JPH04291733A - Gaas device and forming method for t-shaped gate electorode - Google Patents

Abstract

PURPOSE:To stably form a T-shaped gate electrode supporting pattern and to satisfactorily remove an unnecessary resist and metal for a gate electrode. CONSTITUTION:A resist film 2 having a predetermined thickness is formed on a substrate 1, and two line patterns are so plotted that a leg of a T-shaped gate is held by electron beams and a distance between both outer ends is larger than an overhang of the gate. This is developed, rinsed, a resist film 4 for forming an upper part of the gate is formed of photoresist, a gate pattern of a predetermined width is exposed by an ultraviolet ray 3, then developed and rinsed. Then, after the entire surface of the pattern is exposed with the ray 3, Al is deposited in a predetermined thickness by a depositing method to form a metal layer 5 for forming the gate, the resist 4 is then dissolved, and the layer 5 for forming the gate on the resist 4 is simultaneously removed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention can be applied even when the width of the T-shaped foot is extremely narrow compared to the upper protruding part of the T-shaped gate, such as the gate electrode of a field effect transistor. The present invention relates to a GaAs device that is structurally stable and a method for producing a T-shaped gate electrode.

0002

[Prior Art] Shortening the gate length and reducing gate resistance are effective for increasing the frequency and performance of compound field effect transistors.As a method for improving both at the same time,
Formation of T-shaped (mushroom-shaped) gates is being worked on in various fields.

Conventionally, as shown in FIG. 2A, a T-shaped gate has been manufactured by first depositing different types of resists 6 and 6 on a GaAs substrate 1.
7, the upper layer resist 7 is patterned as shown in FIG. 2B, and then the lower layer resist 6 is patterned as shown in FIG. 2C to form a T-shaped pattern, and the resulting pattern is It is formed by depositing an electrode material 8 made of aluminum as shown in FIG. 2D, and then lifting off the lower resist 6 and upper resist 7 as shown in FIG. 2E.

0004

However, as shown in FIG. 3, if the width Lg of the foot portion 10 of the T-shaped gate 9 becomes extremely narrow relative to the protruding portion (eaves portion) 11 at the top of the gate, the gate becomes structurally unstable, and as a result,
There have been problems in that the upper and lower parts of the gate may be torn off during the lift-off process, the gate may fall down, or the gate may become separated from the substrate, resulting in a decline in its function as an electrode.

On the other hand, Japanese Patent Laid-Open No. 63-192277 discloses that the foot portion 1 of the T-shaped gate electrode 9 is as shown in FIG.
It has been proposed to provide gate electrode support patterns 12 on both sides of the T-shaped gate electrode so as to sandwich the foot portions, thereby increasing the stability of the T-shaped gate electrode.

The present invention further develops the structure shown in FIG.
To provide a GaAs device and a method for producing a T-shaped gate electrode, which not only can stably form a T-shaped gate electrode support pattern but also can remove unnecessary resist and gate electrode metal well. The purpose is to

[0007]

[Means for Solving the Problems] In order to achieve the above object, the GaAs device of the present invention includes gate electrode supports made of an insulating material on both sides of the T-shaped gate electrode foot so as to sandwich the foot. A GaAs device having a pattern, characterized in that the distance between both outer ends of the gate electrode support pattern is greater than the length of the upper protruding portion of the T-shaped gate electrode, and the T-shaped gate electrode of the present invention The method for creating the T-shaped gate electrode is to sandwich the legs of the T-shaped gate electrode with resist on the substrate, and to make the T-shaped gate electrode so that the distance between both outer ends is larger than the upper protruding part of the T-shaped gate. a step of patterning a gate electrode support pattern, a step of patterning an upper protruding portion of the T-shaped gate electrode with another resist on the T-shaped gate electrode support pattern, and evaporating a gate electrode metal; The method is characterized by comprising a step of performing lift-off.

[0008]

[Operation] According to the present invention, it is possible to stably form gate support patterns sandwiching the foot portions on both sides of the foot portions of the T-shaped gate electrode, so that resist and unnecessary metal layers can be removed during lift-off and other processes. can be stably removed,
Thus, a structurally stable T-shaped gate electrode can be created.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] HEMT using a GaAs wafer substrate (
High electron mobility transistor: High Electro
A T-shaped gate electrode of an nMobility Transistor device was created using the following procedure.

