Patent Application
20240339309
The present invention relates generally to systems and methods of characterization, and, in particular embodiments, to advanced optical emission spectroscopy (OES) characterization.
Generally, a semiconductor device, such as an integrated circuit (IC) is fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials over a substrate to form a network of electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias) integrated in a monolithic structure. Process flows used to form the constituent structures of semiconductor devices often involve depositing and removing a variety of materials while a pattern of several materials may be exposed in a surface of the working substrate.
Advanced process control that involves process and system characterization and fault detection in semiconductor manufacturing is essential for reproducible production of complex structures. Especially in high-volume manufacturing, plasma system diagnosis is of paramount importance for process consistency. As the minimum dimension of features in a patterned layer has shrunk periodically and new materials have been introduced in ICs, the need for improved plasma system diagnosis to assure process compliance and cost reduction has increased.
In accordance with an embodiment of the present invention, a processing system that includes: a processing chamber configured to hold a substrate to be processed; a first vacuum pump; a second vacuum pump disposed downstream from the first vacuum pump; an exhaust gas line connecting the process chamber and the first vacuum pump, and the first vacuum pump and the second vacuum pump; a plasma power supply including a first RF power source configured to generate a plasma from a portion of an exhaust gas between the first and second vacuum pumps; and an optical emission spectroscopy (OES) measurement assembly including an OES detector configured to measure OES signals from the plasma.
In accordance with an embodiment of the present invention, a plasma processing system that includes: a plasma processing chamber configured to hold a substrate to be processed; a RF power source configured to generate a first plasma in the plasma processing chamber; a first vacuum pump; an exhaust gas line connecting the plasma process chamber and the first vacuum pump; a plasma power supply configured to generate a second plasma from a portion of an exhaust gas downstream from the plasma processing chamber, and an optical emission spectroscopy (OES) measurement assembly including: an OES detector configured to measure first OES signals from the first plasma and second OES signals from the second plasma; a microprocessor, and a non-transitory memory storing a program to be executed in the microprocessor, the program including instructions to: perform a plasma process on a substrate; during the process, record the first or second OES signals associated with a chemical composition of the first or second plasma, and based on the first or second OES signals, estimate a temporal change of the chemical composition to evaluate a progress of the process.
In accordance with an embodiment of the present invention, a method of processing a substrate that includes: plasma processing a substrate in a plasma processing chamber by exposing the substrate to a first plasma; using a vacuum system, remove an exhaust gas from the plasma processing chamber to an exhaust gas line; using an optical emission spectroscopy (OES) measurement assembly connected to the plasma processing chamber, detecting first OES signals from the first plasma during the plasma processing, the first OES signals being associated with a chemical composition of the first plasma; generating a second plasma from the exhaust gas downstream from the plasma processing chamber; using the OES measurement assembly, detecting second OES signals from the second plasma during the plasma processing, the second OES signals being associated with a chemical composition of the second plasma; and based on the first or second OES signals, estimating a temporal change of the chemical composition of the first or second plasma.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
This application relates to systems and methods of process characterization, more particularly to optical emission spectroscopy (OES) for advanced process characterization. In semiconductor manufacturing, plasma processing is used at various stages for depositing and etching various materials to construct complex structures with precision at nanometer scale. Because a plasma is a highly energetic and complex system comprising ion and radical species, it is often challenging to accurately characterize the plasma during operation and monitor the progress of a plasma process. Optical emission spectroscopy (OES) is a powerful spectroscopic tool to analyze atoms and ions present in a plasma by detecting optical emission from excited species, and OES systems have been incorporated to some plasma processing systems. For example, using OES to collect light emission signal from process plasmas, endpoint detection (EPD) of a plasma etch process such as reactive ion etching (RIE) and atomic layer etching (ALE) may be achieved.
