Eutectic bonding of ultrathin semiconductors
View Patent ↗Ultra-high speed semiconductors that are usually very thin and therefore very fragile still require connection to a circuit board and a heat transfer pathway. Ultra-high speed circuits and semiconductor devices are provided with a carrier plate formed on the backside of a wafer or substrate by a variety of deposition methods. The carrier plate is a series of metal layers, each being selected to enable the attachment of a relatively thick copper carrier plate to the backside of the substrate or wafer.
1. A method of forming a carrier on a semiconductor wafer having a plurality of separate semiconductor devices, a substantially planar back side and a thickness less than or equal to 10 mils, said method comprised of:
a) applying a first photoresist layer to the back side;
b) depositing a first contact layer on said back side that is comprised of:
an adhesive titanium layer, followed by an intermediate layer of platinum over the titanium layer, followed by a layer of gold over the platinum layer, the layers of titanium, platinum and gold being deposited onto the back side of the substrate;
c) removing the first photoresist layer to form one or more trench lines;
d) depositing an interconducting layer of aluminum grown on the gold layer of the first contact layer and within the one or more trench lines;
e) applying a second photoresist layer to the layer of aluminum over the one or more trench lines;
f) locally removing the aluminum layer from the gold layer between the second photoresist layer;
g) depositing a binding layer of nickel over the gold layer between the second photoresist layer;
h) depositing a carrier metal layer of copper on the nickel layer between the second photoresist layer;
i) depositing a solder layer on the copper layer between the second photoresist layer; and
j) removing the second photoresist layer.
2. The method of claim 1 wherein depositing is comprised of the steps of:
e-beam evaporating, thermal evaporating, sputtering, plating or screen printing.
3. The method of claim 1 wherein said adhesion layer is deposited to have a thickness that is less than or equal to 500 Angstroms.
4. The method of claim 1 wherein said intermediate layer is deposited to have a thickness that is less than or equal to 500 Angstroms.
5. The method of claim 1 wherein said interconducting layer is deposited to have a thickness that is less than or equal to 1000 Angstroms.
6. The method of claim 1 wherein the binding layer is deposited to have a thickness that is less than or equal to 10,000 Angstroms.
7. The method of claim 1 wherein the carrier metal layer is deposited to have a thickness that is less than or equal to 10 mils.
8. The method of claim 1 , wherein the step of applying the first photoresist layer to the back side comprises the step of:
applying the first photoresist layer to identify one or more saw kerf lines that separate one or more electronic devices of the semiconductor wafer;
the method further comprising the step of dicing said wafer along the one or more saw kerf lines into several separate substrates for the one or more electronic devices.