JP3287745B2 - Exposure apparatus and device manufacturing method - Google Patents

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 devices such as ICs and LSIs, imaging devices such as CCDs, magnetic detectors such as magnetic heads, and display devices such as liquid crystal panels. And a device manufacturing method .

[0002]

2. Description of the Related Art A projection exposure apparatus of this type illuminates an optical integrator comprising a fly-eye lens with light from a light source, and emits light from a secondary light source (surface light source) formed on or near a light exit surface of the optical integrator. Is irradiated on the mask by the condenser lens, and the image of the pattern of the mask is projected on the wafer by the projection optical system. At this time, the light intensity distribution of the secondary light source may be a Gaussian distribution having a peak intensity on the optical axis (normal illumination), or a distribution having a zero intensity on the optical axis and having an off-axis annular intensity (annular illumination). It is.

On the other hand, the optical integrator has four off-axis apertures on the light exit surface side, and the other portions are provided with aperture stops for shielding light. ) By forming a surface light source showing a light intensity distribution having a peak, and irradiating a light beam from this surface light source to a mask (quadrupole illumination), the square parallel to each of the vertical and horizontal pieces of the square can be obtained. The resolving power for vertical and horizontal line patterns extending in the direction is greatly improved.

[0004]

However, in a surface light source exhibiting a light intensity distribution having four peaks at positions corresponding to the four vertices of a square, the direction intersecting both the vertical and horizontal pieces of the square The resolving power of an oblique pattern extending to a point, a pattern having a shape close to a point, and an isolated pattern which is not a repetition is not significantly improved.

An object of the present invention is to provide a projection exposure apparatus and a device manufacturing method capable of improving the resolution of at least one other pattern in addition to the vertical and horizontal patterns.
Is to provide a law .

[0006]

According to the present invention, a surface light source is provided.
The illuminated mask pattern is projected by the projection optical system.
When that, as the surface light source, and four intermediate region between the four peripheral region and the peripheral region adjacent said four peripheral regions at positions corresponding to the four vertices of the central region and the square And 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.
The above problem is solved by using a surface light source having

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

[0008]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 1 shows a semiconductor device such as an IC or LSI, C
1 shows a reduction projection type exposure apparatus that can be used to manufacture devices such as an image sensor 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 shown in FIG. 1, light (i-line) from a light source unit 1 including a lamp is collimated by a collimator lens 2.
Illuminates the optical integrator 3 composed of a fly-eye lens, and emits light from a secondary light source (surface light source) formed at the position of the aperture stop 5 near the light exit surface of the optical integrator 3 Is irradiated on the reticle 8 (mask) via the condenser mirror 6 via the bending mirror 7, and a reduced image of the fine pattern of the reticle 8 is projected on the wafer 10 by the reduction projection optical system 9.

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 are in a conjugate positional relationship (a relationship between an object point and an image point).
When light is supplied from the aperture stop, a light intensity distribution of the secondary light source formed in the opening of the aperture stop 5 also occurs in the opening of the aperture stop 11.

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

In the vicinity of the light exit surface of the optical integrator 3, an ND (Neut) having a certain transmittance distribution is provided.
ral Density) filter 4 is provided, and a secondary light source formed at the position of the diaphragm 5 via the ND filter is located at a position corresponding to the central region and four vertexes of a quadrangle (here, a square). It has four peripheral regions and four intermediate regions between the peripheral regions adjacent to 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 problem occurs. The light intensity in the central area is 10% of the light intensity in the peripheral area
If the light intensity in the central region is less than 40% of the light intensity in the peripheral region, the depth of focus does not improve 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 significantly improved. do not do.

FIG. 2 shows that the aperture stop 5 is formed at the position of the aperture stop 5.
FIG. 3 shows a contour map showing the light intensity distribution of the next light source.

In FIG. 2, the contour line is a line connecting portions having the same intensity, and the intensity at the position corresponding to the four vertices of the above-described rectangle (the peak intensity in the peripheral area) is 100, and A is 2 A peripheral area of the secondary light source, B represents an intermediate area of the secondary light source, C represents a central area of the secondary light source, and r represents a distance (radius) from the center of the secondary light source. The figure on the right side of the contour diagram is a diagram in which the light intensity distribution of the secondary light source is extremely simplified. In a second embodiment of the scanning type exposure apparatus of the present invention, the intensity modulating means includes a diaphragm means having a variable aperture diameter.
Or an interference filter having a variable tilt angle with respect to the exposure light , or an ND filter rotating plate having a transmittance that varies in the rotation direction.
There is a form provided with.

