JPH1050594A - Aligner and projection aligner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align a reticle with a wafer at high accuracy by axially reversing one group of divided light beams, superposing them on the other group of divided light beams by a light-imposing means and irradiating the superposed beams on an alignment mark. SOLUTION: An illumination light from an optical source 5 is once divided into two beams, using an optical fiber 14. One of the beams is axially reversed in one direction and combined with the other beam by an illumination optical system 71, utilizing the Koehler illumination for providing a high-uniformity illumination beam (circular polarized) which is then incident on a polarized beam splitter 72, the light beam illuminated from the splitter 72 passes through a relay lens 73 and λ/4-plate 74 to provide a circularly polarized beam which is then irradiated on an alignment mark 1a on a wafer 1 through an objective 75, chromatic aberration correcting system 76, mirror 80 and reduction type projective lens 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning apparatus and a projection exposure apparatus using the same, and more particularly, to a mask surface or a reticle surface (hereinafter, referred to as a "reticle surface") as a first object in an exposure apparatus for manufacturing a semiconductor. This is suitable for performing relative alignment (alignment) of both when projecting a fine electronic circuit pattern such as an IC or LSI formed thereon onto a wafer as a second object.

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus for manufacturing semiconductors has been required to be able to project and expose a circuit pattern on a reticle surface onto a wafer surface with a high resolution as the density of integrated circuits increases. As a method of improving the projection resolution of the circuit pattern, for example, a method of increasing the NA of the projection optical system by fixing the wavelength of the exposure light or setting the exposure wavelength to g
There are many methods using a short-wavelength light beam from a line to an i-line, or using short-wavelength light such as 248 nm and 193 nm emitted from an excimer laser.

On the other hand, with the miniaturization of circuit patterns, it has been required to align a wafer with a reticle or mask on which an electronic circuit pattern is formed with high precision. Light that exposes the resist applied on the wafer surface when aligning the reticle and wafer (exposure light)
And non-exposed light (hereinafter, referred to as “non-exposure light”), for example, a light having a wavelength of 633 nm from a He—Ne laser.

The applicant of the present invention has proposed a positioning apparatus using non-exposure light, for example, in Japanese Patent Application Laid-Open Nos. 63-32303 and 2-130908.

On the other hand, as a method of detecting the position information of an alignment mark on a wafer surface, an image of the alignment mark is formed on an imaging means (CCD camera or the like) surface by an alignment detecting means, and the alignment mark image is processed. Accordingly, a method of detecting a shift amount from a predetermined position is often used.

[0006] For example, the applicant of the present invention disclosed in Japanese Patent Application Laid-Open No. Hei 3-61802 a system using non-exposure light and passing through a projection lens system.
An optical image of an alignment mark (wafer mark) on a wafer surface is formed on an image sensor such as a CCD camera using a so-called non-exposure light TTL method, and image information obtained from the image sensor is processed to form a wafer mark. An observation device that detects the position and performs alignment is proposed.

[0007]

Generally, the position information of an alignment mark provided on a wafer surface is observed by an observation means, and the position information of the alignment mark is detected by a detection means, so that the wafer and the reticle (or the observation means) are detected. Reference point)
It is important to illuminate the alignment mark on the wafer surface with a uniform illuminance distribution in order to perform high-accuracy alignment. If the illumination distribution of the alignment mark becomes non-uniform, it becomes difficult to detect the position information of the alignment mark image on a predetermined surface (on the CCD surface) with high accuracy, and as a result, the alignment accuracy decreases.

According to the present invention, by appropriately setting the configuration of an illumination optical system, illumination of an alignment mark on a wafer surface is made uniform, detection of position information of the alignment mark on a predetermined surface is performed with high accuracy, and a reticle is provided. It is an object of the present invention to provide an alignment apparatus suitable for manufacturing a semiconductor device capable of aligning a wafer and a wafer with high accuracy, and a projection exposure apparatus using the same.

[0009]

According to a first aspect of the present invention, there is provided an alignment apparatus comprising: (1-1) performing relative positioning between a first object and a second object on a predetermined surface of an alignment mark on the second object surface; In the positioning apparatus, the position information is detected by the alignment detecting means, the light beam from the light source is split into at least two light beams by the light splitting means, and one of the light beams is axis-reversed by the axis reversing means. It is characterized in that the light beam is superimposed on the other light beam by the superposing means and the alignment mark is illuminated with the superimposed light beam.

In particular, (1-1-1) the axis reversing means includes an image rotator.

