CN115507755B - Optical displacement measurement system for high-temperature equipment and method for measuring warpage - Google Patents
Optical displacement measurement system for high-temperature equipment and method for measuring warpage Download PDFInfo
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- CN115507755B CN115507755B CN202211329755.7A CN202211329755A CN115507755B CN 115507755 B CN115507755 B CN 115507755B CN 202211329755 A CN202211329755 A CN 202211329755A CN 115507755 B CN115507755 B CN 115507755B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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Abstract
The invention discloses an optical displacement measurement system for high-temperature equipment and a method for measuring warping, wherein a light emitting module emits detection light with wavelength in a purple or ultraviolet wavelength range, the detection light is reflected by a light reflecting module and then projected onto a measured surface of a measurement object in a rotating state for scanning, the detection light reflected by the measured surface is focused by a light focusing imaging module and then is emitted to a position detection module, position signals at all measurement points on the measured surface are output, and a control module obtains a height profile curve of the corresponding measurement object in one scanning period according to the position signals, compares and analyzes the height profile curve corresponding to one or more scanning periods, and determines the warping degree of the measurement object. The invention can carry out optical measurement on the change of the height of the wafer relative to the detector by utilizing the detection light with purple or ultraviolet wavelength, can effectively solve the problem of measuring the wafer warpage aiming at various contours in high-temperature equipment, and has simple, convenient and practical method and high accuracy.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to an optical displacement measurement system for high-temperature equipment and a method for measuring warpage.
Background
When a thin film deposition process is performed in a high-temperature apparatus, such as a chemical vapor deposition apparatus, a plurality of thin films are sequentially deposited and grown on a wafer substrate, and during the thin film growth process, the wafer is warped due to the stress, and the warping phenomenon affects the subsequent product quality, especially when some critical thin film layers are grown, the warping needs to be strictly controlled. Thus, online real-time measurement and control of warpage is required to reduce the impact on product quality.
Conventional wafer warp measurement methods, such as those disclosed in U.S. patent publication No. US7570368B2, mostly employ a reflected light measurement method, which directs a light beam onto a rotating semiconductor wafer surface such that the light beam is incident on the wafer surface at a series of incidence points, and reflects from each incidence point, detects the position (position in two dimensions) of each reflected light beam incident on a detector, and then calculates the inclination and curvature of the wafer based on the assumption that the main surface of the wafer is a segment of a sphere.
However, the conventional reflected light measurement method has the following problems: (1) Reflected light measurements can only reflect the angle of inclination of the wafer surface and not the contour height of the wafer, and thus cannot intuitively characterize the degree of wafer warpage. (2) The warp measurement is performed using a reflected light measurement method, it must be assumed that the main surface of the wafer is a segment of a sphere, and the tray carrying the wafer is in a horizontal state. Since the reflected light measurement method reflects the tilt feature, the presence of factors such as the tilt of the wafer load and the tilt of the support base (e.g., the tray rotation effect, the tray processing tolerance effect, etc. to tilt it) will affect the accuracy of the measurement results. (3) In the case of a segment of the main surface of the wafer that is not spherical, such as a saddle-shaped wafer, a potato-shaped wafer, or a multi-curved wafer, the degree of warpage of the wafer cannot be accurately known by the conventional reflected light measurement method.
Accordingly, there is a need to provide a new optical measurement technique for high temperature equipment and measuring warpage to solve the above-mentioned problems in the prior art.
Disclosure of Invention
The object of the present invention is to overcome the above drawbacks of the prior art and to provide an optical displacement measurement system for high temperature equipment and a method for measuring warpage.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the present invention provides an optical displacement measurement system for a high temperature apparatus, comprising: the device comprises a light emitting module, a light reflecting module, a light focusing imaging module, a position detecting module and a control module;
the light emitting module, the light reflecting module, the light focusing imaging module and the position detecting module form a light path; the light emitting module is used for emitting detection light with wavelength in a purple or ultraviolet wavelength range;
the detection light is reflected by the light reflection module and then projected onto a detected surface of a measurement object in a rotating state in the high-temperature equipment, so that the detection light scans on the detected surface of the measurement object; the detection light reflected by the detected surface is focused by the light-focusing imaging module and then emitted to the position detection module;
the position detection module outputs position signals at all measuring points on the measured surface;
the control module obtains a height profile curve of the measured object corresponding to one scanning period according to the position signals of the measured points on the measured surface output by the position detection module, compares and analyzes the height profile curve corresponding to one or more scanning periods, and determines the warping degree of the measured object.
