Automatic bar laser chip testing and screening device

Abstract

The invention discloses an automatic bar laser chip testing and screening device, which relates to the technical field of semiconductor laser chip testing, and comprises an objective table on the surface of which a bar laser chip is placed; the probe assembly comprises a probe, and the probe is used for establishing physical contact with the top electrode of the bar laser chip and transmitting an electric signal; the light source detection device is arranged opposite to the probe assembly and is used for detecting the wave band and the optical power of the bar laser chip; and a holder, wherein the objective table is arranged on the holder. According to the method, spectrum monitoring, current compensation and Peltier temperature control are linked, the spectrum drift amount is converted into the current compensation amount and the temperature compensation amount, the physical correlation model is established through the alpha / beta / k coefficient, cross-dimension compensation of spectrum drift is achieved, the temperature of the micro-island structure can be accurately controlled, and the test accuracy of the bar laser chip can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor laser chip testing, in particular to an automatic bar laser chip testing and screening device. BACKGROUND

[0002] Bar laser chips are linear array lasers formed by arranging multiple semiconductor laser single tubes side by side, can be split into multiple independent single tubes, have the characteristics of high power and high reliability, and are widely used in industrial processing, medical treatment and other fields. After the laser is packaged, testing will inevitably lead to product scrap due to chip defects, and detection of the optical power and wavelength of the laser chip before assembly is an important link.

[0003] For example, the prior art scheme (CN111323696A) discloses a laser chip testing device and testing method, which adopts a whole-board copper carrier table structure, and the probe is connected with the laser chip. However, during the testing process, heat is rapidly conducted in the copper plate, resulting in a large temperature difference between adjacent laser chips.

[0004] Especially when batch testing, this problem will be aggravated: Chip self-heating: when the probe passes through the top electrode and is powered on, the laser chip continuously generates heat; Joule heat accumulation: additional heat is generated when the current flows through the copper plate at the bottom of the bar; Heat conduction out of control: the copper plate transversely conducts heat, causing cross-transmission of heat, forming a "heat crosstalk chain". The essence of the heat crosstalk chain is that the transverse heat conduction path of the whole-board copper substrate is not segmented, resulting in the diffusion of heat along the low thermal resistance channel.

[0005] Thus, in the bar laser chip testing, the heat management defects of the whole-board copper carrier table cause triple failure: Heat crosstalk: the transverse heat conduction of the copper plate causes thermal coupling between adjacent chips, increasing the temperature difference; Electrical misalignment: the copper resistivity increases with temperature rise, causing fluctuations in the driving current;

[0006] Optical drift: the increase in chip junction temperature causes wavelength redshift, and the test data is distorted.

[0007] The heat accumulation effect will force the testing to be interrupted for cooling, reducing the efficiency, and will affect the testing accuracy of the bar laser chip. SUMMARY

[0008] The technical scheme of the present application provides a solution significantly different from the prior art to solve the problem of copper plate thermal crosstalk and excessive temperature difference causing interference with the test accuracy of bar laser chips in large batch testing and screening of bar laser chips in the prior art.

[0009] To achieve the above object, the present application provides the following technical scheme: An automatic bar laser chip testing and screening device, comprising: a stage for placing bar laser chips on its surface; A probe assembly comprising a probe for establishing physical contact with the top electrode of the bar laser chip and transmitting electrical signals; A light source detection device opposite the probe assembly for detecting the wavelength and optical power of the bar laser chip; A gimbal for driving the multiple bar laser chips on the stage to move in turn to the focal plane of the light source detection device; A front die placement machine for sucking bar laser chips from the blue film and placing them at equal intervals on the stage; A rear die placement machine for removing tested bar laser chips from the stage.

[0010] Preferably, the stage comprises a copper substrate with a micro-island structure arranged in an array on the surface of the copper substrate, and a thermal insulation layer arranged between adjacent micro-island structures; The thermal insulation layer is made of a low thermal conductivity material, and the thermal conductivity of the thermal insulation layer is configured to block significant heat conduction between adjacent micro-island structures, so that the temperature difference between chips on adjacent micro-island structures during operation is kept within a preset threshold; A cooling element is arranged at the bottom of the micro-island structure for temperature control of the micro-island structure.

