JPH01183809A - Photo assisted cvd system - Google Patents

Abstract

PURPOSE:To prevent the blooming of an ultraviolet lamp, a light-transmitting window, etc., and to increase a film formation rate by passing a gas, which generate no solid matter even when it is excited and decomposed, from a region on the light source side, through a gas passage hole, into a reaction region to react the gas. CONSTITUTION:A substrate 10 is set onto a substrate stage 11, and the inside of a reaction vessel 1 is evacuated by an exhauster. Ultraviolet rays from ultraviolet lamps 5 transmits through a cooling preventive pipe 6, passes a region in a light source chamber 3, and transmits light-transmitting windows 2 and reach into a region in a reaction chamber 4. A gas A8 and a gas B13 do not generate solid matters even when they are excited and decomposed by light, but they are reacted with a gas C15, thus depositing a desired film onto the substrate 10. Since the gas A8 is blown off from the light source chamber 3 to the reaction chamber 4, the gas C15 hardly reaches to the light-transmitting windows 2, and a reaction product is difficult to adhere on the light-transmitting windows 2. Accordingly, the blooming of the light-transmitting windows 2 due to the reaction product formed is prevented while a sufficient film formation rate can be acquired.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to optical CVD (Chemical Vap
□Relates to an apparatus for forming a thin film on a substrate surface using a r-Deposit1on method.

[Conventional technology]

The CVD method is a method of causing a chemical reaction in a gas phase to generate molecules or atoms that do not become a gas phase at the gas temperature, and depositing them on a substrate to form a film.

In the conventional CVD method, the temperature is heated to around 1000°C, a reactive gas containing Si atoms is supplied, and the reactive gas containing Si atoms is supplied through thermal dissociation or during plasma discharge to form plasma particles. Energy is used to dissociate a reactive gas containing Si atoms to form St, SiO□, 5 on the substrate.
A thin film such as iiN4 is formed. In the field of semiconductor manufacturing, etc., these methods tend to cause damage to the substrate due to heat or ions in plasma.

As an alternative method, there is a photo-CVD method. In this method, a reactive gas is supplied to the area irradiated with light, and a thin film of Si, Stow, Sis N 4, etc. is formed on the substrate by a photochemical reaction. This method uses 1000°C
There is no need for heating to high temperatures before and after, and since plasma is not used, there is an advantage that there is no damage caused by heat or damage caused by plasma ions.

FIG. 8 shows the basic configuration of a thin film forming apparatus using this photo-CVD method. 51 is a reaction chamber that can be depressurized to a high vacuum state;
2 is a light source that emits a wavelength necessary for photochemical reaction; 53 is a light transmission window that can transmit light from the light source; 54 is a reactive gas; 55 is a reactive gas inlet; 56 is a reactive gas containing Si atoms; 57 is a reactive gas inlet, 58 is a reactive gas exhaust port, 59 is a substrate on which a thin film is formed, 60 is a heater for the substrate, and 61 is a substrate mounting table.

Conventionally, in such an apparatus, when the reaction gas 56 and the reaction gas 54 containing Si atoms are respectively supplied to the reaction chamber 51 from the reaction gas inlets 55 and 57, the reaction gas 56 containing Si atoms
The reactant gas 54 causes a photochemical reaction by the light irradiated by the light source 52, deposits a reaction product on the substrate 59, and forms a thin film.The gas 61 after the reaction is discharged from the exhaust port 58.

However, in this type of device, there is a problem that reaction products generated by photochemical reactions adhere to the light transmission window, weakening the light from the light source 52, and preventing the reaction gas from being irradiated with light.

An optical CVD apparatus that solves this problem is described in Japanese Patent Application Laid-Open No. 196542/1983.

This photo-CVD apparatus introduces an inert gas flow 115 into a light source chamber 102 disposed within a photochemical vapor deposition apparatus 101, as shown in FIGS. reaction chamber 1 through a light-transmitting window 104 having
It is blown out on 03. The substrate 108 placed on the substrate pedestal 109 is caused to react with the gas excited and decomposed by the light from the low-pressure mercury lamp 106 in the light source chamber 102 and the gas flow 111 supplied from the inlet 113 of the reaction gas inlet 110. A thin film is deposited on the surface. In addition,
In the figure, 107 is a light reflecting plate. Therefore, this light C
In the VD device, adhesion of reaction products to the light transmission window 104 is suppressed.

