JPS5835919A - Manufacture of metal-semiconductor junction electrode - Google Patents

Abstract

PURPOSE:To obtain a metal-semiconductor junction electrode having a high reverse direction withstand voltage and the desired Schottky barrier height by a method wherein a thin Ti layer and a thin TiN layer are adhered being laminated on the surface of a compound semiconductor substrate provided with an ohmic electrode on the back, and the heat treatment is performed during formation or after formation of the layers thereof. CONSTITUTION:An Au-Ge alloy layer and an Ni layer are evaporated being laminated on the back of a GaAs wafer 1 to form the ohmic electrode 2, and the Ti layer 3 made thickness thereof as to 100Angstrom is adhered by sputting on the surface. Then the TiN layer 4 obtained by performing reactive sputtering of Ti in N2 plasma is laminated on the Ti layer 3, and the Ti layer 5 having 100Angstrom thickness is adhered thereon again. After then, an Al layer 6 having about 3,000Angstrom thickness is evaporated thereon, and is formed in the prescribed shape according to the photo etching method. Then the heat treatment is performed for 30sec in the H2 atmosphere held at 450 deg.C to obtain the desired junction electrode. At this constitution, the heat treatment in H2 gas may be performed during the process of formation of the layer 3, 4, or may be performed after formation thereof is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal semiconductor junction electrode using a titanium compound or a titanium alloy as an electrode material.

Conventional metal-semiconductor junction electrodes are made of an underlying semiconductor (e.g., Si
, GaAs, etc.), or by forming a titanium (T1) layer (first layer) on the underlying semiconductor and further forming a metal layer (second layer) on top of it. There is something. .

Among these, the former has the disadvantage that the reverse breakdown voltage is extremely low as will be shown later, and that it is not suitable for mass production due to large variations in characteristics after manufacturing.

On the other hand, in the latter case, the purpose of using the Ti layer was to reduce the stress between the second layer metal and the underlying semiconductor and increase the adhesion strength, so it was easy to control the thickness during manufacturing and the yield was good. As such, a thick T1 layer (eg, 500 mm thick) was used. Therefore, it is not possible to obtain the characteristic height and electrical conductivity of the barrier, which is determined by the metal (electrode material) and semiconductor of the second layer, and only the characteristics determined by the T1 of the first layer are obtained. There were drawbacks.

In order to solve these drawbacks, the present invention aims to improve T1 of the first layer.
This method is characterized by performing heat treatment while reducing the thickness of the material, and will be described in detail below with reference to the drawings.

FIG. 1 is an embodiment of the present invention, and is a sectional view of a manufactured metal semiconductor junction electrode. In the figure, 1 is an n-type gallium arsenide (GaAs) wafer, 2 is an ohmic electrode made of gold, germanium, and nickel provided on the back surface of this wafer 1, 3 is a titanium (T1) layer (first layer), and 4 is titanium nitride. (TiN) layer (second layer), 5 is a T1 layer (third layer), and 6 is an aluminum (Al) layer (fourth layer).

Next, the main steps of the manufacturing method of the present invention will be explained.

■ Deposit gold/germanium alloy on the back side of wafer 1,
Next, nickel is vapor-deposited, and then heated in a hydrogen atmosphere to form an ohmic electrode 2 made of gold, germanium, and nickel.

■ 71 with a thickness of 100A as the first layer on the surface of wafer 1
Layer 3 is formed, for example, by sputtering.

■ A second layer of TiN with a thickness of 500 mm on top of the first layer above.
Layer 4 is formed by reactive sputtering of Ti in nitrogen plasma.

(2) A Ti layer 5 having a thickness of 100X is formed as a third layer on the second layer, for example, by sputtering.

■ Further on top of that is a fourth layer with a thickness of 3000 people.
Layer 6 is formed, for example, by vapor deposition.

■ Next, the electrodes formed from the first to fourth layers have a diameter of 20
Shape it to a size of 0 μm using photolithography.

(2) Heat treatment is then applied for 30 seconds in a hydrogen atmosphere at 450°C. Note that this heat treatment step is performed on the first layer and the second layer.
It may also be performed during formation of the layer or second layer.

