Controlling plasma abatement

Abstract

Apparatus 10 controls a plasma abatement device 20 for treating an effluent stream 30 from a semiconductor processing tool. An optical emission spectrometer 50 measures an emission spectrum from the plasma abatement device and a controller 60 identifies from an intensity peak of the emission spectrum whether an amount of a reagent provided to the plasma abatement device is to be changed. A ratio of a plurality of intensity peaks may be used and compared with look-up information of preconfigured ratios of components in the effluent stream correlated with ratios of peak intensities. A desired ratio of intensities may be identified from the look-up information to optimise a destruction efficiency or an amount of by-product. The reagent may be hydrogen or oxygen. Components of the effluent stream may include hydrogen, oxygen, carbon, or fluorine. A corresponding method is also claimed.

Description

FIELD OF THE INVENTION The field of the invention relates to an apparatus and method for controlling 5 plasma abatement. BACKGROUND Plasma abatement apparatus are known and are typically used for, amongst other things, treating an effluent gas stream from a manufacturing process tool 10 used in, for example, the semiconductor or flat panel display manufacturing industry. During such manufacturing, residual fluorinated or perfluorinated compounds (PFCs) and other compounds exist in the effluent gas stream pumped from the process tool. These compounds are difficult to remove from the effluent gas stream and their release into the environment is undesirable because 15 they are known to have relatively high greenhouse activity. One approach to remove the PFCs and other compounds from the effluent gas stream is to use a radiant burner as described, for example, in EP1773474. However, when fuel gases normally used for abatement by combustion are 20 undesirable or not readily available, it is also known to use a plasma abatement device. Although these apparatus exist for processing the effluent gas stream, they each have their own shortcomings. Accordingly, it is desired to provide an improved 25 technique for processing an effluent gas stream. SUMMARY According to a first aspect, there is provided an apparatus for controlling a plasma abatement device for treating an effluent stream from a semiconductor 30 processing tool, comprising: an optical emission spectrometer configured to measure an emission spectrum from the plasma abatement device when generating a plasma for treating the effluent stream; and a controller configured to identify from at least one measured intensity peak within the emission spectrum whether to change an amount of a reagent provided to the plasma abatement device when generating the plasma for treating the effluent stream. 5 The first aspect recognizes that a problem with existing plasma abatement devices is that it can be difficult to accurately control the composition within the plasma abatement device during abatement of the effluent stream. Accordingly, an apparatus is provided. The apparatus may be for controlling or operating a plasma abatement device. The plasma abatement device may treat an effluent 10 or process stream. The effluent stream may be from a semiconductor processing tool. The apparatus may comprise an optical or visual emission spectrometer. The spectrometer may be configured or arranged to measure or detect an emission spectrum from within the plasma abatement device when treating or abating the effluent stream. The apparatus may comprise a controller configured 15 or adapted to identify or detect from one or more measured intensity peaks within the emission spectrum whether or not to change an amount or quantity of reagent provided to the plasma abatement device when generating the plasma for treating the effluent stream. In this way, the composition within the plasma abatement device can be monitored from its emissions and controlled to achieve 20 desired operating conditions within the plasma abatement device. The optical emission spectrometer may be configured to measure the emission spectrum of the plasma when interacting with the effluent stream and the reagent. 25 The controller may be configured to identify from a plurality of measured intensity peaks within the emission spectrum whether to change the amount of the reagent provided to the plasma abatement device. Accordingly, the controller may utilise more than one measured intensity peak to determine whether or not to change 30 the amount of reagent provided. The controller may be configured to identify from a ratio of the plurality of measured intensity peaks within the emission spectrum whether to change the amount of the reagent provided to the plasma abatement device. Accordingly, a ratio of the relative intensities of peaks within the emissions spectrum may be 5 utilized to determine whether or not to change the amount of reagent provided. The controller may be configured to determine from preconfigured lookup information correlating ratios of measured intensities against premeasured ratios of components in the plasma stream whether to change the amount of the 10 reagent provided to the plasma abatement device. Accordingly, the ratio of the plurality of measured intensity peaks may be referenced against preconfigured or stored look-up information or reference data which correlates or plots ratios of