Manufacturing method for stress compensated X-Y gimbaled MEMS mirror array
View Patent ↗A wafer-level manufacturing method produces stress compensated x-y gimbaled comb-driven MEMS mirror arrays using two SOI wafers and a single carrier wafer. MEMS structures such as comb drives, springs, and optical surfaces are formed by processing front substrate layer surfaces of the SOI wafers, bonding together the processed surfaces, and removing the unprocessed SOI layers to expose second surfaces of the front substrate layers for further wafer-level processing. The bonded SOI wafers are mounted to a surface of the carrier wafer that has been separately processed. Processing wafer surfaces may include formation of a stress compensation layer to counteract physical effects of MEMS mirrors to be formed in a subsequent step. The method may form multi-layered conductive spring structures for the mirrors, each spring having a first conducting layer for energizing a comb drive, a second conducting layer imparting a restoring force, and an insulating layer between the first and second conducting layers.
1. A method of manufacturing a MEMS structure from SOI wafers, each SOI wafer having front and back substrate layers separated by an insulation layer, the method comprising the following steps:
(a) processing a first surface of the front substrate layer of a first SOI wafer;
(b) processing a first surface of the front substrate layer of a second SOI wafer;
(c) bonding the processed first surface of the front substrate layer of the first SOI wafer to the processed first surface of the front substrate layer of the second SOI wafer;
(d) removing the back substrate layer and the insulation layer from the second SOI wafer to expose a second surface of the front substrate layer of the second SOI wafer;
(e) processing the exposed second surface of the front substrate layer of the second SOI wafer;
(f) processing a first surface of a carrier wafer;
(g) bonding the processed second surface of the front substrate layer of the second SOI wafer to the processed first surface of the carrier wafer;
(h) removing the back substrate layer and the insulation layer from the first SOI wafer to expose a second surface of the front substrate layer of the first SOI wafer; and
(i) processing the exposed second surface of the front substrate layer of the first SOI wafer.
2. The method of claim 1 wherein step (a) further comprises depositing a layer of insulation and patterning on the first surface of the front substrate layer of the first SOI wafer.
3. The method of claim 2 wherein step (a) further comprises depositing a conductive layer on the deposited layer of insulation.
4. The method of claim 3 wherein step (a) further comprises depositing one or more bonding pads on the deposited conductive layer.
5. The method of claim 1 wherein step (a) further comprises depositing a stress compensation layer on the first surface of the front substrate layer of the first SOI wafer.
6. The method of claim 1 wherein step (b) further comprises depositing a conductive layer and patterning on the first surface of the front substrate layer of the second SOI wafer.
7. The method of claim 6 wherein step (b) further comprises depositing one or more bonding pads on the deposited conductive layer.
8. The method of claim 7 wherein step (b) further comprises etching the first surface of the front substrate layer of a second SOI wafer.
9. The method of claim 1 wherein step (b) further comprises depositing a conductive layer and patterning on the second surface of the front substrate layer of the second SOI wafer.
10. The method of claim 9 wherein step (e) further comprises etching the second surface of the front substrate layer of the second SOI wafer.
11. The method of claim 1 wherein step (f) further comprises depositing an insulation layer and patterning on the first surface of the carrier wafer.
12. The method of claim 1 wherein step (f) further comprises depositing a conductive layer and patterning on the first surface of the carrier wafer.
13. The method of claim 11 wherein step (f) further comprises etching the first surface of the carrier wafer.
14. The method of claim 1 wherein step (i) further comprises etching the second surface of the front substrate layer of the first SOI wafer to multiple depths.