JPH02125484A - Sorting method for propriety of semiconductor laser - Google Patents

Abstract

PURPOSE:To shorten a time required to sort by sorting elements with final optical outputs in a constant-current operation at a second high temperature in the same degree as the first temperature higher than the temperature at the time of actual use. CONSTITUTION:If a first temperature is, for example, 50 deg.C, a second temperature is 70 deg.C, the constant current of a constant-current operation is 150mA, the operating time is 100 hours, and an optical output value P1 is 5mW, when yield is desirably raised even with low reliability, the current at the time of actual use may be reduced to approximately 60mA, or the value P1 may be reduced to approximately 3mW. Even if the time is reduced to approximately 50 hours, its accuracy is slightly reduced. On the contrary, if reliability is desirably raised even if the yield is reduced, the P1 may be raised to approximately 8mW. When the current is set to a value exceeding 200mA, deterioration except initialization deterioration occurs, and even if the time is increased, its efficiency is deteriorated, but no effect is provided. The second temperature is suitably approximately 50 deg.C to approximately 80 deg.C, and no large difference occurs in the reliability and the yield with this range of the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for selecting semiconductor lasers, particularly for semiconductor lasers with a diameter of 1 μm.
The present invention relates to a method for efficiently selecting long-life semiconductors from μm cow semiconductors.

BACKGROUND OF THE INVENTION Conventionally, a method for selecting the quality of semiconductor lasers in the 1 .mu.m band has generally been carried out by a method called the two-step screening method specified by NTT.

As in the method described above, measure the first threshold current value at 50°C, then perform constant current operation at 70°C and 150 mA for 100 hours, and then measure the second threshold current value at 50°C. And the second
A first step in which a non-defective product is determined if the amount of change in the threshold current value from the first threshold current value is 10% or less;
, 5mW constant output operation for 1100 hours, and the second step is to select non-defective products if the drive current value at the end of energization has a change of 10% or less from the drive current value at the start of energization. Laser pass/fail screening methods are being used.

FIG. 3 shows the results of a reliability test of a semiconductor laser obtained by the conventional semiconductor laser screening method. Element used for measurement to obtain Figure 3
The elements were selected from a suitable wafer of a CtSI laser, and the horizontal axis shows the amount of change in threshold current value in the first step, and the vertical axis shows the deterioration rate in the reliability test by constant output operation of so'csmw conducted after selection. , that is, the amount of change in the drive current is divided by the energization time. In Figure 3,
・The mark indicates a good product that passed both the first and second steps in accordance with conventional semiconductor laser screening, and the Δ mark indicates a product that passed the first step.
The 9 products that passed the step were defective products that did not have enough light output to perform the second step. From Figure 3, the first
It can be seen that an element that passed the step is guaranteed a long life of 10 hours, and an element that passed both the first and second steps is guaranteed a long life of 105 hours.

Problems to be Solved by the Invention However, the conventional semiconductor laser pass/fail screening method consists of a first step that takes about 100 hours and a second step that takes about the same amount of time. There was a problem with the lack of selection.

In view of efficient sorting as described above, the first purpose of the present invention is to shorten the time required for sorting without impairing the yield or reliability by sorting using the final optical output of constant current operation. The second objective is to shorten the time required for sorting without impairing yield or reliability by sorting by driving current at a predetermined optical output.

Means for Solving the Problems In order to achieve the above object, the technical solution of the present invention is as follows:
First, after measuring the first threshold current value at a first temperature higher than the practical temperature, the first threshold current value is measured at a second ambient temperature which is higher than the first temperature, for example, for about 100 hours during actual use. A current larger than the drive current is applied, and then a second threshold current value is measured at the first temperature, and the second threshold current value is selected based on the amount of change in the second threshold current value with respect to the first threshold current value. Further, the selection is made based on the final optical output when energized at the second temperature. Second, after measuring the first threshold current value at a first temperature higher than the temperature during actual use, the first threshold current value is measured at a second ambient temperature that is higher than the first temperature. A current larger than the driving current during actual use is applied for about a period of time, and then a second threshold current value is measured at the first temperature, and the second threshold current value of the first
The selection is made based on the amount of change with respect to the threshold current value of , and further, it is driven at the second temperature with a predetermined optical output, and the selection is made based on the drive current value.

Function The present invention firstly selects elements based on their final optical output in constant current operation at a second warm temperature that is as high as the first temperature that is higher than the temperature in actual use (from C, This is to remove elements that require excessive drive current due to insufficient optical output, and which increase the drive current in constant output operation at the second temperature or which are unable to perform constant output operation. For devices with a light output of After performing constant current operation at a second temperature that is higher than the first temperature, the device is operated at a predetermined optical output at the second temperature and the elements are selected using the drive current, thereby eliminating excessive drive current. When the drive current is applied and the drive current is increased, the device eliminates elements that cannot achieve a predetermined optical output even if the drive current is increased, and when the drive current is low, there is no significant increase in the drive current. Therefore, constant output operation, which takes about the same amount of time as constant current operation, is not required.