measured intensities against premeasured or previously determined ratios of components, elements or compounds in the plasma stream to determine whether 15 or not to change the amount of reagent provided. The preconfigured look-up information may identify a desired ratio of measured intensities associated with a desired ratio of components in the plasma stream. Accordingly, a desired, selected, preferred or target ratio of measured intensities 20 may be associated with a desired, preferred, selected or target ratio of components in the plasma stream. The desired ratio of measured intensities may be associated with the desired ratio of components in the plasma stream which optimises a destruction and 25 removal efficiency of components of the effluent stream. Accordingly, an optimal destruction and removal efficiency may be achieved with a desired, selected, preferred or target ratio of components which is identified by a desired, selected, preferred or target ratio of measured intensities of components in the plasma stream. 30 The desired ratio of measured intensities may be associated with the desired ratio of components in the plasma stream which optimises an amount of a byproduct of components of the effluent stream. Accordingly, an optimal amount of a byproduct of components of the effluent stream may be achieved with a desired, selected, preferred or target ratio of components which is identified by a desired, selected, preferred or target ratio of measured intensities of components 5 in the plasma stream. The preconfigured look-up information may identify emission frequencies of components in the plasma stream. Accordingly, the information may provide information on which frequencies in the emission spectrum need to be measured 10 when determining whether or not to change an amount of the reagent. The controller may be configured to determine from the preconfigured lookup information and the desired ratio of measured intensities whether to change the amount of the reagent provided to the plasma abatement device to achieve the 15 desired ratio of components in the plasma stream. Hence, information may be utilised to determine whether or not to change the amount of reagent provided in order to achieve a desired or target ratio of components in the plasma stream. One measured peak intensity may be associated with the reagent and one 20 measured intensity peak may be associated with a component of the effluent stream and the preconfigured lookup information may correlate ratios of measured intensities of the reagent to measured intensities of the component of the effluent stream against premeasured ratios of the reagent to the component of the effluent stream and identify a desired ratio of measured intensities 25 associated with a desired ratio of the reagent to the component of the effluent stream. Accordingly, the preconfigured look-up information may correlate or plot ratios of measured intensities against premeasured ratios and identify a desired, selected, preferred or target ratio of measured intensities with a desired, selected, preferred or target ratio of the reagent to the component of the effluent 30 stream. In other words, the preconfigured look-up information can determine from the ratio of measured intensities what the ratio of the reagent to the component must be present within the effluent stream to generate that ratio of measured intensities. The preconfigured look-up information can also identify a desired, selected, preferred or target ratio of the reagent to the component in the effluent stream which may or may not differ from the ratio of the reagent to the component currently present within the effluent stream. 5 The controller may be configured to decrease the amount of the reagent provided to the plasma abatement device when the preconfigured lookup information indicates, from the ratio of measured intensity of the reagent to measured intensity of the component of the effluent stream in relation to the desired ratio, 10 that excess reagent is being provided. Accordingly, should the preconfigured look-up information indicate, for the currently measured ratio of intensities, that this is associated with a ratio of the reagent to the component which exceeds the desired, selected, preferred or target ratio, and so excess reagent is currently being provided, the controller may then decrease or reduce the amount of 15 reagent being provided to the plasma abatement device in order to change the ratio of the reagent to the component towards the desired, selected, preferred or target ratio. The controller may be configured to increase the amount of the reagent provided 20 to the plasma abatement device when the preconfigured lookup information indicates, from the ratio of measured intensity of the reagent to measured intensity of the component of the effluent stream in relation to the desired ratio, that insufficient reagent is being provided. Accordingly, should the preconfigured look-up information indicate, for the currently measured ratio of intensities, that 25 this is associated with a ratio of the reagent to the component which fails to achieve the desired, selected, preferred or target ratio, and so insufficient reagent is currently being provided, the controller may then increase the amount of reagent being provided to the plasma abatement device in order to change the ratio of the reagent to the component towards