[0011] Preferably, the thermal insulation layer is a silicon nitride thermal insulation layer, and the width of the silicon nitride thermal insulation layer of the micro-island structure is 1 / 3 of the width of the chip; The cooling element comprises a Peltier element, and the cold end of the Peltier element is attached to the bottom of the micro-island structure through a thermally conductive adhesive layer, and the hot end is connected with a heat dissipation fin.

[0012] Preferably, a vacuum suction hole is arranged on the surface of the micro-island structure, and the vacuum suction hole vertically penetrates the copper substrate downward throughout, and the vacuum suction hole is embedded with an alumina ceramic bushing in the Peltier element mounting area.

[0013] Preferably, the alumina ceramic bushing and the copper substrate are sealed by active metal brazing, and the brazing layer contains a silver-copper-titanium alloy.

[0014] Preferably, the controller is further provided with a double closed-loop control system inside, which dynamically adjusts the Peltier power and driving current according to real-time feedback of the light source detection device. The Peltier power is dynamically adjusted by the controller according to the infrared thermal imager prediction model to realize pre-compensation before heat accumulation.

[0015] Preferably, the double closed-loop control system comprises: a spectrum acquisition module for acquiring wavelength data of the bar laser chip; a current compensation module for changing the output electric power on the probe assembly; a Peltier temperature control module for changing the refrigeration power of the Peltier element.

[0016] Preferably, the logic process of the double closed-loop control system comprises the following steps: S1. The spectrum acquisition module acquires wavelength data of the bar laser chip every interval time; S2. If the wavelength offset Δλ is greater than a first preset threshold, the current compensation module is triggered to output; S3. The Peltier temperature control module is started synchronously, and the refrigeration power of the Peltier is adjusted according to a set formula.

[0017] Preferably, a second preset threshold is further provided in the controller, and if Δλ is still greater than the second preset threshold after current compensation, the bar laser chip is marked as a defective product; The second preset threshold is associated with the Peltier refrigeration efficiency η, and when η drops by more than 10%, the system calibration period is automatically triggered.

[0018] Preferably, in S2, the first preset threshold is dynamically optimized by the controller according to historical test data, and the initial value is M, which is self-adaptively adjusted according to Δλ 阈值 =M+S×log(N) with the increase of test batch number N.

[0019] Wherein, M is the reference value of the first preset threshold; N is the test chip serial number; S is a self-adaptive adjustment coefficient for controlling the rate of threshold increase with the growth of test batch number N.

[0020] Compared with the prior art, the present application has the following advantages: 1.The application is characterized in that: by etching independent micro-islands on a copper substrate, isolating them with a silicon nitride thermal insulation layer, and cooling the bar laser chip through a Peltier point-to-point cooling system, the copper substrate's horizontal heat conduction path is blocked, and the cold energy precisely acts on the single-chip micro-island. The micro-island structure decouples the whole-plate copper carrier into independent thermal management units. The silicon nitride thermal insulation layer blocks the horizontal heat diffusion, and the Peltier vertical cooling path precisely offsets the chip's self-heating and Joule heat, thus solving the problem of heat accumulation and heat crosstalk on the copper substrate from the physical structure and energy transmission path, and maintaining the stability and rationality of the bar laser chip test environment.

[0021] 2.The application links spectrum monitoring, current compensation, and Peltier temperature control together, converts the spectrum drift into current compensation and temperature compensation, establishes a physical correlation model through alpha / beta / k coefficients, realizes cross-dimension compensation of spectrum drift, precisely controls the temperature of the micro-island structure, and improves the bar laser chip test accuracy. Moreover, the linkage mechanism is not a passive response, but predicts the heat drift trend through spectrum data, establishes a physical correlation model through alpha / beta / k coefficients, and actively adjusts the current and temperature before heat accumulation, realizing the leap from "lag correction" to "pre-inhibition". BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of an automatic bar laser chip test screening device of the application;

[0023] Figure 2 It is a structural schematic diagram of a carrier in an automatic bar laser chip test screening device of the application;

[0024] Figure 3 It is a structural schematic diagram of a micro-island structure in an automatic bar laser chip test screening device of the application.

