Base material with bonding bump and manufacturing method for the base material with the bonding bump

Abstract

To provide a base material with a bonding bump having the bonding bump on which a nanoporous Cu layer having a predetermined shape and porosity is stably formed and which can be favorably bonded to a member to be bonded, and provide a manufacturing method of the base material with the bonding bump.SOLUTION: A bonding bump 10 having a structure in which a seed layer 12 and a nanoporous Cu layer 15 are laminated is formed on a surface of a base material 3, and the seed layer 12 is formed of a metal less noble than Cu. A manufacturing method of the same includes: a seed layer forming step of forming the seed layer on a surface of the base material; a resist layer forming step of forming a resist layer in a pattern on the seed layer; a nanoporous Cu layer forming step of forming the nanoporous Cu layer in a region where the resist layer is not formed; a resist layer removing step of removing the resist layer; and a seed layer etching step of removing the seed layer in the region where the nanoporous Cu layer is not formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substrate with bonding bumps that are provided with bonding bumps that can be electrically bonded to a member to be bonded, and a method for manufacturing a substrate with bonding bumps. [Background technology]

[0002] In recent years, the performance of semiconductor devices has been improving, and micro-bonding technology has become increasingly important. Flip-chip mounting is a widely used mounting technique for IC chips, and as shown in Patent Documents 1 and 2, for example, a method is provided in which a bonding bump with a solder layer formed on a protruding electrode is formed and the chip is bonded using this solder layer. However, the mounting technology using solder bumps has problems such as the generation of voids due to stirring and excess solder running down the sides. Therefore, as a joining technique that does not use a solder material, for example, as shown in Patent Document 3, a joining technique that uses a joining bump on which a nanoporous Cu layer is formed instead of a solder layer has been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-006812 [Patent Document 2] Patent Publication No. 2021-090012 [Patent Document 3] Japanese Patent Publication No. 2022-133735 Summary of the Invention [Problem to be solved by the invention]

[0004] When forming a pattern of bonding bumps on the surface of a substrate (semiconductor wafer) such as silicon, a conductive Cu layer is first formed on the surface of the substrate as a plating seed layer, and a resist layer is then formed on this seed layer. Next, protruding electrodes (Cu pillars) are formed by Cu plating, and a nanoporous Cu layer is then formed on these protruding electrodes. After removing the resist layer, the seed layer (Cu layer) is etched into a pattern. Here, because the nanoporous Cu layer has a large surface area, when etching the Cu seed layer (Cu layer), the nanoporous Cu layer may dissolve preferentially, which may result in an unstable shape or a decrease in porosity.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a substrate with bonding bumps, on which a nanoporous Cu layer of a predetermined shape and porosity is stably formed, and which has bonding bumps that can be well bonded to a member to be bonded, and a method for manufacturing the substrate with bonding bumps. [Means for solving the problem]

[0006] In order to solve the above problems, the substrate with bonding bumps of aspect 1 of the present invention is characterized in that a bonding bump having a structure in which a seed layer and a nanoporous Cu layer are stacked on the surface of the substrate is formed, and the seed layer is composed of a metal that is more base than Cu.

[0007] According to the substrate with bonding bumps of aspect 1 of the present invention, the seed layer formed on the surface of the substrate is made of a metal that is more base than Cu, so that when etching the seed layer, the seed layer can be dissolved preferentially over the nanoporous Cu layer, and dissolution of the nanoporous Cu layer can be suppressed, resulting in the stable formation of a nanoporous Cu layer with a predetermined shape and porosity, which can be well bonded to the member to be joined.

[0008] A substrate with bonding bumps according to a second aspect of the present invention is characterized in that, in the substrate with bonding bumps according to the first aspect, a Cu pillar layer is formed between the seed layer and the nanoporous Cu layer. According to the substrate with bonding bumps of aspect 2 of the present invention, a Cu pillar layer is formed between the seed layer and the nanoporous Cu layer, and the Cu pillar layer makes it possible to sufficiently ensure conductivity and strength of the bonding bumps.

