Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-04-18
2001-09-18
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S150000, C438S250000, C427S283000, 43, C451S049000
Reexamination Certificate
active
06291261
ABSTRACT:
The invention relates to a method for treating a two-dimensional subject, in particular a semiconductor wafer, according to the preamble of claim
1
.
So that for example chips premanufactured on a silicon wafer may be sawn off in a sawing device or may be processed in a chip assembly automatic machine, the wafer must be exactly positioned and be adhesed to a carrier foil in a manner free of bubbles. The foil is at the same time tensioned on an annular foil frame, a so-called waferframe. In this manner the very thin and fragile wafers may be easily stored, transported and processed. For an exact removal of the chips from the adhesing foil in equipping automatic machines (die bonders), the carrier foil must be tensioned afterwards, wherein a slight expansion of the wafer is obtained. With this there arise intermediate spaces between the individual chips which simplifies the removal.
The post-tensioning of the carrier foil with known methods is effected directly in the processing device, thus for example on the receiving table of the equipping automatic machine. For this for example a tensioning ring is pressed against the carrier foil which may roughly be compared to the tensioning of a drum. Also vacuum devices are known with which the carrier foil under a vacuum is suctioned into a circumferential groove and by way of this is tensioned (U.S. Pat. No. 4,744,550).
A disadvantage of the known methods lies however in the fact that the foil frame is not standardised, and that the post-tensioning device in each case must always be adapted to the corresponding frame. This requires to some extent expensive machine conversions. Furthermore it has been shown that with the ever increasing diameter of the semiconductor wafers and thus of the foil frame there occurs a sagging of the carrier foil which may no longer be tolerated. With the handling of the foil frames with this for example individual chips may knock against one another at the edges and mutually damage one another (chipping).
It is therefore the object of the present invention to provide a method of the initially mentioned type with which the post-tensioning of the carrier foil is no longer effected directly in the processing plane and with which also large wafer diameters may be handled without danger or damage to the chips. Furthermore overall there is to be achieved a higher flexibility on the manufacture between the process steps of the manufacture of the wafers and the processing of the chips.
According to the invention this object is achieved with a method which comprises the features of claim
1
. The fastening of the foil frame on a quasi overriding adapter frame and the post-tensioning of the carrier foil which occurs with this firstly has the effect that the post-tensioning process does not need to be effected firstly on the processing table, but may be effected at any earlier point in time. On account of the flow behaviour of the carrier foil this tends to post-stretch after the actual tensioning procedure. Since the post-tensioning procedure in the adapter frame takes place long before the actual processing process the post-stretching process is completed on reaching the treatment table.
With an intermediate storage or a mechanised transport no damage may occur any more as a result of sagging. The required process steps are carried out on the adapter frame in the resprospectively tensioned condition. The treatment machine need only accommodate standardised adapter frames and no more foil frames of differing dimensions. Furthermore after the working off of a subject a longer machine interruption is no longer required, since in each case a second adapter frame may be loaded which is immediately available for application at the processing station.
The abutting means serves as an interface for positioning the adapter frame in the process step in a horizontal or vertical or any other working plane. This standardised interface makes easier the handling with each working process.
The subject, on the adapter frame, may be sawn into individual parts, for example into individual chips, in a saw device. In this manner already on sawing or directly after the cut a damage to the subject is avoided. The post-tensioning of the carrier foil may be effected before or after the sawing. With this it is merely important that the foil frame in the adapter frame is sufficiently fixed before the post-tensioning. The subject subdivided into several individual parts may be held on the adapter frame but also in an equipping device on a receiving table in a receiving plane in which in a cycled manner individual parts are released from the carrier foil and are again deposited in a dispensing plane.
The method may be carried out particularly advantageously when the carrier foil on the adapter frame, by way of a clamping ring engaging on the foil frame, is tensioned on a base ring over a circumferential tensioning edge between the subject and foil frame, until a predetermined tensioning force or a predetermined position is achieved and when subsequently the clamping ring is latched with the base ring. The tensioning procedure may with this be largely automated.
For this purpose the base ring may be placed on a lifting device and after the placing of a foil frame onto the tensioning edge may be pressed for latching against the relatively stationary clamping ring. The closing or latching of the adapter frame may be effected in the treatment machine, thus for example in a saw device or in an equipping device.
The invention also relates to a device for the post-tensioning of a carrier foil for a two-dimensional subject, in particular for a semiconductor wafer, which is tensioned over a foil frame, with the features according to claim
6
. The stretching of the carrier foil between a base ring and a clamping ring with the help of a tensioning means effects a uniform stretching of the carrier foil towards the outer side. The tensioning over the tensioning edge at the same time is effected relatively slowly, which has an advantageous effect with respect to the post-stretching of the plastic foil. The base ring and the clamping ring together form an adapter frame which may also accommodate foil frames of differing sizes or differing configurations. The abutting means on the adapter frame permit a tensioning in any treatment device independently of the construction of the foil frame.
The base ring may at the same time comprise a bearing shoulder for the foil frame, which is adjustable relative to the plane. In this manner the desired tensioning force on the carrier foil may be particularly easily set. The abutting shoulder may at the same time be formed by a threaded ring which is screwed onto a neck section provided with an outer thread. Also with relatively large diameters in this manner a fine and jam-free adjustment is easily possible. The bearing shoulder could however also be formed by a slider ring which is fastened on the base ring by way of clamping screws. Also a motoric adjustment of the bearing shoulder would be conceivable, which would make possible a fully automatic movement to a predetermined position.
As a tensioning means advantageously there are arranged several latching elements which are distributed over the circumference of the adapter frame and on which the clamping ring and the base ring may be latched with one another under spring pretensioning. The spring force ensures that the tension on the carrier foil is maintained. The latching elements may be closed by pressure.
It has been proved to be particularly advantageous when the latching elements comprise at least one leaf spring running roughly in the plane of the tensioning edge, and at least in each case one tensioning hook which is preferably able to be deflected out and which can be latched over the end of the leaf spring. With this the leaf spring and the tensioning hook on latching are slightly deflected out. The tensioning hook may at the same time for example be mounted in a jointed manner so that in the latched-in condition it is held in the latching-in position by way
Keller Markus
Stark Kurt
Alphasem AG
Elms Richard
Luu Pho
Shoemaker and Mattare Ltd.
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