JPH05343298A - Exposure apparatus - Google Patents

Abstract

PURPOSE:To decide a malfunction of an initial illuminance of a light source of an exposure apparatus and a decrease in illuminance while using the light source. CONSTITUTION:Relationship between an illuminance P of a luminous flux from a light source 1 to be detected by an illuminance monitor and a using time T1 of the source 1 measured by a timer 13, and relationship between the illuminance when the source 1 is replaced and a using time T1 of an illumination optical system are obtained, and stored in an arithmetic memory 14a. A deciding unit 14b compares the illuminance P to be detected during using of the source with the relation stored in the memory 14a, and judges the source 1 to be faulty if it decreases from the relationships.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for manufacturing semiconductor devices, and more particularly to an exposure apparatus equipped with a mechanism for monitoring the illuminance of a light source.

[0002]

2. Description of the Related Art A conventional exposure apparatus of this type has a structure as shown in FIG. That is, the light flux emitted from the light source 1 such as an ultra-high pressure mercury lamp is uniformly irradiated onto the reticle 9 through the illumination optical system such as the elliptic mirror 2, the reflecting mirrors 3a and 3b, the half mirror 5, the condenser lens 8 and the like. The light flux that has passed through the reticle 9 passes through the projection optical system 10 and the substrate 11 to be exposed.
The image is projected onto the reticle 9 to form an image. On the other hand, the exposure amount for the substrate to be exposed is controlled by moving the shutter 4 back and forth in the optical path to control the exposure time (shutter open time). Therefore, a part of the light flux from the light source 1 is reflected by the half mirror 5 and enters the illuminance sensor 6 to detect the illuminance of the light source 1. Based on the detected illuminance, the controller 12 determines the opening time of the shutter 4 and drives the shutter 4.

By the way, the exposure time needs to be adjusted according to the change of the illuminance of the light flux according to the usage time of the light source and the condition such as the contamination of the optical members of the illumination optical system. Therefore, illuminance monitor 6
The illuminance is sequentially detected by the control unit 12, and the control unit 12 automatically controls the exposure time according to the illuminance of the light flux from the light source.

[0004]

Generally, an ultra-high pressure mercury lamp (lamp) used in an exposure apparatus is provided with two illuminance guarantees, an initial illuminance guarantee and an illuminance guarantee time. The initial illuminance guarantee guarantees the minimum value as the illuminance (initial illuminance) after the new lamp is lit and stabilized, and the illuminance guarantee time can obtain an illuminance at a certain ratio or more with respect to the initial illuminance. It guarantees time. However, some of them are defective, and there are cases where a lamp with low initial illuminance or a lamp whose illuminance drops sharply even within the illuminance guarantee time. When such a defective lamp is attached to the apparatus, the exposure apparatus in the related art does not have a configuration for judging this, and the exposure time corresponding to the appropriate exposure amount based on the illuminance detected by the illuminance monitor. Therefore, if the illuminance is decreased, the exposure time becomes longer, and the throughput is decreased. It is difficult for an operator to detect a lamp failure with a slight decrease in throughput. Therefore, in the conventional apparatus, it is difficult to detect the lamp failure only when the throughput is significantly reduced, and it is difficult to avoid a decrease in the number of processed sheets per unit time.

By the way, generally, the illuminance of the lamp decreases with the passage of time as shown by a curve 20 in FIG. 2, for example. When the illuminance of the lamp drops to a certain value or the lamp is replaced with a new one when the illuminance guarantee time has elapsed, the illuminance increases. However, when the device is used for a long period of time, the illumination optical system becomes dirty, cloudy, changes over time, etc., and even if a lamp with the same initial illuminance as when the device was first used was used,
The illuminance detected by the illuminance monitor does not rise to the same level as when the device was started (P ₁ > P in FIG. 2).
₂ ). That is, the initial illuminance of the lamp decreases as the usage time of the device elapses, as shown by the curve 21.

