CN207282518U - A kind of arc line shaped N electrode and light emitting diode (LED) chip with vertical structure - Google Patents

Abstract

The utility model discloses an arc-shaped N electrode, which comprises an insertion finger and a welding pad; the welding pad is rectangular; the insertion finger is composed of a central area insertion finger and an edge polygon insertion finger; the edge polygon insertion finger is simultaneously It is a left-right symmetrical and up-and-down symmetrical structure; the central area insert finger is composed of a vertical insert finger and an arc-shaped insert finger; the central area insert finger is connected with a pad to form an arc-shaped insert finger, The insert fingers are located inside the edge polygon insert fingers, and the edge polygon insert fingers are connected to the long side of the top of the pad and connected to the bottom of the vertical or arc-shaped insert fingers. The arc-shaped N electrode of the utility model greatly improves the problems of uneven current distribution and serious light absorption of traditional rice-shaped and cross-shaped N electrodes. The utility model also discloses a vertical structure LED chip, including the arc-shaped N electrode, which overcomes the shortcoming of current crowding of the horizontal structure LED chip, and greatly improves the uniformity of current transmission in the chip.

Description

An arc-shaped N electrode and a vertical structure LED chip

technical field

The utility model relates to the field of LED manufacturing, in particular to an arc-shaped N electrode and a vertical LED chip.

Background technique

With the gradual application of LEDs in the field of lighting, the market has higher and higher requirements for the light efficiency of white LEDs. GaN-based vertical structure LEDs have good heat dissipation capabilities and can withstand large current injections. Such a vertical structure LED chip can be equivalent to several The conversion cost is only a fraction of the formal structure chip. Therefore, GaN-based vertical structure LEDs are the direction of the market and an inevitable trend in the development of semiconductor lighting. Compared with the traditional planar structure LED, the vertical structure LED has many advantages: the two electrodes of the vertical structure LED are on both sides of the LED, the current almost all flows vertically through the epitaxial layer, there is no lateral flow of current, the current distribution is uniform, and the resulting The heat is reduced; the sapphire substrate with poor thermal conductivity is removed by bonding and stripping, and replaced with a substrate with good electrical conductivity and high thermal conductivity, which can effectively dissipate heat; the n-GaN layer is the light-emitting surface, which has A certain thickness is convenient for making surface microstructures to improve light extraction efficiency. In short, compared with the traditional planar structure, the vertical structure has obvious advantages in light extraction and heat dissipation.

With the rapid development of semiconductor technology, the internal quantum efficiency of LED can reach more than 90%, while the improvement of external quantum efficiency is not significant, which is affected by many factors, such as LED structure, electrode shape, electrode material, current spreading layer thickness, etc. , has become the dominant factor restricting the improvement of LED luminous efficiency. Compared with other methods of improving LED brightness (such as high reflective film, substrate peeling, surface roughening, etc.), the easiest to operate is to optimize the electrode shape of the chip, which has a great influence on the light output. If the current Insufficient and uneven diffusion will lead to a decrease in light output, and the luminous efficiency of the LED can be improved by rationally designing the shape of the electrode.

In theory, the farther away from the electrode, the smaller the current and the lower the brightness. For the existing vertical electrode structure technology, it is traditionally believed that the I-V performance of LED chips with electrode shapes in the shape of "ten" or "m" is the best. However, the "ten" or "m"-shaped electrodes are in the center of the chip. Since the electrodes are relatively concentrated, the current is also relatively concentrated, which leads to uneven distribution of LED current, especially to the edge of the table. The current distribution is extremely uneven, making The brightness of the edge part is very small. Around the central circular electrode and near the fingers, the current is crowded, and at the edge of the chip, the current is small. The current trend is getting smaller and smaller from the middle to the edge, and the brightness is getting weaker and weaker.

