JPH06204113A - Projection aligner and manufacture of semiconductor device using same - Google Patents

Abstract

PURPOSE:To obtain a projection aligner, in which the quantity of exposing light onto a wafer surface is controlled appropriately and a semiconductor device with high degree of accumulation is obtained when an operation means determines the exposure light quantity onto a substrate surface by using the variation information of transmittance and the measuring result of integrated light quantity from an integrated light quantity detector. CONSTITUTION:When luminous flux from a light source 1 is applied to a pattern on an applied surface by a lighting system and the pattern is projected onto a substrate 14 surface for exposure by means of a projection optical system 13, the lighting system is equipped, between the light source 1 and lighted surface, with a light-dividing member 8 for dividing incident light flux into two fluxes and for guiding one flux to the applied surface side and the other flux to a detector 9. Also, the lighting system has an operation means 19 storing the variation information of transmittance of the optical system 13 from the light-dividing member 8 to the substrate 14. Further, the operation means 19 determines the quantity of exposing light onto the substrate 14 surface by using the variation information of transmittance and the measuring result from the detector 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and a method of manufacturing a semiconductor device using the same, and particularly to ICs and LSIs.
When an electronic circuit pattern on a reticle surface is projected onto a wafer surface by a projection optical system (projection lens) when manufacturing a semiconductor element such as a high precision projection pattern, the wafer surface is always provided with an appropriate exposure amount. The image is obtained.

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus (aligner), which is relatively easy to achieve high resolution and high throughput, has been widely used for manufacturing semiconductor elements such as IC and LSI. In this projection exposure apparatus, as compared with the batch exposure method in which a pattern image is formed on the entire surface of the wafer by one exposure, the wafer is moved every time one exposure is completed and other areas are exposed. A step-and-repeat exposure method is often used in which a pattern image is formed on the entire wafer surface by repeating the above step a plurality of times.

At this time, the projection optical system causes the electronic circuit pattern on the reticle surface to have a predetermined projection magnification on the wafer surface, for example, 1
Reduction projection is performed at / 5 or 1/10. In this case, the image quality of the pattern transferred onto the wafer surface depends on the performance of the illumination device,
For example, the amount of irradiation light (exposure amount) on the surface to be irradiated and its variation are greatly affected.

The applicant of the present invention has proposed a light amount control device which controls the irradiation light amount on a surface to be irradiated to a predetermined value, which is particularly suitable for an exposure device for semiconductor manufacturing, for example, Japanese Patent Laid-Open No. 62-187815.
Japanese Patent Laid-Open Publication No. 63-193130 and Japanese Patent Laid-Open Publication No. 4-48714.

Particularly, in Japanese Unexamined Patent Publication No. 4-48714, an incident light beam is amplitude-divided into two light beams in an optical path between a light source and a surface to be irradiated, and one of the light beams is irradiated to a surface (reticle).
On the side, a half mirror (light splitting member) that guides the other light flux to the photodetector is arranged, and the light flux that has passed through the half mirror is detected by the photodetector. That is, an exposure apparatus is proposed in which the exposure amount on the wafer surface is controlled.

[0006]

A light splitting member is arranged in the optical path between a light source and a surface to be illuminated, and one of two light beams split by the light splitting member is directed to the surface to be illuminated. The method of guiding the other light flux to the photodetector and controlling the exposure amount to the irradiated surface, that is, the wafer surface using the signal obtained by the photodetector is the amount of light incident on the photodetector and the wafer surface. It is premised that the ratio to the amount of upward exposure is always constant.

However, each optical element in the optical path from the light splitting member to the wafer absorbs the exposure light and the transmittance changes with time, or the transmittance changes due to changes in the environment (humidity, temperature, etc.). Then, it becomes difficult to give the optimum exposure amount on the wafer surface even using the signal obtained by the photodetector.

According to the present invention, information on the exposure history of each optical element in the optical path from the light splitting member to the wafer and the variation information of the transmittance due to the environmental change are obtained in advance and stored in the arithmetic means, and the signal from the photodetector is obtained. A projection exposure apparatus capable of appropriately controlling the exposure light amount onto the wafer surface by using the variation information of the transmittance stored in the arithmetic means, and obtaining a highly integrated semiconductor device, and the same. It is an object of the present invention to provide a method for manufacturing a semiconductor device using.

