JPS6152230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a film by vapor deposition.

Recently, a reaction vessel was filled with a photochemically reactive gas consisting of silicon hydrogen compound gas mixed with mercury vapor, a substrate was placed there, and ultraviolet rays at wavelengths of 253.7 nm and 184.9 nm from a mercury lamp were irradiated from outside the reaction vessel. However, by depositing amorphous silicon (hereinafter referred to as a-Si) on the substrate through the photosensitization reaction of mercury, and by adding gases containing oxygen molecules and nitrogen molecules, insulation of silicon dioxide and silicon nitride can be improved. Depositing films and protective films is being investigated.
(Public Patent Publication No. 54-163792, Nikkei Electronics, February 15, 1982 issue) However, the coatings formed by this method such as a-Si, silicon dioxide, silicon nitride, etc. cannot be applied to the process of forming microelectronic circuits. At the time, there was a problem that the mercury used as a photosensitizer had an adverse effect.

Therefore, recently, without using mercury photosensitizer,
A method has been announced in which a photochemically reactive gas consisting of disilane is directly photodecomposed by irradiating it with ultraviolet light with a wavelength of 184.9 nm from a low-pressure mercury lamp, and a-Si is deposited on a substrate. (Jap.J.Appl.Phys. 22 (1983)
L46) The film formed by this method can eliminate the harmful effects of mercury mentioned above, however, the film formation rate is 0.025 nm/
It is slow, about seconds, and is far from practical use.

Therefore, the object of the present invention is to develop a method for forming films of a-Si, silicon dioxide, silicon nitride, etc. without the harmful effects of mercury at a sufficiently fast rate for practical use when applied to the formation process of microelectronic circuits. This is what we provide. And its composition is
Discharge energy is Q (Joule), effective discharge volume is V
(cm ³ ), current half width is t (msec), Q/
Controlling V・t≧10 ² Joule/cm ³・msec, flashing a discharge gas for ultraviolet radiation selected from helium or hydrogen gas under these conditions, and irradiating this flash onto the photochemically reactive gas. , is characterized in that a film made of a decomposition product of a photochemically reactive gas is formed on a substrate.

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

In FIG. 1, a flash discharge lamp 1 is provided with electrodes 2 at both ends thereof, and a window 3 made of lithium fluoride is provided below the central portion thereof. To give an example of each numerical value, the distance L between the electrodes 2 and 2 of this flash discharge lamp 1 is 10 cm, the tube inner diameter D is 1 cm, and therefore the effective discharge volume is π/4・D ²・L=8cm ³ As a power source, the capacity of the discharge capacitor is 20π.
F, the discharge voltage is 10000V, therefore the discharge energy is Q=1000Joule, and the current half-width, which is the time width at half the height of the peak high current value, is controlled to be 0.2 m·sec for discharge. A discharge gas for ultraviolet radiation is sealed inside the flash discharge lamp 1, and the space constitutes a discharge region 4 in which flash light is emitted. On the other hand, a substrate 7 is disposed in the center of the reaction vessel 5 supported by a support 6. A photochemically reactive gas G consisting of silane or disilane is supplied from one side of the reaction vessel 5, and the substrate 7 is reactive gas G
It is covered by. A window 8 made of lithium fluoride is provided above the center of the reaction vessel 5, and this window 8 is connected to the flash discharge lamp 1.
The ultraviolet rays generated by the flash discharge pass through the windows 3 and 8 and are irradiated onto the substrate 7. Therefore, a reaction vessel 5 in which the photochemically reactive gas is in the ultraviolet region 9
The product is photodecomposed internally and deposited on the substrate 7 to form a film. When helium gas is sealed as a discharge gas in the flash discharge lamp 1 at a pressure of 10 Torr, in addition to visible light, ultraviolet rays of 200 nm or less are strongly emitted, and silane and disilane are efficiently photodecomposed and deposited on the substrate 7. A film is formed at a rate of approximately 0.1 nm/time. Therefore, if the flash emission cycle is set to about 3 to 5 times/second, the film formation rate will be approximately 0.4 nm/second, which is 16 times faster than the above-mentioned conventional example that does not use a mercury photosensitizer. and can be put to practical use.

