JP2001235430A - Optical inspection instrument and optical surface inspection instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the generation of cloudiness on an optical member caused by illumination light for inspecting an ultraviolet range without heating the optical member. SOLUTION: Ultraviolet rays with a wavelength of below 400 nm are emitted from a superhigh pressure mercury lamp 101. The ultraviolet rays for inspection irradiate a wafer 103 by a condenser lens 102. The emission light of the wafer 103 forms an image with an objective lens 104 and an imaging lens 105 on a CCD 106. The optical members are arranged in a container 108 filled with a nitrogen gas. The nitrogen gas contains none of sulfur dioxide, ammonium, oxygen and the like which forms ammonium sulfate. This can prevent the ammonium sulfate from adhering to the surface of the optical members such as lens even under a prolonged use of the ultraviolet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing various inspections by irradiating an inspection object with inspection illumination light,
The present invention relates to an apparatus for inspecting a surface by irradiating an inspection object such as a semiconductor wafer or a liquid crystal display panel with illumination light for inspection such as a laser beam.

[0002]

2. Description of the Related Art A surface inspection apparatus of this type irradiates an ultra-high pressure mercury lamp and illumination light from the ultra-high pressure mercury lamp to a surface to be inspected as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-232232. It has an optical system, a CCD that receives light emitted from the surface to be inspected and photoelectrically converts the light, and an image processing device that performs a predetermined process on an image signal photoelectrically converted by the CCD. Based on the image processing result of the image processing apparatus, the state of the surface to be inspected is evaluated by a predetermined evaluation algorithm determined in advance by a CPU or the like.

[0003] Conventional surface inspection devices have used visible light, but with the miniaturization of circuits formed on wafers,
There is a need to use ultraviolet light having a shorter wavelength of 400 nm or less. When the optical system is placed in the air as in a conventional surface inspection device, the surface of the optical member that composes the optical system by irradiating ultraviolet light has ammonium sulfate.
_{((NH 4) 2 S0 4} ) , etc. is deposited, the transmittance or reflectance is disadvantageously lowered.

[0004] In the air, a very small amount of sulfur dioxide (S
There are substances such as O ₂ ) and ammonia (NH ₄ ). This is the same in a clean room of a semiconductor manufacturing plant. Then, these substances, based on the energy of the ultraviolet light combines with oxygen in the air (O ₂₎ and water vapor (H ₂ O), ammonium sulfate _{((NH 4) 2 S0 4} ) is generated, the optical member surface It is believed to adhere to.

To avoid this problem, Japanese Patent Laid-Open No. 4-128
No. 702 and Japanese Patent Laid-Open No. 5-582, an optical member is heated to a temperature higher than the decomposition temperature of ammonium sulfate to prevent ammonium sulfate from adhering to the surface of the optical member.

[0006]

However, these methods heat the optical member, and may adversely affect the optical performance such as deformation of the optical member and change in the refractive index. In particular, in a semiconductor manufacturing process that requires strict temperature control, it is desirable to avoid the operation of heating the device as much as possible, and there is an urgent need to develop a device that hardly affects optical performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical inspection apparatus and an optical surface inspection apparatus which prevent the optical member from being fogged by the irradiation of inspection illumination light without heating the optical member.

[0008]

The present invention will be described with reference to FIG. 1 showing one embodiment. (1) The optical inspection apparatus according to the first aspect of the present invention is an illumination light source 1 for emitting inspection illumination light in a wavelength range in which a fogging phenomenon occurs on the surface of an optical member due to a causative substance in an inspection atmosphere.
01, an optical system 102, 104, 105 for irradiating the inspection target 103 with the illumination light for inspection, a light receiving device 106 for receiving light emitted from the inspection target 103 by the irradiation of the inspection illumination light, and a light source for illumination 101, optical systems 102 and 10
The above object is achieved by providing the container 4, 105, and the container 108 in which the light receiving device 106 is placed in an inert gas atmosphere or vacuum. (2) The optical surface inspection apparatus according to claim 2 has a wavelength of 40
An illumination light source 101 that emits inspection illumination light including ultraviolet light of 0 nm or less, an optical system 102, 104, and 105 that irradiates the inspection target 103 with the inspection illumination light, and an inspection target 103 that is irradiated with the inspection illumination light. Detecting device 106 for detecting the light emitted from the surface of the light source, illumination light source 101, optical systems 102, 104, 105, and container 108 for disposing detecting device 106 in an inert gas atmosphere or vacuum.
The above object is achieved by providing the following. (3) The optical surface inspection apparatus according to claim 3 is claim 2.
In the optical surface inspection device described in the above, the oxygen concentration measuring device 112b disposed outside the container 108 and the container 108 based on the measurement signal from the oxygen concentration measuring device 112b.
And an alarm device 111 for outputting an alarm when the oxygen concentration outside the device becomes equal to or less than a predetermined reference value.

