KR100286698B1 - Semiconductor Wafer Holder with CVD Silicon Carbide Film Coating - Google Patents

Abstract

The present invention relates to a semiconductor wafer holder in contact with an attached object to be attached. The contact portion consists of a sintered silicon carbide substrate and is coated with a condensed CVD silicon carbide film having at least one crystal plane orientation selected from the (111), (110), (220) and (200) crystal planes of the Miller index to provide a corrosive coating. In order to provide high strength and good abrasive properties that can be supported, the surface polishing of the contact portion is promoted to be extremely smooth and free of dirt and pinholes. These materials have large modulus of elasticity, small specific gravity, and small coefficient of thermal diffusion, resulting in high strength in circuit printing, and stability of dimensions despite the heat of exposure, so that there is little change. The material sintered together with the crystallized CVD silicon carbide film of β structure provides an electrical resistance of 10 ¹⁰ Ω · cm or less to provide high conductivity, thereby preventing static electricity and facilitating cleaning.

Description

Semiconductor Wafer Holder with CD Silicon Carbide Film Coating

The present invention relates to a holder for fixing by adsorbing thick film substrates such as semiconductor substrates, alumina and quartz.

Various types of conventional holders are designed to attach the object in contact with the smooth surface of the object to which it is attached. For example, devices used in a semiconductor IC circuit manufacturing process carry and fix a wafer in a pre-installed position. In exposure systems that play an important role in the corrosive process, vacuum chuck devices are used to secure thin film wafers in a plane.

Anodized aluminum alloys and alumina ceramics are known to be used in the contact portion to which the attachment is attached by this type of holder. In order to maintain the accuracy of the adsorption surface due to prolonged wear and the like at the contact portion of the holder, a holder made of aluminum alloy is unsuitable, and when a holder having a contact portion made of alumina-ceramic is also used, the attachment portion is electrically charged. The dust particles adhere to the wafer to be contaminated and reduce the adsorption accuracy of the attached object.

As a result of recent miniaturization in semiconductor IC circuits, it is necessary to ensure that the wafer exposed surface has a complete two-dimensional and extremely smooth plate. Therefore, the surface accuracy of the adsorption surface of the vacuum chuck holder to which the attachment object to be attached is attached for an extremely smooth finish is required.

When the contact surface of the holder is formed by machining, aluminum alloys can be processed smoothly and easily, but are easily degraded. Since alumina ceramics have pin holes and are electrically charged, they tend to adsorb particles and have a large heat diffusion coefficient.

According to the above-mentioned prior art, the properties required for a holder material designed to fix an attachment in contact with a smooth surface of the holder include excellent corrosion resistance, for example, high hardness; The presence of pinholes and no insertion of dust particles due to electrical charging; Small thermal diffusion coefficient; Low specific gravity and high strength; And excellent processability.

The above-described characteristics are described in detail below.

The contact surface between the holder and the attachment is worn out and damaged by repeated attachment. In particular, when a thin object such as a thin wafer is adsorbed to the vacuum chuck holder and its attachment, the surface of the adsorbed wafer must first be modified in an appropriate position for the exposure system to generate light. In other words, it should be as perfect a two-dimensional plane as possible. As a result, high corrosion resistance and high hardness are not only deformed by the damage caused by corrosion of the contact surface between the holder and the attachment substance, but also by microparticles produced by the corroded wear from the contact surfaces therebetween. It is a desirable property of the contact surface to prevent the deformation of the object due to it. In the case of a wafer, fine particles are deposited on the surface, resulting in broken wires and short circuit printing. More specifically, the corrosive coating described above attaches dust to the electrically charged holder. For example, it penetrates into the pinholes of the ceramic surface and causes the same damage as mentioned above.

In the case of a vacuum chuck holder of an exposure system, heat is accumulated by absorption of light at the time it is exposed. As a result, the high coefficient of thermal diffusion of the holder results in a change in the dimensions of the holder such that it is impossible to hold the wafer fixed to the pre-installed holder in a suction and attracted state. In addition, it is desirable to make the thermal diffusion coefficient as small as possible in order to reduce the error of the dimension in the circuit printing.

When a large attachment material is attached, the load on the attachment portion of the holder becomes heavy, and a high mechanical strength material is needed for the holder. On the other hand, the increase in hardness acts against the effort to make the holder lightweight, resulting in an increase in the thickness of the material.

