JP2001291659A - Projection optical device and aligner using the same, and method of manufacturing the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor malfunctions of a NA variable diaphragm of an aligner. SOLUTION: A diaphragmatic operation (opening and closing operation) is carried out, by rotating a cam disc 14 with a motor 16, to rotate each diaphragm blade 12 about a cam shaft 15. An encoder 18 for monitoring a defective rotation of the motor 16 and an encoder 21 for detecting directly the rotational displacement of the cam disc 14 are installed to monitor the malfunction of each diaphragm blade 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection optical apparatus used for an exposure apparatus for manufacturing a semiconductor device or the like, an exposure apparatus using the same, and a device manufacturing method.

[0002]

2. Description of the Related Art In recent years, with miniaturization of patterns and high integration of semiconductor chips, miniaturization has been promoted in a reduced projection type semiconductor exposure apparatus using a short wavelength light source such as an excimer laser. In the future, the miniaturization and high integration will be more and more advanced.

In order to make this ultra-fine processing technology possible, in a semiconductor exposure apparatus, the wavelength of exposure light used for exposure must be further reduced, and the NA (numerical aperture) of a projection optical system must be reduced to the limit. The challenge is to make it bigger.

However, for example, in shortening the wavelength of the above-mentioned exposure light, a KrF laser (wavelength: 246 nm), which is currently used as an excimer light, is designed using a super-resolution technique such as a Levenson or a phase shift mask. Exposure transfer with a line width shorter than the wavelength of 0.18 μm is possible. Since further miniaturization will proceed in the future, a shorter wavelength ArF laser (wavelength 193 nm)
Exposure technology using lithography is being put into practical use, but considering the rising initial costs due to running costs and the cost of glass materials for the optical elements that constitute the exposure optical system, it is now very expensive. turn into.

As one of the methods for solving this problem, there is a recently proposed fine processing technique using a multiple exposure method.

In the multiple exposure method, when one pattern is exposed on a wafer as a substrate to be exposed, different illumination conditions (reticle opening) are used by using a mask original (reticle) on which two drawing patterns are transferred. By performing multiple exposures at a numerical aperture NA and an illumination system aperture ratio σ), a coefficient k1 = 0.3 that determines the resolving power in the following equation can be secured. R (resolution) = k1 · λ (exposure wavelength) / NA

For example, even when a KrF laser is used for exposure light, exposure transfer of a semiconductor chip having a design rule of 0.1 μm can be performed when NA is 0.75.

In a conventional exposure apparatus, when a semiconductor chip is mass-produced, when one pattern is exposed and transferred,
Since the illumination condition of the exposure apparatus is fixedly maintained, the illumination condition is not changed during the wafer processing that is continuously performed, and the illumination condition setting is changed in accordance with the pattern when changing the exposure transfer pattern. Was about to be performed. Therefore, the NA variable stop mechanism of the projection optical system of the conventional exposure apparatus has a relatively simple configuration.

FIG. 7 shows an NA variable aperture mechanism used in a conventional exposure apparatus.
This is a typical NA variable aperture mechanism proposed by the present applicant disclosed in Japanese Patent Application No. 01845. The NA variable stop 110 is an annular fixed base 111 surrounding the optical path of the exposure light.
And a plurality of diaphragm blades 112 disposed thereon so as to overlap in the circumferential direction.
11 pivotally supported by a pivot 113 provided upright.

The cam disk 114 disposed on the diaphragm blade 112 reciprocates as shown by an arrow A, thereby simultaneously rotating all the diaphragm blades 112 around the pivot 113 as shown by a broken line. , The opening amount is adjusted. That is, the cam disk 114 is provided with the cam groove 1 for fitting the cam shaft 115 protruding from each of the aperture blades 112.
The entire aperture mechanism including the fixed base 111, the aperture blades 112, and the cam disk 114 is supported on the frame 101. Cam disk 11 by motor 116
4 is reciprocated, the camshaft 11 is rotated according to the amount of rotation.
Each of the aperture blades 112 is pivoted by a predetermined angle via 5, and the aperture operation, that is, the opening and closing operation of the aperture blades 112 is performed.

The rotational driving force of the motor 116 is transmitted to the cam disk 1 via the relay gear 116a and the hook gear 116b.
The light is transmitted to the motor 14 and its driving range is defined by a light shielding plate 117 attached to a rotation shaft 116c of the motor 116 and a light shielding type photo interrupter (not shown).

At the same time, the output of the encoder 118 linked to the rotating shaft 116c of the motor 116 is introduced to a controller 119 for controlling the motor 116, and the motor 116 is monitored for a rotation failure or the like.

