KR20120109390A - Measuring in-situ uv intensity in uv cure tool - Google Patents

Abstract

PURPOSE: An ultraviolet ray measuring device is provided to produce uniform exposure by rotating an ultraviolet ray lamp assembly or a substrate in the ultra-violet ray hardening. CONSTITUTION: An ultraviolet ray lamp assembly(401) is installed on a processing chamber(413). The ultraviolet ray lamp assembly comprises a transformer and a magnetron. The transformer pumps microwave energy within an ultraviolet ray bulb(405) and a reflector(407). An ultraviolet ray detector assembly(409) is installed under the ultraviolet ray lamp assembly. A chamber window(411) passes through UV radiation from the ultraviolet ray bulb to a substrate(417) under the processing chamber. The substrate is settled on a substrate support portion(415).

Description

Co-position UV intensity measurement of UV curing tool {MEASURING IN-SITU UV INTENSITY IN UV CURE TOOL}

Cross Reference of Related Application

This application claims priority based on US patent application Ser. No. 13 / 070,306, filed March 23, 2011, entitled "Measuring In-situ UV Instensity In UV Cure Tool," the contents of which are incorporated herein. .

Technical field

The present invention relates to a radiation treatment apparatus and method including radiation treatment of a thin film.

Many thin film layers are used to fabricate integrated circuits. Integrated circuit fabrication requires a thin film with certain properties to make the circuit function as designed. For example, materials with low dielectric constants (low-k) are generally needed. By using a low-k material as an intermetal dielectric (ie, an insulating layer that separates a series of levels of conductive metal interconnects), signal propagation delays due to capacitive effects, also known as RC delays, are reduced. Dielectric materials with low dielectric constants will have low capacitances, and therefore the RC delay of integrated circuits composed of these materials will be similarly low.

As another example, materials with specific tensile or compressive stresses are generally needed. Shallow Trench Isolation (STI) film tensile stresses increase transistor drain current and device performance due to high electron and hole mobility. Other applications require the dielectric film to have a compressive stress. These and other properties can be met on the film when deposited or after treatment.

One such treatment may be a heating process in which the substrate is heated to a predetermined temperature for a predetermined time. The heat treatment may remove unwanted particles from the film or change their stress or other properties. However, this heating process has some problems. In particular, the substrate temperature should generally be high for several hours of exposure time (ie, above about 500 degrees Celsius). As is well known in the art, such conditions can damage copper-containing devices, especially in applications where low-k dielectrics are cured and long exposure times are not suitable for mass production. In addition, the use of temperature sensitive nickel silicide excludes the induction of film stress by using a temperature of 400 ° C. or higher, and some SiN films have a curing temperature of up to 480 ° C.

To overcome these disadvantages of heat treatment, other techniques have been developed that utilize film curing with ultraviolet radiation. Irradiation of low-k or spacer nitride films can change desired film properties such as dielectric constant or film stress at low temperatures. However, the use of ultraviolet radiation in such a process can cause harmful side effects if no special effort is made to maintain the substrate temperature at an optimal level while delivering a precise amount of radiation. Precise amounts of radiative transfer can be complicated when the ultraviolet lamp intensity drifts over time and the ultraviolet exposure affects the optical portion.

In other applications, radiation processing can be performed using electromagnetic radiation from portions of the electromagnetic spectrum, including infrared (IR), X-ray, and microwave radiation.

An improved apparatus and method for copy processing are provided. In some embodiments, a semiconductor processing apparatus for radiation curing includes a process chamber and a radiation assembly outside the process chamber. The radiation assembly transmits radiation into the chamber on the substrate holder through the chamber window. The radiation detector sometimes measures the radiation intensity. The assembly includes a gas inlet and an exhaust operable to flow radiation-activated refrigerant gas through the radiation assembly.

In one form, an ultraviolet curing semiconductor processing apparatus includes a process chamber and an ultraviolet radiation assembly outside the process chamber. The ultraviolet radiation assembly transmits radiation into the chamber on the substrate holder through the chamber window. Ultraviolet detectors sometimes measure ultraviolet intensity. The assembly includes a gas inlet and an exhaust operable to flow radiation-activated refrigerant gas through the radiation assembly.

In another aspect, the present invention relates to an ultraviolet device comprising a process chamber and an ultraviolet radiation assembly mounted on the process chamber. The ultraviolet radiation assembly includes one or more ultraviolet radiation light sources, one or more reflectors operable to direct a portion of the ultraviolet radiation through the window toward the substrate holder, and an ultraviolet radiation detector. This detector is mounted under an ultraviolet lamp and is arranged outside of the chamber. The detector is oriented toward the window and detects light reflected on the mirror or calibration substrate disposed above the window. A cover, such as a shutter or iris, protects the detector from ultraviolet radiation when not in use. The ultraviolet intensity detector can withstand the high energy of ultraviolet light. The ultraviolet detector can be a silicon carbide (SiC) photodiode or photodetector. The ultraviolet detector can also include a diffuser. The ultraviolet detector may also include a gas inlet and an exhaust that operate to flow ultraviolet-activated refrigerant gas through the radiation assembly.

The mirror is oriented towards the detector and reflects ultraviolet radiation towards the detector. The mirror may be detachable from the ultraviolet radiation assembly, or may be configured to not interfere with ultraviolet transmission to the chamber during substrate processing. The mirror may be coated with a high temperature ultraviolet coating or a metal coating (eg aluminum coating). The calibration substrate reflects ultraviolet light of the wavelength of interest. The substrate may be a pure silicon wafer, a wafer coated with a high temperature ultraviolet coating, or a wafer to be coated with another suitable coating such as aluminum.

The apparatus may also include a controller configured to execute a set of instructions. The controller measures by measuring 1) UV intensity at UV radiation power, 2) calculating deviation based on measurements and reference intensity, and 3) executing commands to compensate for deviation by adjusting UV radiation power or exposure time. Compensate for the intensity. The controller may also direct cover movement by opening a cover, such as a shutter or iris, to expose the ultraviolet detector to ultraviolet radiation, and executing a command to close the shutter or iris to separate the ultraviolet detector from the ultraviolet radiation.

In another aspect, the present invention relates to a method for calibrating an ultraviolet device. This method may be a simple compensation of the measured ultraviolet intensity, the occurrence of an alarm or warning, or the determination of a management or corrective action. Ultraviolet device calibration may be performed while keeping the chamber in vacuum with the pedestal at high temperature (ie, without shutting down the system or removing the system or chamber from service). The method includes receiving a calibration indication or determining a calibration request, placing a calibration substrate on a substrate holder, setting the ultraviolet radiation power to the first power, and setting the ultraviolet detector output at a predetermined duration. Measuring over and removing the calibration substrate.

