Base with bonding bump, and method for manufacturing base with bonding bump

Abstract

This base with a bonding bump is characterized in that a bonding bump having a structure in which a seed layer and a nanoporous Cu layer are laminated is formed on the surface of a base, and the seed layer is composed of a metal that is less electropositive than Cu.

Description

Substrate with bonding bumps and method for manufacturing substrate with bonding bumps

[0001] The present invention relates to a substrate with bond bumps that can be electrically bonded to a bonded member, and a method for manufacturing such a substrate. This application claims priority to Japanese Patent Application No. 2024-035571, filed on March 8, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, the performance of semiconductor devices has been improving, and micro-bonding technology has become increasingly important. Flip-chip mounting is widely used as a mounting technology for IC chips. For example, Patent Documents 1 and 2 disclose methods for forming bonding bumps with a solder layer on protruding electrodes and bonding using this solder layer. However, mounting technologies using solder-based bonding bumps have problems such as the generation of voids due to stirring and excess solder material leaking along the side surfaces. Therefore, as a solder-free bonding technology, Patent Document 3 discloses a bonding technology that uses bonding bumps with a nanoporous Cu layer formed instead of a solder layer.

[0003] JP 2016-006812 A JP 2021-090012 A JP 2022-133735 A

[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 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, the nanoporous Cu layer is preferentially dissolved when etching the Cu seed layer (Cu layer), which can 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, 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 member to be bonded, and a method for manufacturing the substrate with bonding bumps.

[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 bond bumps according to Aspect 2 of the present invention is characterized in that a Cu pillar layer is formed between the seed layer and the nanoporous Cu layer in the substrate with bond bumps according to Aspect 1. According to the substrate with bond bumps according to Aspect 2 of the present invention, since the Cu pillar layer is formed between the seed layer and the nanoporous Cu layer, the Cu pillar layer can ensure sufficient conductivity and strength of the bond bumps.

[0009] A substrate with bond bumps according to a third aspect of the present invention is the substrate with bond bumps according to the first or second aspect, characterized in that an adhesion layer is formed between the substrate and the seed layer, and the adhesion layer is composed of a metal more noble than Cu. According to the substrate with bond bumps according to the third aspect of the present invention, the adhesion layer is formed between the substrate and the seed layer, ensuring sufficient adhesion between the substrate and the seed layer. This allows stable formation of bond bumps on the surface of the substrate, enabling good bonding to the bonded member via the bond bumps. Furthermore, because the adhesion layer is composed of a metal more noble than Cu, the adhesion layer can be preferentially dissolved over the nanoporous Cu layer during etching, 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] A substrate with bond bumps according to Aspect 4 of the present invention is a substrate with bond bumps according to 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 bond bumps according to Aspect 4 of the present invention, since the seed layer is composed of one or more of Co, Ni, Al, Cr, and Mo, the seed layer can be preferentially dissolved and removed 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 Aspect 5 of the present invention is characterized in that the thickness of the seed layer is within the range of 30 nm to 500 nm inclusive in the substrate with bond bumps according to any one of Aspects 1 to 4. According to the substrate with bond bumps according to Aspect 5 of the present invention, the thickness of the seed layer is within the range of 30 nm to 500 nm inclusive, so that the conductivity of the seed layer is ensured, allowing for stable formation of a Cu pillar layer and 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 bonding bumps according to Aspect 6 of the present invention is characterized in that the substrate is a Si wafer in the substrate with bonding bumps according to any one of Aspects 1 to 5. According to the bonding method for substrates with bonding bumps according to Aspect 6 of the present invention, since the substrate is a Si wafer, 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 seventh aspect of the present invention, the method for bonding a substrate with bonding bumps 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, which allows for the formation of a pattern of bonding bumps with a nanoporous Cu layer. Furthermore, since the seed layer is made of a metal less noble than Cu, the seed layer dissolves preferentially over the nanoporous Cu layer in the seed layer etching step, thereby suppressing dissolution of the nanoporous Cu layer and enabling the stable formation of a nanoporous Cu layer with a predetermined shape and porosity.

[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 member to be bonded, and a method for manufacturing a substrate with bonding bumps.

