EP0878023A1 - Structure de bosse de contact et procede pour la fabriquer - Google Patents

Structure de bosse de contact et procede pour la fabriquer

Info

Publication number
EP0878023A1
EP0878023A1 EP97901650A EP97901650A EP0878023A1 EP 0878023 A1 EP0878023 A1 EP 0878023A1 EP 97901650 A EP97901650 A EP 97901650A EP 97901650 A EP97901650 A EP 97901650A EP 0878023 A1 EP0878023 A1 EP 0878023A1
Authority
EP
European Patent Office
Prior art keywords
layer
tin
contact
bump structure
onto
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.)
Withdrawn
Application number
EP97901650A
Other languages
German (de)
English (en)
Inventor
Ahti Aintila
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.)
Picopak Oy
Original Assignee
Picopak Oy
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 Picopak Oy filed Critical Picopak Oy
Publication of EP0878023A1 publication Critical patent/EP0878023A1/fr
Withdrawn legal-status Critical Current

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    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/11—Manufacturing methods
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    • H01L24/02—Bonding areas ; Manufacturing methods related thereto
    • H01L24/03—Manufacturing methods
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Definitions

  • the invention relates to a contact bump structure according to the preamble of claim 1.
  • the invention also concerns a method of forming a contact bump structure.
  • contact bumps on electronic components are formed by means of autocatalytic processes from nickel with gold deposited thereon.
  • the contact bump structure is later bonded, e.g., by tin solder bonding to a larger circuit substrate/board.
  • the goal of the invention is achieved by depositing the tin solder bumps by means of an autocatalytic process directly onto aluminium contact bump structures formed on a silicon substrate.
  • the contact bump structure according to the invention is characterized by what is stated in the characterizing part of claim 1.
  • One of the principal advantages of the contact bump structure according to the invention is that a metallurgical structure is attained which during the soldering process and under operating conditions does not form brittle intermetal compounds or such uncontrolled intermetallic alloying that is detrimental to the solder bond.
  • the bond structure disclosed herein has an inherent ductility and toughness which are liable to even out stresses caused by the differential thermal expansion rates of the substrate and the bonded component.
  • the invention also makes it possible to implement bump structures that are compatible with conventional surface mounting technology. Moreover, the invention facilitates a high component bonding density without any risk of short circuits.
  • Figure 1 shows a longitudinally sectioned side view of a contact bump structure according to the invention
  • Figure 2 shows the contact bump structure of Fig. 1 after post-treatment
  • Figure 3 shows a longitudinally sectioned side view of a process step suitable for forming an alternative embodiment of the contact bump structure according to the invention
  • Figure 4 shows the contact bump structure of Fig. 3 after post-treatment
  • Figure 5a shows a longitudinally sectioned side view of a third embodiment of the contact bump structure according to the invention.
  • Figure 5b shows the contact bump structure of Fig. 5a after post-treatment
  • Figure 6 shows a fourth alternative embodiment of the contact bump structure according to the invention.
  • the goal of the method according to the invention is both to dispense with the catalyzing zincate bath which is conventionally applied prior to the nickel bath but tends to attack the aluminium layer and is critical in operation, and to accelerate the start of metal deposition in the nickel bath such that no additional etching can occur.
  • a catalyzing zincate bath which is conventionally applied prior to the nickel bath but tends to attack the aluminium layer and is critical in operation, and to accelerate the start of metal deposition in the nickel bath such that no additional etching can occur.
  • Layer 2 is a passivation layer conventionally used in semiconductor element structures.
  • Layer 4 is a thin nickel layer deposited by a catalytic (metal-exchange reaction) process serving to replace the conventional zincate bath. The stresses between the nickel layer 5 deposited from the present process and the aluminium layer 3 remain substantially smaller than those occurring in a contact bump structure processed in a conventional nickel bath. On the nickel layer 5 is deposited a thin copper layer 6 whose sole function is to carry out the metal- exchange reaction with tin.
  • tin layer 7 next deposited by the metal- exchange reaction cannot reach any substantial thickness
  • another tin layer 8 of greater thickness (15-20 ⁇ m) is deposited in an autocatalytic bath thereonto.
  • the contact bump is finally covered by a thin (0.3- 1.0 ⁇ m thick) lead layer 9 which is converted into an eutectic tin-lead alloy by a heat treatment.
  • Figure 2 shows the contact bump of Fig. 1 after the heat treatment.
  • a thick resist layer 10 with vertical walls can be used for depositing a thin, high copper "post" 6 which can yield substantially during thermal expansion thus reducing the risk of bond fractures.
  • the copper post 6 is easily made ductile by subjecting the contact bumps to heat treatment at 150 °C for about 15 minutes.
  • An alternative approach to improve the ductility of the contact bump is to leave the resist in place after the copper deposition step, whereby the tin 7 from the metal-exchange reaction is only allowed to deposit on top the copper post 6 as shown in Fig. 4.
  • the autocatalytically deposited thick tin 8 forms a blob-like ball on the top of the contact bump, wherefrom, during the fusing step, it cannot wet the sides of the copper post 6, these being al ⁇ ready oxidized at this stage of the bump-forming process.
  • tin layer 8 when permitted by the desired contact density, onto the thin nickel layer 5 and the copper layer 6 can naturally be deposited a thick tin layer 8 that in a heat treatment is melted into a blob-like bump bordered by the underlying metallization as shown in Fig. 5b.
  • the yield properties of the tin layer may change somewhat due to the required heat treatment.
  • the contact bumps structures described above can be bonded to a substrate by means of a plurality of techniques well-known from the literature of the art.
  • the most common bonding method is to use solder cream subjected to a fusing step as is conventional in the surface mounting technology.
  • the limits of this method are dictated at high contact densities by the finest achievable raster of solder cream dots, which in the printing process typically is in the order of about 200 ⁇ m.
  • the conductive component in these compounds is a metallic filler comprising nonmelting metallic particles, or preferably, melting solder alloy particles. Even higher still contact densities (with an interbump spacing smaller than 100 ⁇ m) have been attained by directly fusing the contact bump surfaces to the contact pad areas of the substrate, which are coated with a suitable metal, in an inert gas atmosphere or protected by a flux. When using a tin-lead alloy bump on a gold-clad contact area, this metallic bond combination has been processed with good results in a normal dry air atmosphere even without using any flux.
  • the present method offers an interesting, novel possibility of processing metallic microbonds by using certain semimetallic elements (such as bismuth) for making the bond.
  • semimetallic elements such as bismuth
  • a suitable, typically tin or tin-lead alloy coated contact bump and/or substrate is coated electrolytically or chemically by a thin bismuth layer or similar semimetallic compound.
  • the bumps and the substrate are superimposed and heated until the bismuth due to its lowest melting temperature of the materials is melted and forms a solid solution with tin without causing total melting of the tin bump.
  • the metallic bond thus obtained is extremely tough and ductile.
  • solder bond can be formed that is also pro ⁇ tected by an adhesive. This process dispenses with the filler normally applied in the intermediate space remaining between the component and the substrate.
  • a sim ⁇ ilar bonding metallurgy can also be achieved using a bismuth-filled anisotropically conducting adhesive.
  • the multi-step contact bond formation process according to the invention permits a relatively large variation in the bonding temperatures used.
  • Fig. 6 it is possible to simplify the disclosed process appreciably by arranging a metal- exchange reaction to occur directly with the aluminium layer 3. Then, the nickel and copper layers can be omitted and the contact bump is formed by a thin tin layer 7 formed in the metal-exchange reaction, an autocatalytically deposited tin layer 8 and a thin, protective lead layer 9.
  • a proper composition for the tin layer 7 formed by the metal-exchange reaction is known from the chemical tin deposition processes used in the manufacture of aluminium pistons.
  • Typical process param ⁇ eters for a metal-exchange tin bath are: 44.8 g/1 Na 2 SnO,- 3H 2 O, 3-5 min process time at 80 °C, tin layer thickness 4-5 ⁇ m.
  • the method according to the invention is particularly intended for forming contact bumps on semiconductor chips patterned on a homogeneous silicon substrate. After processing, the semiconductor chips processed on the substrate are separated from each other and bonded to larger circuit boards by means of the above- described contact bumps.
  • the autocatalytic deposition method referred to in the present text is also known as the electroless process in which metallic layers are deposited without using an external source of electrical potential.