The procedure for driving the NA variable aperture 110 is as follows. First, an initialization operation of the NA variable aperture mechanism is performed using the motor 116 and the light shielding plate 117. After the completion of the initialization operation, the encoder 118 is reset to set the desired NA.
A predetermined pulse is instructed to the drive driver of the motor 116 so that the diaphragm blade 112 moves to the position. The driving force of the motor 116 drives the cam disk 114 to rotate by a predetermined amount via the relay gear 116a and the rack gear 116b. At this time, the aperture blade 112 performs an arc motion along the locus of the cam groove 114a around the pivot 113 supported by the fixed base 111.

The encoder 118 confirms that the rotation of the motor 116 has not lost synchronism or the like. Note that a similar diaphragm operation is performed by a mechanism using a combination of a linear actuator and a linear encoder (see Japanese Patent Application Laid-Open No. 5-299321).

[0015]

However, according to the above-mentioned prior art, it is not possible to detect any trouble other than the rotation failure of the motor as the driving source, so that the diaphragm operation failure caused by the trouble other than the motor trouble. Occurs, in the semiconductor chip production process, besides confirming defects in the process of, for example, product inspection after exposure,
It was not possible to confirm that exposure was produced under the correct lighting conditions.

In the case where the resolution limit of a semiconductor exposure apparatus is to be improved by using a multiple exposure method in the future, frequent drive control of illumination conditions is required. The arranged NA variable aperture mechanism drives and controls a remarkable number of times compared to the conventional semiconductor chip production process. For this reason, it is required that the trouble detection of the NA variable aperture mechanism be managed quickly and with high reliability.

The present invention has been made in view of the above-mentioned unresolved problems of the prior art, and monitors the motor trouble and directly detects the amount of displacement of the aperture mechanism to improve the reliability of the NA aperture operation. It is an object of the present invention to provide a projection optical apparatus capable of improving productivity and greatly improving the yield of products such as semiconductor devices, an exposure apparatus using the same, and a device manufacturing method.

[0018]

To achieve the above object, a projection optical apparatus according to the present invention is a projection optical apparatus having an NA variable stop for controlling a numerical aperture of a lens barrel, wherein the NA variable stop is provided. A diaphragm mechanism comprising a plurality of diaphragm blades and an opening and closing drive member for opening and closing them, a motor for driving the opening and closing drive member, and a displacement detecting means for directly detecting a displacement of the diaphragm mechanism. It is characterized by the following.

Preferably, an encoder for monitoring the rotation of the motor is provided.

Preferably, the displacement detecting means has a detection encoder for detecting the amount of rotational displacement of the opening / closing drive member.

The displacement detecting means may have a scale and a photo interrupter for detecting the amount of rotational displacement of the opening / closing drive member.

[0022]

A displacement detecting means for directly detecting the displacement of the diaphragm mechanism including the diaphragm blades is provided so that even if the diaphragm operation is abnormal due to a trouble other than the motor trouble, it can be detected quickly.

Since all malfunctions of the NA variable aperture can be detected quickly and reliably, the yield of products such as semiconductor devices can be greatly improved.

Further, since the reliability of the aperture operation of the NA variable aperture is improved, there is an advantage that it can easily cope with a multiple exposure method in which the aperture mechanism is driven many times.

[0025]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an entire exposure apparatus including a projection optical apparatus according to the first embodiment. In this embodiment, a frame 1 of the exposure apparatus supports a lens barrel 2 as a projection optical apparatus.
The wafer W serving as a substrate to be transferred is moved by the wafer stage 3.
And move it to the desired position. The reticle R on which the pattern to be transferred to the wafer W is drawn is held on the reticle stage 4, and the alignment between the wafer W and the reticle R is performed by the alignment optical unit 5.
Exposure light for transferring the reticle pattern onto the wafer W is:
The illumination light is irradiated onto the wafer W from the illumination optical unit 6 which is an illumination optical system, via the lens barrel 2. An outer cylinder 7 supporting the reticle stage 4 is erected on the frame 1, and an NA variable stop 10 is disposed in the lens barrel 2 at a pupil position of an imaging optical system which is a projection optical device.

FIG. 2 shows an NA variable stop 10 arranged in the lens barrel 2, which is an annular fixed base 11 surrounding an optical path of exposure light for transferring a reticle pattern onto the wafer W.
And a plurality of diaphragm blades 12 disposed thereon so as to overlap with each other in the circumferential direction. Each diaphragm blade 12 is supported by a pivot 13 erected on a fixed base 11 so as to be pivotable.