[Problem that the invention seeks to solve]

However, this photo-CVD apparatus has problems such as a decrease in the film formation rate and a deterioration in the film thickness distribution.

That is, the inert gas 1 is supplied from the light source chamber 102 toward the substrate 108.
15. In other words, since a gas that does not contribute to the reaction is sprayed, the concentration of the reactive gas 111 on the light irradiated surface of the substrate 108 is lower than when it was supplied, resulting in a decrease in the film formation rate. The amount of inert gas required to prevent fogging of the light-transmitting window is normally several to ten times as large as the amount of reactant gas.
This effect is particularly large. Furthermore, if the flow rate of the reaction gas 111 is increased to improve this, the total pressure inside the reaction chamber 103 will increase, which will shorten the mean free path of the gas molecules, resulting in a change in the film thickness distribution on the substrate 108. Deteriorate.

Therefore, in the partial pressure in the reaction chamber 103, the inert gas 1
15 is the highest, it is difficult to obtain a sufficient film formation rate, and in addition, since the inert gas 115 is blown onto the substrate 108, the film formation rate is further reduced.

An object of the present invention is to solve the problems of the prior art described above, to prevent fogging of a light transmission window due to reaction products generated by a photochemical reaction, and to obtain a sufficient film formation rate.
Another object of the present invention is to provide a photo-CVD apparatus that can make the film thickness distribution uniform.

[Means for solving problems]

The above purpose is to divide the inside of the reaction vessel into a light region A and a reaction region where light is irradiated from the light source by a partition wall having gas distribution holes, and to do so without supplying inert gas to the light source region.
A gas that is excited and decomposed by light but does not produce solid matter and that forms a thin film is introduced, and a gas that is excited and decomposed by light and reacts with the above gas to form a thin film on the substrate. is introduced into the reaction region.

[Action] Pressure for photochemical reaction (usually 100 mtorr~
At several torr), the partial pressure of the inert gas for preventing fogging of the light-transmitting window can be O, and the reactive gas (i.e., is excited and decomposed by light to form a solid and reacts with the gas from the light source region). This makes it possible to increase the partial pressure of the gas used to form a thin film, thereby increasing the film formation rate.

Alternatively, since the reaction products due to photochemistry are generated in a region separated from the region on the light source chamber side, the reaction products do not flow into the region on the light source chamber side, so that fogging of the light transmission window can be prevented.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic cross-sectional configuration diagram showing a first embodiment of the present invention;
FIG. 2 is a plan view of the light transmission window in FIG. 1.

This optical CVD apparatus includes a light source chamber 3 as a light source area and a reaction chamber 4 as a reaction area, with a light transmitting window 2 inside the reaction vessel l.
It is divided into. As shown in FIG. 2, the light transmission window 2 is made of synthetic quartz glass and has a large number of gas flow holes 2a formed at equal intervals.

A plurality of ultraviolet lamps 5 are installed in the light source chamber 3, and these ultraviolet lamps 5 are surrounded by a cooling prevention tube 6 made of synthetic quartz glass and having an elliptical cross section and capable of transmitting ultraviolet rays.

A light reflecting plate 7 is installed above the ultraviolet lamp 5.
A reaction gas pipe A9 for introducing gas A8 is arranged on the side wall of the light source chamber 3.

The reaction chamber 4 includes a substrate mounting table 11 on which a substrate 10 is placed.
is installed, and a heater 12 for heating the substrate 10 from the bottom surface of the substrate mounting table 11 via the substrate @ placement table 11 is installed. A reaction gas pipe B14 for introducing gas B13 is disposed on the side wall of the reaction chamber 4 near the light transmission window 2, and a gas C1 is provided below the reaction gas pipe B14.
A reaction gas pipe C16 for introducing 5 is provided.

Further, an exhaust port 17 is arranged on the wall surface of the reaction chamber 4 on the side corresponding to the reaction gas pipe B14 and the reaction gas pipe C16.

Next, the operation of the optical CVD apparatus configured as described above will be explained.

First, the substrate IO is set on the substrate mounting table 11, and the inside of the reaction container 1 is evacuated by an exhaust device (not shown). Next, when the heater 12 is energized and the substrate 10 is heated to a predetermined temperature via the substrate mounting table 11, the ultraviolet lamp 5 is turned on.

