JPH06232046A - Photochemical vapor deposition - Google Patents

Abstract

PURPOSE: To execute forming of a thin film continuously by allowing ultraviolet ray to be emitted stably from a discharge region, so as to cause a sound photochemical reaction. CONSTITUTION: A discharge region 31 and a reaction region 32 are partially partitioned by a lower anode plate 41, and an ultraviolet ray 60 from the discharge region 31 is emitted from an opening 40 which is provided to the lower anode plate 41 towards the reaction region 32 and a discharge gas (arrow 47) is supplied to the discharge region 31 from an opening 46 of a slit shape provided to a circumferential ridge of an upper anode plate 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photochemical vapor deposition method mainly used for forming an insulating thin film on the surface of a substrate (wafer), and particularly to ultraviolet rays of short wavelength (vacuum ultraviolet rays).
The present invention relates to a photochemical vapor deposition method capable of radiating a stable state.

[0002]

2. Description of the Related Art Substrate (wafer) utilizing photochemical reaction
An apparatus used for forming an insulating thin film on the surface of a glass is shown in FIG. 6 (for details, see US Pat. No. 40822).
67).

In this device, a discharge region 2 and a reaction region 3 are integrally formed inside a container 1 having a closed structure. The discharge region 2 has a horizontally-arranged annular cathode 4 and a corner of the top of the container. A discharge gas supply port 5 provided in the above, and the reaction region is provided with a base 6 on which a substrate for vapor deposition (not shown) is mounted and a raw material gas outlet 7 and the discharge region is generated. Ultraviolet rays are radiated to the reaction region to cause a photochemical reaction in the raw material gas to deposit the product on the substrate.

In FIG. 6, 6a is a supporting member, 8 is a vacuum outlet, 9 is a reflective coating, 10 is an insulating member, 11a and 11b are mounting plates, 12 is a resistance element, 13 is a high voltage power source,
4 is a reaction gas (arrow).

[0005]

However, the above-mentioned device has the following problems. (1) Since the discharge area and the reaction area are integrally formed,
During use, the source gas soars upward (arrow 14) and enters the discharge region, destabilizes the emission of vacuum ultraviolet rays, and further adheres to the surface of the cathode to stain the surface of the cathode.

(2) As a result of the above, the photochemical reaction becomes unstable and the thin film cannot be continuously formed. Another photochemical vapor deposition method is disclosed in JP-A-61-56278. However, also in this method, as shown in FIG. 7, since the discharge region 22 is formed between the pair of electrodes 21 arranged to face each other and the discharge region and the reaction region 23 are integrally formed, the same problem as described above is caused. There was a point.

In FIG. 7, 24 is a pair of pipes for supplying a discharge gas, 25 is a pipe for supplying a protective gas, 26 is a container, 27 is a pipe for supplying silane, 28
Is a pump for exhausting, 29 is another pipe for exhausting, 19 is a substrate, and 20 is a support. In view of the above problems, the present invention causes a healthy photochemical reaction by stabilizing the radiation of ultraviolet rays generated by the discharge region, and as a result,
An object is to provide a photochemical vapor deposition method capable of continuously forming a thin film.

[0008]

[Means for Solving the Problems]

(1) The discharge gas supplied to the discharge region is discharged to generate short-wavelength ultraviolet light, and the short-wavelength ultraviolet light is used to cause a photochemical reaction in the raw material gas supplied to the reaction region to form a thin film on the substrate surface. In the photochemical vapor deposition method of forming a discharge region, the upper and lower end portions of the ring-shaped cathode are spaced apart from each other in parallel with each other to form a discharge region, and the lower anode plate is separated to react below the discharge region. A region is formed, and a discharge gas is supplied into the discharge region from a slit-shaped opening formed along the periphery of the upper anode plate, and the reaction region is held in a reduced pressure state. A photochemical vapor deposition method characterized in that short-wavelength ultraviolet rays are radiated to a reaction region through an opening provided. (2) A rare gas, hydrogen or deuterium, or a mixed gas thereof is always used as a discharge gas, and an etching gas such as chlorine or carbon hexafluoride is used as a discharge gas at any time. The described photochemical vapor deposition method. (3) The illuminance of the emitted ultraviolet rays is detected by the light receiving unit and converted into an electric signal, and the magnitude of the electric signal sent from the light receiving unit is compared with a predetermined value to make the magnitude of the discharge current substantially constant. The photochemical vapor deposition method according to claim 1, which is held.

