JPH11337441A - Device and method for evaluating cloudy characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of evaluating the state of occurrence of cloudiness and its effects generated by the irradiation of laser light. SOLUTION: A nitrogen gas is used as a carrier gas, and HMDS is used as the first cloudy substance 5. A mechanism which can introduce water as the second cloudy generating substance 6 is adopted. A reaction chamber 27 is provided with a reaction gas introducing part 27c to introduce a reaction gas, a laser light introducing window 27e, etc. Laser light 11 emitted from an excimer laser device becomes incident on an object to be irradiated 10 via the laser light introducing window 27e. Photo-assisted CVD occurs due to the laser light 11 from the excimer laser device and a reaction gas in the vicinity of the surface of the object to be irradiated 10 and is accumulated on the surface of the object to be irradiated 10. It is possible to monitor the degree of growth of the fog substances simultaneously by an acoustic sensor 12 such as a piezoelectric element set on the back surface side of the object to be irradiated 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for evaluating fogging characteristics of an optical element such as an optical material and an optical thin film under a specific environment.

[0002]

BACKGROUND OF THE INVENTION In recent years, in order to increase the degree of integration of semiconductor devices, there is an increasing demand for a high-resolution reduction projection exposure apparatus (stepper) for semiconductor production. One such method is to shorten the wavelength of the light source. Therefore, recently, a stepper using an excimer laser as a light source that can oscillate light in a wavelength range shorter than that of a mercury lamp and has a high output has begun. However, as the wavelength of the light source is shortened, contaminants generated by photodecomposition, thermal decomposition, or photo-CVD of organic gas on the portion of the optical element irradiated with excimer laser light (for example, the surface of a lens or a mirror). Adheres and fogging occurs. When such fogging occurs, scattering or absorption occurs in this portion, and the transmittance and the reflectance of the optical element decrease, and the optical characteristics deteriorate,
It has been found that laser damage of the film occurs from the starting point of the deposit.

[0003]

SUMMARY OF THE INVENTION Under such circumstances,
The optical element as described above is required to have laser durability, not to mention its optical characteristics. Furthermore, it is also required that it is difficult for deposits to be formed on an optical thin film or the like on the element surface, or that problems do not easily occur even if deposits are formed on the element surface.

For this reason, it is necessary to investigate or evaluate the degree of fogging of an optical component and the effect of the fogging on the optical component by reproducing the phenomenon of the occurrence of fogging caused by photodecomposition or thermal decomposition of an organic gas or photo-CVD. There is. Therefore, an object of the present invention is to provide an apparatus and a method capable of evaluating a state of occurrence of fogging generated by laser light irradiation and its influence.

[0005]

In order to solve the above-mentioned problems, the present inventors introduce a fogging substance into a reaction chamber in which an optical component as an object to be measured is set, and apply light or heat to the substance. The present inventors have found that fogging occurs in an optical component or an optical element, and have reached the present invention. According to the present invention, fogging of an optical component or an optical element can be evaluated, and the degree of progress of fogging can be quantitatively evaluated.

That is, the fogging characteristic evaluation device of the present invention
A reaction chamber for accommodating the object to be measured, a gas supply unit for supplying a gas containing a fogging substance that forms fogging on the surface of the object to be measured to the reaction chamber, and measuring the degree of fogging of the object to be measured in the reaction chamber A measuring device. According to this apparatus, the gas supply unit supplies the reaction chamber with a gas containing a fogging substance that forms fogging on the surface of the object to be measured, and the measuring device measures the degree of haze of the object to be measured in the reaction chamber. By appropriately changing the fogging substance and measuring the degree of fogging in each case, it is possible to identify the fogging substance that adversely affects the optical element as the object to be measured, its influence, and the like. Further, it becomes clear how the degree of progress of fogging varies depending on the substance (for example, a film forming material) on the outermost surface of the optical element, and the development of an optical material or an optical thin film that is less likely to fog can be accelerated.

In a preferred embodiment, the object to be measured is 1
An optical element irradiated with a laser in a wavelength range of 50 to 250 nm, wherein the fogging substance is an organic material used in any of semiconductor manufacturing environments. According to this aspect, it is possible to evaluate the timing and state of fogging, the degree of progress of fogging, and the like for the optical components incorporated in the exposure apparatus using the excimer laser.

In a preferred aspect, the measuring device includes a photoacoustic element for detecting an amount of light absorption when the object to be measured is irradiated with light as an acoustic wave. According to this aspect, it is possible to detect the degree of haze of the DUT in the reaction chamber as an acoustic wave corresponding to the amount of light absorption caused by this, and to precisely measure the degree of haze of the DUT. it can.