Further, the position detection module comprises a position sensitive detector provided with an ultraviolet enhanced film.
Further, the light reflecting module comprises a planar mirror or a first concave mirror.
Further, the device also comprises a wavelength selection module, wherein the wavelength selection module is arranged in front of the position detection module and is used for filtering infrared light and visible light.
Further, the light-gathering imaging module comprises an ultraviolet light-transmitting lens, and the wavelength selection module comprises an optical filter arranged between the ultraviolet light-transmitting lens and the position detection module.
Further, the light-gathering imaging module comprises a second concave mirror, and the wavelength selection module comprises an optical filter arranged between the second concave mirror and the position detection module; alternatively, the wavelength selection module includes a filter film disposed on a concave surface of the second concave mirror.
The present invention also provides a method for measuring warpage of a high temperature apparatus, comprising:
projecting detection light with a wavelength in a violet or ultraviolet wavelength range onto a measured surface of a measurement object in a rotating state in the high-temperature device, so that the detection light scans over the measured surface of the measurement object;
the detection light projected onto the detected surface is reflected by the detected surface and then detected by a position detection module, and position signals at all measuring points on the detected surface are output;
and obtaining a height profile curve of the measuring object corresponding to one scanning period according to the position signals of each measuring point on the measured surface, and obtaining the warping degree of the measuring object by comparing the height profile curves of the measuring object corresponding to one or more scanning periods.
Further, the change amount between the height profile curve of the measuring object corresponding to the current scanning period and the height profile curve of the measuring object corresponding to the initial scanning period is calculated, so that the warping degree of the measuring object is obtained.
Further, when the measuring object is a plurality of wafers, calculating the difference between the maximum height and the minimum height in the height profile curve of each corresponding wafer in the current scanning period to obtain the warping degree of each wafer.
Further, performing a high temperature growth process in the high temperature apparatus, the high temperature growth process including a plurality of process time periods, the method of measuring warpage further comprising:
and generating the height profile curves of the measuring objects in each process time period, and calculating the variation among the height profile curves of the measuring objects in each process time period to obtain the warping degree of the measuring objects in different process time periods to be used as the basis of process adjustment.
Further, the projecting the probe light with a wavelength in a violet or ultraviolet wavelength range onto a measured surface of a measurement object in the high-temperature device specifically includes:
and the light emitting module is used for emitting detection light with the wavelength in the purple or ultraviolet wavelength range, the light reflecting module is used for reflecting the detection light and then projecting the detection light onto the measured surface of the measured object, and the light reflecting module comprises a plane reflecting mirror or a first concave mirror.
Further, the detection light projected onto the surface to be detected is detected by a position detection module after being reflected by the surface to be detected, and a position signal at each measurement point on the surface to be detected is output, which specifically includes:
and condensing the detection light projected onto the detected surface and reflected by the detected surface by using an ultraviolet light transmitting lens or a second concave mirror, filtering infrared light and visible light by using an optical filter, detecting after ultraviolet enhancement by using a position sensitive detector provided with an ultraviolet enhancement film, and outputting position signals at all measuring points on the detected surface.
Further, the detection light projected onto the surface to be detected is detected by a position detection module after being reflected by the surface to be detected, and a position signal at each measurement point on the surface to be detected is output, which specifically includes:
and the concave mirror with the filter film is used for condensing the detection light projected onto the detected surface and reflected by the detected surface, filtering infrared light and visible light, reflecting the detection light to the position sensitive detector provided with the ultraviolet enhancement film for ultraviolet enhancement and then detecting, and outputting position signals at all measuring points on the detected surface.
The optical displacement measurement system for the high-temperature equipment and the method for measuring the warpage can utilize the detection light with purple or ultraviolet wavelength to measure the change of the height of the wafer relative to the detector in the high-temperature equipment by adopting the height measurement method, can intuitively represent the warpage degree of the wafer, can prevent the background interference caused by the heat radiation phenomenon in the high-temperature equipment, has high accuracy, is not limited by the loading state or the carrying base state of the wafer, is not limited by the outline shape of the wafer, and is simple, convenient and practical. Furthermore, optical elements such as a concave mirror, an optical filter, an ultraviolet enhanced coating detector and the like are used in the measuring system, so that the signal to noise ratio is improved, and the accuracy of warp measurement is improved.
