KR101025566B1 - Electrical and optical property measuring device of light emitting device - Google Patents

Abstract

PURPOSE: A light emitting device measuring apparatus is provided to measure electrical characteristics using a multi channel probe and to measure the optical characteristic of a part of the light emitting device using a gradually changing characteristic within a wafer. CONSTITUTION: A multi channel probe(310) for measuring electrical characteristics measures a plurality of light emitting devices. An electrical characteristic measuring unit generates electrical characteristic data by measuring the electrical characteristics of the light emitting device formed on the object of a wafer.

Description

Apparatus for measuring electrical and optical characteristics of light emitting device

The present invention relates to an apparatus capable of measuring electrical and optical characteristics of a light emitting device, and more particularly, to an apparatus capable of quickly and accurately measuring electrical and optical characteristics of a light emitting device.

Light emitting devices such as light emitting diodes (LEDs) or vertical cavity surface emitting laser diodes (VCSELs) measure electrical and optical properties after completion of manufacturing. FIG. 1 shows a schematic apparatus for measuring electrical and optical characteristics of a conventional light emitting device.

Referring to FIG. 1, a method of measuring electrical and optical characteristics of a light emitting device is described. First, a wafer 110 on which a light emitting device is formed is mounted on a chuck 120. The chuck 120 is connected to the chuck mover 125. The chuck mover 125 is a device capable of moving the chuck 120 in all three directions of the x-y-z axis. The light emitting device is provided with an electrode pad through which current can flow. Next, the chuck 120 is raised by using the chuck mover 125 so that the electrode pad of the light emitting element contacts the measurement probe 130. The current or voltage is applied to the light emitting device through the current-voltage source 150.

By applying a current or voltage to the light emitting device, the current-voltage measuring device 155 generates electrical property data by measuring electrical properties such as driving voltage and current of the light emitting device. When a current or voltage is applied to the light emitting device, the light emitting device generates light, and a part of the generated light is transmitted to the light quantity measuring device 165 through the light receiving device 160 and a part of the light through the optical fiber 170. It is transmitted to the light spectrum measuring device 175. The light quantity measuring device 165 measures light quantity to generate light quantity data, and the light spectrum measuring device 175 measures light spectrum to generate light spectrum data. Electrical property data and optical property data (light amount data and light spectrum data) generated through the above method are collected and processed by the data processor 180.

In addition, the chuck moving apparatus 125 moves the chuck 120 in the xy-axis direction so as to measure electrical and optical characteristics of other light emitting devices, and repeats the above process, so that all the light emitting devices formed on the wafer 110. Measure the electrical and optical properties of

Typically, the electrical and optical characteristics of the light emitting device are measured on a wafer basis. A small number of light emitting devices are formed on a single wafer, and as many as 100,000 light emitting devices are formed. Since a large number of light emitting devices are formed on one wafer as described above, it takes a long time to measure the electrical and optical characteristics of the light emitting device. To improve this point, a multi-channel measuring apparatus capable of measuring several light emitting devices at the same time by using a multi-channel probe has been introduced. In FIG. 2, four light emitting devices were simultaneously measured using the four channel probe 210. By using the multi-channel probe as described above, several light emitting devices can be measured at one time, and the number of movements of the chuck can be greatly reduced, thereby greatly reducing the measurement time.

However, in the multi-channel measuring apparatus, it is not a big problem to simultaneously measure the electrical characteristics of a plurality of light emitting devices, but there are various problems when simultaneously measuring the optical characteristics of a plurality of light emitting devices. This is because when the optical characteristics of several light emitting devices are simultaneously measured, it is not easy to distinguish the light from each light emitting device by mixing the light from each light emitting device. In particular, when light spreads in a wide angle, such as an LED, other LEDs adjacent to the LED to be measured may distort the amount of light measurement. In addition, the measurement speed may be improved by increasing the number of channels, but the area of the light receiving device 160 should be very large so that light from a large area can be uniformly received. However, since the area of the light receiving element 160 is limited, the number of channels cannot be increased indefinitely. In addition, as the number of channels increases, there is a disadvantage that the light quantity measurement variation between channels increases.

As a result, there is an increasing need for a new type of measuring device capable of accurately and quickly measuring the electrical and optical characteristics of a light emitting device.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting device measuring apparatus capable of quickly and accurately measuring electrical and optical characteristics of a light emitting device.