The calibration indication can be triggered in software by exposure duration, total intensity, elapsed time, number of wafers processed, or the like, or manually triggered by an operator. A calibration substrate is provided to the chamber on the substrate holder. Such calibration substrates may be held in a front opening unified pod (FOUP) in the plant's substrate storage system or storage locker. The calibration substrate may be a pure silicon wafer with a predetermined ultraviolet reflectance or may be coated. Suitable coatings are coatings that are able to withstand periodic ultraviolet exposure with minimal changes in ultraviolet reflectance. Suitable coatings may include high temperature ultraviolet coatings and deposited metals (eg, aluminum).

After the calibration substrate is placed on the substrate holder, the substrate is exposed to ultraviolet radiation at a first power, which can be selected by the operator. The first power may be 50%, 75%, or 100% power. Ultraviolet radiation is reflected back through the window from the calibration substrate and measured by the ultraviolet detector for a predetermined duration. At the end of the measurement duration, the ultraviolet power may be turned off and the ultraviolet detector may be blocked from radiation or the signal measurement may simply be stopped. The calibration substrate can be removed after the measurement duration.

The method may also include opening and closing the cover to protect the ultraviolet detector from the consequences of continuous exposure to ultraviolet radiation during normal operation. The cover can be operated remotely in an open or closed position using a controller.

The method includes calculating ultraviolet intensity based on the measured ultraviolet detector output, calculating deviation based on the calculated ultraviolet intensity and reference intensity, and adjusting the ultraviolet radiation power or exposure time to compensate for the deviation. It may also include. Ultraviolet radiation generated by the lamp first reaches the substrate through the chamber window, and some of the radiation is reflected from the substrate through the window and detected by the ultraviolet detector. Thus, the radiation intensity detected at the detector is different from the radiation intensity seen at the substrate. The controller may be programmed to account for the reflectance of the substrate at various ultraviolet wavelengths to reach a predetermined ultraviolet intensity. This strength only needs to be comparable from test to test. The intensity may be a normalized value based on a predetermined maximum value, or may be an absolute value in units of W / cm ² . In some cases, pure detector output may be used as the strength indicating means. The measured ultraviolet intensity is compared with the desired value and a corrective action is made to compensate for the deviation. For example, when the measured ultraviolet intensity is lower than the desired value, the ultraviolet power can be increased, and when the ultraviolet power can no longer be increased, the exposure time can be increased. If the measured ultraviolet intensity is greater than desired, the ultraviolet power and exposure time can be adjusted accordingly.

In some embodiments, the method includes disposing a mirror between the process chamber and the ultraviolet detector, measuring the reflected ultraviolet radiation, and determining whether a process window between the mirror and the substrate requires cleaning. It may further include. The path is the difference between the ultraviolet radiation reflected from the mirror and the ultraviolet radiation reflected from the substrate. Ultraviolet radiation reflected from the substrate passes through the chamber window twice, while ultraviolet radiation reflected from the mirror is not. Knowing the reflectivity of the mirror and substrate, the controller calculates the difference due to the window. As mentioned above, some ultraviolet curing is deposited on a window, resulting in gaseous byproducts that obscure the window. If the difference due to the window is greater than the specified amount, a window cleaning signal is generated either automatically through the system control or manually via an alarm or warning to the operator.

Other required maintenance or calibration activities can be determined. Such a decision may take the form of an alert or warning to the operator, or even in the form of a log associated with a batch of wafers being processed. In particular, this activity may be to replace the ultraviolet lamp if the measured ultraviolet intensity is too low to compensate for the prolonged treatment time. In addition to window cleaning, the chamber itself may require cleaning, or the detector may not need to be replaced.

These and other features and advantages of the present invention will be described in detail below with reference to the associated drawings.

The apparatus may also include a controller configured to execute a set of instructions. The controller 1) measures the ultraviolet intensity at a given ultraviolet radiation power, 2) calculates the deviation based on the measured value and the reference intensity, and 3) executes the commands to compensate for the deviation by adjusting the ultraviolet radiation power or exposure time. Compensate for the measured intensity. The controller may direct cover movement by opening a cover (eg, opening a shutter or iris) to expose the ultraviolet detector to ultraviolet radiation and executing a command to close the shutter or iris to separate the ultraviolet detector from the ultraviolet radiation.

In another aspect, the present invention relates to a method of calibrating an ultraviolet device. This method may be a simple compensation of the measured ultraviolet intensity, the generation of a warning or alarm, or the determination of maintenance or corrective action. Ultraviolet device calibration can be performed while keeping the pedestal at a high temperature and keeping the chamber under vacuum (ie, without shutting down the system or removing the system or chamber from service). The method includes receiving a calibration indication or determining a calibration request, placing a calibration substrate on a substrate holder, measuring the ultraviolet detector output for a predetermined duration, and removing the calibration substrate. do.

The calibration indication can be software triggered by exposure duration, total intensity, elapsed time, number of wafers processed, or the like, or manually triggered by an operator. The calibration substrate is provided to the chamber on the substrate holder. Such a calibration substrate can be held in a plant storage system or FOUP in a storage locker. The calibration substrate may be a pure silicon wafer with a predetermined ultraviolet reflectance or may be coated. Suitable coatings are coatings that are able to withstand periodic ultraviolet exposure with minimal changes in ultraviolet reflectance. Suitable coatings may include high temperature ultraviolet coatings and deposited metals (eg, aluminum).

After the calibration substrate is placed on the substrate holder, the substrate is exposed to ultraviolet radiation at a first power, which can be selected by the operator. The first power may be 50%, 75%, or 100% power. Ultraviolet radiation is reflected back through the window from the calibration substrate and measured by the ultraviolet detector for a predetermined duration. At the end of the measurement duration, the ultraviolet power may be turned off and the ultraviolet detector may be blocked from radiation or the signal measurement may simply be stopped. The calibration substrate can be removed after the measurement duration.

The method may also include opening and closing the cover to protect the ultraviolet detector from the consequences of continuous exposure to ultraviolet radiation during normal operation. The cover can be operated remotely in an open or closed position using a controller.

