JP5460196B2 - Luminance inspection method - Google Patents

Description

  The present invention relates to an inspection method for inspecting how the characteristics of a light emitting device change after a modified layer is formed and divided on a semiconductor wafer on which the light emitting device is formed.

  As a method of dividing semiconductor wafers, optical device wafers, etc. into devices along the planned division line, a pulsed laser beam that is transparent to the wafer is used, and the focused laser beam is focused on the inside of the area to be divided. Laser processing methods for irradiation have been attempted. The method of dividing a wafer using this laser processing method is to divide the inside of the wafer by irradiating a pulse laser beam having a wavelength that is transmissive to the wafer by aligning the focal point from one side of the wafer. The modified layer is continuously formed along the line, and the workpiece is divided by applying an external force along the line to be divided whose strength is reduced by the formation of the modified layer ( For example, see Patent Document 1).

  In general, when the work piece on which the light emitting device is formed is divided by this method, the luminance of the light emitting device is lowered. Therefore, in order to determine the quality of the division, the luminance reduction rate due to the division is inspected. Is required.

Japanese Patent No. 3408805

  However, since the luminance of the light emitting device may change depending on the condition of the pulse laser beam to be irradiated, it is necessary to consider the relationship with the condition of the pulse laser beam in the luminance inspection. When it is desired to compare how much the luminance is lowered depending on the conditions of the plurality of pulse laser beams, it is necessary to prepare wafers corresponding to the number of conditions.

  The present invention has been made in view of these facts, and the main technical problem thereof is that the number of conditions of the pulse laser beam in dividing the wafer on which the light emitting device is formed by irradiation with the pulse laser beam. It is an object of the present invention to provide an inspection method capable of inspecting how much the luminance is reduced depending on the respective conditions of the pulse laser beam without using a wafer.

The present invention provides a first division line and a first division line inside a sapphire substrate having a light emitting device defined on the surface by the first division line and a second division line intersecting the first division line. A modified layer is formed inside the sapphire substrate by focusing the pulsed laser beam having the first wavelength transmitted through the sapphire substrate along the two split lines, and an external force is applied to the sapphire substrate. When dividing along the first division line and the second division line, and the wavelength of the wavelength transmitted through the sapphire substrate along the first division line and the second division line inside the sapphire substrate. A modified layer is formed inside the sapphire substrate by focusing the pulsed laser beam under the two conditions, and external force is applied to the sapphire substrate to produce sapphire. Compared with the case where the plate is divided along the first division line and the second division line, the case where the pulse laser beam of the first condition is used is compared with the case where the pulse laser beam of the second condition is used. The present invention relates to an inspection method for inspecting a difference in luminance reduction of each light emitting device from the case of using, and includes at least the following steps.
(1) Before dividing the sapphire substrate, measuring the luminance of each light emitting device to obtain the luminance before division;
(2) A step of condensing the pulse laser beam of the first condition along at least two adjacent first division lines to form a modified layer,
(3) A step of condensing the pulse laser beam of the first condition along at least two adjacent second division lines to form a modified layer,
(4) A modified layer is formed by condensing the pulse laser beam of the second condition along at least two adjacent first division lines where the pulse laser beam of the first condition is not condensed. The process of
(5) Forming a modified layer by condensing the pulse laser beam of the second condition along at least two adjacent second division lines where the pulse laser beam of the first condition is not condensed The process of
(6) applying an external force to the sapphire substrate to divide the sapphire substrate along the first planned division line and the second planned division line to form a plurality of sapphire chips;
(7) Among the sapphire chips, the first division planned line where the pulse laser beam of the first condition is condensed and the second division planned line where the pulse laser beam of the first condition is condensed are surrounded. Measuring the luminance of the light emitting device formed on the sapphire chip, and obtaining the luminance after division by the pulse laser beam of the first condition;
(8) Out of the sapphire chips, the first division planned line where the pulse laser beam of the second condition is condensed and the second division planned line where the pulse laser beam of the second condition is condensed are surrounded. Measuring the luminance of the light emitting device formed on the sapphire chip, and obtaining the luminance after division by the pulse laser beam of the second condition;
(9) When the pre-division luminance is compared with the post-division luminance with the pulse laser beam under the first condition and the post-division luminance with the pulse laser beam under the second condition, and the pulse laser beam under the first condition is used A step of inspecting a difference in luminance reduction of each light emitting device from the case where the pulse laser beam of the second condition is used.

