CN115507755A - Optical displacement measurement system for high-temperature equipment and method for measuring warping - Google Patents

Abstract

The invention discloses an optical displacement measurement system for high-temperature equipment and a method for measuring warpage, wherein a light emitting module emits detection light with the wavelength within 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 condensed by a light condensing imaging module and then emitted to a position detection module, position signals of each measurement point on the measured surface are output, a control module obtains a height profile curve of the measurement object corresponding to one scanning period according to the position signals, and the height profile curves corresponding to one or more scanning periods are compared and analyzed to determine the warpage degree of the measurement object. The invention can use the purple or ultraviolet wavelength detection light to optically measure the height change of the wafer relative to the detector, can effectively solve the problem of wafer warpage measurement of various profiles in high-temperature equipment, and has simple, convenient and practical method and high accuracy.

Description

Optical displacement measurement system for high-temperature equipment and method for measuring warping

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 warping.

Background

When a film deposition process is performed in high-temperature equipment such as chemical vapor deposition equipment, a plurality of films are deposited and grown on a wafer substrate in sequence, and in the film growth process, the wafer is warped due to the action of stress, the subsequent product quality is affected by the warping phenomenon, and particularly when certain key film layers are grown, the warping needs to be controlled strictly. Therefore, the warpage needs to be measured and controlled on line in real time to reduce the influence on the product quality.

Conventional wafer warp measuring methods, mostly using reflected light measuring methods, such as US patent publication No. US7570368B2, disclose a method and apparatus for measuring the curvature of a reflecting surface, which directs a light beam onto a rotating semiconductor wafer surface so that the light beam is incident on the wafer surface at a series of incident points and is reflected from each incident point, detects the position (position in two dimensions) at which each reflected light beam is incident on a detector, and then calculates the tilt and curvature of the wafer 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) The reflected light measurement reflects only the angle of tilt of the wafer surface and does not reflect the profile height of the wafer, and thus does not visually characterize the degree of wafer warpage. (2) The warpage measurement is performed using the 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 characteristics, the presence of factors such as the tilt of the wafer load and the tilt of the support base (e.g., tilt due to tray rotation effects, tray machining tolerance effects, etc.) will affect the accuracy of the measurement results. (3) In the case of a fragment in which the main surface of the wafer is aspherical, such as a saddle shape, a potato shape, a multi-curved surface, etc., the degree of warpage of the wafer cannot be accurately known by the above-described conventional reflected light measurement method.

Therefore, there is a need to provide a new optical measurement technique for high temperature equipment and measuring warpage to solve the above problems in the prior art.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned drawbacks of the prior art, and providing an optical displacement measuring system and a method for measuring warpage for high temperature devices.

In order to realize the purpose, the technical scheme of the invention is as follows:

the invention provides an optical displacement measurement system for high temperature equipment, comprising: the device comprises a light emitting module, a light reflecting module, a light condensing imaging module, a position detecting module and a control module;

the light emitting module, the light reflecting module, the light condensing imaging module and the position detecting module form a light path; the light emitting module is used for emitting detection light with the wavelength within the purple or ultraviolet wavelength range;

the detection light is reflected by the light reflection module and then projected onto a measured surface of a measuring object in a rotating state in the high-temperature equipment, so that the detection light is scanned on the measured surface of the measuring object; the detection light reflected by the detected surface is focused by the focusing imaging module and then emitted to the position detection module;

the position detection module outputs position signals at each measuring point on the measured surface;

and the control module acquires a height profile curve of the measured object corresponding to one scanning period according to the position signals of the measuring points on the measured surface output by the position detection module, and compares and analyzes the height profile curves corresponding to one or more scanning periods to determine the warping degree of the measured object.

Further, the position detection module comprises a position sensitive detector provided with an ultraviolet enhancement film.

Further, the light reflection module includes a plane 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 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; or, the wavelength selection module comprises a filter film arranged on the concave surface of the second concave mirror.

The invention also provides a method for measuring warpage for high temperature equipment, comprising the following steps:

projecting probe light having a wavelength in a violet or ultraviolet wavelength range onto a measured surface of an measurement object in a rotating state in the high-temperature apparatus so that the probe light is scanned on the measured surface of the measurement object;

the detection light projected onto the measured surface is reflected by the measured surface and then detected by a position detection module, and position signals at each measurement point on the measured surface are output;

and obtaining a height profile curve of the measuring object corresponding to one scanning period according to the position signals of the measuring points 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 variation 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 to obtain the warping degree of the measuring object.

