Apparatus and method for controlling precursor flow - Patents.com

Abstract

To provide an apparatus for detecting the end of the life of an ampoule and controlling precursor flow.SOLUTION: Provided is an apparatus for controlling precursor flow, including: an ampoule to output a precursor; a sensor assembly communicatively coupled to the ampoule and including a sensor; a control system arranged to determine a precursor flux value using the detector during precursor flow through a cell, the control system comprising: a temperature control processor configured to determine an error value on the basis of the precursor flux value, determine a temperature adjustment ΔT on the basis of the error value, and calculate a new set of temperature set points to be applied to the ampoule; and an end-of-life processor configured to check an end-of-life status of the ampoule when the new set of temperature setpoints is not within the current set of temperature limits for the ampoule.SELECTED DRAWING: Figure 8

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 611,645, filed December 29, 2017, entitled "Techniques for Control of Precursors in Chemical Vapor Deposition Processes," which is incorporated herein by reference in its entirety. [Technical Field]

[0002] The present embodiments relate to vapor deposition processes, and more particularly to controlling precursors in chemical vapor deposition processes. [Background technology]

[0003] Currently, device fabrication, such as semiconductor device fabrication, can require chemical vapor deposition processes to form thin layers with precise film thickness control, including over three-dimensional structures. Such chemical vapor deposition processes include chemical vapor deposition (CVD) and atomic layer deposition (ALD), among other processes.

[0004] Such chemical vapor deposition processes can involve delivering precursors from a solid source, a gas source, or a liquid source such as an ampoule. For example, the precursors can be delivered from an ampoule to a process chamber where they react to form a layer or sublayer on the substrate. With current equipment, the amount of precursor delivered is not adequately characterized, which can lead to variations in precursor delivery from substrate to substrate, from ampoule to ampoule, or over the life of the ampoule. Delays in detecting the end of ampoule life can result in significant wafer (substrate) waste. As a preventative measure, users can track the flow of carrier gas through the ampoule and stop using the precursor in the ampoule well before its actual end of life, resulting in a significant portion of the ampoule fill going unused and increasing overall costs. Summary of the Invention [Problem to be solved by the invention]

[0005] It is with respect to these and other considerations that the present invention is provided. [Means for solving the problem]

[0006] In one embodiment, an apparatus for controlling a flow of a precursor may include a processor and a memory unit coupled to the processor and including a flux control routine. The flux control routine may operate on the processor to monitor the flow of the precursor. The flux control routine may include a flux calculation processor that determines a precursor flux value based on changes in detected light intensity received from a cell of a gas delivery system for delivering the precursor.

[0007] In a further embodiment, a method of controlling a flow of a precursor may include providing a flow of precursor through a gas delivery system, measuring a change in detected light intensity in a cell of the gas delivery system caused by the flow of the precursor, and determining a precursor flux value based on the change in detected light intensity.

[0008] In another embodiment, an apparatus for controlling a flow of a precursor may include a source that outputs a precursor and a sensor assembly communicatively coupled to the source. The sensor assembly may include a cell coupled to the source to receive and conduct the precursor, a light source disposed on a first side of the cell to transmit light into the cell, and a detector disposed on a second side of the cell opposite the light source to detect light transmitted through the cell. The apparatus may also include a control system configured to determine a precursor flux value based on changes in the intensity of the detected light received from the cell during flow of the precursor through the cell. [Brief explanation of the drawings]

