TWI629568B - Illumination device and exposure device including the same - Google Patents

Abstract

An object of the present invention is to appropriately detect the illuminance / intensity of the illuminating light emitted from a light source. The alternating current power of the specific frequency f1 to f4, which is different for each lamp tube, is superimposed at the basic frequency F as the alternating current power supplied to each discharge lamp tube, and the illumination light of each discharge lamp tube is periodically changed. The illuminance sensor 40 detects the illuminance of the synthetic illumination light obtained by superimposing the oscillating illumination light of each discharge lamp. The illuminance measurement unit 45 detects the illuminance of each discharge lamp tube that does not contain an oscillating component in a synchronous manner based on specific frequencies f1 to f4 different from each other.

Description

Illumination device and exposure device including the same

The present invention relates to an illuminating device that can be used in an exposure device and the like, and particularly relates to an illuminance measurement of the illuminating device.

The exposure device uses a short-arc discharge lamp having a large light emission intensity. In order to increase the light emission intensity, a multi-lamp lighting device composed of a plurality of discharge lamp tubes is incorporated (for example, refer to Patent Document 1). Among them, a light source element composed of a discharge lamp tube and a reflector is regularly arranged to constitute a lamp tube unit for illuminating a substrate.

Regarding illumination adjustment, in order to uniformly illuminate the substrate, a constant illumination method is adopted. An illuminance meter is arranged on a platform or the like mounted on the substrate, and the illuminance of the illumination light before the exposure operation is detected. Then, the output of the discharge lamp is adjusted to match the target illuminance (for example, refer to Patent Document 2).

[Advanced technical literature]

Patent Document 1: Japanese Patent Application Publication No. 2012-221726

Patent Document 2: Japanese Patent Application Publication No. 2012-208351

In the case of a multi-lamp lighting device, light emitted from each of a plurality of light sources is condensed into a single illumination light and irradiated onto a substrate. Therefore, the illuminance placed on the platform The meter detects the illuminance (all illuminance) based on all light sources, but does not detect the illuminance of individual light sources.

The light source itself has individual differences, and the proportion of loss due to the use of time varies. Therefore, even if the same power (supply power) is supplied to each light source, the illuminance decreases depending on the light source. However, if the overall illuminance is reduced due to a specific light source, the power supply to all light sources will be uniformly increased under the constant illuminance lighting control.

As a result, the power supply of the light source, which has almost no decrease in contrast, is too large, and the loss is accelerated. This further causes a decrease in the overall illuminance, which is related to the deterioration of the luminous efficiency and shortened life of the multi-lamp lighting device.

On the other hand, when plural illuminance meters are provided beside each light source, the illuminance measured on the light source side and the illuminance measured on the substrate side do not necessarily match. The reason may be the configuration characteristics of the illumination optical system, or there may be illumination light from the outside of the device near the platform. Therefore, when the external light other than the light emitted from the light source overlaps, the illuminance cannot be measured properly.

Therefore, the lighting device needs to be able to detect the illuminance / intensity of the light source appropriately.

The lighting device of the present invention includes a plurality of light sources, each of which emits illumination light; and a light detection unit, which is arranged between the illumination optical system and the illuminated area, and detects the illuminance or intensity of the entire illumination light of the plurality of light sources (hereinafter (Expressed as illuminance / intensity); and a lighting control unit that controls light emission for each of the plurality of light sources. In a constant-illumination lighting mode with a constant illumination, the lighting control The control unit can uniformly control the power supplied to each light source.

The illumination control unit causes the plurality of light sources to emit measurement illumination light whose illuminance / intensity varies with different frequencies of the corresponding plurality of light sources. The light detection unit obtains the illuminance / intensity of the illuminating light of each light source that does not include a fluctuation component from the total of the measured illuminating light in which the measured illuminating light of each light source is superimposed according to different frequencies.

The lighting control unit may measure the illumination light based on the frequency at which the illuminance / intensity changes periodically in response to the periodic change in the power supplied to each light source.

For example, a plurality of light sources individually emit illumination light due to AC power input, and the illumination control unit supplies AC power having a basic frequency and a composite frequency corresponding to a specific frequency of the light source to each light source to emit measurement illumination light.

Considering that the specific frequency is accurately extracted, the lighting control unit may overlap the specific frequency at least twice the basic frequency on the basic frequency. In addition, the specific frequency of the plurality of light sources corresponding to the plurality of light sources may have a frequency interval greater than or equal to an allowable minimum interval.

