JPS6143484A - Formation of electrode in semiconductor device - Google Patents

Abstract

PURPOSE:To form the mushroom-shape electrode by forming an electrode composing material layer by forming a mask layer in which the window of the predetermined size having a rounded edge is opened on a substrate and further removing the mask layer after etching the electrode composing material layer by patterning to cover the window. CONSTITUTION:A resist film 6 is formed on a semiconductor substrate 1 and a window 7 of width L is formed by photolithography. Nextly annealing is done in an oxygen plasma atmosphere so as to round a peripheral edge 8 of the window 7 of the resist film 6. Then a metallic layer 9 is formed on the resist film 6 including the inside of window 7. Subsequently, a resist film 10 of the predetermined pattern is formed on the metallic layer 9 and the metallic layer 9 is etched by using the resist film 10 as a mask to form a metallic electrode 9a which is completed by removing the resist films 6 and 10 after that. Thus the mashroom-shape electrode can be formed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method of forming an electrode of a semiconductor device, and in particular,
This invention relates to an improvement in the method of forming a "mushroom"-shaped electrode used as a gate electrode of a field effect transistor (FEIT).

[Conventional technology]

FIG. 1 is a cross-sectional view showing the state at the main stages to explain the conventional method of forming a mushroom-shaped electrode using the lateral etching process. First, as shown in FIG.
A first metal layer (2) and a second metal layer (3) which are different from each other are formed on a C1 semiconductor substrate (1). Next, as shown in FIG. 1B, a resist is applied thereon and butter-printed by photolithography to form a resist thin film mask (4). Subsequently, as shown in FIG. 1C, the first metal layer (2) and the second metal layer (3) are etched through this resist thin film mask (4) to form a first metal layer pattern. enemy) and the second metal! - After forming Hataan (3a), as shown in diagram @1,
Remove the resist thin film mask (4). Then, as shown in FIG. 1E, the etching speed of the second metal layer pattern (3a) is very low compared to the etching speed of the first metal layer pattern (2a), or the etching cannot be performed at all. The first metal layer pattern (
2a) is laterally etched to form the first metal electrode M.
(2b) is formed, and a second metal layer pattern (3a) and a mushroom-shaped electrode are completed. (5) is the contact surface of this electrode with the surface of the semiconductor substrate (1), and its width is L.

However, in the conventional method described above, the electrode width L (FET gate?l
In the case of the C pole, the gate length) is determined, but it is difficult to control the etching rate in this lateral etching, and there are large variations in etching depending on the position not only between semiconductor substrates but also within the same substrate.

Therefore, in the case of the gate 'la pole of the F version, the gate i length will vary. This is well known, i:5
The electrical characteristics of the FET, especially the transconductance and 1j! It has a great effect on the 1W Dore・Ding/Soryu ID5i1 and deteriorates reproducibility.

In addition, we have been busy inquiring about the special type of metal used for the second metal layer as well as the etching method. The process was also very good, and Ill 9th b f mi was also difficult to 8, and the entry point was b.

[Summary of the invention]

This invention was made in view of the above points, and it is possible to use a single-layer etching method using only 2 #1 resists, without using two metal layers, or lateral etching. The present invention provides a method that does not require the formation of shaped electrodes.

[Invention? 1 Example of Mi IJ] Figure 2 is a cross-sectional view showing the state at the main stages in order to explain one embodiment of this Yumei.First, as shown in Figure 2A, a 1 resist+!
(6) and formed a width L(1) window (
7) (+- form the 0th order, as shown in Figure 2B,
(By annealing in a Norazuma atmosphere or by annealing in a high oxygen atmosphere?
, round the edge (8) of the periphery of the window (7) of the resist film (6) of 41. Next, as shown in FIG. A metal layer (9) is formed on the metal layer (6).A resist film of tin 2 with the required breadth is formed thereon as shown in Figure 42 (-1 This second resist= After etching the metal layer (9) to form gold rA'FIt@C9n) as shown in Figure E with the q ucp t mask,
As shown in FIG. 2F, the first resist film (6) and the second
After removing the resist film α of ゛, a mushroom-shaped metal electrode (9a
) is completed 0 It goes without saying that this method of forming the mushroom-shaped @pole is suitable as a method of forming the gate electrode of an FET.

In the above example, a resist was used as a mask material, but silicon oxide (S1O2), silicon nitride (Si
Insulators such as lN4) may also be used;
The constituent material of the electrode is not limited to a single layer of four gold layers, but may be another conductive material/V or a layered material for electrodes having a layered structure of a conductive film and an insulating film. Furthermore, the d-pole is not necessarily formed so as to be in direct contact with the surface of the semiconductor substrate, but may be formed so as to be in contact with the surface of the semiconductor substrate via one or more insulating thin films.

〔Effect of the invention〕

As explained above, according to the method of the present invention, -1
A mushroom-shaped electrode can be formed only by the etching shown in the figure, and without using the special method of lateral etching. Therefore, the 1"1j problem regarding the material and etching method for forming the electrode is almost eliminated, and the formation of the electrode becomes extremely easy.

In addition, the electrode width (F
In the case of an ET gate electrode, since the gate length is determined, the reproducibility is extremely good. Moreover, the width and shape of the electrode can be confirmed during the process. Furthermore, the presence of the first mask layer prevents the etching liquid or gas used for patterning the electrode constituent material layer from coming into contact with the semiconductor substrate, thereby preventing any adverse effects on the surface of the semiconductor substrate.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the state at the main stage to explain a conventional mushroom-shaped electrode forming method, and FIG. 2 is a sectional view showing the state at the main stage to explain an embodiment of the present invention. It is. In the figure, (1) is the semiconductor substrate, (6) is the first mask layer (first resist film), (7) is the window, (8) is the periphery of the window (7), and (9) is the electrode. Constituent material layer (total flexural layer), (
9a) is an electrode, and αq is a second mask layer (second resist film). In addition, the same reference numerals in the figures do not indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A first step of forming a first mask layer on a semiconductor substrate and opening a window of a desired size therein, a second step of rounding the peripheral edge of the window, and the second step described above. a third step of forming an electrode component layer on the first mask layer including the inside of the window, forming a second mask layer on the electrode component layer; a fourth step of patterning the window so as to be larger than the above dimensions and completely cover the top of the window; a fourth step of etching the electrode component layer through the second mask layer that has undergone this fourth step; 5
and a sixth step of removing the first mask layer and the second mask layer. (2) A photoresist material is used for the first mask layer, and in the second step, the edges of the windows of the first mask layer are rounded by ashing in an oxygen plasma atmosphere. Characteristic claim 1
A method for forming an electrode of a semiconductor device as described in 1. (3) By using a photoresist material for the first mask layer and leaving it in a high-temperature oxygen atmosphere for a required period of time in the second step, the edges of the windows in the first mask layer are rounded. Claim 1 characterized in that
A method for forming an electrode of a semiconductor device as described in 1. (4) The method for forming electrodes of a semiconductor device according to any one of claims 1 to 3, wherein the first mask layer is formed on the semiconductor substrate with an insulating thin film interposed therebetween.