Method of cleaning and micro-etching semiconductor wafers
A method of simultaneously cleaning inorganic and organic contaminants from semiconductor wafers and micro-etching the semiconductor wafers. After the semiconductor wafers are cut or sliced from ingots, they are contaminated with cutting fluid as well as metal and metal oxides from the saws used in the cutting process. Aqueous alkaline cleaning and micro-etching solutions containing alkaline compounds and mid-range alkoxylates are used to simultaneously clean and micro-etch the semiconductor wafers.
1. A method comprising:
a) providing a semiconductor ingot;
b) cutting the semiconductor ingot to form one or more semiconductor wafers comprising inorganic contaminants and organic contaminants; and
c) applying an aqueous alkaline solution consisting essentially of one or more quaternary ammonium hydroxides and one or more alkali metal hydroxides at a weight ratio of 2:1 to 1:2, one or more chelating agents, one or more alkoxylated glycols, mono-methyl ether or mono-methyl ether acetate derivatives thereof and having a weight average molecular weight of 170 g/mole or greater and a flash point of 75° C. or greater and one or more mid-range alkoxylates in sufficient amounts to remove the contaminants and micro-etch the semiconductor wafers.
2. The method of claim 1 , wherein the one or more mid-range alkoxylates are chosen from compounds having a formula:
R 1 —O—[(CH 2 CH(R 2 )—O) x (CH 2 CH 2 O) y ] z —H (I)
wherein x is independently at each occurrence, 0 or a real number from 1 to 11, provided that, in at least one occurrence, x is greater than 0; y is, independently at each occurrence, 0, or a real number from 1 to 20, provided that, in at least one occurrence, y is greater than 0; z is a whole number from 1 to 50; R 1 is a C 6-10 branched or linear alcohol; and R 2 is, independently at each occurrence, —CH 3 or —CH 2 CH 3 .
3. The method of claim 1 , wherein the one or more mid-range alkoxylates are chosen from compounds having a formula:
R 1 —O—(CH 2 CH(R 2 )—O) x (CH 2 CH 2 O) y —H (II)
wherein x is a real number from 1 to 11; y is a real number from 1 to 20; R 1 is C 6-10 branched or linear alcohol; and R 2 is —CH 3 or —CH 2 CH 3 .
4. The method of claim 1 , wherein the weight ratio of the one or more quaternary ammonium hydroxides to the one or more alkali metal hydroxides is 1:1.
5. The method of claim 1 , wherein a pH of the aqueous alkaline solution is 11 and greater.
6. The method of claim 1 , wherein the contaminants comprise metals, metal oxides and organic compounds.
7. The method of claim 1 , wherein the semiconductor wafers are micro-etched to an irregular surface roughness of 0.025 μm to 2 μm peak-to-valley height.