The metal semiconductor junction electrode of the present invention is constructed by the above steps. Regarding the thickness of each layer and its formation method,
The present invention is not limited to this embodiment.

FIGS. 2 and 3 show current-voltage characteristics when the front electrode (A1 layer 6) is biased positively (forward direction) and negatively (reverse direction) with respect to the ohmic electrode 2 on the back surface. In the figure, 7 is the typical characteristic when the product is manufactured using the above-mentioned example, that is, the manufacturing method of the present invention, and 8 is the typical characteristic when it is manufactured using the conventional technique, that is, without using the Ti layer corresponding to the first layer. This is an example of a typical characteristic.

It is clear from FIG. 3 that the electrode according to the present invention has a sufficiently higher reverse breakdown voltage than the electrode according to the conventional method. In addition to the above advantages, the present invention has the following advantages. That is, the height of the Schottky barrier determined from the forward characteristics shown in FIG. 2 is 0.9 eV in the case of the present invention, which is 0.3 eV higher than in the case of the conventional method. The barrier heights determined from the separately measured capacitance-voltage characteristics are almost the same for both, 1.1 eV, indicating that the forward characteristics of this example are significantly improved compared to the conventional technology. It can be seen that there is a large barrier height determined by the second layer of TiN and WenoGaAs. By the way, the barrier height of the metal semiconductor junction electrode where only T1 is formed on GaAs,
The value is 0.2 eV lower than the value of this example.

In the above example, the reason why the properties unique to the material of the second layer are obtained despite the presence of the first layer 71 layer 3 is that T1 of the first layer forms a bond with GaAs through the heat treatment. This is thought to be due to the reaction with the second layer of TiN. The thickness of T1 is limited to 10 to 150X due to the controllability and uniformity of the film thickness and the thickness that can be practically reacted.The conditions of the heat treatment are not limited to the above embodiments, and the activation energy is 1. It was confirmed that a similar effect can be obtained by heat treatment at 450° C. for 30 seconds or more as defined by the Arrhenius law of 3 eV.

The above describes an example using TiN for the second layer, but
The above effect is obtained despite TIN having a high melting point, so the above reaction is not unique to TiN. Therefore, the second layer is not limited to TiN, but may also be made of a titanium compound exhibiting metallic properties (for example, TiC). etc.) and titanium alloys (e.g. Ti-W
, Ti-Mo, etc.) is the same as the case of TiN.

Furthermore, since the above explanation is a common technique for compound semiconductors where it is difficult to obtain a good surface condition,
) is not limited to GaAs as in the above example, and may be, for example, GaAlAs, GaP, etc.1).

As explained above, the metal-semiconductor junction electrode manufactured by the method of the present invention is easy to manufacture, has a high reverse breakdown voltage, and can easily adjust the height of the Schottky barrier determined by the second layer material. Since it has advantages such as being able to obtain high voltage resistance, it has high utility value in high voltage diodes, level shift diodes in integrated circuits, and the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a metal semiconductor junction electrode manufactured according to the present invention, FIG. 2 is a forward current-voltage characteristic of the electrode according to the present invention and the prior art, and 311' is a reverse direction of the electrode according to the present invention and the prior art. This is the current-voltage characteristic. 1... Wafer (semiconductor substrate) 2... Ohmic electrode 3... Titanium (Ti)! (First layer) 4... Titanium nitride (TiN) layer (second layer) 5... Titanium (T1) layer (third layer) 6... Aluminum (Al) layer (fourth layer) 7...・Characteristics of the electrode according to the embodiment of the present invention 8
...Characteristics of electrodes based on conventional technology Patent applicant: Junnosuke Nakamura, patent attorney representing Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] A step of forming a first layer made of titanium having a thickness of 10 to 150 holes on the surface of a compound semiconductor, and a step of forming a second layer made of a titanium compound or an alloy containing titanium on the first layer. and a step of performing heat treatment during or after the formation of the first layer, the second layer, or the second layer.