For example, the lighting control unit may superimpose a specific frequency that satisfies the range of the following expression to the basic frequency. The upper limit value in the formula is derived from the relationship between the power supply and the specific frequency that has not been known in the past based on experience. Among them, fm can be set to a range that satisfies the upper limit value or above the lower limit value.

6 × F ≦ fm ≦ 10 / PW0

Among them, fm represents a specific frequency (kHz), F represents a fundamental frequency (kHz), and PW0 represents AC power (kW) of a rectangular wave having a fundamental frequency F.

As a structure for detecting the illuminance of each light source, for example, the light detection section may be provided with a synchronization detection section.

Alternatively, the light detection unit includes a filter for measuring the illumination light that separates the entire illumination light into each light source, and the light detection unit detects the illuminance of the oscillating illumination light from the amplitude of the measurement illumination light of each light source. /strength.

A lighting device according to another aspect of the present invention includes: a single light source that emits illumination light; and a light detection unit that is disposed between the illumination optical system and the illuminated area and detects the illuminance / intensity of the entire illumination light generated by the light source. And a lighting control unit that controls light emission of the light source. The lighting control unit supplies the light source with alternating current power having a power waveform of the light source and a synthesized frequency corresponding to a specific frequency of the light source superimposed on the light source, thereby causing the light source to emit measurement illumination light that varies with the synthesized frequency. The light detection unit obtains the illuminance / intensity of the illuminating light that does not contain a fluctuation component of the light source from the entire measurement illuminating light of the measurement illuminating light superimposed on the light source based on the combined frequency.

According to the present invention, the illuminance / intensity of the illuminating light emitted from the light source can be appropriately detected (hereinafter sometimes referred to simply as illuminance).

10‧‧‧Exposure device

20‧‧‧Lighting device

20A ~ 20D‧‧‧Light source unit

21‧‧‧Mirror

22A ~ 22D‧‧‧Power circuit

24‧‧‧ Fold back mirror

26‧‧‧ Illumination Optical System

28A ~ 28D‧‧‧Discharge lamp

29A ~ 29D‧‧‧Reflector

30‧‧‧ exposure head

40‧‧‧illumination sensor

45‧‧‧Measurement and Measurement Department

50‧‧‧Control Department

S‧‧‧ substrate

M‧‧‧ half cycle

PW, PW0‧‧‧AC power

W‧‧‧ Power supply amplitude

Wm‧‧‧illuminance amplitude

FIG. 1 is a block diagram of an exposure apparatus according to a first embodiment.

Figure 2 shows the AC power supplied to each lamp during illuminance measurement.

FIG. 3 is a partially enlarged view of the electrode rectangular wave in FIG. 2.

FIG. 4 shows the illuminance fluctuation of the entire illumination light synthesized by the illumination light of each lamp tube detected by the illuminance sensor.

Fig. 5 shows the illuminance of each discharge lamp detected by synchronous detection.

Fig. 6 is a graph showing a temporal change of the filtered illumination light in the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an exposure apparatus according to a first embodiment.

The exposure device 10 projects illumination light onto a substrate S to which a photosensitive material such as a photoresist is applied or adhered to form a pattern. The substrate S is provided on a drawing table (not shown).

The exposure device 10 includes an illumination device 20, an exposure head 30, and a control unit 50. The control unit 50 executes and controls the exposure operation. The lighting device 20 is composed of four light source units 20A-20D. The light source unit 20A includes a discharge lamp tube 28A and a reflector 29A, and the other light source units 20B to 20D also include short-arc discharge lamp tubes 28B, 28C, and 28D and reflectors 29B, 29C, and 29D, respectively.

The discharge lamps 28A to 28D are suitable for short arc discharge lamps, and the mercury content is sealed at 0.15mg / mm ³ or more. The discharge lamps 28A to 28D are lit according to the AC power, and here, the rectangular wave AC power having a frequency (basic frequency) of approximately 0.05 to 0.2 (kHz) is supplied by the power supply circuits 22A to 22D.

The light emitted from the discharge lamp tubes 28A to 28D is collected and emitted through the reflectors 29A to 29D, and is reflected on the folded-back mirror surface 24. The light reflected on the folding mirror surface 24 is incident on the illumination optical system 26. The illumination optical system 26 includes an optical system such as a fly-eye lens, and emits light composed of a light beam having a uniform intensity in space. The light emitted from the illumination optical system 26 is guided to a DMD (not shown) in the exposure head 30 through the mirror 21 and the like.

