CN115513334A - SPAD coaxial TO device and manufacturing method thereof - Google Patents
SPAD coaxial TO device and manufacturing method thereof Download PDFInfo
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Abstract
The application discloses SPAD coaxial TO device and a manufacturing method thereof, relating TO the technical field of coaxial photoelectric devices, wherein the manufacturing method comprises the following steps: after the SPAD is sealed and welded by a pipe cap, the SPAD is installed on a coupling welding platform device base, and an initial light coupling position of the SPAD is obtained; under a plurality of preset alignment bias voltages, acquiring three-dimensional distribution of photo-generated current corresponding to each light coupling position in a line-by-line scanning mode to further obtain a plurality of two-dimensional section data; acquiring alignment bias voltage meeting preset conditions as initial light coupling conditions based on a plurality of pieces of two-dimensional section data under each alignment bias voltage; and under the condition of initial light coupling, when incident light of the tail fiber is converged at the geometric center of the active region and is axially converged in the SPAD chip absorption layer, welding the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device. This application can effectively reduce dark count rate, promotes the single photon detection efficiency under the same bias voltage.
Description
Technical Field
The application relates TO the technical field of coaxial photoelectric devices, in particular TO a SPAD coaxial TO device and a manufacturing method thereof.
Background
At present, a single photon avalanche photodiode (SPAD) has wide applications in the fields of quantum secret communication, quantum imaging, laser radar, biomedical and integrated circuit detection and the like. When the avalanche photodiode APD enters a Geiger mode, namely an external circuit provides reverse bias voltage Vr higher than the breakdown voltage Vbr of the device, the instantaneous response current of the device to extremely weak light can reach mA level, namely the SPAD has single photon detection capability.
Single Photon Detection Efficiency (PDE) is an important parameter characterizing SPAD detection capability, and an increase in PDE can generally be achieved by increasing the over-bias applied across the device. However, under the effects of thermal excitation, band-to-band tunneling, and defect-assisted tunneling, the dark count caused by self-sustaining avalanche induced by dark carriers also increases with the increase of the over-bias. For SPAD, the dark count rate satisfying a certain PDE premise is a single photon performance core index, and determines the extractable degree of single photon avalanche signals. Therefore, how to reduce the dark count rate is a key technology for realizing high-performance SPAD.
Disclosure of Invention
Aiming at the defects in the prior art, the application aims TO provide the SPAD coaxial TO device and the manufacturing method thereof so as TO solve the problem of high dark count rate in the related technology.
The application provides a manufacturing method of an SPAD coaxial TO device in a first aspect, which comprises the following steps:
after the SPAD is subjected to tube cap sealing welding, the SPAD is installed on a coupling welding platform device base, and the position and the angle of the SPAD when the SPAD outputs peak photocurrent are obtained and used as the initial light coupling position of the SPAD;
under the condition of a plurality of preset alignment bias voltages, acquiring three-dimensional distribution of photo-generated current corresponding to each light coupling position from the initial light coupling position in a line-by-line scanning mode, and further acquiring a plurality of two-dimensional section data of sections along different direction planes; in the two-dimensional section data, the abscissa is the light coupling position of the corresponding section, and the ordinate is the photo-generated current value;
acquiring alignment bias voltage meeting preset conditions as initial light coupling conditions based on a plurality of pieces of two-dimensional section data under each alignment bias voltage; the preset conditions are as follows: the electric field of the photo-generated current is uniform and has no edge breakdown, and the falling rate of the photo-generated current at the edge of the active area is greater than a first rate threshold;
and under the condition of the initial light coupling, when the incident light of the tail fiber is converged at the geometric center position of the active region and is axially converged in the SPAD chip absorption layer, welding and fixing the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device.
In some embodiments, when the absolute difference values of the two photo-generated currents respectively at the positions equidistant from the edges of the two active regions in the two-dimensional cross-sectional data are smaller than the first difference threshold, it is determined that the photo-generated current electric field is uniform.
