CN214898335U

CN214898335U - Substrate back defect detection device

Info

Publication number: CN214898335U
Application number: CN202121481660.8U
Authority: CN
Inventors: 于大维; 朱振朋; 陆志毅; 王婷婷; 周许超; 李运锋
Original assignee: Shanghai Micro Electronics Equipment Co Ltd
Current assignee: Shanghai Micro Electronics Equipment Co Ltd
Priority date: 2021-06-30
Filing date: 2021-06-30
Publication date: 2021-11-26
Anticipated expiration: 2031-06-30

Abstract

The utility model provides a substrate back defect detection device, which comprises an illumination unit, a focusing unit and a detection unit; the light beam emitted by the lighting unit reaches the back of the substrate after being reflected by the focusing unit, and enters the detection unit through the focusing unit after being reflected by the back of the substrate, the focusing unit focuses in real time to enable the back of the substrate to be located at the focal plane position, and the detection unit obtains the defects of the back of the substrate. The position of the focal plane is adjusted by adjusting the focusing unit in real time, so that the back surface of the substrate is located at the position of the focal plane, and the problem of low back surface defect detection accuracy in a high-speed rotation state of the substrate can be solved.

Description

Substrate back defect detection device

Technical Field

The utility model relates to a basement defect detecting technical field, in particular to basement back defect detecting device.

Background

As the tolerances of semiconductor device manufacturing processes continue to narrow, the need for improved semiconductor substrate inspection and inspection tools continues to increase. A common inspection tool is a substrate defect detection system, such as a system for substrate backside defect detection.

In the existing system for detecting the defects on the back of the substrate, when the substrate is rotated and detected, the substrate is adjusted to focus in real time, so that the efficiency is low, the substrate in a rotating state is easily damaged, and the local view field area cannot be focused independently. The focusing and image shooting of the local view field area are carried out by adjusting the vertical position of the optical-mechanical detector comprising the lens barrel, the efficiency is low, the device is suitable for the working conditions of static, low-speed and positioning detection of the substrate, and the defect detection of real-time focusing of the substrate in a high-speed rotation state cannot be met. The consistency of the scanning results is affected by the high speed rotational motion of the substrate. That is, the movement and focusing of the focusing optical element in the conventional substrate back defect detection system along the vertical direction may cause the optical axis to shift on the substrate surface, which may cause the overlap or lack of the detection signals of the signal detection unit, and may not allow real-time focusing in the high-speed rotation state of the substrate; the specific movement distance of the focusing optics cannot be determined.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a basement back defect detecting device to solve the problem that the basement back defect detection accuracy is low under high-speed rotation state.

In order to solve the above technical problem, the utility model provides a substrate back defect detecting device, which comprises an illumination unit, a focusing unit and a detection unit; the light beam emitted by the lighting unit reaches the back of the substrate after being reflected by the focusing unit, and enters the detection unit through the focusing unit after being adjusted by the back of the substrate, the focusing unit focuses in real time to enable the back of the substrate to be located at a focal plane position, and the detection unit obtains the back defect of the substrate.

Optionally, the focusing unit includes a vertical measuring device, and the vertical measuring device is configured to measure a height difference between a back position of the substrate and a focal plane position.

Optionally, the focusing unit includes optical prism and micro-motion device, vertical measuring device will basement back position and focal plane position difference in height transmit extremely micro-motion device's controller, the micro-motion device drive optical prism all becomes 45 contained angle directions removal along with incident focusing light optical axis direction and emergent focusing light optical axis direction, so that basement back position is located the focal plane position, and wherein, incident focusing light optical axis direction and emergent focusing light optical axis direction contained angle are 90 degrees.

Optionally, the moving distance of the optical prism is: and Δ d (Δ h sin45 °)/2n, where Δ d is a distance that the optical prism moves along a direction forming an included angle of 45 ° with both the optical axis direction of the incident focusing light and the optical axis direction of the outgoing focusing light, Δ h is a height difference between the back surface position of the substrate and the focal surface position, and n is a refractive index of the optical prism.

Optionally, the optical prism includes two reflecting surfaces, and an included angle between the two reflecting surfaces is 45 degrees.

Optionally, the focusing unit further includes a mirror group and a micro-motion device, and the micro-motion device drives the mirror group to move, so that the back position of the substrate is located at the focal plane position.

Optionally, the reflector group includes two reflectors, and an included angle between the two reflectors is 45 degrees.

Optionally, the focusing unit further includes a liquid prism and a micro-motion device, and the micro-motion device drives a liquid vibration frequency in the liquid prism to change a light refractive index of the liquid prism, so that the back position of the substrate is located at a focal plane position.

