JPS61198733A - Method of forming thin-film - Google Patents

Abstract

PURPOSE:To obtain a thin-film having the excellent quality of film at a low temperature through a CVD method under the irradiation of beams having a wavelength of 400nm-1,000nm. CONSTITUTION:An Si substrate 2 with a clean surface is placed on a boat 3 and carried into a furnace 1, the inside of the furnace is evacuated, N2 is introduced, and a substrate temperature is controlled 16 at 300-600 deg.C under fixed pressure. Parallel beams from a xenon lamp 9 are filtered 13, and beams having a wavelength of 400-1,000nm are projected onto the substrate 2. SiO2C8 H20 is introduced, bonds are excited to the state of vibrations, a reaction is promoted, and an SiO2 film is shaped through thermal decomposition. The introduction of a raw material gas is stopped after a fixed time, the lamp is put out and heating 15 is also stopped, and the substrate 2 is cooled in N2, and extracted. According to the method, the SiO2 film can be formed through a decompression CVD method at a low temperature of 400 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a thin film forming method, and particularly to a chemical vapor deposition method using light.

[Prior art and its problems]

As semiconductor technology advances, semiconductor devices, including ultra-LSIs, are becoming more highly integrated.

Since higher integration of semiconductor circuits is achieved by miniaturizing elements, importance has been placed on techniques for forming fine and highly accurate patterns as well as techniques for forming uniform and good thin films.

One of the methods for forming thin films that has been put into practical use is the chemical vapor deposition method (CVD method). This is a method in which a desired thin film is grown by supplying/or a single gas onto a substrate and by chemical reaction in the gas phase or on the substrate surface.This method includes atmospheric pressure CVD, low pressure CVD,
This includes plasma CVD methods and the like. Among these methods, the atmospheric pressure CVD method forms a thin film at normal pressure (760 Torr), so the deposition rate is fast. However, since gas phase reactions tend to occur and it is not possible to heat the entire reaction chamber, it is necessary to arrange a means for directly and uniformly heating the substrate inside the reaction chamber. Therefore, a large number of substrates cannot be loaded at the same time, resulting in poor productivity. Furthermore, since it is difficult to control the deposition temperature, there are drawbacks such as poor devolatilization uniformity.

In addition, since the low-pressure CVD method forms a thin film under a reduced pressure of ~1 Torr, the deposition rate is slow. There is.

However, since all of these methods use thermal energy to promote the chemical reaction that forms the thin film, the formation temperature is high. 650 to SOO℃ when forming a silicon dioxide film by thermal decomposition of ethyl orthosilicate l-(8104C, H2o, TE01)
It is.

For this reason, although the thin films formed by these methods do not have any excellent advantages, their applications are limited. For example, it is not possible to use a silicon dioxide film produced by thermal decomposition of TEO8 as an interlayer insulating film for multilayer wiring using aluminum. Can not.

In the plasma CVD method, electrical energy is applied to a reactive gas under reduced pressure to create a plasma state, which promotes chemical reactions by creating chemically active excited molecules/atoms, ions, radicals, etc. This is a method of forming a thin film on top, and it is possible to lower the temperature. However, for example, plasma C from a silane (S IH4) ten nitrogen (N2) mixed gas
When a silicon nitride (SisN4) film is formed by the VD method, the composition or stoichiometric ratio of silicon (St) and nitrogen (N) may deteriorate, resulting in poor film quality or hydrogen radicals damaging the underlying layer. In addition, there are drawbacks such as hydrogen being easily incorporated into the film and film deterioration due to thermal distortion etc.

Therefore, in recent years, optical C
Research on the VD method is being actively conducted. For example, output 5
Wavelength 10 of 0W CW carbon dioxide laser (C02 laser)
, 6 μm oscillation light is used to locally heat the substrate to form a polycrystalline silicon film using silicon tetrachloride (St (J4)) as a raw material scrap, or argon fluoride (ArF), krypton fluoride, etc. A method has been proposed for forming polycrystalline silicon by photodissociation using an excimer laser such as (KrF).Since these methods all use a high-output laser as a spot light source, productivity is low. However, it has not been put into practical use due to lack of performance.

Also, using low and high pressure mercury lamps, trace amounts of water can be detected in the reactive gas. A (Hg) is added to cause a photosensitization reaction, and silicon dioxide (Sin, l) and silicon nitride (s i3 N
4) There are also examples where a film was formed. This absorbs light with a wavelength of 2537A from the added Hg or mercury lamp, becomes an excited state of Hg (3P), and collides with the reactive gas to cause energy transfer, thereby transferring and receiving energy for forming a thin film. In this case, there was a problem that mercury Hg, which is the polymerization region, was incorporated into the thin film.

