JP3128396B2 - Exposure method and exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure technique for forming a fine pattern required for manufacturing a semiconductor integrated circuit, and more particularly to an exposure method and an exposure apparatus using polarized light.

[0002]

2. Description of the Related Art In recent years, in the field of photolithography, attempts have been made to improve the resolution of a periodic pattern by utilizing the polarization of light. FIG. 3 shows an example of an exposure apparatus in which illumination light is polarized light using a polarizing plate.
-109601).

In FIG. 3, a polarizing plate 16 is provided in an illumination optical system. In the figure, illumination light emitted from a light source 11 such as a mercury lamp enters a polarizing plate 16 via an elliptical mirror 12, a mirror 13, a condenser lens 14, and an optical integrator 15. The polarizing plate 16 is supported by a support 17 and is rotatable about the optical axis Ax or an axis parallel thereto. This rotation is performed by a motor (not shown) provided on the support 17 or the like. Therefore, the illumination light beam transmitted through the polarizing plate 16 becomes a light beam having a polarization direction (linearly polarized light) corresponding to the rotation direction of the polarizing plate 16.

The light beam having passed through the polarizing plate 16 is guided to condenser lenses 18 and 20 and a mirror 19 to illuminate a pattern 22 on a photomask (reticle) 21 (on the lower surface). The transmitted and diffracted light from the photomask 21 is condensed and imaged by the projection optical system 23 to form an image of the mask pattern 22 on the wafer 24. At this time, if the mirror 19 deviates from a position perpendicular or parallel to the vibration direction of the illumination light, linearly polarized light will be converted into elliptically polarized light.

[0005] The polarization direction of the illuminating light is aligned parallel to the longitudinal direction of the mask pattern 22 by the polarizing plate 16, whereby the contrast of a fine line and space pattern image can be improved, and the integrated circuit can be miniaturized. Become. Except for the fine one-dimensional line-and-space pattern, the fineness of the pattern is relatively low, so that even if the polarization of the illumination light is not accurately optimized for the pattern, the resulting decrease in contrast is slight.

Here, in FIG. 3, the light source 11 is a mercury lamp, but may be another lamp or a laser light source. In particular, when the light source is a laser that emits linearly polarized light or circularly polarized light, one member is used as a member for controlling the polarization state.
A 波長 wavelength plate or a 波長 wavelength plate can be used.

However, this type of apparatus has the following problems. That is, in an actual LSI pattern, not only a pattern in the direction parallel to the linearly polarized light by the polarizing plate 16 but also a pattern that is long in a direction perpendicular thereto and an oblique pattern exist. For this reason, the component parallel to the linearly polarized light improves the resolving power and the depth of focus, but does not have the above-described effect in a pattern that is long in the vertical and oblique directions.

For these reasons, when an actual LSI pattern is transferred, the resolution and depth of focus are determined by the vertical and oblique patterns, and a substantial improvement in resolution and depth of focus cannot be obtained. Occurred.

[0009]

As described above, in a conventional exposure apparatus using linearly polarized light, although the component parallel to the polarization direction improves the resolving power and the depth of focus, a pattern that is long in the vertical and oblique directions is not improved. There is a problem in that there is no improvement effect, and a substantial improvement in resolution and depth of focus cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide the same resolution and depth of focus enhancement effect for patterns in all directions. It is an object of the present invention to provide an exposure method and an exposure apparatus capable of favorably transferring a pattern even in an LSI pattern in which is mixed.

[0011]

In order to solve the above problems, the present invention employs the following configuration. That is, the present invention (claim 1) provides an exposure method in which a photomask is illuminated with polarized light and a pattern on the photomask is reduced and projected onto a wafer via a projection optical system. In the vicinity, a slit filter having a slit shape or an opening close to the slit shape in a predetermined angle direction with respect to the polarization plane of the polarized light is arranged, and the slit filter is rotated in synchronization with this while rotating the polarization plane of the polarized light. The method is characterized in that the photomask is rotated, and the photomask is illuminated with polarized light for each specific rotation position to perform multiple exposure.