In some embodiments, in the three-dimensional distribution, the photo-generated current is taken as a Z-axis coordinate, the row and column positions of the light coupling position are taken as an X-axis coordinate and a Y-axis coordinate, respectively, and the X-axis coordinate and the Y-axis coordinate of the initial light coupling position are both 0;
the plurality of two-dimensional cross-sectional data of the cross-section taken along the different direction planes includes:
the two-dimensional section data of the section of the plane in the direction of the X axis, the two-dimensional section data of the section of the plane in the direction of the Y axis, the two-dimensional section data of the section of the plane in the direction of the X axis after the X axis rotates clockwise for 45 degrees around the Z axis, and the two-dimensional section data of the section of the plane in the direction after the Y axis rotates clockwise for 45 degrees around the Z axis.
In some embodiments, the obtaining, from the initial light coupling position, a three-dimensional distribution of a photo-generated current corresponding to each light coupling position in a line-by-line scanning manner specifically includes:
the light coupling position is adjusted from the original point to the X-axis negative direction until the photo-generated current is attenuated to a preset current value, and the point is taken as the starting point;
moving the photo-generated current to the positive direction of the Y axis by a first step length from the starting point to the positive direction of the X axis, moving the photo-generated current to the positive direction of the Y axis by the first step length after moving the first step length to the negative direction of the X axis when the photo-generated current is attenuated to the preset current value again, moving the photo-generated current to the positive direction of the Y axis by the first step length again until the response test of the half part of the positive direction of the Y axis is completed;
moving a first step length from the starting point to the Y-axis negative direction;
moving the photo-generated current to the positive direction of the X axis by a first step length, moving the photo-generated current to the negative direction of the Y axis by the first step length after moving the photo-generated current to the negative direction of the Y axis by the first step length when the photo-generated current is attenuated to the preset current value again, and moving the photo-generated current to the negative direction of the Y axis by the first step length until the response test of the half part of the negative direction of the Y axis is completed;
and acquiring the photo-generated current at the current light coupling position every time the first step length is moved.
In some embodiments, when the distances from the initial light coupling position to the light coupling positions where the photo-generated current is attenuated to the preset current value are the same, and the absolute value of the difference between the attenuation rates moving in any two directions by a unit distance is smaller than a second difference threshold, it is determined that the incident light of the pigtail converges at the geometric center position of the active region.
In some embodiments, when the distance from the initial light coupling position to each light coupling position where the photo-generated current is attenuated to the preset current value is different, or the absolute value of the difference between the attenuation rates of the unit distance moving in any two directions is not less than the second difference threshold, the initial light coupling condition is updated, and whether the incident light of the tail fiber converges at the geometric center position of the active region is determined again by the updated initial light coupling condition.
In some embodiments, when the tail fiber moves towards the direction close to the SPAD for the second step length, if the attenuation rate of the photo-generated current is greater than the second rate threshold, the tail fiber moves towards the direction away from the SPAD for the third step length until the absolute value of the difference between the photo-generated current and the peak photocurrent is less than the third difference threshold, and it is determined that the incident light ray axially converges in the absorption layer of the SPAD chip;
the third step length is smaller than the second step length.
In some embodiments, if the rate of decay of the photo-generated current is less than or equal to the second rate threshold, the second step size continues to be moved closer to the SPAD until the rate of decay of the photo-generated current is greater than the second rate threshold.
In some embodiments, the alignment bias voltage is set according to a breakdown voltage of the SPAD and is less than the breakdown voltage.
The second aspect of the application provides a SPAD coaxial type TO device, which is manufactured by the manufacturing method.
The beneficial effect that technical scheme that this application provided brought includes:
according TO the SPAD coaxial TO device and the manufacturing method thereof, after the SPAD is subjected TO tube cap sealing welding, an initial coupling position is obtained, and then alignment bias voltage meeting preset conditions is obtained and used as initial coupling conditions; then, under the condition of initial light coupling, when incident light of the tail fiber is converged at the geometric center position of the active region and is axially converged in the SPAD chip absorption layer, welding and fixing the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device; therefore, the generation position of a photon-generated carrier in the active region can be accurately controlled, so that the purposes of controlling the charge persistence effect and effectively reducing the dark counting rate are achieved, and the single photon detection efficiency under the same over-bias voltage can be improved by improving the coupling efficiency; meanwhile, the problem of product quality consistency caused by packaging can be avoided, and the yield of devices can be improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a first flowchart of a manufacturing method in an embodiment of the present application;
FIG. 2 is a graph of the distribution of normalized photo-generated current for different alignment bias voltages in an embodiment of the present application;
FIG. 3 is a schematic diagram of determining that a focus is outside of a device in an embodiment of the present application;
FIG. 4 is a schematic diagram of determining a focus within a device in an embodiment of the present application;
fig. 5 is a second flowchart of a manufacturing method in an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment of the application provides a manufacturing method of an SPAD coaxial TO device, in particular TO an active alignment coupling method of a coaxial photoelectric device, which can solve the problem of high dark counting rate in the related technology.
