Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Reexamination Certificate
1999-07-20
2001-09-18
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
C029S592100
Reexamination Certificate
active
06292346
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a semiconductor wafer-holder, a method for manufacturing the same, and a method for using the same.
2. Related Art Statement
In a semiconductor-manufacturing step such as CVD, sputtering, etching, a semiconductor wafer is set onto a susceptor and heated by heating the susceptor. JP-A-59-124140 discloses that recently, in that case, an electrostatic chuck is used as the susceptor and the semiconductor wafer is heated, while attracted to the susceptor. Moreover, it is known that a heater made of a ceramic material is used as the susceptor, and the semiconductor wafer is directly heated, set onto the ceramic heater. For increasing a production volume of semiconductors, however, the prevention of the temperature change in attracting and releasing cycle of the semiconductor wafer on the susceptor requires heating and cooling the wafer with good responsibility. Thus, an equipment for cooling the wafer is required to be combined to the susceptor.
JP-A-3-3249 suggests a technique of combining the electrostatic chuck to a metallic cooling board of a water cooling type with metallic bonding. In the above technique, the electrostatic chuck made of alumna is bonded to the water cooling board made of aluminum with indium. However, a melting point of indium is about 160° C. and a temperature range usable as indium is at most 150° C. and below, is small, so that indium has an only small temperature range usable for an equipment for manufacturing a semiconductor. The inventors tried to bond the electrostatic chuck and the water cooling board with a metallic wax having a higher melting point, but after bonding, large remaining stresses occur at their boundary, resulting from a difference in heat expansion between a ceramic material and a metal composing the electrostatic chuck and the water cooling board, respectively, and destroyed the electrostatic chuck. Thus, bonding the electrostatic and the water cooling board is difficult. Needless to say, the remaining stresses can be reduced by bonding with a metal having a low melting point such as indium, but as above mentioned, it make the available temperature range small. It can be also conceived to bond the electrostatic chuck and the water cooling board with a resin, but the resin has such a poor heat-resistance that it make the available temperature range very small.
Moreover, JP-A-3-108737 suggests that a path for a refrigerant is formed in a midst ceramic layer of an electrostatic chuck having plural ceramic layers and a surface temperature of the electrostatic chuck is decreased by making flow the refrigerant through the path. However, a quantity of heat resulting from a plasma and electron beams enters a surface of the electrostatic chuck, which heats the surface of the electrostatic chuck. If a basic member of the electrostatic chuck is made of ceramic material having a low thermal conduction and a high dense plasma is employed, a surface temperature of the basic material would arise to a temperature of 700° C. to 800° C. and thereby the basic member is likely to be destroyed. Although the refrigerant is made flow through its path for controlling the surface temperature depriving of the heat therein, in this case, a temperature difference occurs in between the surface of the electrostatic chuck and the path for the refrigerant. Particularly, the generation of the plasma in the surface side of the electrostatic chuck make the temperature difference be large. Thus, it is becoming clear that since a temperature inclination inside the electrostatic chuck is remarkably increased and thereby, large thermal stresses occur, the basic member made of ceramic material is likely to be destroyed.
Moreover, the inventors disclosed in JP-A-7-161,957 that an intervened layer, composed of a binding body of fibers made of thermal resistant material or an expanded body, is formed between a susceptor having a basic member made of ceramic nitride and a metallic cooling equipment, and the intervened layer is pressurized to conduct a heat. The method is an excellent measure in a view of preventing the above problem, but in the case of enhancing the quantity of heat to the semiconductor wafer from the plasma, cooling efficiency is not sufficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to use a susceptor in a high temperature range, particular 200° C. and over, control its temperature, prevent the susceptor from being destroyed, and control the susceptor's temperature in constant even though a quantity of heat to the susceptor is increased, in a controlling technique of a surface temperature of the susceptor made of a ceramic material and further a temperature of a semiconductor wafer by depriving of their quantities of heat with a metallic refrigerant.
This invention relates to a semiconductor wafer-holder comprising a member for holding the semiconductor wafer with a basic member made of a ceramic nitride, a cooling equipment made of a metal, and an intervened layer between the semiconductor wafer-holding member and the cooling equipment, the intervened layer being composed of a metallic foil or a carbon sheet having a thickness of not more than 500 &mgr;m.
This invention also relates to a method for manufacturing a semiconductor wafer-holder comprising the steps of forming a member for holding a semiconductor wafer with a basic member made of ceramic nitride, forming a cooling equipment made of metal, forming an intervened layer composed of a metallic foil or a carbon sheet having a thickness of not more than 500 &mgr;m between the semiconductor wafer-holding member and the cooling equipment, while sandwiched by them, and combining, fastening them mechanically, the semiconductor wafer-holding member, the cooling equipment, and the intervened layer.
This invention further relates to a method for using a semi-conductor wafer-holder having a semiconductor wafer-holding member with a basic member made of ceramic nitride, a cooling equipment made of metal, and an intervened layer composed of a metallic foil or a carbon sheet having a thickness of not more than 500 &mgr;m, sandwiched by the semiconductor wafer-holding equipment and the cooling equipment, comprising the steps of controlling a quantity of heat to be transmitted to between the semiconductor wafer-holding equipment and the cooling equipment by controlling its pressure while pressurizing the intervened layer.
The inventors have found, in the process of repeating experiments to investigate thermal conductance in the semiconductor wafer-holding equipment having the semiconductor wafer-holding member, the metallic cooling equipment and the intervened layer composed of the binding body of fibers made of a thermal resistant material or the expanded body, that in the case of a normal quantity of heat for the semiconductor wafer, the destruction of the member is prevented and a temperature of the member can be controlled in stable so that it may be constant, but in the case of increasing the quantity of heat for the semiconductor wafer and making it 1.6kW, for example, a temperature of the member is increased and may be difficult to be controlled.
Based on the above finding, the inventors have successfully developed a technique that if the quantity of heat for the semiconductor wafer is increased, it can be conducted to the cooling equipment in high efficiency and thereby its destruction and occurrence of cracks in the semiconductor wafer-holding member made of a ceramic material can be prevented. That is, they have formed the intervened layer composed of a metallic foil or a carbon sheet with not more than 500 &mgr;m thickness, between the semiconductor wafer-holding member having a basic member made of a ceramic nitride and the metallic cooling equipment.
As above mentioned, the temperature inclination inside the ceramic basic member composing the semiconductor wafer-holding member such as an electrostatic chuck have to be prevented. If the temperature inclination occurs in the ceramic basic member
Ichikawa Hirokazu
Kawajiri Tetsuya
Ohno Masashi
Yamada Naohito
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Sherry Michael J.
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