End surface film forming method of laser diode bar

Abstract

The end surface film forming method of the laser diode bar of the present invention alternately arranges a plurality of laser diode bars and a plurality of dummy bars at a protrusion provided on the upper surface of the plate in a manner of sandwiching an opening of the plate, the protrusion is used as a reference position, the plurality of laser diode bars and the plurality of dummy bars are neatly arranged, and the end surfaces of the plurality of laser diode bars protrude upward relative to the plurality of dummy bars. Then, an insulating film is formed on the portion of the plurality of laser diode bars that protrudes relative to the plurality of dummy bars.

Description

Technical Field

[0001] The present disclosure relates to a method for forming a film on an end face of a laser diode bar. Background Art

[0002] Patent Document 1 states that in order to obtain a desired reflectivity in optical semiconductor elements such as laser diodes, it is necessary to provide a facet coating, but as electronic components become smaller, the processing is more delicate and it is not easy to perform coating processing while maintaining the electronic components in an optimal state.

[0003] After the semiconductor substrate wafer is divided into laser diode bars, the bars are arranged in a straight line. First, the technology of dividing the semiconductor substrate wafer into functional element chips includes the steps of wafer pasting, dividing, and expanding.

[0004] In "wafer pasting", the wafer is pasted to the adhesive sheet. The adhesive sheet also holds the separated chips. Therefore, the adhesive sheet is selected by studying the contamination of the chip pasting surface caused by the sheet, the impact on the separation quality, whether the chip can be held and easily picked up, etc.

[0005] In "splitting", first, when the split cross section does not require smoothness, a scribing (ruling) line is introduced on the semiconductor substrate along the line to be split with a diamond tool, thereby forming microcracks in the direction of the scribing line. Next, stress is applied to the substrate to open the microcracks, aggravate the cracking, and separate the substrate. The scribing line is not introduced to the entire line to be split, but the starting point and end point of the scribing line are slightly inside the substrate end, thereby preventing the cutting caused by the contact between the diamond tool and the substrate end. This scribing method can better suppress the generation of cracks than the splitting using a rotating blade or laser processing, and the strength of the split chip becomes higher, so it is particularly effective in the case of brittle substrate materials. In the case where the split cross section requires smoothness, such as the end face of a laser diode, a scribing line is introduced on one or both sides of the semiconductor substrate end along the line to be split with a diamond tool, thereby forming microcracks in the direction of the scribing line. The semiconductor substrate has a cleavage plane that is easy to separate, so the cleavage plane direction needs to be parallel to the scribing line. If stress is applied in the direction of the opening of the micro scratches formed by scribing, the micro scratches grow along the cleavage plane to form a cleavage plane with atomic-level smoothness. As a result, the semiconductor substrate is divided into strip-shaped laser diode bars for arranging LD chips with cleavage planes. The interval between the laser diode bars held by the separated adhesive sheet and the adjacent bars is narrow, and they will contact in the case of cleavage separation. In order to pick up the bars in the subsequent process, the bar interval needs to be widened, so the next "expansion" is implemented.

[0006] In "expansion", the adhesive sheet is pulled and stretched. If the characteristics of the adhesive sheet used for separation are not suitable for the subsequent process, there is a case where the expansion process is performed by replacing it with another sheet for expansion. Here, an example of forming a laser diode bar is described.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-123374

[0008] For example, when an insulating film is formed on the cleavage surface of the laser diode end face to control the reflectivity, heat dissipation and device characteristics can be improved by controlling the insulating film material that spreads to the front and back sides of the strip. In terms of controlling the spread of the insulating film, in addition to the high precision of the dummy strip width, the stability of the reference surface of the jig for arranging the strips is also important. However, if the jig is worn out due to cleaning or other reasons, there is a problem that the reference surface of the jig retreats and the relative position of the laser diode strip and the dummy strip changes. Summary of the invention

[0009] The present disclosure is made to solve the above-mentioned problems, and an object of the present disclosure is to provide a method for forming a film on an end surface of a laser diode bar that can suppress a change in the relative position of the laser diode bar and the dummy bar.

[0010] The end face film forming method of the laser diode bar disclosed in the present application comprises: alternately arranging a plurality of laser diode bars and a plurality of dummy bars at a protrusion provided on the upper surface of the plate in a manner separated by an opening of the plate, so that the end faces of the plurality of laser diode bars protrude upward relative to the plurality of dummy bars, and forming an insulating film on the portion of the plurality of laser diode bars that protrudes relative to the plurality of dummy bars.

[0011] Other features of the present disclosure will be set forth below.

[0012] According to this disclosure, by placing the laser diode bar and the dummy bar on the upper end of the protrusion or the inclined surface, it is possible to suppress the change in the relative position of the laser diode bar and the dummy bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a plan view of the plate according to Embodiment 1.

