Semiconductor laser inspection apparatus and semiconductor laser inspection method

Abstract

A semiconductor laser element (2) is placed on a first heating cooler (1). A probe support (4) is installed on a second heating cooler (3). A measurement probe (8) is fixed to the tip of the probe support (4). A micro stage (9) moves the second heating cooler (3) and the probe support (4) so that the tip of the measurement probe (8) abuts against the semiconductor laser element (2). An inspection device (10) inputs an inspection signal to the semiconductor laser element (2) via the measurement probe (8).

Description

Semiconductor laser inspection device and semiconductor laser inspection method

[0001] This application is a divisional application of application number 202080107390.6, which entered the Chinese national phase on May 22, 2023, and is entitled "Semiconductor Laser Inspection Apparatus and Semiconductor Laser Inspection Method". Technical Field

[0002] This disclosure relates to a semiconductor laser inspection apparatus and a semiconductor laser inspection method that uses a probe to contact a semiconductor laser element to inspect the characteristics of the semiconductor laser element. Background Technology

[0003] A semiconductor laser element to be cut is placed on a fixture equipped with a heater and cooler, and a probe is brought into contact with it for characteristic inspection. If a probe at room temperature is brought into contact with a heated or cooled semiconductor laser, the characteristics of the semiconductor laser element will change due to the temperature difference, resulting in measurement deviation. To address this, a technique has been proposed that heat the probe with a heating device during semiconductor wafer inspection to bring it to the same temperature as the wafer. This prevents heat loss from the semiconductor wafer and suppresses measurement deviation. Furthermore, it stabilizes the contact by suppressing probe deformation upon contact.

[0004] However, in the past, because the heating device was separate from the probe, the probe needed to be reheated using the heating device after the inspection. To address this, an inspection device in which a heating device is installed on the probe has been proposed (for example, see Patent Document 1).

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-90345

[0006] To cool the probe, a Peltier element needs to be placed on it. Typical Peltier elements are 10mm x 10mm or larger. Probes used in semiconductor inspection are generally 1mm in diameter and 20-30mm in length. Therefore, there is no space near the probe for a typical Peltier element. With smaller Peltier elements, it is difficult to route the coated wiring that carries the current to the element outwards. Even if a Peltier element is placed on the probe, the supporting components heat up, requiring a cooling mechanism such as water cooling. However, since the supporting components only have holes a few millimeters in diameter, only a small amount of cooling water can pass through, which is insufficient for adequate cooling. Therefore, the probe cannot be cooled, and the characteristics of the semiconductor laser element cannot be prevented from changing when in contact with the probe. Summary of the Invention

[0007] This disclosure is made to solve the aforementioned problems, and its purpose is to provide a semiconductor laser inspection apparatus and a semiconductor laser inspection method that can prevent changes in the characteristics of the semiconductor laser element when it comes into contact with the probe.

[0008] The semiconductor laser inspection apparatus disclosed herein is characterized by comprising: a first heating and cooling unit for mounting a semiconductor laser element; a second heating and cooling unit; a probe holder mounted on the second heating and cooling unit; a measuring probe fixed to the end of the probe holder; a micro-motion stage for moving the second heating and cooling unit and the probe holder so that the end of the measuring probe comes into contact with the semiconductor laser element; and an inspection device for inputting an inspection signal to the semiconductor laser element via the measuring probe.

[0009] In this disclosure, a semiconductor laser element is mounted on a first heating and cooling unit, and a probe holder is mounted on a second heating and cooling unit. Both the first and second heating and cooling units can control the temperature not only at a high temperature but also at a low temperature, thus allowing the temperature of the semiconductor laser element to be close to that of the measuring probe. This prevents changes in the characteristics of the semiconductor laser element when it comes into contact with the measuring probe. Attached Figure Description

[0010] Figure 1 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 1.

[0011] Figure 2 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 2.

[0012] Figure 3 is an enlarged side view of region A, enclosed by the dashed line in Figure 2.

[0013] Figure 4 is a block diagram showing a modified example of the semiconductor laser inspection apparatus according to Embodiment 2.

