SYNCHRONIZATION BETWEEN TEMPERATURE MEASUREMENT DEVICE AND RADIATION SOURCES

Methods, systems, devices, and apparatus measure temperature of a substrate by switching one or more sources between an active state and an inactive state. When in the active state, the one or more sources heat at least one portion of the substrate. When in the inactive state, the one or more sources cause substantially no radiation or a negligible amount of radiation to be generated. A temeprature measuring device is synchronized to the switching between the active and inactive states, such that the temperature measuring device measures the temperature of the at least one portion of the substrate substantially only when the one or more sources are in the inactive state.

TECHNICAL FIELD

The present invention relates to treatment and/or processing of workpieces such as semiconductor wafers and substrates.

BACKGROUND OF THE INVENTION

In process manufacturing of semiconductor devices, various processing steps are performed in which a wafer is heated to desired temperatures on timescales of several seconds or less by heat sources, which can be in the form of high-intensity radiation sources such as LEDs, lasers or lamps. In certain cases, the wafer undergoes thermal processing in order to perform various manufacturing steps including, for example, dopant activation, thermal oxidation, metal reflow and chemical vapor deposition. In other cases, the wafer can be heated as a byproduct of certain processing operations, such as heating of the wafer due to exposure to plasma. The wafer temperature is monitored/measured, for example using radiation thermometers, in order to track the temperature profile of the wafer during processing.

SUMMARY OF THE INVENTION

The present invention is a method, apparatus, device and system for measuring/monitoring parameters of a workpiece/substrate, including the temperature of the workpiece/substrate and the reflectivity and/or emissivity of the workpiece/substrate.

In certain embodiments, the apparatus includes a device and/or one or more sensors configured to measure temperature via measurement of thermal radiation emitted by a substrate or workpiece that is heated by a plurality of radiation sources. The device and/or sensors operate in synchrony with the radiation sources, which switch between a first (“active”) state in which the radiation sources irradiate the substrate so as to heat the substrate, and a second (“inactive”) state in which the radiation sources do not emit radiation or emit a negligible amount of radiation such that any such radiation emitted by the radiation sources is not detected by the device (and/or sensors) or is insufficient to measurably effect measurements performed by the device (and/or sensors). In preferred embodiments, the synchronization of the device (and/or sensors) with the radiation sources is such that the device and/or sensors measure temperature (or thermal radiation) only when the radiation sources are in the inactive state, and more preferably start/begin performing such temperature/thermal radiation measurement precisely when the radiation sources are switched from the active state to the inactive state, and stop performing temperature/thermal radiation measurement of the substrate/workpiece precisely when the radiation sources are switched from the inactive state to the active state. In particularly preferred embodiments, the device and/or sensors begin measuring substrate temperature/thermal radiation exactly when the radiation sources are switched to the inactive state, and the radiation sources are switched back to the active state exactly/precisely when the device and/or sensors stop measuring substrate temperature/thermal radiation.

In certain embodiments, a first sensor operates in synchrony with the radiation sources so as to monitor/measure an intensity parameter, that varies as a function of an intensity of the thermal radiation emitted by the substrate, during periods in which the radiation sources are in the inactive state, and generates a temperature-indicative electrical signal corresponding to the intensity parameter. In some embodiments, the synchronization is provided by a controller that controls switching of the radiation sources between the two states. In other embodiments the synchronization is provided by a second sensor deployed to measure/monitor an intensity parameter that varies as a function of an intensity of the radiation emitted by the radiation sources, and that generates an intensity-indicative electrical signal corresponding to the intensity parameter. In certain embodiments, drops in the intensity-indicative signal are used to synchronize measurements performed by the first sensor with the switching of the radiation sources between the two states.

In further embodiments, the device (and/or sensors) additionally measures radiation during periods in which the radiation sources are switched to the active state in order to capture radiation reflected by the substrate in response to being irradiated by the radiation sources. In such embodiments, the captured reflected radiation can be used in order to measure or calculate the reflectivity and/or the emissivity of the substrate.

According to the teachings of an embodiment of the present invention, there is provided a method for measuring temperature of a substrate. The method comprises: switching one or more sources between: an active state in which the one or more sources heat at least one portion of the substrate, and an inactive state in which the one or more sources cause substantially no radiation or a negligible amount of radiation to be generated; and measuring temperature using a temperature measuring device synchronized to the switching between the active and inactive states such that, the temperature measuring device measures the temperature of the at least one portion of the substrate substantially only when the one or more sources are in the inactive state.

Optionally, the one or more sources irradiate the substrate during the active state so as to heat the substrate.

Optionally, the one or more sources includes a plurality of light-emitting diodes or a plurality of laser sources deployed to irradiate the substrate.

Optionally, the one or more sources includes plasma deployed to bombard the substrate with charged particles during the active state.

Optionally, the temperature measuring device is synchronized to the switching between the active and inactive states via a synchronization signal corresponding to at least one of: the inactive state, transition from the active state to the inactive state, or transition from the inactive state to the active state.

Optionally, the synchronization signal is provided by an intensity sensor deployed to sense radiation emitted by the one or more sources.

Optionally, the synchronization signal is provided by a controller associated with the one or more sources that controls switching of the one or more sources between the active and inactive states.

Optionally, the temperature measuring device includes a sensor that senses radiation emitted by the sources, and is synchronized to the switching of the one or more sources between the active and inactive states by identifying drops in the emitted radiation corresponding to initiation of the inactive state.

Optionally, the temperature measuring device is synchronized to the switching between the active and inactive states such that, the temperature measuring device begins performing temperature measurement at or after the time that the one or more sources are switched from the active state to the inactive state, and the temperature measuring device stops performing temperature measurement of the substrate at or before the time that the one or more sources are switched from the inactive state to the active state.

Optionally, the temperature measuring device is synchronized to the switching between the active and inactive states such that, the one or more sources are switched from the inactive state to the active state when the temperature measuring device stops performing temperature measurement.

Optionally, the active state is associated with at least one irradiation time-interval, and each of the at least one irradiation time-interval is a time interval during which the one or more sources emit radiation at an output power or average output power taken over the entirety of the time interval that is sufficiently high so as to heat the substrate, and the inactive state is associated with at least one measurement time-interval, and each of the at least one measurement time-interval is a time interval during which the one or more sources do not emit radiation or emit radiation at an output power that is sufficiently low so as to be negligible to the temperature measuring device.

There is also provided according to an embodiment of the teachings of the present invention a system for measuring temperature of a substrate. The system comprises: one or more sources deployed in association with the substrate, the one or more sources switchable between: an active state in which the one or more sources heat at least one portion of the substrate, and an inactive state in which the one or more sources cause substantially no radiation or a negligible amount of radiation to be generated; a controller including at least one processor and configured to switch the one or more sources between the active state and the inactive state; and a temperature measuring device configured to measure a temperature of the at least one portion of the substrate, the temperature measuring device and the switching between the active and inactive states are synchronized to each other such that, the temperature measuring device measures the temperature of the at least one portion of the substrate substantially only when the one or more sources are in the inactive state.

Optionally, the at least one temperature measuring device is synchronized to the switching of the one or more sources via a synchronization signal corresponding to at least one of: the inactive state, transition from the active state to the inactive state, or transition from the inactive state to the active state.

Optionally, the synchronization signal is provided to the at least one temperature measuring device by the controller.

Optionally, the system further comprises: at least one intensity sensor deployed to sense radiation emitted by the one or more sources.

Optionally, the at least one intensity sensor provides the synchronization signal to the at least one temperature measuring device.

Optionally, the at least one temperature measuring device measures radiation and is synchronized to the switching of the one or more sources by identifying drops in the radiation measurement corresponding to initiation of the inactive state.

Optionally, the one or more sources irradiate the substrate during the active state so as to heat the substrate.

Optionally, the one or more sources includes a plurality of light-emitting diodes or a plurality of laser sources.