[0009] The substrate with bonding bumps of aspect 3 of the present invention is characterized in that, in the substrate with bonding bumps of aspect 1 or aspect 2, an adhesion layer is formed between the substrate and the seed layer, and the adhesion layer is composed of a metal that is more base than Cu. According to the substrate with bonding bumps of the third aspect of the present invention, an adhesion layer is formed between the substrate and the seed layer, so that the substrate and the seed layer are sufficiently adhered to each other, and bonding bumps can be stably formed on the surface of the substrate, and good bonding to the bonded member can be achieved via these bonding bumps. Furthermore, because the adhesion layer is made of a metal that is more noble than Cu, the adhesion layer can be dissolved preferentially over the nanoporous Cu layer when etching the adhesion layer, suppressing dissolution of the nanoporous Cu layer and resulting in the stable formation of a nanoporous Cu layer with a predetermined shape and porosity.

[0010] The substrate with bonding bumps of aspect 4 of the present invention is a substrate with bonding bumps of any one of aspects 1 to 3, characterized in that the seed layer is composed of one or more of Co, Ni, Al, Cr, and Mo. According to the substrate with bonding bumps of the fourth aspect of the present invention, the seed layer is composed of one or more of Co, Ni, Al, Cr, and Mo, so that the seed layer can be dissolved and removed preferentially over the nanoporous Cu layer. Furthermore, the conductivity of the seed layer is ensured, allowing for stable formation of a Cu pillar layer or a nanoporous Cu layer by plating.

[0011] A substrate with bond bumps according to a fifth aspect of the present invention is a substrate with bond bumps according to any one of the first to fourth aspects, characterized in that the thickness of the seed layer is within the range of 30 nm to 500 nm. According to the substrate with bonding bumps of aspect 5 of the present invention, the thickness of the seed layer is within the range of 30 nm or more and 500 nm or less, thereby ensuring the conductivity of the seed layer, allowing for stable formation of a Cu pillar layer or a nanoporous Cu layer by plating, and allowing for efficient removal of the seed layer by etching, further suppressing dissolution of the nanoporous Cu layer.

[0012] A substrate with bond bumps according to a sixth aspect of the present invention is the substrate with bond bumps according to any one of the first to fifth aspects, characterized in that the substrate is a Si wafer. According to the method for bonding a substrate with bonding bumps of aspect 6 of the present invention, the substrate is a Si wafer, so the Si wafer and the member to be bonded can be stably bonded via the bonding bumps, making it possible to stably form a semiconductor structure.

[0013] The manufacturing method of a substrate with bonding bumps of aspect 7 of the present invention is a manufacturing method of a substrate with bonding bumps that manufactures a substrate with bonding bumps that is any one of aspects 1 to 6, and is characterized by comprising a seed layer formation process for forming a seed layer on the surface of the substrate, a resist layer formation process for forming a patterned resist layer on the seed layer, a nanoporous Cu layer formation process for forming a nanoporous Cu layer in areas where the resist layer is not formed, a resist layer removal process for removing the resist layer, and a seed layer etching process for removing the seed layer in areas where the nanoporous Cu layer is not formed.

