Patent Application
20190131162
The present invention relates to the field of semiconductor manufacturing, more specifically to the use of a heated chuck to hold wafers in place during manufacture and processing.
Electrostatic chucks (ESC) are used in a variety of semiconductor processes to hold the wafer during processing. ESCs employ a platen with integral electrodes which are biased with high voltage to establish an electrostatic holding force between the platen and wafer. ESCs also include heating or cooling elements to control the temperature of a wafer together with systems to control the heating and cooling curves of the wafer. Current ESC solutions are characterized by the high contact area that the platen makes with the wafer itself.
Current ESC solutions provide an expensive solution and suffer from a number of drawbacks. One drawback is that the chucking of the wafer may be non-uniform that may lead to an increase in backside defects of the wafer. The increased number of backside defects in turn also increased the number of front side defects. Another drawback is that due to the direct contact of the ESC to the wafer the backside of the wafer also tends to get scratched and metal contamination may occur. These problems are also exasperated by the lack of adequate solutions to heat and cool the temperature of the wafer. All of these lead to a decrease in semiconductor manufacturing yield and drive up the costs of semiconductor devices.
There exists a need for an ESC solution that provides an economical way of securing a wafer without increasing defects and of providing improved heating and cooling curves.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
It is an object of the present invention to address limitations in the prior art relating to field of semiconductor manufacturing, more specifically to the use of a heated chuck to hold wafers in place during manufacture and processing
An aspect of embodiments of the invention includes an apparatus for supporting a semiconductor wafer comprising a first disk receiving a gas in a central portion of the first disk. The gas being distributed within the first disk. A second disk coupled above the first disk. The second disk comprising a heater. The second disk receiving the gas from the first disk. The gas being heated within the second disk to produce a heated gas. A third disk coupled above the second disk. The third disk receiving the heated gas through the second disk. An upper surface of the third disk comprising a plurality of hemispheres protruding above the surface of the third disk. The plurality of hemispheres supporting the semiconductor wafer. The heated gas passing through the third disk and heating the wafer.
In further embodiments, heat is conducted from the plurality of hemispheres to the wafer. In other embodiments, the wafer is heated by convection from the heated gas.
In other embodiments, the first disk comprises a sprinkler structure positioned in the center of the first disk and a reservoir formed by an outer portion of the disk. The sprinkler structure receives the gas and distributes the gas to a reservoir formed in an outer portion of the first disk.
In further embodiments, the apparatus comprises a reservoir formed between the second disk and the third disk. The heated gas passes through the reservoir as it passes from the second disk to the third disk.
In other embodiments, each of the plurality of bumps comprises a hemisphere and a post. The post of each of the plurality of bumps being received by a hole formed in the upper surface of the third disk.
In other embodiments, each of the plurality of bumps is comprised of sapphire.
In further embodiments, the third disk receives the heated gas through the second disk vis a first plurality of holes formed through the second disk. The heated gas passes through the third disk through a second plurality of holes formed through the third disk. The first plurality of holes is offset from the second plurality of holes.
In another embodiment, the diameter of the first plurality of holes is different from the diameter of the second plurality of holes.
In another embodiment, each of the second plurality of holes comprises an upper portion and a lower portion. The diameter of the upper portion being greater than the diameter of the second portion.
In some embodiments, the heater comprises a coil contained within the second disk. The coil having a substantially rectangular cross section.
In other embodiments, the coil comprises a first portion and a second portion. the first portion positioned in a central portion of the second disk. The second portion positioned in an outer portion of the second disk. In other embodiments, the apparatus further comprises a cooler.
In further embodiments, the third disk comprises a plurality of wafer guards. The plurality of wafer guards blocking a lateral movement of the wafer when the wafer is positioned on the third disk.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
Embodiments of the present invention are directed to providing an improved electrostatic chuck for semiconductor wafer processing and more particularly to a non-electrostatic chuck including an improved backside gas distribution heating solution. One novel feature provides an improved pedestal design that limits the contact area between the platen and a wafer. Another novel feature is the use of a uniform backside gas distribution system. A third novel feature is the use of a heating coil with a square cross section. Embodiments of the invention may help to reduce capital investment as well as maintenance costs.