Most of the time and labor consumption steps of the material processing process are polishing. In particular, in the case of a vacuum chuck holder for attaching a wafer, the surface in contact with the wafer should be extremely smooth because of the modification to obtain flatness through vacuum suction. Therefore, the grindability of the holder material is a decisive factor.

Ceramic materials have recently been developed as materials that meet the above mentioned conditions. However, the presence of ceramic materials requires a lot of processing as well as polishing energy to polish the surface in the extremely smooth steps described above. Intensification of polishing damages the glossy surface and furthermore makes it difficult to obtain a smooth, flat surface of high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor wafer holder made of a ceramic composite which is a silicon carbide film formed by CVD of sintered silicon carbide serving as a contact portion of an attached substance to be attached.

1 is a schematic plan view of a vacuum chuck holder in an embodiment of a semiconductor wafer holder of the present invention.

2 is a schematic cross-sectional view of the vacuum chuck holder of FIG.

3 is a partially enlarged cross-sectional view of a schematic sectional view of the vacuum chuck holder of FIG.

<Description of the code | symbol about the principal part of drawing>

1: annular projection 2: annular recess

3: inlet 4: sleeve shaped part

5: silicon carbide film 6: silicon carbide substrate

The electrical resistance of the sintered silicon carbide composite used in the present invention is preferably 10 ⁶ Pa · cm or less. This property is called a composite with conductivity. In other words, the semiconductor wafer holder according to the present invention has the high strength, light weight, and high hardness of the sintered ceramic, and has a conductivity which has not been obtained in the presence of Al ₂ O ₃ ceramics up to now. In conclusion, the corrosion resistance of the material was increased and the deposition of dust was reduced by preventing the generation of static electricity at the contact with the attachment material.

The CVD film of the present invention is a pinhole-free condensed film present on the surface of a common ceramic. Further, the contact portion between the semiconductor wafer holder and the attachment material should be clean without depositing any foreign material in the pinhole, and even if there is a deposit, the deposit should be easily removable.

As mentioned above, the CVD silicon carbide film of the present invention can be produced to have various kinds of film structures having respective crystalline orientation plates according to the conditions of vapor deposition.

In addition, in particular in the formation of a film having the above function, there is no method for forming a CVD silicon carbide film according to the present invention. If a general method is used, formation by reduced pressure CVD means in a non-acidic atmosphere is preferred.

The ceramic wafer holder of the present invention has a method of attaching an adherent by abutting on a smooth and flat surface, for example, a holder (a vacuum chuck that holds a wafer on a plate in an exposure system in a lithographic process). Holders, etc.) are used to carry the semiconductor substrate and attach the wafer.

A semiconductor wafer holder according to the present invention will be described below with reference to the accompanying drawings.

1 is a perspective view showing a schematic description of a vacuum chuck holder structure for wafer holding, which is an embodiment of a semiconductor wafer holder according to the present invention. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1. 3 is a partially enlarged view of FIG. 2.

The wafer adsorption surface of the vacuum chuck holder WH according to the invention is slightly circular in shape than the diameter of the wafer W. A plurality of annular projections 1 (wafer W supporting portions) and annular recesses 2 (vacuum suction grooves) concentric with the holder WH center are formed in a ring shape at regular intervals on the wafer adsorption surface. Each annular recess 20 has a radial inlet 3 for vacuum adsorption, each inlet 3 communicating with a sleeve 4 (vacuum suction) inside. Extend radially with respect to the holder WH. Continuous decompression of the portion 4 connected to the vacuum source causes negative pressure in the space surrounded by the opposite side of the wafer W and each annular concave portion 2, so that a plurality of annular protrusions 1 behind the opposite side of the wafer W are provided. The top surface of c) is modified for level adjustment.

In this embodiment, the holder WH propor was prepared by coating the sintered silicon carbide substrate with a silicon carbide film produced by CVD.

First, the α-silicon carbide substrate 6 made as shown in FIGS. 1 and 2 was sintered.

Since the sintering flame has already been used to make the annular projection 1 and the recessed portion 2 (0.2 to 0.5 mm depth), the manufactured and sintered holder substrate printed the protrusions and the recessed portions. Processing was again performed to make the ridge width of the annular protrusion 1 exactly 0.2 mm. Grinding was then performed to make the surface coarseness level 0.01 mm.

