JPH0635650B2 - Ultra high purity gas supply device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a system for supplying a high-purity gas to a semiconductor manufacturing apparatus, and more particularly to a technology for supplying an ultra-high-purity gas using a ceramic filter near the final stage.

(Prior Art and Problems Thereof) Various gases are currently used in semiconductor manufacturing equipment and the like. For example, in addition to general gases such as Ar, He, O ₂ , H ₂ and N ₂ , Cl ₂ , CCl ₄ , SiH ₄ and SiCl ₂ H
₂ , SiCl ₄ , BF ₃ , PH ₃ , AsH ₃ , CF ₄ ,
Various gases such as BCl ₃ , CH ₂ F _{2 and} other reactive gases are used. With the progress of high integration of LSI, high purification of these gases is required, and now, various technological developments have realized ultra-high purification of raw material gas and these gas supply systems. However, it is usual to insert a filter in every part of the gas supply system in order to prevent the raw material gas and particles generated from the gas supply system from entering the reaction space of each apparatus. However, these filters
Although it has a certain level of performance to remove the particulates present in the gas, it has the characteristic of gradually releasing the adsorbed gas during the manufacturing, cleaning, and assembly processes, which is a source of gas pollution and poses a major problem. It was FIG. 6 is experimental data showing this problem.

FIG. 6 (a) is a schematic view of an experimental apparatus for measuring degassing from a filter. A filter to be evaluated is attached to an ultrahigh vacuum chamber via a valve, and one side of the filter is sealed. The results obtained by evaluating the degassing amount of a Teflon membrane filter widely used as a gas filter by this device are shown in FIGS.
It shows in (d). Here, (b) of the figure shows the transition of the degree of vacuum, and (c) and (d) of the figure show the transition of the partial pressure of a gas component having a large mass number centered on the atmosphere and hydrocarbons, respectively. It is the result measured using (Q mass). The measurement was performed at room temperature (20 ° C.) for 32 hours, heating the filter at 110 ° C. for 30 hours, and then returning to room temperature for 12 hours. As is clear from FIG. 7C, the Teflon membrane filter releases a large amount of atmospheric components even at room temperature before baking, and releases a large amount of atmospheric components even after baking at 110 ° C. for 30 hours to degas. I know that More important is the result shown in FIG. This shows the measurement results of the degassing characteristics of hydrocarbons having a large mass number in a state where baking was performed at 110 ° C. for 30 hours and then returned to room temperature. Naturally, a large amount of degassing is observed during baking, but it can be seen that the released gas of about 10 ⁻⁹ to 10 ⁻¹⁰ Torr remains even after baking. It is considered that this hydrocarbon gas is the result of adsorption of the organic solvent used in the filter cleaning process.

In order to release a large amount of gas in this way, the filter itself has a structure with a very large effective surface area, and the surface of Teflon has a structure with innumerable holes, and gas is adsorbed on these surfaces. Because it accumulates and this is detached. If such a filter is attached to the piping system, no matter how high the purity of the piping system is, the gas emitted from this filter will contaminate the gas and supply the polluted gas to the semiconductor manufacturing equipment. .

For example, RF for depositing a metal such as aluminum
When a gas such as H ₂ O is mixed in the Ar gas introduced into the sputtering apparatus, the sputtered Al target surface is so active that it is easily oxidized by H ₂ O contained in the atmosphere and Al ₂ is formed on the surface. O ₃ (alumina) is formed. Since Al ₂ O ₃ has a smaller sputtering rate than Al, the sputtering rate of the target is reduced, which causes a problem that the deposition rate is significantly reduced. In addition, since these H ₂ O are also taken into the formed Al film,
There are various inconveniences such as an increase in the wiring resistance of 1 and a decrease in the reliability against electromigration. Further, when H ₂ O is introduced into the RIE apparatus, active O and OH groups are generated in the plasma atmosphere, and for example, when etching polysilicon, SiO ₂ is formed on the surface thereof.
As a result, there are inconveniences such as non-uniformity of etching and a large selection ratio with the underlying SiO ₂ film.

