JP3784884B2 - Sample measurement type environmental test equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an environmental test apparatus capable of controlling the temperature of air sent into a test chamber in which a device under test is placed, and is particularly advantageously used for burn-in testing of semiconductor devices.
[0002]
[Prior art]
In an environmental test apparatus such as a thermostatic bath, a temperature sensor is usually provided at an appropriate position such as an air outlet in the bath, and the output of the heater is controlled so that the detected value becomes the target test temperature. Yes. However, in such a control method, a difference between the temperature at the measurement point and the temperature of the sample position to be tested, a difference between the environmental temperature in the vicinity of the sample and the temperature of the sample itself, etc. occur. The temperature condition of itself could not be controlled accurately. Further, when performing an environmental test while operating a sample, such as a burn-in test of a semiconductor device, the temperature of the sample may rise due to heat generation. In such a test, even if the temperature in the bath was controlled, the difference from the temperature of the sample itself became large, and the temperature management of the sample itself was particularly difficult.
[0003]
In order to solve such problems, the same transistor as the actual sensor is attached to the semiconductor to be tested, the temperature rise during operation of the semiconductor to be tested is calculated from the measured voltage, and the environment where the semiconductor is located is calculated. There has been proposed an invention in which a junction temperature that should be originally managed is calculated by adding a temperature, and this is controlled (see Japanese Patent Laid-Open No. 63-115074). However, since such a test is performed for screening during semiconductor manufacturing, defective products are mixed in the sample, and the measured temperature shows an abnormal value or the sensor fails. For example, the control may run out of control and the inside of the tank may not be controlled at a safe temperature.
[0004]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems in the prior art, can accurately give the target temperature condition to the DUT, and can ensure the safety of temperature control even if an abnormality occurs in the DUT or sensor. It is an object to provide an environmental test apparatus.
[0005]
[Means for Solving the Problems]
For the present invention to solve the above problems, a first aspect of the invention, the environmental testing apparatus that is used in the burn-in test to control the air temperature to be sent to the test chamber in which the DUT comprising a plurality of semiconductor devices placed,
Wherein the semiconductor devices of the particular things in the voltage detecting means and by matching the particular is connected to the terminal that can detect the forward voltage of the particular what constitutes a temperature detecting means for detecting the temperature of the DUT A voltage detecting means for measuring the forward voltage when a minute constant current is passed through the object, and a relationship between the measured forward voltage and the detected temperature of the device under test. differences predetermined amount of a comparing unit for comparing assumed temperature when the temperature the detectable the detected temperature by converting the voltage to the detected temperature is assumed to be normal, and the detection temperature and the assumed temperature from When it becomes larger, a switching unit that sends the detected temperature to the control unit, thereby switching from the control by the detected temperature performed by the control unit to a control that uses a safety control unit, and the detected temperature sent from the switching unit Is prescribed Controlling the air temperature such that said control unit, and the safety control unit for controlling the air temperature to be a safe temperature environment for the switching is switched by section by the DUT, the burn-in test Pre-operation control means for pre-operation performed before , and the pre-operation control means controls the test chamber so as to sequentially become a plurality of different set temperatures, and sets each of the set temperatures. Then, the forward voltage is detected by the voltage detection means when the minute constant current is passed through the specific one of the semiconductor devices, and the correspondence between the detected voltage and the temperature in the test chamber is determined. Control is performed so that the comparison unit inputs the relationship .
[0006]
According to a second aspect of the present invention, in addition to the above, the safety control unit detects the air temperature, and the air temperature is controlled so that the temperature detected by the air temperature detecting unit becomes a predetermined temperature. And a control unit.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the overall configuration of a thermostatic chamber which is an example of an environmental test apparatus to which the present invention is applied. The thermostatic chamber is surrounded by a heat insulating wall 1, and a blower 2 rotated by a motor 2a, a heater 3, a perforated plate 4 provided so as to form an air duct, a test chamber 5 and the like are arranged therein. It is installed. In the test chamber 5, a burn-in board 8 having a large number of sockets 7 mounted with semiconductor devices (hereinafter referred to as “ICs”) 6 as test objects is mounted in a multi-stage or multi-stage and multi-row on a support frame (not shown). To be loaded. Such a constant temperature bath is used for the burn-in test of IC.
