High temperature ion implantation of nitride based hemts

Abstract

A method is disclosed for forming a high electron mobility transistor. The method includes the steps of implanting a Group III nitride layer at a defined position with ions that when implanted produce an improved ohmic contact between the layer and contact metals, with the implantation being carried out at a temperature higher than room temperature and hot enough to reduce the amount of damage done to the Group III nitride layer, but below a temperature at which surface problems causing leakage at the gate or epitaxial layer dissociation would occur. An ohmic contact selected from the group consisting of titanium, aluminum, nickel and alloys thereof is added to the implanted defined position on the Group III nitride layer.

1 . A transistor precursor comprising:
 a layer of gallium nitride;   a layer of aluminum gallium nitride on said gallium nitride layer for generating a two dimensional electron gas at an interface between the layers when a current is applied in a HEMT orientation;   defined implanted regions in the aluminum gallium nitride and gallium nitride layers for improving ohmic characteristics of the layers when an ohmic metal is added to the defined implanted regions; and   said defined implanted regions of said transistor precursor having a temperature of between about 250° and 900° C.   
     
     
         2 . A transistor precursor according to  claim 1  wherein said growth substrate is selected from a group consisting of silicon carbide and sapphire. 
     
     
         3 . A transistor precursor according to  claim 1  further comprising a mask on said aluminum gallium nitride layer, said mask having to find openings that in turn define the implanted regions. 
     
     
         4 . A transistor precursor according to  claim 3  wherein said mask is selected from a group consisting of silicon dioxide, silicon nitride, and combinations of silicon dioxide and silicon nitride. 
     
     
         5 . A transistor precursor according to  claim 1  wherein said defined implanted regions have a temperature of between about 350° and 800° C. 
     
     
         6 . An apparatus formed by a process comprising:
 implanting a Group III nitride layer at a defined position with ions to provide an ion-implanted region, the implantation being carried out at a temperature between 250° C. and 900° C.; and   adding a contact over the ion-implanted region to thereby form an ohmic contact.   
     
     
         7 . An apparatus according to  claim 6  wherein the contact is formed of a metal selected from a group consisting of titanium, aluminum, nickel, and alloys thereof. 
     
     
         8 . An apparatus according to  claim 6  wherein the contact is formed of a material selected from a group consisting of titanium-tungsten-nitride, titanium-nitride, molybdenum, and molybdenum silicides. 
     
     
         9 . An apparatus according to  claim 6  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         10 . An apparatus according to  claim 6  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         11 . An apparatus according to  claim 6  wherein the implantation is carried out at a temperature of at least 800° C. 
     
     
         12 . An apparatus according to  claim 6  wherein the implantation is carried out with an ion beam current between about 30 μA and 130 μA. 
     
     
         13 . An apparatus according to  claim 6  wherein the implantation is carried out with an ion beam current of about 40 μA. 
     
     
         14 . An apparatus according to  claim 13  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         15 . An apparatus according to  claim 13  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         16 . An apparatus according to  claim 6  wherein the implantation is carried out with an ion beam current of about 120 μA. 
     
     
         17 . An apparatus according to  claim 16  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         18 . An apparatus according to  claim 16  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         19 . An apparatus according to  claim 6  wherein the contact is comprised of an alloy of titanium, aluminum, and nickel. 
     
     
         20 . An apparatus according to  claim 6  wherein implanting the Group III nitride layer at the defined position with ions to provide the ion-implanted region comprises implanting the Group III nitride layer at the defined position with ions through a protective layer placed on top of the Group III nitride layer to reduce the amount of damage to the Group III nitride layer. 
     
     
         21 . An apparatus according to  claim 20  wherein the protective layer is a silicon nitride protective layer. 
     
     
         22 . An apparatus according to  claim 6  wherein the process further comprises placing a mask layer on the Group III nitride layer before the step of implanting to prevent implantation at positions other than the defined position. 
     
     
         23 . An apparatus according to  claim 22  wherein the mask layer is an oxide mask layer. 
     
     
         24 . An apparatus according to  claim 6  wherein:
 the apparatus comprises a gallium nitride layer and the Group III nitride layer is an aluminum gallium nitride layer formed on the gallium nitride layer; 
 implanting the Group III nitride layer comprises implanting the aluminum gallium nitride layer at the defined position with ions to provide the ion-implanted region such that the ion-implanted region extends through the aluminum gallium nitride layer into the gallium nitride layer; and 
 adding the contact comprises adding the contact over the ion-implanted region to thereby form the ohmic contact to a 2-DEG formed at an interface of the gallium nitride layer and the aluminum gallium nitride layer. 
 
