Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With means applying wave energy or electrical energy...
Reexamination Certificate
1999-08-18
2001-05-29
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With means applying wave energy or electrical energy...
C156S540000, C156S583100, C156S583200, C156S378000, C156S249000, C156S345420, C438S464000, C414S937000, C414S941000
Reexamination Certificate
active
06238515
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a wafer transfer apparatus capable of, in a process for manufacturing small electronic components such as semiconductor chips, transferring a wafer which has been subjected to dicing and back grinding and to which a protective tape has been stuck, to a ring frame and a transfer tape and peeling the protective tape from the wafer.
BACKGROUND OF THE INVENTION
In the conventional process for producing a wafer of, for example, a semiconductor such as silicon, a wafer is prepared in the form of a disk of large diameter and a circuit pattern is formed on a surface of the wafer. Thereafter, the circuit pattern surface is protected with a protective tape, and back of the wafer is ground. Further, the protective tape is peeled from the wafer surface. The thus obtained semiconductor wafer is held to a ring frame by means of a pressure sensitive adhesive sheet and diced (cut and divided into dice) so that a multiplicity of chips are obtained with the use of a dicing cutter. Thereafter, the chips in that state are subjected to subsequent cleaning, drying and die bonding steps.
Recently, the reduction of the thickness of semiconductor chips such as IC cards is increasingly demanded. The demand for semiconductor chips whose thickness is reduced to about 50 &mgr;m from the conventional 300 to 400 &mgr;m is increasing. However, when such extremely thin wafers are produced by the above back grinding process, there is the danger of carrying failure or wafer cracking caused by wafer warpage during, for example, protective tape peeling, wafer mounting and dicing steps.
The process known as “predicing” as disclosed in Japanese Patent Laid-open Publication No. 5(1993)-335411 has been proposed for coping with the above problem. In this process, a wafer is diced from its surface provided with a circuit to given depth in the direction of wafer thickness so that grooves with bottoms in a dice pattern are formed. Subsequently, a protective tape is stuck to the wafer surface, and the wafer back is ground to the grooves with bottoms so that the wafer is divided into a multiplicity of chips. Thereafter, the wafer covered with the protective tape is held to a ring frame and is subjected to subsequent cleaning, drying and die bonding steps.
However, in any of the above processes, the current situation is that peeling of a protective tape and sticking of a transfer tape to a wafer are carried out by separate devices. In this case, wafer must be carried between separate device, and this is generally performed by placing wafers in a container such as a wafer carrier provided with multi-stage wafer accommodation spaces and transporting the container to subsequent-step device.
Currently, the thickness of wafers tends to become smaller and, on the other hand, the diameter of wafers tends to become larger. The centers of the wafers sink and are deformed by their own weights in the carrier, depending on the ratio of wafer diameter to thickness. As a result, it is difficult to takeout automatically the wafer from the carrier and place it in the carrier. Even if automatic takeout and placing can be conducted, there is the danger of wafers contacting the carrier to thereby suffer from breakage and damaging.
In the predicing process, the wafers are in the state of being divided in a multiplicity of chips and fixed by a protective tape composed of a flexible film, so that, at the time of handling, there is the danger of neighboring chips contacting each other to thereby suffer from breakage.
The present invention provides a wafer transfer apparatus in which a wafer having been divided into a multiplicity of chips by predicing and covered with a protective tape can be transferred continuously and automatically to a transfer tape and a ring frame and the protective tape can be peeled, so that it can be accommodated in a carrier. As a result, wafer transfer apparatus of this invention can prevent cracking caused by the carrying of a thin wafer (chips), breakage and cracking caused by the carrying conducted between devices by means of carriers, etc., and wafer (chips) cracking caused by takeout from the inside of carriers.
SUMMARY OF THE INVENTION
The present invention has been made with a view toward resolving the drawbacks of the prior art and attaining the above object. According to the present invention, there is provided a wafer transfer apparatus for holding a wafer, which is divided into a multiplicity of chips and which surface is stuck with a protective tape, to a ring frame by means of a transfer tape, comprising:
a positioning unit capable of disposing the protective tape stuck wafer on a positioning table and capable of performing a position adjustment of the wafer in longitudinal, lateral and rotational directions, so that the wafer is located in a reference position;
a transfer tape mount unit capable of disposing the protective tape stuck wafer, which has been located in the reference position by the positioning unit, on a transfer tape mount table, and capable of sticking a transfer tape to both a ring frame disposed round periphery of the wafer and back of the wafer, so that the wafer and the ring frame are stuck to each other and integrated; and
a protective tape peeling unit capable of disposing the wafer which has its back covered with the transfer tape and which has been integrated with the ring frame by the transfer tape mount unit, on a protective tape peeling table, and capable of bonding an end of a peeling tape to an end of the protective tape stuck to the wafer surface, and capable of pulling the peeling tape so that the protective tape is peeled from the wafer surface.
By virtue of this construction, chipped wafer division lines are recognized, and a position adjustment is conducted in longitudinal and lateral directions (XY-directions) and rotational direction (&thgr;-direction) so that the wafer is located in a reference position. As a result, accurate die bonding in the die bonding step can be performed. Moreover, the transfer operation and the protective tape peeling operation can be continuously performed without the need to carry by the use of wafer carriers. Therefore, wafer breakage, damaging and cracking can be prevented.
In the wafer transfer apparatus of the present invention, preferably, the protective tape is one having an ultraviolet curable pressure sensitive adhesive, and the wafer transfer apparatus further comprises an ultraviolet irradiating unit capable of irradiating the protective tape with ultraviolet light prior to the peeling of the protective tape from the wafer surface by the protective tape peeling unit.
In the present invention, the ultraviolet irradiating unit is preferably arranged so that the ultraviolet irradiation precedes the sticking of the transfer tape to the wafer.
The radiation curable pressure sensitive adhesive is used in the adhesive of the protective tape and is irradiated with ultraviolet light so that the adhesive strength of the protective tape can be reduced and the protective tape can be easily peeled from the wafer divided into chips in the protective tape peeling step.
Furthermore, in the wafer transfer apparatus of the present invention, it is preferred that the transfer tape is one having an ultraviolet curable pressure sensitive adhesive, and that the wafer transfer apparatus further comprise an ultraviolet irradiating unit capable of irradiating the transfer tape with ultraviolet light after the wafer and the ring frame are stuck to each other by means of the transfer tape.
The radiation curable pressure sensitive adhesive is used in the adhesive of the transfer tape and is irradiated with ultraviolet light so that the pickup adhesive strength of the transfer tape can be reduced and the pickup can be easily performed at the time of picking up the chips from a surface of the transfer tape in the die bonding step.
Moreover, the wafer transfer apparatus of the present invention preferably further comprises an accommodation unit fitted with a frame cassette for accommodating the wafer, which
Kobayashi Kenji
Numata Hideo
Tokubuchi Keisuke
Tsujimoto Masaki
Ball Michael W.
Lintec Corporation
Tolin Michael A.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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