[0014] Figure 5 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 3.

[0015] Figure 6 is an enlarged side view of region A, enclosed by the dashed line in Figure 5.

[0016] Figure 7 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 4.

[0017] Figure 8 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 5.

[0018] Figure 9 is a graph showing the time variation of the wavelength of the emitted light from the semiconductor laser element relative to the set temperature of the measuring probe.

[0019] Figure 10 is a block diagram illustrating the semiconductor laser inspection method according to Embodiment 6.

[0020] Figure 11 is a block diagram illustrating the semiconductor laser inspection method according to Embodiment 7. Detailed Implementation

[0021] The semiconductor laser inspection apparatus and semiconductor laser inspection method according to the embodiments will be described with reference to the accompanying drawings. The same or corresponding components are labeled with the same reference numerals, and sometimes repeated descriptions are omitted.

[0022] Implementation Method 1

[0023] Figure 1 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 1. The heating and cooling unit 1 is a stage on which the semiconductor laser element 2 is placed. A probe holder 4 is mounted on the heating and cooling unit 3. The heating and cooling unit 1 and the heating and cooling unit 3 have Peltier elements, etc., which can control the temperature not only at a high temperature side but also at a low temperature side.

[0024] Temperature sensor 5 is built into heater / cooler 1 to measure the temperature of heater / cooler 1. Temperature sensor 6 is built into heater / cooler 3 to measure the temperature of heater / cooler 3. In this embodiment, the control unit 7 sets the temperatures of heater / cooler 1 and heater / cooler 3 to the same value based on the measurement results of temperature sensors 5 and 6.

[0025] The measuring probe 8 is fixed to the end of the probe holder 4. The micro-stage 9 moves the heating and cooling unit 3 and the probe holder 4 in the vertical and horizontal directions, so that the end of the measuring probe 8 comes into contact with the semiconductor laser element 2 placed on the heating and cooling unit 1.

[0026] The inspection apparatus 10 includes a signal generator 11, an LD drive power supply 12, and a bias tee 13. A modulation signal output from the signal generator 11 and a constant voltage output from the LD drive power supply 12 are coupled at the bias tee 13 to form an inspection signal. The inspection apparatus 10 inputs the inspection signal to the semiconductor laser element 2 via a measuring probe 8. The semiconductor laser element 2 is driven by this inspection signal to perform a characteristic inspection of the semiconductor laser element 2.

[0027] Furthermore, when measurements are performed at room temperature below 25°C, condensation may occur on the measuring probe 8 or the semiconductor laser element 2, potentially causing variations in characteristic values ​​or short circuits during the measurement. Therefore, the entire device needs to be enclosed in a box made of materials such as acrylic and filled with dry air or N2 to prevent condensation.

[0028] In this embodiment, a semiconductor laser element 2 is placed on a heating and cooling unit 1, and a probe holder 4 is mounted on the heating and cooling unit 3. Since the heating and cooling units 1 and 3 can control the temperature not only at a high temperature but also at a low temperature, the temperature of the semiconductor laser element 2 can be brought close to that of the measuring probe 8. This prevents changes in the characteristics of the semiconductor laser element 2 when it comes into contact with the measuring probe 8.

[0029] Furthermore, the control unit 7 sets the temperatures of the heater / cooler 1 and the heater / cooler 3 to the same value. By bringing the measuring probe 8 into contact with the semiconductor laser element 2 in this state for measurement, it is possible to prevent heat from flowing into or out of the semiconductor laser element 2 when the measuring probe 8 is in contact with it. As a result, it is possible to prevent measurement deviations caused by changes in the characteristics of the semiconductor laser element 2.

[0030] Furthermore, in conventional inspection devices, the measuring probe needs to be moved to a heater / cooler to heat and cool its tip each time a measurement is performed. In contrast, in this embodiment, since the heater / cooler 3 can heat and cool the measuring probe 8 via the probe holder 4, it is not necessary to move the measuring probe 8 for heating and cooling.