[0025] In the figure: 100, carrier; 110, copper substrate; 120, micro-island structure; 130, silicon nitride thermal insulation layer; 140, cooling piece; 150, vacuum suction hole; 160, alumina ceramic bushing; 200, light source detection device; 300, gimbal; 400, probe assembly. DETAILED DESCRIPTION

[0026] In the description of the application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", and "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the application can be understood through specific circumstances.

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0028] Please refer to Figures 1-3 The present application provides a technical solution: an automatic bar laser chip test and screening device, comprising: a stage 100, on the surface of which bar laser chips are placed.

[0029] A probe assembly 400, the probe assembly comprising a probe and a microscope 520, the probe being used to establish physical contact with the top electrode (metal contact point) of the bar laser chip and transmit electrical signals such as current and voltage, and the microscope 520 being used to enlarge the alignment picture of the bar laser chip and the probe, so as to ensure that the probe is accurately driven on the micron-level electrode and avoid poor contact or damage to the chip.

[0030] A light source detection device 200, comprising a spectrometer, the light source detection device being arranged opposite to the probe assembly and being used to detect the wavelength band and optical power of the bar laser chip; A gimbal 300, the stage 100 being arranged on the gimbal 300 and being used to drive a plurality of bar laser chips on the stage 100 to be sequentially positioned and moved to the focal plane of the light source detection device 200, so as to realize physical contact between the top electrode of the bar laser chip and the probe on the focal plane. At the same time, the light source detection device 200 detects the wavelength band and optical power of the bar laser chip, judges whether the bar laser chip is qualified, and marks the bar laser chip. The qualified or unqualified bar laser chip is screened by a subsequent back bonder.

[0031] In the present embodiment, the gimbal 300 is a three-axis displacement table, which can move in steps according to the repeated graphical pitch, such as descending, moving right / left, and ascending, so as to ensure that each laser chip on the stage 100 can be tested and lit.

[0032] A front bonder is used to suck the bar laser chips from the blue film and place them on the stage 100 at equal intervals.

[0033] A back bonder is used to take the tested bar laser chips from the stage 100.

[0034] When the device is used to detect a large number of bar laser chips in the whole process, the following problems may exist:

[0035] First, the cumulative effect of local heating of the copper plate when the probe is powered on, second, the temperature crosstalk caused by the overall thermal conductivity of the copper plate, and third, the spectral drift problem. This is indeed a contradiction: in order to have good conductivity, we choose copper material, but the thermal conductivity is too good and becomes a burden, causing heat to accumulate under the chip.

[0036] Among them, the spectral drift refers to the physical nature: the emission wavelength (λ) of the laser chip changes with temperature (T) and current (I): Δλ=αxΔT+β×ΔI; Among them: α is the thermal drift coefficient, which reflects the wavelength shift caused by every 1℃ temperature rise, which is derived from the change of the band gap of the semiconductor material with temperature; β is the current tuning coefficient, which reflects the wavelength blue shift caused by every 1mA current increase, which is derived from the change of the refractive index caused by the change of the carrier concentration; Δλ is the wavelength shift of the bar laser chip, which is monitored in real time by the spot shift sensor; ΔT is the temperature change of the stage 100, which is measured by the infrared thermal imaging sensor; ΔI is the driving current adjustment of the bar laser chip by the controller.

[0037] The drift is manifested as: temperature rise causes the band gap of the semiconductor to narrow, resulting in red shift of the wavelength, which shifts to the long wavelength; The temperature rise of the copper plate causes the driving current to fluctuate, thereby exacerbating the wavelength jitter.