As shown in fig. 1, the method for manufacturing the SPAD coaxial TO device in the embodiment of the present application specifically includes the steps of:
s1, after sealing and welding the tube cap of the SPAD, the SPAD is installed on a coupling welding platform device base, and the position and the angle of the SPAD when outputting peak photocurrent are obtained and used as the initial light coupling position of the SPAD, so that initial coarse alignment is realized.
In this embodiment, after the sealing and welding operation of the SPAD device cap is completed, the integrated device can be mounted on the coupling welding platform device base to perform the peak photocurrent hunting operation, and the input optical power during the hunting operation is 10 μ W. The SPAD and the coupling welding platform are fixed in relative positions, and the initial light coupling position of the SPAD is determined by carrying out multi-axis fine adjustment on the coupling welding platform.
S2, sequentially under a plurality of preset alignment bias voltages, acquiring three-dimensional distribution of photo-generated current corresponding to each light coupling position from the initial light coupling position in a line-by-line scanning mode, and further acquiring a plurality of two-dimensional section data of sections along different direction planes; in the two-dimensional section data, the abscissa represents the light coupling position of the corresponding section, and the ordinate represents the photo-generated current value.
In this embodiment, two-dimensional distribution of the coupling position corresponding to the photo-generated current of 10 μ W incident light power is recorded in a progressive scanning manner. The horizontal and vertical coordinates of the two-dimensional distribution of the light coupling positions correspond to the relative position coordinates of the light spots in the active area.
Alternatively, the optical coupling position abscissa and ordinate records the relative horizontal position of the corresponding light spot on the tube cap lens and the optical axis (i.e. the coincidence central axis of the lens and the SPAD photosensitive surface), but not the absolute position of the corresponding light spot in the active area, so that reference information of the actual position of the light spot in the active area needs to be obtained through optical simulation.
S3, acquiring alignment bias voltage meeting preset conditions as initial light coupling conditions based on a plurality of pieces of two-dimensional section data under each alignment bias voltage; the preset conditions are as follows: the electric field of the photo-generated current is uniform and has no edge breakdown, and the falling rate of the photo-generated current at the edge of the active area is greater than a first rate threshold value, namely the photo-generated current is sensitive to the change of the light coupling position.
In this embodiment, a plurality of alignment bias voltages may be set as much as possible to perform the test selection of the light coupling condition, and further, the test data may be combined and analyzed to find out the relatively optimal initial light coupling condition.
And S4, under the condition of the initial light coupling, when incident light of the tail fiber is converged at the geometric center of the active region and is axially converged in the SPAD chip absorption layer, welding and fixing the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device.
In the manufacturing method of the embodiment, after the SPAD is subjected to tube cap sealing welding, the initial light coupling position is obtained, and then the alignment bias voltage meeting the preset condition is obtained as the initial light coupling condition; then, under the condition of initial light coupling, when incident light of the tail fiber is converged at the geometric center position of the active region and is axially converged in the SPAD chip absorption layer, welding and fixing the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device; therefore, the generation position of a photon-generated carrier in the active region can be accurately controlled, so that the purposes of controlling the charge persistence effect and effectively reducing the dark counting rate are achieved, and the single photon detection efficiency under the same over-bias voltage can be improved by improving the coupling efficiency; meanwhile, the problem of product quality consistency caused by packaging can be avoided, and the yield of devices can be improved.
The manufacturing method of the embodiment is based on active alignment, which is also called active light coupling, and is a common alignment technology in manufacturing of the SPAD coaxial type TO device. In the active light coupling technology, the detector is usually aligned with the optical axis under a working state by an external bias, that is, the coupling welding machine finely adjusts and monitors the change condition of SPAD optical response in the process through four dimensions (three dimensions + rotation angle), records the position and the angle when the optical response current is maximum, and finally fixes the tail fiber ferrule, the metal sleeve and the tube shell at the adjusted positions through puncture welding, lap welding and the like. However, SPAD generally works in geiger mode, and common coupling welding machines do not have quenching and counting capabilities, and cannot really realize that SPAD is put into working state for active alignment. Typically, the SPAD is applied V below the breakdown voltage without modification of the coupled welder hardware UV To perform active light coupling.