[0009]

In a projection exposure apparatus of the present invention, (1-1) a light beam from a light source is illuminated by an illumination device onto a pattern on a surface to be illuminated, and the pattern is projected onto a substrate surface by a projection optical system. At the time of projection and exposure on the light source, the illuminating device splits an incident light flux into at least two light fluxes in an optical path between the light source and the illuminated surface, and one of the light fluxes is divided into the illuminated surface side and the other light flux. It has a light splitting member for guiding the light flux to the integrated light amount detector, and a computing means for storing variation information of the transmittance of the optical system from the light splitting member to the substrate. It is characterized in that the exposure amount on the surface of the substrate is determined using the fluctuation information of the rate and the integrated light amount measurement result from the integrated light amount detector.

(1-2) When a light beam from a light source is illuminated by an illumination device on 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 device operates as the light source. A light splitting member that splits an incident light flux into at least two light fluxes in an optical path between the illuminated surface and one of the light fluxes, and guides the other light flux to the illuminated surface side and the other light flux to an integrated light amount detector, An exposure amount detector for detecting an exposure amount incident on the substrate provided on the surface corresponding to the substrate, and a measurement result obtained by the integrated light amount detector before pattern transfer and a measurement result obtained by the exposure amount detector. And a calculation means for determining the amount of exposure to the substrate by using.

Further, as a method of manufacturing a semiconductor device of the present invention, (1-3) a light beam from a light source is used to illuminate a pattern on a reticle surface with an illumination device, and the pattern is projected onto a wafer surface with a projection optical system. After the exposure, when the semiconductor device is manufactured through a developing process on the wafer, the illumination device splits an incident light beam into at least two light beams in an optical path between the light source and the illuminated surface. A light splitting member that guides one light flux to the illuminated surface side and the other light flux to the integrated light amount detector, and an arithmetic unit that stores variation information of the transmittance of the optical system from the light splitting member to the substrate. And the calculation means determines the exposure amount on the substrate surface using the variation information of the transmittance and the integrated light amount measurement result from the integrated light amount detector. There is.

[0012]

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 near the second focal point via the cold mirror 3. A shutter 4 is arranged near the second focal point of the elliptic mirror 2.

Reference numeral 5 denotes an optical system, which forms an image of the light emitting portion 1b formed in the vicinity of the second focal point on the incident surface 6a of the optical integrator 6. The optical integrator 6 is configured by arranging a plurality of minute lenses 6-i (i = 1 to N) two-dimensionally at a predetermined pitch, and its exit surface 6
A secondary light source is formed near b.

Reference numeral 7 is a condenser lens. A plurality of light beams emitted from the secondary light source in the vicinity of the emission surface 6b of the optical integrator 6 are condensed by the condenser lens 7, and a part of the light beams are reflected by the half mirror 8 as a light splitting member to be directed to the masking blade 10. Then, the surface of the masking blade 10 is uniformly illuminated. The masking blade 10 is composed of a plurality of movable light shielding plates so that an arbitrary opening shape is formed.

Reference numeral 9 denotes a calculation light amount detector, which detects the light flux passing through the half mirror 8 and indirectly detects the exposure amount on the surface of the wafer 14 which will be described later. An image forming lens 11 transfers the opening shape of the masking blade 10 onto the surface of the reticle 12 as a surface to be illuminated, and uniformly illuminates a necessary area on the surface of the reticle 12.

A projection optical system 13 projects the circuit pattern on the surface of the reticle 12 onto the surface of the wafer (substrate) 14 mounted on the wafer chuck 15 in a reduced scale. 16 is a wafer stage.

Reference numeral 17 denotes an exposure amount detector, which is provided so that its light receiving surface is substantially flush with the wafer 14. The exposure amount detector 17 sets the masking blade 10 to 10 mm square in terms of the wafer 14 surface, detects the total luminous flux of the mask 14 and detects the actual illuminance on the surface of the wafer 14, that is, the exposure amount.

Reference numeral 19 denotes an arithmetic means, which has a storage section for storing information of transmittance variation due to exposure history of optical elements arranged in the optical path from the light splitting member 8 to the wafer 14 and transmittance due to environmental changes. The fluctuation information is stored. The calculating means 19 determines the exposure amount on the surface of the wafer 14 using the signal from the integrated light amount detector 9 and the variation information of the transmittance stored in the storage section. The calculation means 19 controls the opening / closing of the shutter 4 to control the exposure amount on the surface of the wafer 14.

In addition to this, the calculating means 19 determines the exposure amount on the surface of the wafer 14 using the measurement result of the irradiation light amount obtained by the integrated light amount detector and the measurement result obtained by the exposure amount detector 17 before the pattern transfer. is doing.

