Abstract There is disclosed an aluminum-zinc alloy ohmic contact for semiconductor materials and methods for providing these ohmic contacts. This aluminum-zinc alloy contact has special application in P-type III-V compound semiconductor materials, and particular advantage in lightly doped P-type III-V compound semiconductors, to decrease the contact resistance, increase uniformity of the contact, improve wire bonding ease and quality, decrease electromigration, and decrease the substrate temperature for contact formation. In addition this alunimum-zinc alloy provides that formation of brittle gold-aluminum intermetallic compounds on the surface of the contact is retarded or eliminated when gold wire is used for wire bonding. The aluminum-zinc contact is also used to advantage on elemental semiconductor materials and with II-VI compound semiconductor materials for the purpose of decreasing electromigration. Most importantly, in the P-type III-V compound semiconductors, a contact made from the aluminum-zinc alloy self-dopes the region directly under the contact, forming a highly doped region below the contact. The highly doped region is formed by zinc atoms from the alloy. Formation of the highly doped region in this manner is thus accomplished without the necessity of separate dopings and/or photolithographic steps.
A METHOD FOR MAKING AN OHMIC CONTACT TO A REGION OF SEMICONDUCTOR COMPRISING THE STEPS OF: FORMING AN INSULATING LAYER ON A SURFACE OF A FIRST REGION OF SEMICONDUCTOR, SAID FIRST REGION OF SEMICONDUCTOR BEING OF A FIRST CONDUCTIVITY TYPE; FORMING AN OPENING IN SAID INSULATING LAYER, EXPOSING SAID SURFACE; FORMING A METAL LAYER ON SAID INSULATING LAYER AND ON SAID EXPOSED SURFACE, SAID METAL LAYER INCLUDING A FIRST METAL AND A SECOND METAL, SUCH THAT IMPURITY IONS OF SAID SECOND METAL ARE OF SAID FIRST CONDUCTIVITY TYPE AND THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE FIRST METAL BEING HIGHER THAN THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE SECOND METAL, DIFFUSING IONS OF SAID SECOND METAL THROUGH SAID EXPOSED SURFACE INTO SAID FIRST REGION OF SEMICONDUCTOR, BY HEATING TO A TEMPERATURE BELOW THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE FIRST METAL, THUS FORMING A RELATIVELY HEAVILY DOPED SECOND REGION OF SAID FIRST CONDUCTIVITY TYPE WITHIN SAID FIRST REGION AT SAID SURFACE AND WHEREIN SAID SECOND METAL DOES NOT FORM AN ALLOY WITH SAID SEMICONDUCTOR.
Claim 2
Independent Claim
174 words
A METHOD FOR MAKING AN OHMIC CONTACT TO A REGION OF SEMICONDUCTOR COMPRISING THE STEPS OF: FORMING AN INSULATING LAYER ON A SURFACE OF A FIRST REGION OF SEMICONDUCTOR, SAID FIRST REGION OF SEMICONDUCTOR BEING OF A FIRST CONDUCTIVITY TYPE; FORMING AN OPENING IN SAID INSULATING LAYER, EXPOSING SAID SURFACE; FORMING A METAL LAYER ON SAID INSULATING LAYER AND ON SAID EXPOSED SURFACE, SAID METAL LAYER INCLUDING A FIRST METAL AND A SECOND METAL, SUCH THAT IMPURITY IONS OF SAID SECOND METAL ARE OF SAID FIRST CONDUCTIVITY TYPE AND THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE FIRST METAL BEING HIGHER THAN THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE SECOND METAL, DIFFUSING IONS OF SAID SECOND METAL THROUGH SAID EXPOSED SURFACE INTO SAID FIRST REGION OF SEMICONDUCTOR, BY HEATING TO A TEMPERATURE BELOW THE ENTECTIC BETWEEN THE SEMICONDUCTOR AND THE FIRST METAL, THUS FORMING A RELATIVELY HEAVILY DOPED SECOND REGION OF SAID FIRST CONDUCTIVITY TYPE WITHIN SAID FIRST REGION AT SAID SURFACE AND WHEREIN SAID SECOND METAL DOES NOT FORM AN ALLOY WITH SAID SEMICONDUCTOR.
Claim 3
Dependent Claim
23 words
The method as recited in claim 1 wherein said metal layer Is a metal alloy of said first metal and said second metal.
Claim 4
Dependent Claim
21 words
The method as recited in claim 1 wherein said relatively heavily doped second region is sufficiently heavily doped to be degenerate.
Claim 5
Dependent Claim
19 words
The method as recited in claim 1 wherein said first region of semiconductor is a type III-V semiconductor compound.
Claim 6
Dependent Claim
16 words
The method as recited in claim 4 wherein said first region of semiconductor is gallium arsenide.
Claim 7
Dependent Claim
13 words
The method as recited in claim 2 wherein said second metal is zinc.
Claim 8
Dependent Claim
13 words
The method as recited in claim 5 wherein said first metal is aluminum.