In re Hirshon

454 F.2d 752, 59 C.C.P.A. 794, 172 U.S.P.Q. (BNA) 436, 1972 CCPA LEXIS 393

• Court: Court of Customs and Patent Appeals
• Decided: February 3, 1972
• Docket: No. 8547
• Status: Published

Opinion

Baldwin, Judge.

This appeal is from the decision of the Patent Office Board of Appeals which affirmed the rejection of claims 13,15 and 32 of appellants’ ■application¹ under 35 USC 103.

The Iwoention

The appealed claims are drawn to an intermediate product in the mass production of micro size semiconductor devices.² The product is .a unitary wafer of semiconductor material which embodies a plurality of semiconductor devices in spaced parallel rows. The claimed product has terminal straps attached so that when the wafer is broken up into individual devices, each will have its set of terminal straps for electrical connection to an external circuit. An illustrative embodiment of the invention is shown in partial top plan view in Figure 2 of the application (modified by adding reference numerals) :

The drawing shows the product as comprising a plurality of' transistors.³ The individual transistors are delineated by dash lines, extending along parallel horizontal grooves 46 in the top surface of the wafer and intersecting vertical dash lines 50.

Each transistor has terminal straps 38 and 40 which are bonded at their lower ends to electrodes for the base and emitter at 28 and 34, respectively. The free ends of straps 38 and 40 extend upwardly over a groove 46 and overlap the body of the adjacent transistor in the row above. Terminal strap 42 is bonded at its upper end to collector electrode 36 and extends downwardly with its free end passing over a groove 46 and overlapping the body of the transistor immediately below.⁴ A protective oxide coating underlies the straps except at the-points of bonding to the electrodes. As appears from the drawing, the free (upper) ends of terminal straps 38 and 40 in one row are parallel to, are spaced apart from, and overlap to some degree the free (lower) ends of terminal straps 42 in the next higher row.

The only independent claim on appeal is claim 32, which reads:

A semiconductor article Raving a plurality of semiconductor devices therein comprising

a flat wafer of a semiconductor material of one conductivity type, a plurality of spaced areas of the opposite conductivity type in a surface of said wafer, said areas of the opposite conductivity type being arranged in a plurality of spaced parallel rows with each row containing a plurality of said areas, each of said areas forming the P-N junction of a semiconductor device with the material of the wafer, a protective oxide film covering said surface of the wafer, a first set of openings through said protective film, each of said openings of said first set exposing at least a portion of a separate one of said areas of opposite conductivity type,

a second set of openings through said protective film, said second set of openings being arranged in a plurality of spaced parallel rows which alternate with the rows of the areas of opposite conductivity type with each of the openings of said second set exposing a portion of the surface of the wafer adjacent a separate one of said areas of opposite conductivity type,

a separate electrode of an electrically conductive metal covering each of the exposed portions of the wafer and the areas of opposite conductivity type,

a first set of flat terminal straps of an electrically conductive metal each secured at one end along a flat surface thereof to a separate one of the electrodes of the areas of ‘the opposite conductivity type with said first set of terminal straps extending from their respective electrodes away from the row of adjacent wafer electrodes, and a second set of flat terminal straps of an electrically conductive metal each secured at one end along a flat surface ■thereof to a separate one of the wafer electrodes with second set of terminal straps extending from their respective electrodes away from the row of adjacent elec'tro'des of the areas of opposite conductivity type, said terminal straps all lying in a plane juxtaposed and parallel to the said surface of the wafer with the longitudinal axe's of the terminal straps secured to the electrodes of the wafer toeing out of alignment with the longitudinal axes of the terminal straps secured to the electrodes ‘of the areas of opposite conductivity type so that the free end portions of 'the terminal straps secured to the wafer electrodes overlap but are spaced from the free end portions of the terminal ¡Straps secured to the non-adjacent electrodes of the are'as of opposite conductivity type.

•Claim 13 adds a requirement that the terminal straps be “in spaced parallel relation” and claim 15 recites the grooves in the top surface of the wafer between the rows of semiconductor devices, those grooves having a protective oxide coating thereon.

The Rejection

The examiner and tbe board considered tlie appealed claims obvious in view of a patent of Da'hl’berg⁵ and a French patent.⁶

Dahlberg discloses a mass production process that provides a wafer of semiconductor material which, like appellants’ wafer, has a plural- . ity of transistors formed therein in columns and rows, with terminal straps attached. A partial top plan view of that wafer, showing but one transistor in full, is found in Figure 2 of the patent:

Intersecting grooves 12 in the top surface of the wafer delineate the individual transistors, each of which includes an emitter electrode 18 and base electrode 20.⁷ Conductive strips 24 and 24' are each bonded at one end to the respective electrodes and extend in opposite directions therefrom in alignment. An insulating layer on the wafer surface underlies the strips, as at 22, 22'. If desired, strips 24, 24' may be extended beyond the main body portion of the transistor and over the grooves “to provide * * * projecting tab[s] of conductive material for use in making terminal connections.”

The French patent discloses various arrangements of electrical connections between semiconductor devices and external circuits, as for example in Figure 5, reproduced below:

Opinion

The appealed claims require but two sets of terminal straps, one strap from each set being connected to one electrode of each individual device. Essentially, the claimed product differs from Dahlberg’s product in that the longitudinal axes of the two straps for each device are out of alignment and free end portions of the straps of one set extending in one direction are long enough to overlap free end portions of straps of the other set extending in a different direction while being spaced therefrom. The straps thus are longer than they could be made if aligned as in Dahlberg.

However, the French patent shows it old to provide semiconductor devices having terminal conductors that are out of alignment and extend in opposite directions to connect to external circuit terminals that are correspondingly disposed. To one skilled in the art wishing to produce devices of like configuration, it would have been obvious to apply the terminal straps by the mass production procedure disclosed by Dahlberg. As already noted, Dahlberg itself suggests that the terminal straps be lengthened for ease in making electrical connections.

The Patent Office thus has made out a strong case that the appealed subject matter would have been obvious to a person having ordinary skid in the art in view of the Dahlberg and French patents.⁸ Appellants not having provided evidence which rebuts that showing, the decision of the board must be affirmed.

1 Serial No. 410,182, filed November 10,1964.

2 The individual devices may have dimensions in the order of 0.010 inch on each side and ■0.003 inch in thickness.

3 Standard reference works reveal that a common form of transistor includes three electrodes designated emitter, base and collector, which are broadly analogous to the-cathode, grid and plate, respectively, of a vacuum tube. In terms of the conductivity characteristics of their elements, such transistors may be of either the NPN or the BNU type.

4 The claimed wafer is made by first treat!ng a slab of semiconductor material to provide-the base, emitter and collector areas and the contacting electrodes for all the transistors. Then, terminal straps, in the form of thin, flat rectangular strips of electrically conductive metal are applied to all of the transistors simultaneously. The methods utilized are not critical to the claimed invention.

5 U.S. Patent No. 3,200,46S, issued August 17, 1965, on an application filed Marcli 16 1962.

6 French Patent No. 1,099,888, published September 12,1955.

7 Dahlberg applies the collector electrodes to the bottom of the "wafer (not shown in Fig. 2).

8 While appellants advance an argument indicating that they regard the claims as requiring that the two electrodes recited for each device be offset longitudinally of the straps as well as transversely, they have not pointed out any consequence of such relationship which shows it to be more than an obvious matter of design choice.