JPH04329643A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide an amplifier that has an extremely short gate and good high-frequency characteristics. CONSTITUTION:Source and drain electrodes 4 and 5 are formed after a window 6 for formation of a gate electrode is opened in an insulating SiN layer 2. According to this method, the interference of reflection from ohmic electrodes can be avoided during the photoprocess for opening the window. This enables manufacture of an amplifier that has an extremely short gate and good high-frequency characteristics.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to field effect transistors, particularly field effect transistors (hereinafter referred to as MES) having a Schottky junction formed on a semi-insulating GaAs substrate.
It is written as FET. ).

0002

[Prior Art] A MESFET using a semi-insulating GaAs substrate on which an active layer and a low resistance layer are deposited has a 10GH
It exhibits high gain and low noise even at high frequencies above z, and is used as a main element in satellite communications and other applications. In general, M
In order to reduce the noise value of an ESFET, it is necessary to improve mutual conductance and reduce gate-source capacitance (hereinafter referred to as Cgs). The most effective way to achieve both is to shorten the gate length. Generally, the transconductance is inversely proportional to the gate length, and Cg
This is because s is proportional to the gate length.

FIG. 3 is a process cross-sectional view showing a conventional method for manufacturing a semiconductor device. FIG. 3(a) shows a GaAs semiconductor substrate 1
In this step, a SiN film 2 is deposited as an insulating film. Figure 3
In (b), an ohmic formation window 3 is opened in the SiN film 2 at the ohmic electrode formation part using a normal photo process and dry etching method, and a part of the GaAs semiconductor substrate 1 is exposed. In FIG. 3(c), a source electrode 4 and a drain electrode 5 are formed. FIG. 3D shows a step of opening a gate electrode forming window 6 in the SiN film 2 in the gate electrode forming area. FIG. 3(e) shows a step of forming the gate electrode 7. After this, wiring is performed to complete the MESFET.

In the conventional semiconductor device manufacturing method as described above, when a gate electrode formation window is opened in an insulating film using a photo process, interference of light reflected from the ohmic electrode surface in addition to the light from the light source causes The window for forming the gate electrode becomes larger than its original dimension (mask size), and the dimensions also vary. As a result, the gate length increases, making it impossible to reduce the noise value and achieve high yield.

[0005]

[Problems to be Solved by the Invention] In the conventional semiconductor device manufacturing method shown in FIG. 3, it is not possible to form a window for forming a gate electrode according to the dimensions, and it is difficult to manufacture a semiconductor device with an extremely short gate length with a high yield. I couldn't.

The present invention has been made in view of this point, and its object is to provide a method for manufacturing a semiconductor device with an extremely short gate length at a high yield.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention includes a step of depositing an insulating film on a semiconductor substrate, and a step of depositing an insulating film on a semiconductor substrate, and providing a first opening in a gate electrode forming portion of the insulating film. a step of exposing a portion of the semiconductor substrate by providing a second opening in the ohmic electrode forming portion of the insulating film; a step of forming an ohmic electrode in the second opening; This is a method of manufacturing a semiconductor device in which the steps of forming a gate electrode in the first opening are performed in this order.

[0008]

[Operation] With the above-described configuration, the present invention forms an ohmic electrode after opening a gate electrode formation window in an insulating film using a photo process in a field effect transistor. No interference from reflected light. Therefore, a gate having an extremely small gate length can be formed with high precision, increasing mutual conductance and reducing Cgs, and making it possible to manufacture devices with extremely low noise values with high yield.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process cross-sectional view of a method for manufacturing a semiconductor device according to a first embodiment of the present invention. Portions in FIG. 1 that are equivalent to those in FIG. 3 are designated by the same reference numerals. FIG. 1A shows a step of depositing a SiN film 2 as an insulating film on a GaAs semiconductor substrate 1. As shown in FIG. In FIG. 1(b), a window 6 for forming a gate electrode is opened in the SiN film 2 using a normal photo process and dry etching method, and a window 6 for forming a gate electrode is opened in a GaAs film.
This is a step of exposing a portion of the semiconductor substrate 1. Figure 1 (
c) is a step in which a window for forming an ohmic electrode is opened in the SiN film 2 to expose a portion of the GaAs semiconductor substrate, and then a source electrode 4 and a drain electrode 5 are formed. Figure 1 (
d) is a step of forming the gate electrode 7 in the gate electrode forming window 6. After this, wiring is performed to complete the MESFET.

