Evaluation of wafer carcass alpha particle emission

Patent metadata

Field	Value
Publication number	US-11927616-B2
Application number	US-202117217341-A
Country	US
Kind code	B2
Filing date	Mar 30, 2021
Priority date	Mar 30, 2021
Publication date	Mar 12, 2024
Grant date	Mar 12, 2024

Abstract

A method for measuring alpha particle emissions may include obtaining a wafer emission rate, wherein the wafer emission rate is measured with a counter. The method may further include covering the wafer with a metal mesh grounded to a cathode of the counter wherein the metal mesh is grounded to the cathode outboard of the wafer and obtaining a mesh and wafer emission rate, wherein the mesh and wafer emission rate is measured with the counter. The method may further include replacing the wafer with a wafer carcass, obtaining a wafer carcass and mesh emission rate, and calculating a wafer carcass emissivity.

First claim

What is claimed is:

1. A method for measuring alpha particle emissions, said method comprising:
obtaining a wafer emission rate, wherein said wafer emission rate is measured with a counter;
covering said wafer with a metal mesh grounded to a cathode of said counter wherein said metal mesh is grounded to said cathode outboard of said wafer;
obtaining a mesh and wafer emission rate, wherein said mesh and wafer emission rate is measured with said counter;
replacing said wafer with a wafer carcass;
obtaining a wafer carcass and mesh emission rate, wherein said wafer carcass and mesh emission rate is measured with said counter;
calculating a wafer carcass emission rate based on said wafer emission rate, said mesh and wafer emission rate, and said wafer carcass and mesh emission rate; and
computing a controlled collapse chip connection emission rate.

2. The method of claim 1 further comprising:
identifying a controlled collapse chip connection effective surface area of said wafer carcass,
wherein said controlled collapse chip connection emission rate is normalized to said controlled collapse chip connection effective surface area and a transmission of the mesh.

3. The method of claim 1 wherein calculating said wafer carcass emission rate comprises:
subtracting said wafer emission rate from said mesh and wafer emission rate to obtain a mesh emission rate; and
subtracting said mesh emission rate from said wafer carcass and mesh emission rate to obtain said wafer carcass emission rate.

4. The method of claim 1 further comprising:
normalizing said wafer carcass emission rate to a surface area of said wafer carcass and a measurement time of said wafer carcass emission rate.

5. The method of claim 1 wherein said wherein said wafer emission rate is measured for between fifty hours and three hundred hours.

6. The method of claim 1 wherein said metal mesh is grounded to said cathode with an electrical conductor.

7. The method of claim 6 wherein said electrical conductor is copper tape.

8. The method of claim 6 wherein:
said metal mesh is substantially square with a length equal to or greater than a radius of said wafer carcass;
said metal mesh has corners outboard of said wafer; and
said electrical conductor grounds said metal mesh to said cathode at one or more of said corners.

9. The method of claim 1 wherein said metal mesh has a transmissivity of at least 80%.

10. A system for measuring alpha particle emissions, said system comprising:
a memory; and
a processor in communication with said memory and an implementation device, said processor being configured to perform operations with said implementation device, said operations comprising:
obtaining a wafer emission rate, wherein said wafer emission rate is measured with a counter;
covering said wafer with a metal mesh grounded to a cathode of said counter wherein said metal mesh is grounded to said cathode outboard of said wafer;
obtaining a mesh and wafer emission rate, wherein said mesh and wafer emission rate is measured with said counter;
replacing said wafer with a wafer carcass;
obtaining a wafer carcass and mesh emission rate, wherein said wafer carcass and mesh emission rate is measured with said counter;
calculating a wafer carcass emission rate based on said wafer emission rate, said mesh and wafer emission rate, and said wafer carcass and mesh emission rate; and
computing a controlled collapse chip connection emission rate.

11. The system of claim 10 , said operations further comprising:
identifying a controlled collapse chip connection effective surface area of said wafer carcass,
wherein said controlled collapse chip connection emission rate is normalized to said controlled collapse chip connection effective surface area and a transmission of said metal mesh.

12. The system of claim 10 wherein calculating said wafer carcass emission rate comprises:
subtracting said wafer emission rate from said mesh and wafer emission rate to obtain a mesh emission rate; and
subtracting said mesh emission rate from said wafer carcass and mesh emission rate to obtain said wafer carcass emission rate.

13. The system of claim 10 , said operations further comprising:
normalizing said wafer carcass emission rate to a surface area of said wafer carcass and a transmission of said metal mesh.

14. The system of claim 10 wherein said wafer emission rate is measured for between fifty hours and three hundred hours.

15. The system of claim 10 wherein said metal mesh is grounded to said cathode with an electrical conductor.

16. The system of claim 15 wherein:
said metal mesh is substantially square with a length equal to or greater than a radius of said wafer carcass;
said metal mesh has corners outboard of said wafer; and
said electrical conductor grounds said metal mesh to said cathode at one or more of said corners.

17. A method for measuring alpha particle emissions, said method comprising:
measuring a wafer with a counter to obtain a wafer emission rate;
covering said wafer with a metal mesh grounded to a cathode of said counter wherein said metal mesh is grounded to a cathode outboard of said wafer;
measuring said metal mesh and said wafer with said counter to obtain a mesh and wafer emission rate;
replacing said wafer with a wafer carcass;
measuring said wafer carcass and said metal mesh with said counter to obtain a wafer carcass and mesh emission rate; and
calculating a wafer carcass emission rate based on said wafer emission rate, said mesh and wafer emission rate, and said wafer carcass and mesh emission rate; and
computing a controlled collapse chip connection emission rate.

18. The method of claim 17 further comprising:
identifying a controlled collapse chip connection effective surface area of said wafer carcass,
wherein said controlled collapse chip connection emission rate is normalized to said controlled collapse chip connection effective surface area.

19. The method of claim 17 wherein:
wherein said metal mesh is grounded to said cathode with an electrical conductor.

20. The method of claim 19 wherein:
said metal mesh is substantially square with a length equal to or greater than a radius of said wafer carcass;
said metal mesh has corners outboard of said wafer; and
said electrical conductor grounds said metal mesh to said cathode at one or more of said corners.

Assignees

• IBM

Inventors

• Gordon Michael S
• Rodbell Kenneth P
• Murray Conal

Classifications

• G01R31/002 Primary

  where the device under test is an electronic circuit · CPC title

• G01T1/178

  for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water · CPC title

• G01T1/24

  with semiconductor detectors · CPC title

• G01T1/169 Primary

  Exploration, location of contaminated surface areas · CPC title

• G01R31/2831

  Testing of materials or semi-finished products, e.g. semiconductor wafers or substrates (G01R31/318511 takes precedence; testing during manufacture H10P74/00) · CPC title