[0031] Furthermore, conventional inspection devices that integrate the measuring probe and heater cannot maintain a low temperature. Moreover, space cannot be guaranteed near the probe for installing a Peltier element or a water-cooling mechanism. In contrast, in this embodiment, the probe holder 4 is mounted on the heater / cooler 3. Thus, the heater / cooler 3 can cool the measuring probe 8 via the probe holder 4.

[0032] Furthermore, since the measuring probe 8 operates at high frequencies of tens of GHz, impedance matching is required. Therefore, the design of the measuring probe 8 has no freedom, and extending the measuring probe 8 from the heater / cooler 3 to the semiconductor laser element 2 is very difficult, requiring a probe holder 4. Therefore, minimizing the temperature difference between the heater / cooler 3 and the end of the measuring probe 8 is crucial to reducing the temperature difference with the semiconductor laser element 2. Therefore, copper, aluminum, or similar materials with high thermal conductivity (below 200 W / m·K) are preferred for the probe holder 4.

[0033] Implementation Method 2

[0034] Figure 2 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 2. Instead of the heating and cooling unit 1 in Embodiment 1, the semiconductor laser element 2 is mounted on a thin metal plate 15 disposed on a heat-insulating material 14 for measurement. One end of a spring 16 is connected to the upper surface of the metal plate 15, and the other end of the spring 16 is connected to the lower surface of the probe holder 4. The spring 16 thermally couples the metal plate 15 and the probe holder 4. Other structures are the same as in Embodiment 1.

[0035] Figure 3 is an enlarged side view of region A, enclosed by the dashed line in Figure 2. A spring support 17 is fixed to the upper surface of the metal plate 15 by screws or other components. A spring fixing component 18 contacts the lower surface of the probe holder 4. A spring fixing pin 19 is installed on the spring fixing component 18. A spring 16 is installed on the spring fixing pin 19. The spring 16 is securely fixed to the spring fixing pin 19; preferably, the outer shape of the spring fixing pin 19 is as close as possible to the inner diameter of the spring 16 for easy heat transfer. With the spring 16 installed on the spring fixing component 18, the end of the spring 16 is inserted into the spring support 17. In this state, the probe holder 4 is placed on the spring fixing component 18.

[0036] Heat from the probe holder 4 needs to be transferred to the metal plate 15. Therefore, the spring 16, spring support 17, spring retaining pin 19, and spring retaining component 18 are preferably made of metal with a thermal conductivity higher than 200 [W / m·K], and preferably of the same material to have the same coefficient of linear expansion.

[0037] Since the spring fixing member 18 is not fixed to the probe bracket 4, the measuring probe 8 can be moved not only vertically but also horizontally when the spring fixing member 18 is in contact with the probe bracket 4. For ease of movement, the contact area between the lower surface of the probe bracket 4 and the spring fixing member 18 can be mirror-polished and lubricated. For thermal conductivity, thermally conductive grease can also be applied to the contact area. To prevent the spring 16 from flying out laterally, it is preferable to deepen the spring support 17 so that a portion of the spring fixing pin 19 is always inserted into the spring support 17.

[0038] In this embodiment, a probe holder 4 is mounted on the heater / cooler 3, and a spring 16 thermally couples the metal plate 15 to the probe holder 4. Therefore, by transferring heat from the heater / cooler 3 to the measuring probe 8 and the metal plate 15, the temperatures of the semiconductor laser element 2 and the measuring probe 8 can be brought close together. This prevents changes in the characteristics of the semiconductor laser element 2 when it comes into contact with the measuring probe 8.

[0039] Figure 4 is a block diagram showing a modified example of the semiconductor laser inspection apparatus according to Embodiment 2. Instead of the heat insulation material 14 in Embodiment 2, support pillars 20 are installed at the four corners of the lower surface of the metal plate 15. The lower surface of the metal plate 15 becomes hollow. The material of the support pillars 20 is preferably a material that does not easily conduct heat, such as resin or ceramic. The above-described effects can also be obtained in this case.

