Dual wafer attachment process

• US 6,287,940 B1
• Filed: 08/02/1999
• Issued: 09/11/2001
• Est. Priority Date: 08/02/1999
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Cole, Barrett E., Ridley, Jeffrey A., Higashi, Robert E.
• Primary Examiner(s): DANG, TRUNG Q
• Application Number:
  US09/365,703
• Time in Patent Office: 771 Days
• Field of Search: 438/455, 438/458, 438/107, 438/108, 438/109, 438/118
• US Class Current: 438/455
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01K 7/028 using microstructures, e.g. made of silicon
• CPC Class Codes: H01L 2224/04105 Bonding areas formed on an encapsulation of the semiconductor or solid-state body, e.g. bonding areas on chip-scale packages
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/73267 Layer and HDI connectors
• CPC Class Codes: H01L 2224/92244 the second connecting process involving a build-up interconnect
• CPC Class Codes: H01L 2225/06541 Conductive via connections through the device, e.g. vertical interconnects, through silicon via [TSV] manufacturing via connections per se H01L21/76898
• CPC Class Codes: H01L 23/481 Internal lead connections, e.g. via connections, feedthrough structures
• CPC Class Codes: H01L 25/0657 Stacked arrangements of devices
• CPC Class Codes: H01L 25/50 Multistep manufacturing processes of assemblies consisting of devices, each device being of a type provided for in group H01L27/00 or H01L29/00 H01L21/50 takes precedence
• 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

Abstract

Producing the microstructures on separate substrates, which are bonded. One of these structures may be temperature sensitive CMOS electronics. There may be a high-temperature thermal sensor on one wafer and low-temperature CMOS electronics. In the case where the bonding material is polyimide, the polyimide on both surfaces to be bonded is soft baked. The wafers are placed in a wafer bonder and, using precision alignment, brought into contact. The application of pressure and heat forms a bond between the two coatings of polyimide. A wafer may need to be removed from a combined structure. One of the bonded structures may be placed on a sacrificial layer that can be etched away to facilitate removal of a wafer without grinding. After wafer removal, a contact from the backside of one of the structures now on polyimide to the other on the wafer may be made. Sacrificial material, for example, polyimide, may be removed from between the structures that are connected via a contact. A microstructure may be bonded with something that is not a microstructure, such as single-or multi-layer material, crystalline or amorphous.

Claims

1. A process for attaching first and second wafers, at least one wafer having a microstructure, comprising:

making a first wafer having low-temperature microelectronics, having a first set of connections;

making a second wafer at a high temperature having a second set of connections mirrored to match the first set of connections;

applying a polyimide layer on a topside of said first wafer;

applying a polyimide layer on a topside of said second wafer;

soft baking said first and second wafers;

facing the topsides of said first and second wafers with each other;

aligning said first and second wafers to each other;

bonding said first and second wafers together under a pressure at a temperature in a non-oxidizing environment;

etching holes through said polyimide layers down to sets the respective of connections; and

sputtering a conductive material into the holes so as to make contact to the sets of connections.

11. The process of claim 1, wherein the fusing the coatings is followed by removing the second wafer.

12. The process of claim 11, wherein the removing the second wafer comprises removing a sacrificial layer to separate the second wafer from the second microstructure.

13. The process of claim 12, wherein the removing a sacrificial layer is preceded by a forming of an access to the sacrificial layer.

14. The process of claim 13 further comprising forming a contact from the first microstructure to the second microstructure.

15. The process of claim 14, wherein the contact is formed from a backside of one of the first or second microstructures.

16. The process of claim 15, further comprising fusing additional wafers, having microstructures and coated with bonding material, to the existing bonded microstructures.

2. A process for a temperature sensitive wafer with a wafer processed at a high temperature, comprising:

forming a hastalloy layer on a first silicon wafer;

forming a YSZ film layer on the hastalloy layer;

patterning and etching the YSZ layer;

forming a Bi_xTiO_y layer on the YSZ layer;

forming a CMR layer on the Bi_xTiO_y layer;

forming a silicon nitride layer on the CMR layer;

patterning and etching the silicon nitrate, CMR and Bi_xTiO_y layers into a resister pattern;

forming a first polyimide layer on the silicon nitride layer and a portion of the hastalloy layer;

planarizing the first polyimide layer to the silicon nitride layer;

cutting a first via through the silicon nitride layer to the CMR layer;

forming a metal layer that fills the first via to contact the CMR layer;

patterning and etching the metal layer;

forming a dielectric layer on the metal layer;

