JPH0458174B2 - - 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.
(Publication of 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 purpose of the present invention is to form a film made of a-Si, silicon dioxide, silicon nitride, etc. without the adverse effects of mercury at a sufficiently fast rate for practical use when applied to the formation process of microelectronic circuits. It provides: The configuration is that the discharge energy is Q (Joule) and the effective discharge volume is V.
(cm ³ ), current half width is t (m sec), Q/
Under these conditions, a discharge gas for ultraviolet radiation selected from argon, xenon, krypton, and neon is emitted as a flash by controlling V・t≧10Joule/cm ³・m sec, and the photochemically reactive gas is irradiated with this flash. The method is characterized in that a film made of a decomposition product of a photochemically reactive gas is formed on the 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 pipe diameter D is 1 cm, and therefore the effective discharge volume is π/4・D ²・L=8cm ³ Therefore, as a power source, the capacity of the discharge capacitor is
200μF, the discharge voltage is 2200V, therefore the discharge energy is Q = 480Joule, and the current half-width, which is the time width at the height of 1/2 of the peak high current value, is 0.2m.
Discharge is controlled by sec. 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 while being supported by a support stand 6.
A photochemically reactive gas G consisting of silane or disilane is supplied from one side of the substrate 7, and the substrate 7 is covered with the photochemically reactive gas G. A window 8 made of lithium fluoride is provided above the center of the reaction vessel 5, and this window 8 faces the window 3 of the flash discharge lamp 1 at a distance d. The generated ultraviolet rays pass through the windows 3 and 8 and are irradiated onto the substrate 7. Therefore, the reaction vessel 5 in which the photochemically reactive gas is the reaction zone 9
The product is photodecomposed internally and deposited on the substrate 7 to form a film. When xenon gas is sealed as a discharge gas in the flash discharge lamp 1 at a pressure of 1500 Torr, in addition to visible light, ultraviolet rays of 180.0 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 0.3 to 0.5 nm/second, which is 10 to 20 times faster than the above-mentioned conventional example that does not use a mercury photosensitizer. A high speed can be obtained and it can be put to practical use. By the way, in flashlight emission, the amount of ultraviolet radiation depends on Q/V・t, so consider Q/V・t as a factor and make sure that Q/V・t is also sufficient so that a sufficient film formation rate can be obtained. It is better to adopt a large value for . According to various experiments, when the discharge gas is argon, xenon, krypton, or neon, 2
×10Joule/cm ³・m sec or more is preferable, but
Sufficient effects can be obtained even at 10Jule/cm ³ m sec or more. Next, to give an example of ultraviolet rays emitted under certain discharge conditions in these discharge gases, for argon, Q = 140 Joule, t = 0.2 m sec, voltage 7 KV
For krypton, ultraviolet rays with a wavelength of 120 to 140 nm are generated at Q = 70 Joule, t = 0.2 m sec, and a voltage of 5 KV. For xenon, ultraviolet rays with a wavelength of 140 to 170 nm are generated under the same conditions as for krypton. were radiated strongly. In each case, the a-Si film was formed at a rate in the range of 0.1 to 1.0 nm/sec because the flash light was emitted at a cycle of 1 to 5 times per second. Furthermore, the relationship between the Q/Vt value and ultraviolet light having a wavelength of 200 nm or less was investigated by flashing six types of flash discharge lamps using different types of discharge gas, and the results are shown in FIG. The relationship between the symbols plotted in Figure 4 and the discharge gas combinations (expressed in weight%) is shown in Table 1.
It is 350Toor.

[Table] The wavelength of the light from these six types of flash discharge lamps ranges from 165 to
The light is received by a detector (R376 phototube manufactured by Hamamatsu Photonics) through a multilayer film filter (manufactured by Acton, USA) that transmits 180 nm ultraviolet light, and its intensity is displayed as a relative value. /Vt value is 10J/cm ³ m sec or more, especially 20J/cm ³ m sec or more, the wavelength
It can be seen that the intensity of ultraviolet light below 200 nm increases. 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 in between, and the window 3 can be replaced by loosening 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 calculating the effective discharge volume V, when the discharge area 4 is composed of a single flash discharge lamp 1 as in the embodiment shown in FIG. 1, simply calculate it 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 attenuation occurs 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 average distance at which visible light is attenuated to 1/10 can be approximated as the 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.
