JP2006059853A - Tray for vapor phase process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tray that is superior in plasma etching resistance and can be stably held and wherein electrostatic chuck is possible. <P>SOLUTION: The tray for the vapor phase process for electrostatic chuck is stuck to a semiconductor board with an inorganic consecutive stomatal sintered body whose thickness is 0.3 to 1.4 mm and whose open porosity is 5 to 50% as a protection board. In this case, the vapor phase process is a plasma etching process, and the protection board is provided with a wall of 0.3-1 mm in width around the outer periphery of a part for mounting an object to be etching, and it is like a shape where a part corresponding to a cut-out part for alignment of the object is removed. The tray can use the electrostatic chuck function set in a conventional plasma etching apparatus without remodeling, and can be stably held and be easily taken out during processing. Furthermore, the temperature of the object to be etched during etching can be controlled appropriately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a vapor process tray capable of electrostatic chucking that can be suitably used in a plasma etching process of a semiconductor substrate that is essential in MEMS or the like.

In recent years, electronic devices are required to be smaller, thinner and lighter, and are becoming increasingly thinner, as represented by mobile phones and IC cards.
Advances in manufacturing technology that supports these, especially the microfabrication technology of semiconductors seen in dry etching technology, is not limited to semiconductor processing, but as a manufacturing technology (MEMS) that combines semiconductor processing, machining, and electronic circuit technology, It has been greatly developed as a manufacturing technology for small devices, so-called micromachines. Application to various sensors such as light, pressure, acceleration, infrared light, magnetism, heat, micro relay, optical switch, micro valve, filter, etc., chemical analysis system such as micro gas chromatography, bio sensor, DNA chip, etc. A wide variety of applied developments have been carried out, and some have been put into practical use as indispensable parts and devices in fields such as machinery, communication, and medical care.

  In dry etching that supports this microfabrication technology, an etching resistant resist pattern is typically formed on a silicon wafer or the like, and this is used as a holding substrate using a silicon wafer or the like on which an etching resistant protective film is formed. It is mounted on the substrate and transferred to the etching zone by an electrostatic chuck. The holding substrate is cooled and controlled to keep the etching temperature constant, and after etching using chlorine plasma or the like, oxygen plasma is applied. For example, a desired three-dimensional shape is produced by repeating a cleaning step consisting of removing the resist by a plurality of times as appropriate.

The processing accuracy of this step includes the accuracy of producing a resist film, but in particular, high accuracy is achieved by making the variation in etching rate smaller. Etching is by removing, for example, exposed solid silicon as gaseous chlorosilane by a chemical reaction. This reaction is completed by (1) supply of chlorine plasma as a reactant onto solid silicon, (2) generation of chlorosilane, and (3) exclusion of chlorosilane generated in the reaction out of the system. This process has a negligible impact compared to liquid phase reactions because the reactants and reaction products are gaseous and (1) and (3) can be controlled relatively easily. .
However, (2) is an exothermic reaction. The chemical reaction rate depends greatly on the temperature. The precise control of the etching amount is to control the reaction temperature more strictly, which can be controlled to some extent by the use of a carrier gas, etc., but contact cooling using a holding substrate with high thermal conductivity. It is most effective to forcibly keep the temperature at a predetermined temperature.
In addition, it is necessary for the holding substrate not to be affected by the etching agent in terms of the number of repeated use. This is also desirable in that the holding substrate and the etching resistant protective film are not etched to generate heat, and more precise temperature control is possible.

Conventionally, as a holding tray for such a use, there is a silicon wafer formed with silicon carbide or an organic protective film. Since silicon carbide has semiconductor characteristics, it can be electrostatically chucked. However, silicon carbide is weak to halogen plasma and is difficult to use as it is, as is silicon.
Therefore, when such a material is used, a protective film such as polyimide is formed and used. However, there is a problem that polyimide used as the organic protective film is gradually attacked by plasma. Moreover, since silicon carbide is extremely hard and difficult to process, it is difficult to provide a desired auxiliary function by auxiliary processing.
As these improvements, carbon carbide is used to form a desired shape, and then a silicon carbide film is formed on the surface (Japanese Patent Laid-Open Nos. 5-283351, 10-223546, etc.), instead of silicon carbide. And an aluminum nitride film formed thereon (JP-A-10-74705). The film forming method has a problem of adhesion between the main body and the formed film and generation of distortion accompanying the film formation, and has not yet been sufficiently practical.