The method for evaluating fogging characteristics according to the present invention comprises the steps of: accommodating an object to be measured in a reaction chamber; and forming a haze on the surface of the object to be measured in the reaction chamber accommodating the object to be measured. The method includes a step of supplying a gas containing a substance and a step of measuring the degree of fogging of an object contained in the reaction chamber. According to this method, a gas containing a fogging substance that forms fogging on the surface of the object to be measured is supplied to the reaction chamber, and the degree of fogging of the object to be measured in the reaction chamber is measured. Then, by measuring the degree of fogging in each case, it is possible to identify the fogging substance which has an adverse effect on the optical element which is the object to be measured, its influence, and the like. Further, it becomes clear how the degree of fogging progresses depending on the substance on the outermost surface of the optical element, and the development of optical materials and optical thin films that are less likely to fog can be accelerated.

[0010] In a preferred embodiment, the fogging characteristic evaluation apparatus of the present invention further includes a uniform gas mixing mechanism between the gas supply unit and the reaction chamber. According to this aspect, a gas containing a fogging substance that forms fogging on the surface of the object to be measured can be introduced into the reaction chamber in a uniformly mixed state, and the fogging is uniformly generated on the surface of the object to be measured. Therefore, the degree of haze can be accurately measured.

Further, the fogging generation apparatus of the present invention comprises a reaction chamber for accommodating an object to be measured, and a gas supply unit for supplying a gas containing a fogging substance which forms fogging on the surface of the object to be measured to the reaction chamber. Prepare. In a preferred embodiment, the fogging generator of the present invention further includes a uniform gas mixing mechanism between the gas supply unit and the reaction chamber.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an apparatus and method for evaluating fogging characteristics according to the present invention. FIG. 1 is a schematic diagram of a fogging characteristic evaluation device according to the present invention. The measuring apparatus includes an illumination system 20 that illuminates the device under test 10, a reaction chamber 27 that is a closed container that stores the device under test 10, and a gas supply unit 30 that supplies a gas for performing an accelerated test of fogging. And a control device 40 for controlling operations of the illumination system 20 and the gas supply unit 30.

First, the illumination system 20 applies a photochemical reaction (photolysis, thermal decomposition, light decomposition) to the fogging substance introduced into the reaction chamber 27.
A laser device 15 for generating an excimer laser beam 11 in an ultraviolet wavelength range necessary for generating fogging on the surface of the device under test 10 by CVD, and a beam shape and power density of the laser beam 11 from the laser device 15 A beam expander 16 and a zoom lens 17 for changing the laser beam, an aperture 18 for adjusting the spot diameter when the laser beam 11 emitted from the zoom lens 17 is incident on the device under test 10, and a reaction chamber containing the device under test 10 Beam stop (laser trap) 1 arranged behind 27 and absorbing laser light
9 is provided.

FIG. 2 is a diagram for explaining the details of the reaction chamber 27 and the gas supply unit 30. The reaction chamber 27 includes a main body portion 27a, a holder 27b that holds the DUT 10 in the main body portion 27a, and a fogging substance gas (a reaction gas containing a fogging substance that forms fogging on the surface of the DUT 10). Gas introducing section 27 for introducing gas into main body portion 27a
c, a reaction gas discharge part 27d for discharging the fogging substance gas to the outside of the main body part 27a, and an aperture 18 of the illumination system 20.
A light introduction window 27e into which the laser light 11 having passed through
A light exit window 27f through which the laser light 11 that has passed through the device under test 10 is emitted is provided. Note that a heater and a thermometer (not shown) are built in the holder 27b that holds the DUT 10, and the DUT 10 and the inside of the reaction chamber 27 are heated to a desired temperature to form fogging. Adjust temperature conditions.

An acoustic sensor 12, which is a photoacoustic element such as a piezo element, is closely fixed to the back surface of the DUT 10 held by the holder 27b, and a photoacoustic wave from the DUT 10 is fixed. Is efficiently transmitted to the photoacoustic sensor 12. The photoacoustic sensor 12 detects a photoacoustic signal generated by a volume change occurring in the object 10 when the object 10 is continuously irradiated with the laser beam 11 having a constant intensity. This fluctuation of the photoacoustic signal is caused by the laser light 1 due to fogging generated on the surface of the device under test 10.
It is considered that this depends on the absorption amount of No. 1. Therefore,
By measuring such a change in the photoacoustic signal with the oscilloscope 112, it is possible to monitor the occurrence of fogging on the surface of the device under test 10 and the progress thereof.

