Silicon Oxide-Nitride-Carbide with Embedded Nanocrystalline Semiconductor Particles

• US 20090217968A1
• Filed: 05/18/2009
• Published: 09/03/2009
• Est. Priority Date: 03/15/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Joshi, Pooran Chandra, Voutsas, Apostolos T.
• Granted Patent: US 9,222,169 B2
• Time in Patent Office: Days
• US Class Current: 136/250
• CPC Class Codes: C23C 16/30 Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
• CPC Class Codes: C23C 16/5096 Flat-bed apparatus
• CPC Class Codes: C23C 16/56 After-treatment
• CPC Class Codes: H01L 21/02126 the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/02321 introduction of substances into an already existing insulating layer H01L21/02227 and subgroups take precedence
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/0234 treatment by exposure to a plasma
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/31608 Deposition of SiO2 H01L21/31625, H01L21/31629 and H01L21/31633 take precedence
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

A solar call is provided along with a method for forming a semiconductor nanocrystalline silicon insulating thin-film with a tunable bandgap. The method provides a substrate and introduces a silicon (Si) source gas with at least one of the following source gases: germanium (Ge), oxygen, nitrogen, or carbon into a high density (HD) plasma-enhanced chemical vapor deposition (PECVD) process. A SiOxNyCz thin-film embedded with a nanocrystalline semiconductor material is deposited overlying the substrate, where x, y, z≧0, and the semiconductor material is Si, Ge, or a combination of Si and Ge. As a result, a bandgap is formed in the SiOxNyCz thin-film, in the range of about 1.9 to 3.0 electron volts (eV). Typically, the semiconductor nanoparticles have a size in a range of 1 to 20 nm.

Claims

1. A method for forming a semiconductor nanocrystalline silicon insulating thin-film with a tunable bandgap, the method comprising:

providing a substrate;

introducing a silicon (Si) source gas and at least one source gas selected from a group consisting of germanium (Ge), oxygen, nitrogen, and carbon into a high density (HD) plasma-enhanced chemical vapor deposition (PECVD) process;

depositing a SiOxNyCz thin-film embedded with a nanocrystalline semiconductor material overlying the substrate, where x, y, z≧

0, and the semiconductor material is selected from a group consisting of Si, Ge, and a combination of Si and Ge; and

,

forming a bandgap in the SiOxNyCz thin-film, in a range of about 1.9 to 3.0 electron volts (eV).

2. The method of claim 1 wherein forming the bandgap in the SiOxNyCz thin film includes forming semiconductor nanoparticles having a size in a range of 1 to 20 nm.

3. The method of claim 1 wherein forming the bandgap in the SiOxNyCz thin-film includes forming a SiOxNyCz thin-film with a refractive index in a range of about 1.9 to 3.5, as measured at a wavelength of 632 nanometers (nm).

4. The method of claim 1 wherein forming the bandgap in the SiOxNyCz thin-film includes forming a SiOxNyCz thin-film with peak optical emission, transmission, and absorption characteristics at a wavelength in a range of 200 to 1600 nm.

5. The method of claim 2 wherein introducing the Si source gas into an HD PECVD process includes using an inductively coupled plasma (ICP) process as follows:

supplying power to a top electrode at a frequency in the range of 13.56 to 300 megahertz (MHz), and a power density of up to 10 watts per square centimeter (W/cm²);

supplying power to a bottom electrode at a frequency in the range of 50 kilohertz to 13.56 MHz, and a power density of up to 3 W/cm²; and

,

using an atmosphere pressure in the range of 1 to 500 mTorr.

6. The method of claim 5 wherein supplying the oxygen source gas includes supplying an oxygen source gas from a source selected from a group consisting of N₂O, NO, O₂, and O₃.

7. The method of claim 5 wherein supplying the nitrogen source gas includes supplying a nitrogen source gas selected from a group consisting of N₂ and NH₃.

