CN114235840A

CN114235840A - Wafer surface defect detection method based on light-section microscope

Info

Publication number: CN114235840A
Application number: CN202111630568.8A
Authority: CN
Inventors: 王伟; 徐敏
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2021-12-29
Filing date: 2021-12-29
Publication date: 2022-03-25
Anticipated expiration: 2041-12-29
Also published as: CN114235840B

Abstract

The invention belongs to the technical field of wafer inspection, and discloses a wafer surface defect detection method based on a light-cut microscope, comprising the following steps: firstly initializing the parameters of a wafer surface defect detection system, then loading and measuring the wafer surface defect detection system through the wafer surface defect detection system The wafer to be tested is reconstructed on the surface of the wafer to be tested according to the collected measurement data, and the wafer inspection result is output. In the present invention, the wafer surface defect detection system is used to perform high-precision and high-efficiency defect detection on the wafer surface, and the three-dimensional contour map, defect morphology and coordinates of the wafer surface to be tested can be obtained, which is convenient for subsequent wafer inspection. Cleaning of circular defects, location calibration or further fine-grained measurement processing. The invention not only reduces the detection time, thereby indirectly improving the flow speed of the wafer manufacturing process, but also can quickly obtain high-precision information of defects, which provides a powerful help for finding the cause of defects in the wafer, and effectively improves the product yield.

Description

Wafer surface defect detection method based on light-section microscope

Technical Field

The invention belongs to the technical field of wafer detection, and particularly relates to a wafer surface defect detection method based on a light-section microscope.

Background

As a strategic basic industry, the technology level and the industrial scale of the integrated circuit industry become important marks for measuring the national economic development and technology strength. In recent years, with the rise of economy and technology, china has become the largest and fastest growing market for integrated circuits on a global scale. The production and manufacturing processes of integrated circuits are very delicate and complex. Among them, the surface defects of the wafer, which is an important basic element for manufacturing the chips, are a main cause of influencing the yield of the chips, so the high-precision detection of the surface defects of the wafer becomes an important part of the process.

In order to improve the yield of chips, a plurality of inspection processes are usually set in the manufacturing process of chips, so as to find the surface defects of the wafer in time during the manufacturing process and improve the process in time. For the detection of the surface defects of the wafer, the primary common method is visual inspection by using a microscope. The carpet type manual detection mode needs repeated manual focusing, has the defects of overlong detection time, low detection efficiency and high labor cost, is easily influenced by eye fatigue of detection personnel and the like to cause false detection, and can also cause the defect problem of defect detection due to overlong detection time to be overlong and cause the loss due to overlow yield of large batches of wafers due to the defect problem. In addition, the microscope used, such as an electron microscope, although it can detect particles of 0.2 nm, it contaminates and destroys the wafer and is relatively inefficient; the atomic force microscope method scans the surface of the structure through a probe, and although the precision is high, the scanning speed is very slow, the required time is relatively long, the efficiency is low, and the like. And the high-precision microscope has high cost, and in the actual production, the number of the microscopes in each factory can not be too many to meet the defect scanning of each key processing machine. Therefore, in order to better cope with different defect detections, improve detection efficiency and reduce erroneous judgment, it is necessary to adopt a high-precision automatic detection method.

Disclosure of Invention

Aiming at the problems and the defects in the prior art, the invention aims to provide a wafer surface defect detection method based on a light section microscope.

Based on the purpose, the invention adopts the following technical scheme:

the invention provides a wafer surface defect detection method based on a light section microscope, which comprises the following steps:

(1) initialization: initializing and setting parameters of a wafer surface defect detection system;

(2) loading: the wafer carrying system is transferred to a loading position from an initial position, then the wafer conveying system loads the wafer to be tested onto the wafer carrying system and positions the center of the wafer to be tested through the wafer positioning device;

(3) measurement: moving the wafer bearing system carrying the wafer to be measured to the measuring area of the optical system, and taking the center of the wafer to be measured as a measuring initial position; then the optical system starts to measure the surface of the wafer to be measured, the wafer bearing system moves step by step while rotating, the light section microscope light section image of the optical system scans the surface of the wafer to be measured comprehensively by the scanning track of the equidistant spiral line, and the graph detector acquires the measurement data; after the scanning action is finished, the wafer bearing system is reset to the initial position;

(4) data processing: the signal processing system carries out surface shape reconstruction according to the collected measurement data and outputs a measurement result;

(5) and (4) ending: and (4) moving the wafer bearing system to the loading position, unloading the measured wafer by the wafer conveying system, and ending the measurement or repeating the steps (2) to (4) to measure the next wafer to be measured.

