JP2007115795A - Method of dry-cleaning rear surface of substrate and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of dry-cleaning the rear surface of a substrate by which foreign matters adhered to the rear surface and the bevel of a substrate can be removed, and to provide an apparatus therefor. <P>SOLUTION: A substrate 2 to be cleaned is conveyed into a container 4, and it is kept suspended in non-contact state. A fluid does not remain by vaporization or volatilization after discharging, and is applied onto the rear surface of the substrate. Foreign matters adhered to the rear surface of the substrate 2 are removed by hitting the fluid, and then, after the removal work, the substrate is taken out from the container. Therefore, the foreign matters adhered to the rear surface or the end of the substrate can be efficiently removed without generating readhesion or recontamination, or without producing dusts from a removing device, irrelevant to the properties of the adhered foreign matters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to dry cleaning of a back surface or an end portion of a substrate used for manufacturing a semiconductor element or a liquid crystal display device, and a foreign matter attached to the back surface or the end portion of the substrate in the course of vacuum processing including plasma processing. The present invention relates to a method and an apparatus for removing water in a dry state.

  Regarding the method and apparatus for removing deposits from the back surface and edge of a semiconductor wafer, as shown in Japanese Patent Publication No. 6-70273 (Patent Document 1), the surface of the semiconductor wafer is an upper portion called a face plate. There is a method in which a plasma is generated between a wafer back surface and a lower electrode called a susceptor by pressing against the electrode to remove deposits from the wafer back surface and edge. However, in this case, it is necessary to press the wafer surface against an electrode that prevents the plasma from flowing in. Therefore, the contact may damage the elements around the wafer, or foreign matter may be generated when the wafer is pressed or peeled off. Had a risk of dust generation. Further, as shown in the specific example, a lift pin that lifts the wafer and presses it against the upper electrode is necessary, and there is a risk of secondary contamination and dust generation due to the lift pin being exposed to the plasma. At the same time, there is a problem in that the adhered foreign matter at the portion where the lift pin contacts cannot be removed.

  Japanese Patent Laid-Open No. 10-22276 (Patent Document 2) discloses that a thin film adhering to the back surface of a wafer during film formation is removed by etching. In this case, the heat shielding plate provided in the plasma and the wafer surface are held with a certain gap, and the back surface of the wafer is etched by the plasma that wraps around the back surface of the wafer. However, in this case as well, since the wafer is pushed up by the lift pins, there is a problem similar to that of Japanese Patent Publication No. 6-70273 (Patent Document 1), and there is a risk of secondary contamination and dust generation from the heat shielding plate. He also had sex.

Further, as a form of holding the wafer edge instead of holding the wafer back surface, Japanese Patent Laid-Open No. 11-101.
No. 26431 (Patent Document 3), a strong holding force is required to grip the edge portion and rotate the wafer, and there is a concern about the occurrence of chipping in the edge portion. There was a problem that it could not be removed.

A technique for holding the wafer in a non-contact manner is described in Japanese Patent Laid-Open No. 2003-297901 (Patent Document 4). The non-contact wafer holding mechanism described in this publication uses the “Bernoulli effect” and uses the principle of sucking the wafer to the holding mechanism with a pressure difference generated between a place where the flow velocity is fast and a place where it is slow. is there. To use the Bernoulli effect,
(1) The wafer is once lifted with a nail, and the wafer holding surface and the opposite surface (the entire wafer) are brought to the same pressure state.
(2) An inert gas is supplied from the center of the wafer so as to be parallel to the wafer and discharged to the outer periphery of the wafer.
(3) At this time, since the flow path area expands from the central part to the outer peripheral part, the gas flow rate is fast in the central part and slow in the peripheral part. For this reason, the pressure at a location slightly away from the central portion is relatively lower than the outer peripheral portion of the wafer and the opposite surface of the wafer.
(4) The wafer is sucked to the holding mechanism by this pressure difference.
With this procedure, the wafer is held in a non-contact manner.

  Therefore, it is considered that the wafer needs to be mechanically chucked and lifted up, although it is the end portion. Moreover, since the change in the cross-sectional area of the flow path is constant, the amount of change in the pressure difference hardly changes even if the gas flow rate is increased. Since giving a high gas flow rate is nothing but supplying a gas having a high gas pressure, there is a possibility that the wafer is blown out. Therefore, the wafer holding force cannot be made variable. Although the technique of this publication is not a technique applied to wafer backside cleaning, if the wafer holding force cannot be made variable, the reaction force change of the cleaning fluid cannot be finely adjusted. Application to backside cleaning is difficult.

