JPS6395661A - Semiconductor element electrode - Google Patents

Abstract

PURPOSE:To increase adhesion between an electrode and a semiconductor substrate, to improve workability and to enhance reliability by forming an Au or Au alloy layer adjacent to the semiconductor substrate with an active or passive element. CONSTITUTION:An electrode functioning as a pad is shaped continuously through a vacuum deposition method using the so-called E-gun. The perforated pattern of a resist is formed to an InGaAsP substrate 1 to which an element is shaped, the substrate is set into a vacuum deposition device using the degree of vacuum of 2X10<-6> torr as a lower limit, and an Au layer 2 in 500Angstrom , a Ti layer 3 in 1000Angstrom , a Pt layer 4 in 1000Angstrom and an Au layer 5 in 5000Angstrom are laminated in succession. Heat treatment is executed in an inert (N2) atmosphere held at 400-450 deg.C, an electrode is also formed on the rear side of the InGaAsP substrate 1, and a plurality of the metallic layers laminated are over-coated with Au 6 in 5000Angstrom , thus shaping a semiconductor element electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an electrode structure of a semiconductor device, particularly an optical semiconductor device, using a semiconductor substrate made of an m-v group compound.

(Prior Art) In optical semiconductor devices such as semiconductor lasers and light emitting diodes, a metal electrode is attached to a semiconductor layer in order to conduct electricity to the semiconductor chip. The metal electrode is generally Ti/Pt.
A multilayer metal film consisting of /Au is used.

(Problems to be solved by the invention) Such electrodes include InP, GaAs, InGaAs.
It has been found that the adhesion force to ■-■ group compound semiconductors such as P is extremely weak. That is, the Ti film which is the adhesive layer has this m-
Although Ti exhibits inherently strong adhesion with group V compound semiconductors,
The T1 film, which has a strong getter effect, is responsible for the small amount of gas and moisture mainly consisting of hydrocarbon that remain in the vacuum equipment used when forming the film, and the extremely small amount of contaminants that coat the surface of this compound semiconductor. It is assumed that the bonding force with the semiconductor is weakened due to preferential bonding.

Moreover, when this Ti film is applied to a ■-■ group compound semiconductor, it is expected that it will react with the constituent elements of this semiconductor, such as P and As, to form a metamorphosed layer with weak adhesive strength at the interface. Furthermore, when a multilayer metal with a Ti layer adjacent to it is deposited on the surface of a ■-V group compound semiconductor containing P and As, which are more likely to dissociate at low temperatures than other elements, and then subjected to heat treatment, the degree of formation of the metamorphic layer increases. It is thought that this will continue to progress.

The present invention relates to a novel semiconductor device electrode for removing the above-mentioned contaminants, and in particular, an object of the present invention is to provide an electrode that has strong adhesion to a semiconductor substrate, is easy to work with, and is highly reliable.

[Structure of the invention]

(Means for Solving the Problem) For this reason, in the semiconductor element electrode according to the present invention, Au or Au is used adjacent to the semiconductor substrate having an active or passive element.
A method is adopted in which an alloy layer is provided and multiple metal layers including an adhesive layer are laminated thereon.

(Function) In this way, in the present invention, after coating the surface of a ■-■ group compound semiconductor substrate with a thin metal layer, depositing a plurality of metal layers including an adhesive layer and performing heat treatment, the adhesive strength is significantly improved. It was completed based on the fact that it has been strengthened by

Here, Table 1 will clarify the comparison of adhesive strength with the conventional technology, but the test method will be described first.

This was done by the Scotch tape peeling method, and if any electrode metal pieces were attached to the tape, an x mark was written, and if no electrode metal pieces were attached, an O mark was written. In the actual test, a glass slide is coated with wax as an adhesive, and a wafer, which is a ①-V group compound semiconductor substrate on which the electrodes are deposited, is placed on the glass slide and then cooled and fixed. In this case, of course, remove air bubbles by rubbing with a cotton swab. This electrode has approximately 1
0CI! After attaching the tape No. 1, the end was peeled off to examine the adhesion of the electrode residue.

In addition, the InGaAsP substrate 1P shown as a type of substrate is a 350 μs thick InP semiconductor substrate with about 1 p of InGa.
An epitaxial layer made of AsP is deposited.