8. The method of claim 5 wherein supplying the carbon source gas includes supplying a carbon source gas selected from a group consisting of alkanes (C_nH_2n+2), alkenes (C_nH_2n), alkynes (C_nH_2n−

2), benzene (C₆H₆), and toluene (C₇H₈).

9. The method of claim 5 wherein supplying the Ge source gas includes supplying a Ge source gas selected from a group consisting of Ge_nH_2n+2, where n varies from 1 to 4, and GeH_xR₄₋

x where R is selected from a group consisting of Cl, Br, and I, and where x varies from 0 to 3.

10. The method of claim 3 wherein introducing the Si source gas includes supplying a source gas selected from a group consisting of SiH4, Si2H6, TEOS (tetra-ethoxy ortho-silicate), Si_nH2_n+2, where n varies from 1 to 4, and SiH_xR₄₋

x where R is selected from a first group consisting of Cl, Br, and I, and where x varies from 0 to 3.

11. The method of claim 5 wherein introducing the Si source gas further includes supplying an inert gas selected from a group consisting of He, Ar, and Kr.

12. The method of claim 1 further comprising:

simultaneous with the HD PECVD process, heating the substrate to a temperature in a range of about 25 to 400°

C.

13. The method of claim 1 further comprising:

annealing the SiOxNyCz thin film as follows;

heating an underlying substrate to a temperature of greater than about 400°

C.;

heating for a time duration in the range of about 10 to 300 minutes;

heating in an atmosphere selected from a group consisting of oxygen and hydrogen, oxygen, hydrogen, and inert gases; and

,

wherein forming the bandgap in the SiOxNyCz thin film includes modifying the size of the semiconductor nanoparticles in response to the annealing.

14. The method of claim 13 wherein annealing includes using a process selected from a group consisting of flash annealing and laser annealing using a heat source having a radiation wavelength selected from a group consisting of about 150 to 600 nanometers (nm) and 9 to 11 micrometers.

15. The method of claim 1 further comprising:

performing a HD plasma treatment on the SiOxNyCz thin film in an H₂ atmosphere, using a substrate temperature of less than 400°

C.; and

,

hydrogenating the SiOxNyCz thin film.

16. The method of claim 15 wherein hydrogenating the SiOxNyCz thin film using the HD plasma process includes:

supplying power to a top electrode at a frequency in the range of 13.56 to 300 MHz, and a power density of up to 10 W/cm²;

supplying power to a bottom electrode at a frequency in the range of 50 kilohertz to 13.56 MHz, and a power density of up to 3 W/cm²;

using an atmosphere pressure in the range of 1 to 500 mTorr; and

,

supplying an atmosphere selected from a group consisting of H₂ and an inert gas, and H₂.

17. The method of claim 1 wherein forming the bandgap in the SiOxNyCz thin film includes forming a SiOxNyCz thin film selected from a group consisting of intrinsic and doped thin films.

18. The method of claim 17 wherein forming the doped SiOxNyCz thin film includes in-situ doping during the HD PECVD process using a source selected from a group consisting of a dopant source gas and a physical sputtering source.

19. The method of claim 1 wherein introducing the Si source gas into the HD PECVD process includes using an energy source selected from a group consisting of a microwave slot antenna, ICP, a hollow cathode, an electron cyclotron resonance (ECR) plasma source, and a cathode-coupled plasma source.

20. The method of claim 1 wherein providing the substrate includes providing a substrate from a material selected from a group consisting of plastic, glass, quartz, Si, SiC, GaN, Ge, and Si₁₋

xGe_x.

21. The method of claim 1 wherein providing the substrate includes forming a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants;

wherein forming the bandgap in the SiOxNyCz thin film includes forming a SiOxNyCz thin film selected from a group consisting of a doped and intrinsic thin film; and

,

the method further comprising;

forming a top electrode overlying the SiOxNyCz thin film doped with the unselected dopant from the first group.