[0014] According to the method for bonding a substrate with bonding bumps of aspect 7 of the present invention, the method includes a seed layer forming step, a resist layer forming step, a nanoporous Cu layer forming step, a resist layer removing step, and a seed layer etching step, so that it is possible to form bonding bumps with a nanoporous Cu layer in a pattern. Furthermore, since the seed layer is made of a metal that is more base than Cu, the seed layer dissolves preferentially over the nanoporous Cu layer during the seed layer etching process, thereby suppressing the dissolution of the nanoporous Cu layer and enabling the stable formation of a nanoporous Cu layer with a predetermined shape and porosity. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a substrate with bonding bumps, in which a nanoporous Cu layer of a predetermined shape and porosity is stably formed and which has bonding bumps that can be well bonded to a bonded member, and a method for manufacturing a substrate with bonding bumps. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic explanatory diagram of a substrate with bonding bumps according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flow diagram showing a method for manufacturing a substrate with bond bumps according to an embodiment of the present invention. [Figure 3] 1A to 1C are explanatory diagrams of a method for manufacturing a substrate with bond bumps according to an embodiment of the present invention. [Figure 4] 1A to 1C are explanatory diagrams of a method for manufacturing a substrate with bond bumps according to an embodiment of the present invention. [Figure 5] 1A to 1C are explanatory diagrams of a method for manufacturing a substrate with bond bumps according to an embodiment of the present invention. [Figure 6] FIG. 10 is a schematic explanatory view of a substrate with bond bumps according to another embodiment of the present invention. [Figure 7] FIG. 10 is a schematic explanatory view of a substrate with bond bumps according to another embodiment of the present invention. [Figure 8] 10A and 10B are cross-sectional photographs of the nanoporous Cu layer in the substrate with bonding bumps of Comparative Example 1 in the Examples, where (a) is before etching the seed layer and adhesive layer, and (b) is after etching the seed layer and adhesive layer. [Figure 9]10A and 10B are photographs showing a cross section of a nanoporous Cu layer in a substrate with bonding bumps in Example 2 of the present invention. (a) shows the seed layer and adhesive layer before etching, and (b) shows the seed layer and adhesive layer after etching. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A substrate with bond bumps according to an embodiment of the present invention and a method for manufacturing the substrate with bond bumps will be described below with reference to the accompanying drawings.

[0018] As shown in FIG. 1, the substrate 1 with bonding bumps according to this embodiment includes a substrate 3 and bonding bumps 10 formed on the surface of the substrate 3. The substrate 3 on which the bonding bumps 10 are formed may be a glass substrate, a silicon substrate, or the like, but in this embodiment, it is a Si wafer that constitutes a semiconductor element.

[0019] As shown in FIG. 1, the bonding bump 10 includes an adhesion layer 11, a seed layer 12, an UBM (Under Bump Metal) layer 13, a Cu pillar layer 14, and a nanoporous Cu layer 15.

[0020] The adhesion layer 11 is formed to improve the adhesion between the substrate 3 and the seed layer 12. Here, the adhesion layer 11 is made of a metal that is less noble than Cu. In this embodiment, the adhesion layer 11 can be made of, for example, Ti (titanium), W (tungsten), or the like. The thickness of the adhesive layer 11 is preferably 10 nm or more, more preferably 30 nm or more, and is preferably 200 nm or less, more preferably 150 nm or less.

[0021] The seed layer 12 is formed for the purpose of conducting current when the above-mentioned UBM layer 13, Cu pillar layer 14, and nanoporous Cu layer 15 are formed by electrolytic plating. In the substrate 1 with bond bumps according to this embodiment, the seed layer 12 is made of a metal less noble than Cu. Specifically, the seed layer 12 is preferably made of one or more of Co, Ni, Al, Cr, and Mo.

[0022] The thickness of the seed layer 12 is preferably within the range of 30 nm to 500 nm. If the thickness of the seed layer 12 is 30 nm or more, conductivity is ensured, and the above-mentioned UBM layer 13, Cu pillar layer 14, and nanoporous Cu layer 15 can be stably formed by electrolytic plating. On the other hand, if the thickness of the seed layer 12 is 500 nm or less, the seed layer 12 can be efficiently removed by etching. The thickness of the seed layer 12 is more preferably 400 nm or less, and even more preferably 300 nm or less, and more preferably 50 nm or more, and even more preferably 100 nm or more.

[0023] The UBM layer 13 is formed to improve adhesion between the seed layer 12 and the Cu pillar layer 14. In particular, when the seed layer 12 is made of a metal that is easily oxidized (e.g., Al, Cr, etc.), it is difficult to perform Cu plating, so it is preferable to form the UBM layer 13. In this embodiment, the UBM layer 13 may be made of, for example, Ni (nickel) or Ni / Pd / Au (ENEPIG: Electroless Palladium Immersion Gold). The thickness of the UBM layer 13 is preferably 1 μm or more, and more preferably 2 μm or more, and is preferably 5 μm or less, and more preferably 3 μm or less.