(1-2) Position where relative positioning between the first object and the second object is performed by detecting position information on a predetermined surface of an alignment mark on the surface of the second object by an alignment detecting means. In the aligning device, the light beam from the light source is split into at least two light beams by the first light splitting device, and one of the light beams is axis-reversed by the first axis reversing device, and then superposed on the other light beam by the first light polymerization device. The superimposed light beam is split into at least two light beams by a second light splitting means, and one of the light beams is inverted by a second axis inverting means in a direction orthogonal to the axis inversion by the first axis inverting means. After that, the second light superimposing means overlaps the other light beam, and the superimposed light beam illuminates the alignment mark.

In particular, (1-2-1) the axis reversing means includes an image rotator.

[0013] The projection exposure apparatus of the present invention comprises: (2-1) the relative positioning of the first object and the second object by using the alignment apparatus of the constitutional requirements (1-1) or (1-2). After that, the pattern on the first object plane is projected and exposed on the second object plane by the projection optical system.

In the method of manufacturing a device according to the present invention, (3-1) the relative positioning between the reticle and the wafer is performed by using the alignment device according to (1-1) or (1-2). The device is characterized in that after the pattern on the reticle surface is projected and exposed on the wafer surface, the wafer is subjected to a developing process to produce a device.

(3-2) After the relative positioning between the reticle and the wafer is performed using the projection exposure apparatus of the constitutional requirement (2-1), the pattern on the reticle surface is projected and exposed on the wafer surface. The device is characterized in that the wafer is later manufactured through a development process.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. The figure shows light that does not expose the resist applied on the wafer (second object) (hereinafter referred to as “non-exposure light”), for example, light with a wavelength of 633 nm from a He-Ne laser or light from a halogen lamp with a wavelength of 590 nm. ~
An alignment target (alignment mark) on a wafer through a projection lens (projection optical system) using light restricted by a 660 nm transmission filter or the like (TTL system).
FIG. 2 is a schematic view of a main part when a position aligning device for detecting an image is applied to a projection exposure apparatus.

In FIG. 1, reference numeral 4 denotes an illumination system, which is a reticle (first object) on which a circuit pattern is formed by exposure light.
3 are illuminated. A projection lens (projection optical system) 2 transfers a circuit pattern on the reticle 3 surface to 1/10 of the circuit pattern on the wafer 1 surface.
Alternatively, the projection is reduced to 1/5. 1a is an alignment mark on the wafer 1 surface.

Next, the position information of the alignment mark 1a is detected, and the reticle 3 or the observation means (positioning microscope)
A method for performing relative alignment (alignment) with the above will be described.

Reference numeral 70 denotes an alignment microscope (microscope) serving as an alignment mark detecting means. The position of the alignment mark 1a on the wafer 1 in a plane perpendicular to the optical axis of the projection optical system 2 (in the X and Y planes). Information is being detected.

The alignment microscope 70 in the present embodiment
Detects the alignment mark 1a in one direction (for example, the Y direction) on the surface of the wafer 1. Although not shown, an alignment microscope for detecting the orthogonal direction (X direction) is also provided, and these enable measurement in the X and Y directions.

Next, the components of the alignment microscope 70 as the alignment detecting means will be described.

The light beam from the light source 5 is incident on the polarization beam splitter 72 via the fiber 14 as an illumination light beam (circularly polarized light) with good uniformity via an illumination optical system 71 using Koehler illumination described later. The luminous flux (P-polarized light) illuminated by the polarization beam splitter 72 is applied to a relay lens 73, λ
The light becomes circularly polarized light through the 板 plate 74, and illuminates the alignment mark 1 a on the wafer 1 via the objective lens 75, the chromatic aberration correction system 76, and the mirror 80, via the reduction projection lens 2.

The signal light reflected by the alignment mark 1 a on the wafer 1 passes through the projection lens 2, the mirror 80, the chromatic aberration correction system 76, the objective lens 75, and the λ / 4 plate 74 again to become S-polarized light. After that, the light enters the polarization beam splitter 72.

The signal light (S-polarized light) incident on the polarization beam splitter 72 passes through the polarization beam splitter 72, passes through a mirror 77 and an erector lens 78, and is incident on an image pickup device, for example, an image pickup surface 79a of a CCD camera 79. An image of the alignment mark 1a on the wafer 1 is formed thereon.

An image signal based on the alignment mark image from the CCD camera 79 is input to a computer (arithmetic means) 61 through a line. The computer 61 measures the position information of the alignment mark image. At this time, the position of the alignment mark 1a is measured as a relative shift amount with respect to a reference mark (not shown) in the microscope 70.

