JPH09115813A - X-ray generator, aligner employing it and fabrication of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a better focus performance by irradiating an object with X-rays generated from an X-ray generator having a light emitting part of variable shape. SOLUTION: A plurality of plasma exciting laser light sources 9 and laser light condensing optical systems 10 are provided in order to produce a plurality of plasma X-ray emission points 1 simultaneously on a target. At the same time, size of each emission point is controlled through the zooming and defocusing mechanisms of laser light condensing optical system thus setting the shape of light emitting part of light source arbitrarily. Size of the light source is decreased, for example, by decreasing the spot of laser light and superposing the spots and coherent illumination is realized. Size of the light source is increased when enlarged laser light spots are arranged and incoherent illumination is realized. Size of the light source is also increased effectively when decreased laser light spots are arrange through intervals and substantially incoherent illumination is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an apparatus using X-rays suitable for exposure apparatus and device production.

[0002]

2. Description of the Related Art As a method of manufacturing a device such as a semiconductor circuit element having a fine pattern, there is an X-ray reduction projection exposure method. This is a mask with a circuit pattern
The pattern is transferred by illuminating with a line, projecting the image of the mask on the wafer surface in a reduced scale, exposing the resist on the surface, and exposing the resist.

An example of a conventional X-ray reduction projection exposure apparatus is shown in FIG.
Shown in This equipment consists of an X-ray source, an illumination optical system, a mask, a projection optical system, a stage on which a wafer is mounted, an alignment mechanism for precisely aligning the mask and wafer positions, and a vacuum for the entire optical system to prevent X-ray attenuation. It consists of a vacuum container for keeping and an exhaust device.

For example, laser plasma is used as the X-ray generation source. In the illumination optical system, X-rays from one emission point of laser plasma generated by irradiating a target with laser light emitted in a pulsed form are condensed by a converging mirror and applied to a reflective mask. The emission point of laser plasma is about several hundred μm, which is close to a point light source. The X-ray emitted from this is collimated by a parabolic mirror whose focus is the position of the light source to illuminate the mask. The projection optical system is composed of a plurality of multilayer film reflecting mirrors and projects the pattern on the mask onto the wafer surface in a reduced scale. A telecentric system is usually used as the projection optical system.

[0005]

However, the conventional X-ray reduction projection exposure apparatus has the following problems to be solved.

That is, when a very fine pattern on the mask is projected on the wafer, the resolution and the depth of focus are not sufficient, and it is difficult to transfer the pattern with extremely high accuracy. Further, even when the phase shift mask is used, the effect of improving the imaging performance due to the phase shift cannot be sufficiently obtained. The reason for this will be described below.

A coherence factor σ is a parameter representing the characteristics of the illumination system. When the mask side numerical aperture of the projection optical system is NA _p1 and the mask side numerical aperture of the illumination optical system is NA _i , the coherence factor is defined as σ = NA _i / NA _p1 . The optimum value of σ is determined by the resolution and contrast required for pattern transfer. In general, σ
If is too small, an interference pattern appears at the edge portion of the image of the fine pattern projected on the wafer, and conversely, if σ is too large, the contrast of the projected image decreases.

[0008] σ called coherent illumination in the case of 0, the optical transfer function OTF spatial frequency given by NA _p2 / lambda of the wafer-side numerical aperture of the projection optical system NA _p2, X-ray wavelength as lambda Shows a constant value up to, but becomes 0 at high frequencies exceeding that, and cannot be resolved. On the other hand, when σ is 1, it is called incoherent illumination,
The OTF decreases as the spatial frequency increases, but it does not become 0 up to the spatial frequency given by 2 × NA _p2 / λ. Therefore, even finer patterns can be resolved.

In the above-mentioned conventional example, the value of σ is close to 0, which is a condition for almost coherent illumination. Therefore, there is a problem that the resolution is not large and a fine pattern cannot be transferred.

