JPS6334779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-solid surface chemical reaction device used for thin film processing, such as a CVD reaction device or a plasma etching reaction device. More particularly, the present invention relates to a surface chemical reaction apparatus having means for aiding the rate of gas-solid surface chemical reactions using deep ultraviolet radiation generated by a discharge tube.

TFDeutch.JCCFan, GWTurner, RL
Chapman, DJ Ehrlich and RMOsgood, Jr.
Recently, excimer lasers have been used to aid in the deposition and indiffusion of metals such as boron and phosphorus, as taught by J.D. in Appl. Phys. Lett. 38, 144 (1981). . In some of these photon-assisted CVDs, the attachment reaction may be accompanied by an instantaneous temperature increase (or non-equilibrium lattice vibrational excitation). However, the photons used need not be those of a coherent radiation field. It is sufficient that sufficient photon flux in the wavelength range useful for chemical reactions exists within a relatively small solid angle (a solid angle of 10 ^-3 steradians is required to provide directionality in thin film processing using surface chemical reactions). is sufficient). Typically, the energy brightness of a gas laser is greater than that of a discharge light source only because its solid angle is as small as 10 ^-6 steradians. This means that the discharge used in gas lasers is more effective than the laser produced by gas lasers for use as photon sources with directionality on the order of 10 ^-3 steradians. Furthermore, with current technology, the energy of photons obtained by laser emission is limited to 6 ev or less. However, there are many interesting photochemical reactions that require higher energy photons.

For example, etching silicon with _Cl2 gas assisted by an argon ion laser.
DJ Ehrlich, RMOsgood Jr. and TFDeu
38, 1018 (1981). In this case too, there is no need for coherence other than local and instantaneous heating effects due to the high energy density of the laser used.

By the way, many far-ultraviolet irradiation light sources that utilize electric discharge are known. In particular, S. HATTORI and T.
Jour.Appl.Phys.39, 5998 (1968) by GOTO
The annular discharge used in the pulsed argon ion laser published in 2007 is an excellent far-UV irradiation source in the spectral range of 70 nm to 100 nm. The above-mentioned document also discloses that when the argon pressure is lowered and the discharge current is increased, the spectral intensity of Ar() decreases, while at the same time the spectral intensities of Ar() and Ar() increase. This thing is
A current density of 10 ³ A/cm ² or more means that the ionization rate in the discharge is extremely high.

It is therefore an object of the present invention to use the far-ultraviolet radiation obtained with a pulsed discharge tube as a photon source for surface photochemical deposition and etching reactions. This requires a pulsed discharge with a high current density in a low noble gas pressure where the ionization rate is high and therefore divalent noble gas ions account for a significant proportion of the total ion density. In order to obtain such a high current density pulse discharge, a cathode structure that can withstand high current density is required. Therefore, in the apparatus according to the present invention, an annular discharge tube of the electromagnetic induction excitation (excitation with a voltage of 10 ^-8 dΦ/dt) type is provided which obtains an initial sustained discharge by means of high frequency electrodeless discharge means.

The invention also provides a high energy brightness photon source that can provide excellent directionality for photochemical deposition or etching reactions useful in microfabrication techniques. Therefore, in the present invention, an annular discharge tube is provided with a constricted straight part, a light emission axis extending within the straight part, and a small orifice on the light emission axis for passing a photon flux toward a chemical reaction vessel. is provided. As a result, 10 ^-2 to 10 ^-3 on the substrate surface where the photochemical reaction takes place
A photon flux with sufficient directionality of steradians can be obtained.

The discharge ultraviolet light source and the photochemical reaction vessel each have their own optimal gas annulus. In particular, far-UV radiation in discharge tubes is sensitive to the presence of low ionization energy particles. Therefore, in the present invention, an intermediate gas container is provided at one end of the light-emitting discharge tube, which can be independently evacuated to both the light-emitting discharge tube and the reaction vessel.
This intermediate gas vessel is connected to the discharge ultraviolet light source and the photochemical reaction vessel via two orifices on the light emission axis.

The light-assisted surface chemical reaction device according to the invention is also adapted for use in photochemical deposition, photochemical etching, photochemical plasma deposition, or photochemical plasma etching.

The present invention will be described below with reference to some embodiments with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the present invention in which the optically assisted surface chemical reaction device of the present invention is used for optically assisted CVD.