The gas supply section 30 includes a nitrogen gas cylinder 1 for containing a nitrogen gas as a carrier gas. The gas supply unit 30 may be provided with an oxygen gas cylinder 101 for accommodating, for example, an oxygen gas that is a reaction gas, as required. The nitrogen gas from the nitrogen gas cylinder 1 is branched and supplied to three flow meters 3 via a pressure reducing valve 2. Two of them are sent to a pair of bubbling devices 4. Thereby, the first fogging substance 5 and the second fogging substance 6 can be sent into the reaction chamber 27 via the reaction gas introducing portion 27c together with the nitrogen gas as the carrier gas. The oxygen gas from the oxygen gas cylinder 101 passes through the pressure reducing valve 102 and the flow meter 103, and is then sent into the reaction chamber 27 via the reaction gas introduction part 27c.

Examples of the first fogging substance 5 include HM
It is conceivable to use DS (hexamethyldisilazane). This HMDS is sometimes used as an adhesion enhancer for a photoresist, and can be considered as an organic material that causes fogging in an optical element constituting an optical system of an exposure apparatus. Here, the mechanism of fogging of HMDS will be considered. Since HMDS is considered to be converted into silanol or siloxane by hydrolysis, water can be introduced as the second fogging substance 6 at the same time as HMDS which is the first fogging substance 5. Furthermore, since these are considered to be oxidized into silicon oxide, oxygen is also introduced at the same time. That is, when HMDS is considered to be the cause of fogging, the gas supply unit 30 supplies nitrogen, nitrogen + HM
A fogging gas in which four kinds of gases of DS, nitrogen + water and oxygen are mixed is supplied to the reaction chamber 27.

The fogging gas in the reaction chamber 27 is taken out of the reaction chamber 27 through a reaction gas discharge part 27d, and collected by, for example, a trap 13 cooled with liquid nitrogen 14. Hereinafter, measurement using the fogging characteristic evaluation device shown in FIGS. 1 and 2 will be described. First, as shown in FIG. 1, after adjusting the power density and the beam shape of the laser beam 11 emitted from the laser device 15 through the beam expander 16, the zoom lens 17, and the aperture 18, the measured light in the reaction chamber 27 is measured. The light is incident on a predetermined position of the object 10. At this time, the nitrogen gas from the nitrogen gas cylinder 1 is branched and supplied to three flow meters 3. As a result, the gas containing the first and second fogging substances 5 and 6 is sent into the reaction chamber 27. At the same time, the oxygen gas cylinder 101
Is fed into the reaction chamber 27 via the flow meter 103.

In the vicinity of the surface of the object 10 to be measured, the laser device 1
The laser beam 11 from 5 and the above-mentioned fogging gas cause photo-CVD, and a fogging substance as a reaction product is deposited on the surface of the measured object 10. At this time, the DUT 10
The degree of growth of the cloudy substance can be monitored by the acoustic sensor 12 fixed to the back side of the substrate. The conditions that can be changed for the fogging characteristic evaluation by the present apparatus include the gas type of the fogging substance gas (atmospheric gas), gas mixture ratio, gas flow rate, laser power, number of shots, oscillation frequency, and temperature of the DUT 10. And the material of the DUT 10 can be considered.

FIG. 5 shows another example of the reaction chamber 27 and the gas supply section 30 of the fogging characteristic evaluation apparatus according to the present invention. The above-described reaction chamber 27 and gas supply unit 30
In addition to the above configuration, a uniform gas mixer 22 is provided in a supply pipe connecting the reaction gas supply unit 30 and the reaction chamber 27, and a shower unit 23 is provided at the tip of the reaction gas introduction unit 27c.

That is, the first fogging substance 5 and the second fogging substance 6 are introduced into the reaction chamber 27 through the uniform gas mixer 22 together with the nitrogen gas as the carrier gas. Therefore, the first fogging substance and the second fogging substance are introduced into the reaction chamber 27 while being uniformly stirred. Further, the gas can be diffused throughout the reaction chamber 27 by the shower section 23 provided at the tip of the reaction gas introduction section 27c.

By these actions, a uniform atmosphere is formed around the object to be measured, so that it is possible to uniformly generate fogging. FIG. 6 is an SEM image showing a cloudy state generated in the reaction chamber 27. From now on, the inside of the reaction chamber 27
It can be seen that fogging has occurred uniformly. The effect of uniformly generating fogging is not only when the generation and growth state of fogging substances is measured by an acoustic sensor such as a piezo element as described above, but also in the reaction chamber, instead of the acoustic sensor, a spectrophotometer for the ultraviolet region is used. It is meaningful when a meter is provided and the amount of absorption is calculated by spectroscopic measurement in In-Situ to detect the generation and growth state of a cloudy substance.