The control unit 50 transmits the grid data to the DMD according to the position of the substrate S relative to the drawing table. The DMD as a spatial light modulator is a micro-rectangular micromirror arranged in a two-dimensional matrix. Each micromirror surface of the DMD is controlled to be ON / OFF according to the grid data.

The illuminance sensor 40 is disposed at one end of the desktop, and moves to the position of the exposure area before the exposure operation starts. During the measurement, the control unit 50 controls the power supply circuits 22A to 22D, and varies the individual light output of the discharge lamp tubes 28A to 28D, so that the individual illumination light and the entire illumination light are oscillated. The illuminance measurement unit 45 detects the illuminance of the illuminating light of an individual lamp tube from the entire illuminating light to be measured.

The control unit 50 performs constant-illumination lighting control, and uniformly controls the power supply to the discharge lamp tubes 28A to 28D. At the same time, the control unit 50 individually monitors the illuminance of each discharge lamp. When the illuminance of the special discharge lamp exceeds a predetermined range, the control unit 50 sends the data of the lamp exchange notification to the screen (not shown). Alternatively, a beep mechanism can be set.

Figure 2 shows the AC power supplied to each lamp during illuminance measurement. FIG. 3 is a partially enlarged view of the electrode rectangular wave in FIG. 2. FIG. 4 shows the illuminance fluctuation of the entire illumination light synthesized by the illumination light of each lamp tube detected by the illuminance sensor. Next, the characteristics of the AC power supplied during the measurement will be described using FIGS. 2 to 4.

In a normal exposure operation, a rectangular wave AC power PW0 having a low frequency F (hereinafter referred to as a fundamental frequency) is sent to the discharge lamps 28A to 28D. The value of the supplied power is the same for any discharge lamp. Here, the fundamental frequency F is set in a range of 0.05 to 0.2 (kHz).

On the other hand, in the case of measurement, that is, more During the substrate change, the periodic inspection start period of the lamp lighting, and the system change period of the exposure device, etc., when the pattern is not formed on the substrate, the control unit 50 supplies a high frequency (hereinafter referred to as a specific frequency) fm overlapping to the basic frequency F AC power PW with overlapping frequency (synthetic frequency).

FIG. 2 shows a waveform of an AC power supply PW0 having a rectangular wave having an amplitude W and a fundamental frequency F, and a waveform of the AC power supply PW having a specific frequency fm (m = 1 to 4) superimposed on the composite frequency of the basic frequency F Waveform. FIG. 3 enlarges the rectangular wave half cycle (M) of the AC power supply PW of FIG. 2. The electric power supplied to the discharge lamps 28A to 28D has AC power waveforms in which specific frequencies f1 to f4 are respectively superimposed on the composite frequency of the basic frequency F. The power supply waveforms of the discharge lamps 28A to 28D are represented by symbols A to D, respectively.

The specific frequencies f1 to f4 are frequencies higher than the basic frequency F, and are set in the range of several kHz to several 100 kHz. The value of the specific frequency fm varies depending on the lamp. The lower limit value of the specific frequency fm is a rectangular waveform set so as not to interfere with the basic AC power PW0. For example, during a period of approximately half the period of the rectangular wave of the fundamental frequency F, a waveform of a specific frequency fm appears at least one period of component, that is, it may be specified to exceed twice the fundamental frequency F.

On the other hand, the upper limit value of the specific frequency fm is set such that the illuminance of the illumination light does not become unstable. Specifically, the illumination light fluctuates in accordance with the fluctuation of the supplied power, that is, the upper limit value is set in a possible range in which the periodic fluctuation of the illuminance / intensity is proportional to the periodic fluctuation of the supplied power.

Fluctuations in illumination light occur due to fluctuations in electrode temperature, mercury evaporation, etc. caused by fluctuations in power supply. In particular, when a short-arc discharge lamp having a mercury content of 0.15 (mg / mm ³ ) or more is enclosed, there is a limit to the rate of change in illuminance, and the reactivity of the illumination light to respond to a change in power supply also has a limit.

Therefore, in the case of a lamp with a large power supply and a high illuminance, the amount of fluctuation in the supply power increases due to the overlap of a specific frequency. On the other hand, the illuminance becomes unable to follow the change in the supply power and it is impossible to measure the correct illuminance change the amount.