However, depending on the types of materials being processed and the process parameters, a change of an optical emission spectrum of plasma during the process may be subtle and relatively difficult to detect. Further, some process conditions require very mild or even zero plasma discharge, leading to limited sensitivity of existing OES methods due to insufficient excitation for optical emissions. New OES methods with improved sensitivity are therefore desired for advanced process characterization, especially in pulsed plasma, low-powered plasma, or plasma-less processes.
Embodiments of the present application disclose improved systems and methods of OES data collection during a semiconductor processing, in which an additional plasma source may be introduced for additional OES data collection. The additional plasma source may be used to generate an additional plasma external to a processing chamber, particularly in an exhaust system downstream from the processing chamber. OES data from the exhaust system (exhaust OES) may collected in addition to OES data from the processing chamber (chamber OES), enabling “dual” OES data collection. The exhaust OES, alone or in combination with the chamber OES, may be used for various types of process characterization such as process monitoring and endpoint detection (EPD). The use of exhaust OES may improve the sensitivity of OES system during a process. This is particularly beneficial for processes where the chamber OES signal from the processing chamber is unstable, weak or absent, such as pulsed plasma, low-powered plasma, or plasma-less processes.
In the following, various examples for dual optical emission spectroscopy (OES) for measuring exhaust OES signals coupled with a processing system are described referring to
In
A vacuum system for the processing system 11 may comprise a first vacuum pump 152 and a second vacuum pump 154, both connected to the processing chamber 110 via the exhaust gas line 120 such that the second vacuum pump is disposed downstream from the first vacuum pump 152. In various embodiments, the first vacuum pump 152 may be a turbomolecular pump. In certain embodiments, the pressure in the portion of the exhaust gas line 120 between the two pumps may be between 1 mTorr and 10 Torr.
As illustrated in
In one or more embodiments, the exhaust OES chamber 165 may be equipped with a temperature controller (e.g., heating/cooling system). In one embodiment, the temperature in the exhaust gas line 120 and/or the exhaust OES chamber 165 may be kept relatively high to prevent residual by-product accumulation on the surfaces.
Disposing the exhaust OES chamber 165 between the first vacuum pump 152 and the second vacuum pump 154 may advantageously benefit the practicality for generating the exhaust plasma in several aspects. First, the pressure may be maintained low as suitable for a gas discharge for the exhaust plasma. Excitation of the exhaust gas further downstream from the processing chamber 110, for example, after the second vacuum pump, would be more difficult and impractical due to higher pressure environment. Second, the proximity of the exhaust OES chamber 165 to the processing chamber 110 may minimize the delay of OES signals responsive to an event (e.g., endpoint or process failure) in the processing chamber 110.
A radio frequency (RF) power source 175 may be used as a power supply for generating the exhaust plasma, and RF electrodes 185 may be disposed outside the walls of the exhaust OES chamber 165. Although not specifically illustrated, any RF power source (e.g., the RF power source 75) may comprise a power generator and a matching network.
The RF electrode 185 may be a conductive helix coiled horizontally around the walls comprising a dielectric (e.g., a ceramic material). The RF electrode 185 may alternatively be shaped like a planar coil. The RF electrode 185 is coupled to the RF power source 175. In various embodiments, the oscillation frequency of the RF power may be about 400 kHz to about 5 GHz and, in certain embodiment about 15 MHz to about 200 MHz. In one embodiment, the frequency of the RF power may be between 20 MHz to 40 MHz, for example 27 MHz. When a resonator helical coil is used for the RF electrode 185, the frequency may be selected in consideration of the coil length such that the coil may sufficiently surround the walls of the exhaust OES chamber 165. The RF electrode 185 may be configured to operate in a purely inductively or capacitively coupled mode to sustain the exhaust plasma with an RF power density of about 0.01 W/cm3 to about 30 W/cm3 within the exhaust OES chamber 165. In one embodiment, the RF power source may be operated in pulsing mode with a peak power up to about 30 W/cm3.