In the method of manufacturing a semiconductor device of the present invention shown in FIG. 1, an ohmic electrode has not yet been formed at the time when a window for forming a gate electrode is opened in an insulating film such as a SiN film using a photo process. Therefore, photoprocessing can be performed without interference from light reflected from the surface of the ohmic electrode, which has been a problem in the past, so that the window for forming the gate electrode can be formed extremely small and with high precision. In the conventional manufacturing method, even if a mask with a gate length of 0.5 μm is used, the actual gate length is about 0.55 μm, but by using the manufacturing method of the present invention, the gate length can be adjusted to 0.5 μm, which is the same as the mask size.
It became possible to reduce the thickness to 5 μm.

Further, FIG. 2 is a process cross-sectional view of a method for manufacturing a semiconductor device according to a second embodiment of the present invention. In FIG. 2, parts equivalent to those in FIGS. 1 and 3 are designated by the same reference numerals. FIG. 2A shows a step of depositing a SiN film 2 as an insulating film on a GaAs semiconductor substrate 1. As shown in FIG. FIG. 2(b) shows a window 6 for forming a gate electrode on the SiN film 2 using a normal photo process and dry etching method.
and ohmic electrode forming window 3 are opened at the same time.
This is a process of exposing a portion of the semiconductor substrate. Figure 2(c)
) is a step of forming the source electrode 4 and the drain electrode 5. FIG. 2(d) shows a step of forming the gate electrode 7. After this, wiring is performed to complete the MESFET.

In the method of manufacturing a semiconductor device of the present invention shown in FIG. 2, an ohmic electrode has not yet been formed at the time when a window for forming a gate electrode is opened in an insulating film such as a SiN film using a photo process. Therefore, photoprocessing can be performed without interference from light reflected from the surface of the ohmic electrode, which has been a problem in the past, so that the window for forming the gate electrode can be formed extremely small and with high precision. Furthermore, by forming the gate electrode forming window and the ohmic electrode forming window at the same time, the number of steps can be reduced.

[0013]

[Effects of the Invention] As described above, the present invention provides the following effects.

1) In a field effect transistor, an ohmic electrode is formed after a gate electrode formation window is opened in an insulating film using a photo process, so interference due to reflected light from the surface of the ohmic electrode occurs during the photo process when opening the window. It is possible to form a gate with an extremely small gate length with high precision without causing any noise, and it is possible to increase mutual conductance and reduce Cgs, and to manufacture devices with extremely low noise values with high yield.

2) In a field effect transistor, an ohmic electrode is formed after a gate electrode formation window is opened in the insulating film using a photo process, so interference due to reflected light from the surface of the ohmic electrode occurs during the photo process when opening the window. It is possible to form a gate with an extremely small gate length with high precision without causing any noise, and it is possible to increase mutual conductance and reduce Cgs, and to manufacture devices with extremely low noise values with high yield. Furthermore, by forming the gate electrode forming window and the ohmic electrode forming window at the same time, the number of steps can be reduced.

[Brief explanation of drawings]

FIG. 1 is a process cross-sectional view showing a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a process cross-sectional view showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 GaAs semiconductor substrate 2 SiN film 3 Window for ohmic electrode formation 4 Source electrode 5 Drain electrode 6 Window for gate electrode formation 7 Gate electrode

Claims (2)

[Claims] 1. A step of depositing an insulating film on a semiconductor substrate, a step of providing a first opening in a gate electrode forming portion of the insulating film to expose a part of the semiconductor substrate, and depositing an ohmic electrode of the insulating film. A step of providing a second opening in the formation part to expose a part of the semiconductor substrate, a step of forming an ohmic electrode in the second opening, and a step of forming a gate electrode in the first opening are performed in this order. 1. A method of manufacturing a semiconductor device, characterized in that: 2. A step of depositing an insulating film on a semiconductor substrate, a step of simultaneously providing an opening in the gate electrode forming portion and an ohmic electrode forming portion of the insulating film to expose a portion of the semiconductor substrate, and depositing an ohmic electrode on the semiconductor substrate. 1. A method of manufacturing a semiconductor device, comprising: a step of forming a gate electrode; and a step of forming a gate electrode.