In the case of the short-arc discharge lamp, the specific frequency must be equal to or less than a maximum value (specific frequency upper limit value fmmax) at which the illuminance can follow the fluctuation of the supplied power. In this embodiment, when the amount of mercury enclosed in the lamp is within a predetermined range, it has been found from experience that the upper limit of the specific frequency can be set from the relationship between the specific frequency and the power supply. Specifically, when the amount of mercury enclosed in the lamp is 0.15 to 0.4 (mg / mm ³ ) and the AC power supplied to the lamp is 0.05 to 0.6 (kW), the upper limit value of the specific frequency can be obtained by the following formula Out. Where fmmax represents the upper limit value (kHz) of the specific frequency.

fmmax = 10 / PW0 .. (1)

In addition to fluctuations in the power supply, the short-arc discharge lamp may have a small change due to the influence of the surrounding environment (for example, the temperature around the lamp). In order to extract a specific frequency without being affected by such an illuminance change, it must be a high frequency that exceeds a certain reference value with respect to the basic frequency.

Specifically, in order to detect the correct fluctuation amount of the illumination light in accordance with the fluctuation of the supplied power, a waveform of a specific frequency fm has at least three periods of components during a half period of the rectangular wave of the fundamental frequency F. That is, as shown in the following formula, it is preferable to specify that the specific frequency fm exceeds 6 times the basic frequency F.

6 × F ≦ fm ≦ 10 / PW0 .. (2)

In addition, the specific frequencies f1 to f4 are set such that the frequency interval between them is equal to or greater than a certain value (the frequency interval must be equal to or greater than the allowable minimum interval). This is to facilitate individual detection processing of illuminance / intensity. Here, when the basic frequency F is 90 Hz, the specific frequencies f1, f2, f3, and f4 can be set to 2.43 (kHz), 2.61 (kHz), 2.79 (kHz), and 2.97 (kHz), respectively. Specific frequencies can also be set at regular intervals.

The individual illuminating light emitted by each discharge lamp tube varies periodically in proportion to the power supply wave of each discharge lamp tube in FIG. 3. Since the illumination sensor 40 detects the entire illumination light after the illumination light of each lamp tube is synthesized, as shown in FIG. 4, the oscillation of the entire illumination light is irregular.

Fig. 5 shows the illuminance of each discharge lamp detected by synchronous detection.

The illuminance measurement unit 45 obtains the illuminance of each discharge lamp by synchronous detection. The illuminance measurement unit 45 detects the illuminance of each discharge lamp at a synchronized time point according to a clock signal sent by the control unit 50 in accordance with a specific frequency f1 to f4.

In FIG. 5, the illuminances of the discharge lamps 28A to 28D are represented by symbols A to D, respectively. Using synchronous detection, the illuminance of each lamp with a DC component is detected from the oscillation of the entire illumination light. The control unit 50 determines from the measured illuminances A to D of each discharge lamp whether there is an illuminance of the discharge lamp outside the specification range. The illuminance at the start of lamp lighting can be used as a reference value, and the illuminance reduction rate based on the reference value can be measured for each discharge lamp.

When there is a discharge lamp whose illuminance falls outside the prescribed range, the operator is informed of the situation. When the operator exchanges a new lamp, the fixed-illuminance lighting control is performed again, and the power is adjusted uniformly.

According to this embodiment mode, the AC supply power of each discharge lamp is an AC supply power whose base frequency F overlaps with a specific frequency f1 to f4 that varies with each lamp, and the illumination light of each discharge lamp is periodically changed. The illuminance sensor 40 detects the illuminance of the combined illumination light superimposed on the oscillating illumination light of each discharge lamp. The illuminance measurement unit 45 detects the illuminance of each discharge lamp that does not contain vibrations in synchronization with specific frequencies f1 to f4 different from each other.

By individually detecting the illuminance of the discharge lamp, it is possible to prevent the supply power of the discharge lamp from being excessively increased under the constant-illumination lighting control that uniformly adjusts the supplied power. As a result, the life of the entire lighting device can be extended. To improve luminous efficiency.

Since the specific frequency fm is considerably higher than the fundamental frequency F, it does not interfere with the rectangular electric power wave of the fundamental frequency F. On the other hand, because the specific frequency fm is not increased too much, it is possible to prevent a situation in which the fluctuation of the emitted light does not follow the unstable oscillation such as the fluctuation of the supplied power. Because the frequency intervals are almost equal, synchronization detection is easy.

Next, a second embodiment will be described with reference to FIG. 6. In the second embodiment, a filter is used to separate the illumination light by the tube, and the light intensity / illumination is measured based on the amplitude of the illumination light. The other structures are the same as those of the first embodiment.