The exhaust OES chamber 165 may comprise an optical port 130 where an optical fiber cable 140 is attached to collect and transmit exhaust OES signals from the exhaust OES chamber 165 to the optical switch 155. In various embodiments, the OES measurement assembly 15 may further comprise an OES detector 160 and a control unit 195. Although not specifically illustrated, the control unit 195 may comprise various electrical components required to perform detection, recording, analysis of the OES signals as well as feedback control of the processing system 11 and the OES measurement assembly. Such components may include a transceiver, an amplifier, an analog-to-digital convertor (ADC), a filter, a memory, and a processor. In various embodiments, the OES measurement assembly 15 may be configured to perform a series of operations according to a command from the control unit 195: operating the optical switch 155 to selectively transmit the chamber or exhaust OES signals to the OES detector 160, OES data acquisition at the OES detector 160, receiving the OES data at the transceiver, filtering the OES data at the filter, and determining a characteristic of the plasma (e.g., the exhaust plasma) at the processor. The characteristic of the plasma may, for example, be plasma density, and/or concentrations of reactive ion species, etch by-product, or other species of interest. The characteristic of the plasma may also include information on electron temperature. In certain embodiments, the OES measurement assembly 15 may be further configured to process the obtained raw OES data by, for example, averaging and/or smoothing prior to determining the characteristic of the plasma.
In acquiring the OES data, the OES detector 160 may include, for example, a spectrometer that samples an optical emission spectrum of a plasma. The spectrum, in this example, may include light intensity as a function of wavelength or frequency. The OES detector 160 may comprise a charge-coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or other type of light detection device or photosensor may be utilized to measure the light intensity at a plasma processing chamber of the plasma processing system 21. In certain embodiments, the sensor 200 may comprise a CCD sensor with a capability of millisecond time resolution. In another embodiment, the sensor 200 may comprise a CMOS image sensor with a capability of microsecond time resolution.
In various embodiments, the optical switch 155 is used to selectively transmit one of the two OES signals: the OES signals form the processing chamber 110 (chamber OES) or the OES signals from the exhaust OES chamber 165 (exhaust OES). Using the optical switch 155, it is possible to use the same OES detector for detecting OES signals from two difference sources. Accordingly, the use of a switching mechanism (e.g., the optical switch 155) can enable the dual OES measurements without duplicating the OES detector that would require a substantial additional manufacturing cost. In certain embodiments, the switching may be realized by using a fiber optic splitter in place of the optical switch. In addition to selecting one of the two OES sources, the optic fiber splitter may have an option to superpose the OES signals from both sources, which may advantageously simply the process of OES data collection. In these embodiments, it may still be possible to perform the deconvolution of the raw data (e.g., mathematical subtraction) to recover information on each of the OES signals. In certain embodiments, the plasma for one of the two OES sources may be powered in a pulsing mode such that the deconvolution may be enabled. In alternate embodiments, the OES detector 160 may comprise a multi-channel detector capable of simultaneously measure multiple OES data series from different sources. In such embodiments, the optical switch 155 or the like may be omitted from the OES measurement assembly 15.
In various embodiments, the memory of the control unit 195 may comprise a non-statutory computer-readable storage media for storing instructions which are executed by the processor to perform the various functions described herein. For example, the memory may generally include both volatile memory and non-volatile memory (e.g., RAM, ROM, or the like). The memory may be referred to as memory or computer-readable storage media herein. The memory is capable of storing computer-readable, processor-executable program instructions as computer program code that may be executed by the processor(s) as a particular machine configured for carrying out the operations and functions described in the implementations herein.