EXAMPLE A first example of the present invention will be described below with reference to FIG. The horizontal axis is the final optical output of constant current operation at the first temperature, which is higher than in actual use, and the second temperature, which is about the same or higher, and the vertical axis is the optical output of the conventional pass/fail screening method for semiconductor lasers. This is the rate of increase in drive current in constant output operation at P(1). In Fig. 1, the . mark indicates an element that passed the first step of the conventional semiconductor laser pass/fail selection method and the second step of the optical output of P(1), and the 0 mark indicates an element that failed the first step. , an element that satisfies the conditions of the second step, and a mark Δ represents an element that failed because the drive current exceeded the specified value during the second step for 1100 hours, and the current supply was stopped. FIG. 1 shows a line with an optical output of 1.1XP (1). 1. Since the Δ mark is in the left region of I Even if the constant output operation is omitted instead of sorting based on whether the final optical output value is larger or smaller than 1.1×P(1),
It can be seen that yield and reliability are not impaired. In this example, the first temperature is 50°C, the second temperature is 70°C, the constant current of constant current operation is 150m, and the operating time is 100 hours.

The optical output (6tLP<1') is shown in the case of s mW, but
If you want to increase the yield even if the reliability is somewhat low, you can lower the constant current to the operating current of 60 m during actual use, or lower the optical output value P (1) to about t-3 mW. . Further, even if the operating time is set to about 60 hours, the accuracy will be reduced to some extent. On the other hand, if you want to increase reliability even if you lower the yield, you can increase it to about p(1)2amw. If the constant current is set to a value exceeding 200 mA, deterioration other than initial deterioration may occur, and even if the operating time is increased, the efficiency will only deteriorate and there will be no effect. The second temperature is 50'
C. to about 80.degree. C. is appropriate, and there is no big difference in reliability9 yield as long as it is within this range. Selection criteria P(1
), in order to be equivalent to the conventional example with constant output operation at P(1), it is better to deviate from this value by several orders of magnitude. This is clear from Figure 1.

A second embodiment of the present invention will be described below with reference to FIG. The horizontal axis is the drive current value when obtaining a predetermined optical output after the constant current operation of step (1) at a first temperature higher than in actual use and a second temperature that is about the same or higher. The vertical axis, the * mark, the 0 mark, and the Δ mark are the same as in FIG. In FIG. 2, the operating current is shown at 0.93 X I (1) (7) life. 0.93
Constant power recommendation '1' at the second temperature.

Even if the constant output operation is omitted, the yield and reliability can be improved by replacing the selection based on operation with the selection based on whether the drive current value when obtaining a predetermined optical output is larger or smaller than 0.93 x I (1). I know it won't hurt. In this example, the first
temperature is 60°C, second temperature is 70”C, constant current I(1) for constant current operation is 150 m, operating time is 100 hours, and the prescribed light output is smW. For the range of these values: This is the same as in the case of the first embodiment.The value of the coefficient 0.93 of I(1), which is the selection criterion, is about the same as that of the conventional example based on constant output operation with a predetermined optical output.
It is clear from FIG. 2 that it is better to have a deviation of several degrees from this value.

Effects of the Invention As described above, the effects of the present invention are that it is possible to efficiently select semiconductor lasers without performing constant output operation, which requires the same amount of time as constant current operation, and without compromising yield or reliability. It can be performed.

[Brief explanation of drawings]

FIG. 1 is a correlation diagram between the optical output and the rate of increase in the operating undercurrent in the first embodiment of the present invention, and FIG. 2 is a correlation diagram between the operating current and the rate of increase in the operating current in the second embodiment of the present invention. FIG. 3 is a correlation diagram showing reliability in the conventional semiconductor laser sorting method. Name of agent: Patent attorney Shigetaka Awano and 1 other person: J! Io (P) No. 4 den (engineering 2)

Claims (2)

[Claims] (1) After measuring the first threshold current value of the semiconductor laser at a first temperature higher than the temperature during actual use,
A current larger than the drive current during actual use is applied for a predetermined period of time at a second ambient temperature that is higher than the temperature of , and then a second threshold current value is measured at the first temperature; The laser is selected based on the amount of change of the second threshold current value with respect to the first threshold current value, and
A semiconductor laser quality selection method, characterized in that the laser is selected based on the final optical output when energized at a temperature of . (2) After measuring the first threshold current value of the semiconductor laser at a first temperature higher than the temperature during actual use,
A current larger than the drive current during actual use is applied for a predetermined period of time at a second ambient temperature that is higher than the temperature of , and then a second threshold current value is measured at the first temperature; The lasers are selected based on the amount of change in the second threshold current value with respect to the first threshold current value, and further, the lasers are driven at the second temperature with a predetermined optical output, and the lasers are selected based on the driving current value. A semiconductor laser quality selection method characterized by the following.