The method includes calculating ultraviolet intensity based on the measured ultraviolet detector output, calculating deviation based on the calculated ultraviolet intensity and reference intensity, and adjusting the ultraviolet radiation power or exposure time to compensate for the deviation. It may also include. Ultraviolet radiation generated by the lamp first reaches the substrate through the chamber window, and some of the radiation is reflected from the substrate through the window to be detected by the ultraviolet detector. Thus, the radiation intensity detected at the detector is different from the radiation intensity seen at the substrate. The controller may be programmed to account for the reflectance of the substrate at various ultraviolet wavelengths to reach a predetermined ultraviolet intensity. This strength only needs to be comparable from test to test. The intensity may be a normalized value based on a predetermined maximum value, or may be an absolute value in units of W / cm ² . In some cases, pure detector output may be used as the strength indicating means. The measured ultraviolet intensity is compared with the desired value and a corrective action is made to compensate for the deviation. For example, when the measured ultraviolet intensity is lower than the desired value, the ultraviolet power can be increased, and when the ultraviolet power can no longer be increased, the exposure time can be increased. If the measured ultraviolet intensity is greater than desired, the ultraviolet power and exposure time can be adjusted accordingly.

In some embodiments, the method includes disposing a mirror between the process chamber and the ultraviolet detector, measuring the reflected ultraviolet radiation, and determining whether a process window between the mirror and the substrate requires cleaning. It may further include. The path is the difference between the ultraviolet radiation reflected from the mirror and the ultraviolet radiation reflected from the substrate. Ultraviolet radiation reflected from the substrate passes through the chamber window twice, while ultraviolet radiation reflected from the mirror is not. Knowing the reflectivity of the mirror and the substrate, the controller calculates the difference due to the window. As mentioned above, some ultraviolet curing is deposited on a window, resulting in gaseous byproducts that obscure the window. If the difference due to the window is greater than the specified amount, a window cleaning signal is generated either automatically through the system control or manually via an alarm or warning to the operator.

Other required maintenance or calibration activities can be determined. Such a decision may take the form of an alert or warning to the operator, or even in the form of a log associated with a batch of wafers being processed. In particular, this activity may be to replace the ultraviolet lamp if the measured ultraviolet intensity is too low to compensate for the prolonged treatment time. In addition to window cleaning, the chamber itself may require cleaning, or the detector may not need to be replaced.

These and other features and advantages will be described in detail below with reference to the associated drawings.

1A-1D are schematic diagrams at various locations of an ultraviolet lamp assembly having an in-situ ultraviolet detector assembly and a mirror.
2A and 2B are process flow diagrams illustrating a process according to some embodiments of the inventions.
3A-3D are schematic diagrams of an ultraviolet detector assembly in accordance with certain embodiments of the present invention.
4 is a schematic diagram of an ultraviolet lamp assembly and chamber in accordance with certain embodiments of the present invention.
5A and 5B are schematic diagrams of a multi-station ultraviolet curing chamber in accordance with certain embodiments of the present invention.
FIG. 6 is a graph showing a graph of% detected ultraviolet signal versus path of use of lamps comparing refrigerant gas of clean N ₂ only and ozone-generating refrigerant gas.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the nature of the present invention. Although the invention has been described in connection with specific embodiments, it is not intended to limit the invention to these embodiments only.

Reference will be made in detail to embodiments of the invention as shown in the accompanying drawings. The same reference numerals will be used to denote the same or similar parts throughout the drawings and the detailed description. In this application, "workpiece", "wafer", and "substrate" will be used interchangeably. The following detailed description assumes that the invention is implemented on a wafer. However, the present invention is not limited to this. The workpiece can be a workpiece of various shapes, sizes, and materials (eg, displays of various sizes).

The present invention relates to an ultraviolet radiation apparatus for processing a semiconductor substrate. Java radiation is used to treat thin films on substrates to achieve various property changes. Ultraviolet radiation can destroy chemical bonds, change material composition, cause chemical reactions, affect density and stress, or otherwise provide power to the substrate.

Typical embodiments of ultraviolet irradiation devices have a plurality of ultraviolet lamps for irradiating the substrate. The ultraviolet lamp can be a flood lamp that generates ultraviolet light at a wide range of wavelengths, or a high intensity light emitting lamp that emits ultraviolet radiation in a smaller spectrum. Monochromatic light sources of ultraviolet radiation, such as certain lasers, may be used. The excitation by the electrode or the microwave energy can be powered by the lamp and inductively connected.

In certain embodiments, two separate mercury bulbs are used in two separate lamp assemblies. Using a two-light structure, the relative orientation of the bulb with respect to the circular substrate changes over time to achieve uniform exposure for each rotating section. Various reflectors are also used in the lamp assembly to direct the generated ultraviolet radiation towards the substrate. Linear bulbs generate light in all directions, but the substrate surface lies on only one side of the bulb. Thus, reflectors are used to direct ultraviolet radiation towards the substrate, which will escape from the pamp assembly. In this way, lamp power is used more efficiently. In other embodiments, the bulb can have other shapes, such as light bulb shapes or toroidal shapes.

In order to obtain various film property changes on the substrate, the degree of cure resulting from exposure to ultraviolet radiation must correspond to the desired degree of changed property. Thus, for some property changes, a small degree of curing is required, in other cases, a large degree of curing is required. The degree of ultraviolet curing is a function of ultraviolet radiation intensity, substrate temperature, and in some cases pressure and gas in the chamber. In order to ensure that the degree of film property change is constant from substrate to substrate, the degree of cure must be controlled over time to ensure uniformity between wafers.

Reliable methods are known for controlling substrate temperature, chamber pressure, and gases present in the chamber. The substrate may be heated or cooled during ultraviolet exposure. Such heating or cooling can be accomplished by controlling the temperature of the pedestal on which the substrate is located, or by adding gas into the chamber at a predetermined temperature. Chamber pressure is controlled via a vacuum pump or common vacuum forelines and pressure gauges. The gas in the chamber can be controlled by first evacuating the chamber and then introducing the desired gas. During some ultraviolet treatment, the gas in the chamber can actively participate in film property changes by reacting with the film.

Ultraviolet radiation intensity is also controlled. The ultraviolet radiation intensity appearing on the substrate depends on several factors. The power applied to the ultraviolet lamps determines how much radiation is generated at the source. The condition of the ultraviolet lamp determines how effectively the power is used to generate ultraviolet radiation. The type of cooling gas in the ultraviolet lamp assembly determines how much radiation is absorbed. The design of the reflector and reflectance determines how much radiation is directed through the chamber window. The type of material used for the chamber window and its cleanliness determines how much of the radiation directed to the window passes. Finally, the radiation reaches the substrate with a certain intensity.

