JP2001110718A - Electron exposure system and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron exposure system which does not have the problem about a reticle or a mask. SOLUTION: An electron beam source 1 is constituted of a transparent substrate 2, a photoelectric cathode film 3 formed on the transparent substrate 2, and a mask film 4 formed on the photoelectric cathode film 3 and equipped with the reversed pattern of a pattern to be transferred. Then, the back side of the photoelectric cathode film 3 is irradiated with excitation light 11 for exciting photoelectrons. At this time, the irradiated region of the excitation lights 11 corresponds to one sub-field. The excitation light 11 is scanned on the electron beam source 1 by a scanning optical system. In this case, the scanning optical system is obtained as an optical system constituted of, for example, an fθ lens 12 or the like. Electron beams 10 are emitted from the electron beam source 1 of the irradiation region of the excitation light 11 and accelerated by an anode 5. Then, the accelerated electron beams 10 allow the image of the electron beam source 1 to be formed as an image on a wafer 8 through a first projecting lens 6 and a second projecting lens 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electron beam exposure apparatus for transferring a desired pattern onto a sensitive substrate such as a wafer, and a method for manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art In recent years, as the line width of a pattern required for a semiconductor has become finer, a conventional exposure apparatus using light has been provided with both high resolution and high throughput of exposure. Investigation of the method of the electron beam exposure apparatus is being advanced. A method which has been well studied for this purpose is a batch transfer method. In this method, one or a plurality of dies are exposed at a time. However, this method has problems in that it is difficult to manufacture a mask serving as a master for transfer, and it is difficult to reduce aberration to a necessary degree or less in a large optical field such as one or more dies. And therefore,
Recently, studies of this type of apparatus have been declining.

[0003] A method which has been recently studied is a method in which one or a plurality of dies are not exposed at one time, but are divided into small areas of about several 100 μm square and transferred and exposed. Such a small area is called a subfield, and such a transfer method is called a division transfer method.

FIG. 6 is a schematic view of an optical system of an electron beam exposure apparatus of a division transfer system. In FIG. 6, an electron beam 102 emitted from an electron source 101 illuminates a shaped opening 104 by a first irradiation lens 131. The electron beam 10 that has exited the forming opening 104
2 forms a shaped aperture image on the reticle 105 by the second irradiation lens 132 and the third irradiation lens 133. The electron beam exiting the reticle 105 forms a reticle image on the wafer 108 by the first projection lens 161 and the second projection lens 162.

[0005] As described above, the electron beam optical system cannot correct the field curvature and astigmatism caused by the lens. Therefore, when a pattern of several tens of millimeters like a semiconductor device is collectively transferred, blur becomes extremely large. For this reason, an image to be transferred is divided into subfields, and each is connected on a wafer to form an exposure pattern for manufacturing the entire semiconductor device. Subfield size is usually reticle 1
It is about 1 mm square on the wafer 05 and about 0.25 mm square on the wafer.

[0006] The forming opening 104 is usually a high melting point metal with a square opening, and its dimensions are such that when the image is formed on the reticle 105 by the second and third irradiation lenses 132 and 133, the image is formed. If the size of the upper sub-field matches the size of the upper sub-field, or if there is a beam portion where no pattern is formed between the sub-fields on the reticle 105, the size is set to be slightly larger than the size of the sub-field. .

The reticle 105 has an exposure pattern to be transferred. Two types of reticles 105 are mainly used. The first type is called a stencil type, in which an exposure pattern is formed as an opening in a silicon thin film of several μm. Of the electron beams, those that pass through the aperture form an image on the wafer, and those that do not pass through the aperture are either absorbed by the reticle or scattered even after passing through the reticle. It is configured so that it is absorbed and does not reach the wafer 108.

The second type is a so-called membrane type in which an exposure pattern is formed as a heavy metal pattern on a very thin film of silicon nitride or the like having a thickness of 1 μm or less. In this case, electrons hitting the heavy metal pattern are absorbed or scattered. Electrons striking the very thin film are imaged on the wafer 108 with little scattering. The scattered electrons are absorbed by the scattered electron absorption aperture 107 and the wafer 1
It does not reach on 08.

[0009]

However, a stencil-type reticle is very difficult to manufacture because a through-hole must be formed uniformly and accurately in a large-area thin-film membrane. Since it is impossible to form the reticle, in such a case, there is a problem that a plurality of reticles having a complementary structure must be used for divided exposure.