Optionally, the one or more sources includes plasma deployed to bombard the substrate with charged particles during the active state.

Optionally, the temperature measuring device is synchronized to the switching between the active and inactive states such that, the temperature measuring device begins performing temperature measurement at or after the time that the one or more sources are switched from the active state to the inactive state, and the temperature measuring device stops performing temperature measurement of the substrate at or before the time that the one or more sources are switched from the inactive state to the active state.

Optionally, the switching between active and inactive states is synchronized to the temperature measuring device, such that the controller switches the one or more sources from the inactive state to the active state when the temperature measuring device stops performing temperature measurement.

Optionally, the active state is associated with at least one irradiation time-interval, and each of the at least one irradiation time-interval is a time interval during which the one or more sources emit radiation at an output power or average output power taken over the entirety of the time interval that is sufficiently high so as to heat the substrate, and the inactive state is associated with at least one measurement time-interval, and each of the at least one measurement time-interval is a time interval during which the one or more sources do not emit radiation or emit radiation at an output power that is sufficiently low so as to be negligible to the temperature measuring device.

There is also provided according to an embodiment of the teachings of the present invention a method that comprises: switching one or more sources between: an active state in which the one or more sources heat the substrate, and an inactive state in which the one or more sources cause substantially no radiation or a negligible amount of radiation to be generated; and measuring thermal radiation emitted by the substrate using a device synchronized with the switching between the active and inactive states such that, the device measures the thermal radiation emitted by the substrate substantially only when the one or more sources are in the inactive state.

Optionally, the method further comprises: calculating a temperature of the substrate based on the measured thermal radiation.

Optionally, the device is synchronized to the switching between the active and inactive states such that, the device begins performing thermal radiation measurement at or after the time that the one or more sources are switched from the active state to the inactive state, and the device stops performing thermal radiation measurement at or before the time that the one or more sources are switched from the inactive state to the active state.

Optionally, the device is synchronized to the switching between the active and inactive states such that, the one or more radiation sources are switched from the inactive state to the active state when the device stops performing thermal radiation measurement.

There is also provided according to an embodiment of the teachings of the present invention a method for measuring temperature of a substrate that is periodically irradiated by a plurality of radiation sources that are switchable between an active state in which the radiation sources irradiate the substrate so as to heat at least one portion of the substrate and an inactive state in which the radiation sources emit substantially no radiation or a negligible amount of radiation. The method comprises: performing, by a temperature measuring device, a temperature measurement of at least one portion of the substrate during the periods for which the radiation sources are in a deactivated state in accordance with a synchronization signal received by the temperature measuring device, the synchronization signal indicative of at least one of: i) periods for which the radiation sources are in the active state, ii) periods for which the radiation sources are in the inactive state, iii) transitions of the radiation sources from the active state to the inactive state, or iv) transitions of the radiation sources from the inactive state to the active state, such that the temperature measuring device begins performing temperature measurement at or after the time that the one or more radiation sources are switched from the active state to the inactive state, and the temperature measuring device stops performing temperature measurement of the substrate at or before the time that the one or more radiation sources are switched from the inactive state to the active state.

Optionally, the method further comprises: terminating the temperature measurement by the temperature measuring device during periods for which the radiation sources are in the active state.

Optionally, the temperature measurement device includes at least one sensor for sensing thermal radiation emitted by the substrate and generating a temperature-indicative signal in response to the sensed radiation, and the method further comprises: de-coupling signal amplification electronics from the at least one sensor before or when the radiation sources are switched from the inactive state to the active state.

Optionally, the synchronization signal is provided to the temperature measuring device by a controller that switches the radiation sources between active and inactive states.

Optionally, the synchronization signal is provided by an intensity sensor deployed to sense radiation emitted by the radiation sources.

There is also provided according to an embodiment of the teachings of the present invention a temperature measuring device for measuring temperature of a substrate that is periodically irradiated by a plurality of radiation sources that are switchable between an active state in which the radiation sources irradiate the substrate so as to heat at least one portion of the substrate and an inactive state in which the radiation sources emit substantially no radiation or a negligible amount of radiation. The temeprature measuring device comprises: a sensor that senses thermal radiation emitted by the substrate and generates a temperature-indicative signal in response to the thermal radiation sensed during periods for which the radiation sources are in the inactive state in accordance with a synchronization signal received by the temperature measuring device, the synchronization signal indicative of at least one of: i) periods for which the radiation sources are in the active state, ii) periods for which the radiation sources are in the inactive state, iii) transitions of the radiation sources from the active state to the inactive state, or iv) transitions of the radiation sources from the inactive state to the active state, such that the temperature measuring device begins performing temperature measurement at or after the time that the one or more radiation sources are switched from the active state to the inactive state, and the temperature measuring device stops performing temperature measurement of the substrate at or before the time that the one or more radiation sources are switched from the inactive state to the active state.

There is also provided according to an embodiment of the teachings of the present invention a temperature measuring device for measuring temperature of a substrate that is periodically irradiated by a plurality of radiation sources that are configured to switch between an active state in which the radiation sources irradiate the substrate so as to heat the substrate and an inactive state in which the radiation sources emit substantially no radiation or a negligible amount of radiation. The temeprature measuring device comprises: a sensor that senses thermal radiation emitted by the substrate and generates a temperature-indicative signal in response to the sensed thermal radiation, the temperature measuring device is synchronized to switching of the radiation sources between the active and inactive states such that the sensor generates the temperature-indicative signal only during periods for which the radiation sources are in the inactive state.

There is also provided according to an embodiment of the teachings of the present invention an apparatus configured to operate with, or as part of, a thermal processing system for processing a substrate, the thermal processing system having a plurality of switchable radiation sources configured to switch between an active state in which the radiation sources irradiate the substrate so as to heat at least one portion of the substrate and an inactive state in which the radiation sources emit substantially no radiation or a negligible amount of radiation. The apparatus comprises: a first sensor for sensing thermal radiation emitted by the substrate and for generating a temperature-indicative signal in response to the sensed thermal radiation; a second sensor for sensing radiation emitted by the radiation sources and for generating a synchronization signal corresponding to the inactive state; an amplifier circuit; and a controllable switch associated with the first sensor and the amplifier circuit and configured to switch, based on the synchronization signal, between: an open position in which the amplifier circuit is de-coupled from the first sensor, and a closed position in which the amplifier circuit is placed in signal communication with the first sensor only during periods in which the radiation sources are in the inactive mode.

There is also provided according to an embodiment of the teachings of the present invention an apparatus configured to operate with, or as part of, a thermal processing system that processes a substrate, the thermal processing system having a plurality of switchable radiation sources configured to switch between an active state in which the radiation sources irradiate the substrate so as to heat at least one portion of the substrate and an inactive state in which the radiation sources emit substantially no radiation or a negligible amount of radiation. The apparatus comprises: a temperature measuring device including at least one sensor for sensing thermal radiation, generating a signal corresponding to the sensed thermal radiation, detecting drops in the signal corresponding to periods in which the radiation sources transition from the active state to the inactive state, and producing a temperature measurement of the at least one portion of the substrate based on the sensed thermal radiation and the detected drops in the signal.

There is also provided according to an embodiment of the teachings of the present invention a method that comprises: switching one or more radiation sources between: an active state in which the one or more radiation sources irradiate at a substrate so as to heat the substrate, and an inactive state in which the one or more radiation sources emit substantially no radiation or emit a negligible amount of radiation; performing by a device synchronized to the switching between the active and inactive states: a first radiation measurement during the inactive state, the first radiation measurement including radiation corresponding to thermal emission by the substrate, and a second radiation measurement during the active state, the second radiation measurement including radiation corresponding to thermal emission by the substrate and radiation reflected by the substrate in response to radiation emitted by the one or more radiation sources; and calculating, based on the first and second radiation measurements, at least one of a reflectivity of the substrate or an emissivity of the substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a method, apparatus, device and system for measuring/monitoring the temperature of a workpiece/substrate.

