JPH11307444A - Projection aligner and manufacture of device using the projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner and a method for manufacturing a device using such a projection aligner which is made less affected by speckles and flares caused by unnecessary diffracted light and scattered light by displaceably arranging a diffracting optical element in a projection optical system and thus satisfactorily correcting aberrations. SOLUTION: A projection aligner comprises an illumination optical system 1 for illuminating a reticle 3 with light from a light source, and a projection optical element 5 including a diffracting optical element 8 for projecting a pattern image of the illuminated reticle 3 onto a substrate. In this case, there is provided means 9 for displacing an optical relative positional relationship between the element 8 and the substrate, and the displacement of the optical relative positional relationship is effected during transfer of the pattern image of the reticle 3.

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 and a method of manufacturing a device using the same, and more particularly, to a device on a reticle or mask (hereinafter collectively referred to as a "reticle") by a projection optical system including a diffractive optical element. When manufacturing a device having a sub-micron or quarter-micron or less pattern such as an IC, LSI, CCD, or liquid crystal panel by projecting and exposing a pattern to a plurality of portions on a wafer by a step-and-repeat method or a step-and-scan method. It is suitable for.

[0002]

2. Description of the Related Art Recently, a diffractive optical element (Diffractive Optic) has been developed.
Many optical systems using an Al Element (hereinafter also referred to as “DOE” and “diffraction element”) have been proposed.

The advantages of the diffractive element are as follows. First, the diffractive element can be formed on a thin flat plate, so that it is easier to reduce the weight compared to the refraction element, and second, the pitch on the diffractive element is controlled. This makes it possible to correct aberrations as complicated as using an aspherical lens. Thirdly, since the sign of the dispersion characteristic of the diffractive element is opposite to that of the refractive element, the chromatic aberration generated by the refractive element Can be corrected with high accuracy.

[0004] As an example utilizing a diffraction element, for example,
SPIE Vol.1354 International LensDesign Conference
(1990) and JP-A-4-213421, JP-A-6-3
24262, JP-A-6-331194, U.S. Pat.
SP5,044,706 utilizes the phenomenon that the chromatic aberration of the diffractive optical element is in the opposite direction to that of a lens that is a normal refractive element, and the positive optical power is applied to the surface of the lens or the surface of the transparent plate. There has been proposed a method of reducing the chromatic aberration of the optical system by providing a diffractive optical element having the following.

A diffractive optical element in which each unit constituting the diffractive element is composed of two or more steps, a so-called binary optics element (for example, GJSwanson,
Technical Report 854, MIT Lincoln Laboratory, 14 Aug
1989 and GJSwanson, Technical Report 914, MIT Linco
ln Laboratory, 1 Mar 1991.

On the other hand, a projection exposure apparatus for manufacturing a semiconductor device in which a diffractive optical element is introduced into a projection optical system and various aberrations are corrected by the action of the diffractive element as compared with the prior art is also disclosed in, for example, Japanese Patent Laid-Open No.
No. 331941, JP-A-7-128590,
It has been proposed in Japanese Patent Application Laid-Open No. 8-17719.

The projection optical system of these projection exposure apparatuses has one
One or a plurality of diffractive optical elements are used to mainly correct longitudinal chromatic aberration and lateral chromatic aberration.

FIG. 9 is a schematic view of a main part of an exposure apparatus using a conventional diffraction element.

In FIG. 1, reference numeral 100 denotes an illumination device, and an excimer laser such as KrF is widely used at present as a light source used for the illumination device. The illuminating light 101 emitted from the illuminating device 100 is an original plate (reticle) 1 on which a circuit pattern is drawn.
Illuminate 02. Then, the illumination light 101 is diffracted, and a projection optical system 104 having a diffraction element 107 as a light flux 103.
Incident on. The luminous flux 105 emitted from the projection optical system 104 reaches a substrate (wafer) 106 coated with a resist, and the pattern on the reticle 102 is reduced on the wafer 106 by usually 1/4 or 1/5. Transferred with high precision. Here, the projection optical system 104 is composed of about 20 refractive lenses in order to realize advanced aberration correction, and the diffraction element 107 is used as a part thereof. FIG. 10 is a schematic sectional view of such a diffraction element 107.