The wafer 1 is placed on a wafer chuck 21. The wafer chuck 21 is mounted on a θ-Z stage (driving means) 22 and attracts the wafer 1 to the chuck surface to thereby prevent the wafer 1 from various vibrations.
Position is not shifted. θ-Z stage 22
Is mounted on the tilt stage 23, and moves the wafer 1 up and down in the focus direction (the optical axis direction of the projection lens 2).

The tilt stage 23 is mounted on an XY stage 24, and corrects the warpage of the wafer 1 so as to minimize the warp of the wafer 1 with respect to the image plane of the projection lens 2. Further, the tilt stage 23 can be driven in the focus direction independently. The driving amount of the XY stage 24 is monitored by the bar mirror 7 and the laser interferometer 8 mounted on the tilt stage 23. The laser interferometer 8 transmits a measured value relating to the driving amount to the computer 6 through a line.

In this embodiment, a global alignment is used as a method of aligning the reticle 3 with the wafer 1 in terms of accuracy and throughput. That is, the alignment marks of several shots in the wafer 1 are measured, the magnification and orthogonality of the array of shots are obtained, the XY stage 24 is driven based on the calculated array grid, and the pattern on the reticle 3 surface is printed on the wafer 1. Is used.

Although the above alignment sequence has been described with reference to global alignment, the present invention is not limited to this. For example, the effects of the present invention can be applied to die-by-die alignment. In the above description of the alignment method, the TTL off-axis alignment method has been described. However, the present invention is not limited thereto. For example, the same applies to the TTL on-axis alignment method and the NON-TTL off-axis alignment method. As applicable.

Next, the incident light beam shown in FIG. 1 is divided into two, and one of the light beams is axis-inverted in one direction, and then combined with the other light beam to obtain an illumination light beam having good uniformity. The configuration of the system 71 and its effects will be described.

FIG. 2 is an enlarged explanatory view of the illumination optical system 71. In FIG. 2, the light beam from the light source 5 is guided to the fiber 14. The luminous flux emitted from the emission surface 14b of the fiber 14 is split into two through a lens 40 and various members described later, and then synthesized, and the aperture 47 is formed by a lens 47.
An image of the emission surface 4b of the fiber 14 is created in S2.

First, the light beam transmitted through the lens 40 enters a polarizing beam splitter (first light splitting means) 41a, and is split into two light beams of an s-polarized light 42s and a p-polarized light 42p. Among them, the s-polarized light 42s is rotated only in one direction by the image rotator 43 as the first axis reversing means via the mirror M1, and the polarized beam splitter 41b as the first superimposing means via the λ / 4 plate 45s. Incident on

On the other hand, the p-polarized light 42p passes through an optical path length correction plate 44 having the same optical path length as that of the image rotator 43, and enters the polarization beam splitter 41b via the mirror M2 and the λ / 2 plate 45p. ing.

Two λ / 2 plates 45 s and 45 p are arranged in the optical path in front of the polarizing beam splitter 41 b so that the s-polarized light 42 s and the p-polarized light 42 p can be adjusted to have the same light amount. The p-polarized light 42p transmitted through the polarizing beam splitter 41b and the s-polarized light 42s reflected from the s-polarized light 42s are changed to circularly polarized light via the λ / 4 plate 46. The light is condensed by the lens 47 and an image of the emission surface 41b of the fiber 14 is formed on the aperture stop AS2.

FIG. 3 is an explanatory diagram of the image rotator 43 shown in FIG. The figure shows a state in which only one direction of the incident light beam La is reversed. In FIG. 3, the incident light flux L
In FIG. 3A, only the X direction is inverted, and the Y direction is not inverted.

FIG. 2 shows a case where the present invention is applied to a detection system in which the alignment direction is only one direction, for example, only the X direction. The direction is aligned with the paper surface of the aperture stop AS2 in FIG. The vertical direction is the direction of alignment measurement. Therefore, the reversal direction of the image rotator 43 is a direction perpendicular to the paper surface (X direction), and FIG. 3 shows a state observed from the direction V shown in FIG.