The cam disk 14, which is an opening / closing drive member disposed on the aperture blade 12, reciprocates as shown by an arrow A in FIG. 2B, thereby simultaneously pivoting all the aperture blades 12. It is configured to be pivoted around as indicated by a broken line 13 to control the aperture of the diaphragm. That is, the cam disk 14 has a cam groove 14 a for fitting a cam shaft 15 protruding from each of the aperture blades 12, and the entire diaphragm mechanism including the fixed base 11, the aperture blade 12 and the cam disk 14 is mounted on the frame 1. Supported. When the cam disk 14 is reciprocated by the motor 16, the respective aperture blades 12 are pivoted by a predetermined angle via the cam shaft 15 in accordance with the amount of rotation, and the aperture operation, that is, the opening / closing operation of the aperture blades 12 is performed.

The rotational driving force of the motor 16 is transmitted to the cam disk 14 via the relay gear 16a and the hook gear 16b, and its driving range is defined by a light shielding plate 17 attached to the rotating shaft of the motor 16 and a light shielding (not shown). Defined by the type photointerrupter. At the same time, the output of the encoder 18 linked to the rotation axis of the motor 16 is introduced to the controller 19 for controlling the motor 16 to monitor the rotation failure of the motor 16 and the like.

Another sensor may be used in place of the light-blocking type photo interrupter.

A second rack gear 20 different from the rack gear 16b is fixed to the cam disk 14, and the second rack gear 20
, A detection encoder 21 serving as a displacement detection means for detecting the rotational position of the cam disk 14 is provided.

In the present embodiment, a rotary encoder is used, but an absolute type or an incremental type may be used.

The outputs of the encoders 18 and 21 are introduced into a controller 19 for controlling the rotation of the motor 16, and the rotation of the motor 16 is monitored by the encoder 18. The displacement of the diaphragm is detected, and the aperture of the diaphragm is directly monitored.

The procedure for driving the NA variable aperture 10 will be described below.

First, using the motor 16 and the light shielding plate 17,
The initialization operation of the NA variable aperture 10 is performed. After the initialization operation, the encoder 21 is reset and initialized.

Next, a predetermined pulse is commanded to the drive driver of the motor 16 so that the aperture blade 12 moves to a desired NA position. The driving force of the motor 16 is a relay gear 16a,
The cam disk 14 is driven to rotate by a predetermined amount via the rack gear 16b. At this time, the diaphragm blade 12 is
The circular motion is performed along the locus of the cam groove 14a about the pivot 13 on the upper side. In this drawing operation, the cam disk 14
The encoder 21 is provided for directly confirming that the drive of the controller has been performed normally.

The motor 16 for driving the aperture mechanism, the relay gear 16a, etc., and the encoder 21 are arranged outside the lens barrel 2. This is because if there is a problem with the NA variable aperture 10 and it is repaired and replaced, if there are many replacement parts in the lens barrel 2, even if it is a simple part defect, Since a split repair work of the lens barrel 2 occurs, as many parts as possible are arranged outside the lens barrel to simplify the work.

FIG. 3 shows a processing follow chart when an error occurs. First, the NA variable aperture 10 is commanded and driven by a predetermined amount set from the illumination conditions (step 2).
3). After the driving of the predetermined amount is completed, the displacement amount is detected by the encoder 21, and it is determined whether or not the detected amount is the predetermined amount (step 24). After this determination, if normal, exposure starts (step 25), and if abnormal,
Immediately, exposure stop is displayed (step 26).

According to the follow described above, if a trouble occurs due to some malfunction of the cam disk 14,
Even when the encoder 18 of the motor 16 is confirmed to be normal, if the change amount of the encoder 21 has not reached the predetermined amount, it is possible to immediately instruct the stop of the exposure.

In particular, in the case of the multiple exposure method, since the number of times of driving the NA variable aperture increases drastically, damage troubles due to wear of the aperture mechanism and the like are expected. Therefore, directly detecting the rotation failure or the like of the cam disk 14 by the encoder 21 and improving the reliability of the NA variable aperture operation greatly contributes to the improvement of the productivity of semiconductor devices and the like.

In the conventional example, the encoder is merely attached to the shaft of the motor, and therefore, only the abnormal operation of the motor can be detected. However, according to the present embodiment, only the abnormal operation of the motor is detected. Instead, since all troubles including troubles in the drive transmission system and troubles in the diaphragm mechanism can be detected, the reliability of the operation of the NA variable diaphragm is greatly improved.

As described above, errors can be detected immediately before exposure for all troubles of the NA variable aperture, so that the production is not carelessly continued after the troubles occur and the defective products are not mass-produced. Significant improvement in yield can be expected.

FIG. 4 shows a second embodiment. This is an NA variable stop 30 arranged at the pupil position of the projection optical system as in the first embodiment, and the cam disk 34 has a black-and-white striped scale 40 printed on its surface. . The motor 36 is a stepping motor as in the first embodiment.

