JPH11271213A - Mask inspection device, exposure device and lighting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mask inspection device, an exposure device and a lighting method capable of reducing interference fringes in a simple optical structure. SOLUTION: A mask inspection device 20 includes a light source 21 for generating coherent light, a uniforming means 24 arranged on the optical axis of the coherent light for uniforming the coherent light, a mask 28 for transmitting the coherent light passing through the uniforming means 24 corresponding to a pattern shape and a detecting means 30 for detecting the intensity of the coherent light passing through the mask 28. It has a deflecting mirror 22 provided between the light source 21 and the uniforming means 24 to be rotationally driven, the deflecting mirror 22 having a reflecting plane 23 inclined at a predetermined angle from a plane perpendicular to the center of rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mask inspection apparatus and an exposure apparatus that use coherent laser light as illumination light, and an illumination method used for the same.

[0002]

2. Description of the Related Art In an exposure apparatus for manufacturing a semiconductor such as a stepper or a mask inspection apparatus for manufacturing a semiconductor, illumination light is reduced and exposed on a wafer through a mask (reticle), and various processes are performed after the illumination. DR from wafer
A semiconductor chip such as an AM is formed.

In recent years, exposure apparatuses and inspection apparatuses using these masks are changing from those using a conventional mercury lamp as a light source to those using an excimer laser. The light emitted from this light source is
The light is incident on the fly-eye lens as an integrator as a substantially parallel light beam. This fly-eye lens is indispensable for uniformly irradiating a mask (reticle), and has a function of reducing luminance unevenness occurring in light rays. For this reason, the light beam that has passed through the fly-eye lens is emitted to the mask (reticle) with reduced luminance unevenness.

Here, a fly-eye lens is, for example, 10 ×
It is composed of ten element lenses, and the light flux is split into and incident on each of the element lenses, thereby reducing the luminance unevenness.

However, when a coherent laser beam, instead of the conventional mercury lamp light, is incident on the fly-eye lens, the luminous flux emitted from the fly-eye lens may be affected by the intensity of the light beam, causing interference fringes on the wafer. is there. When such interference fringes are generated on the wafer, the exposure intensity is not uniform, causing a problem that the processing becomes uneven.

In order to prevent such a problem, a pulsed laser is conventionally used, and a plate-shaped vibrating mirror is vibrated in one direction so as to synchronize with the pulsed light, so that interference fringes are formed. An arrangement for reducing is disclosed.

[0007]

Incidentally, the conventional exposure apparatus and inspection apparatus have the following problems in addition to the generation of interference fringes on the wafer as described above. In other words, when trying to make the illumination light uniform by using a vibrating mirror, the vibration speed of the vibrating mirror is limited to several KHz, and at such a vibration speed, it is necessary to eliminate illumination unevenness at the shooting speed of the line sensor. Is no longer possible.

Further, when pulse light having a large variation in light quantity is used, processing for controlling the total light quantity at the time of exposure is required as compared with the case where continuous light with a stable light quantity is used. That is, it is necessary to perform a process for giving a specific relationship between the pulse light and the vibration mirror, such as synchronizing the oscillation frequency of the pulse light and the vibration frequency of the vibration mirror.

Furthermore, it is difficult to control the vibrating mirror to give a two-dimensional vibration such as drawing a square or a hexagon in accordance with a lattice interference fringe. In this case, it is necessary to perform control for continuously changing the vibration angle of the vibration mirror, and as an example of angle control of the vibration mirror, it is impossible to control the angle in a sawtooth waveform.

When the mirror is vibrated, the vibration may be transmitted to a fly-eye lens, a line sensor, and the like in accordance with the vibration of the mirror. As described above, when vibration is transmitted to a fly-eye lens, a line sensor, or the like at the time of mask inspection or the like, a problem occurs in that the mask pattern is blurred and the detection sensitivity is reduced.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a mask inspection apparatus, an exposure apparatus, an illumination apparatus, and an illumination capable of reducing interference fringes with a simple optical system configuration. It seeks to provide a way.

[0012]

According to a first aspect of the present invention, there is provided a light source for generating coherent light, and the light source is arranged on an optical axis of the coherent light to make the coherent light uniform. A mask inspection apparatus comprising: a homogenizing unit, a mask that transmits the coherent light that has passed through the homogenizing unit according to the pattern shape, and a detecting unit that detects the intensity of the coherent light that has passed through the mask. It has a deflecting mirror rotatably provided between the light source and the equalizing means, and the deflecting mirror has a reflecting surface formed to be inclined at a predetermined angle from a plane orthogonal to the center of rotation. Mask inspection apparatus.