Next, the optical function of the illumination optical system 71 of this embodiment will be described with reference to FIG. FIG. 4 is an explanatory diagram of the intensity distribution on the pupil plane in the configuration of FIG. FIG. 4 (A)
FIG. 4B is an explanatory diagram of an intensity distribution on an emission surface 14b of the fiber 14, FIG. 4B is an explanatory diagram of an intensity distribution on a pupil plane after being split into two by a polarizing beam splitter 41a, and FIG.
Explanatory drawing of intensity distribution on a pupil plane inverted in the direction, FIG. 4 (D)
FIG. 9 is an explanatory diagram of an intensity distribution on a pupil plane after being synthesized by the polarization beam splitter 41b.

FIGS. 4A to 4D show that the larger the value on the pupil plane, the higher the intensity at that position. If the direction of the arrow in FIG. 4A is the direction of the diffracted light of the detection system, the line symmetry of the intensity in the Y-axis direction indicates the uniformity of the detection system. In the actual FIG. 4 (A), the difference between the intensities 90 and 70, 10 and 50, and 80 and 40 becomes uniform. In this example, the intensity distribution is considerably asymmetric and poor in uniformity.

FIG. 4B shows an intensity distribution when the light beam is split into two light beams by the polarization beam splitter 41a of FIG. Now, the characteristics of the optical system, for example, the characteristics of the anti-reflection coating and the polarizing beam splitter and the ideal case without absorption of the glass material will be described with reference to FIGS. The value in FIG. 4B is obtained by halving the value in FIG. 4A.

FIG. 4C shows an intensity distribution in which only the measurement direction is inverted by the image rotator 43. FIG. 4 (D)
Indicates an intensity distribution synthesized by the polarization beam splitter 41b. This value is the value of the sum of FIG. 4B and FIG. 4C, and enables a highly uniform illumination state that is line-symmetric with respect to the measurement direction.

As described above, in the present embodiment, the illumination light is once divided into two light beams, and one light beam is
By combining the two light beams after reversing the axis in the direction, even if a fiber having poor optical performance such as the intensity distribution in FIG. 4A is used, a very uniform fiber as shown in FIG. Good lighting conditions are obtained.

In the present embodiment, an alignment detection system capable of high-accuracy alignment is achieved by eliminating the need for expensive optical components such as a high-precision optical component or a special hologram. I have.

FIG. 5 is a schematic view of a main part of an illumination optical system constituting one element of the positioning microscope according to the second embodiment of the present invention. In the first embodiment, the case has been described in which the alignment microscope, which is one alignment detection system, detects only one direction (for example, detects the position only in the Y direction).

In this embodiment, detection in two directions (position detection in the X direction and Y direction) is performed by one alignment microscope according to the same principle.

FIG. 5 shows a state in which two illumination optical systems 71 shown in FIG. 1 are arranged in series, and 71a and 71b are illumination optical systems, respectively. The illumination optical systems 71a and 71b have substantially the same configuration as the illumination optical system 71 of FIG.

In FIG. 5, the aperture stop A is switched from the fiber 14b to the aperture stop A.
It shows a part of the illumination optical system up to S3, and is divided into two illumination optical systems 71a and 71b. The front illumination optical system 71a has the same configuration as that shown in FIG. 2 described above, and the difference between the rear illumination optical system 71b and the front illumination optical system 71a is only the difference between the attitudes of the image rotators 43X and 53Y. is there.

The image rotator 43X as the first axis reversing means reverses the direction perpendicular to the plane of the drawing. FIG. 6A shows the superimposed state. The direction in the plane of the paper is reversed, and the superimposed state is shown in FIG.

In FIG. 5, reference numeral 51a denotes a second light splitting means, 51 denotes a second light overlapping means, 54 denotes an optical path length correction plate, and 55
s and 55p are λ / 2 plates, 56 is a λ / 4 plate, and 57 is a lens.

In this embodiment, the image rotators are arranged in two different directions as described above. As a result, the intensity distribution of the pupil plane is changed by the aperture stop AS2 as shown in FIG.
As shown in FIG. 8, the intensity distribution at the aperture stop AS3 is changed from the one symmetric with respect to the Y axis to the intensity distribution symmetric with respect to both axes as shown in FIG.

When detection in two directions (position detection in the X direction and Y direction) is possible with one alignment microscope, the image rotator 43R as shown in FIG.
Can be made two-dimensionally uniform by rotating the pupil plane as shown in FIG. 7B by rotating at least one rotation within the integration time of the imaging element that receives light.

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

FIG. 9 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, the circuit design of the semiconductor device will be performed. Step 2
In (mask production), a mask on which a designed circuit pattern is formed is produced.