[0024] The Cu pillar layer 14 is made of a dense Cu plating layer. The Cu pillar layer 14 adjusts the height of the bonding bump 10. In addition, the conductivity and strength of the bonding bump 10 are ensured. The thickness of the Cu pillar layer 14 is more preferably 5 μm or more, and even more preferably 10 μm or more. The thickness of the Cu pillar layer 14 is more preferably 50 μm or less, and even more preferably 30 μm or less.

[0025] The nanoporous Cu layer 15 has nano-sized pores. Here, the nanoporous Cu layer 15 has an average porosity P ave is set to be within the range of 10% to 75%. Average porosity P ave is the average value of the vacancy P calculated as follows. In this embodiment, the vacancy P is calculated at three locations, and the average value of the vacancy P is taken as the average vacancy P. ave is calculated. The porosity P is calculated by analyzing the cross section of the nanoporous Cu layer 15 using a scanning electron microscope to determine the total area S1 of the nanoporous Cu layer 15 and the area S2 of the pores in the nanoporous Cu layer 15, and then using the following formula: Porosity P(%)=(S2 / S1)×100

[0026] The thickness of the nanoporous Cu layer 15 is more preferably 15 μm or less, and even more preferably 10 μm or less, and more preferably 3 μm or more, and even more preferably 5 μm or more.

[0027] Next, a method for manufacturing a substrate with bonding bumps according to this embodiment will be described with reference to FIGS. As shown in FIG. 2, the manufacturing method of the substrate with bonding bumps according to this embodiment includes an adhesion layer forming step S01, a seed layer forming step S02, a resist layer forming step S03, a UBM layer forming step S04, a Cu pillar layer forming step S05, a nanoporous Cu layer forming step S06, a resist layer removing step S07, a seed layer etching step S08, and an adhesion layer etching step S09.

[0028] (Adhesion layer forming step S01) 2 and 3, an adhesion layer 11 is formed on the surface of the substrate 3. There is no particular limitation on the method for forming the adhesion layer 11, but in this embodiment, the adhesion layer 11 is formed by a sputtering method using a sputtering target made of a metal that constitutes the adhesion layer 11.

[0029] (Seed layer formation step S02) 2 and 3, the seed layer 12 is formed on the adhesion layer 11. There is no particular limitation on the method for forming the seed layer 12, but in this embodiment, the seed layer 12 is formed by a sputtering method using a sputtering target made of a metal that constitutes the seed layer 12.

[0030] (Resist layer forming step S03) 2 and 3, a resist layer 20 is formed in a pattern on the seed layer 12. The resist layer 20 formed in a pattern forms openings 21 that expose the seed layer 12.

[0031] (UBM layer formation process S04) 2 and 3, a UBM layer 13 is formed on the seed layer 12. In this embodiment, the UBM layer 13 is formed on the seed layer 12 exposed in the opening 21 formed by the resist layer 20 by electroplating using a plating solution containing metal ions that constitute the UBM layer 13.

[0032] (Cu pillar layer formation step S05) 2 and 4, a Cu pillar layer 14 is formed on the UBM layer 13. In this embodiment, the Cu pillar layer 14 is formed on the UBM layer 13 formed in the opening 21 formed by the resist layer 20 by electroplating using a plating solution containing Cu ions.

[0033] (Nanoporous Cu layer formation step S06) 2 and 4, a nanoporous Cu layer 15 is formed on the Cu pillar layer 14. In this embodiment, the nanoporous Cu layer 15 is formed on the Cu pillar layer 14 formed in the openings 21 formed by the resist layer 20 by electroplating using a plating solution containing Cu ions. Here, the nanoporous Cu layer 15 can be formed by a dealloying method or a direct plating method.