By the way, in flashlight emission, the amount of ultraviolet radiation depends on Q/V・t, so considering Q/V・t as a factor, Q/V・t should also be sufficient so that a sufficient film formation rate can be obtained. It is better to use a large value. According to various experiments, when the discharge gas is helium or hydrogen gas, a sufficient effect can be obtained at 10 ² Joule/cm ³ ·msec or more.

Next, to give an example of ultraviolet rays emitted under certain discharge conditions in these discharge gases, for helium, Q = 500 Joule, T = 0.05 msec, voltage 20 KV
In hydrogen, ultraviolet light with a wavelength of 400 to 100 nm is Q
=500Joule, t=0.05msec, 120~ at voltage 20KV
Each was strongly irradiated with 170 nm ultraviolet light. In each case, the flash was emitted at a cycle of 1 to 5 times per second, so the a-Si film was 0.1 to 5 times per second.
Formed at a speed in the range of 1.0 nm/sec.

By the way, since the transmittance of ultraviolet rays in the air is extremely poor, in the embodiment shown in FIG.
They are placed close together so that it becomes 0. Therefore, as another embodiment, as shown in FIG. 2, the efficiency can be further improved by providing the discharge region 4 and the reaction region 9 in one reaction vessel 5. In this embodiment, the discharge region 4 and the reaction region 9 are separated by a partition plate 10 having a window 3 made of lithium fluoride.
The window 3 is held under pressure between the two, and the window 3 can be replaced by fitting the fastening fitting 16. This is because, in the embodiment shown in FIG. 1, a-Si is deposited on the inner surface of the window 8, which may obstruct the transmission of ultraviolet rays. Then, you can replace it and keep it in a state where ultraviolet rays can easily pass through it. By the way, when the discharge area 4 is composed of a single flash discharge lamp 1 as in the embodiment shown in FIG. 1, the effective discharge volume V can be simply calculated using π/4・D ²・L. However, when the discharge area 4 is configured by disposing the electrode 2 in the reaction vessel 5 as in the embodiment shown in FIG. The distance in the direction perpendicular to the axis where the discharge is attenuated can be calculated as the discharge radius. However, since this discharge radius differs depending on the position on the axis, its average value is adopted. In general commercially available straight tube flash discharge lamps, the discharge radius is defined by the inner surface of the arc tube, so the above average distance at which visible light is attenuated to 1/10 is approximated as the discharge radius of the straight tube flash discharge lamp. can be regarded as the same.

Next, FIG. 3 shows still another embodiment, but in this embodiment, the discharge region where flash light is emitted and the reaction region where the photochemically reactive gas is photodecomposed are not separated, so that flash light emission is normalized. This allows the photochemically reactive gas to be directly irradiated without passing through objects such as lithium windows. In FIG. 3, a first gas pipe 11 is located at the center of the top surface of a stainless steel reaction vessel 5, and two second gas pipes are located near both ends of the top surface.
Gas pipes 12 are provided respectively, and a first gas pipe 12 is provided.
A photochemically reactive gas such as silane or disilane is supplied from a gas pipe 11, and a discharge gas for ultraviolet radiation is supplied from a second gas pipe 12. Reaction container 5
A pair of electrodes 2 are disposed facing each other on the upper side of the electrode 2, and the space between the electrodes 2 and 2 serves as a discharge region 4 and a reaction region 9. The discharge gas mixed with the photochemically reactive gas fills the discharge region 4 in a predetermined amount, and is discharged to the outside of the reaction vessel 5 by the vacuum pump 13. Furthermore, a third gas pipe 14 is provided in the vicinity of the electrode 2 to supply electrode protection gas. In the center of the discharge region 4, an alumina support 6 is arranged to be movable up and down, and a substrate 7 on which a coating is to be formed is placed.

