CN108445017A - A kind of supper-fast silicon substrate surface quality detecting system - Google Patents

Abstract

The invention relates to the technical field of silicon-based surface quality detection, and more particularly relates to an ultra-fast silicon-based surface quality detection system. Including the following devices: mode-locked femtosecond pulse light source, mid-infrared light wave filter, dispersive fiber, erbium-doped fiber amplifier (EDFA), diffraction grating, 4f imaging system based on lens, objective lens, digital coherent receiver, high-speed sampling oscilloscope and Computers required for data processing and restoration. In addition, it also includes the required circulators, couplers, optical fibers, optical fiber polarization controllers, collimators, etc.

Description

An ultra-fast silicon-based surface quality detection system

technical field

The invention relates to the technical field of silicon-based surface quality detection, and more particularly relates to an ultra-fast silicon-based surface quality detection system.

Background technique

Silicon semiconductor material is currently a very critical building block material in many industries today. Silicon semiconductors play an important role in the development of industries such as clean energy and military industry. At present, more than 90% of semiconductor devices in the world are made of silicon materials. In the past few years, the silicon industry has been growing at a rate of more than ten percent per year. Single crystal silicon polished wafers have been widely used in the manufacture of various discrete components; the manufacturing process of silicon is very complicated, due to the imperfection of the industrial process and defects in various processing, it is easy to form defects on the surface of silicon, so that the performance of silicon products have serious consequences. At present, silicon manufacturers control the quality of silicon product processing through batch sampling inspection. In terms of surface quality inspection, they mainly detect defects such as roughness, curvature, cracks, scratches, and oil stains on the product surface. At present, there are many methods for silicon-based surface quality detection technology, but most of them are limited by their cost and speed, which makes it an obstacle to apply large-scale silicon surface quality detection in industry. In 2009, the B.Jalali laboratory in the United States proposed an imaging method based on time stretching, which can greatly increase the imaging speed, reaching tens of MHZ at the fastest. Using this imaging technology, it is possible to observe phenomena that were once undetectable by traditional CCDs. After several years of development, this imaging method based on time stretching has reached a very mature stage. B. Jalali and other laboratories have successfully carried out large-scale cancer cell screening experiments using this imaging technology, achieving high-speed And cell screening with high accuracy. If this technology is applied to the inspection of silicon crystal surface quality in industry, it is bound to greatly increase the detection rate of the silicon crystal industry and greatly reduce the defective rate of products.

Contents of the invention

In order to overcome at least one of the defects described in the above-mentioned prior art, the present invention provides an ultra-fast silicon-based surface quality detection system, combined with coherent detection means, not only can obtain the image information of the silicon-based surface, but also can recover the phase information to identify different surface quality defects. More importantly, since this method is based on the mode-locked femtosecond pulsed laser as the light source, it realizes the number of megahertz imaging frames, which greatly improves some existing silicon-based surface quality detection technologies.

The technical solution of the present invention is: an ultra-fast silicon-based surface quality detection system, which includes a mode-locked femtosecond pulse light source, a mid-infrared light wave filter, a dispersion fiber, an erbium-doped fiber amplifier, a diffraction grating, and a lens-based 4f imaging system, objective lens, digital coherent receiver, high-speed sampling oscilloscope, and computer required for data processing and recovery, as well as some optical fibers, circulators, couplers, fiber polarization controllers, and collimators used in experiments ;

Also includes phase delay lines, lenses, silicon-based samples;

The mode-locked femtosecond pulse light source, mid-infrared light wave filter, dispersion fiber, and erbium-doped fiber amplifier are connected in sequence, and the erbium-doped fiber amplifier is connected to a digital coherent receiver through a phase delay line or a fiber polarization controller, and the digital coherent receiver Then connect the oscilloscope and computer;

The fiber polarization controller is also sequentially connected with a circulator, a collimator, a diffraction grating, a lens, an objective lens, and a silicon-based sample.

Considering the principle of coherent reception, after the filter is filtered, the power should be as equal as possible at different frequencies, so that after being divided into intrinsic light and signal light, the data processed by the coherent receiver will be as accurate as possible. Here we use a waveshaper as our spectral filter.

After using the mode-locked femtosecond pulse laser as the light source, the ultra-fast surface detection of the silicon-based surface is achieved by using the mode-locked femtosecond pulse with the characteristic of high repetition frequency.

Further, the product of the dispersion value of the dispersion fiber and the filtered spectral width should not be greater than the cycle time of the pulse. Otherwise, adjacent signals will overlap in the time domain, so that the image of the silicon-based surface cannot be recovered. The diffraction grating enables light to expand in one dimension in space, and different spatial positions have different frequencies.

Compared with the prior art, the beneficial effect is: compared with some existing silicon-based surface quality detection methods, the present invention can greatly increase the speed of surface quality detection without loss of detection accuracy. And because of the introduction of coherent receiving detection at the end of the detection, we can obtain more accurate phase information, that is, the fluctuation of the surface of the silicon substrate, so that we can accurately distinguish the type of defect on the surface of the silicon substrate detected.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention.

Detailed ways

The accompanying drawings are for illustrative purposes only, and should not be construed as limitations on this patent; in order to better illustrate this embodiment, certain components in the accompanying drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art It is understandable that some well-known structures and descriptions thereof may be omitted in the drawings. The positional relationship described in the drawings is for illustrative purposes only, and should not be construed as a limitation on this patent.

