The present disclosure relates in general to the fields of semiconductor processing. More particularly, the present disclosure relates to the methods, architectures, and apparatus related to temperature calibration and control of semiconductor reactors.
In thermal processing systems, direct workpiece measurement is challenging as temperature measurement instruments, such as thermocouples, often are unable to attach to the workpieces, or workpiece carriers, directly and particularly during processing conditions. Typically, in such cases non-contacting temperature measurement techniques are used, such as pyrometry or phosphor thermometry and alike, or temperatures are determined based on indirect measurements, such as input power. However, such techniques require regular in-situ calibrations under thermal and ambient (gas type and flow) conditions similar to actual semiconductor processing conditions—which often require a contacting measurement device. Thermocouples are often used for this calibration, particularly at high temperatures above 600 degrees C.
In epitaxial processing equipment, the direct attachment of thermocouples to susceptors is often impractical and faces significant technical issues if the wafers are positioned in non-stationary susceptors. In instances when direct workpiece (or container) temperature measurement during processing is not possible or impractical, such as when the workpiece (or container) is not stationary, then the workpiece temperature is commonly deduced from another reference temperature measurement or from input heating power. However, the relationship between actual temperature and the input power or the reference measurement must be determined through system calibration using some form of direct temperature measurement under conditions similar to the real processing conditions. And as this relationship may drift with time and processing cycles, for example, due to changing conditions or aging, it often becomes necessary to recalibrate. Thus, in high volume manufacturing it is important to have a calibration scheme that may be carried out as quickly as possible to reduce and minimize calibration time during which the machine is not in use for actual production.
In thermal processing systems, and particularly those operating at high temperatures, it is often not possible to measure the temperature of the process as the process is being carried out because the presence of temperature measurement devices would negatively influence the outcome of the thermal process. This influence may be exacerbated for high temperature processes in semiconductor or photovoltaic processing, for example in deposition systems where the permanent presence of temperature monitoring devices (such as thermocouples or precision resistors) is not compatible with the process chemistry used and metal emanating from the temperature monitoring devices would negatively affect the quality of the deposited material or the substrates that material is deposited on. Additional complications may occur when the thermal processing systems are in-situ cleaned which may be highly desirable for the uptime and ease of maintenance of such systems but which also creates additional challenges as the cleaning chemistry often attacks the measurement devices.
Further, direct contact between thermocouples and susceptors may introduce contamination to the susceptors and degrade the quality of the resulting epitaxial semiconductor films. As a result, special susceptors with imbedded thermocouples are used for temperature calibration, but swapping such susceptors after use is time-consuming and undesirable in high volume manufacturing, particularly for multi-chamber systems. Additionally, the hollowing of susceptors for thermocouple insertion in conjunction with the presence of such thermocouples often introduces unacceptable measurement errors within the reactor under transient conditions.
Therefore, a need has arisen for temperature calibration and control of thermal processing systems. In accordance with the disclosed subject matter, methods and structures for the non-invasive temperature calibration and in process temperature control of thermal processing systems are provided which substantially eliminate or reduce the cost and fabrication disadvantages associated with previously developed thermal processing systems temperature measurement methods.
According to one aspect of the disclosed subject matter, thermal processing systems and a non-contact and non-invasive temperature measurement assembly which neither damages nor contaminates the process environment is provided. The thermal processing system comprises a chamber housing a pair of susceptors positioned in a face to face arrangement. Each susceptor supporting at least one work piece and forming a processing cavity between the wafers. A thermocouple assembly comprising an encapsulation rod housing at least one thermocouple is positioned to measure the susceptor temperature of the susceptor surface proximate the processing cavity.
These and other aspects of the disclosed subject matter, as well as additional novel features, will be apparent from the description provided herein. The intent of this summary is not to be a comprehensive description of the claimed subject matter, but rather to provide a short overview of some of the subject matter's functionality. Other systems, methods, features and advantages here provided will become apparent to one with skill in the art upon examination of the following FIGUREs and detailed description. It is intended that all such additional systems, methods, features and advantages that are included within this description, be within the scope of any claims.
