JPH0992598A - Exposure system and manufacture of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance an exposure system in resolution to at least another pattern besides horizontal and lateral patterns. SOLUTION: A secondary light source (surface light source) formed on the light projection side of an optical integrator is so formed as to be composed of a center region, four peripheral regions located at the four corners of a rectangle (square in this case), and four intermediate regions each located between the adjacent peripheral regions, wherein the center region C is set 1/10 to 4/10 as high in light intensity as the peripheral region A, and the intermediate region B is set 35/100 to 65/100 as high in light intensity as the peripheral region A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for manufacturing semiconductor elements such as ICs and LSIs, image pickup elements such as CCDs, magnetic detectors such as magnetic heads, and display elements such as liquid crystal panels. Regarding

[0002]

2. Description of the Related Art This type of projection exposure apparatus illuminates an optical integrator composed of a fly's eye lens with light from a light source, and emits light from a secondary light source (surface light source) formed on or near the light emitting surface of the optical integrator. Then, a condenser lens irradiates the mask with the luminous flux of, and a projection optical system projects an image of the mask pattern onto the wafer. The light intensity distribution of the secondary light source at this time is a Gaussian distribution with a peak intensity on the optical axis (normal illumination), or a distribution with a zero intensity on the optical axis and an off-axis peak intensity (annular illumination). Is.

On the other hand, four apertures are provided off-axis on the light emitting surface side of the optical integrator, and an aperture stop is provided to shield the other portions from the light, thereby providing four apertures at positions corresponding to the four vertices of a square. ) By forming a surface light source exhibiting a light intensity distribution having a peak and irradiating the mask with the light flux from this surface light source (quadrupole illumination), it is possible to arrange parallel to the vertical and horizontal pieces of the square. The resolving power for vertical and horizontal lines extending in the direction is significantly improved.

[0004]

However, in a surface light source having a light intensity distribution having four peaks at the positions corresponding to the four vertices of a square, a direction intersecting both vertical and horizontal pieces of the square. The resolving power for an oblique pattern extending in the direction of, a pattern whose shape is close to a point, and a non-repetitive isolated pattern is not improved so much.

An object of the present invention is to provide a projection exposure apparatus capable of improving the resolution for at least one type of other patterns in addition to the vertical and horizontal patterns.

[0006]

According to the present invention, in a projection exposure apparatus for illuminating a fine pattern with a surface light source and projecting an image of the fine pattern by using diffracted light generated by the fine pattern, the surface light source comprises: It has a central region, four peripheral regions at positions corresponding to the four vertices of a quadrangle, and four intermediate regions between adjacent peripheral regions of the four peripheral regions. 10 of the light intensity of the surrounding area
-40%, the light intensity of the intermediate area is 35% of the light intensity of the peripheral area.
By setting the content to ˜65%, the above problem is solved.

In the present invention, the "intensity of the peripheral region" refers to the peak intensity of that region, but the intensity distribution of the peripheral region is not limited to the Gaussian distribution but may be a flat distribution.

[0008]

1 is a schematic view showing an embodiment of the present invention.

FIG. 1 shows a semiconductor device such as IC or LSI, C
1 shows a reduction projection type exposure apparatus that can be used to manufacture devices such as an image pickup device such as a CD, a magnetic detector such as a magnetic head, and a display device such as a liquid crystal panel.

In the projection exposure apparatus of FIG. 1, the light (i-line) from the light source unit 1 including a lamp is collimator lens 2.
The light from the secondary light source (surface light source) which is converted into parallel light by illuminating the optical integrator 3 composed of a fly-eye lens and formed at the position of the aperture stop 5 placed near the light exit surface of the optical integrator 3 Is irradiated onto the reticle 8 (mask) via the condenser lens 6 and the bending mirror 7, and the reduced projection optical system 9 projects a reduced image of the fine pattern of the reticle 8 onto the wafer 10.

The position of the aperture stop 11 of the projection optical system 9 and the position of the aperture stop 5 of the illumination optical system have a conjugate positional relationship (relationship between the object point and the image point), and the light source unit 1 without the reticle 8.
When light is supplied from the aperture stop 5, the light intensity distribution of the secondary light source formed in the aperture of the aperture stop 5 is also generated in the aperture of the aperture stop 11.

