TWI576570B - A telecentric optical arrangement for a radiation thermometer, a method of using a telecentric lens arrangement to reduce stray radiation bias in a radiation thermometer and a system for measuring temperature - Google Patents

Description

Telecentric optics for radiation thermometers, using telecentric lenses Method and temperature measuring system configured to reduce stray radiation in a radiation thermometer

The present invention relates to radiation temperature measurement, and more particularly to reductions in bias values associated with the use of radiation thermometers or pyrometers in chemical vapor deposition reactors (CVD).

Organometallic chemical vapor deposition (MOCVD) is a chemical vapor deposition technique for growing a crystal layer in, for example, a semiconductor fabrication process. The MOCVD process is carried out in a reaction chamber having a specially designed flow flange for transporting a uniform reactor gas stream to the reaction chamber.

During the MOCVD process, the temperature of the crystal layer is typically measured using a non-contact device, such as a radiation thermometer or pyrometer.

Such crystal growth materials include tantalum carbide (SiC), zinc selenide (ZnSe), and gallium nitride (GaN) base materials such as GaN and AlGaN. Some substrate grown materials have emission characteristics that limit the operating wavelength of the radiation temperature measurement. For example, GaN grown on a sapphire substrate may have a transmittance of greater than 50% for wavelengths greater than 450 nm at processing temperatures. Thus, for wavelengths greater than 450 nm, the radiation exiting a substantial portion of the surface of the GaN layer is derived from structures below the substrate of the line of sight of the radiation thermometer (eg, wafer carriers); radiation through the GaN layer does not represent GaN The temperature of the layer. Therefore, the market has developed wavelengths of less than 450 nm (corresponding to blue, For example, Zettler et al., US Patent Application Publication No. US 2011/0064114 (hereinafter referred to as Zettler), which discloses a method for detecting at 250 nm to A pyrometer with a range of radiation in the 450 nm range.

The use of a radiation thermometer has the problem of detecting unwanted radiation, and one source of unwanted radiation is the unfiltered radiation detected outside of the desired bandpass range. Zettler discloses equipment and techniques that illustrate the contribution of filtered radiation. It is pointed out that the narrow bandpass filter cannot completely block the infrared radiation, and the unblocked infrared radiation may cause problems at the operating temperature (about 800 °C) because the spectrum of the target is black body emission power, infrared in the electromagnetic spectrum. The light portion is about 9 orders of magnitude higher than the main bandpass at the narrow bandpass filter (i.e., the desired spectral bandpass used to infer the target temperature). The Zettler method involves the use of a detector that is extremely sensitive over a wide wavelength range (from ultraviolet to infrared wavelengths) and that can filter the incoming radiation by a narrow bandpass filter centered at about 410 nm. A long bandpass filter is then used to effectively block the main bandpass of the narrow bandpass filter, but still allows the infrared and near infrared portions of the electromagnetic spectrum to be filtered by the narrowband pass filter. Zettler infers the difference between the two measurements by the main bandpass of the narrow bandpass filter, ie the signal obtained with only the narrow bandpass filter and the narrowbandpass filter and the long bandpass filter. The difference between the signals obtained.

Another source of unwanted radiation is the contribution of "stray radiation"; stray radiation is redirected to the target by external reflections through the outer casing or other structure and reflected to the radiation The reflected radiation in the line of sight of the thermometer. Considering a wafer carrier having a GaN wafer that is heated to an elevated temperature of 800 ° C by, for example, a microwave heating process, components that operate at elevated temperatures, such as wafer carriers and wafers, Will be sent in all directions Radiation causes the radiation to internally reflect within the reaction chamber. Some of the internally reflected radiation will be incident on the surface to which the radiation thermometer is aimed and become the radiation detected by the radiation thermometer. For a GaN crystal at 800 ° C ° C, the reflectivity at 410 nm is about 0.2, and stray radiation will significantly deviate from the temperature values indicated by the radiation thermometer.

When the target is at or near the highest temperature in the reaction chamber, stray radiation is enough to be a problem, and the microwave heating system is an example. However, when we measure radiation at short or near short wavelengths in the visible spectrum (ie, blue, violet, or ultraviolet wavelengths), if there are other sources operating in the reaction chamber at substantially higher temperatures than the target, The problem will get worse. This heating device converts thermal energy according to the first law of thermodynamics, which requires the resistive heating element to operate at temperatures well above the crystal growth layer. One advantage of thermal radiant heating is that the radiant intensity profile can be customized to provide temperature uniformity throughout the wafer carrier.

For example, consider the condition of black body radiation of the crystal growth layer at 800 °C. According to Planck's law, the blackbody spectral emission power at 410 nm and 800 °C is about 2.0×10 ^-4 W/m ² . Mm. Now consider a heat source such as a resistive heating element that transmits heat to the crystal growth layer through radiation and conduction operating at 1800 ° C. The black body spectral emission power at 410 nm and 1800 ° C is about 1.4 × 10 ³ W / m ² . Μm; this case is increased by about 7 orders of magnitude in the blackbody spectral emission power intensity at 800 ° C (the typical operating temperature of the crystal growth layer during CVD) at the wavelength of interest (Figure 1). Therefore, even if only a slight percentage of the radiation at 410 nm reaches the detector of the radiation thermometer, the indicated temperature deviation is still significant. As such, the stray radiation contribution in the reaction chamber utilizing the resistive heating element can be of the same order of magnitude as the unfiltered radiation contribution recognized by Zettler.

However, Zettler did not mention the contribution of stray radiation or the presence of a reaction chamber. Effectively defeating the effects of radiation sources emitted by the target; in addition, Zettler processes the target in such a way that the target is free to radiate (ie, does not have a contribution to reflection), but actually operates in a crystal growth The target in the CVD reaction chamber at the required temperature is not free radiation.

Therefore, we need a radiation thermometer that is suitable for reducing the effects of unwanted radiation caused by both unfiltered radiation and stray radiation.

Various embodiments of the present invention use so-called "telecentric" telecentric devices, but in an off-focus manner to limit the contribution of reflected stray radiation in at least three different aspects. First, in a telecentric optical device, the primary rays captured by the target are substantially parallel to the optical axis, thus substantially limiting the contribution of stray radiation, especially when the target has a strong specular reflectance element. Secondly, we can also adjust the telecentric optical device so that the solid angle of each point on the target object is extremely small, which can also reduce the contribution of stray radiation. Third, the telecentric optics can be used to capture the collimated beam of radiation emitted by the target, thus further reducing the solid angle of the radiation captured by the radiation thermometer, but increasing the target size (and subsequent The ratio of the signal-to-noise ratio to the effective diameter of the forward optical element. In capturing the collimated beam of radiation, we use telecentric optics in an "out of focus" manner, ie telecentric optics are not used for high quality imaging of the surface of the target. Therefore, the components used in the telecentric optical device do not need to have superior quality as a commercially available telecentric lens system.

Various embodiments of the present invention may or additionally reduce the contribution of stray radiation such that less stray radiation is incident on a target of the radiation thermometer, the stray radiation being measured by radiation The thermometer is detected by installing a reaction chamber and accessories therein. In analyzing the stray radiation in this case, we determined that the surrounding heating elements in the heater array have the greatest contribution to the stray radiation detected by the radiation thermometer. We have also confirmed by both ray trace modeling and verification experiment that providing discontinuity in the portion of the heating element that is closest to the target area of the radiation thermometer will be significantly reduced by Mistakes caused by stray radiation.

"Off-Focus" telecentric optics

Commercially available telecentric lens systems are used, for example, in machine vision systems to provide clear, sharp images with high magnification. These telecentric lens systems provide uniform magnification of all points within an image, regardless of the position of the point in the image. In other words, a telecentric lens system for use in a machine vision system can provide a substantially isometric image, as opposed to a fluoroscopic image provided by a standard imaging system. One of the advantages of commercially available telecentric lens systems is that equidistant images can substantially reduce parallax within the image.

However, at a given setting, the telecentric lens system provides a fairly limited range of equidistant images. This effective range is often referred to as "telecentric depth" (see, for example, Petrozzo Lenses Simplify Non by Petrozzo et al.) -Contact Metrology, "Test & Measurement World, October 15, 2001, p. 5). Thus, the paradigm of the telecentric lens system is such that it can only operate in a narrow range centered on the object plane. The optical components of the machine vision telecentric lens system are of high quality to provide clear, sharp images throughout the image range. Furthermore, commercially available telecentric lens systems typically use high quality fittings to provide the ability to adjust the focal depth of the object plane; the precision imaging capabilities of commercially available telecentric lens systems increase cost.

For various embodiments of the invention, the telecentric concept is utilized in a manner not employed by machine vision systems. In one embodiment, the telecentric optic is used to focus on infinity, but is only mounted a few centimeters from the target. The advantage of this configuration is that the radiation from each point on the target has substantially the same angle of entry into the optical system and does not require the associated high quality imaging and expensive optical components because the purpose is to radiate Aggregation and detection, not target imaging. In other words, we use telecentric optics in an "out-of-focus" or "off-focus" manner to effectively capture the collimated beam of radiation emitted by the surface of the target. This device requires neither high-quality imaging optics nor sophisticated assembly for fine-tuning images.

Structurally, in various embodiments of the invention, the out-of-focus telecentric optical device includes an aperture stop and a first or "object" optical component of one or more optical components (this) It is called "object assembly"). The aperture shutter assembly defines a first focal length of the optical axis and a reference point within the object assembly, and the reference point is on the optical axis. In one embodiment, the aperture shutter is spaced from the reference point of the object assembly by a distance substantially equal to the first focal length of the object assembly. By placing the aperture shutter on the focal length of the object assembly, the object assembly can be effectively focused at infinity. The substantially collimated radiation from the off-target is transmitted through the object assembly, and the radiation from the off-target is focused on the aperture shutter.

In some embodiments, a second or "image" optical component of one or more optical components (referred to herein as an "image component") can face the component on the other side of the aperture shutter and Receiving radiation from the object assembly that travels along the optical axis and through the aperture shutter. The image component defines a second focal length relative to a second reference point within the image component, the second reference point being located on the optical axis.

In one embodiment, a telecentric optics of "bilateral" or "bilateral" is implemented. The device wherein the primary ray of both the target and the image is parallel to the optical axis. In a two-sided device, the focal length of the object assembly defines the target distance, and the aperture shutter is located at the substantially back focal plane of the object assembly and the front focal plane of the image component. In the two-sided telecentric device, not only the radiation collected by the target optical component assembly is substantially collimated, but also the radiation transmitted from the image optical component to the detector is substantially collimated. The advantage of making the radiation between the image optics assembly and the detector become collimated is to additionally remove stray light.

In various embodiments, the out-of-focus telecentric optical device is a kit that is installed with an additional or existing radiation thermometer in a chemical vapor deposition system. In one embodiment, the telecentric lens device includes an aperture shutter and a radiation front component for collecting the radiation from the target, and the telecentric lens device is adapted to position the aperture shutter at a focal length of the forward optical component assembly. . The operating instructions provided by the manufacturer also teach the user to adjust the orientation of the forward optics assembly to intercept radiation emitted by the target within the chemical vapor deposition reaction chamber. In one embodiment, coupling the telecentric lens device to the radiation detector and/or positioning the aperture shutter at a focal length of the forward optical component assembly is performed by the manufacturer; in other embodiments, the aperture shutter The steps of positioning the focal length of the forward optical component and/or positioning the aperture shutter are described in the manufacturer's instructions.