[0040] Implementation Method 3

[0041] Figure 5 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 3. Instead of the heat cooler 3 of Embodiment 1, a probe holder 4 is mounted on the heat insulation material 21. A micro-motion stage 9 moves the heat insulation material 21 and the probe holder 4 in the vertical and horizontal directions. One end of a spring 16 is connected to the upper surface of the heat cooler 1, and the other end of the spring 16 is connected to the lower surface of the probe holder 4. The spring 16 thermally couples the heat cooler 1 and the probe holder 4. Other structures are the same as in Embodiment 1.

[0042] Figure 6 is an enlarged side view of region A, enclosed by the dashed line in Figure 5. A spring fixing component 18 is fixed to the upper surface of the heater / cooler 1 by screws or other components. A spring fixing pin 19 is installed on the spring fixing component 18. A spring 16 is installed on the spring fixing pin 19. The spring 16 is securely fixed to the spring fixing pin 19, and preferably, the outer shape of the spring fixing pin 19 is as close as possible to the inner diameter of the spring 16 for easy heat transfer. A spring support 17 contacts the lower surface of the probe holder 4. With the spring 16 installed on the spring fixing component 18, the end of the spring 16 is inserted into the spring support 17. In this state, the probe holder 4 is placed on the spring support 17.

[0043] Heat from the heater / cooler 1 needs to be transferred to the measuring probe 8. Therefore, the spring 16, spring support 17, spring retaining pin 19, and spring retaining member 18 are preferably made of metal with a thermal conductivity higher than 200 [W / m·K], and preferably of the same material to achieve the same coefficient of linear expansion. The probe holder 4 is made of metal with a thermal conductivity higher than 200 [W / m·K], and preferably its size is reduced compared to embodiment 2 to reduce its heat capacity, thereby facilitating the transfer of heat to the measuring probe 8.

[0044] Since the spring support 17 is not fixed to the probe holder 4, the measuring probe 8 can move not only vertically but also horizontally when the spring support 17 is in contact with the probe holder 4. For ease of movement, the contact area between the lower surface of the probe holder 4 and the spring support 17 can be mirror-polished and lubricated. For thermal conductivity, thermally conductive grease can also be applied to the contact area. To prevent the spring 16 from flying out laterally, it is preferable to deepen the spring support 17 so that a portion of the spring retaining pin 19 is always inserted into the spring support 17.

[0045] In this embodiment, the spring 16 thermally couples the heating and cooling unit 1, which houses the semiconductor laser element 2, to the probe holder 4. Therefore, by transferring heat from the heating and cooling unit 1 to the measuring probe 8 via the spring 16 and the probe holder 4, the temperatures of the semiconductor laser element 2 and the measuring probe 8 can be brought close together. This prevents changes in the characteristics of the semiconductor laser element 2 when it comes into contact with the measuring probe 8.

[0046] Implementation Method 4

[0047] Figure 7 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 4. A temperature sensor 22 is installed in a hole provided in the probe holder 4 or the measuring probe 8. The temperature sensor 22 measures the temperature of the measuring probe 8.

[0048] Before starting the inspection of the semiconductor laser element 2, the temperature of the heater / cooler 3 is pre-adjusted as follows: The control unit 7 sets the heater / cooler 1 and heater / cooler 3 to the product inspection temperature T℃ and stabilizes them. In this state, the temperature sensor 6 measures the temperature of the heater / cooler 3, and the temperature sensor 22 measures the temperature of the probe holder 4. The value obtained by subtracting the temperature measured by the temperature sensor 22 from the temperature measured by the temperature sensor 6 is set as α. The control unit 7 sets the temperature of the heater / cooler 1 to T, and resets the temperature of the heater / cooler 3 to T+α.

[0049] Therefore, since the temperature of the measuring probe 8 is T℃, it can be matched with the set temperature of the heating and cooling unit 1, which sets the temperature of the semiconductor laser element 2. Thus, the temperature of the semiconductor laser element 2 and the measuring probe 8 can be made closer than in Embodiment 1. Other structures and effects are the same as in Embodiment 1. Furthermore, since the temperature measured by the temperature sensor 22 is not used during measurement, the temperature sensor 22 can be removed after the set temperature of the heating and cooling unit 3 has been adjusted.