The OES measurement assembly 15 is capable of collecting a plurality of wavelengths of optical emission spectra emanating from the glow discharge of gases in a plasma. These wavelengths can be associated with the specific chemical species generated from entering reactant gases, can result from gas phase reactions as well as reactions on the wafer and chamber surfaces. The OES measurement assembly 15 may be configured to detect various chemical species relevant in semiconductor fabrication processes, including but not limited to, for example, halides of silicon and the halogen species itself (e.g. Cl, F, and Br). In one or more embodiments, the methods OES may be used to monitor a plasma etch process. For example, the plasma etch process may comprise etching of silicon oxide using a fluorine-containing chemistry, such as a fluorocarbon or hydrofluorocarbon gas. In such embodiments, it is useful to dynamically detect halides of silicon and the halogen species (F) that are released by the decomposition of the fluorocarbon or hydrofluorocarbon gas in order to monitor the plasma etch process for its process and stability. Other detectable byproducts may include carbon monoxide (CO), and carbon dioxide (CO2), formed by reaction of oxygen (O) from a film or gas mixture with carbon (C) from the fluorocarbon or hydrofluorocarbon gas.
The wavelengths of the optical emission spectra can also shift as the surface composition of the wafer is changed by the removal of etched layer. In addition to the change in surface composition of the wafer, operating conditions (e.g., gas flow rates, pressure, and power pulsing conditions) can also lead to a shift in the optical emissions spectra. A temporal analysis based on the detection of these shifts may provide useful information about the characteristic of the plasma and thereby the progress of the plasma process.
In various embodiments, the configuration of the OES measurement assembly 15 may be particularly arranged for the type of plasma discharge typically used in the processing system 11. For example, a range of species and wavelengths for detection may be different for high-density ICP, low-density CCP, electron cyclotron resonance (ECR) plasma, and others.
Although the description of this disclosure is focused on dual OES embodiments with two OES sources (i.e., chamber and exhaust OES), the systems and methods may be applicable to single or more than two OES source(s). For example, in one embodiment, the OES measurement assembly may be solely configured to detect the exhaust OES signals and the optical fiber cable 140 from the processing chamber 110 in
In
In various embodiments, the in-line OES area or a larger area of the exhaust gas line 120 may be fabricated from an optically transparent material (e.g., quartz or sapphire) such that the exhaust OES signals may be directly collected by an optical fiber cable 140 without any optical port. In other embodiments, where the in-line OES area is not optically transparent, an optical port may be formed (not illustrated). In one or more embodiments, the exhaust gas line 120 may be about 0.5 m to 2.0 m long, and the in-line OES area may be about 1 cm to 30 cm long.
In
In
Although the OES measurement assembly 35 is illustrated with an in-line power coupler 230, identical to those in
In various embodiments, as illustrated in
In various embodiments, the systems and methods of OES advanced process characterization may be used to monitor a plasma process using a plasma processing system. For illustrative purposes,
Process gases may be introduced into the plasma processing chamber 610 by a gas delivery system 670. The gas delivery system 670 comprises multiple gas flow controllers to control the flow of multiple gases into the chamber. Each of the gas flow controllers of the gas delivery system 670 may be assigned for each of fluorocarbons, noble gases, and/or balancing agents. In some embodiments, optional center/edge splitters may be used to independently adjust the gas flow rates at the center and edge of the substrate 600. The process gases or any exhaust gases may be evacuated from the plasma processing chamber 610 using vacuum pumps 652. An exhaust gas line 120 connects the plasma processing chamber 610 and the vacuum pumps 652, and extend further downstream, where the OES measurement assembly may be connected for exhaust OES data collection (not shown in
As illustrated in
In various embodiments, the chamber control unit 655 is configured to enable feedback control of a plasma process, for example, based on a process monitoring using the OES methods. The chamber control unit 655 may comprise a function generator including an appropriate digital and/or analog circuitry such as oscillators, pulse generators, modulators, combiners, and the like. The function generator is capable of generating one or more arbitrary waveforms that may be used for both power modulation of the RF power sources and OES data acquisition. In certain embodiments, some of the power modulation may be performed by the RF power sources themselves instead of the function generator. In such cases, the function generator may generate a pulse train synchronized with the power modulation by the RF power sources for OES data acquisition. In certain embodiments, although not illustrated, additional components (e.g., a broadband amplifier and a broadband impedance matching network) may be connected to the RF power sources.
