Method and apparatus for deposition of a iii-v semiconductor layer

Abstract

The invention relates to an apparatus for deposition of a III-V semiconductor layer comprising a process chamber ( 1 ), a susceptor ( 2 ) forming the base of the process chamber ( 1 ) for receiving one or more substrates to be coated, a heater ( 3 ) for heating the susceptor ( 2 ) to a process temperature and a gas inlet element ( 4 ) which comprises at least one first and one second process gas inlet zone ( 5, 6, 7 ), each for introducing process gases into the process chamber ( 1 ). It is proposed that the etching gas inlet ( 9 ) in the flow direction ( 23 ) of the hydride and the MO compound opens into the process chamber ( 1 ) downstream of the process gas inlet zones ( 5, 6, 7 ), wherein a control device ( 22 ) is adapted such that and the process gas inlet zones ( 5, 6, 7 ) and the etching gas inlet ( 9 ) are arranged such that the process gases emerging from the process gas inlet zones ( 5, 6, 7 ) cannot enter into the etching gas inlet ( 9 ) during deposition of the semiconductor layer and the etching gas emerging from the etching gas inlet ( 9 ) during purification of the process chamber cannot enter into the process gas inlet zones ( 5, 6, 7 ). The etching gas inlet ( 9 ) is formed by an annular zone of the process chamber cover around the gas inlet element ( 4 ) and by an annular fastening element ( 8 ) for fastening a cover plate ( 25 ).

1 . An apparatus for deposition of a III-V semiconductor layer comprising a process chamber ( 1 ), a susceptor ( 2 ) forming the base of the process chamber ( 1 ) for receiving one or more substrates to be coated, a heater ( 3 ) for heating the susceptor ( 2 ) to a process temperature and a gas inlet element ( 4 ) which comprises at least one first and one second process gas inlet zone ( 5 ,  6 ,  7 ), each for introducing process gases into the process chamber ( 1 ), wherein the first process gas inlet zone ( 5 ,  7 ) is connected to a hydride source ( 13 ) which provides a hydride of the main group V as process gas and the second process gas inlet zone ( 6 ) is connected to an MO source ( 12 ) which provides a metalorganic compound of the main group III as process gas, wherein an etching gas inlet ( 9 ) is connected to an etching gas source ( 11 ) and wherein valves ( 16 ,  19 ) which can be switched by a control device ( 22 ) and adjustable mass flow controllers ( 17 ,  18 ) are provided in order to introduce the hydride, the MO compound and the etching gas each together with respectively one carrier gas in a mass-flow-controlled manner through a pipeline system ( 21 ) into the process chamber ( 1 ), characterized in that the etching gas inlet ( 9 ) in the flow direction ( 23 ) of the hydride and the MO compound opens into the process chamber ( 1 ) downstream of the process gas inlet zones ( 5 ,  6 ,  7 ), wherein the control device ( 22 ) is adapted such that and the process gas inlet zones ( 5 ,  6 ,  7 ) and the etching gas inlet ( 9 ) are arranged such that the process gases emerging from the process gas inlet zones ( 5 ,  6 ,  7 ) cannot enter into the etching gas inlet ( 9 ) during deposition of the semiconductor layer and the etching gas emerging from the etching gas inlet ( 9 ) during purification of the process chamber cannot enter into the process gas inlet zones ( 5 ,  6 ,  7 ). 
     
     
         2 . The apparatus according to  claim 1 , characterized in that the process chamber ( 1 ) has a circular outline and the gas inlet element ( 4 ) is disposed in the centre of the process chamber ( 1 ) and the etching gas inlet ( 9 ) is formed by an annular zone of the process chamber cover around the gas inlet element ( 4 ). 
     
     
         3 . The apparatus according to  claim 2 , characterized in that the annular zone of the etching gas inlet ( 9 ) is formed by an annular fastening element ( 8 ) for fastening a cover plate ( 25 ). 
     
     
         4 . The apparatus according to  claim 1 , characterized in that the process gas inlet zones ( 5 ,  6 ,  7 ) are fed by gas supply lines which are formed [by] a gas supply element ( 36 ) disposed vertically above the gas inlet element ( 4 ), wherein the gas supply element ( 36 ) is surrounded by a casing body ( 28 ) which forms an etching gas supply line ( 29 ,  29 ′). 
     
     
         5 . The apparatus according to  claim 1 , characterized in that the etching gas supply line ( 29 ) opens into an annular channel ( 29 ′) surrounding the gas supply element ( 36 ) which is connected to a distribution chamber ( 31 ) by a multiplicity of gas passage openings ( 30 ) distributed vertically over the entire circumference of the annular channel ( 29 ′), wherein the openings ( 30 ) act as pressure barriers. 
     
