JP2010199524A - Method of manufacturing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor achieving a highly efficient thin-film polycrystalline silicon (Si) solar cell on a glass substrate. <P>SOLUTION: The method of manufacturing a semiconductor for a solar cell includes: the steps for forming on the glass a large grain size polycrystalline silicon (Si) thin film subjected to orientation control to (110) and (111) by using a solid continuous wave laser excited by semiconductor (excited by diode), and directly growing the polycrystalline silicon Si layer while using the above Si film as a seed crystal. After that, this thin film is irradiated with an energy beam in condition that the Si layer is not molten and Si is grown in solid phase. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor manufacturing method, and more particularly to a semiconductor manufacturing method for realizing a high-efficiency thin-film silicon (Si) solar cell formed on glass.

  Recently, high-efficiency Si-based thin-film solar cells on glass have attracted attention. Current thin-film Si-based solar cells on glass are mainly thin-film Si-based materials made of amorphous or microcrystals.

  However, a thin film Si solar cell made of amorphous or microcrystal has a problem that conversion efficiency is low.

  Thin-film Si-based solar cells on glass, particularly thin-film Si-based solar cells made of amorphous or microcrystals, have a lower conversion efficiency than bulk single-crystal Si solar cells or bulk polycrystalline Si solar cells. This is because the crystal quality of amorphous Si or microcrystalline Si is inferior to that of single crystal Si or bulk polycrystalline Si.

  Therefore, if high-quality polycrystalline Si can be formed on glass, it is expected to bring about a great breakthrough in the conversion efficiency of thin-film Si-based solar cells on glass.

  The present invention has been made in view of the above problems, and in order to form a high-efficiency thin-film Si-based solar cell on a glass substrate, a polycrystalline Si thin film having a large particle diameter is formed while being a thin film Si. An object of the present invention is to provide a semiconductor manufacturing method.

  As a result of intensive studies, the present inventor has conceived the following aspects of the invention.

  A large-grain polycrystalline Si thin film whose orientation is controlled to (110) and (111) is formed by using a semiconductor-excited (diode-excited) solid-state continuous wave laser, and this Si film is used as a seed crystal. The Si layer is grown directly. Finally, this thin film is irradiated with an energy beam again under the condition that the Si layer does not melt, and solid phase growth of Si is performed.

  According to the present invention, it is possible to form polycrystalline Si having a large particle size on glass, and it is more efficient than a thin-film Si-based solar cell made of amorphous Si or microcrystalline Si that is currently in practical use. This thin film Si-based solar cell can be realized on glass at low cost.

  The present invention proposes a semiconductor manufacturing method for realizing a thin film Si solar cell having high conversion efficiency on a glass substrate at a low cost.

Hereinafter, specific embodiments of the present invention will be described in detail. In this example, a large particle size whose orientation is controlled to (110) and (111) using a wavelength of 532 nm, which is the second harmonic of Nd: YVO ₄ , as a solid-state continuous wave laser pumped by a semiconductor (diode pump). After forming a polycrystalline Si thin film and stabilizing the surface by terminating the surface of the Si film with hydrogen, a polycrystalline Si layer is directly grown by plasma CVD using the Si thin film as a seed crystal. Furthermore, laser solid phase growth was realized for this polycrystalline Si thin film by using the same semiconductor excitation (diode excitation) solid-state continuous wave laser as described above.

  FIG. 1 is a schematic structural diagram of a thin film Si-based solar cell formed according to this embodiment.

2 to 4 are schematic schematic views showing a method for producing a Si thin film in the order of steps.
First, as shown in FIG. 2A, an amorphous Si thin film 2 doped with impurities by plasma CVD is grown on a glass substrate 1 by 200 nm. The amorphous Si thin film is formed by mixing silane gas and doping gas.

Subsequently, as shown in FIG. 2B, a semiconductor-excited solid CW laser (Nd: YVO ₄ , wavelength 532 nm) having a wavelength of 532 nm is used, the power is set to 4.0 watts, and the laser scanning speed is 40 cm / s. The low resistance large grain polycrystalline Si layer 3 whose orientation is controlled to (110) or (111) is formed by scanning with (1). The crystal grain size at this time is 3 μm × 20 μm.

  According to past studies conducted by the inventors, it is known that when the thickness of the Si layer is reduced, the crystal grains are oriented in the (110) and (111) directions.

