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:

• introducing a silicon source gas at a first flow rate into a deposition chamber having a substrate whereon a graded germanium film is formed, said deposition chamber set at a first deposition temperature;
• 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 introducing a germanium source gas at an increasing flow rate into said deposition chamber, said germanium source gas is increased to a third flow rate;
• and
• for a second predetermined amount of time, introducing an etchant source gas into said deposition chamber while alternating flows of said etchant source gas and said germanium source gas with a flow of said dopant source gas wherein when said germanium source gas and said etchant source gas are present in said deposition chamber, said dopant source gas flow is shut off and wherein when said dopant source gas is present in said deposition chamber, said germanium source gas and said etchant 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;
• and
• maintaining said germanium source gas flow for a second predetermine 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;
• and
• maintaining said germanium source gas flow for a second predetermine amount of time.