Dual wavelength pyrometer

The various embodiments disclosed herein also include dual wave constant pyrometers that utilize the out-of-focus telecentric concept to measure radiation in the visible/ultraviolet (UV), visible, and infrared spectra (for purposes consistent with the present invention, or may be referred to as "optical" The visible/ultraviolet (UV) and infrared spectra of the spectrum contain wavelengths from 300 nm to 700 nm, and the "visible" spectrum contains wavelengths from 400 nm to 700 nm, and "infrared" The spectrum contains wavelengths greater than 700 nm to 10,000 nm). A common solution for inferring temperature from radiation temperature measurement is the so-called "proportional" pyrometer, which measures the radiation emitted by the target under two different wavelength bandpasses, and the resulting signal The ratio operates on the principle that the temperatures are related to each other. For a gray body emitter (ie, a target with the same emissivity for two different wavelength bandpasses), the effect of emissivity can be effectively eliminated by the quotient of the ratio, so that the signal The proportional relative (vs) temperature is the same as the blackbody correction. A number of methods have also been developed to correct the temperature indicated by the proportional pyrometer when the target is not gray.

The wavelength bandpasses that are close to each other have a greater probability of having the same emissivity (ie, exhibiting graybody behavior) than the wavelength bandpass that is far apart, the different wavelength bands of the standard proportional pyrometer The flux tends to be fairly close to each other in the electromagnetic spectrum. However, for some procedures, we expect to obtain information from different parts of the wavelength spectrum in order to properly control the program. For example, in order to deposit GaN on a sapphire substrate in an MOCVD reactor, a control procedure is to infer the temperature of the wafer carrier using an infrared photothermometer for primary temperature control; however, since both wavelength bands are generally One of the same electromagnetic states, whether optical or infrared, is not suitable for this purpose.

In the dual wavelength pyrometer embodiment of the present invention, a pair of radiation thermometers are utilized to measure radiation from the same object under observation at different wavelength bandpasses. The center wavelength of the bandpass can be in different parts of the electromagnetic spectrum, with the first of the wavelength bandpass being in the visible/UV spectrum and the second of the wavelength bandpass being in the infrared spectrum. In one embodiment, the center wavelengths of the infrared and optical wavelength bandpass are about 900 nm and 400 nm (eg, 930 nm and 405 nm), respectively. The dual wavelength pyrometer of the present invention combines optical (i.e., visible/UV) and infrared light detectors in a single package so that both measurements can be made through a common view. Therefore, providing optical and infrared Both of the optical radiation measurements do not require the use of two views. Another advantage is that the radiation captured by both optical and infrared light measurements can be simultaneously captured from the same target through the same location on the viewing window, thereby eliminating possible inconsistencies caused by non-simultaneous measurements. Due to different targets and through different viewing windows. The combination of out-of-focus telecentric optical components further reduces the contribution of scattered radiation, thus reducing the bias of temperature measurements.

The dual-wavelength pyrometer device of the portion disclosed herein can optionally include a reflectometer for emissivity compensation; the radiation signal is used to infer knowledge of the need for the emissivity or emissivity compensation value of the target. When the layers accumulate on the wafer in the CVD chamber, the wafer may undergo a substantial and non-monotonic emissivity change, such that the intermittent disruption caused by the different wafer layers is reflected, resulting in reflectivity and emissivity. Periodic variation on the top. Some embodiments of the present invention include a reflection counter of a radiation thermometer having one or two dual-wavelength pyrometers integrated in a radiation thermometer, which can be used to infer the emissivity of the target and provide a solution Correction of the indicated temperature. The combination of the extra-focus telecentric optics reduces the contribution of the scattered radiation, which reduces the bias in determining the emissivity.

Structurally, the disclosed telecentric dual-wavelength pyrometer can include one or more object components for transmitting optical elements from the target of the out-of-focus object, the object component defining a focal length relative to a reference point within the object assembly. . In this embodiment, the first aperture shutter is configured to receive radiation transmitted by the object assembly, the object assembly and the first aperture shutter define a first optical axis through the reference point, and the first aperture shutter is located and referenced The points are separated by a distance that is substantially equal to the focal length of the object assembly to focus the first detected portion of the radiation onto the first aperture shutter. In addition, in this embodiment, the second aperture shutter is configured to receive radiation transmitted by the object assembly, the object assembly and the second aperture shutter define a second optical axis through the reference point, and the second aperture shutter is located With reference point At a distance, the distance is substantially equal to the focal length of the object assembly to focus the second detected portion of the radiation onto the second aperture shutter. A first electromagnetic radiation detector can be provided to detect the first detected portion of the radiation transmitted by the object component through the first aperture shutter. Similarly, we can set a second electromagnetic radiation detector to detect the second radiation transmitted by the object component through the second aperture shutter, the first electromagnetic radiation detector, and the second electromagnetic radiation detector. The detecting part is configured to generate the first signal and the second signal respectively, and infer the temperature of the out-of-focus target.

The telecentric dual-wavelength pyrometer may further comprise a first reflective subassembly comprising a first radiation source and a first beam splitter, the first radiation source being used to generate a first beam of electromagnetic radiation, the first beam splitter for transmitting a portion of the first beam along the first optical axis to illuminate the off-target. The second reflective metering component includes a second radiation source, and may further include a second beam splitter, the second beam source is for generating a second beam of electromagnetic radiation, and the second beam splitter is for The optical axis transmits a portion of the second beam to illuminate the off-target.

In one embodiment, the first detected portion of the radiation is in the infrared spectrum of the electromagnetic radiation, and the second detected portion of the radiation is in the visible spectrum of the electromagnetic radiation. The second detected portion of the radiation may define a wavelength bandpass having a wavelength greater than or equal to 400 nm and less than or equal to 410 nm, and the first detected portion of the radiation may define a wavelength bandpass having a wavelength of 930 nm. A reduced aperture assembly can also be used to reduce the first detected portion of the radiation detected by the first electromagnetic radiation detector and the radiation detected by the second electromagnetic radiation detector One of the second detected portions.

Multichannel pyrometer

Embodiments of the present invention further include a "multi-channel" pyrometer system, It is used to infer the spatial temperature distribution by providing a plurality of out-of-focus telecentric radiometers during the manufacturing process to determine the temperature distribution (profile) of the wafer. We expect a uniform temperature distribution to increase wafer yield. However, the overall temperature of the wafer carrier and wafer is controlled by heating elements. Operators can use various secondary parameters to improve between wafers and single wafers. Temperature uniformity inside. The present invention includes means for measuring the uniformity of wafer temperature. A plurality of radiation thermometers are each positioned to view different targets at different locations on a given wafer, and data from each target can be obtained simultaneously. We can adjust the size of the target to provide nearly complete coverage of the body wafer to infer the temperature distribution across the wafer. A temperature uniformity map can be generated and its accuracy can be improved by utilizing a statistical average of the synchronized data over a selected time interval (e.g., 1 minute). The combination of off-focus telecentric optical elements further reduces the amount of radiation scattered within the reaction chamber, which essentially varies with the position of the target on the wafer. The reduction in the amount of scattered radiation reduces the bias of individual temperature measurements and the resulting temperature distribution.

In still other embodiments of the invention, both multi-channel devices and dual wavelength concepts (and selective reflectance measurement capabilities) are combined in the same system. With this arrangement, the temperature profile can have enhanced accuracy provided by dual wavelength and/or emissivity compensation devices.

Structurally, the present invention discloses a multi-channel pyrometer system for inferring a spatial temperature distribution comprising a plurality of radiation thermometers for observing a plurality of corresponding adjacent out-of-focus targets. Each of the plurality of radiation thermometers includes a first telecentric optical device, the first telecentric optical device comprising more than one optical component for transmitting radiation, the object component defining a focal length relative to a reference point within the object assembly . Each of the plurality of radiation thermometers further includes a first aperture shutter for receiving radiation transmitted by the object assembly. The object assembly and the first aperture shutter are defined by a first optical axis of the reference point, the first aperture shutter being located at a distance from the reference point, The distance is substantially equal to the focal length of the object assembly to focus the first detected portion of the radiation from each of the respective plurality of adjacent out-of-focus targets onto the first aperture shutter. Each of the plurality of radiation thermometers further includes a first electromagnetic radiation detector for detecting a first detected portion of the radiation transmitted by the object assembly through the first aperture shutter. The first electromagnetic radiation detector generates a first signal, whereby the first signal can infer the temperature of each of the plurality of adjacent out-of-focus targets. A plurality of radiation thermometers can be used to view the wafers in the wafer carrier, the wafer carriers being disposed in a chemical vapor deposition reaction chamber in which a plurality of adjacent out-of-focus targets are fully subtended by the wafer. Since the wafer carrier rotates, the situation in which the adjacent target is caught by the wafer periodically occurs.

At least one of the plurality of radiation thermometers can include a first reflectance meter component, the first reflectance meter component including a first radiation source and a first beam splitter, the first radiation source being used Generating a first beam of electromagnetic radiation, the first beam splitter for transmitting a portion of the first beam along the first optical axis to illuminate each of the respective plurality of adjacent out-of-focus targets. The second reflective metering component includes a second radiation source, and may further include a second beam splitter, the second beam source is for generating a second beam of electromagnetic radiation, and the second beam splitter is for The optical axis transmits a portion of the second beam to illuminate each of the respective plurality of adjacent out-of-focus targets. In some embodiments, one or both of the first and second reflectance components utilize a chopper to modulate (or modulate) the first beam. Additionally, at least one of the plurality of radiation thermometers can include a reduced aperture assembly to selectively reduce the first detected portion of the radiation detected by the first electromagnetic radiation detector.

In one embodiment, at least one of the plurality of radiation thermometers of the pyrometer system further comprises a second telecentric optical device and a second electromagnetic radiation detector. The second telecentric optical device comprises a second aperture shutter for receiving radiation from the object component, the object assembly and the second aperture shutter defining a second optical axis passing through the reference point, the second aperture shutter being located at a distance from the reference point The distance is substantially equal to the focal length of the object assembly to focus the second detected portion of the radiation from each of the respective plurality of adjacent out-of-focus targets onto the second aperture shutter. The second electromagnetic radiation detector is configured to detect a second detected portion of the radiation transmitted by the object component through the second aperture shutter and generate a second signal, wherein the second signal can infer a plurality of corresponding signals The temperature of each of the adjacent out-of-focus targets. The first detected portion of the radiation is in the infrared spectrum of the electromagnetic radiation, and the second detected portion of the radiation is in the visible spectrum of the electromagnetic radiation. In one embodiment, a cold mirror is disposed along the first optical axis and the second optical axis, the cold mirror transmitting the first detected portion of the radiation and reflecting the second detected portion of the radiation. The second detected portion of the radiation may define a wavelength bandpass having a center wavelength greater than or equal to 400 nm and less than or equal to 410 nm, and the first detected portion of the radiation may define a wavelength bandpass comprising a wavelength of 930 nm.

Spurious emission control

The operational guidelines of various embodiments are to locally reduce the amount of radiation from surrounding heating elements in the vicinity of the target of the radiation thermometer. In one embodiment, the local reduction in the amount of radiation is achieved by including a low heat flux portion on the surrounding heating element such that the radiant heat emitted by the radiation thermometer is much less than the surrounding heating element at the operating wavelength of the radiation thermometer. The rest (for example, less than 2 orders of magnitude). The low heat flux partially eliminates the radiation emitted by the operating wavelength (e.g., visible/UV spectrum) such that at the operating wavelength of the radiation thermometer, the surrounding heating elements do not locally produce stray radiation. The analysis and experiments in this case have shown that reducing the amount of spectral radiation in the target area of the impending radiation thermometer in this way can significantly reduce the bias caused by stray radiation. error.

In another embodiment, local reduction in the amount of stray radiation is achieved by redirecting radiation originating from a portion of the surrounding heating element. In this embodiment, the deflecting surface deflects the radiation originating from a portion of the surrounding heating element away from the target area of the radiation thermometer and is positioned very close to the surrounding heating element. In this way, the amount of stray radiation can be locally reduced.