Drawings
FIGS. 1-4 are schematic diagrams showing an optical displacement measurement system for a high temperature apparatus according to a preferred embodiment of the present invention;
FIG. 5 is a flow chart of a method for measuring warpage in accordance with a preferred embodiment of the present invention;
FIG. 6 is a schematic diagram of a method for measuring wafer warpage according to the method of FIG. 5 in accordance with a preferred embodiment of the present invention;
FIG. 7 is a graph illustrating an exemplary height profile obtained by scanning the same wafer in different scanning cycles in accordance with a preferred embodiment of the present invention; the abscissa in the figure is the rotation angle (unit: degree), and the ordinate is the relative height (unit: micrometer);
FIG. 8 is a graph illustrating an exemplary height profile obtained by scanning a plurality of wafers during the same scanning cycle in accordance with a preferred embodiment of the present invention; the abscissa in the figure is the rotation angle (unit: degree), and the ordinate is the relative height (unit: micrometer).
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.
An optical displacement measurement system 100 for a high temperature apparatus of the present invention is located outside a reaction chamber of the high temperature apparatus, which may be a film forming apparatus for a high temperature growth process of a semiconductor, including a gas phase reaction device, and may be, for example, a metal organic chemical vapor deposition device (MOCVD), a hydride vapor phase epitaxy device (HVPE), a plasma enhanced chemical vapor deposition device, a physical vapor deposition device (PVD), etc. The high temperature device may also be other devices for heating the product. In addition, the present invention does not strictly define a high temperature, and the high temperature may be applied to any temperature higher than room temperature. For example, MOCVD is taken as an example, and a heating component is arranged to heat the reaction cavity, so that the process growth temperature is 500-1500 ℃. The high temperature equipment is provided with a susceptor, and the measurement object 200 is a semiconductor wafer, for example, a semiconductor wafer having different profile shapes, other substrates, or the like; the measurement object 200 may be another product or sample of another type in a high-temperature apparatus or in a high-temperature state. The measurement object 200 is mounted on a base, and the base rotates around the rotation axis with the center line of the base as the rotation axis, thereby rotating the measurement object 200. For example, when a semiconductor process is performed in a high temperature apparatus, a series of thin films are sequentially grown on the measurement object 200, and the measurement object 200 may warp due to stress. The optical displacement measurement system 100 is used for performing optical displacement measurement on the measurement object 200 in a high-temperature apparatus to obtain a change in height of the measurement object 200 due to warpage, thereby reflecting the degree of warpage of the measurement object 200.
An optical displacement measurement system 100 comprising: a light emitting module 110, a light reflecting module 120, a light condensing imaging module 130, a position detecting module 160, and a control module 170.
Wherein the light emitting module 110 is used for emitting detection light with a wavelength in the violet or ultraviolet wavelength range. After being reflected by the light reflection module 120, the detection light is projected onto the surface 201 to be measured of the measurement object 200 in a rotating state in the high-temperature apparatus, so that the detection light scans over the surface 201 to be measured of the measurement object 200. The probe light reflected by the measured surface 201 is focused by the light-focusing imaging module 130 and then directed to the position detection module 160. The position detection module 160 outputs a position signal at each measurement point 400 on the surface 201 to be measured.
The control module 170 obtains a height profile curve of the measured object 200 corresponding to one scanning period according to the position signals at each measuring point 400 on the measured surface 201 output by the position detection module 160, and compares and analyzes the height profile curve corresponding to one or more scanning periods to determine the warping degree of the measured object 200.
The light emitting module 110, the light reflecting module 120, the light condensing imaging module 130 and the position detecting module 160 form a light path, and the set position ensures that the detection light emitted by the light emitting module 110 is incident on the surface of the measurement object 200 through the optical window on the reaction cavity of the high-temperature device, and ensures that the detection light reflected by the measurement object 200 is received by the position detecting module 160.
The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings.
Please refer to fig. 1. In a preferred embodiment, in an optical displacement measurement system 100 for a high temperature device according to the present invention, the light emitting module 110 may employ, for example, a laser 111 having an emission wavelength in the violet or ultraviolet wavelength range (emission wavelength <410 nm). The laser 111 emits detection light, which is incident on the light reflection module 120. The light reflecting module 120 may employ a mirror, for example, a plane mirror 121. The detection light is reflected by the plane mirror 121, and projected onto the surface 201 to be measured of the measurement object 200; the detection light is reflected to the light-condensing imaging module 130 through the detected surface 201 of the object 200, condensed by the light-condensing imaging module 130, and received by the position detection module 160. The light-condensing imaging module 130 may employ, for example, an ultraviolet-transmitting lens 131. The position detection module 160 may employ, for example, a Position Sensitive Detector (PSD) 161.