The contribution of these factors changes in part over time because various parts of the ultraviolet lamp assembly and chamber may be overexposed over time. Overexposure refers to the phenomenon of material change after exposure to high-energy electromagnetic radiation such as ultraviolet light. Clean gases and many plastics will turn blue and / or decompose after prolonged solar exposure in the desert. It is believed that overexposure is caused by the formation of internal defects called color centers, which selectively absorb a portion of the visible light spectrum. Overexposure can permanently modify the physical or mechanical properties of a material and is one of the mechanisms involved in breaking down plastics in the environment. Continued exposure to high-intensity ultraviolet light, as in ultraviolet light conditions, damages the chamber portion, particularly those made of organic polymers, and affects reflectance over time. Some materials, such as Teflon, PTFE, and PFA, may be resistant to UV-induced damage.

Two major factors that affect UV intensity over time in a substrate are the conditions of the chamber window and the UV bulb. The ultraviolet lamp bulbs used for curing receive high power and withstand high cycling, for example for strengths up to 1 W / cm ² . Bulb performance degrades with time. Given the same power input, the output intensity decreases with time. In order to maintain the same intensity output, it is initially subjected to low power, increasing slowly over time to reduce performance degradation. At some point, the bulb is replaced. The bulb can be replaced at any triggering event, regardless of performance. These events can be multiple cycles, total curing time, total time, number of substrates cured, total power, and the like. The bulb may be replaced based on performance, for example, if the bulb fails to output the expected strength. For example, for bulb replacement, the efficient use of bulb and system downtime suggests that performance based methods are preferred. However, for planned purposes, having a periodic replacement designed to be shorter than the useful life of the bulb ensures smooth operation of the ultraviolet bulb and reduces the number of unscheduled downtimes.

The chamber window also affects the ultraviolet intensity at the substrate. Some ultraviolet processes involve changes in the reaction or solvent that release gaseous byproducts. One example is porogen removal. Porogen is removed from the deposited ultra low-k (ULK) layer using ultraviolet radiation and gaseous by-products are removed from the chamber. Sometimes byproducts (usually organic contaminants) are deposited on the chamber portion before they are removed. When deposited on the chamber window, the by-products accumulate over time and cover the window, reducing the ultraviolet radiation passing through. Efforts to reduce these unwanted deposits, such as inert gas curtains under windows or high purge gas flows, do not eradicate them. Thus, although the ultraviolet bulb is working well, the ultraviolet intensity at the substrate can still be reduced.

One attempt to solve the wafer-to-wafer curing uniformity is to measure the UV intensity on the substrate. Light pipes mounted on pedestals or substrate supports can occasionally measure ultraviolet radiation. The light pipe receives radiation at the tip, typically made of sapphire, and sends it through the optical fiber to the photodetector. The change in light pipe measurement over time approximates the value seen on the substrate. However, gaseous contaminants can be deposited on the light pipe, and these contaminants must be cleaned continuously and consistently. Constant high power ultraviolet exposure can overexpose the light pipe material and change its sensitivity. The light pipe is installed in the pedestal, which undergoes a heating cycle to produce a heated pedestal, which changes the transmitted value. The heated pedestal also emits infrared radiation that interferes with the light being measured. Finally, the optical fiber connected from the light pipe is also overexposed, which degrades the signal.

The light pipe is periodically calibrated as the measurement changes over time. The light pipe measures the radiation temperature affected by the chamber environment. Changes in light pipe and environment over time affect the interpretation of the measurements unless periodically corrected. As mentioned above, knowing the UV intensity at the substrate location may not analyze the cause-a low UV intensity may mean poor bulb performance and / or window cleanness. In one aspect, the present invention enables periodic calibration of light pipes that are not affected by conditions in the chamber.

In another form, the present invention is a method of calibrating an ultraviolet device. Measurements from the co-position ultraviolet detector of the present invention can be used to calibrate ultraviolet devices independently of the light pipe. The co-position detection and detector assembly device avoids various problems of the light pipe. The co-position detector is mounted outside the chamber and is therefore not affected by any gaseous contaminants deposited on the detector. In certain embodiments, the detector is protected from overexposure effects by a shutter mechanism that opens only during measurement. The detector is protected from heat cycling by nitrogen purge gas and shielded from pedestal-emitting infrared radiation emitted by the calibration substrate. In some embodiments, the measured value may act to determine the exact therapeutic / management action required because the effects of the unclean window may be separated. Reflecting ultraviolet radiation to an external ultraviolet detector is advantageous because it can be performed under normal ultraviolet curing operating conditions. The calibration substrate can withstand a substrate support temperature of 400 ° C. or higher and can be inserted automatically using system control. The calibration can be done immediately after the UV treatment and there is no need to wait for the cooling of the pedestal or the opening of the chamber. Since the chamber vacuum and temperature are maintained, the time taken to return the chamber to service is also shortened.

1A shows a cross-sectional view of one embodiment of two lamp assemblies using one embodiment of the present invention. The schematic diagram of FIG. 1A shows the structure when the ultraviolet measurement is made. The lamp assemblies are mounted above the process chamber 112 over the window 108. Linear bulb 102 generates ultraviolet radiation in all directions. Some of the generated radiation is irradiated directly to the calibration substrate 110 supported by the substrate support 114. Some of the radiation is reflected from various reflectors before irradiating the substrate. Overhead reflector 104 surrounds the bulb and redirects radiation towards the substrate. Ring reflector 106 surrounds the space above process chamber window 108. The ultraviolet detector 122 is located inside the detector assembly 120. As shown in FIG. 1A, light rays from bulb 102 are reflected from calibration substrate 110 toward ultraviolet detector 120. The light ray may be first reflected from the reflector before reaching the substrate, such as light ray 118. Rays 116 and 118 are both detected by detector 122. Before reaching the detector, the light beam passes through window 108 twice.

FIG. 1B shows a top view of the same lamp assembly as FIG. 1A. The lamp assembly housing 124 surrounds the tubular bulb 102 and the overhead reflector 104 and has a rectangular shape. They are mounted on a ring reflector 106 seated above the process chamber 112. The detector 122 is disposed between the lamp assembly housings and below the bulb.

1C shows the detector assembly 120 in the closed position. As in FIG. 1A, ultraviolet light reflected from the calibration substrate 110 reaches the detector assembly, but the light does not reach the detector 122. The detector assembly 120 has a closed cover that protects the ultraviolet detector from reflected radiation, for example, during ultraviolet curing of the substrate. As required, when the measurement is made, the cover can then be opened to expose the detector to ultraviolet radiation.