The principles and operation of the methods, apparatus, devices and systems according to present invention may be better understood with reference to the drawings accompanying the description.

Referring now to the drawings,FIGS.1-3illustrate various aspects of a workpiece processing system, generally designated10, constructed and operative according to various aspects of the present disclosure. In general terms, the workpiece processing system (hereinafter referred to as “the system”)10, which can be deployed in or as part of a thermal processing chamber for example when implemented as a thermal processing system, includes an apparatus for providing temperature monitoring/measurement during processing of a workpiece12. In general, the workpiece12can be any thin plate-like material substrate, such as a semiconductor wafer, semiconductor substrate, or a glass substrate. Without loss of generality, the workpiece will be referred to hereinafter interchangeably as a substrate12.

The system10generally includes one or more controllable sources14deployed to be switchably activated thus selectively heat the substrate, a controller24for controlling the sources14, and a measuring device16that measures one or more parameters of the substrate12based on radiation emitted or reflected by the substrate12in response to irradiation and/or heating by the sources14. According to a first aspect of the present disclosure, the device16is configured to measure the temperature of the substrate12based on the thermal radiation emitted by the substrate12. In embodiments according to this first aspect of the present disclosure, the device16is also referred to interchangeably as a “temperature measuring device”. According to a second aspect of the present disclosure, the device16measures thermal radiation emitted by the substrate as well as radiation reflected from the substrate in order to enable determination of the reflectivity and/or the emissivity of the substrate12.

According to certain preferred but non-limiting embodiments, the one or more sources14is a plurality of electronically controllable and switchable radiation sources14a-14j, collectively referred to as radiation sources14, which in certain embodiments can be implemented as an array of radiation sources, deployed to irradiate the substrate12so as to heat the substrate12. Although ten radiation sources are illustrated herein for example purposes, the system10may include fewer than ten sources, or more than ten sources, depending on the thermal processing application. In such embodiments, the radiation sources14are also interchangeably referred to as “sources” or “heat sources”. The heat sources14are preferably configured to heat at least part of the substrate12or the entirety of the substrate12to a desirable temperature depending on the application, which can be, for example, 175° C. or higher, and in certain cases 200° C. or higher, and in other cases 300° C. or higher. When used in the context of a rapid thermal processing system, the radiation sources14can be configured to heat the substrate12to even higher temperatures, including 1000° C. or higher.

Parenthetically, although the sources14are implemented as radiation sources for irradiating the substrate12so as to heat the substrate12, other embodiments are contemplated herein in which there is not necessarily a causal relationship between radiation generated by the sources14and the heating of the substrate12. For example, and as will be discussed in subsequent sections of the present disclosure, certain types of sources may be switchably activated to heat the substrate12and as a side-effect or byproduct of the activation of the sources14may cause generation of radiation (i.e., radiation emission) which is not the cause of the substrate heating. Throughout the majority of the remaining portions of the present disclosure, the sources14will be described within the context of being radiation sources for irradiating the substrate12, and where applicable will be more generally described as sources generally configured to be activated which heats the substrate12.

Bearing the above in mind, the radiation sources14are generally configured to switch between operating in two states, namely an active state in which the radiation sources14irradiate the substrate12so as to heat the substrate12, and an inactive state in which the radiation sources14do not irradiate the substrate, either by not emitting radiation or by emitting a negligible amount of radiation over the duration of time for which the radiation sources14are in the inactive state. In certain non-limiting implementations, the intensity (i.e., power) emitted by the sources14can vary between a minimum intensity/power value and a maximum intensity/power, thereby enabling, in combination with the amount of time during which the radiation sources14emit radiation at the minimum and maximum intensity, controlled variability in the desired temperature of the substrate12. The minimum intensity/power value can be, for example, 0 Watts/cm2, and the maximum intensity/power value can be, for example 20 Watts/cm2. These minimum and maximum values may vary depending on the application.

Within the context of this document, the term “active state” is used interchangeably with the terms “activated state”, “active”, and “activated”, and generally refers to the state in which the sources14heat the substrate12. In particularly preferred but non-limiting embodiments in which the sources14are radiation sources, the active state refers to the state in which the radiation sources irradiate the substrate12by emitting radiation over a given period of time that is sufficiently high enough to heat the substrate. In such embodiments, the active state corresponds to a time interval or period of time during which the radiation sources14emit radiation at an output power or average output power (taken over the entirety of that time interval/period) that is sufficiently high so as to measurably heat the substrate (preferably in accordance with a desired temeprature profile). The time-intervals (i.e., time periods) during which the radiation sources14are in the active state are referred to interchangeably as “irradiation time-intervals” or “irradiation periods”. In the general case in which the sources14do not irradiate the substrate but nevertheless heat the substrate when thein the active state, time-intervals during which the sources14are in the active state can be equivalently referred to as “active state time-intervals” or “active state periods” as well as any of the other interchangeable terms used for “active state” in combination with the term “time-interval(s)” or “period(s)”.

Similarly, within the context of this document, the term “inactive state” is used interchangeably with the terms “deactivated state”, “inactive”, and “deactivated”, and generally refers to the state in which the radiation sources14do not irradiate the substrate12, or in the more general case cause substantially no radiation or a negligible amount of radiation to be generated. In embodiments in which the sources14are radiation sources which irradiate the substrate12during the active state, when in the inactive state the radiation sources14do not (i.e., cease to) emit radiation, or emit a negligible amount of radiation (from the perspective of the device16), or emit residual low levels of radiation during short time periods immediately after switching from the active state to the inactive state. In such embodiments, the inactive state corresponds to a time interval or period of time during which the radiation sources14emit radiation at an output power or average output power (taken over the entirety of that time interval/period) that is either zero (i.e., the radiation sources14do not emit any radiation) or is sufficiently low such that the radiation sources14emit a negligible amount of radiation (i.e., a very low non-zero amount of output power, e.g., <<1 Watt/cm2). The time-intervals during which the radiation sources14are in the inactive state are referred to interchangeably as “measurement time-intervals” or “measurement periods”. In the general case in which the sources14do not irradiate the substrate but nevertheless heat the substrate when thein the active state, time-intervals during which the sources14are in the inactive state can be equivalently referred to as “inactive state time-intervals” or “inactive state periods” as well as any of the other interchangeable terms used for “inactive state” in combination with the term “time-interval(s)” or “period(s)”.

A single measurement time-interval corresponds to the period of time between a first time-instance and a second time-instance, whereby the first time-instance is the instance of time at which the radiation sources14assume the inactive state and the second time-instance is the instance of time at which the radiation sources14assume the active state consecutively after assuming the inactive state.

Within the context of this document, the term “negligible amount of radiation” generally refers to any amount of radiation that is not detectable by the temperature measuring device16or is insufficient to noticeably effect temperature measurements of the substrate12performed by the temperature measuring device16.

The controller24is electrically associated with the radiation sources14and is configured to actuate the radiation sources14to turn on and off so as to control the radiation sources14to switch between the active and inactive states at an appropriate switching rate. In certain embodiments, the switching rate can be static/constant, and can be pre-programmed into the controller24. In other embodiments, the switching rate can be dynamic. The switching rate can depend on the rate of heating and the desirable temperature to which the substrate12is to be heated, which may depend on the particular heat treatment application. The controller24is preferably further configured to adjust the intensity/power of the radiation emitted by the radiation sources14when in the active state. In addition, and as will be discussed in further detail in subsequent sections of the present disclosure, the controller24can employ various techniques for controlling the switching between active and inactive states, and the radiation intensity output of the radiation sources14. In a preferred but non-limiting implementation, the controller24employs pulse width modulation (PWM) to control the switching and radiation intensity output of the radiation sources14.