Referring to
Referring to
Each bump 303, which preferably takes the form of a post with a hemispheric top is inserted into each of the similarly sized hole 302 formed in the upper surface of the top pedestal layer 101. The post 303 may be press fitted into place. In an exemplary embodiment, each bump 303 is made of sapphire though ruby and other materials may also be used. The post 303 may be 0.3 mm in diameter and 0.5 mm long. The hemispheric top may be 0.15 mm in radius and protrude above the surface of the top pedestal 101 by 0.15 mm. In use, the wafer is supported on the tops of the hemispheric bumps 303. The hemispheric shape limits the contact surface between the pedestal 100 and the wafer 400 while presenting a smooth surface to minimize scratches. Reducing the contact area aids in minimizing the defects on the silicon wafer back side, reduces metal contamination, reduces backside scratches, and reduces the number front defects coming due to backside defects. The improved design also increases the efficiency of conduction heat transfer going upwards to the silicon backside and distributes the airflow more uniformly.
A second major aspect of embodiments of the invention includes the use of backside gas technology with a uniform gas distribution to control the wafer temperature, increase the temperature ramp rate of the wafer and improve the heating quality. The pedestal 100 uses a three-layer distribution to distribute heated gas from the bottom of the pedestal, up through the layers in proximity to a heating element, finally heating the backside of the wafer. The three layers are mounted together using screws, bolts or other means as known in the art. Heating is done using both convection and conduction heat transfer. Heat conduction happens where the pedestal 100 contacts the wafer 400 at the bumps 303. Heat convection happens with heat radiated from the heated gas. In use, the gas enters the pedestal and moves upwards through the three layers. The distribution of the gas in the three layers products a stable backside pressure.
Referring to
Referring to
The second layer 201 also comprises a heating coil 207208 or element to increase the temperature of the pedestal 100. This causes the gas to be heated. As the heated gas moves upwards through the pedestal 100, from first 101, to second 201, to third layer 301, it helps in increasing the temperature ramp rate. The heating coil 207208 enters the second layer 201, typically through the center of the layer and is routed to evenly cover the area of the layer. Referring to
Alignment pins 205 are included to align the three layers and mounting holes 204 are distributed around the perimeter. Alignment pins 205 may be placed in the top and bottom of the second layer with corresponding alignment holes to receive them in the first and third layers. Alternatively, the alignment pins may and alignment holes may be reversed. A second gas reservoir is formed between the second and third layers to allow the gas to circulate and redistribute before passing through the holes in the third layer.
Referring to
Preferably the pedestal 100 is made of stainless steel though other materials may also be used.
The ensuing description provides representative embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing an embodiment or embodiments of the invention. It being understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Accordingly, an embodiment is an example or implementation of the inventions and not the sole implementation. Various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention can also be implemented in a single embodiment or any combination of embodiments.
Reference in the specification to “one embodiment”, “an embodiment”, “some embodiments” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment, but not necessarily all embodiments, of the inventions. The phraseology and terminology employed herein is not to be construed as limiting but is for descriptive purpose only. It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be construed as there being only one of that element. It is to be understood that where the specification states that a component feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.
Reference to terms such as “left”, “right”, “top”, “bottom”, “front” and “back” are intended for use in respect to the orientation of the particular feature, structure, or element within the Figures depicting embodiments of the invention. It would be evident that such directional terminology with respect to the actual use of a device has no specific meaning as the device can be employed in a multiplicity of orientations by the user or users.
Reference to terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, integers or groups thereof and that the terms are not to be construed as specifying components, features, steps or integers. Likewise, the phrase “consisting essentially of”, and grammatical variants thereof, when used herein is not to be construed as excluding additional components, steps, features integers or groups thereof but rather that the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.