If it is decided that the illuminance monitor value is a constant value (P _{L in} FIG. 2) and the illuminance is defective and the lamp is replaced without considering the change of the illumination optical system, the apparatus is used. As the time becomes longer, the lamp replacement interval becomes shorter as shown in FIG. 2, which is not suitable for practical use. On the contrary, even if the change of the illumination optical system is taken into consideration, the change of the optical system is not constant depending on the usage environment of the device, and therefore the initial illuminance decrease pattern (curve 21) cannot be stored in advance as data, and therefore the time The illuminance limit P _L cannot be set with the function of.

In view of the conventional problems as described above, the present invention automatically determines the initial illuminance or the abnormality of the illuminance decrease of the lamp mounted on the exposure apparatus, taking into consideration the change with time of the illumination optical system, It is an object of the present invention to provide an exposure apparatus that can minimize a decrease in throughput.

[0008]

In order to solve the above problems, in the present invention, a light beam from a light source (1) is converted into an optical system (2, 3).
When illuminating the object (11) via a, 3b, 5, 8, 10), the optical system (2, 3a, 3b, 5, 8, 10)
In an exposure apparatus provided with an illuminance detection means (6) for detecting at least a part of a light flux passing through at least a part of the light flux and detecting information (P) relating to the illuminance of the light flux, information on a usage time of the light source (1) ( T ₂ ) and a time measuring means (13) for obtaining information (T ₁ ) relating to the use time of the optical system; the use time of the light source (T ₂ ) and the illuminance detected by the illuminance detecting means (6) in advance as basic data ( P) the first relationship (22), and the second relationship between the operating time (T ₁ ) of the optical system when the light source is replaced and the illuminance (P) detected by the illuminance detecting means (6). Calculation storage means (14a) for obtaining (21) and storing the first and second relationships (22, 21); Illuminance (P) and second relationship obtained when the light source (1) is replaced. Based on (21) and
The initial illuminance of the replaced light source is determined to be good or bad, and the illuminance reduction of the light source in use is abnormal based on the illuminance (P) obtained during use of the light source (1) and the first relationship (22). And a determination means (14b) for doing so.

[0009]

According to the present invention, the illuminance of the light source with respect to the use time of the device is detected during use of the device, and the initial illuminance defect of the light source is determined based on the relationship between the use time and the illuminance. It is possible to judge the illuminance defect in consideration of the influence of the change of the illumination optical system of the device.

Further, since the relation of the illuminance with respect to the usage time of the light source is obtained in advance as the basic data, and the illuminance of the light source with respect to the actual usage time of the light source is detected and compared with the basic data, an abnormality in the decrease in the illuminance of the light source is detected. It becomes possible to judge.

[0011]

1 is a diagram showing a schematic structure of an exposure apparatus according to an embodiment of the present invention. Since the basic structure is the same as that of the conventional exposure apparatus shown in FIG. 4, a different structure will be described below. Originally, the data P from the illuminance monitor 6 detected for the purpose of controlling the exposure time, together with the time T ₁ from the start of using the apparatus measured by the timer 13 and the time T ₂ after the replacement of the lamp 1 are calculated by the computer. It is stored in the storage operation unit 14a of 14. The data to be stored are the illuminance when the lamp has stabilized for a certain period of time after the lamp replacement (initial illuminance) and the illuminance at every predetermined time after the use of the lamp is started. Based on the stored data P, T ₁ , and T ₂ , the computer 14 determines the pattern of the temporal change of the optical system (which causes the decrease in the initial illuminance of the lamp shown by the curve 21 in FIG. 2) and the basic lamp. The illuminance reduction pattern (solid line 22 in FIG. 3) is obtained by the storage / calculation unit 14a. Then, based on these patterns and the illuminance P detected by the monitor 6, the determining unit 14b determines the initial illuminance of the lamp and an abnormality in the illuminance decrease (illuminance defect). When the computer 14 determines that the lamp has poor illuminance, a signal is output to the alarm 15 or the like to prompt the operator to replace the lamp.