Optionally, the height difference between the back surface position of the substrate and the focal plane position is: Δ h is (n-n ') (L1+ L2+ L3), where Δ h is a height difference between a back surface position and a focal surface position of the substrate, n is an initial refractive index of the liquid prism, n' is a refractive index after vibration of the liquid prism, and L1, L2, and L3 are optical path distances of the light beam in the liquid prism.

Optionally, the focusing unit further includes a wedge prism set and a micro-motion device, and the micro-motion device drives the wedge prism set to move, so that the back position of the substrate is located at the focal plane position.

Optionally, the wedge prism group includes two wedge prisms, and the micro-motion device drives the two wedge prisms to move relatively, so that the back position of the substrate is located at the focal plane position.

Optionally, the height difference between the back surface position of the substrate and the focal plane position is: and delta h is L cos theta, wherein delta h is the height difference between the back surface position and the focal plane position of the substrate, L is the translation amount of the inclined surfaces of the two wedge-shaped prisms, and theta is the wedge angle of the wedge-shaped prisms.

Optionally, the illumination unit comprises a bright field light source and a dark field illumination system.

Optionally, the dark field illumination system comprises 0 degree and 90 degree directional illumination to highlight defect features within the detected field of view.

Optionally, when the focusing unit focuses in real time, the optical axis of the light beam incident to the back surface of the substrate does not shift in the plane where the back surface of the substrate is located.

The utility model provides a basement back defect detecting device, including lighting unit, focusing unit and detection unit, lighting unit sends the light beam process the focusing unit reachs the basement back after adjusting, warp behind the basement back reflection the focusing unit gets into the detection unit, the position of focusing unit real-time adjustment focal plane, so that the back of basement is located the focal plane position, can solve the problem that the accuracy of back defect detection is low under the high-speed rotation state of basement.

Drawings

Fig. 1 is a schematic view of a substrate back defect detection apparatus according to a first embodiment of the present invention;

fig. 2 is a schematic diagram of a real-time focal plane adjustment according to a first embodiment of the present invention;

fig. 3 is a working side view of a substrate back defect detecting apparatus according to a first embodiment of the present invention;

fig. 4 is a bottom view of the substrate back defect detecting apparatus according to the first embodiment of the present invention;

fig. 5 is a schematic movement diagram of a substrate back defect detecting apparatus according to a first embodiment of the present invention;

fig. 6 is a schematic view illustrating a step-by-step rotation of a substrate back defect detecting apparatus according to a first embodiment of the present invention;

fig. 7 is a schematic view of a dark field illumination system of a substrate back defect detecting apparatus according to a first embodiment of the present invention;

fig. 8 is a top view of a substrate back defect detecting apparatus according to a first embodiment of the present invention;

fig. 9 is a schematic view of a substrate suction clamping device according to a first embodiment of the present invention;

fig. 10 is a schematic view of measurement results of a bright field and a dark field according to a first embodiment of the present invention;

fig. 11 is a flowchart of a method for detecting defects on a backside of a substrate according to a first embodiment of the present invention;

fig. 12 is a schematic diagram of the real-time focal plane adjustment according to the second embodiment of the present invention;

fig. 13 is a flowchart of a method for detecting defects on the back surface of a substrate according to a second embodiment of the present invention;

fig. 14 is a flowchart of a method for detecting defects on the back surface of a substrate according to a third embodiment of the present invention;

fig. 15 is a schematic diagram of a real-time focal plane adjustment according to a fourth embodiment of the present invention;

fig. 16 is a schematic diagram of the real-time focal plane adjustment of embodiment five of the present invention;

in the figure, the position of the upper end of the main shaft,

10-an opto-mechanical system; 101-bright field light source; 102-a reflecting unit; 103-an imaging objective lens; 104-a focusing unit; 104 a-an optical prism; 104a 1-optical prism first reflective surface; 104a 2-optical prism second reflective surface; 204 a-mirror group; 204a1 — first mirror; 204a 2-second mirror; 304 a-a liquid prism; 304a 1-liquid prism first reflective surface; 304a 2-liquid prism second reflective surface; 404 a-double wedge prism; 404a1 — a first wedge prism; 404a 2-second wedge prism; 104 b-a vertical measuring device; 104 c-a half-mirror; 104 d-a micro-motion device; 105-dark field illumination system; 105a-0 pole illumination; 105b-90 pole illumination; 106-a detection unit;

11-a stepper motor;

20-a rotating electrical machine;

21-a substrate; 22-a suction cup; 23-base snap;

a-the direction of the optical axis of the incident focusing light; b-emitting the focusing optical axis direction.

Detailed Description

The substrate back defect detecting device of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more fully apparent from the following description and appended claims. It should be noted that the drawings are in simplified form and are not to precise scale, and are provided for convenience and clarity in order to facilitate the description of the embodiments of the present invention.