[0034] In the dealloying method, copper and a metal species that is electrochemically less noble than copper are co-deposited on the Cu pillar layer 14 by electroplating to form a copper alloy plating film, and then the less noble metal species in the copper alloy plating film are dealloyed to form a nanoporous Cu layer 15 with a porous structure having fine pores. In this dealloying method, it is possible to form a nanoporous Cu layer 15 having a desired porosity and shape by controlling the deposition ratio and deposition form of copper and metal species less noble than copper.

[0035] Next, the copper alloy plating and dealloying methods will be described in detail. Copper alloy plating is performed by forming a copper-zinc alloy plating film using a copper-zinc alloy plating solution containing, for example, copper salt, zinc salt, and additives and solvents that control the deposition of copper and zinc. This copper alloy plating must contain copper, and can be performed by electroless plating or electrolytic plating. Metal species that are electrochemically less noble than copper (e.g., Fe, Mn, etc.) can also be selected as alloy species.

[0036] The copper ion concentration of the copper-zinc alloy plating solution is preferably in the range of 0.0025 mol / L to 0.1 mol / L, and the zinc ion concentration is preferably in the range of 0.1 mol / L to 0.8 mol / L. The zinc ion concentration is made higher than the copper ion concentration because copper is preferentially deposited over zinc due to the difference in standard oxidation-reduction potential. The pH of the plating solution is preferably 6.1 or higher to adjust the deposition balance between copper and zinc. In addition, the cathode current density is set to 0.3 A / dm 2 More than 0.8A / dm 2 Set within the following range.

[0037] The copper and zinc ion sources for copper alloy plating can be copper salts and zinc salts known as metal ion sources for plating systems. Examples include sulfates, pyrophosphates, acetates, chlorides, and sulfamates. Trisodium citrate and potassium pyrophosphate are used as conductive and supporting salts as additives for controlling the deposition of copper and zinc to form a copper-zinc alloy plating film with a smooth surface. Brighteners can include surfactants such as amino acids, compounds selected from their salts, and alkanolamines. An example of a surfactant is (ethylenedinitrilo)tetrakis(2-propanol). Amino acids can be used as long as they are water-soluble and do not cause precipitation with copper salts (copper ions) or zinc salts (zinc ions) at any concentration. Examples include glycine, serine, alanine, tyrosine, aspartic acid, glutamic acid, histidine, and the like, or their respective salts.

[0038] The dealloying of the formed copper-zinc alloy plating film can be achieved by, for example, an etching reaction using a chemical solution or an electrochemical anodic reaction. In this embodiment, acid dealloying is performed by immersing and stirring the copper alloy film in a solution containing hydrochloric acid at a concentration of 0.002 mol / L to 0.5 mol / L at a temperature ranging from 20°C to 35°C for 30 minutes or longer (depending on the thickness of the plating film). This results in the formation of a nanoporous Cu layer 15. It is preferable that the dealloying be performed so that the zinc concentration in the nanoporous Cu layer 15 after dealloying is 0.6 at% or less, as measured by energy dispersive X-ray analysis (EDX).

[0039] In the direct plating method, a Cu pillar layer 14 is electroplated using a Cu plating solution containing an azole-based additive, which is a copper ion electrodeposition inhibitor, to form a nanoporous Cu layer 15 with a porous structure having fine pores. In this direct plating method, it is possible to form a nanoporous Cu layer 15 having a desired porosity and shape by controlling the type and content of additives contained in the Cu plating solution and the plating conditions.

[0040] The Cu plating solution used is an acidic electrolytic copper plating solution containing a soluble copper salt, an azole compound having 2 to 3 nitrogen atoms in a five-membered ring, which is a copper ion electrodeposition inhibitor represented by the following formulas (1) to (4), an acid, and water. If necessary, a brightener, a surfactant, an antioxidant, etc. may also be added. The Cu plating solution used has a copper concentration of 0.1 mol / L or more, an azole compound concentration of 10 mmol / L or more and 50 mmol / L or less, and a chlorine chloride ion concentration of 10 ppm or less.

[0041] [ka]

[0042] In the above formulas (1) to (4), R1 to R4 may be the same or different from one another and are any of an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, and an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atom of any of these groups is substituted with a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, or a mercapto group, or any of an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, and a hydrogen atom.

