JPH0729816A - Projection aligner and fabrication of semiconductor element employing it - Google Patents

Abstract

PURPOSE:To transfer the pattern of a reticle easily with high revolving power onto the surface of a wafer by providing means for measuring the incident angle of a light beam, coming from a position conjugate to a secondary light source, to the surface of a substrate thereby monitoring the inclination angle of wafer main light beam accurately. CONSTITUTION:A light emitting section 1a, a second focal point 4, and the incident plane 6a of an optical integrator 6 are substantially in a conjugate relationship. A masking blade 10, a reticle 12, and a wafer 15 are also in a conjugate relationship. Furthermore, the diaphragm and the pupil plane 14 of a projection optical system 13 are substantially in a conjugate relationship. A pattern on the surface of the reticle 12 is reduction projected onto the surface of the wafer 15. The inclination angle of wafer main light beam is determined from the distance between the centers of effective light source images on and off the optical axis formed on the pupil plane 14 of the projection optical system 13.

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 semiconductor element manufacturing method using the same, and more specifically, a so-called stepper, which is a semiconductor element manufacturing apparatus, appropriately illuminates a pattern on a reticle surface. High resolution can be easily obtained.

[0002]

2. Description of the Related Art The recent progress in manufacturing technology of semiconductor devices is remarkable, and accompanying it, the progress of fine processing technology is remarkable.
In particular, the optical processing technology has reached the level of microfabrication technology with submicron resolution, with the production of 1M DRAM semiconductor devices as the boundary. In many cases, a method of fixing the exposure wavelength and increasing the NA (numerical aperture) of the optical system has been used as a means for improving the resolution.

Recently, however, various attempts have been made to improve the resolution by changing the exposure wavelength from g-line to i-line and using an exposure method using an ultra-high pressure mercury lamp. In addition, various methods have been proposed for improving the resolution by using light of a shorter wavelength, which is represented by an excimer laser. It is known that the effect of using light having a short wavelength generally has an effect that is inversely proportional to the wavelength, and the depth of focus becomes deeper as the wavelength becomes shorter.

In addition to this, the present applicant changes the illumination method on the reticle surface, that is, changes the light intensity distribution (effective light source distribution) formed on the pupil surface of the projection optical system accordingly. Thus, an exposure method with a higher resolution and a projection exposure apparatus using the same are disclosed in, for example, Japanese Patent Application No. 3-28.
No. 631 (filed on February 22, 1991).

[0005]

There are various actual manufacturing processes of a semiconductor integrated circuit, such as a process requiring a high pattern resolution performance and a process not requiring such a pattern resolution performance. Further, the pattern shape formed on the reticle surface includes various horizontal and vertical patterns as well as oblique patterns. For this reason, various illumination methods (deformed illumination methods) are adopted according to the pattern shape.

On the other hand, the projection optical system used in the projection exposure apparatus comprises a bi-telecentric optical system or a single-sided telecentric optical system, and the principal ray (the center of the secondary light source, the center of the optical integrator, or the center of the diaphragm) on the wafer side. (Light ray passing through) is vertically incident (the incident angle of the principal ray at this time is hereinafter referred to as “wafer principal ray inclination angle”). At this time, unless the chief ray is incident vertically on the wafer, the image quality of the projected pattern image is deteriorated due to the influence of various aberrations such as distortion.

When a modified illumination method is used in which the illumination method is switched between various illumination methods depending on the pattern shape, as a method for eliminating the illuminance unevenness that occurs on the illuminated surface, for example, there is a method of operating the zoom function of the illumination system. At this time, the inclination angle of the chief ray of the wafer may not be vertical but may change variously.

However, the inclination angle of the chief ray of the wafer, which greatly affects the image performance, is accurately measured with a simple structure,
There was a problem that it was very difficult to monitor.

The present invention is a projection exposure apparatus and a projection exposure apparatus capable of easily exposing and transferring a pattern on a reticle surface onto a wafer surface with a high resolution by accurately monitoring a tilt angle of a chief ray of a wafer with a simple structure. It is an object of the present invention to provide a method for manufacturing a semiconductor device used.