FIG.2is a schematic block diagram of the controller24, showing a processor26, which can be one or more computer processors (e.g., microprocessors, microcontrollers, signal processors, and the like) coupled to a computer storage medium, represented schematically as memory28. Such processors include, or may be in communication with computer readable media (e.g., memory28), which stores computer program code or instruction sets that, when executed by the processor, cause the processor to perform actions. Types of computer readable media include, but are not limited to, electronic, optical, magnetic, or other storage or transmission devices capable of providing a processor with computer readable instructions. The memory28can be any type of memory for storing data and information, and can also store computer program code or instruction sets for executing by the processor26.

In certain embodiments, the individual radiation sources14a-14jare independently controllable by the controller24, such that the controller24can independently and selectively turn each radiation source on and off. In other embodiments, the radiation sources14are collectively switched on and off by the controller24, such that when the controller24issues an “on” control command, all of the radiation sources14are switched on simultaneously, and when the controller24issues an “off” control command, all of the radiation sources14are switched off simultaneously.

The temperature measuring device16(also referred to as a “temperature measurement device” or simply “device”) is deployed to measure the temperature of portions of the substrate12, which may be part of the substrate12or the entirety of the substrate12. In certain embodiments, the temperature measuring device16is implemented as a radiation thermometer, such as a temperature probe, which can be a standalone component that is independent from the radiation sources14and controller24of the system10, or can be integrated together with other components of the system10.

In certain preferred embodiments, the radiation sources14are deployed relative to the substrate12so as to irradiate the substrate12from a wide range of angles, such that the entirety of the substrate12is heated. In such embodiments, the radiation sources14can be configured as an array of heat sources.

In a particularly preferred but non-limiting set of implementations, the sources14are implemented as a plurality of electronically switchable light-emitting diodes (LEDs) (optionally deployed in an array), or as an arrangement of laser sources, configured to emit radiation at a particular wavelength range and preferably from a wide range of angles in order to heat the substrate12to the desired temperature. LEDs and lasers provide several advantages over incandescent and other types of lamps in thermal processing, in particular the precision with which the LEDs and lasers can be electronically controlled. In addition, LEDs and lasers can be rapidly switched on and off, allowing the LEDs to go from emitting zero power to full power (and vice versa) in a small fraction of a second.

It is noted, however, that the radiant output of LEDs, lasers or other radiation sources can overlap at least partially with a particularly desirable wavelength range for measuring the temperature of the substrate12by the temperature measuring device16. This can be seen in the example illustrated inFIG.4, where the temperature measuring device16operates at approximately 950 nm, and the sources emit peak radiation at approximately 870 nm but also emit radiation up to 950 nm. Thus, the radiation emitted by the LEDs/lasers/sources—when switched on—can interfere with the temperature measurement of the substrate12. Even LED and laser heat sources that operate far from the temperature probe operation wavelength band, for example near 500 nm, still emit broadband radiation that, although generally weak, can still overlap and interfere with the temperature measuring devices16operating at longer wavelengths near, for example, near 950 nm. This is illustrated inFIG.5, where the radiation sources14emit narrowband peak radiation near 500 nm, but still emit broadband radiation (shown in the close-up view ofFIG.6) that is strong enough to interfere with low thermal signal levels emitted by the substrate12when heated to various example temperature levels (175° C., 200° C., and 300° C. in this example). Thus, temperature measurements that are performed during periods in which the radiation sources14are in the active state can obscure the temperature readings of the substrate12.

In order to prevent radiation from the radiation sources14from obscuring of the temperature readings of the substrate12, the temperature measuring device16according to embodiments of the present disclosure is synchronized to the switching of the radiation sources14between the active and inactive states, such that the temperature measuring device16begins performing temperature measurement at the same time, or a small amount of time after the time, that the sources14are switched from the active state to the inactive state, and such that the temperature measuring device16stops performing temperature measurement of the substrate12at the same time, or a small amount of time before the time, that the sources14are switched from the inactive state to the active state. In this way, the only meaningful temperature measurements performed by the temperature measuring device16are performed during periods in which the radiation sources14are in the inactive state. Note that the “small amount of time” at the beginning and/or end of the inactive-state during which the device16does not measure temperature, is generally chosen to be an interval of sufficient length to allow for whatever uncertainty may exist between the synchronization signals and the exact time of the transition of the sources14to/from the inactive state. The addition of these small intervals at the beginning and/or end of the inactive state when the device16does not measure, is to ensure that even in the face of uncertainty in the precise time of the transition to/from the inactive state, the device16will still always measure only when the sources14are in the inactive state. Additionally, in the typical case where the device16requires a certain minimum amount of time to complete a temperature measurement, allowance may be taken to ensure that the inactive-to-active transition of the sources14does not occur while the device16is in the middle of such a temperature measurement. (So, in practice the device16may only be allowed to begin a temperature measurement if there is sufficient time to complete this measurement prior to the next inactive-to-active transition of the sources14).

Generally, the substrate12temperature will drop each time the radiation sources are placed in the inactive state, resulting in a heating profile qualitatively similar to that shown schematically inFIG.7. In situations where tight control of the temperature profile is required, and/or situations where the cooling of the substrate is rapid during the inactive-state time-intervals, it is generally desirable to reduce to a minimum the time-interval during which the radiation sources14are in the inactive-state, in order to reduce the magnitude of the temperature-drops which occur during the inactive-state time-interval. To this end, the radiation sources14can preferably be implemented as LEDs, lasers, or other radiation sources with rapid response-times. (LEDs and lasers each typically have rise/fall-times on-the-order of 1 μsec or faster). Use of rapid-response-time radiation sources allows the temperature measurement to begin nearly immediately after the initiation of the inactive state, and allows the active-state to be reestablished nearly immediately after the completion of the temperature measurement. This differs from radiation sources with slower-response-times such as, for example, incandescent radiation sources, which have rise/fall-times on the order of a few 0.1 seconds or longer. Such slower-response-time radiation sources require delaying the start of the temperature measurement until the radiation level from the slow-response-time source has decayed to the point that it no longer interferes with the temperature measurement. Similarly, the slow-response-time radiation source requires some time to return fully to the active state after the completion of the inactive state temperature measurement. Thus, the magnitude of the temperature drops during the inactive-state time-intervals can be made smaller by the use of LED, laser or other rapid-response-time radiation sources.

In certain preferred but non-limiting implementations, a pulse-width-modulation (PWM) control method can be used to vary the average power applied to the radiation sources.FIGS.13A and13Bshow exemplary PWM voltage waveforms used for PWM control. When the PWM control method is used, there are two potential ways to synchronize between the temperature probe and the radiation sources:a) When the temperature-probe measurement-time is long relative to the PWM cycle time T, it is required to put the radiation sources in the inactive state for one or more entire PWM cycles in order to capture a temperature measurement. This case is illustrated inFIG.13A, which shows one inactive-state (measurement time interval), preceded and followed by active-state intervals where higher average power is applied to the radiation sources.b) When the temperature-probe measurement-time is short relative to the PWM cycle-time T, it may be possible to fit a temperature measurement inside the low-voltage intervals which are inherently present during each PWM cycle (whenever the PWM duty-cycle is <100%). In this implementation, the inactive-state occurs naturally during the PWM cycle, eliminating the need to insert special inactive-state measurement intervals in-between the PWM voltage pulses. This approach is illustrated schematically inFIG.13B. The approach shown in this figure requires not only rapid temperature measurement times (<<T), but also rapid switching between active and inactive states. As mentioned previously, LED and laser radiation sources are particularly well suited to this situation where rapid switching is needed.

It will be appreciated that achieving the inactive state does not require application of precisely zero voltage, current, power, or other appropriate excitation to the radiation sources, but rather only requires that sufficiently low excitation be applied to ensure that the radiation sources emit at levels below that which will interfere with the temperature probe measurement.

