Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
1998-04-20
2001-03-20
Everhart, Caridad (Department: 2825)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S744000, C257S915000, C438S602000, C438S603000, C438S604000
Reexamination Certificate
active
06204560
ABSTRACT:
The present invention relates generally to diffusion barriers and more particularly to a titanium nitride diffusion barrier which is useful in non-silicon technologies. Non-silicon technologies include technologies based on compound semiconductors, for example, gallium arsenide (GaAs) or indium phosphide (InP). The invention has particular application in the field of high power semiconductor laser diodes.
Diffusion barriers are commonly used in semiconductor devices for purposes of preventing device degradation as a result of the tendencies of certain types of materials to diffuse into or react with adjacent material layers. As an example, in a semiconductor structure including a gold layer immediately adjacent to a gallium arsenide layer or separated from the gallium arsenide layer by an adhesion layer, the gold has a tendency to diffuse into the layer of gallium arsenide while the gallium arsenide has a tendency to diffuse into the gold layer. In a gallium arsenide laser diode including this layer structure, diffusion of the gold into the gallium arsenide can cause significant degradation of the laser diode in a relatively short time frame. At the same time, it should be appreciated that simply avoiding the use of materials such as gold is problematic since gold is commonly used as the outermost layer in metallized ohmic contact structures of optoelectronic devices (i.e., structures for use in making external electrical connections with the overall device). The usefulness of the outermost gold layer resides in its ability to form a suitable adhesion surface for the attachment of bonding wires. Underlying layers of the ohmic contact structure (including most diffusion barrier layers) do not exhibit adhesion characteristics which are compatible with the attachment of bonding wires. Gold also provides a low resistivity material for integrating multiple devices on a single chip.
In the past, platinum and chromium have served as a diffusion barrier within contact structures in many compound semiconductor device technologies. Unfortunately, however, it has been discovered that, for example, platinum diffusion barrier layers exhibit certain problems, as will be seen at an appropriate point below.
It should be mentioned that current semiconductor devices such as laser diodes are encountering power limitations which may be related to the stability of the ohmic contact and specifically in a direct way to the use of the diffusion barrier layers. In particular, as manufacturers push devices to ever higher power and with that higher current levels, the devices operate at higher temperatures. It has been found that platinum diffusion barrier layers become somewhat inefficient in resisting the phenomenon of diffusion at the anticipated operating temperatures of future devices. Moreover, platinum is a very expensive material. Thus, avoiding the use of platinum can lead to a decrease in material and production costs.
As will be seen hereinafter, the present invention provides a highly effective diffusion barrier layer for use in non-silicon technologies that does not exhibit the problems which have been discovered with regard to the use of platinum diffusion barrier layers. As another advantage, the diffusion barrier layer of the present invention provides an effective barrier at temperatures which significantly exceed effective maximum temperatures that are associated with prior art platinum diffusion barrier layers.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, there is disclosed herein a titanium nitride diffusion barrier layer and associated method for use in non-silicon semiconductor technologies. In one aspect of the invention, a semiconductor device includes a non-silicon active surface. The improvement comprises a contact serving to form an external electrical connection to the non-silicon active surface in which the contact includes at least one layer consisting essentially of titanium nitride.
In another aspect of the invention, a semiconductor ridge waveguide laser is disclosed which includes a semiconductor substrate and an active layer disposed on the substrate. A cladding layer is supported partially on the substrate and partially on the active layer. The cladding layer includes a ridge portion disposed in a confronting relationship with the active region. A metallization structure substantially covers the ridge portion and includes at least one layer consisting essentially of titanium nitride.
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M.F. Zhu, et al. “Stable ohmic contact to GaAs with TiN”, Thin Solid Films vol. 119, No. 1, p. 5-9, Sep. 1984.*
Zhu M. F. et al.; “Stable Ohmic Contact to GaAs with TiN Diffusion Barrier”; Apr. 1994; International conference on metallurgical coatings, San Diego, CA.
Daetwyler Andreas
Deutsch Urs
Harder Christoph
Heuberger Wilhelm
Jakubowicz Abram
Everhart Caridad
Pritzkau Michael
Shear Stephen C.
Uniphase Laser Enterprise AG
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