In some embodiments, the diffusion profile of the low concentration region after two diffusions may not be uniform everywhere or the edge curvature of the active region is not ideal due to the diffusion process, and the non-optimized large alignment bias voltage may amplify the non-uniformity of the electric field distribution in the active region, thereby causing alignment failure.
When the size of the light coupling spot is larger than that of the photosensitive surface, or light coupling errors occur and exceed a certain tolerance range, the coupling efficiency is reduced, the PDE under the same over-bias voltage is further influenced, and simultaneously, a charge sustaining effect is introduced, namely after photogenerated carriers are generated in regions except for a depletion region in an absorption layer, the carriers cannot immediately cross a valence band step of an InGaAs/InP material interface due to insufficient field intensity of longitudinal electric field components of the regions, but reach the depletion region through transverse drift for a certain time under the action of transverse electric field components, and avalanche is caused. Taking the gated quenching mode as an example, such delayed no light avalanche would greatly increase the probability of triggering miscounting in applications where SPAD is used at rates above 6.67 MHz. Therefore, it is necessary to ensure that photons are accurately coupled to the center of the active region, so that the photon absorption and photon-generated carrier generation positions are accurately controllable.
On the basis of the foregoing embodiment, in this embodiment, when the absolute difference values of the two photo-generated currents respectively at the positions equidistant from the edges of the active regions on the two sides in the two-dimensional cross-sectional data are both smaller than the first difference threshold, it is determined that the photo-generated current electric field is uniform. Optionally, the first difference threshold is 5%, and when the absolute value of the difference between the two photo-generated currents at the equidistant positions from the edges of the active regions on the two sides is greater than 5%, a large deviation exists between the position found by the automatic peak searching and the actual geometric center position, and it is determined that the photo-generated current electric field is not uniform.
In this embodiment, when the self-coupling light position is 0 in a certain two-dimensional cross-section data, the self-coupling light position is calculated towards both sides, and if the drop rate of two adjacent photo-generated current values is not less than the preset value, the position far away from the position where the self-coupling light position is 0 is determined as the edge of the active region.
Optionally, the preset value is 20%, which is determined by the APD detection sensitivity and the source table accuracy.
In this embodiment, the first rate threshold is 2.5 μ A/μm, i.e. the drop rate of the photo-generated current at the edge of the active region needs to be greater than 2.5 μ A/μm.
At this time, since the drop rate of the photo-generated current value at the edge of the active area needs to be not less than 20%, i.e. the relative drop rate is not less than 10%/μm, and the absolute value of the drop rate needs to be greater than 2.5 μ A/μm, it indicates that the photo-generated current in the central area of the active area needs to reach at least 25 μ A, so as to eliminate the erroneous judgment caused by the measurement error of the source table.
On the basis of the above embodiment, in this embodiment, in the three-dimensional distribution, the photo-generated current is taken as a Z-axis coordinate, the row and column positions of the light coupling position are taken as an X-axis coordinate and a Y-axis coordinate, respectively, and the X-coordinate and the Y-coordinate of the initial light coupling position are both 0.
Preferably, the plurality of pieces of two-dimensional cross-sectional data taken along different direction planes are vertical direction planes passing through the Z axis. Wherein, a plurality of two-dimensional cross section data are equipped with four, include respectively: the two-dimensional section data of the section of the plane in the direction of the X axis, the two-dimensional section data of the section of the plane in the direction of the Y axis, the two-dimensional section data of the section of the plane in the direction of the X axis after the X axis rotates clockwise for 45 degrees around the Z axis, and the two-dimensional section data of the section of the plane in the direction after the Y axis rotates clockwise for 45 degrees around the Z axis.
Two-dimensional section data of a section of a plane in the direction of the X axis, namely a Y coordinate of a light coupling position is 0; two-dimensional sectional data of a section of the plane in the direction of the Y axis, that is, the X coordinate of the light coupling position is 0.