In one embodiment, a restraint system for spurious radiation received by a radiation thermometer is disclosed. The limiting system comprises: a chemical vapor deposition (CVD) reaction chamber; a wafer carrier for rotating about a rotating axis, the wafer carrier comprising a top surface, a bottom surface, and an outer edge, the top surface being substantially planar and defining a Target plane. A plurality of heating elements are disposed under the wafer carrier for radiating and heating the bottom surface of the wafer carrier. The plurality of heating elements can comprise a peripheral heating element in close proximity to one of the outer edges of the wafer carrier, the surrounding heating element can substantially surround the remaining heating elements of the plurality of heating elements, or comprise two surrounding surrounding heating elements Above heating element. The surrounding heating element can include a low heat flux portion along a designated portion of the surrounding heating element, the low heat flux portion operating at a substantially reduced temperature relative to the remainder of the surrounding heating element. In one embodiment, the low heat flux portion operates at a temperature that is at least 300 ° C lower than other portions of the heating element that operate at the maximum operating temperature.

In one embodiment, a radiation thermometer is used to view a target that is very close to the "axis of reduced scattered radiation." The axis of the reduced scatter radiation is coplanar with the target object plane and extends from a rotational axis and over the low heat flux portion of the heating element. The low heat flux portion of the surrounding heating element can include an electrical connector.

In one embodiment, the target is located in a rectangular region on the plane of the wafer, the wafer plane including a portion of the axis that reduces the scattered radiation, the rectangular region being extended by a spindle To the outer edge of the wafer carrier and having a width approximately equal to the width of the tangential dimension of the designated portion of the surrounding heating element.

The confinement system can further comprise a cylinder located within the CVD reaction chamber defining a cylindrical axis substantially concentric with the axis of rotation and having an interior surface, an exterior surface, and a top edge. The inner surface defines a cylindrical inner diameter, the outer surface defines a cylindrical outer diameter, and the top edge defines an upper plane substantially orthogonal to the cylinder axis. The wafer carrier can define an outer diameter of the carrier that is larger than the inner diameter of the cylinder of the cylinder. The restriction system can also include a mandrel located within the CVD reaction chamber, the mandrel being concentric with the axis of rotation and having an end portion for coupling with the wafer carrier. In one embodiment, a radiation thermometer is used to detect radiation in the visible/UV portion of the electromagnetic spectrum.

In various embodiments of the invention, different mechanisms are disclosed for reducing scattered radiation emitted by a designated portion of the surrounding heating portion. In an embodiment, the mechanism can include one of a radiation trap and a radiation deflector located adjacent a designated portion of the surrounding heating portion.

In the remaining embodiments, a method of limiting stray radiation received by a radiation thermometer is disclosed in which the target system is located in a chemical vapor deposition reaction chamber. The limiting method includes providing a wafer carrier and heater array for operation in a chemical vapor deposition reaction chamber. The wafer carrier is adapted to rotate about a rotational axis and has a lower surface and a substantially planar upper surface, the upper surface defining a target object plane. The heater array includes a surrounding heating element that includes a low heat flux portion along a designated portion of the surrounding heating element. We also provide operational instructions on tangible media, including the following steps: 设置 Place the heater array in the chemical vapor deposition reactor; ̇ Place the wafer carrier on the heater array in the chemical vapor deposition reactor Square, with the upper surface facing up; ̇ adjust the radiation thermometer to observe the target near the axis of the reduced scatter radiation, the axis of the reduced scatter radiation is coplanar with the target object plane, and extends from the axis of rotation and over the heating element The low heat flux portion.

Other aspects and advantages of the invention will be apparent from the description and appended claims.

Referring to Figure 1, there is shown a curve 10 of the spectral blackbody emission power according to Planck's law at various temperatures; a visible spectral region 12 approximately coincident with a wavelength band of 400 nm to 700 nm is also indicated In Figure 1. Regarding the effect of the previously discussed temperature on the black body emission power at 410 nm, we will mark the first and second reference points 14 and 16 at 1073K and 2073K (corresponding to 800 ° C and 1800 ° C respectively) in Figure 1. in.

Referring to Figures 2 and 3, an embodiment of an MOCVD reactor system 20 utilizing a radiation thermometer 22 is disclosed, wherein the radiation thermometer 22 has an out-of-focus telecentric optical device 24. The MOCVD reactor system 20 includes a reaction chamber 26 operatively coupled to the flow flange 28 to define a housing 30; the flow flange 28 includes a laminar flow plate 31 through which the gas system of the MOCVD system is passed Into the reaction chamber 26. A wafer carrier 32 is disposed within the reaction chamber 26. The wafer carrier 32 has a top surface 34 and a bottom surface 36 and is operatively coupled to a mandrel 38. The top surface 34 defines a wafer pocket 35, and the spindle 38 defines a rotating shaft 40. Each of the wafer pockets 35 is used to place the wafer 41 therein. The body shutter 42 can be inserted into the reaction chamber in a movable manner Aside from the inner wall of 26 and surrounding the wafer carrier 32.

The resistance heating array 44 is disposed below the wafer carrier 32 and is radiantly coupled to the bottom surface 36 of the wafer carrier 32. The resistive heating array 44 can include a surrounding heating element 45 and can be surrounded by a cylinder 46 or a reflective plate 48 for bonding to enhance radiant coupling between the resistive heating array 44 and the wafer carrier 32.

The radiation thermometer 22 is mounted on top of the flow flange 28 and is oriented such that the top surface 34 of the wafer carrier 32 is viewed through the viewing window 52. In an embodiment, the viewing window 52 is disposed in a recess 54 that can be actively cooled.

The out-of-focus telecentric optical device 24 includes a first or forward optical component assembly 62 (referred to herein as an "object assembly" 62) and a second or rearward optical component assembly 64 (herein referred to as "image" Component "64). The object assembly 62 is characterized by having an effective radius dimension 65 (Fig. 4), i.e., the object assembly 62 is effective to transmit radiation to the largest radius dimension of the aperture shutter 66.

The aperture shutter 66 is located between the object assembly 62 and the image assembly 64. In one embodiment, the object assembly 62 and the image assembly 64 and the aperture shutter 66 are concentrically arranged along an optical axis; the optical axis 68 is the axis that is transmitted by the radiation detected by the radiation thermometer 22. The optical axis 68 can be straight, as exemplified herein; or can be meandering, such as when transmitting radiation using a planar or concentrating mirror. The optical axis 68 can be at the center of the out-of-focus target 72 and is characterized by an out-of-focus target region 74. The radiation thermometer 22 also includes a detector 76 for detecting electromagnetic radiation.

It should be noted that for the purposes of the present invention, an "optical component" can include a plurality of optical components (as shown) or can comprise a single component, such as a single lens. Although the optical components exemplified herein contain lenses, it should be understood that other components can be used to complete the radiation transmission. Loss, such as a focusing mirror or fiber bundle.

In one embodiment, the orientation of the radiation thermometer 22 is adjusted such that the optical axis 68 is substantially perpendicular to the top surface 34 of the wafer carrier 32 (FIG. 2). In another embodiment, the orientation of the radiation thermometer 22 is adjusted such that the optical axis 68 is at an acute angle relative to the direction of the top surface 34 of the vertical wafer carrier 32 (Fig. 3). In one embodiment, a light trap 82 is placed in a mirrored angle of the optical axis 68 in three dimensions (FIG. 3); in other words, the light trap 82 is set to be opposite Subreflecting the reflection from the optical axis 68 of the hypothetical reflective surface at the top surface 34 of the wafer carrier 32.

The out-of-focus telecentric optics 24 of the radiation thermometer 22 will now be described in greater detail with reference to FIG. The object assembly 62 is characterized by having a focal length F1 that is measured by a reference point 84 on the optical axis 68 on or in the object assembly 62. The "focal length" is the distance at which the ray is focused by the object assembly 62 from the reference point to the parallel optical axis 68. In the case of the out-of-focus telecentric optical device 24, the aperture shutter 66 is located at this convergence point, i.e., at the focal length F1 of the object assembly 62.

The illustrated out-of-focus telecentric optics 24 further has distances L1 and L2, L1 is the distance between the image component 64 and the aperture shutter 66, and L2 is the distance between the image component 64 and the detector 76. The aperture shutter 66 is also characterized by having a major dimension, where "major dimension" refers to the diameter of the circular aperture or the largest dimension of the non-circular aperture (e.g., the diagonal of the rectangular aperture).

In one embodiment, the distance L1 is substantially equal to the focal length of the image component 64 such that the radiation transmitted by the image component 64 to the detector 76 is substantially collimated, and the device is referred to herein as "bilateral". ) telecentric optical device. In a bilateral telecentric optical device, not only is the radiation collected by the object assembly 62 substantially collimated, but the radiation transmitted by the image component 64 to the detector 76 is also substantially collimated (as shown). Radiation that will be transmitted by image component 64 to detector 76 One of the advantages of collimation is the elimination of extra stray light. Such stray radiation may result from the surface of the various optical components in the system and the off-axis radiation entering the radiation thermometer 22. The radiation between the image component 64 and the detector 76 is collimated to resist radiation entering the image component 64 at an angle that is not parallel to the optical axis 68.

In one embodiment, the distance L2 can also be substantially equal to the focal length of the image component 64; however, in bilateral telecentric optics, L2 is not limited to any particular size.

The beam 88 is characterized by a cluster of rays comprising a central or "primary" ray 92, all derived from an infinitesimal point 94 on the target 72. The beam 88 contains all of the rays originating from an infinitesimal point 94 within a solid angle 96 centered at the main ray 92, which is parallel to but offset from the optical axis 68. Each of the infinitesimals 94 within the target region 74 emits the same beam of rays that are received by the object assembly 62.

The solid angle 96 is a function of the primary dimension 86 and the target distance L3, and L3 is the distance from the foremost surface 95 of the object assembly 62 to the target 72. The smaller the solid angle 96 of the beam 88, the closer the rays in the beam 88 and the optical axis 68 will be parallel, and the more stray light can be removed. For a given target distance L3, the smaller the main dimension 86, the smaller the solid angle 96. Moreover, for a major dimension 86 of a given aperture shutter 66, a longer target distance L3 would provide a smaller solid angle 96 to enhance the removal of stray light. In general, the target distance L3 does not have a specific size due to the out-of-focus, parallel ray gathering, and the non-limiting embodiment of the target distance L3 of the MOCVD reaction chamber is less than 2 meters. In one embodiment, the target distance L3 is substantially the focal length of the object assembly 62, which functions to substantially focus the predetermined beam 88 as a predetermined beam 88 passes through the aperture shutter 66, as shown in FIG. In an embodiment, the target distance L3 is an order of 200 mm to 300 mm (eg, 250 mm).

The radiation thermometer 22 can optionally be provided with a reduced size aperture assembly 97 and/or a shutter assembly 98. In one embodiment, each of the reduced size aperture assembly 97 and the shutter assembly 98 can include a plate 99 mounted to the actuator 100. In the case of a reduced size aperture assembly 97, the plate 99 includes an aperture 101 having a reduced size relative to the aperture of the aperture shutter 66 to interfere with at least the major dimension 86 of the aperture shutter 66. On the other hand, the plate 99 of the shutter assembly 98 is a blank.

In operation, the plate 99 can be independently disposed to not contact, or partially or completely block, radiation that passes through the aperture shutter 66. With respect to the reduced size aperture assembly 97, when the aperture 101 is in the deployed position, it can be centered on the optical axis 68, thereby partially blocking radiation and reducing the effective aperture of the radiation thermometer 22. In the case of the shutter assembly 98, switching the plate 99 from the standby position to the deployed position completely blocks the target radiation from reaching the detector 76. Both the reduced size aperture assembly 97 and the shutter assembly 98 are shown in expanded form in FIG. In an embodiment, the aperture 101 has a diameter in the range of 1-12 mm.

Functionally, a reduced size aperture assembly 97 can be installed to avoid saturation of the detector as temperature increases. As noted above, the blackbody spectral emission power can be increased by orders of magnitude, especially in the visible/UV spectrum. We can utilize the reduced size aperture assembly 97 to reduce the amount of radiation reaching the detector 76, thereby avoiding saturation. Similarly, the shutter assembly 98 can be utilized to protect the detector 76 from damage in extreme radiation conditions.