the desired, selected, preferred or 30 target ratio. The controller may be configured to not change the amount of the reagent provided to the plasma abatement device when the preconfigured lookup information indicates, from the ratio of measured intensity of the reagent to measured intensity of the component of the effluent stream in relation to the 5 desired ratio, that sufficient reagent is being provided. Accordingly, should the preconfigured look-up information indicate, for the currently measured ratio of intensities, that this is associated with a ratio of the reagent to the component which matches or achieves the desired, selected, preferred or target ratio, and so appropriate reagent is currently being provided, the controller may then leave the 10 amount of reagent being provided to the plasma abatement device unchanged. The component of the effluent stream may comprise at least one of: hydrogen, oxygen, carbon and fluorine. 15 The reagent may comprise at least one of: hydrogen and oxygen. The controller may be configured to determine from a plurality of the preconfigured lookup information, each plotting ratios of measured intensities against premeasured ratios of different components in the plasma stream, 20 whether to change the amount of the reagent provided to the plasma abatement device. Hence, different sets of preconfigured or stored look-up information or reference data may be provided. Each set of information may correlate or plot ratios of measured intensities against premeasured or previously determined ratios of different components, elements or compounds. 25 The apparatus may comprise the plasma abatement device. According to a second aspect, there is provided a method, comprising: measuring an emission spectrum from a plasma abatement device when 30 generating a plasma for treating an effluent stream; and identifying from at least one measured intensity peak within the emission spectrum whether to change an amount of a reagent provided to the plasma abatement device when generating the plasma for treating the effluent stream. The method may comprise measuring the emission spectrum of the plasma when 5 interacting with the effluent stream and the reagent. The method may comprise identifying from a plurality of measured intensity peaks within the emission spectrum whether to change the amount of the reagent provided to the plasma abatement device. 10 The method may comprise identifying from a ratio of the plurality of measured intensity peaks within the emission spectrum whether to change the amount of the reagent provided to the plasma abatement device. 15 The method may comprise determining from preconfigured lookup information correlating ratios of measured intensities against premeasured ratios of components in the plasma stream whether to change the amount of the reagent provided to the plasma abatement device. 20 The preconfigured lookup information may identify a desired ratio of measured intensities associated with a desired ratio of components in the plasma stream. The desired ratio of measured intensities may be associated with the desired ratio of components in the plasma stream which optimises a destruction and 25 removal efficiency of components of the effluent stream. The desired ratio of measured intensities may be associated with the desired ratio of components in the plasma stream which optimises an amount of a byproduct of components of the effluent stream. 30 The preconfigured lookup information may identify emission frequencies of components in the plasma stream. The method may comprise determining from the preconfigured lookup information and the desired ratio of measured intensities whether to change the amount of the reagent provided to the plasma abatement device to achieve the 5 desired ratio of components in the plasma stream. One measured intensity peak may be associated with the reagent and one measured intensity peak is associated with a component of the effluent stream and the preconfigured lookup information may correlate ratios of measured 10 intensities of the reagent to measured intensities of the component of the effluent stream against premeasured ratios of the reagent to the component of the effluent stream and may identify a desired ratio of measured intensities associated with a desired ratio of the reagent to the component of the effluent stream. 15 The method may comprise decreasing the amount of the reagent provided to the plasma abatement device when the preconfigured lookup information indicates, from the ratio of measured intensity of the reagent to measured intensity of the component of the effluent stream in relation to the desired ratio, that excess 20 reagent is being provided. The method may comprise increasing the amount of the reagent provided to the plasma abatement device when the preconfigured lookup information indicates, from the ratio of measured intensity of the reagent to measured intensity of the 25 component of the effluent stream in relation to the desired ratio, that insufficient reagent is being provided. The method may comprise not changing the amount of the reagent provided to the plasma abatement device when the preconfigured lookup information 30 indicates, from the ratio of measured intensity of the reagent to measured intensity of the component of the effluent stream in relation to the desired ratio, that sufficient reagent is being provided. The component of the effluent stream may comprise at least one of: hydrogen, oxygen, carbon and fluorine. 