JPH02239613A - Forming method of fine pattern - Google Patents

Abstract

PURPOSE:To form an overhang-shaped opening advantageous for a lift-off by using a resist film as a foundation pattern, selectively exposing the film, giving temperature difference in the thickness direction of the film and developing the film. CONSTITUTION:A resist film 11 is applied onto a substrate 10, and regions (b), (e) are exposed selectively. The width (w) of the exposed regions is brought to approximately the thickness of the film 11 at that time. Temperature difference is given to the film 11 in the thickness direction after pre-baking, and the thickness of the lower half of the film 11 is held at 20 deg.C and the thickness section 11b of an upper half at 40 deg.C. When the film 11 is exposed to a developer at approximately 40 deg.C under the state, the region (b) is melted and removed for approximately sixty sec, and the region (e) is melted and removed for approximately thirty-four sec. When developing is continued, regions (a), (c), (d), (f) are exposed to the developer, but the rates of dissolution in the regions (d), (f) are made larger than those of the regions (a), (c) by approximately threefold, thus increasing the opening radius r1 of the upper section 11b by approximately 294nm though the opening radius r2 of the lower section 11a is increased by approximately 840nm through developing for approximately seven min. Accordingly, the whole opening shape is formed in an overhang shape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming fine patterns, and is useful for forming fine electrode patterns in semiconductor devices, for example. (Explanation) Conventional technology The lift-off method is known as a method for forming fine electrode patterns for semiconductor devices.The lift-off method, as shown in FIG. In the step of forming a base pattern (2) for lift-off on the substrate (A in the same figure), a monopolar material is vapor-deposited or sputtered from the substrate to form a soft polarized material on the exposed surface of the substrate (1) and on the base pattern (2), respectively. The step of depositing the films (3a) and (3b) (FIG. B), and the electrode film (3b) on top of the base pattern (2)
The process involves removing the electrode film (3a) of the desired pattern and leaving only the electrode film (3a) in the desired pattern (C in the same figure). The important thing in the J-Futosaifu method is the base pattern (2
). }: The electrode film (3b) can be sharply and completely removed by lifting, and for this purpose, in the process shown in FIG. It has to stop. As shown in FIG. 6A, the reason why the opening in the base pattern (2) is formed into a shape having a small diameter d1 at one part and a diameter d at a large lower part, that is, an overhang shape, is to prevent the above-mentioned tangling. ．． A method of forming such a bar hang shape is described, for example, in J. M.
Frary and P. Seese, ”'Lift
-off Techiniquas for Fine
Line Metal Patterning,”
Semiconductor International
nal, Vol. 4, No. 12, P. 72 ~ 88 (
198l). <<C) Problems to be Solved by the Invention The present invention provides a novel method that can more easily form the vertical bar hang shape of the base pattern in the lift process. <2> Means for Solving the Problems The method for forming a fine pattern according to the present invention, as shown in FIG. 3, includes the steps of depositing a resist film (11) on a substrate (10) (A in the same figure); Step (B) of selectively exposing the resist film (1l) in a desired pattern (l2);
11) in a state where a temperature difference is applied in the thickness direction (C in the same figure); A step of depositing the desired films (13a) and (13b) (FIG. 3D) and a step of removing the desired film (13b) deposited thereon together with the residual resist film (11) (FIG. 3E) (e) It is known that the dissolution rate of the working resist film is largely dependent on the developer temperature. Figure 2 shows this situation.
OFPR-800 (manufactured by Tokyo Ohka), which is a body resist, was subjected to a punobake at 85°C to 90°C for 130 minutes, and then exposed with Canon PLA-300F, and then NMD-3 (manufactured by Tokyo Ohka) was used as a developer. ) was used to investigate the remaining film rate when development was performed for 1 minute at various developer temperatures. In addition, Bost Bake is 120
The experiment was carried out at ℃ for 30 minutes. As is clear from the figure, the lower the developer temperature, the lower the residual film ratio, that is, the slower the dissolution rate. Conventionally, the developer temperature is precisely controlled so that there is almost no difference in the dissolution rate of the resist film, but the present invention actively reduces the difference in the dissolution rate of the resist film due to the difference in developer temperature. It was used for Hereinafter, the principle of the present invention will be explained with reference to FIG. 1.