The illustrated actuator 100 is a rotary actuator that rotates the plate 99 into the optical shaft 68 when in the deployed position and rotates the plate 99 away from the optical shaft 68 when in the standby position. It should be understood that this exemplary device is not limiting, and that we can mount a number of actuators of any type, including mobile devices that can move the plate 99 linearly into or out of the optical path, or for active control. Adjustable aperture (iris) device with aperture size.

Those skilled in the art will recognize that there is a trade-off between the size of the desired solid angle 96 and the size of the target region 74 that achieves a predetermined signal to noise ratio; in other words, for a given target distance L3, a smaller stereo An angle 96 (e.g., a smaller major dimension 86) can be used for the larger target area 74, such that the stray radiation is typically enhanced to remove, whereas the smaller target area 74 requires a larger solid angle 96 (e.g., a smaller primary Size 86). The target size is limited by other factors, including the size of the viewport 52, the effective radius dimension of the image component 64, and the desired field of view of the target 72 on the wafer carrier 32. Therefore, in the case of a smaller target area 74 requiring a major size 86 of the larger aperture shutter 66, in the case of a shorter target distance L3, the stray light removal measure of the out-of-focus telecentric optical device 24 may become invalid.

In certain non-limiting embodiments, the aperture size shutter 66 has a major dimension 86 of the component assembly 66 having an effective radius dimension of less than about 1/3. In one embodiment, the major dimension 86 of the aperture shutter 66 is in the range of 1 mm to 20 mm.

With respect to the target of a typical crystal growth material, the inter-reflected radiation that is specularly reflected by the target 72 has a strong reflection component; in other words, most of the radiation incident on the surface of the crystal growth structure will Reflect at the same angle as the angle of incidence. Thus, an unbalanced amount of stray radiation entering a standard radiation thermometer (i.e., without a telecentric optical device) is reflected away from the target 72 at an angle that is not parallel to the optical axis 68, thereby reducing the beam 88. The solid angle 96 also substantially reduces the amount of stray radiation.

Consider the orientation of the radiation thermometer 22 in Figure 2. The radiation reflected by the target 72 into the radiation thermometer 22 should have been reflected or reflected by the viewing window 52. A viewport (window) 52 can be used to reduce the amount of radiation reflected there, for example by using an anti-reflective coating and/or A viewing window 52 that can be actively cooled is disposed within the recess 54 to limit the amount of radiation incident on the viewing window 52.

Consider the orientation of the radiation thermometer 22 in Figure 3. The optical trap 82, as generally described and arranged as shown in FIG. 3, has the function of capturing radiation that would be incident on the target 72 at the specular angle of reflection of the optical axis 68; as described above, the anti-reflection within the recess 54 is utilized. The window, light trap 82 can also be used to limit the mutual reflection of radiation to be transmitted to the target 72.

To demonstrate the theory of operation of the telecentric telecentric optics 24, we utilized the Advanced System Analysis Program (ASAP) and the 3D ray tracing program (ASAP) provided by Breault Research Organization, Inc., Tucson, Arizona, USA. Three dimensional ray tracing program), which simulates the geometry and operating conditions of the outer casing 30 substantially as shown in FIG. 2 and described herein. The ASAP model is executed to identify stray radiation paths and analyze stray radiation entering the viewing window 52. We set the surrounding heating element 45 to a radiation source operating at 1800 ° C, and model the wafer carrier 32 (modeled to include wafers in the wafer pocket 35) into a radiation source and scattering medium at 800 ° C. Both. It is assumed that the wafer pocket 35 carries a wafer 41 having an emissivity of 0.8 at the wavelength of interest. Based on Planck's law, the black body emission power of the radiation source is established at a wavelength of 405 nm, and the inner wall of the outer casing 30 (including the body block) The door 42, the laminar flow plate 31, and the viewing window 52) are modeled as a scattering medium.

The radiation thermometer 22 is modeled for two different concentrating optical elements: a "standard" optical device having a target diameter of 10 mm at a 1:1 magnification; and an off-focus telecentric optical device as described herein, having A target diameter of about 30 mm. Comparing the amount of 405 nm radiation emitted by the target 24 and directly entering the radiation thermometer 22 ("signal radiation") with the radiation thermometer 22 ("stray radiation") which reflects each other inside the casing 30 and enters each optical device (405 nm) radiation The amount is shown in Table 1.

ASAP predicts that for a radiation thermometer using standard optical components, at a wavelength of 405 nm, about 70% of the radiant flux on the detector is due to stray radiation; however, using the extra-focus telecentric optics 24 The stray radiation contribution was reduced to 39%. The stray light contribution causes temperature errors of about 41 ° C and 16 ° C, respectively; in other words, the temperature measurement of the out-of-focus telecentric optical device 24 is almost 2/3 smaller than that of the standard lens system.

Referring to Figures 5 and 5A, we also verify the out-of-focus telecentric optical device 24 experimentally. For this experiment, the MOCVD reactor system uses a flow extender 104 that extends over the top surface of the wafer carrier 32 and is attached to the upper end 106 of the body door 42 by a connector 108. . Flow spreaders can be used to improve the thermal characteristics of the flow and crystal growth environment, but the propensity to observe the stray radiation signals received by the wafer carrier 32 and the radiation thermometer 22 of the wafer 41 is also greatly increased. The reactor system operates with the wafer carrier (the GaN crystal growth material on the wafer contained in the wafer pocket) at about 800 ° C for an extended period of time, so that the thermal environment inside the enclosure is in a steady state (quasi-steady State) (Also even MOCVD reaction The components of the system are thermally saturated). After the power is supplied to the resistance heating array, the first measurement is performed using a radiation thermometer; then, the power supply to the resistance heating array is cut off, and the second measurement is performed using the radiation thermometer within a ten second period. At a wavelength of 405 nm, the stray radiation from the resistive heating array stops almost immediately upon power cut off, however due to the thermal capacitance of the target, the target continues to emit radiation at substantially the same transmit power as before the power supply was stopped. Therefore, it is assumed that the first measurement includes the stray radiation component from the resistance heating array at a wavelength of 405 nm, and the second measurement is no. We conducted experiments on both standard optical pyrometers using standard in-focus optics and radiation thermometers using extra-focus telecentric optics 24, both of which operate normally at 405 nm. The results are shown in Table 2.

The measurement results show that for a radiation thermometer using standard optical components, at the wavelength of 405 nm, about 64% of the radiant flux on the detector is due to stray radiation; on the other hand, the extra-focus telecentric optical device is used. 24 reduces the stray radiation contribution to approximately 31%. These stray light quantities cause temperature errors of about 34 ° C and 12 ° C, respectively, and the temperature measurement bias of the out-of-focus telecentric optical device 24 is again about 2/3 smaller than that of the standard lens system.

In one embodiment, the detector 76 includes a photon counter (ie, a photomultiplier tube) having a cutoff wavelength of 700 nm, so it is insensitive to infrared radiation. Therefore, the use of PMT as a detector greatly eliminates the suspicion of improper filtering in the infrared portion of the spectrum identified by the Zettler case. The PMT can be filtered by the filtering device 102, and only the wavelengths in the blue, violet, or ultraviolet regions are detected.

Another advantage of PMT is that it provides a fast time response, which is one of the considerations for CVD chambers that utilize high speed wafer carriers, such as those manufactured by Veeco Instruments, Somerset, New Jersey, USA. TURBODISC system. A general description of the TURBODISC system can be found in "Reactor Design Optimization Based on 3D CFD Modeling of Nitrides Deposition in MOCVD Vertical Rotating Disc Reactors" published by Mitrovic et al., June 2005 (available at http://www.wpi.edu) /C/C/IV/Mitrovic.pdf) in /academics/che/HMTL/CFD. Such a high speed system may require a pick rate of 10 kHz for data from the radiation detector 76, which PMT can provide.

Non-limiting examples of spectra transmitted by the filtering device include a central wavelength in the range of 380 nm to 420 nm and a band width (full width at half maximum) in the range of 10 nm to 70 nm. In an embodiment, the filtering device 102 further includes a band pass filter that combines the colored glass filters. A non-limiting example of a filter combination is a 10BPF25-400 bandpass filter from Newport (center wavelength 400±3.5 nm; half-full full amplitude 25±3.5 nm) with FGB25 from Thorlabs A colored glass filter (local cutoff wavelength of 400 nm), which is combined to define a primary band pass, allows for the passage of a nominal bandpass radiation between 390 nm and 420 nm.

In one embodiment, a non-limiting example of the components and layout of the out-of-focus telecentric optical device 24 includes that the object assembly 62 is a plano-convex lens that includes a diameter of 50.8 mm and a focal length of 249.2 mm (eg, Available from Thorlabs' LA1301-A), the lens is located 249.2 mm (F1) from the aperture shutter 66; the image assembly 64 is a plano-convex lens containing a diameter of 25.4 mm and a focal length of 75.0 mm (plano-convex Lens) (e.g., LA1608-A from Thorlabs, Inc.) located 75 mm (L1) from the aperture shutter 66 and 75 mm (L3) from the detector. In another embodiment, the object assembly 62 further comprises an Acrosand (achromatic) achromatic doublet having a diameter of 50.8 mm and a focal length of 100 mm (eg, AC508-100 from Thorlabs). A), which combines the above-mentioned plano-convex lenses to shorten the focal length F1 of the object assembly to about 87 mm while shortening the overall length of the assembly. In this latter device, an Eckromand doublet having a shorter focal length (e.g., 30 mm) can be used, for example, as the image component 64 to be closer to the aperture (e.g., AC254-030-A from Thorlabs). ).

The lenses in the above reference examples may comprise any material suitable for transmitting radiation in the visible/UV spectrum of the electromagnetic spectrum, such as borosilicate glass, barium fluoride and molten vermiculite; It is coated with an anti-reflective coating.

Alternatively, the extra-focus telecentric optics 24 disclosed herein may be combined using other filtering devices and techniques. For example, a detector and a filtering device Zettler can be installed. In some embodiments, a water-cooled CCD or a solid state detector such as an avalanche photodiode may be used.

In operation, the wafer carrier 32 rotates about the axis of rotation 40 while being heated by the radiation of the heating array 44. The rotational speed of the wafer carrier 32 about the axis of rotation 40 can be substantially determined The operating parameters and design criteria of the MOCVD reactor system 20 are varied.

The radiation thermometer 22 and the out-of-focus telecentric optical device 24 are not limited to systems in which a heating source other than a resistive heater is provided. The present invention may include various embodiments, such as some CVD reactor systems may use a microwave heating source. .

Referring to Figures 6A and 6B, there are illustrated multi-channel devices 110 and 111 for detecting spatial temperature variations on wafer 41 in accordance with one embodiment of the present invention. In the illustrated embodiment, the plurality of radiation thermometers 22a, 22b, and 22c that make up the extra-focus telecentric optics 24 are adapted to simultaneously observe the wafer 41 as the wafer 41 is rotated through the viewing window 52. Individual targets 72a, 72b and 72c. The plurality of radiation thermometers 22a, 22b, and 22c may be arranged such that when the wafer carrier 32 is rotated about the rotational axis 40 to a predetermined orientation, all of the targets 72a, 72b, and 72c may be aligned by the wafer 41 ( Subtend).

In one embodiment, the plurality of radiation thermometers 22a, 22b, and 22c are arranged such that the targets 72a, 72b, and 72c are concentrated along a line 112 extending substantially along the radius coordinate R, the radius coordinate R being It extends radially outward by the rotating shaft 40 and passes through the center of the wafer 41 (Fig. 6A). In another embodiment, the plurality of radiation thermometers 22a, 22b, and 22c are arranged such that the targets 72a, 72b, and 72c are along a line 114 that is substantially perpendicular to the radius coordinate r and passes through the center of the wafer 41. Concentration (Figure 6B). Still other embodiments may define other patterns, such as the formation of a non-linear type of object, or the object being aligned along a line defining an acute angle with respect to the radial coordinate r.