In order to solve the above technical problem, the light emitting device measuring apparatus according to the present invention, the measurement of the wafer by using a multi-channel probe for measuring the electrical properties that can measure the electrical properties of the plurality of light emitting devices together An electrical characteristic measuring unit configured to generate electrical characteristic data by measuring electrical characteristics of a light emitting device formed in a target region; An optical characteristic measuring unit configured to generate optical characteristic data by measuring optical characteristics of some of the light emitting elements formed in the measurement target area by using an optical characteristic measuring probe capable of measuring optical characteristics of the light emitting element; And a data processor configured to calculate optical property data of the unmeasured light emitting device in the measurement target area from the optical property data of the light emitting device generated by the optical property measuring unit.

According to the present invention, the electrical characteristics of a light emitting device that does not cause a big problem even when measured using a multi channel probe are measured using a multi channel probe, and the optical characteristics of the light emitting device are gradually changed in one wafer. After measuring the optical characteristics of only a portion of the light emitting device by using, the optical properties of the non-measured light emitting device is calculated through the data processing unit, thereby quickly measuring the electrical and optical properties of the light emitting device. For example, when measuring about 10,000 light emitting elements, the conventional apparatus takes more than 30 minutes, but it does not take 7 minutes when using the measuring apparatus according to the present invention. In addition, even if the optical properties are not measured for all the light emitting devices, the error is very small, less than 0.5%, using the measuring device according to the present invention, it is possible to quickly and accurately measure the electrical and optical properties of the light emitting device.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the device for measuring the electrical and optical characteristics of the light emitting device according to the present invention. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

3 is a view schematically showing a preferred embodiment of the light emitting device measuring apparatus according to the present invention.

Referring to FIG. 3, the light emitting device measuring apparatus 300 according to the present invention includes an electrical characteristic measuring unit 310, an optical characteristic measuring unit 320, a chuck transfer unit 330, and a data processing unit 340. do.

The electrical characteristic measuring unit 310 generates electrical characteristic data by measuring electrical characteristics of a light emitting device formed on the wafer 301, and includes a current-voltage source 311, a switching box 312, and a multi-channel probe. A card 313 and a current-voltage measuring device 314.

The current-voltage source 311 is for applying a current or voltage to the light emitting element. The switching box 312 allows the current-voltage source 311 and the multi-channel probe card 313 to be connected when the number of channels of the current-voltage source 311 is smaller than that of the multi-channel probe card 313.

The multi-channel probe card 313 is a multi-channel probe is arranged, the multi-channel probe is in contact with the electrode pad of the light emitting element. When the multi-channel probe is in contact with the electrode pad of the light emitting device, the current or voltage of the current-voltage source 311 is applied to the light emitting device. The number of channels of the multi-channel probe card 313 can be increased by a desired number. When the number of channels is increased by the number of light emitting elements in the measurement target region of the wafer 301, the wafer 301 and the multi-channel probe card 313 only once. ), All electrical characteristics of the light emitting element in the measurement target area can be measured. Here, the measurement target region means a region in which the light emitting elements to be measured are formed among the light emitting elements formed on the wafer 301, and is measured when all the light emitting elements formed on the wafer 301 are to be measured. The target area becomes the entire wafer 301.

If there are N light emitting elements formed in the measurement target region and the number of channels of the multi-channel probe card 313 is P, the electrical characteristics of all the light emitting elements in the measurement target region can be measured with approximately N / P times of contact. . Therefore, since the number of channels of the multi-channel probe card 313 is larger than in the related art, the time required for measuring the electrical characteristics of the light emitting device formed on one wafer is significantly reduced compared with the conventional art. In addition, since the accuracy of the electrical characteristics of the light emitting device does not become a problem even when using the multi-channel, the accuracy of the electrical characteristics does not matter even when measured using the multi-channel probe card 313 as in the present embodiment.

An example of the multi-channel probe card 313 is shown in FIG. 4. As shown in FIG. 4, the multi-channel probe card 313 may be configured, wherein the P channel is in contact with the P-type electrode pad of the light emitting device, and the N channel is in contact with the N-type electrode pad of the light emitting device. do. To this end, the pitch of the probe array 316 formed on the multi-channel probe card 313 is matched with the pitch of the electrode pad of the light emitting device.

The current-voltage measuring device 314 is connected to the driving voltage and current of the light emitting device through a current or voltage applied to the light emitting device through the current-voltage source 311, the switching box 312, and the multi-channel probe card 313. It is a device that generates electrical property data by measuring the same electrical property.

As a result, by using the electrical characteristic measuring unit 310 of the present embodiment, it is possible to accurately and quickly measure the electrical characteristics of the light emitting device formed on one wafer.