The present invention has been made to solve the above problems, and an X-ray generator capable of obtaining better imaging performance than ever, a high-performance exposure apparatus using the same, and a device. The purpose is to provide a production method.

[0011]

The X-ray generator of the present invention for solving the above-mentioned problems is characterized in that the form of the light emitting portion is variable.

The X-ray irradiator of the present invention is characterized by including an X-ray generator having a variable light emitting section and an irradiating means for irradiating the object with X-rays from the device.

The X-ray exposure apparatus of the present invention comprises an irradiation means for irradiating the mask with X-rays from an X-ray generator having a variable light emitting section, and an optical means for projecting the irradiated mask pattern onto a wafer. It is characterized by having means.

The X-ray illuminating method of the present invention is characterized in that an object is incoherently illuminated by changing the form of the X-ray emitting section.

The device production method of the present invention is characterized by producing a device using the above apparatus.

[0016]

Embodiments of the present invention will be described below.

According to a preferred embodiment of the present invention, the light source is formed into a planar surface having a finite size, X-rays emitted from the light source are condensed by an illumination optical system, and an object such as a mask is Koehler-illuminated. At this time, X-rays emitted from different points on the light source surface illuminate the mask at different angles. If the light source has a finite size, the angular spread of the X-rays that illuminate the mask will have a finite size. The coherence factor can be changed by changing the form (shape, size, position, etc.) of the X-ray emitting section. Further, if the light emission intensity distribution of the light source is made non-uniform, the angular distribution of the X-rays illuminating the mask becomes non-uniform, resulting in modified illumination.

As described above, by appropriately setting the shape of the light emitting portion, the angular distribution of the X-rays that illuminate the mask is controlled, and the coherence factor and the coherence factor σ of the illumination system are set to optimum values. Also, modified illumination such as annular illumination and oblique illumination can be performed. Since it is possible to illuminate under the optimal illumination condition according to the exposure condition, it is possible to improve the imaging performance such as resolution and depth of focus.

The present invention can be widely applied to devices requiring X-ray illumination. Examples include an X-ray exposure apparatus, an X-ray microscope apparatus, an X-ray inspection apparatus, an X-ray processing apparatus, and a medical X-ray apparatus. Hereinafter, specific examples in which the present invention is applied to an X-ray reduction image forming exposure apparatus will be described.

[0020]

【Example】

<Embodiment 1> FIG. 1 shows a block diagram of a first embodiment of the present invention. In the figure, a plurality of YAG laser light sources 9, a laser beam focusing optical system 10, and a laser plasma target 1 are shown.
1, a filter 12, a rotating parabolic reflector 3, a reflective mask 4 and a mask stage 7 on which the mask is mounted, a projection optical system 5, a resist-coated wafer 6 and a wafer stage 8 on which the resist is coated. To be done. The reflection type mask 4 is formed by forming a transfer pattern by an X-ray absorber on a multilayer film reflecting mirror, and a phase shift mask in which a step corresponding to the pattern is provided in the multilayer film can also be used.

In this structure, each laser beam emitted from the plurality of YAG laser light sources 9 is focused on another position on the target 11 by the laser beam focusing optical system 10 to generate high temperature plasma X. Generate a line. Here, the laser beam condensing optical system is provided with a zooming or defocusing mechanism so that the position and size of the laser beam spot on the target can be controlled.

The projection optical system 5 is composed of two aspherical reflecting mirrors, and a multilayer film is provided on the reflecting surface. A telecentric system is used as the projection optical system. The image-side numerical aperture NA _p2 of the optical system is set according to the used wavelength λ, the required resolution, the depth of focus, and the like, and a value of about 0.05 to 0.2 is used. For example, when the image-side numerical aperture NA _p2 is 0.1 and the projection magnification is 1/5, the object (mask) _-side numerical aperture NA _p1 is 0.02.

