Structure having cavities and process for producing such a struc

Details Structure having cavities and process for producing such a struc Structure having cavities and process for producing such a struc

1996-08-01

1998-09-08

Breneman, R. Bruce

Etching a substrate: processes

Adhesive or autogenous bonding of two or more...

216 2, 216 36, 216 52, 216 56, 216 62, 216 65, 216 88, 438 53, H01L 2158

Patent

active

058040862

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a structure having a substrate able to support a surface film or section made from a non-conducting material for the possible production of integrated circuits and internal cavities beneath the surface film in the substrate, as well as a process for producing such a structure.
The invention applies in general terms to the fields of microelectronics and in particular microelectronic devices requiring a good heat dissipation.


PRIOR ART

Structures having internal cavities are known in microelectronics, particularly for their heat dissipation capacity. Document (1) "Formation of silicon reentrant cavity heat sinks using anisotropic etching and direct wafer bonding" by Ajay Goyal et al, IEEE Electron Device Letters, vol. 14, No. 1, January 1993 illustrates this.
This document discloses a two-part structure. A first part serves as the substrate for e.g. producing integrated circuits. It is joined by a second part in which are etched cavities. This document also suggests the use of a cooling fluid within the cavities. The cavities e.g. make it possible to retain vapours of the cooling fluid and give the structure the property of absorbing significant thermal variations of the integrated circuit or circuits of the first part.
In general terms, in such structures, and for technical manufacturing reasons, the first part carrying the integrated circuits is relatively thick. The thickness of this part is one of the main limitations to the efficiency of heat dissipation by the cavities, because the heat produced must traverse said thickness before arriving at the second part having the cavities.
An object of the present invention is to produce two-part structures, where the first part which may have integrated circuits is very thin and where the second part is provided with cavities.
The fact of having a first thin part makes it possible to envisage for the structures various applications where the cavities can also fulfil functions other than that of heat dissipation. It is e.g. possible by making openings in the first thin part, to carry out in the cavities of the second part other technological operations such as metal depositions in order to produce connections and/or electrodes or operations permitting the production of various elements.


DESCRIPTION OF THE INVENTION

In order to increase the efficiency of the heat dissipation of two-part structures as described hereinbefore and/or envisage novel uses for such structures, the present invention relates to a process for producing a structure incorporating a substrate, a thin surface film made from a non-conducting material joined to one face of the substrate, said substrate having cavities flush with said face, comprises the following successive stages: plane of the substrate face at least one dimension which is a function of the thickness of the surface film, in order to correctly secure the latter,
Joining is understood to mean any operation between the substrate and the wafer making it possible to ensure an adequate bonding energy between said two elements such that they do not separate during subsequent operations. Reference can e.g. be made to surface treatment operations permitting the production of interatomic bonds, adhesion operations, etc.
The term non-conducting layer relates both to a single layer produced from a semi-conductor material or insulating material and a plurality of sublayers, whereof at least one is made from a semi-conductor or insulating material.
Several variants are possible for thinning the wafer. It is firstly possible to reduce the thickness of the wafer by mechanical, chemical or mechanochemical abrasion treatments.
The abrasion of the wafer can take place by grinding or polishing processes, which are known per se. The choice of the dimensions of the cavities as a function of the thickness of the surface section or film avoids deformations of the wafer and irregularities of the thinning during abrasion.
In the case of particularly fragile structures or when it is wished to obtain

REFERENCES:
patent: 4121334 (1978-10-01), Wallis
patent: 4894709 (1990-01-01), Philips et al.
patent: 5034343 (1991-07-01), Rouse et al.
patent: 5198371 (1993-03-01), Li
patent: 5374564 (1994-12-01), Bruel
patent: 5415727 (1995-05-01), Gal et al.
patent: 5632854 (1997-05-01), Mirza et al.

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