Method for producing polycrystalline silicon germanium and suitable for micromachining
The invention relates to methods for preparing as-deposited, low-stress and low resistivity polycrystalline silicon-germanium layers and semiconductor devices utilizing the silicon-germanium layers. These layers can be used in Micro Electro-Mechanical Systems (MEMS) devices or micro-machined structures.
1 . A method of producing a polycrystalline SiGe layer on a substrate, the method comprising:
a) depositing onto the substrate a first layer comprising a polycrystalline silicon-germanium, wherein the depositing comprises non-plasma chemical vapor deposition conducted at a first temperature less than or equal to about 520° C.; and
b) depositing onto the first layer a second layer comprising a polycrystalline silicon-germanium, wherein the depositing comprises plasma enhanced chemical vapor deposition or plasma assisted chemical vapor deposition at a second temperature less than or equal to about 520° C., whereby a polycrystalline SiGe layer comprising the first layer and the second layer is obtained.
2 . The method according to claim 1 , further comprising:
depositing a nucleation layer onto the substrate at a third temperature less than or equal to about 520° C., wherein the depositing is conducted before step a).
3 . The method according to claim 2 , wherein the nucleation layer comprises silicon or Si x Ge 1-x wherein 0.10≦x.
4 . The method according to claim 1 , wherein the first layer comprises Si y Ge 1-y wherein 0.10≦y≦1.
5 . The method according to claim 1 , wherein the first layer comprises Si y Ge 1-y wherein 0.50≦1-y≦0.70.
6 . The method according to claim 1 , wherein the second layer comprises Si z Ge 1-z wherein 0.10≦z≦1.
7 . The method according to claim 1 , wherein the second layer comprises Si z Ge 1-z wherein 0.50≦1-z≦0.70.
8 . The method according to claim 1 , wherein the first temperature, the second temperature, and the third temperature are each less than or equal to about 500° C.
9 . The method according to claim 1 , wherein the first temperature, the second temperature, and the third temperature are each less than or equal to about 450° C.
10 . The method according to claim 1 , wherein the first temperature equals the second temperature, and the second temperature equals the third temperature.
11 . The method according to claim 1 , wherein the first temperature equals the second temperature, the second temperature equals the third temperature, and the third temperature equals about 450° C.
12 . The method according to claim 11 , wherein the second layer comprises Si z Ge 1-z wherein 0.50≦1-z≦0.70.
13 . The method according to claim 11 , wherein the second layer comprises Si z Ge 1-z wherein 0.60≦1-z≦0.70.
14 . The method according to claim 1 , wherein step a) and step b) are performed at a pressure of from about 1 to about 10 Torr.
15 . The method according to claim 1 , wherein a plasma power is from about 10 to about 100 W.
16 . The method according to claim 1 , wherein a plasma power density is from about 20 to about 200 mW/cm 2 .
17 . The method of claim 1 , wherein the polycrystalline SiGe layer has an electrical resistance of less than about 10 mΩcm.
18 . The method of claim 1 , wherein the polycrystalline SiGe layer has a compressive stress of less than about 20 MPa and a tensile stress of less than about 100 MPa.
19 . A method of producing a polycrystalline SiGe layer on a substrate, the method comprising:
a) depositing onto the substrate a first layer comprising a polycrystalline silicon-germanium by a non-plasma chemical vapor deposition technique at a temperature of less than or equal to 520° C. and at a rate of less than about 10 nm/min; and
b) depositing onto the first layer a second layer comprising a polycrystalline silicon-germanium by a plasma enhanced chemical vapor deposition technique at a temperature of less than or equal to 520° C. and at a rate of about 50 nm/min or more, whereby a polycrystalline SiGe layer comprising the first layer and the second layer is obtained.
20 . The method of claim 19 , wherein step b) is conducted at a rate of about 100 nm/min or more.