[0038] Therefore, the following scheme is proposed to solve the above problems: In this embodiment, the stage 100 includes a copper substrate 110, and a micro-island structure 120 is arranged in an array on the surface of the copper substrate 110. A heat insulation layer is arranged between adjacent micro-island structures 120.

[0039] The heat insulation layer is made of a low thermal conductivity material, and the thermal conductivity thereof is configured to be able to block significant heat conduction between adjacent micro-island structures 120, so that the temperature difference of the chips on adjacent micro-island structures 120 during work is kept within a preset threshold.

[0040] Specifically, the heat insulation layer can be a silicon nitride heat insulation layer 130, which has a thermal conductivity significantly lower than that of the copper substrate 110, and the width of the silicon nitride heat insulation layer 130 of the micro-island structure 120 is 1 / 3 of the width of the chip.

[0041] A cooling member 140 is arranged at the bottom of the micro-island structure 120, and the cooling member 140 is used for temperature control of the micro-island structure 120.

[0042] Among them, the micro-island structure 120 can be processed by the following method: Step 1: The surface of the copper substrate 110 is coated with photoresist, and the micro-island array pattern is exposed by UV. Step 2: DRIE etching depth forms square micro-island structures 120.

[0043] Step 3: LPCVD deposition of silicon nitride to fill the gaps, followed by CMP polishing.

[0044] The cooling component 140 includes a Peltier element, and the cold end of the Peltier element is bonded to the bottom of the micro-island structure 120 through a thermally conductive adhesive layer. Its hot end is connected to a heat dissipation fin. The Peltier element adjusts the temperature in real time according to the feedback from the infrared thermal imager to avoid the overall temperature of the copper substrate 110 rising, especially to adjust the temperature at the micro-island structure 120 in real time.

[0045] The spectrometer collects spectra at regular intervals, and we compensate for drift by dynamically adjusting the drive current.

[0046] Therefore, the device also includes a controller, which is equipped with a dual closed-loop control system. The dual closed-loop control system dynamically adjusts the Peltier power and drive current based on the real-time feedback from the light source detection device 200. The Peltier power is dynamically adjusted by the controller based on the infrared thermal imager prediction model to achieve pre-compensation before heat accumulation.

[0047] The dual closed-loop control system includes: The spectral acquisition module is used to acquire wavelength data of the bar laser chip; The current compensation module is used to change the output power on the probe assembly 400; The Peltier temperature control module is used to change the cooling power of the Peltier element.

[0048] The logic process of a dual-closed-loop control system mainly includes the following steps: S1. The spectral acquisition module acquires the wavelength data of the bar laser chip at regular intervals; S2. If the wavelength offset Δλ > the first preset threshold, trigger the current compensation module to output: ΔI = -(Δλ - α × (T_real-time − T_reference)) / β; S3. Simultaneously start the Peltier temperature control module and adjust the Peltier's cooling power according to the following formula: ΔT=-k×Δλ; Where k is the wavelength-temperature compensation conversion coefficient, representing the amount of temperature change that needs to be compensated for per nanometer wavelength shift.

[0049] In S2, the first preset threshold is dynamically optimized by the controller based on historical test data. The initial value is M, and it increases by Δλ as the number of batch tests increases. 阈值 =M+S×log(N) Adaptive adjustment.

[0050] Wherein, M is the reference value of the first preset threshold, which is an empirical value based on industry standards, experimental data or theoretical calculation, and represents the sensitivity threshold of the system to wavelength drift at the initial stage of testing.

[0051] For example: the wavelength tolerance of common industry laser chips, such as DFB lasers, is usually ±0.1 nm. Through testing 1000 chips, it was found that the wavelength fluctuation of 95% of the qualified products was <0.1 nm. N is the test chip serial number. S is an adaptive adjustment coefficient for controlling the rate of threshold increase with the growth of test batch N. As an optimization parameter, it can be obtained by machine learning training historical data: as the test batch N increases, the drift error increases due to system heat accumulation, so the threshold needs to be gradually relaxed to avoid false triggering. For example, the threshold is increased by 0.01 nm for every 100 batches.

