Method of forming a germanium film on a semiconductor substrate that includes the formation of a graded silicon-germanium buffer layer prior to the formation of a germanium layer

A method of forming a semiconductor device comprising:

• placing a substrate in a deposition chamber operated at a first deposition temperature;
• introducing a silicon source gas at a first flow rate into said deposition chamber;
• for a first predetermined amount of time, simultaneously decreasing said first flow rate to a second flow rate and decreasing said first deposition temperature to a second deposition temperature while increasing the flow rate for a germanium source gas into said deposition chamber until said germanium source gas reaches a third flow rated, wherein said silicon source gas is decreased and said germanium source gas is increased at different rates;
• introducing a dopant source gas into said deposition chamber when said germanium source gas is introduced into said deposition chamber;
• and
• for a second predetermined amount of time, introducing an etchant source gas into said deposition chamber wherein when said germanium source gas and said dopant source gas are present in said deposition chamber, said etchant source gas flow is shut off and wherein when said etchant source gas is present in said deposition chamber, said germanium source gas and said dopant source gas flows are shut off.

A method of forming a graded germanium film having a silicon-germanium buffer layer and a germanium layer on a semiconductor substrate:

• obtaining a deposition temperature and a deposition pressure in a deposition chamber used for said forming of said graded germanium film;
• placing said semiconductor substrate in said deposition chamber;
• introducing a silicon source gas flow into said deposition chamber;
• while ramping down said deposition temperature, simultaneously decreasing said silicon source gas flow and increasing a germanium source gas flow for a first predetermined amount of time, wherein said silicon source gas is decreased and said germanium source gas is increased at different rates;
• and
• maintaining said germanium source gas flow for a second predetermined amount of time.

A method of selectively forming a graded germanium film having a silicon-germanium buffer layer and a germanium layer on a semiconductor substrate comprising:

• obtaining a deposition temperature and a deposition pressure in a deposition chamber used for said forming of said graded germanium film;
• placing said semiconductor substrate in said deposition chamber, said semiconductor substrate comprising a dielectric mask;
• introducing a silicon source gas flow into said deposition chamber;
• while ramping down said deposition temperature, simultaneously decreasing said silicon source gas flow and increasing a germanium source gas flow for a first predetermined amount of time, wherein said silicon source gas is decreased and said germanium source gas is increased at different rates;
• and
• maintaining said germanium source gas flow for a second predetermined amount of time.