Japanese Patent Publication No. 6-70273 Japanese Patent Laid-Open No. 10-22276 JP-A-11-26431 JP 2003-297901 A

  With the recent reduction of semiconductor device patterns and the increase in size of liquid crystal substrates, for example, even in dry etching of semiconductor devices, the number of foreign particles adhered to the substrate surface is required to be 0.16 μm or more and 10 wafers or less. It is becoming. This is because the adhered foreign matter becomes a mask in processing, or remains on the substrate to cause a short circuit between wirings, which is a major factor in reducing the product yield. In addition, in order to prevent a decrease in yield, a frequent cleaning operation for removing foreign matters is required, and therefore a factor that causes a decrease in productivity is incorporated. Further, regarding the adhesion of foreign substances, the upper limit value of the number of foreign substances adhering to the substrate after processing is gradually decreasing not only on the front surface of the substrate but also on the back surface and the end portion of the substrate (referred to as a bevel portion). . The reason is that there is a problem of transfer of foreign matter adhered to the back surface or bevel of the substrate due to cross-contamination in the substrate storage container or during wet cleaning performed as a post-treatment. .

  Therefore, it is indispensable to remove the adhered foreign substances on the back surface and bevel portion of the substrate, but in the conventional technology, the back surface of the substrate is held by a lift pin, the outer periphery portion of the substrate is held, and a support mechanism for a contact structure is provided. Needed and had the problem of causing secondary contamination and dusting.

  Further, in the prior art, as a specific removing means, plasma is used to remove adhered foreign substances on the back surface or bevel portion of the substrate. However, when removing adhered foreign matter with plasma, if the adhered foreign matter is organic, it can be removed by oxidation with oxygen plasma or the like. However, if the attached foreign matter is inorganic, it can be removed with plasma. It is necessary to convert the substance into a substance that can be easily converted, and depending on the material processed into the substrate, it is difficult to select a gas to be used.

  In addition, although the substrate itself is etched to remove the adhering substance with the force of vaporizing the substrate substance, there is a problem that the substrate itself is processed. Further, in this case, the adhered foreign matter was used as a mask, and the foreign matter could be removed, but the portion where the foreign matter adhered to the substrate remained in the convex shape due to the etching, and the foreign matter in the substrate face plate foreign matter inspection apparatus In the detection, it is difficult to determine whether the foreign matter is an attached foreign matter or a convex portion of the substrate, and it is difficult to verify the effect of removing the attached foreign matter.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a dry cleaning method and apparatus for a back surface of a substrate that can solve the above-described problems and can remove foreign substances adhering to the back surface and bevel portion of the substrate with a simple structure. .

  As one of the characteristic means of the present invention, the substrate is placed in a downflow flow of clean air at a pressure around atmospheric pressure, so that the removed foreign substance on the back surface or bevel portion of the substrate is re-applied to the substrate. Prevent adhesion.

  As a second means, the surface of the substrate is supported by a non-contact holding device, and the inconvenience due to contact with lift pins or the like is eliminated.

  A third means is to apply a fluid capable of giving a physical and thermal action to the back surface and bevel portion of the substrate. This makes it possible to remove the adhered foreign matter on the back surface of the substrate regardless of the nature of the organic matter, inorganic matter, etc., and without damaging the substrate itself. And, by this fluid, for example, an impact action by the solid in the fluid directly hitting the adhered foreign substance, a thermal action when the solid hits the substrate and liquefies, an action in which the liquefied fluid agglomerates into a fine foreign substance, A combination of the action of a liquid in a fluid directly agglomerating against a minute foreign substance, the action of a solid directly against the agglomerated large foreign substance, and the action of a gas in the fluid directly against the agglomerated foreign substance are combined. It is.

  As a fourth means, as the fluid applied to the back surface of the substrate or the bevel portion, a gas, a solid that does not remain after vaporization or volatilization after processing, a fluid consisting of a single liquid, or a combination thereof, are used. That is. For example, a gas-solid obtained by mixing a vaporizable solid with a gas or a fluid formed by mixing a vaporizable solid with a volatile liquid can be used. As a result, the fluid from which the adhering foreign matter on the back surface of the substrate has been removed can be discharged out of the container without remaining in the substrate or the container that accommodates the substrate, and secondary contamination by the fluid can be eliminated.

  According to the present invention, the foreign matter adhering to the back surface or bevel portion of the substrate by vacuum processing does not cause re-adhesion or re-contamination, no dust is generated from the removing device, and It can be efficiently removed regardless of properties, and the yield and productivity of semiconductor elements and liquid crystal display devices can be improved.

