JP2002302758A - Manufacturing method for polycrystal silicon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deposit a polycrystal silicon thin film on a glass substrate without heating or annealing silicon and quartz glass substrate. SOLUTION: First and second boxes 11 and 12 are communicated with each other, a pulse ion beam generation source is disposed in the first box 11, and a target and a substrate are disposed in the second box 12. The pulse ion beam generation source comprises a cathode 14 formed so as to surround an anode 13, and the solid target 17 disposed in the second box 12 is disposed in an inclined manner by the predetermined angle. The substrate 18 is supported by a supporting device 19 and disposed at the position facing the target 17. The voltage and the current are supplied to the anode 13 to operate the ion beam generation source and generate the ion beam. When the target 17 is irradiated with the beam, aberration plasma is generated in the target in the range of proton. The generated plasma is scattered perpendicular to the target surface and vapor-deposited on the substrate 18 to manufacture a thin film on the substrate 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for producing a polycrystalline silicon thin film using a pulsed ion beam evaporation method.

[0002]

2. Description of the Related Art Recently, a polysilicon thin film (poly-Si) has been developed.
Is widely used in various electronic devices (for example, thin film transistors (TFTs), solar cells, peripheral circuits of liquid crystal displays, and electrodes of silicon ICs). This is because the mobility of polysilicon is much higher than the carrier mobility of hydrogenated amorphous silicon (a-Si: H).

[0003]

[0005] Plasma-excited CVD (hereinafter abbreviated as PECVD) is one of the methods for producing a polysilicon thin film. However, from SiH ₄ / H ₂ gas to PECVD
The polycrystalline silicon thin film formed by the method described above has a problem that the electrical characteristics are inferior to the thin film formed by low pressure CVD or solid phase crystallization. PECVD is performed at a high temperature (typically 400 ~
Heat treatment at 1000 ° C.) is required, and there is a drawback that a dangerous gas (flammable or explosive) such as SiH ₄ needs to flow during film formation.

The present invention has been made in view of the above circumstances, and does not heat and anneal a silicon or quartz glass substrate using a pulsed ion beam evaporation method, but has a high crystallinity on the substrate. An object is to provide a method for manufacturing a polycrystalline silicon thin film capable of forming a crystalline silicon thin film.

[0005]

According to the present invention, in order to achieve the above-mentioned object, a first invention is to provide a pulsed ion beam source in a evacuated box and at a certain distance from the source. A pulsed ion beam evaporation method for providing a solid target and irradiating the solid target with ablation plasma generated from a pulsed ion beam source,
Plasma generated by ablation plasma applied to the target is deposited on a substrate to be processed, and a polycrystalline silicon thin film having high crystallinity is formed on the substrate to be processed without heating and annealing. It is a feature.

A second invention is characterized in that the substrate to be processed is made of a silicon and quartz glass substrate.

A third invention is characterized in that the crystallinity of the polycrystalline silicon thin film can be changed by increasing the ablation plasma density.

In each of the above-mentioned inventions, the lifetime of the ablation plasma generated from the pulse ion beam having a pulse width of 50 ns is 20 μs, so that the instantaneous film forming speed is cmcm / s. At this time, it was found that the crystallinity of the polycrystalline silicon thin film became better as the ablation plasma density increased, and that the silicon particle diameter of the thin film also became smaller.

In the pulse ion beam evaporation method, when a solid target is irradiated with a pulsed proton ion beam, a high-density ablation plasma is generated by the range of protons in the target. From this, a thin film can be produced very efficiently using this plasma.

After announcing the first production of a ZnS thin film in 1988 by the above pulsed ion beam evaporation method, various thin films such as YBCO (oxide superconductor), ITO (In, SnO
₂ Transparent electrode), BaTiO ₃ , BN, SiC, TiO ₂ , ZrO ₂ , Al
N "was produced by the above-described vapor deposition method.

