Patent ID: 8821743

Claim:
A manufacturing method of a grating, the method comprising: providing a substrate and a plurality of etching gas comprising carbon tetrafluoride (CF 4 ), sulfur hexafluoride (SF 6 ) and argon (Ar 2 ); forming a patterned mask layer on a surface of the substrate; placing the substrate with the patterned mask layer in a microwave plasma system; guiding the plurality of etching gas into the microwave plasma system to etch the substrate so that a plurality of cavities having wall about perpendicular to the surface of the substrate are formed on the substrate, comprising three stages: in a first etching stage, the CF 4 and Ar 2 etching gases are guided into the microwave plasma system simultaneously, wherein the flow volume of CF 4 and Ar 2 is in the range of 40 sccm to 120 sccm, the flow volume of CF 4 is in the range of 10 sccm to 100 sccm, and the flow volume of Ar 2 is in the range of 1 sccm to 30 sccm; in a second etching stage, the CF 4 , Ar 2 , and SF 6 etching gases are guided into the microwave plasma system simultaneously, wherein the flow volume of CF 4 , Ar 2 , and SF 6 is in the range of 40 sccm to 120 sccm, and the flow volume of SF 6 is greater than the flow volume of CF 4 ; in a third etching stage, the CF4, Ar2, and SF6 etching gases are guided into the microwave plasma system, wherein the flow volume of CF 4 is greater than the flow volume of SF 6 , the flow volume of CF 4 is in the range of 20 sccm to 80 sccm, the flow volume of SF 6 is in the range of 5 sccm to 50 sccm, and the flow volume of Ar 2 is in the range of 5 sccm to 40 sccm; and removing the patterned mask layer.