Generally, when making vertical structure LEDs, metal silver is usually used as the reflective layer, but due to the easy diffusion of Ag, a current blocking layer (barrier) will be made to wrap the reflective layer, and there will be about 5 μm to 10 μm around each chip. Reflective layer (as shown in Figure 1), in Figure 1, the reflective layer 20 is surrounded by the current blocking layer 10, because the reflective layer 20 is used to reflect light, and the blocking layer 10 is extremely weak due to material limitations, causing this area to reflect light There will be a large part of the loss, and after the general "cross" or "m" shaped N electrode is evaporated, the current distribution in this area is not uniform, and the contribution to light emission is also greatly reduced.

Utility model content

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this utility model is to provide an arc-shaped N electrode, which greatly improves the problems of uneven current distribution and serious light absorption of traditional rice-shaped and cross-shaped N electrodes. .

Another object of the present invention is to provide a vertical structure LED chip, which overcomes the shortcoming of current crowding of the horizontal structure LED chip, and greatly improves the uniformity of current transmission in the chip.

The purpose of this utility model is achieved through the following technical solutions:

An arc-shaped N electrode, including an insert finger and a pad; the pad is rectangular; the insert finger is composed of a central area insert finger and an edge polygon insert finger;

The edge polygonal insert finger is a left-right symmetrical structure and an up-down symmetrical structure at the same time;

The pad and the central area finger are located inside the edge polygonal finger, and both have left-right symmetrical structures, and the axis of symmetry is the left-right axis of symmetry of the edge polygonal finger; the top of the central area finger is in contact with the pad, and The long side of the pad is vertical, and the bottom end is in contact with the edge polygonal finger;

The central area fingers include arc-shaped fingers and vertical fingers; the vertical fingers are located on the left and right symmetry axes of the edge polygon fingers.

The center region insert finger is composed of two vertical insert fingers and a ring insert finger, and the ring insert finger is symmetrical about the left-right symmetry axis of the edge polygon insert finger; the first vertical insert finger connects the ring insert finger and the pad ; The second vertical finger connects the ring finger and the edge polygon finger.

The radius range of the ring finger is 150um-250um.

The central region insert finger is composed of a vertical insert finger and a curved insert finger; the vertical insert finger is connected to the curved insert finger and the pad; the curved insert finger is connected to the edge polygon insert finger; the curved insert finger is a parabola opening downwards.

The equation of the parabola is y ² =kx, where 0.5<k<2.

The width of the insert fingers ranges from 4 μm to 11 μm; the length of the long side of the pad ranges from 50 μm to 100 μm, and the length of the short side ranges from 30 μm to 80 μm.

A vertical structure LED chip, including the arc-shaped N electrode.

The vertical structure LED chip includes a p-electrode layer, a reflective layer, a current blocking layer, an epitaxial layer, and an arc-shaped N electrode from bottom to top, and the shape of the current blocking layer is similar to that of the arc-shaped N electrode. The size of the flow blocking layer is 18%-25% larger than the size of the arc-shaped N electrode; the epitaxial layer includes P-GaN, quantum well and N-GaN sequentially from bottom to top.

The p-electrode layer sequentially includes a seed layer, a bonding layer, a doped silicon substrate layer, and an anti-oxidation layer from bottom to top.

The preparation method of the current blocking layer is as follows:

Use PECVD to first grow a layer of SiO ₂ on the surface of P-GaN, and then evenly layer a layer of positive photoresist, use a positive photolithography plate to expose the photoresist corresponding to the vertical projection area of the arc-shaped N electrode pattern, and use BOE The solution washes away the SiO ₂ in the exposed area, uses the photoresist as a mask, and uses ICP to perform O ₂ plasma surface bombardment micro-treatment on the GaN in the exposed area, and then uses a fully automatic stripper to remove the remaining photoresist. A series of metal layers such as mirror and protective layer are grown on the surface of the mirror, and the mirror and P-GaN form a micro-processed area to form a Schottky contact, form a high barrier area, and form a current blocking layer.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

(1) The arc-shaped N electrode of the utility model greatly improves the problems of uneven current distribution and serious light absorption of traditional rice-shaped and cross-shaped N electrodes. The arc-shaped central area simplifies the complexity of the P-shaped and cross-shaped patterns, and the main part of the central area of the electrode is placed on the edge, which improves the light absorption problem of the electrode; at the same time, the polygonal insert fingers on the edge solve the problem of cross-shaped or P-shaped electrode edges Part of the current is weaker and less problematic to distribute.