Also disclosed are those using aluminum nitride having extremely excellent plasma etching resistance (Japanese Patent Laid-Open Nos. 7-86379, 7-153706, 8-306629, and 11-100200). JP, 2000-63179, A, etc.). For example, Japanese Patent Laid-Open No. 7-86379 discloses a main body mainly composed of aluminum nitride in which a dense film made of aluminum nitride is formed and a heat generating circuit is provided inside the main body. Japanese Patent Application Laid-Open No. 11-100300 and Japanese Patent Application Laid-Open No. 2000-63179 disclose a material in which a small amount of rare earth elements and a small amount of lithium are added to impart semiconductivity to provide electrostatic chucking properties. Although these are excellent in terms of resistance to plasma etching, aluminum nitride has a drawback that it is difficult to process like silicon carbide.
Japanese Patent Laid-Open No. 5-283351 Japanese Patent Laid-Open No. 10-223546 JP-A-10-74705 JP 7-86379 A JP 7-153706 A JP-A-8-306629 Japanese Patent Laid-Open No. 11-100300 JP 2000-63179 A

  From the above, it is apparent that there is a need for a holding substrate having etching resistance and high thermal conductivity and capable of electrostatic chucking. In addition, it is very important for the holding substrate that the object to be etched can be stably held on the holding substrate under use conditions. For this purpose, it is more preferable that auxiliary processing or auxiliary tools for this purpose can be appropriately installed on the mounting portion of the workpiece (etched object) and the periphery thereof.

  In order to solve the above problems, electrostatic chucking is possible, and in particular, it can be applied to conventional processes as it is, achieving both high thermal conductivity and etching resistance, and attaching auxiliary tools by auxiliary processing as appropriate. As a result of diligent research to develop an easy-to-use gas-phase process tray, we previously proposed a vapor-phase process tray for an electrostatic chuck made by bonding an inorganic continuous pore sintered body to a semiconductor substrate as a protective substrate ( Japanese Patent Application No. 2003-404206). Furthermore, as a result of intensive studies on application of the proposed tray to a chlorine plasma etching process using a 6-inch silicon wafer, the present invention has been achieved.

  That is, the present invention is for a gas phase process for an electrostatic chuck formed by bonding an inorganic continuous pore sintered body having a thickness of 0.3 to 1.4 mm and an open porosity of 5 to 50% as a protective substrate to a semiconductor substrate. In the tray, the gas phase step is a plasma etching step, and the protective substrate is formed with a wall having a width of 0.3 to 1 mm around the outer periphery of the portion to be etched, It is a vapor phase process tray having a shape formed by removing a portion corresponding to a cut portion (such as orientation flat or V cut).

In the present invention, the semiconductor substrate is a silicon wafer having a thickness of 0.3 to 0.8 mm, the inorganic continuous pore sintered body is an aluminum nitride-boron nitride composite (AlN-h-BN), nitride aluminum - silicon carbide - boron nitride complexes (AlN-SiC-h-BN ), alumina - is preferably one selected from boron nitride complexes _{(Al 2 O 3 -h-BN} ).
The present invention is also a vapor phase process tray in which the adhesion is preferably performed with a thermoplastic polyimide resin.