In the section of the means for solving the problems described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the embodiments.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of an optical surface inspection apparatus according to the present invention will be described with reference to FIG. This surface inspection apparatus includes an illumination light source, that is, an ultra-high pressure mercury lamp 101, an optical system, that is, a condenser lens 102, an objective lens 104, and an imaging lens 105, and a light receiving device, that is, a CCD 106.
And an image processing device 107 for inspecting the surface of the wafer 103 to be inspected by inspection illumination light. Wafer 103 is held on stage ST. By operating the stage ST, the surface of the wafer 103 can be swung to change the incident angle of the inspection illumination light.

In the closed container 108, an ultra-high pressure mercury lamp 101, a condenser lens 102, and an objective lens 10
4, an imaging lens 105 and a CCD 106 are arranged. These components arranged in the container 108 are called optical members for convenience. A nitrogen gas supply device 109 is connected to the container 108, and the inside of the container 108 is replaced with nitrogen gas. For example, before starting the inspection, nitrogen gas is filled until a predetermined nitrogen gas concentration is reached. During the inspection, the nitrogen gas supply device 109 shuts off the container 108. During the inspection, the nitrogen gas may be continuously supplied to the container 108.

A pressure measuring device 110 is provided in the closed container 108.
, An oxygen concentration measuring device 112a is also provided. Outside the sealed container 108, an oxygen concentration measuring device 112b and an alarm device 111 are provided. The outside of the closed container 108 is called a working room. The working room is a so-called clean room, and an operator places a wafer 10 in a container 108 in the working room.
3 is loaded and unloaded, and the wafer 10 is
3 is rocked.

The pressure measuring device 110 measures the pressure inside the container 108. The oxygen concentration measuring device 112a measures the oxygen concentration inside the container 108. Oxygen concentration measuring device 112b
Measures the oxygen concentration outside the container 108, i.e. in the working chamber. Pressure measuring device 110 and oxygen concentration measuring device 11
2a and 112b are each connected to the alarm device 111.

In the surface inspection apparatus configured as described above,
Ultra-high pressure mercury lamp 101 emits inspection illumination light in the ultraviolet region such as an i-line having a wavelength of 365 nm and a j-line having a wavelength of 313 nm. This illumination light is uniformly irradiated on the wafer 103 by the condenser lens 102. Wafer 103
If there is a foreign substance or a scratch on the upper part, the reflected light intensity or the diffracted light intensity of that part is emitted differently from the other parts. Wafer 1
The light emitted from 03 passes through the objective lens 104 and the imaging lens 105 and is received by the CCD 106. CC
D106 converts the received light from wafer 103 into an electric signal corresponding to the intensity and outputs the electric signal to image processing apparatus 107. The image processing device 107 performs predetermined image processing on the image signal output from the CCD 106 and evaluates the surface state of the wafer 103 based on the image signal after the image processing. For example, the image processing apparatus 107 has a CPU, and the wafer 1 is processed by a predetermined evaluation algorithm.
No. 03 surface defect is detected.

As described above, the ultra-high pressure mercury lamp 101
The inspection illumination light in the ultraviolet light range, such as an i-line having a wavelength of 365 nm and a j-line having a wavelength of 313 nm, is emitted. Therefore, when the optical member is disposed in the air as in the related art, ammonium sulfate or the like adheres to the surfaces of the condenser lens 102, the objective lens 104, the imaging lens 105, and the CCD 106.