[0043] Specific examples of soluble copper salts include copper sulfate, copper oxide, copper carbonate, copper alkanesulfonates such as copper methanesulfonate and copper propanoate, copper alkanolsulfonates such as copper isethionate and copper propanolsulfonate, and copper organic acids such as copper acetate, copper citrate, and copper tartrate. These can be used alone or in combination of two or more.

[0044] Furthermore, the acid may be an organic acid or an inorganic acid. Examples of these include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid; and organic acids such as citric acid, tartaric acid, and formic acid. These may be used alone or in combination of two or more. The water may be pure water such as ion-exchanged water or distilled water.

[0045] As for the plating conditions, for example, a DC power source is used to set the current density in the copper sheet 4 or substrate 4a to be plated at 0.1 A / dm 2 ~5A / dm 2 Approximately, preferably 0.4A / dm 2 ~1.0A / dm 2 The liquid temperature is maintained at about 30 to 150 minutes, preferably about 60 to 120 minutes, and air and jet stirring or rocking stirring is performed. When Cu plating is performed under the above conditions, the azole compound, which acts as a copper ion electrodeposition inhibitor, as well as the copper ions, are adsorbed onto the Cu pillar layer 14 (cathode surface). The presence of the azole compound strongly inhibits the electrodeposition of copper ions, favoring copper nucleation, and a nanoporous Cu layer 15 made of copper particles is formed on the cathode surface as a copper plating film.

[0046] (Resist layer removal step S07) After the nanoporous Cu layer 15 is formed as described above, the resist layer 20 is removed using a resist removal liquid, as shown in Figures 2 and 5. The resist removal liquid to be used is selected depending on the material that constitutes the resist layer 20. By removing the resist layer 20, the UBM layer 13, the Cu pillar layer 14, and the nanoporous Cu layer 15 formed after the resist layer forming step S03 are formed in a pattern.

[0047] (Seed layer etching step S08) Next, as shown in Figures 2 and 5, the seed layer 12 exposed by removing the resist layer 20 (the seed layer 12 in the areas where the UBM layer 13, Cu pillar layer 14, and nanoporous Cu layer 15 are not formed) is removed by etching. In this embodiment, since the seed layer 12 is made of a metal that is less noble than Cu, dissolution of the nanoporous Cu layer 15 and the Cu pillar layer 14 is suppressed by selecting an etching solution. For example, when the seed layer 12 is made of Co or Ni, the etching solution may be (1) nitric acid + sulfuric acid + phosphoric acid + acetic acid, (2) nitric acid + hydrochloric acid + water, or (3) nitric acid + hydrogen peroxide + carboxylic acid.

[0048] (Adhesion layer etching process S09) Next, as shown in Figures 2 and 5, the adhesion layer 11 exposed by removing the seed layer 12 (the adhesion layer 11 in the areas where the seed layer 12, UBM layer 13, Cu pillar layer 14, and nanoporous Cu layer 15 are not formed) is removed by etching.

[0049] Through the steps described above, the substrate 1 with bonding bumps according to this embodiment is manufactured.

[0050] According to the substrate 1 with bonding bumps of this embodiment configured as described above, since the seed layer 12 is made of a metal that is more base than Cu, when etching the seed layer 12 in the seed layer etching step S08, the seed layer 12 can be dissolved preferentially over the nanoporous Cu layer 15, and dissolution of the nanoporous Cu layer 15 can be suppressed, resulting in the stable formation of a nanoporous Cu layer 15 with a predetermined shape and porosity, which can be well bonded to the member to be joined.

[0051] In the substrate 1 with bonding bumps of this embodiment, when a Cu pillar layer 14 is formed between the seed layer 12 and the nanoporous Cu layer 15, the dense structure of the Cu pillar layer 14 makes it possible to sufficiently ensure conductivity and strength of the bonding bumps 10.