[0016] 1 is a schematic cross-sectional view of a substrate with bond bumps according to one embodiment of the present invention; FIG. 2 is a flow diagram showing a method for manufacturing a substrate with bond bumps according to one embodiment of the present invention; FIG. 3 is a schematic cross-sectional view illustrating a method for manufacturing a substrate with bond bumps according to one embodiment of the present invention; FIG. 4 is a schematic cross-sectional view illustrating a method for manufacturing a substrate with bond bumps according to one embodiment of the present invention; FIG. 5 is a schematic cross-sectional view illustrating a method for manufacturing a substrate with bond bumps according to one embodiment of the present invention; FIG. 6 is a schematic cross-sectional view of a substrate with bond bumps according to another embodiment of the present invention; FIG. 7 is a schematic cross-sectional view of a substrate with bond bumps according to another embodiment of the present 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] 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, a Si wafer constituting a semiconductor element is used.

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

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

[0021] The seed layer 12 is formed for electrical conduction when the 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 that is less noble than Cu. Specifically, the constituent material of the seed layer 12 is preferably one or more of Co, Ni, Al, Cr, and Mo.

[0022] Furthermore, the thickness of the seed layer 12 is preferably in the range of 30 nm or more and 500 nm or less. 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. The thickness of the seed layer 12 is 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.), Cu plating is difficult, 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. The thickness of the UBM layer 13 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 height of the bonding bump 10 is adjusted by the Cu pillar layer 14. The conductivity and strength of the bonding bump 10 are also ensured by the Cu pillar layer 14. Here, "dense" means that the average porosity is P ａｖｅ is in the range of 0% or more and 10% or less. 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 The average porosity P is in the range of 10% to 75%. ａｖｅ is the average value of the porosity P calculated as follows. In this embodiment, the porosity P is calculated at three locations, and the average value of the porosity P is taken as the average porosity P ａｖｅ The porosity P is calculated by determining the total area S1 of the nanoporous Cu layer 15 and the area S2 of the pores in the nanoporous Cu layer 15 through image analysis of the cross section of the nanoporous Cu layer 15 using a scanning electron microscope, and then calculating the porosity P 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 bond bumps according to this embodiment will be described with reference to Figures 2 to 5. As shown in Figure 2, the method for manufacturing a substrate with bond 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] 2 and 3, the 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] 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] 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 exposing the seed layer 12.

[0031] 2 and 3 , the 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 openings 21 formed by the resist layer 20 by electrolytic plating using a plating solution containing metal ions that constitute the UBM layer 13.

[0032] 2 and S05 in Fig. 4, the 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] 2 and S06, the 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 electrolytic plating using a plating solution containing Cu ions. Here, examples of methods for forming the nanoporous Cu layer 15 include a dealloying method and a direct plating method.

[0034] In the dealloying method, copper and a metal species electrochemically less noble than copper are codeposited on the Cu pillar layer 14 by electrolytic plating 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, by controlling the deposition ratio and deposition form of copper and the metal species less noble than copper, it is possible to form a nanoporous Cu layer 15 with a desired porosity and shape.

[0035] Next, copper alloy plating and dealloying methods will be described in detail. Copper alloy plating involves 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. Furthermore, the cathode current density is set to 0.3 A / dm ２ 0.8A / dm or more ２ Set within the following range.

[0037] The copper ion 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 copper-zinc alloy plating films with smooth surfaces. 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, to remove zinc from the copper-zinc alloy 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 having a porous structure with 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 the additive 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 two to three 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]

[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 ~5 A / dm ２ Approximately, preferably 0.4 A / dm ２ ~1.0 A / dm ２The solution is heated to a temperature of approximately 30 to 150 minutes, preferably approximately 60 to 120 minutes, and then air and jet stirring or rocking stirring is performed. When Cu plating is performed under these conditions, the azole compound, which acts as a copper ion electrodeposition inhibitor, is adsorbed onto the Cu pillar layer 14 (cathode surface) along with the copper ions. The presence of the azole compound strongly suppresses 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 solution, as shown in S07 of Figures 2 and 4. The resist removal solution to be used is selected depending on the material constituting the resist layer 20. By removing the resist layer 20, the UBM layer 13, Cu pillar layer 14, and nanoporous Cu layer 15 formed after the resist layer formation step S03 are formed in a pattern.

[0047] (Seed Layer Etching Step S08) Next, as shown in S08 of FIGS. 2 and 5 , the seed layer 12 (the seed layer 12 in the region where the UBM layer 13, the Cu pillar layer 14, and the nanoporous Cu layer 15 are not formed) exposed by removing the resist layer 20 is removed by etching. Here, in this embodiment, since the seed layer 12 is made of a metal that is more base 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, examples of the etching solution include (1) nitric acid + sulfuric acid + phosphoric acid + acetic acid, (2) nitric acid + hydrochloric acid + water, and (3) nitric acid + hydrogen peroxide + carboxylic acid.