The rotating parabolic reflector 3 is a reflector using a multilayer film or a metal single layer film, and is installed so that the laser plasma target 11 as a light source is located at the focal position. Therefore, X emitted from a certain point on the light source surface
After the line is reflected by the paraboloidal reflector 3, it becomes parallel light and illuminates the entire surface of the mask 4. Further, X-rays emitted from another point on the light source surface are also converted into parallel light and illuminate the entire surface of the mask 4. Since the projection optical system 5 uses a telecentric system, the Koehler illumination condition is satisfied.

At this time, X-rays emitted from different points on the light source surface are incident on the mask at different angles. That is, if the focal length of the rotating parabolic reflector 3 is f and the distance between two points on the light source surface is d, the angle of the X-ray emitted from these two points and incident on a certain point on the mask is opened. Is d / f (rad). If the size of the entire light source consisting of multiple light emitting points is D, the angular spread of the light illuminating the mask is D / f (rad)
Becomes Therefore, the numerical aperture NA _i of the illumination system is D / (2 × f)
Becomes At this time, the coherence factor σ is σ = D
/ (2 × f × NA _p1 ). f = 200mm, NA _p1 = 0.0
In the case of 2, if D = 8 mm, σ = 1.0, and incoherent illumination is realized.

In this embodiment, a plurality of plasma excitation laser light sources 9 and a plurality of laser light focusing optical systems 10 are provided, and a plurality of plasma X-ray emission points 1 are simultaneously generated on a target. At the same time, the size of each light emitting point can be controlled by the zooming and defocusing mechanism of the laser light focusing optical system, and the form of the light emitting portion of the light source can be arbitrarily set.

FIG. 2 shows some examples of the shape of the light emitting portion of the light source. As shown in FIG. 2A, if the laser light spots are made small and overlapped, the light source size D becomes small, the coherence factor σ approaches 0, and coherent illumination is realized. If the laser light spots are enlarged and arranged as shown in FIG.
Becomes larger, and the coherence factor σ approaches 1 and incoherent illumination is realized. Even if the laser light spots are made small and arranged at intervals as shown in FIG. 2C, the effective light source size D becomes large, and almost incoherent illumination is realized. Further, by controlling the form of the light emitting unit, it is possible to realize modified illumination such as oblique illumination or annular illumination. As shown in FIGS. 2 (4) and (5), by arranging the laser light spots in an annular shape or arranging them apart from each other, the angular distribution of X-rays incident on the mask is shifted from the uniform distribution, and the resolution, depth of focus, and other factors are combined. Image performance can be improved.

<Second Embodiment> FIG. 3 shows a block diagram of a second embodiment of the present invention. The difference from the embodiment of FIG. 1 is that two laser light deflection mirrors 13 and respective driving devices 14 are used as a configuration for generating a plurality of light emitting points.

The laser light emitted from the laser light source 9 is directed to the target 11 by the laser light focusing optical system 10.
It is focused on the surface and generates high-temperature plasma to generate X-rays. Then, the irradiation position on the target 11 is two-dimensionally controlled by the deflecting mirror composed of two reflecting mirrors and its driving device. The laser light source 9 receives a deflection position signal from the control system of this driving device, and controls the timing of light emission based on this information. That is, the deflection reflecting mirror is moved so that the laser beam is directed to a preset irradiation position, and the laser is emitted when the angle of the reflecting mirror reaches a set value. In this way, it is possible to freely determine the number and the positions of the plurality of light emitting points 1 of the laser plasma.

The projection optical system is composed of two aspherical reflecting mirrors 5, and a non-telecentric system is used. A multilayer film is provided on the reflecting surface of each reflecting mirror. The spheroidal reflecting mirror 3 is arranged so that the laser plasma target 11 as a light source is located at the first focus position and the entrance pupil of the projection optical system is located at the second focus position. Therefore, the X-ray emitted at a certain time is reflected by the spheroidal reflecting mirror 3 and irradiates the entire surface of the mask 4. Then another one on the light source surface
The X-ray emitted from the point at another time also illuminates the entire surface of the mask 4. X-rays emitted from different points on the light source surface at different times illuminate the mask at different angles. The distribution of the light emitting points 1 of the light source corresponds to the distribution of the angles of the X-rays incident on one point on the mask.