In certain embodiments, power sources may comprise a DC power source. The RF and/or DC power sources (e.g., the RF power sources 640, 642, and 644) may be configured to generate a continuous wave (CW) RF, pulsed RF, DC, pulsed DC, a high frequency rectangular (e.g., square wave) or triangular (e.g., sawtooth) pulse train, or a combination or superposition of more than one such waveform. In addition, power sources may be configured to generate a periodic function, for example, a sinusoid whose characteristics such as amplitude and frequency may be adjusted during a plasma process.
A typical frequency for the RF source power can range from about 0.1 MHz to about 6 GHz. In certain embodiments, the RF power sources 142 and 144 may be used to provide a low frequency RF power and a high frequency RF power at the same time, respectively.
In certain embodiments, the plasma etch process may be carried out using a pulsed plasma. The pulsed plasma in this disclosure refers to any type of plasma where a source power, a bias power, or both is pulsed at any frequency. In various embodiments, a pulsing at a frequency between 0.1 kHz and 100 kHz may be used to modulate the plasma source power or the bias power. In certain embodiments, a RF pulsing at a kHz range may be used to power the plasma. In various embodiments, any duty ratio (e.g., 0.1% to 99.9%) may be used for any plasma tool. In certain embodiments, a moderate duty ratio between 10% to 70% or 10% to 80% may be used for capacitively coupled plasma (CCP), and 3% to 90% for inductively coupled plasma (ICP). In one embodiment, a sinusoidal RF signal of 1 MHz may be modulated with an on-off frequency of 100 Hz. In another embodiment, a DC signal may be modulated with an on-off frequency of 100 Hz. In yet another embodiment, a square DC pulse signal of 1 MHz may be modulated with an on-off frequency of 100 Hz. In an alternate embodiment, cyclic modulation of RF or fast DC pulse waveform may be performed at a lower frequency (e.g., <100 Hz) using an algorithm.
The configuration of the plasma processing system 60 illustrated in
Further, the systems and methods of OES are based on the use of exhaust OES and thus it is possible to operate with a weak chamber plasma or even in the absence of a chamber plasma. Conventionally, it may be difficult to obtain sufficient OES signals for process monitoring for weak or pulsed plasma processes. Due to the stringent process requirement, it may often be impossible to change the plasma condition for the purpose of ideal OES data collection. Various embodiments of OES methods with exhaust OES may overcome this issue because the exhaust plasma may be powered independently from the chamber plasma. In other words, a high discharge power may be used for the exhaust plasma to obtain strong exhaust OES signals. In addition, the OES systems and methods may also applied to a non-plasma (e.g., thermal) processing system such as chemical vapor deposition (CVD) or atomic layer deposition (ALD) chamber.
In
As described above, various embodiments of exhaust OES data collection may use a high discharge power for the exhaust plasma for improved OES signal intensity. However, the inventors of this application identified potential issues of shorter hardware lifetime and higher level of contamination due to the high discharge power. These issues may be overcome by a combined use of an adjustable base (pilot) source power and secondary power (e.g., short duty power spikes) during a process of interest. In various embodiments, the exhaust plasma condition may be dynamically controlled by synchronizing the secondary power with exhaust OES data collection. Such embodiments may advantageously optimize the power usage for the exhaust OES for a target process characterization process (e.g., endpoint detection) and thereby extend the hardware lifetime and reduce the contamination.
In
Still referring to
In various embodiments, each of the power spikes 810 provides power for a short excitation time τex, for example, between 0.1 ms and 5 s. In certain embodiments, τex may be between 0.1 ms and 1 s. Short excitation time τex may advantageously extend the hardware lifetime. Further, in one or more embodiments, the excitation time τex may be shorter than the OES time resolution (i.e., time required to perform one OES measurement). In other embodiments, the excitation time τex may be longer than the OES time resolution.
