JPH08179513A - Aligner - Google Patents

Abstract

PURPOSE: To make it possible to easily and rapidly determine unequal illuminance and to correct the unequal illuminance at need. CONSTITUTION: A real reticle drawn with circuit patterns is inserted into an optical path after the correction of the unequal illuminance is executed in the absent state of the reticle (step 1). The illuminance in a position on a wafer corresponding to a light transparent part for measurement is measured (step 2). Whether the illuminance is uniform or not is decided by a permissible value in an arithmetic section (step 3). This flow is ended in the case of YES and a member for correcting the unequal illuminance is selected and its driving quantity and direction are calculated from the quantitative relation of the illuminance at the respective measurement points in the case of NO (step 4). The member for correcting the unequal illuminance is driven according to the instruction of the arithmetic section and the operation is returned again to the step 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus which projects and exposes a fine circuit pattern of a semiconductor element in the process of manufacturing the semiconductor element.

[0002]

2. Description of the Related Art In recent years, semiconductor device circuits have become more and more miniaturized, and the demands for higher resolution and wider depth for semiconductor exposure apparatuses have become even greater. Step-and-repeat type reduction projection exposure apparatus
There are various types of exposure equipment such as (stepper), mirror projection aligner, scan type exposure equipment, etc., but for any exposure equipment, the unevenness of the illuminance on the surface of the exposed substrate such as the wafer surface (illuminance Even if the pattern line width on the mask or reticle (hereinafter referred to as the reticle) is the same, the line width changes on the wafer surface due to the illuminance unevenness. Strict line width management is required for the manufacture of semiconductor devices, so it is very important to reduce the value of uneven illuminance.

Taking a stepper as an example, conventional illuminance unevenness measurement is performed in the following procedure.

1. Remove the reticle from the light path.

[0005] 2. The illuminance is measured by scanning the wafer surface with an illuminometer that can measure the illuminance of an area smaller than the entire illumination area.

3. Calculate the value of uneven illuminance.

However, even if the uneven illuminance is corrected after the above procedure, since the reticle is inserted in the optical path during the actual exposure, the light incident on the light shielding portion (Cr surface) of the reticle is reflected, Return light to the illumination optical system is generated. This return light is reflected again on the optical member of the illumination optical system,
The reticle will be illuminated. At this time, the light that has passed through the reticle and has reached the wafer surface is called flare light, and there is a problem in that the illuminance unevenness corrected after the above procedure is exacerbated again.

[0008]

Various methods of predicting and correcting the illuminance unevenness due to the flare light are conceivable, but the conventionally known method takes time because of complicated steps. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an exposure apparatus having a means for detecting uneven illuminance generated according to a transfer pattern of a reticle in a simple and short time, and an uneven illuminance detection method used in this exposure apparatus. To do. The present invention also provides
Another object of the present invention is a method of manufacturing a semiconductor device using the exposure apparatus and the uneven illuminance detection method of the present invention.

[0010]

In order to achieve the above object, the first invention of the present application is, in an exposure apparatus having an illuminance measuring means for measuring the illuminance of a plurality of measurement points on an exposed surface, a transfer pattern is formed. A light-transmitting portion that transmits exposure light is provided at at least one location of the exposed mask, the mask is placed at a predetermined position in the optical path of the exposure light, and the transfer pattern portion and the light-transmitting portion are exposed by the exposure light. Simultaneously illuminating, measuring the illuminance of the exposure light transmitted through the light transmitting portion at a plurality of measurement points on the surface to be exposed, the measurement value obtained as a result, the mask is present in the optical path of the exposure light. It is characterized in that the illuminance unevenness when detecting is detected. As a result, since it is not necessary to go through the complicated procedure of the related art, it becomes possible to easily detect the illuminance unevenness due to the flare light in a short time.

In the second invention of the present application, a light transmitting portion for transmitting exposure light is provided at least at one position of the mask on which the transfer pattern is formed, and the mask is placed at a predetermined position in the optical path of the exposure light. Simultaneously illuminating the transfer pattern portion and the light transmitting portion with exposure light, measuring the illuminance of the exposure light transmitted through the light transmitting portion at a plurality of measurement points on the exposed surface, and a measurement value obtained as a result. The uneven illuminance detection method detects the uneven illuminance when the mask is present in the optical path of the exposure light. As a result, since it is not necessary to go through the complicated procedure of the related art, it becomes possible to easily detect the illuminance unevenness due to the flare light in a short time.