[0048] (Adhesion layer etching step S09) Next, as shown in S09 of Figures 2 and 5, the adhesion layer 11 exposed by removing the seed layer 12 (the adhesion layer 11 in the region where the seed layer 12, the UBM layer 13, the Cu pillar layer 14, and the 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 bond 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 bond bumps 10 can be stably formed on the surface of the substrate 3, enabling good bonding to the bonded members via the bond bumps 10. Furthermore, because the adhesion layer 11 is made of a metal that is more base than Cu, the adhesion layer 11 can be dissolved preferentially over the nanoporous Cu layer 15 when etching the adhesion layer 11, which can suppress dissolution of the nanoporous Cu layer 15 and result in the stable formation of a nanoporous Cu layer 15 with a predetermined shape and porosity.

[0053] In the substrate 1 with bond 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 preferentially dissolved and removed 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, and 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] The method for manufacturing a substrate with bond bumps according to this embodiment 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, making it possible to form a pattern of bond bumps 10 each having a nanoporous Cu layer 15. Since the seed layer 12 is made of a metal less noble than Cu, the seed layer 12 dissolves preferentially over the nanoporous Cu layer 15 in the seed layer etching step S08, suppressing dissolution of the nanoporous Cu layer 15 and enabling stable formation of a nanoporous Cu layer 15 with a predetermined shape and porosity.

[0057] Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. For example, in the present embodiment, a UBM layer is formed between the seed layer and the Cu pillar layer. However, the present invention is not limited thereto. As shown in FIG. 6, a bond bump 110 may be formed in which a Cu pillar layer 14 is formed directly on the seed layer 12 without forming a UBM layer. Also, as shown in FIG. 7, a bond bump 210 may be formed in which a UBM layer is formed on the seed layer, and a nanoporous Cu layer is formed on the UBM layer, without forming a Cu pillar layer.

[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 adhesion layer having the material and thickness shown in Table 1 was formed on the surface of this silicon wafer by sputtering. Next, a seed layer having the material and thickness shown in Table 1 was formed on the formed adhesion layer by sputtering. Thereafter, a 30 μm thick resist layer having an opening (circular cross section, opening diameter 25 μm) was formed on the seed layer.

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

[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 was CuSO ４ ・5H ２ The plating solution contained 100 mM of HCl and 15 mM of 3,5-Diamino-1,2,4-triazole. 3,5-Diamino-1,2,4-triazole is an azole compound represented by the above formula (4). The current density during plating was 1.5 ASD (A / dm ２ )

[0062] Next, the resist layer was removed using a resist remover. Thereafter, the seed layer exposed by removing the resist layer was removed by etching. The etching conditions are shown in Table 2. After removing the seed layer, the exposed adhesion layer was removed by etching. The etching conditions are 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 porosity P is taken as the average value. ａｖｅThe porosity P was calculated by subjecting a cross section of the obtained substrate with bonding bumps along the thickness direction of the nanoporous Cu layer to CP processing and then observing the cross section with an SEM. The cross section SEM image at 10,000x magnification was binarized and subjected to image analysis to determine the observed area S1 of the nanoporous Cu layer and the area S2 of the pores in the nanoporous Cu layer, and 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 removed by etching. The nanoporous Cu layer was evaluated as "good" when its height after etching was 80% or more of its height before etching, and as "unacceptable" when its height was less than 80%. The height of the nanoporous Cu layer was calculated as the average of the values ​​measured at five locations. The etching process conditions for the seed layer and adhesion layer, as well as the height change before and after etching of the nanoporous Cu layer, are shown in Table 2. Figures 8A and 8B show cross-sectional observations of the nanoporous Cu layer of Comparative Example 1, and Figures 9A and 9B show cross-sectional observations of the nanoporous Cu layer of Invention Example 2.

[0066]

[0067]

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

[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, and a method for manufacturing the substrate with bonding bumps.

[0070] REFERENCE SIGNS LIST 1 Substrate with bonding bumps 3 Substrate 10 Bonding bumps 11 Adhesion layer 12 Seed layer 13 UBM layer 14 Cu pillar layer 15 Nanoporous Cu layer

Claims

1. A substrate with bond bumps, characterized in that the substrate surface has bond bumps formed thereon, each having a structure in which a seed layer and a nanoporous Cu layer are laminated, and the seed layer is made of a metal that is more base than Cu.

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

3. The substrate with bonding bumps according to claim 1, characterized in that an adhesion layer is formed between the substrate and the seed layer, and the adhesion layer is made of a metal that is more base than Cu.

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

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

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

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

Images