5 The reagent may comprise at least one of: hydrogen and oxygen. The method may comprise determining from a plurality of the preconfigured lookup information, each plotting ratios of measured intensities against premeasured ratios of different components in the plasma stream, whether to 10 change the amount of the reagent provided to the plasma abatement device. Accordingly, the ratio of the plurality of measured intensity peaks may be referenced against preconfigured or stored look-up information or reference data which correlates or plots ratios of measured intensities against premeasured or 15 previously determined ratios of components, elements or compounds in the plasma stream to determine whether or not to change the amount of reagent provided. Further particular and preferred aspects are set out in the accompanying 20 independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. Where an apparatus feature is described as being operable to provide a function, 25 it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described further, with 30 reference to the accompanying drawings, in which: FIG. 1 illustrates an apparatus 10 according to one embodiment; FIG. 2 is a flowchart describing the general operation of the apparatus according to one embodiment; FIGS. 3A to 3C illustrate example spectrum; and FIG. 3D illustrates example ratio information plotting elemental molar ratios 5 against intensity ratios. DESCRIPTION OF THE EMBODIMENTS Before discussing the embodiments in any more detail, first an overview will be provided. Plasma abatement is widely considered as an abatement technology io with performance and environmental merits. Reagents are used to react with effluent stream or process gas and to form by-products. However, it has been found that either too much or too little reagent has a negative effect on the plasma abatement’s performance. Therefore, it is important to ensure that the reagent dosing is optimal. Some embodiments provide a technique which 15 analyses the spectrum of a plasma produced by a plasma abatement device when abating an effluent stream from a semiconductor processing tool and uses that spectrum to adjust the operating conditions within the plasma device. Typically, an amount of reagent introduced into the effluent stream is adjusted in order to improve the destruction and removal efficiency of the plasma device 20 and / or to adjust an amount of a byproduct produced within the plasma device. The spectrum of the plasma is measured using a spectrometer. Optical Emission Spectroscopy (OES) is a rapid method for determining the elemental compositions, based on the wavelength of the emitted light. In the semiconductor industry, OES is often used inside etch chambers at low pressures for end point 25 detection. Typically, for expected components within the effluent stream, wavelengths of interest within the spectrum relating to elements within those components are identified. Emission spectrum information relating wavelengths with elements or compounds is readily available. Typically, the ratio of intensities of peaks at those wavelengths of interest is determined. The ratio of those 30 intensities is compared with stored information which plots the ratio of intensities against elemental or molar ratios within the plasma stream. Such stored information can be generated by operating the plasma device with differing known elemental ratios of components within the effluent stream and measuring the emission spectrum for those differing known elemental ratios. Hence, it is possible to determine an elemental ratio for a measured ratio of intensities from the stored information. An assessment can then be made of how to adjust the 5 amount of reagent in order to achieve a desired or target elemental ratio. That desired or target elemental ratio may be known from operating the plasma device at different elemental ratios to achieve a known destruction and removal efficiency of the plasma device and / or to adjust an amount of a byproduct produced within the plasma device. For example, should it be determined from 10 the stored information that, for the measured ratio of intensities, the elemental ratio has an excess of reagent, then the amount of reagent can be reduced, and vice-versa. Through this approach, optimal elemental ratios within the plasma device can be achieved in order to improve the destruction and removal efficiency. Likewise, optimal elemental ratios within the plasma device can be 15 achieved in order to provide an excess or deficit of a component (such as a reagent or byproduct or other component) within the abated effluent stream. Plasma Abatement FIG. 1 illustrates an apparatus 10 according to one embodiment. The apparatus 20 10 is used for controlling a plasma abatement device 20. The plasma abatement device 20 has an inlet which receives an effluent stream 30 to be abated. The plasma abatement device 20 has an outlet which provides an abated effluent stream 40. Coupled with the plasma abatement device 20 is an optical emission spectrometer 50 which measures the optical emission spectrum produced by the 25 plasma abatement device 20 when abating or treating the effluent stream 30. The optical emission spectrometer 50 is coupled with a controller 60. The controller 60 typically contains a microprocessor 