(Object of the Invention) The present invention has been made in view of the above points, and an object thereof is to enable supply of ultra-high purity gas in a gas system using a filter.

(Summary of the Invention) A high-purity gas supply device of the present invention is a device that supplies gas to a semiconductor manufacturing apparatus, and is provided with a gas heating means, and at least a part of a pipe for guiding the gas to a gas inlet of the manufacturing apparatus is made of ceramic A filter is arranged, and a mechanism for purging gas out of the system is provided between the manufacturing apparatus and the ceramic filter.

(Embodiment of the Invention) A first embodiment of the present invention will be described with reference to FIG.

The figure shows a case where the present invention is applied to a gas system that supplies Ar gas, for example, from an Ar purifying device to a semiconductor manufacturing device (for example, an RF bias sputtering device). Reference numeral 1 is a ceramic filter, and 2, 3 and 4 are valves.
Valves 3 and 4 are normally two-way three-way valves with a small dead zone. In the apparatus of this embodiment, A of high purity is used.
The following procedure is used to supply r gas to the manufacturing apparatus. First, the valve 4 is closed, and the valves 2 and 3 are opened.
The r gas is released to the atmosphere via the check valve 5. At this time, the gas is heated by passing an electric current from the power source 6 to the pipes 7 and 3'and energizing and heating the pipes.

For example, if the pipe 7 is a 1/4 inch diameter stainless pipe, and the flow rate of Ar gas is about 1 to 2 / min, then about 6
The gas and piping can be heated to about 200 ° C. by passing a current of about 0 A. In this way about 200 ℃
By heating the gas and the gas pipes to pass the gas through the ceramic filter 1 and then removing the gas out of the system,
Impurity gas adsorbed in the filter can be effectively removed. After performing such degassing operation, the power supply 6 is turned off, the gas and the piping system are returned to room temperature, the valve 3 is closed, and the valve 4 is opened to supply the gas to the manufacturing apparatus. By doing so, it became possible to supply an ultra-high purity gas that does not contain various impurity gas components adsorbed to the filter including atmospheric components.

Next, the reason why the ultra high purity gas can be supplied by the present invention will be described. First, the ceramic filter used in this embodiment uses alumina ceramic as a filter element. This element has a substantially uniform hole of about 0.1 μm, which allows it to capture and remove particles of 0.01 μ or more due to Brownian motion of the particles. Further, although the ceramic is porous, it has a smaller effective surface area than the conventional Teflon membrane, the amount of adsorbed gas accumulated is small, and it can be easily desorbed by heating. Further, while the heat resistance limit of the conventional membrane filter is about 120 ° C, this ceramic filter has a high temperature heat resistance even for heating above 200 ° C, so baking at a sufficiently high temperature is possible. It has the characteristic that it is possible. 2 (a), (b), (c),
These are the results obtained by performing the same experiments as in FIGS. 6 (b), (c), and (d) on the ceramic filter, respectively. As is clear from FIG. 2B, the degas partial pressure of atmospheric components at room temperature before baking is slightly lower than that of the membrane filter, but not so large. However, after baking at 110 ° C. for 30 hours, it can be seen that all the gas components were below the detection sensitivity and were not detected. Further, there is a difference of three digits or more in the amount of released gas centering on hydrocarbon having a large mass. As is clear from this experimental data, it is clear that the ceramic filter can easily desorb and eliminate the adsorbed gas by increasing the temperature as compared with the membrane filter.

In this embodiment, the filter 1 is heated to about 200 ° C.,
Since the gas of 1 to 3 / min is flown, the gas adsorbed on the filter can be desorbed and eliminated in an extremely short time.

In this embodiment, the system for supplying the Ar gas to the RF bias sputtering apparatus has been described, but the gas is not limited to Ar, and other gases such as N ₂ and O ₂ as well as the gases mentioned at the beginning of the present specification may be used. I don't care. It goes without saying that the invention can be similarly applied to any other device.

