JPH0251654B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a method for removing components to be removed such as hydrogen fluoride contained in waste gas containing fluorine compounds discharged from a dry etching device. The present invention relates to a gas adsorption trapping device.

[Background of the Invention] In recent years, precision electronic components such as LSIs are increasingly manufactured by dry etching silicon wafers. Fluorine compounds are particularly effective for dry etching silicon wafers, and examples of such fluorine compounds include sulfur fluoride compounds (e.g., SF ₆ ), fluorine-substituted chlorinated hydrocarbons (e.g., C ₂ ClF ₅ , C ₂ Cl ₂ F ₄ ) and fluorinated hydrocarbons (e.g. CF ₄ , CHF ₃ )
etc. are used.

The waste gas used for dry etching of silicon wafers contains unreacted etching gas, reaction products of silicon and etching gas and their decomposition products, sulfur and sulfur compounds that are decomposition products of etching gas, It also contains various components such as anti-corrosive oil used in vacuum pumps to maintain reduced pressure inside dry etching equipment. The above-mentioned components contained in waste gas need to be removed for environmental reasons. Further, for example, when a sulfur fluoride compound is used, sulfur may be generated by decomposition, and this sulfur may clog the pipes, so waste gas treatment is also required.

Conventionally, chlorine compounds such as boron trichloride have been mainly used when dry etching materials other than silicon wafers, such as aluminum. After being treated using an adsorption tower type gas adsorption device equipped with an adsorbent layer, it is discharged.

On the other hand, waste gas used in dry etching of silicon wafers is generally treated with an alkaline scrubber and then discharged.

In other words, silicon wafers are generally dry etched using a fluorine compound as mentioned above, and the waste gas discharged from the dry etching equipment reacts with water in the adsorbent to form hydrogen fluoride. Contains substances that produce Hydrogen fluoride is difficult to adsorb with conventionally used adsorption devices filled with activated carbon or the like.

For this reason, waste gas containing fluorine compounds, such as waste gas from dry etching of silicon wafers, is treated using an alkaline scrubber, and adsorption tower type equipment filled with adsorbent is rarely used. It has not been.

[Object of the Invention] The present invention provides a gas adsorption trapping device that can effectively trap and remove components to be removed contained in waste gas containing fluorine compounds discharged during dry etching of silicon wafers and the like. The purpose is to provide.

More specifically, it is an object of the present invention to provide an adsorption column type gas adsorption trapping device that can effectively trap and remove components to be removed contained in dry etching waste gas containing fluorine compounds. .

[Summary of the Invention] The present invention provides a gas adsorption/trapping device comprising an adsorbent layer provided inside a container having a gas inlet and a gas outlet, the gas adsorption/trapping device being provided with an adsorbent layer on the side of the gas outlet with respect to the adsorbent layer. The apparatus is equipped with a fluorine component trapping section made of alumina and/or zeolite for trapping fluorine compounds in the dry etching equipment waste gas, and an acidic component trapping section made of soda lime for trapping acidic components. A gas adsorption/trapping device is characterized in that:

[Effects of the Invention] By using the gas adsorption trapping device of the present invention, which includes an adsorbent layer, a fluorine component trapping section, and an acidic component trapping section, it is possible to use a fluorine compound as in the case of dry etching of silicon wafers. Components to be removed such as sulfur, fluorine compounds, and acidic components can be effectively captured and removed from dry etching waste gas.

That is, sulfur, sulfur compounds, corrosion-resistant oil, etc. contained in the waste gas are mainly adsorbed by the adsorbent layer. Fluorine compounds such as hydrogen fluoride are mainly captured in the fluorine component trapping section, and further, acidic components such as hydrogen chloride are mainly captured in the acidic component trapping section.

In this way, by using the gas adsorption trapping device of the present invention, it is possible to remove fluorine compounds, which are difficult to completely adsorb and remove with conventional adsorption tower type gas adsorption devices that use adsorbents such as activated carbon. It has become possible to effectively treat the dry etching waste gas containing

[Detailed Description of the Invention] The waste gas treated by the gas adsorption trapping device of the present invention is, for example, the waste gas discharged during dry etching of silicon wafers and the like. Such waste gas contains fluorine compounds.