According to a second aspect of the present invention, in the deflecting mirror, an uneven shape is formed on a reflecting surface, and the optical axis angle of the coherent light is changed by the uneven shape. It is a mask inspection device.

According to a third aspect of the present invention, there is provided a light source for generating coherent light, a homogenizing means arranged on an optical axis of the coherent light to homogenize the coherent light, and a coherent light passing through the homogenizing means. And a mask that transmits light according to the pattern shape to expose the photosensitive substrate. The exposure device further includes a deflecting mirror rotatably provided between the light source and the homogenizing means. The exposure apparatus is characterized in that the mirror has a reflecting surface formed to be inclined at a predetermined angle from a plane perpendicular to the center of rotation.

According to a fourth aspect of the present invention, in the deflecting mirror, the concave and convex shape is formed on the reflecting surface, and the optical axis angle of the coherent light is changed by the concave and convex shape. An exposure apparatus.

According to a fifth aspect of the present invention, in the illumination method for irradiating the object with coherent light emitted from the light source, the reflecting means having the reflecting surface is driven to rotate about the rotation axis, and the rotation driving is performed. A rotational reflection step of changing the angle of the optical axis of the coherent light on the reflection side with respect to the optical axis on the incident side of the coherent light, and the coherent light reflected by the rotational reflection step is made incident on the uniformizing means. A homogenizing step for uniformizing the coherent light, and an emitting step of causing the coherent light emitted from the uniformizing step to enter and emit corresponding to a desired pattern shape, and emitting the coherent light to an object. And a lighting method.

According to a sixth aspect of the present invention, in the rotational reflection step, the rotating means is driven to rotate n times (n is a natural number) within a recognition time of the detection means or an exposure time to the photosensitive substrate. Item 4. The illumination method according to Item 3.

According to the first aspect of the present invention, a deflecting mirror driven to rotate is provided between the light source and the equalizing means, and the deflecting mirror is formed to be inclined at a predetermined angle from a plane perpendicular to the center of rotation. Since the light is reflected by the reflected surface, the optical axis angle of the coherent light changes as the reflection surface is driven to rotate. For this reason, at a predetermined position of the detecting means, the interference fringes generated after passing through the equalizing means move and are detected, so that the accumulated brightness becomes uniform.

According to the second and fourth aspects of the present invention, the deflecting mirror has irregularities formed on the reflecting surface, and the unevenness causes a change in the optical axis angle of the coherent light. It is rotationally driven to draw a trajectory having a diameter different from the trajectory drawn by the coherent light irradiation area,
Or, the position of the locus to be drawn shifts. This makes it possible to irradiate coherent light over the entire surface of the detection means by drawing not only a locus having a predetermined diameter but also a locus having a different diameter.

According to the third aspect of the present invention, the brightness accumulated on the photosensitive substrate can be made uniform, so that the occurrence of exposure failure can be prevented. According to the fifth aspect of the present invention, the reflection means having the reflection surface is driven to rotate about the rotation axis, and the light of the coherent light on the reflection side with respect to the optical axis on the incident side of the coherent light is driven by the rotation. Since the rotation reflection step for changing the angle of the axis is provided, it is possible to make the accumulated brightness uniform by rotating the interference fringes generated after passing through the equalizing means.

According to the sixth aspect of the present invention, the rotational reflection step is driven to rotate n times (n is a natural number) within the recognition time of the detection means or the exposure time to the photosensitive substrate. By the light portion and the dark portion of the interference fringe reaching the object an equal number of times by n times of rotation driving,
It is possible to make the accumulated brightness the same as other positions.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram showing the configuration of the pattern inspection apparatus 20. The pattern inspection apparatus 20 has a laser light oscillation source 21 that oscillates laser light. The laser light oscillation source 21 emits not a pulse oscillation laser light but a continuous oscillation laser light.

When the laser light is emitted from the laser light oscillation source 21, the laser light is directed to the deflection mirror 22. The deflecting mirror 22 is formed in a cylindrical shape or a cylindrical shape, and as shown in FIG. It is formed to make α. That is, the mirror surface 23 is in a state where the shape is an elliptical plane.

The inclination angle α corresponds to the angle at which the interference fringes move N periods, and is a value determined according to the relationship with the width of the interference fringes. The mirror surface 23 is formed by mirror-polishing a metal or a dielectric multilayer film having a high reflectivity.

The laser light reflected from the deflecting mirror 22 enters a fly-eye lens 24. The fly-eye lens 24 is constituted by, for example, a 10 × 10 element lens 25, and has a structure in which the incident laser light has uniform luminance unevenness.