Referring to Figure 6C, a multi-channel cluster 120 of radiation thermometers 22a-22e for measuring the morphology of targets 72a-72e is illustrated. Multi-channel cluster 120 can provide two-dimensional information about the temperature distribution of wafer 41 along lines 112 and 114, for example.

The various embodiments illustrated in Figures 6A-6C can achieve a "blue" wavelength centered at a wavelength range of, for example, 400 nm to 410 nm (e.g., 405 nm). In one embodiment, a plurality of radiation detectors (eg, radiation thermometers 22a-22c of FIG. 6A) use a single pedestal for the radiation concentrating lens, shutter/aperture, filter, and detector lens to provide A denser design with better spatial resolution. In one non-limiting embodiment, target 72 (as shown in Figures 6C-72e) can be 11 mm x 22 mm and still provide an appropriate signal to noise ratio. This configuration of leaving a space of 1.5 mm to 10 mm between the targets allows us to have a density of the radiation thermometer 22 or less at a diameter of about 104 inches per wafer (i.e., for 3) The 吋 wafer has a column of three thermometers, one column of six thermometers for 6 吋 wafers, one column of eight thermometers for 8 吋 wafers, etc., using a column of radiation thermometers 22.

The output signals from the radiation thermometers 22a, 22b and 22c can be obtained and stored on the data acquisition system 115. In one embodiment, the data capture system 115 includes: a signal processor 116 that adjusts and digitizes signals from the radiation thermometers 22a, 22b, and 22c; a memory device 117 that stores digital data; and a controller 118, such as a computer. The time-correlation signal data from each of the radiation thermometers 22a, 22b, and 22c can be retrieved and stored in the memory device 117. Controller 118 can also perform tasks immediately, such as converting signal data to temperature, calculating average and standard deviation, and plotting temperature profiles of wafer 41 and/or wafer carrier 32. Although the data capture system 115 is drawn for use in the structure of Figure 6A, it can be used with any of the radiation thermometers described herein. Moreover, various systems that are available to those skilled in the art are also suitable for data retrieval.

The data retrieval system 115 can also be used to synchronize the data stream when the data acquired by a given wafer 41 is properly positioned relative to the radiation thermometer. with The stepping enables the correlation portion corresponding to the data stream received when observing, for example, the objects 72a, 72b, and 72c, can be extracted, and the relevant portions of the data stream can be averaged for a period of time for statistical purposes. deal with. In one embodiment, the synchronization and statistical processing of the data is done on the fly. An example of a synchronizing routine is disclosed in U.S. Patent No. 6,349,270 ("Gurary") to Gurary et al.

Referring to Figures 7A and 7B, an MOCVD reactor system 220 utilizing a radiation thermometer 222 for viewing a target 224 within the MOCVD reactor system 220 is illustrated. The MOCVD reactor system 220 includes a reaction chamber 226 operatively coupled to the flow flange 228 to define a housing 230. The flow flange 228 includes a laminar flow plate 231 through which the gas used in the MOCVD process is passed through the laminar flow plate 231. In chamber 226. The wafer carrier 232 is disposed in the reaction chamber 226. The wafer carrier 232 has a top surface 234 defining a target object plane 233. The target 224 of the radiation thermometer is disposed substantially on the target object plane 233; the top surface is also defined. To support the wafer pocket 235 of the substrate or wafer 237. Wafer carrier 232 also includes a bottom surface 236 and is operatively coupled to a mandrel 238 defining a rotational axis 240. The body door 242 can be removably inserted into the inner wall of the adjacent reaction chamber 226 and surround the wafer carrier 232.

The heater array 244 is located below the wafer carrier 232 and is radiantly coupled to the bottom surface 236 of the wafer carrier 232. The heater array 244 can be surrounded by a cylinder 246 and can also be constrained below by the filament mounting plate 248 to enhance the radiative coupling between the heater array 244 and the wafer carrier 232. The cylinder 246 defines a cylindrical axis 250 that is substantially concentric with the axis of rotation 240.

The radiation thermometer 222 is mounted over the flow flange 228 and is positioned to view the top surface 234 of the wafer carrier 232 through the viewing window 252. In an embodiment, the viewing window 252 is located in a recess 254 that can be actively cooled.

The heater array 244 can include a peripheral heating element 264, which is so named since the surrounding heating element 264 defines the periphery of the heater array 244. Although the surrounding heating element 264 described herein is a single heating element, it is contemplated that the surrounding (outermost) heating element is comprised of two or more heating elements.

To promote uniform heating, the surrounding heating elements 264 in the illustrated embodiment are located proximate the interior surface 266 of the cylinder 246. The plurality of rays 268 are depicted as being emitted from the surrounding heating elements, internally reflected within the outer casing 230, and entering the radiation thermometer 222.

Referring to Figure 8, there is shown an area near the top edge 272 of the cylinder 246 and the outer edge 274 of the wafer carrier 232 in one embodiment. A gap 276 is defined between the outer edge 274 and the top edge 272 to enable the wafer carrier 232 to freely rotate. The rays 268a, 268b, and 268c, which are illustrated as being emitted by the surrounding heating element 264, represent three types of radiation exiting the gap 276: the ray 268a represents direct radiation that is not reflected away from the gap 276; the ray 268b represents scattering from the interior of the cylinder 246. Surface 266 and radiation from outer edge 274 of wafer carrier 232; ray 268bc represents radiation that scatters away from bottom surface 236 of wafer carrier 232 and filament mounting plate 248.

In operation, wafer pocket 235 can be loaded with substrate 237 (eg, sapphire). The wafer carrier 232 rotates about the rotating shaft 240 and the heater array 244 heated to a temperature of about 1800 ° C, and the gas is introduced through the laminar flow plate 231 to form a crystalline growth material (eg, GaN) on the wafer carrier 232, including Wafer pocket 235 and any substrate 237 contained therein. During the operation, the temperature of the crystal growth material was 800 ° C.

The operating conditions of the outer casing 230 as shown in Figs. 7A and 7B are modeled using a three-dimensional ray tracing program. A ray tracing model is performed to identify the stray radiation path and analyze the stray radiation entering the viewing window 252. Assuming that the surrounding heating element 264 is continuous and set to operate at 1800 Radiation source at °C temperature. Wafer carrier 232 (modeled to include wafer 237 in wafer pocket 235) is modeled as both a radiation source and a scattering medium at 800 °C. According to Planck's law, the black body emission power of the radiation source is established at a wavelength of 405 nm. The inner wall of the outer casing 230 (including the body shutter 242, the laminar flow 231, and the viewing window 252) is also simulated as a scattering medium.

The radiation thermometer 222 at two different locations is modeled: the "outer" position, at the center of the outermost wafer pocket 235 near the radius R (see Figure 7A); the "intermediate span" position, at the outer position About (2/3) R between the rotating shafts 240. The amount of 405 nm radiation emitted by the target 224 and directly entering the radiation thermometer 222 ("signal radiation") is inter-reflected in the outer casing 230 and enters the radiation thermometer 222 ("stray radiation"). The amount of 405 nm radiation was compared and the results are shown in Table 3.

The ray tracing model predicts that for a peripheral annular heating element 264 that forms a continuous loop and a radiation thermometer 222 that is concentrated at an external location, about 97% of the radiant at a wavelength of 405 nm is detected on a detector of a standard radiation thermometer. The amount is attributed to stray radiation. In the middle position, we predict that stray radiation contributes about 70% of all signals, and these stray radiation contributions cause temperature errors of approximately 127 ° C and 41 ° C, respectively. Furthermore, the results of the ray tracing model indicate that the detection of the radiation thermometer About 92% of the stray radiation from the detector is derived from the scattered radiation exiting the bottom surface 236 of the wafer carrier 232 and the filament mounting plate 248 (shown as ray 268c in Figure 8).

Referring to Figure 9, a heater array 244a including an internal heating element 304 and an ambient heating element 264a is illustrated in an embodiment. Flow flange 228 and wafer carrier 232 are removed in this figure to clearly show the layout of heater array 244a; mandrel 238, body stop 242, and filament mounting plate 248 are also visible in this figure. Heating elements 264a and 304 include electrical connectors 306 and 308, respectively.

The electrical connector 306 occupies the arcuate section 310 of the surrounding heating element 264a, the resistance of the arcuate section 310 has been substantially reduced compared to other isometric arcuate sections of the surrounding heating element; in other words, the arcuate section 310 constitutes ambient heating A low heat flux portion 312 of element 264a. The electrical connector 306 operates at a substantially reduced temperature compared to the high resistance portion of the surrounding heating element 264a, for example, in a non-limiting embodiment, the surrounding heating element 264a is at a maximum operation nominally 2000 °C. Operating at temperature. Under this operating condition, but the electrical connector 306 is operated at about 1500 ° C, and the nominal temperature across the arc segment 310 is set to below 1700 ° C, or a higher resistance portion than the surrounding heating element 264a. Low at least 300 ° C. Thus, in terms of operating temperature, the low heat flux portion 312 (i.e., electrical connector 306) of the surrounding heating element 264a operates at a temperature substantially lower than the remainder of the surrounding heating element 264a, causing a low heat flux at a wavelength of 405 nm. The amount of radiation of the amount portion 312 is about 2 orders of magnitude lower than the high resistance portion of the surrounding heating element 264a (see Figure 1).

The internal heating element 304 of the heater array 244a can be configured such that the first half length 314 is within the first semicircle and the second half length 316 is within the second semicircle. Thus, a discontinuous section 318 is located between the first half length 314 and the second half length 316, both of which are electrically connected only to the mandrel 238. One of the devices 308 is connected at a position.

An experiment was conducted at a wavelength of 405 nm to determine the relative contribution of the amount of stray radiation from the surrounding heating element 264a as compared to the heater array 244a as a whole. Internal heating element 304 and surrounding heating element 264a are fully powered and controlled to maintain wafer carrier 232 at a steady state temperature approaching 800 °C, as is done in normal crystal growth operations. Next, the power supplied to the surrounding heating element 264a is limited such that the surrounding heating element 264a operates only at about half the capacity, but the control system can still heat the wafer carrier 232 at or near 800 °C. In this manner, the amount of radiation at the 405 nm wavelength of the surrounding heating element 264a can be reduced to a negligible extent while the wafer carrier 232 is essentially maintained at a temperature near 800 ° C, and the internal heating element 304 is actually higher. Operating at temperature to compensate for the reduced heat input from the surrounding heating element 264a. Next, the power supplied to the surrounding heating element 264a is also limited to about half the capacity, measured with a radiation thermometer under all three operating conditions, and the third condition is applied immediately after limiting the capacity of the internal heating element 304 (peripheral heating) Both element 264a and internal heating element 304 are at half capacity). Based on these measurements, we determine that the ambient heating element 264a contributes between 80% and 90% of the stray radiation received by the radiation thermometer 222. Thus, it was verified that only the radiation originating from the surrounding heating element 264 needs to be modeled without the simplification of the entire heater array 244 of Figure 7A.

I have thus developed a theory that since this large portion of stray radiation is derived from the surrounding heating element 264, we can locally control the stray radiation by locally limiting the radiation emission from the surrounding heating elements. In other words, if the target 224 of the radiation thermometer 222 is fixed to the area of the target plane 233 that is very close to the area of the surrounding heating element 264, and the radiation emitted by the surrounding heating element 264 has been substantially reduced, captured or transmitted. And dissipate, it should be reduced by the spoke The stray radiation received by the thermometer.

