JPS60106131A - Exposing method by electron beam - Google Patents

Abstract

PURPOSE:To eliminate a change in the amount of exposure and thereby to enable the formation of a pattern of very high accuracy, by etching the surface of a photoelectron generating film with gas plasma prior to an exposure in an electron beam exposure method wherein ultraviolet rays are applied on a photoelectron generating film having a desired pattern and photoelectrons emitted from the photoelectron generating film are reduced, image-formed and projected so as to transfer the photoelectron generating film. CONSTITUTION:In a reticle 3, a platinum film 11 is connected on the whole surface of a substrate 10, and further thereon a photoelectron generating film pattern is formed of a gold film 12. This reticle 3 is put in a sub-chamber 23 provided with an opposite electrode 25 for generating gas plasma, and an argon gas, for instance, is introduced therein to attain a degree of vacuum at several Torr below zero. Then, a power of 13.56MHz and several hundreds of watts is impressed to apply plasma etching onto the surface of the reticle, and thereby impurities on the surface of the gold film are remved. Thereafter a high vacuum is formed in the sub-chamber 23, and then the reticle 3 is transferred into a main chamber 21. According to this method, UV rays are applied on a purified photoelectronic film of the reticle, and a wafer quantity of generated beams.

Description

DETAILED DESCRIPTION OF THE INVENTION +a) Technical Field of the Invention The present invention relates to a photoelectron image reduction projection type electron beam exposure method, and particularly to an exposure method for sharply drawing.

lbl Technology background Ultraviolet ray exposure has traditionally been used as exposure technology, but it was found to be inconvenient for microfabrication due to the limitations of light wavelength (approximately 4,000 people at most), so electron beam exposure became more important. It has become. However, the electron beam exposure method requires beam scanning, takes a long time to process, and is not suitable for mass production. For this reason, shaped beam methods such as a variable rectangular beam have been developed for electron beam exposure, but these also have restrictions on pattern shape. On the other hand, an X-ray exposure method has been developed, but this method has been reduced because lenses cannot be created.

Imaging is not possible and this is a hindrance.

Therefore, it can be said that a mass-produced exposure method capable of microfabrication has not yet been developed, and intensive machining is still being carried out. A photoelectron image projection type electron beam exposure method has long been proposed as an exposure method for microfabrication and mass production, and a schematic cross section thereof is shown in FIG. As shown in the figure, coil N in high vacuum
A mask 1 and a wafer (substrate to be exposed) 2 are placed facing each other in a strong magnetic field formed by the method, and an electric field is applied to both. This is a batch exposure method in which a photoelectric film (for example, palladium or cesium iodide) on the surface is excited to generate photoelectrons, and a pattern of equal magnification on the mask surface is printed onto a semiconductor substrate.

However, with this method, it is difficult to create a uniform strong magnetic field, and the method of printing a pattern of equal magnification on the entire surface is inflexible and has problems with pattern accuracy. Furthermore, in the method of irradiating UV light from the back side of the mask, it is very difficult to select the material, film thickness, etc. of the photoelectric film, and for this reason, it has rarely been used in the past.

(C) Prior Art and Problems However, the present inventors have studied and proposed an electron beam exposure apparatus using a photoelectronic image reduction projection method that eliminates these problems. FIG. 2 shows a schematic sectional view of this embodiment. According to this method, in place of a mask in a high vacuum (vacuum container not shown), the reduction rate is 115 to 1/10.
Using a curved reticle 3, the reticle 3 and the wafer 2 are
An electrode φ1. φ2. φa and φ4 are provided to form a desired electric field, and photoelectrons emitted by the electric field are imaged by an electromagnetic lens and printed as a reduced pattern on the semiconductor substrate 2. In this method, since there is a wide distance between the reticle 3 and the wafer 2, light for photoelectron excitation is irradiated onto the curved surface of the reticle 3 via a reflecting mirror 5' using a plurality of xenon mercury lamps 4. It is.

With this structure, the shortcomings of the old device are resolved, and the reduced projection method allows fine patterns to be exposed with high accuracy (all at once.However, there are still problems with this new exposure method, which are: Substances that affect the photoelectron generation efficiency adhere to the film surface of the photoelectron emission film pattern, and the generation efficiency deteriorates.Such substances often remain physically adsorbed, but sometimes they react with other substances. substances are produced.

(d) Object of the Invention The present invention proposes an electron beam exposure method that eliminates the adverse effect on exposure sensitivity due to such deterioration in photoelectron generation efficiency and in which constant photoelectrons are emitted from a photoelectron generation film.

(e) Structure of the Invention The object of the invention is to irradiate a photoelectron generating film having a desired pattern with ultraviolet light, and project the photoelectrons emitted from the photoelectron generating film into a reduced image, thereby generating electrons for transferring the photoelectron generating film. This is achieved by an electron beam exposure method that includes a step of etching the surface of the photoelectron generating film with gas plasma.

(f) Examples of the invention An embodiment will be described in detail below with reference to one drawing.

