Method for removing a sacrificial layer on semiconductor wafers
One or more embodiments are directed to methods of removing a sacrificial layer from semiconductor wafers during wafer processing. In at least one embodiment, the sacrificial layer is removed from a wafer during an O 2 plasma etch step. In one embodiment, the sacrificial layer is poly(p-phenylene-2, 6-benzobisoxazole) (PBO) or polyimide. The O 2 plasma etch step causes a residue to form on the wafer. The residue is removed by immersing the wafer a solution that is a mixture of the tetramethylammonium hydroxide (TMAH) and water.
1. A method, comprising:
forming a layer of PBO or polyimide on a first side of a semiconductor wafer, the first side of the semiconductor wafer including a plurality of dice with active surfaces, each die of the plurality of dice including a plurality of conductive bond pads on the active surfaces;
processing a back side of the semiconductor wafer; and
removing the layer of PBO or polyimide, wherein removing includes:
etching the layer of PBO or polyimide in an O 2 plasma etch step, wherein the etching leaves residue on the plurality of conductive bond pads, wherein the residue consists of silicon, oxygen, or carbon or any combination thereof; and
immersing the wafer in a solution that includes TMAH and water, wherein the solution removes the residue on the plurality of conductive bond pads.
2. The method of claim 1 , wherein processing the back side of the semiconductor wafer includes etching through the wafer to form membranes.
3. The method of claim 1 , wherein the solution is 4%-6% TMAH and a remaining portion of the solution being H 2 O.
4. The method of claim 1 , wherein the wafer is immersed in the solution for about 30 seconds to 1 minute.
5. The method of claim 1 , wherein the solution is maintained at a temperature of about 75° C. while the wafer is immersed therein.
6. The method of claim 1 , further comprising rinsing the wafer in deionized water after immersing the wafer in the solution.
7. The method of claim 1 , further comprising dicing the wafer to form individual semiconductor dice.
8. A method, comprising:
forming a layer of PBO or polyimide on a first side of a semiconductor wafer, the first side of the semiconductor wafer including a plurality of dice with active surfaces;
processing a back side of the semiconductor wafer;
in an O 02 plasma etch step, removing the layer of PBO or polyimide and forming a residue on at least a portion of the first side of the wafer, wherein the residue consists of silicon, oxygen, or carbon or any combination thereof; and
immersing the wafer in a solution to remove the residue, the solution being a combination of TMAH and water.
9. The method of claim 8 , wherein the residue consists of silicon, oxygen, and carbon.
10. The method of claim 8 , wherein the wafer is immersed in the solution for about 30 seconds to 1 minute.
11. The method of claim 8 , wherein the solution is 4%-6% TMAH and a remaining portion of the solution is H 2 O.
12. The method of claim 8 , wherein the residue is formed on bond pads of the plurality of dice.
13. The method of claim 12 , wherein the bond pads include one or more layers that are made of a noble metal.
14. The method of claim 8 , wherein forming the layer of PBO or polyimide includes depositing the PBO or polyimide and curing the deposited PBO or polyimide.
15. A method, comprising:
forming a layer of PBO or polyimide on a first side of a semiconductor wafer, the first side of the semiconductor wafer including a plurality of dice with active surfaces and bond pads at the active surfaces;
processing a back side of the semiconductor wafer;
in an O 2 plasma etch step, removing the layer of PBO or polyimide, while removing the layer of PBO or polyimide a residue forms on the first side of the wafer, wherein the residue consists of silicon, oxygen, or carbon or any combination thereof; and
removing at least some of the residue by immersing the wafer in a solution that includes TMAH and water.
16. The method of claim 15 , wherein the solution is 4%-6% TMAH and a remaining portion of the solution is H 2 O.
17. The method of claim 15 , wherein the solution is maintained at a temperature of about 75° C. and the wafer is immersed in the solution between 30 seconds and 1 minute.
18. The method of claim 15 , wherein the residue consists of silicon, oxygen, and carbon.
19. The method of claim 15 , wherein the first side of the semiconductor wafer has a passivation layer.
20. The method of claim 19 , wherein the bond pads have an outer surface made of platinum or gold.