Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With workpiece support
Reexamination Certificate
2002-12-03
2004-04-06
Hassanzadeh, Parviz (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With workpiece support
C156S345510, C118S725000, C118S728000, C438S715000
Reexamination Certificate
active
06716304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer holder for a semiconductor manufacturing apparatus and to a method of manufacturing the wafer holder. Examples of the holder include a holder which has at least one of a heater serving a function of heating a semiconductor wafer from below, an electrostatic chuck electrode used for generating an electrostatic force between the electrode and a semiconductor wafer in order to secure the wafer, and a plasma lower electrode used for generating plasma.
2. Description of the Background Art
For etching of a semiconductor wafer surface or depositing of a film thereon, a method has been employed according to which gas for etching or for film deposition is supplied by means of a batch processing system to a large number of wafers held on racks, and then the wafers are heated as required from the outer periphery (hot wall method).
However, as requirements become severer for higher integration and speed of semiconductor devices, a problem arises of non-uniform etching and unequal quality of completed films due to difference in temperature and gas flow depending on the location in a semiconductor manufacturing apparatus. Then, another type of semiconductor manufacturing apparatus has gradually been used instead that employs a single wafer processing system in which a plurality of etching apparatuses and film deposition apparatuses are arranged side by side and wafers are transported automatically by a loader through the apparatuses where the wafers are processed one by one. In a semiconductor manufacturing apparatus of such a single wafer processing type, a method is employed according to which the loader transports the wafer onto a wafer holder in a chamber of an etching apparatus or film deposition apparatus, the wafer is secured to the holder by an electrostatic chuck or statically fastened to the holder by enhancing surface precision of a wafer-supporting surface of the holder, and then heat is directly applied to the holder to uniformly heat the wafer. It is thus necessary that at least the portion of the holder, which is in contact with the wafer, is formed of a material having corrosion resistance against a highly corrosive gas such as halogen gas and the like and having a high heat conductivity, and that the holder itself has an electrostatic chuck function and a mechanically fixing function, as well as a heater function.
Aluminum nitride has been attracting attention as a material for the holder because of its corrosion resistance and high heat conductivity. The holder has been produced by providing a coil or wire of refractory metal such as molybdenum and the like between compact pieces formed of aluminum nitride powder and hot-press sintering them so as to produce a conductive layer, as a heater or electrostatic chuck electrode, embedded in the holder. Regarding a holder having a heater embedded therein, Japanese Patent No. 2604944, for example, discloses a heater-embedded structure for enhancing uniformity of heating on a heat-generating surface. A method has been employed for producing a holder having a conductive layer embedded between stacked compact pieces. According to this method, paste containing tungsten or molybdenum is printed on a surface of an aluminum nitride compact piece, such compact pieces are stacked, and the aluminum nitride compact pieces and the paste are sintered simultaneously.
However, the above method, according to which coil or wire of refractory metal such as molybdenum is provided between aluminum nitride compact pieces and then they are hot-press sintered, has a problem that the coil or wire mounted on the compact piece is displaced from its original position through a handling process before the subsequent hot-press sintering process, resulting in products having respective characteristics considerably different from each other, as well as short-circuit. In order to avoid this, a method is employed by which grooves are made in a compact piece to insert a coil or wire into the grooves. In this case, the precision of a conductor pattern for generating a heater or electrostatic chuck electrode is governed by the pattern precision of grooves formed in a compact piece. However, it is difficult to form grooves having a fine pattern in an aluminum nitride compact piece. If grooves having a width and an interval of 5 mm or less are formed in the compact piece, a thin wall between the grooves is likely to be partially lost. In terms of mass production, the grooves should be formed at intervals of at least 10 mm. Therefore, it has been difficult to produce a conductor for a heater or electrostatic chuck electrode with a fine and highly precise pattern by forming grooves in a compact piece.
Another problem is that production of a large-sized sintered aluminum nitride piece by the hot-press sintering method as discussed above requires a large-sized apparatus which raises equipment cost and accordingly increases manufacturing cost.
In addition, when paste of refractory metal such as tungsten is printed on an aluminum nitride compact piece and then another compact piece is layered thereon to simultaneously sinter the aluminum nitride compact pieces and the metal paste, difference in density between the compact pieces and non-uniform heating cause shrinkage resulting from the sintering to vary depending on location or product. Then, it is difficult to produce a conductive layer with a high precision pattern. According to another method employed, surfaces of compact pieces are wetted with a solvent, and then the compact pieces are stacked, heated, and pressure-bonded and thereafter degreased and sintered. In the heating process, the pressure-bonded portion is subject to partial or entire peeling and thus production is difficult to achieve through stable processes.
If a holder is manufactured through the simultaneous sintering as discussed above, high-precision control of shrinkage in the sintering is difficult. The possibility of peeling of the bonded portion makes it difficult to enhance manufacture yield, resulting in increase in manufacturing cost.
Any of the methods above employs simultaneous sintering of the aluminum nitride compact pieces and coil or wire of refractory metal or metal paste. Therefore, material for the conductive layer is limited to refractory metal such as tungsten and molybdenum. Then, silver-palladium alloy and the like having a low melting point cannot be used as a material for the conductive layer. A problem here is that the range of controlling an amount of generated heat is restricted when such a conductive layer is used as a heater.
Ceramic such as aluminum nitride used as a material for a holder is advantageously fabricated to have a high heat conductivity in order to allow a resultant holder to uniformly heat a semiconductor wafer held thereon. However, the ceramic like the aluminum nitride should be sintered at high temperature for a long period of time in order to enable the sintered ceramic to have a high conductivity. If a ceramic compact piece is sintered at high temperature for a long period of time, abnormal grain growth could occur in tungsten or molybdenum used as a material for a conductor, or an agent used for sintering aluminum nitride and the like could excessively react with an agent added for firing metal paste of tungsten or molybdenum to cause breaking of the conductive layer or defect in bonding. For this reason, the compact piece of ceramic such as aluminum nitride should be sintered at a low temperature of 1800° C. or less for a short period of time. Consequently, the ceramic such as aluminum nitride cannot be sintered to have a high heat conductivity and a resultant holder cannot provide uniform heating. There is thus a limit to manufacturing of a holder capable of heating a wafer uniformly.
SUMMARY OF THE INVENTION
One object of the present invention is accordingly to provide a wafer holder for a semiconductor manufacturing apparatus that can overcome the above problems, can be manufactured to have a high heat conduc
Higaki Kenjiro
Ishii Takashi
Kuibira Akira
Matsui Yasuyuki
Nakata Hirohiko
Fasse W. F.
Fasse W. G.
Hassanzadeh Parviz
Sumitomo Electric Industries Ltd.
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