As shown in FIG. 2, the light intensity distribution of the secondary light source, that is, the surface light source in this embodiment 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 25%. The intensity is 50% of the light intensity in the peripheral area A. The positions of the four peripheral regions C (where the peak intensity occurs) are positions at a distance r = 0.6 from the center of the secondary light source. The value of this distance r is determined by projecting the aperture of the aperture stop 11 larger than the aperture of the aperture stop 5 back to the aperture stop 5 side, and calculating the distance from the center of the secondary light source to the position of the peripheral area C by the radius of the aperture image. Is normalized (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 rectangle, and four intermediate regions between neighboring 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 in the middle region is 35% of the light intensity in the peripheral region.
Since the condition of ６５65% is satisfied, high resolving power is exhibited for vertical and horizontal patterns on the reticle 8 and oblique patterns or point-like patterns.

According to the projection exposure apparatus of this embodiment, the following two effects can be obtained simultaneously. (1) The depth of focus can be extended as compared with normal illumination. (2) It is possible to eliminate the proximity effect and the limitation of the pattern, which are 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 higher than that of the normal illumination. The following table shows 0.32 μmL / S on the image plane for each illumination method.
7 shows the calculated depth of focus for the pattern. (Conditions: i-line, NA 0.6, stigmatic lens)

[0021]

[Table 1]

From this table, it can be seen that the depth of focus of this embodiment is deeper than that of normal illumination, and that the depth of focus is almost the same as that of annular illumination.

Next, the proximity effect of the effect (2) and the limitation of the pattern 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 annular illumination and quadrupole illumination, patterns are stuck together at a narrow part.
In the case of the normal illumination and this embodiment, it is clearly separated. This is because 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 made longer than that of normal illumination, and the problems of annular illumination and quadrupole illumination can be eliminated or reduced. The features of the present embodiment are summarized as follows. -Depth of focus is larger than that of normal illumination, and almost the same depth of focus as that of annular illumination can be obtained. -Adjacent patterns do not stick to each other due to proximity effect . · The orphaned pattern becomes narrower is greatly reduced. -It can respond to patterns in oblique directions to some extent.・ High contrast.

In this embodiment, the light intensity in the central region is 25% and the light intensity in the middle region is 50%. In consideration of the above, the light intensity distribution may be set to another value.

For example, increasing the light intensity in the central region is effective for reducing the proximity effect and improving the contrast.
There is a disadvantage that the depth of focus is reduced. Similarly,
Increasing the light intensity in the intermediate region increases the adaptability to a 45 ° oblique pattern, but has the disadvantage of reducing the depth of focus. If the light intensity of each area is adjusted in consideration of the balance of these effects, it becomes possible to produce an optimum effective light source shape suitable for each circuit pattern depending on the shape of the circuit pattern to be printed. You can do as follows. (1) If contact between adjacent patterns poses a problem, the light intensity in the central region is increased. (2) If contraction in the longitudinal direction of the pattern becomes a problem, lower the light intensity in the central region. (3) A pattern including many oblique sides increases the light intensity in the intermediate region. (4) An almost vertical and horizontal pattern lowers the light intensity in the middle area.

The projection exposure apparatus of the above embodiment performs exposure while the reticle 8 and the wafer 10 are stationary or almost stationary with respect to the illumination optical systems (1 to 7) and the projection optical system 9. The illumination optical system (1-7) and the projection optical system 9
On the other hand, the present invention can be applied to an apparatus that performs exposure while scanning the reticle 8 and the wafer 10 . In the case of this scanning exposure, the illumination light for illuminating the reticle 8 is slit-shaped light extending in a direction orthogonal to the scanning direction.

The projection exposure apparatus of each of the above embodiments uses an optical system mainly composed of a lens assembly as the projection optical system 9. The projection optical system 9 includes a concave mirror or a concave mirror and a lens assembly. The following 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) and ArF (wavelength: 193 n) are used as the light source.
m) Excimer lasers and other types of light sources may be used.