An ultraviolet light emitting discharge tube 1 having a diameter of 0.6 cm and a length of 10 cm is provided with a side discharge path 2 having a diameter of 1.6 cm, thereby forming an annular discharge path. An external electrode 3 for exciting and maintaining a weak high-frequency discharge is provided for a part of this annular discharge path, and this electrode 3 is supplied with a high-frequency output with a frequency of 13.56 MHz from an RF power supply indicated by block 4. Ru. A pulse transformer core 5 with a cross-sectional area of 30 cm ² is provided in the annular discharge path consisting of the light-emitting discharge tube 1 and the side discharge path 2, and a coil 6 consisting of two turns is wound around the core 5. ing.
This coil 6 is supplied with 200A and 400V from the pulse power supply 7.
pulse voltage is supplied. The duration of this pulse voltage and the number of pulse repetitions are, for example,
It can be 15μs (3 millivolts per second turns) and 500pps.

The core 5 has a toroidal shape, for example, and 2
The wound coil 6 constitutes the primary side of the pulse transformer, and the secondary side constitutes an annular discharge path. When the above-mentioned pulse voltage is applied to the primary coil 6 from the pulse power source 7, a pulsed discharge is generated in the annular discharge path that is the secondary side. in this case,
The external electrode 3 acts to generate plasma by constant discharge in a part of the annular discharge path in order to facilitate the start of pulsed discharge.

A discharge gas, for example argon, is supplied to the annular discharge channel via a first gas inlet 8 from a first gas container 9 . In this case the argon gas pressure is monitored by a pressure gauge 10 and the first mass flow control device 1
Controlled by 1.

The light emitting discharge tube 1 has an Ar() spectrum,
67.1nm, 67.2nm, 71.8nm, 72.3nm, 72.6nm,
Intense deep ultraviolet radiation of 92.0 nm and 93.2 nm is emitted in the direction of the optical emission axis 12.

The light emitting tube 1 passes through a first orifice 13 provided along the light emitting axis 12 to the intermediate gas container 1.
It is connected to one end of 4. This intermediate gas container 1
The other end of 4 is hermetically inserted into the reaction vessel 15 with an O-ring seal 16. Ultraviolet radiation from the light-emitting discharge tube 1 is introduced into the reaction vessel 15 through a first orifice 13, an intermediate gas vessel 14 and a second orifice 17 with a diameter of 3 mm.

The reactor 15 is first evacuated by a first rotary vacuum pump 18 and a diffusion pump 19, and is then maintained evacuated using the first rotary vacuum pump 18 to inject air through a second gas inlet 20. The pressure of methyl methacrylate supplied from the second gas container 21 under control by the second mass flow control device 22 is maintained at a constant value of 0.2 Torr.

A second orifice 17 to 15 on the light emission axis 12
A substrate 24 is mounted on a substrate stand 23 provided at a position of cm. The surface of substrate 24 is wetted with a monolayer of methyl methacrylate monomer molecules. The photon flux from the light-emitting discharge tube 1 generates methyl methacrylate radicals, which initiate surface polymerization of the monomer molecules. In this way, the substrate 24
The thickness of the polymer film of methyl methacrylate that is formed on top increases.

The intermediate gas container 14 is also continuously evacuated by a second rotary vacuum pump 25 to prevent gas molecules generated in or introduced into the reaction container 15 from entering the light-emitting discharge tube 1. It will be done like this. A part of the spectral components emitted backward from the light-emitting discharge tube 1 passes through the spectral filter 26 and is detected by the photodetection diode 27 and displayed on the indicator 28, and the output signal of the indicator 28 is transmitted to the substrate. It can be used to control surface chemical reactions at 24.

FIG. 2 shows a second embodiment of the invention when used in light-assisted plasma chemical deposition.

Portions designated by reference numerals 1 to 24 in FIG. 2 are substantially the same as those shown in FIG. 1 and have the same functions.

The silane gas in the second gas container 21 is supplied to the reaction container 15 via the second gas inlet 20 under the control of the second mass flow controller 22 .

A reaction plasma tube 29 is connected to the reaction vessel 15 as shown in the figure, and this plasma tube 29
A high frequency coil 30 is provided around the , and this coil 30 is connected to a high frequency current source 31 with a frequency of 13.56 MHz.
It is connected to the. Therefore, a discharge is excited in the plasma tube 29 by the coil 30 supplied with a high frequency current from the high frequency current source 31. Further, O ₂ gas stored in a third gas container 33 is supplied to the plasma tube 29 through a third gas inlet 32 under the control of a third mass flow control device 34 .

