JPS63193079A - Method for accelerated test of semiconductor device - Google Patents

Abstract

PURPOSE:To exclude the effect of a measuring temperature to seize a change in characteristics of a sample accurately and efficiently and thereby to implement the supposition of lifetime, screening or the like in a short time and with high reliability, by a method wherein the temperature in a constant temperature apparatus containing the sample is varied periodically in the vicinity of a prescribed value. CONSTITUTION:The system consists of a constant temperature apparatus 1 and a data collecting apparatus 2, and a sample is set in the constant temperature apparatus 1. The constant temperature apparatus 1 is provided with a temperature sensor 11, a sawtooth wave generator 12, a reference voltage source 13, a differential amplifier 15, a heater 17, etc., while the data collecting apparatus 2 is provided with a sample temperature monitoring element 21, a sample characteristic measuring element 22, etc. A sawtooth wave voltage of the sawtooth wave generator 12 is superposed on a reference voltage V0, and a control voltage thus obtained is inputted to the differential amplifier 15 to vary the temperature of the sample 3 periodically. When the temperature of the sample accords with a prescribed temperature T0 in the rising process of the temperature, for instance, a trigger signal is delivered to conduct the measurement of characteristics.

Description

[Detailed Description of the Invention] [Summary] The present invention, in accelerated testing of semiconductor devices, periodically changes the temperature in a thermostatic chamber containing a sample in the vicinity of a predetermined value, so that the temperature of the sample reaches a predetermined value. By measuring the characteristics at a certain time, the influence of the measured temperature can be eliminated by keeping the measured temperature at a constant value with high accuracy, and fluctuations in the characteristics of the sample can be accurately and efficiently grasped, allowing life estimation or screening to be carried out in a short time. This enables implementation with high reliability.

[Industrial application field]

The present invention relates to an accelerated testing method for semiconductor devices, and particularly to an improvement in an accelerated testing method that repeatedly measures characteristics at a predetermined high temperature.

For example, semi-quadruple lasers used as light sources in long-distance, large-capacity optical communication trunk systems require high reliability to ensure stable operation over many years, especially in submarine repeaters that cannot be replaced even if they fail. A lifespan guarantee of several decades is required.

In order to guarantee such reliability, we maintain the temperature of the semiconductor laser at, for example, 70 degrees Celsius, keep the optical output constant, and operate it for more than several thousand hours.During this period, we frequently measure the driving current, etc. Estimate the amount of change after 10,000 hours. The accuracy of the life estimated in this case depends on the current measurement accuracy and the length of the test time, but the biggest factor that reduces the current measurement accuracy is the variation in element temperature.

This long test time is a huge burden,
In order to shorten the process or improve estimation accuracy, there is a strong demand for improving measurement accuracy by eliminating fluctuations in element temperature.

[Conventional technology]

For example, when screening or evaluating the lifespan of semiconductor devices such as semiconductor lasers by high-temperature accelerated aging as described above, the accuracy of the measurement equipment, changes in temperature, and the effects of disturbances such as external noise are included in the measurement data. ,
It cannot be distinguished from variations in the characteristics of the original semiconductor device. To deal with this, test times are lengthened so that the effect of characteristic fluctuations is sufficiently large in response to external disturbances, and for example, life evaluations that require more than 100,000 hours take several thousand hours or more. However, among the above-mentioned disturbances, one that has a large influence on the current amount is temperature instability.

In current high-temperature accelerated testing, a method is used to stabilize the temperature of the sample at a constant value. For example, as shown in Figure 3,
The temperature of the sample 31 is monitored by a temperature sensor 32, compared with a reference voltage vrar by a differential amplifier 33 to amplify the error, and the current of the heater 34 is controlled to maintain the temperature of the sample 31 at a constant value.

In this method, first, in order to maintain a constant temperature in steady state, the reference voltage V,. , is stable, differential amplifier 3
However, since the differential amplifier 33 uses a DC amplifier, it is difficult to maintain stability for a long time, for example, at 100°C. In order to have stability of 0.01℃, a stability of lXl0-' is required, but in reality, the stability is only about lXl0-'', and the limit is about 0.1℃. Furthermore, it is necessary to maintain the reference voltage source and the differential amplifier at a constant temperature, making the device expensive and difficult to handle.

In addition, if a transient temperature change occurs due to, for example, sample exchange, the time constant of the system is increased to improve static stability in steady state, resulting in overshoot and a considerable length of time. Temperature oscillates over time. Furthermore, in systems intended to be highly stable, such as double thermostats, the time from when the control system performs an action to change the temperature until the temperature actually changes becomes increasingly long, and it takes a very long time for the temperature to stabilize. It takes a long time.

[Problem that the invention seeks to solve]

As mentioned above, in order to statically maintain the temperature at a constant value, conventional accelerated testing methods require extremely high accuracy and stability in all elements that make up the temperature control system, but still do not achieve satisfactory results. Furthermore, increasing the time constant of the system to improve static stability has the paradox of decreasing the response speed to transient temperature fluctuations.

The present invention aims to solve the problem including this contradiction by changing the viewpoint from the conventional one.

[Means for solving problems]

The above-mentioned problem is solved by the semiconductor device according to the present invention, in which the temperature in a thermostatic chamber containing a sample is periodically changed in the vicinity of a predetermined value, and the characteristics of the sample are measured when the temperature of the sample is at the predetermined value. The problem is solved by an accelerated testing method for equipment.

Note that in order to improve measurement accuracy, it is desirable to perform the characteristic measurement when the temperature changes are in the same direction.