Further, although only a current-carrying heating method has been described as a heating method, for example, a conventional method in which a heater is wound around a pipe or a method of enclosing a gas supply system in one box and heating the whole box may be used. Moreover, it is preferable that the baking operation of the filter described here is performed periodically, and the gas is always supplied to the manufacturing apparatus with the adsorbed gas removed.

FIG. 3 (a) is a piping diagram showing a second embodiment of the present invention. This is a convenient system to use when it is difficult to release a large amount of SiH ₄ , PH ₃ , CCl ₄ , other reactive gas, or special gas into the atmosphere. Here, the valves 302 and 304
2 and 303 and 305 each have a small dead zone
It is desirable to use a continuous three-way valve. When baking the ceramic filter 301, valves 302 and 30 are used.
3 is closed and 304 and 305 are opened to supply gas from the N ₂ gas cylinder and purge the gas out of the system by the check valve 306. The gas discharged from the N ₂ gas cylinder passes through a regulator, a flow rate adjusting valve, and a filter 307, then is heated to about 200 ° C. by current heating by a power source 308, and then sent to the filter. When the degassing by baking the filter is completed, the valves 304 and 305 are closed, and
2, 303 is opened to supply the reactive gas to the manufacturing apparatus.

Also in this embodiment, it is possible to completely avoid gas contamination due to degassing from the filter.

In this embodiment, if the valve is immediately switched to introduce the reactive gas into the chamber after the baking of the filter is completed with N ₂ gas, the residual N ₂ will be mixed in the pipe. For example, in order to avoid this, after completing the purging of N ₂ gas, the valve 304 may be closed, the valve 302 may be opened, and the reactive gas may be purged through 306 for a while to expel the N ₂ gas remaining in the system. As a matter of course, in this case, the gas released from 306 needs to be safely treated and guided to the exhaust duct.

Also, for example, as shown in FIG. 3 (b), the valves 309, 31
0 is added, and after the heating N ₂ gas purge is completed, the valves 302, 304, 303, and 310 are closed with 30
5, 309 are opened, vacuum exhaust is performed to remove N ₂ remaining in the filter and the piping system, and then the valve 305 is closed,
The target gas may be sent to the manufacturing apparatus by opening 302 and 303. The valves 309 and 310 are preferably two-way three-way valves with a small dead zone.

Further, although the second embodiment of the present invention has been described by taking the case where the reaction gas 311 is supplied to the apparatus as an example, the present invention is not limited to this.
For example, when expensive He gas is used as 311
It is economical to bake the filter with inexpensive N ₂ . Furthermore, for example, as 311 Ar, He, N
_{In the} case of using a cylinder for ₂ or the like, for example, when it is necessary to effectively remove O ₂ gas molecules adsorbed on the filter, for example, an H ₂ gas cylinder is used as the cylinder of 312, and this is used as the third cylinder. With the same configuration as in FIG.
When heated and supplied to the filter, O ₂ can be discharged to the outside of the system more quickly due to the substitution adsorption effect.

Since a ceramic such as Al ₂ O ₃ has a property of adsorbing a gas such as H ₂ O and CO _2, such a gas gradually accumulates in the flowing gas,
When a certain amount is accumulated, the adsorbed gas begins to desorb, which causes pollution. Therefore, the ceramic filter needs to be regularly purged at high temperature to remove the adsorbed gas. Therefore, the gas supply device of the present invention is extremely effective.

Further, in FIG. 1 and FIG. 3, the gas pipe connection to the manufacturing apparatus is made by a straight pipe. For example, as shown in FIG. 4, a spiral pipe 401 or a U-shape 402 is used. It is preferable to have a degree of freedom. Alternatively, the pipe may have a bent portion. This is because it is possible to prevent the gas system from having a degree of freedom during the maintenance of the apparatus or the maintenance of the gas system, which causes an excessive force to cause a leak in the piping system. In addition, when you have to disconnect the piping to maintain the equipment,
The piping can be easily removed without mixing the atmosphere into the piping system. Currently available joints with external leak below the detection limit (2 × 10 ^-11 Torr / sec), no dead zone and no particle generation are MCG.
(Metal C-Ring) joint only. However, this M
To attach / detach the CG joint, it is necessary to move the pipe system by about 1 mm. If the pipe has a bent part, a U-shaped cushion, and a spiral part, it is easy to attach and detach the pipe from the stand. The valves 4, 403 and 404 are closed, the MCG joint of the device section and the MCG joint between the valves 4 and 403 are removed, and the piping is removed.