FIGS. 1A to 1F are cross-sectional views showing the manufacturing process of the HEMT device according to the present invention, in which 1 indicates the HEMT device.
2 is a resist for forming the lower part of the T-shaped gate, 3 is light or ionizing radiation, 4 is a resist for forming the upper part of the T-shaped gate, and 5 is a metal for the T-shaped gate.

First, as shown in FIG. 1A, the HEMT G
Negative EB resist SAL-601- on aAs substrate 1
9 coated with ER7 (manufactured by Shipley) using a spinner.
Prebaking at 0°C for 30 minutes to form a uniform resist film 2 with a thickness of 0.3 μm, and then using an electron beam to form two line patterns with a width of 0.3 μm so as to sandwich the T-shaped gate foot with a width of 0.25 μm. After drawing the image so that it remains, perform a post-exposure bake at 110 °C for 5 minutes, and heat it at 23 °C with an alkaline aqueous solution.
, immersed for 2 minutes, developed, rinsed with pure water at 23°C for 30 seconds, and separated by 0.25 μm as shown in Figure 1B.
．． A line pattern with a width of 3 μm was obtained. Note that in FIG. 1B, the distance L between both outer ends of the two line patterns is larger than the eaves of the T-shaped gate.

Next, as shown in FIG. 1C, a novolac positive photoresist AZ-1350 (manufactured by Hoechst) was applied.
was coated with a spinner and baked at 90°C for 30 minutes to form a resist film 4 for forming the upper part of the T-shaped gate with a film thickness of 0.8 μm.
A gate pattern of the same width was exposed, then developed by immersing it in an alkaline aqueous solution containing tetramethylammonium hydroxide as its main component at 23°C for 1 minute, and then dipping it in pure water for 1 minute.
After rinsing for a minute, a resist pattern as shown in FIG. 1D was obtained.

Next, after exposing the entire surface of the resist pattern as shown in FIG. 1D to ultraviolet rays 3, as shown in FIG. 1E,
After depositing Al to a thickness of 0.6 μm by vapor deposition to form a metal layer 5 for forming a T-shaped gate, the resist 4 is dissolved using an alkaline aqueous solution containing tetramethylammonium hydroxide as a main component, and at the same time, the resist 4 is dissolved. 4
The upper T-shaped gate forming metal layer 5 is removed, and the resist 2 is supported with its legs sandwiched between resists 2, as shown in FIG. 1F.
．． A T-shaped gate electrode with a gate length of 25 μm was created.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. It should be noted that this is an example of the resist, and is not limited to this. The same applies to the developing solution and the rinsing solution.

[0016]

[Effects of the Invention] As described above, according to the present invention, the distance between both outer ends of the support pattern consisting of two line patterns provided at the bottom of the T-shaped gate is made larger than the eaves of the T-shaped gate. Therefore, the resist film 4 for forming the upper part of the T-shaped gate and the metal layer 5 for forming the T-shaped gate can be lifted off well, and the gate length can be reduced to 0 due to the support pattern.
．． Even when the T is as small as 15 μm or less,
Not only can the legs of the gate be stably supported, but also the T-shaped gate can be created with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a manufacturing process of a T-shaped gate for a HEMT device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the manufacturing process of a conventional T-shaped gate for HEMT devices.

FIG. 3 is a cross-sectional view of a T-shaped gate obtained by a conventional method.

FIG. 4 is a diagram showing a gate electrode support pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... GaAs substrate for HEMT, 2... Resist for forming the lower part of T-shaped gate, 3... Light or ionizing radiation, 4... Resist for forming the upper part of T-shaped gate, 5... Metal for T-shaped gate.

Claims (2)

[Claims] 1. In a GaAs device comprising a gate electrode support pattern made of an insulating material on both sides of a T-shaped gate electrode foot so as to sandwich the foot, the distance between both outer ends of the gate electrode support pattern is as follows: is larger than the length of the upper protruding portion of the T-shaped gate electrode. 2. A T-shaped gate electrode is formed on the substrate so that the legs of the T-shaped gate electrode are sandwiched between resists, and the distance between both outer ends is larger than the upper protruding part of the T-shaped gate.
a step of patterning a T-shaped gate electrode support pattern, a step of patterning an upper protruding portion of the T-shaped gate electrode using another resist on the T-shaped gate electrode support pattern, and vapor deposition of a gate electrode metal. and a step of performing lift-off.