[0052] Logarithmic function log(N): simulates the thermal fatigue effect of the test equipment with the increase of batches. The heat accumulation rate gradually slows down with the growth of N, changes fast at the initial stage, and saturates at the later stage, conforming to the logarithmic growth model.

[0053] For example: through regression analysis of 10000 laser chip test data, the threshold adjustment formula is obtained: Δλ 阈值 =0.1+0.01×log(N); Wherein: N is the test batch serial number (N≥1); The coefficient 0.01 is obtained by least squares fitting of historical error curves (fitting goodness R 2 =0.95); The initial value 0.1 nm is 2 times the standard deviation (σ) of the wavelength fluctuation of qualified chips, i.e. 95% confidence interval.

[0054] Test data table:

[0055] Batch N Actual average drift (nm) Formula calculated threshold (nm) 1 0.05 0.10 100 0.12 0.12 1000 0.13 0.13

[0056] In this embodiment, the double closed-loop formula is not a simple algebraic relationship, but a dynamic feedback model based on thermal-electric-optical coupling: Current compensation formula: ΔI=-(Δλ-αΔT) / β, which is essentially to reverse the thermal drift by modulating the refractive index through carrier concentration. Temperature compensation formula: ΔT=-k×Δλ, wherein k is jointly calibrated by Peltier refrigeration efficiency η and thermal drift coefficient α (k=α / η), which reflects the accurate matching of energy transfer.

[0057] For example: if a red shift Δλ=+0.2 nm (offset to long wavelength) is detected, the temperature needs to be lowered: ΔT=-0.5×0.2=-0.1℃. That is, the cold end of the Peltier needs to be reduced by 0.1℃ to offset the wavelength shift.

[0058] For example, when the ambient temperature fluctuates or the bar laser chip power changes, that is, greater than the first preset threshold, the controller calculates the required compensation amount by the formula and reduces the temperature by the Peltier: (1) Peltier cooling; (2) Current reverse compensation: ΔI = -(Δλ-αΔT) / β.

[0059] That is, we solve the problem of thermal crosstalk and spectral drift by combining "partition thermal isolation" and "current compensation" to improve the detection accuracy of the bar laser chip.

[0060] In this embodiment, a vacuum suction hole 150 is arranged on the surface of the micro-island structure 120. The vacuum suction hole 150 is used to improve the tightness between the bar laser chip and the micro-island structure 120. The vacuum suction hole 150 vertically penetrates the copper substrate 110 downward, and the vacuum suction hole 150 is embedded with an alumina ceramic bushing 160 in the Peltier element mounting area. The alumina ceramic bushing 160 and the copper substrate 110 are sealed by active metal brazing, and the brazing layer contains silver-copper-titanium alloy. To ensure that the air tightness of the vacuum suction hole 150 is not affected by the Peltier temperature, the airflow is physically isolated from the Peltier, and the airflow disturbance to the working temperature of the Peltier is avoided.

[0061] Further, in order to distinguish the drift caused by the test environment temperature rise (which needs to be compensated) and the drift caused by the chip itself defect (which should be judged as a defective product), so as to avoid the misjudgment of the bar laser chip, a second preset threshold is also set in the controller. The key is whether the drift is repeatable. The wavelength of a high-quality bar laser chip should be stable at ±0.02nm after temperature compensation, while a defective product will continue to drift. A second judgment threshold can be set: when the compensation current exceeds the nominal value, automatic re-inspection is triggered.

[0062] The following is the double-threshold judgment logic: When the detected wavelength shift Δλ is greater than the first preset threshold; Start current compensation to maintain stable test conditions; After compensation, Δλ is still greater than the second preset threshold, and the bar laser chip is judged as a defective chip (self-defect), otherwise it is recorded as a qualified product.

[0063] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made shall be included in the protection scope of the present application.