[0010] In the case of a membrane type reticle, there is no such a problem. However, since electrons contributing to exposure are inelastically scattered when passing through a thin film, the spread of kinetic energy is increased, and chromatic aberration is caused. There is a problem that blur is increased.

Both types of reticles have a beam for each subfield as a measure against the strength of the thin film and heat radiation. Due to the presence of this beam, the ratio between the amount of beam deflection on the wafer and the amount of beam deflection on the reticle deviates from the reduction magnification, causing an increase in aberration.

The present invention has been made in view of such circumstances, and provides an electron beam exposure apparatus free from the problems of these reticles (or masks) and a method of manufacturing a semiconductor device using the same. As an issue.

[0013]

A first means for solving the above problems is to provide a photocathode formed on a transparent substrate,
It has a pattern formed on a photocathode and having a pattern to be formed on a sensitive substrate, a mask film for preventing electron emission, and a light source for generating excitation light for emitting an electron beam from the photocathode. An electron beam exposure apparatus (claim 1).

In this means, the excitation light emitted from the light source impinges on the photocathode through the transparent substrate, and emits an electron beam from the photocathode. This electron beam is absorbed by the mask film, but a pattern is formed on the mask film, and since the mask film does not exist in that portion, the electron beam passing through this portion is emitted, accelerated, and then accelerated. An image is formed on a sensitive substrate such as a wafer by an optical system.

As described above, the present electron beam exposure apparatus uses an electron beam emitted from an electron beam source without using a reticle or a mask, and patterns the electron beam. Is eliminated. Further, since the transparent substrate can have a certain thickness to have strength, the beam required for the reticle or the mask is not required. Therefore, if the image of the pattern of the electron beam source is transferred at a predetermined reduction magnification, a desired pattern is transferred to the sensitive substrate, and the aberration does not increase.

A second means for solving the above-mentioned problem is as follows.
The first means, comprising: a scanning optical system for scanning light for scanning on a photocathode; and a deflector for deflecting the generated electron beam (claim 2). It is.

In this means, the light from the light source is changed into scanning light by the scanning optical system, and scanning is performed on the photocathode. Therefore, the electron beam can be emitted also from the photocathode surface located at a position away from the optical axis of the electron beam optical system. The generated electron beam is deflected by the deflector and forms an image on the sensitive substrate through a predetermined orbit. Therefore, the exposure transfer can be performed in a wide range without moving the photocathode surface or the sensitive substrate, thereby improving the throughput. The deflection of the electron beam is the same as the method of deflecting the electron beam passing through the reticle and forming an image on the sensitive substrate through a predetermined trajectory in a conventional electron beam exposure transfer apparatus. As described above, the deflection operation is simplified because the existence of the beam need not be considered.

A third means for solving the above-mentioned problem is as follows.
The second means, wherein the scanning optical system changes light from a light source into rotational scanning light emitted from one point on an optical axis, and further converts the light into scanning light parallel to the optical axis. The scanning light is converted into light, and forms a scanning light in which the angle between the rotational scanning light and the optical axis and the distance of the parallel scanning light away from the optical axis are proportional to the angle. (Claim 3).

In this means, the light emitted from the light source is converted into rotational scanning light by, for example, a vibrating mirror or the like. At this time, the virtual image of the light source is set at a fixed position on the optical axis. Then, using a fθ lens (a lens in which the angle between the light beam incident from the front focal point and the optical axis and the distance between the position where the emitted parallel light beam is emitted and the optical axis) is used, etc. The angle between the axis and the distance from which the parallel scanning light is separated from the optical axis is proportional to the angle.

In this way, knowing the angle between the rotational scanning light and the optical axis, it is possible to know how far the parallel scanning light irradiates the position of the photocathode from the optical axis. The angle that the rotation scanning light forms with the optical axis can be known from the angle of a mirror or the like that generates the rotation scanning light. Therefore, in this means, the control of the scanning light becomes easy, and the synchronization of the scanning light with the deflector of the electron beam optical system becomes easy.

A fourth means for solving the above problem is as follows.
A step of exposing and transferring the pattern formed on the mask film on the photocathode to a wafer or the like using the electron beam exposure apparatus of any of the first to third means. A method of manufacturing a semiconductor device (claim 4).

