Method and apparatus for applying thin liquid coatings
View Patent ↗Systems and methods for applying a thin layer of a liquid to the surface of a wafer with topography formed therein. The systems and methods include spreading a deposit of the liquid into a thin film on a wafer support, lowering the wafer onto the film, removing the wafer with an adhering layer of the film, positioning the wafer over a device wafer with the liquid film disposed between the wafers, curing the thin layer. The thin layer may be a UV adhesive which bonds the wafers upon exposure to UV light.
1. A method for forming a thin layer of liquid on the surface of a first wafer, wherein the first wafer surface has topography formed therein, comprising:
disposing a plurality of spacers on a wafer support surface;
depositing a quantity of the liquid between the spacers;
thinning the quantity of liquid by translating a bar over the spacers to form a liquid film on the support surface;
lowering the first wafer onto the liquid film; and
removing the first wafer from the wafer support.
2. The method of claim 1 , further comprising:
disposing the first wafer on a plurality of supports placed on a surface of a second wafer;
aligning the first wafer to the second wafer;
contacting a surface of the first wafer to the surface of the second wafer by removing the supports, with the thin layer of liquid disposed therebetween; and
curing the liquid film.
3. The method of claim 1 , wherein the liquid is at least one of a UV-curable adhesive, a lubricant and a photoresist.
4. The method of claim 2 , wherein curing the liquid film further comprises:
at least one of exposing the liquid film to a source of ultra-violet radiation, exposing the liquid film to a source of heat, and exposing the liquid film to a source of visible radiation.
5. The method of claim 1 , further comprising:
evacuating a chamber containing the first wafer and the liquid film; and releasing air bubbles from the liquid film into the chamber.
6. The method of claim 2 , wherein the plurality of supports is a plurality of
shims resting on the surface of the second wafer.
7. The method of claim 6 , further comprising:
removing the shims so that the first wafer is resting on the second wafer.
8. The method of claim 1 , further comprising:
forming at least one trough in the support surface, between the spacers, and extending across a substantial portion of the support surface and substantially parallel to the spacers.
9. The method of claim 1 , further comprising:
raising one edge of the first wafer from the wafer support, by raising an elevator pin housed in a through hole in the support, wherein an opposing edge of the first wafer is held against a wafer seat.
10. The method of claim 9 , wherein the wafer seat includes a feature that mates with a corresponding feature on the first wafer, in order to orient the first wafer in a pre-determined orientation with respect to the second wafer.