[ EXAMPLES one ]

Fig. 1 is a schematic view of a substrate back defect detection apparatus according to a first embodiment of the present invention. The substrate of this embodiment is, for example, a wafer. As shown in fig. 1, the substrate back defect detecting apparatus includes an optical mechanical system 10 and a stepping motor 11, the stepping motor 11 is connected to the optical mechanical system 10 and drives the optical mechanical system 10 to move, the optical mechanical system 10 includes an illumination unit, a focusing unit 104 and a detection unit 106, a light beam emitted by the illumination unit is reflected by the focusing unit 104 to reach the back of the substrate 21, and then is reflected by the back of the substrate 21 and enters the detection unit 106 through the focusing unit 104, the focusing unit 104 focuses in real time to enable the back of the substrate 21 to be located at a focal plane position, and then the detection unit 106 obtains the back defect of the substrate 21.

In the present embodiment, the illumination unit includes a bright field light source 101 and a dark field illumination system 105. Further, a reflection unit 102 and an imaging objective lens 103 are disposed between the bright field light source 101 and the focusing unit 104. The reflection unit 102 is used for changing the optical path, which facilitates the flexible arrangement of the position of the optical element. The imaging objective 103 is used for projection imaging. The light beam emitted by the illumination unit enters the imaging objective 103 after being reflected by the reflection unit 102, and the light beam enters the focusing unit 104 after being emitted from the imaging objective 103.

In this embodiment, when the focusing unit 104 focuses in real time, the optical axis of the light beam incident on the back surface of the substrate is not shifted in the plane of the back surface of the substrate.

Fig. 2 is a schematic diagram of a real-time focal plane adjustment according to an embodiment of the present invention. In this embodiment, the focusing unit 104 further includes a vertical measuring device 104b for measuring a height difference between the back surface position and the focal surface position of the substrate 21. The focusing unit 104 comprises an optical prism 104a and a micro-motion device 104d, the optical prism 104a comprises an optical prism first reflecting surface 104a1 and an optical prism second reflecting surface 104a2, and the included angle between the optical prism first reflecting surface 104a1 and the optical prism second reflecting surface 104a2 is 45 degrees. Vertical measuring device 104B will the back position of basement 21 and the difference in height of focal plane position transmit extremely micro-motion device 104 d's controller, micro-motion device 104d drive optical prism 104a all becomes 45 contained angle directions along with incident focusing optical axis direction A and emergent focusing optical axis direction B and removes, so that the back of basement 21 is located the focal plane position, wherein, the contained angle of incident focusing optical axis direction A and emergent focusing optical axis direction B is 90. The focusing unit 104 can focus in real time in a state where the substrate 21 is rotated at a high speed. The two reflecting surfaces of the optical prism 104a are placed at an angle of 45 degrees, the vertical measuring device 104b obtains the vertical position in real time and feeds the vertical position back to the controller of the micro-motion device 104d, and the micro-motion device 104d controls the optical prism 104a to move according to the direction shown in fig. 2. In the moving process, the included angle of 45 degrees is kept constant between the two reflecting surfaces to ensure that the emitted principal ray is constant, and only the optical path is changed for focusing.

The moving distance of the optical prism 104a is:

Δd＝(Δh*sin45°)/(2n) (1)

and delta d is the distance of the optical prism moving along the direction forming an included angle of 45 degrees with the optical axis direction of the incident focusing light and the optical axis direction of the emergent focusing light, delta h is the height difference between the back position of the substrate and the position of the focal plane, and n is the refractive index of the optical prism.

Fig. 3 is the utility model discloses basement back defect detecting device working side view, fig. 4 is the utility model discloses a basement back defect detecting device working bottom view, fig. 5 is the utility model provides a basement back defect detecting device motion schematic diagram, fig. 6 is the utility model provides a rotatory step motion schematic diagram of basement back defect detecting device of first.

Referring to fig. 3-6, in the present embodiment, the rotating motor 20 is used for rotating scanning, and the stepping motor 11 is used for moving the optical mechanical structure 10 to step. The rotary motor 20 serves as an execution end of the rotational scanning of the substrate 21. The angular velocity of the rotary motor 20 increases as the scanning radius decreases. The stepping motor 11 drives the optical mechanical system 10 to move horizontally, and the linear scanning speed of the rotating motor 20 is constant during stepping. Without affecting the function of the opto-mechanical system 10, the installation position of the stepping motor 11 is not limited, and for example, the stepping motor may be installed at the bottom, the left side, or the right side of the opto-mechanical system 10 (installed at the right side of the opto-mechanical system 10 in fig. 1), so as to drive the opto-mechanical system 10 to move. The rotating motor 20 can move from the edge of the substrate 21 to the center of circle or from the center of circle to the edge during the rotation process. The number of steps of the stepping motor 11 is set to be N according to the size of the field of view and the detection index, for example, a 12-inch substrate is detected, where N is 13, and N may be other values. The arrows in said fig. 3 refer to the direction of movement of the light beam.