22. The method of claim 21 wherein forming the top and bottom electrodes includes forming the top and bottom electrodes in-situ from the SiOxNyCz thin film.

23. The solar cell comprising:

a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants;

a SiOxNyCz thin film with a bandgap in a range of about 1.9 to 3, embedded with semiconductor nanoparticles, where x, y, z≧

0, the semiconductor material is selected from a group consisting of Si, Ge, and a combination of Si and Ge; and

,

a top electrode overlying the SiOxNyCz thin film doped with the unselected dopant from the first group.

24. The solar cell of claim 23 wherein the top and bottom electrodes are a doped SiOxNyCz material.

25. The solar cell of claim 23 wherein the semiconductor nanoparticles have a size in a range of 1 to 20 nanometers (nm).

26. The solar cell of claim 23 further comprising:

a second solar cell including;

a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants;

a light absorbing layer;

a top electrode overlying the light absorbing layer with the unselected dopant from the first group;

wherein at least a second solar cell is situated in a position selected from a group consisting of overlying the first solar cell, underlying the first solar cell, and both underlying and overlying the first solar cell.

27. The solar cell of claim 26 wherein the second solar cell light absorbing layer, top electrode, and bottom electrode are a SiOxNyCz material.

28. The solar cell of claim 23 further comprising:

a second solar cell underlying the first solar cell and a third solar cell underlying the second solar cell, where the second and third solar cells each include;

a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants;

a light absorbing layer; and

,

a top electrode overlying the light absorbing layer with the unselected dopant from the first group;

wherein the first solar cell SiOxNyCz thin film has a first bandgap;

wherein the second solar cell intrinsic layer has a second bandgap, less than 1.9 eV; and

,

wherein the third solar cell intrinsic layer has a third bandgap, less than the second bandgap.

29. The solar cell of claim 28 wherein the second and third solar cell electrodes are a SiOxNyCz material.

30. The solar cell of claim 23 wherein the solar cell SiOxNyCz thin film is selected from a group consisting of doped and intrinsic materials.

31. A method for solar cell light wavelength conversion, the method comprising:

providing a SiOxNyCz thin film with a bandgap in a range of about 1.9 to 3 eV, embedded with semiconductor nanoparticles, where x, y, z≧

0, and the semiconductor material is selected from a group consisting of Si, Ge, and a combination of Si and Ge, and a solar cell underlying the SiOxNyCz thin film, the solar cell comprising a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants, a long wavelength light absorbing layer overlying the bottom electrode, and a top electrode overlying the long wavelength light absorbing layer doped with the unselected dopant from the first group;

exposing the SiOxNyCz thin film to incident light;

in the SiOxNyCz thin film, absorbing short wavelengths of light, shorter than about 500 nanometers (nm);

in response to absorbing the light wavelengths, emitting long wavelengths of light from the SiOxNyCz thin film, longer than about 500 nm; and

,

the solar cell light long wavelength absorbing layer absorbing wavelengths of light longer than 500 nm.

32. A solar cell light wavelength conversion device, the device comprising:

a SiOxNyCz thin film with a bandgap in a range of about 1.9 to 3 eV, embedded with semiconductor nanoparticles, where x, y, z≧

0, and the semiconductor material is selected from a group consisting of Si, Ge, and a combination of Si and Ge, the SiOxNyCz thin film, absorbing short wavelengths of incident light, shorter than about 500 nanometers (nm), and in response to absorbing the light wavelengths, emitting long wavelengths of light, longer than about 500 nm; and

,

a solar cell underlying the SiOxNyCz thin film, the solar cell comprising;

a bottom electrode doped with a material selected from a first group consisting of n-type and p-type dopants;

a long wavelength light absorbing layer overlying the bottom electrode for absorbing wavelengths of light longer than 500 nm; and

,

a top electrode overlying the long wavelength light absorbing layer doped with the unselected dopant from the first group.