JPH01175733A - Exposure method - Google Patents

Abstract

PURPOSE:To reduce the influence of secondary electrons and facilitate formation of a finer pattern and facilitate suppression of difference in exposure rate caused by the difference in pattern width by a method wherein a resist film and a conductive film are successively built up on a substrate and the exposure to X rays or charge beams is carried out while a voltage is applied between the substrate and the conductive film. CONSTITUTION:A resist film 2 and a conductive film 3 are successively built up on a substrate 1 and the exposure to X rays or charged beams 10 is carried out while a voltage is applied between the substrate 1 and the conductive film 3. For instance, a PMMA resist film 2 with a thickness of 1mum is applied to the silicon wafer 1 and, after the wafer is pre-baked at 170 deg.C, a carbon film 3 with a thickness of 1000Angstrom is deposited by vacuum evaporation. Then a stainless steel foil 6 is attached to the carbon film 3 of the upper surface of the exposed substrate and connected to the cathode of a 100V source 9 and to the ground 7. Also, a stainless steel foil 8 is attached to the wafer 1 and connected to the anode of the 100V source 9. In this state, the exposure is carried out with electron beams 10. With this constitution, a force toward the silicon wafer 1 is applied to secondary electrons by an electric field in the resist so that the lateral spread of the secondary electrons can be reduced.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an exposure method.

BACKGROUND ART As patterns become finer, pattern transfer techniques using light exposure have the disadvantage that resolution deteriorates due to the influence of diffracted light. Therefore, X-ray exposure, electron beam, and ion beam exposure techniques that are free from the influence of diffracted light are being developed.

In particular, X-ray exposure can be expected to have a high throughput because pattern transfer can be performed by negative exposure.

The X-ray exposure method is a method of exposing a resist coated on an exposure substrate by irradiating X-rays through an X-ray mask. The X-rays entering the resist collide with resist-forming molecules (carbon, oxygen, hydrogen, etc.) and are exposed to secondary electrons generated by the resist-forming molecules.

Interlayer points to be solved by the invention Normally, X-rays generated from an X-ray source [electronically excited X-ray source, plasma X-ray source, synchrotron radiation (SOR)] have a wavelength distribution. Secondary electrons generated by monochromatic X-rays affect an area of approximately 0.1 μm due to forward scattering.

The damping force of X-rays (0.8 for secondary electrons generated by radiation)
Affects the μm range. In particular, backscattering at the substrate becomes significant. Therefore, when forming a pattern, it is difficult to form a pattern that is smaller than the range of the generated secondary electrons, and it is difficult to form an ultra-fine pattern. In addition, when a pattern in which a large pattern width area and a small pattern width area coexist is exposed with the same exposure amount, the exposure amount in the small pattern width area is lower than that in the large pattern width area due to the influence of secondary electrons as described above. There was a problem with the amount of exposure being too small.This is because the resist is exposed by forward scattering of secondary electrons and backscattered electrons from the substrate even in charged beam (electron beam, ion, etc.) exposure. , the same problem (proximity effect) arises as with X-ray exposure.

Means for Solving the Problems The exposure method of the present invention involves sequentially laminating a resist film and a conductive film on a substrate, and applying an X-ray or a charged beam while applying a voltage between the substrate and the conductive film. It is exposed to light.

Effect: According to the exposure method of the present invention, since an electric field perpendicular to the substrate is applied to expose the substrate with X-rays or a charged beam, the range due to scattering of secondary electrons can be shortened.

Embodiment An embodiment of the exposure method of the present invention will be described with reference to a sectional view of an exposure substrate shown in FIG.

