JPH0531292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming fine patterns.

Conventional structure and problems In the semiconductor lithography process, an organic polymer thin film called photoresist is used.The photoresist is irradiated with light or a charged beam, and the dissolution rate of the irradiated and non-irradiated areas in the developer is determined. Use differences to form patterns. At this time, the thin polymer film in the irradiated area is crosslinked, and the existing resist is called a negative resist, and the thin polymer film in the irradiated area is decomposed and the resist that is removed is called a positive resist.

In general, negative resists have lower contrast (about γ~1) than positive resists, and because they swell during development, they are difficult to use for ultrafine processing. In contrast, a method has been proposed in which a novolak resin-based positive photoresist is used to form an inverted negative pattern by electron beam exposure. In other words, a novolak resin-based positive photoresist with a wavelength of 300 to 400 nm is applied to the substrate by electron beam exposure.
After irradiating with ultraviolet light, a reversal negative pattern is formed by developing with an alkaline developer. By this method, it is possible to form a reversed negative pattern with high contrast and no swelling. However, this method requires an ultraviolet irradiation device and has the drawback of increasing the size of the entire system.

For these reasons, a pattern forming method that can form an inverted negative resist pattern without using any special equipment has been desired.

OBJECT OF THE INVENTION The present invention solves this problem, and the purpose of the present invention is to form a high-contrast, non-swelling reversal negative pattern without the use of special equipment.

Structure of the Invention In other words, the present invention provides a pattern in which a novolak resin-based positive resist is applied onto a substrate, prebaked, predetermined portions are irradiated with a charged beam, heat treated at a temperature of 80°C or more and 150°C or less, and then developed with an organic solvent. This method enables efficient formation of fine resist patterns.

DESCRIPTION OF EMBODIMENTS Examples of the present invention will be described below with reference to step-by-step sectional views of FIGS. 1a to 1c. As shown in Figure 1a, a positive photoresist 2, well known as OFPR-800 manufactured by Tokyo Ohka Co., Ltd., is applied to a thickness of 1 μm on a silicon wafer 1, and prebaked at 85°C for 20 minutes. conduct.

Next, as shown in FIG. 1b, a pattern is exposed using an electron beam 3 at an exposure dose of 38 μc/cm ² . After this, after baking at 120℃ for 20 minutes, developing with an organic solvent of isoamyl acetate for about 20 seconds, the first
As shown in FIG. c, the exposed portion 4 remains and an inverted negative pattern 5 is formed.

FIG. 2 shows the relationship between the contrast and the intermediate baking temperature when the exposure amount was 38 μc/cm ² . At lower temperatures, an inverted pattern cannot be formed, and as the temperature rises, the contrast increases.
At temperatures above 150°C, thermal curing occurs and no pattern is formed.

In addition, by performing an intermediate bake at 100℃ or higher, the contrast of general negative resist (γ
It can be seen that the value is higher than ~1).

FIG. 3 shows the relationship between line width change and development time for a 2 μm line pattern at an exposure dose of 38 μc/cm ² . This graph shows that, unlike general negative resists, the line width can be controlled by the development time. From this, a highly accurate pattern can be formed.

Although we have talked about OFPR-800 resist here, other novolak resin resists, such as Shippray's product name AZ-1350J or Tokyo Ohka Co., Ltd.'s product name OFPR-1000, can also be used. A pattern is obtained.

Further, although pattern exposure is performed using an electron beam here, an inverted pattern can also be obtained using X-rays or an ion beam.

Effects of the Invention As detailed above, in the present invention, a novolak resin-based positive photoresist is applied onto a substrate, and after prebaking, a predetermined portion is irradiated with a charged beam.
This is a pattern forming method in which heat treatment is performed at 150°C or lower and then development is performed using an organic solvent.By using the present invention, a negative pattern with high contrast, no swelling, and high pattern accuracy can be obtained without using any special equipment. can be formed.

[Brief explanation of the drawing]

FIGS. 1A to 1C are cross-sectional views in order of steps for explaining an embodiment of the present invention. Figure 2 is a characteristic diagram showing the relationship of contrast to the intermediate baking temperature when the exposure amount is 38μc/cm ² in the example of the present invention, and Figure 3 is the 2μm line when the exposure amount is 38μc/cm ² in the example of the present invention. FIG. 3 is a characteristic diagram showing the relationship between line width change and development time in a pattern. 1... Silicon wafer, 2... Novolak resin positive resist, 3... Electron beam, 4... Exposure section, 5... Resist pattern.

Claims (1)

[Claims] 1 A pattern forming method in which a novolak resin-based positive resist is applied onto a substrate, prebaked, a charged beam is irradiated onto a predetermined area, heat treated at a temperature of 80°C or higher and 150°C or lower, and then developed with an organic solvent.