JPS63245961A - Manufacture of t-shaped gate - Google Patents

Abstract

PURPOSE:To remove an insulating film under an overlay without corroding a gate metal by forming an overlay gate, then protecting a gate side with an insulating film different from that under the overlay, and etching it. CONSTITUTION:After an overlay gate is formed, an insulating film Si3N4 film different from an SiO2 film 5 is grown, and anisotropically etched to retain the Si3N4 film 6 only on the sidewall of a gate electrode made of an Au layer 1, a Pt layer 2, a Ti layer 3 and a WSi layer 4. Thereafter, the film 5 under the overlay is etched. Accordingly, a gate metal is protected by the film 6, the film 5 under the overlay is removed without corroding the gate metal to obtain a T-shaped gate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a field effect transistor, and particularly to a method for manufacturing a KT type gate.

[Conventional technology]

This is essential for shortening the gate length when increasing the frequency of field effect devices, but conversely, this increases the siggate resistance with a small gate cross-sectional area. Then, the gate cross-sectional structure is determined as the second
As shown in the figure, the conventional practice is to use a T-shape to reduce gate resistance. This type of shaped electrode has the same shape as the gate in the so-called overlay structure shown in FIG.
If left as is, the stray capacitance below the overlay will be large, and to avoid this, it is necessary to remove the insulating layer below the overlay.

[Problem that the invention seeks to solve]

However, when this insulating layer portion is removed, there is a fear that the metal layer forming the gate will also be eroded at the same time. For example, 8i01 is usually used as the insulating layer,
Furthermore, in order to reduce the gate resistance, a low resistance metal such as Au is usually coated on top of the metal layer for the gate, but in order to further improve the adhesion of these metals, Ti is coated on top of the metal layer. It has a structure in which metals such as are interposed in the middle. So the aforementioned Sin! When Ti is etched with hydrofluoric acid, the sides of Ti are also etched at the same time. A conceivable way to compensate for this drawback is to protect the gate with a photoresist or the like and then perform etching. However, when the gate size is short, it is difficult to cover the gate with accuracy. A slight misalignment of the tab will expose the gate, and in the end, this method cannot avoid the above-mentioned danger.

[Means for solving problems]

The present invention compensates for these drawbacks by protecting the sides of the gate with an insulating film different from the insulating film below the overlay after forming the overlay gate, and then using an etching solution that erodes only the insulating film below the overlay. It is characterized by being removed by.

To explain in more detail, first, if there is a partial step such as a metal layer on a flat surface, SiO! , 5isN, or the like is anisotropically dry-etched using a gas selective to the metal layer, and the technique of leaving the insulating film only on the sidewalls of the metal layer is well known as a sidewall processing technique. Therefore, after forming the overlay gate, by growing an insulating film different from the insulating film below the overlay and using the above-mentioned sidewall processing technique, the side surfaces of the gate are protected by the insulating film different from the insulating film below the overlay. After that, the purpose can be achieved by etching the insulating film below the overlay using an etching solution that is selective to the above two types of insulating films.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) to 1(C) show an embodiment of the T-type gate manufacturing method according to the present invention. First, FIG. 1(a) is a cross-sectional view after the overlay gate is formed.The insulating film is made of Sin, and the gate metal composition is WSi-Ti-Pt-Au.

Pt is for preventing Au diffusion, and the film thickness is, for example, 5iOt=
Grow fi2000A by law. Next, the Si3N4 is dry etched to the above film thickness (by RIE using CF gas, for example), leaving Si and N only on the gate sidewalls as shown in FIG. 1(b). Next, the T-shaped gate shown in FIG. 1(c)K is obtained by etching the lower part of the overlay 5i02 using, for example, a hydrofluoric acid:ammonium fluoride solution (6).

〔Effect of the invention〕

As explained above, according to the present invention, in a field effect transistor having a T-type gate structure, the insulating film at the bottom of the overlay, which inhibits characteristics due to its stray capacitance, is made such that the gate sidewall is different from the insulating film at the bottom of the overlay described on the left. By protecting the gate metal with an insulating film, the gate metal can be removed without being eroded.

[Brief explanation of drawings]

1(a) to 1(c) are cross-sectional views showing the manufacturing method according to the present invention.
FIG. 1(b) shows the state after the protective sidewall film is formed, and FIG. 1(c) shows the state after the overlay lower insulating film is removed. FIG. 2 is a sectional view of a T-type gate, and FIG. 3 is a sectional view of an overlay gate. The numbers in the figure represent the following. 1...-Au layer, 2-----P layer, 3.
...4i layer, 4...-WSi layer, 5...-3
ift, 6...5isN, 7...gate metal, 8...insulating film. Agent Patent attorney Uchihara 8 ゛・“′.l
', ,,:,,',,i',) 箭 1 fig. (θ) kuishi ii fig. (b) fig. 1 (C) ``2'' section 3 fig.

Claims (1)

[Claims] A step of forming a first insulating layer on a main plane of a wafer on which an element is formed in a field effect transistor having a T-type gate structure; and a step of opening a gate electrode window in the first insulating layer to form an overlay gate. , growing a second insulating layer different from the first insulating layer, etching the second insulating layer anisotropically by dry etching, and etching the second insulating layer only on the sidewall of the overlay part of the overlay gate;
A method for manufacturing a T-type gate, comprising the steps of: leaving an insulating layer; and etching the first insulating layer with an etching solution that does not corrode the second insulating layer.