JP4529352B2 - Laminated wafer for semiconductor manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique of a dummy wafer that can be attracted to an electrostatic wafer holding device provided in various apparatuses used in, for example, a semiconductor manufacturing process.
[0002]
[Prior art]
The following three cases are generally implemented as dummy wafers. First, there is a method in which a dummy wafer is used only for transport or for the purpose of testing in a semiconductor wafer processing apparatus having the electrostatic wafer holding apparatus. Second, by introducing a dummy wafer into a semiconductor wafer processing apparatus having an electrostatic wafer holding apparatus and mounting it on the previous wafer holding apparatus, unwanted materials such as dust adhering to the previous wafer holding apparatus are removed. There is a method of cleaning the processing apparatus by adsorbing and collecting the wafer. Each will be described below.
[0003]
In semiconductor manufacturing processes, for example, plasma etching equipment, plasma CVD equipment, ion implantation equipment, ion doping equipment, ashing equipment, stepper equipment, lithography equipment, other physical property evaluation of wafers, inspection purposes such as particle evaluation in inspection equipment, products Silicon dummy wafers are generally used for conditioning such as wafer lot adjustment and lot-to-lot adjustment, or particle removal of each device. This silicon dummy wafer has a lower purity, flatness, etc., and a lower price than a normal quality wafer on which semiconductor elements are formed.
[0004]
In recent years, electrostatic chucks have attracted attention as a wafer holding device that can omit the mechanical clamping mechanism. Wafers that can be attracted to the holding device are of the same level as the silicon described below, such as silicon. Limited to materials made of conductive material.
[0005]
Japanese Patent Laid-Open No. 7-240401 discloses a plasma etching apparatus and the like that uses a glassy graphite dummy wafer having low chemical reactivity and extends its life. For the same purpose, Japanese Patent Application Laid-Open No. 2001-302397 proposes a dummy wafer made of hard SiC.
[0006]
Furthermore, a dummy wafer in which a conductive layer made of silicon, silicon carbide or the like is formed on one surface of an insulator base of aluminum nitride, alumina, or quartz by the present inventor is disclosed in Japanese Patent Application Laid-Open No. 11-29800. Has been proposed.
[0007]
As the number of times of use increases, inside the above devices, various unnecessary items harmful to the formation of semiconductor elements and wafer processing, such as fragments from silicon wafers, resist contamination, formation in plasma, or metallic mechanical components, Metal contaminants that are detached from the vacuum container material and other particles taken in by transporting the wafer are attached. In particular, in the electrostatic wafer chucking apparatus, there is a great concern that the operation of the apparatus accompanying the performance deterioration due to these unnecessary substances and the performance of the semiconductor element will be adversely affected, and means for preventing this are regularly taken. At present, cleaning such as particle removal of plasma generators in these semiconductor manufacturing processes is handled by manual parts and container cleaning. However, this method introduces new artificial contamination, so dummy wafers are used as much as possible. It corresponds by using.
[0008]
A dummy wafer used for such a purpose is generally called a cleaning wafer, and in recent years, its role is regarded as important as semiconductor devices are miniaturized. As an example, US Pat. No. 5,746,928 proposes a method in which a dummy wafer is mounted and the state of the excited plasma of the plasma etcher is made larger than that during normal operation. Similarly, Japanese Patent Application Laid-Open No. 2000-260671 discloses that a specific dummy wafer is charged and then mounted and cleaned, and Japanese Patent Application Laid-Open No. 7-240401 uses glassy graphite as a wafer material. ing.
[0009]
Furthermore, the present inventor has also conducted an experiment for imparting resistance in plasma by sandwiching a metal plate such as thin copper with a polyimide sheet or the like in order to provide conductivity, There was a risk that the metal used was contaminated from the peripheral portion and the wafer surface was not flat.
[0010]
[Problems to be solved by the invention]
However, the conventional dummy wafer or cleaning wafer has the following drawbacks.
[0011]
Silicon wafers have drawbacks in life such as being easily sputtered by plasma in an etching apparatus and being easily broken. In the use, management such as the number of times used is necessary. Although it can be recycled, it does not have a significant price advantage compared to purchasing a new wafer, and eventually becomes disposable and the management cost becomes high.
[0012]
Silicon carbide is very expensive compared to silicon itself, so it is formed by depositing the same high-purity material on the surface of an inexpensive base material using the CVD method. Some impurities are deposited by the reaction of the plasma and contaminate the inside of the apparatus. Further, since this material is very hard, it has a drawback that it damages the contact surface of an electrostatic wafer suction device or the like.
[0013]
Since glassy graphite has low oxidation resistance, the sputtering rate becomes very large in oxygen plasma, causing generation of particles in a short time and shortening the life. This material cannot be used in any reactive plasma atmosphere.