     
     
         25 . An apparatus formed by a process comprising:
 placing a protective layer on a Group III nitride layer;   implanting the Group III nitride layer through the protective layer at a defined position with ions to provide an ion-implanted region, the implantation being carried out with an ion beam current between about 30 μA and 130 μA; and   adding an ohmic contact over the ion-implanted region.   
     
     
         26 . An apparatus according to  claim 25  wherein the protective layer is a silicon nitride protective layer. 
     
     
         27 . An apparatus according to  claim 25  wherein the implantation of the Group III nitride layer with ions is carried out at a temperature of between about 250° C. and 900° C. 
     
     
         28 . An apparatus according to  claim 25  wherein the contact is comprised of an alloy of titanium, aluminum, and nickel. 
     
     
         29 . An apparatus according to  claim 25  wherein:
 the apparatus comprises a gallium nitride layer and the Group III nitride layer is an aluminum gallium nitride layer formed on the gallium nitride layer; 
 implanting the Group III nitride layer comprises implanting the aluminum gallium nitride layer at the defined position with ions to provide the ion-implanted region such that the ion-implanted region extends through the aluminum gallium nitride layer into the gallium nitride layer; and 
 adding the contact comprises adding the contact over the ion-implanted region to thereby form the ohmic contact to a 2-DEG formed at an interface of the gallium nitride layer and the aluminum gallium nitride layer. 
 
     
     
         30 . An apparatus comprising:
 a Group III nitride layer;   an ion-implanted region in the Group III nitride layer; and   adding a contact over the ion-implanted region to thereby form an ohmic contact;   wherein, after the ion-implanted region has been formed in the Group III nitride layer, at least 25 percent of all visible light having a wavelength in a range of and including 400 nanometers (nm) to 700 nm transmits through the Group III nitride layer.   
     
     
         31 . An apparatus according to  claim 30  wherein, after the ion-implanted region has been formed in the Group III nitride layer, at least 40 percent of all visible light having a wavelength in a range of and including 450 nm to 700 nm transmits through the Group III nitride layer. 
     
     
         32 . An apparatus according to  claim 30  wherein, after the ion-implanted region has been formed in the Group III nitride layer, at least 50 percent of all visible light having a wavelength in a range of and including 550 nm to 700 nm transmits through the Group III nitride layer. 
     
     
         33 . An apparatus according to  claim 30  wherein, after the ion-implanted region has been formed in the Group III nitride layer, at least 56 percent of all visible light having a wavelength in a range of and including 600 nm to 700 nm transmits through the Group III nitride layer. 
     
     
         34 . An apparatus according to  claim 30  wherein the ion-implanted region is formed by implanting the Group III nitride layer at a defined position with ions, the implantation being carried out at a temperature between 250° C. and 900° C. 
     
     
         35 . An apparatus according to  claim 30  wherein the contact is formed of a metal selected from a group consisting of titanium, aluminum, nickel, and alloys thereof. 
     
     
         36 . An apparatus according to  claim 30  wherein the contact is formed of a material selected from a group consisting of titanium-tungsten-nitride, titanium-nitride, molybdenum, and molybdenum silicides. 
     
     
         37 . An apparatus according to  claim 30  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         38 . An apparatus according to  claim 30  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         39 . An apparatus according to  claim 30  wherein the implantation is carried out at a temperature of at least 800° C. 
     
     
         40 . An apparatus according to  claim 30  wherein the implantation is carried out with an ion beam current between about 30 μA and 130 μA. 
     
     
         41 . An apparatus according to  claim 30  wherein the implantation is carried out with an ion beam current of about 40 μA. 
     
     
         42 . An apparatus according to  claim 41  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         43 . An apparatus according to  claim 41  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         44 . An apparatus according to  claim 30  wherein the implantation is carried out with an ion beam current of about 120 μA. 
     
     
         45 . An apparatus according to  claim 44  wherein the implantation is carried out at a temperature of at least 350° C. 
     
     
         46 . An apparatus according to  claim 44  wherein the implantation is carried out at a temperature of at least 650° C. 
     
     
         47 . An apparatus according to  claim 30  wherein the contact is comprised of an alloy of titanium, aluminum, and nickel. 
     
     
         48 . An apparatus according to  claim 30  wherein:
 the apparatus comprises a gallium nitride layer and the Group III nitride layer is an aluminum gallium nitride layer formed on the gallium nitride layer; 
 the ion-implanted region extends through the aluminum gallium nitride layer into the gallium nitride layer; and 
 the contact forms the ohmic contact to a 2-DEG formed at an interface of the gallium nitride layer and the aluminum gallium nitride layer.