[0009] [Figure 1A]FIG. 1 illustrates a system for chemical vapor deposition in accordance with an embodiment of the present invention. [Figure 1B] FIG. 1B illustrates one embodiment of a control system for the system of FIG. 1A. [Figure 1C] FIG. 1 illustrates another system for chemical vapor deposition in accordance with an embodiment of the present invention. [Figure 2A] 10A-10C illustrate the operation of a sensor assembly according to an embodiment of the present invention. [Figure 2B] 10A-10C illustrate the operation of a sensor assembly according to an embodiment of the present invention. [Figure 3A] 2B illustrates an exemplary signal collected by the sensor assembly of FIG. 2A. [Figure 3B] 2B illustrates an exemplary signal collected by the sensor assembly of FIG. 2A. [Figure 4] 4A-4C are graphs of various outputs of a control system according to an embodiment of the present invention. [Figure 5] 1 is a composite graph showing precursor flux and integrated flux over time, according to some embodiments. [Figure 6A] 1 is an exemplary graph illustrating the relationship between integrated flux or related entities and operating parameters of a system, according to an embodiment of the present invention. [Figure 6B] 1 is an exemplary graph illustrating the relationship between integrated flux or related entities and operating parameters of a system, according to an embodiment of the present invention. [Figure 6C] 1 is an exemplary graph illustrating the relationship between integrated flux or related entities and operating parameters of a system, according to an embodiment of the present invention. [Figure 6D] 1 is an exemplary graph illustrating the relationship between integrated flux or related entities and operating parameters of a system, according to an embodiment of the present invention. [Figure 7] FIG. 10 illustrates the behavior of integrated precursor flux as a function of time with and without temperature compensation, according to an embodiment of the present invention. [Figure 8]FIG. 1 illustrates an exemplary process flow according to an embodiment of the present invention. [Figure 9A] FIG. 1 illustrates an exemplary process flow according to an embodiment of the present invention. [Figure 9B] FIG. 1 illustrates a model system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The drawings are not necessarily to scale. The drawings are merely representations that are not intended to depict specific parameters of the invention. The drawings are intended to depict exemplary embodiments of the invention and therefore should not be considered limiting in scope. In the drawings, like numbering represents like elements.

[0011] Additionally, certain elements in some of the figures may be omitted or drawn out of scale for illustrative clarity. The cross-sectional views may be in the form of "slice" or "close-up" cross-sections, omitting, for illustrative clarity, certain background lines that would otherwise be visible in a "true" cross-section. Additionally, some reference numbers may be omitted in certain figures for clarity.

[0012] The present embodiments will now be described more fully with reference to the accompanying drawings, in which several embodiments are shown. The subject matter of the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numerals refer to like elements throughout.

[0013] The embodiments described herein provide novel processing and control of precursors in chemical vapor deposition processes, such as atomic layer deposition (ALD) processes. ALD generally involves sequential exposure to two or more reactants to deposit a given monolayer of material. In various embodiments, the chemical vapor deposition process may be performed to deposit any suitable material, including oxides, nitrides, carbides, dielectrics, semiconductors, or metals. The chemical vapor deposition process may include precursor flow control, as detailed in subsequent embodiments.

[0014] Referring now to FIG. 1A, a system 100 for chemical vapor deposition is shown, according to an embodiment of the present invention. The system 100 generally involves the use of at least one precursor provided as a gaseous species to a process chamber referred to as a deposition chamber 110. In different embodiments, the system 100 may be employed to perform chemical vapor deposition (CVD) or atomic layer deposition (ALD). The embodiments are not limited in this context. The system 100 includes a source, such as an ampoule 104, which may contain a solid, liquid, or gas. The ampoule 104 may be maintained at an elevated temperature to generate a gaseous species, which may be referred to herein as a precursor. The ampoule 104 may be coupled to a delivery system 114 configured to direct at least one, and possibly multiple, gaseous species to the deposition chamber 110, as in known CVD or ALD systems. For example, the delivery system 114 may include multiple gas lines, valves, and flow controllers. At least a portion of the delivery system 114 may be housed within the high temperature chamber 106, which is maintained at an elevated temperature relative to the ampoule 104 to ensure that the precursor remains in a gaseous state at least until it enters the deposition chamber 110.

[0015] System 100 may further include a sensor assembly 108 positioned to monitor the flow of at least one precursor between ampoule 104 and deposition chamber 110. Sensor assembly 108 may be coupled to a control system 112, which may output information or signals to a user and may also send control signals to control operating parameters of system 100, including temperature, precursor flow, etc. Details of an embodiment of control system 112 are shown in FIG. 1B and discussed further below.