To show an example of operation in the apparatus having the above configuration, the substrate 7 is a glass plate with a thickness of 1 mm and a diameter of 100 mm,
Silane gas is supplied from the first gas pipe 11 at 2 c.c./min.
Helium gas is supplied as a discharge gas from the second gas pipe 12 at a flow rate of 1 c.c./min, the electrode 2 is made of tungsten, Q = 1000 Joule, t = 0.05 msec,
V=150cm ³ , that is, Q/V・t=133Joule/cm ³・
Controlled to msec, maximum current 3KA, initial voltage
When flash discharge is carried out under the conditions of 10 KV and 1 discharge per second, the substrate 7 is surrounded by the plasma of the discharge, and a-Si with a thickness of 36 nm is deposited on its surface in about 1 minute. In other words, the a-Si film can be formed on the substrate 7 at a film formation rate of about 0.6 nm/sec.

By the way, in this example, silane is efficiently photodecomposed by radiation light of 170 nm or less from hydrogen or helium discharge, but silane itself also contributes to the discharge, and this discharge also causes a-Si to be decomposed. It is known that a film is formed. However, when forming a film only by discharging silane itself without using hydrogen or helium discharge, the film formation rate is about 0.1 nm/sec when the supplied energy is 3.3 W/cm ³ in average power. In this example, which uses hydrogen or helium discharge, the average power supplied is 3.3 W/cm ³ and the film formation rate is
It can be seen that it is 0.017 nm/sec, which is an improvement of about 6 times.

Next, the a-Si produced by photodecomposition of the photochemically reactive gas is deposited at locations other than the substrate 7 within the mean free path of electrons and ions generated by the discharge, but over a long period of time. When the device is activated, electrode 2
Protective gas is blown out from the third gas pipe 14, which is an electrode protective gas supply mechanism provided near the electrode 2, and this causes the gas to accumulate on the electrode 2 and deteriorate the performance of the electrode 2. It has come to restrict the approach of people. However, without providing the third gas pipe 14, the second gas pipe 1
The discharge gas from the electrode 2 may also be blown out from the vicinity of the electrode 2 and spread to the discharge region 4 so as to serve as an electrode protection gas.

To describe another example, if silane or disilane is selected as the photochemically reactive gas and a trace amount of hydrogen phosphide, hydrogen boride, or hydrogen arsenide is further mixed into the gas, a-Si can be Films doped with boron, phosphorus, or arsenic are also available.

The above examples are all examples of film formation of a-Si used in solar cells and semiconductor devices, or a-Si doped with other elements, but other materials such as silicon nitride and silicon dioxide are also used. An insulating film can also be formed. For example, silane is supplied from the first gas pipe 11 at 2 c.c./min.
Hydrazine is mixed and flowed at a flow rate of 5 c.c./min, and helium gas is flowed as a discharge gas for ultraviolet radiation from the second gas pipe 12 at a flow rate of 1 c.c./min.
500Joule, t=0.01msec, V=150cm ³ , that is, Q/
When the flash discharge is performed at a cycle of 1 time/sec with V・t=330, the substrate 7 disposed in the discharge area 4
A silicon nitride film is formed at a rate of about 3 nm/sec. At this time, the supplied energy was 3.3 W/cm ³ , and considering the input energy, the film formation rate was very excellent. In addition to hydrazine, nitrogen, ammonia, etc. can also be used.

Similarly, when forming an insulating film such as silicon dioxide, for example, silane is supplied from the first gas pipe 11 at a flow rate of 2 c.c./min and from the second gas pipe 12.
A similar flash discharge may be performed by flowing N ₂ O gas at a flow rate of 4 c.c./min. When nitrogen and oxygen components are added to the photochemically reactive gas in this way, if these components deteriorate the electrode 2, an electrode protection gas should be flowed or a discharge region 4 that emits flash light should be used.
The method illustrated in FIG. 1 and FIG. 2, in which a reaction region 9 for photodecomposition and a reaction region 9 for photodecomposition are partitioned, may be adopted.