In this embodiment, the wafer 1 is processed as described above.
The patterns on the reticle 12 surface are transferred to the wafer surface by appropriately setting the exposure amounts on the four surfaces. Then, a semiconductor device is manufactured through a predetermined developing process.

Next, a method of controlling the exposure amount on the surface of the wafer 14 by the calculating means 19 of this embodiment will be described.

The parameters by which the transmittance of each optical element from the light splitting member 8 to the surface of the wafer 14 fluctuates due to the exposure history are previously obtained by experiments.

2 to 4 show the illuminance (measured value) I ₁ on the integrated light amount detector 9 and the wafer 1 during exposure and non-exposure.
Ratio of illuminance (actual illuminance) I ₂ on 4 surfaces (exposure correction value)
The change in _{φ (= I 1 / I 2} ) is an explanatory view showing the horizontal axis represents time t.

In FIG. 2, when exposure is performed for the first time (t = t ₀ ), the ratio (hereinafter referred to as “exposure correction value”) φ at that time is φ = 1.

In the figure, sections A, C, and E show changes in the exposure correction value φ during exposure, and sections B and D show changes in the exposure correction value φ during non-exposure.

Now, exposure is started from t = t ₀ (section A). The value of the exposure correction value φ _K at a certain time (t = t _K ) in this section A is φ _K = f ₁ (t _K −t ₀ , e _A , e _B , φ ₀ ) ...
・ ・ It becomes (1).

Here, e _A is the amount of light incident on the imaging lens 11 per unit time, e _B is the amount of light incident on the projection optical system B per unit time, and φ ₀ is the exposure correction immediately before the start of exposure. Value, in this case φ ₀ = 1. Light intensity e _A ,
Since e _B depends on the reflected light from the light splitting member 8, the opening area S _m of the masking blade 10 and the average transmittance R _r of the reticle 12, equation (1) is expressed as φ _K = f ₂ (t _K −t ₀ , I ₁ , S _m , R _r , φ ₀ ) (2)

By inputting (or automatically reading) the opening area S _m of the masking blade 10 and the average transmittance R _r of the reticle 12 to the calculating means 19 during exposure, the exposure correction value φ that changes from moment to moment is obtained. The exposure amount is calculated and accurately controlled based on the exposure correction value φ.

Next, it is assumed that the exposure is stopped at t = t ₁ and the exposure is restarted at t = t ₂ . The exposure correction value φ _{1 at} t = t ₁ is φ ₁ = f ₂ (t ₁ −t ₀ , I ₁ , S _m , R _r , φ
₀₎ is calculated by, t = exposure in t ₂ correction value phi ₂
Is calculated by φ ₂ = f ₃ (t ₂ −t ₁ , φ ₁ ).
After starting exposure, the exposure correction value at t = t _J φ _J is phi _J =
It is calculated by f ₂ (t _J −t ₂ , I ₁ , S _m , R _r , φ ₂ ). In this way, by storing the immediately previous exposure correction value and the elapsed time from the exposure history, the current exposure correction value can always be calculated. The functions f ₂ and f ₃ are obtained in advance by experiments.

In this embodiment, the exposure correction value φ during exposure
The exposure amount is controlled for each shot, but the exposure time for one shot is very short, and there is almost no change in the exposure correction value. 1 for each wafer
Exposure may be performed by calculating one exposure correction value φ.

FIG. 3 shows one exposure correction value φ for each shot.
It is explanatory drawing when calculating and exposing. Time t ₀
The first shot during ~t _1, t ₂ second shot during ~t _3, the change in the exposure correction value of each time doing the exposure of the third shot between t ₄ ~t ₅ is a dotted line It is shown.

In this embodiment, the exposure correction value φ ₀ is used as the first shot, the exposure correction value φ ₂ is used as the _second shot, and the exposure correction value φ ₄ is used as the fixed exposure correction value for each shot in the third shot. ing. Each exposure correction value (φ ₁ , φ
₂ , φ ₃ ...) Is calculated in the same way as in the first embodiment.

FIG. 4 is an explanatory diagram in which one exposure correction value is calculated for each wafer and exposure is performed. The exposure of the first wafer and the exposure of the second wafer from time t ₂ are performed during the time t _{0 to} t ₁ , and the exposure of each wafer includes exposure of a large number of shots.

