JPS59105804A - Purification of reactive gas for semiconductor - Google Patents

Abstract

PURPOSE:To obtain reactive gas from which a carbon compound is sufficiently removed, by performing a silane or germane liquification and gasification process at least one time. CONSTITUTION:Vessels 2, 3, 4 are evacuated while dewers 6, 7 are filled with liquid nitrogen. A silane mixture is transferred to the vessel 2 from a silane bomb 1 to be liquified in said vessel 2. In this case, pressure is adjusted to 0.5- 5atm. during liquification work. The liquified silane in the vessel 2 is transferred to the vessel 3 to perform purification due to liquification and gasification for 5-50hr while controlling pressure to 0.5-3atm. and a temp. to -100 deg.C. The liquified silane is transferred to the vessel 4 which is, in turn, regulated to a room temp. and the pressure in the bomb 1 is raised to 10-25atm.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a reactive gas for semiconductors having a purity of 98% or higher, typically silane or germane, is subjected to at least one liquefaction/vaporization step and further freed from residual oxygen. , water, and hydrocarbons are maintained at 0.0122M or less by filling the stainless steel container with a mirror-finished inner surface.This allows for highly purified reactive gases from which oxygen and carbon impurities have been sufficiently removed. The purpose is to fill containers.

In the present invention, silicon oxide, which is an impurity in silane, is mixed with fluoride, especially fluorine or hydrogen fluoride, which is mixed with 0.1 to 10 parts of silane, and generally 3 to 5 parts of silane, in a high-pressure container as shown in the following reaction formula. React, HL1F,'----→2BF SiOL + 4HF→SiF4 + 2HLO↓Silicon oxide is reacted with water and silicon fluoride, and this water is -90
It is intended to be purified by remaining in the trap during the liquefaction (-x2o to -140"C)/vaporization (-100 to -1100) process at ~-150°C. At this time, it remains in the high-pressure vessel. The fluorine or hydrogen fluoride undergoes the following reaction, SiH4+ 2Fz→ SiF, J + H Engineering Sin,
-1-4HF-→SiF+↓+4) b Silicon fluoride (
Bp-=95.7°C) is also liquefied and left as necessary to obtain ultra-high purity silane.

The present invention reduces the concentration of oxygen or carbon, particularly oxygen, remaining in the reactive gas after being purified by removing heavy metals, water, oxide impurities, especially ultrafine silicon oxide powder, remaining in the reactive gas after being purified. cm or less, preferably 1 x 10~5
The purpose is to make it possible to obtain X10"cInJ.

Conventionally, reactive gases for semiconductors have been filled in iron cylinders, and semiconductor device manufacturers and laboratories have simply used them in plasma vapor deposition equipment (PCVD equipment), low pressure vapor deposition equipment (LPCvD equipment), or It was used in epitaxial growth equipment. However, although silane, which is typically a reactive gas for semiconductors, is chemically produced at the time of raw material production, its purity is 6N to 7N, and its impurities are less than IPPM. This is clear from the fact that the oxygen/6 concentration in FZ single crystal silicon using raw material silane is 1 to 9×10 am or less. However, if such raw materials are transferred to a transfer tank, 3. When subdividing into common iron high-pressure cylinders of υ, 10 or 47 mm, due to insufficient control, hydrocarbons from the oil component were mixed in, and ultrafine silicon oxide powder was formed due to air leaks. In particular, 0.1 to 0.01% of oxygen impurities, including oxides, were mixed in.

For this reason, the patent application filed by the present inventor is semi-amorphous semiconductor (55-263886155, 3, 3 application) or semiconductor device for photovoltaic generation having PM with microcrystals or P-N junction (49-71738849゜). When attempting to fabricate a hydrogenated non-single crystal semiconductor containing an amorphous semiconductor using the PCVD method, the oxygen or carbon is incorporated into the silicon semiconductor as a silicon oxide insulator or carbon clusters. This caused the contamination and deteriorated the properties of the semiconductor.

In particular, when this mixed oxygen mixes into a hydrogenated non-single crystal semiconductor, if it forms 5 to 50 oxygen clusters, it acts as a recombination i center, and if it has a dangling bond, it acts as a 5i- 0-H... forms Si bonds, acts as a cause of photodegradation (called the Stebleronski effect) in the semiconductor, and also combines to form 8i-
In the case of configuring 0'-8i, it acts as a local insulating current barrier, deteriorating the characteristics as a semiconductor in all aspects.