100 and a memory 110 which stores data and instructions. The controller 60 receives information relating to the emission spectrum measured by the optical emission spectrometer 50 over a 30 link 55 and provides a control signal over a link 65 to a reagent controller 70. The reagent controller 70 couples with an inlet conduit carrying the effluent stream 30 and operates to adjust an amount of one or more reagents being mixed with the effluent stream 30 within the inlet conduit to vary the amount of reagent being supplied to the plasma abatement device 20. The controller 60 stores spectrum information 80 which identifies wavelengths of 5 elements or compounds interest within the spectrum. The controller 60 also stores ratio information 90 which plots the ratio of intensities of elements or compounds likely to be present within the plasma abatement device 20 against elemental molar ratios, together with one or more optimal points on that curve. The ratio information 90 typically contains ratio curves for different elements likely io to be present within the plasma abatement device 20. General Operation FIG. 2 is a flowchart describing the general operation of the apparatus 10, according to one embodiment. At step S10, the effluent stream 30 is provided to 15 the plasma abatement device 20, which generates a plasma to abate compounds within the effluent stream 30 and produce the abated effluent stream 40. The optical emission spectrometer 50 measures the spectrum generated within the plasma abatement device 20 and sends data representative of the spectrum over the link 55 to the controller 60. 20 At step S20, the processor 100 receives the spectrum data and identifies wavelengths of interest within the spectrum associated with elements or compounds of interest which are required to be monitored to control the operation of the plasma abatement device 20 as indicated by the spectrum information 80. 25 At step S30, the ratio of the intensities between the measured wavelengths of interest is determined. At step S40, the appropriate curve from the ratio information 90 related to the 30 elements or compounds of interest is obtained and the location on that curve for that ratio of intensities is determined. At step S50, it is determined whether the measured ratio of intensities is indicated by the curve to be optimal and, if not, whether a reagent needs to be increased or decreased to achieve an optimal ratio. Processing then returns to step S10. 5 Example Operation FIGS. 3A to 3D shown an example operation of the apparatus 10 in more detail. FIGS. 3A to 3C illustrates an example spectrum provided by the optical emission spectrometer 50 to the controller 60 during operation of the plasma abatement device 20 when abating the effluent stream 30 with differing amounts of reagent io being supplied. FIG. 3D illustrates example ratio information 90 plotting elemental molar ratios of O:C against intensity ratios of O:C. In this example, it is expected that the effluent stream 30 will contain perfluorocarbons (PFCs) as well as other compounds. The effluent stream 30 is 15 typically dosed with reagents H2 and O2. The H2 and O2 react with the PFC to produce various species. Other byproducts are produced. In this example, it is expected that CF4 is present (for example at 300 SCCM) and it is already premixed with H2 (again, expected to be at 300 SCCM). However, the amount of O2 present is unknown. Experimentation has shown that providing O:C at an optimal 20 ratio of 2:1 maximises the destruction and removal efficiency of the plasma abatement device 20. The controller 60 operates to improve the destruction and removal efficiency by adjusting the amount of O2 provided based on the emission spectrum from the plasma abatement device 20. 25 Accordingly, the spectrum information 80 identifies wavelengths of 248nm for C and 777nm for O as wavelengths of interest within the spectrum measured by the optical emission spectrometer 50. Hence, as illustrated in FIG. 3A, the spectrum provided by the optical emission 30 spectrometer 50 is analysed at 248nm and 777nm. The ratios of the intensities of those peaks are determined. In this case, the relative intensity of peak 110A:110B (O:C) is approximately 1:1 (O:C). The ratio information 90 is examined and a curve plotting ratios of 0:C is located, as shown in FIG. 3D. As mentioned above, this curve has been generated previously under controlled conditions by running the plasma abatement device 20 with CF4 at 300 SCCM, premixed with H2 at 300 SCCM, varying the amounts of O2 and measuring the 5 ratios of the peaks 110A: 110B as the amount of O2 is changed. In this case, the intensity ratio 1:1 (O:C) indicates an elemental molar ratio of around 1:1 (O:C) which is below the optimal ratio of 2:1 (O:C). Accordingly, the controller 60 provides a signal over the link 65 to the reagent controller 70 to increase the amount of O2 reagent being supplied with the effluent stream 30. 10 Likewise, as illustrated in FIG. 3B, the spectrum provided by the optical emission spectrometer 50 is analysed at 248nm and 777nm. The ratios of the intensities of those peaks are determined. In this case, the relative intensity of peak 110A:110B (O:C) is approximately 1:14 (O:C). The ratio information 90 is 15 examined and a curve plotting ratios of O:C is located, as shown in FIG. 3D. In this case, the intensity ratio 1:14 (O:C) indicates an elemental molar ratio of around 1:3 (O:C) which is above the optimal ratio of 2:1 (O:C). Accordingly, the controller 60 provides a signal over the link 65 to the reagent controller 70 to decrease the amount of O2 reagent being supplied with the effluent stream 30. 