First, the tray of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a plan view for explaining the tray (1) of the first embodiment. This tray 1 is formed with a thin side wall (edge wall) (3) on the outer periphery of the tray excluding the orientation flat portion, and the workpiece to be processed mounted on the inner mounting portion is held by this wall. The orientation flat (2) has a shape obtained by cutting and removing a part of the tray including the side wall (edge wall). The orientation flat 2 is used as a positioning reference portion when the product to be processed is mounted on the tray, and as a separation start portion from the tray bottom surface when the product to be processed is taken out when the plate is in a plate shape.
FIG. 2 is a diagram for explaining the layer structure of the portion A in FIG. 1, and for bonding the AlN-based protective substrate (21) having the side wall (edge wall) portion (23) and the Si substrate (22) protruding. It is formed by bonding at the bonding portion following the resin (24). It is essential that the thickness of the resin layer in the bonded portion is as thin as possible. In the production of this tray, the bonding resin penetrates the AlN-based protective substrate 21. The Si substrate 22 is formed by bonding a substrate having a width substantially smaller than that of the AlN-based protective substrate 21.

  The semiconductor substrate used in the tray of the present invention is typically a silicon wafer. Those having similar semiconductivity, for example, silicon carbide or those imparting semiconductivity, for example, an aluminum nitride-based continuous pore sintered body impregnated or attached with a conductive compound, etc. The range is 0.2 to 1.5 mm, and preferably the thickness is 0.3 to 0.8 mm. Regardless of being extremely thin, the strength is inferior if it is thin, and it becomes difficult to integrate the protective substrate. In addition, since it is protected by an etching-resistant protective substrate, it is not necessary to substantially consider thinning by etching, so a desired thickness considering strength and electrostatic force is sufficient and thick. There is no particular meaning to do it, it becomes heavy and disadvantageous.

The inorganic continuous pore sintered body used for the protective substrate in the present invention has a thickness of 0.3 to 1.4 mm and an open porosity of 5 to 50 vol%, preferably 5 to 35 vol%, particularly 10 to 30 vol%. A smaller amount of 2 vol% or less is preferable. The average pore diameter is 0.05 to 10 μm, preferably 0.1 to 5 μm. Further, in the vapor phase process, heating or cooling from the back surface is performed when performing vacuum deposition, sputtering, vapor phase etching, or the like.
In the present invention, specifically, an aluminum nitride-boron nitride composite (AlN-h-BN), an aluminum nitride-silicon carbide-boron nitride composite in which silicon carbide is 5% or less, particularly 3 to 0.5%. Examples thereof include those selected from (AlN—SiC—h—BN) and alumina-boron nitride composites (Al ₂ O ₃ —h—BN), and aluminum nitrides having a high thermal conductivity are particularly preferable.

  This protective substrate is surface-treated with thermal decomposition by an aluminum-based organic compound, specifically, aluminum tris (ethyl acetyl acetate) (product name: ALCH-TR, manufactured by Kawaken Fine Chemical Co., Ltd.), etc. The aluminum-based chelate compound impregnated, air-dried, heat-dried, heat-treated and surface-treated by thermal decomposition is preferable because it improves the affinity with the resin used for adhesion. Moreover, depending on the case, the thing which carried out the adhesion impregnation process to the pore inner wall surface with a thermosetting resin solution can also be used conveniently. In addition, when this resin impregnation process is performed, it is preferable to remove the surface resin on the surface (surface to be etched side) side by performing a plasma etching process in advance.

This protective substrate is provided with a recess for mounting the workpiece or a side wall (edge wall) around the outer periphery of the workpiece mounting portion, and a portion corresponding to a positioning portion such as an orientation flat or V-cut of the mounted object. The planar shape is cut and removed.
In the processing, first, a disk having a predetermined thickness and diameter is prepared. Next, this is usually fixed precisely to an auxiliary tool, and this is fixed on a processing table (table), and usually has a desired circular depth corresponding to the mounting portion, for example, about 0.05 to 0.5 mm. The dent is formed by cutting, and the bottom surface is polished and smoothed. Next, a portion corresponding to a positioning portion such as an orientation flat or V cut of the mounted object is cut and removed. Here, the procedure of cutting and polishing into the circular recess can be carried out by integrated processing on the same processing equipment and processing table, which is preferable from the viewpoint of processing accuracy. Moreover, it is preferable to perform the cutting and removal of the portion corresponding to the positioning portion such as orientation flat and V-cut while being fixed to the auxiliary tool. In addition, in the state fixed to the auxiliary tool, even if a crack or the like is generated during processing, it is not known, but a crack may be generated due to this during separation. In these cases, cracks and the like are suppressed by taking into consideration such as slowing the processing speed.