In the case where an excimer laser is used as a light source, the present applicant's Japanese Patent Application Laid-Open No. 5-476 is used as an illumination optical system.
No. 39 can be applied. The illumination optical system described in this publication can change the intensity distribution of light incident on the optical integrator in various ways. For example, using this illumination optical system, a certain reticle can be used in accordance with the present invention. A secondary light source (surface light source) is formed, and for another type of reticle, a light intensity distribution in which the central region has the highest light intensity or a light intensity distribution in which the entire secondary light source exhibits substantially uniform light intensity is preferably 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 flow of manufacturing 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 fabrication), a mask (reticle 304) on which the designed circuit pattern is formed is fabricated. On the other hand, in step 3 (wafer manufacture), 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), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. 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), a wafer (wafer 30
The surface of 6) is oxidized. 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. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a resist (sensitive material) is applied to the wafer. Step 16 (exposure) uses the projection exposure apparatus to expose the wafer using the circuit pattern image of the mask (reticle 304). Step 17
In (development), the exposed wafer is developed. Step 18
In (etching), portions other than the developed resist are scraped off. In step 19 (resist stripping), unnecessary resist 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 is possible to manufacture a highly integrated device which has been 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 of at least one type of other pattern in addition to the vertical and horizontal patterns.

[Brief description of the drawings]

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

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

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

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

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

FIG. 6 is a view showing a wafer process of FIG. 5;

[Explanation of symbols]

 100 Secondary light source A Peripheral part of secondary light source B Middle part of secondary light source C Central part of secondary light source

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (21)

(57) [Claims] 1. A pattern of a mask illuminated by a surface light source
In a projection exposure apparatus for projecting light from a projection optical system , the surface light source is located between four peripheral regions located at positions corresponding to four vertices of a central region and a square, and adjacent peripheral regions of the four peripheral regions. 10 and <br/> light intensity of the central region and four intermediate region of the light intensity of the peripheral region
A surface having a light intensity distribution that is 40% and the light intensity of the intermediate region is 35 to 65% of the light intensity of the peripheral region.
A projection exposure apparatus capable of forming a light source . 2. The projection according to claim 1, further comprising intensity distribution changing means for changing a ratio of a light intensity between the peripheral region and the central region and a ratio between a light intensity between the peripheral region and the intermediate region. Exposure equipment. 3. A second light source having a highest light intensity in the central region .
2. The projection exposure apparatus according to claim 1 , wherein a surface light source having a light intensity distribution can be formed . 4. The projection exposure apparatus according to claim 1, wherein the entire surface light source can form a surface light source having a third light intensity distribution indicating substantially uniform light intensity. 5. The method according to claim 1, wherein the fine pattern includes a vertical line and a horizontal line, and the vertices of the rectangle are different from the respective directions parallel to the vertical and 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 said quadrangle is a square. 7. The quadrangle has a vertex of approximately 4 in each direction parallel to the vertical and horizontal lines as viewed from the center of the surface light source.
6. The projection exposure apparatus according to claim 5, wherein the direction is 5 degrees. 8. The projection exposure apparatus according to claim 1, wherein the surface light source is formed at or near a light exit surface of an optical integrator illuminated with light from the light source. 9. An apparatus according to claim 8, wherein said optical integrator has a fly-eye lens. 10. The projection exposure apparatus according to claim 8, wherein said light source is a laser. 11. The projection exposure apparatus according to claim 10, wherein said laser is a KrF excimer laser. 12. The projection exposure apparatus according to claim 10, wherein said laser is an ArF excimer laser. 13. The projection exposure apparatus according to claim 8, wherein said light source is a lamp. 14. The projection exposure apparatus according to claim 8, wherein the optical system that projects the fine pattern image has a lens assembly. 15. An 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 apparatus according to claim 19, wherein the exposure is performed while the mask on which the fine pattern is formed and the object on which the image of the fine pattern is projected are stopped or almost stopped with respect to the surface light source. 1. A projection exposure apparatus. 20. The projection according to claim 1, wherein the exposure is performed while scanning the mask on which the fine pattern is formed and the object on which the image of the fine pattern is projected with respect to the surface light source. Exposure equipment. 21. Exposure of a wafer with a device pattern using any one of the projection exposure apparatuses according to claim 1.
And a step of developing the exposed wafer .