Examples of gases introduced into a dry etching apparatus for dry etching silicon wafers include SF ₆ , C ₂ ClF ₅ , C ₂ Cl ₂ F ₄ ,
Mention may be made of _CF4 and _CHF3 . These gases may be used alone or in a mixture of two or more types. It may also be diluted with an inert gas such as nitrogen. Among these gases, SF ₆ is increasingly being used alone or in combination with other gases. Particularly recently, gases in which a sulfur fluoride compound such as SF ₆ is mixed with a small amount of a fluorine-substituted halogenated hydrocarbon such as C ₂ ClF ₅ have been preferred.
The gas adsorption trapping device of the present invention is particularly suitable for treating waste gas from dry etching using a gas containing such a sulfur fluoride compound.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings, taking as an example a method for treating waste gas discharged during dry etching of silicon wafers using the gas adsorption/trapping apparatus of the present invention.

FIG. 1 is a diagram schematically showing an example in which the gas adsorption trapping device of the present invention is arranged between a gas generation device and a breakthrough detection device.

When the above-mentioned dry etching gas is introduced into the dry etching device (gas generation device) 1 to perform dry etching of a silicon wafer, a part of the dry etching gas reacts with the silicon of the silicon wafer to form silicon tetrafluoride (SiF). ₄ ) Generate. In addition, C ₂ ClF ₅ is used as a dry etching gas.
etc., silicon tetrachloride (SiCl ₄ ) is produced in addition to silicon tetrafluoride. An example of this gas generating device is an RIE dry etching device.

Such products and unreacted dry etching gas are introduced into the gas adsorption trapping device 3 from the gas inlet via the vacuum pump 2. This vacuum pump is arranged to keep the inside of the gas generator 1 at a reduced pressure and to send the generated gas to the gas adsorption trapping device 3. Corrosion-resistant oil is normally used in the vacuum pump 2 to protect the pump from dry etching gas. Further, the entire pump is usually sealed with an inert gas such as nitrogen gas.

The gas adsorption/trapping device 3 of the present invention into which the above-mentioned waste gas is introduced is basically an adsorbent in which an adsorbent is filled inside a container having a gas inlet 4 and a gas outlet 5. It consists of 6 layers. Furthermore, the gas adsorption/trapping device 1 of the present invention has a fluorine component capturing section 7 made of alumina and/or zeolite and an acidic component capturing section 8 made of soda lime on the side of the gas outlet 5 with respect to the adsorbent layer 6. It is equipped.

There are no particular restrictions on the shape, capacity, etc. of the gas adsorption/trapping device 3 of the present invention, and ordinary devices can be used. An example of the shape is an adsorption tower type.

The waste gas discharged from the gas generation device 1 and introduced into the gas adsorption trapping device 3 first comes into contact with an adsorbent to remove sulfur, sulfur compounds among the components to be removed contained in the waste gas, and the vacuum pump. The corrosion-resistant oil of No. 2 is adsorbed and removed. Since the adsorption performance of the adsorbent for these components is relatively good, these components hardly flow out from above the adsorbent. Therefore, the trapping action in the fluorine component trapping section and the acidic component trapping section, which will be described later, is not affected by sulfur, sulfur compounds, anticorrosive oil, and the like.

In addition to the above-mentioned components, a portion of other components to be removed, such as dry etching gas, is also adsorbed in this layer.

Examples of the adsorbent forming the adsorbent layer 6 include activated carbon and titanium dioxide, which can be used alone or in combination. A particularly preferred adsorbent is activated carbon. Note that the above-mentioned adsorbent may be surface-treated according to a known technique or may have other components added thereto.

In the adsorbent layer 6, part of the components to be removed in the waste gas is adsorbed by the adsorbent, and new compounds are generated by the reaction between the moisture contained in the adsorbent and some of the components in the waste gas. generate.