Further, three-dimensional distribution of photo-generated current corresponding to each light coupling position is obtained from the initial light coupling position in a line-by-line scanning mode, and the method specifically comprises the following steps:
firstly, adjusting the light coupling position from the original point to the X-axis negative direction until the photo-generated current is attenuated to a preset current value, and taking the point as a starting point;
and secondly, moving the photo-generated current to the positive direction of the X axis by a first step length from the starting point to the positive direction of the X axis until the photo-generated current is attenuated to a preset current value, moving the photo-generated current to the positive direction of the Y axis by the first step length after moving the photo-generated current to the positive direction of the Y axis by the first step length, and moving the photo-generated current to the positive direction of the X axis by the first step length after moving the photo-generated current to the negative direction of the Y axis until the response test of the half part of the positive direction of the Y axis is completed.
Then, the first step is moved from the starting point to the Y-axis negative direction.
And finally, moving the part in the positive direction of the X axis by a first step length until the photo-generated current is attenuated to a preset current value, moving the part in the negative direction of the Y axis by the first step length after moving the part in the negative direction of the Y axis by the first step length, and moving the part in the positive direction of the X axis by the first step length after moving the part in the negative direction of the Y axis again until the response test of the half part in the negative direction of the Y axis is completed.
In this embodiment, each time the first step length is moved, the photo-generated current at the current light coupling position is obtained, and then the three-dimensional distribution of the photo-generated current corresponding to each light coupling position can be obtained.
In this embodiment, taking the first step size as 2 μm and the preset current value as 10 μ a as an example, obtaining the three-dimensional distribution of the photo-generated current corresponding to each light coupling position specifically includes:
a. manually adjusting the light coupling position to the X-axis negative direction until the light-generated current is attenuated to 10 muA, and taking the point as a starting point;
b. moving by stepping 2 mu m from the starting point to the positive direction of the X axis, and recording the photo-generated current of each stop point until the photo-generated current is attenuated to 10 mu A again;
c. moving the film to the positive direction of the Y axis for 2 micrometers, moving the film to the negative direction of the X axis in a stepping mode for 2 micrometers, and recording the photo-generated current of each stop point until the photo-generated current is attenuated to 10 micrometers again and stops;
d. moving the film to the positive direction of the Y axis for 2 micrometers, moving the film to the positive direction of the X axis in a stepping mode for 2 micrometers, and recording the photo-generated current of each stop point until the photo-generated current is attenuated to 10 micrometers again and stops;
e. repeating the steps c and d until the response test of the positive half part of the Y axis is completed;
f. returning to the starting point;
g. moving the film to the negative direction of the Y axis for 2 micrometers, moving the film to the positive direction of the X axis by stepping for 2 micrometers, and recording the photo-generated current of each stop point until the photo-generated current is attenuated to 10 micrometers and stops;
h. moving the film to the Y-axis negative direction for 2 micrometers, moving the film to the X-axis negative direction by stepping for 2 micrometers, and recording the photo-generated current of each stop point until the photo-generated current is attenuated to 10 micrometers and stops;
i. and g and h are repeated until the response test of the negative direction half part of the Y axis is completed.
Alternatively, if a dwell point just around 10 μ A (. + -. 0.5 μ A) cannot be found or both sides cannot be found simultaneously, then the step size can be considered to be reduced to 1 μm.
In this embodiment, the alignment bias voltage is set according to a breakdown voltage of the SPAD and is smaller than the breakdown voltage. Wherein a plurality of V below breakdown voltage can be set UV And a plurality of alignment bias voltages that are less than the breakdown voltage.
Specifically, the breakdown voltage of the SPAD of the present embodiment is about 80V, and four groups of V below the breakdown voltage are preset UV Voltages of 7V, 5V, 3V, 2V, and 60V, 65V, 70V which is less than the breakdown voltage, respectively, are 7 groups.
In this embodiment, the two-dimensional cross-sectional data obtained by cross-section of the plane in the direction of the Y axis corresponding to the three-dimensional distribution of the photo-generated current at the light coupling position is compared with the distribution of the normalized photo-generated current at different alignment bias voltages as shown in fig. 2.
When the bias voltage is not higher than 70V, the change of the photo-generated current is obviously and smoothly close to the vertex, and in the central area of the active area, part of the photo-generated current is less than 25 muA, so that the condition that the bias voltage is not higher than 70V is difficult to eliminate misjudgment caused by measurement errors of the source meter; v UV The bias voltage is higher under the condition of 3V or 2V, and is too close to the breakdown voltage, and the curve of the bias voltage is already asymmetric to a certain extent. Therefore, if the SPAD itself has edge breakdown, it is easy to make a false determination in the coupling mode of automatically searching the electric field peak value by using this condition.