The reticle 8 and the wafer 10 are each held on a movable stage (not shown). Also, the reticle 8 is
Each has a vertical and horizontal pattern extending in a direction parallel to the vertical and horizontal sides of a quadrangle described later, and at least one of a diagonal pattern and a dot pattern.

In the vicinity of the light exit surface of the optical integrator 3, there is an ND (Neut) having a certain transmittance distribution.
Ral Density) filter 4 is provided, and the secondary light source formed at the position of diaphragm 5 via this ND filter is located at the central region and at the positions corresponding to the four vertices of a quadrangle (square here). It has four peripheral regions and four intermediate regions between adjacent peripheral regions of the four peripheral regions, and the light intensity of the central region is 10 to 40% of the light intensity of the peripheral region. The condition that the light intensity is 35 to 65% of the light intensity in the peripheral region is satisfied.

If this condition is not satisfied, the following problems will occur. Light intensity in the central area is 10% of light intensity in the peripheral area
If the light intensity is less than the above value, the clearness is deteriorated or the pattern image is deformed. If the light intensity in the central region exceeds 40% of the light intensity in the peripheral region, the depth of focus is not improved much. On the other hand, if the light intensity of the intermediate region is less than 35% of the light intensity of the peripheral region, the adaptability to the oblique pattern is lost, and if the light intensity of the intermediate region exceeds 65% of the light intensity of the peripheral region, the depth of focus is greatly improved. do not do.

In FIG. 2, 2 is formed at the position of the aperture stop 5.
The contour map which shows the light intensity distribution of a secondary light source is shown.

In FIG. 2, a contour line is a line connecting portions having the same intensity, and the intensity at the positions corresponding to the four vertices of the quadrangle (peak intensity of the peripheral region) is drawn as 100, and A is 2 A peripheral region of the secondary light source, B is an intermediate region of the secondary light source, C is a central region of the secondary light source, and r is a distance (radius) from the center of the secondary light source. The figure on the right side of the contour diagram is a very simplified drawing of the light intensity distribution of the secondary light source.

As shown in FIG. 2, in the light intensity distribution of the secondary light source, that is, the surface light source in this embodiment, the light intensity of the central region C is 25% of the light intensity of the peripheral region A, and the light intensity of the intermediate region B is The intensity is 50% of the light intensity of the peripheral area A. Further, the positions of the four peripheral regions C (where peak intensities occur) are positions at a distance r = 0.6 from the center of the secondary light source. The value of the distance r is such that the aperture of the aperture stop 11 which is larger than the aperture of the aperture stop 5 is back-projected to the aperture stop 5 side, and the distance from the center of the secondary light source to the position of the peripheral region C at the radius of this aperture image. Is a standardized value (aperture image radius = 1).

In the projection exposure apparatus of this embodiment, the light intensity distribution of the surface light source is such that the light intensity of the central region C is 25% of the light intensity of the peripheral region A and the light intensity of the intermediate region B is the light intensity of the peripheral region A. 50% of the intensity, having a central region, four peripheral regions at positions corresponding to the four vertices of a quadrangle, and four intermediate regions between adjacent peripheral regions of the four peripheral regions. , The light intensity of the central region is 10-40 of the light intensity of the peripheral region.
%, The light intensity in the middle area is 35% of the light intensity in the peripheral area.
Since the condition of being in the range of up to 65% is satisfied, a high resolution is exhibited with respect to the vertical and horizontal patterns on the reticle 8 and oblique patterns or dot patterns.

According to the projection exposure apparatus of this embodiment, the following two effects can be obtained at the same time. (1) The depth of focus can be extended compared to normal lighting. (2) It is possible to eliminate the proximity effect and the pattern limitation, which have been problems in the annular illumination and the quadrupole illumination.

First, the depth of focus of the effect (1) will be described. In this embodiment, the depth of focus is improved as compared with normal illumination. The following table shows 0.32 μmL / S at the image plane for each illumination method.
The depth of focus calculated for the pattern is shown. (Conditions: i-line, NA 0.6, aberration-free lens)

[0021]

[Table 1]

From this table, it is understood that the present embodiment has a deeper depth of focus than ordinary illumination, and a depth of focus approximately the same as that of ring illumination can be obtained.