The following people conducted spurious radiation detection experiments to test this theory. The radiation thermometer 222 is used to detect electromagnetic radiation of a narrow bandpass that is 405 nm across the nominal center, and the second, ie, infrared radiation thermometer 320 (Fig. 7A) is used to detect the cross-track. The center is 900 nm band-pass electromagnetic radiation. As previously mentioned, at 405 nm, the change in spectral blackbody emission power is extremely sensitive to temperature changes (reference symbols 14 and 16 of Figure 1), and therefore, a radiation thermometer 222 for detecting radiation at 405 nm, It is also extremely sensitive to stray radiation originating from the surrounding heating element 264. However, at a wavelength of 900 nm (again with reference to Figure 1 and Planck's law), in the temperature region of interest (nominally 2100K), at 900 nm, the change in spectral blackbody emission power is extremely sensitive to temperature changes (see Figure 1 for reference). Symbol 322). Thus, the infrared light radiation thermometer 320 operating at 900 nm is substantially less sensitive to stray radiation originating from the surrounding heating elements, and is therefore more sensitive to changes in the temperature of the wafer carrier 232 (nominally at 1100K; see Reference symbol 324) of Figure 1.

Therefore, the stray radiation detection experiment is based on the temperature indicated by the detector sensitive to stray radiation (radiation thermometer 222) and the reference device insensitive to stray radiation (infrared radiation thermometer) 320) Comparison of the indicated temperatures.

Referring to Figure 10, a typical stray radiation signature 330 is illustrated. The stray radiation characteristic 330 is based on a comparison of the infrared light temperature signal 332 and the optical (or "blue light") temperature signal 334, wherein the infrared light temperature signal 332 is generated by the infrared light radiation thermometer 320, and the optical temperature signal 334 is detected by the infrared light. A radiation thermometer 222 that measures radiation at a nominal wavelength of 405 nm is produced. For the data shown in FIG. 10, both the radiation thermometer 222 and the infrared radiation thermometer 320 observe the target position at a similar position on the target plane 233 (ie, from the axis of rotation 240). Similar to the radius). Further, the data in Fig. 10 has been normalized so that the initial temperatures shown in the initial cooling period (the first zone I of Fig. 10) have the same trajectory.

For stray radiation detection experiments, the MOCVD reactor system 220 is used to cause the wafer carrier to reach a first control temperature. Next, we adjust the control temperature downward to a set point temperature below one of the first elevated temperatures. As shown by temperature signals 332 and 334, the first zone I of the stray radiation feature 330 indicates that the wafer carrier 232 exhibits a steady drop in cooling, and when the temperature controller of the MOCVD system 220 establishes a control balance at the lower set point temperature, The second zone II of the stray radiation signature 330 illustrates the response of the temperature signals 332 and 334.

During the above procedure, the infrared light temperature signal 332 substantially follows the true temperature profile (change) of the wafer carrier; in other words, in the second region II of the stray radiation feature 330, the true temperature of the wafer carrier 232 is experienced first. A progressive inflection 336 followed by a substantially monotonic rise 338. The progressive recursion 336 and the monotonically rising 338 phenomenon on temperature are the result of the thermal mass of the wafer carrier 232.

However, the optical temperature signal 334 is characterized by a sharp recursion 342 in the second region II of the stray radiation signature 330 and a subsequent substantial overshoot 344 and a slight deficiency (lower difference) before reaching the control equilibrium temperature 348. ) (undershoot) 346. The optical temperature signal 334 is a convolution of the signal emitted by the wafer carrier 232 and the stray radiation incident on the target object 233 target 224 and reflected into the radiation thermometer 222, overshoot 344 and the low difference 346 is a characteristic of the proportional gain temperature profile experienced by heater array 244 in response to a new set point. Since the optical temperature signal 334 is dominated by the stray radiation component, as predicted by the ray tracing model, it is believed that the optical temperature signal 334 closely follows the control temperature profile of the heater array 244. Track).

Therefore, we can quantitatively determine whether the radiation received by the radiation thermometer 222 has a component of strong scattered radiation. The temperature signal following the contour similar to the infrared light temperature signal 332 (the progressive recursion with monotonous rise) is not dominated by the scattered radiation, but follows a contour similar to the optical temperature signal 334 (with a sharp overshoot of substantial overshoot) The temperature signal is dominated by scattered radiation.

Referring to Figure 11, the objects 224a, 224b, 224c, and 224d are observed at a number of different locations on the target object plane 233 by utilizing a radiation thermometer 222 that is again used to detect radiation at a nominal wavelength of 405 nm. Perform spurious radiation detection experiments. Although FIG. 11 depicts the exposed heater array 244a, it should be understood that during the spurious radiation detection experiment, the wafer carrier 232 is positioned at the proper location and operates in a rotational mode. Thus, FIG. 11 illustrates the orientation of heater array 244a with respect to target 224a-224d falling on target plane 233 above heater array 244a.

In order to test the theory that the low heat flux portion of the surrounding heating element 264a is reduced, the heater array 244a is arranged such that the low heat flux portion 312 approaches the targets 224a and 224b and approaches the target 224c and The portion of the surrounding heating element 264a of 224d is a continuous portion 350 and has a high heat flux. Although the targets 224a and 224d are diametrically opposed, both are at a radial distance of about 195 mm (7.68 吋) from the axis of rotation 240. Similarly, although the targets 224b and 224c are diametrically opposed, both are at a radial distance of about 142 mm (5.6 吋) from the axis of rotation 240.

Referring to Figures 12A and 12B, the results of the test are shown. The optical temperature signals 352 and 354 of Figure 12A are obtained from the targets 224a and 224d, i.e., at the outer radial position. note: The optical temperature signal 354 obtained at a continuous, high heat flux portion near the surrounding heating element 264a has a high profile profile of the stray radiation component (with a sharp reversal 342a of the overshoot 344a). However, the optical temperature signal 352 obtained at a low heat flux region 312 near the surrounding heating element 264a has the same temperature profile characteristics as the infrared light radiation signal 332 of FIG. 10 (a progressive recursion 336a with a monotonous rise 338a at temperature) .

With respect to Figure 12B, optical temperature signals 356 and 358 are obtained from targets 224b and 224c at intermediate span positions, respectively. The optical temperature signal 358 obtained at a mid-span position near the continuous, high heat flux portion of the surrounding heating element 264a also has a high profile profile of the stray radiant flux (with a sharp overshoot 342b of the overshoot 144b) However, the optical temperature signal 356 obtained at a mid-span position near the low heat flux region 312 of the surrounding heating element 264a has the same temperature profile characteristics as the infrared light radiation signal 332 of FIG. 10 (having a monotonous rise 338b in temperature) Progressive recursion 336b).

Thus, on the target plane 233, its self-rotating axis 240 extends in the radial direction and over the center of the low heat flux region 312, defining a reduced axis 362 of scattered radiation (Fig. 11). The target 224 on the target plane 233 near the axis 362 has a reduced stray radiation component such that a reduced temperature deviation is obtained compared to the target temperature obtained elsewhere on the target plane 233. In one embodiment, the target 224 is concentrated along the axis 362, or in contact, or partially overlapping; in another embodiment, the target 224 is within the rectangular region 364 of reduced stray radiation, the length of which 366 is defined to extend from the axis of rotation 240 to the outer edge 274 of the wafer carrier 232, and its width 368 is defined by the chord of the arc segment 310.

Referring to Figures 13A and 13B, a radiation trap 372 for capturing a portion of the radiation emitted by a designated portion 374 of ambient heating element 264 is illustrated in an embodiment. In an embodiment, the radiation trap 372 includes a hole 376 defined on the body door 242 and having a tangential dimension 378. In an embodiment, the surrounding heating element 264 designation portion 374 is defined as an arcuate segment that is adjacent to the radiation well 372 and has the same tangential dimension 378.

In operation, a portion of the radiation 380 emitted by the designated portion 374 is transferred into the aperture 376 by direct radiation or reflection away from each surface of the radiation trap 372. Radiation trap 372 thus locally limits the transfer of radiation by capturing radiation 380. In this embodiment, the axis 362 of the reduced scattered radiation is defined as the target plane 233 and extends from the axis of rotation 240 and through the center of the tangential direction of the aperture 376. The width 368 of the reduced stray radiation rectangular region 364 is defined by the chord of the tangent dimension 378.

Referring to Figure 14, an embodiment of a radiation deflector 392 is shown to deflect a portion of the radiation emitted by a designated portion 394 of the surrounding heating element 264. In one embodiment, the radiation deflector 392 includes a convexity 396 that projects radially inwardly toward the outer edge 274 of the wafer carrier 232, which may be characterized as having a tangential dimension 398. In an embodiment, the designated portion 394 of the surrounding heating element 264 is defined adjacent the radiation deflector 392 and has the same arcuate segment as the tangent dimension 398 of the convex portion 396.

In operation, a portion of the radiation 402 emitted by the designated portion 374 is transmitted into the convex portion 396 by direct radiation or reflection away from the surfaces of the proximity radiation deflector 392. The radiation deflector 392 thus leaves the plane 404 defined by the axis of rotation 240 by scattering the radiation 402 and locally limits the incidence of radiation by the protrusions 396. In this embodiment, the axis 362 of reduced scatter radiation is defined by the convergence of target plane 233 and plane 404 and extends from rotating shaft 240 and through radiation deflector 392. The width 368 of the rectangular region 364 that reduces stray radiation is defined by the chord of the tangent dimension 398 of the radiation deflector 392.

In the disclosed embodiment, the heating element is provided with at least one of the above-described techniques for locally reducing stray radiation, and a set of operational instructions is provided to the tangible medium (eg, a written copy of the paper or The computer accessibility device, wherein the operation command indicates how to position the radiation thermometer relative to the heating element to reduce the stray radiation component. We can use this combination to, for example, improve existing CVD reactor systems.

Referring to Figure 15, an embodiment of a dual wavelength pyrometer 420 is illustrated. The dual wavelength pyrometer 420 includes two radiation thermometers 422 and 424, each for viewing different center wavelengths, such as 930 nm and 405 nm wavelengths, respectively. Each of the radiation thermometers 422 and 424 can also include an out-of-focus telecentric optical device 24, the elements of which are labeled in Figure 15, and the component symbols are the same as previously described.

In one embodiment, the radiation thermometers 422 and 424 of the dual wavelength pyrometer 420 collectively use a common object assembly 62. A cold mirror 426 can be used to transmit the (reflected) visible/UV spectral radiation beam 434 to the radiation thermometer 424 while the infrared radiation beam 432 is transmitted to the radiation thermometer 422. Alternatively, a cold beam mirror 426 can be replaced with a beam splitter (not shown).

In terms of function, the dual-wavelength pyrometer 420 can simultaneously measure the radiation signals emitted by the common target 72, and the cold mirror 426 can cause most of the visible/UV spectral radiation to be transmitted to the radiation thermometer 424. At the same time, most of the infrared light radiation is passed through the radiation thermometer 422. For example, there are cold mirrors 426 that effectively reflect more than 90% of the visible or visible/UV spectrum of radiation, while maintaining a minimum of 83% penetration for wavelengths greater than 800 nm, see "Cold Light", DichroTec Thin Films LLC (You can browse the web: http://www.dtthinfilms.com/cold-mirrors.html). For embodiments in which the filter wavelengths of the two radiation thermometers 422 and 424 are in the visible/UV or infrared spectrum, appropriate splitting can be used. Alternatively, a reduced size aperture assembly 97 as described above may be used, as illustrated in FIG. 15 for the radiation thermometer 424, or as one or both of the radiation thermometers 422 and 424. can.

In various embodiments, one or both of the radiation thermometers 422 and 424 can be configured with a reflectometer subassembly 442 that can include a radiation source 444 (referred to as a radiation source 444a and 444b is used for radiation thermometers 422 and 424), detector 446, and beam splitter 448, respectively. Radiation sources 444a and 444b are adjusted or selected to emit a beam 452 comprising spectral in-band spectral emissions that are passed by individual filtering devices 102a and 102b of individual radiation thermometers 422 and 424. In Fig. 15, beam 452 and optical axis 68 are separated from each other into beams 452a and 452b and optical axes 68a and 68b of radiation thermometers 422 and 424, respectively. Thereafter, beams 452a and 452b are collectively referred to as beam 452. Select detectors 446 (referred to as detectors 446a and 446b for radiation thermometers 422 and 424, respectively) in response to wavelength bands emitted by individual radiation sources 444a or 444b and by individual radiation thermometers 422 The wavelength passed by the filtering device 102 of 424. In an embodiment, the reflective metering component 442 includes a chopper 458 for modulating the beam 452 as it exits the radiation source 444.