  Generally, foreign substances adhering to the substrate are considered to be due to adsorption force due to static electricity, intermolecular bonding force, chemical bonding force, or diffusion force into the substrate. Currently, wet cleaning is the mainstream for removing foreign substances adhering to the back surface of a substrate. For example, scrub treatment with a rotating brush in a pure water flow is applied. The advantage of wet treatment is that electrostatic force can be canceled by washing water, intermolecular bonding force can be canceled by contact with a rotating brush, and chemical bonding force and diffusion force can be canceled by selecting a cleaning solution. . However, wet cleaning requires drying after cleaning and after-treatment of the cleaning liquid, and is an expensive device including incidental facilities.

  For that reason, it is desired to convert the wet process into a dry process. The disadvantages of using plasma, which is one form of dry treatment, are as described above, but the effect of removing foreign substances attached by intermolecular bonding force, chemical bonding force and diffusion is not great.

  Therefore, in the present invention, the substrate surface is held in a non-contact manner, and the back surface and the bevel portion of the substrate are dry cleaned. The invention will be described below with reference to examples.

  FIG. 1 is a schematic view of the apparatus of the present invention. The container 4 contains a substrate holder 1 that holds the substrate 2 in a non-contact manner and a fluid ejection nozzle 3 that ejects a cleaning fluid to the back surface of the substrate 2. The fluid ejection nozzle 3 is movable in the horizontal direction. A fan 5 that sucks and discharges clean air is provided above the container 4, and a filter 6 is provided below the fan 5. An exhaust cylinder 7 is provided at the lower part of the container 4, and clean air that has flowed down is discharged out of the container 4. The discharged clean air may be returned to the upper part of the container 4 by a duct and circulated. The exhaust tube 7 can be provided with a filter that adsorbs the removed foreign matter and an adsorption device for reusing the used fluid. An intermediate portion of the container 4 has an opening 8 for loading and unloading the substrate 2, and includes an opening / closing mechanism 9 that opens and closes the gate in response to loading and unloading of the substrate 2. Although not shown, the substrate 2 is carried in and out of the substrate 2 by using a transfer arm by a transfer robot, holding the back surface of the substrate 2 and directly under the substrate holder 1.

  FIG. 2 shows a schematic structure of the substrate holder 1. The substrate holder 1 is provided with a flat portion corresponding to the surface of the substrate 2, and in a form surrounding the periphery corresponding to the supply port 11 and a supply port 11 of clean air at a plurality of locations in the surface, A substrate holding modular 23 provided with a suction port 12 is disposed. It is desirable that the substrate holding modulars 23 be arranged concentrically at equal intervals at three or more locations in the plane portion and fixed by screws or the like. Pressurized air is individually supplied to the supply port 11 by a clean air supply device 15, and the suction port 12 is connected to the vacuum exhaust device 21, and the clean air supplied from the supply port 11 is partially and individually supplied. Suction and exhaust. By appropriately maintaining the supply pressure, the intake pressure, and the pressure balance of clean air flowing out from the end of the substrate into the container 4, the substrate 2 can be held while being floated in a non-contact manner while being received from the transfer arm. .

  The substrate holder 1 is provided with gap sensors 13 for measuring a spatial gap with the substrate 2 at a plurality of locations in the vicinity of the outer peripheral portion of the plane portion. Based on these measured values, the control device 20 The pressure gap between the supply port 11 and the suction port 12 of the holding modular 23 is adjusted to control the space gap to be within a certain range. Further, a plurality of position sensors 14 for detecting the position of the outermost peripheral portion of the substrate 2 are provided on the substrate holder 1 to control the position so that the substrate 2 is not detached from the substrate holder 1 and to confirm the holding position of the substrate 2. I do.

  For example, a capacitive sensor is used as the gap sensor 13, and an optical sensor is used as the position sensor 14.

  By controlling the space gap and the substrate position, the substrate 2 is held in the substrate holder 1 in a non-contact manner. Then, using the fluid ejection nozzle 3, for example, a gas solid produced by mixing the vaporizable solid into the gas, or a vaporizable solid mixed with the volatile liquid was used. A fluid using one or a combination of fluids from a liquid solid is applied to the back surface or bevel portion of the substrate 2 to apply a physical and thermal action to the foreign matter attached thereto. As a result, foreign substances adhering to the back surface or bevel portion of the substrate 2 can be removed with an electrostatic force or with an intermolecular bonding force. Needless to say, the fluid used may be a gas, a solid that does not remain after vaporization or volatilization after treatment, or a liquid alone or a combination thereof. .

  In addition, even if a liquid is used, since the liquid is volatile, it is highly possible that a part of the liquid is a gas when discharged from the ejection nozzle 3, and a cooling effect by adiabatic expansion. May solidify some of them and mix them.