In this embodiment, by controlling the irradiation position of the excitation laser light, the form of the light emitting portion of the light source is changed,
Modified illumination such as oblique illumination and ring illumination can be realized. For example, by arranging the laser light spots in an annular shape or arranging the laser light spots apart from each other, the angular distribution of the X-rays incident on the mask can be shifted from the uniform distribution, and the imaging performance such as resolution and depth of focus can be improved.

FIG. 4 shows some examples of laser light irradiation patterns. If only one point is irradiated as shown in FIG. 4 (1), the light emitting point becomes a small circle, which is close to coherent illumination. As shown in FIG. 4 (2), if the light is uniformly radiated two-dimensionally, the size of the light emitting point becomes large and the light becomes close to incoherent illumination. If irradiation is performed in a ring shape as shown in FIG. 4C, the light emitting point becomes an annular shape, and ring illumination can be realized. FIG. 4 (4) shows an example in which the ring-shaped irradiation is performed and the inside thereof is also sparsely irradiated. FIG. 4 (5) shows an example in which four areas are irradiated, and the light emitting points are a plurality of spots, and oblique illumination is realized.

As described above, according to this embodiment, a single laser beam is two-dimensionally deflected and the laser emission timing is controlled in synchronization with the deflection angle, so that a plurality of emission points are time-series. Is generated to determine the form of the light emitting unit. As a result, it is not necessary to provide a plurality of laser light sources, and the X-ray generator can be downsized.

<Embodiment 3> FIG. 5 shows a block diagram of a third embodiment of the present invention. This embodiment corresponds to the embodiment shown in FIG. 1 and FIG.
This embodiment is a fusion of the embodiments, and is characterized in that a plurality of sets of a laser light source and a laser beam deflecting device are provided.

The laser beams emitted from the plurality of laser light sources 9 are respectively supplied to the target 11 by the laser beam focusing optical system 10 having a zooming and defocusing mechanism.
It is focused on the surface and generates high-temperature plasma to generate X-rays. The size, position and number of light emitting points by each laser can be freely controlled, and the shape of the light emitting unit can be freely set.

In this embodiment, a plurality of laser light sources are used,
Each is independently deflected and irradiated onto the target. Therefore, the number of light emitting points per unit time can be increased. Therefore, the X-ray generation amount of the entire light source can be increased, so that the exposure time can be shortened and the throughput is improved.

<Embodiment 4> FIG. 6 shows a block diagram of a fourth embodiment of the present invention. In this embodiment, an optical integrator (fly-eye lens) 23 that generates a secondary light source,
It is characterized in that an aperture 24 capable of selecting an aperture shape that defines the shape of the secondary light source is provided. Target 1
An image of this aperture is projected onto the area 1. Therefore,
The form (shape, size, position, etc.) of the light emitting portion of the laser plasma can be controlled by selecting the aperture of the aperture 24.

FIG. 7 shows some examples of aperture shapes. If a simple circular opening is used as shown in FIG. 7A, the light emitting portion has a circular shape with a finite size. If the aperture is made smaller, the size of the light emitting part becomes smaller and it becomes closer to coherent illumination.
If the aperture is made larger, the size of the light emitting part becomes larger and it becomes closer to incoherent illumination. If a donut-shaped opening is formed as shown in FIG. 7 (2), the light emitting portion becomes an annular shape with a finite size, and ring illumination can be realized. FIG. 7 (3) shows an example in which a donut-shaped opening reduces the internal transmittance. FIG.
(4) and (5) are examples in which a plurality of apertures are arranged, and the light emitting portion becomes a plurality of spots, and modified illumination such as oblique illumination is realized.

