Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-06-21
2004-08-24
Lee, Eddie C. (Department: 2811)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S111000, C438S110000, C438S113000, C438S106000, C438S107000, C438S114000, C438S121000, C438S052000, C438S680000, C438S681000, C438S124000, C438S123000, C438S005000, C438S050000, C257S678000, C257S684000, C257S726000, C257S725000, C257S417000, C257S415000, C257S418000, C029S829000, C029S827000
Reexamination Certificate
active
06780767
ABSTRACT:
BACKGROUND OF THE INVENTION
Semiconductor components in a wafer assembly, in which the components are connected to a frame by means of in each case one holder and are formed from the same silicon wafer. The invention also relates to a method for fabricating semiconductor components in a wafer assembly of this type.
During fabrication of semiconductor components from a silicon wafer ((100) silicon wafer), the individual components, together with a frame and a holder which connects the component to the frame, are produced from a single silicon wafer. The holder comprises a bar which extends transversely across the component and is fixed to the frame on both sides. These bars, the only purpose of which is to fix the components to the frame, are fabricated by photolithographic patterning of the wafer front surface with subsequent dry or wet chemical etching processes for shaping. The opening up of the components and of the frame, i.e. the separation of the components from the frame, is effected by photolithographic patterning of the wafer front surface and/or the wafer back surface with subsequent dry or wet chemical etching processes for shaping. The component itself is then broken out of the frame by applying pressure to the component until the bar breaks. Alternatively, the bar may also be broken by the application of a torsional load by rotating the component out of the wafer plane.
In this method of fabricating the semiconductor component, the bars are fabricated from the wafer front surface, so that all the fabrication and machining processes carried out on the semiconductor component have to be adapted to the fabrication process used for the bars. Consequently, there is a considerable interdependency between fabrication of the bars and processing of the semiconductor component. There are generally no crystallographically preferred breaking edges, since these require additional process steps. Therefore, during the breaking-out operation, there are no reproducible broken edges formed on the bars, or the bars may splinter when the semiconductor component is broken out, and these splinters may cause damage to the semiconductor component. A further drawback is that the thickness of the bars usually has to be defined by time-controlled etching during the opening up of the semiconductor components.
The present invention is therefore based on the object of proposing a possible way of eliminating the above-mentioned drawbacks.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved by the semiconductor components in a wafer assembly in which the components are connected to a frame by means of in each case one holder and are formed from the same silicon wafer, wherein the holder on one side connects the respective component to the frame and has a desired breaking point and by a method for fabricating semiconductor components having semiconductor components which are connected to a frame by holder means and are formed from the same silicon wafer, comprising the following steps: photolithographic patterning of the wafer back surface with a holder on one side, wherein the holder connects the semiconductor component to the frame; producing a desired breaking point on the holder by means of an etching operation between the frame and the semiconductor component; and opening up the semiconductor component and the frame by photolithographic patterning of the wafer front surface or back surface with subsequent chemical etching for shaping.
Accordingly, the semiconductor components in a wafer assembly have a holder which connects the respective component to the frame on one side and has a desired breaking point. In principle, this desired breaking point may be designed in various ways in the form of a thinning of the material in the region of the holder. The desired breaking point is advantageously formed by a groove between the frame and the component, which is preferably of V-shaped design. According to a preferred embodiment, the surfaces of the V-groove form (111) crystal planes. According to the method, a single-sided holder is produced, which holder in each case connects the component to the frame, by photolithographic patterning of the wafer back surface with subsequent etching of a groove in a region in which the frame has a thickened portion. The opening up of the component and of the frame is effected by photolithographic patterning of the wafer front surface and/or back surface with subsequent dry or wet chemical etching processes for shaping. If the process sequence is selected in a suitable way, the opening-up operation may take place at the same time as the fabrication of the holder.
The production of the desired breaking point may in principle be effected by means of a known etching operation, in which, according to a preferred configuration of the method, the V-groove is produced by wet chemical anisotropic etching.
The last of the three method steps mentioned above in connection with the opening up corresponds to the measures which are also employed in the prior art and is generally known. However, the lithographic patterning of the single-sided holder takes place on the wafer back surface. Therefore, the fabrication of the holder is completely independent of the processing of the wafer front surface. The cut edge of the converging crystallographic (111) planes of the V-groove according to a preferred configuration defines a desired breaking edge. The application of pressure to a component leads to the component tilting and therefore to the semiconductor component breaking out of the frame along the desired breaking edge. The result is the formation of a defined broken edge. Splintering of the silicon crystal is considerably reduced if not completely prevented. The risk of the component being damaged when it is being broken out is therefore likewise considerably reduced.
When the two surfaces of the V-groove converge, the depth etching stops on account of the crystallographic properties of the silicon. Consequently, very simple, time independent control of the thickness of the desired breaking point can be achieved during production.
In principle, it is also conceivable for the holder described above to be provided on a plurality of sides, for example on both sides of the semiconductor component in accordance with the prior art, but in this case the above-described advantages relating to the breaking out of the semiconductor component no longer apply in the manner which has been described above, and consequently the semiconductor component may once again be damaged.
The method provides an inexpensive way, which entails reduced scrap, of fabricating semiconductor components in a wafer assembly.
REFERENCES:
patent: 4670092 (1987-06-01), Motamedi
patent: 5998234 (1999-12-01), Murata et al.
patent: 197 34 530 (1998-02-01), None
Patent Abstracts of Japan Publication No. 11186565, entitled Semiconductor Acceleration Sensor and Manufacture Thereof, By Funahashi, published Jul. 9, 1999.
Patent Abstracts of Japan Publication No. 04102066, entitled Acceleration Sensor and Its Manufacture, By Sato, published Apr. 3, 1992.
An article entitled “Silicon as a Mechanical Material”, By Kurt E. Peterson, published by Proceedings of the IEEE, vol. 70, No. 5, May, 1982, pp. 420-457.
Bachman & LaPointe P.C.
Im Junghwa
Lee Eddie C.
Nanoworld AG
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