Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

• US 10,361,083 B2
• Filed: 08/26/2015
• Issued: 07/23/2019
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Mazur, Eric, Shen, Mengyan
• Primary Examiner(s): Padgett, Marianne L
• Application Number:
  US14/836,609
• Publication Number:
  US 20160005608A1
• Time in Patent Office: 1,427 Days
• Field of Search: 427554, 427555, 427556, 427596, 427597, 438217, 438231, 438232, 438246-249, 438289-291, 438301-308
• CPC Class Codes: B23K 26/1224 in vacuum
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0259 Microstructure
• CPC Class Codes: H01L 21/02686 Pulsed laser beam
• CPC Class Codes: H01L 21/2252 using predeposition of impurities into the semiconductor surface, e.g. from a gaseous phase
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 21/302 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
• CPC Class Codes: H01L 21/67075 for wet etching
• CPC Class Codes: H01L 29/30 characterised by physical imperfections; having polished or roughened surface
• CPC Class Codes: H01L 29/34 the imperfections being on the surface
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Claims

1. A method for processing a silicon substrate, comprising:

disposing a solid substance on a surface of a silicon substrate, wherein said solid substance comprises an electron-donating constituent,

placing said surface in contact with a liquid such that at least a portion of said liquid is in contact with said solid substance,

subsequently, irradiating said surface of the substrate with a plurality of laser pulses having a pulse width in a range of about 50 femtoseconds to about 500 femtoseconds in presence of said liquid on said surface so as to incorporate said electron-donating constituent of said solid substance as a plurality of inclusions within an upper layer of the substrate.

2. The method of claim 1, wherein said electron-donating constituent is a sulfur-containing substance such that said inclusions comprise sulfur.

3. The method of claim 1, wherein said solid substance comprises sulfur powder.

4. The method of claim 1, wherein said liquid comprises an aqueous solution.

5. The method of claim 1, wherein said liquid comprises any of water, alcohol, sulfuric acid and silicon oil.

6. The method of claim 1, wherein said semiconductor substrate is any of a doped and undoped silicon wafer.

7. The method of claim 1, wherein said laser pulses have a wavelength of less than or about 800 nm.

8. The method of claim 1, wherein said upper layer has a thickness in a range of about 100 nm to about 1 micrometer.

9. The method of claim 1, wherein the laser pulses are applied to a plurality of surface locations and wherein a number of the laser pulses applied to each surface location is in a range of 1 to about 2500.

10. The method of claim 1, wherein placing said surface in contact with said liquid comprises disposing a layer of said liquid having a thickness in a range of about 1 mm to about 20 mm on said surface.

11. The method of claim 1, wherein each of said laser pulses has an energy in a range of about 10 microjoules to about 400 microjoules.