On the other hand, in step 3 (wafer manufacture), a wafer 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 a semiconductor chip using the wafer prepared in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

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. 10 is a detailed flowchart of the wafer process in step 4 described above. First step 11
In (oxidation), the surface of the wafer is oxidized. Step 1
In 2 (CVD), an insulating film is formed on the wafer surface.

In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. Step 14 (ion implantation) implants ions into the wafer. Step 1
In step 5 (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 (developing), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

The use of the manufacturing method of the present embodiment makes it possible to easily manufacture a highly integrated semiconductor device.

[0061]

According to the present invention, by appropriately setting the configuration of the illumination optical system, the illumination of the alignment mark on the wafer surface is made uniform, and the position information of the alignment mark on the predetermined surface can be detected with high accuracy. Thus, it is possible to achieve a positioning apparatus suitable for manufacturing a semiconductor device and a projection exposure apparatus using the same, which can position the reticle and the wafer with high accuracy.

In particular, according to the present invention, a highly accurate optical component or an expensive optical component such as a dedicated hologram is not required for the illumination optical system for uniformly illuminating the alignment mark, and the wafer is precisely positioned. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a part of FIG. 1;

FIG. 3 is an explanatory view of an axis reversing means (image rotator) of FIG. 1;

FIG. 4 is an explanatory diagram of an intensity distribution on a pupil plane in FIG. 1;

FIG. 5 is a schematic view of a main part of a part of Embodiment 2 of the present invention.

FIG. 6 is an explanatory diagram showing a reversal state of a light beam according to the second embodiment of the present invention.

FIG. 7 is an enlarged explanatory view of a part of FIG. 5;

FIG. 8 is an explanatory diagram of an intensity distribution on a pupil plane in FIG. 6;

FIG. 9 is a flowchart of a method for manufacturing a semiconductor device according to the present invention.

FIG. 10 is a flowchart of a method for manufacturing a semiconductor device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wafer 1a Alignment mark 2 Reduction projection optical system 3 Reticle 4 Exposure illumination optical system 14 Fiber 21 Wafer chuck 22 θ-Z stage 23 Tilt stage 24 XY stage 40, 47, 50, 57 Lens 41a, 41b, 51a, 51b Polarization Beam splitter 42s, 52s s-polarized light 42p, 52p p-polarized light 43, 43X, 53, 53Y image rotator 44, 54 optical path length correction plate 45s, 45p, 55s, 55p λ / 2 plate 46, 56 λ / 4 plate 70 Positioning microscope 71 (71a, 71b) Illumination optical system 72 Polarizing beam splitter 73 Relay lens 74 λ / 4 plate 75 Objective lens 76 Chromatic aberration correction system 77, 80 Mirror 79 CCD camera AS2, AS3 Aperture stop

Claims (7)

[Claims] 1. A positioning apparatus for performing relative positioning between a first object and a second object by detecting position information on a predetermined surface of an alignment mark on a surface of the second object by an alignment detecting means. The light beam from the light source is split into at least two light beams by the light splitting means, and one of the light beams is axis-reversed by the axis reversing means, and then superimposed on the other light beam by the light polymerization means. An alignment device, which illuminates an alignment mark. 2. The alignment apparatus according to claim 1, wherein said axis reversing means includes an image rotator. 3. A positioning apparatus for performing relative positioning between a first object and a second object by detecting position information on a predetermined surface of an alignment mark on the second object surface by an alignment detecting means. Splitting the light beam from the light source into at least two light beams by the first light splitting means;
One of the light beams is axis-reversed by the first axis reversing means, and then superposed on the other light beam by the first light polymerization means. The superimposed light beam is split into at least two light beams by the second light splitting means. One of the light beams is converted into the first light by the second axis inverting means.
After the axis is reversed in a direction orthogonal to the axis reversal by the axis reversing means, the second light superimposing means is superimposed on the other light beam, and the superimposed light beam illuminates the alignment mark. Matching device. 4. The apparatus according to claim 3, wherein said axis reversing means includes an image rotator. 5. A pattern on the first object surface after performing relative positioning between a first object and a second object using the alignment device according to claim 1. Is projected and exposed on a second object plane by a projection optical system. 6. A pattern on the reticle surface is projected and exposed on the wafer surface after performing a relative positioning between the reticle and the wafer by using the positioning device according to any one of claims 1 to 4. And manufacturing the device through the developing process after the wafer is processed. 7. A step of developing the wafer after projecting a pattern on the reticle surface onto the wafer surface after performing relative positioning between the reticle and the wafer using the projection exposure apparatus according to claim 5. A device manufacturing method, wherein the device is manufactured via a device.