Preferably, the wafer conveying system is a robot with a vacuum adsorption mechanism; the positioning precision of the wafer conveying system for loading the wafer onto the wafer bearing system is 0.05 mm.

Preferably, the wafer bearing system is a high-precision air-flotation turntable with a vacuum adsorption mechanism, and the motion parameters of the high-precision air-flotation turntable are as follows: radial run-out < 50 nm, axial run-out < 20 nm, rotational positioning resolution 1 '' and repeated positioning accuracy 0.5 ''.

Preferably, the wafer conveying system loads and unloads the wafer by using a vacuum adsorption mechanism; after the wafer bearing system receives the wafer to be tested, the vacuum adsorption mechanism fixes the wafer to be tested on the high-precision air-flotation turntable through suction, and the suction is removed during unloading.

Preferably, the parameters of the wafer surface defect detecting system in step (1) include a path parameter of the wafer conveying system, a suction parameter of the vacuum adsorption mechanism, a rotation speed parameter and a step distance parameter of the wafer carrying system, a sampling frequency parameter of the optical system, and a diameter parameter of the wafer to be detected.

Preferably, the rotation speed parameter set in step (1) is 50 rpm, the stepping distance parameter is 1.2 mm, the sampling frequency parameter is 50 Hz, and other parameters are set according to actual conditions.

Preferably, the measuring process in step (3) is performed under dark field; the diameter of the field of view of the light section microscope is 3 mm; in the step (3), the fields of view of the scanning tracks of the equidistant spiral line are overlapped by 20%.

Preferably, the pattern detector is a 4K × 4K ultra-high-definition CMOS detector.

Preferably, the initialization process in step (1) is performed only before the measurement of the same batch of wafers.

More preferably, the wafer carrying system moves through a guide rail; the guide rail is a static oil pressure linear guide rail.

Compared with the prior art, the invention has the following beneficial effects:

according to the wafer surface defect detection method provided by the invention, the detection device can be used for carrying out high-precision and high-efficiency defect detection on the wafer surface, and the three-dimensional profile, the defect appearance and the coordinates of the detected surface of the wafer can be obtained, so that the cleaning, position calibration or further fine measurement processing of the defects at the later stage is facilitated. In one embodiment, the method of the invention needs about 8000 points to sample the whole surface of a 12 inch wafer, and takes about 2.6 min; the lateral resolution is 0.75 μm, and a tilt angle of 15 ° can achieve a longitudinal resolution of 0.19 μm. On one hand, the detection method reduces the detection time, thereby indirectly improving the circulation speed of the wafer manufacturing process; on the other hand, the defect information can be obtained quickly, powerful help is provided for searching the causes of the defects generated by the wafer, the yield of products is effectively improved, and the method has great significance for the semiconductor manufacturing industry.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a wafer surface defect detection system according to the present invention;

FIG. 2 is a schematic diagram of the structure of the inspection apparatus of the present invention, wherein 1 is an industrial robot, 2 is a vacuum adsorption mechanism of the industrial robot, 3 is a light section microscope, 4 is a high precision air floating turntable (with a vacuum adsorption mechanism), 5 is a guide rail, 6 is a wafer, and 7 is a wafer positioning apparatus;

fig. 3 is a schematic diagram of a scanning and measuring path of the light section microscope of the present invention, in which a is a relative position and a moving direction of a wafer to be measured and a light section image during scanning and measuring, and b is a scanning moving track of the light section image.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by the following embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

Example 1

The embodiment of the invention provides a wafer surface defect detection method based on a light section microscope, which comprises the following steps as shown in figure 1:

(1) initialization: and initializing and setting parameters of the wafer surface defect detection system.

