Microchannels for BioMEMS devices
View Patent ↗A method is disclosed for making a MEMS device wherein anhydrous HF exposed silicon nitride is used as a temporary adhesion layer allowing the transfer of a layer from a Carrier Wafer to a Device Wafer.
1. A method of making a MEMS device, comprising:
depositing a silicon nitride layer on a carrier wafer;
chemically modifying said silicon nitride layer by exposure to anhydrous hydrofluoric acid to form a modified surface layer subject to thermal decomposition into gaseous by-products;
forming a patterned first photopolymer layer on said modified surface layer;
forming a patterned second photopolymer layer on a device wafer;
bonding the patterned first and second photopolymer layers of the carrier wafer and the device wafer together to form an integrated device by applying heat and pressure; and
applying heat to decompose said modified surface layer and thereby separate the carrier wafer from the device wafer.
2. A method as claimed in claim 1 , wherein said carrier wafer and device wafer are silicon wafers.
3. A method as claimed in claim 1 , wherein the silicon nitride layer is deposited by low pressure chemical vapor deposition at a temperature in a range from 750 to 900° C.
4. A method as claimed in claim 1 , wherein said patterned first and second photopolymer layers comprise a negative tone photopolymer.
5. A method as claimed in claim 1 , wherein said carrier and device wafers when bonded together form microchannels.
6. A method as claimed in claim 5 , wherein the patterned first photopolymer layer on the carrier wafer forms a lid portion of said microchannels and said patterned second photopolymer layer on the device wafer forms a base of said microchannels.
7. A method as claimed in claim 1 , wherein after separation of said carrier wafer and said device wafer, said bonded patterned first and second photopolymer layers are subjected to hardening treatment.
8. A method of forming a MEMS device containing microchannels, comprising:
depositing a silicon nitride layer on a carrier wafer;
modifying a surface portion of said silicon nitride layer by exposure to anhydrous hydrofluoric acid to form a modified surface layer;
forming a patterned first photopolymer layer on said modified surface layer;
forming a patterned second photopolymer layer on a device wafer;
bonding said patterned first and second photopolymer layers together to form an integrated device containing the microchannels; and
releasing said carrier wafer by heating said structures to decompose said modified surface layer.
9. A method as claimed in claim 8 , wherein said patterned first photopolymer layer provides a lid portion of said microchannels, and said patterned second photopolymer layer provides a base portion of said microchannels.
10. A method as claimed in claim 8 , wherein said patterned first and second photopolymer layers are stabilized by baking at a temperature not exceeding 95° C. prior to bonding said patterned first and second photopolymer layers together.
11. A method as claimed in claim 8 , wherein after bonding said patterned first and second photopolymer layers are subjected to hardening treatment.
12. A method as claimed in claim 8 , wherein said patterned first and second photopolymer layers are bonded together by applying heat and pressure to said carrier and device wafers.
13. A method as claimed in claim 8 , wherein the silicon nitride layer has a thickness lying in the range of 0.05 μm to 1.0 μm.
14. A method as claimed in claim 8 , wherein the patterned second photopolymer layer deposited on the device wafer is deposited in separate steps as two photopolymer sublayers.
15. A method as claimed in claim 8 , wherein the exposure to anhydrous hydrofluoric acid is carried out in the presence of an organic volatile component.
16. A method as claimed in claim 8 , wherein said carrier and device wafers are silicon wafers.