Fig. 7 is a schematic view of a dark field illumination system of a substrate back defect detecting apparatus according to a first embodiment of the present invention. As shown in fig. 7, the dark field illumination system 105 includes 0-pole illumination and 90-pole illumination to highlight defect features within the detected field of view.

In this embodiment. The dark field illumination system 105 illuminates the dark field in the directions of 0 degrees and 90 degrees, the illumination range is 30 degrees to 60 degrees, and the defect characteristics in the detected field of view are highlighted. And completing the rotating scanning dark field detection of the whole substrate through N steps. The bright field light source 101 irradiates, and the bright field adopts coaxial irradiation to detect defects in a view field. And completing the rotary scanning bright field detection of the whole substrate by N steps.

Fig. 8 is a top view of the first embodiment of the present invention showing the operation of the substrate back defect detecting device, and fig. 9 is a schematic view of the first embodiment of the present invention showing the substrate adsorbing and clamping device. As shown in fig. 8-9, in this embodiment, the suction gripping means of the substrate comprises a substrate catch 23 and a suction cup 22. The base 21 is fixed by three-point dispersion distributed buckles, so that the base 21 can keep stability under rotation to perform accurate detection. Because the gravity influence of basement 21 can lead to deformation when the back of basement 21 detects, brings the deviation to the testing result, for the basement deformation influence that eliminates because gravity leads to, the upper surface of basement 21 utilizes sucking disc 22 increases the adsorption affinity, makes basement 21 can keep good roughness under the rotation.

In this embodiment, the detection unit 106 is, for example, a high-frequency camera detector, and is used for detecting defects in cooperation with a high-strobe light source, and detecting a field-of-view high-speed image. The high frequency camera detector is for example an area camera or a line camera. The area array camera, the 0-pole illumination 105a and the 90-pole illumination 105b of the high-frequency flash dark field light source and the bright field light source 101 form a detection system, and a single picture is taken of a picture irradiated by the high-frequency flash light source. The line camera and the 0-pole illumination 105a and the 90-pole illumination 105b of the normally bright dark field light source, and the bright field light source 101 form a detector system for detecting a shot image of a detected object irradiated by the normally bright light source. Compared with an area-array camera, the linear array camera has higher frequency, and completes picture synthesis on the acquired single-frame pixel image.

Fig. 10 is a schematic view of measurement results of a bright field and a dark field according to a first embodiment of the present invention. As shown in fig. 10, in the present embodiment, the method for collecting and processing the detection data includes, for example: firstly, collecting and processing bright field and dark field detection data; second, the bright field dark field defect is identified and calculated using an image identification algorithm, such as, but not limited to, machine vision, neural network, and the like. The measurement results of the bright field and the dark field are shown in fig. 10, and the defect images at different positions of the back surface of the wafer in the bright field and the defect images at different positions of the back surface of the wafer in the dark field are shown.

Fig. 11 is a flowchart of a method for detecting defects on a backside of a substrate according to a first embodiment of the present invention. As shown in fig. 11, a method for detecting defects on the back surface of a single-detector substrate with real-time focusing includes the following steps:

before step S10, the substrate is pre-aligned and the loading process is performed to ensure that the substrate rotation angle has been adjusted in place.

Step S10, the substrate is placed and fixed.

Specifically, in step S10, the substrate 21 is placed, the substrate is held by the substrate holder 23, and the substrate is sucked onto the rotary motor 20 by the suction cup 22. Further, after the substrate is sucked, step S101 is executed to detect whether the substrate 21 is correctly sucked, if so, step S20 is executed, otherwise, step S10 is returned to.

And step S20, configuring a dark field incidence angle and an illumination range, initializing a position by a stepping motor, moving to the edge of the substrate, and rotationally scanning the dark field.

Specifically, in step S20, the step motor 11 moves the opto-mechanical system 10 to the edge of the substrate 21 for preparation, then the focusing unit 104 is turned on for focal plane detection, the detection unit 106 adopts a high-frequency free exposure mode, different angular velocities are set according to the size of the substrate 21 and the circumference of a single turn, the dark field illumination system 105 illuminates from 0 ° and 90 ° directions, and a suitable illumination range is selected from 30 ° to 60 °. In addition, the irradiation strobe time Δ t and the number of steps N are set, and the present procedure is exemplified by 13 steps. Then, the rotating motor 20 drives the substrate 21 to perform a rotating scan, the dark field illumination system 105 performs an illumination, and the detection unit 106 performs a high frequency image taking in combination with a high stroboscopic light source.