According to a second aspect of the present invention, there is provided an exposure apparatus for illuminating a photomask with an illumination optical system and reducing and projecting a pattern on the photomask onto a wafer via a projection optical system. A polarizing member that is provided inside and controls the polarization state of the illumination light beam to the photomask; a slit filter that is provided at or near the pupil position of the projection optical system and has a slit-like or close-like opening; and a slit. A rotation mechanism for synchronously rotating the slit filter and the polarizing member about the optical axis while maintaining the longitudinal direction of the filter opening and the polarization plane of the light transmitted through the polarizing member at a predetermined angle. And characterized in that:

Here, it is desirable that the predetermined angle described in claim 1 and the predetermined angle described in claim 2 be 90 °. The photomask used in the present invention may be a normal mask having a light-shielding portion and a light-transmitting portion, or may be a phase shift mask. In particular, a so-called Levenson-type phase shift mask in which a phase shifter is provided at every other opening provided periodically has a large effect.

[0014]

The operation of the present invention will be described with reference to FIG. When linearly polarized light passing through the polarizer 1 is used as a light source, the periodic pattern A long in the direction parallel to the polarization plane forms an image by scalar interference (TE mode), and the periodic pattern B long in the vertical direction forms an image by vector interference (TM mode). I do. An image formed by scalar interference has a good image contrast because the amplitude of the electric field is synthesized as a scalar sum. In the pattern B formed as an image by the vector interference, the image contrast is reduced because the amplitude synthesis on the image plane is performed by the vector sum. This tendency increases as the pattern size decreases. Therefore,
By placing the slit filter 7 that transmits only the TE mode light, which is advantageous for image formation, at the pupil position, the resolution of only the pattern A is improved, and the spectrum from the pattern B, which is the TM mode light, does not reach the image plane. Do not image. In other words, a pattern that is long in the direction perpendicular to the polarization plane is not transferred.

Next, the polarizer 1 and the slit filter 7 are
Rotate by 0 degrees and expose further. Then, in this state, the periodic pattern long in the direction parallel to the polarization plane becomes B, so that B
Is diffracted into scalar interference (TE mode), and the image contrast is improved. In this state, the diffracted light from the pattern A in the TM mode is blocked by the slit filter 7 and does not reach the image plane. Therefore, it is possible to satisfactorily transfer even an actual device pattern in which both vertical and horizontal lines are mixed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an exposure apparatus according to one embodiment of the present invention. In this embodiment, the polarizing plate 1 is provided in the illumination optical system, and the slit filter 7 is provided in the projection optical system. In the figure, illumination light emitted from a light source such as a mercury lamp enters a polarizing plate 1 via an elliptical mirror, a mirror, a condenser, and a lens optical integrator (not shown).

The light beam transmitted through the polarizing plate 1 is guided to a condenser lens 2 to illuminate a pattern on a photomask (reticle) 3. The photomask 3 may be a normal mask having a light shielding portion and a light transmitting portion, or may be a phase shift mask. The figure shows a so-called Levenson-type phase shift mask in which a phase shifter 4 is provided at every other opening provided periodically.

The transmitted diffracted light from the photomask 3 is condensed and imaged by the projection optical system 5 to form an image of the mask pattern on the wafer 6. At or near the pupil position of the projection optical system 5, there is provided a slit filter 7 in which the area (opening) through which the exposure light is transmitted has a slit shape or a shape close thereto.

The polarizing plate 1 and the slit filter 7 are installed such that the plane of polarization of the polarized light formed by the polarizing plate 1 is perpendicular to the longitudinal direction of the slit filter 7. A synchronous control controller 8 is mounted so that the polarizing plate 1 and the slit filter 7 can be synchronously rotated about the optical axis while maintaining this positional relationship.

In such a configuration, when exposure is performed in the state shown in FIG. 1, the periodic pattern A long in the direction parallel to the polarization plane is transferred, and the periodic pattern B long in the direction perpendicular to the polarization plane is not transferred. At this time, the periodic pattern A is transferred in the TE mode as described above. Next, when the polarizing plate 1 and the slit filter 7 are rotated by 90 degrees and exposed, in this state, a long periodic pattern B is transferred in a direction parallel to the polarization plane, and the periodic pattern A is not transferred. At this time, the periodic pattern B is transferred in the TE mode as described above.

