This invention relates to systems and methods for securing semiconductor wafers during spinning.
In semiconductor fabrication, various layers of insulating, conducting and semi-conducting materials are deposited to produce semiconductor devices that provide desired electrical functions in an integrated circuit (IC) device.
During fabrication, semiconductor processing apparatus treat wafer surfaces by furnishing required treating liquids and gases to a wafer surface while rotating the wafer at a high speed. Such spinning or rotating-type substrate processing requires an arrangement that minimizes slippage between a substrate and retaining members which hold the substrate while the substrate is spinning since slippage causes the substrate surface to be chipped and generated particles, and also causes dust to adhere to the substrate surface. This also causes the processing liquid to flow unevenly, which eventually deteriorates the quality of processing.
Generally, the wafer retaining mechanism is broadly classified into two types. One is a so called vacuum chuck type that conducts vacuum-suction to one side surface of the wafer, and the other is a type that holds the outer peripheral edge of the wafer by means of three or more chuck pieces. Since the treating can be applied to only one side surface of the wafer according to the former, the latter is chiefly employed when it is desired to treat both side surfaces simultaneously.
U.S. Pat. No. 4,788,994 discloses a wafer holding mechanism that horizontally holds, one at a time, wafers which are sequentially transported thereto. Wafers are treated with liquids such as an etching, rinsing liquid, and the like, at the same time that the wafer is rotated at a high speed. The mechanism includes a hollow rotary shaft having an upper end thrust into a housing, a rotary plate horizontally mounted on the upper end of the rotary shaft, chuck pieces provided on the rotary plate for holding an outer peripheral edge of the wafer, the chuck pieces being movable in the radial direction of the rotating plate between a holding position wherein the wafer is tightly held by the chuck pieces and a release position wherein the wafer is free to be removed from the chuck pieces.
U.S. Pat. No. 5,376,216 discloses a plurality of substrate holding members and a substrate pressing member being disposed on a rotation stage at a peripheral portion. The substrate pressing member includes a magnet and is pivotally supported by the rotation stage. A ring-shaped permanent magnet is located below the rotation stage and forms a ring around the rotation axis of the rotation stage. When a substrate mounted on the rotation stage is rotated and processed, the ring-shaped permanent magnet is positioned in the vicinity of the magnet of the substrate pressing member. This creates a magnetic force between the magnets, causing the substrate pressing member to pivot so that the substrate pressing member contacts the edge of the substrate with a predetermined amount of pressure.
U.S. Pat. No. 5,989,342 discloses a substrate holding apparatus that holds a rotating substrate without idly rotating the substrate and keeps the substrate in proper balance while the substrate is rotated. In a revolvable holding member, a column-shaped holding part is disposed on a top surface of a column-shaped supporting part, at an eccentric position with respect to a rotation axis of the supporting part. The revolvable holding member is supported by a rotation base for free rotation, and linked to a magnet holding part which incorporates a permanent magnet. On the other hand, a ring-shaped magnet which is disposed in a processing liquid collecting cup is freely driven by an air cylinder in a vertical direction. As the ring-shaped magnet is moved upward or downward and crosses a predetermined line as viewed in a positional relationship relative to the permanent magnet, which is at a height where the permanent magnet is disposed, the direction of a magnetic line of flux of the ring-shaped magnet is reversed. As a result, the direction of the revolving force which acts upon the permanent magnet is reversed, whereby the revolvable holding member holds or releases a substrate.
In a first aspect, an apparatus for holding a rotatable wafer having a wafer side and a wafer edge includes one or more clamps proximally positioned around a wafer perimeter, each of said clamps including a clamp edge adapted to engage said wafer edge.
In another aspect, an apparatus for holding a rotatable wafer having a wafer side and wafer edge clamp housing and a clamp rotatably positioned in said clamp housing, said clamp having a clamp edge adapted to engage said wafer edge.
Advantages of the system may include one or more of the following. The clamp provide for a substrate holding apparatus which, with a simple structure and securely holds and releases a substrate. The substrate can be rotated without causing idle rotation of the substrate, while keeping excellent balance.
These and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements.
A first tub or bowl 150 collects waste materials during the processing of the wafer 100, and a second tub or bowl 152 collects material generated during the processing of the bottom side of the wafer 100. Drains 154-156 are provided at the bottom of the first tub or bowl 150 to provide liquid and air exhaust for the first tub 150. Similarly, a drain 158 is provided at the bottom of the second tub 152 to remove materials from the second tub 152.
The bowl 150 has a shroud 140 to collect liquid and drain hole to vent air and liquid to a drainpipe. The shroud 140 can be moved up and down: the shroud 140 is in a lower position during wafer loading and un-loading, and is at an upper position during wafer rotation process sequences. The assembly moves the shroud 140 up and down using magnets located inside the outer housing 132. A labyrinth seal between inner and outer tub applied to prevent liquid getting into bearing. Additional protection, a felt ring seal is located between outer bearing drive housing to prevent moisture from getting into the bearing. From the outer bearing assembly, positive pressure airline supplies dry air to the bearing assembly. The foregoing protection prevents moisture from getting into the bearing assembly: there is no metallic material, hardware and mechanism that is exposed liquid. Hence, the arrangement advantageously prevents any corrosion and contamination to the substrate or wafer 100. Although a belt-drive system has been described, the drive system can also be a direct drive motor system.
The shroud 140 has a mesh that minimizes liquid from flashing back into the wafer during high speed spinning. The spacing between the shroud and mesh can be from 0.125″ to 1.0″, and preferably is 0.25″. The movement of the shroud is actuated by one or more actuators such as air cylinders. The moving end of the actuator is provided with a magnet that magnetically attaches to a corresponding magnet mounted on the shroud 140. The shroud 140 is at a first position (down position) during wafer loading or unloading and the shroud is at a second position (up position) during wafer rotation or processing.
Similar to the clamp 300, the clamp 500 provides a clamp edge 502 that engages the wafer edge 307. A seat 503 supports the wafer 100 at a rest position. The clamp 500 has a body with an elevated portion 504 that cooperates with the seat 503 in securing the wafer 100 at low speed. The clamp has a weight 510 mounted on one side. At high rotational speed, the weight 510 experiences a centrifugal force and moves away from the center of the wafer 100. As the weight 510 moves away from the wafer center, the edge 502 engages the wafer edge 307 to clamp the wafer 100 in place during rotation.
Although the invention has been described with reference to particular embodiments, the description is only an example of the inventor's application and should not be taken as limiting. Various adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.