[0016] According to an embodiment of the present invention, the control system 112 may be implemented using a combination of hardware and software. The control system 112 may include various hardware elements, software elements, or a combination of hardware and software. Examples of hardware elements include devices, logic devices, components, processors, microprocessors, circuits, processor circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, etc.), integrated circuits, application-specific integrated circuits (ASICs), and programmable logic devices (PLDs). Examples of hardware elements may also include digital signal processors (DSPs), field-programmable gate arrays (FPGAs), memory units, logic gates, registers, semiconductor devices, chips, microchips, chipsets, etc. Examples of software elements include software components, programs, applications, computer programs, application programs, system programs, software development programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, and functions. Examples of software elements may also include methods, procedures, software interfaces, application program interfaces (APIs), instruction sets, computational code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. The decision whether an embodiment is implemented using hardware and / or software elements may vary according to any number of factors, such as desired computational speed, power level, thermal tolerance, processing cycle budget, input data rate, output data rate, memory resources, data bus speed, and other design or performance constraints, as desired for a given embodiment.

[0017] As an example, control system 112 may include various hardware outputs that may be embodied as signals for controlling other components of system 100, may be output on a user interface, or may be output in other ways. In some examples, the hardware outputs may be employed as inputs by control system 112 to control components of system 100, as described in more detail below. Table I includes a list of exemplary hardware outputs, according to some embodiments of the present invention. In this example, temperature, such as the temperature of ampoule 104, may be output, as well as gas pressure, precursor concentration, and health monitors (reference signals). [Table 1]

[0018] These outputs may be collected periodically, intermittently, and synchronously, or separately (in time) from one another.

[0019] We now return to Table II. A set of operations or functions that may be performed by control system 112 according to some embodiments of the present invention are shown, where these functions are detailed in the following discussion. [Table 2]

[0020] 1B, another diagram of the control system 112 is shown. In various embodiments, the control system 112 may include a processor 150, such as a known type of microprocessor, a dedicated semiconductor processor chip, a general-purpose semiconductor processor chip, or similar device. The control system 112 may further include a memory or memory unit 160 coupled to the processor 150, which includes a control routine 162, as described below. The flux control routine 162 may run on the processor 150 to control precursor fluxes or precursor flows within the system 100, as described in more detail below. In some embodiments, the flux control routine 162 may include an end-of-life processor 164, an excursion processor 166, and a clog detection processor 168, a temperature control processor 170, and a flux calculation processor 172, where implementations of these processors are described with respect to the embodiments described below.

[0021] The memory unit 160 may include an article of manufacture. In one embodiment, the memory unit 160 may include any non-transitory computer-readable or machine-readable medium, such as an optical, magnetic, or semiconductor storage device. The storage medium may store various types of computer-executable instructions to implement one or more logic flows described herein. Examples of computer-readable or machine-readable storage media include any tangible medium capable of storing electronic data, including volatile or non-volatile memory, removable or non-removable memory, erasable or non-erasable memory, writable or rewritable memory, etc. Examples of computer-executable instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, object-oriented code, visual code, etc. The embodiments are not limited in this context.

[0022] The memory unit 160 may include a system database 180 containing parameters for the operating system 100. Exemplary parameters include, for example, a baseline ampoule side temperature and a baseline ampoule bottom temperature, where these parameters may be set as a starting point for control actions to be performed, such as for temperature compensation. Other parameters to be controlled may include flow rate, as well as deposition time. Additional parameters, which may be stored in the system database 180, may be used to assign limits to ensure that the temperature of the process remains within a safe range. Among these parameters are minimum ampoule side temperature, maximum ampoule side temperature, minimum ampoule bottom temperature, maximum ampoule bottom temperature, hot chamber temperature, and precursor degradation temperature.

[0023] Referring now to FIG. 1C, a system 118 for chemical vapor deposition according to a further embodiment of the present invention is shown. System 118 involves the use of multiple precursors provided as gaseous species to a process chamber, commonly referred to as deposition chamber 110. System 118 may operate similarly to system 100, except that system 118 includes a first ampoule 104A for a first precursor and a second ampoule 104B for a second precursor. Control system 112 may operate to independently control first ampoule 104A and second ampoule 104B according to principles detailed in the following discussion. This configuration facilitates control of two different precursors, where different precursors may be used in a CVD or ALD process, forming different condensed species. In other embodiments, a system such as system 100 or system 118 may be coupled with a gas flow device that delivers gaseous precursors from a gas source to the deposition chamber, e.g., NH3 or H2. As such, a CVD or ALD system can use a gas source to deliver a gas precursor, while at least one other precursor is delivered from an ampoule under active control according to embodiments described herein.