  According to the present invention, since a single sapphire substrate can be used to inspect how much the brightness is reduced depending on the conditions of a plurality of pulsed laser beams, it is not necessary to use as many wafers as the number of conditions, and extremely efficient. Is.

It is a perspective view which shows an example of the sapphire substrate supported by the ring frame via the tape. It is a perspective view which shows an example of the division | segmentation scheduled line which forms a modified layer by laser irradiation. It is a perspective view which shows the example of two light emitting devices used as the object of a brightness | luminance test | inspection.

  A sapphire substrate 1 shown in FIG. 1 is a substrate on which a plurality of light emitting devices D are formed, and the thickness thereof is, for example, 80 to 110 [μm], and each light emitting device D has a plurality of first divisions. It is formed in a region partitioned by the planned line L1 and a plurality of second divided planned lines L2. The first scheduled division line L1 and the second scheduled division line L2 intersect and are cut along the two first scheduled division lines L1 and the two second scheduled division lines L2. Thus, a rectangular sapphire chip C including the light emitting device D is formed. A typical example of the light emitting device D is an LED.

  The sapphire substrate 1 is attached to the tape T when the first division planned line L1 and the second division planned line L2 are cut and divided into individual sapphire chips. The ring frame F is attached to the peripheral edge of the tape T, and the sapphire substrate 1 is supported integrally with the ring frame F via the tape T.

  When the sapphire substrate 1 is divided into individual sapphire chips using laser light, a pulsed laser beam having transparency with respect to the sapphire substrate along the first scheduled division line L1 and the second scheduled division line L2. The light is condensed and a continuous modified layer is formed inside the sapphire substrate 1. The pulse laser beam focused inside the sapphire substrate 1 when the modified layer is formed may reduce the luminance of the light emitting device D near the focused position depending on the conditions. Therefore, in order to determine the quality of the divided sapphire chip, it is inspected in advance how much the luminance of the light emitting device D is lowered depending on the condition of the pulse laser beam. Hereinafter, the procedure will be described.

(1) First Step First, before dividing the sapphire substrate 1 (before irradiating a pulse laser beam to the division planned line), the luminance before division of each light emitting device D shown in FIG. 1 is measured. The measurement of luminance is performed, for example, in a state where a predetermined voltage is applied to the electrode of each light emitting device D.

(2) Second Step At least two adjacent ones of the first scheduled division lines L1, for example, the first scheduled division lines L14 and L15 shown in FIG. 2 are selected, and the selected first scheduled division line L14, A pulsed laser beam is condensed inside the sapphire substrate along L15, and a modified layer is continuously formed inside the sapphire substrate. The pulse laser beam irradiation is performed while relatively moving the sapphire substrate 1 and a laser light irradiation head (not shown). One continuous modified layer is formed on one division planned line by one feed of the sapphire substrate 1 (in one pass). The same applies to the subsequent third to fifth steps. The wavelength of the pulse laser beam to be irradiated is a wavelength that can pass through the sapphire substrate, and the condition of the pulse laser beam at this time is the first condition. The elements constituting the conditions include the type of laser light source, wavelength, output, frequency, NA (numerical aperture), and the formation position (depth) of the modified layer. The first condition is set as follows, for example.
Output: 0.3 [W]
Wavelength: 1064 [nm]
Frequency: 100 [kHz]
Sapphire substrate feed rate: 600 [mm / s]
Modified layer depth: 30 μm (distance from incident surface to lower part of modified layer)
The modified layer is a layer in which any one of density, refractive index, mechanical strength, and other physical characteristics is different from the surroundings, for example, a melt-processed region, a crack region, and a dielectric breakdown region. In addition, there are refractive index changing regions, and there are also regions where these are mixed. Note that the laser beam is preferably focused from the back surface of the sapphire substrate 1, that is, from the non-formed surface side where no device is formed.

(3) Third Step A pulsed laser beam is collected along the at least two adjacent lines of the second scheduled division line L2 under the same condition as the first condition, and the modified layer is formed on the sapphire substrate. Form. Here, the second scheduled line L2 to be irradiated with the pulsed laser beam intersects the first scheduled lines L12 and L13 in which the modified layer is formed in the second step and is adjacent to the two. Yes, for example, the second scheduled division lines L23 and L24 shown in FIG.