The surface supporting the wafer and the groove surface of the substrate were processed simultaneously with forming the film. That is, the surfaces of the annular protrusions 1 and the annular recesses 2 were subjected to chemical vacuum deposition of high purity silicon carbide under two different conditions of vacuum deposition to obtain respective formations of the silicon carbide film 5. . One condition was reduced pressure vapor deposition under a non acidic atmosphere at a vapor deposition temperature of 1300 ° C. with a vapor deposition rate of 10 to several tens of μm / h. On the other hand, the other was a standard pressure vapor deposition in a non-acid atmosphere at the same vapor deposition temperature at the vapor deposition rate as described above.

The two surfaces of the resulting vacuum chuck holder were then processed into diamond powder for 5 hours, and the film surface obtained by vapor deposition under the reduced pressure atmosphere mentioned above was made by grinding at 8 kPa rms. The other film surface obtained by vapor deposition under the above standard pressure environment was made at 500 kW rms.

As indicated in the above description, the fabrication of the semiconductor wafer holder of the present invention is easy because it consists of the formation of a sintered silicon carbide substrate having a continuous coating of CVD silicon carbide film. In addition, sintered silicon carbide is not used directly on the contact with the support but on the surface is CVD silicon carbide which facilitates grinding, thereby supporting the smooth and flat surface, which is the most critical element. Provides excellent mobility of the contact surface with Furthermore, the present invention allows the surface of the CVD silicon carbide film to be polished smoothly and flat with less grinding energy consumption while preventing loss as much as possible by orienting the crystallinity and adjusting the degree of cracking. In particular, by coating the CVD silicon carbide film in a non-acidic environment at reduced pressure, the resulting film forms an unusual crystal structure, thereby facilitating the formation of the most smooth and flat surface by the polishing method.

The degree of freedom of the silicon carbide film from the pinhole and the conductivity of the semiconductor wafer holder in accordance with the present invention prevent dust from adsorbing due to the generation of static electricity. The holder is therefore made easy to clean. Another advantage arising from using sintered silicon carbide is that the high stiffness due to the high stiffness and light weight characteristics of the ceramic makes it possible to support the holding material and adjusts to obtain a stable uniform surface for a long time. Is to make it. There is a high dimensional stability characteristic as a result of the small constant of thermal expansion which is an advantage when changing dimensions due to thermal accumulation problems. As preferred constituents of the present invention, sintered α-silicon carbide or sintered β-silicon carbide may be used as the substrate and β structure crystallized silicon carbide may be used as the CVD silicon carbide film.

The above-mentioned CVD silicon carbide film is preferably composed of a vapor deposition film having a crystal plate orientation of at least one of the crystal planes 111, 110, 220, and 200 of the Miller index. Most preferably, the CVD silicon carbide film comprises components of the crystalline plane 220 orientation of the Miller index, which has a 50-fold X-ray diffraction intensity over other crystal plate orientations.

Electrical discharge machining methods are generally used to overcome the processing problems of conventional ceramic materials. Nevertheless, the parts subjected to electrical discharge machining constitute dents and pinholes, usually relying on the stepwise polishing process, which is the most difficult step in working with ceramic materials, to smooth the attachment material and contact surfaces. In the semiconductor wafer holder of the present invention, a sintered silicon carbide substrate is first formed, and the surface thereof is subsequently coated with a CVD silicon carbide film to facilitate its manufacture.

Further, in the semiconductor wafer holder of the present invention, the sintered silicon carbide is not directly used in the contacting portion with the deposit, but the CVD silicon carbide film is used on the surface to facilitate polishing, so that the most important characteristics of the holder, namely, adhesion It improves the workability that the contact surface with the object is extremely smooth and flat.

Furthermore, the present invention is characterized by improving the difficulty of surface polishing due to the non-orientation of the degree of crystal of the general silicon carbide material surface, adjusting the degree of cracking, and using the relatively small abrasive energy to maximize damage It can be polished to an extremely smooth and flat surface while reducing the occurrence of.

Example 1

In the physical properties of the vacuum chuck holder shown in Table 1 below, the silicon carbide film was formed of each material used in a general holder in reduced pressure chemoprecipitation under non-acidic atmosphere of the embodiment. Physical properties of the metals, ceramics, and stainless steels representing the respective materials and alumina are shown in Table 1.

