Method of forming a micro-electromechanical system (MEMS) having a gap stop

• US 8,119,431 B2
• Filed: 12/08/2009
• Issued: 02/21/2012
• Est. Priority Date: 12/08/2009
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Park, Woo Tae, Karlin, Lisa H., Liu, Lianjun
• Primary Examiner(s): DANG, PHUC T
• Application Number:
  US12/632,940
• Publication Number:
  US 20110133294A1
• Time in Patent Office: 805 Days
• Field of Search: 438/50
• US Class Current: 438/50
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/035 Soldering
• CPC Class Codes: B81C 3/001 Bonding of two components
• 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

Abstract

A method of forming a micro-electromechanical system (MEMS) includes providing a cap substrate, providing a support substrate, depositing a conductive material over the support substrate, patterning the conductive material to form a gap stop and a contact, wherein the gap stop is separated form the contact by an opening, forming a bonding material over the contact and in the opening, wherein the gap stop and the contact prevent the bonding material from extending outside the opening, and attaching the cap substrate to the support substrate by the step of forming the bonding material. In addition, the structure is described.

Claims

1. A method of forming a micro-electromechanical system (MEMS) comprising:

providing a cap substrate;

providing a support substrate;

depositing a conductive material over the support substrate;

patterning the conductive material to leave a conductive portion that forms a gap stop and a contact, wherein the gap stop is separated form the contact by an opening;

forming a bonding material over the contact and in the opening, wherein the gap stop and the contact prevent the bonding material from extending outside the opening; and

attaching the cap substrate to the support substrate by the step of forming the bonding material;

wherein forming the bonding material comprises;

forming a semiconductor layer over the conductive material; and

heating the cap substrate and the semiconductor layer to form the bonding material and bond the cap substrate to the support substrate; and

further comprising forming a stack over the conductive material wherein the step of forming the semiconductor layer is part of the step of forming the stack;

wherein the step of forming the stack over the conductive portion further comprises;

forming a seed layer comprising silicon over the conductive portion; and

forming a first layer comprising silicon and germanium over the seed layer; and

wherein the step of forming the semiconductor layer further comprises forming a second layer comprising germanium over the first layer.

2. The method of claim 1, further comprising:

patterning the stack before the step of patterning the conductive material.

3. The method of claim 2, further comprising:

forming an oxide prior to forming the conductive material;

patterning the oxide before the step of forming the stack over the conductive material; and

removing the oxide after the step of patterning the conductive material.

4. The method of claim 2, wherein providing the cap substrate further comprises providing a cap substrate having an aluminum layer formed in contact with one surface of the cap substrate and wherein after the step of forming the bonding material, the aluminum layer is in contact with the bonding material.

5. The method of claim 4, wherein the bonding material comprises a eutectic material comprising aluminum and germanium.

6. The method of claim 1, wherein the step of depositing the conductive material further comprises depositing doped polysilicon.

7. The method of claim 1, wherein the step of attaching the cap substrate to the support substrate further comprises forming a capacitor in an area of the cap substrate and the support substrate.

8. A method of forming a micro-electromechanical system (MEMS) comprising

providing a first structure, wherein the first structure comprises a cap wafer and a first conductive material formed on an edge of the cap wafer;

providing a second structure, wherein the step of providing the second structure comprises;

providing a support wafer;

depositing a second conductive material over the support wafer;

patterning the second conductive material to form an opening in the second conductive material, a gap stop, and a contact, wherein the opening is between the gap stop and the contact; and

forming a semiconductor stack over the contact; and

bonding the first structure to the second structure by heating the semiconductor layer so it flows into the opening and the gap stop and the contact stop the semiconductor layer from flowing outside of the opening;

wherein the step of heating the semiconductor layer comprises heating the semiconductor stack to form a eutectic bonding material; and

wherein the step of forming the semiconductor stack comprises;

forming a seed layer comprising silicon over the second conductive material;

forming a first semiconductor layer over the seed layer, wherein the first semiconductor layer comprises silicon and germanium; and

forming a second semiconductor layer over the first semiconductor layer, wherein the second semiconductor layer comprises germanium; and

wherein the step of heating the semiconductor stack to form the eutectic bonding material comprises forming an aluminum and germanium comprising eutectic bonding material.

9. The method of claim 8, further comprising patterning the stack before the step of patterning the second conductive material.

10. The method of claim 9, further comprising:

forming an oxide prior to forming the second conductive material;

patterning the oxide before the step of forming the semiconductor stack; and

removing the oxide after the step of patterning the second conductive material.

11. The method of claim 8, wherein the step of depositing the second conductive material further comprises depositing doped polysilicon.

12. The method of claim 8, wherein after the step of bonding the first structure to the second structure, the first structure and the second conductive material are separated from each other by a dimension that is approximately equal to a height of the gap stop.