Patent Application
20050006325
(1) Technical Field
The present invention relates to a wafer cassette which holds a plurality of semiconductor substrates and more particularly to a cassette for containing and supporting a plurality of thin substrates such as semiconductor wafers and for storing and handling the fragile wafers, each of which are loaded and unloaded numerous times during the forming of integrated circuits therein.
(2) Description of the Prior Art
A cassette has been conventionally used for storing and supporting a plurality of fragile semiconductor substrates. The stored substrates, each of which are loaded and unloaded many times during the manufacturing process, both manually and automatically, are susceptible to damage. Cassettes are typically molded as a one-piece container is described with reference to
The substrates are usually loaded or unloaded when the cassette is in a vertical position as shown in
The present invention is concerned with substrate damage during transportation. A plurality of substrates contained in a cassette is held in place only if the cassette is placed in a horizontal position. The substrates are reasonably secure as provided by grooves that have an elongated V shaped cross-section. The V grooves are formed on opposing inner sides of the cassette and provide a means to hold and support a plurality of substrates at various process steps throughout manufacturing. If the cassette is placed in a vertical position, any source of vibration, caused by a myriad of disturbances, can effect the position of substrates within the cassette. The substrates may jut out and be exposed to damage by interfering with handling hardware, as shown in
Typically, substrates are arranged within the cassette outside of a semiconductor process operation. The cassette is thereafter transported, with its compliment of substrates inside, to a processing station. Some processing stations are designed to process the substrates while in the cassettes. Therefore, a list of primary goals for providing a universal cassette design is as follows: a) safely contain the substrates in a stacked and space saving array. b) Allow as much access to each substrate without inhibiting processing fluids from making contact with all surfaces on a substrate. c) Have a reasonable spacing between substrates for accessing each for removal and insertion. d) Choose a cassette material that is compatible with processing chemicals and with its contents while maintaining dimensional integrity between cassettes.
Accordingly, a primary object of the present invention is to provide a curbing member that substantially reduces a substrate movement from jutting forward when a cassette is placed in a vertical position and bumped.
Another object of the present invention is to provide a channel design that allows freedom of movement for the substrate, one that does not induce stresses by overly constraining. This is common in the prior art when the substrate moves against the inner apex of the groove promoting breakage or chipping of the highly stressed edges.
Still another object of the present invention is to provide a cassette design that does not change the overall cassette dimensions or its spacing between substrates.
Accordingly, the present invention provides a solution to eliminate the abovementioned problems. To achieve the foregoing objects, in accordance with a first object of the present invention, there is provided a substrate cassette that embodies grooves, each with a curbing member that prevents substrates from jutting forward when a cassette is placed in a vertical position and bumped.
The present invention relates to a wafer cassette which holds a plurality of semiconductor substrates and more particularly to a cassette for containing and supporting a plurality of thin substrates such as semiconductor wafers and for storing and handling the fragile wafers, each of which are loaded and unloaded numerous times during the forming of integrated circuits therein.
The cassette is molded in one piece made in the form of an open container having only four sides with a wide opening at the top for inserting and removing substrates, and a narrower opening, relative to the outside dimensions of a substrate, at the bottom of the cassette. This allows maximum exposure to process fluids while securely containing each of a plurality of substrates. The four sides include two side panels and two end panels. Each side panel has a straight upper portion and a curved lower portion the curved portions converge inward forming the narrower opening for the bottom. A plurality of substrate supporting channels is molded into each interior panel surface. The channels are provided on each of the side panels of the cassette in parallel and in alignment with the supporting channels on the opposite side. The supporting channels have a slight open draft angle of about three degrees. Each channel has a molded curbing member disposed preventing a substrate from jutting forward when a cassette is placed in a vertical position and bumped.
The present invention is concerned with substrate damage, in a cassette because of movement during transportation. Refer now to
Typically, substrates are arranged within the cassette outside of a semiconductor process operation. The cassette is thereafter transported, with its compliment of substrates inside, to a processing station. Some processing stations are designed to process the substrates while in the cassettes. The primary goals for a universal cassette design are as follows: a) safely contain the substrates in a stacked and space saving array. b) Allow access to each substrate without inhibiting process fluids from making contact with all surfaces on a substrate. c) Have a repeatable and precise spacing between substrates for accessing each for removal and insertion. d) Choose a cassette material that is compatible with process chemicals and temperatures while maintaining dimensional integrity between cassettes. e) Provide proper drainage of process fluids by having no fluid traps.
In the following particular embodiment of the substrate cassette, of the present invention, is described in detail by making reference to the accompanying drawings.
Referring now to
Referring to
While the invention has been particularly shown and described with reference to the preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the inventions.