(4) Fourth step Of the first scheduled division line L1, the first division planned line in which the pulse laser beam is not condensed under the first condition, that is, the first layer on which the modified layer has been formed. Two adjacent first scheduled division lines other than the planned division lines L14 and L15 are selected, and the selected two first divided planned lines are selected under a second condition different from the first condition. A pulsed laser beam is condensed along the sapphire substrate 1 to form a continuous modified layer on the sapphire substrate 1. Here, the second condition may be that at least one of the various components is different from the first condition. One of the first planned division lines to be subjected to reformed layer formation under the second condition is one of the first planned division lines to be condensed to form a modified layer in the second step. It is desirable to select such that it is adjacent to one of the first scheduled division lines L14 and L15. That is, as a result, it is desirable that the modified layer is formed on the four consecutive first division lines under two conditions. For example, the modified layer may be formed under the second condition along the first division lines L12 and L13 shown in FIG. For example, the second condition is set as follows.
Output: 0.4 [W]
Wavelength: 1064 [nm]
Frequency: 100 [kHz]
Sapphire substrate feed rate: 600 [mm / s]
Modified layer depth: 30 μm (distance from incident surface to lower part of modified layer)

(5) Fifth Step Of the second scheduled division line L2, the second scheduled division line in which the pulse laser beam is not condensed under the first condition, that is, among the second scheduled division line L2. , Select two adjacent second scheduled division lines other than the second scheduled division lines L23 and L24 in which the modified layer has already been formed, and the second divided planned lines are selected along the selected second scheduled division line. The pulsed laser beam is focused under the same conditions as the second condition, and a continuous modified layer is formed on the sapphire substrate 1. One of the second planned division lines to be focused on forming the modified layer under the second condition is one of the second planned divided lines to be condensed to form the modified layer in the third step. It is desirable to select so as to be adjacent to one of the second scheduled division lines L23 and L24. That is, as a result, it is desirable that the modified layer is formed under two conditions on the four consecutive second division lines. For example, the modified layer may be formed under the second condition along the first division lines L25 and L26 shown in FIG.

  As described above, when the reformed layer is formed for each of the four consecutive first scheduled dividing lines and the second scheduled divided line, the sapphire chip C1 cut out only by the first condition, The sapphire chip C2 cut out only by the second condition is generated. That is, the sapphire chip C1 shown in FIG. 2 is an area surrounded by the first scheduled division lines L14 and L15 and the second scheduled division lines L23 and L24. The modified layer is formed under the conditions described above. On the other hand, the sapphire chip C2 is an area surrounded by the first scheduled division lines L12 and L13 and the second scheduled division lines L25 and L26. These four planned division lines are all under the second condition. Thus, a modified layer is formed. Therefore, the first light emitting device D1 constituting the sapphire chip C1 is affected only by the first condition, and the second light emitting device D2 constituting the sapphire chip C2 is only affected by the second condition. Affected. Note that the second to fifth steps may be performed in any order.

(6) Sixth Step Next, by applying an external force to the sapphire substrate on which the modified layer is formed, the sapphire substrate 1 is divided into the first scheduled division lines L12, L13, L14, L15 and the second scheduled division line L23. , L24, L25, and L26 are divided into a plurality of sapphire chips. As the external force, for example, there is a force for extending the tape T in the horizontal direction. After applying the external force, the first sapphire chip 1 and the second sapphire chip C2 are peeled from the tape T and picked up as shown in FIG. When the tape T is of an ultraviolet curable type, before the sapphire chips are peeled from the tape T, the adhesive force is lowered by irradiating the tape T with ultraviolet rays.

(7) Seventh step Among the sapphire chips formed by the division, the first division lines L14 and L15 on which the pulse laser beam of the first condition is condensed and the pulse laser beam of the first condition are condensed. The luminance of the light emitting device D1 that constitutes the first sapphire chip C1 surrounded by the second scheduled division lines L23 and L24 is measured, and the luminance (first luminance) after division by the pulse laser beam of the first condition is measured. 1 division luminance).

(8) Eighth Step In the sapphire chip formed by the division, the first division lines L12 and L13 on which the pulse laser beam of the second condition is condensed and the pulse laser beam of the second condition are collected. The luminance of the light emitting device D2 constituting the second sapphire chip C2 surrounded by the condensed second scheduled dividing lines L25 and L26 is measured, and the luminance after division by the pulse laser beam under the second condition ( 2nd luminance after division).

(9) Ninth step Then, the pre-division luminance measured in the first step, the first post-division luminance measured in the seventh step, and the second post-division luminance measured in the eighth step are compared, The difference between the pre-division luminance and the first post-division luminance and the difference between the pre-division luminance and the second post-division luminance are obtained. By obtaining each difference in this way, it is possible to inspect the difference in luminance reduction of the light emitting device due to the difference in conditions when forming the modified layer.