The active time-interval and the measurement time-interval will now be discussed in further detail. For clarity of illustration, the time-intervals will be described in the non-limiting context of the sources14being radiation sources whereby the active time-interval is equivalently referred to as the irradiation time-interval. As should be apparent, the irradiation time-interval and the measurement time-interval can each include multiple intervals. Typically, the irradiation time-intervals alternate with the measurement time-intervals corresponding to the active/inactive state switching of the radiation sources14, such that the radiation sources14go through successive alternating active and inactive state cycles and such that there is interleaving between the irradiation time-intervals and the measurement time-intervals.FIG.7illustrates an example of the state of the radiation sources14over time as the radiation sources14are cycled between active and inactive states, together with the trend of the temperature profile of the substrate12resulting from the switching. As can be seen in the example illustrated inFIG.7, the substrate12temperature increases (i.e., the substrate12“heats up”) during the periods in which the radiation sources14are in the active state, and decreases (i.e., the substrate12“cools down”) during the periods in which the radiation sources14are in the inactive state. In the illustrated example, the substrate12temperature increases according to a non-linear function with respect to time during each irradiation time-interval.

Each of the irradiation time-intervals is long enough so as to allow enough time for the substrate12to heat up to the appropriate temperature. Irradiation time-intervals in a range of 0.25 to 10 seconds have been found to be particularly effective for heating a semiconductor wafer, however the interval length may vary based on the particular thermal processing application. In addition, each of the measurement time-intervals is preferably shorter than the irradiation time-intervals, and is also preferably short enough such that, compatibly with the synchronization with the switching time of the radiation sources14, the temperature of the substrate12is measured (by the temperature measuring device16) while having minimal effect on the time-dependent temperature profile. Measurement time-intervals in a range of 0.01 to 0.1 seconds have been found to be particularly effective for measuring the temperature of a semiconductor wafer that is heated for intervals of 0.25 to 10 seconds, but again the measurement time-interval length may vary depending upon the particular processing application.

In certain preferred embodiments, the device16measures temperature (and/or thermal radiation) emitted by the substrate12continuously or nearly continuously over the entirety of the duration of the measurement time-interval.

Parenthetically, it is noted that the irradiation time-intervals do not necessarily need to be of equal length. Similarly, the measurement time-intervals also do not necessarily need to be of equal length. For example, the irradiation time intervals can successively increase or decrease throughout the duration of the thermal processing of the substrate, and the measurement time-intervals can remain constant or can vary based, for example, on the length of each preceding irradiation time-interval.

FIG.3shows a schematic illustration of the temperature measuring device16according to certain embodiments of the present disclosure. In the illustrated embodiment, the temperature measuring device16includes a sensor20coupled to a processor18. The processor18can be one or more computer processors (e.g., microprocessors, microcontrollers, signal processors, and the like). The sensor20is configured to detect/sense/measure radiation (thermal radiation, radiation intensity) emitted by the substrate12and generate a temperature-indicative electrical signal in response to the sensed thermal radiation. The sensor20is preferably sensitive to radiation in a particular wavelength range chosen to provide high sensitivity to changes in the temperature of substrate12, within the expected range of desirable processing temperatures to which substrate12will be heated by the radiation sources14. In one non-limiting example, the sensor20is sensitive to radiation having wavelength at or near 1000 nm. The sensor20can be more than one sensor, for example, an array of sensors. The sensor20can measure the temperature of the substrate12based on the relationship between thermal radiation (irradiance) and temperature given by the Stefan-Boltzmann law, the Planck function, or using a look-up table (which can be stored in a memory associated with the processor18).

In the illustrated embodiment, the temperature measuring device16also includes optics23, represented schematically by a lens23(which can be an assembly of lenses, which can be refractive or reflective), for directing thermal radiation from a scene toward the sensor20. Alternatively, the optics23can be implemented as an optical fiber or fibers (e.g., a fiber optic bundle) or as a light pipe. The optics23is deployed to define a field of view corresponding to the region from which thermal radiation will arrive. When the device16is deployed to measure the temperature/thermal radiation of the substrate12, the device16is positioned such that the part of the substrate12that is to be measured is in the field of view of the scene/region defined by the optics23. Depending on the deployment configuration of the device16relative to the substrate12, the “part of the substrate” can include one or more portions of the of the substrate12or can include the entirety of the substrate12.

In certain embodiments, the processor18, the sensor20and the optics23are maintained within a single casing or mechanical body.

Parenthetically, the thermal radiation emitted by the substrate12is generally weak, and therefore the sensor20—in response to sensing thermal radiation—may generate a proportionally weak temperature-indicative signal that requires some amplification by amplifier circuitry. Therefore, although not shown in the drawings, the sensor20output is preferably coupled to an amplifier circuit (e.g., a pre-amplifier) which amplifies the signal generated by the sensor20.

The synchronization between the temperature measuring device16and the switching of the radiation sources14can be provided in various ways. According to one set of non-limiting implementations, exemplified inFIG.1, the controller24is electrically associated with (i.e., electrically linked to) the temperature measuring device16and provides a synchronization signal to the temperature measuring device16corresponding to the irradiation time-intervals and/or the measurement time-intervals. As will be discussed, the synchronization signal can correspond to the inactive state, and/or the transition from the active state to the inactive state, and/or the transition from the inactive state to the active state. Since the controller24controls the switching rate of the radiation sources14, the controller24can also provide timing information, for example in the form of the synchronization signal, to the temperature measuring device16such that the temperature measuring device16only measures the temperature of the substrate12during periods corresponding to the measurement time-interval. The processor18can receive the synchronization signal, and control the timing of the sensor20such that the sensor20only measures thermal radiation during the measurement time-interval. In other implementations, the sensor20continuously measures thermal radiation intensity, and the processor18controls a switch that switchably couples the sensor20to an amplifier circuit to close the switch only during the measurement time-interval such that the sensor20output is in signal communication with the amplifier circuit only during the measurement time-interval and not in signal communication with the amplifier circuit during the irradiation time-interval. A variation of this implementation will be discussed in subsequent sections of the present disclosure with reference toFIG.10.

In another set of non-limiting implementations, the sensor is sensitive to radiation emitted by both the radiation sources14and the substrate12, and continuously senses/measures thermal radiation intensity. In such implementations, the processor18can be programmed to process the signal generated by the sensor20in order to identify sudden drops in the signal which are indicative of drops in measured radiation intensity. Such drops typically correspond to periods in which the radiation sources14transition to the inactive state. Therefore, the processor18can produce, output and/or store or write to storage (e.g., write to a computer memory linked to the processor18) only the segment or segments of the signal that are measured after detected sudden signal drops (which correspond to the measurement time-interval, i.e., when the radiation sources14are in the inactive state), such that only the temperature measurement during the measurement time-interval are output by the temperature measuring device16. The processor18can similarly be programmed to stop recording measured data when sudden signal increases are detected, corresponding to the transition of the radiation sources to the active state. Accordingly, the apparatus of the present invention produces a temperature measurement of the substrate12based on the sensed radiation and the detected sudden drops and increases in the intensity of this sensed radiation. Alternately, rather than identifying the inactive state (for which data should be recorded) based on the change in the measured signal (sudden increases and decreases), the processor18could identify the inactive state as whenever the sensed radiation signal drops below a certain threshold signal level.

Referring now toFIGS.8and9, a system and apparatus is illustrated in which synchronization is provided between the temperature measuring device16and the switching of the radiation sources14according to further embodiments of the present disclosure in which an additional sensor is employed to sense radiation emitted by the radiation sources14. Looking first atFIG.8, an intensity sensor30(which can be more than one intensity sensor) is deployed to sense radiation emitted by the radiation sources14and is electrically associated with the temperature measuring device16. The intensity sensor is sensitive to radiation at the particular range of wavelengths emitted by the radiation sources14, and the sensor20is sensitive to radiation in the particular range of wavelengths emitted by the substrate12when heated by the sources14. Although not illustrated, the intensity sensor30can be associated with optics for directing radiation from a scene (which in this case includes the radiation sources14) toward the sensor30. Alternatively, the sensor30can be associated with dedicated optics that direct radiation from the radiation sources14toward the sensor30.