In certain embodiments, a series of power spikes may be applied by a power pulse train having a frequency, for example, in the range of 1 Hz and 10 kHz, for the time period t3. In one or more embodiments, t3 may be a half of t2 or less. In other embodiments, t1 is longer than t3 by a factor of at least 2. This factor, in another embodiment, may be at least 5, or in yet another embodiment, may be at least 10.
OES data collection may be performed in synchronization with the power spikes 810. In various embodiments, the timing of each OES measurement may be synchronized with each of the power spikes 810 with a delay. Having the delay in synchronization may be advantageous in obtaining more stable OES signals at fully excited phase rather than a transitory phase where the excitation process is still in progress. The duration of delay may be determined according to discharge conditions and the power matching unit. In certain embodiments, the delay may be between 10 μs and a few seconds.
Although four spikes are illustrated in
In addition, while the constant power level with constant duty ratio (i.e., constant excitation time τex) are illustrated in
In
In various embodiments of OES process characterization, OES data collection may be repeated as a cyclic process, alternating the chamber and exhaust OES. For example, the OES signal source (i.e., the chamber or exhaust OES) may be switched every 10 ms. The collected data may be analyzed separately to evaluate the confidence level individually. Alternately, a user may manually switch the OES signal source depending on the type of process and monitoring.
In
Various algorithms may be designed depending on criteria used for determining the process endpoint. In one embodiment, the algorithm may determine an initial endpoint based on the exhaust OES data and the chamber OES or the electrostatic probe data may be used to confirm or update the initial endpoint to output a final endpoint. The algorithm may also detect an EPD failure in the event of unsuccessful data collection.
In another embodiment, the algorithm may first examine the level of chamber OES signal and decide if it is sufficient to perform EPD singly based on the chamber OES. If the chamber OES signal is strong enough, EPD may be performed using the chamber OES and may bypass the steps of generating and analyzing the exhaust plasma. Only when the chamber OES is determined to be too weak for EPD, the exhaust plasma may be generated and EPD may be performed using the exhaust OES with or without including electrostatic probe data.
The inventors of this application demonstrated through experiments the utility of the exhaust OES in accordance with various embodiments. In one example, a plasma etch process was performed to etch an organic layer formed over a substrate, and OES data from both the processing chamber and the exhaust line were monitored for endpoint detection (EPD). First,
Further,
Example embodiments of the invention are described below. Other embodiments can also be understood from the entirety of the specification as well as the claims filed herein.
Example 1. A processing system that includes: a processing chamber configured to hold a substrate to be processed; a first vacuum pump; a second vacuum pump disposed downstream from the first vacuum pump; an exhaust gas line connecting the process chamber and the first vacuum pump, and the first vacuum pump and the second vacuum pump; a plasma power supply including a first RF power source configured to generate a plasma from a portion of an exhaust gas between the first and second vacuum pumps; and an optical emission spectroscopy (OES) measurement assembly including an OES detector configured to measure OES signals from the plasma.
Example 2. The processing system of example 1 further including a second RF power source configured to generate a processing plasma in the processing chamber, where the OES measurement assembly is further configured to measure OES signals from the processing plasma.
Example 3. The processing system of one of examples 1 or 2, further including a remote plasma chamber connected to the exhaust gas line and the first RF power source, the plasma being generated in the remote plasma chamber.
Example 4. The processing system of one of examples 1 to 3, where the OES measurement assembly includes an optical switch configured to select one of the OES signals from the plasma and the processing plasma and transmit the selected OES signals to the OES detector.
Example 5. The processing system of one of examples 1 to 4, where the optical switch is further configured to combine the OES signals from the plasma and the processing plasma and transmit the combined OES signals to the OES detector.
Example 6. The processing system of one of examples 1 to 5, the plasma power supply includes a plasma power coupler.
Example 7. The processing system of one of examples 1 to 6, where the plasma power supply includes a coil that surrounds a portion of the exhaust line and is configured to generate the plasma in the portion of the exhaust line.