During the process, the object 200 is rotated, so that the probe light scans over the surface 201 of the object 200, and a plurality of measurement points 400 are formed on the surface 201. The position detection module 160 detects the light signals reflected at each measurement point 400 on the measured surface 201, converts the light signals into position signals (i.e., the change of the height distance between the measured object 200 and the PSD, which is mapped by the surface height fluctuation of the measured object 200 due to warpage), outputs the position signals to the control module 170, and obtains the height profile curve of the measured object 200 corresponding to one scanning period through the control module 170. One scanning cycle may be, for example, a time when the measurement object 200 rotates one rotation.
In the prior art, a reflected light measuring system is used for measuring the wafer warpage, and the wafer inclination angle is calculated by a complex algorithm and on the premise that the main surface of the wafer is a segment of a sphere, the positions of reflected light of different incidence points entering the detector are used for calculating the curvature. Once the wafer is loaded and the measured surface 201 is tilted (not horizontal), measurement errors may be caused, or the wafer may be more complex to calculate the tilt angle and curvature due to stress that may cause non-spherical segments of the wafer's major surface (e.g., saddle-shaped, potato-shaped, multi-curved, etc.).
The optical measurement system of the present invention does not measure the wafer inclination to calculate the warpage, but measures the change in the height of the wafer relative to the detector to intuitively represent the degree of warpage of the wafer, and even if the measured surface 201 of the wafer is inclined or a segment of the main surface of the wafer is not spherical after the wafer is loaded, the degree of warpage of the wafer can be determined by the relative change in the measured height value of the wafer profile, so that the problem of measuring wafer warpage of various profiles can be effectively solved, and the optical measurement system is simple, practical and high in accuracy.
In addition, when applied to measurement of high temperature equipment, the measurement surface is the surface of a high temperature object, and if a displacement measurement system adopts conventional visible light (such as red light) as detection light, there is a problem of background interference caused by heat radiation of the surface of the object, so that measurement cannot be performed normally. Therefore, the embodiment of the invention adopts the laser with the wavelength in the purple or ultraviolet wavelength range as the detection light, and can effectively prevent the interference of the thermal radiation phenomenon on displacement measurement.
Further, an ultraviolet enhancement module 150 may be added to the position sensitive detector 161; the ultraviolet enhancement module 150 may be provided with an ultraviolet enhancement film 151, for example. In a preferred embodiment, the ultraviolet enhancement film 151 may be a Lumogen (C22H 16N2O 6) fluorescent film, and the fluorescent film layer may be formed on the position sensitive detector 161 by a physical vapor deposition process to form the ultraviolet enhancement film coated position sensitive detector 161. The detection light enters the position sensitive detector 161 after the ultraviolet enhancement function of the ultraviolet enhancement film 151, so that the response capability of the position sensitive detector 161 to the detection light in the purple or ultraviolet range is improved, the detection sensitivity is improved, and the measurement accuracy is improved.
In the embodiment of the invention, the light reflection module 120 adopts the plane mirror 121 to reflect the detection light emitted by the laser 111 and change the direction of the detection light, so that the detection light is projected onto the measured surface 201 of the measured object 200 from the optical window on the reaction cavity of the high-temperature equipment. That is, by using the light reflection module 120, the installation position of the light emission module 110 is not limited, and flexibility of the optical displacement measurement system 100 in application to high temperature equipment is improved. In a preferred embodiment, the plane mirror 121 is used to reflect the probe light emitted from the laser 111, such as the probe light in the horizontal direction, and then to project the reflected probe light in the vertical direction onto the surface 201 of the horizontally placed measurement object 200. In another preferred embodiment, referring to fig. 2, the light reflecting module 120 employs the first concave mirror 122 instead of the planar mirror 121 in fig. 1, which has the advantage that the planar mirror 121 is changed to a concave mirror, so that the detection light can be projected to the measurement object 200 from the optical window on the reaction cavity of the high temperature device, and the concave surface of the first concave mirror 122 can be utilized to better collect the detection light from the laser 111, thereby improving the signal-to-noise ratio.