In conclusion, V can be expressed UV And =5V or 7V as initial conditions to complete subsequent sample alignment operation.
Based on the above embodiments, in this embodiment, when the distances from the initial light coupling position to the light coupling positions where the photo-generated current is attenuated to the preset current value are the same, and the absolute value of the difference between the attenuation rates moving in any two directions by a unit distance is smaller than the second difference threshold, it is determined that the incident light of the pigtail converges at the geometric center of the active region.
Further, when the distance from the initial light coupling position to each light coupling position where the photo-generated current is attenuated to the preset current value is different, or the absolute value of the difference of the attenuation rates of moving in any two directions by a unit distance is not less than a second difference threshold, updating the initial light coupling condition, and judging whether the incident light of the tail fiber converges at the geometric center position of the active area again according to the updated initial light coupling condition.
Preferably, the alignment bias voltage corresponding to the initial light coupling condition is reduced by 2V, which can be used as the updated initial light coupling condition to determine whether the incident light converges at the geometric center of the active region again.
On the basis of the above embodiment, in this embodiment, when the tail fiber moves in the direction close to the SPAD by the second step length, if the decay rate of the photo-generated current is greater than the second rate threshold, the tail fiber moves in the direction away from the SPAD by the third step length until the absolute value of the difference between the photo-generated current and the peak photocurrent is less than the third difference threshold, and it is determined that the incident light is axially converged in the SPAD chip absorption layer. The third step length is smaller than the second step length.
Further, when the tail fiber moves towards the direction close to the SPAD for the second step length, if the attenuation rate of the photo-generated current is smaller than or equal to a second rate threshold value, the tail fiber continues to move towards the direction close to the SPAD for the second step length until the attenuation rate of the photo-generated current is larger than the second rate threshold value.
In the embodiment, the coupling welding machine is controlled by compiling scripts, so that the coupling welding platform can automatically complete adjustment in the axial direction and the horizontal direction.
In this embodiment, the breakdown voltage is 80V, and V below the breakdown voltage UV For example, if the initial light coupling condition is 5V, that is, the alignment bias voltage corresponding to the initial light coupling condition is 75V, and then the radiation type scanning method determines whether the incident light converges at the geometric center of the active region with the initial light coupling position as the origin.
Specifically, the script automatically realizes that the optical fiber is moved by preset distances (stepping 0.5 μm) respectively along the positive direction of the X axis, the negative direction of the X axis, the positive direction of the Y axis and the negative direction of the Y axis so as to confirm the geometric symmetry of the response, namely, when the distance from the geometric center to each point is equal when the photo-generated current is attenuated to 10 μ A, and the attenuation rates of the moving unit distance are equivalent in each direction (namely, the absolute value of the difference value of the attenuation rates is not less than a second difference threshold), and then the incident light of the tail fiber is judged to be converged at the position of the geometric center of the active area. Wherein, the preset distance can be designed by referring to the radius of the photosensitive surface. In this embodiment, the predetermined distance is 8 μm.
If the result is not consistent, it indicates that the incident light of the tail fiber is not converged at the geometric center of the active region under the initial light coupling condition. At this time, the alignment bias voltage 2V corresponding to the initial light coupling condition may be lowered, and then the process is repeated until the determination condition is satisfied.
And the position of the tail fiber is fixed, so that the script controls the movement of the coupling welding platform to realize the movement of the light coupling position.
Taking the second step size as 0.8 μm, taking the third step size as 0.4 μm as an example, taking the vertical direction of the tail fiber close to the SPAD as the negative direction of the Z axis, and taking the vertical direction of the tail fiber far from the SPAD as the positive direction of the Z axis. After the incident light of the tail fiber is converged at the geometric center position of the active region, the tail fiber is required to move by stepping 0.8 μm along the negative direction of the Z axis, namely to gradually approach the SPAD, and if the photocurrent does not drop obviously monotonically, namely the attenuation rate of the photo-generated current is less than or equal to a second rate threshold, as shown in FIG. 3, the focus is determined to be outside the device, and the object distance (namely the distance between the end face of the tail fiber and the lens) is required to be continuously shortened; when the photo-generated current starts to decrease obviously and monotonously, namely the attenuation rate of the photo-generated current is larger than a second rate threshold value, as shown in fig. 4, the focus is judged to enter the device and part of light rays are blocked by the diaphragm, at the moment, the tail fiber is moved by stepping 0.4 mu m along the positive direction of the Z axis, namely, the tail fiber is gradually far away from the SPAD until the photo-generated current returns to the maximum value near the peak photocurrent again, namely the absolute value of the difference value between the current photo-generated current and the peak photocurrent is smaller than a third difference threshold value, at the moment, the incident light is judged to be converged in the absorption layer of the SPAD chip in an upward direction, and the diameter of a light spot is minimum.