The laser light emitted from the fly-eye lens 24 is emitted toward the phase plate 26. Phase plate 26
, The phase is randomized and the coherence is reduced.

The laser light passing through the phase plate 26 passes through a plurality of optical elements 27 such as mirrors and lenses, and is incident on a reticle (mask) 28. The reticle 28 has a pattern shape having a size of about 4 of a pattern shape size irradiated on a resist of a semiconductor wafer as a photosensitive substrate.
The portion through which the laser light is transmitted is formed of transparent glass as a material.

The laser beam that has passed through the reticle 28 and has been processed into an optical image of a predetermined pattern is
, Is converted into a desired magnification, and is irradiated onto the CCD line sensor 30. The line sensor 30 includes a plurality of line sensor elements 31 arranged in the same direction as shown in FIG. The number of lines of the line sensor element 31 is, for example, 96 stages, and the information recognized by each line sensor element 31 is accumulated so that a predetermined image is recognized as a whole.

Instead of using the line sensor 30 described above, a configuration in which the resist on the surface of the photosensitive substrate is irradiated after passing through the lens 29 may be used. An inspection method using the pattern inspection apparatus 20 having the above configuration will be described below.

When using the pattern inspection apparatus 20, it is necessary to drive the deflection mirror 22 to rotate at a sufficient speed. For example, according to trial calculations at the present time, the exposure time of one pixel is about 3 ms, the number of rotations is about 20,000 rpm, and the interference fringes can make one rotation. Therefore, the effect of obtaining uniform illumination is further improved by rotating the interference fringes twice or three times during one pixel exposure time.

With the use of the deflecting mirror 22 which is driven to rotate at such a rotational speed, the interference fringes as shown in FIG. Move. That is, by making just one round, the bright portion and the dark portion forming the interference fringes move accordingly, and if the brightness is superimposed, the accumulated brightness becomes uniform.

The actual recognition by the line sensor 30 is as follows. That is, in the above-described configuration, the line sensor 30 is described as being constituted by, for example, 96 stages of line sensor elements 31, but in the following description, the line sensor 30 will be described as having four stages for simplification.

First, assuming that the line sensor 30 has just passed from end to end while the interference fringe makes one rotation,
Each of the one-stage line sensor elements 31 has one of the interference fringes.
One quarter of the rotation is performed.

However, each line sensor element 3
By superimposing the information (brightness) recognized in step 1 on the line sensor elements 31 in all four stages, the line sensor 30
The whole is the same as the recognition when one rotation is performed on the interference fringes.

The above is an example of the case where the line sensor element 31 has four stages. However, the same is basically applied to the case where the line sensor element 31 has 96 stages or the like. This allows
As a whole, the line sensor 30 can obtain uniform brightness by reducing the difference in brightness between interference fringes.

When the line sensor 30 is not the above-described TDI sensor but an area sensor, recognition is performed over the entire area as shown in FIG. 3B. One rotation can be recognized within the exposure time of each pixel.

According to such a mask inspection apparatus 20,
When the deflecting mirror 22 is rotationally driven, the interference fringes generated by the entire laser beam are rotationally driven after passing through the fly-eye lens 24, and the bright and dark portions of the interference fringes change one after another with this rotational driving. . Therefore, it is possible to make the accumulated brightness at an arbitrary irradiation position of the line sensor 30 uniform.

In this case, the interference fringes rotate n times (n is a natural number) until the line sensor 30 has completely passed, so that the bright and dark portions of the interference fringes reach the line sensor the same number of times. This makes it possible to average the accumulated brightness with that of other positions.

The case where the line sensor 30 is irradiated with laser light has been described above. However, the same applies to the case where the photosensitive substrate is irradiated with laser light. In this case, in FIG. The reactive substrate is positioned at the exposure position. In this case, it is possible to prevent exposure unevenness from occurring on the surface of the photosensitive substrate.

Also, without using a configuration using a laser beam,
A configuration using other coherent light may be used. (Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.

In this embodiment, the deflection mirror 22
The other configuration is the same as the configuration described in the above-described first embodiment, and the configuration of the deflecting mirror 22 is different.

That is, in the mask inspection apparatus 20 of the present embodiment, the shape of the mirror surface 42 of the deflecting mirror 41 is different from the shape of the above-described first embodiment. The mirror surface 42 is provided with a first mirror surface 43 provided at a predetermined angle α similarly to the mirror surface 23 of the first embodiment, and is different from the first mirror surface 43 at a angle β instead of α. It is configured by being combined with the second mirror surface 44 provided.