In this means, since no reticle or mask is used, the problems caused by having these are eliminated, and an original plate for exposure transfer can be easily manufactured, and aberrations can be reduced. Transfer accuracy can be improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of an optical system of an electron beam exposure apparatus according to an embodiment of the present invention. In FIG. 1, the trajectory when the electron beam is deflected is omitted, and only the paraxial trajectory is shown. In FIG. 1, 1 is an electron beam source, 2 is a transparent substrate, 3 is a photocathode film, 4 is a mask film, 5 is an anode, 6
Is a first projection lens, 7 is a second projection lens, 8 is a wafer,
9 is a scattered radiation absorption aperture, 10 is an electron beam, 11 is excitation light, 1
2 is an fθ lens.

The electron beam source 1 comprises a transparent substrate 2 and a transparent substrate 2
It comprises a photocathode film 3 formed thereon and a mask film 4 formed on the photocathode film 3 and having an inverted pattern of a pattern to be transferred. The photocathode film 3 is made of, for example, a metal such as gold or platinum, a low work function material, or a semiconductor having a small or negative electron affinity. The mask film 4 is formed of, for example, heavy metal or an amorphous insulator having a short mean free path of electrons in the film.

Excitation light 11 for exciting photoelectrons is irradiated from the back side of the photocathode film 3. At this time, the irradiation area of the excitation light 11 corresponds to one subfield. The excitation light 11 is scanned on the electron beam source 1 by a scanning optical system. The scanning optical system is an optical system including, for example, the fθ lens 14 and the like. Electron beam source 1 in the irradiation area of excitation light 11
Emits an electron beam 10 and is accelerated by the anode 5. The accelerated electron beam 10 forms an image of the electron beam source 1 on the wafer 8 by the first projection lens 6 and the second projection lens 7.

Although a detailed description of the electron beam optical system is omitted,
Considering the photocathode film 3 of the electron beam source 1 as a reticle, the configuration may be the same as that of a conventional electron beam optical system. However,
Since there is no electron beam source 1 corresponding to the beam of the reticle, the correction by the deflector is reduced correspondingly.

FIG. 2 shows the embodiment shown in FIG.
FIG. 4 shows a beam deflection mode when scanning with excitation light and irradiating a portion away from the optical axis of the electron beam source 1. In FIG. 2, 10a and 10b are electron beams, 11a and 11b are excitation lights, 13 is an excitation light source, 14 is a scanner, 15 is a deflector, and other reference numerals are the same as those shown in FIG. Show. In FIG. 2, the illustration of the electron beam optical system is omitted except for the deflector.

The excitation light emitted from the excitation light source 13 is converted into scanning light by a scanning optical system, and scans the transparent substrate 2 of the electron beam source 1 in the x-axis direction, for example, 11a → 11b. The scanning optical system is the optical scanner 14 and the fθ lens 1
It consists of 2 etc. The optical scanner 14 rotates around the irradiation point of the excitation light, and forms a virtual image of the excitation light source 13 at a fixed point on the optical axis. This fixed point is located at the front focal point of the fθ lens.

Therefore, when the optical scanner 14 rotates by θ, the excitation light emitted from the fixed point is inclined by 2θ and is incident on a position away from the optical axis of the fθ lens 12, but f
In the θ lens, light incident at a certain incident angle from the focal point is output as parallel light from a position away from the optical axis by a distance proportional to the incident angle. Therefore, the optical scanner 1
Since the rotation angle of 4 and the amount of deflection of the excitation light are proportional to each other, the control of the amount of deflection of the excitation light is easy, and the synchronization mechanism for moving the electron beam source 1 and the wafer 8 is simplified.

The electron beams 10a and 10b obtained by the irradiation of the excitation lights 11a and 11b are deflected and imaged on the wafer 8 by a projection lens (not shown) and a deflector 15. Since the mask film 4 formed for generating the pattern of the electron beam 10 is formed on the transparent substrate 1 via the photocathode 3,
There is no need to have a beam for each subfield. Therefore,
Since the ratio between the amount of deflection of the electron beam on the electron beam source 1 side and the amount of deflection of the electron beam on the wafer side can be maintained at a reduced magnification, aberration is reduced, and a good image can be formed. In addition, since the deflection amount of the electron beam may be determined according to the rotation angle of the optical scanner 14, the control of the deflectors of the optical scanning system and the electron beam optical system can be easily synchronized.

FIG. 3 shows an example of a manufacturing process of the electron beam source 1 according to the present invention. Photocathode 3 is formed on transparent substrate 2
(a). This is made of a metal such as gold or platinum, a low work function material, or a semiconductor material having a low / negative electron affinity as described above. Next, a mask film 4 is formed (b). This is made of a heavy metal or an amorphous insulator having a short mean free path of electrons in the film as described above. Next, resist 16
Is applied, and the reverse pattern of the pattern to be transferred to the wafer by lithography is patterned (c).
Is etched (d), and the resist 16 is removed (e).