[0010]

The projection exposure apparatus of the present invention is (1-1) illuminating a light beam from a light source with a lighting system to a pattern on a surface to be illuminated, and projecting the pattern onto a substrate surface with a projection optical system. The optical system that condenses the light flux from the light source to form a secondary light source when the image is projected and exposed on the optical system, and forms an image of the secondary light source in the vicinity of the pupil plane of the projection optical system; It is characterized in that it has a detecting means for measuring an incident angle of a light ray emitted from a position conjugate with the secondary light source on the substrate surface in a plane conjugate with the pupil plane of the projection optical system.

In particular, the detecting means detects a pinhole provided in the vicinity of the surface to be illuminated or a surface conjugate with the surface to be illuminated, and the light passing through the pinhole in order to detect light from the projection optical system. Having a detector provided in a plane conjugate with the pupil plane, and the detection means, in order to detect the light through the pinhole and the pinhole provided in the vicinity of the substrate surface, It is characterized in that it has a detector provided in a plane conjugate with the pupil plane of the projection optical system.

Further, as a method of manufacturing a semiconductor device of the present invention, (1-2) a light flux from a light source is condensed by an illumination system to illuminate a pattern on a reticle surface, and the pattern is projected on a wafer by a projection optical system. After the wafer is projected on the surface and exposed to light, when the wafer is subjected to a developing process to manufacture a semiconductor device, the illumination system collects a light beam from the light source to form a secondary light source,
An image of the secondary light source is formed in the vicinity of the pupil plane of the projection optical system, and the detection means provided in a plane conjugate with the pupil plane of the projection optical system detects the light rays emitted from a position conjugate with the secondary light source. The feature is that the incident angle to the substrate surface is measured.

In particular, the detecting means detects a pinhole provided in the vicinity of the surface to be illuminated or near a surface conjugate with the surface to be illuminated, and the light passing through the pinhole, in order to detect light from the projection optical system. Having a detector provided in a plane conjugate with the pupil plane, and the detection means, in order to detect the light through the pinhole and the pinhole provided in the vicinity of the substrate surface, It is characterized in that it has a detector provided in a plane conjugate with the pupil plane of the projection optical system.

[0014]

Embodiment 1 FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention.

In the figure, 2 is an elliptical mirror. Reference numeral 1 denotes a light emitting tube as a light source, which has a light emitting portion 1a of high brightness that emits ultraviolet rays, far ultraviolet rays, and the like. The light emitting unit 1a is arranged near the first focus of the elliptical mirror 2. Reference numeral 3 denotes a cold mirror, which is composed of a multilayer film and transmits most of infrared light and reflects most of ultraviolet light. The elliptic mirror 2 forms a light emitting portion image (light source image) 1b of the light emitting portion 1a in the vicinity of the second focal point 4 via the cold mirror 3.

Reference numeral 5 denotes a lens system, which is composed of a condenser lens, a zoom lens, and the like, and forms a light emitting portion image 1b formed in the vicinity of the second focal point 4 on the incident surface 6a of the optical integrator 6. Optical integrator 6
Is a plurality of minute lenses (fly's eye lens) 6-i (i = 1
To N) are two-dimensionally arranged at a predetermined pitch, and a secondary light source is formed near the exit surface 6b.

Reference numeral 7 denotes an aperture, which is a normal aperture and FIG.
The pupil plane 14 of the projection lens 13 as shown in (A) and (B)
It is composed of an aperture stop for annular illumination 7a for changing the above light intensity distribution, an aperture stop for quadrupole illumination 7b, and the like. Reference numeral 7p is an actuator, which switches the diaphragm 7. In this embodiment,
By changing the diaphragm 7, various illumination methods are switched.