[0024] In various embodiments, the sensor assembly 108 may be configured with any suitable components for monitoring precursors, including electromagnetic radiation, acoustic signals, and the like. Embodiments are not limited in this context. The sensor assembly 108 can determine precursor flux or concentration by measuring changes in signal strength of an appropriate signal transmitted through the sensor assembly 108, as described in more detail below. Referring to FIGS. 2A and 2B , the operating principle of the sensor assembly 108, according to some embodiments of the present invention, is illustrated. The sensor assembly 108 may include a light source 120, such as an infrared, visible, or ultraviolet light source, and a detector 122 facing the light source 120. The detector 122 may be any detector appropriate for the type of radiation source used in the light source 120. The sensor assembly 108 may further include a chamber, shown as a cell 124, configured to receive and direct the precursor 126 as it travels from the ampoule 104 to the deposition chamber 110. When precursor 126 is absent from cell 124, detector 122 can register a signal such as background signal 130, as shown in FIG. 2A. Background signal 130 represents the transmitted (detected) intensity as a function of the wavelength of radiation from light source 120. In some embodiments, background signal 130 may be featureless, as shown in FIG. 3A. When precursor 126 is present in cell 124, the precursor can absorb the radiation emitted by light source 120, and detector 122 registers precursor signal 134. For clarity, precursor signal 134 is shown exhibiting peak 136, but in some embodiments, precursor signal 134 may include multiple features, including multiple peaks. Notably, the presence of precursor 126 in cell 124 may reduce the overall intensity of detected radiation in precursor signal 134, as opposed to background signal 130. As described in more detail below, in various embodiments, recording background signal 130, as well as monitoring precursor signal 134, is employed to control the operation of a deposition process across multiple examples.

[0025] As further shown in FIGS. 3A and 3B , the sensor assembly can also collect a reference signal 132, which indicates relative changes in detector performance of the detector 122 over time. Changes in the intensity of the reference signal 132 can indicate degradation of the detector 122's performance. By collecting the reference signal 132 at various instances in conjunction with measurements of the background signal 130 and the precursor signal 134, the amount of precursor 126 can be accurately determined over time. In particular, the absorption of light by the precursor 126 may be directly proportional to the partial pressure of the precursor 126 in the cell 124. As such, physical modeling can be employed to calculate precursor flux at multiple instances based on repeated measurements of the precursor signal 134, facilitating better control of the chemical vapor deposition process involving the precursor 126. In addition to measuring precursor flux, the cell pressure, such as the total pressure in the cell 124, can also be measured.

[0026] 4, a graphical illustration of various outputs of control system 112 is shown, in accordance with an embodiment of the present invention. Curve 402 illustrates the temperature of ampoule 104 as a function of time. In this example, the temperature is relatively constant as a function of time. During the deposition process, changes in temperature can result in changes in precursor flux by heating ampoule 104 and creating higher precursor partial pressures.

[0027] Curve 406 represents the baseline intensity of the detector, for example, indicating that the detector continues to function the same over the measured period. The health of the sensor can be determined from a comparison of a baseline intensity value taken at a point in time with the baseline intensity at the current point in time. Thus, if the baseline intensity value substantially deteriorates over time, this deterioration can be considered an indication of poor sensor health. Curve 408 represents the pressure in the chamber as a function of time, while curve 404 represents the concentration of the precursor as a function of time. As shown, the precursor is delivered in a series of pulses of concentration 412, resulting in corresponding pulses of pressure.

[0028] Referring now to FIG. 5 , a curve 502 is shown representing the precursor flux transported through a system, such as the flux of precursor conducted through sensor assembly 108. According to various embodiments of the present invention, physics-based calculations are performed to determine the precursor flux, which does not require a constant pressure or temperature at a sensor, such as detector 122, or in the gas lines used to direct the precursor from the ampoule to the deposition chamber. In the example of FIG. 5 , curve 502 shows a series of pulses 506 representing pulses in the precursor flux generated by pulses of precursor. Curve 504 represents the integral flux of precursor over time, representing the sum of pulses 506. Curve 504 can indicate the amount of precursor delivered to the deposition chamber at any given time instance. A sensor assembly, such as sensor assembly 108, may be maintained in operation during the chemical vapor deposition process, so that any pulse 506 is recorded, where the integral flux at a given instance represents the sum of all flux pulses recorded at that point.