The first mirror surface 43 and the second
Are arranged adjacent to each other (FIG. 5 shows a configuration in which the first mirror surface 43 and the second mirror surface each have four surfaces).

In the mask inspection apparatus 20 having the above configuration, the trajectory of the optical axis drawn by only the first mirror surface 43 (that is, the mirror surface 23 in the first embodiment) is shown in FIG. As shown, according to the first mirror surface 43 and the second mirror surface 44 of the present embodiment, since the inclination angle of the second mirror surface 44 with the inclination angle β is smaller than α, The deviation of the axis is small, and therefore, as shown in FIG. 6B, a small diameter locus and a large diameter locus are alternately drawn.

Thus, the trajectory is drawn with the diameter shifted, so that the interference fringes can be moved, and the brightness can be made more uniform. Although the second embodiment of the present invention has been described above, the present invention can be variously modified in addition to the above. Hereinafter, this will be described.

In the above-described embodiment, the shape of the reflecting surface 42 of the deflecting mirror 41 is made up of the first mirror surface 43 and the second mirror surface 44. The shape may be a shape including two or more mirror surfaces having different inclination angles, or various other uneven shapes may be provided on the mirror surface. In addition, various modifications can be made without departing from the scope of the present invention.

[0048]

As described above, according to the present invention,
The optical axis angle of the coherent light changes with the rotation of the reflection surface. For this reason, at predetermined positions of the detecting means, the interference fringes generated after the elapse of the equalizing means move and are detected, so that the accumulated brightness becomes uniform.

Further, if the uneven surface is formed on the reflecting surface of the deflecting mirror, the optical axis angle of the coherent light changes due to the uneven surface. Further, by drawing loci having different diameters, it becomes possible to uniformly irradiate coherent light over the entire surface of the detection means.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a mask inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a deflection mirror according to the embodiment.

FIG. 3 is a plan view showing a configuration of a line sensor according to the embodiment.

FIG. 4 is a schematic diagram showing a state of interference fringes according to the embodiment.

FIG. 5 is a diagram showing a configuration of a deflecting mirror according to the embodiment.

FIG. 6 is a plan view showing the trajectory of the optical axis due to rotational driving of the deflection mirror according to the embodiment.

[Explanation of symbols]

 Reference Signs List 20 mask inspection apparatus 21 laser light oscillation source 22, 41 deflecting mirror 23, 42 mirror surface 24 fly eye lens 28 reticle 30 line sensor 43 first mirror surface 44 second mirror surface

Claims (6)

[Claims] 1. A light source for generating coherent light, a homogenizing means arranged on the optical axis of the coherent light to homogenize the coherent light, and a coherent light passing through the homogenizing means according to a pattern shape. A mask inspection apparatus comprising: a mask to be transmitted; and detection means for detecting the intensity of coherent light passing through the mask, comprising: a deflection mirror rotatably provided between the light source and the equalization means. A mask inspection apparatus, wherein the deflecting mirror has a reflecting surface formed to be inclined at a predetermined angle from a plane perpendicular to the center of rotation. 2. The mask inspection apparatus according to claim 1, wherein the deflecting mirror has a concave-convex shape on a reflection surface, and the concave-convex shape causes a change in an optical axis angle of the coherent light. 3. A light source for generating coherent light, a homogenizing means arranged on the optical axis of the coherent light to homogenize the coherent light, and a coherent light passing through the homogenizing means according to a pattern shape. A mask for transmitting light to the photosensitive substrate and exposing the photosensitive substrate, further comprising a deflecting mirror rotatably provided between the light source and the equalizing means, wherein the deflecting mirror is positioned with respect to the center of rotation. An exposure apparatus having a reflecting surface formed at a predetermined angle from all the orthogonal planes. 4. The exposure apparatus according to claim 3, wherein the deflecting mirror has an uneven shape formed on a reflecting surface, and the unevenness changes the optical axis angle of the coherent light. 5. An illumination method for irradiating an object with coherent light emitted from a light source, wherein a reflecting means having a reflecting surface is driven to rotate about a rotation axis, and the coherent light is emitted along with the rotation. A rotational reflection step for changing the angle of the optical axis of the coherent light on the reflection side with respect to the optical axis on the incident side; and making the coherent light reflected by the rotational reflection step incident on the homogenizing means to homogenize the coherent light. A coherent light emitted from the homogenization step, and emitted in accordance with a desired pattern shape, and an emission step of emitting the coherent light to an object. Characteristic lighting method. 6. The illumination method according to claim 3, wherein in the rotation reflection step, the rotating means is driven to rotate n times (n is a natural number) within a recognition time of the detection means or an exposure time to the photosensitive substrate. .