Therefore, in this embodiment, in order to avoid such a fogging phenomenon of the optical member, the optical member is arranged in a closed container 108, and the inside of the closed container 108 is supplied from a nitrogen gas supply device 109. Nitrogen (N ₂ ) gas. Nitrogen gas does not contain causative substances (sulfur dioxide, ammonia, oxygen, etc.) that form ammonium sulfate. Therefore, even when the inspection illumination light in the ultraviolet region is used for a long time, it is possible to prevent ammonium sulfate from adhering to the surface of the optical member.

The inside of the sealed container 108 is set at 1030 h.
When the pressure is increased to Pa (hectopascal) or more, it is possible to easily detect that the nitrogen gas leaks from the container 108 and the inside of the container 108 is depressurized. The pressure measuring device 110 detects this change in pressure and outputs an alarm signal to the alarm device 111. The alarm device 111 emits an alarm sound so that the operator can know that the nitrogen gas has leaked.

On the other hand, the oxygen concentration measuring device 112 outside the container
When the oxygen concentration detected in b becomes less than 18.5%, the alarm device 11 issues an alarm and notifies the worker that the oxygen concentration in the work room has decreased. The oxygen concentration measurement device 112a detects the oxygen concentration in the container 108 and can detect that oxygen has flowed into the container 108 or that the container 108 has been sufficiently filled with nitrogen gas. Therefore, the oxygen concentration measuring device 112a is connected to the display device 113 installed in the work room, and the oxygen concentration in the container 108 is sequentially displayed.

The oxygen concentration in the working room may fluctuate locally due to the airflow in the working room. Therefore, the oxygen concentration measuring device 112 is provided in the working room outside the closed container 108.
It is preferable to dispose the oxygen concentration measuring device 112c connected to the alarm device 111 at a location different from b. In this case, the quantity and position of the oxygen concentration measuring device 112c arranged in the working room depend on obstacles that can change the airflow in the working room, that is, the size and shape of the working room, the arrangement of other devices and ventilation ducts, and the like. It has to be determined appropriately.

As the gas filled in the closed vessel 108, an inert gas such as helium (He) or argon (Ar) can be used in addition to the nitrogen used in the present invention. In this specification, these gases such as helium (He) and argon (Ar) are collectively referred to as an inert gas in addition to nitrogen. Instead of filling and supplying the container 108 with the inert gas, a vacuum atmosphere may be set in the container.

Second Embodiment An optical surface inspection apparatus according to a second embodiment of the present invention will be described with reference to FIG. This surface inspection apparatus includes an illumination light source, that is, a low-pressure mercury lamp 201, an optical system, that is, a concave mirror 202, a concave mirror 204, and an imaging lens 205.
, A light receiving device, that is, a CCD 206, and an image processing device 2
07. In the second embodiment, the low-pressure mercury lamp 201, the concave mirror 202, the concave mirror 204, the imaging lens 205, and the CCD 206 are referred to as optical members, and these are disposed in a closed vessel 208.

The closed vessel 208 is provided with a nitrogen gas supply device 209.
And the inside of the closed vessel 208 is replaced with nitrogen gas. In the second embodiment, the nitrogen gas supply device 209 supplies nitrogen gas from the gas supply line L1 to the container 208,
The nitrogen gas in the container 208 is recovered from the gas return line L2. That is, the nitrogen gas is circulated inside the container 208. An oxygen concentration measuring device 212a is provided in the closed container 208.
And an airflow measuring device 210 are provided. Outside the sealed container 208, an alarm device 211 and an oxygen concentration measurement device 2
12b.

The airflow measuring device 210 measures the airflow in the container 208. The oxygen concentration measuring device 212a measures the oxygen concentration inside the container 208. Oxygen concentration measuring device 212b
Measures the oxygen concentration in the working chamber outside the container 208. Airflow measuring device 210, oxygen concentration measuring devices 212a and 212
12b are each connected to the alarm device 211.

The light emitted from the low-pressure mercury lamp 201 illuminates the wafer 203 telecentrically by the concave mirror 202. If there is any foreign matter or scratch on the wafer 203,
The reflected light intensity and the diffracted light intensity at that portion are emitted differently from the other portions. The diffracted light including the zero-order light (reflected light) emitted from the wafer 203 passes through the concave mirror 204 and the imaging lens 205 to form an image on the CCD 206. CCD
The light image received at 206 is converted into an electric signal corresponding to the light intensity and input to the image processing device 207. The image processing device 207 detects a defect on the wafer 203 based on the input image signal. Also, as described above, the wafer 20
The stage 3 is swung by the stage ST, and the incident angle of the illumination light for inspection with respect to the wafer 203 can be changed.

