Substrate bonding using a selenidation reaction

Details Substrate bonding using a selenidation reaction Substrate bonding using a selenidation reaction

2001-03-30

2003-03-25

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

Having selenium or tellurium elemental semiconductor component

C438S455000, C438S456000, 14, 14

Reexamination Certificate

active

06537846

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a compound bond layer formed by a selenidation reaction. The compound bond layer adhesively bonds two or more substrates to each other. More specifically, the present invention relates to a polycrystalline or an amorphous compound bond layer formed by a selenidation reaction and including a first multi-stacked layer of selenium and indium or selenium-tellurium and indium formed on a bonding surface of an active substrate and a second multi-stacked layer of selenium and indium or selenium-tellurium and indium formed on a mounting surface of a base substrate. The resulting compound bond layer adhesively bonds the active substrate and the base substrate to each other without having to apply pressure to achieve the bonding and the compound bond layer can be dissolved so that the active substrate and the base substrate can be non-destructively detached from each other.
BACKGROUND ART
It is well known in the microelectronics art to use wafer bonding to bond one wafer to another wafer in order to efficiently manufacture complementary metal-oxide semiconductor (CMOS) circuitry or to fabricate micromachined structures such as Microelectromechanical Systems (MEMS). Prior wafer bonding process include silicidation, oxidation such as in a silicon-on-insulator (SOI) wafer bond, and metal hot pressing.
FIGS. 1
a
through
1
c
illustrate a prior silicidation wafer bonding process
100
In
FIG. 1
a
, a Wafer A that is to be bonded to a Wafer B has a metal M deposited on a surface thereof. Alternatively, the metal M could be deposited on a surface of Wafer B. The metal M can be a metal such as tungsten (W) and wafers (A, B) can be silicon (Si) wafers. Next, in
FIG. 1
b
, the wafers (A, B) are urged in to contact with each other and pressure P and heat H are applied to effectuate a silicidation reaction. The surfaces of the wafers (A, B) that are in contact with the metal M define an interface i. Typically, the heat H is in the range of about 300 degrees centigrade to about 450 degrees centigrade. Finally, in
FIG. 1
c
, the silicidation reaction has proceeded to completion with the metal M reacting with the wafers (A, B) and diffusing beyond the interface i and into the material of the wafers (A, B) to form a metal silicide M+W. For example, if the metal is tungsten (W) and the wafers (A, B) are silicon, then the metal silicide M+W is WSi.
FIGS. 2
a
through
2
c
illustrate a prior oxidation wafer bonding process
200
. In
FIG. 2
a
, a Wafer A that is to be bonded to a Wafer B has a dielectric material D deposited on a surface thereof. Alternatively, the dielectric material D could be deposited on a surface of Wafer B. Typically, the dielectric material D is silicon oxide (SiO
2
) and wafers (A, B) are silicon (Si) wafers. Next, in
FIG. 2
b
, the wafers (A, B) are urged in to contact with each other and pressure P and heat H are applied to effectuate a bonding of Wafer A to Wafer B. The surfaces of the wafers (A, B) that are in contact with the dielectric material D define an interface i. For the oxidation wafer bonding process
200
, the heat H can be in a range of about 700 degrees centigrade to about 900 degrees centigrade. Finally, in
FIG. 2
c
, the bonding is completed and the dielectric material D has not diffused beyond the interface i.
FIGS. 3
a
through
3
c
illustrate a prior metal hot pressing wafer bonding process
300
. In
FIG. 3
a
, a Wafer A and a Wafer B that are to be bonded to each other have a soft metal S deposited on a surface thereof. For instance, the soft metal S can be gold (Au) and wafers (A, B) can be silicon (Si) wafers. Next, in
FIG. 2
b
, the wafers (A, B) are urged in to contact with each other and pressure P and heat H are applied to effectuate a bonding of Wafer A to Wafer B. The surfaces of the wafers (A, B) that are in contact with the soft metal S define an interface i. The heat H can be in a range of about 400 degrees centigrade to about 500 degrees centigrade. Finally, in
FIG. 2
c
, the bonding is completed and the soft metal S has not diffused beyond the interface i.
There are several disadvantages to the prior wafer bonding processes. First, for CMOS circuitry or other temperature sensitive components such as MEMS structures, the high temperatures (i.e. the heat H) required by the prior wafer bonding process can damage the CMOS circuitry or the MEMS structures. For instance, prior wafer bonding processes can require temperatures in excess of 500 degrees centigrade. CMOS integrated circuits can be damage when exposed to temperatures of about 500 degrees centigrade or more. Moreover, there may be applications yet to be identified that can not tolerate temperatures that are even close to the high temperatures of the prior wafer bonding processes but would non-the-less benefit from wafer bonding techniques. Additionally, heat is also required in the deposition of some bonding materials such as silicon oxide (SiO
2
). Some applications that are heat sensitive may require a bonding material that can be deposited at low temperatures.
Second, the high pressure (i.e. the pressure P) that is used to urge the wafers into contact with each other can result in breakage, distortion, stress, or damage to the wafers or to the resulting wafer bond.
Third, once the wafers are bonded to each other it is not possible to non-destructively detach the bonded wafers from each other. Therefore, a non-reversible wafer bond precludes situations where it would be desirable to separate the wafers or to salvage the wafers.
Fourth, the prior wafer bonding processes are not amendable to bonding two or more substrates (i.e. two or more of the wafers A) onto a single substrate (i.e. the wafer B). In some application it may be desirable to bond a several substrates onto a single substrate.
Fifth, the prior wafer bonding processes often require that the wafers or substrates to be bonded be made from identical materials or similar materials. For example, in some prior wafer bonding processes the wafers (A, B) must be made from silicon (Si). Therefore, flexibility in selecting the material for the wafers is limited and applications that require different materials for the wafers are not accommodated by the prior wafer bonding processes.
Finally, some prior wafer bonding processes result in the bonding material chemically reacting with the wafers and diffusing into the wafers. In some applications it may be desirable to eliminate any diffusion or interfacial reaction between the wafer and the bonding material.
Therefore there is a need for a bonding process that can be accomplished at temperatures that are much lower than the prior wafer bonding processes so that damage to circuitry or other structures residing on the bonded wafers is eliminated and applications that can only tolerate much lower temperatures can be wafer bonded. Additionally, there is a need for a bonding material that can be deposited at low temperatures. There also exists a need for a wafer bonding process that does not require the application of pressure in order to bond the wafers to each other. Additionally, there exists a need for a wafer bond material that allows for the bonded wafers to be non-destructively detached from each other. There is also a need for a bonding material that will not react with nor diffuse the wafer. Moreover there is a need for a wafer bonding process that allows for two or more substrates to be mounted and bonded to a single substrate. Lastly, there exists a need for a wafer bonding process in which dissimilar substrates can be bonded to each other.
SUMMARY OF THE INVENTION
The aforementioned needs are met by the substrate bonding process of the present invention. The high temperature problem is solved by using a selenidation reaction that requires temperatures that are significantly lower than the prior wafer bonding processes. The problems associated with depositing the bonding material at high temperatures are also solved by a choice of bonding materials for the present invention. Those materials can be

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