[0014] Figure 2 This is a diagram showing how the laser diode bars and the dummy bars are aligned.

[0015] Figure 3 It is a cross-sectional view of the structure before film formation.

[0016] Figure 4 This is a side view of the laser diode bar and the dummy bar after film formation.

[0017] Figure 5It is a diagram showing a method of forming a film on the end face of a laser diode bar according to a comparative example.

[0018] Figure 6 It is a diagram showing a method of forming a film on the end face of a laser diode bar according to a comparative example.

[0019] Figure 7 It is a diagram showing a method of forming a film on the end face of a laser diode bar according to a comparative example.

[0020] Figure 8 This is a cross-sectional view of a plate etc. according to the second embodiment. DETAILED DESCRIPTION

[0021] The end surface film forming method of the laser diode bar according to the embodiment will be described with reference to the drawings. The same reference numerals are given to the same or corresponding components, and duplicate descriptions may be omitted.

[0022] Implementation method 1.

[0023] Figure 1 It is a top view of the plate 10 of Embodiment 1. An opening 10a is formed in the plate 10. A protrusion 10b is provided on the upper surface 10c of the plate 10 in a manner across the opening 10a. The protrusion 10b is a portion extending higher than the upper surface 10c in the positive z direction. According to one example, the protrusion 10b is provided in a straight line to the left and right of the opening 10a of 10 when viewed from above. According to other examples, the protrusion is provided along the opening 10a at a position away from the opening 10a. The stopper 12 is fixed to the plate 10 to prevent the laser diode bar and the dummy bar placed on the protrusion 10b from tipping over in the negative y direction.

[0024] In the end face film forming method of the laser diode bar of the first embodiment, first, a plurality of laser diode bars and a plurality of dummy bars are alternately arranged on the protrusion 10b. According to one example, after the bar is lifted up with a needle through the adhesive sheet and the bar is peeled off from the adhesive sheet, the bar is moved to a jig for arranging the bars in an orderly manner using tweezers or a suction chuck. This process is called bar picking. Afterwards, as Figure 2 As shown, the laser diode bar 20 and the dummy bar 30 are arranged neatly on the protrusion 10b. The material of the laser diode bar 20 is, for example, a compound semiconductor. According to one example, the functional element is formed in a regular pattern by performing groove processing on the surface of the laser diode bar 20 in a previous process or stacking different types of materials.

[0025] Figure 3 1 is a diagram showing that the laser diode bar 20 and the dummy bar 30 are placed on the protrusion 10b. For the sake of convenience, the dummy bar 30 is shown only in outline. The plate 10 is set on the lower fixture 40. When the laser diode bar 20 and the dummy bar 30 are arranged on the protrusion 10b, the end face 20a of the laser diode bar 20 protrudes upward relative to the dummy bar 30. Figure 3 As shown, the end face 20b of the laser diode bar 20 and the bottom face of the dummy bar 30 are in contact with the protrusion 10b and are at the same height. According to one example, the end face 20a is the front end face, and the end face 20b is the rear end face. Figure 3 It can be seen that the plurality of dummy bars 30 are longer in the lateral direction than the plurality of laser diode bars 20 .

[0026] Figure 4 2 is a diagram showing the height of the laser diode bar 20 and the dummy bar. If a plurality of laser diode bars 20 and a plurality of dummy bars 30 are alternately arranged on the protrusion 10b, the end faces 20a of the plurality of laser diode bars 20 protrude upward relative to the plurality of dummy bars 30. Figure 4 As shown, the end faces 20b of the laser diode bars 20 and the bottom faces of the dummy bars 30 are in contact with the protrusion 10b and are at the same height. In this way, the laser diode bars 20 and the dummy bars 30 are arranged in order on the protrusion 10b.

[0027] Next, an insulating film is formed on the portions of the laser diode bars 20 that protrude relative to the dummy bars 30. The insulating film is formed, for example, to control the reflectivity of the laser diode. Figure 4 The middle figure shows that the insulating film 22 is formed on the end face 20 a and the front and back surfaces of the laser diode bar 20 .

[0028] Figures 5 to 7 FIG. 1 is a diagram showing a method for forming a film on the end face of a laser diode bar according to a comparative example. Figure 5 1 shows that the laser diode bar 20 and the dummy bar 30 are placed on the upper surface of the board 10. In this way, if the laser diode bar 20 and the dummy bar 30 are placed on the flat surface of the board 10, the flat surface will be worn out due to repeated use of the board. Figure 6 , 7 is a diagram showing a plate 10 with loss. If the upper surface of the plate 10 is lost, the position of the laterally short laser diode bar 20 is lowered, while the position of the laterally long dummy bar 30 remains almost unchanged. As a result, the relative positions of the laser diode bar 20 and the dummy bar 30 are shifted. Figure 7 As shown, if the loss of the upper surface of the plate 10 increases, the position of the end face 20a of the laser diode bar 20 drops to a position below the upper end of the dummy bar 30, and the Figure 4 The insulating film 22 is shown.