The wafer surface defect detection system comprises a detection device and a signal processing system. The detection device comprises a wafer conveying system, an optical system, a wafer bearing system, a guide rail and a wafer positioning device; the signal processing system comprises a control module, a driving module, a data acquisition module and a human-computer interaction interface. The parameters of the wafer surface defect detection system are input into the signal processing system, and data processing is carried out by a control module and a driving module in the signal processing system. Meanwhile, the control module and the driving module system control the movement tracks of the wafer conveying system and the wafer bearing system, the suction force of the vacuum adsorption mechanism, the sampling frequency of the optical system and the like. The optical system includes a light section microscope and a pattern detector.

Wherein the wafer bearing system is a high-precision air-floating rotary table 4 with a vacuum adsorption mechanism, the radial runout of the high-precision air-floating rotary table 4 is less than 50 nm, the axial runout is less than 20 nm, the rotary positioning resolution is 1 ', and the repeated positioning precision is 0.5'. The wafer conveying system is an industrial robot 1 with a vacuum adsorption mechanism 2, and the positioning precision of the wafer loaded by the industrial robot 1 to the high-precision air floatation rotary table 4 is 0.05 mm.

The parameters of the wafer surface defect detection system comprise path parameters of carrying, loading and unloading of the wafer by the wafer conveying system, suction parameters of the vacuum adsorption mechanism, rotating speed parameters and stepping distance parameters of the wafer bearing system during rotation and stepping movement, sampling frequency parameters of the optical system and diameter parameters of the wafer to be detected. The set rotating speed parameter is 50 rpm, the stepping distance parameter is 1.2 mm, the sampling frequency parameter is 50 Hz, the wafer diameter parameter is 12 inch, and other parameters are set according to actual conditions.

(2) Loading: the high-precision air-floating rotary table 4 is transferred from the initial position to the loading position. The industrial robot 1 loads the wafer 6 to be measured on the high-precision air flotation rotary table 4 at the loading position by means of the vacuum adsorption mechanism 2 according to the transportation and loading path parameters initialized and set in the step (1), fixes the wafer to be measured on the high-precision air flotation rotary table through the vacuum adsorption mechanism on the high-precision air flotation rotary table, and simultaneously positions the center of the wafer to be measured through the wafer positioning device 7 on the high-precision air flotation rotary table 4. The specific detection device is shown in fig. 2.

(3) Measurement: the high-precision air-flotation turntable 4 loaded with a wafer 6 to be measured moves to a measurement area of a light cutting microscope 3 through a static oil pressure linear guide rail 5, and the center of the wafer to be measured is used as a measurement starting position; and then the light cutting microscope 3 starts to perform surface measurement on the wafer 6 to be measured according to the sampling frequency set in the step (1), at the moment, the high-precision air-flotation turntable 4 rotates and moves step by step along the guide rail, the light cutting image (the diameter of a view field is about 3 mm) of the light cutting microscope 3 is completed to perform comprehensive scanning on the surface of the wafer 6 to be measured, and the graph detector synchronously acquires measurement data, wherein the scanning motion track is an equidistant spiral line (as shown in figure 3), and the view fields are overlapped by 20%. And after the scanning action is finished, the high-precision air-floating rotary table 4 is reset to the initial position.

The light section microscope is an instrument for measuring the surface quality of a processed workpiece according to a light section principle, namely, a light band is used for sectioning a surface to obtain a section profile curve, and an intersection line of the light band and the surface section reflects the micro-topography profile shape of the measured surface, so that the light section microscope is widely applied to surface measurement of engineering parts. The whole measuring process is carried out in a dark field, and a graph detector adopted in the measuring process is a 4 Kx 4K ultra-high-definition CMOS detector.

(4) Data processing: and a data acquisition module in the signal processing system reconstructs the surface according to the acquired measurement data, outputs a three-dimensional profile of the surface of the wafer to be measured on a human-computer interaction interface, displays the defect appearance and the coordinates thereof, and can store the measurement data as required.

