JPH02260627A - Formation of semiconductor film and device therefor - Google Patents

Abstract

PURPOSE:To perform one continuous processing within a short time by a method wherein a substrate is arranged in a reaction chamber while an amorphous film is crystallized and simultaneously mixed with an impurity element during glow discharging process in a high-frequency field. CONSTITUTION:A substrate 2 is arranged in a reaction chamber 30 and then a transparent window 16 is covered with the shielding plate 14a of a shutter 14. Then, after sufficiently vacuumizing the reaction chamber 30 by a vacuum pump, SiH4 gas is led into the reaction chamber 30 from a leading-in port 10. At this time, the pressure in the reaction chamber 30 and the temperature of the substrate 2 is kept at proper level and high-frequency field is generated so as to effect glow discharge between electrodes 12. During the glow discharging process, the mounting bed 4 of the substrate 2 is impressed with DC voltage in specific polarity while an amorphous film formed on the substrate 2 is irradiated with laser beams. Through these procedures, the amorphous film is crystallized and simultaneously doped with an impurity element to form a semiconductor film so that a delicate one continuous processing may be performed in the simple chamber 30 within a short time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention involves forming an amorphous film on a substrate placed in a reaction chamber, and then crystallizing the amorphous film in the reaction chamber or a predetermined reaction chamber. The present invention relates to a method for forming a semiconductor film and an apparatus therefor, which performs doping and mixing of impurity elements (hereinafter also referred to as doping).

(Prior Art) Conventionally, for example, after crystallizing an amorphous silicon (hereinafter abbreviated as a-St) film formed on a substrate, this crystalline silicon (hereinafter abbreviated as c-3t) is The following techniques are widely known as techniques for mixing impurity elements such as boron (B) and phosphorus (P) into a film (for example, Japanese Utility Model Application Publication No. 148113/1983, Japanese Patent Application Laid-open No. 2824/1983).
(See Publication No. 30).

■ A technique in which the c-3L film is placed in a heat treatment furnace and heat treated in an atmosphere of a gas containing impurity elements (hereinafter also referred to as doping gas) to perform vapor phase diffusion, or a glass layer containing impurity elements. A technique for diffusing impurity elements into the c-3i film by forming a glass layer and using the glass layer as a diffusion source.

■ Impurity atoms are converted into high-energy ion beams.
- This is the so-called ion implantation technology that implants into the 3L film.

(2) A technique in which an amorphous layer containing an impurity element is formed on a c-Si film, and the amorphous layer is irradiated with a laser to diffuse the impurity element and crystallize it.

(Problems to be Solved by the Invention) However, the above conventional technology has the following problems.

In the technique (2), in order to accurately control the concentration distribution in the diffusion of impurity elements, for example, surface oxidation of the film → patterning of the oxide film by etching → formation of an amorphous layer containing the impurity element → removal of the amorphous layer A semiconductor film is formed through complicated steps such as → heat treatment → oxide film removal. Therefore, there is a problem that the process is complicated and takes a long time as in the above process.

In the technique (2), impurity atoms are injected into the crystal with high energy, which damages the crystal and requires extra heat treatment (heat treatment temperature of 400 to 1000 degrees Celsius) to recover the crystal.
Is required. In particular, when impurities are implanted at a high concentration, fatal lattice defects are likely to occur, which is a problem. Furthermore, it also has disadvantages in that the device is large and the processing capacity is low, resulting in high cost.

In the technique (2), it is necessary to form an amorphous layer containing an impurity element again on the crystallized layer, which increases the number of steps, which in turn makes the process more complicated and takes longer.

Therefore, in order to solve the above-mentioned problems of the prior art, the present invention has developed a semiconductor film that can perform consistent processing from the formation of an amorphous film to crystallization and doping of impurity elements in a simple reaction chamber in a short time and with precision. The problem to be solved is to provide a forming method and an apparatus therefor.

(Means for solving problems) The above problem is solved by the following means.