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, a high temperature growth process is performed in the high temperature apparatus, the high temperature growth process including a plurality of process time periods, the method of measuring warpage further including:

and generating a height profile curve of the measured object in each process time period, and calculating the variation between the height profile curves of the measured object in each process time period to obtain the warping degree of the measured object in different process time periods to be used as a basis for process adjustment.

Further, the projecting of the probe light having a wavelength in a violet or ultraviolet wavelength range onto the measured surface of the measurement object located in the high temperature apparatus specifically includes:

the method comprises the steps of using a light emitting module to emit detection light with the wavelength in a purple or ultraviolet wavelength range, using a light reflecting module to reflect the detection light and project the detection light to a measured surface of the measured object, wherein the light reflecting module comprises a plane reflecting mirror or a first concave mirror.

Further, the detecting light projected onto the measured surface is reflected by the measured surface and then detected by a position detecting module, and a position signal at each measuring point on the measured surface 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 out infrared light and visible light by using an optical filter, performing ultraviolet enhancement detection by using a position sensitive detector provided with an ultraviolet enhancement film, and outputting position signals of each measurement point on the detected surface.

Further, the detecting light projected onto the measured surface is reflected by the measured surface and then detected by a position detecting module, and a position signal at each measuring point on the measured surface is output, which specifically includes:

the method comprises the steps of utilizing a concave mirror with a filter film to condense and filter infrared light and visible light of detection light projected onto a detected surface and reflected by the detected surface, reflecting the detection light to a position sensitive detector with an ultraviolet enhancement film to carry out ultraviolet enhancement and then detecting, and outputting position signals of all measuring points on the detected surface.

The optical displacement measuring system for the high-temperature equipment and the method for measuring the warping provided by the invention can utilize the purple or ultraviolet wavelength detection light and adopt a height measurement method to measure the height change of the wafer in the high-temperature equipment relative to the detector, can visually represent the warping degree of the wafer, can prevent the background interference of the heat radiation phenomenon in the high-temperature equipment on the measurement, have high accuracy, are not limited by the loading state or the bearing base state of the wafer and the contour shape of the wafer, and are 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 the warpage measurement is improved.

Drawings

FIGS. 1-4 are schematic structural diagrams of 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 of measuring warpage in accordance with a preferred embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a method of measuring wafer warpage according to the method of FIG. 5 in accordance with a preferred embodiment of the present invention;

FIG. 7 is a diagram showing an exemplary height profile obtained by scanning the same wafer in different scanning cycles according to one embodiment of the present invention; the abscissa of the graph is the rotation angle (unit: degree) and the ordinate is the relative height (unit: micrometer);

FIG. 8 is an exemplary graph of a height profile obtained from a plurality of wafers scanned in a same scan cycle in accordance with a preferred embodiment of the present invention; the abscissa of the graph is the rotation angle (unit: degree) and the ordinate is the relative height (unit: micrometer).

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention. Unless defined otherwise, technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and similar words are intended to mean that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items.

An optical displacement measurement system 100 for a high temperature device of the present invention is located outside a reaction chamber of the high temperature device, and the high temperature device may be a film forming device for a semiconductor high temperature growth process, including a vapor phase reaction device, which 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), or the like. The high temperature device may also be another device for heating the product. In addition, the present invention is not strictly limited to elevated temperatures, which may be applied to any temperature above room temperature. Illustratively, taking MOCVD as an example, the MOCVD is provided with a heating assembly to heat the reaction chamber, so that the process growth temperature is 500-1500 ℃. The high temperature apparatus is provided with a base, the measuring object 200 is a semiconductor chip, for example, a semiconductor wafer or other substrate having different contour shapes; the measurement object 200 may be various other products or samples in a high-temperature apparatus or in a high-temperature state. The measurement object 200 is provided 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 series of thin films are sequentially grown on the object 200 during a semiconductor process in a high temperature apparatus, the object 200 may be warped due to stress. The optical displacement measurement system 100 is used for performing optical displacement measurement on the measurement object 200 in the high-temperature apparatus to obtain a height change of the measurement object 200 due to warpage, thereby reflecting the warpage degree of the measurement object 200.

Optical displacement measurement system 100, comprising: the light emitting module 110, the light reflecting module 120, the condenser imaging module 130, the position detecting module 160, and the control module 170.