Step S30, measuring the vertical position and judging whether the back of the substrate is positioned at the focal plane position; if so, the next step is performed (step S40); if not, the micro-motion device drives the optical prism to move according to a preset angle, and the back surface of the substrate is adjusted to be located at the focal plane position.

Specifically, in step S30, during the rotation of the substrate 21, the vertical measuring device 104b measures the vertical height in real time and feeds back the height difference Δ h between the back surface of the substrate and the focal plane, the distance of moving the optical prism 104a according to Δ h is Δ d, the moving angle of the optical prism 104a forms 45 ° with the optical axis, and the moving distance of the optical prism 104a satisfies:

Δd＝(Δh*sin45°)/(2n) (1)

In step S40, the detecting unit 106 obtains the picture after dark field illumination after 13 steps.

Specifically, in step S40, the stepping motor 11 drives the opto-mechanical system 10 to move, and the dark field rotation scanning determines whether the cycle number reaches 13, if not, the stepping movement and the dark field rotation scanning are continuously executed, and if so, the next step is performed.

Step S50, the dark field detection is finished, and the stepping motor 11 carries the opto-mechanical system 10 to move to the edge of the substrate 21.

In step S60, the bright field light source 101 irradiates and repeats N (for example, 13) step-by-step rotational scans, and the detection unit 106 acquires a picture after bright field illumination.

Specifically, in step S60, the stepping motor 11 drives the optical-mechanical system 10 to move, and the open-field rotation scanning determines whether the cycle number reaches 13; if not, continuing to execute stepping motion and bright field rotary scanning; if so, the next step is performed (step S70).

In step S70, the dark field and bright field photographed pictures are collected and processed to complete the back defect detection of the substrate 21 once.

[ example two ]

Fig. 12 is a schematic diagram of the real-time focal plane adjustment according to the second embodiment of the present invention. As shown in fig. 12, the difference between the second embodiment and the first embodiment is that the focusing unit 104 of the substrate backside defect inspection apparatus employs a mirror group 204a instead of the optical prism 104a in the first embodiment as a real-time focusing optical path reflection apparatus, the mirror group 204a is composed of a first mirror 204a1 and a second mirror 204a2, and the first mirror 204a1 and the second mirror 204a2 are disposed at an included angle of 45 °. The vertical measuring device 104b obtains a vertical position in real time and feeds the vertical position back to the controller of the micro-motion device 104d, and the micro-motion device 104d controls the mirror group 204a to move according to the direction shown in fig. 12. And in the moving process, the included angle of 45 degrees is kept unchanged so as to ensure that the emitted main light ray is unchanged, and only the optical path is changed for focusing.

In this embodiment, a dual detector is adopted for performing rotary scanning, the detection unit 106 includes a first detector and a second detector, the first detector is used for obtaining a picture of dark field illumination, the second detector is used for obtaining a picture of bright field illumination, the pictures of dark field and bright field can be completed by one step, the detection of the defect on the back of the substrate is completed, and the efficiency is improved.

Fig. 13 is a flowchart of a substrate back defect detection method according to the second embodiment of the present invention, and as shown in fig. 13, a method for detecting defects of a substrate back with two detectors and capable of focusing in real time includes the following steps:

before step S10, the substrate is pre-aligned and the loading process is performed. The substrate 21 is rotated by an angle adjusted in place.

Step S10, the substrate is placed and fixed.

In step S10, the substrate 21 is placed, clamped by the substrate clamp 23, and sucked onto the rotary motor 20 by the suction cup 22.

Step S101 is further included after the step S10, and it is detected whether the substrate 21 is correctly adsorbed, if yes, the next step is performed, and if no, the step returns to step S10.

And step S20, configuring a dark field incidence angle and an irradiation range, initializing a position by a stepping motor, moving to the edge of the substrate, and rotationally scanning.

In step S20, the stepper motor 11 moves the opto-mechanical system 10 to the edge of the substrate 21 for preparation; the focusing unit 104 is turned on to perform focal plane detection, the first detector and the second detector adopt a high-frequency free exposure mode, and the first detector and the second detector respectively use different optical filters; different angular velocities are set according to the substrate size and the single turn perimeter, and dark field illumination system 105 illuminates from 0 ° and 90 ° directions, selecting a suitable illumination range in the range of 30 ° to 60 °. The irradiation strobe time Δ t and the number of steps N are set, and the process is exemplified by 13 steps. The dark field illumination and the bright field illumination are simultaneously irradiated, the rotating motor 20 drives the substrate to carry out rotary scanning, and the first detector and the second detector simultaneously take pictures after 13 stepping at high frequency. The first detector is used for shooting dark field illumination pictures, and the second detector is used for shooting bright field illumination pictures.