In some embodiments, the reflective metering component 442 can also include more than one focusing component 454, 456, such as a lens or spherical mirror that focuses or collimates the beam 452. In an embodiment, focusing element 454 can include a lens group that is similar to telecentric device component 62 or image component 64.

In operation, beam 452 from radiation source 444 of reflectance meter component 442 is passed through beam splitter 448. In one embodiment, the first portion 462a or 462b of the beam 452 passes through the beam splitter 448 and is incident on the detector 446. The signal generated by the detector 446 provides the beam 452. Indication of strength. Due to the orientation of the beam splitter 448, the detector does not actually see the radiation originating from or reflected by the target 72. A second portion 464 of beam 452 (referred to as 464a or 464b, respectively for radiation thermometers 422 and 424, and collectively referred to as 464) is reflected by beam splitter 448 and is substantially transmitted along individual optical axes 68a or 68b, And reaching the target 72 via the cold mirror 426. Next, a portion of the second portion 464 of the beam 452 is reflected from the target 72, returned along the individual optical axes 68a or 68b of the individual radiation thermometers 422 or 424 via the cold mirror 426, through the beam splitter 448 and the filtering device 102. So as to be detected by the individual detectors 76a, 76b of the radiation thermometer 422 or 424.

In one embodiment, the layout and components of the reflective metering component 442 are specifically designated, and the second portion of the beam 452 is 464 in conjunction with the two passes of the object component 62 and the optical path through the individual image components 64a or 64b. Focusing on the image plane of the individual detectors 76a, 76b. In addition, the reflectance meter component 442 can be specifically designated to cause the radiation of the reflectance meter component to "underfill" the target 72; in other words, the target 72 illuminated by the radiation from the reflectance component 442. The area is smaller than the target 72 and is completely contained within the target 72.

In terms of function, the reflectance measurement of the target 72 is less than the possible misalignment to provide spatial tolerance. In short, during the CVD process, the wafer 41 can be deformed or "bent" due to the thermal gradient present in the wafer 41. The bending phenomenon may cause a portion of the second portion 464 of the beam 452 that is reflected from the target 72 and received by the detectors 76a, 76b to be redirected, especially when the target object is highly reflective. The reorientation of this reflective portion will cause the reflected radiation to laterally migrate at the image plane of the detectors 76a, 76b. By being less than the target 72, the reflective portion can migrate laterally to some extent and still fully align to the detectors 76a, 76b, and thus is sufficiently detected by the detectors 76a, 76b. .

Although FIG. 15 depicts reflective metering component 442 in both radiation thermometers 422 and 424, it should be understood that reflective metering component 442 is not necessary and that either or both of radiation thermometers 422 and 424 may be utilized. It is not necessary to use it for implementation or for two radiation thermometers. Similarly, it is not necessary to use the chopper 458 or the remaining beam modulating means, and the reflective metering component 442 does not need to utilize this.

Referring to Figures 16A and 16B, there are shown individual composite signals 472a and 472b generated by detectors 76a, 76b in an embodiment, wherein detectors 76a, 76b are used to view illumination by reflective metering component 442. Target 72. The composite signal 472a is characterized by a signal generated by the reflection counter 442 that selects the chopper 458 or other modulation device, and the composite signal 472b can be characterized as having a modulation signal 474 that is driven on the baseline signal 476. The baseline intensity 478 of the baseline signal 476 represents the transmit power of the target 72, and the valley to peak amplitude 482 of the modulated signal 474 represents the portion of the second portion 464 of the beam 457 that is reflected from the target 72.

The composite signal 472b is characterized by a signal generated by the reflectance counter component 442 that does not modulate the beam 452; rather, the composite signal 472b includes a pulse or step signal 484 having a number 485 extending from the baseline signal 476. The step signal 484 can be generated by supplying power to the radiation source 444, in which case the step signal 484 may drift during the duration of the step signal 484. To compensate for this drift, the detector 446 can be used to track the intensity of the beam 452 and normalize the step signal 484 against the signal from the detector 446 to provide a normalized signal 486. The amplitude of the normalized signal 486 represents the reflectivity of the target 72.

For example, the reflectance sub-assembly 442 can be utilized to compensate for variations in the emissivity of the target 72. The emissivity of the target can be inferred from the reflectance measurement, as described in U.S. Patent No. 6,349,270 ("Gurary") to Gurary et al. In the CVD process, how the emissivity is inferred from the reflectance measurements in the wafer environment on the wafer carrier. The indication of the emissivity of the target can be utilized to improve the accuracy of the temperature determination.

The portion of the second portion 464 of the beam 457 sensed by the detector 76a or 76b, which is also the same as the radiation emitted by the target 72, undergoes the same collimation procedure as discussed above in relation to FIG. By. In other words, only the reflected reflected radiation from the second portion 464 and substantially parallel to the primary ray 92 is detected by the detector 76a or 76b, such that if it is first scattered from the target 72 or the viewing window 52. Any amount of radiation will also become insignificant. Thus, regardless of where the target 72 is located on the wafer 41, the amount of scattered radiation originating from the second portion 464 of the beam 457 is extremely small. By essentially eliminating the scattered radiation component, the results show that the reflectivity characteristics between different targets are more consistent.

In the illustrated dual wavelength pyrometer 420, the beam splitter 448, the cold mirror 426, the object assembly 62, and the viewing window 52 are before the second portion 464 of the beams 452a and 452b reaches the individual detector 76a or 76b. The second portion 464 of the beams 452a and 452b is attenuated twice, and the second portion 464 of the beams 452a and 452b is attenuated once by the target 72, the filtering device 102, and the image component 64. Thus, the second portion 464 of the beam 452 may experience significant attenuation, so the radiation source is required to have sufficient power to provide a detectable reflectance signal. A non-limiting example of a radiation source with sufficient power is a light emitting diode (LED) operating in the range of about 1 mW to about 10 mW. We can adjust the light emitting diode to carry the filtering through the individual radiation thermometer 422 or 424. The energy in the narrow spectral range of device 102. For example, for a filtering device 102 having a center wavelength of about 405 nm and a 25 nm order band pass, a non-limiting example of an LED radiation source is LED 405E, which is a Thorolabs company in Newton, New Jersey, USA. Made It has a center wavelength of about 405 nm ± 10 nm and a spectral width of about 15 nm (full width at half maximum). For a filtering device 102 having a center wavelength of about 930 nm and a 10 nm order bandpass, a non-limiting example of an LED radiation source is OD-1390, which is manufactured by Opto Diode, Inc. of Newbury Park, California, USA. It has a center wavelength of about 943 nm and a spectral bandpass of about 60 nm (full width at half maximum).

Referring to Figure 17, a combined system 490 of multiple channels and dual wavelengths in an embodiment is illustrated. In the illustrated embodiment, a plurality of dual wavelength pyrometers 420a, 420b and 420c are provided to view objects 72a, 72b and 72c along line 114. Each of the dual-wavelength pyrometers 420a, 420b, and 420c includes an individual pair of radiation thermometers 422a/424a, 422b/424b, 422c/424c, each of which is configured to observe the selected wavelength band. Pass as described with reference to FIG.

We can configure the radiation thermometers 422 and 424 of the dual-wavelength pyrometer 420 so that the transmission axes of the optical elements lie in a common plane (for example, the plane 492, which is illustrated by the extension of the radiation thermometers 422c and 424c in FIG. On the axis). In addition, the internal components of the radiation thermometers 422 and 424 can be configured such that the width 494 orthogonal to the common plane 492 is equal to the width of the radiation thermometers 22a, 22b and 22c of FIGS. 6A and 6B. This configuration will provide the dual-wavelength pyrometer 420 with the same lateral footprint as the radiation thermometer 22, thereby enabling the dual-wavelength pyrometers 420a, 420b, and 420c to be along any arbitrary line or in other patterns. The object was observed in the same manner as described above with respect to FIGS. 6A and 6B and FIG.

In another embodiment, only one of the pyrometers of the multi-channel device is dual wavelength. In this device, we assume that temperature correction and/or emissivity compensation from a single dual wavelength pyrometer is applicable to the entire wafer and is therefore suitable for all targets.

Thus, the multi-channel and dual-wavelength combination system 490 can achieve enhanced accuracy of dual-wavelength, out-of-focus telecentric devices while providing spatial temperature uniformity information.

Although the discussion herein focuses primarily on the application of MOCVD reactor systems, it is important to note that the principles illustrated herein can be applied to other types of CVD processing chambers as well as to processing chambers that typically use radiation thermometers. Moreover, for the purposes of the present invention, the terms "thermometer" and "radiation thermometer" are synonymous, "detector" is an electromagnetic radiation detector, and "beam" is a beam of electromagnetic radiation.

The following references are hereby incorporated by reference in their entirety in their entirety by reference in their entirety in their entirety in the the the the the the the the the 6,349,270; by Petrozzo et al., "Telecentric Lenses Simplify Non-Contact Metrology," Test & Measurement World, October 15, 2001; by Mitrovic et al., "Reactor Design Optimization Based on 3D CFD Modeling of Nitrides Deposition in MOCVD Vertical Rotating Disc Reactors, June 2005 (available at http://www.wpi.edu/academics/che/HMTL/CFD in CRE_IV/Mitrovic.pdf); "Cold Mirrors," DichroTec Thin Films LLC (available at http://www.dtthinfilms.com/cold-mirrors.html).

Relative terms such as upper and lower, front and back, left and right are mentioned in the specification for convenience of explanation and are not limited to any particular orientation. All dimensions indicated in the drawings may be varied by the possible design and intended use of the particular embodiments without departing from the scope of the invention.

Each of the additional figures and methods described herein can be used separately or in combination with the remaining features and methods to provide an improved apparatus, system, and method of making or using the same. Therefore, to The disclosed embodiments are in the broadest sense, and the combinations of the features and methods described herein are not necessary, but are merely illustrative of representative embodiments.

Although the embodiments of the present invention are disclosed as described above, it is not intended to limit the scope of the present invention, and those skilled in the art can devise shapes according to the scope of the present application without departing from the spirit and scope of the present invention. It is to be understood that the scope of the invention is defined by the scope of the appended claims.