The light emitting module 110 is configured to emit probe light having a wavelength in a violet or ultraviolet wavelength range. The probe light is reflected by the light reflection module 120 and then projected onto the surface 201 of the measurement object 200, which is located in a high temperature apparatus and is in a rotating state, so that the probe light is scanned on the surface 201 of the measurement object 200. The probe light reflected by the surface 201 to be measured is condensed by the condensing imaging module 130 and then emitted to the position detection module 160. The position detection module 160 outputs a position signal at each measurement point 400 on the measured surface 201.

The control module 170 obtains a height profile curve of the measurement object 200 corresponding to one scanning period according to the position signal at each measurement point 400 on the measured surface 201 output by the position detection module 160, and performs comparison analysis on the height profile curves corresponding to one or more scanning periods to determine the warping degree of the measurement object 200.

The light emitting module 110, the light reflecting module 120, the condensing imaging module 130, and the position detecting module 160 form a light path, and the light path is set at a position that ensures that the detection light emitted by the light emitting module 110 is incident on the surface of the measurement object 200 through an 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 provides a more detailed description of embodiments of the present invention, with reference to the accompanying drawings.

Please refer to fig. 1. In a preferred embodiment of the optical displacement measuring system 100 for high temperature devices of the present invention, the optical transmission module 110 can employ a laser 111 with an emission wavelength in the violet or ultraviolet wavelength range (emission wavelength <410 nm), for example. The laser 111 emits probe light, which is incident to the light reflection module 120. The light reflection module 120 may employ a mirror, for example, a plane mirror 121. Reflecting the probe light by the plane mirror 121 to project the probe light onto the measurement surface 201 of the measurement object 200; the detection light is reflected to the condensing imaging module 130 through the measured surface 201 of the measurement object 200, condensed by the condensing imaging module 130, and received by the position detection module 160. The condenser 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 manufacturing process, the measurement object 200 is in a rotating state, so that the probe light is scanned on the surface 201 of the measurement object 200 to form a plurality of measurement points 400 on the surface 201. The position detection module 160 detects the optical signals reflected at the measurement points 400 on the measured surface 201, converts the optical signals into position signals (i.e., the changes in the height distance between the measured object 200 and the PSD, which are mapped by the surface height fluctuation of the measured object 200 due to warping), 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, measuring the time of one revolution of the object 200.

In the prior art, a wafer warpage is measured by using a reflected light measurement system, and on the premise of assuming that the main surface of the wafer is a segment of a spherical surface, the wafer inclination angle is calculated by using the positions of reflected lights of different incidence points incident on a detector, so that the curvature is calculated. The wafer tilt angle and curvature can be more complicated to calculate once the wafer is loaded with a tilted (non-horizontal) surface 201, which can cause measurement errors, or due to stress that results in non-spherical segments (e.g., saddles, potato-shaped, multi-curved surfaces, etc.) of the wafer's major surface.

The optical measurement system of the invention intuitively represents the warping degree of the wafer by measuring the height change of the wafer relative to the detector instead of calculating the warping by measuring the wafer inclination, and can judge the warping degree of the wafer by the relative change of the height value of the measured wafer contour even if the measured surface 201 of the wafer is inclined or the main surface of the wafer is aspheric after the wafer is loaded, thereby effectively solving the problem of measuring the warping of the wafer with various contours, and being simple, convenient and practical and having high accuracy.

In addition, when the displacement measuring system is applied to measurement of high-temperature equipment, the measurement surface is the surface of a high-temperature object, and if the displacement measuring system adopts conventional visible light (such as red light) as detection light, the problem of background interference caused by heat radiation of the surface of the object exists, so that the measurement cannot be normally carried out. Therefore, the embodiment of the invention adopts the laser with the wavelength within the purple or ultraviolet wavelength range as the detection light, and can effectively prevent the thermal radiation phenomenon from interfering the displacement measurement.

Further, an ultraviolet enhancement module 150 may be additionally disposed on the position-sensitive detector 161; the uv-enhancing module 150 may be provided with a uv-enhancing film 151, for example. In a preferred embodiment, the uv-enhancing thin film 151 may be a Lumogen (C22H 16N2O 6) phosphor, and the uv-enhanced coated position-sensitive detector 161 may be formed by forming a phosphor layer on the position-sensitive detector 161 by a physical vapor deposition process. The detection light enters the position sensitive detector 161 after being subjected to the ultraviolet enhancement effect of the ultraviolet enhancement film 151, so that the response capability of the position sensitive detector 161 in the purple or ultraviolet range is improved, the detection sensitivity is improved, and the measurement accuracy is improved.