[0009]

[Action]

(1) Since the discharge region and the reaction region are partially partitioned by the lower anode plate, the invasion of the reaction gas into the discharge region can be significantly reduced. (2) Since a part of the discharge gas supplied to the discharge region is dropped along the surface of the cathode through the slit-shaped opening formed in the peripheral portion of the upper anode plate, a kind of air curtain is formed. , There is no fear of bringing the reaction gas close to the cathode. Therefore, the surface of the cathode is not polluted by attaching spatter to the cathode. (3) As a result of the above (1) and (2), stable discharge can be performed, and ultraviolet radiation can be stabilized. (4) Since the inner wall surface of each electrode and the inner wall surface of the reaction region are cleaned using chlorine gas or carbon hexafluoride gas,
A stable discharge and a healthy photochemical reaction can be maintained. (5) By controlling the discharge current, it becomes possible to keep the radiation intensity of ultraviolet rays constant. Therefore, a constant vapor deposition rate can be maintained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a photochemical vapor deposition apparatus, which is a first embodiment for carrying out the method of the present invention, in which a discharge region 31 is formed on a side close to an upper portion and a reaction area is formed on a side close to a lower portion. It is composed of a container 33 having a closed structure in which a region 32 is formed, a high-voltage DC power supply device 34 that causes a discharge in the discharge region, and the like.

The container 33 has a lid 36 having a discharge gas supply port 35 formed in the center of a circular top plate, and an annular hollow cathode 38 which is pressed against a lower surface of the lid by a seal ring 37. And a cylindrical reaction container 39 having an upper opening
And a flange and cathode 3 formed on the upper part of this reaction vessel
It is composed of a lower anode plate 41, which is narrowly attached between 8 via a seal ring 37 and has a circular hole 40 in the center thereof, and a fastener 42 for integrally fastening these,
The discharge area 31 and the reaction area 32 are vertically divided by a lower anode plate 41.

The discharge area 31 is surrounded by the cathode 38, a lower anode plate 41, and a disc-shaped upper anode plate 43 which is spaced apart from the lower anode plate 41. On the other hand, cylindrical shield plates 44 and 45 are disposed to prevent deterioration of the material of the seal ring 37 due to ultraviolet rays and leakage of ultraviolet rays. The hollow portion of the cathode 38 is used as a flow path for the cathode liquid.

The upper anode plate 43 is attached to the lower surface of the lid 36 via a proper number of bolts and nuts with a gap, and the peripheral portion of the upper anode plate 43 and the upper shield plate 4 are attached.
4, a slit-shaped gap 46 is formed in an annular shape, and the discharge gas (arrow 47) supplied from the supply port 35 is blown to the discharge region 31 through the gap 46. Has become.

At the center of the reaction region 32, that is, just below the hole 40 of the lower anode plate, a base 49 on which a substrate 48 (silicon wafer, glass substrate or the like) is placed is arranged via a supporting member (not shown). Above the table 49, there is a nozzle device 51 for spraying a source gas (arrow 50) toward the substrate 48, and on the lower surface of the table 49 is a heater 52 (electric heater, etc.) for heating the substrate 48. It is installed.

The nozzle device 51 includes an annular hollow distribution portion 53, and a nozzle portion 54 which projects inward from the inside of the distribution portion obliquely downward and has a slit-shaped nozzle formed in an annular shape at the tip. , The raw material gas (arrow 5
0) to supply pipe 55 and the like,
The supply pipe 55 penetrates the side wall of the reaction vessel 39 and extends outward, and is connected to a raw material gas storage tank (not shown). A gas inlet 56 is provided at the bottom of the reaction vessel 39 to keep the inside of the vessel under reduced pressure.

The power supply device 34 comprises a direct current high voltage power source 58 and a variable direct current resistor 59 having one terminal connected to the ground. The high voltage power source 58 has a negative electrode connected to a cathode 38 via a lead wire and a positive electrode. Is connected to another terminal of the DC resistor 59, and each of the anode plates 41 and 43 is connected to the ground via a conductor.