  The semiconductor substrate to which the protective substrate is bonded is appropriately formed in a desired range selected from a desired range of 0.2 to 1.5 mm, preferably a thickness of 0.3 to 0.8 mm. Used except for oxide films. When the workpiece (mounting object) is a semiconductor, the size and the planar shape can be used by polishing as it is. In other cases, the size and planar shape of the semiconductor substrate are the shape of the workpiece (mounting object). To match.

The main substrate manufactured above and the semiconductor substrate are bonded and integrated to form a main tray.
In adhering, first, an auxiliary material is attached to the recess of the protective substrate, and an adhesive resin layer is formed on the opposite surface. Then, on this adhesive layer forming surface, a cleaned semiconductor surface is usually removed except for oxides, etc., and an adhesive resin layer is formed thinly on this surface as appropriate, and then superimposed, and further appropriately in a dedicated mold. After being placed on or temporarily bonded together, both are bonded and integrated by heating and pressing.
The adhesive layer is usually formed from a resin. In the case of this application, those excellent in plasma resistance are preferred, thermoplastic resins are preferred, and thermoplastic polyimide resins and polybenzimidazoles are particularly preferred.
Note that the protective substrate and the semiconductor substrate are determined in consideration of the process to be used and the electrostatic chuck capability of the process. For example, when the thinnest part of the protective substrate is required to be less than 0.3 mm, for example, about 0.1 mm due to thickness restrictions, the thin part is gradually polished and removed after the two are bonded and integrated. A method of manufacturing can be selected.

In the present invention, the adhesive integration is usually performed by heating and pressurizing a semiconductor substrate thinned in the same manner as a ceramic thinly polished to a thickness of 0.5 mm or less, for example, about 0.3 mm. In addition, since the ceramic plate as the protective substrate has a protruding side wall (edge wall), the operation is extremely delicate.
First, in order to crimp without damage,
(1). Do not apply or generate a sudden pressure load,
(2). Pressure applied to the same part from above and below,
(3). In particular, avoid the generation of extra stress if there is a part that is not pressure-loaded,
Etc. are essential.

The above (1) is achieved by the pressure load mechanism of the press and the method of contacting the hot platen with the pressed product. As the apparatus, the previously proposed air plunger type decompression press machine (Japanese Patent Laid-Open No. 2002-192394) is suitable, and soft contact by lowering the upper heating plate using the air plunger as a damper, This is dealt with by absorption of pressure generation (reverse pressure) due to thermal expansion of heat by compressible gas.
(2) will be dealt with by using auxiliary tools such as auxiliary molds and applying temporary bonding. In particular, the use of an adhesive that deteriorates under heat and pressure bonding conditions and can be easily separated without losing adhesive force is a simple and excellent method with a wide range of applications.
(3) is an item that should be taken into consideration as appropriate from the actual situation, and this item is to avoid large temperature fluctuations and rapid temperature changes under the maximum press pressure load condition. For example, in order to avoid the occurrence of thermal stress or the like, the maximum pressure is applied after approaching the maximum temperature, and the operation such as lowering the temperature after reducing the pressure is appropriately adopted.

Next, in order to maintain high thermal conductivity, it is essential to make the adhesive layer between the protective substrate and the semiconductor substrate as thin as possible. This is because the resin adhesive layer is made thinner during the adhesive integration under heating and pressure. This can be achieved for the first time by forming an adhesive layer with the minimum necessary thickness in advance and pressing most of it into the continuous pores of the protective substrate with pressure.
Depending on the heating / pressurizing time, it can be pushed to a certain extent, that is, the resin adhesive layer can be thinned. However, in consideration of productivity and the like, it is preferable that a sufficient thermal conductivity can be ensured by an average of several μm or more. From this point, it is preferable that the thickness of the resin adhesive layer to be formed first is selected from the range of several μ to several tens μ. In addition, although related to the improvement of adhesive strength, it is preferable that the surface including the continuous pore surface of the protective substrate has improved affinity with the adhesive resin, and in the case of nitride ceramics such as aluminum nitride Is usually mandatory.

