JPH05275682A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the components of an alloyed electrode from diffusing in a lateral direction near the upside of a semiconductor by a method wherein electrode material specified in the weight ratio of Au to Ge is laminated and alloyed into an ohmic electrode. CONSTITUTION:An electrode material where the weight ratio of Au to Ge (weight of Ge/weight of Au) is set less than 0.14 is laminated. A first Ge layer 19, an second Au layer 20, and a third Ni layer 21 are successively laminated on a contact layer 16 for the formation of an N-type ohmic electrode 17. The weight ratio of Au to Ge is set to 0. 21. The layers 19, 20, and 21 are set to 400, 300, and 300Angstrom in thickness respectively. The laminate is alloyed by heating. Therefore, the components of ohmic electrode material can be restrained from diffusing in a lateral direction near the upside of a compound semiconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor device having an n-type ohmic junction.

[0002]

2. Description of the Related Art As a conventional technique, for example, an epitaxially grown InAlAs layer or InGaAs is used.
As an electrode material for obtaining an n-type ohmic junction with low resistance contact on a compound semiconductor having a layer, Au, Ni, A
uGe (Ge content, ie wt% in AuGe is 1
2 w%, and the Ge / Au weight ratio is 0.1364). For example, Au is 2000 angstroms, Au is
For example, 900 angstroms of Ge and 580 angstroms of Ni (equivalent film thicknesses of Au, Ge, and Ni converted here are 2600 angstroms, 300 angstroms, and 580 angstroms, respectively) are performed. For details, see Solid-state Electrics,
Vol.30, No.12, pp1345-1349 etc.

[0003]

[Problems to be Solved by the Invention] However, InAlAs
As an n-type ohmic electrode material of MESFET having a contact layer or InGaAs layer as a contact layer, Ni,
When Au and Ge are used as main components, the weight ratio of Au and Ge is not optimized, or Au, Ge and N
The respective film thicknesses of i are not optimized. For this reason, after the alloying process to reduce the contact resistance, the electrode components diffuse irregularly in the lateral direction near the top of the compound semiconductor,
When forming a MESFET or the like having a short gate length, there is a problem that the gate and the source / drain are short-circuited.
In addition, there is a problem that the contact resistance between the ohmic electrode and the contact layer is high when the diffusion in the lateral direction is suppressed.

Therefore, an object of the present invention is to provide a compound semiconductor device which solves the above problems.

[0005]

SUMMARY OF THE INVENTION The present invention provides In
Form a crystal growth layer of AlAs or InGaAs,
In the compound semiconductor device in which the ohmic electrode containing Au, Ge, and Ni as the main components is provided on the crystal growth layer, the ohmic electrode has a weight ratio of Au and Ge (weight of Ge) /
It is characterized by being formed by stacking and alloying electrode materials satisfying (weight of Au)> 0.14.

Further, the present invention provides a compound semiconductor device in which a crystal growth layer of InAlAs or InGaAs is formed on a substrate, and an ohmic electrode containing Au, Ge and Ni as a main component is provided on the crystal growth layer. The electrode comprises a first layer of Au having a thickness of between 20 Å and 600 Å, a second layer of Ge having a thickness of between 20 Å and 500 Å, and a thickness of between 20 Å and 400 Å. It is characterized in that it is formed by sequentially stacking and alloying a third layer made of Ni.

[0007]

According to the above structure, the ohmic electrode of the present invention is made of an electrode material containing Au, Ge and Ni as main components, and the weight ratio of Au and Ge is (weight of Ge) / (Au).
Electrode weight)> 0.14, the electrode components are laterally diffused near the upper part of the compound semiconductor after alloying while maintaining a low contact resistance in the ohmic electrode. It becomes possible to prevent it.