In a preferred embodiment, the ultraviolet-transmitting lens 131 can be made of a material that can transmit ultraviolet light to increase the signal intensity. For example, the ultraviolet light transmitting lens 131 may be an ultraviolet quartz lens that transmits light having a wavelength of 410 to 365 nm.
Further, the optical displacement measurement system 100 also includes a wavelength selection module 140. The wavelength selection module 140 is disposed before the position detection module 160, and is used for filtering infrared light and visible light. In an embodiment of the present invention, the wavelength selection module 140 may, for example, use an optical filter 141. Specifically, on the optical path of the rear side of the ultraviolet-transmitting lens 131, an optical filter 141 and an ultraviolet-enhanced plating position-sensitive detector 161 are sequentially disposed. The filter 141 can be used to filter infrared and visible light in the probe light projected onto the surface 201 to be measured and reflected by the surface 201 to eliminate interference of the light with the wavelengths on the measurement. In this way, the ultraviolet or ultraviolet detection light passes through the filter 141 to filter out the infrared and visible light, and then passes through the ultraviolet enhancement film 151, so that the enhanced ultraviolet light enters the position sensitive detector 161, and the signal to noise ratio is further improved, thereby improving the measurement accuracy.
Further, the control module 170 may be an upper computer 171. Alternatively, the control module 170 may be provided on the host computer 171. The position-sensitive detector 161 may output the detected optical signal as a voltage signal by an analog quantity to generate a position signal of the measured surface 201 at each measurement point 400. The upper computer 171 (control module 170) can generate a height profile curve of the measurement object 200 corresponding to one scanning period by calculation according to the position signals at each measurement point 400 on the measured surface 201 output by the position sensitive detector 161. The upper computer 171 may also compare and analyze the corresponding height profile curves in one or more scan periods to determine the degree of warpage of the measurement object 200.
For example, when the measurement object 200 shown in fig. 1 is located at the first position a (for example, no warpage occurs), the upper computer 171 calculates and generates a first height profile curve reflecting the measurement surface 201 of the measurement object 200 from the first position signal (previous position signal) of the measurement object 200 surface (measurement surface 201) at each measurement point 400 formed by the projection of the probe light output from the position sensitive detector 161 in one scanning cycle. When the position of the measurement object 200 changes (for example, when the position changes due to warpage), the upper computer 171 can calculate and generate a second height profile curve reflecting the measured surface 201 of the measurement object 200 from the second position signal (current position signal) of the surface of the measurement object 200 at each measurement point 400 output from the position sensitive detector 161 in one scanning cycle in a state where the measurement object 200 is at the second position B. The upper computer 171 compares the second height profile curve with the first height profile curve to obtain the variation difference therebetween, so as to determine the height variation of the measurement object 200 caused by the warpage, thereby representing the degree of warpage by the height variation, and being quite visual.
In addition, since the height profile curve is formed by the heights at the measurement points on the measured surface 201 of the measurement object 200, which can be fitted to the profile of the current warp of the measurement object 200, the current warp degree of the measurement object 200 can also be characterized by calculating the difference between the maximum height and the minimum height of the current profile curve.
Fig. 3 shows another preferred embodiment of the present invention. Unlike the embodiment shown in fig. 1 described above, in this embodiment, the spot imaging module 130 employs a second concave mirror 132 instead of the ultraviolet light transmitting lens 131 in fig. 1. The concave surface of the second concave mirror 132 is used to collect the reflected light reflected by the surface 201 to be measured, reflect the collected light again, filter the infrared light and the visible light on the reflected light path through the optical filter 141, and enter the position sensitive detector 161.
A further advantage of this embodiment over the embodiment shown in fig. 1 is that the conventional optical lens is generally impermeable to short wavelength light, and therefore requires the use of an ultraviolet transmissive material, such as an ultraviolet quartz lens, which is permeable to light having a wavelength of 410-365 nm, but impermeable to ultraviolet light of a shorter wavelength, which is detected by the position sensitive detector 161, and is costly. The concave mirror (the second concave mirror 132) used in this embodiment makes the detected light reach the position sensitive detector 161 through reflection, so that the ultraviolet light with shorter wavelength can be detected by the position sensitive detector 161, and the problem that the common optical glass cannot transmit deep ultraviolet light is effectively solved.
In addition, the second concave mirror 132 is used to reflect the reflected light from the measured surface 201, so that the optical path is turned, and the occupied area of the system 100 on the high-temperature device is positively reduced.
