JPH02208919A - Irradiation light quantity controller - Google Patents

Abstract

PURPOSE:To control the quantity of light projected on the irradiation surface of a method wherein a part of the flux of light, emitted rom an illuminator, is picked out, it is made to irradiate on an optical material, the change of optical property of the optical material is detected, and the quantity of irradiation light is controlled. CONSTITUTION:A light source 15 is pulse-oscillated, the irradiation on the surface of a reticle 2 is started by an optical system of illumination 1, the surface of a wafer 4 is exposed to light, and at the same time, a part of the luminous flux emitted from the light source 15 is made to irradiate on a photoresist 7a. Then, the quantity of light projected on the photoresist 7a is detected by a photodetector 11, the output signal sent from the photodetector 11 is detected by a luminous energy controller 22, and when the prescribed value is attained, a shutter means 23 is closed by the luminous energy controller 22, or the irradiation to the reticle surface 2 is discontinued by stopping the pulse oscillation from the light source 15, and the luminous energy per one light exposure to the surface of the wafer 4 is properly set.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an irradiation light amount control device, and particularly to an irradiation light amount control device that uses a light source such as an excimer laser that emit pulsed light and has a relatively short light emission time to control a surface to be irradiated, such as a semiconductor. When irradiating a mask or reticle (hereinafter referred to as "reticle") surface on which an electronic circuit pattern is formed in an exposure apparatus for manufacturing elements, it is possible to control the amount of irradiation light on the irradiated surface to be constant. The present invention relates to an irradiation light amount control device that can be used.

(Prior Art) In recent semiconductor manufacturing technology, as electronic circuit patterns become highly integrated, an exposure apparatus that can form high-density electronic circuit patterns is required.

Generally, when transferring an electronic circuit pattern on a reticle surface onto a wafer surface, in order to maintain a good resolution line width of the electronic circuit pattern transferred onto the wafer surface, it is necessary to It is necessary to set the irradiation light amount appropriately.

Generally, the optimal value of the amount of irradiation light irradiated onto the reticle surface is determined in advance depending on the resist used, and is controlled by various methods so that the amount of irradiation light is the optimal value at this time.

On the other hand, various exposure apparatuses using excimer lasers having an oscillation wavelength in the deep UV region have recently been proposed for the purpose of increasing resolution.

The oscillation of this excimer laser is pulsed light emission, and the light emission time of 1 pulse is very short, 10~30 nsec, and the oscillation pulse waveform at this time is constantly changing. For this reason, when a pulsed excimer laser is used as a light source in an exposure apparatus, it is important to configure the exposure apparatus so that the surface to be irradiated is illuminated with a constant amount of light.

(Problem to be solved by the invention) In order to control the amount of light irradiated onto the irradiated surface with high precision so that it reaches a predetermined value using an excimer laser that emits pulses with a short light emission time as a light source, it is necessary to use a deep UV region (wavelength 250 nm).
There is a need for an integrated light amount type detection means that has sufficient sensitivity to light (nearby) and has high-speed response that can follow high-speed pulse oscillations.

The present invention uses an optical member such as a resist or photochromic material whose optical properties change depending on the amount of irradiation light when irradiating the irradiated surface such as a reticle surface using a light source such as a pulsed excimer laser. An object of the present invention is to provide an irradiation light amount control device suitable for, for example, an exposure apparatus for manufacturing semiconductor devices, which can satisfactorily control the irradiation light amount so that it always has an optimum value.

(Means for Solving the Problems) The present invention extracts a part of the luminous flux from the erroneous illumination means when illuminating the surface to be illuminated by the illumination means, and uses it as an optical member whose optical properties change according to the amount of irradiation light. The invention is characterized in that the amount of light irradiated onto the surface to be irradiated is controlled by detecting a change in the optical properties of the optical member using an optical detection means.