20 Finally, as illustrated in FIG. 3C, the spectrum provided by the optical emission spectrometer 50 is analysed at 248nm and 777nm. The ratios of the intensities of those peaks are determined. In this case, the relative intensity of peak 110A:110B (0:0) is approximately 1:6 (O:C). The ratio information 90 is 25 examined and a curve plotting ratios of O:C is located, as shown in FIG. 3D. In this case, the intensity ratio 1:6 (O:C) indicates an elemental molar ratio of around 1:2 (O:C) which is at the optimal ratio of 2:1 (O:C). Accordingly, the controller 60 provides a signal over the link 65 to the reagent controller 70 to keep the amount of O2 reagent being supplied with the effluent stream 30 30 unchanged. It will be appreciated that a similar technique can be used to, for example, generate O2 (or other) byproducts which may be helpful in the abatement process. In that example, an alternative optimal ratio greater than 2:1 (0:C) may be selected which is known to generate the required amounts of byproducts. 5 Accordingly, the spectrum provided by the optical emission spectrometer 50 is analysed, the relative intensity of peak 110A:110B (O:C) is determined, the ratio information 90 examined and the controller 60 provides a signal over the link 65 to the reagent controller 70 to control the amount of O2 reagent being supplied with the effluent stream 30 to achieve the alternative optimal ratio in order to 10 generate the required amount of O2 (or other) byproducts. Hence, it can be seen that some embodiments use Optical Emission Spectroscopy (OES) technology to indicate the reagent / process gas ratios in plasma abatement. Based on the OES indication, reagent dosing is controlled 15 with a closed-loop control approach, to ensure that the reagent / process gas ratio is optimal. The benefit of using an optimal reagent / process ratio is two-fold: on the one hand, optimal reagent / process gas ratios ensure optimal DRE; on the other hand, optimal reagent / process gas ratios can selectively form by-products. Both benefits lead to easy-to-manage downstream gas treatments, which 20 ultimately, provide efficiency and environmental improvements. This approach provides for a fast response, minimal process gas information is needed from the semiconductor processing tool, results in high DRE performance and provides for flexibility - the process can be tuned to produce desired by-products. 25 As mentioned above, the process gases in plasma abatement emit light. Each species emits light at specific colours, corresponding to certain light wavelengths. Optical Emission Spectroscopy inspects the light in plasma chamber and displays the light spectrum typically within the visible range (200-800nm). A database of wavelengths subject to individual gas species has been well established and is 30 widely available. However, work on analysing plasma light of multiple gas species is limited. By carrying out experimental tests, spectrums for different combinations of representative process gases (mainly PFC and noble gases in this case, but can be different species in variants) and reagents (H2 &O2 in this case, can be different reagents in variants) were obtained. Through an analysis of the experimental spectrums in conjunction with the database, peaks at certain wavelengths were selected to reflect the amount of their respective species in the 5 plasma. After further tests, the correlations between the selected peak intensities and the flow rates of their respective species were established, which provides guidelines to map measured intensities to actual flow rates in the plasma chamber. In operation, process gases flow to the plasma chamber at constantly changing rates and emit light with constantly changing colour. OES monitors the 10 colour with typically 100ms (or other suitable) sampling intervals and converts peak intensity ratios to gas species ratios within the control software. One example of calculated gas species ratio against time and instantaneous spectrum for the 200-800nm range is set out above. The calculated gas species ratios were fed into a controller (such as a proportional-integral-derivative (PID) 15 controller) and used to rectify the reagent feeding rate, towards the optimal reagent / process ratio. The PID controller then drives the reagent Mass Flow Controllers (MFCs) to complete the control loop. During operation, in addition to analysing light spectrums, the controller may also log data in pre-configured directories for further usage. 20 Although the embodiments set out above are directed to abatement of etch process (mainly PFCs) by adding reagents (H2 &O2), it will be appreciated that this approach may be used for abatement of other process gases and / or reagents. 25 Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing 30 from the scope of the invention as defined by the appended claims and their equivalents. REFERENCE SIGNS Apparatus 10 Plasma Abatement Device 20 5 Effluent Stream 30 Abated Effluent Stream 40 Optical Emission Spectrometer 50 Link 55 Controller 60 io Link 65 Reagent Controller 70 Spectrum Information 80 Ratio Information 90 Microprocessor 100 15 Memory 110