In other words, adsorbents are generally subjected to heat treatment to reduce the amount of water absorbed, but since adsorbents absorb water over time, they usually contain less than 10% moisture by weight when used. is adsorbed.

On the other hand, the waste gas introduced into the gas adsorption trapping device 3 contains many substances that decompose upon contact with water. For example, the dry etching gas SF ₆ and its decomposition products SF ₄ and SOF ₂ are
While passing through the adsorbent layer 6, it comes into contact with water and is partially decomposed into sulfur dioxide and hydrogen fluoride. Hydrogen fluoride generated in this way is difficult to adsorb and remove with an adsorbent such as activated carbon, and some of it is absorbed into the adsorbent layer 6.
flows out from the top of the In addition, not only hydrogen fluoride decomposed and produced in the adsorbent layer, but also hydrogen fluoride produced in the dry etching equipment, SiF ₄ produced by contact between the silicon wafer and the dry etching gas, etc. Since it is difficult to remove by adsorption, a portion flows out from the upper part of the adsorbent layer 6.

In this way, part of the target components to be adsorbed is adsorbed in the adsorbent layer 6, and the waste gas that contains newly generated hydrogen fluoride etc. in the adsorbent layer is then transferred to the fluorine component trapping section 7. be introduced. The fluorine component trapping section 7 is made of alumina, zeolite, or a mixture of both. In this fluorine component trapping section 7, fluorine compounds such as hydrogen fluoride mainly react with aluminum oxide (alumina) and are captured as aluminum trifluoride. Furthermore, compounds such as silicon tetrafluoride (SiF ₄ ), which are generated by the reaction with silicon in the silicon wafer in the dry etching equipment and are not adsorbed by the adsorbent layer, are captured as aluminum trifluoride and silicon dioxide. be done.

The alumina or zeolite constituting the fluorine component trapping section 7 can be one that is used for normal purposes, but the pressure loss and waste gas when the waste gas passes through the fluorine component trapping section 7 can be used. It is preferable to use a granular material in consideration of the contact area with the material. In the present invention, it is particularly preferable to use granular alumina.

The fluorine component trapping section 7 is usually arranged in a layered manner on the adsorbent layer 6. However, the fluorine component capturing section 7
For example, it may be in the form of a separately prepared cylindrical container filled with alumina and/or zeolite.

The waste gas in which the fluorine compounds have been trapped as described above is then introduced into the acidic component trapping section 8 made of soda lime.

When the dry etching gas contains a chlorine compound such as C ₂ ClF ₅ , hydrogen chloride is produced in addition to hydrogen fluoride by contact of these with the water contained in the adsorbent layer 6 . This hydrogen chloride is also difficult to be adsorbed by the adsorbent layer 6, and is not captured by the fluorine component trapping section 7. Furthermore, silicon tetrachloride and the like bonded to silicon in the silicon wafer are difficult to be adsorbed by the adsorbent layer 6, and are not captured by the fluorine component trapping section 7.

The acidic component trapping section 8 traps acidic components such as hydrogen chloride and silicon tetrachloride by utilizing the strong basicity of soda lime. Furthermore, if hydrogen fluoride and the like are not completely captured by the fluorine component capturing section 7, it is possible to capture hydrogen fluoride and the like as well.

It is preferable to use granular soda lime in consideration of the pressure loss and the contact area with the waste gas when the waste gas passes through the acidic component trapping section 8 made of soda lime. Such soda lime is generally used for capturing carbon dioxide gas, and in the present invention, soda lime that is normally used for such purposes can be used.

Soda lime rarely changes its shape even if it absorbs acidic components. Furthermore, unlike sodium hydroxide, it does not have deliquescent properties, so particles are less likely to fuse together and clog the device.

Note that such soda lime is usually produced by immersing quicklime in a concentrated solution of sodium hydroxide, heating it, and pulverizing it.

The acidic component trapping section 8 made of soda lime is provided on the gas outlet 5 side with respect to the adsorbent layer 6. Further, it is preferable that the fluorine component trapping section 7 is also provided on the gas outlet 5 side.

