Patent Application
20130121802
This disclosure relates generally to a wafer transport system and, more specifically, to systems used to transport wafers between a wire saw and a processing apparatus.
Semiconductor wafers are typically formed by cutting an ingot with a wire saw machine. These ingots are typically made of silicon or other semiconductor or solar grade material. The ingot is connected to structure of the wire saw by a bond beam and an ingot holder. The ingot is bonded with adhesive to the bond beam, and the bond beam is in turn bonded with adhesive to the ingot holder. The ingot holder is connected by any suitable fastening system to the wire saw structure.
In operation, the ingot is contacted by a web of moving wires in the wire saw that slice the ingot into a plurality of wafers. The bond beam is then connected to a hoist and the wafers are lowered onto a cart. The wafers are then lowered into a liquid-filled tank that is incorporated into the cart. The cart includes a lifting mechanism to lower the wafers into the tank. The cart is then moved to a position adjacent a processing apparatus (e.g., a cleaner) and the wafers are raised by the lifting mechanism. The wafers are then pushed off of the cart and into the processing apparatus.
Known carts have numerous disadvantages, such as the weight of the cart due to the liquid-filled tank and housekeeping problems caused by the liquid spilling onto the floor when moving the cart. Other disadvantages include a lack of alignment aids to facilitate the loading of the wafers onto the cart without damaging the edges of the wafers. Thus, there exists a need for a more efficient and effective system to transport the wafers from the wire saw to the processing apparatus.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A first aspect is a cart for transporting wafers from a wire saw to a processing apparatus after the wafers are cut from an ingot. The cart comprises a frame having opposing ends and a support sized for receiving a wafer assembly including the wafers, rollers positioned in the support, and an upright member connected to one of the ends of the frame. The rollers have opposing ends connected to the frame and a tapered portion positioned adjacent the ends for guiding the wafer assembly to a first position as the wafer assembly is lowered onto the support of the frame. The upright member has an alignment member disposed for guiding the wafer assembly to the first position as the wafer assembly is placed on the support of the frame.
Another aspect is a system for transporting wafers to a processing apparatus. The system comprises a frame and an alignment system. The frame has a support sized for receiving a wafer assembly including the wafers. The alignment system is connected to the frame and is disposed for guiding the wafer assembly to a first position as the wafer assembly is lowered onto the support of the frame.
Still another aspect is a method of positioning a wafer assembly in a first position on a cart for transporting the wafer assembly from a wire saw to a processing apparatus, the wafer assembly including wafers cut from an ingot by the wire saw. The method comprises lowering the wafer assembly into contact with an alignment member connected to an upright member of the cart, the alignment member disposed for guiding the wafer assembly to the first position as the wafer assembly is lowered towards the frame, and placing the wafer assembly onto rollers connected to the frame, the rollers having a tapered portion for guiding the wafer assembly.
Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring to the drawings, an exemplary cart for transporting wafers to a processing apparatus after the wafers are cut from an ingot is shown in
The cart 100 includes a frame 110 having a support 120 sized for receiving the wafer assembly. The support 120 forms a top of the cart 100. The frame also has opposing ends (i.e., a first end 112 and a second end 114) connected by a pair of spaced-apart sides 116, 118. The frame 110 has a bottom 122 positioned opposite the support 120. In the example embodiment, four wheels 124 are connected to the bottom 122 of the frame 110 so that the cart 100 can be moved easily by a user. Some or all of these wheels 124 may be casters in the example embodiment. As described in greater detail below, the first end 112 of the cart 100 is configured for placement adjacent the processing apparatus 200.
An alignment system 130 is connected to the frame 110 and is disposed to guide the wafer assembly to a first position as the assembly is lowered onto the support 120 of the frame 110. In the first position, the wafer assembly is at rest on the support 110. In a second position, the wafer assembly is spaced from the support 110. In the example embodiment, the alignment system 130 includes rollers 140 and an upright member 160. In other embodiments only one of these may be used to guide the wafer assembly to the first position.
The rollers 140, as best seen in
As shown in
The upright member 160 is best shown in
The guides 168, 170 and the upright member 160 form a channel 172 (best shown in
The varying width of the channel 172 results from each guide 168, 170 having an angled portion 178, 180. In the example embodiment, these angled portions 178, 180 extend along less than all of the length of the guides 168, 170. In other embodiments, the angled portions 178, 180 extend from the first end 174 of the channel 172 to the second end 176 of the channel 172. In these embodiments, the guides 168, 170 are triangle-shaped.