Next, the handling procedure and operation of this device will be described. First, the gas suction port 56 at the bottom of the reaction container is connected to a vacuum pump (not shown), and the discharge gas (from the supply port 35 is adjusted from the supply port 35 while adjusting the suction amount so that the internal pressure of the reaction container 39 is always in a predetermined reduced pressure state. An arrow 47) [rare gas, hydrogen or deuterium, or a mixed gas thereof] is supplied to the discharge region 31, while a raw material gas (higher-order silicon hydride such as silane or disilane, or the like) is supplied through the nozzle device 51. A mixed gas with a carrier gas) is supplied to the reaction region 32.

When a high DC voltage is applied between the upper and lower anode plates 41 and 43 and the cathode 38, the discharge gas causes a DC abnormal glow discharge, and a disk-shaped plasma 31a is generated in the discharge region 31. To do. This plasma 31a is an ultraviolet ray (vacuum ultraviolet ray) 60 having a wavelength of 180 nm or less.
This ultraviolet ray irradiates the upper surface of the substrate 48 through the hole 40 in the lower anode plate.

The ultraviolet rays 60 cause a photochemical reaction in the source gas (arrow 50) to generate amorphous silicon and crystalline silicon (single crystal or polycrystalline silicon), and a mixture of these is deposited on the surface of the substrate 48. Then, a thin film of silicon is formed.

When the source gas (arrow 50) is blown onto the substrate, part of it rises upward as shown by arrow 50a, but the upper periphery of the reaction region 32 is partitioned by the lower anode plate 41, so that the discharge region. The entry of the raw material gas into 31 is remarkably suppressed. Therefore, the plasma 31a is stabilized and the vacuum ultraviolet radiation is also stabilized.

When the discharge gas (arrow 47) is introduced into the discharge region 31, a part of the discharge gas blown out from the slit-shaped gap 46 is lowered along the surface of the cathode 38 (arrow 47a). Form a kind of air curtain.
Therefore, even if the raw material gas enters the discharge area, the raw material gas is not likely to approach the cathode 38 to cause abnormal discharge, and the emission of vacuum ultraviolet rays is stopped and the fixed raw material gas is attached to the cathode 38 as in the conventional case. It does not cause inconvenience.

When carrying out the method of the present invention using the apparatus of the first embodiment, an etching gas such as chlorine or carbon hexafluoride may be used as a discharge gas. According to this method, the first
In addition to forming a thin film similar to that of the above embodiment, the inner wall surface of the discharge region 31 and the inner wall surface of the reaction region 32 are self-cleaned by using an etching gas, so that more stable plasma can be generated. The etching gas is supplied from the supply port 35 as needed through a switching valve (not shown) using a well-known method.

A second embodiment of a photochemical vapor deposition apparatus for carrying out the method of the present invention is shown in FIG. In this example, since the radiant intensity of the emitted vacuum ultraviolet rays is kept constant,
A control device 61 described below is added, and other than that, there is no difference from the first embodiment. The control device 61 is
A light receiving unit 62 that detects and amplifies the intensity of vacuum ultraviolet light by photoelectric conversion and sends out an electric signal corresponding to the intensity, and a variable DC resistance by comparing the magnitude of the electric signal sent from this light receiving unit with a predetermined value. A control circuit 64 for controlling the circuit 63 and the like are used. The light receiving unit 62 and the control circuit 64 have known structures.

An arrow 65 indicates an electric signal, 66 indicates a comparator,
67 is a circuit for setting a predetermined value, 68 is a signal output conversion circuit, and arrow 69 is a control signal. Further, although the light receiving portion is attached to the distributing portion 53 of the nozzle device 51 according to FIG. 4, it may be attached to a portion close to the substrate on the table.