In the embodiment of the present invention, the light reflection module 120 employs the plane mirror 121 to reflect the detection light emitted from 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 measurement object 200 from the optical window on the reaction cavity of the high temperature device. That is, by using the light reflection module 120, the installation position of the light emitting module 110 is not limited, and the flexibility of the optical displacement measurement system 100 when applied to high temperature devices is improved. In a preferred embodiment, the plane mirror 121 is used to project the probe light emitted from the laser 111, such as the probe light in the horizontal direction, onto the surface 201 of the measurement object 200 in the horizontal direction after being reflected. In another preferred embodiment, referring to fig. 2, the light reflection module 120 employs the first concave mirror 122 instead of the plane mirror 121 in fig. 1, which is advantageous in that the plane mirror 121 is changed to a concave mirror, and in addition to projecting the detection light to the measurement object 200 from the optical window on the reaction chamber of the high temperature apparatus, the concave surface of the first concave mirror 122 can be used to better condense the detection light from the laser 111, thereby improving the signal-to-noise ratio.

In a preferred embodiment, the uv-transparent lens 131 is made of a material that is capable of transmitting uv light, so as to increase the signal strength. For example, the uv 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 in front of the position detection module 160 and is used for filtering out infrared light and visible light. In the embodiment of the present invention, the wavelength selection module 140 may adopt an optical filter 141, for example. Specifically, on the optical path at the rear side of the ultraviolet transmitting lens 131, the optical filter 141 and the ultraviolet enhancement coating position sensitive detector 161 are sequentially disposed. The filter 141 is used to filter infrared and visible light in the probe light projected onto the measured surface 201 and reflected by the measured surface 201, so as to eliminate the interference of these wavelengths to the measurement. Therefore, the purple or ultraviolet detection light passes through the optical filter 141 to filter out the infrared light and the visible light, and then passes through the ultraviolet enhancement film 151, so that the enhanced ultraviolet light enters the position sensitive detector 161, the signal-to-noise ratio is further improved, and the measurement precision is improved.

Further, the control module 170 may be an upper computer 171. Alternatively, the control module 170 may be disposed on the upper computer 171. The position sensitive detector 161 can output the detected optical signal as a voltage signal by analog quantity to generate a position signal of the measured surface 201 at each measuring point 400. The upper computer 171 (the control module 170) may generate a height profile curve of the corresponding measurement object 200 in one scanning period by calculation according to the position signal at each measurement point 400 on the measured surface 201 output by the position sensitive detector 161. In addition, the upper computer 171 may compare and analyze the corresponding height profile curves in one or more scanning cycles, so as to determine the degree of warpage of the measurement object 200.

For example, when the measurement object 200 shown in fig. 1 is originally located at the first position a (for example, no warp occurs), the upper computer 171 generates a first height profile curve reflecting the measurement object 201 of the measurement object 200 by calculation based on a first position signal (previous position signal) on each measurement point 400 formed by projection of the detection light on the surface (measurement object 201) of the measurement object 200 output by the position sensitive detector 161 in one scanning cycle. When the position of the measurement object 200 changes (for example, the position changes due to warping), the measurement object 200 is in the second position B, and the upper computer 171 calculates and generates a second height profile curve reflecting the measured surface 201 of the measurement object 200 according to a second position signal (current position signal) of the surface of the measurement object 200 on each measurement point 400, which is output by the position sensitive detector 161, in one scanning cycle. The upper computer 171 compares the second height profile curve with the first height profile curve to obtain a variation difference between the second height profile curve and the first height profile curve, and then the height variation of the measurement object 200 caused by the warpage can be determined, so that the warpage degree is represented by the height variation, and the method is very visual.

Furthermore, since the height profile curve is formed by the heights of the measurement points on the measured surface 201 of the measurement object 200, which can be fitted to the profile of the current warpage of the measurement object 200, the current warpage level 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. The difference from the above-mentioned embodiment shown in fig. 1 is that in this embodiment, the condensing imaging module 130 employs a second concave mirror 132 instead of the ultraviolet-transmitting lens 131 in fig. 1. The concave surface of the second concave mirror 132 is used to condense and reflect the reflected light reflected by the detected surface 201 in the detection light projected onto the detected surface 201, and the reflected light enters the position sensitive detector 161 after the infrared light and the visible light are filtered by the optical filter 141.