3B shows the state at the end of the exposure step, and FIGS. 1B to 1D show the progress of development in the development step shown in FIG. 3C. In FIG. 1A, the resist Ill (11) deposited on the substrate (10) is OFPR-80 with a thickness of about 1.74 cm.
Assume that the regions (b) and (e) indicated by dots in the figure are selectively exposed at an exposure dose of 50 m)/cm" (exposure wavelength 436 nm). At this time, the exposed region width W is, for example, a resist film. After the pre-baking, a temperature difference is applied in the thickness direction of the resist film (11).
> The thickness of the lower half (lla) is maintained at 20°C, and the thickness of the upper half (llb) is maintained at 40°C. At this time, as a characteristic of OFPR-800, the dissolution rate of the resist film in each region (a) to (f') 4 divided by dotted lines in the figure is as shown in the table below. When the resist film (1 liter) is exposed to a developer at 40°C, the area (b) is dissolved and removed in about 60 seconds (Fig. 1B), and then the area (e) is removed in about 34 seconds. ) are dissolved and removed (Fig. 1C). When development is continued further, areas (a), (c) and (d) (f
') is exposed to the developer, but the dissolution rate in regions (d) (f') is about 3% lower than that in regions (a) (C).
The lower part (ll
The aperture radius r of a; increases by about 840 am, whereas
The opening radius r of the upper part (llb>) increases by only about 294 nm, and the overall opening shape becomes a bar hang shape (Fig. 1D).In reality, the temperature in the resist film <1l> is In the thickness direction of the film, it changes continuously, not in a stepwise manner, so the resulting opening is not stepwise, but in the shape of a bar hang that gradually expands toward the substrate <<10>>. The developing process of the first embodiment of the present invention will be explained with reference to Fig. 4.A silicon wafer (10b) serving as a substrate (1G) in Fig. 1 is held on a vacuum chuck (l4). ) is coated with a resist film (1l) similar to that shown in Fig. 1, and this film is selectively exposed in a desired pattern.The chuck (14) is rotatable and has a temperature control mechanism. Therefore, the temperature of the chuck (14) is maintained at 20°C, and a developer solution (15) at 40°C is sprayed onto the resist film (11).The spraying is performed intermittently, and the intervals are set as follows. , the minimum time sufficient to remove the old developer. During spraying, the chuck (14) is rotated. By this, a temperature difference can be applied in the thickness direction of the Resis 1 film (11).The thermal conductivity of the silicon wafer (10b) is 4 x 10
-'cal/Cm-Sec *'C, whereas that of the resist film (l1) is 7 x 10"'ca
l/cm ・see ・℃, and the latter is about 3
Therefore, most of the temperature difference between the chuck and the developer is concentrated in the resist film (11), and a bar hang-shaped opening is efficiently formed in the resist film (11).Second Embodiment of the Wooden Invention The developing process will be explained with reference to FIG. 5. In this example, a developing solution (15) is contained in a tank (16) equipped with stirring and temperature control functions, and the resist deposited on the silicon wafer (10b) is A membrane (11) is placed in contact with the surface of the developer (15).
b) is held by the chuck (14) as in the case of Fig. 4. Therefore, in this case as well, a temperature difference is imparted to the resist film (1l) in its thickness direction, resulting in an overhang-shaped resist film (1l). An opening is formed.In each of the above embodiments, it goes without saying that the value of the temperature difference can be changed as appropriate. By using a film, after selective exposure, and developing the film by applying a temperature difference in its thickness direction, it is possible to form an opening in the form of a bar hang, which is advantageous for lift reduction.

[Brief explanation of drawings]

Figures 1A to D are cross-sectional views for each step to explain the development principle of the present invention, Figure 2 is a curve diagram showing development characteristics, and Figure 3A.
6E to 6E are cross-sectional views according to steps for explaining the present invention;
5 and 5 are schematic diagrams for explaining the developing method according to the embodiment of the present invention, and sections A to C are sectional views for explaining the conventional method. Figure 1

Claims (1)

[Claims] (1) A step of depositing a resist film on a substrate, a step of selectively exposing the resist film in a desired pattern, a step of developing the resist film while applying a temperature difference in the thickness direction, and the developing step The step of depositing a desired film on the exposed substrate surface and the remaining resist film, and the step of removing the desired film deposited thereon along with the residual resist film are sequentially performed. How to form fine patterns.