The intensity sensor30generates the synchronization signal based on detecting/sensing radiation in the wavelength range of relevance, specifically the detecting/sensing of radiation emitted by the radiation sources14. In certain non-limiting implementations, the intensity sensor generates the synchronization signal upon detecting/sensing radiation emitted by the radiation sources14. In other non-limiting implementations, the intensity sensor30generates the synchronization signal in the event that no radiation in the wavelength range of relevance is detected/sensed by the intensity sensor30.

The intensity sensor30provides the synchronization signal to the temperature measuring device16, which performs a thermal radiation measurement (via the sensor20) according to the synchronization signal such that the sensor20only measures thermal radiation (emitted by the substrate12) during the measurement time-interval (corresponding to inactive periods of the radiation sources14). For example, the processor18of the temperature measuring device16can command the sensor20to perform thermal radiation measurements in response to receipt of the synchronization signal from the intensity sensor30.

FIG.9shows an alternative configuration similar toFIG.8, but in which the intensity sensor30is integrated as part of the temperature measuring device16such that both sensors20,30are deployed within a single casing or mechanical body. Here, just as inFIG.8, the intensity sensor30detects/senses/measures radiation emitted by the radiation sources14in order to determine when the radiation sources14are in the inactive state (corresponding to the measurement time-interval) and/or when the radiation sources14are in the active state (corresponding to the irradiation time-interval). Each of the sensors20and30can have separate optics (i.e., sensor20can be associated with optics23as inFIG.3, and sensor30can have separate optics as alluded to above with reference toFIG.8). Alternatively, the sensors20and30can share optics (e.g., optics23fromFIG.3), which can be deployed to direct radiation from both the radiation sources14and the substrate12toward the sensors20and30.

In the embodiment illustrated inFIG.9, the processor18can receive the synchronization signal from the intensity sensor30and can command the sensor20to perform thermal radiation measurements based on the received synchronization signal.

FIG.10illustrates another embodiment that is similar toFIG.1, except here the temperature measuring device16also includes an amplifier circuit22for amplifying the temperature-indicative signal generated by the sensor20, and a switch21that selectively places the sensor20into signal communication with the amplifier22. The sensor20also continuously measures thermal radiation intensity and in addition to being sensitive to radiation in the particular range of wavelengths emitted by the substrate12when heated by the sources14, may also be sensitive to radiation at the particular range of wavelengths emitted by the radiation sources14. Nominally, the switch21can be in the open position such that the sensor20is de-coupled from (i.e., not in signal communication with) the amplifier22. Thus, when the switch21is in the open position the output signal generated by the sensor20in response to any radiation measurements is not amplified. When the switch21is in the closed position, the sensor20is placed into signal communication with the amplifier22such that the output signal generated by the sensor20in response to any thermal radiation measurements is amplified by the amplifier22. The switching of the switch21between the open and closed positions is controlled by control input received from the controller24in the form of a synchronization signal such that the amplifier22is de-coupled from the sensor20at the time, or an amount (small amount) of time before the time, that the radiation sources14are switched from the inactive state to the active state. In the illustrated example, the processor18acts as a relay which actuates the switch21to open and close based on the synchronization received from the controller24. The controller24provides the synchronization signal in correspondence with the switching of the radiation sources14between the active and inactive states, such that when the radiation sources14are in the active state the switch21is in the open position so as to de-couple the amplifier22from the sensor20, and when the radiation sources14are in the inactive state the switch21is in the closed position. Thus, the switch is primarily closed during the measurement time-interval such that the amplifier22amplifies signals generated by the sensor20only during the measurement time-interval, and the switch21is primarily open during the irradiation time-interval such that the thermal radiation intensity measurement performed by the sensor20is not amplified and the temperature measurement performed by the device16is effectively interrupted/terminated.

The synchronization signal utilized in the embodiments of the present disclosure can take on various forms, including, for example, forms of a time-varying signal that is continuous over a specified time-duration, one or more pulse or step signals, one or more trigger-type signals that can include pulse/step signals, or a digital signal. In one non-limiting example, the synchronization signal is a pulse or step that takes on a high or low value or values when the radiation sources14are in the active state, and takes on a low or high value or values when the radiation sources14are in the inactive state. In such an example, the temperature measuring device16measures temperature (via thermal radiation sensing by the sensor20) during time-intervals during which the synchronization signal has low or high value(s) (corresponding to the inactive time-interval).

In another non-limiting example, for each of the inactive time-intervals the synchronization signal can include a start trigger pulse that indicates the beginning of the inactive time-interval, and an end trigger pulse that indicates the end of the inactive time-interval. In such an example, the temperature measuring device16begins to measure temperature upon receipt of the start trigger pulse and continues to measure temperature until receiving the end trigger pulse. In another similar non-limiting example, for each of the active time-intervals the synchronization signal can include a start trigger pulse that indicates the beginning of the active time-interval, and an end trigger pulse that indicates the end of the active time-interval. In such an example, the temperature measuring device16begins to measure temperature upon receipt of an end trigger pulse (associated with the end of one active time-interval) and continues to measure temperature until receiving a start trigger pulse (associated with the beginning of the next active time-interval). In yet another similar non-limiting example, a single trigger pulse can be used to indicate the transition of the radiation sources to the inactive state, with the inactive state pre-programmed to last for a duration equal to or slightly longer than the time required for the temperature probe to take a single measurement. At the end of this preprogrammed time-interval, the radiation sources automatically return to the active state, without sending a trigger pulse to indicate this transition.

It should be apparent that combinations of the above are also contemplated herein. For example, the synchronization signal can include start and end trigger pulses of high or low value indicating the beginning and end, respectively, of an active time-interval, and can include start and end trigger pulses of low or high value indicating the beginning and end, respectively, of an inactive time-interval.

In certain non-limiting implementations, the synchronization signal can act as a trigger signal that triggers the temperature measuring device16to begin measuring the temperature of the substrate12, while in other implementations the synchronization signal can act as a trigger signal that triggers the temperature measuring device16to stop measuring the temperature of the substrate12. In yet other non-limiting implementations, the receipt of the synchronization signal (by the temperature measuring device16) triggers the temperature measuring device16to measure the temperature of the substrate12, while in other implementations the absence of the receipt of the synchronization signal triggers the temperature measuring device16to measure the temperature of the substrate12.

With continued reference toFIGS.4-10, refer now toFIG.11, which illustrates an example of a synchronization signal that can be used to provide synchronization between the temperature measuring device16and the switching of the radiation sources14between active and inactive states. Here, the switching of the radiation sources from active to inactive state occurs on the rising-edge of the synchronization signal, when the signal increases from a “low” signal level (designated AL) to a “high” signal level (designated AH). These instances occur at times labeled TINACin the figure. Measurement device16initiates its temperature measurement simultaneously with this rising signal, and completes the temperature measurement within a pre-specified time interval (designated TMEASinFIG.11), after which the radiation sources14automatically return to the active state, at times labeled TACin this figure. Thus, the temperature measuring device16is able to measure the temperature of the substrate12only during the measurement time-intervals, i.e., during periods in which the radiation sources14are in the inactive state.

The synchronization signal can, for example, be implemented as an electrical signal, where the “high” and “low” amplitude values correspond to high and low voltages used to generate the signal, e.g., 5 volts for “high” and 0 volts for “low”.

The synchronization between the temperature measuring device16and the switching of the radiation sources14between the active and inactive states, in particular when implemented as LEDs or laser sources, provides a significant advantage over conventional substrate temperature monitoring solutions by enabling the temperature measuring device16to measure temperature/thermal radiation only during periods in which the radiation sources14are in the inactive state (and preferably for the entirety of the duration of the period when the radiation sources14are in the inactive state). By doing so, the temperature measuring device does not suffer from the effects of glare from the much stronger heating radiation sources, which will in general hinder the ability of the temperature probe to be able to accurately detect the typically orders-of-magnitude smaller thermal radiation signal emanating from the substrate12.