FIG. 11 is an enlarged view of a part of FIG. 10, and here is shown as an 8-stage binary diffraction element. The surface of the diffraction element 107no has an essentially continuous shape (a so-called blazed shape) except for a discontinuous jump portion at the annular zone boundary. The manufacturing process of semiconductor devices can be applied to device manufacturing, and the above-mentioned document by GJ Swanson provides a detailed description of the manufacturing method. The formation of the eight-stage structure is realized by repeating the steps of resist application → exposure → development → etching three times using three different mask patterns. However, it is known that great care must be paid to the overlapping of the three mask patterns at that time. By forming the surface of the diffraction element in a stepped shape, there is an advantage that a structure with a fine pitch, which cannot be processed conventionally, can be manufactured with high accuracy. Therefore, by applying the binary diffractive element manufactured as described above to a projection optical system, a very high-performance exposure apparatus for manufacturing a semiconductor element is realized.

[0011]

However, in practice, it is difficult to accurately form the step shape on the surface of the diffraction element into a rectangular shape. The resulting shape is as shown in FIG. Causes include an overlay error when overlaying a plurality of mask patterns, and non-uniformity in the speed at which the surface is dug by etching. FIG.
3 is a light beam 110 for the diffraction element having the shape shown in FIG.
Represents the state of incidence. When an ideal staircase shape is manufactured, most of the light in the direction of a desired order (usually the first order) except for a part of the incident light beam which is distributed to a higher diffraction order. Is bent, but if there is a spike like 111, 112.113 on the surface as shown in FIGS. 12 and 13, a large amount of scattered light 114, 115,
116 occurs. These lights interfere with each other in a complicated manner on the wafer 106 and become noise components with respect to the original circuit pattern image as a speckle pattern. Therefore, there is a problem that the imaging characteristic of the projection optical system is largely deteriorated. This is the biggest problem when applying a diffraction element to a high-precision imaging optical system such as a projection exposure optical system, not limited to the binary type.

Means for alleviating such problems include: averaging the speckle pattern with a light source having a wide wavelength bandwidth; and coherence to reduce the degree of coherence between adjacent points on the circuit pattern. Parameter σ (Sigma)
・ Use a resist whose reaction progresses non-linearly with respect to the amount of incident light to prevent the speckle pattern from being transferred to the resist. A sufficient effect cannot be obtained.

According to the present invention, the diffractive optical element is arranged at an appropriate position in the projection optical system, and the optical relative position between the diffractive optical element and the wafer is within the time required for transferring the circuit pattern image on the reticle surface. By displacing the relationship, it is possible to minimize the occurrence of speckle and uneven exposure due to unnecessary diffracted light and scattered light generated from the diffractive optical element, and to manufacture a projection exposure apparatus capable of easily obtaining high optical performance and a device using the same. The purpose is to provide a method.

[0014]

A projection exposure apparatus according to the present invention comprises: (1-1) an illumination optical system for illuminating a reticle with light from a light source, and projecting a pattern image of the illuminated reticle onto a substrate. A projection optical system including a diffractive optical element, a driving unit for displacing an optical relative positional relationship between the diffractive optical element and the substrate, Relative positional displacement,
The transfer is performed during the transfer of the reticle pattern image.

In particular, (1-1-1) the diffractive optical element is displaced in the optical axis direction.

(1-1-2) The substrate is displaced in the optical axis direction.

(1-1-3) An optical member disposed between the diffractive optical element and the substrate is displaced in an optical axis direction.

(1-1-4) Two or more of the diffractive optical element and the substrate, and at least two optical members disposed between the diffractive optical element and the substrate are displaced in the optical axis direction.

(1-1-5) The displacement of the optical relative positional relationship between the diffractive optical element and the substrate is performed within a range in which the imaging characteristic of the pattern image of the reticle is not impaired.