[0010]
The temperature control system of the thermostatic bath includes junction temperature detection (sensor) ICs 61 to 65 constituting temperature detection means, sensor IC sockets 7 (71 to 75) mounted with these, and printed wiring 61a connected thereto. ˜65a, and the junction voltage drop measurement board 91 which is also a voltage detection means to which these are connected, the control unit 21 for controlling the junction temperature which is the detected temperature detected by the measurement board 91 to be a predetermined value, the device under test A safety control unit 22 that can control the temperature so as to be a safe temperature environment for the IC that is a product, a comparison calculation unit 23 as a comparison unit that compares the detected junction temperature with an assumed temperature when it is assumed to be normal, When the difference between the detected temperature and the assumed temperature exceeds a predetermined amount, the safety control unit 22 is used from the control by the control unit 21. And a switching unit 24 or the like for switching to the control that. The code | symbol 25 is a setting part which sets the control target value of junction temperature and the blower outlet temperature of the air in a tank. The control unit 21, the safety control unit 22, the comparison calculation unit 23, the switching unit 24, and the like are integrally formed in the control device 20 by, for example, a microcomputer.
[0011]
The junction temperature detection ICs 61 to 65 are the same as the other ICs 6 but are extra terminals that are not used during the test and can detect a junction voltage drop (Vf) that is a forward voltage. Connected to the board unit 91. Such ICs 61 to 65 are arranged at the four corners and the central part of the burn-in board 81 shown in the figure as appropriate stages of the burn-in board 8 in this example as specific ICs. However, there may be only one junction temperature detection IC, or there may be a larger number including other stages and columns.
[0012]
The junction voltage drop measurement board 91 is formed on a part of the driver / test board 9 installed outside the thermostatic bath. The junction temperature detection ICs 61 to 65 are IC sockets 71 to 75 and printed wirings 61a to 65a. , And the edge connector and relay board unit 10. The junction voltage drop Vf when a small constant current is passed through each IC can be measured. This Vf has a substantially linear relationship with the junction temperature Tj, and has the same characteristics for the same IC. The relationship between Vf and Tj of a specific IC to be produced and tested is obtained in advance by, for example, a method described later. This relationship is expressed as a curve, a numerical table, a mathematical expression, or the like.
[0013]
The comparison calculation unit 23 includes an input part for inputting the above-described curve or mathematical expression in advance, receives the actual measurement value Vfp of the junction voltage drop at the time of the test of the IC measured by the measurement board 91, and receives this It is converted into the junction temperature actual measurement value Tjp by the curve etc. Then, for example, a junction temperature setting value Tjs set by the temperature setting device 25 is input from the setting device 25 as an assumed temperature when the junction temperature is assumed to be normal, and Tjp and Tjs are compared. Note that Tjs may be replaced with Vf in the setting device 25, and the comparison calculation unit 23 may compare the set value Vfs of Vf with the actual measurement value Vfp.
[0014]
The normal value of Tjp varies depending on the type of IC, but is about 200 ° C., for example. As a result of this comparison, if the difference is a large value of about 50 ° C. or more, for example, the normal fluctuation range in the control state of the junction temperature is clearly exceeded, so that the sensor IC is defective. Judgment is made and this is excluded from the actual measurement values used for temperature control. Instead of the difference (50 ° C. in the above), a ratio such as 30% may be used.
[0015]
Next, since there are a plurality (five) of actual measurement values Tjp in this example, the average value, median value, and standard deviation value excluding the simple average value, maximum value, and minimum value from those in the normal range. Or the like, and this is used as an output value. When there is no Tjp in the normal range, an abnormal signal is transmitted. Of course, such a calculation is not performed when there is only one measurement point of Tj.
