Semiconductor device manufacturing: process – Forming schottky junction
Reexamination Certificate
1998-09-11
2001-05-01
Everhart, Caridad (Department: 2812)
Semiconductor device manufacturing: process
Forming schottky junction
C257S472000, C257S475000, C438S571000, C438S572000, C438S573000
Reexamination Certificate
active
06225200
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor having a schottky-barrier junction, and especially relates to a method for manufacturing a schottky diode having an increased schottky-barrier and a low reverse leakage current.
BACKGROUND OF THE INVENTION
Recently, the III-V compounds, such as GaAs, having larger bandgaps than that of Si, are used for fabricating schottky diodes. Such schottky diode structures having larger bandgaps and carrier mobilities are often applied in rectifiers or transistors used in high-speed communication systems.
FIGS.
1
(
a
) and
1
(
b
) illustrate structures of schottky diode structures, each of which includes a substrate
1
, an epitaxial layer
2
and a metal layer
3
. A schottky barrier is formed at the junction of the metal layer
3
and the epitaxial layer
2
. In a schottky diode manufacturing process, the surface state, surface oxidation, concentrations of background impurities and the existence of defects of the epitaxial layer
2
will affect the potential barrier of the schottky barrier greatly. The schottky barrier pinning phenomena caused by the high surface state and concentration of the deep impurities will limit the potential barrier of the schottky barrier under some specified value, about 0.8 eV for GaAs, for example. Furthermore, the reverse breakdown voltage of a schottky is also affected by the background impurity concentration, while the reverse leakage current is determined by the conditions of the factors mentioned above. Accordingly, it is conceivable to lower the surface state density or the impurity concentration of the epitaxial layer for increasing the height of the schottky barrier and the reverse breakdown voltage and lowering the reverse leakage current.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for manufacturing a semiconductor device having a schottky diode structure with higher schottky barrier and lower leakage current.
The other object of the present invention is to provide a schottky diode structure having higher schottky barrier and breakdown voltage, and lower reverse leakage current.
The present invention provides a semiconductor device having a schottky barrier junction, which includes: a substrate; an epitaxial layer covering the substrate and lightly doped with a dopant selected from a group consisting of a rare earth element and an oxidant of a rare earth element; and a metal layer covering the epitaxial layer and forming the schottky barrier junction with the epitaxial layer.
In accordance with one aspect of the present invention, the substrate is preferably a n-type compound semiconductor substrate or a semi-insulating substrate.
In accordance with another aspect of the present invention, the epitaxial layer is preferably a gallium arsenide (GaAs) layer.
In accordance with another aspect of the present invention, the epitaxial layer is preferably an Indium phosphide (InP) layer.
In accordance with another aspect of the present invention, the epitaxy layer is preferably an n-type epitaxy layer.
In accordance with another aspect of the present invention, the dopant is preferably a praseodymium (Pr).
In accordance with another aspect of the present invention, the dopant is preferably an ytterbium (Yb).
In accordance with another aspect of the present invention, the dopant is preferably a praseodymium oxide or an ytterbium oxide.
In accordance with another aspect of the present invention, the dopant preferably has a weight percent less than 10
−3
in the epitaxial layer.
In accordance with another aspect of the present invention, the metal of the metal layer is preferably one selected from a group consisting of nickel, gold, silver, aluminum, titanium, palladium, and platinum.
In accordance with another aspect of the present invention, the epitaxial layer preferably has an inversion layer between the epitaxial layer and the metal layer.
In accordance with another aspect of the present invention, the device is preferably a schottky diode.
In accordance with another aspect of the present invention, the device is preferably a gallium arsenide transistor.
The present invention further provides a method for forming a structure having a schottky barrier junction. The method includes steps of: a) preparing a substrate; b) forming an epitaxial layer having a dopant selected from a group consisting of rare earth element and oxidant of rare earth element over the substrate; and c) forming a metal layer over the epitaxial layer to thus form the schottky barrier junction between the metal layer and the epitaxial layer.
In accordance with another aspect of the present invention, the epitaxial layer is preferably formed by a liquid phase epitaxy (LPE) method.
In accordance with another aspect of the present invention, the step b) preferably includes steps of: b1) preparing a solution containing the dopant; and b2) epitaxially growing the epitaxial layer on the substrate with the solution.
In accordance with another aspect of the present invention, the step b1) preferably includes steps of: b11) preparing a solvent of the solution in a container; b12) adding the dopant into the solvent; b13) preheating the solvent; b14) cooling the solvent into a room temperature; and b15) adding a solute into the solvent.
In accordance with another aspect of the present invention, the dopant preferably has a weight percent less than 1% in the solvent.
In accordance with another aspect of the present invention, the dopant is preferably a praseodymium (Pr).
In accordance with another aspect of the present invention, the dopant is preferably an ytterbium (Yb).
In accordance with another aspect of the present invention, the dopant is preferably a praseodymium oxide or an ytterbium oxide.
In accordance with another aspect of the present invention, the solvent is preferably a gallium.
In accordance with another aspect of the present invention, the solute is preferably a GaAs.
In accordance with another aspect of the present invention, the solvent is preferably anindium.
In accordance with another aspect of the present invention, the solute is preferably an InP.
In accordance with another aspect of the present invention, the solvent is preferably pre-heated at a temperature above 900 for 12 hours.
In accordance with another aspect of the present invention, the step b2) preferably includes steps of: b21) heating the solution again to a supersaturated condition; b22) cooling the solution to a saturated temperature of the solution; and b23) immersing the substrate in the solution.
In accordance with another aspect of the present invention, the solute is preferably GaAs, the solvent is Ga, and under the supersaturated condition in the step b21), the solution has a temperature of about 820.
In accordance with another aspect of the present invention, in the step b22) the solution is preferably cooled at a temperature gradient of about 1 per minute.
In accordance with another aspect of the present invention, the container is preferably a boat having a bin for holding the solution and a slidable substrate holder for holding the substrate.
In accordance with another aspect of the present invention, the boat is preferably made of graphite.
In accordance with another aspect of the present invention, wherein during an executing period of the step b2), the bin is preferably covered by a graphite cover for obtaining a saturated carbon vapor in the bin.
In accordance with another aspect of the present invention, the epitaxial layer is preferably formed with an inversion p-type layer formed on a surface of the epitaxial layer.
In accordance with another aspect of the present invention, the substrate is preferably a heavily doped n-type substrate or a semi-insulating substrate; the epitaxial layer is preferably a n-type epitaxial layer; and the inversion layer is preferably a p-type epitaxial layer.
In accordance with another aspect of the present invention, the boat is preferably made of refractory material.
The present invention may best be understood throug
Chang Liann-Be
Wang Hang-Thung
Everhart Caridad
National Science Council
Rosenman & Colin, LLP.
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