[0052] In the substrate 1 with bonding bumps of this embodiment, when the adhesion layer 11 is formed between the substrate 3 and the seed layer 12, the substrate 3 and the seed layer 12 are sufficiently adhered to each other, and the bonding bumps 10 can be stably formed on the surface of the substrate 3, enabling good bonding to the bonded members via the bonding bumps 10. Furthermore, because the adhesion layer 11 is made of a metal that is more base than Cu, it can be dissolved preferentially over the nanoporous Cu layer 15 when etching the adhesion layer 11, preventing dissolution of the nanoporous Cu layer 15 and resulting in the stable formation of a nanoporous Cu layer 15 with a predetermined shape and porosity.

[0053] In the substrate 1 with bonding bumps of this embodiment, when the seed layer 12 is composed of one or more of Co, Ni, Al, Cr, and Mo, the seed layer 12 can be dissolved and removed preferentially over the nanoporous Cu layer 15 in the seed layer etching step S08. Furthermore, the conductivity of the seed layer 12 is ensured, and the Cu pillar layer 14 and the nanoporous Cu layer 15 can be stably formed by plating.

[0054] In the substrate 1 with bonding bumps of this embodiment, when the thickness of the seed layer 12 is within the range of 30 nm or more and 500 nm or less, the conductivity of the seed layer 12 is ensured, the Cu pillar layer 14 and the nanoporous Cu layer 15 can be stably formed by plating, and the seed layer 12 can be efficiently removed by etching, further suppressing the dissolution of the nanoporous Cu layer 15.

[0055] In the substrate 1 with bonding bumps of this embodiment, when the substrate 3 is a Si wafer, the Si wafer and the member to be bonded can be stably bonded via the bonding bumps 10, making it possible to stably form a semiconductor structure.

[0056] According to the manufacturing method of the substrate with bonding bumps of this embodiment, since it includes a seed layer forming step S02, a resist layer forming step S03, a nanoporous Cu layer forming step S06, a resist layer removing step S07, and a seed layer etching step S08, it is possible to form bonding bumps 10 with a nanoporous Cu layer 15 in a pattern. Furthermore, since the seed layer 12 is made of a metal that is more base than Cu, the seed layer 12 dissolves preferentially over the nanoporous Cu layer 15 in the seed layer etching step S08, thereby suppressing the dissolution of the nanoporous Cu layer 15 and enabling the stable formation of a nanoporous Cu layer 15 with a predetermined shape and porosity.

[0057] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. For example, in this embodiment, a UBM layer is formed between the seed layer and the Cu pillar layer, but this is not limited to this. As shown in FIG. 6, the bond bump 110 may be formed by forming a Cu pillar layer 14 directly on the seed layer 12 without forming a UBM layer. Alternatively, as shown in FIG. 7, a bond bump 210 may be formed without forming a Cu pillar layer, by forming a UBM layer on a seed layer, and then forming a nanoporous Cu layer on the UBM layer. [Example]

[0058] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0059] A silicon wafer was prepared as a substrate. An adhesive layer having the material and thickness shown in Table 1 was formed on the surface of the silicon wafer by sputtering. Next, a seed layer having the material and thickness shown in Table 1 was formed on the formed adhesive layer by sputtering. Thereafter, a resist layer having a thickness of 30 μm and having openings (circular in cross section, opening diameter 25 μm) was formed on the seed layer.

[0060] In the openings formed by the resist layer, a UBM layer having the material and thickness shown in Table 1 was formed by plating. Next, a Cu pillar layer was formed to the thickness shown in Table 1 by plating using a Cu plating solution.

[0061] Then, a nanoporous Cu layer having the average porosity and thickness shown in Table 1 was formed by a direct plating method. The plating solution used to form the nanoporous Cu layer contained 100 mM CuSO4·5H2O and 15 mM 3,5-Diamino-1,2,4-triazole. In addition, the current density during plating was set to 1.5 ASD (A / dm 2 ) was decided.

[0062] Next, the resist layer was removed using a resist remover. The seed layer exposed by removing the resist layer was then removed by etching under the etching conditions shown in Table 2. After removing the seed layer, the exposed adhesion layer was removed by etching under the etching conditions shown in Table 2.