Modulus of elasticity (kg / mm ² ) importance Surface pore state Electric resistance (Ω ・ ㎝) Strength (Hv) Thermal Diffusion Coefficient (× 10 ^-6 / ℃) Stainless steel 20,000 8.1 usually 7 × 10 ^-5 200 17.3 Al ₂ O ₃ 35,000 3.8 Bad ≥10 ¹⁴ 1,800 7.1 Sintered SiC + Chemically Deposited SiC Film 40,000 3.1 Good 10 ⁶ 2,500 4.1

The following contents were obtained from Table 1. CVD silicon carbide synthesis according to the present invention in comparison of the property values applicable for use in the evaluation of holders requiring flatness and the elastic modulus with respect to the specific gravity shown in both cases, the material for transporters requiring small size and high performance. It is shown that the material is most suitable for large elastic modulus and small specific gravity. Of the three materials, the CVD silicon carbide constituent has the smallest heat diffusion coefficient, so there is little change in dimensions even when heat is accumulated due to long exposure times. In other words, using such a material to construct a vacuum chuck holder results in little dimension error in the circuit printing of the wafer held by suction.

There are very few pinholes on the surface chemically deposited from vapor or on contact surfaces with adherents. Further, when the dust is deposited on the suction surface is very small, there is little possibility that the flatness of the adherent material is degraded by the presence of dust between the contact surface and the adherent material. The high hardness also makes it impossible to produce small particles resulting from deposition on corrosive coatings and adherents.

Sintered α-silicon carbides used as substrates exhibit an electrical resistance of about 10 ⁶ Pa · cm. However, since the carbide has the constituent structure of the crystallized CVD silicon carbide film of? Structure according to the present invention, the carbide exhibits a thermal resistance of 10 ⁶ kPa · cm or less which provides excellent conductivity to the ceramic, and furthermore, by electrostatic There is no dust deposit on the resulting holder. If there is some dust deposition, such deposits can be easily removed. Therefore, the holder is easy to clean.

Furthermore, the small heat diffusion coefficient responds to changes in the minor dimensions of the holder through heat accumulation at exposure time. As a result, when a wafer is attached, a high sensitivity photosensitive agent is used when it is exposed to low illumination light for a long time, and is attached in a range where an error in the dimensions of the holder is allowed.

Example 2

The comparison of the vapor deposited film with the non-oriented vapor deposited film obtained in an arrangement for crystal plane orientation on the (220) and (111) planes in the Miller index indicates that the oriented film is non-oriented in terms of polishing energy and time required for polishing. Not only is it much less energy-consuming than a oriented film, it is also superior in terms of the apparent difference in glossiness of the surface.

Example 3

Comparing the crystal structures of the vapor deposition film under reduced pressure and the vapor deposition film under normal atmospheric pressure by X-ray diffraction, the result shows that the crystal structure of the film formed under reduced pressure is approximately (52) planes which are approximately 52 times the (111) plane in the Miller index. On the other hand, it has a value of about 32 times under normal atmospheric pressure. Since polishing makes the non-oriented crystal structure material more difficult than the material of the oriented crystal structure, the film formed under reduced pressure having more orientations in the orientation of the (220) plane provides excellent crushability.

Simple modifications or variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent by the appended claims.

The semiconductor wafer holder having the CVD silicon carbide film coating of the present invention has a high elastic modulus, a small specific gravity and a small thermal diffusion coefficient of the constituent material, so that the strength is high in circuit printing, and the change is maintained by maintaining the stability of the dimension despite the heat of exposure. Almost none, the material sintered with the β-structured crystallized CVD silicon carbide film provides an electrical resistance of 10 ¹⁰ Ω · cm or less to provide high conductivity, preventing static electricity and facilitating cleaning.

Claims (1)

The contact portion of the semiconductor wafer holder consists of a sintered silicon carbide substrate coated with a CVD silicon carbide film, the CVD silicon carbide film comprising a structural component of (220) crystal plane orientation of Miller index, the structural component being crystal plane orientation A semiconductor wafer holder, characterized in that it has an X-ray diffraction intensity of at least 32 times that of the other structural components of.