That is, in a method of introducing an amorphous film forming gas into a reaction chamber, forming an amorphous film on a substrate by high frequency glow discharge, and mixing an impurity element into the amorphous film to form a semiconductor film, The substrate is placed in the reaction chamber or another reaction chamber, a gas containing an impurity element is introduced, and during glow discharge of a high frequency electric field, a DC voltage of a predetermined polarity is applied to the mounting table of the substrate, and the This problem is solved by a semiconductor film forming method characterized by irradiating an amorphous film with a laser beam to crystallize it and at the same time mix in the impurity element.

Further, a reaction chamber that can be evacuated is provided with a substrate coated with an amorphous film, a transparent window provided in the reaction chamber, and a surface of the substrate coated on the substrate from outside the reaction chamber through the transparent window. A laser beam generating means for crystallizing an amorphous film by irradiating it with a laser beam, a voltage applying means for applying a DC voltage of a predetermined polarity to the substrate mounting table, and a means for mixing an impurity element into the reaction chamber. This problem is solved by a semiconductor film forming apparatus having a gas introducing means for introducing a gas, and a high frequency electric field generating means for generating a high frequency electric field to decompose the gas by glow discharge.

(Function) Next, the function of the above semiconductor film forming method and apparatus will be explained.

The amorphous film is irradiated with a laser beam generated by a laser beam generating means. Further, the doping gas selectively introduced by the gas introducing means is decomposed during high frequency glow discharge decomposition. In this way, the impurity element is doped while crystallizing the amorphous film. At this time, a desired semiconductor film can be formed by variously controlling the magnitude and polarity of the voltage applied to the substrate side, the substrate temperature, the type and amount of doping gas, and the like.

(Example) An example according to the present invention will be described with reference to the drawings.

FIG. 1 is an overall schematic configuration diagram of a semiconductor film forming apparatus 1.
30 in the figure is a reaction chamber, and FIG. 1 shows the inside of the reaction chamber 30.

A mounting table 4 is fixed to the inner wall 18 of the reaction chamber 30 via an insulating material 6. The mounting table 4 is mainly made of stainless steel, and is heated and temperature maintained by a heater 8. The heater 8 is electrically connected to a power source (not shown) via a terminal T. Further, the mounting table 4 is also electrically connected to a direct current power source DC.

The DC power source DC can change the magnitude and polarity of the voltage applied to the mounting table 4.

A substrate 2 having a thickness of about 1 mm is fixed to the six stand 4. The substrate 2 is made of borosilicate glass (e.g. #
7059), but quartz glass or the like may also be used.

A transparent window 16 made of quartz glass is attached to a reaction chamber 30 above the substrate 2 in the figure, and a laser beam generator 28
Laser light from the can pass through.

A shutter 14 is attached to the reaction chamber 30 on the left side of the transparent window 16 in the figure, and a lever 14b closes the shielding plate 14a.
can be moved.

Note that when laser light is generated, the shielding plate 14a is moved to a position where it does not obstruct the optical path of the laser light.

The laser beam generator 28 includes an oscillator 26 and an optical fiber 2.
4, a condenser lens 22, etc., the beam diameter on the substrate 2 is adjusted to an appropriate diameter, and it can be freely moved outside the reaction chamber 30.

The reaction chamber 30 includes a gas inlet 10 for introducing an amorphous film forming gas and a doping gas used in crystallizing the amorphous film, and a gas outlet 2 for discharging these gases.
0 is set. Monosilane (SiH4) is used as the amorphous film forming gas, but disilane (Si2Ha) etc. may also be used.As the doping gas, diborane (B2Hs) etc. are used to form a P-type semiconductor film; Honefin (PH, ) or the like is used to form the . The above gas is contained in a gas cylinder (not shown), and introduced into the reaction chamber 30 by a control device (not shown). Note that the doping gas is used after being diluted with hydrogen (H2) or an inert gas. Further, the gas exhaust port 20 communicates with a vacuum pump (not shown).

In the figure, reference numeral 12.12 is an electrode, which is electrically connected to a high frequency power source RF to cause glow discharge.

Next, the operation of this embodiment will be explained.