[0014]
Accordingly, an object of the present invention is to provide a dummy wafer or a cleaning wafer that can be used for a versatile application in a semiconductor manufacturing apparatus as described above, which has a long lifetime and is inexpensive.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the wafer according to claim 1 uses, as its material, a polyimide sheet which is a relatively inexpensive resin widely used in the market for mass production. Since a normal polyimide sheet is an insulator, it cannot be adsorbed to an electrostatic adsorption type wafer holding device. However, in the present invention, a polyimide sheet having conductivity is used, and this sheet is laminated to a conventional wafer thickness. Thus, it can be used without problems in the existing semiconductor manufacturing process. In order to maintain the conductivity of the entire wafer, each layer needs to be bonded in such a way as to make electrical contact with each adjacent layer.
[0016]
The wafer according to claim 2 has a mechanical strength equivalent to that of a conventional silicon semiconductor or silicon carbide by forming a part of the sheet of the laminated wafer from aramid fibers having higher mechanical rigidity. It is something to have. This aramid material is also conductive. Aramid materials are 20% lighter than steel materials, but have 7 times the tensile strength and flexibility. Further, by introducing a highly rigid material into the laminated structure, there is an effect that the flatness of the wafer can be easily obtained.
[0017]
The wafer according to claim 3 is made of a semiconductor material such as conventional silicon, gallium arsenide, gallium phosphide, indium phosphide on the upper surface, specifically, the surface opposite to the side attracted by the electrostatic wafer holding device. To do. For the other layer portion, the conductive polyimide or the conductive aramid material shown in claim 1 or claim 2 is used. By adopting such a configuration, it is possible to match the electrical characteristics such as the surface resistance value with a conventionally used silicon wafer or the like.
[0018]
According to a fourth aspect of the present invention, there is provided a cleaning method for a semiconductor manufacturing apparatus, in which fine dust, particles and the like on an electrostatic wafer holding device adsorption surface are taken into a flexible polyimide surface layer constituting a laminated wafer, and this is taken out of the apparatus. It is a means to remove.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0020]
In FIG. 1, an embodiment in which a conductive laminated wafer 1a is formed by heat-sealing a conductive polyimide sheet 2 having two upper and lower layers and a five-layer conductive aramid material portion 3 will be described.
[0021]
Although the polyimide sheet is sold as a general-purpose product, it is necessary to use a conductive material in the present invention, so a material called “Kapton XC” manufactured by DuPont is used. Generally, a polyimide material has a heat resistance of −270 ° C. to 400 ° C., and also has high elasticity and mechanical strength. It is also resistant to radiation and chemicals. Therefore, it can be said that the polymer material is physically, electrically and chemically strong. In the present invention, in addition to the above characteristics, a polyimide sheet is used which is made conductive by adding a conductive filler such as carbon fine particles. Since Although the sheet resistance of the conventional semiconductor silicon wafer is approximately 100~1000Ω / cm ^2, the sheet resistance of the material is having the following or equivalent sheet resistance 50~1000Ω / cm ² and the silicon wafer, electrostatic Adsorption can be performed on the adsorption-type wafer holding device.
[0022]
A material called aramid is an aromatic polyamide that has the same molecular bonds as nylon used in clothing. In addition to the high rigidity described above, this material has corrosion resistance and flexibility equivalent to polyimide. The aramid material form in the present invention is a knitted aramid fiber having a thickness of about 10 μm. In order to maintain the conductivity of the entire laminated wafer, this aramid material is also used by adding conductivity by weaving a conductive filler such as carbon fiber in an aramid fiber. Since it is fibrous, it is difficult to measure the sheet resistance value, but the volume resistivity is in the range of about 10 ⁶ to 10 ⁸ Ω · cm.
[0023]
A wafer used in a semiconductor manufacturing apparatus is required to have a certain level of flatness. This is because if the wafer is bent or uneven, there is a risk that the wafer will drop out of the normal path due to non-uniformity of the suction force in the transfer system or electrostatic wafer holding device. In particular, the importance has increased with the recent increase in wafer diameter (current diameter: 300 mm, future diameter: 450 mm). In the present invention, since a resin such as polyimide or aramid is used as a constituent material of the wafer, the wafer has high flexibility. Therefore, when the wafer according to the present invention is adsorbed by the electrostatic wafer holding apparatus, the entire wafer is elastically deformed following the adsorbing surface, so that the holding and adsorbing property of the wafer can be improved compared to a hard silicon wafer or the like.