Claims

1. An automated bar laser chip test sorting device, characterized by, It comprises: a carrier (100) on which the bar laser chip is placed; a probe assembly (400) comprising probes for establishing physical contact with the top electrode of the bar laser chip and transmitting electrical signals; a light source detection device (200) arranged opposite to the probe assembly for detecting the wavelength and optical power of the bar laser chip; a gimbal (300) on which the carrier (100) is arranged, the gimbal (300) being used to drive the multiple bar laser chips on the carrier (100) to move to the focal plane of the light source detection device (200) in sequence; a front dicing machine for sucking the bar laser chip from the blue film and placing it on the carrier (100) at equal intervals; a rear dicing machine for taking the tested bar laser chip from the carrier (100); the carrier (100) comprises a copper substrate (110) on the surface of which a micro-island structure (120) is arranged in an array, and a heat insulation layer is arranged between adjacent micro-island structures (120); the heat insulation layer is made of a low thermal conductivity material, and the thermal conductivity thereof is configured to block significant heat conduction between adjacent micro-island structures (120), so that the temperature difference between the chips on adjacent micro-island structures (120) during operation is kept within a preset threshold; a cooling element (140) is arranged at the bottom of the micro-island structure (120), and the cooling element (140) is used to control the temperature of the micro-island structure (120).

2. The automatic bar laser chip testing and screening device according to claim 1, wherein: the heat insulation layer is a silicon nitride heat insulation layer (130), and the width of the silicon nitride heat insulation layer (130) of the micro-island structure (120) is 1 / 3 of the width of the chip; the cooling element (140) comprises a Peltier element, and the cold end of the Peltier element is attached to the bottom of the micro-island structure (120) through a heat-conducting glue layer, and the hot end is connected with a heat dissipation fin.

3. The automatic bar laser chip testing and screening device according to claim 2, wherein: vacuum suction holes (150) are arranged on the surface of the micro-island structure (120), and the vacuum suction holes (150) vertically penetrate the copper substrate (110) downward throughout, and the vacuum suction holes (150) are embedded with alumina ceramic bushings (160) in the Peltier element mounting area.

4. The automatic bar laser chip testing and screening device according to claim 3, wherein: the alumina ceramic bushing (160) and the copper substrate (110) are sealed by active metal brazing, and the brazing layer contains silver copper titanium alloy.

5. The automatic bar laser chip testing and screening device according to claim 3, further comprising a controller, and a double closed-loop control system is arranged in the controller, and the double closed-loop control system dynamically adjusts the Peltier power and driving current according to the real-time feedback of the light source detection device (200). ​ And the Peltier power is dynamically adjusted by the controller according to the infrared thermal imager prediction model to realize pre-compensation before heat accumulation. 6.The automatic bar laser chip testing and screening device according to claim 5, characterized in that: The double closed-loop control system comprises: The spectrum acquisition module is configured to acquire wavelength data of the bar laser chip; The current compensation module is configured to change output electric power on the probe assembly (400) ; The Peltier temperature control module is configured to change refrigeration power of the Peltier element. 7.The automatic bar laser chip testing and screening device according to claim 6, characterized in that: The logic process of the double closed-loop control system comprises the following steps: S1.The spectrum acquisition module acquires wavelength data of the bar laser chip every interval time; S2.If the wavelength offset Δλ is greater than a first preset threshold, the current compensation module is triggered to output; S3.The Peltier temperature control module is started synchronously, and refrigeration power of the Peltier is adjusted according to a set formula. 8.The automatic bar laser chip testing and screening device according to claim 7, characterized in that: A second preset threshold is further set in the controller, and if Δλ is still greater than the second preset threshold after current compensation, the bar laser chip is marked as a defective product; The second preset threshold is associated with Peltier refrigeration efficiency η, and when η drops by more than 10%, a system calibration cycle is automatically triggered. 9.The automatic bar laser chip testing and screening device according to claim 8, characterized in that: In S2, the first preset threshold is dynamically optimized by the controller according to historical test data, and the initial value is M, which is adjusted adaptively by Δλ 阈值 =M+S×log(N) with the increase of the number of batch tests. M is a reference value of the first preset threshold; N is a test chip serial number; S is an adaptive adjustment coefficient for controlling the rate at which the threshold increases with the test batch N.

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