Method of fabricating x-ray absorbers for low-energy x-ray spectroscopy

Patent metadata

Field	Value
Publication number	US-10074764-B2
Application number	US-201615280369-A
Country	US
Kind code	B2
Filing date	Sep 29, 2016
Priority date	Sep 29, 2016
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A method of forming low-energy x-ray absorbers. Sensors may be formed on a semiconductor, e.g., silicon, wafer. A seed metal layer, e.g., gold, is deposited on the wafer and patterned into stem pads for electroplating. Stems, e.g., gold, are electroplated from the stem seed pads through a stem mask. An absorber layer, e.g., gold, is deposited on the wafer, preferably e-beam evaporated. After patterning the absorbers, absorber and stem mask material is removed, e.g., in a solvent bath and critical point drying.

First claim

What is claimed is:

1. A method of forming low-energy x-ray absorbers, said method comprising:
forming stem seed pads on a wafer;
electroplating stems from said stem seed pads using a temperature below 65° C.;
deposit an absorber layer above said stems on said wafer using a low temperature; and
patterning absorbers from said absorber layer;
wherein said wafer is a semiconductor wafer, and forming said stem seed pads comprises:
forming superconducting sensors at selected locations on said wafer;
depositing a seed metal layer onto said semiconductor wafer; and
patterning said seed metal layer, at least one seed pad being formed at each selected location.

2. A method as in claim 1 , wherein the seed metal comprises gold and the semiconductor wafer is a silicon wafer.

3. A method as in claim 2 , wherein the gold seed layer is thirty hundredths of a micron (0.35 μm) thick or less (<0.35 μm).

4. A method as in claim 2 , wherein the stems and absorber layer are gold and forming superconducting sensors includes forming superconductor traces to one or more stem pad locations.

5. A method as in claim 4 , wherein the superconductor traces are formed from niobium.

6. A method as in claim 1 , wherein electroplating the stems comprises:
forming a stem mask layer on said stem seed pads;
patterning said stem mask layer to define stems at a temperature below 65° C.; and
electroplating metal through the stem mask pattern from the stem seed pads.

7. A method as in claim 6 , wherein the stem seed pads and the stem metal are the same metal and said stem mask layer is thinner than 4.3 μm thick.

8. A method as in claim 7 , wherein the stem seed pads include a gold seed layer on a titanium adhesion layer, the stems are gold and patterning said mask layer opens an individual mold <3.5 μm in diameter at each stem location.

9. A method as in claim 1 , wherein said upper surface is selectively removed to expose the upper end of each stem, depositing said absorber layer comprises e-beam evaporating absorber material onto the stem mask and exposed stems, and patterning said absorbers is at a temperature below 65° C.

10. A method as in claim 9 , wherein patterning said absorbers comprises:
forming an absorber mask layer on said absorber layer;
patterning said absorber mask layer; and
etching exposed areas of said absorber layer.

11. A method as in claim 1 , further comprising removing stem and absorber masks, removing said stem and absorber mask comprising:
washing away said absorber mask material and stem mask layer material in a solvent bath; and
removing the solvent.

12. A method as in claim 11 , wherein the seed layer, stems and absorber layer are gold, the solvent bath is acetone followed by methanol, and removing the solvent comprises critical point drying said wafer for a surface tension-free release.

13. A method of forming low-energy x-ray absorbers, said method comprising:
forming superconducting sensors at selected locations on a semiconductor wafer;
depositing a seed metal layer onto said semiconductor wafer;
patterning stem seed pads from said seed metal layer, at least one stem seed pad being formed at each selected location;
forming a stem mask on the wafer at a temperature below 65° C.;
electroplating stems through said stem mask from said stem seed pads;
depositing an absorber layer on said stem mask;
forming an absorber mask defining an absorber pattern on said absorber layer;
patterning absorbers from said absorber layer at a temperature below 65° C.;
and removing said absorber mask and said stem mask.

14. A method as in claim 13 , wherein the seed metal layer, electroplated stems and absorber layer are gold.

15. A method as in claim 14 , wherein depositing said absorber layer comprises e-beam evaporating gold onto said semiconductor wafer and contacting the electroplated gold stems.

16. A method as in claim 15 , wherein said semiconductor wafer is a silicon wafer and depositing the gold seed layer comprises depositing a titanium adhesion layer on said silicon wafer and a gold seed layer thirty hundredths of a micron (0.35 μm) thick or less (<0.35 μm) onto said titanium adhesion layer.

17. A method as in claim 15 , wherein said stem mask layer is thinner than 4.3 μm thick, said mask layer comprises individual stem molds 3.5-5.0 μm in diameter at each stem pad and electroplating fills each individual mold to the upper surface of said mask layer.

18. A method as in claim 13 , wherein removing said absorber mask and stem m ask layer comprises:
washing away mask material in a solvent bath; and
removing the solvent.

19. A method as in claim 18 , wherein the solvent bath is acetone followed by methanol, and removing the solvent comprises critical point drying said wafer for a surface tension-free release.

20. A method of forming low-energy x-ray absorbers, said method comprising:
forming superconducting sensors at selected locations on said silicon wafer;
depositing a gold seed layer onto a silicon wafer;
patterning stem seed pads from said gold seed layer, at least one stem seed pad being formed at each selected location;
forming, at a temperature below 65° C., a stem mask thinner than 4.3 μm thick, wherein said stem mask comprises an individual stem mold 3.5-5.0 μm in diameter at each stem seed pad;
electroplating gold stems through said stem mask from said stem seed pads at a temperature below 65° C.;
e-beam evaporating a gold absorber layer on said stem mask;
forming an absorber mask defining an absorber pattern on said absorber layer; patterning absorbers from said absorber layer at a temperature below 65° C.;
washing away absorber mask and stem mask material in a solvent bath; and
removing the solvent.

21. A method as in claim 20 , wherein depositing the gold seed layer comprises depositing a titanium adhesion layer on said silicon wafer and a gold layer thinner than 0.35 microns (<0.35 μm) onto said silicon wafer and electroplating fills each individual mold to the upper surface of said mask layer.

22. A method as in claim 20 , wherein the solvent bath is acetone followed by methanol, and removing the solvent comprises critical point drying said wafer for a surface tension-free release.

Assignees

• Nasa

Inventors

• Stevenson Thomas R
• Balvin Manuel A
• Denis Kevin L
• Sadleir John E
• Nagler Peter C

Classifications

• H10P76/00

  Manufacture or treatment of masks on semiconductor bodies, e.g. by lithography or photolithography · CPC title

• H01L31/18 Primary

  Electricity · mapped topic

• G01N23/083

  the radiation being X-rays · CPC title

• G21K1/10

  Scattering devices; Absorbing devices; Ionising radiation filters · CPC title

• H01L21/027

  Electricity · mapped topic