Since the inspection illumination light including far ultraviolet light (wavelength 248 nm) is emitted from the low-pressure mercury lamp 201, the inspection illumination light is irradiated in the air for a long time as in the first embodiment. Then, ammonium sulfate adheres to the surfaces of the concave mirror 202, the concave mirror 204, the imaging lens 205, and the CCD 206.

In order to avoid this phenomenon, the optical member is replaced with nitrogen (N
_Two) Place in a closed vessel 208 filled with gas.
You. A nitrogen gas supply device 209 is provided inside the container 208.
Nitrogen (N _Two) Supply and circulate gas. Nitrogen in container 208
To produce ammonium sulfate by supplying
Ingredients (sulfur dioxide, ammonia, oxygen, etc.) in container 2
08 can be removed. Therefore, the ultraviolet region
Even if the inspection illumination light is used for a long time,
The adhesion of ammonium sulfate can be prevented.

As described above, the airflow measuring device 210 measures the airflow inside the container 208. For example, when a hole is opened in the container 208 and nitrogen leaks from the hole to change the airflow in the container 208, the airflow measuring device 210 measures the change in the airflow. When the airflow measuring device 210 detects a change in the airflow, the alarm device 211 is driven and an alarm sounds. An oxygen concentration measurement device 212a is installed inside the container 208, and an oxygen concentration measurement device 212b is installed outside the container 208, connected to the alarm device 222. The oxygen concentration measurement device 112a and the oxygen concentration measurement device 112a of the first embodiment are respectively provided. Concentration measuring device 112b
Performs the same function as.

Also in the second embodiment, it is preferable to provide a plurality of oxygen concentration measuring devices in the work room where the container 208 is installed.

Third Embodiment An optical surface inspection apparatus according to a third embodiment of the present invention will be described with reference to FIG. The surface inspection device shown in FIG.
Excimer laser 301, rotating polygon mirror 301a, concave mirror 302, concave mirror 304, imaging lens 305, C
A CD 306 and an image processing device 307 are provided. The rotating polygon mirror 301a and the concave mirror 302 are accommodated in a sealed container 308a, the concave mirror 303 is accommodated in a sealed container 308b, and the imaging lens 305 and the CCD 306 are sealed in the sealed container 308b.
8c. In addition, the closed containers 308a, 3
Quartz glass is attached to the entrance and exit windows of 08b and 308c.

In the surface inspection apparatus according to the third embodiment, a laser beam is emitted from an excimer laser 301 having a wavelength of 193 mm. The beam diameter of the laser beam is enlarged by a beam expander (not shown), deflected by a rotating polygon mirror 301 a disposed on the focal plane of the concave mirror 302, and reflected by the concave mirror 302. The laser beam reflected by the concave mirror 302 scans the wafer 303, thereby
3 The entire surface is irradiated with a laser beam. Light emitted from the wafer 303 is transmitted to the concave mirror 304 and the imaging lens 305.
The light is converted into an electric signal corresponding to the light intensity by the CCD 306 through the
Detect the above defects. The wafer 303 is held on the stage ST as in the above embodiments.

Since the wavelength of the laser light used in the third embodiment is far-ultraviolet light, the first embodiment and the second embodiment
When the laser beam is used for a long time in the air, the concave mirror 302, the concave mirror 304, the imaging lens 30
5. Ammonium sulfate adheres to the surface of the optical member constituted by the CCD 306.

To avoid this phenomenon, the excimer laser 3
01, the rotating polygon mirror 301a in the closed container 308a, the concave mirror 304 in the closed container 308b, the imaging lens 30
5. The CCD 306 is placed in the closed container 308c. Then, by filling the inside of each of the closed containers 308a to 308c with nitrogen gas, the causative substances (sulfur dioxide, ammonia, oxygen, etc.) that generate ammonium sulfate in each container are removed. Thereby, even if the excimer laser is used for a long time, it is possible to prevent ammonium sulfate from adhering to the optical member surface.