In the gas phase process using the main tray manufactured as described above, after completion of the predetermined processing, the work piece mounted on the main tray is appropriately transferred between the multi-stage processing steps or during the processing step. It is preferable that it can be carried out simply and accurately, for example, by taking it out from the tray, performing a predetermined process, and mounting it again on the tray. This loading and unloading can be performed using a positioning portion such as an orientation flat or a V-cut, which is preferable.
For example, the orientation of the orientation flat guide (V cut guide) in which the tip portion coincides with the orientation flat portion or the V cut portion of the tray and the upper portion is wider than the orientation flat portion, and the wafer which is usually opposite to this is provided. A method of using an auxiliary tool provided with guides at a plurality of surrounding locations and dropping the orientation flat (V cut guide) with the orientation flat (V cut guide) is exemplified.
Next, the removal is performed by blowing a gas such as air in accordance with the orientation flat (V cut) to lift the wafer from the bottom surface of the tray and then removing the wafer with a removal tool. In addition, when it is processed into an assembly of fine products by etching or the like, an extraction method is appropriately devised and selected in consideration of the shape of the manufactured product.
In addition, an auxiliary pressing jig and the like can be appropriately provided on the tray.

  As described above, the tray of the present invention can be used without improving the set electrostatic chuck function of a conventional plasma etching apparatus, can be stably held during the process, and can be easily taken out. The temperature control can be suitably performed, and its significance is extremely high.

Hereinafter, the present invention will be specifically described with reference to examples and the like.
Example 1
Production of protective substrate.
Aluminum pore-silicon carbide-boron nitride based continuous pore sintered body having a thickness of 0.64 mm and a diameter of 151.0 mm (SiC 0.5%, h-BN 13%, bulk density 2.53 g / cm ³ , true porosity) A disk with a surface of 16.5 vol% and an average pore diameter of 0.52 μm was polished to prepare a thickness of 0.625 mm, surface roughness Ra: 0.3 μm, parallelism of 10 μm, and flatness of 10 μm.
In this disk, a recess (diameter 150.0 mm, depth 0.3 mm) (side wall (edge wall) average thickness 0.4 mm) for storing a workpiece is formed, and the recess has a surface roughness Ra: 0. The surface was polished so that the flatness was 5 μm or less and 20 μm or less.
Next, the portion corresponding to the orientation flat of the silicon wafer that is planned to be etched is cut and removed so that the protective substrate portion is slightly exposed at the time of mounting, separated from the processing support base, cleaned by heat treatment, and further aluminum A surface treatment (hereinafter referred to as “AN1”) prepared by impregnation of an aqueous compound solution, air drying, heat treatment, and thermal decomposition was prepared.

Thermoplastic polyimide resin containing biphenyltetracarboxylic anhydride (BPDA) as the main acid anhydride component (manufactured by Ube Industries, Ltd., trade name: Iupite UPA-221, concentration 20 wt%) and 90 wt parts and N-dimethylacetamide (DMAC) ) 10 wt parts were mixed to prepare an adhesive solution (hereinafter referred to as PI-18).
A resin-impregnated hardened aluminum nitride-based inorganic continuous pore sintered body plate having a planar shape corresponding to the concave portion corresponding to AN1 and having a thickness of 0.4 mm is produced, and this is used as the concave portion of AN1. Temporarily attached. Next, the adhesive solution PI-18 was applied to the surface of AN1, which is the opposite side, with a coater, and the coating side was up, and it was naturally dried all day and night, and then dried at 120 ° C./30 minutes to form an adhesive layer. A protective substrate (hereinafter referred to as AN1-PI) was obtained. The adhesive layer thickness was about 9 μm.
Further, a silicon wafer with an orientation flat (thickness: 625 μm, diameter: 150.0 mm) was polished to a thickness of 0.4 mm, and an oxide layer was removed.