In FIG. 1D, mirror 126 is located above the process window to perform another specification. For this measurement, only the ultraviolet light reflected from the mirror, for example only the ray 124, is measured. This measurement eliminates the effect of window cleanliness from the result, since the light ray 124 does not pass through the window 108 before detection. As an example, the light rays 128 do not reach the detector because of the mirror 108 in its path. Thus, the pass rate of the window is eliminated from this measurement.

The results from the measurement of FIG. 1A over time correspond to the ultraviolet intensity as confirmed by the calibration substrate. However, this intensity is different from the above-described light pipe because the window pass is included once again. The results from the measurements of FIG. 1A over time correspond to the conditions of the ultraviolet bulb 102. Since the effect of window deposits is eliminated, these measurements provide a good indication as to whether the bulb is performing as expected. The time difference in displacement between time A and time B for the measurement of FIG. 1A and time A and time B for the measurement of FIG. 1D indicates how much the chamber window reduces ultraviolet transmission. For example, if the measurements of FIG. 1A show a 75% decrease over a period of time and the measurements of FIG. 1A show a 90% decrease over the same time period, an additional 15% must appear from window passing. The trigger can then be set, and below the set point the window must be cleaned.

process

In one aspect, the present invention relates to a method for calibrating a semiconductor ultraviolet curing device. 2A and 2B are process flow diagrams showing certain embodiments of the present invention. Calibration usually occurs after a triggering event. In step 201, a calibration indication is received or a calibration requirement is determined. The calibration indication is received from the system or operator from a downstream process that has determined unacceptable inter-wafer uniformity. Indications from the operator may be initiated as part of preventive care or as part of trouble-shootings for analyzing ultraviolet intensity loss.

Alternatively, calibration requirements may be determined, such as the control system determining that a triggering event has occurred. The triggering event may be based on an accumulation of consumption-based variables, performance-based measurements, such as ultraviolet intensity from the light pipe, or an absolute number of substrates or time being processed. The variable that indicates the consumption of the ultraviolet bulb may be the total power. Ultraviolet bulbs can have life expectancy measured in terms of total power. An example of a cumulative value of the variable event may be the total power consumption from the lamp assembly. The total power consumed can be over many or only a few substrates, processed for long durations or for very short times. This kind of marking reflects the consumption of the consumable life, but is harder to track or calculate than other kinds of marking. Another kind of indication is a measure of performance. In this case the measurement may be the ultraviolet intensity from the light pipe. Changes in light pipe measurements within several substrates, or hours, processed may indicate a change in performance or window transmittance of the ultraviolet bulb. As mentioned above, other variables affect light pipe measurements and, by themselves, cannot be used to determine therapeutic action. The last kind of indication may be the number of substrates processed or the passage of time. This kind of indication is not directly related to the consumption of life expectancy, but instead can be used when consumption-based variables are difficult to measure or calculate. For illustrative purposes, a calibration trigger may occur every 8 hours regardless of which substrate has been processed. A calibration trigger can also occur after every 100 substrate treatments, whether or not the treatment has been done for 15 minutes or 15 seconds.

Calibration is initiated by placing the calibration substrate on the substrate holder in step 203. The calibration substrate reflects ultraviolet radiation into the detector during the measurement. The reflectivity of the substrate at various ultraviolet wavelengths is known and hardly changes over time. Ultraviolet detector measurements from the same substrate can be compared and the ultraviolet intensity difference can be determined. The substrate may be a simple silicon wafer or a coated silicon wafer. The coating may be, for example, a high temperature ultraviolet coating that is resistant to ultraviolet radiation and high temperatures, such as metals or metal oxides. Dielectric coatings applied using ION beams can withstand 400 ° C. operating temperatures and may be suitable for the present invention.

In one embodiment, two or more calibration substrates are used that have different reflectances at the ultraviolet wavelengths of the band of interest. The intensity measured from the two substrates is compared to separate the intensity measurements at the ultraviolet wavelength or wavelength of interest. In a simple example, two identical substrates can be made, but one substrate can have a dielectric coating designed to absorb ultraviolet radiation at a wavelength of 250 nm. By comparing the measured intensities, the UV intensities of the 250 nm wavelength can be separated. This technique can be extended to measure ultraviolet intensity at two or more wavelengths of interest and may even employ three or more calibration substrates. In some ultraviolet curing processes, the desired reaction is generated using radiation of a particular wavelength. For these processes, it may be important to know the intensity at a particular wavelength.

When not in use, the calibration substrate may be maintained within or outside the semiconductor processing system. For example, the substrate may be stored in a wafer storage system of a manufacturing plant or in a front opening unified pod (FOUP) close to a semiconductor processing device. In addition, the device may include a slot for storing a calibration substrate accessible to the system robotic arm.

The ultraviolet radiation power is set at step 205 to the first power value. This first power may be 100% power. Ultraviolet intensity measurements are taken at the same power value for ease of comparison. The ultraviolet lamp can be turned on or off when the calibration substrate is located, and in some cases, the ultraviolet lamp can already be set to the first power value.

In certain embodiments, the ultraviolet detector is protected by an assembly that opens and closes the cover to sequentially detect ultraviolet light and separate the detector from ultraviolet radiation. This cover may be a shutter or an iris. In optional step 207, the shutter is opened to expose the ultraviolet detector to ultraviolet radiation. While the cover or shutter is open, the ultraviolet detector measures radiation at step 209 and provides an output. This output is read or measured over a predetermined duration. When the measurement is complete, the shutter is closed to separate the ultraviolet detector from ultraviolet radiation (step 211).

Steps 203-211 may be repeated during calibration. As mentioned above, two or more calibration substrates may be used and thus may require repetition of the measurement step. The measurement can also be repeated using a mirror between the ultraviolet detector and the chamber window, which will be further explained in steps 219 and 221 below.

2A continues to FIG. 2B. In step 213, the ultraviolet intensity is calculated based on the detector output measured in step 209. The ultraviolet detector output can be a current or a voltage. The current or voltage is converted into equivalent ultraviolet intensity, which can be W / cm ² or simply a percentage of maximum. In step 215, the deviation between the calculated ultraviolet intensity and the reference intensity is calculated. The reference intensity is the expected value for that power level. Based on this deviation, adjustment of the ultraviolet curing process parameters can be made. If the deviation is very small or absent, no adjustments need to be made. However, if the deviation is within a range in which the adjustment of the ultraviolet radiation power or exposure time can effectively compensate for this deviation, an adjustment may be made at step 217. For example, if the measured intensity is higher than the expected reference intensity, the ultraviolet radiation power is reduced to affect the same ultraviolet intensity. More generally, the measured intensity is lower than the expected reference intensity. A preferred adjustment may be to increase the ultraviolet radiation power if the power is not yet at its maximum. If the power is already at full power, the exposure time can be increased to compensate for the deviation. Increasing exposure time reduces system throughput, which is undesirable. Thus, such adjustments can be made intentionally if the resulting throughput is within desired limits.