  For these solids, liquids and gases, solid sources such as carbon dioxide, pure water, argon and other cooling solids, normal temperature, normal pressure, high temperature, normal pressure, normal temperature, reduced pressure, high temperature, reduced pressure, The one that vaporizes is selected. For increasing the temperature, it is possible to select heating the downflow clean air with a heater or the like. Further, light pressure reduction can be dealt with by evacuating the exhaust cylinder 7 part. In this case, it goes without saying that the sealing effect against the outside air including the exhaust pipe 7 is enhanced. As the liquid source, there are fluids such as liquefied carbon dioxide, liquefied argon, and pure water. Regarding the gas, there are clean air, inert gas such as nitrogen gas, and argon.

  In general, static electricity is generated between the substrate 2 and the fluid discharged from the ejection nozzle 3 or friction between particles contained in the fluid ejected from the ejection nozzle 3 in the dry state. Is desirable. Furthermore, there is a problem of generation of a water mark or the like on the substrate 2 due to condensation of moisture in the air, and dew point management in the container 4 is also necessary.

  Further, the fluid ejection nozzle 3 can be moved by the XY stage 10 disposed outside the container 4 and its control device 20 so that the ejection fluid can be uniformly applied to the bevel portion and the entire back surface of the substrate 2. Placed in.

  However, there is a possibility that the substrate 2 receives a reaction force due to the fluid of the fluid ejection nozzle 3 and the substrate 2 collides with the substrate holder 1. For this reason, the gap sensor 13 captures a change in the spatial gap between the substrate holder 1 and the substrate 2, and the control device 20 pressurizes clean air at the supply port 11 of the substrate holding modular 23 and vacuums the suction port 12. The reaction force is absorbed by the air cushion effect generated by the pressure balance due to exhaust. Although the reaction force of the fluid striking the substrate 2 varies depending on the movement of the fluid ejection nozzle 3, the substrate holding modular 23 provided at a plurality of locations, for example, strengthens the air cushion effect at one location and holds the substrate 2 at other locations. If control such as enhancing the effect is performed, it is possible to respond to fluctuations in the reaction force, and the substrate 2 is not dropped. In other words, in the configuration of the present invention, the substrate 2 is held in a non-contact manner by controlling the balance force by gas supply and vacuum evacuation by independently controlling the plurality of substrate holding modulars 23 provided.

  After dry cleaning, a transfer arm (not shown) is inserted directly under the substrate 2 to weaken the suction force of the substrate holder 1, thereby transferring the substrate 2 onto the transfer arm and carrying it out of the container 4.

It is a longitudinal cross-sectional view which shows the apparatus structure of this invention. It is a longitudinal cross-sectional view of the substrate holder part of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate holder, 2 ... Substrate, 3 ... Fluid ejection nozzle, 4 ... Container, 5 ... Fan, 6 ... Filter, 7 ... Exhaust tube, 8 ... Opening part, 9 ... Opening / closing mechanism, 10 ... XY stage, 11 ... supply port,
DESCRIPTION OF SYMBOLS 12 ... Suction port, 13 ... Gap sensor, 14 ... Position sensor, 15 ... Clean air supply apparatus, 20 ... Control apparatus, 21 ... Vacuum exhaust apparatus, 22 ... Fluid supply apparatus, 23 ... Substrate holding modular.

Claims (3)

The substrate to be cleaned is transported into a container, the substrate is suspended and held in a non-contact manner, and a fluid that does not remain after vaporization or volatilization is released to the back surface of the substrate. By removing the foreign matter adhering to the back surface of the substrate,
A dry cleaning method for a back surface of a substrate, wherein the substrate is carried out of the container after the removing operation. Substrate holding means for holding the substrate to be cleaned in a non-contact manner by a balance between gas supply and suction, fluid supply means for releasing a fluid for removing foreign substances on the back surface of the substrate, the substrate holding means, and the fluid A substrate back surface dry cleaning apparatus provided with a control means for controlling a supply means,
The substrate holding means includes a plurality of substrate holding modulars including a supply port for ejecting gas to the substrate and a suction port for sucking the gas provided around the supply port,
The fluid supply means includes a fluid ejection nozzle that ejects a fluid that does not remain after vaporization or volatilization to the back surface of the substrate, and a nozzle movement that moves the fluid ejection nozzle on a plane parallel to the substrate plane. With means,
The control means controls the gas supply and suction states of the plurality of substrate holding modulars independently for each substrate holding modular, and moves the nozzle moving means to apply the fluid to the entire back surface of the substrate. The substrate back surface dry cleaning apparatus is characterized by being controlled as follows. In claim 2,
The substrate backside dry cleaning apparatus, wherein the substrate holding means includes a gap sensor for measuring a distance from the substrate and a position sensor for detecting a position of an outermost peripheral portion of the substrate.

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