Sensor arrangement and method for monitoring a status of a wall of device

Abstract

A sensor arrangement for monitoring material deposition on a section of wall of a device or for monitoring the status of a section of a wall of a device, the sensor arrangement comprising: - a temperature sensing element, which is attachable or attached to said section of the wall, - a heat transducer, which is attachable or attached to said section of the wall, wherein the heat transducer is designed to deliver a thermal pulse to said section of the wall, and - a processing unit operationally connected to said temperature sensing element for receiving a measured temperature of said section of the wall, wherein the processing unit is arranged and configured to store a time course of said measured temperature and / or to evaluate a characteristic of said time course of said measured temperature. Further in the scope of the invention lies method using the apparatus.

Description

[0001] SENSOR ARRANGEMENT AND METHOD FOR MONITORING A STATUS OF A WALL OF DEVICE

[0002] TECHNICAL FIELD

[0003] The invention addressed herein relates to the technical field of measuring and testing. Specifically, the invention may be used in the technical field of monitoring the status of a technical facility, in particular of a vacuum deposition device. In a specific application, the invention relates to the field of semiconductor fabrication. More specifically, the invention relates to an apparatus for monitoring material deposition on a wall of a device, for monitoring the status of the wall itself, and to a method for such monitoring.

[0004] BACKGROUND OF THE INVENTION

[0005] As an illustrative example of technological relevance, wafer processing tools used in semiconductor manufacturing suffer from accumulation of deposits, i.e. byproduct buildup, on the chamber walls of a vacuum deposition chamber. From time to time the chamber walls need to undergo a cleaning process. Information on the appropriate time for the next cleaning process is valuable, as too frequent cleaning increases downtime of the facility, and too late cleaning involves the risk of, e.g., buildup flaking off during processing, resulting in particle contamination and yield loss as well as impacting other process parameters (e.g., film deposition thickness) . Quartz crystal microbalance (QCM) sensors have been used to monitor deposition inside various facilities. A QCM has

[0006] P220857 extremely high sensitivity, but it must come in contact with the media inside the device under test. I.e., it needs to be mounted on the inside of the device under test, e.g. inside a pipe, duct or processing chamber. QCM's are not suitable to monitor gross phenomena, such as deposition of layer thickness in the order of millimeters or centimeters of deposition. QCM's are not suitable for cases, where liquids or sludges are present. QCM based sensors are limited to monitoring relatively low amounts of material, typically, at maximum microns of deposited layer. In addition, sensors based on QCM technology are highly localized and measure mass change at the active area of the quartz crystal only.

[0007] The object of the invention is an apparatus or a method, which avoids or at least reduces problems of the state of art. More specifically, an object of the present invention is to provide an alternative apparatus or a method for monitoring the status of a device with respect to material deposition on its interior walls.

[0008] SHORT DESCRIPTION OF THE INVENTION

[0009] This object is achieved by a sensor arrangement according to claim 1.

[0010] The inventive sensor arrangement is a sensor arrangement for monitoring material deposition on a section of wall of a device or for monitoring the status of a section of a wall of a device. The wall of such a device may be a wall of chamber, of a duct or of a pipe of the device. The sensor arrangement comprises:

[0011] P220857 - a temperature sensing element , which is attachable or attached to said section of the wall ,

[0012] - a heat transducer , which is attachable or attached to said section of the wall , wherein the heat transducer is designed to deliver a thermal pulse to said section of the wall , and

[0013] - a processing unit operationally connected to said temperature sensing element for receiving a measured temperature of said section of the wall .

[0014] The processing unit is arranged and configured to store a time course of the measured temperature . In addition, or as an alternative , the processing unit is arranged and configured to evaluate a characteristic of the time course of the measured temperature .

[0015] The temperature sensing element may for example be a thermocouple , a thermistor, or any other suitable temperature sensor .

[0016] The heat transducer may for example be an electrical resistance heater, e . g . in form of a heating j acket . It may be reali zed as light emitting source , e . g . a laser diode , shining light on the section of said wall , creating local heating .

[0017] The processing unit generally may be adapted for storing and analyzing data from the at least one temperature sensing element . As a preparing step, either the temperature sensing element or the processing unit may comprise an analog to digital converter, such that the data analysis may be performed on digital data .

[0018] P220857 In an embodiment , the temperature sensing element , the heat transducer and optionally said processing unit are arranged in a common sensor unit . The sensor unit may be attachable as a whole to a section of the wall of a device in such a way that both, the temperature sensing element and the heat transducer, are in thermal contact to said section of the wall and are positioned spaced from each other .

[0019] Further in the scope of the invention is the method according to claim 3 .