A further advantage of this embodiment over the embodiment shown in fig. 1 is that the conventional optical lens generally cannot transmit short wavelength light, so it is necessary to use an ultraviolet transparent material, such as an ultraviolet quartz lens, to transmit light with a wavelength of 410-365 nm, but ultraviolet light with a shorter wavelength cannot be transmitted to be detected by the position sensitive detector 161, and the cost is high. The concave mirror (second concave mirror 132) adopted in this embodiment makes the detection light reach the position sensitive detector 161 by reflection, and not only can play a role of condensing light, but also can make the ultraviolet light with shorter wavelength detected by the position sensitive detector 161, thereby effectively solving the problem that the ordinary optical glass cannot transmit deep ultraviolet light.

In addition, the present embodiment uses the second concave mirror 132 to reflect the reflected light from the measured surface 201, so as to make the optical path turn, thereby having a positive effect on reducing the occupied area of the system 100 on the high-temperature equipment.

Fig. 4 shows yet another preferred embodiment of the present invention. The difference from the embodiment shown in fig. 3 is that in the present embodiment, the wavelength selective module 140 employs a filter film disposed on the concave surface of the second concave mirror 132, and the filter film and the second concave mirror 132 can form an integrated structure. For example, the 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, i.e. a new integrated light-gathering imaging and wavelength selecting module 134 is formed, so that the second concave mirror 132 has both light-gathering reflection and light-filtering effects, and the integration level of the optical displacement measurement 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 simultaneously, the infrared light and the visible light are filtered, so that the occupied area of the system 100 on the high-temperature equipment can be further reduced.

In other embodiments, planar mirror 121 in the embodiments corresponding to fig. 3-4 described above may be replaced with first concave mirror 122 in the embodiment of fig. 2 to achieve a system 100 configuration with comprehensively optimized performance.

The method for measuring warpage according to the present invention is described in detail by the following embodiments 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 measured surface 201 of a measurement object 200 in a rotating state in a high-temperature apparatus so that the probe light is scanned on the measured surface 201 of the measurement object 200;

step S2: the detection light projected onto the measured surface 201 is reflected by the measured surface 201 and then detected by the position detection module 160, and position signals at each measurement point 400 on the measured surface 201 are output;

and step S3: according to the position signals of the measuring points 400 on the measured surface 201, the height profile curve of the corresponding measuring object 200 in one scanning period is obtained, and the warping degree of the measuring object 200 is obtained by comparing the height profile curves of the corresponding measuring objects 200 in one or more scanning periods.

Please refer to fig. 6. In a preferred embodiment, a method for measuring warpage according to the present invention is further described by taking high temperature equipment as an example for performing a high temperature film growth process such as CVD, PVD, etc. on a wafer.

The wafer 300 is placed on a susceptor (not shown) in a high temperature apparatus; the base is mounted on a support base. The wafer 300 placed on the susceptor is driven to rotate synchronously by driving the susceptor to rotate on the support base.

During the high temperature growth of the film on the wafer 300 in the high temperature equipment, the wafer is usually warped to different degrees due to the stress. This warpage phenomenon affects subsequent product quality, and thus warpage measurement is required for control.

The warp measurement of the wafer 300 may be accomplished using, for example, any of the optical displacement measurement systems 100 for high temperature devices of the present invention described above.

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 detection light emitted from the laser 111 is reflected by the light reflection module 120, such as the plane mirror 121 or the first concave mirror 122, and then is projected onto the surface (i.e., the measured surface 201) of the wafer 300. Since the wafer 300 is in a rotating state, the probe light is caused to scan on the measured surface of the wafer 300, forming a plurality of measurement points 400 on the measured surface of the wafer 300.

The light-gathering imaging module 130, such as the uv-transmitting lens 131 or the second concave mirror 132, may be used to gather the reflected light reflected by the measured surface of the detection light projected onto the measured surface of the wafer 300, and then the wavelength selection module 140, such as the filter 141, filters out the infrared light and the visible light, and then the position sensitive detector 161 with the uv-enhancement film 151 is used to perform uv-enhancement detection, so as to output the position signal of each measurement point 400 on the measured surface of the wafer 300.