Fig. 6 is a graph showing a temporal change of the filtered illumination light in the second embodiment.

In the second embodiment, the illumination measurement unit 45 includes a conventional filter circuit, and the entire illumination light is transmitted through the filter circuit to be separated into the illumination light of each discharge lamp. Then, the illuminance of the illuminating light of each discharge lamp was obtained by the following formula. Among them, Em (m = 1 ~ 4) represents the photos of each discharge lamp detected through the filter. Degree, Vm represents the amplitude of the power supplied with a specific frequency of each discharge lamp, and Wm represents the amplitude of the illumination light of each discharge lamp. Meanwhile, k and Y represent coefficients according to the optical characteristics of the illumination optical system and the like.

Em = k × (Wm / Vm) + Y .. (3)

One discharge lamp may be used instead of a plurality of discharge lamps to constitute a lighting device. In this case, even when external light other than the lamp enters the illuminance sensor, the illuminance / intensity of the illumination light of each discharge lamp can be accurately detected. A discharge lamp that supplies DC power is also applicable, and a light source other than the discharge lamp can also be used.

[Example]

In the following, an embodiment is used to describe a discharge lamp that satisfies the formula (1).

The discharge lamp according to the embodiment of the present invention is constituted by a single discharge lamp as a light source, and the amount of mercury enclosed is set to 0.15 to 0.4 (mg / mm ³ ). Next, an experiment was performed to confirm the followability of the illuminance variation while changing the specific frequency and power supply.

First, measure illuminance without overlapping specific frequencies. Next, the illuminance is detected when a specific frequency is superimposed. Then, the illuminance is measured separately for different supplied power. The following Table 1 shows the experimental results.

From Table 1, it can be seen that the relationship between the power supply (kW) and the specific frequency (kHz) within the range where the illuminance followability is confirmed is that the product of the power supply (kW) and the specific frequency (kHz) is 10 or less. Even when the supplied power is between 0.05 and 0.6 (kW), the same upper limit value can be derived when several specific frequencies are prepared in accordance with the supplied power.

Claims (9)

An illumination device includes: a plurality of light sources each emitting illumination light; a light detection unit disposed between an illumination optical system and an illuminated area to detect the illuminance / intensity of the entire illumination light of the plurality of light sources; and lighting control The light control unit controls the light sources of each of the plurality of light sources, wherein the lighting control unit causes the light sources of the plurality of light sources to respectively emit illuminance / intensity for measuring illumination light that varies with different frequencies corresponding to the plurality of light sources. The output unit obtains the illuminance / intensity of the illuminating light of each light source that does not contain a variable component from the total of the measured illuminating light after the measured illuminating light of each light source overlaps according to different frequencies; wherein the plurality of light sources are individually due to AC Electric power is input to emit illumination light; the illumination control unit supplies AC power having a basic frequency and a composite frequency corresponding to a specific frequency of the light source to each light source to emit measurement illumination light. The lighting device according to item 1 of the scope of the patent application, wherein the lighting control unit emits the measurement lighting light according to the frequency of the periodic variation of the illuminance / intensity due to the periodic variation of the power supplied to each light source. The lighting device according to item 1 of the scope of patent application, wherein the lighting control section overlaps the specific frequency at least twice the basic frequency with the basic frequency. The lighting device according to item 1 of the scope of patent application, wherein the lighting control section overlaps a specific frequency that satisfies the following formula to the basic frequency, 6 × F ≦ fm ≦ 10 / PW0, where fm represents a specific frequency (kHz) , F represents the fundamental frequency (kHz), and PW0 represents the AC power (kW) of a rectangular wave having the fundamental frequency F. The lighting device according to item 1 of the scope of patent application, wherein a specific frequency of a plurality of light sources corresponding to a plurality of light sources has a frequency interval greater than an allowable minimum interval. The lighting device according to any one of claims 1 to 5, wherein the light detection section has a synchronization detection section. The lighting device according to any one of claims 1 to 5, wherein the light detection section has a filter for measuring the illumination light that separates the entire illumination light into each light source, and the light detection section separates from each light source The illuminance / intensity of the oscillating illumination light is detected in the measurement of the amplitude of the illumination light. The lighting device according to any one of claims 1 to 5, in which the lighting control unit uniformly controls the power supplied to each light source. An exposure device includes the illumination device according to any one of claims 1 to 5.