1. Field of the Invention
The present invention relates to devices useful for lifting and carrying objects. More particularly, the present invention relates to detachable wafer carrier handle assemblies and combinations thereof with wafer carriers.
2. Description of the Invention's Background
In the production of semiconductor devices such as transistors, it is common to simultaneously produce a plurality of semiconductor elements on one substrate composed of a semiconductor material, such as monocrystalline silicon, and to then break the substrate into individual elements for mounting in suitable enclosures. Such semiconductor substrates, or wafers, are often processed at least partially in batches, such that a number of wafers will go through at least several processing steps at the same time. To enable relatively rapid transfer of the wafers from one processing step to the next with minimal contamination of the wafers by human contact, various wafer carriers are used to hold the wafers, generally in a vertically upright, horizontally spaced array.
Two types of wafer carriers are commonly used in the industry. A high temperature wafer carrier is typically used during high temperature processing steps, wherein the temperature is greater than about 200 degrees Celsius, and is often made from a plurality of quartz rods that form a "basket" or "rack" for supporting the wafers. A low-temperature wafer carrier is typically used during lower temperature processing steps, and is often made of such plastics as polytetrafluoroethylene (Teflon.RTM.) or polypropylene. A low-temperature wafer carrier is often formed as a "cassette", such that it generally includes a base having a plurality of slots or grooves therein to receive and hold a plurality of wafers vertically upright and spaced uniformly and horizontally from each other, and a pair of flanges on opposite sides of an upper portion of the base. The flanges generally provide a means whereby some form of a handling apparatus can attach to the wafer carrier to allow manipulation of the wafer carrier, such as removal of the wafer carrier from one processing step and movement to the next step.
Various handling apparatuses are known in the prior art. For example, various robotic handling apparatuses are known, such as those disclosed in U.S. Pat. Nos. 5,054,834, 5,110,01, 5,123,804, 5,236,295 and 5,356,261, for robotically manipulating a wafer carrier during or between processing steps. Such handling apparatuses have the disadvantage, however, that they are relatively expensive and thus tend to be used most often in situations where human intervention is unacceptable or undesirable, such as in high temperature situations or in situations where the risk of contamination from human intervention is too high.
Other types of handles are known, such as those disclosed in U.S. Pat. Nos. 4,515,104, 4,572,101 and 5,033,406, that are specifically adapted to enable lifting and movement of "rack"- or "basket"-shaped wafer carriers of the type often used during high temperature processing steps. Such handles are often designed to lift a wafer carrier from the end or side of the carrier, and thus tend to have the disadvantage that they are relatively unstable, which can increase the chance that a user will accidentally drop one or more wafers off of the carrier during use of the handle.
Yet other types of prior art handles are known, such as the handle disclosed in FIG. 1 of U.S. Pat. No. 5,364,144 and the handle disclosed in FIG. 1 of this application, that are more specifically adapted for use with the "cassette" style of wafer carrier more often used in lower temperature processing steps.
Such handles can include an attachment piece, such as the hooks 12 of FIG. 1 of the '144 patent or the attachment piece 1 of FIG. 1 of the instant application, for sliding around the flanges of the wafer carrier until the attachment piece abuts stops below the flanges, and a handle piece, such as the ring 11 of FIG. 1 of the '144 patent or the handle 2 of FIG. 1 of the instant application, to enable lifting of the wafer carrier.
Such handles generally thus are intended to support a wafer carrier through contact of the attachment piece with the flanges and the stops at one end of the wafer carrier, such that the counterbalancing weight of wafers in the opposite end of the carrier restrains the attachment piece from sliding away from the stops and off of the flanges. However, it is common to make such handles out of the same materials as the carrier, i.e., Teflon.RTM. or polypropylene, and as a result there is normally a very low coefficient of friction between the attachment piece and the flanges. Such handles thus normally slide off of a wafer carrier relatively easily, especially when there are only a small number of wafers in the carrier and thus a low counterbalancing weight, or when a handle is left on a carrier during a processing step that involves agitation, such as agitation of a fluid in which the carrier is immersed.
In view of the above, it is an object of the present invention to provide an improved wafer carrier handle assembly that is readily capable of detachable attachment to a wafer carrier.
It is another object of the present invention to provide an improved combination wafer carrier and detachable wafer carrier handle assembly.
A further object of the present invention is to provide a wafer carrier handle assembly and a combination wafer carrier and wafer carrier handle assembly that are relatively inexpensive.
It is a further object of the present invention to provide a wafer carrier handle assembly that is useful for handling wafer carriers designed for relatively lower-temperature processing steps.
Yet another object of the present invention is to provide a wafer carrier handle assembly that restrains sliding movement of a wafer carrier relative to the wafer carrier handle assembly.
Another object of the present invention is to provide a wafer carrier handle assembly and a combination wafer carrier and wafer carrier handle assembly that are relatively easy to use.