(Formation of a-3i film) The transparent window 16 is covered with the shielding plate 14a of the shutter 14. Furthermore, after the inside of the reaction chamber 30 is sufficiently evacuated by a vacuum pump, SiH4 gas is introduced from the gas inlet IO. At this time, the inside of the reaction chamber 30 is heated to 0.01 to 5 Torr.
While maintaining the appropriate pressure of r, the temperature of the substrate 2 is kept at 100
Maintain a suitable temperature of ~500°C.

In the above condition, 13.56MHz, 5 to several 100
A high-frequency electric field is generated under conditions such as W to cause a glow discharge between the electrodes 12 and 12, and an a-3i film containing hydrogen is deposited on the substrate 2 to an appropriate thickness by the plasma generated during the glow discharge. .

Note that at this time, since the transparent window 16 is covered by the shutter 14, formation of the a-Si film on this surface is prevented as much as possible.

(Formation of Semiconductor Film) There are at least the following various methods for forming a semiconductor film by crystallizing the a-3i film formed as described above and doping with an impurity element.

<Method 1> After forming the a-3t film on the substrate 2, the shutter 14 is opened and the reaction chamber 30 is sufficiently evacuated (~10-5
Next, a doping gas diluted with hydrogen or the like (B2 H6 gas to make the semiconductor film P-type, PH3 gas to make it N-type) is introduced (0.01 to 5 torr), Furthermore, a high frequency electric field is generated at the electrodes 12.12 to decompose the doping gas in a glow discharge. In this state, the a-Sill is irradiated with a laser beam having a predetermined beam diameter by the laser beam generator 28 and scanned in a predetermined direction. Note that at this time, since the shutter 14 does not cover the transparent window 16, the laser light transmitted through the transparent window 16 becomes a laser beam and crystallizes a-3ill.

Furthermore, at this time, if the doping layer is to be deepened, a DC voltage is applied to the negative side while the laser beam is scanning, so that the impurity elements, which have mainly become cations, are deeply mixed into the crystallized c-5i film.

Figure 2 shows a layer of the a-3i film formed by scanning a laser beam in the direction SL shown in the figure from area A1 to area A2, and applying a DC voltage to the negative side just in area A2 while scanning the laser beam. As can be understood from Figure 0, which shows the result that a crystalline layer 3 is formed when
In the region A1, a shallow doped layer 3b is formed and many layers 3a are completely undoped. on the other hand,
A deep doped layer 3C is formed in region A2.

Note that the reason why the shallow doped layer 3b is formed in the region A1 is due to the plasma generated by the same high frequency electric field when the laser beam scans the region A2 and the voltage applied to the substrate 2 side.

FIG. 3 shows the crystallized c-3i layer 3 of FIG. 2 etched by wet etching using an acid or alkaline solution.
This shows the result of removing the doped layer 3b in the area A1. Soaking and etching
Note that the etching may be a dry etching method. <Method 2> In the above method 1, the polarity of the DC voltage applied to the substrate side is corrected while plasma is generated by a high-frequency electric field during laser beam scanning. Method 1 can also be achieved by inverting the value to negative.

Figure 4 shows the state of the doped layer formed in crystalline c-S i Jl 103 when the polarity of the DC voltage is alternately changed between positive and negative. When the polarity is positive, positive ions of impurity elements in the plasma are repelled to the positive electrode on the substrate side, so that a shallow doped layer 103b is formed. On the other hand, when the polarity of the voltage is negative, the cations of the impurity element are strongly attracted to the substrate side, so the deep doped layer 103c
is formed. Note that 103a in the figure is an undoped layer. By etching the film thus obtained, unnecessary shallow doped layer 103b can be removed.

<Method 3> In Method 2 above, by keeping the polarity of the DC voltage applied to the substrate 2 side negative during laser beam scanning and changing the type of doping gas introduced into the reaction chamber 30, P-type and N-type The semiconductor film can be freely formed.

FIG. 5 shows that the doping gas introduced into the reaction chamber 30 is PH, gas, or 82H6 gas to form crystalline c-Si.
Figure 2 of 0 illustrates the results obtained for layer 203.
05a is a layer in which impurity elements of phosphorus (P) and boron (B) are mixed, and is a layer in which P-type and N-type semiconductors are mixed.

