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Pyramid Shaped Electrical Feedthrough in Silicon Wafers

IP.com Disclosure Number: IPCOM000086439D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Magdo, S: AUTHOR

Abstract

Electrical connections having high current conducting capability are established between opposite surfaces of a silicon substrate by the alternative methods of Figs. 1 and 2. These methods produce pyramid shaped feedthrough connections, Fig. 1 yielding open-ended via holes and Fig. 2 yielding vias that are closed at the narrower end.

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Pyramid Shaped Electrical Feedthrough in Silicon Wafers

Electrical connections having high current conducting capability are established between opposite surfaces of a silicon substrate by the alternative methods of Figs. 1 and 2. These methods produce pyramid shaped feedthrough connections, Fig. 1 yielding open-ended via holes and Fig. 2 yielding vias that are closed at the narrower end.

In Fig. 1A, both sides 2 of silicon wafer 1 are coated with Si(3)N(4) and the bottom coating is photolithographically windowed where feedthrough connections are desired. The masked wafer then is etched with a preferential etch such as a KOH solution to yield the indicated structure. The Si(3)N(4) residue is removed and the resulting structure is oxidized (3), as shown in Fig. 1B.

Preferably metal 4 (e.g., Al or Cu) is evaporated through a mask onto the bottom surfaces of the apertured silicon wafer. Then, the same metal is evaporated through a second mask onto the top surface of the wafer to produce the structure shown in Fig. 1C. This sequence of evaporation is preferred because it produces improved metal coverage at the critical areas 5, whereby increased current conducting capability is achieved.

In the alternative method (Fig. 2A), silicon wafer 6 is processed in the same way, except that only the Si(3)N(4) (7) on the bottom surfaces of the wafer is removed. Sputtered SiO(2) (8) then is deposited over the bottom surfaces.

The Si(3)N(4) layer 7 of Fig. 2A is removed and the e...