Further, the ohmic electrode of the present invention is Au,
It is made of an electrode material containing Ge and Ni as main components, Au has a film thickness of 20 angstroms to 600 angstroms, and Ge has a film thickness of 20 angstroms to 500 angstroms.
The film thickness is between angstroms, and Ni is formed with a film thickness between 20 angstroms and 400 angstroms. Therefore, similarly to the above, while maintaining low contact resistance in the ohmic electrode, the electrode component is a compound after alloying. It becomes possible to prevent lateral diffusion near the top of the semiconductor.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1A is a cross-sectional view of a modulation-doped MESFET according to an embodiment of the present invention. As shown in the figure, a buffer layer 12 formed by epitaxial crystal growth of undoped InP is formed on a semi-insulating semiconductor substrate 11 using InP, and a channel layer 13 formed by epitaxial growth of undoped InGaAs is formed on the buffer layer 12. , A spacer layer 14 in which undoped InAlAs is epitaxially grown, In added with an n-type dopant
An AlAs doping layer 15 is formed, and an InGaAs contact layer 16 having an n-type dopant added thereto is formed.
Are sequentially formed. Furthermore, this contact layer 16
A pair of ohmic electrodes 17 are formed on the upper surface of the contact layer 16 to form an n-type ohmic contact, and the upper portions of the contact layer 16 and the doping layer 15 are removed by etching between the pair of ohmic electrodes 17. By forming the gate electrode 18 for forming the Schottky junction on the
A MESFET having a recess structure is configured.

FIG. 1B is a sectional view of the MESFET according to the embodiment of the present invention immediately after the n-type ohmic electrode material is laminated. As shown in the figure, a first layer 19 using Ge is laminated on the contact layer 16, and the first layer 19 is formed.
An n-type ohmic electrode 17 is formed by stacking a second layer 20 made of Au on the second layer 20 and further stacking a third layer 21 made of Ni on the second layer 20. Among Au, Ge and Ni laminated in the electrode material of this example, Au and G
The weight ratio of e is (weight of Ge) / (weight of Au) = 0.2
And the film thicknesses of Au, Ge and Ni are 400 angstrom, 300 angstrom and 300 angstrom, respectively.
It is 300 angstroms. After lamination, 450 ℃
The alloy was formed by heating at the temperature of 60 seconds for 60 seconds.

Here, regarding the influence of the weight ratio of Au and Ge, in order to compare the characteristics of the n-type ohmic junction and the presence or absence of lateral diffusion of the electrode material in the embodiment of the present invention, a conventional method is used. As an example, the weight ratio of Au and Ge is (Ge
N weight) / (Au weight) = 0.136
A prototype of MESFET having a stack of i and AuGe (Ge content 12 w%) as an ohmic electrode was manufactured.
FIG. 2 is a cross-sectional view of a conventional MESFET immediately after the n-type ohmic electrode is laminated. As shown in the figure, as a conventional example,
An alloy of AuGe is used for the first layer 22, and Ni is used for the second layer 23 laminated thereon.
The conditions for alloying the n-type ohmic electrode material are the same as those in the examples of the present invention.

FIG. 3 shows the lateral diffusion of the ohmic electrode material in the MESFET in the upper part of the compound semiconductor. FIG. 3A shows an embodiment of the present invention.
(B) shows a conventional example.

Further, regarding the influence of the film thickness when Au, Ge, and Ni are laminated, the characteristics of the n-type ohmic junction and the presence or absence of lateral diffusion of the electrode material in the embodiment of the present invention are compared with the conventional example. In addition, the following three types of MESFETs were prototyped. FIG. 4 shows conventional examples A, B of n-type ohmic electrodes,
It is sectional drawing immediately after each lamination | stacking of C. In any of the conventional examples shown in the drawings, the first layer 19 made of Ge is laminated on the contact layer 16, the second layer 20 made of Au is laminated on the first layer 19, and The third layer 21 made of Ni is laminated on the two layers 20 to form the n-type ohmic electrode 17. As the conventional example A, Au, Ge and Ni
The film thickness when laminated is 700 angstroms, 3
00 angstroms and 300 angstroms (shown in FIG. 4 (a)), as conventional example B, Au, G
The film thicknesses of e and Ni when laminated are 500 angstroms, 600 angstroms and 300 angstroms, respectively (shown in FIG. 4 (b)). As conventional example C, the film thicknesses of Au, Ge and Ni when laminated are 40
0 Å, 400 Å, 500
Three types of ME in Angstrom (shown in Fig. 4 (c))
It is an SFET. Also in this prototype, the conditions for alloying the n-type ohmic electrode material are the same as those in the embodiment of the present invention.