As shown in fig. 5, the manufacturing method of the present embodiment specifically includes:
a1, mounting the SPAD to a coupling welding platform device base after sealing and welding a tube cap;
A2. initializing XYZ-T four-dimensional coarse alignment, and determining an initial light coupling position;
A3. acquiring three-dimensional distribution of photo-generated current corresponding to the light coupling position under multiple groups of alignment bias voltages, and further acquiring multiple two-dimensional section data of sections along different direction planes;
A4. acquiring alignment bias voltage meeting preset conditions as initial light coupling conditions based on a plurality of pieces of two-dimensional section data under each alignment bias voltage;
A5. controlling an XY plane to automatically optimize alignment by a script, judging whether incident light is converged at the geometric center position of the active area, and if so, turning to A7; otherwise, turning to A6;
A6. the initial light coupling conditions are updated and the transition is made to A5.
A7. Controlling a Z central axis to automatically optimize alignment by a script, judging whether an incident light axis is upwards converged in an SPAD chip absorption layer, and if so, turning to A9; otherwise, turning to A8;
A8. the distance between the end face of the pigtail and the lens is adjusted and the direction is turned to A7.
A9. And (4) performing puncture welding, performing two-dimensional confirmation alignment through radiation type scanning, and then performing lap welding.
In this embodiment, for the SPAD devices in the same batch, the initial light coupling condition 75V found above may be directly used for light coupling, the geometric center position of the active region is found in a radiation type scanning manner according TO the initial light coupling position of the device, and when it is determined that the light spot axially converges in the absorption layer of the SPAD chip, the tail fiber and the SPAD device are puncture-welded, and after two-dimensional confirmation alignment is performed again through radiation type scanning, lap welding is performed TO obtain the SPAD coaxial TO device.
The application also provides an embodiment of the SPAD coaxial TO device, and the SPAD coaxial TO device is manufactured by the manufacturing method.
The SPAD coaxial TO device of the embodiment is suitable for the manufacturing methods, and can ensure that an optical path in the device is realized: (1) incident light rays are converged at the geometric center position of the active region in the horizontal direction; (2) the incident light rays are converged in the SPAD chip absorption layer in the axial direction (namely the light spot diameter is minimum); the dark count generated by the dark time delay avalanche caused by the generation position of the photon-generated carrier at the periphery of the active region is effectively reduced, and the performance of the SPAD in related applications is improved.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as the case may be.
It is noted that, in this application, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A manufacturing method of an SPAD coaxial TO device is characterized by comprising the following steps:
after the SPAD is subjected to tube cap sealing welding, the SPAD is installed on a coupling welding platform device base, and the position and the angle of the SPAD when the SPAD outputs peak photocurrent are obtained and used as the initial light coupling position of the SPAD;
under the condition of a plurality of preset alignment bias voltages, acquiring three-dimensional distribution of photo-generated current corresponding to each light coupling position from the initial light coupling position in a line-by-line scanning mode, and further acquiring a plurality of two-dimensional section data of sections along different direction planes; in the two-dimensional section data, the abscissa is the light coupling position of the corresponding section, and the ordinate is the photo-generated current value;
acquiring alignment bias voltage meeting preset conditions as initial light coupling conditions based on a plurality of pieces of two-dimensional section data under each alignment bias voltage; the preset conditions are as follows: the electric field of the photo-generated current is uniform and has no edge breakdown, and the falling rate of the photo-generated current at the edge of the active area is greater than a first rate threshold;
and under the initial light coupling condition, when the incident light of the tail fiber is converged at the geometric center position of the active region and is axially converged in the SPAD chip absorption layer, welding and fixing the tail fiber and the SPAD device TO obtain the SPAD coaxial TO device.