Optional measurements using mirrors to separate the effect of the chamber window deposits may be made at the same time as or after the computational step and the calibration substrate measurement. The mirror may be located between the process chamber and the ultraviolet detector at step 219. In some embodiments, mirror placement can be performed mechanically by using a robot arm or solenoid. In another embodiment, the operator may perform this mirror arrangement when the ultraviolet bulb is off. For example, a door on the side of the lamp assembly can be opened and a mirror can be inserted into the slot. The mirror is highly reflective to ultraviolet light. In certain embodiments, the mirror may be part of the same calibration substrate that is used inside the chamber. In other embodiments, the mirror may be part of a metal or glass coated with a reflective material.

In step 221, ultraviolet intensity measurement is performed to measure the ultraviolet radiation reflected from the mirror. This step can be performed by repeating steps 205-211. During the measurement, it is not important whether the calibration substrate is on the substrate holder because the light reflected from the substrate is not measured. After the ultraviolet intensity is measured, the mirror can be removed at step 223. Similar to the placement step, the mirror may be removed by an operator, or mechanically, and may be removed automatically or manually.

As mentioned above, the ultraviolet intensity reflected from the mirror can be used to determine the cleanliness of the process window. From the window cleanliness and from the deviation computed in step 215, a number of management activities can be performed. In step 225, the activity to be performed is determined. For example, if window cleanliness is involved in most deviations, the windows are cleaned by performing remote plasma cleaning or manually cleaning the interior by separating the chamber. In another example, if the cause of the deviation is not window cleanliness, the ultraviolet bulb may be replaced. Chamber separation is avoided if possible because it requires powering down the entire system and takes considerable time. Knowing the deviations and whether the windows are not clean, the system or operator can determine the optimal maintenance activities to minimize downtime.

Other steps may be performed in addition to the steps of FIGS. 2A and 2B. For example, as described above, a comparison of the measured UV intensities using various calibration substrates can be made to analyze the UV intensity at a particular wavelength, which is important for the process. Another method for analyzing ultraviolet intensity at a particular wavelength includes adding a filter between the detector and the window using a wavelength specific detector. One of ordinary skill in the art will be able to design various ways to measure the UV intensity as a whole at a particular wavelength or in various bands using the concepts disclosed herein.

In some embodiments, methods and assemblies are provided to prevent or reduce sensor contamination. Contaminants can accumulate on the face of the detector and / or window to dim the ultraviolet light. This causes a downward drift of the detected ultraviolet signal. Drift is a side effect of blurring the sensor and does not indicate ultraviolet light reaching the sensor plane. Contamination may be caused by ultraviolet-induced decomposition of organic impurities in the outgass and / or inert gas flows from the outgass from the potential contaminating surface near the detector. Ultraviolet light decomposes organic compounds exposed to ultraviolet light, causing hydrocarbon outgass and condensation on the optical surface of the detector. Accumulated condensed hydrocarbons absorb ultraviolet light, causing downward drift of the detected signal.

The method includes flowing a gas mixture comprising molecular oxygen (O ₂ ) over the optical surface of the detector. For example, in certain embodiments, clean dry air (CDA) available from a plant source may be combined with one or more inert gases such as helium (He), argon (Ar), or nitrogen (N ₂ ). Supplied as a mixture. Molecular oxygen reacts in the presence of ultraviolet light of short wavelengths (approximately 160-250 nm) to form ozone (O ₃ ). Ozone reacts with organic contaminants on the optical surface to form gaseous products that can be purged. In some embodiments, a constant flow of refrigerant gas, including CDO or other O ₂ containing gas, is used throughout the step. In some embodiments, the refrigerant gas consists essentially of molecular oxygen and one or more inert gases. FIG. 6 is a graph showing the percentage of ultraviolet signal detected over the usage path of a lamp, comparing refrigerant gas containing only clean N ₂ (data series 603) with ozone-generating refrigerant gas (data series 601). . The clean N ₂ flow contains a certain amount of organic contaminants as indicated by the signal drift. Ozone purging shows no drift. The same ultraviolet light that causes contamination continues to clean the contaminants and eliminate side effects.

By controlling the amount of molecules in the gas mixture, it is possible to control the amount of ozone generated. If too much ozone is present in the detector assembly, the ozone may absorb ultraviolet light and inaccurately measure the ultraviolet intensity. This can also damage organic materials (eg cables, printed circuit boards) near the detector. In certain embodiments, refrigerant gas may be actively pumped from the detector assembly to control the amount of ozone in the assembly. The addition of an inert gas (eg N ₂ ) can be used to dilute the O ₂ containing gas and reduce the total amount of ozone. In addition to the amount of O ₂ containing gas, the amount of ozone present is also affected by the removal rate of the exhaust hardware. An example flow, using ozone emission hardware capable of venting 40-50 SLMs, is shown below.

In some embodiments, ozone levels between about 5 and 15 pmm ozone are used. In some embodiments, O ₂ is about 5-15% of the total gas flow. Thus, when air is used as the O ₂ containing gas, air flow contributions between about 20% and 100% of the total gas flow appear. Low O ₂ contributions (eg 1% -5%) can be used to lower ozone levels if necessary for the reasons mentioned above.

Device

3A and 3B detail one embodiment of the detector assembly seen from different angles. In FIG. 3A, the ultraviolet detector 301 is located inside the assembly 300. Detector 301 faces an opening or slot 305 that allows reflected ultraviolet radiation to enter the assembly. Cover 303 may move to cover openings or slots 305 to separate ultraviolet detector 301 from reflected ultraviolet radiation. During ultraviolet lamp operation, an inert gas (about 1-10 slm), such as argon or nitrogen, can flow through the inlet 307 into the assembly to cool any assembly and remove any particles that appear from the moving cover. The inert gas includes nitrogen in some embodiments, which may be placed at room temperature or cooled. As will be further described below, in some embodiments, the oxygen containing gas is flowed through the assembly instead of or in addition to the inert gas. For example, a mixture of nitrogen and clean dry air (CDA) can flow through the assembly.

