Methods for depositing, releasing and packaging micro-electromechanical devices on wafer substrates
A method for forming a MEMS device is disclosed, where a final release step is performed just prior to a wafer bonding step to protect the MEMS device from contamination, physical contact, or other deleterious external events. Without additional changes to the MEMS structure between release and wafer bonding and singulation, except for an optional stiction treatment, the MEMS device is best protected and overall process flow is improved. The method is applicable to the production of any MEMS device and is particularly beneficial in the making of fragile micromirrors.
1 . A spatial light modulator comprising;
a lower silicon substrate comprising a plurality of circuitry, electrodes and deflectable mirrors;
a glass substrate bonded in spaced apart relationship to the lower substrate;
an intermediate substrate disposed between the upper and lower substrates and having an open area for defining a cavity between the silicon substrate and the glass substrate, with the deflectable mirrors within the gap;
a light blocking material on a lower side of the glass substrate and provided as a rectangular light blocking mask;
wherein the mirrors comprise substantially square mirror plates and hinges that allow the mirror plates to move relative to the upper and lower substrates;
wherein tbe mirrors are formed on the lower silicon substrate in a rectangular array area, and wherein the mirrors have a plurality of mirror edges that are neither parallel nor perpendicular to edges of the rectangular array area;
a RAM cell at each mirror location.
2 . The spatial light modulator of claim 1 , wherein a group of the mirror edges of the mirrors is neither parallel nor perpendicular to the edges of the rectangular array area, and another group of the edges is parallel to rectangular array area edges.
3 . The spatial light modulator of claim 1 , wherein the mirror edges are approximately 45 degrees relative to the rectangular array area edges.
4 . The spatial light modulator of claim 1 , wherein no mirror edges are parallel or perpendicular to edges of the rectangular array area.
5 . The spatial light modulator of claim 3 , wherein each mirror has a switching axis that is at a non-parallel and non-perpendicular angle to at least one edge of the mirror.
6 . The spatial light modulator of claim 1 , wherein each mirror has a switching axis parallel to at least one edge of the active area.
7 . The spatial light modulator of claim 5 , wherein each mirror has a switching axis at an angle of from 40 to 55 degrees to one or more edges of each mirror.
8 . The spatial light modulator of claim 1 , wherein each mirror has a front edge that is non-perpendicular to any edge of the active area.
9 . The spatial light modulator of claim 1 , wherein each mirror is a square mirror having four edges defining the square mirror, wherein the four edges of each mirror is neither parallel nor perpendicular to any edges of the active area.
10 . The spatial light modulator of claim 1 , wherein addressing rows connect to every other mirror.
11 . The spatial light modulator of claim 1 , wherein addressing columns connect to every other mirror.
12 . The spatial light modulator of claim 1 , wherein hinges are disposed below each mirror and are held on support posts.
13 . The spatial light modulator of claimn 5 , wherein the mirrors comprise hinges that extend parallel to the leading and trailing edges of the active area.
14 . The spatial light modulator of claim 1 , wherein the mirrors have jagged edges.
15 . The spatial light modulator of claim 1 , wherein the mirrors have square mirror plates that have no edges parallel or perpendicular to the edges of the rectangular array area, and wherein the cavity comprises a getter and a lubricant.
16 . The spatial light modulator of claim 15 , wherein the RAM cell is an SRAM or DRAM cell.
17 . The spatial light modulator of claim 16 , wherein the binges are torsion hinges having a thickness of 50 Å to 2100 Å.
18 . The spatial light modulator of claim 17 , wherein the substrates are bonded together with an epoxy.
19 . The spatial light modulator of claim 18 , further comprising a lubricant within the gap for decreasing stiction of the mirrors.
20 . The spatial light modulator of claim 19 , further comprising a getter within the gap.
21 . The spatial light modulator of claim 18 , wherein the epoxy is a UV cure epoxy.
22 . The spatial light modulator of claim 20 , wherein the glass substrate is bonded in an offset relation to the silicon substrate.
23 . The spatial light modulator of claim 22 , wherein bond pads are exposed on the silicon substrate due to the offset bond.
24 . The spatial light modulator of claim 23 , wherein bond wires are connected to the bond pads on the silicon substrate.
25 . The spatial light modulator of claim 15 , wherein the RAM cell is a DRAM cell.
26 . The spatial light modulator of claim 24 , wherein the getter is disposed on the glass substrate.
27 . The spatial light modulator of claim 20 , wherein the getter is disposed on the silicon substrate.
28 . The spatial light modulator of claim 19 , wherein the lubricant is an organic lubricant.
29 . The spatial light modulator of claim 20 , wherein the getter is a moisture getter.
30 . The spatial light modulator of claim 20 , wherein the getter is a particle getter.
31 . The spatial light modulator of claim 20 , wherein the getter is a hydrogen getter.
32 . The spatial light modulator of claim 20 , wherein the getter is a metal oxide getter.
33 . The spatial light modulator of claim 20 , wherein the getter is a zeolite getter.
34 . The spatial ligbt modulator of claim 15 , further comprising a getter within the gap.
35 . The spatial light modulator of claim 20 , wherein the getter is a combination getter.
36 . The spatial light modulator of claim 28 , wherein the number of mirrors is from 6,000 to about 6 million.
37 . The spatial ligbt modulator of claim 64 , wherein the RAM cell is an SRAM cell.