Although this example has the advantage of high film formation speed, ions and electrons generated during flash discharge may be incorporated into the film and deteriorate the film properties, and if such a reduction becomes a problem. The distance between the photochemically reactive gas and the substrate 7 may be made sufficiently larger than the mean free path of ions or electrons, even if the film formation rate is sacrificed to some extent.

As explained above based on several examples,
In the present invention, the discharge gas is selected from helium or hydrogen gas so as to efficiently radiate ultraviolet rays, and when the discharge energy is QJoule, the effective discharge volume is Vcm ³ , and the half-width of current is tmsec, Q/V・t≧
10 ² Joule/cm ³ msec to emit light, irradiate a photochemically reactive gas with the flash of ultraviolet rays, and form a film on a substrate made of a reaction product of the reactive gas, It is possible to provide a film forming method that can form a film at a very high speed without the adverse effects of mercury even when applied to the formation process of microelectronic circuits.

The present invention provides a method according to claim 3, in which a discharge region and a reaction region are separated, and a method according to claim 5, in which both regions are separated sufficiently by the mean free path of electrons and ions. This does not exclude adding a small amount of mercury as a discharge gas for radiation.

[Brief explanation of the drawing]

1, 2, and 3 are all cross-sectional views of devices used in embodiments of the present invention. 1... Flash discharge lamp, 2... Electrode, 3, 8...
Window, 4...Discharge area, 5...Reaction container, 7...Substrate, 9...Reaction area, 10...Dividing plate, 11...
First gas pipe, 12...Second gas pipe, 13
...Vacuum pump, 14...Third gas pipe (electrode protection gas supply mechanism).

Claims (1)

[Claims] 1. Control to Q/Vt≧10 ² Joule/cm ³ msec, where discharge energy is Q (Joule), effective discharge volume is V (cm ³ ), and current half width is t (msec). Under these conditions, a discharge gas for ultraviolet radiation selected from helium or hydrogen gas is flashed, and the flash is irradiated onto the photochemically reactive gas to form a film made of decomposition products of the photochemically reactive gas on the substrate. A film forming method characterized by forming a film. 2. The film forming method according to claim 1, wherein the flash is emitted within a container configured to directly irradiate the photochemically reactive gas without being blocked by an object. 3. The film forming method according to claim 1, wherein a space containing a discharge region that emits flash light and a space containing a reaction region where a photochemically reactive gas is photodecomposed are separated. 4. The film forming method according to claim 2, wherein the photochemically reactive gas and the substrate are located within or near the effective discharge volume. 5. A discharge region and a reaction region in which a substrate is arranged are provided in the same container, and the distance between the two regions is sufficiently greater than the mean free path of electrons and ions generated due to flash light emission. The method for forming a film according to item 2. 6. The film forming method according to claim 2, wherein an electrode protective gas supply mechanism is provided near the electrode, and the protective gas is supplied from there. 7. The film forming method according to claim 1, wherein the photochemically reactive gas contains a hydrogen compound of silicon. 8. The film forming method according to claim 7, wherein the discharge gas further contains at least one compound selected from arsenic, phosphorus, and boron. 9. The film forming method according to claim 7, wherein the photochemically reactive gas further contains nitrogen, ammonia, or nitrogen oxide. 10. The film forming method according to claim 3 or 6, wherein the photochemically reactive gas contains a hydrogen compound of silicon and oxygen or a compound of oxygen. 11. The film forming method according to claim 7, wherein the silicon hydrogen compound is silane or disilane. 12 Compounds of arsenic, phosphorus, and boron are hydrogen arsenide,
9. The method for forming a film according to claim 8, wherein hydrogen phosphide or hydrogen boride is used. 13. The film forming method according to claim 3 or 5, wherein the discharge gas contains mercury.