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
  • Wire Bonding (AREA)

Abstract

L'invention concerne une structure de bosse de contact, formée sur une plage de contact (3) en aluminium sur un substrat en silicium (1) et un procédé pour former cette structure de bosse de contact. Selon l'invention, cette structure de bosse de contact comprend une bosse en étain (8) formée par une réaction autocatalytique sur la plage de contact (3)
EP97901650A 1996-02-02 1997-01-30 Structure de bosse de contact et procede pour la fabriquer Withdrawn EP0878023A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI960502 1996-02-02
FI960502A FI960502A (fi) 1996-02-02 1996-02-02 Nystyrakenne ja menetelmä nystyjen muodostamiseksi
PCT/FI1997/000047 WO1997028562A1 (fr) 1996-02-02 1997-01-30 Structure de bosse de contact et procede pour la fabriquer

Publications (1)

Publication Number Publication Date
EP0878023A1 true EP0878023A1 (fr) 1998-11-18

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EP97901650A Withdrawn EP0878023A1 (fr) 1996-02-02 1997-01-30 Structure de bosse de contact et procede pour la fabriquer

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EP (1) EP0878023A1 (fr)
FI (1) FI960502A (fr)
WO (1) WO1997028562A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6434817B1 (en) * 1999-12-03 2002-08-20 Delphi Technologies, Inc. Method for joining an integrated circuit

Family Cites Families (1)

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Publication number Priority date Publication date Assignee Title
US5156997A (en) * 1991-02-11 1992-10-20 Microelectronics And Computer Technology Corporation Method of making semiconductor bonding bumps using metal cluster ion deposition

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9728562A1 *

Also Published As

Publication number Publication date
WO1997028562A1 (fr) 1997-08-07
FI960502A0 (fi) 1996-02-02
FI960502A (fi) 1997-08-03

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