[0063] Here, the nanoporous Cu layer in the obtained substrate with bonding bumps was evaluated as follows.

[0064] (Average porosity of nanoporous Cu layer) Average porosity P ave is the average value of the porosity P calculated as follows. In the examples, the porosity P is calculated at three locations, and the average value of the porosity P is taken as the average porosity P ave was calculated. The porosity P was determined by subjecting a cross section of the resulting substrate with bonding bumps along the thickness direction of the nanoporous Cu layer to CP processing and observing the cross section with an SEM. The 10,000x cross-sectional SEM image was binarized and analyzed to determine the observed area S1 of the nanoporous Cu layer and the area S2 of the pores in the nanoporous Cu layer, and then the porosity P was calculated using the following formula. Porosity P(%)=(S2 / S1)×100

[0065] (Height change before and after etching) The cross section of the nanoporous Cu layer was observed (FIB-SEM) after the resist layer was removed. The cross section of the nanoporous Cu layer was also observed (FIB-SEM) after the seed layer and adhesion layer were etched away. The nanoporous Cu layer was evaluated as "good" if its height after etching was 80% or more of its height before etching, and as "poor" if it was less than 80%. The height of the nanoporous Cu layer was calculated as the average of the values ​​measured at five locations. FIG. 8 shows an observation of a cross section of the nanoporous Cu layer of Comparative Example 1, and FIG. 9 shows an observation of a cross section of the nanoporous Cu layer of Invention Example 2.

[0066] [Table 1]

[0067] [Table 2]

[0068] In Comparative Example 1-3, the seed layer was made of Cu, and when the seed layer and the adhesion layer were removed by etching, the nanoporous Cu layer was dissolved first. Here, in Figure 8, the nanoporous Cu layer could not be confirmed after etching. In contrast, in Examples 1-9 of the present invention, the seed layer and adhesion layer were made of a metal less noble than Cu, and as shown in Figure 9, for example, even after the seed layer and adhesion layer were removed by etching, the nanoporous Cu layer did not dissolve and maintained its shape.

[0069] From the results of the above confirmation experiments, it was confirmed that the present invention can provide a substrate with bonding bumps, which can stably form a nanoporous Cu layer with a predetermined shape and porosity and can be well bonded to the bonded member, as well as a method for manufacturing the substrate with bonding bumps. [Explanation of symbols]

[0070] 1. Substrate with bonding bumps 3 Base material 10 Bonding Bumps 11 Adhesion layer 12 Seed layer 13 UBM layer 14 Cu pillar layer 15 Nanoporous Cu layer

Claims

1. A bonding bump having a structure in which a seed layer and a nanoporous Cu layer are stacked is formed on a surface of the substrate, The substrate with bonding bumps is characterized in that the seed layer is made of a metal that is less noble than Cu.

2. The substrate with bond bumps according to claim 1 , wherein a Cu pillar layer is formed between the seed layer and the nanoporous Cu layer.

3. 2. The substrate with bond bumps according to claim 1, wherein an adhesion layer is formed between the substrate and the seed layer, and the adhesion layer is made of a metal that is less noble than Cu.

4. 2. The substrate with bond bumps according to claim 1, wherein the seed layer is made of one or more of Co, Ni, Al, Cr, and Mo.

5. 2. The substrate with bond bumps according to claim 1, wherein the seed layer has a thickness in the range of 30 nm to 500 nm.

6. 2. The substrate with bond bumps according to claim 1, wherein the substrate is a Si wafer.

7. A method for manufacturing a substrate having bond bumps according to any one of claims 1 to 6, comprising the steps of: A method for manufacturing a substrate with bonding bumps, comprising: a seed layer formation process for forming a seed layer on the surface of a substrate; a resist layer formation process for forming a patterned resist layer on the seed layer; a nanoporous Cu layer formation process for forming a nanoporous Cu layer in areas where the resist layer is not formed; a resist layer removal process for removing the resist layer; and a seed layer etching process for removing the seed layer in areas where the nanoporous Cu layer is not formed.

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