[0024]
Since wafers used in semiconductor manufacturing equipment have standardized dimensions, it is necessary to make them to a predetermined thickness. Since the thickness of the conductive polyimide sheet 2 is 0.04 mm, for example, when an 8-inch laminated wafer is manufactured, the thickness of the upper and lower layers of the conductive polyimide sheet 2 is set to a standard thickness of 0.75 mm. Is laminated and shaped so that the total thickness of the conductive aramid material portion 3 is 0.67 mm, thereby forming a conductive laminated wafer. Adhesives are not used for attaching each layer, but a heat fusion shaping method is used in which heat is applied to each layer subjected to plasma treatment and bonded by mechanical pressure. Accordingly, there is no need to worry about gas release from the adhesive in a vacuum, and there is an advantage that the working process is simplified. As another method, it is possible to use a conductive epoxy adhesive and attach each layer to form.
[0025]
According to the experiment, the volume resistivity of the conductive laminated wafer manufactured according to this example was in the range of about 10 ² to 10 ⁴ Ω · cm. The surface roughness was about 0.1 to 0.5 μm. The holding power equivalent to that of the semiconductor wafer could be maintained with respect to the adsorption by the electrostatic wafer holding device.
[0026]
Since the aramid fibers are exposed in the end face processing of the laminated wafer end face, there is a concern of water vapor adsorption or fiber detachment, but the entire circumference of the laminated wafer end face is sealed with resin or glass. It can respond. In the case of resin, the conductive polyimide sheet 2 on both surface layers is made larger than the conductive aramid material part 3, and the conductive polyimide sheets 2 on both surface layers are bonded to each other at the outer peripheral part to form a conductive aramid material part. It is also possible to have a structure that wraps 3 and is not exposed to the outside.
[0027]
FIG. 2 shows a conductive laminated wafer 1b having a silicon layer as a semiconductor substrate material at the bottom of the laminated surface. In this configuration, an example in which the surface of a wafer piece is constituted by a silicon material portion 5 of a conventional semiconductor is shown. Although not shown in FIG. 2, not only one surface but also both surfaces can be constituted by the silicon material portion 5. As a method for forming the silicon layer, a sputtering method, a CVD method, or the like can be considered. Further, as a material to be formed on the surface, not only silicon but also semiconductor wafer materials such as gallium arsenide, gallium phosphide, and indium phosphide are possible. Furthermore, it may be necessary in the future to form a metal layer such as aluminum or copper instead of a semiconductor material on the surface. In this case, a sputtering method, a plating method, or the like can be used as the forming method. By adopting a structure in which one side is made of a semiconductor such as silicon, the electrostatic type wafer device is surely adsorbed by the contact of a resin such as a flexible conductive polyimide, and in the conventional semiconductor manufacturing equipment, By exposing only the surface formed of silicon or the like, similarity in physical properties such as surface electrical characteristics with a wafer manufactured using only a conventional semiconductor can be enhanced.
[0028]
When manufacturing semiconductor elements, the problem is that dust, particles, etc. in the manufacturing apparatus reduce the yield. In recent years, not only the surface on which semiconductor elements are formed, but also the back surface, that is, the management of one surface contacting the electrostatic wafer attracting apparatus has been required. This is because the dust and particles on the back surface cause a focus shift in the exposure apparatus. Further, when the dust and particles are metallic, the dust and particles detached from the wafer in the cleaning layer or the like adhere to the wafer to be processed next. If this contaminates the semiconductor junction region and the like, the junction potential setting fluctuates, and an element with a correct design cannot be formed. International guidelines on these events are compiled by an organization called the International Semiconductor Technology Roadmap (ITRS) and published on the Internet homepage, http: // public. itrs. net / _o For example, in the 2001 front-end processing of the year AD, the allowable particle guideline is 300 mm diameter wafer, the critical particle size is 0.058 μm on the wafer surface and 94 per wafer; 0.2 μm on the backside of the wafer, There are 468. The simple point indicated by this guideline is that dust and particles can be removed on the back side of the wafer. Normally, particles are measured by loading a non-measurement wafer into a laser scan type particle counter. The presence of particles on the backside of the wafer means that the particles are adhered during the transfer of the wafer or while being processed in a certain semiconductor manufacturing apparatus, and the state is maintained. In principle, there is no particle adhesion to the initial wafer just manufactured and shipped, and transfer between devices is generally performed in a clean environment. This is considered to occur in a semiconductor manufacturing apparatus with a high frequency. Therefore, it is possible to prevent diffusion from one semiconductor manufacturing apparatus to another system by positively capturing and capturing dust, particles, and the like by the back surface of the cleaning wafer.