A third invention of the present application is a method of manufacturing a semiconductor device using the exposure apparatus of the first invention of the present application or the illuminance distribution correction method of the second invention of the present application. By this method, the semiconductor element can be manufactured accurately.

[0013]

[Embodiment] An embodiment relating to detection and correction of illuminance unevenness will be described below.

FIG. 1 is a schematic diagram of a stepper that best illustrates the features of the present invention.

Reference numeral 1 is a light source that emits ultraviolet rays, such as a high pressure mercury lamp. The light source can be freely moved in the x, y, and z directions in the drawing by the actuators 101, 102, and 103.

Reference numeral 2 is an elliptical mirror. Reference numeral 2a is the first focal point, and the light emitting portion 1a of the light source 1 is placed near the first focal point 2a. The image 1b of the light emitting portion 1a placed near the first focal point 2a by the elliptical mirror 2 is formed near the second focal point 2b.

A cold mirror 3 reflects ultraviolet rays and transmits infrared rays. A shutter 4 determines the exposure time. A condenser lens 5 has a second focal point 2b.
The light from is made incident on an optical integrator 6 such as a fly-eye lens so as not to be blocked.

Reference numeral 7 denotes an aperture stop, which is an actuator 7
The illuminance unevenness correction diaphragm 7a can be switched by p. The illuminance unevenness correction diaphragm 7a changes the illuminance unevenness symmetrical with respect to the optical axis by utilizing the angle characteristic of the coating. That is, since the positions of the optical integrator emitting unit 6b and the reticle 14 are optically in the relationship between the pupil and the image, the optical integrator emitting unit 6b is not included.
The angle of the light ray at corresponds to the position on the reticle 14. Therefore, if the transmittance of a light ray incident at a large angle is made lower than that of a light ray incident at a small angle with respect to the optical axis, the illuminance at the periphery of the reticle 14 becomes lower than that at the center.

Reference numeral 8 denotes a condenser lens, which is a zoom lens for eliminating the uneven illuminance because the illuminance unevenness symmetrical with respect to the optical axis changes when the illumination method is switched.

Reference numeral 9 denotes a half mirror, which transmits most of the light but reflects a few percent of the light, and the illuminance is measured by the light measuring device 10. The information on the illuminance from this measuring device is sent to the calculator 24 and used for calculating the illuminance unevenness.

Reference numeral 11 is a reflecting mirror, and 13 is an image forming lens. A masking blade 12 is a field stop, which masks the illumination light according to various exposures. Since the masking blade 12 and the reticle 14 are held in a conjugate relationship by the condenser lens 13, the masking blade 12 can freely change the illumination range of the reticle 14.

Reference numeral 15 is a reticle stage. Reference numeral 16 is a drive device for taking in and out the reticle. A reticle changer 17 can store a plurality of reticles. The image of the reticle 14 is projected onto the wafer 2 by the projection optical system 18.
Projected to 0.

The projection optical system may be a dioptric optical system composed of only lenses, or may be a catadioptric optical system including a reflecting surface. Reference numeral 21 is a wafer chuck, and 22 is a wafer stage.

Reference numeral 23 denotes an illuminance measuring device for measuring the illuminance on the wafer surface, which can move together with the wafer stage 22. Therefore, it is possible to measure the illuminance for all the exposure areas on the wafer 17.

FIG. 2 is a schematic view of the reticle 14, which is the most characteristic part of this embodiment. The shaded area is the circuit pattern area, and P ₁ ,
It is characterized in that the light transmitting portions (illuminance measuring points) of P ₂ , P ₃ and P ₄ are provided. It goes without saying that the light-transmitting portion is selected in the area illuminated by the exposure light even outside the circuit pattern. In this embodiment, the circular light transmitting portion is used, but the shape is not limited. Further, the position thereof may be anywhere other than the circuit pattern portion, and the number thereof is not limited to four and may be any number.

FIG. 3 shows a procedure for correcting the uneven illuminance when the reticle 14 is used.

Each step of FIG. 3 will be described. At this time, it is assumed that the correction of the illuminance unevenness has been completed without the actual reticle.

Step 1 An actual reticle with a circuit pattern drawn is inserted into the optical path.

[0029] measuring the illuminance I ₁ ~I ₄ Step 2 measuring light transmitting portion P ₁ to P _4.

Step 3 In the calculation section, I ₁ = I ₂ = I ₃
= I ₄ is determined with a certain allowable value. Yes
In case of NO, in case of NO, I _n (n = 1, 2, 3,
From the quantitative relationship of 4), the illuminance unevenness correcting member is selected and its driving amount and direction are calculated.