3B is a side view of the assembly of FIG. 3A. The ultraviolet detector 301 also includes a diffuser 311 installed on its surface. Diffusers incorporate light from various directions and are well known in the art. Inert gas injected from inlet 307 exits the assembly under cover 303. As shown, a small gap exists between the bottom of the ultraviolet detector assembly and the cover.

In the embodiment shown in FIG. 3B, the solenoid 309 is farther outward to expose the detector 301 to reflected ultraviolet radiation, or to cover the opening 305 to separate the detector 301. Rotate the cover 303 in place. In other embodiments, other mechanical means can be used to perform the operation of covering and opening the opening. For example, the cover or shutter can be moved by a lead screw or stepper motor. The cover may be an iris with a plurality of pieces that rotate at the same time. Suitable mechanisms are remotely controllable mechanically or electronically from the exterior of the lamp assembly.

3C is a schematic diagram of another embodiment of a detector assembly. Detector 301 faces an opening or slot 305 that allows ultraviolet radiation to enter the assembly. Gas enters inlet 307 and flows over optical surfaces 315a, 315b, 317 and exits outlet 319. The optical surface may be a lens, window, filter, or the like. An exhaust pump 321 connected to the outlet 319 pumps gas to the outside. In some embodiments, a plurality of inlets and / or outlets are configured to establish a flow path over the optical surface or other surface where contaminants may occur. 3D is a schematic diagram of a light pipe sensor structure, including an ultraviolet detector 301. Ultraviolet light is introduced through the opening 305 and transmitted to the detector 301 through the light pipe 330. Gas enters inlet 307 and exits to outlet 319.

4 is a schematic diagram of a process chamber suitable for practicing the present invention. The ultraviolet lamp assembly 401 is mounted above the process chamber 413. Each lamp assembly 401 includes a transformer and a magnetron (not shown) that pumps microwave energy into the lamp, ultraviolet bulb 405, and reflector 407. As shown, the ultraviolet detector assembly 409 is mounted below between the two lamp assemblies 401. The chamber window 411 passes ultraviolet radiation from the bulb 405 to the substrate 417 under the chamber. The substrate 417 is seated on the substrate support 415, which may be heated and / or cooled. As shown, a heater coil 419 is installed in the substrate support 415.

In some embodiments, the process chamber includes a plurality of stations, each having a substrate support, a chamber window, and an ultraviolet lamp assembly. 5A and 5B are schematic diagrams of multi-station chambers suitable for practicing the present invention. Chamber 501 includes four stations 503, 505, 507, 509. Each station includes a substrate support 513. The pin 519 is provided in the substrate support 513. Four carrier rings are connected to a spindle 511 that rotates about an axis. When a new substrate is inserted into the chamber, for example at station 507, the substrate is placed on the robotic arm. The carrier ring lowers the substrate to the substrate support so that the substrate rests on the pins 519. After the substrate process is completed at one station, the carrier ring lifts the substrate and rotates 90 degrees to the next station, lowering the substrate again for processing. Thus, the substrate enters the chamber at station 507 and then passes through each of the four stations, and then exits the chamber.

5B shows a top view of the same multistation chamber with ultraviolet lamp assembly 515 above each station. The ultraviolet detector assembly 517 is located near the center between the two lamp assemblies. The lamp assembly has a different relative orientation with respect to the substrate as the substrate moves through each station. This relative difference in orientation ensures that each circular cross section of the substrate is exposed to the same amount of ultraviolet radiation. Because the ultraviolet bulb is tubular and the substrate is round, different parts of the substrate are irradiated with different amounts of ultraviolet radiation at each station. By varying the relative orientation of the bulb with respect to the substrate, this difference is overcome. In general, the configuration of four stations with different orientations is sufficient to ensure relatively uniform ultraviolet irradiation. Of course, the relative orientation is not limited to that shown in FIG. 5B, and a plurality of orientations of the lamp axis may be selected to optimize wafer processing uniformity. Uniform exposure may be achieved by rotating the substrate or lamp assembly during ultraviolet curing.

In certain embodiments, system controller 521 may be used to control process conditions during UV curing, calibration, substrate insertion and removal, and the like. The controller generally includes one or more memory elements and one or more processors. The processor may include a CPU or computer, analog and / or digital input / output connections, stepper motor controller board, and the like.

In certain embodiments, the controller controls all activity of the device. The system controller includes a set of instructions for controlling timing, gas mixture, gas injection rate, chamber pressure, chamber temperature, substrate temperature, ultraviolet power level, ultraviolet cooling gas and flow, remote plasma cleaning, and other parameters of a particular process. Run the system control software. Other computer programs stored in memory elements associated with the controller may also be used in some embodiments.

In general, there will be a user interface associated with the controller 521. The user interface may include a display screen, graphical software display of the device and / or process conditions, and a user input device (eg, pointing device, keyboard, touch screen, microphone, etc.).

Computer program code for controlling the ultraviolet curing and calibration process may be written in conventional computer readable programming languages (eg, assembly language, C, C ++, Pascal, Fortran, etc.). Compiled object code or script can be executed by a process to perform the tasks identified in the program.

Controller parameters relate to process conditions such as ultraviolet power, ultraviolet cooling gas and flow rate, process duration, process gas composition and flow rate, temperature, pressure, and substrate temperature. These parameters are provided by the user in the form of a prescription and can be entered using the user interface. Controller parameters related to calibration conditions such as exposure duration, ultraviolet power setting for measurement, and the location of the calibration substrate may also be entered using the user interface. Additional parameters may be entered during setup or installation of the ultraviolet detector assembly, such as the conversion formula of the ultraviolet detector output to ultraviolet intensity, deviation limits for bulb replacement and window cleaning, and whether the ultraviolet intensity at a particular wavelength is determined. These additional parameters may change from time to time during system maintenance.

Signals for process monitoring may be provided by analog and / or digital input connections of the system controller. Signals for controlling the process are output on the analog and digital output connections of the ultraviolet curing device.

System software can be designed or configured in various ways. For example, various chamber component subroutines or control objects may be recorded to control the operation of the chamber components needed to perform the ultraviolet intensity measurement and calibration process of the present invention. Examples of programs or sections of programs for this use include substrate positioning codes, process gas control codes, pressure control codes, heater control codes, and ultraviolet lamp control codes.