In particularly preferred synchronization implementations, the synchronization enables the device16to start the temperature measurement exactly at the moment the radiation sources14are switched to the inactive state, and return the radiation sources to the active state exactly at the moment that the temperature probe completes its temperature measurement. Such synchronization implementations reduce to a minimum the duration of the inactive state, thus reducing the uncontrolled cooling of the substrate12which occurs during the inactive state intervals, as shown schematically inFIG.7. Furthermore, reduction of the inactive state time interval to an absolute minimum, can allow more frequent inactive state measurement intervals to be inserted into the heating profile, which can be of particular importance when used in combination with a closed-loop temperature control scheme, where more-frequent temperature measurements allow for more frequent control corrections by the temperature controller—leading to tighter and more robust temperature control.

It is noted, however, that the measurement and synchronization schemes disclosed herein may also be applicable to situations that do not require precise closed-loop control, such as for data recording or collection purposes, or scenarios in which an alarm or warning is issued if the measured temperature is outside of a preferred temperature range.

Attention is now directed toFIG.12which shows a flow diagram detailing a process (i.e., method)1200for measuring/monitoring the temperature of a substrate in accordance with embodiments of the disclosed subject matter. Reference is also made toFIGS.1-11. The process and sub-processes ofFIG.12are performed by the sources14, the temperature measuring device16and associated components thereof, including the sensor20and optionally the sensor30. Some of the processes and sub-processes ofFIG.12are computerized processes performed by the controller24and/or the processor18. The aforementioned processes and sub-processes are for example, performed automatically and preferably in real-time. It is assumed that prior to performing the process ofFIG.12, the substrate12is already deployed in a substrate processing system, such as a thermal processing chamber, that includes sources of the heat and/or radiation (e.g., sources14), which in certain embodiments are deployed for irradiating the substrate12so as to heat the substrate, and a computerized control device (e.g., controller24) for switching the sources on and off so as to control switching between the active and inactive states, as well as in certain embodiments controlling the level of radiation intensity emitted by the sources when in the active state.

The process1200begins at step1202where the controller24switches the sources14to the active state such that the sources14heat the substrate12. In the context of thermal processing, the sources14are radiation sources that when switched to the active state in step1202irradiate the substrate12, thereby heating the substrate12during an irradiation time-interval. At step1204, the controller24switches the sources14to the inactive state such that the sources14cause no radiation or a negligible amount of radiation to be generated. In the context of thermal processing, when switched to the inactive state at step1204, the sources14no longer irradiate the substrate12such that the sources14emit no radiation or a negligible amount of radiation. The sources12are maintained in the inactive state during a measurement time-interval. At step1206, the temperature measuring device16, deployed in proximity to the substrate12, begins measuring the temperature of the surrounding environment so as to measure the temperature of the substrate12at the beginning of the measurement time-interval (which is the end of the irradiation time-interval). Following the completion of the temperature measurement, the process1200then moves to step1208—which is generally identical to step1202—in which the controller24switches the sources14to the active state such that the sources14heat the substrate12. Due to the synchronization between the temperature measuring device16and the switching of the sources14between the active and inactive states, the temperature measuring device stops measuring the temperature of the surrounding environment such that no thermal radiation emitted by the substrate and no radiation caused (and in the context of thermal processing emitted) by the sources14is captured by the temperature measuring device16. The process1200then returns to step1204and repeats itself until the temperature monitoring is terminated.

In certain embodiments, the process1200includes an additional step1210in which a synchronization signal is provided to the temperature measuring device16(either by the controller24or by an intensity sensor30deployed to measure radiation intensity emitted by the radiation sources14), that indicates when the radiation sources14are in the active and inactive states such that the temperature measuring device16can start and stop the temperature measurement in synchrony with the switching between the active and inactive states.

Although embodiments of the present disclosure have been described thus far as having a temperature measuring device16synchronized with the switching rate of sources14that are electronically controlled by a dedicated controller24that is separate from the temperature measuring device16, other embodiments are possible in which the controller is integrated as part of the temperature measuring device. Such embodiments may be of particular value when the temperature measuring device is implemented as a temperature probe that is integrated as part of a thermal processing system. In such embodiments, the processor of the temperature monitoring device can be configured to perform the functions of the controller24described above (for example with reference toFIGS.1and2), and the controller24itself can be removed. Thus, the processor of the temperature measuring device, e.g., the processor18, can control the switching of the radiation sources14between active and inactive states and provide synchronization to the sensor20(or an amplifier switch, for example the switch21inFIG.10).

Although the temperature control/monitoring/measuring methods, apparatus and devices of the present disclosure are particularly suitable for use with radiation sources14implemented as a plurality of electronically controllable and switchable LEDs or lasers, the methods, apparatus and devices are also useful when deployed with radiation sources14implemented as lamps or other incandescent sources. In such implementations, it may be advantageous to add a time delay to the measurement time-interval start time in order to account for the time it takes for residual radiation emission to dissipate after the lamps or other incandescent sources are switched off. The delay can be dynamically included in the synchronization signal, or can be programmed into the processor18of the temperature measuring device16. The addition of such a delay-time to the measurement-interval start-time can also be used to compensate for delays introduced by other elements of the system besides the radiation sources themselves, but which lead to a delay in the time required for the radiation sources to reduce their radiation output to a negligible level. For example, the radiation-source power-supply could also introduce delays or time-dynamics to the reduction of the radiant output by the radiation sources, and these delays and time-dynamics can also be compensated by the addition of a time-delay to the measurement-interval start time.

The various sensors described herein are sensors of electromagnetic radiation that can be sensitive to radiation in specific wavebands or wavelength regions of the electromagnetic spectrum. These sensors can also be referred to as “detectors”, and can be implemented in various ways, including, for example, as photodetectors, photosensors, photodiodes, or any other type of sensing device that can convert sensed electromagnetic radiation into an electrical current or other type of information bearing signal. In certain embodiments, the sensor20and/or the sensor30generates/generate analog signals in response to sensed radiation, whereas in other embodiments the sensor20and/or the sensor30generates/generate digital signals in response to sensed radiation. In embodiments in which an analog signal is generated by the sensor(s), analog-to-digital conversion circuitry is preferably in signal communication with the sensor(s) in order to convert the analog signal to a digital signal.

As mentioned, the radiation sources (e.g., LEDs, lasers) have a peak emission wavelength that may be different from the wavelength at which the temperature measuring device, according to the embodiments disclosed herein, is operative. In embodiments in which a sensor is utilized to detect the absence or presence of radiation (in a wavelength range of relevance) emitted by the radiation sources in order to generate a synchronization signal (e.g., intensity sensor30), it should be understood that such a sensor most preferably operates at or near the peak emission wavelength of the radiation sources. In addition, it should be understood that the wavelength values and ranges described above and illustrated in the drawings are exemplary only, and were generally provided in order to more clearly demonstrate the temperature measuring/monitoring methodology of the embodiments of the present disclosure. The teachings according to the embodiments of the present disclosure can be applied to radiation emission and measurement for other wavelength values and ranges, as should be apparent to those of ordinary skill in the art.

As mentioned above, according to a second aspect of the present disclosure, the device16is also configured to measure radiation in order to enable determination of the reflectivity and/or the emissivity of the substrate12. As discussed above, the device16is generally configured to measure radiation from the substrate12(as well as the environment surrounding the substrate12), and so can be used, in combination with the synchronization methodology described above, to determine and/or calculate and/or monitor and/or measure one or more parameters of the substrate12in addition to temperature, including in particular the reflectivity and/or emissivity of the substrate12. The following paragraphs describe the methodology for determining the reflectivity and/or emissivity of the substrate12according to this aspect of the present disclosure, with continued reference toFIGS.1-13Band with particular reference toFIG.14.

