US20230035647A1 - Electroforming process - Google Patents

Electroforming process Download PDF

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Publication number
US20230035647A1
US20230035647A1 US17/757,606 US202017757606A US2023035647A1 US 20230035647 A1 US20230035647 A1 US 20230035647A1 US 202017757606 A US202017757606 A US 202017757606A US 2023035647 A1 US2023035647 A1 US 2023035647A1
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US
United States
Prior art keywords
layer
substrate
conductive coating
partially overlapping
process according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
US17/757,606
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English (en)
Inventor
Marco Herman Laurens Hubert Kusters
Joris Antonius Wilhelmus Münninghoff
Nicolas Hildenbrand
Roy Gerardus Johannes Joseph Alberts
Johannes Hendrikus Maria Berenschot
Harm Gerrit Knol
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Veco BV
Original Assignee
Veco BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Veco BV filed Critical Veco BV
Assigned to VECO B.V. reassignment VECO B.V. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KNOL, HARM GERRIT, BERENSCHOT, Johannes Hendrikus Maria, ALBERTS, Roy Gerardus Johannes Joseph, HILDENBRAND, NICOLAS, KUSTERS, MARCO HERMAN LAURENS HUBERT, MÜNNINGHOFF, Joris Antonius Wilhelmus
Publication of US20230035647A1 publication Critical patent/US20230035647A1/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/003—3D structures, e.g. superposed patterned layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/10—Moulds; Masks; Masterforms
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/02—Electroplating of selected surface areas
    • C25D5/022—Electroplating of selected surface areas using masking means
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium

Definitions

  • the present invention relates to an electroforming process for forming a metal structure.
  • Electroforming is an electrodeposition process for forming a product of one or more metal layers on a removable substrate.
  • the substrate is placed in an electrolytic bath in electrical contact with a cathode.
  • ions of the metal to be deposited are solved into the electrolyte. These ions flow to the substrate where they are replenished with electrons and deposit on the substrate surface as a layer of neutral metal molecules.
  • the metal product Once the metal product has a desired thickness, it is removed from the substrate.
  • a pattern of a non-conductive coating is applied on parts of the substrate defining the geometrical outline of the structure to be electroformed.
  • a non-conductive coating is usually applied on the substrate by means of a photolithographic process using a UV-sensitive photoresist coating material.
  • the photoresist can for example be applied by spin coating to obtain a very smooth layer of uniform thickness.
  • Parts of the photoresist are selectively exposed to UV-light, e.g., by using laser direct imaging (LDI), or by using a photomask. If the photoresist is a positive photoresist, the exposed parts are removed. If the photoresist is a negative photoresist, the non-exposed parts are removed.
  • a patterned coating of the photoresist will remain on the substrate.
  • the electrically conductive substrate with the photoresist pattern forms a mandrel. Electroforming will only take place on sections of the substrate not shielded by the photoresist pattern.
  • US 2005/0253606 discloses an electrodeposition process for forming complex multi-layer structures with staggered layers and recesses. Each layer must be planarized before a next layer can be applied.
  • NL 1031259 discloses an electroforming process involving forming a metal layer on a substrate and a sacrificial layer supporting the structure after removal of the substrate.
  • the object of the invention is achieved with a process of electroforming a metal structure, the process comprising the following steps:
  • a first layer is deposited on a substrate followed by one or more next layers partially overlapping the first layer to form an intermediate structure having a substrate surface facing the substrate;
  • the intermediate structure is removed from the substrate and one or more further layers are deposited on said substrate surface of the intermediate structure.
  • the uncovered surface of the intermediate structure is just as flat as the substrate it was made on. Therefore, further layers can be applied on this side of the intermediate structure without the need of first planarizing it.
  • the first layer itself can comprise one or more layers.
  • the partially overlapping layer can comprise one or more layers.
  • the layers can be formed by electrodeposition.
  • the first layer protrudes relative to this next layer.
  • the first layer will also protrude relative to the one or more layers on the substrate surface of the intermediate structure. This way, the first layer will protrude from the outer layers at both sides, e.g., to form a tip.
  • the layers at both sides of the first layer may be symmetrical or asymmetrical.
  • a layer of a sacrificial material is formed over the intermediate structure before the intermediate structure is removed from the substrate.
  • the layer of sacrificial material can removed, for example by selective etching.
  • Suitable sacrificial materials include for example copper, silver or a polymeric material.
  • the body of sacrificial material forms an auxiliary substrate, supporting the intermediate structure after removal of the substrate when the further layers are applied on the substrate side of the intermediate structure.
  • the substrate side is the side of the intermediate structure directly contacted by the substrate before removal of the substrate.
  • the substrate is a mandrel with a non-conductive coating pattern, such as a photoresist pattern, defining an outline of at least the first layer.
  • a non-conductive coating pattern such as a photoresist pattern
  • the photoresist Before forming the overlapping layer, the photoresist can be at least partially removed so a new photoresist pattern can be applied to confine the overlapping layer.
  • the complete photoresist coating can completely be removed and replaced with a fresh photoresist coating of the desired patter.
  • the first layer can be of a different material than the overlapping layer and/or the layers deposited on the opposite side.
  • This is particularly suitable for making a structure with a multilayer body of a first material, such as nickel or a nickel alloy, and a protruding tip of a second material, such as rhodium.
  • a structure can for example be used as a test probe of a probe card for testing semiconductors on a wafer.
  • the process may for example comprise the following steps to manufacture a structure with a tip:
  • the first layer is covered with a fresh non-conductive coating, e.g., a photoresist;
  • parts of the non-conductive coating are removed to expose a part of the substrate, adjacent one side of the first layer;
  • a second layer is electroformed on the exposed parts of the substrate surface
  • parts of the non-conductive coating on top of the first layer are removed and a third layer is electroformed on top of the exposed parts of the second layer and on top of an adjacent part of the first layer;
  • the remaining parts of the non-conductive coating are removed and the body of sacrificial material is applied on top of the first and third layers;
  • the substrate is removed to expose a substrate side of the intermediate structure
  • a further non-conductive coating is applied covering the part of the first layer projecting from the third layer and covering uncovered parts of the sacrificial layer adjacent the first layer;
  • the non-conductive coating and the sacrificial material are removed.
  • Substrates for electroforming are made of conductive material, e.g., a metal, passivated to allow subsequent separation of the finished electroformed structure.
  • Non-conductive substrates can for example be made of glass, silicon, or plastic polymeric material, and require the deposition of a conductive layer prior to electrodeposition.
  • the sacrificial material can be any material allowing selective etching without affecting the materials of the final structure. Suitable sacrificial materials include for instance copper, silver or polymeric materials.
  • the non-conductive coating is typically a photoresist material, e.g., a positive or negative photoresist, although other types of non-conductive coatings can also be used, if so desired.
  • the process according to the present invention allows producing multilayer metal structures with projecting inner layers on any scale, also on a very small scale, e.g., micrometer-scale, in a very accurate and reliable manner.
  • the thickness of the photoresist layer can for example be in the range of 10 to 100 micrometer, but can also be outside this range, if so desired.
  • the thickness of the electroformed layers can for example be in the range of 10 to 100 micrometer per layer, but can also be outside this range, if so desired.
  • suitable metals include, inter alia, nickel, nickel alloys, such as nickel-palladium alloy; chromium, rhodium, copper or copper alloys.
  • suitable electroplating baths for nickel include, i.a., a Watts bath (NiSO4), a sulphamate bath, and examples of suitable electroplating baths for copper include a copper sulphate bath.
  • FIGS. 1 A-N showing consecutive steps of an exemplary embodiment of a process according to the invention.
  • FIG. 1 A shows a substrate 2 partly covered by a non-conductive coating of a photoresist 3 .
  • the photoresist 3 is applied, e.g., by means of spin coating, to form a UV-sensitive coating of a uniform thickness.
  • Parts of the photoresist 3 are removed after selective exposure to UV-light, e.g., by means of laser direct imaging.
  • the top surface 2 of the substrate 1 has conductive bare sections 4 and non-conductive sections 3 coated with the photoresist, as shown in FIG. 1 A .
  • the mandrel 1 is then placed in an electrolytic bath and electro-conductively connected to a cathode.
  • a rhodium layer 7 is deposited on the conductive sections 4 of the mandrel 1 ( FIG. 1 B ).
  • the thickness of the rhodium layer 7 does not exceed the thickness of the photoresist 3 .
  • the mandrel 1 is then taken from the electrolytic bath and spin coated with a second photoresist layer 8 , which covers the first photoresist 3 and the rhodium layer 7 .
  • the first photoresist may be removed and complete replaced by the fresh second photoresist.
  • Parts of the second photoresist 8 are selectively exposed to UV for curing and the uncured parts are washed away.
  • FIG. 1 D the first and second photoresist layers directly adjacent the rhodium layer 7 are removed leaving part of the substrate 2 uncovered ( FIG. 1 D ).
  • the mandrel 1 is then placed in a second electrolytic bath and connected to the cathode, the anode being configured to release nickel cations.
  • a nickel layer 9 is deposited on the uncovered electro-conductive section of the mandrel's top surface 2 .
  • the nickel layer 9 has the same thickness as the rhodium layer 7 ( FIG. 1 E ).
  • the mandrel 1 is removed from the electrolytic bath and to allow removal of a part of the photoresist 8 on top of the rhodium layer 7 adjacent the nickel layer 9 ( FIG. 1 F ).
  • the mandrel 1 is then returned to the same electrolytic bath and a further nickel layer 10 is electroformed on top of the uncovered part of the rhodium layer 7 and the first nickel layer 9 ( FIG. 1 G ).
  • the resulting intermediate structure has a rhodium tip projecting from a nickel body.
  • the rest of the photoresist is subsequently removed ( FIG. 1 H ).
  • the copper can be applied by means of electroforming or by any other suitable deposition process.
  • the thickness of the copper layer is about the same as the thickness of the mandrel 1 , but can be more if so desired.
  • the copper, nickel and rhodium layers 7 , 10 , 11 are jointly removed from the mandrel 1 ( FIG. 1 J ).
  • the mandrel side 12 of the rhodium layer i.e., the side facing the mandrel before its removal, is now uncovered. This side 12 is just as flat as the mandrel surface 2 and therefore a very suitable substrate for electroforming further layers, without the need of a planarization step.
  • a new photoresist layer 13 is applied and cured on top of the projecting part of the rhodium layer 7 ( FIG. 1 K ). The rest of the rhodium layer 7 remains uncovered, just as the nickel layer 10 .
  • the structure is then returned into the second electrolytic bath and again connected to the cathode.
  • a further layer 14 of nickel is deposited on the uncovered parts of the rhodium layer 7 and the adjacent surface of the nickel part 10 ( FIG. 1 L ).
  • the last photoresist 13 and the copper 11 can now be removed, e.g., by selective etching.
  • the remaining final structure 15 comprises a nickel body 16 with one end sandwiching a projecting rhodium tip.
  • the layer in line with the rhodium tip can be a different material, e.g., copper, e.g., sandwiched by layers of nickel or nickel alloys.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
US17/757,606 2019-12-20 2020-12-18 Electroforming process Pending US20230035647A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL2024542A NL2024542B1 (en) 2019-12-20 2019-12-20 Electroforming process
NL2024542 2019-12-20
PCT/NL2020/050804 WO2021125959A1 (en) 2019-12-20 2020-12-18 Electroforming process