Next, the proximity effect of effect (2) and the limitation of patterns will be described. FIG. 4 shows a result of performing a light intensity distribution simulation of an image for each illumination method using the reticle pattern shown in FIG.

In the annular illumination and the quadrupole illumination, the patterns are stuck to each other at the constricted portion,
In the normal lighting and the present embodiment, they are separated clearly. This is because the light from the center of the surface light source is effective in reducing the proximity effect.

As described above, in this embodiment, the depth of focus can be extended more than that of normal illumination, and the problems of annular illumination and quadrupole illumination can be solved or reduced. The features of this embodiment are summarized as follows.・ The depth of focus is larger than that of normal lighting, and the depth of focus is almost the same as that of annular lighting.・ Adjacent patterns do not stick to each other due to proximity effect.・ The isolated pattern becomes thin, but it is greatly reduced.・ It is possible to deal with diagonal patterns to some extent.・ High contrast.

In this embodiment, the light intensity in the central region is 25% and the light intensity in the intermediate region is 50%. In consideration of the above, a light intensity distribution other than this may be set.

For example, increasing the light intensity in the central region is effective in reducing the proximity effect and improving the contrast.
The disadvantage is that the depth of focus decreases. Similarly,
Increasing the light intensity in the intermediate region improves the adaptability to the oblique pattern in the 45 ° direction, but has the disadvantage of decreasing the depth of focus. When the light intensity of each region is adjusted in consideration of the balance of these effects, it is also possible to create an optimum effective light source shape that matches each circuit pattern depending on the shape of the circuit pattern to be printed. You can do the following: (1) If contact between adjacent patterns poses a problem, increase the light intensity in the central region. (2) If the shrinkage of the pattern in the longitudinal direction is a problem, reduce the light intensity in the central region. (3) For a pattern including many diagonal sides, the light intensity in the intermediate region is increased. (4) A pattern composed almost vertically and horizontally reduces the light intensity in the intermediate region.

The projection exposure apparatus of the above-described embodiment performs exposure while the reticle 8 and the wafer 10 are stationary or almost stationary with respect to the illumination optical system (1 to 7) and the projection optical system 9. However, the present invention is not limited to this. , The illumination optical system (1 to 7) of the reticle 8 and the wafer 10, and the projection optical system 9 can be applied to an apparatus for performing exposure while scanning. In the case of this scanning exposure, the illumination light that illuminates the reticle 8 is slit-shaped light that extends in the direction orthogonal to the scanning direction.

The projection exposure apparatus of each of the above-described embodiments uses an optical system mainly composed of a lens assembly as the projection optical system 9, but the projection optical system 9 includes a concave mirror or a concave mirror and lens assembly. Those provided with and can be used.

Although the projection exposure apparatus of each of the above embodiments uses a lamp as a light source, a KrF excimer laser (wavelength about 248 nm), ArF (wavelength 193n) are used as the light source.
m) Excimer laser or other type of light source may be used.

When an excimer laser is used as the light source, it is used as an illumination optical system by the applicant of the present invention.
Those described in Japanese Patent No. 39 can be applied. Since the illumination optical system described in this publication can change the intensity distribution of the light incident on the optical integrator in various ways, for example, using this illumination optical system, the 2nd invention of the present invention is applied to a certain reticle. A secondary light source (surface light source) is formed, and for another type of reticle, a light intensity distribution having the highest light intensity in the central region and a light intensity distribution showing a substantially uniform light intensity over the entire secondary light source may be formed. .

Next, an embodiment of a device manufacturing method using the projection exposure apparatus of each of the above embodiments will be described.

FIG. 5 shows a manufacturing flow of devices (semiconductor chips such as IC and LSI, liquid crystal panels and CCDs). In step 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (mask manufacturing), a mask (reticle 304) on which the designed circuit pattern is formed is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer (wafer 306) is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and 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 chips using the wafer created 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), the semiconductor device produced in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 6 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer (wafer 30
6) Oxidize the surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a resist (sensitive material) is applied to the wafer. In step 16 (exposure), the projection exposure apparatus exposes the wafer with an image of the circuit pattern of the mask (reticle 304). Step 17
In (development), the exposed wafer is developed. Step 18
In (etching), parts other than the developed resist are scraped off. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, a circuit pattern is formed on the wafer.

By using the manufacturing method of this embodiment, it becomes possible to manufacture a highly integrated device, which was difficult in the past.