In particular, in the present invention, the illumination means has a light source that emits pulsed light, the optical member has a material whose transmittance changes depending on the amount of irradiated light, and the detection means makes the light beam incident on the optical member. It is characterized by having a light-emitting element for transmitting the light and a light-receiving element for receiving the light beam transmitted through the optical member.

(Embodiment) FIG. 1 is a schematic diagram of the fI section of an embodiment in which the present invention is applied to a reduced projection type exposure apparatus for semiconductor manufacturing.

In the figure, reference numeral 15 denotes a light source, which is, for example, an injection locking type excimer laser.

1 is an illumination optical system, which takes out a part of the pulsed light flux from the light jll with a half mirror (not shown) and guides it to an integrated light amount measuring means 21, which will be described later, and other light fluxes to be irradiated. The light is guided onto two surfaces of the reticle. 3
is a projection optical system, which projects the electronic circuit pattern on the two surfaces of the reticle onto the fourth surface of the wafer at a predetermined magnification. A wafer chuck 5 is placed on a movable stage (not shown) and fixes the wafer 4 by suction.

6 is a condenser lens that condenses a part of the luminous flux from the light source 15 divided by the illumination optical system 1, and makes it enter an optical member 7, which will be described later. The optical member 7 is made of a material 7a having a function as an integrated light amount detection means whose optical properties such as transmittance and polarization conditions change depending on the amount of irradiated light, such as a photoresist material, a photochromic material, a magneto-optical recording material, etc., on a glass substrate. 7b. The figure shows a case where photoresist is used.

7b is a transparent glass substrate, and a photoresist 7a is coated on the surface thereof. Reference numeral 9 denotes a driving means such as a motor, which controls the rotation of the optical member 7. 10 is a light emitting element, a light source! The glass substrate 7b is transparent to the light from the light emitting element 1O.

Further, it is set so that the light beam from the light emitting element 1O is incident on the area on the surface of the photoresist 7a that is illuminated by the light beam from the condenser lens 6. A light receiving element 11 receives the light beam from the light emitting element 10 that has passed through the photoresist 7a.

Reference numeral 22 denotes a light amount control means, which turns off, for example, the shutter means 23 and the light source 15, based on the output signal from the light receiving element 11, so that the amount of light irradiated onto the two surfaces of the reticle becomes a preset value. It's in control.

Next, a method of controlling the amount of light irradiated onto the two surfaces of the reticle in this embodiment will be described.

First, the driving means 9 is stopped and the optical member 7 is set at a predetermined position.

The light source 15 is pulse-oscillated and the illumination optical system 1 starts irradiating the 2 surfaces of the reticle, exposing the 4 surfaces of the wafer and at the same time using part of the light beam from the light source 15 to illuminate the photoresist 7.
Irradiate a. The photoresist 7a has a property that the transmittance of the irradiated area changes depending on the amount of irradiated light. Therefore, the amount of light that passes through the irradiation area of the photoresist 7a of the light beam from the light emitting element 10 changes. At this time, the change in transmittance of the irradiated area of the photoresist 7a is detected by the light receiving element it. That is, the light receiving element 11 detects how much of the irradiation light from the light source 15 is incident on the reticle 2 surface.

Generally, the appropriate exposure amount to the wafer 4 is known, and the transmittance of the photoresist 7a when the appropriate exposure amount is reached is also known.

Therefore, in this embodiment, the light amount control means 22 detects whether the output signal from the light receiving element It has reached a predetermined value, and when the output signal reaches the predetermined value, the light amount control means 22 causes the shutter means 23 to
The irradiation onto the reticle 2 surface is stopped by closing the light source 15 or by stopping the pulse oscillation from the light source 15.

In this way, the amount of irradiation light for one exposure onto the wafer surface is appropriately set.

Next, a movable stage (not shown) is driven to move the wafer 4 by a predetermined amount for the next exposure. At this time, the driving means 9 is rotated by a predetermined amount to change the position of the optical member 7. The light beam from the condenser lens 6 is made to enter the unirradiated area of the photoresist 7a.