In addition, such oxygen is 13.
In the production of non-single-crystal semiconductors using the glow discharge method that utilizes a high-frequency discharge of 56MH2, the quantum theoretical 5~
It was found that the material should be made amorphous by inhibiting orderliness in the short range order of 200X and preventing microcrystallinity. It has been found that purification of silane, which is the starting material of the present invention, is extremely important when attempting to remove these and create a silicon thin film as an original semiconductor by the PCVD method.

The present invention is directed to such semiconductors, especially at low temperatures (room temperature to 400'C, typically 200 to 300'C), where the addition of oxygen has a significant deteriorating effect.
The present invention relates to a purification method for producing high-purity silane for forming a semiconductor film at 0'C.

The details will be explained below according to the drawings.

FIG. 1 is a block diagram showing a purification method in which silane is particularly used as a reactive gas for semiconductors according to the present invention. In the case where Y borane or phosphine diluted with germane or hydrogen etc. is prepared instead of silane, it can be prepared in the same manner as described below.

In the drawing, a high-pressure container (cylinder) of silane containing 0.1 to 10 grams of fluorine or hydrogen fluoride, generally 1 to 5%.
(1), liquefaction vaporization term 1 container (2), second container 5 (
3), the final container of 783 (generally used for stainless steel hone bara) (4), and the residual moisture in the purge hydrogen αΦ. The block diagram in FIG. 1 applies to two-stage purification, and is the same whether it is one-stage or multi-stage purification.

In the drawings, cleaning of the containers and the piping system connected to them in 1.2.3 will be abbreviated.

Table 1 shows the plowing process based on the block diagram of FIG.

Cleaning the purification equipment 1, all valves are closed, mixing cylinder 720
0-3500CK heating.

3. When NL (j3) and V3B are opened, the mixer 07) is exhausted from the flow meter (39).

4. Oil-free exhaust system (IQ on, V2B, V
44. Cook (59) 1st race - V24. V23°V21
．． Open V46. Container (4), (3), (2),
(5) is evacuated to 1×10 to 1×10 torr. Approximately 1 to 5 hours.

5. With V29 open, hydrogen is purified in container (5) (77K) and then introduced to bring the inside of container (4) to about 1 atmosphere.

5. V44, close the cock (59) and container (2),
/3) is filled with hydrogen and after the pressure reaches 1 atm or more, open V23.

The adsorbate in containers (2) and (3) is heated and removed by hydrogen. Approximately 1 to 5 hours.

7. Set V22 closed, V46 closed, and V44 open. container(
2), (3 people (4) were evacuated again and lXl0 t
orr or less.

8. Turn off the heaters (9), (10), (36) using the controller a℃, α7) and turn off the containers (2), (3).
, (4) are at room temperature.

Table 1 Furthermore, in this manner, adsorbed substances, particularly water and carbon dioxide gas, on the inner walls of the containers (2), (3), and (4) in the apparatus 00) constituting the purification section were removed. At this time, the container is made of stainless steel and has a mirror-finished inner surface that is sufficiently flat so that it can withstand a pressure of up to 150 kg/cmL to prevent residual fine powder (particularly silicon oxide fine powder) from sticking to the recesses of the inner wall. This has been fixed so that it does not become impossible to remove the file.

Further, in containers (2), (3), and (4), adsorbed oxygen,
In order to remove water, when the inside of the container heated to 200 to 350" (!) was evacuated from the outside, a vacuum device α was used to prevent hydrocarbons, especially oil vapor, from flowing back.

In other words, in the present invention, since the vacuum in the cylinder container was conventionally simply evacuated to 10 to 10 torr using a rotary pump, hydrocarbons were mixed in to the order of 0.1 torr. In order to find out the facts and remove the contamination of such impurities, we mainly used turbo pumps to evacuate to 9 x 10 to 10 torr, and back diffusion of oil components to 9 x 10 torr.
In the following, the specific pressure was reduced to 10 to 10 torr.

Thus, the residual content of water, carbon dioxide, and hydrocarbons in the containers (2), (3), and (4) is O, IPPM preferably 0.1
Vacuuming was carried out sufficiently until the pressure reached ~10 PPB.

Next, seal the first container (2) with liquid nitrogen 1506 (3).
A reactive gas for semiconductors, which is a mixed gas of silane and fluorine, was transferred to the cylinder (1) and liquefied in the container (2). Furthermore, this container (2) was once again subjected to liquid-gas purification and transferred from container (4) to the second-stage manufacturing device. At this time, the vaporization temperature is -110-39060, preferably -10
After transferring for a long time from 0 to -105'O L for 5 to 50 hours, the product is further purified by liquefaction and vaporization.
The container (4) was filled with V-prepared silane. The liquefaction-vaporization process of this silane is shown in Table 2 below.

Confirm with the compound gauges (30), (31), (32) that the silane gas liquefaction/vaporization purification 1, containers (2), (3), and (4) are evacuated.