Although not shown in the figure, when a 45-degree pattern exists, the polarizing plate 1 and the slit filter 7 are further set to 45 degrees for further exposure. Even if the pattern is an oblique pattern other than 45 degrees, the polarizing plate 1, the slit filter 7
Is exposed by rotating by a corresponding angle.

FIG. 2 shows the result of simulating the transfer characteristics by the exposure method of this embodiment. The horizontal axis is the line width of the line and space pattern, and the vertical axis is the depth of focus. The depth of focus is defined based on the image contrast, and three types of resists capable of resolving with an image contrast of 40%, 50%, and 60% are assumed. Solid line is TE mode, broken line is TM
Mode, dash-dot line is unpolarized.

From these results, it can be seen that T compared to non-polarized light exposure.
It can be seen that the depth of focus is significantly improved in the E mode. In addition, since the depth of focus of the TM mode is lower than that of the non-polarized light, it is necessary to avoid imaging by light of the TM mode. From this, the effectiveness of the slit filter 7 became clear.

As described above, in the present embodiment, the polarizing plate 1 is provided in the illumination optical system, the slit filter 7 is provided at the pupil position of the projection optical system, and these are rotated in synchronization with each other, so that the periodic pattern is changed to TE. It is possible to transfer only in the mode. Therefore, the same resolving power and the same depth of focus can be obtained not only in a pattern in one direction but also in a pattern in all directions. can do.

The present invention is not limited to the embodiment described above. In the embodiment, a mercury lamp is used as a light source, but another lamp or a laser light source may be used. In particular, lasers whose light sources emit linearly or circularly polarized light,
In the case of emitted light, a half-wave plate or a quarter-wave plate can be used as a member for controlling the polarization state. Further, in the embodiment, the Levenson type phase shift mask is used as a mask, but the present invention is not limited thereto, and a normal mask, a halftone type phase shift mask, a rim type phase shift mask, a shifter only phase shift mask, etc.
Other phase shift masks may be used. In addition, various modifications can be made without departing from the scope of the present invention.

[0026]

As described above in detail, according to the present invention, a polarizing member and a slit filter having a slit-like or long opening in the direction perpendicular to the plane of polarization are rotated synchronously and rotated at a specific angle. By irradiating polarized light and performing multiple exposure, it is possible to transfer well even an actual device pattern in which both vertical and horizontal lines are mixed.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a result of simulating transfer characteristics by the exposure method of the present embodiment.

FIG. 3 is a diagram illustrating an example of an exposure apparatus in which illumination light is polarized light using a polarizing plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polarizer 2 ... Condenser lens 3 ... Photomask 4 ... Phase shifter 5 ... Projection optical system 6 ... Wafer 7 ... Slit filter 8 ... Synchronous control controller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-67914 (JP, A) JP-A-1-143216 (JP, A) JP-A-5-109601 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521

Claims (2)

(57) [Claims] 1. An exposure method for irradiating a photomask on which a pattern having long sides in at least two different directions is formed with polarized light and projecting it on a wafer via a projection optical system, comprising: At the imaging position of the polarized light, a slit-shaped opening having a long slit in the direction perpendicular to the polarization plane of the polarized light is provided, and a slit filter through which the polarized light of the polarized light is transmitted is disposed. Rotating the polarization plane and rotating the slit filter in synchronization with this, the photomask is rotated by the polarized light at each position where the long side direction of the pattern on the photomask is parallel to the polarization plane of the polarized light. An exposure method, comprising illuminating and exposing the pattern on the photomask to the wafer. 2. An exposure apparatus for illuminating a photomask on which a pattern having long sides in at least two different directions is formed by an illumination optical system and reducing and projecting the same onto a wafer via a projection optical system, wherein the illumination optical system A polarizing member for controlling the polarization state of the illumination light beam to the photomask, and a slit-shaped opening provided at a position where the polarized light transmitted through the polarizing member forms an image in the projection optical system. Having a slit filter through which the polarized light is transmitted, and the slit filter in a state where the longitudinal direction of the opening of the slit filter and the polarization plane of the light transmitted through the polarizing member are held to be perpendicular to each other. An exposure apparatus, comprising: a rotation mechanism for synchronously rotating a polarizing member about an optical axis.