In the first and second embodiments, only the case where the filter and the purge line are brought immediately before the apparatus has been described, but the present invention is not limited to this and may be provided at any other place. Needless to say.

Although all the embodiments described with reference to FIGS. 1, 3, and 4 have been described only for the case of supplying one kind of gas to the manufacturing apparatus, a normal apparatus may appropriately switch two or more kinds of gas, Alternatively, they are often mixed and used.

For example, FIG. 5 (a) shows an embodiment of the present invention by exemplifying a case where two or more kinds of gases (here, three kinds of gases A, B, and C are explained as an example) are used by switching. is there. Here, the pipes for supplying the gases A, B, and C to the supply system and the apparatus are omitted, but the pipes as shown in FIGS. 1 and 3 may be used. Each gas line is provided with a ceramic filter (501), and the mechanism for discharging the gas to the outside of the system by baking is the same as that described in FIG.

Now, the reason why the filter is not provided in the pipe 506 for supplying the apparatus but individually in each gas line is as follows. This is because the ceramic filter adsorbs a large amount of these gas molecules at the same time as filtering the gas, so that if one filter is commonly used, another gas component will be mixed. Obviously, this problem does not occur in this embodiment.

Further, in order to reduce mutual interference of the gases, it is preferable that the valves 504 and 505 are not independent valves but two-way three-way valves with a small dead zone.
The same applies to the valves 504 'and 505'.

Further, FIG. 5 (b) shows an embodiment in which baking of the filter is performed with another gas (for example, N ₂ ).
_The method of baking each ceramic filter (501) with _two gases is the same as that described in FIG. Again, a pair of valves 504, 505 and valves 504 ', 50
All 5'pairs are double-type 3 with few dead zones.
It is better to use a one-way valve.

Although the power supply and wiring for baking are omitted in FIG. 5, it goes without saying that this may be performed in the same manner as in FIGS. 1 and 3.

Further, when it is desired to avoid exposing the pipe to the atmosphere when replacing the filter or the like, one valve may be inserted before and after the filter, and after closing these, the filter may be removed.

Further, it is preferable to introduce a structure similar to that described in FIG. 4 as a means for giving the piping flexibility when removing the filter so as to facilitate maintenance.

(Effects of the Invention) According to the present invention, it is possible to completely remove outgas from a filter, and it is possible to supply an ultrahigh-purity gas to a semiconductor manufacturing apparatus.

[Brief description of drawings]

FIG. 1 is a drawing showing a first embodiment of the present invention, FIG. 2 is experimental data showing the degassing characteristics of a ceramic filter, and FIG.
(A), (b) is drawing which shows the 2nd Example of this invention,
4 and 5 are drawings showing other embodiments, and FIGS. 6 (a), (b), (c), and (d) are measurement systems and experimental data of degassing characteristics of a conventional membrane filter. It is a drawing showing. 1, 304, 501 ... Ceramic filter, 3 ', 3
05 '... Purge line.

Claims (2)

[Claims] 1. An apparatus for supplying a gas to a semiconductor manufacturing apparatus, wherein a gas heating means is provided, and a ceramic filter is arranged at least at a part of a pipe for guiding the gas to a gas inlet of the manufacturing apparatus. A high-purity gas supply device characterized in that a mechanism for purging gas outside the system is provided between the ceramic filters. 2. The ultra-high purity gas supply device according to claim 1, wherein the ceramic filter is arranged immediately before the gas introduction port.