Publications (1)

Publication Number Publication Date
US20230035647A1 true US20230035647A1 (en) 2023-02-02

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Family Applications (1)

Application Number Title Priority Date Filing Date
US17/757,606 Pending US20230035647A1 (en) 2019-12-20 2020-12-18 Electroforming process

Country Status (8)

Country Link
US (1) US20230035647A1 (de)
EP (1) EP4077768A1 (de)
JP (1) JP2023507177A (de)
KR (1) KR20220118447A (de)
CN (1) CN114929942A (de)
NL (1) NL2024542B1 (de)
TW (1) TW202132626A (de)
WO (1) WO2021125959A1 (de)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7241689B2 (en) 2003-02-04 2007-07-10 Microfabrica Inc. Microprobe tips and methods for making
NL1031259C2 (nl) 2006-03-01 2007-09-04 Stork Veco Bv Elektroformeringswerkwijze.

Also Published As

Publication number Publication date
CN114929942A (zh) 2022-08-19
WO2021125959A1 (en) 2021-06-24
TW202132626A (zh) 2021-09-01
JP2023507177A (ja) 2023-02-21
KR20220118447A (ko) 2022-08-25
NL2024542B1 (en) 2021-09-02
EP4077768A1 (de) 2022-10-26

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Owner name: VECO B.V., NETHERLANDS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KUSTERS, MARCO HERMAN LAURENS HUBERT;MUENNINGHOFF, JORIS ANTONIUS WILHELMUS;HILDENBRAND, NICOLAS;AND OTHERS;SIGNING DATES FROM 20220614 TO 20220616;REEL/FRAME:060306/0352

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