[0029] 4 and 5 are directed to precursor flux monitoring, in other embodiments, by-products or secondary precursors may be monitored. For example, in some chemical systems, precursors may decompose during transport, where the precursor and by-products of the decomposition may pass through a detector cell. Thus, by adding additional detectors, such a detector system may be used to determine the relative flow of precursors versus by-products, such that there is a precursor detector, a by-product detector, and a health detector.

[0030] Determination of precursor flux and integral precursor flux may be used to monitor, characterize, or control a deposition process according to various embodiments of the present invention. Figures 6A, 6B, 6C, and 6D are exemplary graphs illustrating the relationship between integral flux or related entities and certain experimental or operational parameters of a system such as system 100. The data shown represent the deposition of cobalt using a (3,3-dimethyl-1-butyne) dicobalt hexacarbonyl (CCTBA) precursor. This chemical system is merely exemplary; in other embodiments, other metallo-organic or halogen species may be used to deposit cobalt or other metals.

[0031] Figure 6A shows the relationship between integrated flux and deposition time for measurements collected over the deposition time window, as shown. The integrated flux is determined using the sensor assembly as described above. As shown, the integrated flux shows a good linear fit with deposition time. Figure 6B shows the relationship between carrier gas flow rate and integrated flux, again showing linear behavior over carrier flow rates between 100 sccm and 400 sccm. Figure 6C shows the relationship between ampoule bottom temperature and integrated flux, again showing linear behavior over the temperature range between 32°C and 38°C.

[0032] In Figure 6D, the measured thickness of the deposit as a function of flux is shown, showing a linear relationship for two different units (alpha and beta). The data on the right represents data collected towards the beginning of the ampoule's life, while a decline in flux and deposit thickness occurs as the ampoule precursor material is consumed.

[0033] 6A-6D show how the integral flux in a chemical vapor deposition system, such as cobalt, is sensitive to parameters including deposition time, carrier flow rate, and ampoule temperature. In other embodiments, the dilution flow of any other stream into the process chamber, the number of deposition steps, or chamber pressure may be adjusted to control precursor flux.

[0034] In some embodiments, information about precursor flux may be used to dynamically control the deposition process, for example, to achieve process stability and prevent or counter drift in the deposition process. Figure 7 illustrates the integral precursor flux behavior as a function of time for an atomic layer deposition system for depositing TaN. Diamond symbols represent the integral precursor flux as a function of time up to about wafer 4500 when no temperature adjustments are made during a series of depositions. Lower and upper limits are indicated by horizontal dashed lines. As shown, the precursor flux when no temperature adjustments are made generally remains between the upper and lower limits until the instance of processing about wafer 1500, and at higher wafer numbers, it drops significantly below the lower limit. Considering that the upper and lower limits may represent target operating ranges, the results indicate that uncompensated flow of precursor cannot maintain the process within the target operating range beyond wafer 1500. Triangle symbols represent the integral precursor flux as a function of time when temperature adjustments are made during a series of depositions, according to an embodiment of the present invention. In this data set, the temperature of the precursor ampule may be adjusted according to a procedure detailed below. As a result, the integrated flux is maintained over the entire range measured (up to wafer 3500).

[0035] Referring now to FIG. 8, a process flow 800 is shown in accordance with an embodiment of the present invention. Process flow 800 may be implemented by a processor, as described above and illustrated in the figure. In particular, some operations may be performed by multiple processors. In block 802, an integral precursor flux is set for a given deposition process. A set point may be established, where the integral flux is determined based on measurements of the precursor using a sensor assembly according to the above-described embodiments. In various embodiments, multiple parameters may be set or monitored. For example, a baseline ampoule side temperature and a baseline ampoule bottom temperature may be set as starting points for temperature compensation to be performed. Additional parameters may be used to assign limits to ensure the temperature of the process remains within a safe range. Among these parameters are minimum ampoule side temperature, maximum ampoule side temperature, minimum ampoule bottom temperature, maximum ampoule bottom temperature, hot chamber temperature, and precursor degradation temperature.