In the first to third embodiments described above, examples of complete Koehler illumination have been shown. However, complete Koehler illumination is not always necessary and sufficient performance can be obtained if it is close to Koehler illumination. Obtainable. However, when illuminated under conditions close to critical illumination, not only the angular distribution of X-rays that illuminate the mask does not become the desired distribution, but also the X-ray intensity distribution on the mask surface reflects the spatial distribution of light emitting points. As it becomes a ghost, the illuminance unevenness becomes large. Therefore, it is preferable that the illumination is as close to Koehler illumination as possible.

According to the above embodiment, the angular distribution of the X-rays that illuminate the mask can be controlled by appropriately setting the aperture shape, and the coherency optimal value of the illumination system can be set, and the annular zone can be set. Modified illumination such as illumination or oblique illumination can be performed. Since it is possible to illuminate under the optimal illumination condition according to the exposure condition, it is possible to improve the imaging performance such as resolution and depth of focus.

<Embodiment 5> Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described.

FIG. 8 shows a flow of manufacturing minute devices (semiconductor chips such as IC and LSI, liquid crystal panels, CCDs, thin film magnetic heads, micromachines, etc.). Step 1
In (circuit design), a circuit of a semiconductor device is designed.
Step 2 is a process for making a mask on the basis of the circuit pattern design. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process,
An actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 9 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been difficult to manufacture conventionally, at a low cost.

[0044]

According to the present invention, it is possible to obtain better imaging performance than ever before, and by applying this to device production, it is possible to produce high-performance devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a diagram showing some examples of light emitting point patterns of a light source.

FIG. 3 is a configuration diagram of a second embodiment.

FIG. 4 is a diagram showing some examples of light emitting point patterns of a light source.

FIG. 5 is a configuration diagram of a third embodiment.

FIG. 6 is a configuration diagram of a fourth embodiment.

FIG. 7 is a diagram showing some examples of aperture shapes of a light source.

FIG. 8 is a diagram showing a flow of device production.

FIG. 9 is a diagram showing a detailed flow of a wafer process.

FIG. 10 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 Light Emitting Point 2 X-ray 3 Illumination Optical System X-ray Condensing Mirror 4 Mask 5 Projection Optical System 6 Wafer 7 Mask Stage 8 Wafer Stage 9 Laser Light Source 10 Laser Condensing Optical System 11 Target 12 Filter 13 Laser Beam Deflection Optical System 14 Deflection Optical system controller 23 Optical integrator 24 Aperture

Claims (15)

[Claims] 1. An X-ray generator, wherein the shape of the light emitting portion is variable. 2. An X-ray irradiating device comprising: an X-ray generating device having a variable light emitting section; and irradiating means for irradiating an object with X-rays from the device. 3. An irradiation means for irradiating the mask with X-rays from an X-ray generator having a variable shape of a light emitting portion, and an optical means for projecting the irradiated mask pattern onto a wafer. X-ray exposure device. 4. The device according to claim 1, wherein the form of the light emitting unit is at least one of shape, size and position of the light emitting unit. 5. The apparatus according to claim 3, wherein the optical means is a reduction imaging optical system. 6. The apparatus according to claim 2, wherein the irradiating means irradiates by almost Koehler illumination. 7. The X-ray generator is a laser plasma X
4. The device according to any one of claims 1 to 3, comprising a radiation source. 8. The apparatus according to claim 7, wherein the irradiation shape of the laser that excites the plasma is controlled. 9. The apparatus according to claim 7, wherein the size of the irradiation region of the laser that excites the plasma is controlled. 10. The apparatus according to claim 7, wherein the irradiation position of the laser that excites the plasma is controlled. 11. The apparatus according to claim 7, wherein the irradiation position and timing of the laser that excites the plasma is controlled. 12. The apparatus according to claim 7, wherein the shape of the aperture provided in the optical path of the laser for exciting the plasma is changed. 13. An X-ray illuminating method, which comprises incoherently illuminating an object by switching the form of the X-ray emitting section. 14. A device production method, which produces a device using the apparatus according to claim 1. 15. A device manufactured by using the manufacturing method according to claim 14.