Creation of hyperdoped semiconductors with concurrent high crystallinity and high sub-bandgap absorptance using nanosecond laser annealing

Patent metadata

Field	Value
Publication number	US-2017365476-A1
Application number	US-201515524539-A
Country	US
Kind code	A1
Filing date	Nov 12, 2015
Priority date	Nov 12, 2014
Publication date	Dec 21, 2017
Grant date	—

Abstract

In one aspect, a method of processing a semiconductor substrate is disclosed, which comprises incorporating at least one dopant in a semiconductor substrate so as to generate a doped polyphase surface layer on a light-trapping surface, and optically annealing the surface layer via exposure to a plurality of laser pulses having a pulsewidth in a range of about 1 nanosecond to about 50 nanoseconds so as to enhance crystallinity of said doped surface layer while maintaining high above-bandgap, and in many embodiments sub-bandgap optical absorptance.

First claim

1 . A method of processing a semiconductor substrate, comprising:
incorporating at least one dopant in a semiconductor substrate so as to generate a doped polyphase surface layer, optically annealing said surface layer via exposure to a plurality of laser pulses having a pulsewidth in a range of about 1 nanosecond to about 50 nanoseconds so as to enhance crystallinity of said doped surface layer.

2 . The method of claim 1 , wherein said incorporating step results in formation of a plurality of light-trapping surface textures in a top surface of said surface layer.

3 . The method of claim 2 , wherein said optically annealing step substantially preserves said light-trapping surface textures.

4 . The method of claim 2 , wherein said surface textures are characterized by a plurality of undulations having a peak-to-trough amplitude in a range of about 100 nanometer to about 100 micrometers.

5 . The method of claim 1 , wherein said optically annealed doped surface layer exhibits an absorptance for at least one sub-bandgap wavelength equal to or greater than about 50%.

6 . The method of claim 1 , wherein said optically annealed doped surface layer has a thickness in a range of about 10 nm to about 200 nm.

7 . The method of claim 3 , wherein said optically annealed doped surface layer exhibits an absorptance in a range of about 50% to 100% for said at least one sub-bandgap wavelength.

8 . The method of claim 1 , wherein said optical annealing step results in at least 50% recrystallization of said polyphase doped surface layer.

9 . The method of claim 1 , wherein said optical annealing step results in at least 80% recrystallization of said polyphase doped surface layer.

10 . The method of claim 1 , wherein said dopant has a concentration greater than solid solubility limit of said dopant in said semiconductor.

11 . The method of claim 1 , wherein said dopant has a concentration in a range of about 0.01 to about 1.5 atom percent in said semiconductor surface layer.

12 . The method of claim 8 , wherein said semiconductor substrate comprises silicon and said dopant comprises a chalcogen.

13 . The method of claim 1 , wherein said dopant is any of an electron-donating and a hole-donating species.

14 . The method of claim 1 , further comprising the step of thermally annealing said doped surface layer prior to said optical annealing step.

15 . The method of claim 7 , wherein said thermal annealing step comprises exposing said doped surface layer to an elevated temperature in a range of about 200 deg. C. to about 1400 deg. C.

16 . The method of claim 1 , wherein said optical annealing laser pulses have a central wavelength in a range of about 195 nm to about 355 nm.

17 . The method of claim 1 , wherein said optical annealing laser pulses have a fluence in a range of about 0.1 to about 2.5 J/cm 2 .

18 . The method of claim 1 , wherein said incorporating step comprises:
irradiating a surface of the semiconductor substrate with one or more laser pulses having a pulse width in a range of about 10 femtoseconds to about 10 picoseconds while exposing said substrate surface to any of said dopant and a compound having said dopant as a constituent.

19 . The method of claim 16 , wherein said dopant comprises a chalcogen.

20 . The method of claim 16 , wherein said laser pulses employed in the incorporating step have a pulsewidth in a range of about 10 femtoseconds to about 1 picosecond.

21 . The method of claim 16 , wherein said step of exposing said substrate comprises bringing a substrate surface into contact with a gas containing any of said dopant and a compound having said dopant as a constituent.

22 . The method of claim 16 , wherein said step of exposing said substrate comprises applying a film containing any of said dopant and a compound having said dopant as a constituent to a surface of said substrate.

23 . The method of claim 1 , wherein said optically annealed doped surface layer forms a diode junction with underlying bulk substrate.

24 . The method of claim 1 , wherein said substrate is any of silicon, germanium, silicon carbide, and gallium arsenide.

25 . The method of claim 1 , wherein said incorporating step comprises implanting dopant ions in said semiconductor substrate so as to form said doped surface layer.

26 . The method of claim 19 , wherein said implanting step comprises exposing said semiconductor to a dopant ion beam.

27 . The method of claim 21 , wherein said dopant ion beam has an ion energy in a range of about 20 keV to about 200 keV.

28 .- 55 . (canceled)

Assignees

• Harvard College

Inventors

• Mazur Eric
• Franta Benjamin
• Aziz Michael J
• Pastor David

Classifications

• H10P14/3816

  Pulsed laser beam · CPC title

• H10P34/42

  with electromagnetic radiation, e.g. laser annealing (laser cutting H10P54/20) · CPC title

• H10P14/3411 Primary

  Silicon, silicon germanium or germanium · CPC title

• H10P34/422 Primary

  using incoherent radiation · CPC title

• H01L31/02363

  Electricity · mapped topic