In this embodiment, a fixed exposure correction value is used during each wafer exposure. In this case, exposure and non-exposure are repeated many times during the exposure of one wafer, but the exposure correction value φ ₁ may be calculated every moment and the exposure correction value φ ₁ may be calculated. Since the non-exposure time is short, the entire exposure of one wafer may be regarded as one exposure, and the exposure correction value φ ₁ may be calculated from the average incident light amount.

When the transmittance changes due to a change in the environment, it is better to monitor the change in the environment with a sensor (not shown) and correct the result and the calculation.

FIG. 5 is a schematic view of the essential portions of Embodiment 2 of the present invention.

This embodiment is different from the embodiment 1 of FIG. 1 in that the light source 20 emits pulses such as a KrF excimer laser as a light source.
Is different, and the other configurations are the same.

In this embodiment, since exposure and non-exposure are repeated even during one-shot exposure, the concept of average incident light amount described above is applied.

In each of the above embodiments, the exposure correction value is calculated based on the exposure history, but the exposure amount detector 17 is used for calibration for each shot, each wafer or each wafer lot. The exposure correction value may be calculated.

Further, in order to correct the deviation between the calculated value of the exposure correction value and the actual value at the time of execution, calibration may be performed every certain period.

[0042]

As described above, according to the present invention, the variation information of the transmittance due to the exposure history of each optical element in the optical path from the light splitting member to the wafer is obtained in advance and stored in the calculating means. By using the signal from the detector and the variation information of the transmittance stored in the control means, the exposure light amount on the wafer surface is appropriately controlled so that a highly integrated semiconductor device can be obtained. The projection exposure apparatus and the method for manufacturing a semiconductor device using the projection exposure apparatus can be achieved.

[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 diagram of an exposure correction value according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an exposure correction value according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an exposure correction value according to the first embodiment of the present invention.

FIG. 5 is a schematic view of the essential portions of Embodiment 2 of the present invention.

[Explanation of symbols]

 1, 20 Light source 2 Elliptical mirror 3 Cold mirror 4 Shutter 5 Optical system 6 Optical integrator 7 Condensing lens 8 Light splitting member 9 Integrated light amount detector 10 Masking blade 11 Imaging lens 12 Reticle 13 Projection optical system 14 Wafer 17 Exposure amount detection Vessel 19 computing means

Claims (3)

[Claims] 1. When illuminating a pattern on a surface to be illuminated with a light flux from a light source by a lighting device and projecting the pattern onto a substrate surface by a projection optical system to expose the pattern, the lighting device uses the light source and the irradiation target. A light splitting member that splits an incident light flux into at least two light fluxes in an optical path between the light flux and the surface, and guides one of the light fluxes to the illuminated surface side and the other light flux to the integrated light amount detector, and the light flux. And a calculation unit that stores variation information of the transmittance of the optical system from the dividing member to the substrate, the calculation unit having the variation information of the transmittance and the integrated light amount measurement result from the integrated light amount detector. The projection exposure apparatus is characterized in that the exposure amount on the substrate surface is determined by using. 2. When illuminating a pattern on a surface to be illuminated with a light beam from a light source by a lighting device and projecting the pattern onto a surface of a substrate by a projection optical system for exposure, the lighting device uses the light source and the light to be illuminated. A light splitting member that splits an incident light flux into at least two light fluxes in an optical path between the light flux and the surface, and guides one of the light fluxes to the illuminated surface side and the other light flux to the integrated light amount detector, which corresponds to the substrate. An exposure amount detector for detecting the amount of exposure incident on the substrate provided on the surface, and using the measurement result obtained by the integrated light amount detector and the measurement result obtained by the exposure amount detector before pattern transfer A projection exposure apparatus comprising: a calculation unit that determines an exposure amount on the substrate. 3. A semiconductor device is provided with a light beam from a light source, which illuminates a pattern on a reticle surface by an illuminating device, projects the pattern onto a wafer surface by a projection optical system to expose the wafer, and then develops the wafer through a developing process. When manufacturing the, the illuminating device splits the incident light flux into at least two light fluxes in the optical path between the light source and the illuminated surface, and one of the light fluxes is directed to the illuminated surface side and the other light flux is directed to the other light flux. The light dividing member that guides light to the integrated light amount detector, and a calculating unit that stores variation information of the transmittance of the optical system from the light dividing member to the substrate, the calculating unit having the transmittance of the optical system. A method of manufacturing a semiconductor device, wherein the exposure amount on the surface of the substrate is determined by using the variation information and the integrated light amount measurement result from the integrated light amount detector.