etching a second via through the dielectric and metal layers to the first polyimide layer;

forming a second polyimide layer on the dielectric layer;

forming CMOS electronics on a second silicon wafer;

forming a third polyimide layer on the CMOS electronics;

patterning and etching a third via through the third polyimide layer to the CMOS electronics;

forming a metal layer that fills the third via to contact the CMOS electronics, on the third polyimide layer;

planarizing the metal layer to the third polyimide layer;

forming a fourth polyimide layer on portions of the third polyimide layer and the metal layer;

aligning first and second wafers, having the second and fourth polyimide layers proximate to each other;

press-bonding the second and fourth polyimide layers to each other;

cutting an access hole through the first silicon wafer to the hastalloy layer;

etching away the hastalloy layer to release the first silicon layer;

milling the first polyimide layer and the YSZ layer to thin the YSZ layer;

removing the first polyimide layer;

removing a portion of the second and fourth polyimide layers to provide a path via the second via to the metal layer situated in the third via;

forming a contact post in the second via to the metal layer situated in the third via; and

remove the second, third and fourth polyimide layers;

wherein the contact post and the metal layer situated in the third via provide structural support and thermal isolation between the YSZ, Bi_xTiO_y, CMR and silicon nitride layers and the CMOS electronics and second silicon wafer.

3. A process for attaching a temperature-sensitive wafer to high temperature wafer, comprising:

forming a hastalloy layer on a first wafer;

forming a YSZ layer on the hastalloy layer;

patterning and etching the YSZ layer;

forming a titanate layer on the YSZ layer;

forming a CMR layer on the Bi_xTiO_y layer;

forming a first dielectric layer on the CMR layer;

patterning and etching the first dielectric, CMR and titanate layers into a resistor pattern;

forming a first polyimide layer on the first dielectric layer and a portion of the hastalloy layer;

planarizing the first polyimide layer to the first dielectric layer;

cutting a first via through the first dielectric layer to the CMR layer;

forming a metal layer that fills the first via to contact the CMR layer;

patterning and etching the metal layer forming a second dielectric layer on the metal layer;

etching a second via through the second dielectric and metal layers to the first polyimide layer;

forming a second polyimide layer on the dielectric layer;

forming CMOS on a second wafer;

forming a third polyimide layer on the CMOS;

aligning the first and second wafers and having the second and third polyimide layers proximate to each other;

press-bonding the second and third polyimide layers to each other;

cutting an access hole through the first wafer;

removing the hastalloy layer via the access hole to release the first wafer;

removing the first polyimide layer;

punching a hole through the second via and second and third polyimide layers to the CMOS;

forming a contact post through the metal layer, dielectric layer, and second and third polyimide layers via the hole; and

removing the second and third polyimide layers to result in thermal isolation between the CMOS and the metal layers.

4. A process for attaching first and second wafers comprising:

forming a first microstructure on the first wafer;

forming a second microstructure on the second wafer;

coating the first microstructure with a first sacrificial bonding material having a first thickness;

coating the second microstructure with a second sacrificial bonding material having a second thickness;

aligning the first and second wafers;

bringing the first and second sacrificial bonding materials into contact; and

fusing the coatings and forming a bond between the first and second sacrificial bonding materials and between the first and second microstructures such that the first and second thicknesses of the first and second sacrificial bonding materials, respectively, determine a separation between the first and second microstructures.

5. The process of claim 4, wherein the first wafer is silicon.

6. The process of claim 5, wherein the second wafer is made of silicon.

7. The process of claim 6, wherein the first microstructure formed on the first wafer is microelectronics.

8. The process of claim 7, wherein the first and second sacrificial bonding materials are polyimide.

9. The process of claim 8, wherein the first and second thicknesses of the first and second sacrificial bonding materials, respectively, are approximately equal.

10. The process of claim 9, wherein the fusing the coatings is followed by removing the sacrificial bonding materials.

17. A process for attaching first and second silicon wafers comprising:

forming microelectronics on the first silicon wafer;

forming a microstructure on the second silicon wafer;

coating the microelectronics with a first sacrificial polyimide bonding material having a first thickness;

coating the microstructure with a second sacrificial polyimide bonding material having a second thickness;

aligning the first and second silicon wafers;

bringing the first and second sacrificial polyimide bonding materials into contact; and

fusing the coatings and forming a bond between the first and second sacrificial polyimide bonding materials and between the microelectronics and the microstructure such that the first and second thicknesses of the first and second sacrificial polyimide bonding materials, respectively, determine a separation between the microelectronics and the microstructure.