A pin 190, as best shown in
A plate 192 is positioned on the underlying surface adjacent the processing apparatus 200, as shown in
The plate 192 has a slot 194 sized for receiving the pin 190 such that the slot in the plate and pin cooperate to position that cart 100 adjacent the processing apparatus 200 in an unloading position. The slot 194 has a tapered portion 196 disposed away from the processing apparatus 200 having a width substantially greater than that of the pin 190. The width of the tapered portion 196 decreases nearer the processing apparatus 200 to a width that is only slightly greater than that of the pin 190 (e.g., about 2 to 3 mm).
In operation, the wafer assembly is removed from the wire saw after the ingot is cut into wafers by the saw. The wafer assembly may be attached to a mobile hoist or other suitable structure before or after removal from the wire saw. The mobile hoist is then used to transport the wafer assembly to a position vertically above the cart 100 and/or the cart is moved to a position where it is vertically beneath the mobile hoist. As the mobile hoist nears the cart 100, the pin 190 protruding from the cart engages the slot 194 formed in the plate 192 attached to the mobile hoist. The slot 194 and the pin cooperate to the cart 100 to the desired unloading position underneath the hoist.
The mobile hoist and the wafer assembly are then lowered towards the support of the cart. As the mobile hoist and wafer assembly are lowered towards the support, a portion of the mobile hoist is first received with the channel adjacent its first end. As the width of the channel at its first end is substantially greater than that of the mobile hoist, a user manipulating the mobile hoist is able to position the mobile hoist in the channel with relative ease. The mobile hoist and wafer assembly continue to be lowered, and the angled portions of the guides aid in positioning the mobile hoist and wafer assembly laterally with respect to the cart.
A bottom of the wafer assembly contacts the rollers as the mobile hoist and assembly are further lowered. The bottom of the assembly contacts the tapered portions of the rollers which further aids in the lateral position of the wafer assembly with respect to the cart. Moreover, the positioning of the wafer assembly on the tapered portions elevates the bottom of the wafer assembly above the middle portions of the rollers. This elevation or spacing apart prevents interference or other contact between any structures depending from the bottom of the assembly and the middle portions of the rollers.
After being lowered into the first position on the support, the mobile hoist may be disconnected from the wafer assembly. The cart is then rolled or otherwise moved towards the processing apparatus. As the cart nears the processing apparatus, the pin protruding from the bottom of the cart engages the slot in the plate. The slot and the pin cooperate to guide the cart to an unloading position adjacent the processing apparatus.
Once in the unloading position, the wafer assembly is moved along the rollers into the processing apparatus. As the bottom of the wafer assembly is elevated above the middle portions of the rollers, the cart can be relatively easily moved over the rollers. After unloading, the cart is moved from the unloading position and the process can be repeated for another wafer assembly.
The cart described herein has features which aid in aligning the wafer assembly with respect to the cart. This alignment results in the rapid precise and/or repeatable placement of the wafer assembly on the cart. The cart also has features which aid in positioning the cart with respect to the processing apparatus. These features reduce the amount of time required to transport the wafer assembly from the wire saw to the processing apparatus.
This reduction in time permits the wafers to be transported without being submersed in a tank filled with liquid, as required in prior systems. These prior systems lacked the features of the cart described herein and thus required greater amounts of time to transport the wafer assembly from the wire saw to the processing apparatus. During these longer periods of time, the surfaces of the wafer would dry and react with the atmosphere if left un-submersed. Accordingly, prior systems required the submersion of wafers in a liquid to prevent unwanted chemical reactions with the atmosphere. These prior systems thus incorporated large tanks for holding a liquid in which the wafer assembly was submersed in during transport.
The cart described herein lacks such a submersion tank and the difficulties associated with such a tank. The cart has a significantly reduced mass compared to tanks having a liquid-filled tank. This reduces the amount of force required to move and position the tank adjacent the processing apparatus. Accordingly, a single user is able to move and position the cart. The pin protruding from the bottom also aids the user moving the cart such that a single user is able to position the cart with respect to the mobile hoist and the processing apparatus.
As usage of the cart disclosed herein reduces the amount of time required to position the wafer assembly on the cart and align the cart with respect to the processing apparatus, there is insufficient time for the surfaces of the wafers to dry. Accordingly, the wafer assembly does not have to be submersed in a tank of liquid to protect the surfaces of the wafers from chemical reactions with the atmosphere.
When introducing elements of the present disclosure or the embodiments thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