The optical characteristic measuring unit 320 generates optical characteristic data by measuring optical characteristics of some of the light emitting elements formed on the wafer 301, and includes a current-voltage source 321, a switching box 322, A probe 323 for measuring optical characteristics, a light receiving element 324, a light amount measuring device 325, an optical fiber 326, and a light spectrum measuring device 327 are provided.

The current-voltage source 321 is for applying a current or voltage to the light emitting device. The switching box 322 connects the current-voltage source 321 and the optical characteristic measurement probe 323. The current-voltage source 321 and the switching box 322 may use the current-voltage source 311 and the switching box 312 of the electrical characteristic measuring unit 310 and the current through the switching boxes 312 and 322. It is possible to select where the current or voltage of the voltage sources 311 and 321 are to be applied. In the present embodiment, the electrical characteristic measuring unit 310 and the optical characteristic measuring unit 320 are described as using the common current-voltage sources 311 and 321 and the switching boxes 312 and 322, but the present invention is not limited thereto. The electrical characteristic measuring unit 310 and the optical characteristic measuring unit 320 may include respective current-voltage sources and switching boxes.

The optical property measuring probe 323 is in contact with the electrode pad of the light emitting device to apply a current or voltage to the light emitting device. The optical characteristic measurement probe 323 may be single channel or multi channel. When the optical characteristic measuring probe 323 is multi-channel, and the number of channels of the current-voltage source 321 is smaller than the number of channels of the optical characteristic measuring probe 323, the optical characteristic measuring probe through the switching box 322. A current or voltage may be applied to each channel of the 323.

The light receiving element 324 is a light receiving element. When a current or voltage is applied to the light emitting element, the light emitting element generates light, and receives some of the generated light. The light quantity measuring device 325 is a device for generating light quantity data by measuring the light quantity from the light received by the light receiving element. The optical fiber 326 transmits light for measuring the light spectrum to the light spectrum measuring device 327. The optical spectrum measuring apparatus 327 generates optical spectrum data by measuring the optical spectrum received through the optical fiber 326.

Although not shown in the present embodiment, the optical characteristic measurement unit 320 may further include a wafer expansion device (not shown). Wafer expansion devices are devices that widen the gap between light emitting elements in a wafer. The optical characteristics are difficult to accurately measure due to the interference of adjacent light emitting devices. If the distance between the light emitting devices is increased by using a wafer extension device, the interference by adjacent light emitting devices is reduced, so that the optical properties of the light emitting devices can be measured more accurately. It becomes possible.

The optical characteristic measuring unit 320 measures the optical characteristics of the light emitting device and generates optical characteristic data in the same manner as described above. However, if the optical characteristics of all the light emitting elements formed in the measurement target region of the wafer 301 are measured, the measurement time is too long, and only the optical characteristics of the light emitting elements of some light emitting elements in the measurement target region are measured. For example, optical characteristics of the light emitting device may be measured at intervals of N × M. The optical characteristic data of the non-measured light emitting device is calculated through the data processor 340 to be described later. In the case of the optical characteristics, the optical characteristic data of the remaining light emitting elements, which are generated by measuring only a part of the light emitting elements and generating the optical characteristic data but not measured, are calculated from some assumptions, and do not differ significantly from the actual optical characteristic data. As a result, by using the optical characteristic measuring unit 320 of the present embodiment, it is possible to accurately and quickly measure the optical characteristics of the light emitting device formed on one wafer.

The chuck transfer unit 330 includes a chuck transfer unit 332 which transfers the chuck 331 between the chuck 331 on which the wafer is mounted, and between the electrical characteristic measurement unit 310 and the optical characteristic measurement unit 320. The chuck transfer means 332 moves the chuck 331 to the left and right and up and down so that all the light emitting elements in the wafer 301 are multi-channel probe card 313 and the optical characteristic measurer 320 of the electrical characteristic measurer 310. Contact with the probe 323 for measuring optical characteristics of To this end, the chuck transfer means 332 is provided with a drive means for moving the chuck 331 in all three directions x-y-z axis.

The data processor 340 is connected to the electrical characteristic measuring unit 310 and the optical characteristic measuring unit 320, and the electrical characteristic data (driving voltage, current, etc.) and the optical characteristic measuring unit generated from the electrical characteristic measuring unit 310. Optical characteristic data (light quantity, light spectrum, wavelength, etc.) generated from 320 is collected and processed. In particular, the data processor 340 calculates the optical characteristic data of the light emitting device for which the optical characteristic is not measured from the optical characteristic data of the light emitting device generated by the optical characteristic measuring unit 320.