20‧‧‧MOCVD reactor system

22‧‧‧radiation thermometer

22a-22e‧‧‧radiation thermometer

24‧‧‧Out-of-focus telecentric optics

26‧‧‧Reaction room

28‧‧‧Flow flange

38‧‧‧ mandrel

41‧‧‧ wafer

44‧‧‧Resistive heating array

46‧‧‧Cylinder

52‧‧‧View window

62‧‧‧ ‧ components

66‧‧‧ aperture shutter

72,72a-72e‧‧‧ Targets

74‧‧‧Out-of-focus target area

84‧‧‧ reference point

144b‧‧‧Overshoot

117‧‧‧ memory device

99‧‧‧ tablet

98‧‧‧Shutter assembly

97‧‧‧Reduced size aperture assembly

96‧‧‧solid angle

95‧‧‧front surface

94‧‧‧Infinitely small

92‧‧‧main rays

88‧‧‧ray beam

30‧‧‧Shell

31‧‧‧ laminar flow board

32‧‧‧ wafer carrier

34‧‧‧ top surface

35‧‧‧ Wafer Bag

36‧‧‧ bottom

40‧‧‧Rotary axis

42‧‧‧ body door

45‧‧‧ surrounding heating elements

48‧‧‧ reflector plate

54‧‧‧ Groove

64, 64a, 64b‧‧‧ image components

68,68a,68b‧‧‧Optical axis

76‧‧‧Detector

82‧‧‧Light trap

118‧‧‧ Controller

120‧‧‧Multi-channel cluster

116‧‧‧Signal Processor

115‧‧‧Data Acquisition System

112,114‧‧‧ Straight line

110,111‧‧‧Multichannel device

108‧‧‧Connector

106‧‧‧Upper

104‧‧‧Flow Extender

102,102a,102b‧‧‧Filter device

101‧‧‧ aperture

86‧‧‧Main size

222‧‧‧radiation thermometer

224, 224a-224d‧‧‧ Targets

226‧‧‧Reaction room

220‧‧‧Reactor system

233‧‧‧ Target plane

235‧‧‧wafer bags

237‧‧‧Substrate

240‧‧‧Rotary axis

244,244a‧‧‧heater array

248‧‧‧Film installation board

252‧‧‧View window

264,264a‧‧‧ surrounding heating elements

268a-268c‧‧‧ray

274‧‧‧Outside of wafer carrier

304‧‧‧Internal heating elements

308‧‧‧Electrical connector

312‧‧‧Low heat flux section

318‧‧‧discontinuous line

316‧‧‧ second half long

332‧‧‧Infrared light temperature signal

336,336a, 336b‧‧‧ progressive recursion

338,338a, 338b‧‧‧ monotonous rise

342,342a, 342b‧‧‧Quick recurve

344,344a,334b‧‧‧Overshoot

366‧‧‧ length

372‧‧‧radiation trap

352, 354, 356, 358‧ ‧ optical temperature signal

100‧‧‧Actuator

228‧‧‧Flow flange

230‧‧‧ Shell

231‧‧‧ laminar flow board

232‧‧‧ wafer carrier

234‧‧‧Top surface of the target plane

236‧‧‧Bottom of wafer carrier

238‧‧‧ mandrel

242‧‧‧ body door

246‧‧‧Cylinder

250‧‧‧Cylinder axis

254‧‧‧ Groove

266‧‧‧ Internal surface of the cylinder

272‧‧‧Top edge of the cylinder

276‧‧‧ gap

306‧‧‧Electrical connector

310‧‧‧ arc segments

314‧‧‧ first half long

320‧‧‧Infrared radiation thermometer

330‧‧‧Stermatous radiation characteristics

334‧‧‧ optical temperature signal

346‧‧‧low

348‧‧‧Control equilibrium temperature

350‧‧‧Continuous Department

364‧‧‧Rectangular area

368‧‧‧Width

374‧‧‧Specified part of the surrounding heating element

376‧‧‧ hole

362‧‧‧ Reduced scatter axis

380‧‧‧ radiation

394‧‧‧Specified part of the surrounding heating element

398‧‧‧ Tangential size

404‧‧‧ plane

422,422a-422c‧‧‧radiation thermometer

424‧‧‧radiation thermometer

426‧‧‧Cold Mirror

432‧‧‧Infrared radiation beam

434‧‧‧radiation beam

442‧‧‧reflection counting components

444,444a,444b‧‧‧radiation source

446,446a,446b‧‧‧Detector

472a, 472b‧‧‧ composite signal

474‧‧‧Modulation signal

482‧‧• trough to crest amplitude

485‧‧‧ intensity

494‧‧‧Width

65‧‧‧ Radius size

378‧‧‧ Tangential size

392‧‧‧radiation deflector

396‧‧‧ convex part

402‧‧‧ radiation

420, 420a, 420b, 420c‧‧‧ dual wavelength pyrometer

448‧‧‧beam splitter

452a, 452b‧‧‧beam

454, 456 ‧ ‧ focusing components

457‧‧‧ reflected beam

458‧‧‧Chopper

462,462a,462b‧‧‧The first part of the beam

464, 464a, 464b‧‧‧ the second part of the beam

476‧‧‧ baseline signal

478‧‧‧ Baseline strength

484‧‧‧pulse or step signal

486‧‧‧Formalization signal

492‧‧‧ plane

490‧‧‧Multi-channel and dual-wavelength combination system

268‧‧‧ray

Figure 1 is a graph showing the blackbody emission power according to Planck's law at various temperatures; Figure 2 is a cross-sectional view of an out-of-focus telecentric radiation thermometer in an exposed embodiment, the external telecentric radiometer is operated Time is coupled to the MOCVD reaction chamber; FIG. 3 is a cross-sectional view of an out-of-focus telecentric radiation thermometer in an exposed embodiment and a light trap coupled to the MOCVD reaction chamber during operation; FIG. An out-of-focus telecentric optical device in an embodiment is disclosed; FIG. 5 is a cross-sectional view of an out-of-focus telecentric radiation thermometer in an exposed embodiment coupled to a flow extender during operation FIG. 5A is a partially enlarged cross-sectional view of the MOCVD reaction chamber and the flow extender of FIG. 5; and FIGS. 6A-6C illustrate a multi-channel device for obtaining a spatial temperature distribution of the wafer in an exposed embodiment; 7A is a cross-sectional view of a MOCVD reaction chamber having a radiation thermometer; FIG. 7B is a three-dimensional cross-sectional view of the MOCVD reaction chamber of FIG. 7A having various accessory devices for modeling radiation scattering; Figure 8 is a schematic view of radiation emitted from a portion of the surrounding heating element of Figure 7A; Figure 9 is a plan view of the heating element device in the reaction chamber (removed wafer carrier) of the disclosed embodiment; Figure 10 is infrared radiation A comparison chart of a thermometer and an optical radiation thermometer, both of which observe the wafer carrier during a heating cycle of the heater array; FIG. 11 is a plan view of FIG. 9 illustrating a spurious radiation detection in an exposed embodiment Alignment of the target of the heater array for the test; FIG. 12A is a comparison diagram of the response of the radiation thermometer for observing the high heat flux portion of the surrounding heating element and approaching the surrounding a wafer carrier at a radial position outside the low heat flux portion of the heating element; and FIG. 12B is a response comparison diagram of the radiation thermometer for observing the high heat flux portion of the surrounding heating element and approaching the surrounding a wafer carrier at a mid-span radius of the low heat flux portion of the heating element; FIG. 13A is a partial plan view of the wafer carrier in the reaction chamber of the disclosed embodiment, the reaction chamber including a local radiation trap; 13B is a cross-sectional view of the partial radiation trap of FIG. 13A; FIG. 14 is a schematic view of a reaction chamber using a local radiation deflector in an embodiment; FIG. 15 is a dual-wavelength high temperature of the wafer viewed through the viewing window in an exposed embodiment. FIG. 16A and FIG. 16B are representative views of a composite signal received by a pyrometer using a reflectance sub-assembly in an embodiment; and FIG. 17 illustrates a dual use of an acquisition space temperature distribution in an exposed embodiment. High wavelength Multi-channel device for the thermometer.

20‧‧‧MOCVD reactor system

22‧‧‧radiation thermometer

24‧‧‧Out-of-focus telecentric optics

26‧‧‧Reaction room

28‧‧‧Flow flange

30‧‧‧Shell

31‧‧‧ laminar flow board

32‧‧‧ wafer carrier

34‧‧‧ top surface

35‧‧‧ Wafer Bag

36‧‧‧ bottom

38‧‧‧ mandrel

40‧‧‧Rotary axis

41‧‧‧ wafer

42‧‧‧ body door

44‧‧‧Resistive heating array

45‧‧‧ surrounding heating elements

46‧‧‧Cylinder

48‧‧‧ reflector plate

52‧‧‧View window

54‧‧‧ Groove

62‧‧‧ ‧ components

64‧‧‧Image components

66‧‧‧Aperture shutter (shutter)

68‧‧‧ Optical axis

72‧‧‧ Targets

74‧‧‧Out-of-focus target area

76‧‧‧Detector

Claims (16)

A telecentric optical device for a radiation thermometer for mitigating the effect of stray radiation on a temperature measurement of a target comprising: an aperture shutter; having one or more optical components An object assembly for transmitting radiation to the aperture shutter, the object assembly and the aperture shutter defining an optical axis, the object assembly defining one of a first reference point relative to the object assembly a focal length, the first reference point being located on the optical axis and spaced apart from the aperture shutter by a distance substantially equal to the first focal length of the object assembly to transmit the radiation from the object through the object An assembly for focusing the radiation from the target onto the aperture shutter, the object assembly being disposed in a recess for defining a depth of stray radiation incident on the component; and an electromagnetic radiation And a detector for generating at least a portion of the radiation transmitted by the component through the first aperture shutter to the electromagnetic radiation detector to generate a signal indicating the temperature measurement of the target. The telecentric optical device of claim 1, further comprising an image component having one or more optical components opposite the object component and on the other side of the aperture shutter for receiving The object assembly is transported along the optical axis and radiates through the aperture shutter, the image component defining a second focal length relative to one of the second reference points within the image component, the second reference point being located on the optical axis . The telecentric optical device of claim 2, wherein the second reference point of the image component is spaced from the aperture shutter by a distance substantially equal to the second focal length of the image component. The telecentric optical device of any one of claims 1 to 3, wherein the aperture shutter defines one The primary dimension is about 1/3 or less of the effective radius dimension of the component. The telecentric optical device of any one of claims 1 to 3, wherein the electromagnetic radiation detector is a photon counter having a cutoff wavelength of about 700 nm. The telecentric optical device according to any one of claims 1 to 3, further comprising a filtering device having a major band pass in a wavelength range of less than 450 nm and configured to filter incident on the electromagnetic One of the radiation detectors senses the radiation on the area. The telecentric optical device of claim 6, wherein the primary bandpass of the filtering device has a center wavelength in a range of 380 nm to 420 nm, and a band width in a range of 20 nm to 50 nm. The telecentric optical device of claim 6, wherein the filtering device comprises a band pass filter. The telecentric optical device of any of claims 1 to 3, wherein the distance between the target and the object assembly is less than 2 m. The telecentric optical device of any of claims 1 to 3, wherein the object assembly comprises at least one lens. A method of using a telecentric lens arrangement to reduce stray radiation in a radiation thermometer, the radiation thermometer providing a temperature measurement for a target in a chemical vapor deposition reaction chamber, the method comprising the steps of: setting A telecentric lens device comprising an aperture shutter and a first optical component assembly for collecting radiation from the target, the telecentric lens device for locating the aperture The shutter is positioned at a focal length of the first optical component assembly to Capturing collimated radiation emitted by the target, the component being disposed in a recess sufficient to define a depth of stray radiation incident on the object assembly; providing a plurality of instructions on a tangible medium, The instructions include: adjusting an orientation of the first optical component assembly to intercept radiation emitted by the target within the chemical vapor deposition reaction chamber. The method of reducing stray radiation in a radiation thermometer according to claim 11, wherein the instructions provided in the step of providing a plurality of instructions further comprise positioning the aperture shutter to the first optical component The focal length is on. The method of reducing stray radiation in a radiation thermometer according to claim 11 or 12, wherein the instructions provided in the step of providing a plurality of instructions further comprise: operatively coupling the telecentric lens device with an electromagnetic Radiation detector. A method of reducing stray radiation in a radiation thermometer as claimed in claim 13 further comprising positioning the aperture shutter at the focal length of the first optical component assembly. The method of reducing stray radiation in a radiation thermometer according to claim 14, further comprising: operatively coupling the telecentric lens device and the electromagnetic radiation detector. A temperature measuring system for measuring a temperature of a target in a chemical vapor deposition reaction chamber, the temperature measuring system comprising: a radiation thermometer coupled to the chemical vapor deposition reaction chamber operatively, The radiation thermometer includes a means for defining a target within the chemical vapor deposition reaction chamber; wherein the radiation thermometer is oriented to observe the target at a distance, the distance being caused by the target The radiation transmitted to the object assembly is out of focus, the object assembly being disposed in a recess sufficient to limit the depth of stray radiation incident to the object assembly, and the radiation thermometer is included in the chemistry A means of defining the target in a vapor deposition reaction chamber.