     
         6 . The apparatus according to  claim 1 , characterized in that the distribution chamber ( 31 ) is an annular chamber which is in fluidic communication with the process chamber ( 1 ) with the gas passage openings ( 10 ) forming the etching gas inlet ( 9 ). 
     
     
         7 . The apparatus according to  claim 1 , characterized by a purge gas supply line ( 26 ) for supplying a purge gas into the distribution chamber ( 31 ). 
     
     
         8 . The apparatus according to  claim 1 , characterized by at least one pressure barrier in the etching gas supply line ( 29 ) which is in particular formed by a gas passage opening ( 30 ). 
     
     
         9 . The apparatus according to  claim 8 , characterized in that the pressure barrier ( 30 ) is disposed downstream of the gas distribution chamber ( 31 ). 
     
     
         10 . A method for depositing a III-V semiconductor layer onto one or more substrates to be coated, which are received by a susceptor ( 2 ) forming the base of a process chamber ( 1 ), which susceptor ( 2 ) is heated by a heater ( 3 ) to a process temperature, wherein for deposition of the semiconductor layer, process gases are introduced into the process chamber ( 1 ) in each case through first and a second process gas inlet zones ( 5 ,  6 ,  7 ) of a gas inlet element ( 4 ), wherein a hydride of the main group V is introduced through a first process gas inlet zone ( 5 ,  7 ) and a metalorganic compound of the main group III is introduced through the second process gas inlet zone ( 6 ) into the process chamber ( 1 ) and wherein for purification of the process chamber after deposition of the semiconductor layer an etching gas is introduced through an etching gas inlet ( 9 ) into the process chamber ( 1 ), wherein the mass flow of the process gases and the etching gas is controlled by mass flow controllers ( 17 ,  18 ) controlled by a control device ( 22 ), characterized in that the etching gas is fed into the process chamber ( 1 ) through an etching gas inlet ( 9 ) disposed in the flow direction ( 23 ) of the hydride and the MO compound opens into the process chamber ( 1 ) downstream of the process gas inlet zones ( 5 ,  6 ,  7 ), wherein during deposition of the semiconductor layer the mass flows of the gases flowing through the process gas inlet zones ( 5 ,  6 ,  7 ) into the process chamber ( 1 ) and of a purge gas flowing through the etching gas inlet ( 9 ) into the process chamber ( 1 ) are adjusted so that the process gases do not enter into the etching gas inlet ( 9 ) and that during purification of the process chamber ( 1 ) the mass flows of the etching gas flow introduced through the etching gas inlet ( 9 ) into the process chamber ( 1 ) and the purge gas flows fed through the process gas inlet zones ( 5 ,  6 ,  7 ) into the process chamber ( 1 ) are adjusted in such a manner that no etching gas enters into the gas supply lines disposed upstream of the process gas inlet zones ( 5 ,  6 ,  7 ). 
     
     
         11 . The method according to  claim 10 , characterized in that the process chamber ( 1 ) has a circular outline and the gas inlet element ( 4 ) is disposed in the centre of the process chamber ( 1 ) and the etching gas inlet ( 9 ) is formed by an annular zone of the process chamber cover around the gas inlet element ( 4 ). 
     
     
         12 . The method according to  claim 10 , characterized in that the process gas inlet zones ( 5 ,  6 ,  7 ) are supplied by gas supply lines which are formed [by] a gas supply element ( 36 ) disposed vertically above the gas inlet element ( 4 ), wherein the gas supply element ( 36 ) is surrounded by a casing body ( 28 ) which forms an etching gas supply line ( 29 ,  29 ′). 
     
     
         13 . The method according to  claim 10 , characterized in that the etching gas supply line ( 29 ) opens into an annular channel ( 29 ′) surrounding the gas supply element ( 36 ), which is connected to a distribution chamber ( 31 ) by a multiplicity of gas passage openings ( 30 ) distributed over the entire circumference of the annular channel ( 29 ′), wherein the openings ( 30 ) act as a pressure barrier. 
     
     
         14 . The method according to  claim 10 , characterized in that the etching gas is Cl 2  and the purge gas during the purification step is N 2 . 
     
     
         15 . The method according to  claim 10 , characterized in that the process gases comprise elements of the main group V and/or elements of the main group III and in particular are NH 3  and TMGa and the purge gas during layer deposition is H 2  or N 2 .