Reference numeral 8 is a condenser lens (condenser lens). The condenser lens 8 is composed of a zoom system in order to correct illuminance unevenness on the reticle surface, which will be described later, when the illumination method is switched. A plurality of light beams emitted from the secondary light source near the emission surface 6b of the optical integrator 6 are condensed by the condenser lens 8, reflected by the mirror 9 and directed to the masking blade 10, and the surface of the masking blade 10 is uniformly illuminated. is doing. The masking blade 10 is composed of a plurality of movable light shielding plates so that an arbitrary opening shape is formed.

Reference numeral 11 denotes an imaging lens (condenser lens)
That is, the opening shape of the masking blade 10 is transferred to the surface of the reticle 12 as the irradiation surface, and the necessary area on the surface of the reticle 12 as the irradiation surface is uniformly illuminated.

Reference numeral 13 is a projection optical system (projection lens),
The circuit pattern on the surface of the reticle 12 is reduced and projected onto the surface of the wafer (substrate) 15 placed on the wafer chuck. 1
Reference numeral 4 is a pupil plane of the projection optical system 13. The condenser lens 8 and the imaging lens 11 form an optical system that forms an image on the exit surface 6b on the pupil plane 14 of the projection optical system 13.

In the present embodiment, the light emitting portion 1a, the second focal point 4 and the incident surface 6a of the optical integrator 6 have a substantially conjugate relationship. Further, the masking blade 10, the reticle 12, and the wafer 15 are in a conjugate relationship.
Further, the diaphragm 7 and the pupil plane 14 of the projection optical system 13 have a substantially conjugate relationship.

In the present embodiment, with the above-described structure, the pattern on the surface of the reticle 12 is reduced and projected onto the surface of the wafer 15 by reduction projection exposure. Then, a semiconductor device is manufactured through a predetermined developing process.

In this embodiment, the inclination angle of the chief ray of the wafer is determined from the distance between the centers of the effective light source image on the optical axis and the off-axis effective light source image on the pupil plane 14 of the projection optical system 13.

Next, a method of measuring an effective light source image on the pupil plane 14 of the projection optical system 13 will be described.

In this embodiment, when measuring an effective light source image, the reticle 12 is moved away from the optical path, or a so-called dummy reticle made of glass having the same thickness as the reticle and transmitting light is attached. Further, the wafer 15 is also moved out of the optical path.

In FIG. 1, 101 is a pinhole placed near the position of the wafer 15 for measuring an effective light source image,
The pinhole 101 is configured so that the actuator 102 can freely move the effective light source image to a desired position. Reference numeral 100 is a detector for detecting an effective light source image, and is configured so that it can be moved by an actuator 103 as the pinhole 101 moves.

Due to the principle of the pinhole camera, the pupil plane 14
Image is formed on the surface of the detector 100. At this time, by shifting the detector 100 in the direction of the wafer optical axis 14a,
The size (magnification) of the effective light source image can be changed. In this way, the detector 100 provided on the plane conjugate with the pupil plane 14
To measure the distribution of the effective light source image.

In this embodiment, the position of the pinhole 101 is moved to measure the effective light source image at various positions on the axis and off the axis. Pinhole 101 at this time
The detector 100 is also moved in accordance with the movement of. The detector 100 is placed below the pinhole 101, and the size of the effective light source image increases toward the bottom.

The image of the effective light source to be measured is composed of the images of the individual fly's eye lenses constituting the optical integrator 6.

As the detector 100, for example, 2 such as CCD
If a dimension detector is used, the effective light source image distribution can be measured at one time. Further, the effective light source image distribution may be measured by scanning the inside of a plane parallel to the wafer 15 surface using a detector having a small measurement area.

The detector 100 is moved in a plane parallel to the wafer surface corresponding to the position of the pinhole 101 on the wafer 15. As a result, effective light source images can be measured at various positions on and off the axis.

In this embodiment, when obtaining an effective light source image, the diaphragm 7 in FIG. 1 is first replaced with a diaphragm 7c having a center mark as shown in FIG. 3B. At this time, the light coming from the center mark becomes the chief ray. The center of the effective light source image is obtained by measuring the position of the center mark with the detector 100. As the diaphragm 7c with a center mark, a cross-shaped wire is drawn with a wire or the like, or a thin glass with a center mark is used.

