include acrylic esters such as MA and methacrylic esters such as MMA. Although illustrated, it is not limited to these.

  As the substrate 11, a metal substrate such as SUS, copper, or aluminum, a Si substrate, a glass substrate, or the like can be used. However, when the metal layer is formed by electroplating, it is necessary to make the surface of the substrate 11 conductive. Therefore, in the case of a nonconductive substrate such as a Si substrate or a glass substrate, titanium is previously formed on the upper surface. A base conductive layer made of aluminum, copper or a combination of these is formed by sputtering or the like.

  After the resist film 12 is formed on the surface of the conductive substrate 11, the surface of the resist film 12 is irradiated with ultraviolet rays 31 through a mask 20, as shown in FIG. As the mask 20, a glass having a light shielding portion formed in a shape corresponding to the shape of a member to be formed by using chromium is used. When a resist containing a polymer, a monomer, and a photopolymerization initiator is irradiated with ultraviolet rays or the like, the monomer is polymerized by the action of the photopolymerization initiator and becomes difficult to dissolve in the solvent. Therefore, when the resist film after irradiation is immersed in the solvent, the portion not irradiated with light is dissolved, and the portion irradiated with light (exposed portion 14) remains undissolved, and a resist pattern is formed. (Development).

  FIG. 2A is a cross-sectional view of the resist pattern formed as described above. In this embodiment, the interval between the convex portions of the resist pattern is about 10 μm (this interval corresponds to the thickness of the member to be manufactured). As shown in FIG. 2B, the resist film 12 of this resist pattern is irradiated with ultraviolet rays 32. As a result, the hardness of the resist film 12 increases to 15 or more in terms of Vickers hardness (post-cure). The amount of the ultraviolet light 32 is in the range of 1.5 to 6 times that of the ultraviolet light 31. The ultraviolet rays 31 and 32 may be different types of ultraviolet rays, for example, the ultraviolet rays 31 may be near ultraviolet rays, and the ultraviolet rays 32 may be far ultraviolet rays. And as a photosensitive substance in a resist, for example, a photopolymerization initiator, two or more kinds of those sensitive to near ultraviolet rays and those sensitive to far ultraviolet rays can be used.

  After the post cure, as shown in FIG. 3A, the metal layer 16 is formed on the substrate 11 by electroplating, and the recess 15 of the resist pattern is filled with the metal layer 16. As a metal to be plated, nickel, a nickel-based alloy, cobalt, a nickel-cobalt alloy, copper, or the like can be used, but is not limited thereto. The metal layer 16 formed by plating is grown until the recess 15 is filled and a pedestal is formed on the upper side. As a result, as shown in FIG. 3A, a layer composed of the metal layer 16 and the resist film 12 whose upper part is not smooth is formed. In electroplating, variations in current density occur, resulting in uneven plating thickness.

  Therefore, polishing for smoothing the surfaces of the metal layer 16 and the resist film 12 is performed. FIG. 3B shows a cross-sectional view of the metal layer 16 and the resist film 12 after polishing. The polishing method is not particularly limited as long as the surfaces of the metal layer 16 and the resist film 12 are smoothed. In this embodiment, a polishing plate having diamond particles on the polishing surface is used, and the metal layer 16 and the resist film are used. This is performed until the thickness of 12 reaches about 50 μm (corresponding to the height of the member to be manufactured).

  After polishing, the resist film 12 is removed as shown in FIG. Examples of the removal method include oxygen plasma ashing and peeling with a solvent. Thereafter, a fine spring whose sectional view is shown in FIG. 4B is obtained by peeling the substrate 11 or removing the substrate 11 by etching. As the etching, wet etching can also be adopted, but there is a problem that the springs stick to each other due to surface tension of a solvent or the like, and therefore, dry etching without such a problem is preferably employed.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention includes all modifications within the scope of the claims and their equivalents.

It is explanatory drawing which shows the process of one Embodiment of this invention. It is explanatory drawing which shows the process of one Embodiment of this invention. It is explanatory drawing which shows the process of one Embodiment of this invention. It is explanatory drawing which shows the process of one Embodiment of this invention. It is explanatory drawing which shows the process of a prior art. It is explanatory drawing which shows the process of a prior art.

Explanation of symbols

1, 11 Substrate 2, 12 Resist film 3 X-ray 31, 32 Ultraviolet ray 4, 14 Exposed part 5, 15 Recess 6, 16, Metal layer 7, 20 Mask

Claims (8)

  A patterning step of forming a desired resist pattern on the substrate by development after radiation exposure of the resist film formed on the substrate, a step of forming a metal layer on the substrate to fill the recesses of the resist pattern, A method for manufacturing a fine metal member, comprising: a polishing step for grinding or polishing a resist pattern and a surface layer portion of the metal layer; and a step for removing the substrate and the resist pattern after the polishing step. Before, the manufacturing method of the fine metal member characterized by further having the post-cure process for making the Vickers hardness of the said resist pattern 15 or more.   The method for producing a fine metal member according to claim 1, wherein a surface of the substrate has conductivity, and the metal layer is formed by electroplating.   The method for producing a fine metal member according to claim 1 or 2, wherein the radiation used for exposure in the patterning step is ultraviolet light or visible light.   The method for producing a fine metal member according to claim 3, wherein a negative photoresist is used for forming the resist pattern.   The method for producing a fine metal member according to any one of claims 1 to 4, wherein the post-cure process is performed by irradiating the resist pattern with radiation.   The method for producing a fine metal member according to claim 5, wherein ultraviolet rays or visible rays are used as the radiation.   5. The fine metal member according to claim 4, wherein the post-cure process is performed by irradiating the resist pattern with radiation having an exposure amount of 1.5 to 6 times the radiation exposure amount in the patterning step. Manufacturing method. The method for producing a fine metal member according to claim 7, wherein the radiation irradiation in the post-cure process is performed before the process of forming a metal layer on the substrate.

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