As mentioned above, these conventional photoCVD methods either use high-energy short-wavelength light (λ (350 mm)) to cause photolysis of the raw material gas, or use a high-output light source to heat the substrate. It was either that.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to form a thin film with good film quality at a low temperature.

[Summary of the invention]

Therefore, in the present invention, when forming a thin film by chemical vapor deposition, the surface on which the thin film is to be formed is irradiated with light having a wavelength of 400 nm to 11000 nm.

That is, by irradiating light with a wavelength of 400 nm to 11000 nm, the bonds of the source gas are excited into a vibrational state,
I'm trying to accelerate the reaction.

By the way, when the wavelength range of the irradiation light is set to λ (350 nm), the reaction gas enters an electronically excited state and photodecomposition is likely to occur, causing a gas phase reaction. Also, when the wavelength range of the irradiation light is set to λ (1000 nm), the bonding hands of the reaction gas It is impossible to excite it into a vibrational state.

〔Effect of the invention〕

According to the present invention, it is possible to form high-quality thin films at high speed at low temperatures.

This method can be applied to both normal pressure CVD and low pressure CVD, but it is particularly difficult to form a thin film with uniform thickness and quality in normal pressure CVD. According to the method of the present invention, it is possible to form a thin film with uniform thickness and quality.

Further, the effect of the method of the present invention using light irradiation is particularly remarkable in forming a thin film at low temperatures.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a chemical vapor deposition apparatus used in the method of the embodiment of the present invention.

This device consists of a quartz reactor l with a length Im1 and an inner diameter of 25 cm, a boat 3 for supporting a substrate 2 on which a thin film is to be formed in the reactor, and a boat 3 for irradiating light from both sides of the substrate 2. first and second optical systems 4 and 5 disposed outside the reactor, a temperature control system 6 for heating and controlling the inside of the reactor 1 to a desired temperature, an exhaust system 7 and a gas supply system. 8, in which a thin film is formed by chemical vapor deposition while exciting a reactive gas into a vibrational state by irradiating the substrate 2 with light in a predetermined wavelength range.

The first and second optical systems include first and second light sources 9 and 10, each consisting of a first and second xenon lamp.
, first and second focusing lenses 11.12, and first and second interference filters 13.14 for wavelength selection, and is configured so that output growth can be selected as appropriate. .

Further, the temperature control system 6 includes a three-zone system heater 15 disposed around the reactor and a temperature controller 16, and is configured to control the temperature inside the reactor. Furthermore, the gas supply system 8 is connected to the reactor via first and second stop pulps 17, 18, and is supplied to the reactor by opening and closing operations of the first and second stop pulps 17, 18. A gas controller 19 is provided to control the amounts of TEOS gas and nitrogen (N,) gas.

Furthermore, first and second windows made of optically polished quartz are installed at both ends of the reactor with O-ring seals to prevent the transmission of the irradiated light from the first and second optical systems, respectively. It is possible.

The first window is attached to an entrance 22 that can be opened and closed, and substrates can be taken in and taken out by opening and closing the entrance 22. 23 is a pressure gauge, 24 is an automatic leak valve, and 25 is a backfill gas line.

Next, a method of forming a silicon dioxide film by thermal decomposition of TEO8 using this apparatus will be described.

First, as shown in FIG. 2(a), a single crystal silicon substrate 2 is used as the substrate 2, and after an appropriate surface cleaning treatment, it is placed on a boat 3 and carried into the reactor l through the inlet 22. do.

Next, the exhaust line 7 is driven to evacuate the inside of the reactor, and then the first stop pulp 17 is opened and N2 gas is caused to flow.
When the indicated value of the pressure gauge 23 reaches a predetermined value, the heater 15 is driven, and the temperature controller 16 controls the installation temperature to 300 to 800° C. while monitoring the substrate temperature.

After that, the first xenon lamp 9 is turned on, the first condensing lens 11 converts the light into parallel light, the first interference filter 13 selects the wavelength, and the wavelength λ=400 to 600 nm.
The surface of the substrate 20 is irradiated with light.

After confirming the temperature stability, the second stop pulp 18 is opened, TEOS gas is introduced for a predetermined period of time, and the second stop pulp 18 is opened.
As shown in Figure (b), a silicon dioxide film 100 is formed.