  Subsequently, the Si layer 4 (FIG. 3A) in which the (110) or (111) surface is hydrogen-terminated by wet processing is formed. It is known that the (110) plane and the (111) plane are surfaces that can be neatly terminated with hydrogen. Thereby, the epitaxial growth by PECVD using the following seed layer can be stabilized and performed with good reproducibility.

Subsequently, by using PECVD, the 2 μm silicon layer 5 is epitaxially grown at 350 ° C. under hydrogen dilution conditions (SiH ₄ : H ₂ = 5: 95) (FIG. 3B). This silicon thin film layer was an intric layer without doping impurities. The hydrogen dilution amount is not limited to the present embodiment, but is a mixed gas of silane gas and hydrogen gas as long as the hydrogen gas amount is larger than the silane gas amount.

  Subsequently, without breaking the vacuum on the grown Si thin film, an Si layer 6 doped with impurities is grown to 200 nm preferably using a chamber different from the chamber in which the intrinsic Si layer is formed (FIG. 4). . The impurity doped in this step is doped with a different type of impurity from the impurity doped in the seed (seed) crystal layer. Here, different types of impurities mean that if the seed crystal is n-type, the thin film layer is p-type. Conversely, if the seed crystal layer is p-type, the thin film layer is n-type. To do.

  Subsequently, the thin film Si layer after the growth is irradiated with laser at a low power set so that the Si layer is not melted to complete the Si thin film (FIG. 5). In this example, Si solid phase growth was realized by using a laser power of 2.0 W and scanning at a laser scanning speed of 40 cm / s. Since the Si layers 55 and 66 formed here are subjected to solid phase growth by laser irradiation, higher quality crystals are formed than the Si layers 5 and 6 before laser irradiation.

  The final form is shown in FIG. Polycrystalline Si having a large particle size for solar cells can be formed on glass.

  In this embodiment, hydrogen treatment is performed at 450 ° C. for 60 minutes before solid phase growth using a laser.

  Further, after solid phase growth using a laser, hydrogenation treatment is performed at 400 ° C. for 60 minutes.

It is the schematic which shows embodiment of this invention. It is the schematic which shows the semiconductor manufacturing method by embodiment of this invention in process order. FIG. 3 is a schematic view illustrating the semiconductor manufacturing method according to the embodiment of the present invention in the order of steps subsequent to FIG. 2. FIG. 4 is a schematic view illustrating the semiconductor manufacturing method according to the embodiment of the present invention in the order of steps subsequent to FIG. 3. FIG. 5 is a schematic diagram illustrating a semiconductor manufacturing method according to an embodiment of the present invention following FIG. 4.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Impurity-doped amorphous Si thin film 3 (110) or (111) oriented large grain silicon polycrystalline thin film 4 by laser crystallization 4 Hydrogen-terminated polycrystalline Si thin film 5 Silicon thin film (in Trinsic layer)
6 Polycrystalline Si layer 55 doped with impurities Intrinsic Si layer 66 solid-phase grown by laser irradiation 66 Si layer doped with impurities solid-phase grown by laser irradiation

Claims (7)

Using a semiconductor-excited (diode-excited) solid-state continuous wave laser, a large grain polycrystalline silicon (Si) thin film whose orientation is controlled to (110) and (111) is formed on glass, and this Si film is used as a seed ( A polycrystalline Si layer is directly grown as a seed crystal.
Thereafter, Si thin-phase growth is performed by irradiating the thin film with an energy beam under a condition that the Si layer does not melt. A large-grain polycrystalline Si thin film whose orientation is controlled to (110) and (111) formed using a semiconductor-excited (diode-excited) solid-state continuous wave laser has a thickness of 300 nm or less. Claim 1. 2. A semiconductor-excited (diode-excited) solid-state continuous wave laser having a wavelength of 300 to 600 nm is used. 2. An energy beam such as continuous wave laser, pulse laser, lamp annealing, and heated gas beam is used as energy beam irradiation for Si solid phase growth performed in the final stage. 2. The energy beam solid phase growth is performed under the condition that the Si layer does not melt. 2. The Si surface is terminated with hydrogen when directly growing polycrystalline Si on an orientation-controlled seed crystal layer having a large grain size. 2. The method of claim 1, wherein each layer is doped in order to form a junction as necessary.