2. Exhaust system aei on, V2B, V44. V24.
V23 open. V26. V27. V46. V2
2. Confirmation of closure.

3. The container (2) was filled with Dewar (6) K liquid nitrogen to a temperature of -150±10'O.

4. Open the cock of the silane fluoride (approximately 3% mixture) cylinder (1), open 21, and pour the silane in the cylinder into the container (2) K while watching the flow meter (41) and supplying liquid nitrogen so as not to overflow. During the liquefaction process, check the pressure gauge (3 is 0.5~
The pressure shall be 5 atm.

5. After transferring the mixed silane from the silane cylinder (1), close V21 and close the cock.

6. Close V24 and fill with Dewar (7) K liquid nitrogen.

Container (3) wo-150-1-10'O(!: L7'
n.

7. Open V23. The liquefied silane in the container (2) is transferred to the container (3) over a period of time, and the liquefied silane is purified by vaporization for 5 to 5 minutes.
It will take 0 hours. Flowmeter (4 are 10-500cc
The Z portion is typically up to 100cc10. Coupled meter (3
1) is 0.5 to 3 atm, and container (2) is -90 to -1
05'O typically -100°C, controlled by K controller as desired. In this way, liquefaction and vaporization purification is performed.

After completing this 8, close V23, V2'7. V2B, V
Confirmed the closure of 26.

9, V24. V44. Open the cock (59) and turn the duer (7) =90~-105'O Typically -109
°C and phase shift the liquefied silane to a container (a high-pressure stainless steel cylinder was used in the present invention) (4), item 7. Take the same precautions.

10. After bringing the container (4) (corresponding to the end cylinder) to room temperature and filling the cylinder to an internal pressure of 10 to 25 atm, purification is completed by closing the V44.

Table 2 In this purification step, since the silane oxide in the cylinder (1) was in the form of fine powder of silicon oxide, it could be purified by removing it as water based on the reaction formula described above.

Furthermore, during this vaporization? , In order to prevent the J-puff from transferring the liquid to the next stage, a sintered stainless steel filter (2
~5μ0 mesh) Two stages were provided in each container (2) and (3), and a method was used for blocking by immersing them in liquefied silane.

In this way, the silane after making the sheath has an oxygen level of 0, 0 or less for IPP.
B (10-10 am) can be done at Kt,
In addition, it has become possible to reduce the carbon content to IPPM or less.

In addition, by physically refining the subsequent silane, which had previously only been made by chemical 4'r'; Furthermore, 1/10'~l/1
0” or less.

Finally, the evacuation of the silane remaining in the impurity-containing containers <2) and (3) after being purified by the purification method of the present invention shown in FIG. 1 will be briefly described below.

Exhaust residual silane gas impurities 1. Confirm that all valves are closed.

2. Open V38 and connect mixer (
Exhaust (+8) via li.

3H404 to V29. V46. V24. Open V23 and fill containers (2) and (3).

4. Open V22, flow meter 09)K and gradually start flowing H juice 5iH4)/NL21 from about 50CCZ minutes through mixer α7)K.
Set to 00.

1 to 3 hours.

5. Heat the flow meter (49), (45) long enough until the difference in flow rate disappears. Evacuation of impurities in containers (2), (3) for 1 to 5 hours.

7, V22. V23. V24. V4.6. V29 closed, compound gauge 00) (31) held hydrogen at 0.5 to 3.0 atm.

Table 3 Using the method for purifying reactive gas and its tζ as described above, it was possible to fill a high-pressure container with ultra-high purity reactive gas for semiconductors.

The plasma OVD method using the glow discharge method was performed using such high-purity silane gas at O.1 torr.

250°a, Ry output (13,56MHz), IOW,
A non-single crystal silicon semiconductor was formed under conditions using 100% silane.

This undoped silicon film was fabricated using a MAXMA (camecan cylinder), and the curve (5) indicates that the residual content inside the stainless steel container of the present invention was reduced to 10 torr or less without performing the liquefaction/vaporization purification of the present invention. In other words, the inner wall of the container is mirror-finished and a high pressure and heat resistant container with a stainless steel ring is used.In addition, when filling silane, such a container is preferably made at a temperature of 100 bC or more. is heated for 250 to 300 degrees to sufficiently exhaust the adsorbate.By devising the container itself as in the present invention and paying sufficient attention to the filling method, oxygen, etc., can be mixed in. Ha':l/100~1/1oo
I was able to get it down to OK.

In the drawing (55), almost no residual silane was left, so it is presumed that the silicon oxide remaining in the container came out.

