Fluid viscosity control during wafer bonding
Techniques and mechanisms for bonding a first wafer to a second wafer in the presence of a fluid, the viscosity of which is greater than a viscosity of air at standard ambient temperature and pressure. In an embodiment, a first surface of the first wafer is brought into close proximity to a second surface of the second wafer. The fluid is provided between the first surface and the second surface when a first region of the first surface is made to contact a second region of the second surface to form a bond. The viscosity of the fluid mitigates a rate of propagation of the bond along a wafer surface, which in turn mitigates wafer deformation and/or stress between wafers. In another embodiment, the viscosity of the fluid is changed dynamically while the bond propagates between the first surface and the second surface.
1. A system for bonding wafers, the system comprising:
a first wafer holder;
a second wafer holder;
a wafer deformer comprising a heating element;
a chamber housing both the first wafer holder and the second wafer holder and having a fluid inlet port therein;
a valve fluidly coupled to the fluid inlet port; and
a controller controllably coupled to the valve, the wafer deformer, and the heating element, the controller to provide signals to the valve, the wafer deformer, and the heating element to perform a method comprising:
bringing a first surface of a first wafer to within a distance of a second surface of a second wafer, wherein the distance is in a range of 30 microns and 150 microns;
providing a fluid between the first surface and the second surface, wherein the fluid has a viscosity greater than a viscosity of air at standard ambient temperature and pressure;
heating the fluid with the heating element;
contacting a first region of the first surface to a second region of the second surface to form a bond therebetween; and
propagating the bond to bond the first surface to the second surface.
2. A system for bonding wafers, the system comprising:
a first wafer holder to hold a first wafer having a first surface;
a second wafer holder to hold a second wafer having a second surface, wherein the second surface is to be held at a distance from the first surface wherein the distance is to be in a range of 30 microns and 150 microns;
a wafer deformer to deform a portion of the first wafer to contact the second wafer;
a chamber housing both the first wafer holder and the second wafer holder and having a fluid inlet port therein;
a valve fluidly coupled to the fluid inlet port; and
a controller controllably coupled to the valve and the wafer deformer, the controller to provide a first signal to the valve to supply a fluid between the first surface and the second surface, wherein the fluid has a viscosity greater than a viscosity of air at standard ambient temperature and pressure, and to provide a second signal to the wafer deformer to deform the first wafer;
wherein the wafer deformer comprises a first heating element, wherein the controller is controllably coupled to the first heating element, and the controller is to provide a third signal to the first heating element to heat the fluid.
3. The system of claim 2 , further comprising a second heating element, wherein the controller is controllably coupled to the second heating element and the controller is to provide a fourth signal to the second heating element to heat the fluid.
4. The system of claim 2 , wherein the wafer holder further comprises a second heating element, wherein the controller is controllably coupled to the second heating element and the controller is to provide a fourth signal to the second heating element to heat the fluid.
5. The system of claim 2 , wherein the fluid comprises air at not less than 2 atmospheres (atm).
6. The system of claim 2 , wherein the fluid comprises argon, neon, or xenon at not less than standard ambient temperature (25° C.) and not less than standard ambient pressure (1 atm).
7. The system of claim 2 , wherein the controller is to send a fourth signal to the valve to increase pressure of the fluid during bonding of the first and second wafers.
8. The system of claim 2 , wherein the fluid is at a temperature of not less than 100° C.
9. The system of claim 2 , further comprising a dispense arm and pump to provide a liquid between the first surface and the second surface such that the liquid is on the first surface and only between a first portion of the first surface around a center of the first wafer and a second portion of the second surface around a center of the second wafer and comprising the second region.