2. The method of fabricating the SPAD coaxial TO device of claim 1, wherein:
and when the absolute difference values of the two photo-generated currents at the positions which are respectively equidistant from the edges of the active regions at the two sides in the two-dimensional section data are smaller than a first difference threshold value, judging that the photo-generated current electric field is uniform.
3. The manufacturing method of the SPAD coaxial TO device according TO claim 1, wherein in the three-dimensional distribution, the photo-generated current is taken as a Z-axis coordinate, the row and column positions of the light coupling position are taken as an X-axis coordinate and a Y-axis coordinate, respectively, and the X-axis coordinate and the Y-axis coordinate of the initial light coupling position are both 0;
the plurality of two-dimensional cross-sectional data of the cross-section taken along the different direction planes includes:
the two-dimensional cross section data of the section of the direction plane along the X axis, the two-dimensional cross section data of the section of the direction plane along the Y axis, the two-dimensional cross section data of the section of the direction plane after the X axis rotates clockwise by 45 degrees around the Z axis, and the two-dimensional cross section data of the section of the direction plane after the Y axis rotates clockwise by 45 degrees around the Z axis.
4. The manufacturing method of the SPAD coaxial TO device according TO claim 3, wherein the three-dimensional distribution of the photo-generated current corresponding TO each coupling position is obtained from the initial coupling position in a line-by-line scanning manner, specifically comprising:
the light coupling position is adjusted from the original point to the X-axis negative direction until the photo-generated current is attenuated to a preset current value, and the point is taken as the starting point;
moving the photo-generated current to the positive direction of the Y axis by a first step length from the starting point to the positive direction of the X axis, moving the photo-generated current to the positive direction of the Y axis by the first step length after moving the first step length to the negative direction of the X axis when the photo-generated current is attenuated to the preset current value again, moving the photo-generated current to the positive direction of the Y axis by the first step length again until the response test of the half part of the positive direction of the Y axis is completed;
moving a first step length from the starting point to the Y-axis negative direction;
moving to the positive direction of the X axis by a first step length until the photo-generated current is attenuated to a preset current value, moving to the negative direction of the Y axis by the first step length after moving to the negative direction of the Y axis by the first step length, and moving to the negative direction of the Y axis by the first step length again until the response test of the half part of the negative direction of the Y axis is completed when the photo-generated current is attenuated to the preset current value again;
and acquiring the photo-generated current at the current light coupling position every time the first step length is moved.
5. The method of fabricating the SPAD coaxial TO device of claim 1, wherein:
and when the distances from the initial light coupling position to the light coupling positions where the photo-generated current is attenuated to a preset current value are the same and the absolute value of the difference of the attenuation rates moving in any two directions by a unit distance is smaller than a second difference threshold, judging that the incident light of the tail fiber is converged at the geometric center position of the active region.
6. The method of fabricating the SPAD coaxial TO device of claim 5, wherein:
when the distances from the initial light coupling position to the light coupling positions where the photo-generated current is attenuated to the preset current value are different, or the absolute value of the difference of the attenuation rates of the unit distance moving in any two directions is not less than a second difference threshold, updating the initial light coupling condition, and judging whether the incident light of the tail fiber is converged at the geometric center position of the active area again according to the updated initial light coupling condition.
7. The method of fabricating the SPAD coaxial TO device of claim 1, wherein:
when the tail fiber moves towards the direction close to the SPAD for the second step length, if the attenuation rate of the photo-generated current is greater than a second rate threshold value, the tail fiber moves towards the direction far away from the SPAD for the third step length until the absolute value of the difference value between the photo-generated current and the peak photocurrent is smaller than a third difference threshold value, and the incident light is judged to be axially converged in an absorption layer of the SPAD chip;
the third step size is smaller than the second step size.
8. The method of fabricating the SPAD coaxial TO device of claim 7, wherein:
and if the decay rate of the photo-generated current is less than or equal to the second rate threshold, continuously moving the second step size towards the direction close to the SPAD until the decay rate of the photo-generated current is greater than the second rate threshold.
9. The method of fabricating the SPAD coaxial TO device of claim 1, wherein: the alignment bias voltage is set according to a breakdown voltage of the SPAD and is less than the breakdown voltage.
10. A SPAD coaxial type TO device is characterized in that: which is produced by the production method according to any one of claims 1 to 9.
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