Krypton gas is supplied as a discharge gas from the second gas pipe 12 at a flow rate of 20c.c./min, the electrode 2 is made of tungsten, Q=3000Joule, t=0.05m
sec, V=2650cm ³ , that is, Q/V・t=23Joule/
Controlled to cm ³・m sec, current 5A, voltage 3KV, 3
When the flash discharge is performed under the conditions of discharge times/second, the substrate 7 is surrounded by the plasma of the discharge, and a-Si with a thickness of 35 nm is deposited on its surface in about 1 minute. In other words, a
-A film of Si can be formed. By the way, in this example, the krypton discharge
Although silane is efficiently photodecomposed by 123.6 nm synchrotron radiation, silane itself also contributes to the discharge, and it is known that this discharge also forms an a-Si film. . However, when forming a film only by the discharge of silane itself without using krypton discharge, the film formation rate is 0.1 nm/cm when the supplied energy is 3.4 W/cm ³ in average power.
In this example using krypton discharge, the average power supplied is 3.4 W/cm ³ and the film formation rate is 0.6 nm/sec, which is an improvement of about 6 times. Next, the a-Si produced by photodecomposition of the photochemically reactive gas is deposited in places other than the substrate 7 within the mean free path of electrons and ions generated by the discharge, but if the a-Si is deposited in a place other than the substrate 7, When 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 thereby deposits on the substrate 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 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 embodiments are all about the formation of films doped with a-Si or other elements used in solar cells and semiconductor devices, but the formation of insulating films such as silicon nitride and silicon dioxide is also possible. can. For example, silane is mixed and flowed at a flow rate of 2 c.c./min and hydracine is mixed at a flow rate of 5 c.c./min from the first gas pipe 11, and krypton gas is flowed at a flow rate of 20 c.c./min from the second gas pipe 12 as a discharge gas for ultraviolet radiation. Flow at a flow rate of /min, Q=3000Joule,
t=0.05m sec, V=2650cm ³ , that is, Q/V・t=
22.6 and flash discharge is performed at a cycle of 3 times/second, a silicon nitride film is formed on the substrate 7 disposed in the discharge region 4 at a rate of about 1.5 nm/second. At this time, the supplied energy was 3.4 W/cm ³ , and considering the input energy, the film formation rate was very excellent. In addition to hydrazine, nitrogen, ammonia, nitrogen oxide, 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, 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. In this case, the distance between the photochemically reactive gas and the substrate 7 should be made sufficiently larger than the mean free path of ions and electrons, even if the film formation speed is sacrificed to some extent. As explained above based on several examples,
In the present invention, the discharge gas is selected from argon, xenon, krypton, and neon so as to efficiently radiate ^ultraviolet rays, and Q/ It emits light under control such that V・t≧10Joule/cm ³・m sec, irradiates a photochemically reactive gas with a flash of the ultraviolet light, and forms a film made of a reaction product of the reactive gas on the substrate. Furthermore, 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 a process for forming a microelectronic circuit. The present invention provides a method according to claim 3, in which a discharge region and a reaction region are separated, and a method described in claim 5, in which both regions are separated by a distance greater than the mean free path of electrons or ions. This does not exclude the addition of trace amounts of.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are all sectional views of an apparatus used in an embodiment of the present invention, and FIG. 4 is an explanatory diagram of data. 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. When discharge energy is Q (Joule), effective discharge volume is V (cm ³ ), and current half width is t (m sec), Q/Vt≧10Joule/cm ³ m sec. Under these conditions, argon, xenon,
It is characterized by flashing a discharge gas for ultraviolet radiation selected from krypton and neon, and irradiating a photochemically reactive gas with the flash to form a film made of a decomposition product of the photochemically reactive gas on a substrate. Film formation method. 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 1, 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.