CN106855395A - A kind of optical detection evaluation method of silicon chip anode linkage technique deformation - Google Patents

Abstract

The present invention relates to Micro Electro Mechanical System device precision geometric measurement method, more particularly to a kind of optical detection evaluation method of silicon chip anode linkage technique deformation.Described method comprises the following steps：Step one, scanning survey：Using optical profilometer, coordinate TTM object lens, scanning obtains the profile data of device to be detected；Step 2, data processing：On the basis of device original shape profile is obtained, it is removed edge effect and the treatment of metewand is set, to obtain the true three-dimension appearance profile of expected device；Step 3, evaluates and judges：Based on the profile by data processing, make the two-dimentional transversal of the appearance profile in the x, y direction respectively, check inclination and the torsional deformation amount of profile, and according to the profile valley and peak parameters of setting, judge whether the deformation of appearance profile meets design requirement.There is provided a kind of method for judging the deformation of silicon chip anode linkage technique.

Description

An optical detection and evaluation method for deformation of silicon wafer anodic bonding process

technical field

The invention relates to a method for measuring precise geometric quantities of micro-electromechanical system devices, in particular to an optical detection and evaluation method for the deformation of a silicon chip anodic bonding process.

Background technique

Bonding technology is one of the key technologies in the processing technology of silicon micro-devices. It is to permanently connect parts of different or the same materials in silicon micro-devices for the fabrication, assembly and packaging of devices. Silicon-glass anode bonding is one of the bonding technologies, that is, the intermediate active device is formed by etching single crystal silicon material, and the upper and lower parts are packaged by special glass bonding. The bonded device is a three-layer structure similar to a "sandwich": glass-silicon wafer-glass, with a gap of several microns to tens of microns between the glass and the silicon wafer.

The bonding process is the effect of electric field and high temperature, and there must be residual stress. Therefore, the outline of the intermediate active device will undergo stress deformation, and the stress deformation of different bonding processes is different due to different electric field and temperature parameters. Due to the limited bonding gap, if the deformation is too large, the movable device will be stuck or stuck, which will affect the accuracy and survival rate of the device. Therefore, it is necessary to measure the deformation of the device outline after packaging to guide the adjustment of bonding process parameters, in order to minimize the amount of stress and deformation as much as possible, and at the same time control the quality of bonding packaging. At present, there is no effective method for judging the deformation of the anodic bonding process of silicon wafers.

Contents of the invention

The purpose of the present invention is to provide a non-contact accurate measurement and evaluation method for the deformation of the outline of the active device in the transparent packaging glass after the silicon micro-device is anodically bonded.

The technical solution of the present invention is: an optical detection and evaluation method for the deformation of silicon wafer anodic bonding process, which is characterized in that: the method includes the following steps:

Step 1, scanning measurement: use an optical profiler with a TTM objective lens to scan to obtain the profile data of the device to be inspected;

Step 2, data processing: on the basis of obtaining the initial outline of the device, perform processing to remove edge effects and set evaluation benchmarks to obtain the real three-dimensional outline of the expected device;

Step 3, evaluation and judgment: based on the data-processed contour, make a two-dimensional cross-section of the contour in the X and Y directions respectively, check the inclination and twisting deformation of the contour, and according to the set contour valley and Peak parameter, to judge whether the deformation of the outline conforms to the design requirements.

As an improvement of the technical solution, when removing the influence of the edge effect, 3%-4% of the data of the edge of the contour are eliminated.

As an improvement of the technical solution, when evaluating the local deformation of the device, it is also necessary to perform the processing of setting the evaluation reference, that is, to remove the placement inclination.

As an improvement of the technical solution, an optical profiler and a transparent material measuring objective lens are used to obtain the profile data of the device to be inspected with a small package gap.

As an improvement of the technical solution, when evaluating the overall process deformation of the device, the outer frame of the device is selected as the reference plane for leveling; when evaluating the local process deformation of the device, only the measured area needs to be focused and leveled.

As an improvement of this technical solution, the parameters of the optical profiler are set as follows: the measurement mode is VSI or the Z-axis scanning range is greater than 50 μm, the objective lens type is TTM, and the scanning length is based on the peak-to-valley value of the measured surface profile Increase by 10-20%, the average measurement is 3-8 times, and the retrace length is 20% of the scan length.

The beneficial effects of the present invention are: the present invention is used in the manufacturing process of micro-electromechanical systems (MEMS) devices, belongs to the category of process detection and control, and solves the problem that silicon-glass bonding devices with small package gaps cannot be visually and accurately detected and evaluated. The application can improve the quality of the bonding process such as consistency and repeatability.

The present invention determines the evaluation method to reflect the magnitude of the residual stress of the silicon chip bonding process by measuring the deformation before and after the bonding of the device or the comparison of different bonding parameters, which can intuitively and accurately observe the contour deformation and damage of the intermediate movable device in the packaging glass Wait. It solves the problem of not being able to directly observe the device structure and evaluate the bonding stress at present, and plays a very important role in optimizing the bonding process parameters and improving the performance and quality of the device.

detailed description

The technical solution will be described in further detail below.

The method described in this technical solution is to use an optical profiler, select a TTM (through transparent material measurement) objective lens, set specific measurement parameters for detection, then adopt a method for judging the maximum deformation of a two-dimensional section line, and set specific evaluation parameters and The index evaluates the maximum amount of deformation to judge whether the deformation of the silicon wafer micro-device meets the design requirements after bonding.