Step S30, measuring the vertical position, and determining whether the back of the substrate is located at the focal plane position, if yes, performing the next step, otherwise, the micro-motion device drives the mirror group 204a to move according to the preset angle, and adjusts the back of the substrate to be located at the focal plane position.

In step S30, during the rotation of the substrate 21, the vertical measuring device 104b measures the vertical height in real time and feeds back the measured vertical height to the controller of the micro-motion device 104d of the mirror group, and the main light ray is not changed and the focus is adjusted by changing the optical path while keeping the 45 ° included angle unchanged.

In step S40, the detection unit 106 obtains pictures after dark field illumination and bright field illumination after 13 steps.

In step S40, the stepping motor 11 drives the opto-mechanical system 10 to move, and the dark field and the bright field rotate and scan simultaneously, and determines whether the cycle number reaches 13, if not, the stepping motor and the dark field rotate and scan are continuously executed, and if yes, the next step S50 is performed. The first detector is used for shooting dark field illumination pictures, and the second detector is used for shooting bright field illumination pictures.

And step S50, collecting and processing the pictures shot in the dark field and the bright field, and completing the back defect detection of the substrate once.

[ EXAMPLE III ]

The difference from the first embodiment is that the detection unit 106 in this embodiment includes a first detector and a second detector, the first detector and the second detector are not operated at the same time, the first detector is used for taking a dark field illumination picture, the second detector is used for taking a bright field illumination picture, the dark field illumination and the bright field illumination are irradiated at a staggered time sequence, and the alternate operation is controlled by using a synchronization signal. The rotating motor 20 drives the substrate 21 to perform rotating scanning, and the first detector and dark field illumination work simultaneously when the rising edge of the synchronous signal is detected; the falling edge of the synchronization signal, the second detector works simultaneously with the bright field illumination.

Fig. 14 is a flowchart of a method for detecting defects on the back surface of a substrate according to a third embodiment of the present invention. As shown in fig. 14, a method for detecting defects on the back of a dual-detector substrate with real-time focusing includes the following steps:

Step S10, the substrate is placed and fixed.

The step S10 further includes a step S101 of detecting whether the substrate 21 is correctly adsorbed, if so, proceeding to the next step, and if not, returning to the step S10.

And step S20, configuring a dark field incident angle and an illumination range, initializing a position of a stepping motor, moving to the edge of the substrate, and turning off dark field illumination, bright field illumination and dark field illumination.

In step S20, the stepper motor 11 moves the opto-mechanical system 10 to the edge of the substrate 21 for preparation; the focusing unit 104 is turned on to detect a focal plane, the first detector and the second detector adopt a high-frequency free exposure mode, different angular velocities are set according to the size of the substrate 21 and the circumference of a single circle, the dark field illumination system 105 illuminates from 0-90 degrees, a proper illumination range is selected within a range of 30-60 degrees, illumination strobe time delta t and stepping times N are set, and the process takes the example that N is 13 steps. The dark field illumination and the bright field illumination are irradiated in a staggered time sequence, and the alternate work is controlled by using a synchronous signal. The rotating motor 20 drives the substrate 21 to perform rotating scanning, and the first detector and dark field illumination work simultaneously when the rising edge of the synchronous signal is detected; the falling edge of the synchronization signal, the second detector works simultaneously with the bright field illumination.

And step S30, measuring the vertical position, judging whether the back of the substrate is positioned at the focal plane position, if so, carrying out the next step, and if not, driving the reflector group to move according to a preset angle by the micro-motion device, and adjusting the back of the substrate to be positioned at the focal plane position.

In step S30, in the rotation process of the substrate 21, the vertical measuring device 104b measures the vertical height in real time and feeds back the height difference Δ h between the back surface of the substrate and the focal surface, moves the optical prism or the mirror group Δ d according to Δ h, adjusts the optical prism or the mirror group to translate Δ d along the angular bisector of the included angle of the mirror group while keeping the included angle of 45 ° unchanged with the principal ray unchanged, and satisfies the following requirements:

Δd＝(Δh*sin45°)/(2n) (1)

In step S40, the stepping motor 11 drives the opto-mechanical system 10 to move, perform rotational scanning, turn on dark field illumination, turn off bright field illumination, take dark field pictures with the first detector, turn on bright field illumination, turn off dark field illumination, take bright field pictures with the second detector, determine whether the cycle number reaches 13, if not, continue to perform stepping motion and rotational scanning, and if so, perform the next step. The first detector is used for shooting dark field illumination pictures, and the second detector is used for shooting bright field illumination pictures.