[0050] Implementation Method 5

[0051] Figure 8 is a block diagram showing the semiconductor laser inspection apparatus according to Embodiment 5. A wavelength meter 23 for measuring the wavelength of the emitted light from the semiconductor laser element 2 is added to the structure of Embodiment 1. The temperature of the heating and cooling unit 3 is pre-adjusted before starting the inspection of the semiconductor laser element 2 as follows.

[0052] The temperature of the heater / cooler 3 was varied from T-10°C to T+10°C in increments of 1°C relative to the set temperature T of the heater / cooler 1. At each temperature, the time variation of the wavelength of the emitted light from the semiconductor laser element 2 when in contact with the measuring probe 8 was measured. Figure 9 is a graph showing the time variation of the wavelength of the emitted light from the semiconductor laser element relative to the set temperature of the measuring probe. The horizontal axis represents the set temperature of the measuring probe 8. The vertical axis represents the absolute value of the time variation of the wavelength of the emitted light from the semiconductor laser element 2 when in contact with the measuring probe 8. The time variation of the wavelength is plotted as a parabola with a minimum point.

[0053] Next, if the temperature at which the wavelength variation over time becomes minimal is set to T', the temperature of the heater / cooler 3 is changed from T'-1°C to T'+1°C in units of 0.1°C to obtain the wavelength variation over time. The temperature T at which the wavelength variation over time becomes minimal is then determined through this measurement. The control unit 7 sets the heater / cooler 3 to this determined temperature T.

[0054] With the heating and cooling unit 3 set to temperature T", the time variation of the wavelength becomes minimal, meaning that the temperature of the semiconductor laser element 2 is consistent with that of the measuring probe 8. By making the above adjustments, the temperatures of the semiconductor laser element 2 and the measuring probe 8 can be brought close together. This prevents changes in the characteristics of the semiconductor laser element 2 when it comes into contact with the measuring probe 8.

[0055] Implementation Method 6

[0056] Figure 10 is a block diagram illustrating the semiconductor laser inspection method according to Embodiment 6. A wavelength meter 23 for measuring the wavelength of the emitted light from the laser element placed on the metal plate 15 is added to the structure of Embodiment 2. The temperature of the heating and cooling unit 3 is pre-adjusted before starting the inspection of the semiconductor laser element 2 as follows.

[0057] A temperature setting laser element 24, whose relationship between wavelength and temperature is known in advance, is placed on a metal plate 15. While changing the temperature of the heating cooler 3, the wavelength of the output light of the temperature setting laser element 24 is measured by a wavelength meter 23. The temperature of the heating cooler 3 is fixed when the wavelength corresponds to the desired temperature.

[0058] After removing the temperature-setting laser element 24 from the metal plate 15, the semiconductor laser element 2 is placed on the metal plate 15 while the temperature of the heater / cooler 3 is fixed. Then, similarly to Embodiment 2, the end of the measuring probe 8 is brought into contact with the semiconductor laser element 2 to inspect it. This allows for high-precision matching with the temperature conditions for inspecting the semiconductor laser element 2. Other structures and effects are the same as in Embodiment 2.

[0059] Implementation Method 7

[0060] Figure 11 is a block diagram illustrating the semiconductor laser inspection method according to Embodiment 7. A wavelength meter 23 for measuring the wavelength of the emitted light from the laser element placed on the heat cooler 1 is added to the structure of Embodiment 3. The temperature of the heat cooler 1 is pre-adjusted before starting the inspection of the semiconductor laser element 2 as follows.

[0061] A temperature setting laser element 24, whose wavelength-temperature relationship is known in advance, is placed on the heating and cooling unit 1. While changing the temperature of the heating and cooling unit 1, the wavelength of the output light of the temperature setting laser element 24 is measured by a wavelength meter 23. The temperature of the heating and cooling unit 1 is fixed when the wavelength corresponds to the desired temperature.