[0016]
The switching unit 24 receives the output of the comparison calculation unit 23 and sends it to the control unit 21 if it is the average value of Tjp in the normal range, etc., but if it is an abnormal signal, it sends it to the safety control unit 22. The control is switched from the control by the control unit 21 to the control using the safety control unit 22. When there is only one measured value of Tj, that value or an abnormal signal is transmitted.
[0017]
When the control unit 21 receives the average value of Tjp and the like, as in normal temperature control, the control unit 21 determines the set value Tjs set by the setting unit 25 from the deviation of these values, the rate of change of the actual measurement value, and the like. The control value which controls the output of the heater 3 is transmitted. Thereby, the temperature of the air sent to the test room is controlled.
[0018]
The junction temperature of the IC is the power consumption of the IC when energized when testing the IC, the amount of heat generated thereby, the amount of heat released due to the temperature difference between the temperature of the IC itself and the ambient temperature, the outlet of the IC and the constant temperature bath Therefore, it can also be indirectly controlled by estimating the relationship between the junction temperature and the outlet air temperature from these relationships and controlling the outlet air temperature as a set value. However, with such control, the junction temperature cannot be accurately controlled. According to the control of the present invention, the temperature of the IC itself is detected using the IC itself to be tested, and the air temperature at the outlet, which is the condition for determining the junction temperature, is controlled through the output control of the heater. Therefore, the junction temperature that should be managed originally can be maintained at the set value with high accuracy. Further, since it is not necessary to attach or detach the junction temperature sensor for each sample to be tested, no extra operation or time is required during the test.
[0019]
When the safety control unit 22 receives the abnormal signal from the switching unit 24, the safety control unit 22 inputs the actual measurement value Tp of the temperature sensor 10, and the heating control unit 22 sets the setting value Ts set by the setting unit 25 that is also input. Control the output. From the above relationship, this Ts is a value such that the junction temperature becomes the target test temperature when the IC is not defective, and is the outlet temperature when the junction temperature control is normally performed. Equivalent to. For example, if the junction temperature is 200 ° C when the outlet temperature is 100 ° C, Ts is 100 ° C.
[0020]
Unlike the sensor IC using the same IC as the device under test, the temperature sensor 10 is unlikely to be a defective product and does not self-heat, so that the detected value hardly becomes abnormal. Therefore, if the detection value of the junction temperature is abnormal, if the control is performed using the temperature sensor 10, the temperature inside the tank is controlled to an almost appropriate value even if the junction temperature cannot be accurately controlled. It is possible to maintain an environmental temperature that is safe for the IC. As a result, the safety of the IC to be tested is ensured, and the test need not be interrupted. However, instead of controlling the inside of the tank to the set temperature in this way, the safety control unit 22 may perform control for maintaining the current temperature, control for gradually lowering the inside temperature of the tank, and the like.
[0021]
FIG. 2 shows an example of a method for obtaining the relationship between the junction voltage drop Vf of the IC and the junction temperature Tj, and a preliminary operation performed prior to the actual burn-in test using the thermostat shown in FIG. 1 and a part of its control device. This process is shown in a flowchart.
[0022]
Preliminary operation preparation (S-1) is the same as when performing the burn-in main test. As shown in FIG. 1, the burn-in board 8 in which the IC 6 to be tested is mounted in the IC socket 7 is placed in a multi-stage or multi-stage and many It is mounted in a row, and devices and control devices are made operable by turning on a power supply (not shown). The burn-in board 8 includes a burn-in board 8 (81) equipped with sensor ICs 61-65.
[0023]
In the calibration temperature setting (S-2), the temperature setting unit 25 sets the temperature of the air outlet or the inlet corresponding to the time when the IC is operating from the normal temperature step by step. If the temperature at the time of operation of the IC is 200 ° C., for example, the temperature is set to about five steps at regular intervals from normal temperature to 200 ° C.