Claims

1. An apparatus for controlling a plasma abatement device for treating an effluent stream from a semiconductor processing tool, comprising:5 an optical emission spectrometer configured to measure an emissionspectrum from said plasma abatement device when generating a plasma for treating said effluent stream; anda controller configured to identify from at least one measured intensity peak within said emission spectrum whether to change an amount of a reagent io provided to said plasma abatement device when generating said plasma for treating said effluent stream.

2. The apparatus of claim 1, wherein said optical emission spectrometer is configured to measure said emission spectrum of said plasma when interacting 15 with said effluent stream and said reagent.

3. The apparatus of claim 1 or 2, wherein said controller is configured to identify from a plurality of measured intensity peaks within said emission spectrum whether to change said amount of said reagent provided to said plasma 20 abatement device.

4. The apparatus of claim 3, wherein said controller is configured to identify from a ratio of said plurality of measured intensity peaks within said emission spectrum whether to change said amount of said reagent provided to said plasma 25 abatement device.

5. The apparatus of claim 3 or 4, wherein said controller is configured to determine from preconfigured lookup information correlating ratios of measured intensities against premeasured ratios of components in said plasma stream30 whether to change said amount of said reagent provided to said plasma abatement device.

6. The apparatus of any one of claims 3 to 5, wherein said preconfigured lookup information identifies a desired ratio of measured intensities associated with a desired ratio of components in the plasma stream.5 7. The apparatus of claim 6, wherein said desired ratio of measuredintensities is associated with said desired ratio of components in the plasma stream which optimises a destruction and removal efficiency of components of said effluent stream.io 8. The apparatus of claim 6 or 7, wherein said desired ratio of measured intensities is associated with said desired ratio of components in the plasma stream which optimises an amount of a byproduct of components of said effluent stream.15 9. The apparatus of any one of claims 5 to 8, wherein said preconfiguredlookup information identifies emission frequencies of components in the plasma stream.

10. The apparatus of any one of claims 6 to 9, wherein said controller is20 configured to determine from said preconfigured lookup information and said desired ratio of measured intensities whether to change said amount of said reagent provided to said plasma abatement device to achieve said desired ratio of components in the plasma stream.25 11. The apparatus of any one of claims 6 to 10, wherein one measuredintensity peak is associated with said reagent and one measured intensity peak is associated with a component of said effluent stream and said preconfigured lookup information correlates ratios of measured intensities of said reagent to measured intensities of said component of said effluent stream against30 premeasured ratios of said reagent to said component of said effluent stream and identifies a desired ratio of measured intensities associated with a desired ratio of said reagent to said component of said effluent stream.

12. The apparatus of claim 11, wherein said controller is configured to: decrease said amount of said reagent provided to said plasma abatement device when said preconfigured lookup information indicates, from said ratio of 5 measured intensity of said reagent to measured intensity of said component of said effluent stream in relation to said desired ratio, that excess reagent is being provided;increase said amount of said reagent provided to said plasma abatement device when said preconfigured lookup information indicates, from said ratio of io measured intensity of said reagent to measured intensity of said component of said effluent stream in relation to said desired ratio, that insufficient reagent is being provided; andnot change said amount of said reagent provided to said plasma abatement device when said preconfigured lookup information indicates, from15 said ratio of measured intensity of said reagent to measured intensity of said component of said effluent stream in relation to said desired ratio, that sufficient reagent is being provided.

13. The apparatus of any one of claims 5 to 12, wherein said component of 20 said effluent stream comprises at least one of: hydrogen, oxygen, carbon and fluorine.

14. The apparatus of any preceding claim, wherein said reagent comprises at least one of: hydrogen and oxygen.2515. The apparatus of any one of claims 5 to 14, wherein said controller is configured to determine from a plurality of said preconfigured lookup information, each plotting ratios of measured intensities against premeasured ratios of different components in said plasma stream, whether to change said amount of 30 said reagent provided to said plasma abatement device.

16. The apparatus of any preceding claim, wherein said apparatus comprises said plasma abatement device.

17. A method, comprising:5 measuring an emission spectrum from a plasma abatement device whengenerating a plasma for treating an effluent stream; andidentifying from at least one measured intensity peak within said emission spectrum whether to change an amount of a reagent provided to said plasma abatement device when generating said plasma for treating said effluent stream.io

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