Adhesion with semiconductor substrate (silicon wafer).
On the adhesive layer of the adhesive layer forming protective substrate, the silicon wafer with orientation flat from which the oxide layer obtained above was removed was positioned and temporarily fixed. Around this, a 1.2 mm thick, 21 cm square cotton paper with a 153 mm diameter circle cut out was placed.
On the top and bottom, a 0.4 mm thick aluminum alloy plate / silicone cushion sheet (trade name; PORON HT-1500, manufactured by Rogers Co., Ltd.) / Aluminum alloy plate is placed, and this is the heat of the vacuum press. Inserted between the boards. The press atmosphere was reduced to 10 mmHg or less, the temperature was raised at 10 ° C./minute, held at 230 ° C. for 15 minutes at a surface pressure of 0.3 MPa, then opened to the atmosphere, allowed to cool, and a silicon wafer with a protective substrate ( Hereinafter, it was referred to as AN1-Si).

Process test.
A 5-inch silicon wafer to be processed having a thickness of 100 μm was set on the vapor-phase process tray AN1-Si-P so that the position of the silicon wafer was adjusted at the orientation flat portion. This was set on an electrostatic chuck for a silicon wafer, transferred, and etched with chlorine plasma on a cooling plate (−20 ° C. setting).
During the etching, the temperature of the silicon wafer to be processed was measured at the center and four points around the silicon wafer. As a result, the temperature was maintained at 101 to 104 ° C. at all the measurement points.

Wash and separate.
When the etching was interrupted and the etching was taken out of the tray while blowing air on the orientation flat part, it was easily removed.
After completion of the predetermined etching, the etching was taken out from the tray while blowing air on the orientation flat portion.
Also, the tray is usually cleaned (cleaned with oxygen plasma, etc.) and circulated for reuse.

Example 2
In Example 1, a tray using a V-cut having a width and a cutting depth of about 5 mm in place of the orientation flat as an object to be etched was prepared and tested in the same manner.
During the etching, the temperature of the silicon wafer to be processed was measured at the center and four points around the silicon wafer. As a result, the temperature was maintained at 101 to 104 ° C. at all the measurement points.
Further, when the etching was interrupted and the etching was taken out from the tray while air was blown to the orientation flat portion, it was easily removed.

FIG. 3 is a plan view for explaining the tray according to the first embodiment. FIG. 2 is a sectional view showing a layer structure of a portion A in FIG.

Explanation of symbols

1 tray 2 orientation flat 3 side wall (edge wall)
21 AlN-based protective substrate 22 Si substrate 23 Side wall (edge wall) portion 24 The protruding adhesive resin

Claims (4)

In a gas phase process tray for an electrostatic chuck formed by bonding an inorganic continuous pore sintered body having a thickness of 0.3 to 1.4 mm and an open porosity of 5 to 50% to a semiconductor substrate as a protective substrate, the gas phase The process is a plasma etching process, and the protective substrate is formed with a wall having a width of 0.3 to 1 mm around the outer periphery of the part to be etched, and corresponds to a cut part for positioning the etched object A tray for a gas phase process, which has a shape formed by removing the gas. 2. The vapor phase process tray according to claim 1, wherein the semiconductor substrate on which the tray is formed by bonding is a silicon wafer having a thickness of 0.3 to 0.8 mm. The inorganic continuous pore sintered body is an aluminum nitride-boron nitride composite (AlN-h-BN), an aluminum nitride-silicon carbide-boron nitride composite (AlN-SiC-h-BN), or an alumina-boron nitride composite. _{(Al 2 O 3 -h-BN} ) gas phase process tray according to claim 1, wherein those selected from. The tray for a gas phase process according to claim 1, wherein the adhesion is performed with a thermoplastic polyimide resin.

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