Although the pitch of the scale 40 is set to be substantially equal to the amount that can be driven with the minimum resolution of the motor 36,
The relationship between the two is obtained from the specification value to be controlled.

The photo interrupter 41 includes a scale 40
The output is introduced to the controller 39, and when the NA variable aperture 30 is driven, the pattern detected by the photo interrupter 41 is counted to calculate the moving distance, and the cam distance is calculated. Disk 3
4 is to detect the rotation amount. Since the fixed base 11, the aperture blades 12, the pivots 13, the camshafts 15 and the like are the same as those in the first embodiment, they are denoted by the same reference numerals, and description thereof is omitted.

As for the driving procedure, as in the first embodiment, first, the motor 36 and the light shielding plate 37 are used to drive the NA.
The variable aperture 30 is initialized. After the initialization operation, the counter of the controller 39 is reset and initialized.

Next, a predetermined pulse is commanded to the drive driver of the motor 36 so that the aperture blade 12 moves to a desired NA position. The driving force of the motor 36 is a relay gear 36a,
The cam disk 34 is driven to rotate by a predetermined amount via the rack gear 36b. At this time, the diaphragm blade 12 is
A circular motion is made along the locus of the cam groove 34a around the upper pivot 13.

As in the first embodiment, not only the abnormal operation of the motor 36 can be detected by the encoder 38, but also all troubles including troubles in the drive transmission system, troubles in the throttle mechanism, and the like can be detected. .

In particular, since the rotational displacement of the cam disk 34 is directly detected by the scale 40, there is no transmission system until the position is detected. Further, since the photointerrupter 41 can be easily replaced from the outside of the lens barrel, the reliability and the speed can be further increased.

Next, an embodiment of the device manufacturing method will be described. FIG. 5 shows a manufacturing flow of a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (mask production), a mask (reticle) as an original on which the designed circuit pattern is formed is produced. In step 3 (wafer manufacturing), a wafer as a substrate is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. 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). . Step 6
In (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. 6 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes 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 expose a circuit pattern on the mask onto the wafer by printing. Step 17
In (development), the exposed wafer is developed. Step 18
In (etching), portions other than the developed resist image are scraped off. In step 19 (resist removal), the unnecessary resist after the etching is removed by a known substrate processing method. 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 conventionally difficult to manufacture.

[0052]

Since the present invention is configured as described above, the following effects can be obtained.

The exposed and transferred wafer is guaranteed to be exposed under a desired illumination condition, so that the yield in semiconductor chip production can be improved, and the manufacturing cost of semiconductor devices and the like can be greatly reduced. .

Further, there is an advantage that it is possible to cope with ultra-miniaturization by a multiple exposure method.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an exposure apparatus according to a first embodiment.

FIG. 2 shows the NA variable aperture of the apparatus of FIG. 1;
(A) is an exploded perspective view showing a state disassembled in the vertical direction,
(B) is a plan view.

FIG. 3 is a flowchart illustrating a method of driving an NA variable aperture.

FIG. 4 is a plan view showing an NA variable stop according to a second embodiment.

FIG. 5 is a flowchart showing a semiconductor manufacturing process.

FIG. 6 is a flowchart showing a wafer process.

FIG. 7 is a plan view showing an NA variable stop according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 frame 2 lens barrel 3 wafer stage 4 reticle stage 5 alignment optical unit 6 illumination optical unit 7 outer cylinder 10, 30 NA variable aperture 12 aperture blade 13 pivot 14, 34 cam disk 14 a, 34 a cam groove 15 cam axis 16, 36 motor 17, 37 Light shielding plate 18, 21, 38 Encoder 19, 39 Controller 40 Scale 41 Photo interrupter

Claims (6)

[Claims] 1. A projection optical apparatus having an NA variable stop for controlling a numerical aperture of a lens barrel, wherein the NA variable stop is constituted by a plurality of aperture blades and an opening / closing drive member for opening and closing these blades. And a motor for driving the opening and closing drive member, and a displacement detecting means for directly detecting a displacement of the diaphragm mechanism. 2. The projection optical apparatus according to claim 1, further comprising an encoder for monitoring rotation of the motor. 3. The projection optical device according to claim 1, wherein the displacement detecting means has a detection encoder for detecting a rotational displacement amount of the opening / closing drive member. 4. The projection optical device according to claim 1, wherein the displacement detecting means includes a scale and a photo interrupter for detecting a rotational displacement amount of the opening / closing drive member. 5. An exposure apparatus comprising: the projection optical device according to claim 1; and an illumination optical system for exposing a substrate via the projection optical device. 6. A device manufacturing method comprising a step of exposing a wafer by the exposure apparatus according to claim 5.