Fig. 4 shows a further preferred embodiment of the invention. Unlike the embodiment shown in fig. 3, in this embodiment, the wavelength selection module 140 uses a filter film disposed on the concave surface of the second concave mirror 132, and the filter film may be formed integrally with the second concave mirror 132. For example, the optical filter film may be directly attached to the concave surface of the second concave mirror 132 or coated on the concave surface of the second concave mirror 132, that is, a new integrated light-focusing imaging and wavelength selecting module 134 is formed, so that the second concave mirror 132 has the light-focusing reflection and filtering effects at the same time, and the integration level of the optical displacement measuring system is further improved.
By using the concave surface of the second concave mirror 132, the reflected light reflected by the measured surface 201 in the laser beam projected onto the measured surface 201 is reflected again, and meanwhile, filtering of infrared light and visible light is also realized, so that the occupied area of the system 100 on high-temperature equipment can be further reduced.
In other embodiments, the planar mirror 121 in the embodiments described above with respect to fig. 3-4 may be replaced with the first concave mirror 122 in the embodiment of fig. 2 to achieve a system 100 configuration with overall optimized performance.
A method of measuring warpage according to the present invention will be described in detail with reference to the accompanying drawings.
Please refer to fig. 5. The invention relates to a method for measuring warpage, which comprises the following steps:
step S1: projecting probe light having a wavelength in a violet or ultraviolet wavelength range onto a surface 201 to be measured of a measurement object 200 in a rotating state in a high-temperature apparatus, so that the probe light scans over the surface 201 to be measured of the measurement object 200;
step S2: the detection light projected onto the detected surface 201 is reflected by the detected surface 201 and then detected by the position detection module 160, and position signals at each measuring point 400 on the detected surface 201 are output;
step S3: according to the position signals at each measuring point 400 on the measured surface 201, a height profile curve of the measured object 200 corresponding to one scanning period is obtained, and the warping degree of the measured object 200 is obtained by comparing the height profile curves of the measured object 200 corresponding to one or more scanning periods.
Please refer to fig. 6. In a preferred embodiment, a method of measuring warpage according to the present invention is further described by taking a high temperature apparatus for performing a high temperature film growth process such as CVD or PVD on a wafer as an example.
The wafer 300 is placed on a susceptor (not shown) in a high temperature apparatus; the base is mounted on the support base. The wafer 300 placed on the susceptor is rotated synchronously by driving the susceptor to rotate on the supporting susceptor.
During high temperature growth of the film in the high temperature apparatus, the wafer 300 is typically subjected to various degrees of warpage due to stress. This warpage affects the subsequent product quality, and therefore requires measurement of warpage for control.
Warp measurement of wafer 300 may be accomplished using an optical displacement measurement system 100 such as any of the above described embodiments of the present invention for high temperature equipment.
First, the light emitting module 110, for example, the laser 111 is activated to emit probe light having a wavelength in the violet or ultraviolet wavelength range. The light reflection module 120, such as the plane mirror 121 or the first concave mirror 122, reflects the probe light emitted by the laser 111 and projects the probe light onto the surface (i.e. the surface 201 to be measured) of the wafer 300. Since the wafer 300 is in a rotating state, the probe light is scanned over the surface to be measured of the wafer 300, and a plurality of measurement points 400 are formed on the surface to be measured of the wafer 300.
The light-condensing imaging module 130, such as the ultraviolet-transmitting lens 131 or the second concave mirror 132, condenses the reflected light reflected by the surface to be measured in the detected light projected onto the surface to be measured of the wafer 300, filters the infrared light and the visible light by the wavelength selecting module 140, such as the optical filter 141, performs ultraviolet enhancement by the position sensitive detector 161 provided with the ultraviolet enhancement film 151, and outputs the position signal of each measuring point 400 on the surface to be measured of the wafer 300.
The second concave mirror 132 with the filter film 142 may be used to collect the detected light reflected by the surface to be measured, filter out the infrared light and the visible light, and reflect the collected light to the position sensitive detector 161 with the ultraviolet enhancement film 151 for ultraviolet enhancement, and then output the position signal of each measuring point 400 on the surface to be measured of the wafer 300.
The control module 170, such as the host computer 171, obtains a height profile of the wafer 300 corresponding to a scan cycle according to the position signals at each measurement point 400 on the measured surface of the wafer 300 output by the position sensitive detector 161. One of the scan periods may be, for example, a time when the wafer 300 rotates one revolution.