After stopping the introduction of the TEOS gas, the first xenon lamp 9 is turned off, the driving of the heater 15 is stopped, and the substrate 2 is cooled in a nitrogen atmosphere, and the substrate 2 is taken out from the reactor.

The silicon dioxide film thus formed became 2 to 100 times thicker within the same time at 400 to 800° C. compared to the conventional case without irradiation with light. That is, 2
~100 times faster deposition rates can be obtained. Furthermore, the film thickness and film quality are extremely uniform and good.

Further, although it has been impossible to form a silicon dioxide film at a low temperature of 400° C. using the conventional low pressure CVD method, it is possible to form a silicon dioxide film using the method of the present invention.

In the embodiment, a case has been described in which light irradiation is performed from the front side of the substrate, but as another embodiment of the present invention, only the second xenon lamp 10 is turned on and light irradiation is performed from the back side of the substrate. You may do so. That is,
For example, as shown in FIG. 3(a), there are connection holes 201 on the surface.
A single crystal silicon substrate 200'i on which a silicon thermal oxide film 202 is formed so as to have a silicon thermal oxide film 202 is used as the substrate 2.
As shown in Figure (b), the wavelength λ=4 from the back side of the substrate 200.
A silicon dioxide film 203 is formed in the same manner as in the previous embodiment while performing light irradiation of 00 to 600 ntn. At this time, the single crystal silicon base &200 has a wavelength λ = 400 to 60
The thermal oxide film 202 transmits 0 nm light, or the thermal oxide film 202 does not transmit this source. Excitation is performed to selectively increase the film deposition rate in this area, and as a result, it is possible to obtain a flat surface shape with small steps.

In yet another embodiment, both the first and second optical systems may be driven to irradiate sources with different wavelengths. That is, using a substrate as shown in FIG. 3(a), as shown in FIG. 4, light of a wavelength λ1 that excites the reaction gas into a vibrational state is irradiated from the surface side of the substrate, and
From the back side, as in the other embodiments described above, light with a wavelength λ2 that transmits through single crystal silicon but not through the thermal oxide film is irradiated. As a result, a silicon dioxide film can be selectively and rapidly formed within the connection hole, and a silicon dioxide film with a flat surface can be formed in a shorter time.

In addition, in the above examples, the formation of silicon dioxide group by TEO8 thermal decomposition was shown, and in addition, formation of polycrystalline silicon film by monosilane thermal decomposition, monosilane/
Formation of silicon nitride film from and ammonia, formation of aluminum film using inbutylaluminum, trimethylaluminum, aluminum trichloride, aluminum tribromide, and formation of aluminum alloy film by adding sila/, tungsten hexafluoride・Formation of tungsten film from tungsten pentachloride and hydrogen, formation of tungsten silicide film by adding silane, formation of molybdenum film, titanium film, molybdenum silicide film,
The method of the present invention can also be applied to the formation of other thin films, such as the formation of titanium silicide films.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the chemical vapor deposition @ system used in the method of the embodiment of the invention, FIGS. 2(a) and (b) are diagrams showing the thin film forming process of the embodiment of the invention, and FIG. Figures (a) and (
b) is a diagram showing the M-film forming process of another embodiment of the present invention;
FIG. 4 is a diagram showing a thin film forming process according to still another embodiment of the present invention. 1... Reactor, 2... Substrate, 3... Boat, 4...
... first optical system, 5 ... second optical system, 6 ... temperature control system, 7 ... exhaust system, 8 ... gas supply system, 9.
・・First light source, lO・−・i@2 light source, 11...
First condensing lens, 12...-Second condensing lens,
13... First interference filter, 14... Second interference filter, 15... Heater, 16... Temperature controller, 17... First stop pulp, 18...・Second
stop valve, 19... gas controller, 20...
First window, 21... Second window, 22... Entrance, 23
...Pressure gauge, 24...Automatic leak valve, 25...
Backfill scrap line, 100... silicon dioxide film, 200... single crystal silicon substrate, 201...
Connection hole, 202... thermal oxide film, 203... silicon dioxide film. Figure 2 (Q) Figure 2 (b) Figure 3 ((1) λ

Claims (1)

[Scope of Claim] A method for forming a thin film, characterized in that when forming a thin film on a substrate by chemical vapor deposition, the substrate is irradiated with light having a wavelength of 400 nm to 1000 nm.