Generally, they are arranged in a layered manner on the adsorbent layer 6 so that the waste gas that has passed through the adsorbent layer 6 and further passed through the fluorine component trapping section 7 passes through a layer made of soda lime. However, acidic component trapping section 8
For example, the acidic component trapping portion may be formed by filling a separately prepared cylindrical container with soda lime.

When the fluorine component trapping section is arranged in a layered manner on the adsorbent layer and the acidic component capturing section is further arranged in a layered manner on top of the fluorine component capturing section, the adsorbent 100 forming the adsorbent layer 6
The amount of alumina and/or zeolite constituting the fluorine component trapping section 7 is within the range of 100 to 300 parts by volume, and the amount of soda lime constituting the acidic component trapping section 8 is within the range of 50 to 200 parts by volume. It is preferable to use it in

The waste gas that has thus passed through the adsorbent layer 6, the fluorine component trapping section 7, and the acidic component trapping section 8 is sent from the gas outlet 5 of the gas adsorption trapping device 3 to the breakthrough detection device 9.
will be introduced in

The breakthrough detection device 9 is provided close to the gas discharge port 5 of the gas adsorption trapping device 3 and in series with the adsorbent layer 6. Usually, the breakthrough detection device 9 includes methyl red, congo red, etc., which are sensitive to acidic gases such as hydrogen fluoride or hydrogen chloride.
Phenyl sulfophthalene (Phenyl Red)
The carrier is filled with an acidic gas detection agent such as .

When the gas adsorption trapping device reaches breakthrough, the hue of the detection agent changes as the acidic gas flowing out from the upper part of the acidic component trapping section 8 flows into the breakthrough detection device 9, so the hue changes. This gas adsorption trapping device can be used until the color changes, and the gas adsorption trapping device is replaced when the color changes.

After the components to be removed are captured and removed by the gas adsorption trapping device of the present invention, the waste gas that passes through the breakthrough detection device 9 does not contain components to be adsorbed such as fluorine compounds or chlorine compounds, and is therefore discharged as is. can do. However, when replacing the gas adsorption/trapping device, trace amounts of fluorine compounds may leak out, so it is preferable to release them through an alkaline scrubber (not shown) or the like.

The above description focuses on an example of the gas adsorption/trapping device of the present invention in which the adsorbent layer 6 is first disposed in the direction of flow of waste gas, then the fluorine component capturing section 7 and then the acidic component capturing section 8 are disposed. However, in the gas adsorption trapping device of the present invention,
It is also possible to first arrange the adsorbent layer in the flow direction, then arrange the acidic component trapping section, and then arrange the fluorine component trapping section. When the fluorine component trapping section and the acidic component trapping section are arranged oppositely, the waste gas from which sulfur, sulfur compounds, corrosion-resistant oil, etc. have been removed in the adsorbent layer in the same manner as above is Hydrogen chloride and fluorine compounds are removed in the acidic component trapping section, and if the fluorine compounds are not completely removed in the acidic component trapping section and flow out, they are captured in the fluorine component trapping layer.

Next, examples of the present invention will be shown.

[Example 1] A RIE etching device, a vacuum pump, and a gas adsorption trapping device were connected as shown in FIG. 1, and a silicon wafer was dry etched. Note that ballast nitrogen is introduced into the vacuum pump at a flow rate of 5 to 6 minutes per minute, and fluorine-based corrosion-resistant oil is used in this vacuum pump.

RIE etching equipment (type: electrode connection method, anode coupling, processing conditions: output 85W, pressure
A 3-inch silicon wafer was loaded into the chamber (0.2 Torr), and 20 mL each of SF ₆ and C ₂ ClF ₅ were charged into the device.
Dry etching of silicon wafers was carried out using a feed rate of cc/min.

The waste gas discharged from the RIE etching device was introduced into the gas adsorption trapping device via a vacuum pump.