When the wafer 300 is a single wafer, the center axis of the wafer 300 is generally coincident with the rotation axis of the susceptor, and therefore, the position where probe light is projected onto the surface to be measured of the wafer 300 is generally deviated from the center point of the wafer 300 at the time of measurement, and the distance between the position and the center point of the wafer 300 is set to r (r is smaller than the size of the wafer). At this time, the height profile obtained in one scan period is the profile at the radius r on the wafer 300.
Specifically, as shown in fig. 6 and 7, for example, assuming that the illustrated wafer 300 has not been warped during the initial scanning period t1, an initial height profile h1 is obtained during the initial scanning period t1 based on the heights (relative heights) measured at the respective measurement points 400 at the radius r on the wafer 300. If the wafer 300 is a planar surface, the initial height profile h1 is a straight line, and if the wafer 300 is a non-planar shaped surface, the initial height profile h1 is a curved line.
Assuming that the illustrated wafer 300 is warped due to stress after being grown through a high temperature process, a current height profile h2 is obtained from the heights measured at each measurement point 400 at the radius r on the wafer 300 during the current scan period t 2. The current height profile h2 is a straight line if the wafer 300 is warped and is a segment of a sphere, and the current height profile h2 is a curve if the wafer 300 is warped and is shaped (e.g., saddle-shaped, potato-shaped, multi-curved, etc.).
In this way, the upper computer 171 (control module 170) reflects the magnitude of the warpage amplitude at each measurement point of the wafer 300 by calculating the amount of change h (h=h2-h 1) between the height profile h2 corresponding to the current scanning period and the height profile h1 corresponding to the initial scanning period.
The upper computer 171 may also compare the average value of each height value in the corresponding height profile h1 in the initial scanning period with the average value of each height value in the corresponding height profile h2 in the current scanning period, so as to determine the warpage amplitude of the wafer. Alternatively, the calculated height values may be compared with a reference height value, such as a height corresponding to a nominal thickness of the wafer 300 or with a mean value of the height values, to determine the warpage magnitude. Other methods of industry may be used to determine the warpage magnitude.
When the wafer 300 is a plurality of wafers, the wafers 300 may be distributed around the rotation axis of the susceptor, where the central axis of each wafer 300 does not coincide with the rotation axis of the susceptor, and the probe light scans the plurality of wafers. Preferably, the position of the probe light projected onto the measured surface of one of the wafers 300 is located at the center point of the wafer (assuming that the distance between the center point of the wafer and the center of the susceptor is R), and the scan trajectory of the probe light on the measured surface of the wafer is on the circumference with the center of the susceptor as the origin radius R, so that the obtained height profile curve in one scan cycle is the warp profile of the plurality of wafers 300 (e.g., wafer 300-1, wafer 300-2, etc.), as shown in fig. 8. The degree of warpage of each wafer 300 is obtained by calculating the difference between the maximum height and the minimum height in each wafer scan curve during the current scan cycle. Similarly, the magnitude of the warpage amplitude at each measurement point 400 of the wafer 300 can also be reflected by calculating the amount of change between the corresponding height profile in the current scan period and the corresponding height profile in the initial scan period.
In general, a high temperature growth process is performed in a high temperature apparatus, which may include a plurality of process time periods. The upper computer 171 can also generate the height profile curves of the wafer 300 in each process time period according to different process time periods, and calculate the variation between the height profile curves of the wafer 300 in each process time period, so as to obtain the warpage degree conditions in different process time periods, thereby being convenient for timely process adjustment in the process.
In summary, the invention measures the warpage phenomenon of the wafer in the high temperature equipment by adopting the height method, and has the advantages that the change of the height of the wafer relative to the position sensitive detector can be intuitively measured, so compared with the traditional method for measuring the warpage by adopting the reflected light, the method is more intuitive, has higher accuracy, can effectively solve the displacement measurement problem of the high temperature equipment, can be applied to the warpage measurement of the wafer 300 which is used for the high temperature growth process, is in high-speed rotation and has different outlines (such as saddle shape, potato shape, multiple curved shapes and other different outlines), is not influenced by the shape of the wafer 300, and is simple, convenient and practical.
While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.