[For production]

As shown in FIG. 1 (al), the accelerated testing method according to the present invention is performed by setting the temperature in the thermostatic chamber in which the sample is stored in the vicinity of a predetermined value T0, setting the amplitude to about ±ΔT=0.5°C, and changing the period. The temperature change rate at which the sample is considered to be in thermal equilibrium is selected and changed periodically, and the required characteristic measurements are repeated when the sample temperature is at a predetermined temperature T0.

It should be noted that it is generally desirable to unify the timing of this characteristic measurement so that the direction of temperature change is either rising or falling in order to improve measurement accuracy, and the characteristic measurement is performed without dividing the temperature rise time and temperature fall time equally. You may want to increase the side time. Further, the measurement period may be several times the period of temperature change.

This accelerated testing method can be carried out using an apparatus as illustrated in the block diagram of FIG. 1(e). In the figure, 1 is a constant temperature device, 2 is a data collection device, and a sample 3 is installed in the constant temperature device 1. The constant temperature device 1 includes a temperature sensor 11,
The data collection device 2 includes a sawtooth generator 12, a reference voltage source 13, a differential amplifier 15, a heater 17, and the like, and a sample temperature monitoring section 21, a sample characteristic measuring section 22, and the like.

As shown in FIG. 1(b), a control voltage obtained by superimposing the sawtooth voltage of the sawtooth wave generator 12 on the reference voltage v0 is input to the differential amplifier 15, and the temperature of the sample 3 is increased as shown in FIG. 1(a). For example, during the temperature rising process, the sample temperature reaches a predetermined temperature T.
0, a trigger signal is sent out as shown in the figure (C1) to measure the characteristics.

For the temperature control system of this method, a relatively simple one that can provide a certain degree of long-term stability can be used;
), even if the temperature change range fluctuates considerably, the measured temperature is always maintained at the predetermined temperature T0.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 2 is a block diagram showing an example of a system in which the present invention is applied to a semiconductor laser.

1 is a constant temperature device, 2 is a data collection device, and constant temperature device 1
Inside, a semiconductor laser as a sample 3 is housed in a metal block in contact with a temperature sensor 11 and mounted together with a light receiving device 23 .

The constant temperature device 1 includes a sawtooth generator 12, a reference voltage source 13, an adder 14, a differential amplifier 15, a heater current control circuit 16, a heater 17, etc., and the data collection device 2 includes a thermometer as a sample temperature monitoring section 21. is the temperature sensor 11 in the constant temperature device 1
The light receiving device 23 is connected to the sample characteristic measuring section 22.
In addition, an optical output setting voltage source 24, a current-voltage converter 25,
It includes a differential amplifier 26, a voltmeter 27, a processor 28, a timer 29, a recorder 30, and the like.

As mentioned above, the temperature inside the thermostatic chamber is determined by superimposing the sawtooth voltage of the sawtooth wave generator 12 on the reference voltage v0 by the adder 14 and applying it to the differential amplifier 1.
5, the heater current control circuit 16 operates to eliminate the difference between this and the output of the temperature sensor 11, and the sample 3
The temperature changes periodically as shown in FIG. 1(a). In this example, for example, the temperature rises for 1.5 hours and the temperature drops for 0 hours.
．． One cycle is 5 hours.

Maintaining the output light of the semiconductor laser of the sample 3 at a predetermined constant value is performed by the light receiving device 23, the light output setting voltage source 24, the current-voltage converter 25, the differential amplifier 26, etc., as in the conventional case.

The sample characteristics are measured by monitoring with a high precision thermometer such as a quartz thermometer connected to the temperature sensor 11.
The data is input to the processor 28 at a cycle of about 10 seconds, and the timer 29 makes a measurement request based on a predetermined measurement cycle. For example, when the temperature matches the predetermined temperature T0 during the temperature rising process, the data shown in FIG. Connect the trigger signal to the voltmeter 2 as shown.
7 to sample the voltage measurement corresponding to the laser drive current.

This measured value is recorded in the processor 28 or in the recorder 30 as required.

〔Effect of the invention〕

As explained above, according to the present invention, in accelerated testing of semiconductor devices, the characteristic measurement temperature is maintained at a constant value with high accuracy, the influence of the measurement temperature is eliminated from the measured value, and the characteristic fluctuations of the sample are accurately and efficiently understood. As a result, it becomes possible to perform life estimation, screening, etc. in a shorter time and with higher reliability than before.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a conventional example. In the figure, 1 is a constant temperature device, 2 is a data acquisition device, 3 is a sample (semiconductor laser), 11 is a temperature sensor, 12 is a sawtooth wave generator, 13 is a reference voltage source, 14 is an adder, and 15 is a differential amplifier. ,
17 is a heater, 16 is a heater current control circuit, 21 is a sample temperature monitoring section (thermometer), 22 is a sample characteristic measurement section, 23 is a light receiving device, 24 is a light output setting voltage source, 25 is a current voltage converter, 26 is a differential amplifier, 27 is a voltmeter, 28 is a processor, 2
9 indicates a timer, and 30 indicates a recorder. The water patrol's phoenix is 1.
67079Figure 3

Claims (1)

[Claims] 1) Periodically changing the temperature in a thermostatic chamber containing a sample in the vicinity of a predetermined value, and measuring the characteristics of the sample when the temperature of the sample is at the predetermined value. An accelerated testing method for semiconductor devices characterized by: 2) The accelerated testing method for a semiconductor device according to claim 1, wherein the characteristic measurement is performed when the temperature changes are in the same direction.