A nitrogen gas or an inert gas may be supplied and circulated to each of the closed containers 308a to 308c. As in the first and second embodiments, all of the optical members may be housed in a single closed container. Also in the second embodiment, it is preferable to provide a plurality of oxygen concentration measuring devices in the work room where the containers 308a to 308c are installed.

The present invention is not limited to the surface inspection apparatus described above. That is, an illumination light source that emits inspection illumination light in a wavelength range that causes a fogging phenomenon on the surface of an optical member due to a causative substance in the air, an optical member that irradiates the inspection object with inspection illumination light, and an illumination light source The present invention can be applied to various optical inspection apparatuses including a container in which an optical system and an optical system are arranged in an inert gas atmosphere or in a vacuum.

[0035]

According to the present invention, the optical member is made of nitrogen (N ₂ ),
By arranging in an inert atmosphere such as argon or helium or in a vacuum, a causative substance for generating a cloudy substance is not contained in the container, that is, in the optical path atmosphere of the inspection illumination light. As a result, no fogging substance is generated even when the illumination light for inspection such as ultraviolet light is irradiated, and no impurities adhere to the surface of the optical member arranged in the apparatus. Therefore, when the inspection illumination light such as ultraviolet light is used, the transmittance and the reflectance of the optical member are not reduced. In other words, it is possible to prevent the optical performance of the optical member from deteriorating, and it is possible to effectively inspect a surface to be inspected such as a semiconductor wafer. Further, unlike the conventional case, it is not necessary to heat the optical member for the purpose of preventing the optical member from fogging, so that the deterioration of the optical performance due to heat can be prevented. Further, since the alarm is issued when the oxygen concentration outside the container is equal to or less than the predetermined reference value, the safety of the worker is ensured even if nitrogen gas or inert gas leaks from the container.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of an optical inspection apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the optical inspection apparatus according to the present invention.

FIG. 3 is a schematic view showing a third embodiment of the optical inspection apparatus according to the present invention.

[Explanation of symbols]

101: ultra-high pressure mercury lamp 102: condenser lens 103, 203, 303: wafer 104: objective lens 105, 205, 305: imaging lens 106, 206, 305: CCD 107, 207, 307: image processing device 108, 2
08: closed container 109, 209: nitrogen gas supply device 110:
Pressure measuring devices 111, 211, 311: Alarm devices 212a, 212b, 212c: Oxygen concentration measuring device 201: Low pressure mercury lamp 202, 204: Concave mirror 210: Air flow measuring device 301: Excimer laser 301a: Rotating polygon mirror 302, 3
04: concave mirror 308a, 308b, 308c: sealed container

Continued on the front page F-term (reference) 2F065 AA49 CC19 CC25 DD11 DD15 FF01 FF04 FF63 GG03 GG04 GG21 HH04 HH12 HH18 JJ08 LL09 LL14 LL19 LL62 MM16 PP12 QQ31 2G051 AA51 AB01 AB07 BA05 CA04 CB86 DB01 BA092 DH12 DH31 DH38 DH49 DH60 DJ02

Claims (3)

[Claims] An illumination light source for emitting illumination light for inspection in a wavelength range where a fogging phenomenon occurs on the surface of an optical member due to a causative substance in an inspection atmosphere, and an optical system for irradiating the inspection illumination light to an inspection object And a light receiving device for receiving light emitted from the inspection object by irradiation of the inspection illumination light, and arranging the illumination light source, the optical system, and the light receiving device in an inert gas atmosphere or vacuum. An optical inspection device, comprising: 2. An inspection light source for emitting inspection illumination light including ultraviolet light having a wavelength of 400 nm or less, an optical system for irradiating the inspection illumination light to an inspection target, and the inspection by irradiation of the inspection illumination light. A light receiving device for receiving light emitted from a surface of an object, and a container for arranging the light source for illumination, the optical system, and the light receiving device in an inert gas atmosphere or vacuum are provided. Optical surface inspection device. 3. The optical surface inspection apparatus according to claim 2, wherein the oxygen concentration measuring device disposed outside the container and oxygen outside the container based on a measurement signal from the oxygen concentration measuring device. An optical surface inspection device, further comprising: an alarm device for outputting an alarm when the concentration becomes equal to or less than a predetermined reference value.