Patent Application
20060066333
Embodiments of the present invention relate to the fields of manufacturing semiconductors and hard disk drives, and more particularly to systems and methods for aligning wafers as utilized in the manufacture of semiconductors and hard disk drives.
Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 40 years ago and resembles a phonograph. That is, the hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that spin at a standard rotational speed. A plurality of magnetic read/write transducer heads, for example, one head per surface of a disk, is mounted on the actuator arm. The actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly, e.g., the arm and head, is known as a head gimbal assembly (HGA).
In operation, the plurality of hard disks is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, refinements of the disk and the head have provided great reductions in the size of the hard disk drive. For example, the original hard disk drive had a disk diameter of 24 inches. Modem hard disk drives are generally much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Refinements also include the use of smaller components and laser advances within the head portion. That is, by reducing the read/write tolerances of the head portion, the tracks on the disk can be reduced in size by the same margin. Thus, as modern laser and other micro recognition technology are applied to the head, the track size on the disk can be further compressed.
A second refinement to the hard disk drive is the increased efficiency and reduced size of the spindle motor spinning the disk. That is, as technology has reduced motor size and power draw for small motors, the mechanical portion of the hard disk drive can be reduced and additional revolutions per minute (RPM) can be achieved. For example, it is not uncommon for a hard disk drive to reach speeds of 15,000 RPM. This second refinement provides weight and size reductions to the hard disk drive and increases the linear density of information per track. Increased rates of revolution also provide a faster read and write rate for the disk and decrease the latency, or time required for a data area to become located beneath a head, thereby providing increased speed for accessing data. The increase in data acquisition speed due to the increased RPM of the disk drive and the more efficient read/write head portion provide modern computers with hard disk speed and storage capabilities that are continually increasing.
A wafer is a basic “building block” upon which numerous processing actions take place to produce semiconductor devices. Wafers also form a similar building block for the production of magnetic read and/or write heads and disks as used in hard disk drives. The production of such devices can comprise many different processing steps. It is not uncommon for hundreds of operations to be performed on wafers. Frequently, such production processes require that wafers be moved from one machine to another. Generally, wafers are grouped together for such transport between machines or storage. Wafers are typically moved among a variety of wafer processing equipment in wafer carriers known as cassettes. Sometimes such a cassette is also known as a “boat.”
A cassette is generally constructed from an engineering plastic. It typically comprises a plurality of slots that support and isolate each wafer. A cassette may hold up to about two dozen wafers, sometimes more. Although there are a variety of styles of cassettes available from a variety of manufacturers, a cassette is typically closed on top and bottom surfaces and closed on three sides. A fourth side is typically open, allowing for individual wafers to be moved in and out of the cassette by wafer processing equipment.
When viewed in cross section, a cassette may have a generalized “C” shape. For example, the top, bottom and back of the “C” shape are closed, while the front of the “C” shape is open. The wafers are moved in and out of such openings.
Unfortunately, wafers sometimes do not maintain a desired alignment within a cassette. For example, various handling operations, e.g., a “bump,” of a cassette can dislodge one or more wafers from their desired position within the cassette. Further, errors by automated wafer handling equipment can sometimes incorrectly place a wafer into a cassette.
Such misaligned wafers can frequently cause a processing disruption at a subsequent processing stage. For example, a wafer that is misaligned in a cassette can be incorrectly accessed by a processing device. Such an incorrect access can result in incorrect placement of a wafer within the processing device. Typically, after a time-out interval, the processing device will detect the incorrect placement of the wafer and reject that wafer. A common response to such a situation stops production flow and requires manual intervention to restore normal production. Manual intervention is not only costly in terms of direct costs and production delays, but further has the potential to introduce deleterious contamination onto the wafer and/or into the processing equipment. Contamination thus introduced can result in defects that have a detrimental effect upon production yield. In some cases, such defects may not be detected until much later in a production process.
Accordingly, there is a need for systems and methods for aligning wafers. Additionally, in conjunction with the aforementioned need, systems and methods for automatically aligning wafers while minimizing contamination opportunities are desired. A further need, in conjunction with the aforementioned needs, is for aligning wafers in a manner that is compatible and complimentary with existing wafer processing systems and manufacturing processes.