The second concave mirror 132 with the filter film 142 may also be used to condense, filter, and detect infrared and visible light reflected by the detected surface of the detection light projected onto the detected surface of the wafer 300, and then reflect the condensed and filtered detection light to the position sensitive detector 161 with the uv enhancement film 151 for uv enhancement and detection, so as to output a position signal at each measurement point 400 on the detected surface of the wafer 300.

The control module 170, such as the upper computer 171, obtains a height profile curve of the wafer 300 corresponding to one scanning period according to the position signals at the measuring points 400 on the measured surface of the wafer 300 output by the position sensitive detector 161. One scan cycle may be, for example, the time for one rotation of the wafer 300.

When the wafer 300 is a single wafer, the central axis of the wafer 300 generally coincides with the rotation axis of the susceptor, and therefore the position of the probe light projected onto the measured surface of the wafer 300 is generally deviated from the center point of the wafer 300 at the time of measurement, and the distance between this 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 curve obtained in one scanning cycle is the profile curve at 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 within the initial scanning period t1, the initial height profile curve h1 is obtained from the heights (relative heights) measured at the respective measurement points 400 at the radius r on the wafer 300 within the initial scanning period t 1. If the wafer 300 is a flat surface, the initial height profile curve h1 is a straight line, and if the wafer 300 is a non-flat profile, the initial height profile curve 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 curve h2 is obtained from the heights measured at the respective measuring points 400 at the radius r on the wafer 300 during the current scanning period t 2. If the wafer 300 is warped and then shaped as a spherical segment, the current height profile curve h2 is a straight line, and if the wafer 300 is warped and then shaped as a special (e.g., saddle-shaped, potato-shaped, multi-curved, etc.), the current height profile curve h2 is a curved line.

In this way, the upper computer 171 (the control module 170) reflects the magnitude of the warpage amplitude at each measurement point of the wafer 300 by calculating the variation h (h = h2-h 1) between the height profile curve h2 corresponding to the current scanning period and the height profile curve h1 corresponding to the initial scanning period.

The upper computer 171 may also compare the average value of each height value in the height profile curve h1 corresponding to the initial scanning period with the average value of each height value in the height profile curve h2 corresponding to the current scanning period to determine the warpage amplitude of the wafer. Alternatively, each calculated height value may be compared to a reference height value, such as a height corresponding to a nominal thickness of the wafer 300 or to an average of the height values, etc., to determine the magnitude of the warpage. Other methods of determining the magnitude of the warpage may be used in the industry.

When the wafer 300 is a plurality of wafers, the wafers 300 may be distributed around the axis of rotation of the susceptor, such that the central axis of each wafer 300 does not coincide with the axis of rotation 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 during measurement 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 scanning track of the probe light on the measured surface of the wafer is on the circle with the origin at the radius R, so that the height profile curve obtained in one scanning cycle is the outline of warpage of a plurality of wafers 300 (e.g., wafer 300-1, wafer 300-2, etc.), as shown in fig. 8. The warpage level of each wafer 300 can be obtained by calculating the difference between the maximum height and the minimum height in each wafer scan curve in the current scan cycle. Similarly, the magnitude of the warpage amplitude at each measuring point 400 of the wafer 300 can also be reflected by calculating the variation between the corresponding height profile curve in the current scanning period and the corresponding height profile curve in the initial scanning period.

Generally, 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 can obtain the warpage conditions in different process time periods by calculating the variation of the wafer 300 between the height profile curves in each process time period, so as to facilitate the process adjustment in time in the process.

In summary, the present invention is directed to a wafer warpage phenomenon in a high temperature device, and a height method is adopted for measurement, which has the advantages that the change of the height of the wafer relative to a position sensitive detector can be intuitively measured, so that the method is more intuitive and has higher accuracy compared with the conventional method for measuring the warpage by using reflected light, the problem of displacement measurement for the high temperature device can be effectively solved, and the method can be applied to the warpage measurement for the wafer 300 which is in a high temperature growth process and rotates at a high speed and has different profiles (such as a saddle shape, a potato shape, a multi-time curved surface shape, etc.), and is not influenced by the shape of the wafer 300, and the method is simple and practical.

