Mirror structure with single crystal silicon cross-member

• US 20060087717A1
• Filed: 12/08/2005
• Published: 04/27/2006
• Est. Priority Date: 06/18/2004
• Status: Active Grant

• Current Assignee: Miradia Inc. (Walsin Lihwa Corporation)
• Original Assignee: Miradia Inc. (Walsin Lihwa Corporation)
• Inventors: Woo, Howard, McGinley, Brian K., Mohn, Jonathan D.
• Granted Patent: US 7,369,297 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

Hydrogen cleave silicon process for light modulating mirror structure using single crystal silicon as the base cross-member. Existing processes use two critical alignment steps that can contribute to higher actuation voltages and result in lower manufacturing yields. The hydrogen cleave process simplifies the manufacturing process to one step: transferring a thin film of single crystal silicon to the CMOS substrate, resulting in minimal alignment error and providing large bonding area.

Claims

1. A method of fabricating a mirror structure, the method comprising:

forming a cavity in a first substrate;

implanting hydrogen ions in a second substrate;

bonding the first substrate to the second substrate; and

separating a portion of the second substrate.

2. The method of claim 1 wherein the first substrate comprises addressing and control circuitry formed using CMOS techniques.

3. The method of claim 1 wherein the cavity is formed in a first side of the first substrate.

4. The method of claim 3 wherein the cavity is etched to a predetermined distance from the first side of the first substrate.

5. The method of claim 4 wherein the predetermined distance is 0.5 to 1.0 μ

m.

6. The method of claim 1 wherein the second substrate is a single piece of material.

7. The method of claim 6 wherein the single piece of material is single crystal silicon.

8. The method of claim 1 wherein separating a portion of the second substrate comprises cleaving off a carrier wafer portion of the second substrate.

9. The method of claim 1 further comprising depositing a reflective layer to form a mirror plate coupled to the second substrate.

10. A method of fabricating a mirror structure for a micro mirror used in display applications, the method comprising:

forming a recessed region in a bonding side of a first substrate;

performing hydrogen doping of a silicon substrate to form a carrier wafer portion of the silicon substrate;

joining the bonding side of the first substrate to the silicon substrate; and

separating the carrier wafer portion of the silicon substrate.

11. The method of claim 10 further comprising:

forming a first metal layer coupled to the silicon substrate;

depositing a sacrificial layer coupled to the first metal layer;

patterning a via down to the first metal layer;

depositing a second metal layer coupled to the sacrificial layer and in the via to form a mirror plate; and

etching the mirror plate to form the micro mirror.

12. The method of claim 10 wherein separating the carrier wafer portion of the silicon substrate comprises a hydrogen-induced silicon layer cleavage process.

13. The method of claim 12 wherein the hydrogen-induced silicon layer cleavage process comprises a physical process.

14. The method of claim 12 wherein the hydrogen-induced silicon layer cleavage process comprises heating at under 400°

C.

15. A micro mirror for a spatial light modulator, the micro mirror comprising:

a first substrate comprising;

addressing and control circuitry formed using CMOS techniques and adapted to receive actuation signals; and

a cavity formed in a bonding side of the first substrate and adapted to provide a motion space during motion of the micro mirror in response to the actuation signals;

a silicon cross-member coupled to the bonding side of the first substrate; and

a micro mirror coupled to the silicon cross-member and adapted to move in response to the actuation signals.

16. The micro mirror of claim 15 wherein the micro mirror rotates about an axis of rotation aligned with an axis of the silicon cross-member in response to the actuation signals.

17. The micro mirror of claim 15 further comprising a reflective surface coupled to the micro mirror.

18. The micro mirror of claim 15 wherein the silicon cross-member is fabricated from a portion of a silicon substrate defined by a hydrogen-induced silicon layer cleavage process.

19. The micro mirror of claim 18 wherein the hydrogen-induced silicon layer cleavage process comprises:

implanting hydrogen ions to a predetermined depth in the silicon substrate to form a carrier wafer portion of the silicon substrate; and

cleaving off the carrier wafer portion of the silicon substrate.

20. The micro mirror of claim 18 wherein the cavity is formed by an etching process to form a region that is recessed to a predetermined depth with respect to the bonding surface of the first substrate.