Method of making a hermetic seal in a solid-state device

• US 4,895,291 A
• Filed: 05/04/1989
• Issued: 01/23/1990
• Est. Priority Date: 05/04/1989
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Ozimek, Edward J., Carnall, Edward Jr.
• Primary Examiner(s): Godici, Nicholas P.
• Assistant Examiner(s): Heinrich, Samuel M.
• Application Number:
  US07/347,091
• Time in Patent Office: 264 Days
• Field of Search: 228/121, 228/123, 228/124, 228/193, 228/227, 228/263.12, 29/841
• US Class Current: 228/121
• CPC Class Codes: B23K 1/19 taking account of the properties of the materials to be soldered
• CPC Class Codes: B23K 35/001 Interlayers, transition pieces for metallurgical bonding of workpieces
• CPC Class Codes: H01L 21/50 Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01079 Gold [Au]

Abstract

A method of making a hermetic seal for a solid-state device is disclosed. The device includes a ceramic housing having a cavity for an element such as an image sensor. A cover formed of a transparent material is sealed to the housing to close the cavity. A metallization support is formed on the cover and on the housing. In order to form a hermetic seal at a relative low temperature, a layer of indium is coated on the metallization support of either the cover or the housing, and a layer of tin is coated on the support of the other of the two parts. The cover is then placed on the housing, and the parts are placed in a furnace where a temperature under the melting temperature of the composite alloy of tin and indium is maintained for a period long enough to diffuse the tin and indium together. The temperature is then raised to a temperature sufficient to melt the alloy, and the device is then slowly cooled to ambient temperature.

Claims

1. A method of making a hermetic seal in a solid-state device, said method comprising the steps of:

forming a metallization support on a housing;

forming a metallization support on a cover for said housing;

forming a layer of indium on one of said supports;

forming a layer of tin on the other of said supports;

positioning said cover and said housing such that said layers of indium and tin are in contact with each other;

heating said cover and housing to a temperature of between about 70% and about 90% of the melting temperature of a composite alloy of tin and indium to diffuse said tin and indium together;

heating said cover and housing to a temperature sufficient to melt said alloy after said diffusion is complete; and

slowly cooling the cover and housing to ambient temperature.

2. A method, as defined in claim 1, wherein each of said supports includes a layer of nickel and a layer of gold thereon.

3. A method, as defined in claim 1, wherein said metallization supports are cleaned using a plasma etch prior to being coated with a layer of indium or tin.

4. A method, as defined in claim 1, wherein said melting temperature of the composite alloy is about 125°

C.

6. A method, as defined in claim 1, wherein said housing is formed of a ceramic material.

7. A method, as defined in claim 1, wherein said cover is transparent.

8. A method, as defined in claim 1, wherein alternating layers of indium and tin are formed on each of said supports, and a top layer on said one support is indium and a top layer on said other support is tin.

5. A method, as defined in claim 5, wherein said cover and housing are heated to a temperature of 100°

C. to diffuse said tin and indium together.

9. A method of making a hermetic seal in a solid-state device, said method comprising:

forming a metallization support on a housing, said support having a base layer of tungsten and a gold layer deposited on the tungsten layer;

forming a metallization support on a cover for said housing, said support having a base layer of a titanium-tungsten alloy and a gold layer deposited on the alloy;

forming alternating layers of indium and tin on one of said supports, the top layer on said one support being indium;

forming alternating layers of tin and indium on the other of said supports, the top layer on said other support being tin;

positioning said cover and said housing such that said top layers of indium and tin are in contact with each other;

heating said cover and housing to a temperature of about 100°

C. for about four hours to diffuse said tin and indium together;

heating said cover and housing to a temperature of about 130°

C. for about 10 minutes; and

slowly cooling the cover and housing to ambient temperature.