Step 4 The illuminance unevenness correcting member is driven in accordance with the instruction from the arithmetic unit, and the process returns to Step 2.

As the illuminance unevenness correcting member in step 4,
A zoom lens 8 for correcting uneven illuminance symmetrical with respect to the optical axis, an uneven illuminance correction plate 7a capable of correcting both symmetric and asymmetric illuminance unevenness, and asymmetrical uneven illuminance by adjusting positions with actuators 101 and 102, and an actuator. There is a lamp 1 or the like that can correct symmetrical illuminance unevenness by adjusting the position at 103.

FIG. 4A shows a state in which the illuminance is adjusted without using the reticle so as to eliminate the unevenness. The vertical axis of FIG. 4 is the illuminance, and the horizontal axis is the coordinates with the center of the wafer as the origin. FIG.
Each step of is performed on the premise of this state.

FIG. 4B shows an illuminance distribution when the reticle is inserted in the state of FIG. From this figure, it can be seen that the flare light causes uneven illuminance. The illuminance distribution in step 1 of FIG. 3 shows this state.

FIG. 4C shows the light transmitting portions P ₁ , P ₂ , P.
₃ shows the illuminance distribution after measuring the illuminance at the positions on the substrate surface corresponding to P ₃ and P ₄ and correcting the illuminance unevenness determined from the measured values. This illuminance distribution is obtained when each step in FIG. 3 is completed. In this embodiment, since the illuminance unevenness is determined by measuring only the illuminance at four points, the illuminance uniformity on the entire surface is slightly inferior to the case of (A), but is significantly improved as compared to (B). . Irregularity of illuminance due to flare light has a smooth distribution, so few measurement points (4 points in this case)
Even in the illuminance distribution obtained by, the illuminance unevenness can be considerably improved only by correcting the illuminance at each measurement point to be equal.

Next, a second embodiment relating to uneven illuminance correction will be described.

In this embodiment, the reticle shown in FIG. 5 is used. This reticle is P in the reticle of the first embodiment.
_{1 to} P ₄ , a plurality of transmissive parts P ₁ ′, P
It is characterized by having ₁ ″ to P ₄ ′ and P ₄ ″.
In this case, the process of step 3 is different from that of the first embodiment.

[0038] 'After measuring the I _n "and, I _n' I _n and I
_The slope a _n is calculated from the value of _n ″, and I ₁ ′ =
I ₂ ′ = I ₃ ′ = I ₄ ′ and a ₁ = a ₂ = a ₃ = a ₄ =
Whether or not it becomes 1 is determined by providing a certain allowable value. If the uneven illuminance exceeds the allowable value, the uneven illuminance correction means similar to the first embodiment corrects the uneven illuminance.

According to this method, the illuminance unevenness can be calculated more strictly than in the first embodiment, so that the illuminance unevenness can be corrected more strictly.

Next, a third embodiment relating to correction of uneven illuminance will be described.

This embodiment also uses the reticle shown in FIG. 5, but the process of step 3 is different from that of the first and second embodiments.

After measuring I _n ′ and I _n ″, four points diagonally aligned, I _n ′, I _{n + 2} ′, I _n ″, I _{n + 2} ″ (n =
Interpolation functions f ₁₃ and f ₂₄ are calculated from the values of 1 and 2).

For example, if interpolation is performed with a polynomial, since there are four sampling points in the present embodiment, approximation with a third-order polynomial is performed, and f (x) = a ₀ + a ₁ x + a ₂ x ² + a ₃ x ³ becomes x. I _n ′, I _{n + 2} ′, I _n ″, I _{n + 2} ″ (n = 1,
By substituting each of 2) and solving it, a ₀ ~
Determine a ₃ and obtain f ₁₃ and f ₂₄ . And f ₁₃ = f ₂₄
= Whether or not it is a constant is determined by setting a certain allowable value. If the illuminance unevenness exceeds the allowable value, the illuminance unevenness correction means similar to those in the first and second embodiments corrects the illuminance unevenness. The interpolation function is not limited to the above-described polynomial interpolation,
It may be an angle interpolation, a Spline interpolation, an interpolation by a trigonometric function, an approximate interpolation by a least square method, or the like.

With this method, the illuminance unevenness can be calculated more strictly than in the second embodiment, so that the illuminance unevenness can be corrected more strictly than in the second embodiment. Also at this time,
Four or more points may be arranged along the diagonal line of the light transmitting portion. In that case, naturally, the interpolation accuracy is further improved.