The features, nature, and advantages of the disclosed subject matter may become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference numerals indicate like features and wherein:
The following description is not to be taken in a limiting sense, but is made for the purpose of describing the general principles of the present disclosure. The scope of the present disclosure should be determined with reference to the claims. Exemplary embodiments of the present disclosure are illustrated in the drawings, like numbers being used to refer to like and corresponding parts of the various drawings.
And although the present disclosure is described with reference to specific embodiments, such as chemical vapor deposition (for example epitaxial deposition) processing using a lamp heated thermal reactor, one skilled in the art could apply the principles discussed herein to other materials, technical areas, and/or embodiments without undue experimentation. For example, the temperature calibration methods provided herein may be applicable to any thermal wafer processing (such as annealing) in a reactor providing a uniform thermal environment heated by, for example, lamp heating, inductive heating or resistive heating.
The disclosed subject matter provides non-contact and non-invasive temperature measurement for thermal processing systems which neither damage nor contaminate the process environment or susceptors. Further, the disclosed calibration structures and methods may be carried out quickly and integrated with a material handling system of the processing equipment for automated in-situ calibration and high volume manufacturing. And, in some embodiments, direct temperature measurement during thermal processing may be performed without contacting susceptors.
In operation, the disclosed subject matter is applicable to any thermal processing system wherein workpieces are placed inside enclosed containers that may be heated. The following methods and tools for non-invasive and fast temperature calibration are described with reference to thermal processing equipment wherein the workpieces are confined within a cavity of substantially unidirectionally uniform temperature chamber. In one embodiment, this application is in a semiconductor deposition system in which semiconductor wafers are placed into carriers, commonly called susceptors, positioned in a face-to-face arrangement inside processing chambers—an application particularly relevant for the epitaxial deposition of crystalline materials such as crystalline silicon. Such systems may also be used for deposition of non-crystalline material layers as well as other processing applications such as thermal annealing, oxidation, and/or nitridation of semiconductor wafers. The chamber cavity and workpieces (wafers) positioned therein may be heated using lamps, or commonly known inductive and resistive heating methods and structures. And in some embodiments, the direct temperature measurement may be obtained during processing using non-invasive devices positioned proximate the thermal processing.
Next, in the case of epitaxial growth, deposition gases are injected into cavity space 105 between the susceptors from one direction (from the top as shown in
The epitaxial deposition above may require temperature calibration both between deposition processes and during (in-situ) deposition for the controlled and uniform deposition of a semiconductor layer. However, attaching thermocouples to the susceptors for temperature calibration may be challenging as the susceptors are not stationary (for example, they may be loaded into and unloaded from the quartz chambers along with the semiconductor wafers). Further, positioning/attaching thermocouples to susceptors by drilling thermocouple holes into the susceptors may create challenges such as, for example: the susceptors may be too thin and mechanically weak to support the formation of long thermocouple holes while increasing susceptor thickness may increase heating and cooling times thus increasing processing time and decreases throughput. Further, increasing susceptor wall thickness may also increase the amount of energy required to heat the susceptors to a desired deposition temperature thus decreasing volume production. Additionally, thermocouple holes in the susceptors may be exposed to deposition and cleaning processing further affecting deposition. And if susceptors with corresponding thermocouple holes are limited to temperature calibration and not used during deposition, then swapping susceptors (from temperature calibration susceptors with corresponding attached thermocouples to processing susceptors without corresponding thermocouples) may increase calibration time and tool cost and result in increased susceptor management in an automated tool.
The disclosed thermocouple designs and corresponding chamber structures provide in-situ temperature calibration without the need to use special calibration susceptors.
Furthermore, the thermocouple assembly may be integrated with moving mechanisms processing equipment within a single or multi-chamber deposition system for automated in-situ calibration, shown schematically by cross-sectional diagram of the multi-chamber thermocouple assembly 110 in
The disclosed thermocouple assembly structures also provide for bi-directional susceptor cavity temperature mapping—in other words, temperature mapping of the epitaxial deposition systems shown in
The disclosed temperature calibration systems and methods provide fast temperature calibration for high-volume manufacturing which in some instances may be further integrated with epitaxial processing equipment for automated in-situ calibration and measurement. In some instances, this may include the permanent incorporation of thermocouples inside high temperature processing equipment with mobile susceptors (for example epitaxial deposition reactors).