[0036] In block 804, a substrate or wafer is processed according to a given deposition process. The flow proceeds to block 806, where the integrated chamber flux is calculated for the precursor, as represented by curve 504, for example. In block 808, a sensor, such as detector 122, is checked to verify that it is reading correctly and that the baseline reading is correct. A determination that the sensor requires a flow adjustment proceeds to block 810, where in one mode, a signal is sent to the user indicating that the sensor requires adjustment, and in the other mode, an adjustment to the sensor is automatically made. The flow then returns to block 804. If in block 808, the sensor does not require adjustment, the flow proceeds to block 812, where the integrated precursor flux from block 806 is checked against certain control limits. If the precursor flux indicates that the process is under control or within the control limits, the flow proceeds to block 814, where no adjustment to the ampoule temperature is made. The flow then returns to block 804, where the wafer is processed without having the ampoule temperature adjusted for the precursor.

[0037] In some embodiments, two sets of limits may be specified, such as failure limits and warning limits, as illustrated in process flow 800. When the warning limits are exceeded, the condition triggers a temperature update. The failure limits are broader, and when exceeded, the condition indicates that something has changed in the system (rather than the gradual drift expected over the life of the ampoule) and additional action is required.

[0038] In process flow 800, if a fault condition (fault band condition) is detected at block 812, the flow proceeds to block 816, where the ample idle time is checked. Then, if the first wafer is being processed, the flow returns to block 814. If the first wafer is not being processed, the flow proceeds to block 818, where fault detection and classification is performed. Then, the flow proceeds to block 820, where a notification signal is sent to notify a user that an excursion has been detected. The flow may then proceed to block 814. In different implementations, the processing may be stopped or the user may be notified while processing continues via block 804.

[0039] If a warning band condition is determined in block 812, flow proceeds to block 822 where an error calculation is performed.

number

[0040] In different embodiments, the warning and failure limits may be assigned by a user or, alternatively, may be calculated automatically in a software routine. In some examples, the limits represent a given number of standard deviations from the mean of the sample set.

[0041] In particular, the error calculation in block 822 may include experimentally determined control limits based on sensor noise and thickness sensitivity. The calculated error value may be based on subtracting the integrated flux from an upper control limit (UCL) or a lower control limit (LCL). Flow then proceeds to block 824.

[0042] At block 824, a temperature increment ΔT is determined. In one embodiment, the temperature increment is determined as follows:

number

[0043] In block 826, the temperature increment ΔT is rounded to the nearest level, such as the nearest 0.5° C. Flow then proceeds to block 828, where new setpoints are calculated for the side and bottom temperatures of the ampoule. K =T K-1 +ΔT, where T K is the temperature at time k, and T k-1 is the previous temperature setpoint. Flow then proceeds to block 830.

[0044] In block 830, the set point determined in block 828 is checked against the current temperature limits for the ampoule containing the precursor. If the set point is within the limits in block 830, the flow then proceeds to block 832. These limits may include the ampoule side temperature minimum, ampoule side temperature maximum, ampoule bottom temperature minimum, ampoule bottom temperature maximum, hot chamber temperature, and precursor degradation temperature.

[0045] In block 832, the ampoule temperature setpoint is updated based on the new setpoint determined in block 828. Flow then proceeds to block 834 to wait for the precursor fluxes to stabilize and then returns to block 804.

[0046] If the setpoint is not within the limits in block 830, the flow proceeds to block 836, where the end of life of the precursor ampoule is checked. If it is determined in block 836 that the ampoule is at the end of its life, the flow proceeds to block 838, where a signal is sent to notify the user for preventive maintenance. The flow then proceeds to block 840, where the temperature increment is recalculated based on the most conservative limit. The most conservative limit may represent the lowest applicable maximum temperature or the highest applicable minimum temperature. The flow then returns to block 828. If it is determined in block 836 that the ampoule is not at the end of its life, the flow proceeds directly to block 840. The end of life determination can be made based on when the temperature compensation can no longer maintain the deposition process within acceptable process conditions.