Claims (10)
1. An optical displacement measurement system for a high temperature device, comprising: the device comprises a light emitting module, a light reflecting module, a light focusing imaging module, a position detecting module and a control module;
the light emitting module, the light reflecting module, the light focusing imaging module and the position detecting module form a light path; the light emitting module is used for emitting detection light with wavelength in a purple or ultraviolet wavelength range;
the detection light is reflected by the light reflection module and then projected onto a detected surface of a measurement object in a rotating state in the high-temperature equipment, so that the detection light scans on the detected surface of the measurement object; the detection light reflected by the detected surface is focused by the light-focusing imaging module and then emitted to the position detection module;
the position detection module outputs position signals at all measuring points on the measured surface;
the control module obtains a height profile curve of the measured object corresponding to one scanning period according to the position signals of each measuring point on the measured surface output by the position detection module, compares and analyzes the corresponding height profile curve in one or more scanning periods, and determines the warping degree of the measured object;
the light-gathering imaging module comprises a second concave mirror, and the wavelength selection module comprises an optical filter arranged between the second concave mirror and the position detection module; alternatively, the wavelength selection module includes a filter film disposed on a concave surface of the second concave mirror.
2. The optical displacement measurement system for a high temperature device of claim 1, wherein the position detection module comprises a position sensitive detector provided with an ultraviolet-enhancing film.
3. The optical displacement measurement system for a high temperature device of claim 1, wherein the light reflecting module comprises a planar mirror or a first concave mirror.
4. The optical displacement measurement system for a high temperature device of claim 1, wherein another implementation of the focused imaging module is: the light-gathering imaging module comprises an ultraviolet-transmitting lens, and the wavelength selection module comprises an optical filter arranged between the ultraviolet-transmitting lens and the position detection module.
5. A method for measuring warpage of a high temperature device, comprising:
projecting detection light with a wavelength in a violet or ultraviolet wavelength range onto a measured surface of a measurement object in a rotating state in the high-temperature device, so that the detection light scans over the measured surface of the measurement object;
the detection light projected onto the detected surface is detected by a position detection module after being reflected by the detected surface, and position signals at all measuring points on the detected surface are output, specifically comprising the following steps: condensing the detection light projected onto the detected surface and reflected by the detected surface by using an ultraviolet light transmitting lens or a second concave mirror, filtering infrared light and visible light by using an optical filter, detecting after ultraviolet enhancement by using a position sensitive detector provided with an ultraviolet enhancement film, and outputting position signals at all measuring points on the detected surface;
and obtaining a height profile curve of the measuring object corresponding to one scanning period according to the position signals of each measuring point on the measured surface, and obtaining the warping degree of the measuring object by comparing the height profile curves of the measuring object corresponding to one or more scanning periods.
6. The method according to claim 5, wherein the amount of change between the height profile of the measurement object corresponding to the current scanning period and the height profile of the measurement object corresponding to the initial scanning period is calculated to obtain the degree of warpage of the measurement object.
7. The method according to claim 5, wherein when the measurement object is a plurality of wafers, a difference between a maximum height and a minimum height in the height profile of each wafer corresponding to the current scanning period is calculated to obtain the degree of warpage of each wafer.
8. The method of measuring warpage of claim 5, wherein a high temperature growth process is performed in the high temperature apparatus, the high temperature growth process comprising a plurality of process time periods, the method of measuring warpage further comprising:
and generating the height profile curves of the measuring objects in each process time period, and calculating the variation among the height profile curves of the measuring objects in each process time period to obtain the warping degree of the measuring objects in different process time periods to be used as the basis of process adjustment.
9. The method of measuring warpage according to claim 5, wherein the projecting the probe light having a wavelength in a violet or ultraviolet wavelength range onto the measured surface of the measurement object in the high temperature apparatus, specifically comprises:
and the light emitting module is used for emitting detection light with the wavelength in the purple or ultraviolet wavelength range, the light reflecting module is used for reflecting the detection light and then projecting the detection light onto the measured surface of the measured object, and the light reflecting module comprises a plane reflecting mirror or a first concave mirror.
10. The method of measuring warpage according to claim 5, wherein the probe light projected onto the surface to be measured is reflected by the surface to be measured and then detected by a position detection module, and the position signal at each measurement point on the surface to be measured is outputted, specifically comprising:
the second concave mirror is not matched with the optical filter to filter infrared light and visible light, but the second concave mirror with the optical filter film is used for condensing the detected light projected onto the detected surface and reflected by the detected surface, filtering infrared light and visible light, then reflecting the detected light to the position sensitive detector provided with the ultraviolet enhancement film to carry out ultraviolet enhancement and then detecting, and outputting position signals at all measuring points on the detected surface.
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