(5) And (4) after the measurement is finished, moving the high-precision air-floating rotary table 4 to a loading position, unloading the measured wafer 6 by the industrial robot 1, and finishing the measurement in the current round or repeating the steps (2) to (4) to measure the next wafer to be measured.

The measurement result shows that about 8000 points are needed to be sampled after the surface universe of one 12 inch wafer is scanned, and about 2.6 min is consumed. System lateral resolution without considering differential image enhancement computational imaging techniquesh0.75 μm; when the angle of inclination isβAt 15 deg., the achievable longitudinal resolution is in accordance withhsinβThe calculation was 0.19. mu.m.

In conclusion, the present invention effectively overcomes the disadvantages of the prior art and has high industrial utilization value. The above-described embodiments are intended to illustrate the substance of the present invention, but are not intended to limit the scope of the present invention. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention.

Claims

1. a wafer surface defect detection method based on light-section microscope, is characterized in that, comprises the steps:

(1) Initialization: Initialize the parameters of the wafer surface defect detection system;

(2) Loading: The wafer carrier system is transferred from the initial position to the loading position, and then the wafer transport system loads the wafer to be tested onto the wafer carrier system and locates the center of the wafer to be tested by the wafer positioning device;

(3) Measurement: The wafer carrier system carrying the wafer to be tested moves to the measurement area of the optical system, and the center of the wafer to be tested is used as the starting position for measurement; then the optical system starts to measure the surface of the wafer to be tested, At this time, the wafer carrying system moves step by step while rotating, and the optical section of the optical system scans the surface of the wafer to be measured with the scanning trajectory of the equidistant spiral, and the pattern detector collects the measurement data ; After the scanning action is completed, the wafer carrier system is reset to the initial position;

(4) Data processing: The signal processing system reconstructs the surface shape according to the collected measurement data, and outputs the measurement results;

(5) End: The wafer carrier system moves to the loading position, the wafer transport system unloads the wafers that have been measured, and ends the measurement or repeats steps (2) to (4) to measure the next wafer to be tested.

2 . The wafer surface defect detection method according to claim 1 , wherein the wafer transport system is a robot with a vacuum adsorption mechanism; the wafer transport system loads wafers onto the wafer carrier system. 3 . The positioning accuracy is 0.05 mm.

3. The wafer surface defect detection method according to claim 2, wherein the wafer carrying system is a high-precision air-floating turntable with a vacuum adsorption mechanism, and the motion parameter of the high-precision air-floating turntable is: The runout is less than 50 nm in the axial direction, and the runout in the axial direction is less than 20 nm.

4 . The wafer surface defect detection method according to claim 3 , wherein the wafer transport system uses a vacuum adsorption mechanism to load and unload wafers; after the wafer carrier system receives the wafer to be tested, the vacuum adsorption mechanism The wafer to be tested is fixed on the high-precision air-floating turntable by suction, and the suction is removed when unloading.

5 . The wafer surface defect detection method according to claim 4 , wherein the parameters of the wafer surface defect detection system in step (1) include a path parameter of a wafer transport system, a suction force parameter of a vacuum adsorption mechanism, The rotational speed parameter and step distance parameter of the wafer carrier system, the sampling frequency parameter of the optical system, and the diameter parameter of the wafer to be tested; among them, the rotational speed parameter is set to 50 rpm, the step distance parameter is 1.2 mm, and the sampling frequency parameter is 50 Hz.

6 . The wafer surface defect detection method according to claim 5 , wherein the measurement process in step (3) is carried out in a dark field; the diameter of the field of view of the light section microscope is 3 mm; step (3) ), the fields of view of the scan trajectories of the equidistant spirals overlap by 20%.

7 . The wafer surface defect detection method according to claim 1 , wherein the pattern detector is a 4K×4K ultra-high-definition CMOS detector. 8 .

8 . The wafer surface defect detection method according to claim 1 , wherein the initialization process in step (1) is performed only before the measurement of the same batch of wafers. 9 .