In operation, freshly grown substrates are placed on the surface of the substrate 24 mounted on the substrate stand 23 in the reaction vessel 15.
The silane molecules absorbed into the SiO ₂ film react with excited O ₂ molecules or excited O atoms to form SiO ₂ molecules, which are subsequently incorporated into the SiO ₂ film on the substrate ₂₄ . The purity of the SiO ₂ film thus formed on the substrate 24 is significantly improved by the photon flux from the light-emitting discharge tube 1 .

Referring now to FIG. 3, there is shown a third embodiment of the invention for use in optically assisted plasma etching, in which parts corresponding to FIGS. 1 and 2 are designated by the same reference numerals.

The reaction plasma tube 29, in which a discharge is excited internally by the high-frequency coil 30 to which a current with a frequency of 13.56 MHz is supplied from the high-frequency power supply 31, has a third
A mixed gas of O ₂ gas from the gas container 33 and Cl ₂ gas from the fourth gas container 35 controlled by the fourth mass flow controller 36 is supplied through the third gas inlet 32 . Ru.

Eventually, SiCl ₄ molecules are created on the surface of the silicon wafer 24' mounted on the substrate stand 23 provided in the reaction vessel 15 on the light emission axis 12, and these volatile molecules fly away from the substrate. As a result, the wafer will be etched. Although the detailed chemical reaction mechanism is unknown, the ultraviolet photon flux from the light emitting discharge tube 1 significantly enhances the chlorination of Si atoms on the surface of the Si wafer.

As shown in the three embodiments of the present invention described above, a surface chemical reaction device equipped with an annular discharge ultraviolet light source is capable of supplying a reaction gas by combining various reaction gas supply means and various substrate materials. It can be used in a variety of deposition or etching reactions, with or without a reaction plasma tube to create the excited species. Further, in order to obtain even better results, a substrate heating means can also be combined.

The annular discharge ultraviolet photon source described above also has a high energy brightness (photon flux per unit solid angle) enhanced in the direction of the light emission axis and a narrow source area limited by the second orifice. Therefore, directionality can be given to the surface chemical reaction in the direction of the light emission axis.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the apparatus of the present invention implemented in light-assisted CVD, FIG. 2 is a similar diagram to FIG. 1 showing the apparatus of the invention implemented in light-assisted plasma chemical deposition, and FIG. 1 is a diagram similar to FIG. 1 showing the apparatus of the invention implemented in light-assisted plasma etching; FIG. In the figure, 1: light emitting discharge tube, 2: side discharge path,
3: External electrode, 4: High frequency power supply, 5: Core, 6:
Coil, 7: Pulse power supply, 8: First gas inlet,
9: first gas container, 14: intermediate gas container, 1
5: reaction container, 24: substrate.

Claims (1)

[Scope of Claims] 1. A chemical reaction vessel in which a substrate whose surface is to be subjected to a chemical reaction is housed to perform a photochemical reaction, an annular discharge path, and an electromagnetic induction excitation that excites pulsed magnetic flux to the annular discharge path. a device for supplying a light emitting discharge body, and a discharge excitation means for an initial sustained discharge, the light radiation generating a photon flux of high energy brightness giving directionality to the photochemical reaction in the chemical reaction vessel. a discharge tube device; and an intermediate gas container disposed between the reaction vessel and the light-emitting discharge tube device and having means for discharging the light-emitting discharge body from the light-emitting discharge tube device and the gas from the chemical reaction vessel. A light-assisted surface chemical reaction device comprising: 2. The apparatus according to claim 1, wherein the chemical reaction vessel comprises exhaust means for maintaining the atmospheric pressure therein at a value suitable for surface photochemical reactions. 3. Claim 1, wherein the surface photochemical reaction carried out in the chemical reaction container is an adhesion reaction of a solid thin film.
Equipment described in Section. 4. The apparatus of claim 1, wherein the surface photochemical reaction in the chemical reaction vessel etches a portion of the substrate material. 5. The apparatus according to claim 1, wherein the chemical reaction vessel is equipped with a plasma device necessary for carrying out a photochemical plasma reaction. 6. The apparatus according to claim 5, wherein the photochemical plasma reaction is photochemical plasma deposition. 7. The apparatus according to claim 5, wherein the photochemical plasma reaction is photochemical plasma etching.