Although only the embodiment in which the light transmitting portion for measuring the illuminance is provided in the peripheral portion of the transfer pattern of the reticle has been described above, there is a possibility that the light transmitting portion can be provided in the central portion of the reticle depending on the transfer pattern. To be Needless to say, when the illuminance distribution measurement as in the above-described embodiments is performed with such a reticle, more strict measurement can be performed than in the above-described three embodiments.

Next, an embodiment of a method of manufacturing a semiconductor device using the projection exposure apparatus of FIG. 1 will be described. 6 shows a semiconductor device (semiconductor chip such as IC or LSI, liquid crystal panel or CC
The manufacturing flow of D) is shown. In step 61 (circuit design), the circuit of the semiconductor device is designed. In step 62 (mask production), a mask (reticle 14) on which the designed circuit pattern is formed is produced. On the other hand, in step 63 (wafer manufacturing), a wafer (wafer 2
0) is produced. Step 64 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by the lithography technique using the mask and the wafer prepared above. The next step 65 (assembly) is called a post-process, and is a process of forming a chip using the wafer created in step 64, and includes an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. Including. In step 66 (inspection), the semiconductor device manufactured in step 65 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 67).

FIG. 7 shows a detailed flow of the wafer process. In step 71 (oxidation), the wafer (wafer 2
The surface of 0) is oxidized. In step 72 (CVD), an insulating film is formed on the surface of the wafer. In step 73 (electrode formation), ions are implanted on the wafer. Step 75
In (resist processing), a resist (sensitive material) is applied to the wafer. In step 76 (exposure), the projection exposure apparatus exposes the wafer with the image of the circuit pattern of the mask (reticle 14). In step 77 (developing), the exposed wafer is developed. In step 78 (etching), parts other than the developed resist are scraped off. In step 79 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, a circuit pattern is formed on the wafer.

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

[0049]

According to the present invention, it is possible to detect and correct illuminance unevenness in a state where an actual reticle on which a desired circuit pattern is drawn is placed, and it is possible to perform highly accurate exposure.

[Brief description of drawings]

FIG. 1 is a diagram of a stepper of the present invention.

FIG. 2 is a diagram showing a reticle used in the first embodiment.

FIG. 3 is a flowchart showing a procedure for correcting uneven illuminance.

FIG. 4 is a diagram showing an illuminance distribution in each step of FIG.

FIG. 5 is a diagram of a reticle used in the first and second embodiments.

FIG. 6 is a diagram showing a manufacturing process of a semiconductor device.

FIG. 7 is a diagram showing details of the wafer process during the process of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 14 Reticle 18 Projection lens 20 Wafer 23 Illuminance measuring instrument 24 Arithmetic unit 101-103 Actuator

Claims (7)

[Claims] 1. An exposure apparatus having an illuminance measuring means for measuring the illuminance at a plurality of measurement points on an exposed surface, wherein at least one location of a mask on which a transfer pattern is formed is provided with a light transmitting section for transmitting exposure light. The mask is placed at a predetermined position in the optical path of the exposure light, the transfer pattern portion and the light transmission portion are simultaneously illuminated by the exposure light, and the illuminance of the exposure light transmitted through the light transmission portion is controlled by the exposure light. An exposure apparatus which measures unevenness on the surface to be exposed corresponding to the transfer pattern of the mask, by measuring at a plurality of measurement points on the exposure surface, and measuring values obtained as a result. 2. The exposure apparatus according to claim 1, further comprising a correction unit that corrects the uneven illuminance. 3. A transfer pattern portion is provided with a light transmitting portion which transmits exposure light at least at one location of a mask having a transfer pattern formed thereon, and the mask is placed at a predetermined position in an optical path of the exposure light. And simultaneously illuminating the light transmitting portion with exposure light, measuring the illuminance of the exposure light transmitted through the light transmitting portion at a plurality of measurement points on the exposed surface, and by the measurement values obtained as a result, the mask Unevenness detection method for detecting unevenness in illuminance on the surface to be exposed corresponding to the transfer pattern. 4. The mask, wherein the light transmitting portion for measuring the illuminance is located outside the transfer pattern. 5. The mask according to claim 3, wherein there are a plurality of light transmitting portions for measuring the uneven illuminance, and the light transmitting portions are located symmetrically with respect to the optical axis. 6. The mask according to claim 4, wherein a plurality of light transmitting portions for measuring unevenness in illuminance are provided in a radial direction centered on an optical axis. 7. An exposure apparatus according to any one of claims 1 and 2, an illuminance distribution correction method according to claim 3, or any one of claims 4 to 6.
A method for manufacturing a semiconductor device using the described mask.