(1-1-6) The displacement of the optical relative positional relationship between the diffractive optical element and the substrate is caused by unnecessary diffracted light or scattered light generated from the diffractive optical element interfering on the wafer surface. It is characterized in that it is sufficient for averaging the intensity distribution of speckles generated due to such factors.

The method of manufacturing a device according to the present invention comprises the steps of: (2-1) using the projection exposure apparatus of the constitution (1-1) to project and expose a pattern on a reticle surface onto a wafer surface by a projection optical system; It is characterized in that devices are manufactured through a wafer development process.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a projection exposure apparatus according to a first embodiment of the present invention. This embodiment shows a case where the present invention is applied to a step-and-repeat or step-and-scan projection exposure apparatus for lithography of submicron or quarter micron or less.

In the figure, reference numeral 1 denotes a lighting device, which is a mercury lamp or K
A light beam from a light source such as an rF laser or an ArF laser is condensed and emitted as a uniform light beam. 2 is a lighting device 1
Reference numeral 3 denotes a reticle on which a circuit pattern is drawn. The light beam 4 diffracted by the pattern on the reticle 3 enters the projection optical system 5, passes through the diffractive optical element 8, and is guided as a light beam 6 onto the wafer 7. A photoresist is applied to the wafer 7, and a circuit pattern on the reticle 3 is transferred by exposure. Here, a diffraction element (diffraction optical element) 8 is arranged in the optical path of the projection optical system 5, for example, near the stop. On the surface of the diffraction element 8,
A lattice having a staircase structure is formed by the conventional manufacturing method, and the shape is not an ideal lattice shape due to the influence of an error at the time of manufacturing, as described with reference to FIGS. In the present embodiment, a driving mechanism (driving means) 9 is provided around the diffraction element 8, and the position of the diffraction element 8 in the optical axis direction 11 can be changed by drive control from a controller 10. ing.

FIG. 2 shows an example of a pattern on the reticle 3. FIG. 2 shows the amplitude transmittance of light, and schematically shows a part of a complicated circuit pattern.

FIG. 3 shows an optical image (reticle pattern image) of a pattern on the reticle 3 formed on the wafer 7 by an ideal projection optical system. Here, “ideal” means that the projection optical system 5 as a whole is aberration-corrected with high accuracy, and that the diffraction element 8 does not generate scattered light as described with reference to FIG. However, actually, scattered light is generated from the diffraction element 8, and the light intensity distribution formed on the wafer 7 is as shown in FIG.

In FIG. 4, reference numeral 20 denotes the light intensity corresponding to the original circuit pattern. 21 is a pattern whose intensity changes abruptly in position compared to the light intensity 20 of the pattern,
This is a so-called speckle pattern. Since the resist is exposed in areas where the speckle intensity is strong,
A pattern originally not existing on the reticle is transferred onto the wafer. This poses a serious problem when transferring a circuit pattern with high accuracy.

In general, it takes about 0.5 seconds to print a pattern on a reticle onto a wafer at a time (since a predetermined amount of energy must be accumulated to expose a resist). Exposure does not end instantly. Considering the speckle pattern 21, if a configuration is possible in which the distribution fluctuates during the exposure time, a portion having a particularly large intensity can be eliminated by the averaging effect.

In this embodiment, the speckle pattern due to averaging is eliminated by moving or vibrating the diffraction element 8 in the direction of the optical axis (the direction of the arrow 11 in FIG. 1) within one exposure time. I have.

FIGS. 5A and 5B are diagrams illustrating the change of the speckle pattern when the diffraction element 8 is changed in the optical axis direction. In FIG. 5A, reference numeral 22 denotes a speckle pattern formed on the wafer when the diffraction element 8 is arranged at the position A. In FIG. 5B, reference numeral 23 denotes a speckle pattern formed at the wafer position when the diffraction element 8 is arranged at the position B. Here, the position A of the diffraction element 8
And the amount of displacement of the position B in the optical axis direction is represented by Δ. Since the position where the diffraction element 8 is placed and the position where the wafer 7 is placed are not in an optically conjugate relationship, the diffraction element 8
The speckle pattern generated due to the scattered light generated from the laser beam greatly changes due to a change in the optical relative positional relationship between the diffraction element 8 and the wafer 7. In the figure, when comparing the distribution of the speckle patterns 22 and 23, the influence appears as a difference in the position of the peak intensity.