Often it is difficult to incorporate thermocouples in high temperature reactors, such as those described above, for a number of reasons including the risk of exposure to potentially corrosive gases and contamination of the susceptors and the deposition process by the thermocouples and their leads. Other problems incorporating thermocouples in high temperature reactors include challenges avoiding or managing depositions on thermocouples and thermocouple holders during processing. The present disclosure presents solutions to such problems utilizing structure designs such as encapsulation, locations, and mounting of thermocouples and feedthroughs, as well as through the utilization of different reactor zones or regions containing different temperatures and gasses. In the latter case, the thermocouples may be positioned either in a zone that does not receive deposition gas, but only purge gas such as hydrogen, or the thermocouple may be exposed to the same deposition and etching gases as required for processing. The thermocouples are enclosed within the same, approximately isothermal susceptor that encloses the workpieces/wafers and housed in materials similar to those of the susceptor. Generally, thermocouple assembly epitaxial deposition incorporation is described with reference to the following embodiments: thermocouple assembly positioned outside process area and outside the susceptor (
To minimize the effect of the thermocouple assembly during processing, the thermocouple assembly comprising rods housing the thermocouples may be made of the same or similar materials to that of the susceptors. For example, in some instances, the heated reactor may comprise materials such as quartz chamber walls and silicon carbide, silicon, or silicon carbide coated graphite based susceptors (for instance such susceptors made from isostatically pressed graphite as well as from carbon composite materials) and may further comprise a thermocouple or a set of thermocouples enclosed and encapsulated in a rod made of susceptor like material and arranged alongside the susceptor or susceptors. Encapsulated temperature measurement spots may then be calibrated using above mentioned calibration thermocouple arrangements.
The thermocouple encapsulation material may be the same or similar to the susceptor material—thus, the same cleaning mechanisms (for example high temperature HCl gas etching of deposited silicon) may be employed to repeatedly strip deposit from the encapsulated thermocouple. Further, an electrical feedthrough and hole in the encapsulation may be positioned in an area not subject to corrosive gases or an area where corrosive gasses are present in highly dilute concentrations and temperatures are below the reaction threshold of the corrosive gases. In some instances, the feedthrough entry zones may also optionally be purged with gases such as hydrogen.
The diagrams of
In some embodiments, the lower flange plate may be segmented, for example into an outer and an inner part such that a stationary outer part contains the permanent feedthroughs for the thermocouples and an easily detachable inner part allows for easy maintenance access to the inside of the flange. An arrangement advantageous for maintenance to a bottom flow nozzle or for retrieval of debris or lost wafers.
In some instances, the thermocouple arrangements shown
In the embodiments shown in
And in embodiments where feedthroughs are established from the stationary bottom part of the flange, mobile electrical feedthroughs are not required.
In embodiments utilizing a vertical loading of the susceptors into the reactor, the susceptors may be hoisted down into the reaction chamber, thereby enclosing the encapsulated thermocouple rod. The thermocouple rod enclosure may provide reactor gas access to the enclosed thermocouple rod for purging, deposition, and etch. In another embodiment, the encapsulated thermocouple rod may be supported in the upper region of the reactor by a quartz lobe that is part of an upper mobile flange lid of the reactor.
Embodiment variations relating to the designs shown in
In operation, the disclosed subject matter provides a non-invasive and non-contact method for the temperature calibration and control of a confined reactor chamber providing an accurate reading of the susceptor and workpiece temperature within the chamber. In the reactor embodiments disclosed, a face to face susceptor arrangement provides a substantially uniform temperature distribution in width of the cavity between the facing susceptors. Thus, the thermocouple assembly may be deployed to calibrate and control the deposition process temperatures using thermocouples positioned to form a one or two dimensional temperature measurement map.
The foregoing description of the exemplary embodiments is provided to enable any person skilled in the art to make or use the claimed subject matter. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the innovative faculty. Thus, the claimed subject matter is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Further, it is intended that all such additional systems, methods, features, and advantages that are included within this description be within the scope of the claims.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/635,824 filed Apr. 19, 2012, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61635824 | Apr 2012 | US |