By way of introduction, the reflectivity and transmissivity of the substrate can be used to determine the emissivity of the substrate12(as a consequence of the first and second laws of thermodynamics), by the relation: emissivity=1'reflectivity−transmissivity.

For the special case where the measuring device operates in a waveband where the transmissivity of the substrate is effectively zero (a waveband where the substrate is opaque), the emissivity can be determined by a measurement of the substrate reflectivity alone (since the transmissivity is nearly zero).

Therefore, if the reflectivity of the substrate12can be determined within a waveband where the substrate is effectively opaque, then the emissivity of the substrate12within that waveband can easily be calculated therefrom. According to certain embodiments of the second aspect of the present disclosure, the reflectivity of the substrate12is first determined, and the emissivity of the substrate12is subsequently calculated based on the determined reflectivity.

According to certain embodiments, the reflectivity of the substrate12is determined based on measurements (performed by the device16) made when the radiation sources14are in the inactive state and the active state. The following paragraphs describe a particular exemplary method by which the substrate reflectivity can be determined from the inactive and active state measurements.

With reference toFIG.14, when the radiation sources are in the inactive state, the measurement device16collects thermal radiation from the substrate12. This radiation is represented by the wavy arrow32. When the radiation sources are switched to the active state, the measurement device16continues to collect thermal radiation emitted by the substrate12, and in addition collects (a) radiation emitted by the radiation sources14after reflection off the substrate12, as represented by the thick dashed arrow34, and also (b) radiation emitted by the radiation sources14which impinges on the measurement device16without first reflecting off the substrate12, as represented by the thin dotted arrow35. It will be appreciated that the arrows shown inFIG.14represent only exemplary paths which could be taken by each class of radiation described in this paragraph.

Let Iinactivebe the radiation intensity incident on device16when the radiation sources14are in the inactive state, and Iactiveactive be the radiation intensity incident on device16when the radiation sources are in the active state with a particular power setting, which we will refer to as power Preflectivity. Note that the difference between these two signals Idifference=Iactive−Iinactive, does  not depend on the intensity of the thermal-self-emission being emitted by the substrate12, but does contain information about radiant intensity34reflected off the substrate12.

To convert Idifferenceinto a reflectivity value representing the reflectivity of the substrate12, it is necessary to perform a calibration procedure. There are many possible ways to calibrate this measurement, and one exemplary method is described here as follows:

Measure Idifferencewhen two substrates12of known reflectivity ρref1and ρref2respectively are placed in the system10. The two values of Idifferencefor these two substrates are referred to as Idiffi1and Idiff2(corresponding to the measurements with substrates of reflectivity ρref1and ρref2respectively). For example, typically in semiconductor processing applications, a bare silicon wafer can be used as one of the reference substrates, with known reflectivity ρref1=0.32 at 950 nm wavelength and 30° C. The other reference reflectivity can be, for example, a system10where the substrate12has been removed entirely, resulting in ρref2=0. (Note that in this case, it may be necessary in some system designs to also remove any reflective surfaces immediately behind substrate12, which may reflect radiation into device16even in the absence of the substrate16). Then the general reflectivity ρ of any substrate placed in system10can be calculated as:

where the constants C1and C2are given in terms of the calibration measurements as:

The above equations are appropriate for situations where the reflected radiation34collected by the measurement device16typically undergoes only one reflection from substrate12prior to impinging on measurement device16. In cases where the geometry of system10is such that a significant intensity of reflected radiation34undergoes multiple reflections off the substrate12prior to impinging on measurement device16, the above equation needs to be modified to account for the effects of these multiple reflections. These multiple-reflection effects are referred to as “cavity effects” and formulas for modifying the above equation to account for these effects are well known to those of ordinary skill in the art.

Considering now the general case where it is desired to perform all of the following three actions while processing a given substrate12: (a) heat the substrate to a desired temperature profile, (b) measure the substrate temperature (or thermal self-emission) and (c) measure the substrate reflectivity (and hence the emissivity of an opaque substrate), the required actions are respectively: (a) place the radiation sources in the active state at some power-setting which is expected to give the desired substrate heating profile, (b) periodically place the radiation sources in the inactive state to measure the temperature (and Iinactivefor the reflectivity measurement), and (c) periodically put the radiation sources in the active state at power-setting Preflectivityto measure Iactiveor the reflectivity measurement.

Note that it is expected that the substrate emissivity (and reflectivity) will change very slowly relative to the substrate temperature, so that the three measurements described in the previous paragraph do not need to be performed at the same frequency. Generally, it is expected that most (>80%) of the processing time would be allocated to (a) heating the wafer to the desired temperature profile. The remaining <20% of the processing time would be allocated to measuring temperature (thermal self-emission) and emissivity (reflectivity) of the substrate12, with the temperature measurement being performed considerably more frequently than the emissivity measurement. For example, if the emissivity of the substrate is thought to vary only very weakly as a function of temperature, it may be advantageous to measure the emissivity only once upon entry of the substrate into the processing system10, and after that, only heat the substrate12and measure its temperature, without repeating the reflectivity measurement during the course of processing of that substrate. Alternately, the emissivity of the substrate12could be measured, for example, once every 10 temperature measurements, over the course of processing the substrate.

Although the invention has been described within the context of a thermal processing system used for heating and processing a substrate, the temperature measuring/monitoring/tracking methodology described herein is applicable to any heat treatment processes in which the temperature of a workpiece needs to be measured/monitored/tracked while being heated, at least intermittently or periodically, by one or more sources.

As previously mentioned, in certain wafer processing systems the sources14cause heating of the substrate12and cause generation of radiation, but there is no causal relationship between radiation that is generated when the sources14are in the active state and the heating of the substrate12. In other words, in certain cases the sources14themselves are not radiation sources that irradiate the substrate12so as to heat the substrate12, and any radiation that is generated as a result of (caused by, due to) the sources14being in the active state is not the cause of heating of the substrate but is rather a byproduct or side-effect of some other aspect of the wafer process. Plasma-etching or plasma-deposition systems is one example of such a process, in which a wafer is heated due to physical bombardment of the wafer by charged particles in the plasma. The collision of these particles with each other and the wafer also cause radiation to be generated (i.e., emission of radiation), which can interfere with wafer temperature measurement. However, the generated radiation is not the cause of the heating of the wafer, but is a byproduct of the particle bombardment. Nevertheless, in order to accurately measure/sense the wafer thermal emission, it may be useful to be able to turn plasma off so as to eliminate interfering plasma radiation during wafer temperature measurement.

Accordingly, and as previously discussed, the sources14according to the embodiments of the present disclosure are not necessarily limited to radiation sources that irradiate the substrate, but in general are sources which cause heating of the substrate12when in the active state. Further, the inactive state more generally corresponds to the state in which the sources14cause substantially no radiation or a negligible amount of radiation to be generated so as to not interfere with substrate temperature measurement. In certain particularly preferred embodiments, the sources14are radiation sources such as LEDs or lasers that irradiate the substrate thereby heating the substrate, and which can also be controlled to quickly turn on and off such that the radiation sources emit no radiation or a negligible amount of radiation when in the inactive state. In other embodiments, the sources14cause heating of the substrate when in the active state, for example when implemented as plasma in the case of plasma-etching or plasma-deposition systems. In such embodiments, the sources14cause substantially no radiation or a negligible amount of radiation to be generated when the sources are in the inactive state, which in the example of the sources being plasma refers to the state in which no charged particles bombard the wafer, such that the charged particles do not collide with each other or the wafer thereby resulting in no radiation or a negligible amount of radiation being generated.

To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions which do not allow such multiple dependencies. It should be noted that all possible combinations of features which would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the invention.