[0047] Referring now to FIG. 9A, a process flow 900 according to a further embodiment of the present invention is shown. The process flow 900 may be implemented by a clog detection processor 168 and may be used to determine the presence and location of clogs in a delivery system for chemical vapor deposition. A model delivery system 930 including a precursor ampoule 932 and a sensor assembly 934 is shown in block form in FIG. 9B. Moving to the process flow 900, a determination is made in block 902 as to whether the pressure in the gas line delivering the precursor 902 is too high. The transducer pressure may be measured immediately downstream of the carrier mass flow controller in the gas line. An indication of "too high" may be determined statistically. A set of "good" recipes may be employed to determine the expected mean and standard deviation (sigma). Here, a deviation on the order of three sigma is used to determine whether the pressure is high (depending on the sample size and acceptable confidence level). If not, the flow proceeds to block 904, indicating that no clog is detected in the gas line. If, at block 902, the transducer pressure is high, then flow proceeds to block 906 where a determination is made as to whether the pressure in the sensor assembly 934 is too high. If so, then flow proceeds to block 908 where a signal is sent indicating that a clog is detected downstream of the sensor assembly 934. If the pressure is not too high in the sensor assembly 934, then flow proceeds to block 910.

[0048] At block 910, in bypass mode, as indicated by position 4 in FIG. 9B , a determination is made as to whether the transducer pressure is high. If not, the flow proceeds to block 912, where a determination is made as to whether the precursor flux is low. The determination as to whether the precursor flux is low may be made by measuring the precursor flux with sensor assembly 934. In particular, the measured precursor flux is compared to "good" data using a statistical approach including mean and standard deviation. If the precursor flux is not low at block 912, the flow proceeds to block 914, where a signal is sent indicating that a clog exists at the precursor ampoule 932 inlet, as indicated by position 2. If the precursor flux is determined to be low at block 912, the flow proceeds to block 916, where a signal is sent indicating that a clog exists at the precursor ampoule 932 outlet, as indicated by position 3.

[0049] If a determination is made in block 910 that the transducer pressure is high in bypass mode, flow proceeds to block 918 where a determination is made as to whether the precursor flux is low. If not, flow proceeds to block 920 where a signal is generated indicating that a clog exists upstream of the precursor ampoule 932 inlet, as indicated by position 1. If so, flow proceeds to block 922 where a signal is sent indicating a clog between the precursor ampoule 932 outlet and the sensor assembly 934, as indicated by position 4.

[0050] In summary, this embodiment provides the advantages of determining precursor flux during operation of a chemical vapor deposition system, determining such changes in precursor flux in real time, and dynamically adjusting operating parameters, such as ampoule temperature, in real time to maintain precursor flow within acceptable limits. Other advantages include the ability to determine or predict the end of life of a precursor ampoule, so replacement does not have to occur before corrections can be made to maintain precursor flow within limits. Further advantages include the ability to determine the presence of blockages at multiple different locations in the precursor delivery system.

[0051] The scope of the present invention is not limited to the specific embodiments described herein. Various embodiments of the present invention and modifications thereof, as well as those described herein, will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Therefore, such other embodiments and modifications are intended to be included within the scope of the present invention. Furthermore, the present invention has been invented herein in the context of a particular implementation in a particular environment for a particular purpose. Those skilled in the art will recognize that its utility is not limited in this respect, and that the present invention may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full breadth and spirit of the invention as described herein.

Claims

1. 1. An apparatus for controlling the flow of a precursor, the apparatus comprising: an ampoule for outputting a precursor; a sensor assembly in the hot chamber communicatively coupled to the ampoule, the sensor assembly comprising: a cell coupled to the ampoule for receiving and conducting a precursor; a light source disposed on a first side of the cell and transmitting light into the cell; a detector for detecting light transmitted through the cell; and a control system arranged to determine a flux value of the precursor using the detector during flow of the precursor through the cell, the control system comprising: determining an error value based on the precursor flux value; determining a temperature adjustment ΔT based on the error value; calculating a new set of temperature setpoints to be applied to said ampoule; a temperature control processor configured to check the new set of temperature setpoints against a temperature limit of the ampoule; an end-of-life processor configured to check an end-of-life condition of the ampoule when the new set of temperature setpoints is not within the temperature limits of the ampoule; The apparatus, wherein the ampoule temperature limits are set by at least one of an ampoule side temperature minimum, an ampoule side temperature maximum, an ampoule bottom temperature minimum, an ampoule bottom temperature maximum, a hot chamber temperature, and a precursor degradation temperature.