The pulse ion beam evaporation method uses an "ETIGO-II" pulse-power generator device of Nagaoka University of Science and Technology. Ion beam (LIB) by this device
Are generated by diodes (MIDs) that are geometrically focused and insulate electrons with a magnetic field. A flash board in which a polyethylene sheet is covered on the anode (aluminum) of the above apparatus is used as an ion source. The ionic species are found to be mostly protons (about 75%) from the measurement of the energy spectrum, with the balance being carbon.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural explanatory view showing an embodiment of the present invention. In FIG. 1, reference numerals 11 and 12 denote 10 ^-4 Torr.
The first and second boxes are set at a pressure of
Part of the surfaces of the first and second boxes 11 and 12 are joined together, and the joining surfaces are cut out to form the two boxes 11 and 12 in communication with each other.
A pulse ion beam generation source is arranged in the first box 11, and a solid target and a substrate to be processed are arranged in the second box 12.

The pulse ion beam generating source arranged in the first box 11 is constituted by a cathode 14 formed so as to surround the anode 13. Aluminum is used as a material of the anode 13, and the aluminum is coated with a polyethylene sheet to form a flash board 15, and the flash board 15 is used as an ion source.

The second box 12 is provided with a solid target 17 supported by a support device 16 on the inner wall surface at a predetermined distance z from the anode 13. Solid target 17
Are arranged at a predetermined angle (about 45 °). At a position facing the tilted solid target 17, a substrate 18 to be processed is arranged by being supported by a supporting device 19. The distance between the solid target 17 and the substrate 18 is about
70 mm to 80 mm.

In the embodiment configured as described above, a beam voltage of 1 MV and a current of 70 kA are supplied to the anode 13 to operate the ion beam generating source to generate an ion beam. When the generated ion beam is irradiated on the solid target 17, high-density ablation plasma is generated in the solid target 17 by the range of protons. At this time, the energy density of the ion beam was 25 to 100 J / cm ² as a result of measurement at the geometrical focus.
Met. The beam diameter on the solid target 17 was 20 mm. As the solid target 17, single-crystal silicon having a diameter of 50 mm and a thickness of 10 mm was used.

The plasma generated from the solid target 17 scatters in the direction perpendicular to the target surface and
8 and a thin film is formed on the substrate 18. The substrate 18 includes a silicon wafer (100), quartz glass,
A slide glass or stainless steel was used. The temperature of the substrate 18 was room temperature, and the pressure of the second box (chamber) 12 was 10 ^-4 Torr. Representative experimental conditions are summarized in Table 1.

[0018]

[Table 1]

The behavior of the ablation plasma when operated as described above was measured using a high-speed camera (ULTRNAC FS50).
1, NACInc) is shown in FIG. 2 described below. The crystal structure of the thin film formed on the substrate 18 was examined with an XRD apparatus (RINT2000 ⁺ , RIGAKU) using a diffractometer. At this time, the crystal grain size having a specific crystal plane (nkl) was calculated from the half width (FWHM) of the XRD spectrum using Scherrer's formula. In addition, the film thickness is measured with a step gauge (SURF COM130A, Tokyo se
imitu).

FIG. 2 is a diagram drawn based on a high-speed photograph of the ablation plasma taken by the high-speed camera.
In FIG. 2, t = 0 indicates that the irradiation of the ion beam on the solid target 17 has started. From FIG. 2, it was found that the ablation plasma was generated by the irradiation of the ion beam. And solid target 1
The plasma irradiated to 7 spreads in a direction perpendicular to the surface of the solid target 17. Thus, the ablation plasma reaches the substrate 18 where a thin film is formed. The plasma is generated for 20 μs after beam irradiation.

FIG. 3 is an X-ray diffraction pattern diagram of silicon (100) and a silicon thin film formed on a quartz glass substrate.
From FIG. 3, diffraction peaks corresponding to plane orientations (110), (220), and (311) were always observed. The deposition rate of the silicon thin film was about 200 nm / shot. The lifetime of the ablation plasma is approximately 20 μs, and the pulse width of the pulsed ion beam is 50 ns. Therefore, the instantaneous film forming speed is cmcm / s. From the data of the XRD apparatus, it can be calculated that the particle diameter d of the silicon thin film is on the order of nm using the Schuler equation.

D = 0.9λ / βcos θ (1) where d is the particle diameter, λ is the wavelength of the X-ray, β is the FWHM, and θ is the Bragg angle.