[ EXAMPLE IV ]

Fig. 15 is a schematic diagram of the real-time focal plane adjustment according to the fourth embodiment of the present invention. As shown in fig. 15, the difference from the first embodiment is that the focusing unit 104 of the substrate backside defect inspection apparatus employs a liquid prism 304a instead of the optical prism 104a in the first embodiment, the liquid prism 304a includes a liquid prism first reflection surface 304a1 and a liquid prism second reflection surface 304a2, and the included angle between the liquid prism first reflection surface 304a1 and the liquid prism second reflection surface 304a2 is set at 45 °, so as to serve as a real-time focusing optical path reflection apparatus. The focusing purpose is achieved according to the influence of the vibration frequency of the liquid on the reflectivity of the light. The vertical measuring device 104b obtains a vertical position in real time and feeds the vertical position back to the controller of the micro-motion device 104d, and the micro-motion device 104d controls the vibration frequency of liquid in the liquid prism 304a, so that the refractive index of the light is changed and focusing is performed.

The embodiment also provides a single detector substrate back defect detection method capable of focusing in real time, which comprises the following steps:

Step S10, the substrate is placed and fixed.

In step S20, the stepper motor 11 moves the opto-mechanical system 10 to the edge of the substrate 21 for preparation; the focusing unit 104 is turned on for focal plane detection, and the detection unit 106 adopts a high-frequency free exposure mode; different angular velocities are set according to the size of the substrate 21 and the circumference of a single turn, and the dark field illumination system 105 illuminates from 0 ° and 90 ° directions, selecting a suitable illumination range within the range of 30 ° to 60 °. The irradiation strobe time Δ t and the number of steps N are set, and the process is exemplified by 13 steps.

The rotary motor 20 drives the substrate 21 to perform rotary scanning. The dark field illumination system 105 illuminates, in combination with a high strobe light source, the detection unit 106 performs a high frequency beat.

Step S30, measuring the vertical position, and determining whether the back of the substrate is located at the focal plane position, if so, performing the next step, otherwise, driving the liquid prism 304a to move according to a preset angle by the micro-motion device, and adjusting the back of the substrate to be located at the focal plane position.

In step S30, during the rotation of the substrate 21, the vertical measuring device 104b measures the vertical height in real time and feeds back the height difference Δ h between the back surface of the substrate and the focal plane, and changes the liquid vibration frequency according to the Δ h movement to change the refractive index from n to n', so as to satisfy the following requirements:

Δh＝(n-n’)*(L1+L2+L3) (2)

wherein Δ h is a height difference between a back surface position and a focal surface position of the substrate, n is an initial refractive index of the liquid prism, n' is a refractive index after vibration of the liquid prism, and L1, L2, and L3 are optical path distances of the light beam in the liquid prism.

In step S40, the stepping motor 11 drives the opto-mechanical system 10 to move, and the dark field rotation scanning determines whether the cycle number reaches 13, if not, the stepping motion and the dark field rotation scanning are continuously performed, and if so, the next step S50 is performed.

In step S60, the bright field light source 101 irradiates and repeats 13 stepping rotational scans, and the detection unit 106 acquires a bright field illuminated picture.

In step S60, the stepping motor 11 drives the opto-mechanical system 10 to move, and the bright field rotation scanning determines whether the number of cycles reaches 13, if not, the stepping movement and the bright field rotation scanning are continuously performed, and if so, the next step S70 is performed.

[ EXAMPLE V ]

Fig. 16 is a schematic diagram of the real-time focal plane adjustment of embodiment five of the present invention; the difference from the first embodiment is that the focusing unit 104 of the substrate backside defect detection apparatus employs a double wedge prism 404a instead of the optical prism 104a in the first embodiment as an optical path reflection apparatus capable of focusing in real time. The double wedge prism 404a includes a first wedge prism 404a1 and a second wedge prism 404a 2. The optical path is changed by the relative movement of the two wedge prisms. The vertical measuring device 104b obtains a vertical position in real time and feeds the vertical position back to the controller of the micro-motion device 104d, and the micro-motion device 104d controls the two wedge prisms to move relatively, so that the optical path is changed for focusing.

Step S10, the substrate is placed and fixed.

In step S20, the stepper motor 11 moves the opto-mechanical system 10 to the edge of the substrate 21 for preparation; the focusing unit 104 is turned on for focal plane detection, and the detection unit 106 adopts a high-frequency free exposure mode; different angular velocities are set according to the substrate size and the single turn perimeter, and dark field illumination system 105 illuminates from 0 ° and 90 ° directions, selecting a suitable illumination range in the range of 30 ° to 60 °. The irradiation strobe time Δ t and the number of steps N are set, and the process is exemplified by 13 steps.

And step S30, measuring the vertical position, and judging whether the back surface of the substrate is positioned at the focal plane position, if so, carrying out the next step S40, and if not, driving the first wedge-shaped prism to move according to a preset angle by the micro-motion device, and adjusting the back surface of the substrate to be positioned at the focal plane position.