In the figure, 203b is an N-type semiconductor layer because only phosphorus (P) is mixed therein. Further, 203c in the figure is a P-type semiconductor layer because only boron (B) is mixed therein. Therefore, by etching the surface of the film thus obtained to remove the layer 203a in which P-type and N-type semiconductor portions are mixed, a desired semiconductor film can be obtained in the same manner as in Method 1 above.

Although this embodiment shows an example in which a semiconductor film is formed on one substrate in the reaction chamber 30, a plurality of semiconductor films may be formed.
Furthermore, when forming various semiconductor films on a plurality of substrates, a shutter is provided above each substrate, and the semiconductor film can be formed on the substrates only when the shutter is in an open state. In addition, the reaction chamber 1 in this embodiment may be used as one chamber of an in-line method, that is, the formation of the a-3i film and the formation of the semiconductor film are performed in separate reaction chambers. . By doing so, a layer-efficient semiconductor film can be formed.

(Effects of the Invention) As explained above, the semiconductor film forming method and device of the present invention can consistently perform the formation, crystallization, and doping of an amorphous film in the same reaction chamber or in an in-line reaction chamber. can. Furthermore, it is possible to control the DC voltage applied to the substrate side and the type of doping gas while irradiating and scanning the heated substrate with a laser beam. In other words, the conventional process of diffusing impurity elements, which is complicated and takes a long time, is no longer necessary to form a semiconductor film. In addition, in order to create areas where doping is not required, it is possible to avoid applying a high frequency electric field and DC voltage during laser scanning, or to reverse the polarity of the DC voltage. The regions can be formed on the same substrate by changing the type of doping gas introduced. Furthermore, the doping depth can be adjusted by changing various conditions such as the magnitude of the DC voltage, the amount of doping gas introduced, and the high-frequency electric field.

Therefore, it is expected that a desired semiconductor film can be efficiently formed using an extremely simple device.

[Brief explanation of drawings]

An embodiment according to the present invention is shown in FIGS. 1 to 5. Figure 1 is an overall schematic diagram of the semiconductor film forming apparatus, Figures 2-
Figure 5 shows an impurity element-mixed layer of a thin film crystallized by laser scanning an amorphous film, and Figure 2 shows cases where a high frequency electric field and DC voltage are applied during laser scanning and when they are not. Figure 3 is a diagram showing the results of etching the surface layer in Figure 2, Figure 4 is a diagram showing the results of changing the polarity of the DC voltage to positive or negative during laser scanning, and Figure 5 is a diagram showing the results of etching the surface layer of Figure 2. FIG. 6 is a diagram showing the results of alternately changing the type of doping gas during laser scanning. 1. 4. 10. 14. 20. 28. 30, DC. RF, T, Semiconductor film forming apparatus 2, Substrate mounting table 8, Heater gas inlet 12, Electrode shutter 16, Transparent window Gas outlet Laser beam generator Reaction chamber DC power source High frequency power source Power terminal L, Laser beam SL, Scanning direction No. Figure 2 Applicant (663) Kyocera Corporation Agent Patent Attorney 1) Katsuhiko Hara Figure B

Claims (2)

[Claims] (1) In a method of introducing an amorphous film forming gas into a reaction chamber, forming an amorphous film on a substrate by high frequency glow discharge, and mixing an impurity element into the amorphous film to form a semiconductor film. , installing the substrate in the reaction chamber or another reaction chamber, introducing a gas containing an impurity element, and applying a DC voltage of a predetermined polarity to the mounting table of the substrate during glow discharge of a high-frequency electric field; A method for forming a semiconductor film, characterized in that the amorphous film is irradiated with a laser beam to crystallize and at the same time mix the impurity element. (2) a reaction chamber that can be evacuated, in which a substrate coated with an amorphous film is placed; a transparent window provided in the reaction chamber; a laser beam generating means for crystallizing the amorphous film by irradiating the amorphous film with a laser beam; a voltage applying means for applying a DC voltage of a predetermined polarity to the mounting table for the substrate; and a means for mixing an impurity element into the reaction chamber. A semiconductor film forming apparatus comprising: a gas introducing means for introducing a gas; and a high frequency electric field generating means for generating a high frequency electric field to decompose the gas by glow discharge.