Patent Number: 
Section: claims

1. A method comprising:placing a GaAs die having a thickness of less than approximately 50 microns on a lead frame having a die attach surface comprising a soft solder; andheating the soft solder to attach the die to the lead frame. 2. The method as in claim 1, further including encapsulating the GaAs die in a plastic die package. 3. The method as in claim 1, wherein the GaAs die comprises:said GaAs substrate having an active surface and a backside surface;a diffusion barrier layer overlying the backside surface; anda copper back-metal layer overlying the diffusion barrier. 4. The method as in claim 3, wherein the GaAs substrate has a thickness of between approximately 15 microns and 50 microns. 5. The method as in claim 3, wherein the GaAs substrate has a thickness in the range of approximately 15–35 microns. 6. The method as in claim 3, wherein the GaAs substrate has a thickness of less than approximately 25 microns. 7. The method as in claim 3, wherein the copper back-metal layer has a thickness sufficient to provide mechanical support for the GaAs substrate during a soft-solder die attach process. 8. The method as in claim 3, wherein after the soft solder is heated, gold is intermingled with the soft solder. 9. A method comprising:forming a diffusion barrier layer overlying a backside surface of a GaAs substrate;forming a stress relief layer overlying the diffusion barrier layer;forming a copper back-metal layer overlying the stress relief layer; andforming an oxidation resistant layer overlying the copper-back metal layer. 10. The method as in claim 9, wherein the stress relief layer and the oxidation resistant layer comprise gold layers. 11. The method as in claim 9, further comprising coupling the oxidation resistant layer to a die attach surface of a lead frame. 12. The method as in claim 11, further comprising encapsulating the GaAs substrate, the stress relief layer, the copper back-metal layer and the oxidation resistant layer in a plastic die package. 13. The method as in claim 9, wherein coupling the oxidation resistant layer to a die attach surface comprises reflowing a soft solder layer overlying the die attach surface so as to form a solder joint between the die attach surface and at least the oxidation resistant layer. 14. The method as in claim 9, wherein the GaAs substrate has a thickness of between approximately 15 microns and 50 microns and the back-metal layer has thickness of between approximately 11 microns to 15 microns. 15. A method comprising:forming a semiconductor die comprising a GaAs substrate and a copper back-metal layer overlying a backside surface of the GaAs substrate;disposing the semiconductor die at a soft solder layer of a die attach surface of a lead frame;reflowing the soft-solder layer so as to form a solder joint between the die attach surface and the semiconductor die;electrically coupling the semiconductor die to one or more leads of the lead frame; andencapsulating the semiconductor die and the lead frame in a plastic die package. 16. The method as in claim 15, wherein forming the semiconductor die comprises forming a stress-relief layer overlying the backside surface of the GaAs substrate, wherein the stress relief layer is between the backside surface of the GaAs substrate and the back-metal layer. 17. The method as in claim 15, wherein forming the semiconductor die comprises forming an oxidization resistant layer overlying the back-metal layer. 18. The method as in claim 15, wherein forming the semiconductor die comprises forming a stress-relief layer overlying the backside surface of the GaAs substrate, wherein the stress-relief layer is between the backside surface and the back-metal layer. 19. The method as in claim 15, wherein reflowing the soft solder layer comprises providing sufficient heat to at least partially melt the copper back-metal layer. 20. The method as in claim 15, wherein the GaAs substrate has a thickness of between approximately 15 microns and 50 microns and the back-metal layer has thickness of between approximately 11 microns to 15 microns.