Note that the case of exposure using an electron beam will be described here. The substrate has a diameter of 3 inches and a plane orientation of (100
), silicon wafer 1 with specific resistance of 10ohm-c+a
was used. 1 μm thick PMM on silicon wafer 1
A (polymethyl methacrylate) resist 2 is applied and prebaked at a temperature of 170° C. for 30 minutes. Then P.M.
A carbon film 3 is deposited on the MA resist 2 to a thickness of 100 OA using vacuum evaporation. This was carried out using an electron beam evaporator with an emission current of 250 mA for 15 seconds. An exposure substrate, in which a PMMA resist 2 and a carbon film 3 are laminated on a silicon wafer 1, is mounted on a substrate holder 4 of an electron beam exposure device.Usually, in electron beam exposure, the substrate is However, in this embodiment, the substrate holder 4 and the exposure substrate are electrically separated by an insulator 5. moreover,
A stainless steel foil 6 is attached to the carbon film 3 on the upper surface of the exposed substrate, and connected to the negative electrode of a 100V power supply 9 and ground 7. Also,
Similarly, a stainless steel foil 8 is attached to the silicon wafer 1, and the positive electrode of a 100V power supply 9 is connected thereto.

Electron beam exposure is performed using an exposure substrate having such a configuration. Electrons 10 emitted from the electron gun of the exposure device are sent to the carbon film 3
The PMMA resist 2 below is exposed. usually,
The incident electrons collide with particles in the carbon film 3 and the PMMA resist 2, causing scattering of secondary electrons. The scattered electrons move in random directions, but because they are subjected to force in the direction of the silicon wafer 1 due to the electric field in the resist, their spread in the lateral direction is reduced. In addition, as the scattering cross section increases, the energy loss of the resist increases and the range of electrons becomes shorter (
Therefore, the apparent sensitivity of the resist increases.

Although an electron beam is used as an exposure source in the embodiment, exposure is performed in the resist using a similar mechanism in charged beam exposure using ions as an exposure source. In addition, in X-ray exposure, exposure is performed by secondary electrons generated in the resist, so the electric field is
The same effect is given to line exposure. 0 in Figure 2(a)
．． This figure shows the accumulated energy loss in the resist when a 2 μm wide pattern and a 0.2 μm wide pattern are exposed on a 5 μm thick PMMA resist using a conventional method. Figure 2(b)
2 shows the accumulated energy distribution in the resist when exposed in the same manner using the present invention. At this time, the electric field strength is IK
V/m. From this, when patterns with different pattern widths are exposed using the present invention, the pattern exposure amount is approximately constant regardless of the pattern width. FIG. 3 shows the relationship between the distance from the point of incidence and the energy stored in the resist when an electron beam is incident on a 0.5 μm thick PMMA resist using electric field strength as a parameter. Here, the electric field of zero corresponds to the conventional method. From this, it can be seen that the stored energy distribution in the method of the present invention is steeper than in the conventional method, and the spread of electrons in the resist is small. The spread of electrons in the resist increases as the electric field strength becomes weaker, and decreases as the electric field strength increases. FIG. 4 shows the relationship between electric field strength and electron scattering distance in the lateral direction in the resist. As the electric field strength increases, the scattering distance becomes shorter, and above a certain strength, it becomes almost constant.

Effects of the Invention According to the exposure method of the present invention, the influence of secondary electrons is reduced, making it possible to form finer patterns and reducing the difference in exposure amount depending on the pattern width when different areas of the exposure area are exposed at once. can be reduced.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an exposed substrate for explaining the exposure method of the present invention, and Figure 2 is the distribution of energy stored in the resist when patterns with different pattern widths are exposed to electron beams on a 0.5 μm thick PMMA resist. Figure 3 shows a 0.5 μm thick P M with electric field strength as a parameter.
A diagram showing the relationship between the distance from the incident point when an electron beam is incident on the M A resist and the storage tank energy in the resist. Figure 4 shows the relationship between the electric field strength and the horizontal scattering distance of electrons in the resist. It is a diagram showing the relationship. 1...Silicon wafer, 2...PM
MA resist, 3... carbon film, 4...
...Substrate holder, 5...Insulator, 6, 8.
...Stainless steel foil, 7...Earth, 9...100V power supply, 10...Electronic. Name of agent: Patent attorney Toshio Nakatsume and 1 other person E-Siliconway 2-PMAM Regis 5-11 Light shadow crack 1fuC, 8~Stainless Mt. /rn) 8--l1leI Biyoshio-c'J i Each C Vψ5I match 171

Claims (1)

[Claims] An exposure method comprising sequentially laminating a resist film and a conductive film on a substrate, and exposing the substrate to X-rays or a charged beam while applying a voltage between the substrate and the conductive film.