FIG. 3 (Al is a plan view of the reticle 3 used in the exposure apparatus according to the present invention, and FIG.
1 is deposited on the entire surface, and a photoelectron generation film pattern made of a gold (Au) film 12 is formed thereon. The substrate 10 may be made of glass, ceramic, metal, etc., but the platinum film 11
is a material with a high threshold energy that does not emit photoelectrons when receiving UV light energy from a mercury lamp, in other words, it has a work function (6.4 eV) that is higher than the UV light energy (4.9 eV). 12 is a work function (4,7e
When the surface of the gold film 12 is irradiated with a mercury lamp, photoelectrons are emitted from the gold film pattern. Photoelectric film (
In addition to the gold thin film, silver (Ag),
Silicon (Si) is also used.

However, if impurities exist on the surface of such a photoelectronic film, the work function changes and becomes a large work function value, resulting in a decrease in photoelectron generation efficiency. Even a small monoatomic layer of such impurities has an effect, and this is an important problem when operating the present exposure apparatus. Many of the impurities are organic substances such as vacuum pump oil, and C (carbon) and CH groups adhere to the surface. Even in the case of a photoelectric film made of a chemically extremely stable gold film that also adsorbs oxygen and water, a monoatomic layer of these substances is formed on its surface.

The present invention is a method of removing these impurities and exposing a clean surface to UV light, and FIG. 4 shows a schematic diagram of an electron beam exposure apparatus of one embodiment. Reference numeral 21 denotes a main chamber (main processing chamber) for performing exposure processing, and inside thereof there is a reflector 3, a wafer 2 placed on a stage 22 facing it, and an electrode φ and an electromagnetic coil L provided therebetween. It is being There is a subchamber 23 on the side of this main chamber 21, and both are separated by a gate valve 24, and the reticle 3 can be moved by opening the gate valve. Since the reticle 3 must be replaced for each process, such a subchamber 23 is often provided as a preliminary chamber for replacing the reticle 3. This is because the high-vacuum main chamber 21 is not frequently exposed to the atmosphere, and the inside of the main chamber 21 can be kept clean.

Now, a counter electrode 25 for gas plasma generation is provided in such a subchamber 23, and for example, argon (Ar) gas is introduced to create a vacuum of less than a tenth of Torr, and a gap between the subchamber 23 and the reticle 3 housed in the subchamber is created. 13.56 MII
The reticle surface is plasma etched by applying a power of several 100-Z. By doing so, impurities on the surface of the gold film are removed, and then the subchamber 23 is made into a high vacuum, and then the reticle 3 is moved to the main chamber 2I. If this shift occurs, UV rays will be exposed to the cleaned photoelectric film of the reticle.
Irradiates the wafer with light and exposes the wafer with a constant amount of beam generation.
can be done. In addition to argon, oxygen (02), CCl4,
Even if a chlorine-based gas such as BBr3 is used, cleaning can be achieved in the same way, depending on the type of impurity.

Other gases may also be used.

Although the above example is an example of the electron beam exposure method according to the present invention, it is not necessarily necessary to perform it in a subchamber. For example, plasma etching may be performed in another room so that it can be accommodated in the main chamber without exposure to the atmosphere. In addition, a counter electrode 25 is installed in the main chamber,
It is also possible to perform this in the main chamber. Furthermore, a method may be adopted in which plasma gas is drawn into the subchamber 23 or the main chamber 21 for etching.

In addition, although such plasma etching processing for a reticle is normally performed periodically, it is also conceivable to perform the plasma etching process irregularly while checking the exposure amount with a detector.

In short, the purpose of the present invention is to freely perform etching treatment on a photoelectric film in combination with exposure treatment.

(g) Effects of the Invention As is clear from the above explanation, the present invention eliminates fluctuations in the exposure amount in the batch exposure method using an electron beam, and greatly contributes to the formation of extremely high-precision patterns. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an old photoelectronic image projection type electron beam exposure method, FIG. 2 is a schematic diagram of a photoelectronic image reduction projection type electron beam exposure method related to the present invention, and FIGS. 3(a) and (
bl is a plan view and a sectional view of a reticle, and FIG. 4 is a schematic diagram of an electron beam exposure apparatus according to an embodiment of the present invention. In the figure, 1 is a mask, 2 is a wafer, 3 is a reticle, 4 is a xenon mercury lamp, 5 is a reflection & 1.10 is a reticle substrate,
11 is a platinum film, 12 is a gold film, 21 is a main chamber, 2
2 is a stage, 23 is a subchamber, 24 is a gate valve, and 25 is a counter electrode for plasma etching. lff1 M 21st Section Figure 3 Figure 4 Fu

Claims (1)

[Claims] In an electron beam exposure method in which a photoelectron generating film having a desired pattern is irradiated with ultraviolet light and photoelectrons emitted from the photoelectron generating film are reduced and projected, the photoelectron generating film is transferred. An electron beam exposure method comprising a step of etching a surface with gas plasma.