In general, the optical properties formed in a single wafer do not change rapidly, but change gradually. These characteristics are shown in FIGS. 5 and 6. FIG. 5 is a diagram showing a general wavelength distribution of a wafer on which a light emitting element is formed, and FIG. 6 is a diagram showing a general light amount distribution.

As shown in Figs. 5 and 6, the optical characteristics (wavelength, amount of light) do not change suddenly but gradually change depending on the position in the wafer. Therefore, the optical characteristics of adjacent light emitting devices are almost the same. For this reason, the data processor 340 may calculate optical characteristic data of the light emitting device that has not been measured. For example, after measuring the optical properties of one light emitting device in one block using N × M light emitting devices as one block, it is inferred that the optical properties of all light emitting devices in one block are the same, or to adjacent blocks. It can be inferred that the optical properties change linearly.

The optical characteristic data is generated by measuring the optical characteristics of all of the light emitting elements in the wafer, and the optical characteristic data is generated by measuring only a portion of the light emitting elements at intervals of four light emitting elements, and then the optical characteristic data of the remaining unmeasured light emitting elements is data. Table 1 shows a comparison of the results calculated by the processor 340. At this time, the optical characteristics were selected the light amount and wavelength. Table 1 infers that the non-measured optical property data between the measured optical property data changes linearly, and shows the results of calculating the unmeasured optical property data using linear interpolation.

For example, in Table 1, wavelength data of light emitting device 0 is 461.33, and wavelength data of light emitting device 4 of adjacent block is 461.17. In this case, light emitting devices between light emitting devices 0 and 4, that is, light emitting devices 1, 2, and 3, were calculated using linear interpolation to gradually decrease from 461.33 to 461.17. That is, the first light emitting device was calculated as 461.29, the second light emitting device was 461.25, and the third light emitting device was calculated as 461.21. In Table 1, linear interpolation is used, but in addition to linear interpolation, various other interpolation methods such as Newton interpolation may be used. 7 and 8 show graphs of the wavelength data and the light quantity data calculated using this method. Reference numeral 710 of FIG. 7 and reference numeral 810 of FIG. 8 are graphs showing measured data, and reference numeral 720 of FIG. 7 and reference numeral 820 of FIG. 8 are graphs showing data calculated through the above method. . The points indicated by the arrows in the graphs 720 and 820 showing the calculated data are measured data, and the rest are calculated data. In addition, reference numeral 730 of FIG. 7 and reference numeral 830 of FIG. 8 are graphs showing an error between actually measured measurement data and calculated data.

Table 1 Accuracy comparison of optical properties of the present invention

As shown in Table 1, FIG. 7 and FIG. 8, the wavelength data showed almost no error, and in the case of the light quantity data, there was a slight error, but there was almost no error such that the maximum error was 0.5%. appear.

Therefore, the optical characteristic measuring unit 320 measures all the optical characteristics of the light emitting device without measuring all the optical characteristics, and then calculates the optical characteristic data of the light emitting device not measured from the optical characteristics measured by the data processor 340. In this case, a large error does not occur, and the measurement time can be greatly reduced.

Hereinafter, a method of measuring electrical and optical characteristics of the light emitting device by using the light emitting device measuring apparatus 300 shown in FIG. 3 will be described.

In this embodiment, the electrical and optical properties of the light emitting device are measured separately. At this time, the order of measuring the electrical and optical properties is irrelevant to the present invention. That is, the electrical properties of the light emitting device may be measured first and then the optical properties may be measured, or the optical properties of the light emitting device may be measured first and then the electrical properties may be measured. However, in this case, the electrical characteristics of the light emitting device are first measured, and then the optical characteristics are measured.

First, the wafer 301 is seated on the chuck 331, and the chuck 331 is transferred to the electrical characteristic measuring unit 310 using the chuck transfer means 332. Then, the electrode pad of the light emitting device of the 1-1st block and the probe of the multi-channel probe card 313 are contacted using the chuck transfer means 332, and a current or voltage is supplied to the light emitting device through the current-voltage source 311. Is applied. The current-voltage measuring device 314 measures electrical characteristics of the light emitting device and generates electrical characteristic data. Next, if the electrical characteristics of all the light emitting devices in the measurement target region have not been measured, the chuck 331 is moved to the 1-2 block using the chuck transfer means 332, and the light emitting devices of the 1-2 block are moved. Contact the electrode pads and the probes of the multi-channel probe card 313. This process is repeated until the electrical properties of all light emitting devices in the measurement target area are measured. The generated electrical characteristic data is transmitted to the data processor 340.