[0029] In contrast, in Embodiment 1, since a plurality of laser diode bars 20 and dummy bars 30 are placed on the protrusion 10b, the reference position of all bars is the protrusion 10b. Since the protrusion 10b becomes the reference position of the bar, even if the loss of the plate 10 increases, the reference can be guaranteed as long as the protrusion 10b exists. Therefore, the change in the relative position of the laser diode bar 20 and the dummy bar 30 can be suppressed. In addition, in order to improve the loss resistance, the shape of the protrusion can be changed from a rectangular shape to a rounded shape, or the length of the protrusion in the x direction can be adjusted.

[0030] The modified examples, correction examples, or alternatives described in Embodiment 1 can be applied to the end surface film forming method of the laser diode bar in the following embodiments. The end surface film forming method of the laser diode bar in the following embodiments will be mainly described with respect to the differences from Embodiment 1.

[0031] Implementation method 2.

[0032] exist Figure 8 The plate 10 and the lower jig 40 used in the end face film forming method of the laser diode bar of the second embodiment are shown. The upper surface of the plate 10 has inclined surfaces 10g and 10h whose height increases as it approaches the opening 10a. The inclined surfaces 10g and 10h are surfaces extending in the positive y direction. According to an example, the plate 10 is two plate materials placed on the lower jig 40 having the inclined surfaces 40a and 40b. For example, the two plate materials can be fixed to the lower jig 40 by any method. In this example, the thickness of the plate 10 is uniform, and the plate 10 is placed on the inclined surfaces 40a and 40b, thereby providing the plate 10 with the inclined surfaces 10g and 10h. According to other examples, the upper surface of the lower jig 40 may not be an inclined surface but a flat surface. In this case, the inclined surfaces 10g and 10h are provided by forming the plate 10 to be thicker as it approaches the opening 10a.

[0033] In the end surface film forming method of the laser diode bar of the second embodiment, the plurality of laser diode bars 20 and the plurality of dummy bars 30 are alternately arranged at the highest portions of the inclined surfaces 10g and 10h. As a result, the end surfaces 20a of the plurality of laser diode bars 20 protrude upward relative to the plurality of dummy bars 30. In addition, the end surfaces 20b of the plurality of laser diode bars 20 and the lower ends of the plurality of dummy bars 30 are in contact with the highest portions of the inclined surfaces 10g and 10h.

[0034] Next, an insulating film is formed on the portions of the laser diode bars 20 that protrude relative to the dummy bars 30. Figure 4Insulating film 22 is shown. In this embodiment, the highest edge portion of plate 10 becomes the reference position of multiple laser diode bars 20 and multiple dummy bars 30. Even if the loss of plate 10 increases, this edge portion continues to be the reference position, so that the change in the relative position of the laser diode bar and the dummy bar can be suppressed. In addition, the inclination angle of inclined surfaces 10g and 10h can be adjusted so that the edge portion is durable against loss.

[0035] Description of Reference Numerals

[0036] 10...plate; 10a...opening; 10b...protrusion; 10c...upper surface; 20...laser diode bar; 30...dummy bar; 10g, 10h...inclined surfaces.

Claims

1. A method for forming a film on the end face of a laser diode bar, characterized in that: have: Alternately arranging a plurality of laser diode bars and a plurality of dummy bars at a protrusion provided on the upper surface of the plate in a manner of sandwiching the opening of the plate, so that end surfaces of the plurality of laser diode bars protrude upward relative to the plurality of dummy bars; and An insulating film is formed on portions of the plurality of laser diode bars that protrude relative to the plurality of dummy bars.

2. The method for forming a film on the end face of a laser diode bar according to claim 1, characterized in that: The protrusions are provided linearly on the left and right of the opening of the plate in a plan view.

3. A method for forming a film on the end face of a laser diode bar, characterized in that: have: The upper surface of the plate having the opening is an inclined surface whose height increases toward the opening, and a plurality of laser diode bars and a plurality of dummy bars are alternately arranged at a portion of the inclined surface with the highest height, so that end surfaces of the plurality of laser diode bars protrude upward relative to the plurality of dummy bars; and An insulating film is formed on portions of the plurality of laser diode bars that protrude relative to the plurality of dummy bars.

4. The method for forming a film on the end face of a laser diode bar according to claim 3, characterized in that: The plates are two sheets placed on a lower fixture with an inclined surface.

5. The method for forming a film on an end face of a laser diode bar according to any one of claims 1 to 4, characterized in that: The plurality of dummy bars are laterally longer than the plurality of laser diode bars.

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