Hereinafter, specific embodiments will be described.
In the present embodiment, a laser beam for illuminating the
KrF light having a wavelength of 248 nm is used as the light 11.
You. In addition, the laser beam 11 is 100 mJ / cm ^Two/ Pu
The oscillation frequency was adjusted to be 1 Hz and the oscillation frequency was 40 Hz. This
Therefore, KrF is provided in the light introduction window 27e and the light exit window 27f.
Wavelength transparent synthetic quartz glass or fluorite used as substrate
A film that is anti-reflective at KrF wavelength
A film was formed.

As described above, the atmosphere gas is HMD.
A four-component mixed gas containing S is used. HMDS concentration is 1p
Although it can be set variably from pm to 20%, in this example, the HMDS concentration was adjusted to, for example, 1%. The temperature of the reaction chamber 27 was room temperature, and the photoacoustic signal was monitored with the number of shots as the horizontal axis. K as the object to be measured 10
The measurement was performed using two types of films each having an antireflection film formed on one side at an rF wavelength. The first object to be measured is KrF
A film having an antireflection film at one wavelength was formed on one surface, and a second object to be measured was a film having an antireflection film at a KrF wavelength formed on one surface and a thin protective film formed thereon.

The results are shown in FIGS. FIG. 3 is a graph showing a change in the absorption amount of the first DUT (anti-reflection film), and FIG. 4 is a graph showing a change in the absorption amount of the second DUT (anti-reflection film + protective film). It is. Note that the horizontal axis indicates the number of pulses of the laser beam applied to the device under test, and the vertical axis indicates the intensity of the photoacoustic signal (that is, the degree of cloudiness). As is clear from these graphs, it was found that changing the outermost surface material of the measured object changed the degree of fogging.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment. For example, assuming not only HMDS but also various organic materials as the fogging substance, introducing such an organic material into the reaction chamber 27 makes it easy to evaluate the fogging characteristics of the measured object with respect to these organic materials. can do. As the light source, a light source that emits light of 150 to 250 nm, for example, an ArF excimer laser (193 nm),
Any of a solid laser, a fourth or fifth harmonic of a YAG laser, an excimer lamp, and the like can be used for evaluation.

[0027]

According to the present invention, the fogging substance which adversely affects the optical member can be identified, the influence, etc. can be found. Further, it can be seen that the degree of fogging progress differs depending on the outermost surface material of the film, and the development of the film which is hard to fog can be accelerated. . Since uniform fogging can be generated on the surface of the measured object, the degree of fogging can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fogging characteristic evaluation device.

FIG. 2 is a schematic diagram illustrating the structure of a reaction chamber and a gas supply unit.

FIG. 3 is a graph showing a photoacoustic signal change of a first evaluation object.

FIG. 4 is a graph showing a photoacoustic signal change of a second evaluation object.

FIG. 5 is a schematic diagram illustrating the structure of another example of a reaction chamber and a gas supply unit.

FIG. 6 is an SEM image showing a cloudy state generated in the reaction chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nitrogen gas cylinder 2, 102 Pressure reducing valve 3, 103 Flow meter 4 Bubbling device 5 First fogging substance 6 Second fogging substance 10 DUT 11 Laser beam 12 Photoacoustic sensor 14 Liquid nitrogen 15 Laser device 22 Uniform gas mixer 23 shower part 27 reaction chamber 30 reaction gas supply part

Claims (7)

[Claims] A reaction chamber accommodating an object to be measured; a gas supply unit configured to supply a gas containing a fogging substance that forms fogging on the surface of the object to be measured to the reaction chamber; A fogging characteristic evaluation device comprising: a measuring device for measuring the degree of fogging of an object to be measured. 2. The object to be measured is an optical element irradiated with a laser in a wavelength range of 150 to 250 nm, and the fogging substance is an organic material used in any semiconductor manufacturing environment. The fogging characteristic evaluation device according to claim 1, wherein: 3. The fogging characteristic evaluation according to claim 1, wherein the measuring device includes a photoacoustic element that detects an amount of light absorption when the object to be measured is irradiated with light as an acoustic wave. apparatus. 4. A step of accommodating an object to be measured in a reaction chamber, and supplying a gas containing a fogging substance that forms fogging on the surface of the object to be measured to the reaction chamber accommodating the object to be measured. And a step of measuring the degree of fogging of the object to be measured accommodated in the reaction chamber. 5. The fogging characteristic evaluation apparatus according to claim 1, further comprising a uniform gas mixing mechanism between said gas supply unit and said reaction chamber. 6. A fogging apparatus comprising: a reaction chamber for accommodating an object to be measured; and a gas supply unit that supplies a gas containing a fogging substance that forms fogging on the surface of the object to be measured to the reaction chamber. 7. The fogging apparatus according to claim 6, further comprising a uniform gas mixing mechanism between the gas supply unit and the reaction chamber.