  Note that it is preferable that the two light emitting devices to be subjected to luminance measurement are located as close as possible. This is because if the two light emitting devices are separated from each other, the conditions other than the pulse laser beam also differ, and the difference affects the brightness of each light emitting device. This is because it cannot be reflected on the luminance of each light emitting device. For example, when the tape T is irradiated with ultraviolet light for picking up a light emitting device, the intensity of the ultraviolet light varies depending on the position of the ultraviolet light source and the direction of irradiation, so the luminance of the light emitting device changes depending on the intensity of the ultraviolet light. May occur. However, if the two light emitting devices are close to each other, there is no great difference in the intensity of the ultraviolet rays, so that the difference in the influence of the ultraviolet rays can be reduced. As shown in FIG. 2, if the division planned line irradiated with the pulse laser beam of the first condition and the planned division line irradiated with the pulse laser beam of the second condition are both continuous, they are close. Two light emitting devices in position can be targeted for luminance measurement.

  In the embodiment described above, two light emitting devices are targets for luminance measurement, but three or more light emitting devices may be targets for luminance measurement. For example, when three light-emitting devices are targeted, a pulse laser beam is irradiated to two adjacent first division planned lines under the first condition, the second condition, and the third condition. And irradiating a pulse laser beam to two adjacent second division lines adjacent to each other under the first condition, the second condition, and the third condition, Six modified layers may be formed on each of the second division lines. Even when three or more light emitting devices are to be subject to luminance measurement, if the division lines to be irradiated with the pulse laser beam of each condition are continuous, the light emitting devices at closer positions are subject to luminance measurement. can do.

1: Sapphire substrate C (C1, C2): Sapphire chip D (D1, D2): Light emitting device L1 (L12, L13, L14, L15): First division planned line L2 (L23, L24, L25, L26): Second division line T: Tape F: Ring frame

Claims (1)

A first division line and a second division inside a sapphire substrate having a light emitting device defined on the surface by the first division line and a second division line intersecting the first division line. A modified layer is formed inside the sapphire substrate by focusing the pulsed laser beam having the first wavelength that passes through the sapphire substrate along a predetermined line, and an external force is applied to the sapphire substrate to make the sapphire substrate the first. The second condition of the wavelength transmitted through the sapphire substrate along the first planned division line and the second planned division line inside the sapphire substrate when divided along the planned division line and the second planned division line By condensing the pulsed laser beam, a modified layer is formed inside the sapphire substrate, and external force is applied to the sapphire substrate to place the sapphire substrate first. In the case of using the pulse laser beam of the first condition and the case of using the pulse laser beam of the second condition in comparison with the case of dividing along the division planned line and the second scheduled line of And an inspection method for inspecting a difference in luminance reduction of each light emitting device,
Before dividing the sapphire substrate, measuring the luminance of each light emitting device to obtain the luminance before division;
A step of condensing the pulse laser beam of the first condition along at least two adjacent lines to be divided to form a modified layer;
A step of condensing the pulse laser beam of the first condition along at least two adjacent lines to be divided to form a modified layer;
Forming a modified layer by condensing the pulse laser beam of the second condition along at least two adjacent lines to be divided where the pulse laser beam of the first condition is not condensed And a process of
Forming a modified layer by focusing the pulse laser beam of the second condition along at least two adjacent lines to be divided where the pulse laser beam of the first condition is not focused And a process of
A step of applying an external force to the sapphire substrate to divide the sapphire substrate along the first division line and the second division line to form a plurality of sapphire chips;
Among the sapphire chips, a first division line on which the pulse laser beam of the first condition is condensed and a second division line on which the pulse laser beam of the first condition is condensed are surrounded. Measuring the luminance of the light emitting device formed on the sapphire chip that has been obtained to obtain the luminance after division by the pulse laser beam of the first condition;
Of the sapphire chip, the first division line on which the pulse laser beam of the second condition is condensed and the second division line on which the pulse laser beam of the second condition is condensed Measuring the luminance of the light emitting device formed on the sapphire chip surrounded by the step, and obtaining the luminance after division by the pulse laser beam of the second condition;
When using the pulse laser beam of the first condition by comparing the luminance before the division with the pulse laser beam under the first condition and the luminance after the division with the pulse laser beam under the second condition And a step of inspecting a difference in luminance reduction of each of the light emitting devices when the pulse laser beam of the second condition is used.

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