JPS6197944A - Formation of metal electrode - Google Patents

Abstract

PURPOSE:To contrive accomplishment of excellent characteristics of a semiconductor element by a method wherein the thickness of an electrode is sufficiently secured when the electrode is formed by performing a lift-off method, and the resistance of the electrode is made smaller. CONSTITUTION:The first high molecular material layer 6 is coated on SiO2 2, a resist pattern 3 is formed thereon as the second high molecular material layer, and an etching is performed on the first high molecular material layer 6 using said resist 3 as a mask. Then, another etching is performed on the SiO2 2. An aluminum (Al) film 5 is vapor-deposited as the first metal film, the resist 3 is removed using alcohol, and the Al film 5 located on the resist 3 is removed. An Al film 7 is vapor-deposited again as the second metal film, the first high molecular material layer 6 is then removed, and the Al film 7 is also removed. The formed electrode 4 has sufficient thickness, and it has the cross-section of trapezoidal form.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for forming metal electrodes.

Conventional Structure and its Problems In recent years, as semiconductor devices have become highly integrated, electrodes must also be formed very thin.

Here, a conventional electrode manufacturing process called the lift-off method, which is practically used to form fine electrodes, will be briefly explained.

FIGS. 1a to 1d are cross-sectional views of the electrode manufacturing process in the order of steps. 1 is the substrate, 2 is SiO2.

3 is a resist, 4 is an electrode, and 6 is a metal film. Figure 1a
Coating resist 3 on SiO22 and exposing.

FIG. 3 is a cross-sectional structural view of the device after development and etching of SiO22 using the resist 3 as a mask.

FIGS. 1b to 1c are cross-sectional structural views of a device in which metal films 4 and 5 are formed by vapor deposition of metal. As the metal vapor deposition process progresses, the metal film 6 on the resist 3 is connected, and the growth of the metal film 4 in the opening immediately below is stopped. FIG. 1d is a cross-sectional view of a device in which the metal film 5 on the resist 3 is removed from the device surface by removing the resist 3 with alcohol, and a wiring layer is formed using the metal film 4.

To explain in detail the metal vapor deposition process using the conventional lift-off method for forming electrodes, as shown in FIG. It is narrower in comparison, and the cross-sectional shape of the electrode 4 is trapezoidal. Furthermore, FIG. 1C shows a state in which the electrode formation pattern is completely closed. Even if vapor deposition is continued in this state, the thickness of the electrode does not increase and the cross-sectional shape remains triangular. From the above, when forming e-thin electrodes by the conventional lift-off method, the cross-sectional shape of the electrodes is always triangular and the thickness can only be formed thin, which has the disadvantage of high electrical contact resistance.

OBJECTS OF THE INVENTION The present invention provides a method for forming a metal electrode that eliminates the problems seen in the above-mentioned conventional examples and can realize a low-resistance metal electrode.

Structure of the Invention The present invention provides a method for forming a first metal film by vapor deposition on a two-layer structure pattern of a lower first polymer material layer and an upper second polymer material layer formed on a substrate. , a lift-off step of removing the second polymer material layer, and a lift-off step of removing the first polymer material layer after depositing the second metal film again. A method by which finely patterned metal electrodes are formed in a thick film. Here, the first metal film and the second metal film may be made of the same material or different materials, and the first polymer material layer and the second polymer material layer are Those with noticeable differences in etching are used.

Description of examples The method for forming a metal electrode of the present invention will be explained using examples.

FIGS. 2a to 2e are cross-sectional views in the order of steps of the electrode manufacturing process of the present invention. The component numbers in the figure are the same as in FIG.

Further, 6 is a first polymer material layer. FIG. 2a is a cross-sectional view of the De Kuis structure before metal deposition. A structure different from the conventional one is to apply a first polymer material layer 6 on SiO22,
A resist pattern 3 is formed thereon as a second polymer material layer. Using this resist 3 as a mask, the first polymer material layer 6 is etched, and then SiO22 is etched. FIG. 2 shows a process of depositing an aluminum (Az) film 5 as the first metal film. FIG. 2C shows a process in which the resist 3 is removed with alcohol and the At film 6 on the resist 3 is removed. Next, FIG. 2d shows At as the second metal film again.
This is the process of vapor depositing the film 7. FIG. 2e shows that the first polymeric material layer 6 is removed and the A
This is the process of removing the t-film. The difference from the conventional process is that the resist 3 is removed and At
After removing the film 5, the At film 7 is deposited again, then the polymer material 6 is removed, and the At film 7 on the polymer material 6 is removed by lift-off.

The electrode 4 formed according to the present invention has a large thickness and a trapezoidal cross-sectional shape. As a result, the electrode resistance can be reduced compared to conventional electrodes, and the performance of the device can be improved.

Specific embodiments of the present invention will be described. S on Si substrate
io2 is grown to a thickness of 0.7 μm, and a polymer material called polyimide iso-intra-quinadione (commonly known as PIQ) is grown on top of the first polymer material layer to a thickness of 1 μm.
Coated. On top of that, a positive resist was applied as a second polymer material layer, exposed and developed to a size of 0.76 μm.
A resist pattern was formed. Using this resist as a mask, PIQ was etched with a mixture of hydrazine hydrate and ethylenediamine. Kongo liquid is commonly known as P
Etching of 0 and Sio2 called IQ etchant was performed. Next, a first At vapor deposition having a thickness d of 0.5 μm was performed, and after the vapor deposition was completed, the resist was removed with alcohol, and the 10th At film on the resist was removed. Next, a second A7 vapor deposition is performed again to a thickness of 0.5 μm, and after the vapor deposition is completed, the PIQ is removed using a PIQ etchant.
The second At film on Q was removed. 81 with the above process
As a result of investigating the At electrode formed on the substrate, the electrode width was 0.76 compared to the A/= electrode formed using the conventional process.
Although it is the same as μm, it was confirmed that the electrode cross-sectional area is larger and the electrode resistance can be reduced.

Effects of the Invention As described above, the present invention makes it possible to sufficiently increase the thickness of the electrode and reduce the electrode resistance when forming the electrode by the lift-off method, which greatly contributes to improving the performance of semiconductor devices. It is.

[Brief explanation of drawings]

1A to 1D are step-by-step cross-sectional views of an electrode manufacturing process using a lift-off method, and FIGS. 2A-2E are step-by-step cross-sectional views showing an electrode manufacturing process using a lift-off method improved by the present invention. 1...Substrate, 2...S iO2, 3...
...Resist, 4...Electrode, 5,7...
...At film, 6...polymer material. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 20

Claims (1)

[Claims] After depositing the first metal film on a two-layer pattern of a lower first polymer material layer and an upper second polymer material layer formed on the substrate, the second polymer material layer is deposited. A method for forming a metal electrode, comprising a lift-off step of removing the first polymer material, and a lift-off step of removing the first polymer material after depositing the second metal film again.