Thereafter, such operations are sequentially repeated to expose the entire surface of the wafer 4.

When the entire exposed area of the photoresist 7a is exposed, the optical member 7 is replaced with an optical member coated with another photoresist.

In this embodiment, a photochromic material may be used instead of a photoresist as an optical member whose optical properties change depending on the amount of irradiated light.

In photochromic materials, areas irradiated with light (particularly ultraviolet light) are colored by photochemical action, and the transmittance changes. It has an optical property that restores it to its original appearance after a certain amount of time has passed after the parent's irradiation has finished. Therefore, the amount of light irradiated onto the reticle surface can be controlled in the same sequence as in the embodiment shown in FIG. In particular, if the drive means rotates the optical member by a predetermined amount and sequentially irradiates the areas coated with the photochromic material, by the time the area coated with the photochromic material that has already been irradiated with light is irradiated again, the area is already irradiated. Since it has been restored to its original appearance, it has the unique feature of eliminating the need to replace optical components.

In this embodiment, if a semiconductor laser that emits infrared light is used as the light emitting element, the optical properties will not change even if the photochromic material is irradiated, so there is an advantage in that the degree of freedom in assembly is increased.

Furthermore, photochromic materials have the property that when a colored region is heated, the speed of decolorization and restoration becomes faster. Therefore the light coated with photochromic material? By providing a heater near the member to heat it, the throughput of the exposure apparatus can be improved. Of course, the heating means is not limited to this configuration.

In addition, in this embodiment, a magneto-optical recording material may be used as the optical member, and the polarization characteristics that change depending on the amount of irradiated light may be detected using a polarization microscope or the like.

It is preferable to add a magnetic eraser as a method for erasing the magnetism at this time, since there is no need to replace the optical member and the configuration is simplified.

(Effects of the Invention) According to the present invention, when illuminating an irradiated surface using an excimer laser or the like that emits short-time pulses in the ultraviolet region, which is a sensitive region that cannot be directly received by a light-receiving element, Using an optical member that has an integrated light amount detection function whose optical properties change depending on the amount of irradiated light, a part of the light flux from the illumination system is divided and irradiated to the optical member, and the optical properties of the optical member at this time are measured. By optically detecting the change, it is possible to achieve an irradiation light amount control device that can control the amount of light irradiated onto the irradiated surface with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of a -'X embodiment when the present invention is applied to an exposure apparatus for manufacturing semiconductor devices. In the figure, l is the illumination optical system, 2 is the reticle, 3 is the projection optical system,
4 is a wafer, 5 is a wafer chuck, 6 is a condenser lens, 7
7a is an optical member, 7a is a photoresist, 7b is a glass substrate, 9 is a driving means, IO is a light emitting element, 11 is a light receiving element, 1
5 is a light source, 21 is an integrated light amount measuring means, 22 is a light amount control means, and 23 is a shutter.

Claims (4)

[Claims] (1) When illuminating a surface to be illuminated by an illumination means, a part of the luminous flux from the illumination means is taken out and incident on an optical member whose optical properties change depending on the amount of irradiated light, and the optical properties of the optical member are An irradiation light amount control device, characterized in that the amount of irradiation light onto the irradiated surface is controlled by detecting a change in properties using an optical detection means. (2) The illumination means has a light source that emits pulsed light, the optical member has a material whose transmittance changes depending on the amount of irradiated light, and the detection means makes the light beam incident on the optical member. Claim 1 characterized in that it has a light emitting element for transmitting light and a light receiving element for receiving the light beam transmitted through the optical member.
The irradiation light amount control device described above. (3) The irradiation light amount control device according to claim 1, wherein the optical member is configured to include a photoresist, a photochromic material, or a magneto-optical recording material. (4) The irradiation light amount control device according to claim 1, wherein the optical member is made of a photochromic material, and a heater for heating the photochromic material is provided.