FIGS. 6A and 6B show changes in the light intensity distributions 24 and 25 of the reticle pattern image formed on the wafer 7 when the diffraction element 8 is similarly varied. Since the reticle 3 and the wafer 7 are originally in an optically conjugated positional relationship, when a part of the members constituting the projection optical system 5 fluctuates, the influence of aberrations caused by the fluctuation is large. Although the characteristics of the optical image deteriorate to some extent, the position of the optical image does not greatly change. In particular, when the diffraction element 8 moves in the optical axis direction, the optical image fluctuates only in the defocus direction (optical axis direction), and does not fluctuate in a plane orthogonal to the defocus direction (on the wafer surface). Here, the movement amount of the circuit pattern image in the defocus direction naturally depends on how to select the magnitude of the shift amount Δ.

Therefore, in the present embodiment, the magnitude of the deviation amount Δ is determined as follows. First, the range in which the fluctuation of the circuit pattern image on the reticle is substantially negligible, that is, the difference between the light intensity distributions 24 and 25 of the circuit pattern image in FIG. 6 is negligible, and at the same time, the speckle as described in FIG. The range is set such that the fluctuations of 22 and 23 appear largely. Since the position of the diffraction element 8 is sensitive to the distribution of the speckle pattern and not sensitive to the pattern on the reticle, such a selection becomes possible. More precisely, it is determined in consideration of the configuration data of the projection optical system 5 and the size of the scattered light generated from the diffraction element 8, but a typical value is 1
It is known that the thickness is about 10 μm to about 10 μm. In order to completely average the speckle pattern, the diffraction element 8 may be moved up and down a plurality of times with an amplitude of Δ within one exposure time. The driving of the diffraction element 8 is performed by the controller 1.
0 controls the driving mechanism 9. The drive mechanism 9 includes an actuator such as a piezo element or an ultrasonic motor, and moves the diffraction element 11 with high accuracy by a signal from the controller 10.

FIGS. 7A and 7B show the light intensity distribution (20 & 21) on the wafer when the speckle pattern averaging function is turned off and the light intensity distribution when the function is turned on in this embodiment. It is explanatory drawing of the comparison of 30. In the light intensity distribution 30, the speckle pattern is averaged,
It can be seen that the background component is uniform as a whole. The light intensity of the background component is small,
As a result, the resist is not exposed, so that only the circuit pattern on the reticle can be accurately transferred to the resist.

Recently, instead of collectively transferring the pattern on the reticle onto the wafer, the reticle is illuminated with an illumination light beam having a slit shape, and the reticle and the wafer are scanned in a predetermined direction at a predetermined speed. A so-called scanning projection exposure apparatus that transfers the entire pattern on a reticle has begun to spread, but the present embodiment can be similarly applied to such a scanning projection exposure apparatus.

In the above description, only the diffraction element used in the projection optical system is changed in the optical axis direction. However, the essence of the present invention is to change the relative positional relationship between the diffractive optical element that is the source of the scattered light and the wafer on which the resist is applied within one exposure time. Therefore, the same effect can be obtained even if the stage on which the wafer is mounted is changed in the optical axis direction. Alternatively, the same effect can be obtained by changing the optical member existing between the diffractive optical element and the wafer.

FIG. 8 shows a configuration in which the refractive element 40 among the refractive elements constituting the projection optical system 5 is made variable. Further, a configuration in which the wafer 7 is moved in the optical axis direction is shown.
In the method of changing the refractive element 41 between the reticle 3 and the diffractive optical element 8 that does not exist between the diffractive optical element 8 and the wafer 7 in the optical axis direction, the effect of reducing the speckle is reduced. It is possible enough.

In this embodiment, an example has been described in which one diffraction element is arranged at or near the aperture stop position of the projection optical system. However, two or more diffraction elements may be used, and one diffraction element between these diffraction elements may be used. One or two or more relative positional relationships may be changed.