[0020] It is a method of monitoring material deposition on a section of a wall of a device or of monitoring the status of a section of a wall of a device . The sensor arrangement according to the invention is used in the method . The method comprises the steps of

[0021] - contacting the temperature sensing element to the section of the wall and contacting the heat transducer to the section of the wall ,

[0022] - applying a first heat pulse to the section of the wall by means of the heat transducer,

[0023] - measuring a first time course of temperature following the application of the first heat pulse by means of the temperature sensing element ,

[0024] - at a later time , applying a second heat pulse to the section of the wall by means of the heat transducer,

[0025] - measuring a second time course of temperature following the application of the second heat pulse by means of the temperature sensing element , and

[0026] - evaluating by means of the processing unit a di f ference

[0027] P220857 between the first and said second time course of temperature .

[0028] In a variant of the method, the device is a vacuum deposition device . The section of a wall may be an atmospheric side section of a processing chamber, of a pipe or of a duct .

[0029] In a variant of the method, the time course of the measured temperature is evaluated to measure or detect at least one of

[0030] -a deposition of material on a wall ,

[0031] -an occurrence of clogging inside a pipe or a duct ,

[0032] - changes in heat insulation,

[0033] - changes in filling level of a container containing a chemical , such as a precursor,

[0034] - presence or absence of a gas flow in a pipe .

[0035] The sensor arrangement and the method of the present invention enable , by making use of a sensing element and heat transducer , to observe thermal mass change or changes in heat insulation quality . This may be due to internal deposition, or due to damage or disturbance of heat insulation . The section of the wall under test may be heated using a heater j acket or other heating element ( like a resistor or light emitting source ) . The heat transducer may be powered and controlled to generate a thermal pulse which will then be imparted into the examined obj ect . The rate of temperature change ( increase and decrease ) may be evaluated based on the measured time course of the

[0036] P220857 temperature monitored using the temperature sensing element. The temperature measurements may be captured using an analog-to-digital converter and stored for further analysis. Reference behavior of the system in captured and similarly recorded (e.g. immediately after system installation, in the know "clean" state) .

[0037] The rate of heating and cooling (temperature change) is determined by the heater power, quality of the heat insulation, thermal mass of the system, and mass flow rate of fluid carried by the system. If heat capacity of the carried fluid is small (gas under low pressure, as in vacuum systems) , then heat losses due to heating of the fluid can be neglected. This is why this approach is well suited for monitoring of vacuum or gas systems. In this case, transported fluids have low thermal mass and low thermal conductivity. If heater power and heater insulation stay unchanged, temperature change is determined by the thermal mass of the system.

[0038] The sensor arrangement can be realized as a small heater with a built-in temperature sensor to monitor local thermal mass changes, such as deposition / clogging inside a pipe at a particular spot (e.g., bend, constriction, or a known cold spot) . Alternatively, temperature pulse probing can be used with a heat trace, allowing to monitor global thermal mass changes. Such a heat trace may be used for other purposes, as e.g. for a required heating of a wall of the device. In such a case heat trace power supply may be modified to use pulse width modulation of electrical power,

[0039] P220857 and augmented control logic which imparts a square wave pattern on top of " steady-state" power level (heat pulsing is applied) . A monitoring algorithm may be used to control the power supply mean heating power and to analyze and record changes to the rate of heating and cooling upon changes in power level . Depending on the application, a system under test could be heated to a temperature di f ference above setpoint to avoid excessive heating and increased power consumption . Depending on the sensitivity needed and depending on the si ze of the system under test , smaller or larger temperature pulses may be required .

[0040] An advantage of the sensor arrangement is that it may be mounted externally, thus it can be reali zed in a form, which enables simply retrofitted on existing systems without any disruption to production . Alternatively, existing heat trace (heater j acket ) may be used as an element of the sensor arrangement by using a specially designed power supply and controller which implements this sensing / monitoring scheme . This sensor arrangement may be used to monitor dangerous environments or chemicals inside chambers and / or pipes , since no part of a sensor needs to come into direct contact with content of the system under test . The sensor arrangement may be used to monitor gross phenomena , e . g . , large amounts of deposits measured in millimeters or centimeters , solids or sludges .

[0041] The sensor arrangement described above may be in contact with the examined obj ect , in case that there is a heating isolation . Alternatively, heating, as well as temperature

[0042] P220857 sensing, be done in a remote way to the examined obj ect for example using a light source as heat transducer and a microbolometer or another MEMs device to probe the heat change based on emitted radiation .

[0043] The sensor arrangement according to the invention may be reali zed in a simple was and can may be produced in a small form- factor and inexpensively . For example , it may be manufactured as a small tape heater with a built-in thermal sensor . Since the sensor arrangement monitors signals in a very low frequency region (< 1Hz ) , the cost of electronics , analog-to-digital converters , and signal processors can be kept at a minimum . The sensor arrangement can be retrofitted on operational systems with no disruptions since it may be mounted externally to a wall of a device and this way avoids disturbing the integrity of a pipe / duct / chamber wall ( i . e . it does not require wall penetration) .

