Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W72/00—Interconnections or connectors in packages
  • H10W72/071—Connecting or disconnecting
  • H10W72/073—Connecting or disconnecting of die-attach connectors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W72/00—Interconnections or connectors in packages
  • H10W72/30—Die-attach connectors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W72/00—Interconnections or connectors in packages
  • H10W72/071—Connecting or disconnecting
  • H10W72/073—Connecting or disconnecting of die-attach connectors
  • H10W72/07331—Connecting techniques
  • H10W72/07336—Soldering or alloying
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W72/00—Interconnections or connectors in packages
  • H10W72/30—Die-attach connectors
  • H10W72/351—Materials of die-attach connectors
  • H10W72/352—Materials of die-attach connectors comprising metals or metalloids, e.g. solders

Definitions

• the present invention relates to die attached SiC and a procedure for attaching a SiC die to a package.
• Silicon devices are bonded to packages, typically hermetic packages, to protect the silicon device from the environment. Additionally, the package provides heat sinking to prevent thermal damage of the silicon device.
• One method of bonding a silicon device to a package is called "scrubbing.” As illustrated in Fig. 1, a vacuum collett 8 picks up a Si chip 6 and scrubs the Si chip 6, called a die or silicon die, back and forth into the package 2 plated in gold 4 at a designated position. This "scrubbing" takes place after heating the gold plated package 2,4 and the silicon die 6 to above 370°C. The scrubbing procedure results in the formation of a Au- Si eutectic which bonds the silicon device to the package.
• SiC requires applying a solderable metalization to the back of the SiC chip or SiC die. Then, a Au-Sn or Au- Si solder preform is used to form a joint between the SiC die and the package. Typically, this process requires fixtures to position the SiC die and solder preform on the package, and passing the fixtured SiC die, solder preform and package through a furnace to form the solder joint. Additionally, the joint or bond layer between the Sic die and package is quite thick - on the order of 370,000 to 500,000 A; where A stands for angstroms. Such a thick joint adversely increases the thermal resistance of the SiC - package.
• One object of the present invention is to provide a simple die attach procedure for SiC.
• Another object of the present invention is to provide a die attach procedure for SiC which uses the well known scrubbing technique.
• a further object of the present invention is to provide a die attach procedure for Sic which forms a thin bond layer.
• a die attach procedure for SiC which includes the steps of providing a Sic die; forming a first layer, preferably a nickel layer, on the SiC die; forming a second layer, preferably an amorphous silicon layer, on the first layer; and scrubbing the Sic die into a package typically plated with gold so that a Au-Si eutectic is formed.
• die attached SiC which includes a package having a plating, usually gold, formed thereon; a Sic die; a first layer, preferably a nickel layer, bonded to the
• SiC die a second layer, preferably an amorphous silicon layer, bonded to the first layer and the package.
• the second layer forms a eutectic with the plating on the package.
• Fig. 1 illustrates the procedure for scrubbing a silicon die into a gold plated package
• Figs. 2-3 illustrate the die attach procedure for SiC according to the present invention.
• a layer of nickel (Ni) 14 is deposited on a back surface 12 of a SiC die 10.
• the nickel layer 14 is deposited to a thickness of 2,000 - 10,000 A, where A is angstroms.
• the thickness of the nickel layer 14 should be about 5000 A.
• the nickel layer 14 may be deposited using any well-known deposition technique such as E-beam evaporation.
• the SiC die 10 with the nickel layer 14 is subjected to Rapid
• RTA Thermal Annealing
• Annealing causes the nickel layer 14 to react with the SiC die 10. Consequently, annealing provides a good bond between the SiC die 10 and the nickel layer 14 at the atomic level, and provides a good oh ic contact to the SiC die 10 (i.e., reduces the high contact resistance between the SiC die 10 and the nickel layer 14 prior to annealing) .
• furnace annealing Other methods of annealing, such as furnace annealing, may be used instead of RTA.
• any material such as platinum, which bonds to SiC and amorphous silicon (or one of the substitutes for amorphous silicon discussed below) may be used.
• the substitute for nickel must not, however, be consumed by the Au-Si eutectic discussed in detail below; otherwise, the joint provided between the SiC and amorphous silicon would be destroyed.
• an amorphous silicon layer 16 is deposited on the nickel layer 14.
• the amorphous silicon layer 16 may be deposited using the well known technique of chemical vapor deposition at approximately 400°C. Other deposition techniques such as sputtering, however, may be used.
• the amorphous silicon layer 16 is deposited to a thickness of 5,000 - 30,000 A. Preferably the amorphous silicon layer 16 should have a thickness of 10,000 - 15,000 A. Because of the nickel layer 14, the amorphous silicon layer 16 bonds to the SiC die 10. In this way, the nickel layer 14 may be thought of as an adhesive layer. Consequently, as discussed above, any other material or compound which bonds to SiC and amorphous silicon may be used instead of nickel.
• the die attach procedure of the present invention is not limited to the use of amorphous silicon.
• Other materials such as tin and germanium, which bond to the adhesive layer and form a eutectic with the plating on the package, may be used.
• the substitutes for amorphous silicon preferably, should form a eutectic with the plating on package at a sufficiently low temperature to prevent damage to the SiC device.
• Amorphous silicon is preferred, though, because amorphous silicon allows high temperature processing of, for example, the SiC wafer while still forming a eutectic with gold at low temperatures.
• the procedure according to the present invention is expected to be applied to entire SiC wafers. Therefore, after the application of both the nickel layer and the amorphous silicon layer, the SiC wafer can be further processed, tested and diced into individual chips.
• the SiC chip or die is scrubbed into a gold plated package.
• the amorphous silicon layer 16 and the gold plating form a Au-Si eutectic, and bond the SiC die to the package.
• the resulting bond layer of nickel, amorphous silicon, and gold is only about 60,000 A thick. This is almost an order of magnitude thinner than conventional soldering techniques. Furthermore, such a thin bond layer minimizes thermal resistance.
• the present invention utilizes the relatively simple and known scrubbing technique as opposed to the relatively complex solder bonding method which can require expensive fixturing.
• the die attach procedure for SiC according to the present invention can be used with other packages or plated packages which form a eutectic with amorphous silicon or a substitute therefor.

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• Die Bonding (AREA)

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Citations (5)

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• 1996
  • 1996-02-13 US US08/600,777 patent/US5851852A/en not_active Expired - Lifetime
• 1997
  • 1997-01-31 WO PCT/US1997/001790 patent/WO1997030474A1/en not_active Ceased
  • 1997-01-31 DE DE69711852T patent/DE69711852T2/de not_active Expired - Lifetime
  • 1997-01-31 JP JP52938597A patent/JP3971456B2/ja not_active Expired - Lifetime
  • 1997-01-31 EP EP97905753A patent/EP0880801B1/en not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (1)

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