Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Reexamination Certificate
1999-07-02
2001-06-26
Ballato, Josie (Department: 2836)
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
C323S312000, C279S128000
Reexamination Certificate
active
06252758
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for reducing particles from an electrostatic chuck and an equipment for manufacturing a semiconductor.
2. Related Art Statement
In each step of conveying a semiconductor wafer, exposure, film-forming by CVD, sputtering, etc., micro-processing, cleaning, etching, dicing, or the like, an electrostatic chuck is employed for attracting and holding the semiconductor wafer.
Particularly, from the views of using, as an etching gas or a cleaning gas, a halogen-based corrosive gas such as ClF
3
, an equipment for manufacturing a semiconductor requires a high heat conduction for rapidly heating and cooling a semiconductor wafer with holding it and requires a high shock resistance not to be destroyed due to such a remarkably temperature change. Thus, a material made of dense aluminum nitride, dense alumina, or the like is promised.
On the other hand, inside the semiconductor-manufacturing equipment, the occurrence of particles, which results in defects of the semiconductor, is needed to be prevented. The particles are mainly generated from a backside surface of the semiconductor, a part of which stacks on the semiconductor wafer directly, the other part of which spreads out and stacks on a wall of a chamber. Then, the particles are peeled off of the wall, and thereby results in defects of a semiconductor.
In view of the above problems, JP A 7-245336 discloses a method in which convex-concave portions in an attracting face of an electrostatic chuck made of ceramic material are ground by irradiating a plasma and the fine protuberances of the convex-concave portions are removed, and thereby the occurrence of particles is reduced. The method is based on the finding of the cause of particles' occurrence that a silicon wafer having relatively low hardness is ground by the convex-concave portions when the silicon wafer contacts the convex-concave portions.
Moreover, JP A 8-55900 discloses a method in which a contacting shock of a silicon wafer with an electrostatic chuck is reduced by slowly rising a voltage to the electrostatic chuck when the silicon wafer is stuck to the electrostatic chuck, and thereby the particles' occurrence due to the convex-concave portions of the attracting face in the electrostatic chuck is decreased.
In a film-forming process such as a CVD or a sputtering, it is required to epitaxially grow a semiconductor film on a wafer, and thus, the wafer is required to be heated to a higher temperature range of not less than 100° C., particularly not less than 200° C. In that time, an attracting face of an electrostatic chuck is heated by a heater built-in the electrostatic chuck or a heater provided so as to be contacted with the electrostatic chuck in the lower side thereof.
In the electrostatic chuck, the wafer has a lower temperature when the wafer is stuck onto the attracting face of the electrostatic chuck, and the wafer has increasing temperature toward a saturated temperature with time past after attracting. The inventors found that, in such an electrostatic chuck or a semiconductor-manufacturing equipment, even though the contacting shock of the wafer with the electrostatic chuck just after attracting is relaxed and reduced, more particles than expectation occurs. It is difficult to reduce such particles as occurs with temperature rise of the wafer by a conventional method.
SUMMARY OF THE INVENTION
It is an object of the present invention to reduce such particles as occurs with a temperature rise of a wafer after setting the wafer onto an attracting face of an electrostatic chuck.
This invention relates to a method for reducing particles from an electrostatic chuck, comprising the steps of: setting a wafer onto an attracting face of an electrostatic chuck in a state that a temperature of the wafer is lower than that of the attracting chuck, attracting the wafer onto the attracting face by applying a voltage with the electrostatic chuck, releasing stress due to a difference in heat expansion between the wafer and the electrostatic chuck by sliding the wafer relative to the attracting face before the wafer's temperature arrives at a saturated temperature, and increasing the wafer's temperature to the saturated temperature from its lower temperature than that of the attracting face.
This invention also relates to a method for reducing particles from an electrostatic chuck, comprising the steps of: setting a wafer onto an attracting face of an electrostatic chuck, and attracting the wafer onto the attracting face by applying a pulsed voltage with the electrostatic chuck.
This invention further relates a method for reducing particles from an electrostatic chuck, comprising the steps of: setting a wafer onto an attracting face of an electrostatic chuck in a state that a temperature of the wafer is lower than that of the attracting face, and attracting the wafer onto the attracting face by applying a stepwise or continuously increasing voltage toward a saturated voltage with the electrostatic chuck.
This invention still further relate to a method for reducing particles from an electrostatic chuck, comprising the steps of: setting a wafer onto an attracting face of an electrostatic chuck, attracting the wafer into the attracting face by applying a voltage to the electrostatic chuck, and flowing a backside gas between the attracting face and the wafer when the voltage is applied to the electrostatic chuck.
This invention also relate to an equipment for manufacturing a semiconductor, comprising: an electrostatic chuck having an attracting face for setting a semiconductor wafer, a power supply for applying a voltage to the electrostatic chuck, and a backside gas-supplying equipment for flowing a backside gas between the attracting face and the wafer.
The inventors has studied to reduce particles as occurs with temperature rise of a wafer after attracting it onto an attracting face of an electrostatic chuck. Accordingly, they have got the following knowledge. That is, it has been conceived since before that the wafer have hardly stuck onto the attracting face of the electrostatic chuck made of ceramic material when the particles occur due to the shocks of the wafer colliding with the attracting face. Consequently, a means to reduce the shocks at the collision has been given. The inventors found, however, contrary to their expectations that the particles occur actually due to the difference of heat expansion between the wafer and the electrostatic chuck after the wafer is stuck onto the electrostatic chuck.
The inventors has, based on the above finding, found that a means, whereby the stresses due to the difference of the heat expansion between the wafer and the electrostatic chuck are released by sliding the wafer relative to the attracting face during the time of arriving at a given saturated temperature of the wafer from just attracting the wafer onto the electrostatic chuck, is adopted and thereby the particles are remarkably reduced.
The wording “saturated temperature” means a stable temperature of the wafer when a given heat value is afforded a system containing the wafer and the electrostatic chuck in a state that the wafer is stuck onto the electrostatic chuck with a given attracting power. Thus, when the desired attracting power or the heat value to the system changes, the saturated temperature change, too.
REFERENCES:
patent: 5320982 (1994-06-01), Tsubone et al.
patent: 5746928 (1998-05-01), Yen et al.
patent: 5793192 (1998-08-01), Kubly et al.
patent: 5910011 (1999-06-01), Cruse
patent: 6084763 (2000-07-01), Hirano et al.
patent: 59-181622 (1984-11-01), None
patent: 7-245336 (1995-09-01), None
patent: 8-55900 (1996-02-01), None
patent: 8-316297 (1996-11-01), None
patent: 11-67883 (1999-03-01), None
patent: 11-251418 (1999-08-01), None
Nagao Mie
Ohno Masashi
Ushikoshi Ryusuke
Ballato Josie
NGK Insulators Ltd.
Parkhurst & Wendel LLP
Rios Roberto
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