FIG. 4 is a flowchart showing an example of the embodiment of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following main processes. Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer) Electron beam source manufacturing process for manufacturing an electron beam source used for exposure (or electron beam source preparing process for preparing an electron beam source) Wafer processing process for processing processing Chip assembly process for cutting out chips formed on the wafer one by one and making them operable Chip inspection process for inspecting the completed chips It consists of processes.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps. A thin film forming step (using CVD, sputtering, etc.) for forming a dielectric thin film, a wiring portion, or a metal thin film for forming an electrode portion to be an insulating layer (using CVD or sputtering, etc.) An oxidation process for oxidizing the thin film layer or the wafer substrate Lithography process to form resist pattern to selectively process etc. Etching process to process thin film layer and substrate according to resist pattern (for example, using dry etching technology) Ion / impurity implantation / diffusion process Resist stripping process Inspection Step of Inspecting Wafer The wafer processing step is repeatedly performed for a required number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern The above-described semiconductor device manufacturing process, wafer processing process, and lithography process are well known, and will not require further explanation.

In this embodiment, since the electron beam exposure apparatus according to the present invention is used in the step of FIG. 4 and no reticle or mask is used, the problem of the reticle or mask is solved. The pattern can be exposed and transferred onto the wafer by a simple method with good transfer accuracy.

[0036]

As described above, according to the first aspect of the present invention, the electron beam emitted from the electron beam source is patterned without using a reticle or a mask. Such a problem caused by the reticle or the mask is solved. In addition, since the transparent substrate can have a certain thickness to have strength, the beams required for the reticle or mask are not required, and the image of the pattern of the electron beam source can be transferred at a predetermined reduction magnification. Since the desired pattern is transferred to the substrate, the aberration does not increase.

According to the second aspect of the present invention, since a wide range of exposure and transfer can be performed without moving the photocathode surface or the sensitive substrate, the throughput is improved. According to the third aspect of the present invention, the control of the scanning light is facilitated, and the tuning of the scanning light with the deflector of the electron beam optical system is facilitated.

In the invention according to the fourth aspect, since no reticle or mask is used, the problem caused by having these is eliminated, and an original plate for exposure transfer can be easily manufactured, and aberrations can be easily obtained. And transfer accuracy can be improved. Therefore, a semiconductor device having a fine pattern can be manufactured with high throughput.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical system of an electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a beam deflection mode when the excitation light is scanned to irradiate a portion of the electron beam source 1 away from the optical axis in the embodiment shown in FIG.

FIG. 3 is a diagram showing an example of a manufacturing process of an electron beam source according to the present invention.

FIG. 4 is a diagram showing a method for manufacturing a semiconductor device as an example of an embodiment of the present invention.

FIG. 5 is a diagram showing an outline of a lithography step.

FIG. 6 is a schematic view of an optical system of a conventional split transfer type electron beam exposure apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron beam source, 2 ... Transparent substrate, 3 ... Photocathode film, 4 ... Mask film, 5 ... Anode, 6 ... First projection lens, 7 ... Second projection lens, 8 ... Wafer, 9 ... Scattering ray absorption aperture , 10 ... electron beam, 10a, 10b ... electron beam, 11 ... excitation light, 11a,
11b: excitation light, 12: fθ lens, 13: excitation light source,
14 scanner, 15 deflector, 16 resist

Claims (4)

[Claims] 1. A photocathode formed on a transparent substrate, a mask film formed on the photocathode and having a pattern to be formed on a sensitive substrate for preventing electron emission, and an electron beam emitted from the photocathode. An electron beam exposure apparatus, comprising: a light source that generates exciting light. 2. The apparatus according to claim 1, further comprising: a scanning optical system that uses the excitation light as scanning light for scanning the photocathode, and a deflector that deflects the generated electron beam. Electron beam exposure equipment. 3. The electron beam exposure apparatus according to claim 2, wherein the scanning optical system changes light from the light source into rotational scanning light emitted from one point on the optical axis. , Which converts the light into scanning light parallel to the optical axis, wherein the angle formed by the rotational scanning light and the optical axis and the distance from which the parallel scanning light is separated from the optical axis are in a proportional relationship. An electron beam exposure apparatus that forms such scanning light. 4. One of claims 1 to 3
13. A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a pattern formed on a mask film on a photocathode to a wafer or the like, using the electron beam exposure apparatus described in the above section.