Further, the center of the effective light source image can be obtained without using a stop having a center mark. For example, the effective light source image is composed of the images of the minute lenses forming the fly-eye lens, and the opening of the elliptical mirror 2 is visible in the image of each minute lens. Since the center of the fly-eye lens and the center of the opening of the elliptical mirror 2 are substantially coincident with each other and the center of the opening of the elliptical mirror 2 is dark, the center of the effective light source image can be easily determined from this. You can

The tilt angle of the chief ray of the wafer is determined as follows.

In FIG. 3, the distance between the on-axis and off-axis pinholes 101 placed on the surface of the wafer 15 is represented by a,
Let b be the distance between the pinhole 101 and the detector 100, and measure the distance L between the centers of the effective light source images (images of the central diaphragm) formed by the respective pinholes.

At this time, the wafer principal ray tilt angle φ is determined by φ = tan ⁻¹ ((La−a) / b).

In this embodiment, the detector 100 measures not only the wafer principal ray tilt angle φ, but also the effective light source distribution / shape, the amount of light reaching the wafer (corresponding to the exposure amount), and the like.

For example, when obtaining the shape of the effective light source image, the major axis L1 or L2 of the effective light source image of FIG. 3B is measured and obtained. If a two-dimensional detector such as CCD is used, L1 and L2 can be measured at one time. Also, by using a detector with a small measurement area and moving it, L
The shape of the effective light source image can be measured even by measuring 1 and L2.

Although a high pressure lamp such as a mercury lamp is used as the light source 1 in this embodiment, an ultraviolet light source such as an excimer laser may be used.

FIG. 4 is a schematic view of a part of a second embodiment of the present invention. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

In this embodiment, the pinhole 100 is arranged near the reticle 12 surface instead of the wafer surface 15 and the effective light source image is measured by the detector 100 as compared with the first embodiment shown in FIG. They are different, and other configurations are the same.

In this embodiment, the pinhole 101 is moved in a plane parallel to the surface of the reticle 12 in the same manner as in Embodiment 1 of FIG. 1 to measure the effective light source images at various on-axis and off-axis positions. Then, the wafer principal ray tilt angle φ is obtained from this.
The detector 100 is also moved corresponding to the movement of the pinhole 101.

FIG. 5 is a schematic view of a part of a third embodiment of the present invention. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

This embodiment is different from Embodiment 1 in FIG. 1 in that a half mirror 104 is provided between the imaging lens 11 and the reticle 12.
Is arranged, and the effective light source image is measured by the pinhole 101 and the detector 100 by using the light flux reflected by the half mirror 104, and the inclination angle φ of the principal ray of the wafer is obtained. Are the same.

In FIG. 5, the pinhole 101 is arranged at a position substantially conjugate with the reticle 2. Then, in the same manner as in Example 1 of FIG. 1, the detector 100 measures an effective light source image by the principle of the pinhole camera. Pinhole 1
01 is moved in a plane optically parallel to the surface of the reticle 12 to measure effective light source images at various positions on and off the axis. The detector 100 is also moved corresponding to the movement of the pinhole 101.

In this embodiment, the tilt angle of the chief ray of the wafer cannot be directly measured. Therefore, by measuring the angle at which the principal ray is tilted at the position corresponding to the reticle, the angle at which the principal ray is incident on the wafer is determined. For example, in FIG. 3, at a certain wafer position, in order for the chief ray to be incident vertically, at a corresponding reticle position, the chief ray must be incident at an angle θ (this is because the ray tracing of the projection lens is skipped). It's easy to see). Therefore, the tilt angle of the chief ray of the wafer is obtained by measuring the deviation from this angle θ.

Also in this embodiment, the effective light source image measuring means measures not only the wafer principal ray tilt angle but also the effective light source distribution / shape, the amount of light reaching the wafer (corresponding to the exposure amount), and the like. . Next, an embodiment of a method of manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.

FIG. 6 shows a flow of manufacturing a semiconductor device (semiconductor chip such as IC or LSI, liquid crystal panel, CCD or the like). In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured.