As shown in Figure 1, a kind of ultra-fast silicon-based surface quality detection system, wherein, comprises mode-locked femtosecond pulse light source 1, mid-infrared light wave filter 2, dispersive optical fiber 3, erbium-doped optical fiber amplifier 4, diffraction grating 9, 4f imaging system based on lens, objective lens 11, digital coherent receiver 13, high-speed sampling oscilloscope 14 and computer 15 required for data processing and recovery, also includes some optical fibers, circulator 7 and coupler needed in the experiment , fiber polarization controller 6, collimator 8;

It also includes a phase delay line 5, a lens 10, and a silicon-based sample 12;

A mode-locked femtosecond pulse light source 1, a mid-infrared light wave filter 2, a dispersion fiber 3, and an erbium-doped fiber amplifier 4 are connected in sequence, and the erbium-doped fiber amplifier 4 is connected to a digital coherent receiver 13 through a phase delay line 5 or a fiber polarization controller 6 , the digital coherent receiver 13 is then connected to the oscilloscope 14 and the computer 15;

The fiber polarization controller 6 is also sequentially connected with a circulator 7 , a collimator 8 , a diffraction grating 9 , a lens 10 , an objective lens 11 , and a silicon-based sample 12 .

Time-stretch-based ultrafast silicon-based surface imaging has the following steps.

First, the mode-locked femtosecond pulsed laser light source with a repetition rate of tens of megahertz has a width of about 15 nanometers in the frequency spectrum after passing through the light wave filter, and the power of light of different frequencies remains approximately the same at this time. At this time, the filtered pulsed light is time-stretched through the dispersion fiber. In the time domain, it is a pulse with a wider pulse width than the original pulse (generally extended to the nanosecond level), and at this time due to the effect of dispersion, the In the simultaneous domain, there are already lights of different frequencies. At this point, it is equivalent to completing the one-to-one mapping from time to frequency.

Then, the time-frequency-mapped light is amplified through an erbium-doped fiber amplifier (EDFA). Because the light at this time has been greatly attenuated in power due to the effect of the dispersion fiber, so the power needs to be amplified at this time. After passing through the erbium fiber amplifier (EDFA), it is divided into two paths through the coupler, the intrinsic path and the signal path, and the power of the two paths is kept equal.

On the signal path, the light is incident on the spatial light path through the collimator. The space part first passes through a diffraction grating. The function of the diffraction grating is to correspond light of different frequencies to different spatial positions, which is actually equivalent to completing the one-to-one mapping process from frequency to space. Afterwards, the expanded light passes through the 4f system, and then collimates and enters the objective lens. At this time, the silicon-based sample is placed on the working focal length of the objective lens. It passes through the objective lens, the 4f system, the diffraction grating, the collimator and is coupled into the optical fiber in turn, and finally reaches the circulator and is transmitted to the coherent receiver.

On the eigenpath, a phase delay line is placed, and the optical path of the eigenpath and the signal path are consistent by adjusting the optical path. The role of the phase delay line is to precisely adjust the optical path so that the light in the eigenpath and the signal path can produce a beat frequency effect after reaching the coherent receiver.

After being detected by a coherent receiver, a high-speed sampling oscilloscope is used to obtain the beat-frequency data. Since this scheme adopts coherent detection technology, there are 4 channels of data to be collected, and the acquired data is transmitted to the computer for data processing in real time, and the image of the silicon-based surface is obtained after a certain algorithm recovery process. Put the restored surface image into the silicon-based surface defect classification and recognition module, so as to realize the ultra-fast quality inspection of the silicon-based surface.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (3)

1. An ultra-fast silicon-based surface quality detection system is characterized in that it includes a mode-locked femtosecond pulse light source (1), a mid-infrared light wave filter (2), a dispersion fiber (3), and an erbium-doped fiber amplifier (4 ), a diffraction grating (9), a lens-based 4f imaging system, an objective lens (11), a digital coherent receiver (13), a high-speed sampling oscilloscope (14) and a computer (15) required for data processing and recovery, and also includes Some optical fibers used in the experiment, circulator (7), coupler, fiber polarization controller (6), collimator (8); It also includes a phase delay line (5), a lens (10), and a silicon-based sample (12); The mode-locked femtosecond pulse light source (1), mid-infrared light wave filter (2), dispersion fiber (3), and erbium-doped fiber amplifier (4) are connected in sequence, and the erbium-doped fiber amplifier (4) passes through the phase delay line (5) or the fiber optic polarization controller (6) is connected to a digital coherent receiver (13), and the digital coherent receiver (13) is then connected to an oscilloscope (14) and a computer (15); The fiber polarization controller (6) is also sequentially connected to a circulator (7), a collimator (8), a diffraction grating (9), a lens (10), an objective lens (11), and a silicon-based sample (12). 2. An ultra-fast silicon-based surface quality detection system according to claim 1, characterized in that: the product of the dispersion value of the dispersion fiber and the filtered spectral width should not be greater than the cycle time of the pulse. 3. A kind of ultra-fast silicon-based surface quality detection system according to claim 1, characterized in that: said diffraction grating enables light to be expanded one-dimensionally in space, and different spatial positions have different frequency.