[0024]
In temperature control (S-3), the thermostat is operated, and the temperature of the heater 3 is controlled by the safety control unit 22 so that the outlet or inlet temperature measured by the sensor 10 becomes the set temperature. In the junction temperature measurement (S-4), a minute current is passed through the sensor ICs 61 to 65, and Vf is measured by the junction voltage drop measurement board 91.
[0025]
In the junction temperature stability determination (S-5), it is determined whether or not the temperature of the junction portion of the IC has become substantially the same as the temperature in the tank after the temperature in the tank has stabilized. This determination is made, for example, when the change rate of Vf has converged within a certain range.
[0026]
In the junction voltage drop storage (S-6), Vf is measured after the junction temperature stability determination (S-5), and this data and the set temperature of the temperature setting unit at this time are associated with each other and stored in the comparison calculation unit 23. In this preliminary operation, a voltage for operating the IC is not applied. As a result, even if a small constant current is passed through the IC, the IC does not generate heat, so the set internal bath temperature becomes substantially the same as the junction temperature.
[0027]
The end determination (S-7) is performed each time the above steps (S-1) to (S-6) are executed for one temperature setting. For example, as described above, the set temperature is set to five levels. When such a process is repeated five times, an end determination is made and the preliminary operation ends. The comparison calculation unit 23 stores five set temperatures from normal temperature to 200 ° C., that is, the junction temperature, and Vf measured corresponding to each of the set temperatures.
[0028]
The preliminary operation as described above may be performed through human operation, or may be performed at the initial calibration temperature by using a timer or counter, exchanging sensor values or control signals, or inputting necessary data in advance. All of them including the setting may be automatically performed. Such a preliminary operation needs to be performed only once for one type of IC. In a burn-in test that is repeatedly performed after replacing a burn-in board on which an IC is mounted, data stored in the first preliminary operation is stored. used.
[0029]
FIG. 3 shows a configuration example of a control portion when the controller 20 is provided with a preliminary operation control unit 26 that can automatically perform the preliminary operation.
The preliminary operation control unit 26 includes a Ts application portion 26 a that sequentially gives different set temperatures to the setter 25, an instruction portion 26 b that instructs the switching unit 24 to switch to control using the safety control unit 22, and the junction voltage measurement board 91. The measured Vf is inputted to calculate the rate of change, and when this converges within a certain range, the Vf applying portion 26c that gives the Vf at that time to the comparison calculation unit 23 and the temperature detected by the sensor 10 are inputted and inputted. A Tp giving portion 26d to be given to the comparison calculation unit 23 is provided.
[0030]
According to the control unit 26, the preliminary operation flow shown in FIG. 2 can be automatically performed. That is, when, for example, five stages of temperature are set in the Ts application portion 26a (S-2), 26a gives the first temperature to the setting device 25, and the instruction portion 26b uses the Ts and Tp for the safety controller 22 using Ts and Tp. The safety control unit 22 controls the temperature (S-3), the Vf measurement board 91 measures Vf (S-4), and the value is assigned to the Vf application portion. 26c inputs and calculates the rate of change, and determines whether or not the junction temperature is stable depending on whether or not it has converged within a certain range (S-5). This is stored, and the Tp giving portion 26d gives the Tp at that time to the comparison calculation unit 23 as the temperature corresponding to this. As a result, the first calibration is completed, the Tp application part 26d sends an end signal to the Ts application part 26a, 26a sends the second temperature to the setting device 25, and the same measurement is performed thereafter. In the preliminary operation, the correspondence between Vf and Tp corresponding to the junction temperature is measured.
[0031]
Since Tp becomes substantially the same value as Ts when the temperature is stable, the Tp application portion 26d is not provided, and Ts is sent to the comparison calculation unit 23 as the junction temperature corresponding to Vf by the Ts application portion 26a or the setting unit 25. It may be.