Taking the measurement of silicon-glass-bonded silicon microdevices with the Contour GT optical profiler as an example, the detailed steps in completing the method are illustrated:

Step 1, scanning measurement: use an optical profiler with a TTM objective lens to scan to obtain the profile data of the device to be inspected. First, select the same glass material as the bonding packaging glass, and the thickness must be the same, make an optical path compensation sheet, and put it in a specific position of the TTM objective lens. Then, install the TTM objective lens equipped with the compensation film on the objective lens seat of the instrument, and set the measurement parameters as follows: the measurement mode (Measurement Type) is VSI, the objective lens model (Objective) is 2×TTM, and the field of view eyepiece (Multiplier) is Select 0.55× for the overall measurement of the device, and 2× for the local measurement of the device (selection principle: use with the objective lens, the field of view should include the sample area to be measured, and fill the field of view as much as possible), and the scanning length (Length) should be used when performing the device The overall measurement is 25 μm, and the local measurement of the device is 8 μm (selection principle: increase 10-20% on the basis of the measured surface profile peak-valley value), the measurement average (Averaging) is selected 3-8 times, the selection principle: According to the accuracy required by the measurement, the higher the accuracy requirement, the larger the setting value, the more measurement times, and vice versa, the smaller the value, the less measurement times. The system error calibration is usually set to 8, the retrace length (Backscan) is 5 μm when the overall measurement of the device is performed, and 2 μm when the local measurement of the device is performed. The selection principle: 20% of the scan length, and the modulation signal threshold (Threshold) is 5%. After the measurement parameters are set, calibrate and store the system error of the instrument, and choose to eliminate the system error during measurement. Finally, keep the measurement parameters unchanged, place the device under test on the sample stage, focus on the area to be measured, and select the measurement reference plane. When performing overall device measurement, select the device frame as the reference plane for leveling; when performing partial device measurement , you only need to focus and level the area to be measured for measurement.

Step 2, data processing: on the basis of obtaining the initial profile of the device, the process of removing edge effects and setting evaluation benchmarks is performed to obtain the real three-dimensional profile of the expected device. The edge effect refers to the phenomenon of data jump caused by software errors in the phase unwrapping operation at the boundary of the measurement area, and the measurement results presented at this time are not true. In order to ensure the authenticity and reliability of the measurement results, the influence of the edge effect must be removed after the measurement. The specific operation is to use the Mask (masking frame) function of the instrument software to eliminate 3%-4% of the data on the edge of the contour, that is, select a rectangle or other suitable The graphics box retains the data of 97%-96% of the area inside the contour, and performs Mask processing. The operation of setting the evaluation standard is processed on the basis of selecting the measurement reference plane. Use the item removal (Terms Removal) function of the instrument software to remove the placement tilt (Tilt only) only when performing local measurement and evaluation of the device to eliminate The influence of uneven device placement on the results during measurement.

Step 3, evaluation and judgment: based on the data-processed contour, make a two-dimensional cross-section of the contour in the X and Y directions respectively, check the size of the oblique deformation and twisting deformation of the contour, and make the contour according to the set valley value and peak parameters to judge whether the deformation of the contour conforms to the design requirements. The evaluation judgment is based on the comparison of the deformation and warpage of the outline of the middle movable part of the silicon micro-device before and after bonding or under different bonding parameters as the evaluation standard, and the deformation requirement should be as small as possible. At this time, the micron-scale fluctuations of the two-dimensional cross-section in the X and Y directions represent the oblique deformation and twisting deformation of the contour respectively. Check the maximum deformation in the X and Y directions (either the valley value or the peak value) , which is the size of the oblique deformation and twist deformation of the device profile, and can also provide the direction of deformation. Therefore, the measurement and evaluation of the micro-device contour deformation inside the packaging material after the silicon chip anodic bonding process is realized.

Claims (6)

1. the optical detection evaluation method that a kind of silicon chip anode linkage technique deforms, it is characterized by： Described method comprises the following steps：

Step one, scanning survey：Using optical profilometer, coordinate TTM object lens, scanning is obtained Take the profile data of device to be detected；

Step 2, data processing：On the basis of device original shape profile is obtained, it is removed Edge effect and the treatment of setting metewand, to obtain the true three-dimension profile of expected device Profile；

Step 3, evaluates and judges：Based on the profile by data processing, respectively X, Make the two-dimentional transversal of the appearance profile in Y-direction, check inclination and the torsional deformation amount of profile, And according to the profile valley and peak parameters of setting, judge whether the deformation of appearance profile meets and set Meter is required.

2. the optics inspection of a kind of silicon chip anode linkage technique deformation according to claim 1 Evaluation method is surveyed, it is characterized by：When the influence of edge effect is removed, contour edge is rejected The data of 3%-4%.

3. the optics inspection of a kind of silicon chip anode linkage technique deformation according to claim 1 Evaluation method is surveyed, it is characterized by：When the local deformation of device is evaluated, evaluation base is also carried out The treatment that standard is set, i.e. removal are placed and inclined.

4. the optics inspection of a kind of silicon chip anode linkage technique deformation according to claim 1 Evaluation method is surveyed, it is characterized by：Object lens are measured using optical profilometer and through transparent material, Obtain the profile data of small package gap device to be detected.

5. the optics inspection of a kind of silicon chip anode linkage technique deformation according to claim 4 Evaluation method is surveyed, it is characterized by：When the process distortions of device entirety are evaluated, outside selector Frame is levelling as datum level；When the process distortions of device part are evaluated, only need to be by tested region Focusing is levelling.

6. the optics inspection of a kind of silicon chip anode linkage technique deformation according to claim 4 Evaluation method is surveyed, it is characterized by：The parameter of optical profilometer is done into following setting：Measurement pattern Be that VSI or Z axis sweep limits are more than 50 μm, object lens model TTM, sweep length be Increase 10-20% on the basis of surveyed surface profile peak-to-valley value, measurement is averagely selected 3-8 times, flyback Length is the 20% of sweep length.