In step S30, during the rotation of the substrate 21, the vertical measuring device 104b measures the vertical height in real time and feeds back the height difference Δ h between the back surface and the focal plane of the substrate 21, and changes the translation L of the first wedge prism 404a1 according to the Δ h movement, and the first wedge prism 404a1 translates along the inclined surface, where the translation L satisfies:

Δh＝L*cosθ (3)

and L is the translation amount of the inclined plane of the first wedge-shaped prism, and theta is the wedge angle of the wedge-shaped prism.

In summary, the substrate back defect detecting device provided in the embodiment of the present invention includes an illumination unit, a focusing unit and a detection unit; the light beam emitted by the illumination unit reaches the back of the substrate after being reflected by the focusing unit, enters the detection unit through the focusing unit after being reflected by the back of the substrate, and the position of the focal plane is adjusted by adjusting the focusing unit in real time, so that the back of the substrate is positioned at the position of the focal plane, and the problems that the specific moving distance of the focusing optical element cannot be determined in the high-speed rotation state of the substrate and the accuracy of wafer back defect detection is low can be solved.

It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, similar parts between the embodiments may be referred to each other, and different parts between the embodiments may also be used in combination with each other, which is not limited by the present invention.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and any modification and modification made by those skilled in the art according to the above disclosure are all within the scope of the claims.

Claims

1. The device for detecting the defects on the back surface of the substrate is characterized by comprising an illumination unit, a focusing unit and a detection unit, wherein light beams emitted by the illumination unit reach the back surface of the substrate after being adjusted by the focusing unit, and enter the detection unit through the focusing unit after being reflected by the back surface of the substrate, the focusing unit focuses in real time to enable the back surface of the substrate to be located at a focal plane position, and the detection unit obtains the defects on the back surface of the substrate.

2. The apparatus of claim 1, wherein the focusing unit comprises a vertical measuring device for measuring a height difference between the back surface position of the substrate and the focal surface position.

3. The apparatus of claim 2, wherein the focusing unit further comprises an optical prism and a micro-motion device, the vertical measuring device transmits the height difference between the back position and the focal plane position of the substrate to the controller of the micro-motion device, and the micro-motion device drives the optical prism to move along an included angle of 45 ° with both the optical axis direction of the incident focusing light and the optical axis direction of the emergent focusing light, so that the back position of the substrate is located at the focal plane position, wherein the included angle between the optical axis direction of the incident focusing light and the optical axis direction of the emergent focusing light is 90 °.

4. The substrate backside defect inspection apparatus of claim 3, wherein the optical prism moves by a distance of:

Δd＝(Δh*sin45°)/2n，

5. The substrate backside defect inspection apparatus of claim 3, wherein the optical prism comprises two reflecting surfaces, and an included angle between the two reflecting surfaces is 45 degrees.

6. The apparatus of claim 2, wherein the focusing unit further comprises a mirror group and a micro-motion device, the micro-motion device moving the mirror group to make the substrate back position located at the focal plane position.

7. The apparatus of claim 6, wherein the set of mirrors comprises two mirrors, and the angle between the two mirrors is 45 degrees.

8. The apparatus of claim 2, wherein the focusing unit further comprises a liquid prism and a micro-motion device, the micro-motion device drives a vibration frequency of the liquid in the liquid prism to change a light refractive index of the liquid prism, so that the substrate back position is located at a focal plane position.

9. The apparatus for detecting defects on the back surface of a substrate according to claim 8, wherein the height difference between the position of the back surface of the substrate and the position of the focal plane is:

Δh＝(n-n’)*(L1+L2+L3)，

10. The apparatus of claim 2, wherein the focusing unit further comprises a wedge prism set and a micro-motion device, wherein the micro-motion device drives the wedge prism set to move so that the substrate back position is in the focal plane position.

11. The apparatus for detecting defects on the back of a substrate as claimed in claim 10, wherein the wedge prism set comprises two wedge prisms, and the micro-motion device drives the two wedge prisms to move relatively to automatically adjust the focal plane.

12. The apparatus for detecting defects on the backside of a substrate of claim 10, wherein the height difference between the backside position of the substrate and the focal plane position is:

Δh＝L*cosθ，

and L is the translation amount of the inclined planes of the two wedge prisms, and theta is the wedge angle of the wedge prisms.

13. The substrate backside defect inspection apparatus of claim 1, wherein the illumination unit comprises a bright field light source and a dark field illumination system.

14. The substrate backside defect inspection apparatus of claim 13, wherein the dark field illumination system includes 0 degree and 90 degree directional illumination to highlight defect features within the field of view being inspected.

15. The substrate back defect detection apparatus of claim 1, wherein the focusing unit focuses in real time without shifting an optical axis of the light beam incident to the substrate back in a plane in which the substrate back is located.