1. Field of the Invention
This invention relates to a chuck system, and more particularly, to a chuck system applicable to a semiconductor fabrication process for holding a workpiece and controlling the processing temperature thereof.
2. Description of the Related Art
Chuck systems are used for holding a workpiece in various applications. In a semiconductor manufacturing process, a chuck system holds a semiconductor wafer in place during wafer processing operations. The manufacture of a semiconductor device usually involves hundreds of processing steps applied onto a semiconductor wafer to form electronic devices and circuits thereon. Various kinds of chuck systems are operated with various processes or processing chambers. During processing of a semiconductor wafer, a chuck system usually holds the wafer firmly in place to enhance the stability of the process. The chuck system also controls the temperature of the wafer during the process. Stability and temperature control of a chuck system promote uniformity during wafer processing for a given wafer as well as uniformity for the semiconductor manufacturing process in general.
An electrostatic chuck system generally holds a wafer on a platform by employing an electrostatic force, either by placing opposite charges on the wafer and the platform or by placing charges on either the wafer or the platform. Comparing with traditional chucking approaches, which are predominately mechanical chucks, an electrostatic chuck system avoids direct contact with the side of the semiconductor wafer that electronic components and devices are to be formed, i.e., device side. In sub-micron and deep sub-micron semiconductor processing, the feature size of devices on a wafer dives is extremely small and therefore control of processing parameters in each processing step becomes extremely important.
Taking a plasma processing chamber as an example, parameters such as chamber pressure, chamber temperature, and wafer temperature are vital. Typically, a plasma processing step involves the application of electromagnetic energy onto a wafer to proceed with high energy processes such as etching the wafer surface or depositing a new material onto the wafer. The plasma reaction, especially in a typical plasma etching process, increases the temperature on the wafer and therefore a cooling system is needed to maintain the surface temperature of the wafer within a prescribed range.
FIGS. 1a and 1b illustrate a conventional wafer cooling design of an electrostatic chuck system 12 in a plasma processing chamber 10. FIG. 1a illustrates the side view of the chuck system 12 that supports a wafer 14. FIG. 1b illustrates the top view of the chuck system 12 that has a plurality of gas holes 16 on the upper surface of the chuck system 12 that supports the wafer shown in FIG. 1a. The gas holes 16 vent gas during wafer processing operations to enhance thermal transfer between the wafer 14 and the chuck system 12. FIG. 1b also illustrates the use of four push pins, or lift pins, 18 in the electrostatic chuck system 12. FIG. 1c illustrates the cross-sectional view of the wafer 14 and the supporting surface 12a of the electrostatic chuck system 12. As illustrated in FIG. 1c, the contact area of the cooling gas holes 16 and the backside of the wafer 14 are limited to the opening area of the gas holes 16.
The limited area of cooling contacts leads to several problems during the plasma processing operations. Once the plasma processing chamber 10 is turned on to allow plasma bombardment of the wafer surface in an etching or deposition process, the surface temperature of the wafer 14 is raised significantly. However, the limited cooling contacts provided by the gas holes 16 dissipate heat efficiently only in the area around where the gas holes 16 are provided. The accumulation of energy on the wafer surface, especially in areas located far away from the gas holes, increases the wafer temperature and therefore may vary the processing characteristics. The local accumulation of energy also results in the non-uniformity of the temperature distribution across the entire wafer. The irregular temperature distribution may cause deformation of the wafer. Moreover, the irregular temperature distribution also varies the effectiveness of plasma bombardment on different areas of the wafer surface and induces other process defects that impacts the yield and uniformity of products. In order to avoid these problems, the power density of the operating plasma has to be reduced and such adjustments usually increase the processing time of each wafer and reduce the production efficiency of the plasma processing chamber 10.
Accordingly, the present invention is directed to a chuck system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structures particularly pointed out in the written description and claims thereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the invention as embodied and broadly described, the present invention provides a chuck system that includes a pedestal having an upper surface for supporting a semiconductor wafer, a plurality of gas holes passing through the pedestal, the gas holes providing channels for gas to travel therethrough, and a plurality of grooves on the upper surface of the pedestal, the grooves connecting the gas holes.
In one aspect of the invention, the chuck system further includes a gas supplying device that pumps gas to the gas holes and grooves.
In another aspect of the invention, the gas holes include a first set of gas holes arranged in a circular pattern on the pedestal in a first radius and a second set of gas holes arranged in a circular pattern on the pedestal in a second radius, the second radius being greater than the first radius.
In yet another aspect of the invention, the chuck system also includes a center gas hole in the center of the pedestal and grooves connecting between the center gas hole and the first set of gas holes, the grooves being curved grooves on the upper surface of the pedestal.
In still another aspect of the invention, the grooves comprise a first set of circular grooves connecting the first set of gas holes and a second set of circular grooves connecting the second set of gas holes.
Also in accordance with the present invention, there is provided an electrostatic chuck system that includes a pedestal having an upper surface for supporting a semiconductor wafer, a plurality of gas holes passing through the pedestal, the gas holes providing channels for gas to reach the semiconductor wafer, and a plurality of grooves on the upper surface of the pedestal, the grooves including liner grooves and curved grooves connecting between the gas holes.
Further in accordance with the present invention, there is provided a chuck system that includes a pedestal having an upper surface for supporting a semiconductor wafer, a plurality of gas holes passing through the pedestal, the gas holes providing channels for gas to reach the semiconductor wafer. The gas holes include a center gas hole in the center of the pedestal, a first set of gas holes arranged in a circular pattern on the pedestal in a first radius, and a second set of gas holes arranged in a circular pattern on the pedestal in a second radius, the second radius being greater than the first radius. The chuck system also includes a plurality of grooves on the upper surface of the pedestal, wherein the grooves include center grooves connecting between the center gas hole and the first set of gas holes, the grooves being curved grooves on the upper surface of the pedestal, first circular grooves connecting between the first set of gas holes, second circular grooves connecting between the second set of gas holes, linear grooves connecting between the first set of gas holes and the second set of gas holes, and curved grooves connecting the second set of gas holes to the first circular grooves connecting between the first set of gas holes.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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