[0044] The present invention may provide a solution to the following problems :

[0045] • Monitoring of deposition / clogging inside pipes and ducts . The sensor arrangement may monitor both, global changes ( deposition along a pipe system when using a heat trace as the sensor ) and highly locali zed changes in the immediate vicinity of a small , dedicated sensor . The sensor arrangement may be used to monitor deposition inside vacuum forelines in semiconductor process equipment . Vacuum foreline and exhaust line clogging is a signi ficant problem

[0046] P220857 in semiconductor manufacturing, often leading to significant disruption of production and financial losses.

[0047] • Monitoring for changes in heat insulation / heat trace of pipes / ducts (i.e. detecting damage to heat trace / insulation) .

[0048] • Monitoring ampule or other container precursor level, by interpreting the effect of a thermal weight in contact with a wall of a container to derive the amount of material inside the container.

[0049] • Performing flow measurement by using a short pulse which will allow measuring the internal flow inside a pipe.

[0050] BRIEF DESCRIPTION OF THE DRAWING

[0051] Embodiments of the current invention are described in more detail in the following with reference to the figure. This is for illustrative purposes only and are not to be construed as limiting. It shows in

[0052] Fig. 1 a partial cross-sectional schematic view of an exemplary device.

[0053] DETAILED DESCRIPTION OF THE DRAWING

[0054] Fig. 1 shows a sensor arrangement 10 attached to a section of a wall 20. This wall may e.g. be the wall of a tube of a vacuum device. On an inside of said wall, material deposition 21 may occur, as indicated with a dotted crosssection. On the outside of said wall, the elements of the sensor arrangement are attached. These are a temperature sensing element 11, which may e.g. be a thermocouple connected to a readout device being able to determine the temperature d, and a heat transducer, which may e.g. be an

[0055] P220857 electrical resistance heater. The heat transducer is designed to deliver a thermal pulse to the section of the wall, at which the sensor arrangement is attached. This may be realized, as an example, by delivering electrical power to the heater element in form of a rectangular pulse. The sensor arrangement further comprises a processing unit 13 operationally connected to the temperature sensing element. As indicated by the arrow shown in dashed lines, a time course 14 of the measured temperature can be stored. A temperature d versus time t graph is shown for two different time courses 14 and 14' . The form of the first time course 14 may e.g. reflect the situation without material deposition on the wall and the form of the second time course 14' may e.g. reflect the situation with material deposition on the wall as measured at a later time then the first time course. The time courses shown here differ in characteristics, as for example maximum temperature reached, steepness of rising temperature, delay to maximum temperature, integral under the curve d(t) , etc. Such characteristics may be evaluated by the processing unit .

[0056] P220857 Reference numbers

[0057] 10 sensor arrangement

[0058] 11 temperature sensing element

[0059] 12 heat transducer 13 processing unit

[0060] 14 , 14 ' time course of measured temperature

[0061] 20 wall

[0062] 21 material deposition d temperature t time

[0063] P power

[0064] P220857

Claims

Claims1. A sensor arrangement (10) for monitoring material deposition (21) on a section of wall (20) of a device or for monitoring the status of a section of a wall of a device, the sensor arrangement comprising:- a temperature sensing element (11) , which is attachable or attached to said section of the wall,- a heat transducer (12) , which is attachable or attached to said section of the wall, wherein the heat transducer is designed to deliver a thermal pulse to said section of the wall, and- a processing unit (13) operationally connected to said temperature sensing element for receiving a measured temperature of said section of the wall, wherein the processing unit is arranged and configured to store a time course of said measured temperature and / or to evaluate a characteristic of said time course (14, 14' ) of said measured temperature.

2. The sensor arrangement according to claim 1, wherein said temperature sensing element, said heat transducer and optionally said processing unit are arranged in a common sensor unit, which sensor unit is attachable as a whole to a section of said wall of a device in such a way that both, the temperature sensing element and the heat transducer, are in thermal contact to said section of the wall and are positioned spaced from each other.P2208573 . A method of monitoring material deposition on a section of a wall of a device or of monitoring the status of a section of a wall of a device , wherein the sensor arrangement according to claim 1 or 2 is used, the method comprising the steps of- contacting said temperature sensing element to said section of the wall and contacting said heat transducer to said section of the wall ,- applying a first heat pulse to said section of the wall by means of said heat transducer,- measuring a first time course of temperature following the application of said first heat pulse by means of said temperature sensing element ,- at a later time , applying a second heat pulse to said section of the wall by means of said heat transducer,- measuring a second time course of temperature following the application of said second heat pulse by means of said temperature sensing element ,- evaluating by means of said processing unit a di f ference between said first and said second time course of temperature .4 . The method according to claim 3 , wherein said device is a vacuum deposition device , and / or wherein said section of a wall is an atmospheric side section of a processing chamber, of a pipe or of a duct .

5. The method according to claim 3 or 4 , wherein said time course of the measured temperature is evaluated to measure or detect at least one ofP220857-a deposition of material on a wall ,-an occurrence of clogging inside a pipe or a duct ,- changes in heat insulation,- changes in filling level of a container containing a chemical , such as a precursor,- presence or absence of a gas flow in a pipe .P220857

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