[0029]
In the present invention, in particular, the structure described in claim 2 or claim 3, that is, an aramid material having high rigidity is used for the intermediate layer, and a surface that comes into contact with the suction surface of the electrostatic wafer holding device is formed of a polyimide layer. By doing so, it becomes easier to implement as a cleaning wafer. In this structure, the wafer is pressed against the wafer holding device with a uniform force over the entire surface of the wafer during suction. When the cleaning wafer is uniformly pressed against the surface of the electrostatic wafer holding device, dust, particles and the like existing on the entire contact surface bite into the cleaning wafer layer or the surface of the wafer holding device. Here, if the surface hardness of the cleaning wafer can be made lower than that of the wafer holding device adsorption surface, the cleaning wafer can be more easily taken into the surface layer of the cleaning wafer. The surface of the electrostatic wafer holding device can be, for example, silicon carbide, alumina, or an equivalently hard alloy. The Knoop hardness of silicon carbide alumina is 2500Hk and 2100Hk, respectively. The amount of dust and particles is 300 Hk when the composition is iron, which is most harmful to semiconductor manufacturing. Polyimide is about 100 Hk, which is about the same as ordinary plastic. Accordingly, the surface of the cleaning wafer is relatively soft, and the surface of the electrostatic chuck is formed of a hard material. It can be considered that dust, particles and the like to be adsorbed are generally harder than the surface of the cleaning wafer. As for the method of use, the cleaning wafer is introduced into the semiconductor manufacturing apparatus as usual, and a certain applied voltage is applied to the electrostatic wafer holding apparatus, and it is adsorbed for a certain period of time. Thereafter, the applied voltage is turned off, the suction is released, and the outside of the apparatus is transferred. When this manufacturing apparatus is empty or when necessary, a plurality of cleaning wafers, for example, one lot is carried out, and if necessary, this sequence is repeated a plurality of times. In addition, cleaning wafers can be identified by changing the color of each side, and the use frequency and life of the cleaning wafer can be managed. In addition, the used wafer can be regenerated by scraping the surface and removing it together with adhering dust.
[0030]
According to an experiment in a semiconductor etching apparatus, the effect of the cleaning wafer according to the present example in the electrostatic wafer holding apparatus on the ceramic surface was confirmed to remove 10 to 1000 minute dusts in one attachment / detachment.
[0031]
In this example, the example of conductive polyimide was given as the surface resin of the laminated wafer. However, other materials such as polyethylene, polyethylene terephthalate, acetylcellulose, polycarbonate, polypropylene, aramid, polycarbodiimide, and nylon are made conductive. It is also possible to use a given material or a rubber-based material such as silicon.
[0032]
【The invention's effect】
By adopting the laminated wafer structure of the present invention, conventionally, for example, without performing costly manufacturing processes such as surface polishing and thickness management after circular wafer creation by round cutting after pulling up a cylindrical silicon single crystal. First, a laminated sheet having a predetermined thickness is formed by fusing sheets having a predetermined thickness to each other, and thereafter, a sheet having a predetermined thickness is formed into a circular shape or an arbitrary shape, which is more suitable for mass production. This has the effect of lowering the price of the final wafer in synergy with the cheapness of the material. Further, since polyimide is used as a material, a dummy wafer having a long-term resistance to all use environments such as reactive and oxidative plasma can be provided. Further, this wafer has a characteristic that it exhibits an effect as a cleaning wafer for removing dust, particles and the like on the surface of the electrostatic wafer holding device by selecting the hardness of the surface layer.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a wafer having a structure in which a hard material is embedded in a laminated wafer.
FIG. 2 is an example in which one side of a laminated wafer is made of a semiconductor material such as silicon.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a The conductive laminated wafer 1b which has an aramid layer in the lamination | stacking middle part The conductive laminated wafer 2 which has a silicon layer in the lamination | stacking surface lower part 2 Conductive polyimide sheet 3 Conductive aramid material part 4 Silicon material part

Claims (4)

It is a dummy wafer used in a semiconductor wafer processing apparatus, etc., and its material configuration is made by stacking a plurality of thin film conductive polyimide sheets and heat-sealing, thereby making it possible to adsorb and desorb to the electrostatic wafer holding apparatus. A conductive laminated wafer characterized by the above. The conductive laminated wafer according to claim 1, wherein the material structure includes at least one conductive aramid material, or a portion made of a polymer material mechanically stronger than equivalent polyimide. 3. The conductive laminated wafer according to claim 1, wherein the material structure is such that at least one layer of silicon material, gallium arsenide, gallium phosphide, indium phosphide or an equivalent semiconductor substrate material is the surface. In the semiconductor manufacturing apparatus, the mechanical hardness of the surface material of the laminated wafer according to any one of claims 1, 2, and 3 is made of a material lower than the material of the wafer mounting surface of the electrostatic wafer holding device. A few wafers are introduced into and mounted on the semiconductor manufacturing apparatus, a predetermined voltage is applied to the wafer holding apparatus, and the wafer is pressed and adhered to the holding apparatus surface by maintaining the suction force for a certain period of time. A method for cleaning a semiconductor manufacturing apparatus, which takes in dust and particles into a wafer surface constituent layer, cancels application of a predetermined voltage, cancels adsorption, and transfers the wafer outside the semiconductor manufacturing apparatus.

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