The ultraviolet lamp control program may include code for setting a power level for an ultraviolet lamp, initial ramping up of lamp power, and final ramping down of lamp power. The substrate positioning program may include program code for controlling the chamber components used to load the substrate into the pedestal or chuck. The process gas control program may include code for controlling the gas composition and flow rate prior to ultraviolet curing and, optionally, for flowing the gas into the chamber to stabilize the pressure in the chamber. The pressure control program may include code for controlling the pressure in the chamber, for example by adjusting the throttle valve in the exhaust system of the chamber. The heater control program may include code for controlling the current for the heating unit used to heat the substrate. Alternatively, the heater control program may control the delivery of heat transfer gas, such as helium, to the wafer chuck.

Examples of chamber sensors that can be monitored during UV curing and calibration include mass flow controllers, pressure sensors (eg, pressure gauges), thermocouples located on the pedestal or chuck, and the ultraviolet detector assembly and the ultraviolet detectors of the pedestal. Include. Appropriately programmed feedback and control algorithms can be used with data from these sensors to manage desired process conditions.

In one embodiment, the controller includes instructions for performing calibration, process parameter adjustment, and management activity determination according to the method described above. For example, such an instruction may specify the parameters needed to perform ultraviolet curing and calibration. Such commands may include measurement using a user-provided formula or conversion table, and calculation of results based on integration of measurement results over time (eg, integration of UV intensity measurements over exposure time), It can be compared with a threshold. The comparison result can be used in a logic sequence in which an alarm or warning is issued, in which process parameters change, or in which the system is shut down.

Suitable semiconductor processing tools can be constructed using one or more ultraviolet process chambers. Suitable semiconductor process tools are Novellus Systems, Inc., San Jose, California, USA. Company SOLA and modified VECTOR. Another suitable semiconductor processing tool is Applied Materials, Inc., Santa Clara, California. Includes Centura and Producer sold by the company.

Details regarding the ultraviolet lamp assembly, reflector, process chamber window, and temperature control on the substrate holder are presented in co-pending US patent application Ser. No. 11 / 688,695, entitled "Multi-Station Sequential Curing of Dielectric Films." The contents are included in the present invention.

For convenience, the discussion of the ultraviolet lamp assembly and the in-situ ultraviolet detector assembly targeted two linear bulb structures for the ultraviolet light source, but the invention is not so limited. For example, a co-positioned ultraviolet detector can operate with any number of bulbs (eg, three, four, five) in any kind of structure (eg parallel, end-to-end connection, etc.). have. Co-located ultraviolet detectors work with other types of bulbs as well as linear bulbs. As ultraviolet bulbs improve and techniques for constructing ultraviolet lamp assemblies advance, the use of co-positioned ultraviolet detectors for monitoring bulb performance continues to apply.

While the invention has been described with reference to various embodiments, many variations are possible within the scope of the invention. There may be many alternative ways of implementing the methods and apparatus of the present invention. Accordingly, the following claims are to be construed as including all such variations, substitutions, and modifications within the true spirit and scope of the present invention. In the claims, the singular forms “an”, “an”, and “an”, unless otherwise specified, mean “one or more”.

Claims (18)

In the ultraviolet device,
A process chamber comprising a substrate holder and a window;
An ultraviolet radiation assembly external to the processor chamber and operative to direct ultraviolet radiation through the window toward the substrate holder;
A detector assembly comprising an ultraviolet radiation detector, one or more gas inlets, and a gas outlet, the detector assembly configured to flow gas across one or more optical surfaces of the ultraviolet radiation detector from one or more gas inlets to a gas outlet;
Includes a controller,
The controller includes instructions for flowing a gas mixture comprising inert gas and molecular oxygen into one or more gas inlets during operation of the ultraviolet detector.
UV device. The gas mixture of claim 1, wherein said gas mixture comprises air.
UV device. The gas mixture of claim 1, wherein the gas mixture comprises air and N ₂ .
UV device. The gas mixture of claim 1, wherein the gas mixture consists essentially of air and one or more inert gases.
UV device. The method of claim 1, wherein the molecular oxygen comprises about 5% to 20% of the gas mixture.
UV device. The method of claim 1, wherein air comprises about 20% to 100% of the gas mixture.
UV device. 7. An exhaust pump as claimed in any preceding claim, further comprising an exhaust pump operative to pump gas from the detector assembly through the gas outlet.
UV device. 7. The ultraviolet radiation assembly of claim 1, wherein the ultraviolet radiation assembly comprises an ultraviolet light source operative to emit ultraviolet radiation having a wavelength between about 160 nm and 200 nm.
UV device. In the ultraviolet device,
(a) a process chamber comprising a substrate holder and a window,
(b) an ultraviolet radiation assembly located outside the process chamber,
The ultraviolet radiation assembly includes one or more ultraviolet lamps, one or more reflectors operable to direct a portion of the ultraviolet radiation from the one or more ultraviolet lamps through the window toward the substrate holder, and the reflected light through the window. An ultraviolet intensity detector positioned to receive ultraviolet radiation from at least one ultraviolet lamp, a gas inlet, and a gas outlet, wherein a gas flow path from the gas inlet to the gas outlet comprises the optical surface of the ultraviolet intensity detector The gas inlet and gas outlet are arranged to
UV device. 10. The apparatus of claim 9, further comprising a cover configured to separate the ultraviolet intensity detector from one or more ultraviolet lamps.
UV device. Directing ultraviolet radiation from an ultraviolet radiation light source located outside the process chamber through a process chamber window;
Measuring ultraviolet radiation reflected from a substrate in the process chamber using an ultraviolet radiation detector located at a detector assembly outside the process chamber;
Flowing the refrigerant gas through the detector assembly while measuring the ultraviolet radiation such that the refrigerant gas contacts the optical surface of the ultraviolet radiation detector,
The refrigerant gas contains molecular oxygen
Way. 12. The method of claim 11, further comprising generating ozone in the detector assembly from the refrigerant gas.
Way. 13. The method of claim 12, further comprising maintaining an ozone concentration of about 5-15 ppm in the detector assembly during the measurement.
Way. The method of claim 11, wherein the molecular oxygen has a content between about 5% and 20% of the refrigerant gas.
Way. 12. The method of claim 11, wherein the refrigerant gas comprises air
Way. The method of claim 15, wherein the air has a content of about 20% to 100% of the refrigerant gas.
Way. The method of claim 11, wherein flowing the refrigerant gas through the detector assembly comprises pumping a gas mixture comprising ozone from the detector assembly to the outside.
Way. The method of claim 11, wherein the ultraviolet radiation comprises ultraviolet radiation having a wavelength between about 160 nm and 250 nm.
Way.

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