[0032]
The burn-in test is conducted as follows.
As in the preliminary operation, a burn-in board including the burn-in board 8 (81) equipped with the sensor ICs 61 to 65 is mounted. In the setting device 25, for example, 200 ° C. is set as the junction temperature Tjs. For example, an operating voltage of about 5 V is applied to all the ICs 6 including the sensor ICs 61 to 65, and a small constant current of, for example, about 10 μA is applied to the sensor ICs 61 to 65 to detect the junction voltage Vf. Made possible. When a start button for a burn-in test (not shown) is pressed, the devices and the control device are activated to start the burn-in test.
[0033]
In each of the sensor ICs 61 to 65, each junction voltage drop Vfp is detected via the board 91, and this is sent to the comparison calculation unit 23. In the comparison calculation unit 23, the Vfp is converted into the junction temperature actual measurement value Tjp from the relationship between Vf and Tj stored in the preliminary operation or the like, and each Tjp is set temperature Tjs (200 ° C in the previous example). Compared with In this case, when using the preliminary operation data measured stepwise as described above, the middle of each step may be calculated by calculating the proportional portion, or a curve supplemented with a straight line or the like in advance is created. This may be read.
[0034]
When the IC is put into an operating state and the temperature rises due to its power consumption, when this is not a defective product and is operating normally, Tjp becomes about 200 ° C. due to the environmental temperature plus the temperature rise. Accordingly, if the detected Tjp exceeds the range of, for example, about 150 ° C. to 230 ° C., it is regarded as a defective product and excluded, and the average value of other detected values is sent to the switching unit 24. . If all Tjp are not within the above range, an abnormal signal is sent to the switching unit 24. Since the temperature inside the thermostatic chamber is low immediately after the start, Tjp becomes abnormally low. Therefore, from the start until a certain time, control by the outlet temperature is used, or an abnormal signal to be sent to the switching unit 24 is reserved. Measures are taken.
[0035]
When the switching unit 24 receives the average value of Tjp in the normal range, this signal is sent to the control unit 21. When the control unit 21 receives the average value of Tjp or the like, the control unit 21 provides the heater 3 with an output corresponding to the deviation between the two values so that this becomes the set value Tjs set by the setter 25. By controlling the amount, the temperature of the air sent to the test chamber is controlled, and as a result, the junction temperature that further increases due to heat generation is controlled to a set value. According to such control, it is possible to accurately and easily detect the junction temperature at which the temperature is different from that of the air outlet, and to control with high accuracy.
[0036]
When the switching unit 24 receives the abnormal signal, this signal is sent to the safety control unit 22. Accordingly, the safety control unit 22 inputs the actual measurement value Tp of the temperature sensor 10 and controls the output of the heater 3 so that the set value Ts set by the setting device 25 becomes, for example, 100 ° C. By this control, when the IC 6 to be tested is not defective like the sensor ICs 61 to 65, the junction temperature thereof is about 200 ° C., and the safety of the IC is ensured. The test can be continued.
[0037]
When the IC junction temperature of the IC is exposed to the target temperature for a predetermined time, the data of the IC to be tested is measured, and the non-defective product / defective product can be screened, the burn-in test ends. Thus, according to the thermostatic chamber of the present invention, the burn-in test can be automatically completed safely and accurately without interrupting the test.
In addition, although the case where the environmental test apparatus was a thermostat was demonstrated above, this invention is applicable also to other environmental test apparatuses provided with the humidity control function in addition to temperature control.
[0038]
【The invention's effect】
As described above, according to the present invention, in the first aspect of the invention, the temperature of the DUT is detected by the temperature detecting means, and the control unit controls the temperature so that the temperature reaches a predetermined value. The temperature of the test object itself can be directly detected and accurately controlled. However, environmental test equipment is intended for test objects that generate heat, and such test objects may be defective due to defective products, etc., or the temperature detection means may fail. If control is performed by detecting the temperature of the DUT, control will run away. Therefore, the invention of claim 1 further includes a safety control unit, a comparison unit, and a switching unit. The detected temperature is compared with a normal temperature, and if the temperature is abnormal, the switching unit uses the control unit. Since the control is switched from the control to the control by the safety control unit, the control runaway is prevented, and the safety of the apparatus and the DUT is ensured.
