Methods for elimination of arsenic based defects in semiconductor devices with isolation regions
View Patent ↗Methods of preparing conductive regions such as source/drain regions for silicidation procedures, has been developed. The methods feature removal of native oxide as well as removal of deposited arsenic based defects from conductive surfaces prior to deposition of a metal component of subsequently formed metal silicide regions. Arsenic ions implanted for N type source/drain regions are also implanted into insulator regions such as insulator filled shallow trench isolation regions. A hydrofluoric acid cycle used as a component of the pre-silicidation preparation procedure can release arsenic from the shallow trench isolation regions in the form of arsenic based defects, which in turn can re-deposit on the surface of source/drain region. Therefore pre-silicidation preparation treatments described in this invention feature removal of both native oxide and arsenic based defects from conductive surfaces prior to metal silicide formation. Methods include wet etch procedures featuring hydrofluoric acid and hydrogen peroxide, as well as spin dry and dry etch procedures both employed post hydrofluoric acid treatment to remove re-deposited arsenic based defects.
1. A method of forming metal silicide regions on a semiconductor substrate, comprising the steps of:
providing insulator filled, shallow trench isolation (STI) regions in top portions of said semiconductor substrate;
providing a gate insulator layer on a portion of said semiconductor substrate not occupied by said insulator filled STI regions, and providing a conductive gate structure comprised with insulator sidewall spacers, on said gate insulator layer;
performing an ion implantation of a dopant to form a source/drain region in a portion of said semiconductor not covered by said conductive gate structure;
performing a pre-metal silicide formation treatment further comprising:
plasma oxidizing the surface of the source/drain region to form an oxide thereon,
treating the oxide with a first agent to remove the oxide, the treating resulting in dopant based defects,
forming the dopant based defects into a solid compound or gas compound using a second agent wherein the first agent to the second agent has a ratio between about 1:1 to 1000:1, and
removing the solid or gas compound; and
forming said metal silicide regions on said source/drain region and on a top surface of said conductive gate structure.
2. The method of claim 1 , wherein:
performing the ion implantation forms an N type source/drain region: and
removing the solid compound includes:
forming the solid compound as a water soluble product; and
rinsing away the water soluble product.
3. The method of claim 1 , wherein removing the gas compound includes forming the gas compound as a volatile product using hydrogen.
4. The method of claim 1 , wherein removing the solid compound includes spin drying the semiconductor substrate in a non-oxidizing gas.
5. The method of claim 1 , wherein said ion implantation procedure is performed using arsenic ions, implanted at an energy between about 10 to 100 KeV, at a dose between about 1E 15 to 1E16 atoms/cm 2 .
6. The method of claim 1 , wherein said pre-metal silicide formation treatment is a wet treatment using a solution comprised with hydrogen peroxide as the second agent.
7. The method of claim 6 , wherein said wet treatment used for said pre-metal silicide formation treatment is a solution of hydrofluoric (HF) acid as the first agent and hydrogen peroxide as the second agent, with a ratio of HF to hydrogen peroxide between about 1:1 to 1000:1.
8. The method of claim 6 , wherein said wet treatment used for pre-metal silicide formation treatment is an initial dilute hydrofluoric (HF) acid cycle followed by a HF/hydrogen peroxide cycle, with a ratio of HF as the first agent to hydrogen peroxide as the second agent between about 1:1 to 1000:1.
9. The method of claim 6 , wherein said wet treatment used for pre-metal silicide formation treatment uses hydrogen peroxide as the second agent spiked into a de-ionized water rinse performed after hydrofluoric (HF) acid as the first agent, at a hydrogen peroxide:water ratio between about 1:50 to 1:1000.
10. The method of claim 1 , wherein said pre-metal silicide formation treatment is performed using an initial hydrofluoric (HF) acid only procedure with HF as the first agent, followed by a spin dry procedure, wherein the spin dry procedure can be performed in nitrogen using a single wafer or batch tool.
11. The method of claim 1 , wherein said pre-metal silicide formation treatment is performed using aqueous hydrofluoric (HF) acid as the first agent followed by a hydrogen dry etch treatment, wherein a dry etch ambient is comprised with a hydrogen/argon or hydrogen/nitrogen ratio between about 1:0 to 1:100, at a pressure between about 20 to 300 millitorr, at an rf power between about 150 to 2000 watts, and performed at a temperature between about 15 to 40° C.
12. The method of claim 1 , wherein said metal silicide regions are comprised of cobalt silicide or titanium silicide.