The ultraviolet light from the ultraviolet lamp 5 passes through the anti-cooling tube 6, passes through the area of the light source chamber 3, and then passes through the light transmission window 2 to reach the area of the reaction chamber 4. At this time, gas A8 is introduced into the light source chamber 3 from the reaction gas pipe A9, gas B13 is introduced into the reaction chamber 4 from the reaction gas pipe B14, and gas C15 is introduced from the reaction gas pipe C16, respectively.

Here, gas A8 and gas B13 are gases that do not produce solid substances even when excited and decomposed by light and serve as raw materials for thin films. Further, gas C15 is excited and decomposed by light, and gas A
8 or gas B13 to form a thin film.

This gas C15 is normally a gas that produces solid matter when it is decomposed by excitation with light, but the gas introduced into the reaction chamber 4 does not necessarily have to produce solid matter through excitation decomposition; Any gas may be used as long as it is capable of producing a desired film through a photochemical vapor phase reaction with the above gas.

Therefore, the type of each gas should be arbitrarily selected depending on the required material of the thin film, examples of which are shown in Table 1.

Table 1 As shown in Table 1, gas A8 and gas B13 do not produce solid substances even when they are excited and decomposed by light, but a desired film is deposited on the substrate 10 by reacting with gas C15.

Usually, this reaction pressure is from several 100 m torr to several torr.
rr, but since the capacity of the vacuum pump is constant, the total amount of gas that can flow in this pressure range is limited. In the first embodiment shown in FIG. 1, since no inert gas is used to prevent fogging of the light transmission window 2, more reaction gas can flow even at the same pressure. Therefore, the partial pressure of the reaction gas becomes high, and the film formation rate can be increased.

In addition, since the light transmission window 2 is formed with a large number of gas flow holes 2a as shown in FIG.
Since the gas C15 is blown out, the gas C15 rarely reaches the light transmission window 2, and reaction products are less likely to adhere to the light transmission window 2. Furthermore, since the gas B13 is flowing parallel to the light transmitting window 2 on the lower surface side of the light transmitting window 2, the reaction products flow into the light source chamber 3 side from the gas flow hole 2a formed in the light transmitting window 2. can be more reliably prevented.

Next, the irradiation intensity at 254 nm and 185 nm, which are the emission wavelengths of a low-pressure mercury lamp used for optical CVD, is usually determined by the mercury vapor pressure in the discharge tube.

Furthermore, the mercury vapor pressure in the discharge tube is determined by keeping the temperature at the base of the discharge tube constant (30°C to 40°C) in the case of commercially available low-pressure mercury lamps.
°C) and is devised to keep it at an appropriate value at all times. However, when inert gas flows into the vicinity of the discharge tube,
The surface of the discharge tube is cooled by the gas, the mercury concentration in the discharge tube changes, and the irradiation intensity of the emission wavelength decreases as shown in FIG.

Furthermore, when an inert gas is introduced, the irradiation intensity decreases, and the energy necessary to excite and decompose the reaction gas cannot be obtained, resulting in a decrease in the film formation rate. This relationship is shown in FIG.

In the first embodiment, since the anti-cooling tube 6 is installed to cover the ultraviolet lamp 5, the ultraviolet lamp 5 is always
The surface of the film can be maintained at a predetermined temperature, the maximum energy required to excite and decompose the reaction gas can be applied to the reaction gas, and the film formation rate can be improved.

Note that instead of the cooling prevention tube 6, a cooling prevention plate may be arranged only in the area where the gas A8 introduced into the light source chamber 3 directly collides with the ultraviolet lamp 5 or in the root portion of the discharge tube.

The results of film formation according to the above embodiments are shown in FIG. Third
As is clear from the figure, the irradiation intensity does not decrease even when gas A8 is introduced into the reaction vessel, and the partial pressure of gas C15 is also high.
Therefore, the film formation rate is improved by 5 to 7 times.

The present invention also includes a case in which, in the first embodiment, a light transmission window is installed as a part of the wall of the reaction container on the side of the light source region, and the ultraviolet lamp is arranged outside the container.

FIG. 4 is a sectional view showing another embodiment of the light transmitting window in the optical CVDq apparatus of the present invention.

In the light transmission window 21, the gas flow holes 22 have a tapered shape in which the cross-sectional area of the gas passage gradually increases from the light source chamber 3 side toward the reaction chamber 4 in the cross-sectional direction of the light transmission window 21.