[0039]
In addition, when the device under test is a large number of semiconductor devices, a specific one of the semiconductor devices is defined as the temperature detection means, and voltage detection means connected to a terminal capable of detecting the forward voltage is provided. The junction temperature to be originally managed can be directly and easily detected accurately using a certain relationship between the junction temperature of the semiconductor device and the forward voltage.
[0040]
Further, since the preliminary operation control means is provided, it is possible to automatically perform the preliminary operation for calibration for obtaining the correspondence between the forward voltage and the junction temperature of the semiconductor device. As a result, it is not necessary for a person to perform a complicated operation that takes time and has measurement items and judgment items, thereby saving labor and improving calibration accuracy.
[0041]
In the invention of claim 2 , the safety control unit is an air temperature control unit, and the temperature of the air sent into the test chamber is detected and controlled so that the temperature becomes a predetermined temperature. Even in the case of a non-defective product or the like, the burn-in test can be completed by switching from the control based on the temperature detection to the outlet temperature control, and the efficiency of the test is not reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an overall configuration of a thermostatic chamber which is an example of an environmental test apparatus to which the present invention is applied.
FIG. 2 is a flowchart showing a preliminary operation process for calibrating a sensor IC in the thermostatic chamber.
FIG. 3 is a block diagram illustrating a configuration example of a portion related to a preliminary operation control unit.
[Explanation of symbols]
5 Test chamber 6 Semiconductor device (device under test)
10 Temperature sensor (Air temperature detection means)
21 control part 22 safety control part 23 comparison calculation part (comparison part)
24 switching unit 26 preliminary operation control unit (preliminary operation control means)
61-65 Junction temperature detection (sensor) IC (temperature detection means)
71-75 IC socket for sensors (temperature detection means)
91 Junction voltage drop measurement board (temperature detection means)

Claims (2)

In the environment test apparatus that is used in the burn-in test to control the air temperature to be sent to a test chamber that DUT is placed consisting of a large number of semiconductor devices,
Wherein the semiconductor devices of the particular things in the voltage detecting means and by matching the particular is connected to the terminal that can detect the forward voltage of the particular what constitutes a temperature detecting means for detecting the temperature of the DUT A voltage detecting means for measuring the forward voltage when a minute constant current is passed through the object, and a relationship between the measured forward voltage and the detected temperature of the device under test. differences predetermined amount of a comparing unit for comparing assumed temperature when the temperature the detectable the detected temperature by converting the voltage to the detected temperature is assumed to be normal, and the detection temperature and the assumed temperature from When it becomes larger, a switching unit that sends the detected temperature to the control unit, thereby switching from the control by the detected temperature performed by the control unit to a control that uses a safety control unit, and the detected temperature sent from the switching unit Is prescribed Controlling the air temperature such that said control unit, and the safety control unit for controlling the air temperature to be a safe temperature environment for the switching is switched by section by the DUT, the burn-in test Pre-operation control means for pre-operation performed before , and the pre-operation control means controls the test chamber so as to sequentially become a plurality of different set temperatures, and sets each of the set temperatures. Then, the forward voltage is detected by the voltage detection means when the minute constant current is passed through the specific one of the semiconductor devices, and the correspondence between the detected voltage and the temperature in the test chamber is determined. An environmental test apparatus, characterized in that control is performed so that the comparison unit inputs the relation . The said safety control part has an air temperature detection part which detects the said air temperature, and an air temperature control part which controls so that the temperature detected by this air temperature detection part may become predetermined | prescribed temperature, It is characterized by the above-mentioned. environmental testing apparatus according to 1.

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