Further, the heat treatment was performed at 430°C for 5 minutes in an inert atmosphere, abandoning the 400°C to 450°C applied to the formation of ohmic electrodes (when forming them on m-V group semiconductor substrates).

Comparison of the first side plate As shown above, the electrode in which the Au layer is formed adjacent to the surface of the ■-V group compound semiconductor substrate and the Ti, Pt, and Au layers are further laminated has clearly higher adhesion strength than the conventional electrode. It is clear that there has been an improvement.

Note that A formed adjacent to this m-v group compound semiconductor substrate
The thickness of the U layer is required to be 100 to 2,500 people.

This is because it has been confirmed that the effect is not sufficient if the thickness is less than 100 Å, and that it can perform its function if it is less than 2,500 Å, and the cost caused by coating more than necessary with economically expensive metals. Avoid close-ups.

It has also been confirmed that in addition to the Au single layer, an AuGe layer also provides the same effect.

Ti formed continuously on this Aμ layer or AuGe layer
The applicable thickness of the layer and PT layer is 100 to 5,000 layers, with 1,000 layers being the most preferable value. Also, the top layer of Au is a type of Al thin metal wire that is bonded by thermocompression.

An Al, Cu layer, etc. can be appropriately selected from Cu or Au thin wires, and the PT layer acts as a barrier layer against the diffusion of metal atoms that is expected to occur as a result of stacking a plurality of metal layers.

In addition, it should be noted that the Ti layer not only exhibits the getter function as mentioned above, but also plays a role in ensuring adhesion with the PT and Au layers, and that it can be replaced with the Cr layer. do.

(Example) Embodiments of the present invention will be described in detail with reference to the drawings.

In this example, the present invention is applied to a semiconductor substrate 1 made of InGaAsP, and although not shown, active elements or passive elements have already been formed on this semiconductor substrate 1.

This active or passive element has its electrode wired to a specific position on this semiconductor substrate, a pad made of so-called A1 or A1 alloy is provided on the saw, this semiconductor substrate is mounted on a heat sink, and the heat sink is further fixed to the stem and the leads are connected. Electrical connections are made using thin metal wires, and the leads are brought into contact with the equipment used to connect the circuit.

The electrode of the present invention, which functions as a pad, is continuously formed by a vacuum evaporation method using so-called E-Gun.

An open resist pattern was formed on the InGaAsP substrate 1 on which the device was formed, and after setting it in a vacuum evaporation apparatus with a lower limit of 2XIP'torr, an Au layer 2 was deposited with a thickness of 500 Ti.
Layer 3 is layered by 1000 layers, PT layer 4 is layered by 1000 layers, and Au layer 5 is layered by 5000 layers. Next, 400℃ to 450℃
A heat treatment was performed for about 5 minutes in an inert (N2) atmosphere maintained at ℃, an electrode (not shown) was formed on the back side of this InGaAsP semiconductor substrate 1, and A was applied to the laminated multiple metal layers.
Semiconductor element electrodes are formed by overcoating 5,000 layers of u6.

After this overcoating, a plurality of laminated metal layers other than the electrodes are removed by a lift-off method using the resist as a spacer, but it goes without saying that various other conventional means can be applied.

Furthermore, the conductivity type of the semiconductor substrate can be either P or n type.

〔Effect of the invention〕

As mentioned above, Au is placed adjacent to the ■-■ group compound semiconductor substrate.
It has been found that providing an AU alloy layer or an AU alloy layer can provide extremely strong adhesive strength, and if this is applied as an electrode of a semiconductor element to connect with an external lead, highly reliable characteristics can be obtained. This occurs in conventional electrodes that utilize the excellent adhesive strength of an adhesive layer such as Ti. The formation of metamorphic layers can be avoided and the semiconductor device characteristics can be fully exhibited over a long period of time.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a semiconductor element electrode according to the present invention.

Claims (1)

[Claims] A semiconductor element electrode characterized in that a layer made of Au or an Au alloy is provided adjacent to the surface of a semiconductor substrate having an active or passive element, and a plurality of metal layers including an adhesive layer are laminated thereon.