JPS6033306B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming an electrode metal film by a lift-off method in a method of manufacturing a semiconductor device.

The lift-off method is a practical method for forming fine metal film patterns or insulating film patterns in photolithography, particularly for obtaining submicron-order patterns with high precision.

This method will be explained using FIG.

In FIG. 1A, 1 is a semiconductor substrate, and 2 is a photoresist film that acts as a substrate. In some cases, an oxide film (for example, Si02) may be used in addition to the photoresist to increase the film thickness. FIG. b shows a state in which a material to be patterned, such as a metal film, is deposited on the entire surface of the substrate 1.

Figure c shows the metal film pattern after lift-off. In this case, the thickness a of the photoresist film 2 and the metal film 3,
There are practical restrictions on b, and good patterning cannot be achieved unless b is used.

On the other hand, as for the type of photoresist film 2, in the case of submicron patterns, a positive type photoresist (product name AZ-1350) with excellent resolution is currently exclusively used, and its film thickness a is 0.25. ~0.40 mountain m.

If it is thicker than this, the resolution tends to deteriorate. Therefore, the thickness b of the metal film to be patterned is 0.1 to 0.2
It is about rm.

For example, when this is applied to the fabrication of a FET gate, if the gate length is 1 French m, the medium is 30 French m, and the material is AI, the gate resistance will be about 400. Reducing this is the key point for FET devices. The present invention proposes a new method of increasing the metal film thickness, for example, in order to reduce the above-mentioned gate resistance.

Next, the present invention will be explained in detail using FIG.

FIG. 2a shows the conventional method shown in FIG. 1b in which a photoresist pattern 21 is further superimposed without lift-off.

Furthermore, FIG. b shows a state in which the metal film 31 is deposited over the entire surface again. Thereafter, when lift-off is performed, a metal pattern with increased thickness is obtained as shown in Figure c. The above method is fundamentally different from the method of repeating lift-off of the same pattern twice because the second layer of photoresist 21 is formed without lifting off the first layer of photoresist 2. This means that the pattern does not change. In other words, the conventional "two-round lift-off method" takes into account the accuracy of mask alignment, and the second metal film 31
It is inevitable that the metal film 21 will protrude beyond the first metal film 21 and the pattern will become thicker. However, the method according to the present invention is characterized in that such a possibility does not exist at all. Further, even if the mask alignment is slightly misaligned, lift-off is possible if the second pattern overlaps the first pattern by half or 1'3 or more. As described above, the method of the present invention makes it possible to increase the thickness of the film without changing the shape of the pattern in contact with the semiconductor and to lift off the pattern.
It is highly effective for creating gate electrodes. It goes without saying that the present invention can be applied to patterning of substrates other than photoresists and thin film materials other than metal films, and the thickness and formation conditions thereof can be determined as appropriate.

It is clear that the present invention can also be applied to a lift-off method in which this method is repeated two or more times based on the same principle.

[Brief explanation of the drawing]

1A to 1C are diagrams for explaining a conventional lift-off method, and FIGS. 2A to 2C are diagrams for explaining a lift-off method according to an embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is a photoresist, 3 is a metal film, and 21 and 31 are the second layer photoresist and metal film. Note that the same reference numerals in each figure indicate the same or corresponding parts.
Figure 1 Figure 2

Claims (1)

[Claims] 1 After forming a thin film material to be processed on the entire surface of the first spacer layer patterned on the semiconductor surface, a second spacer layer with the same pattern as the first layer is further formed without removing the spacer. By stacking and patterning the layers, depositing the thin film material to be processed again, and simultaneously removing the first and second layer spacers,
A method for manufacturing a semiconductor device, comprising forming a pattern of overlapping thin films to be processed.