A method for improving the effect of preventing fogging of the light transmission window 21 is to increase the blowing speed of the gas A8 and to increase the surface of the opening on the reaction chamber 4 side that is covered with the gas A8. In the case of the light transmission window 21 shown in FIG. 4, the pressure difference between the light source chamber 3 side and the reaction chamber 4 is large, the blowing speed of the gas A8 is high, and the gas A8 flows along the taper on the reaction chamber 4 side. Since the gas is blown out while spreading, the area covered by the gas A8 on the side surface of the reaction chamber 4 is larger than that of the light transmitting window 2 having a cylindrical gas flow hole 2a as shown in FIG.

FIG. 5 is a schematic cross-sectional configuration diagram showing a second embodiment of the optical CVD apparatus of the present invention.

In FIG. 5, a reaction vessel 31 is partitioned by a partition wall 33 in which a small-diameter gas flow hole 32 is formed in the center thereof, and an excitation chamber (light source chamber) 34 as a light source region and a formation chamber ( The reaction chamber is divided into 35 sections. A light transmission window 36 is arranged on the ceiling surface side on the side of the excitation chamber 34, and an ultraviolet lamp 37 is arranged above the light transmission window 36.

A reaction gas pipe A39 for introducing gas A38 into the chamber is disposed on the side wall of the excitation chamber 34.

Substrate mounting table 4 for mounting the substrate 40 in the forming chamber 35
1 is installed, and a heater 42 for heating the substrate 40 via this substrate mounting table 41 is installed. Further, a reaction gas pipe C44 for introducing gas C43 into the chamber is disposed on the side wall of the forming chamber 35. This reaction gas pipe C
An exhaust port 45 is provided in the side wall of the forming chamber 35 corresponding to the exhaust port 44 .

Next, the operation of the optical CVD apparatus of the second embodiment will be explained.

Gas A3 as exemplified in Table 1 from reaction gas pipe A39
B is introduced into the excitation chamber 34. This gas A3B is excited by the light from the ultraviolet lamp 37 that passes through the light transmission window 36. The excited gas A3B passes through the small-diameter gas flow hole 32 formed in the partition wall 33 and enters the low-pressure forming chamber 35 through the corrugated plate reaction gas pipe C44, where it undergoes a chemical reaction with the gas C43 as exemplified in Table 1. The products generated by this are deposited on the substrate 40 to form a thin film.

In this case, the exhaust gas is discharged through the exhaust port 45 on the side of the forming chamber 35, and the excitation chamber 34 and the forming chamber 35 are communicated with each other through the small-diameter gas flow hole 32, so that the pressure in the excitation chamber 34 is lower than that in the forming chamber. 35, and the excited and decomposed gas of gas A38 is ejected from the gas flow hole 32. Therefore, the reaction products generated in the formation chamber 35 flow into the excitation chamber 34. Therefore, clouding of the light transmission window 36 due to adhesion of reaction products is prevented, and the intensity of light from the ultraviolet lamp 37 can be kept constant at all times, eliminating the need for cleaning the light transmission window 36.

In such a device, for example, S using SiH4 and 0□
When tow is formed on the substrate 40, 02 is supplied from the reaction gas pipe A39, and 02 is excited by irradiation from an ultraviolet lamp 37 having a wavelength of 180 to 300 nm through the light transmission window 36. 0□ forms 03 with light having a wavelength of 180 to 300 nm, and further generates 0 radical. The generated 0 radicals flow from the excitation chamber 34 to the formation chamber 35 through the gas flow hole 32. 200 radicals are reaction gas pipe 44
reacts with SiH4 introduced into the formation chamber 35 from
, and deposited on the substrate 40.

Further, in the apparatus in the second embodiment, for example, S i H
When forming 5isNa using a and NH, NHx is introduced from the reaction gas pipe A39 and irradiated through the light transmission window 36 with an ultraviolet lamp 37 that emits a wavelength of 210 nm or less to excite NH. NH, generates NH,, NH,N with light having a wavelength of 210 nm or less. The excited NH,, NH, and N are transferred from the excitation chamber 34 to the gas distribution hole 32.
The gas flows through the formation chamber 35 and reacts with 5iHa supplied from the reaction gas pipe C44 to produce St3Ng, and the substrate 4
Deposit on 0.

FIG. 6 is a schematic cross-sectional configuration diagram showing a third embodiment of the optical CVD apparatus of the present invention.

This CVD apparatus differs from the apparatus of the second embodiment in that, as shown in the figure, an excitation chamber 34 and a formation chamber 35, which are partitioned by a partition wall 33 having gas circulation holes 32, are arranged horizontally. . Therefore, in FIG. 6, the same or equivalent members as in FIG. 5 are indicated by the same reference numerals. The third embodiment also has the same effects as the second embodiment shown in FIG.