On the other hand, in step 3 (wafer manufacture), 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 a lithography technique using the mask and the wafer prepared above.

The next step 5 (assembly) is called a post-process, which is a process of forming a semiconductor chip using the wafer manufactured in step 4, an assembly process (dicing, bonding), a packaging process (chip encapsulation). Etc. are included. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 7 shows a detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed 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 in the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer.

In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the above-described exposure apparatus. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been difficult to manufacture in the past.

[0054]

According to the present invention, by setting each element as described above, the inclination angle of the chief ray of the wafer can be measured with high accuracy, and various patterns on the reticle surface can be easily formed on the wafer surface with high resolution. It is possible to achieve a projection exposure apparatus capable of performing exposure and transfer onto a substrate and a method for manufacturing a semiconductor device using the same.

In particular, the inclination angle of the chief ray of the wafer, which greatly affects the image performance of the projected pattern image, can be accurately monitored. Particularly in an illumination system having a plurality of illumination modes having a zoom lens function, a prism exchanging function, an aperture exchanging function, etc., it is possible to monitor whether or not each of the illumination modes has a desired wafer chief ray tilt angle.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of the diaphragm shown in FIG.

FIG. 3 is an enlarged explanatory view of a part of FIG.

FIG. 4 is a schematic view of a main part of a second embodiment of the present invention.

FIG. 5 is a schematic view of a main part of a third embodiment of the present invention.

FIG. 6 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

FIG. 7 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

 1 Light source 2 Elliptical mirror 3 Cold mirror 5 Lens system 6 Optical integrator 7 Aperture 7a Iris diaphragm 8 Condensing lens 9 Mirror 9a Half mirror 10 Masking blade 11 Imaging lens 12 Reticle 13 Projection optical system 14 Pupil surface 15 Reticle 100 Detector 101 Pinhole

Claims (6)

[Claims] 1. When a light beam from a light source is illuminated by an illumination system onto a pattern on a surface to be illuminated and the pattern is projected onto a substrate surface by a projection optical system for exposure, the illumination system reflects the light beam from the light source. An optical system that condenses light to form a secondary light source and forms an image of the secondary light source near the pupil plane of the projection optical system, and the secondary light source in a plane conjugate with the pupil plane of the projection optical system. And a detection unit that measures an incident angle of a light beam emitted from a conjugate position with the substrate surface. 2. The projection means of the projection optical system for detecting a pinhole provided in the vicinity of the illuminated surface or near a surface conjugate with the illuminated surface and light passing through the pinhole. The projection exposure apparatus according to claim 1, further comprising a detector provided in a plane conjugate with the pupil plane. 3. The detection means is provided in a plane conjugate with a pupil plane of the projection optical system for detecting a pinhole provided in the vicinity of the substrate surface and light passing through the pinhole. The projection exposure apparatus according to claim 1, further comprising: 4. A wafer is subjected to a developing treatment step after a light flux from a light source is condensed by an illumination system to illuminate a pattern on a reticle surface, the pattern is projected onto a wafer surface by a projection optical system and exposed. When manufacturing a semiconductor device via the illumination system, the illumination system collects a light flux from the light source to form a secondary light source,
Forming an image of the secondary light source near the pupil plane of the projection optical system,
A semiconductor element characterized in that an incident angle of a light beam emitted from a position conjugate with the secondary light source on the substrate surface is measured by a detecting means provided in a plane conjugate with the pupil plane of the projection optical system. Manufacturing method. 5. The projection means of the projection optical system for detecting a pinhole provided in the vicinity of the illuminated surface or near a surface conjugate with the illuminated surface and the light passing through the pinhole. 5. The method of manufacturing a semiconductor device according to claim 4, further comprising a detector provided in a plane conjugate with the pupil plane. 6. The detection means is provided in a plane conjugate with a pupil plane of the projection optical system for detecting a pinhole provided in the vicinity of the substrate surface and light passing through the pinhole. 5. The method for manufacturing a semiconductor device according to claim 4, further comprising a container.