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

FIG. 14 is a flowchart for manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

Step 1 (circuit design) in this embodiment
Now, we will design the circuit of the semiconductor device. 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
The (wafer process) is called a pre-process, 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 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. 15 is a detailed flowchart of the wafer process in step 4 described above.

Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface.

In step 13 (electrode formation), electrodes are formed 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.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), unnecessary resist after etching is removed.

By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, a highly integrated semiconductor device can be easily manufactured.

[0048]

According to the present invention, as described above, the diffractive optical element is arranged at an appropriate position in the projection optical system, and the diffractive optical element is placed within the time required for transferring the circuit pattern image on the reticle surface. A projection exposure apparatus that can easily obtain high optical performance by displacing the optical relative positional relationship with the wafer to minimize the occurrence of speckles and uneven exposure due to unnecessary diffracted light and scattered light generated by the diffractive optical element. And a device manufacturing method using the same.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an amplitude transmittance of a pattern on a reticle.

FIG. 3 is an explanatory diagram of an ideal optical image of a circuit pattern formed on a wafer.

FIG. 4 is an explanatory diagram of an influence of a speckle pattern on a wafer surface.

FIG. 5 is an explanatory diagram of a relationship between a position of a diffraction element and a speckle pattern.

FIG. 6 is an explanatory diagram of a relationship between a position of a diffraction element and a pattern on a reticle.

FIG. 7 is an explanatory diagram of an optical image before and after averaging a speckle pattern.

FIG. 8 is a schematic diagram of averaging a speckle pattern by means other than a diffraction element.

FIG. 9 is a schematic view of a projection exposure apparatus having a conventional diffraction element.

FIG. 10 is a schematic cross-sectional view of a diffraction element in an ideal state.

FIG. 11 is an enlarged view of a cross section of a diffraction element in an ideal state.

FIG. 12 is a sectional view of a diffraction element actually formed.

FIG. 13 is an explanatory diagram of generation of scattered light from a diffraction element.

FIG. 14 is a flowchart of a device manufacturing method of the present invention.

FIG. 15 is a flowchart of a device manufacturing method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 illumination device 2 illumination light 3 reticle (mask) 4 light beam 5 projection optical system 6 light beam 7 wafer 8 diffractive element 9 driving device 10 controller 11 moving direction of diffractive element

Claims (8)

[Claims] 1. A projection exposure apparatus comprising: an illumination optical system that illuminates a reticle with light from a light source; and a projection optical system that includes a diffractive optical element that projects a pattern image of the illuminated reticle onto a substrate. Driving means for displacing the optical relative positional relationship between the diffractive optical element and the substrate is provided, and the displacement of the optical relative positional relationship between the diffractive optical element and the substrate is changed during transfer of the reticle pattern image. A projection exposure apparatus. 2. The projection exposure apparatus according to claim 1, wherein said diffractive optical element is displaced in an optical axis direction. 3. The projection exposure apparatus according to claim 1, wherein said substrate is displaced in an optical axis direction. 4. An apparatus according to claim 1, wherein an optical member disposed between said diffractive optical element and said substrate is displaced in an optical axis direction. 5. The apparatus according to claim 1, wherein at least two of the diffractive optical element, the substrate, and optical members disposed between the diffractive optical element and the substrate are displaced in an optical axis direction. 1. A projection exposure apparatus. 6. The optical system according to claim 1, wherein the displacement of the optical relative positional relationship between the diffractive optical element and the substrate is performed within a range in which the imaging characteristic of the pattern image of the reticle is not impaired. 6. The projection exposure apparatus according to any one of claims 1 to 5, 7. The displacement of the optical relative positional relationship between the diffractive optical element and the substrate is caused by speckle generated by unnecessary diffracted light or scattered light generated from the diffractive optical element interfering on a wafer surface. 7. The projection exposure apparatus according to claim 1, which is sufficient for averaging the intensity distribution of the projection exposure. 8. After projecting a pattern on a reticle surface onto a wafer surface by a projection optical system using the projection exposure apparatus according to claim 1, the wafer is subjected to a developing process. A method for manufacturing a device, comprising manufacturing a device by using the method.