FIG. 7 is a schematic cross-sectional configuration diagram showing a fourth embodiment of the optical CVD apparatus of the present invention.

This optical CVD apparatus differs from the second embodiment shown in FIG. 1 in that an ultraviolet lamp 37 is disposed within an excitation chamber 34 and a light transmission window 36 is omitted. Therefore, FIG. 7 also has the same structure as the first embodiment shown in FIG.
Or equivalent parts are indicated by the same reference numerals.

In addition to the effects achieved by the apparatus of the second embodiment shown in FIG.
The ultraviolet lamp 3 is built in and does not have a light transmission window 37.
The intensity of the light from 7 can be increased, so that more reaction gas A3B is excited in the excitation chamber 34, and the deposition rate of the thin film produced in the formation chamber 35 becomes faster.

〔Effect of the invention〕

As described above, according to the present invention, a gas that does not produce solid matter even if it is excited and decomposed is introduced into the region on the light source side where an ultraviolet lamp or the like is installed, and excited species such as radicals generated by the excitation and decomposition are absorbed into the gas. Since it is introduced into a reaction area divided by a partition wall with circulation holes and reacted there, it is possible to prevent fogging of ultraviolet lamps and light transmission windows installed on the light source side, and to maintain a constant irradiation intensity at all times. This improves the film formation rate and eliminates the need for cleaning work such as ultraviolet lamps and light transmission windows.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional configuration diagram showing a first embodiment of the optical CVD apparatus of the present invention, FIG. 2 is a plan view of a light transmission window in the optical CVD apparatus of FIG. 1, and FIG. A graph showing the relationship with the film formation rate, FIG. 4 is a cross-sectional view showing another embodiment of the light transmission window in the optical CVD apparatus of the present invention, and FIG. 5 is a graph showing the second embodiment of the optical CVD apparatus of the present invention. A schematic cross-sectional configuration diagram showing
FIG. 6 is a schematic cross-sectional configuration diagram showing a third embodiment of the optical CVD apparatus of the present invention, FIG. 7 is a schematic cross-sectional configuration diagram showing a fourth embodiment of the optical CVD apparatus of the present invention, and FIG. Conventional optical CVD
A schematic cross-sectional configuration diagram showing an example of the device, FIG. 9 is a conventional optical C
A schematic cross-sectional configuration diagram showing another example of the VD device, FIG. 1O is a plan view of the light transmission window in the device of FIG. 9, and FIG. FIG. 12 is a graph showing the relationship between lamp surface temperature and lamp irradiation intensity, and FIG. 13 is a graph showing the relationship between light irradiation and film formation rate in a conventional photo-CVD apparatus. 1.31... Reaction vessel, 2.33...
Partition wall, 2a, 32... Gas distribution hole, 3, 34
・・・・・・Light source chamber (excitation chamber), 4.35・・・・・・
Reaction chamber (formation chamber), 5゜37... Ultraviolet lamp, 6... Cooling prevention tube, 7... Light reflecting plate, 8.38... Gas A, 9.39...
Reaction gas tube A, 10.40...Substrate, 11.4
1...Substrate mounting table, 12.42...Heater, 13...Gas B, 14...Reaction gas pipe B, 15.43... ...Gas C, 16, 44
...Reaction gas pipe C, 17°45...Exhaust port. Agent Masaru Nishimoto, Patent Attorney - Figure 1 Figure 2 Figure 2: Light transmission E3 near Ii source! 4: β response official 5゛ elephant datoi izumi u〉pu 6°7gf-1' defense suga 9.7Q Kunkasu good A10: X m +42f:1Ejf
S￥-B E'! l;:=n7 Kan C Figure 3 Time Figure 4 Figure 5 Figure 6 Figure 9 Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] (1) A reaction vessel in which a gas phase chemical reaction using light energy is carried out is divided into a light source region and a reaction region by a partition wall having gas circulation holes, and the light source region is provided with a reaction vessel that is excited and decomposed by light. A substrate is provided with a gas inlet for introducing a gas that does not produce solid matter and is a raw material for a thin film, is excited and decomposed by light in the reaction region, and is placed in the reaction region to react with the gas. An optical CVD apparatus characterized by being provided with a gas inlet and an exhaust port for depositing a thin film on a surface.