Next, each pattern obtained by the computer 14 will be described with reference to FIGS. 1, 2 and 3. In the above configuration, first, a lamp whose initial illuminance is known is attached to the device, and the value detected by the illuminance monitor 6 is stored in the computer 14. From this value, the illuminance detected by the illuminance monitor (P _{s in} FIG. 3) when the lamp with the lowest initial illuminance of the guaranteed initial illuminance value is attached is obtained. this is,
This is because it is considered that the illuminance detected by the illuminance monitor 6 is the illuminance of the light flux passing through the illumination optical system and is slightly lower than the illuminance of the lamp itself. Now, let S _{a be} the illuminance of the lamp whose illuminance is known, P _{a be} the value of the illuminance monitor when the lamp is attached, and S _{min be} the minimum initial illuminance of the guaranteed value, P _S = P _a S _min. / S _a . That is, when the lamp to be actually used is attached, it is determined that the value P on the illuminance monitor is greater than P _{S and} that the value is good, and if the value P is small, the product is defective.

After that, since the above-mentioned change occurs in the optical system with the use of the apparatus, the initial illuminance (P ₁ , P ₂ , P ₃ , ...) Is detected by the monitor 6 every time the lamp is replaced, and the optical system of the optical system is detected. The pattern of change over time is obtained by using, for example, the least square method. Then, based on this pattern, the illuminance P _S in consideration of the device usage time at the time of lamp replacement is determined to determine the initial illuminance abnormality. Needless to say, when the pattern of the initial illuminance decrease is obtained, the data of the defective lamp is excluded.

On the other hand, since a lamp such as an ultra-high pressure mercury lamp shows a characteristic illuminance drop as shown in FIG. 3, data of illuminance with respect to usage time is obtained in advance to obtain a model pattern of illuminance drop with use of the lamp. Can be set. That is, the guaranteed illuminance P _nE when a certain lamp has passed the illuminance guaranteed time T _E is determined as a percentage of the initial illuminance P _n as a standard of the lamp, and is obtained based on this. Guaranteed illuminance P _nE of lamp with initial illuminance P _n after time T _E
Based on the model pattern described above, the basic data of the decrease in illuminance with respect to the use time (solid line 2 in FIG.
2) is asked. Then, when the value P of the illuminance monitor 6 in use of the lamp is lower than the illuminance given by the model pattern, that is, when the broken line 23 in FIG.

The illuminance P _nE is used as basic data until the lamp burst guarantee time T _B after the illuminance guarantee time T _E has elapsed.
Although an ultra-high pressure mercury lamp is used as a light source in the present invention, a light source such as a laser or a halogen lamp may be used.

[0016]

As described above, according to the present invention, the relationship between the usage time of the device and the illuminance and the relationship between the usage time of the light source and the illuminance is compared with the illuminance detected by the illuminance monitor. It is possible to accurately determine the illuminance defect of the light source. At this time, if the warning device or the like is used to prompt the operator for a defect in the light source, the decrease in throughput of the exposure apparatus can be suppressed to a minimum.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the illuminance of a light source and the usage time of an illumination optical system of an exposure apparatus.

FIG. 3 is a diagram showing a relationship between illuminance and usage time of a light source.

FIG. 4 is a diagram showing a schematic configuration of an exposure apparatus according to a conventional technique.

[Explanation of symbols]

 1 Light source 6 Illuminance sensor 13 Timer 14a Memory calculation unit 14b Judgment unit 15 Alarm

Claims (3)

[Claims] 1. When irradiating an object with a light beam from a light source through an optical system, at least a part of the light beam through at least a part of the optical system is detected to obtain information about the illuminance of the light beam. In an exposure apparatus provided with an illuminance detecting means for detecting, a time measuring means for obtaining information about a usage time of the light source and information about a usage time of the optical system; a usage time of the light source and the illuminance detection means as basic data in advance. The second relationship between the illuminance detected by the illuminance detected by the illuminance detecting means and the second relationship between the illuminance detected by the illuminance detecting means and the operating time of the optical system when the light source is replaced is obtained. An arithmetic storage unit for storing the first and second relationships; an initial illumination of the replaced light source based on the illuminance and the second relationship obtained when the light source is replaced. And a determination unit that determines whether the illuminance of the light source is in use is abnormal based on the illuminance and the first relationship obtained during use of the light source. Exposure equipment. 2. The exposure apparatus according to claim 1, wherein the second relationship is updated every time the light source is replaced. 3. The exposure apparatus according to claim 1, wherein the exposure apparatus further includes warning means for issuing a warning based on the judgment of the judgment means.