Next, the chuck 331 is transferred to the optical property measuring unit 320 using the chuck transfer means 332, and the electrode pad and the optical property measuring probe of the light emitting device of some of the light emitting devices of the 2-1 block. 323 is contacted. In addition, light is generated by applying a current or voltage to the light emitting device through the current-voltage source 321, and thus the optical characteristics of the light emitting device are measured through the light quantity measuring device 325 and the light spectrum measuring device 327. Measure and generate optical property data. Next, if the optical characteristics of all blocks in the measurement target region have not been measured, the chuck 331 is moved to the 2-2-2 block by using the chuck transfer means 332, and a part of the light emitting devices of the 2-2 block are used. The electrode pad of the light emitting device and the optical characteristic measurement probe 323 are contacted. This process is repeated until the optical properties of all blocks in the area to be measured are measured. The generated optical characteristic data is transmitted to the data processor 340.

Next, the optical processor 340 calculates optical property data of the light emitting device that is not measured from the optical property data of the measured light emitting device. The method of calculating the optical characteristic data of the unmeasured light emitting device is as described above. For example, it is assumed that the optical characteristic data of the light emitting device measured in the block 2-1 and the optical characteristic data of the light emitting device measured in the block 2-2 are linearly changed, and the light emission measured in the 2-1 block Optical characteristic data of the light emitting device between the device and the light emitting device measured in the block 2-2 may be calculated.

Using this method, it is possible to accurately measure the electrical and optical characteristics of the light emitting device within a short time. This is shown in Table 2 and Table 3.

[Table 2] Measurement time using a conventional measuring device

[Table 3] Measurement time using the light emitting device measuring apparatus according to the present invention

Table 2 shows the time required to measure the electrical and optical characteristics of the light emitting device using a conventional measuring device, Table 3 shows the electrical and optical properties of the light emitting device using the light emitting device measuring apparatus according to the present invention It shows the time taken to measure. Table 2 and Table 3 show the time required to measure the electrical and optical characteristics of all the light emitting devices formed on the wafer, 10,000 light emitting devices are formed on a single wafer.

The time taken when using a conventional measuring device is approximately 33.3 minutes, as shown in Table 2. This takes a long time because it has to measure 10,000 light emitting elements and move the chuck. In contrast, the time required for using the light emitting device measuring apparatus 300 according to the present invention takes about 6.5 minutes, as shown in Table 3. The time for transferring the chuck 331 from the electrical characteristic measuring unit 310 to the optical characteristic measuring unit 320 (about 10 seconds) and the time for calculating the optical characteristic data of the light emitting device not measured by the data processing unit 340 ( 1 to 2 seconds), the measurement time can be significantly reduced by using the light emitting device measuring apparatus 300 according to the present invention. When the light emitting device measuring apparatus 300 according to the present invention is used, although the electrical and optical characteristics of the light emitting device are separately measured, the measurement is performed for each block, so that the chuck movement time is reduced and the overall measurement time is greatly reduced. will be.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

1 is a view schematically showing a conventional light emitting device measuring apparatus.

2 is a conceptual diagram of a multi-channel measuring apparatus capable of simultaneously measuring four light emitting devices by using a four-channel probe.

3 is a view schematically showing a preferred embodiment of the light emitting device measuring apparatus according to the present invention.

4 is a view schematically showing an example of a multi-channel probe card provided in the light emitting device measuring apparatus according to the present invention.

5 is a diagram illustrating a general wavelength distribution of a wafer on which a light emitting device is formed.

6 is a view showing a general light quantity distribution of a wafer on which a light emitting element is formed.

7 is a graph showing wavelength data and an error obtained by using the light emitting device measuring apparatus according to the present invention.

8 is a graph showing the light amount data and the error obtained by using the light emitting device measuring apparatus according to the present invention.

Claims (3)

The electrical characteristic data is measured by measuring the electrical characteristics of the light emitting elements formed in the measurement target region of the wafer using a multi channel probe for measuring electrical characteristics of the plurality of light emitting elements together. Generating electrical property measuring unit; An optical characteristic measuring unit configured to generate optical characteristic data by measuring optical characteristics of some of the light emitting elements formed in the measurement target area by using an optical characteristic measuring probe capable of measuring optical characteristics of the light emitting element; And And a data processor configured to calculate optical property data of the unmeasured light emitting device in the measurement target area from the optical property data of the light emitting device generated by the optical property measuring unit. The method of claim 1, The data processing unit, And calculating optical property data of the non-measured light emitting device so that the optical property in the measurement target region is gradually changed. The method according to claim 1 or 2, The optical characteristic measuring unit further comprises a wafer expansion device for widening the interval between the light emitting elements in the wafer.

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