FIG. 5 shows the lateral diffusion of the ohmic electrode material in the MESFET in the upper part of the compound semiconductor. FIG. 5A shows an example of the present invention.
(B) shows a conventional example.

In the MESFET manufactured as described above, the contact resistance between the contact layer and the n-type ohmic electrode 17 is 0.1 to 0.2 Ωmm in both the embodiment of the present invention and some conventional examples. However, in the n-type ohmic electrode 17 of the conventional example, the lateral diffusion 24 of the electrode material occurred, so that the gate electrode 18 and the ohmic electrode 17 were short-circuited, and the MESFET did not operate normally. There was not a little. On the other hand, in the example of the present invention, almost all the MESFETs worked normally without the lateral diffusion of the electrode material.

Therefore, according to the present invention, the ohmic electrode material can be prevented from laterally diffusing above the compound semiconductor, the contact resistance at the electrode can be reduced, and the performance of the compound semiconductor device can be improved.

[0018]

As described above in detail, the ohmic electrode of the present invention is made of an electrode material containing Au, Ge and Ni as the main components, and the weight ratio of Au and Ge is (the weight of Ge) / (Au). Of the electrode material such that Au has a thickness of between 20 Å and 600 Å and Ge has a thickness of between 20 Å and 500 Å. Since Ni is deposited and alloyed with a film thickness of 20 angstroms to 400 angstroms, lateral diffusion of the ohmic electrode material components existing in the conventional ones in the upper part of the compound semiconductor is prevented. Suppressed. Therefore, it is effective to use it for a compound semiconductor MESFET or the like which requires a short distance between electrodes.

[Brief description of drawings]

FIG. 1 is an embodiment of a modulation-doped MES according to the present invention.
Cross-sectional view of FET and MESFE which is an embodiment of the present invention
FIG. 6 is a cross-sectional view of a T-type ohmic electrode material immediately after being laminated.

FIG. 2 is a cross-sectional view of an n-type ohmic electrode of a conventional MESFET immediately after being laminated with an electrode material.

FIG. 3 is a diagram showing a state of lateral diffusion of an ohmic electrode material in a compound semiconductor in a MESFET.

FIG. 4 is a cross-sectional view of an n-type ohmic electrode of a conventional MESFET immediately after being laminated with an electrode material.

FIG. 5 is a diagram showing a lateral diffusion state of an ohmic electrode material in a MESFET in the upper part of a compound semiconductor.

[Explanation of symbols]

11 ... Substrate, 16, 19 ... Contact layer, 17 ... Ohmic electrode, 18 ... Gate electrode, 19 ... First layer, 20 ... Second layer, 21 ... Third layer, 24 ... Electrode material diffused in the lateral direction thing.

Claims (2)

[Claims] 1. InAlAs or InGa on a substrate
A crystal growth layer of As is formed, and Au,
In a compound semiconductor device provided with an ohmic electrode containing Ge and Ni as main components, the ohmic electrode is formed by laminating an electrode material having a weight ratio of Au and Ge of (Ge weight) / (Au weight)> 0.14. And a compound semiconductor device formed by being alloyed. 2. InAlAs or InGa on a substrate
A crystal growth layer of As is formed, and Au,
In a compound semiconductor device provided with an ohmic electrode containing Ge and Ni as main components, the ohmic electrode has a thickness of 20 Å to 60 Å.
A first layer of Au having a thickness between 0 angstroms, a second layer of Ge having a thickness of 20 angstroms to 500 angstroms, and a first layer of Ni having a thickness of 20 angstroms to 400 angstroms. A compound semiconductor device, which is formed by sequentially stacking three layers and alloying.