2. 10. The apparatus of claim 1, wherein the control system further comprises a flux calculation processor, the flux calculation processor comprising: receiving a first reference signal in the cell generated in a first step, the first reference signal being indicative of a performance of the detector in the first step for detecting an intensity of light from a light source; receiving a background signal generated in the first step by the detector; receiving a second reference signal generated in a second step subsequent to the first step, the second reference signal being indicative of the performance of the detector in the second step for the detector; receiving a precursor signal generated in a third step subsequent to the first step as the precursor flows through the cell, thereby determining a flux value of the precursor.

3. 3. The apparatus of claim 2, wherein the flux calculation processor comprises: An apparatus configured to calculate an integrated flux of the precursor by determining flux values ​​of the precursor at a plurality of stages.

4. 10. The apparatus of claim 1, wherein the temperature control processor comprises: An apparatus configured to determine a warning zone condition based on the precursor flux value, and adjust a temperature of the ampoule based on the warning zone condition.

5. 5. The apparatus of claim 4, wherein the temperature control processor comprises: adjusting the temperature by determining a temperature adjustment ΔT; [Equation 1] where P, I, D are the proportional, integral, and derivative gains, and [Equation 2] is an error based on the current temperature limit of the ampoule.

6. 10. The apparatus of claim 1, wherein the temperature control processor comprises: and adjusting the temperature by applying the new set of temperature setpoints to control heating of the ampoule when the new set of temperature setpoints is within a temperature limit of the ampoule.

7. 10. The apparatus of claim 1, wherein the end-of-life processor comprises: recalculating ΔT based on a most conservative limit to generate a conservative ΔT when an ampoule end-of-life condition is not met, the most conservative limit representing the lowest of the ampoule side temperature minimum, the ampoule side temperature maximum, the ampoule bottom temperature minimum, the ampoule bottom temperature maximum, the hot chamber temperature, and the precursor degradation temperature; and calculating a new set of temperature setpoints to apply to the ampoule based on the conservative ΔT.

8. 10. The apparatus of claim 1, wherein the end-of-life processor comprises: recalculating ΔT based on a most conservative limit when an ampoule end-of-life condition is not met to generate a conservative ΔT, the most conservative limit representing the highest of the ampoule side temperature minimum, the ampoule side temperature maximum, the ampoule bottom temperature minimum, the ampoule bottom temperature maximum, the hot chamber temperature, and the precursor degradation temperature; and calculating a new set of temperature setpoints to apply to the ampoule based on the conservative ΔT.

9. 10. The apparatus of claim 1, wherein the control system further comprises an excursion processor, the excursion processor comprising: An apparatus configured to determine a fault condition based on the precursor flux values, and to send a deviation notification signal when the substrate being processed during the fault condition is not the first substrate.

10. 10. The apparatus of claim 1, wherein the control system further comprises a clog detection processor, the clog detection processor comprising: receiving a pressure reading of a transducer in a gas line delivering said precursor; receiving a flux value of the precursor; An apparatus configured to determine a clog location based on pressure readings of the transducer and flux values ​​of the precursors.

11. 10. The apparatus of claim 1, a processor; a memory unit coupled to the processor and containing a flux control routine, The flux control routine operates on the processor to monitor a flow of precursors, the flux control routine comprising: a flux calculation processor configured to determine a flux value of the precursor based on a change in intensity of the detected signal received from a cell of the gas delivery system for delivering the precursor; receiving a pressure reading of a transducer in a gas line delivering said precursor; receiving a flux value of the precursor; a clog detection processor configured to determine a clog location based on the pressure readings of the transducer and the precursor flux values.

12. 12. The apparatus of claim 11, wherein the flux control routine further comprises a temperature control processor, the temperature control processor comprising: An apparatus configured to determine a warning zone condition based on the precursor flux value, and adjust a temperature of the ampoule based on the warning zone condition.

13. 12. The apparatus of claim 11, wherein the clog detection processor is further configured to determine that a clog exists between the ampoule containing the precursor and the cell when the transducer pressure reading is above a first deviation from an expected average value of the pressure and when the precursor flux value is below a second deviation from an expected average value of the precursor flux.

Images