A photochemical vapor deposition apparatus which is a third embodiment for carrying out the method of the present invention is shown in FIG. This example
A window 72 for collecting the ultraviolet rays 71 is provided in a corner of the lid 73, and a light receiving portion 74 described below is attached to the upper portion of the window 72. Other than that, there is no difference from the second embodiment. The light receiving portion 74 has a transparent plate-shaped piece 75 made of a material that is not affected by the discharge gas, for example, magnesium difluoride, on the light receiving side thereof, and through this plate-shaped piece 75, in the discharge region. The generated ultraviolet ray 71 is received and the electric signal 76 photoelectrically converted is sent to the control circuit 64 described in FIG.
Reference numeral 77 is a seal ring, 78 is a window frame for attaching the light receiving portion to the lid, and 79 is a mounting bolt.

Further, the present invention is not limited to the above-mentioned embodiment, and for example, instead of making the cross-sectional shape of the reaction vessel 39 circular, it may be formed into an elliptical shape or a closed curve whose curvature continuously changes. Needless to say, various changes can be made without departing from the spirit of the present invention.

[0027]

As described above, the present invention exhibits the following excellent effects. (1) Since the peripheral areas of the discharge region and the reaction region are partitioned by the lower anode plate, it is possible to prevent the reaction gas from entering the discharge region. (2) Since a part of the discharge gas supplied to the discharge area is lowered along the surface of the cathode to form a kind of air curtain, the reaction gas is brought close to the cathode even when the reaction gas enters the discharge area. There is no fear of causing it.

(3) As a result of the above items (1) and (2), stable discharge can be performed, and ultraviolet radiation can be stabilized. (4) When an etching gas such as chlorine or carbon hexafluoride is used as the discharge gas, the discharge region and the like can be self-cleaned, so that stable plasma can be obtained and the vacuum ultraviolet radiation is also stabilized. (5) By controlling the discharge current, the radiation intensity of vacuum ultraviolet rays can be kept constant, and the vapor deposition rate can be kept constant.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a photochemical vapor deposition apparatus that is a first embodiment for carrying out the method of the present invention and a configuration of a DC power supply apparatus.

FIG. 2 is a view from the direction of the arrows II-II in FIG.

3 is a view from the direction of the arrow III-III in FIG.

FIG. 4 is a block diagram showing a lateral cross section of a partial cross section of a photochemical vapor deposition apparatus that is a second embodiment for carrying out the method of the present invention, and the configurations of a DC power supply apparatus and a control apparatus.

FIG. 5 is an explanatory view showing a partial cross section of a photochemical vapor deposition apparatus which is a third embodiment for carrying out the method of the present invention and a mounting position of a light receiving portion.

FIG. 6 is a diagram showing a cross section of a conventional photochemical vapor deposition apparatus and a configuration of a DC power supply apparatus.

FIG. 7 is a diagram showing a cross section of another conventional photochemical vapor deposition apparatus in a horizontally long shape.

[Explanation of symbols]

 31 …… Discharge area 32 …… Reaction area 38 …… Anion 40 …… Opening 41 …… Lower anode plate 43 …… Upper anode plate 46 …… Slit-like opening 47 …… Discharge gas (arrow) 60 …… Ultraviolet light 62 ...... Light receiving part 64 ...... Control circuit

Claims (3)

[Claims] 1. A substrate is prepared by discharging a discharge gas supplied to a discharge region to generate short-wavelength ultraviolet rays and causing a photochemical reaction in the raw material gas supplied to the reaction region using the short-wavelength ultraviolet rays. In the photochemical vapor deposition method of forming a thin film on the surface, upper and lower end portions of an annular cathode are spaced apart from each other in parallel with each other to form a discharge region, and a lower anode plate is separated to form a discharge region. A reaction region is formed below, and a discharge gas is supplied into the discharge region from a slit-shaped opening formed along the periphery of the upper anode plate, and the reaction region is maintained in a reduced pressure state. A photochemical vapor deposition method characterized in that short-wavelength ultraviolet rays are radiated to a reaction region through an opening provided in a central portion. 2. A rare gas, hydrogen or deuterium, or a mixed gas thereof is always used as the discharge gas, and an etching gas such as chlorine or carbon hexafluoride is used as the discharge gas at any time. 1. The photochemical vapor deposition method according to 1. 3. The illuminance of the emitted ultraviolet rays is detected by a light receiving section and converted into an electric signal, and the magnitude of the electric current sent from the light receiving section is compared with a predetermined value to determine the magnitude of the discharge current. The photochemical vapor deposition method according to claim 1, which is held constant.