[0036]

As described above, according to the present invention, it is possible to provide a projection exposure apparatus and a device manufacturing method capable of improving the resolving power for at least one other pattern in addition to the vertical and horizontal patterns.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a projection exposure apparatus of the present invention.

FIG. 2 is an explanatory diagram showing the intensity distribution of the secondary light source of FIG.

FIG. 3 is a diagram showing a fine pattern used for simulating an image intensity distribution.

FIG. 4 is a diagram showing a result of simulation.

FIG. 5 is a diagram showing a manufacturing flow of a semiconductor device.

FIG. 6 is a diagram showing the wafer process of FIG. 5;

[Explanation of symbols]

 100 secondary light source A peripheral portion of secondary light source B middle portion of secondary light source C central portion of secondary light source

Claims (21)

[Claims] 1. A projection exposure apparatus for illuminating a fine pattern by a surface light source and projecting an image of the fine pattern by using diffracted light generated by the fine pattern, wherein the surface light source includes a central region and four rectangular regions. 4 at the position corresponding to the vertex
One peripheral region and four intermediate regions between adjacent peripheral regions of the four peripheral regions, the light intensity of the central region is 10 to 40% of the light intensity of the peripheral region, and The light intensity of the intermediate region is 35 to 6 of the light intensity of the peripheral region.
A projection exposure apparatus characterized by being 5%. 2. The projection according to claim 1, further comprising intensity distribution changing means for changing a light intensity ratio of the peripheral area and the central area and a light intensity ratio of the peripheral area and the intermediate area. Exposure equipment. 3. The projection exposure apparatus according to claim 1, wherein a second light intensity distribution having the highest light intensity in the central region is formed. 4. The projection exposure apparatus according to claim 1, wherein the entire surface light source forms a third light intensity distribution showing a substantially uniform light intensity. 5. The fine pattern includes vertical lines and horizontal lines, and the vertices of the quadrangle are in directions different from the respective directions parallel to the vertical lines and the horizontal lines when viewed from the center of the surface light source. The projection exposure apparatus according to claim 1. 6. The projection exposure apparatus according to claim 5, wherein the quadrangle is a square. 7. The vertices of the quadrangle are approximately 4 in each direction parallel to the vertical and horizontal lines when viewed from the center of the surface light source.
6. The projection exposure apparatus according to claim 5, wherein the projection exposure apparatus is in a direction forming 5 degrees. 8. The projection exposure apparatus according to claim 1, wherein the surface light source is formed on or near a light exit surface of an optical integrator which is illuminated with light from the light source. 9. The projection exposure apparatus according to claim 8, wherein the optical integrator has a fly-eye lens. 10. The projection exposure apparatus according to claim 8, wherein the light source is a laser. 11. The projection exposure apparatus according to claim 10, wherein the laser is a KrF excimer laser. 12. The projection exposure apparatus according to claim 10, wherein the laser is an ArF excimer laser. 13. The projection exposure apparatus according to claim 8, wherein the light source is a lamp. 14. The projection exposure apparatus according to claim 8, wherein the optical system for projecting the fine pattern image has a lens assembly. 15. The projection exposure apparatus according to claim 8, wherein the optical system for projecting the fine pattern image has a concave mirror. 16. The optical system for projecting the fine pattern image has a lens assembly.
Projection exposure equipment. 17. A light intensity distribution in which the light intensity of the central region is 10 to 40% of the light intensity of the peripheral region and the light intensity of the intermediate region is 35 to 65% of the light intensity of the peripheral region. 9. The projection exposure apparatus according to claim 8, further comprising a filter having a predetermined transmittance distribution for forming. 18. The projection exposure apparatus according to claim 17, wherein the filter is provided on a light exit surface side of the optical integrator. 19. The exposure is performed while the mask on which the fine pattern is formed and the exposed object on which the image of the fine pattern is projected are stationary or substantially stationary with respect to the surface light source. 1. Projection exposure apparatus. 20. The projection according to claim 1, wherein exposure is performed while scanning the surface light source with a mask on which the fine pattern is formed and an exposure target on which an image of the fine pattern is projected. Exposure equipment. 21. A device manufacturing method including a step of transferring a device pattern onto an object to be exposed by using any one of the projection exposure apparatus according to claim 1.