[0062] After removing the temperature-setting laser element 24 from the heater / cooler 1, the semiconductor laser element 2 is placed on the heater / cooler 1 while the temperature of the heater / cooler 1 is fixed. Then, similarly to Embodiment 3, the end of the measuring probe 8 is brought into contact with the semiconductor laser element 2 to inspect the semiconductor laser element 2. This allows for high-precision matching with the temperature conditions for inspecting the semiconductor laser element 2. Other structures and effects are the same as in Embodiment 3.

[0063] Explanation of reference numerals in the attached figures

[0064] 1...First heating and cooling unit; 2...Semiconductor laser element; 3...Second heating and cooling unit; 4...Probe bracket; 5, 6, 22...Temperature sensor; 7...Control unit; 8...Measurement probe; 9...Micro stage; 10...Inspection device; 15...Metal plate; 16...Spring; 20...Support column; 23...Wavemeter; 24...Temperature setting laser element.

Claims

1. A semiconductor laser inspection device, characterized in that, It comprises: a metal plate on which a semiconductor laser element is mounted; a heater / cooler; a probe holder mounted on the heater / cooler; a measuring probe fixed to the end of the probe holder; a micro-motion stage for moving the heater / cooler and the probe holder so that the end of the measuring probe abuts against the semiconductor laser element; an inspection device for inputting an inspection signal to the semiconductor laser element via the measuring probe; and a spring, one end of which is connected to the upper surface of the metal plate and the other end of which is connected to the lower surface of the probe holder, thermally coupling the metal plate and the probe holder without passing through the measuring probe.

2. The semiconductor laser inspection device according to claim 1, characterized in that, Supports are installed at the four corners of the lower surface of the metal plate, and the lower surface of the metal plate is hollow.

3. A semiconductor laser inspection device, characterized in that, It comprises: a heating and cooling unit for mounting a semiconductor laser element; a probe holder; a measuring probe fixed to the end of the probe holder; a micro-motion stage for moving the probe holder so that the end of the measuring probe abuts against the semiconductor laser element; an inspection device for inputting an inspection signal to the semiconductor laser element via the measuring probe; and a spring, one end of which is connected to the upper surface of the heating and cooling unit and the other end of which is connected to the lower surface of the probe holder, thermally coupling the heating and cooling unit to the probe holder without passing through the measuring probe.

4. The semiconductor laser inspection apparatus according to any one of claims 1 to 3, characterized in that, The thermal conductivity of the spring is higher than 200 W / m·K.

5. A semiconductor laser inspection method, characterized in that, The apparatus comprises the following steps: placing a temperature-setting laser element on the metal plate of the semiconductor laser inspection apparatus according to claim 1 or 2, wherein the relationship between wavelength and temperature is known in advance; while changing the temperature of the heating and cooling unit, measuring the wavelength of the output light of the temperature-setting laser element with a wavelength meter; fixing the temperature of the heating and cooling unit at a moment when the wavelength corresponds to the desired temperature; and after removing the temperature-setting laser element from the metal plate, placing the semiconductor laser element on the metal plate while the temperature of the heating and cooling unit is fixed, and placing the end of the measuring probe against the semiconductor laser element to inspect the semiconductor laser element.

6. A semiconductor laser inspection method, characterized in that, The apparatus comprises the following steps: placing a temperature-setting laser element on the heating and cooling unit of the semiconductor laser inspection apparatus according to claim 3, wherein a wavelength-temperature relationship is known in advance; while changing the temperature of the heating and cooling unit, measuring the wavelength of the output light of the temperature-setting laser element with a wavelength meter; fixing the temperature of the heating and cooling unit when the wavelength corresponds to the desired temperature; and after removing the temperature-setting laser element from the heating and cooling unit, placing the semiconductor laser element on the heating and cooling unit while the temperature of the heating and cooling unit is fixed, and placing the end of the measuring probe against the semiconductor laser element to inspect the semiconductor laser element.

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