Polysilicon over-etch using hydrogen diluted plasma for three-dimensional gate etch
Methods of polysilicon over-etch using hydrogen diluted plasma for three-dimensional gate etch are described. In an example, a method of forming a three-dimensional gate structure includes performing a main plasma etch on a masked polysilicon layer formed over a semiconductor fin. The method also includes, subsequently, performing a plasma over etch on the masked polysilicon layer based on a plasma generated from gaseous composition including hydrogen gas (H 2 ).
1. A method of forming a three-dimensional gate structure, the method comprising:
performing a main plasma etch on a masked polysilicon layer formed over a semiconductor fin, wherein the main plasma etch is performed at a pressure of approximately 6 mTorr, a source power of approximately 600 W, a bias power of approximately 40 W, and with a chemistry based on SF 6 (approximately 35 sccm), N 2 (approximately 90 sccm), CH 2 F 2 (approximately 68 sccm), and He (approximately 200 sccm), at a temperature of approximately 60 degrees Celsius; and, subsequently,
performing a plasma over etch on the masked polysilicon layer based on a plasma generated from gaseous composition including hydrogen gas (H 2 ).
2. The method of claim 1 , wherein the plasma over etch is performed at a pressure approximately in the range of 40-100 mTorr, a source power approximately in the range of 300-1000 W, a bias power approximately in the range of 80-250 W, and with a chemistry based on O 2 (approximately 3-15 sccm), HBr (approximately 100-500 sccm), and H 2 (approximately in the range between 0-500 sccm), at a temperature approximately in the range of 20-80 degrees Celsius.
3. The method of claim 2 , wherein the plasma over etch is performed at a pressure of approximately 70 mTorr, a source power of approximately 450 W, a bias power of approximately 180 W, and with a chemistry based on O 2 (approximately 9 sccm), HBr (approximately 300 sccm), and H 2 (approximately 300 sccm), at a temperature of approximately 45 degrees Celsius.
4. A method of etching a sample in an etch chamber, the method comprising:
introducing a substrate into an etch chamber, the substrate comprising a hardmask layer disposed on a polysilicon layer disposed over a plurality of semiconductor fins;
in a first operation in the etch chamber, etching the hardmask layer to provide a patterned hardmask layer disposed on the polysilicon layer; and
in a second operation in the etch chamber, performing a main plasma etch on a polysilicon layer having the patterned hardmask thereon, wherein the main plasma etch is performed at a pressure of approximately 6 mTorr, a source power of approximately 600 W, a bias power of approximately 40 W, and with a chemistry based on SF 6 (approximately 35 sccm), N 2 (approximately 90 sccm), CH 7 F 2 (approximately 68 sccm), and He (approximately 200 sccm), at a temperature of approximately 60 degrees Celsius; and
in a third operation in the etch chamber, performing a plasma over etch on the polysilicon layer having the patterned hardmask thereon to form a three-dimensional gate structure, the plasma over etch based on a plasma generated from gaseous composition including hydrogen gas (H 2 ).
5. The method of claim 4 , wherein the hardmask layer comprises a material selected from the group consisting of silicon dioxide, silicon nitride and silicon oxy-nitride.
6. The method of claim 4 , further comprising:
subsequent to the first operation and prior to the first operation, performing an ashing and cleaning operation.
7. The method of claim 4 , wherein the plasma over etch is performed at a pressure approximately in the range of 40-100 mTorr, a source power approximately in the range of 300-1000 W, a bias power approximately in the range of 80-250 W, and with a chemistry based on O 2 (approximately 3-15 sccm), HBr (approximately 100-500 sccm), and H 2 (approximately in the range between 0-500 sccm), at a temperature approximately in the range of 20-80 degrees Celsius.
8. The method of claim 7 , wherein the plasma over etch is performed at a pressure of approximately 70 mTorr, a source power of approximately 450 W, a bias power of approximately 180 W, and with a chemistry based on O 2 (approximately 9 sccm), HBr (approximately 300 sccm), and H 2 (approximately 300 sccm), at a temperature of approximately 45 degrees Celsius.
9. A method of forming a three-dimensional gate structure, the method comprising:
performing a main plasma etch on a masked polysilicon layer formed over a semiconductor fin; and, subsequently,
performing a plasma over etch on the masked polysilicon layer based on a plasma generated from gaseous composition including hydrogen gas (H 2 ), wherein the plasma over etch is performed at a pressure of approximately 70 mTorr, a source power of approximately 450 W, a bias power of approximately 180 W, and with a chemistry based on O 2 (approximately 9 sccm), HBr (approximately 300 sccm), and H 2 (approximately 300 sccm), at a temperature of approximately 45 degrees Celsius.
10. The method of claim 9 , wherein the main plasma etch is performed at a pressure approximately in the range of 4-10 mTorr, a source power approximately in the range of 300-1000 W, a bias power approximately in the range of 0-100 W, and with a chemistry based on SF 6 (approximately 10-70 sccm), N 2 (approximately 50-200 sccm), CH 2 F 2 (approximately 25-75 sccm), and He (approximately 0-500 sccm), at a temperature approximately in the range of 20-80 degrees Celsius.
11. A method of etching a sample in an etch chamber, the method comprising:
introducing a substrate into an etch chamber, the substrate comprising a hardmask layer disposed on a polysilicon layer disposed over a plurality of semiconductor fins;
in a first operation in the etch chamber, etching the hardmask layer to provide a patterned hardmask layer disposed on the polysilicon layer; and
in a second operation in the etch chamber, performing a main plasma etch on a polysilicon layer having the patterned hardmask thereon; and
in a third operation in the etch chamber, performing a plasma over etch on the polysilicon layer having the patterned hardmask thereon to form a three-dimensional gate structure, the plasma over etch based on a plasma generated from gaseous composition including hydrogen gas (H 2 ), wherein the plasma over etch is performed at a pressure of approximately 70 mTorr, a source power of approximately 450 W, a bias power of approximately 180 W, and with a chemistry based on O 2 (approximately 9 sccm), HBr (approximately 300 sccm), and H 2 (approximately 300 sccm), at a temperature of approximately 45 degrees Celsius.
12. The method of claim 11 , wherein the hardmask layer comprises a material selected from the group consisting of silicon dioxide, silicon nitride and silicon oxy-nitride.
13. The method of claim 11 , further comprising:
subsequent to the first operation and prior to the first operation, performing an ashing and cleaning operation.
14. The method of claim 11 , wherein the main plasma etch is performed at a pressure approximately in the range of 4-10 mTorr, a source power approximately in the range of 300-1000 W, a bias power approximately in the range of 0-100 W, and with a chemistry based on SF 6 (approximately 10-70 sccm), N 2 (approximately 50-200 sccm), CH 2 F 2 (approximately 25-75 sccm), and He (approximately 0-500 sccm), at a temperature approximately in the range of 20-80 degrees Celsius.