Example 8. The processing system of one of examples 1 to 7, further including a RF sensor configured to detect electrical parameters of the plasma.
Example 9. A plasma processing system that includes: a plasma processing chamber configured to hold a substrate to be processed; a RF power source configured to generate a first plasma in the plasma processing chamber; a first vacuum pump; an exhaust gas line connecting the plasma process chamber and the first vacuum pump; a plasma power supply configured to generate a second plasma from a portion of an exhaust gas downstream from the plasma processing chamber, and an optical emission spectroscopy (OES) measurement assembly including: an OES detector configured to measure first OES signals from the first plasma and second OES signals from the second plasma; a microprocessor, and a non-transitory memory storing a program to be executed in the microprocessor, the program including instructions to: perform a plasma process on a substrate; during the process, record the first or second OES signals associated with a chemical composition of the first or second plasma, and based on the first or second OES signals, estimate a temporal change of the chemical composition to evaluate a progress of the process.
Example 10. The plasma processing system of example 9, where the portion of the exhaust gas is downstream from the first pump.
Example 11. The plasma processing system of one of examples 9 or 10, further including a remote plasma chamber connected to the exhaust line via a gas inlet, the second plasma being generated in the remote plasma chamber.
Example 12. The plasma processing system of one of examples 9 to 11, where the OES measurement assembly includes an optical switch configured to select one of the first and second OES signals and transmit the selected OES signal to the OES detector.
Example 13. The plasma processing system of one of examples 9 to 12, where the program further includes an instruction to perform an endpoint detection of the process based on the first or second OES signals.
Example 14. A method of processing a substrate that includes: plasma processing a substrate in a plasma processing chamber by exposing the substrate to a first plasma; using a vacuum system, remove an exhaust gas from the plasma processing chamber to an exhaust line; using an optical emission spectroscopy (OES) measurement assembly connected to the plasma processing chamber, detecting first OES signals from the first plasma during the plasma processing, the first OES signals being associated with a chemical composition of the first plasma; generating a second plasma from the exhaust gas downstream from the plasma processing chamber; using the OES measurement assembly, detecting second OES signals from the second plasma during the plasma processing, the second OES signals being associated with a chemical composition of the second plasma; and based on the first or second OES signals, estimating a temporal change of the chemical composition of the first or second plasma.
Example 15. The method of example 14, further including performing an endpoint detection (EPD) process based on the estimated temporal change of the chemical composition of the first or second plasma.
Example 16. The method of one of examples 14 or 15, where generating the second plasma includes applying a base source power and a series of power spikes to an electrode or coil connected to the vacuum system, the series of power spikes being correlated with a timing of detecting the second OES signals.
Example 17. The method of one of examples 14 to 16, further including switching between detecting first and second OES signals by using an optical switch of the OES measurement assembly.
Example 18. The method of one of examples 14 to 17, further including: comparing signal intensities of the first and second OES signals; and selecting first or second OES signals with a higher signal intensity than the other, where estimating the temporal change of the chemical composition is based on the selected OES signal.
Example 19. The method of one of examples 14 to 18, further including: measuring electrical parameters of the second plasma; and performing an endpoint detection (EPD) process based on the measured electrical parameters.
Example 20. The method of one of examples 14 to 19, further including performing first and second endpoint detection (EPD) processes, the first EPD process being based on the first or second OES signals, the second EPD process being based on measured electrical parameters of the second plasma.
Example 21. The method of one of examples 14 to 20, where the vacuum system includes a vacuum pump, and where the second plasma is generated from the exhaust gas downstream from the vacuum pump.
Example 22. The processing system of one of examples 1 to 8, further including an optical fiber cable that transmit the OES signals from the plasma to the OES measurement assembly.
Example 23. The plasma processing system of one of examples 9 to 13, further including a first optical fiber cable that transmits the first OES signals from the plasma processing chamber to the OES measurement assembly and a second optical fiber cable that transmits the second OES signals from the portion of the exhaust gas to the OES measurement assembly.
While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