The gas adsorption capture device is made of stainless steel with a diameter of 165 mm and a height of 300 mm, and has a gas inlet and a gas outlet. Inside, there is activated carbon (shape:
Columnar shape, average short axis length: 4 mm, average long axis length: 5 mm, moisture content: 3.0% by weight, manufactured by Kuraray Chemical Co., Ltd., product name: 4GS) 2 is filled. Further, the upper part of the activated carbon is filled with alumina (2 to 4 mm in diameter, manufactured by Sumitomo Aluminum Co., Ltd.) 3 to form a fluorine component trapping section made of alumina. Furthermore, the upper part of the fluorine component trapping section made of alumina is filled with 1.5 soda lime (manufactured by Wako Pure Chemical Industries, Ltd., trade name: Soda Lime No. 1) to form an acidic component trapping section made of soda lime. ing.

A breakthrough detection device was placed at the gas outlet of this gas adsorption trapping device via a connecting pipe. The breakthrough detection device is made by mixing 1 g of methyl orange, 100 ml of water, and 100 c.c. of alumina with a diameter of 2 to 4 mm, then drying the mixture at 50°C, and placing the breakthrough detection agent in a glass container. .

As a result of collecting the waste gas introduced into the gas adsorption trapping device as described above between the vacuum pump and the gas adsorption trapping device and analyzing it using GC mass spectrometry,
This gas contains 0.36% by volume SF ₆ , 0.39% by volume
It was confirmed that it contained C ₂ ClF ₅ and 0.01% by volume of CF ₄ .

After taking 5000 ml of this waste gas and bubbling it into 250 ml of ultrapure water, we measured the fluorine ion and chlorine ion concentrations contained in this ultrapure water using an ion chromatograph. The elementary ion concentration was 1200 ppm, and the chlorine ion concentration was 300 ppm.

As a result of collecting the gas discharged after removing the target components with the above gas adsorption trapping device and analyzing it using GC mass spectrometry, it was found that SF ₆ in this gas was
0.03% by volume, _{C2ClF5 is} 0.004% by volume, and _CF4 is
It had decreased to 0.007% by volume.

In addition, after bubbling this gas into ultrapure water using the same procedure as above, we measured the fluorine ion and chloride ion concentrations, and found that no fluoride or chloride ion concentrations were detected in this waste gas. .

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an arrangement example in which the gas adsorption and capture device of the present invention is connected between a gas generation device and a breakthrough detection device. 1: Gas generator (dry etching device),
2: Vacuum pump, 3: Gas adsorption capture device, 4: Gas inlet, 5: Gas outlet, 6: Adsorbent layer, 7:
Fluorine component capturing section, 8: Acidic component capturing section, 9: Breakthrough detection device.

Claims (1)

[Scope of Claims] 1. A gas adsorption/trapping device comprising an adsorbent layer provided inside a container having a gas inlet and a gas outlet, wherein the adsorbent layer is located on the gas outlet side with respect to the adsorbent layer.
A fluorine component trapping section made of alumina and/or zeolite for trapping fluorine compounds in the dry etching equipment waste gas and an acidic component trapping section made of soda lime for trapping acidic components are provided. A gas adsorption trapping device characterized by: 2. A patent claim characterized in that a fluorine component capturing section is provided on the gas outlet side with respect to the adsorbent layer, and an acidic component capturing section is further provided on the gas outlet side with respect to the capturing section. The gas adsorption trapping device according to scope 1. 3. The gas adsorption/trapping device according to claim 2, wherein the fluorine component trapping section and the acidic component trapping section are provided in a layered manner in this order on the gas outlet side with respect to the adsorbent layer. . 4. The gas adsorption and trapping device according to claim 1, wherein the fluorine component trapping portion is made of granular alumina. 5. The gas adsorption and trapping device according to claim 1, wherein the adsorbent is activated carbon. 6 The dry etching equipment waste gas is SF ₆ ,
Claim 1, characterized in that the exhaust gas is a dry etching gas containing at least one gas selected from the group consisting of C ₂ Cl ₂ F ₄ , C ₂ ClF ₅ , CF ₄ and CHF ₃ gas adsorption capture device.