When the liquefaction-vaporization purification of the present invention was carried out as in the present invention, a curve (55) was obtained. And the oxygen concentration in this is a curve (1/10 to 1/1 compared to 5).
I was able to get it down to 000. Even if all the gas remaining in the container is used in the row, it is clear that the silicon oxide component does not increase in the gas because the measurement point (5"I) does not increase as much as the measurement point (55). did.

Furthermore, when silane is used as a reactive gas for semiconductors in the method of the present invention, the container shown in FIG.
Assuming that the cylinder is 10 kg, the silane, etc. is filled with 4B3 gr, the residual amount is 10 g, the residual pressure is 0.5 Kg/cm', and the silane is contained in a container with an internal volume of 1.5 kg. l-, container (2
), and container (3) is designed so that the residual gas and impurities are
In the same manner as in 3), the system was cooled to 1150±10° and then used by opening the valve (a) from the operating system 0 to the atmospheric temperature as shown in the figure. In addition, this container (4) is a stainless steel cylinder with impurities of 0.01 PPM or less inside, and its working pressure can be set to 15 to 17 Kg/c rL, and it can be moved to other locations, compared to conventional It has the feature that it can be used in exactly the same way as the silane cylinder used.

Instead of silane, the reactive gas for the semiconductor may be germane, diborane diluted with hydrogen, phoscine, or arsine.

Their chemical properties are shown in Table 4 below.

Ge horse diborane 2'7.67-92.8 0', 95
1.22 0.470LH6 Huosuhin 34゜00-8'i','/4 L 14
6 1.380 0.746PH.

Arsin '77.95 -62.48 2.695
3.48 1.604 Table 4 That is, when using these reactive gases, it and 100%
To obtain a concentration of , the same procedure as for silane can be carried out as described above. Also, if you want to dilute with hydrogen, after filling the necessary system with a reactive gas for semiconductors, as shown in Figure 1, 1 hydrogen is pressurized from A4 through the cold trap (5) and the valve (46). It is sufficient to fill the gas and dilute it to a predetermined concentration of 50 to 5000 PPM, for example 500 to 101000 PP. Furthermore, if the dilution gas is hydrogen or helium, VCa41 may be introduced in the same manner.

As is clear from the above explanation, in the present invention, the mixed amount of oxygen and carbon in the reactive gas for semiconductors is IPPM or less, preferably 1
By eliminating impurities that get mixed in when dividing the reactive gas into cylinders in order to obtain ~100 PPBK, and in addition, using a combination of liquefaction-abrasive purification and adsorption methods of the reactive gas during this division, it is possible to This method is characterized in that the amount of oxide gas mixed in is less than /10,000 9, and the purified reactive gas makes it possible for the first time to control the purification of the plasma OVD method and LPOVD method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the reactive gas purification method of the present invention. Figure 2 shows H1 using the silane obtained by the method of the present invention.
η The residual oxygen concentration in solid silicon is compared with the conventional method. / 5 q concave wrinkle

Claims (1)

[Claims] 1. A mixed reactive gas of a semiconductor reactive gas with a purity of 9 days or more and a fluoride gas, which is filled in a high-pressure container, is heated to a first temperature maintained below the boiling point of the reactive gas. A step of introducing the liquefied reactive gas into a container and liquefying it, and a step of vaporizing the liquefied reactive gas at a temperature equal to or higher than the boiling point and collecting the vaporized reactive gas in a second container are performed at least once. A method for purifying a reactive gas for semiconductors, characterized in that heavy metals, carbon dioxide, hydrogen, water, and oxide impurities in the reactive gas are removed and purified by heating the reactive gas. 2. In claim 1, the mixed reactive gas is produced by filling a high-pressure container with fluorine or hydrogen fluoride, which is a fluoride gas, at a concentration of 0.1-10 g together with silane. The method is characterized in that silicon oxide is changed into silicon fluoride and mixed into the liquefied reactive gas, and when the reactive gas is vaporized, it remains as water in the first container to purify the reactive gas. Reactive gas purification method for semiconductors. 3. After cleaning the inside of the container, the first container and the second container are heated to 100-450'O, and the remaining impurities are removed by vacuuming.
A reactive gas for semiconductors having a purity of 96% or more and a heptadide gas are placed in a first container in which the temperature of the reactive gas is maintained at a temperature below the hydrogen point of the reactive gas [a step of liquefying the reactive gas by four people; Heavy metals in the reactive gas are removed by at least one step of vaporizing the liquefied reactive gas at a temperature equal to or higher than the boiling point and collecting the vaporized reactive gas in a second container. , a method for purifying a reactive gas for semiconductors, characterized by purifying it by removing impurities such as hydrocarbons, water, oxides, and fluorides.