Systems and methods for aligning wafers are disclosed. A first method provides for placing a wafer carrier comprising a mis-aligned wafer into an acceptance port. A wafer alignment fixture is moved relative to the wafer carrier and perpendicular to the plane of the mis-aligned wafer. The wafer alignment fixture comprises a spring action member. A force from said spring action member is exerted upon the mis-aligned wafer to achieve a desirable alignment of the mis-aligned wafer within the wafer carrier.
Reference will now be made in detail to the alternative embodiment(s) of the present invention, system and method for aligning wafers. While the invention will be described in conjunction with the alternative embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Some portions of the detailed descriptions that follow (e.g., method 400) are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “placing” or “moving” or “determining” or “calculating” or “delaying” or “measuring” or “terminating” or “initiating” or “locating” or “indicating” or “transmitting” or “receiving” or “advancing” or “comparing” or “processing” or “computing” or “translating” or “determining” or “excluding” or “displaying” or “recognizing” or “generating” or “assigning” or “initiating” or “collecting” or “transferring” or “switching” or “accessing” or “retrieving” or “receiving” or “issuing” or “measuring” or “conveying” or “sending” or “dispatching” or “advancing” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Wafer alignment fixture 100 comprises a cantilever arm 110. Via well known techniques of analysis, physical parameters of cantilever arm 110, e.g., type of material, shape, thickness and the like, can be determined such that cantilever arm 110 acts as a spring. That is, in the plane of
As viewed in
In accordance with one embodiment of the present invention, wafer alignment fixture 100 is approximately 27 cm tall and about 1 cm thick (dimension not shown in
In accordance with the same embodiment of the present invention, cantilever arm 110 is about 1 cm wide. The gap between cantilever arm 110 and body 130 begins approximately 3 cm from the bottom of wafer alignment fixture 100. The gap between cantilever arm 110 and body 130 is about 1 cm wide.
As discussed previously, misaligned wafers, e.g., wafer 220, can frequently cause a processing disruption at a processing stage. For example, a wafer that is misaligned in a cassette can be incorrectly accessed by a processing device. Such an incorrect access can result in incorrect placement of a wafer within the processing device. Typically, after a time-out interval, the processing device will detect the incorrect placement of the wafer and reject that wafer.
Referring now to
Referring once again to
In accordance with an embodiment of the present invention, mounting bracket 140 can be mounted to a wall of a wafer washing station, or any other cassette acceptance port, e.g., a “sending station” or a “receiving” station, that is not vertical. Wafer alignment fixture 100 can then be attached via screws 141, 142 and 143 to mounting bracket 140 in order to compensate for an angular difference between a mounting surface of a cassette acceptance port and a desired plane of wafer alignment. For example, there can be a varying separation between lower portions of body 130 and mounting bracket 140 in comparison to upper portions of body 130 and mounting bracket 140.
Still referring to
In 420, a wafer alignment fixture comprising a spring action member is moved perpendicular to the plane of the mis-aligned wafer. For example, a wafer cassette comprising the mis-aligned wafer can be moved past a stationary wafer alignment fixture. Such a movement can be a part of a loading or unloading process performed to load a cassette into, or remove a cassette from wafer processing equipment. Alternatively, a wafer alignment fixture can be moved past a stationary or moving wafer cassette.
In 430, the spring action member exerts a force upon the mis-aligned wafer causing the mis-aligned wafer to achieve a desirable alignment within the wafer carrier.
Thus, embodiments of the present invention provide an apparatus and method for aligning wafers. Additionally, embodiments provide a method and system for correcting both single plane and coupled plane imbalances in a disk stack. Embodiments of the present invention further provide for balancing disk assemblies in a manner that is compatible and complimentary with existing hard disk systems and manufacturing processes.
While the method of the embodiment illustrated in flow chart 400 shows specific sequences and quantity of steps, the present invention is suitable to alternative embodiments. For example, not all the steps provided for in the methods are required for the present invention. Furthermore, additional steps can be added to the steps presented in the present embodiment. Likewise, the sequences of steps can be modified depending upon the application.
Embodiments in accordance with the present invention, system and method for aligning wafers, are thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.