Although the embodiments of the present invention have been described in detail hereinabove, it is apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it is to be understood that such modifications and variations fall within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention as described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims (13)

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 condensing imaging module, a position detecting module and a control module;

the light emitting module, the light reflecting module, the light condensing imaging module and the position detecting module form a light path; the light emitting module is used for emitting detection light with the wavelength within the purple or ultraviolet wavelength range;

the detection light is reflected by the light reflection module and then projected onto a measured surface of a measurement object in a rotating state in the high-temperature equipment, so that the detection light is scanned on the measured surface of the measurement object; the detection light reflected by the detected surface is focused by the focusing imaging module and then emitted to the position detection module;

the position detection module outputs position signals at each measuring point on the measured surface;

and the control module acquires a height profile curve of the measured object corresponding to one scanning period according to the position signals of the measuring points on the measured surface output by the position detection module, and compares and analyzes the height profile curves corresponding to one or more scanning periods to determine the warping degree of the measured object.

2. The optical displacement measurement system for high temperature equipment of claim 1, wherein the position detection module comprises a position sensitive detector provided with an ultraviolet-enhanced thin film.

3. The optical displacement measurement system for a high temperature apparatus of claim 1, wherein the light reflection module comprises a plane mirror or a first concave mirror.

4. The optical displacement measurement system for high temperature equipment of claim 1, further comprising a wavelength selection module disposed before the position detection module for filtering out infrared light and visible light.

5. The optical displacement measurement system for high temperature equipment of claim 4, wherein the light gathering imaging module comprises an ultraviolet light transmitting lens, and the wavelength selection module comprises a filter disposed between the ultraviolet light transmitting lens and the position detection module.

6. The optical displacement measurement system for a high-temperature device according to claim 4, wherein the light-gathering imaging module comprises a second concave mirror, and the wavelength selection module comprises a filter disposed between the second concave mirror and the position detection module; or, the wavelength selection module comprises a filter film arranged on the concave surface of the second concave mirror.

7. A method of measuring warpage for a high temperature device, comprising:

projecting probe light having 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 apparatus so that the probe light is scanned on the measured surface of the measurement object;

the detection light projected onto the measured surface is reflected by the measured surface and then detected by a position detection module, and position signals at each measurement point on the measured surface are output;

and obtaining a height profile curve of the measuring object corresponding to one scanning period according to the position signals of the measuring points 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.

8. The method of measuring warpage as claimed in claim 7, wherein the amount of change between the height profile curve of the measurement object corresponding to the current scanning period and the height profile curve of the measurement object corresponding to the initial scanning period is calculated to obtain the warpage level of the measurement object.

9. The method of claim 7, wherein when the measured object is a plurality of wafers, the difference between the maximum height and the minimum height in the height profile curve of each wafer corresponding to the current scanning period is calculated to obtain the warpage level of each wafer.

10. The method of measuring warpage of claim 7, wherein a high temperature growth process is performed 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 a height profile curve of the measured object in each process time period, and calculating the variation between the height profile curves of the measured object in each process time period to obtain the warping degree of the measured object in different process time periods to be used as the basis for process adjustment.

11. The method for measuring warpage as claimed in claim 7, wherein the projecting of the probe light having a wavelength in the violet or ultraviolet wavelength range onto the measured surface of the measurement object located in the high temperature apparatus specifically includes:

the method comprises the steps of using a light emitting module to emit detection light with the wavelength in a purple or ultraviolet wavelength range, using a light reflecting module to reflect the detection light and project the detection light to a measured surface of the measured object, wherein the light reflecting module comprises a plane reflecting mirror or a first concave mirror.

12. The method according to claim 7, wherein the step of detecting the probe light projected onto the measured surface by a position detection module after being reflected by the measured surface and outputting a position signal at each measurement point on the measured surface comprises:

and condensing the detection light projected onto the measured surface and reflected by the measured surface by using an ultraviolet light transmitting lens or a second concave mirror, filtering out infrared light and visible light by using an optical filter, performing ultraviolet enhancement by using a position sensitive detector provided with an ultraviolet enhancement film, detecting, and outputting position signals of each measuring point on the measured surface.

13. The method according to claim 7, wherein the detecting light projected onto the surface to be measured is reflected by the surface to be measured and then detected by a position detecting module, and a position signal at each measuring point on the surface to be measured is output, specifically comprising:

the method comprises the steps of utilizing a concave mirror with a filter film to condense and filter infrared light and visible light of detection light projected onto a detected surface and reflected by the detected surface, reflecting the detection light to a position sensitive detector with an ultraviolet enhancement film to carry out ultraviolet enhancement and then detecting, and outputting position signals of all measuring points on the detected surface.

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