Using Schuler's equation (1), the particle sizes of the silicon and silicon thin films on the quartz glass substrate are 44 nm and 60 nm, respectively.

FIG. 4 is an X-ray diffraction pattern diagram showing the difference in the XRD pattern of the silicon thin film generated on the silicon substrate by the 10-shot irradiation depending on the installation position of the substrate. In FIG. ) ^{-10 -4} Torr,
z (distance between anode and target) = 200 mm, d _TS (distance between target and substrate) = 80 mm, and θ (beam / target angle) = 45 °.

FIG. 4 shows that the ablation plasma directly reaches the surfaces of the samples No. 1 and No. 2. Further, diffraction peaks of planes (111), (220) and (311) can be observed. These peak intensities increase as approaching the center of the ablation plasma. It was found that the integrated intensity of the plane (111) of the No. 1 sample was 9.3 times larger than that of the No. 7 sample. FIG. 4 shows that the crystallinity of the thin film is better at the center because the plasma density is much higher at the center of the plasma than at the periphery.

As can be seen from FIG. 4, the XRD spectrum (X
The crystal grain size can be evaluated from the Schuller equation using the full width at half maximum (FWHM) of the line diffraction pattern). Table 2 summarizes the thickness of the thin film and the particle diameter with respect to the deposition rate.

[0027]

[Table 2]

From Table 2 above, it can be seen that the grain size of the polysilicon thin film formed on the silicon substrate decreases as it approaches the center of the ablation plasma, similarly to the result shown in FIG. From these results, it has been found that the pulsed ion beam evaporation method is very suitable as a method for forming a polycrystalline silicon thin film without heating and annealing the substrate. However, the electrical properties of the prepared thin film have not been clarified yet.

[0029]

As described above, according to the present invention,
A polycrystalline silicon thin film can be formed on a silicon or quartz glass substrate by using a pulse ion beam evaporation method, and high crystallinity can be obtained without annealing. The life of the ablation plasma is about 20 μs because the pulse width is an ion beam with a pulse width of 50 ns, and the instantaneous film forming speed is up to cm / s. The crystallinity of the polycrystalline silicon thin film improves as the ablation plasma density increases, and the crystallinity is related to the particle size, and the smaller the better, the better.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram drawn based on a high-speed photograph of ablation plasma taken by a high-speed camera.

FIG. 3 is an X-ray diffraction pattern diagram of silicon (100) and a silicon thin film formed on a quartz glass substrate.

FIG. 4 is an X-ray diffraction pattern diagram showing a difference in an XRD pattern of a silicon thin film generated on a silicon substrate by irradiation with 10 shots depending on an installation position of the substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... 1st box 12 ... 2nd box 13 ... Anode 14 ... Cathode 15 ... Flash board 16 ... Supporting device 17 ... Target 18 ... Substrate 19 ... Supporting device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/285 301 H01L 21/285 301Z 31/04 31/04 X (72) Inventor Toshiaki Suzuki Shinagawa, Tokyo 2-1-1-17 Osaki-ku F-term in Meishinsha Co., Ltd. (Reference) 4K029 AA06 AA08 AA09 AA24 BA35 BB08 CA05 DC37 EA06 4M104 AA01 AA10 BB01 BB37 DD36 HH20 5F045 AA18 AB03 AE13 AF03 AF11 BB12 BB18 CA13 AA06 AA10 DD16 HH04

Claims (3)

[Claims] 1. A pulsed ion beam source and a solid target at a certain distance from the source in a vacuum-evacuated box, and the solid target is irradiated with ablation plasma generated from the pulsed ion beam source. A pulse ion beam evaporation method, in which a plasma generated by ablation plasma applied to the target is deposited on a substrate to be processed, and a polycrystalline silicon thin film having high crystallinity is heated and annealed on the substrate to be processed. A method for producing a polycrystalline silicon thin film, characterized in that the method is not performed. 2. The method according to claim 1, wherein the substrate to be processed is made of a silicon or quartz glass substrate. 3. The method according to claim 1, wherein the crystallinity of the polycrystalline silicon thin film is changed by increasing ablation plasma density.