(2) The vertical structure LED chip of the present invention overcomes the shortcoming of current crowding of the horizontal structure LED chip, and greatly improves the uniformity of current transmission in the chip.

(3) The utility model utilizes the method of ICP etching a part of p-type GaN to contact to form a high-resistance region of Schott barrier, and then to form a current blocking layer. The method of forming a current blocking layer in the vertical projection area corresponding to the N electrode replaces the method of depositing _SiO2 directly under the N electrode as a current blocking layer, so that the current can be more fully utilized and more fully diffused to the entire chip.

(4) The utility model adopts a metal electrode protective layer to replace SiO ₂ to prevent the diffusion and oxidation of the Ag reflector, and the ability to reflect light is greatly enhanced, reducing the influence of the protective layer on the reflection efficiency of the Ag reflector.

Description of drawings

FIG. 1 is a schematic structural diagram of a reflective layer surrounded by a P electrode layer in the prior art.

FIG. 2 is a schematic diagram of an arc-shaped N electrode in Embodiment 1 of the present invention.

3 is a schematic cross-sectional view of a vertical structure LED chip according to Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of an arc-shaped N electrode in Embodiment 2 of the present invention.

Detailed ways

The utility model will be described in further detail below in conjunction with the examples, but the implementation of the utility model is not limited thereto.

Example 1

As shown in Figure 2, the arc-shaped N electrode of this embodiment includes an insertion finger and a pad 11; the pad is rectangular; the insertion finger is composed of a central area insertion finger and an edge polygonal insertion finger 12; The edge polygonal finger 12 is a square; the pad and the center region finger are located inside the edge polygon finger, both of which are left-right symmetrical structures, and the axis of symmetry is the left-right axis of symmetry of the edge polygon finger; the top of the center region finger It is in contact with the pad, and is perpendicular to the long side of the pad, and the bottom end is in contact with the edge polygonal finger.

The central area fingers are composed of a first vertical finger 13 , a second vertical finger 15 and a ring-shaped finger 14 . The circular ring finger is symmetrical about the left-right symmetry axis of the edge polygon finger; the first vertical plug and the second vertical finger are located on the left-right symmetry axis of the edge polygon finger; the first vertical finger connects the ring finger and the pad ; The second vertical finger connects the ring finger and the edge polygon finger.

The width range of the insert finger in this embodiment may be 4 μm to 11 μm; the length of the long side of the pad is 50 μm-100 μm, and the length of the short side is 30 um-80 um; the radius range of the circular insert finger 150um-250um; the material of the N electrode is one or more of Al, Ti, Au, Ni or similar metals.

As shown in Figure 3, the LED chip with a vertical structure in this embodiment includes a p-electrode protective layer 100, a reflective layer 110, a current blocking layer 120, an epitaxial layer 130, and an arc-shaped N electrode 140 from bottom to top. The shape of the layer 120 is similar to that of the arc-shaped N-electrode 140 , and the size of the flow-blocking layer 120 is 18%-25% larger than that of the arc-shaped N-electrode 140 . Wherein, the epitaxial layer includes P-GaN 131 , quantum well 132 and N-GaN 133 sequentially from bottom to top. The p-electrode protection layer sequentially includes a seed layer, a bonding layer, a doped silicon substrate layer, and an anti-oxidation layer from bottom to top.

The preparation method of the current blocking layer of the present embodiment is as follows:

Use PECVD to first grow a layer of SiO ₂ on the surface of P-GaN, and then evenly layer a layer of positive photoresist, use a positive photoresist plate to expose the photoresist corresponding to the vertical projection area of the arc-shaped N electrode pattern, and use BOE The solution washes away the SiO ₂ in the exposed area, uses the photoresist as a mask, and uses ICP to perform O ₂ plasma surface bombardment micro-treatment on the GaN in the exposed area, and then uses a fully automatic stripper to remove the remaining photoresist. A series of metal layers such as mirror and protective layer are grown on the surface of the mirror, and the mirror and P-GaN form a micro-processed area to form a Schottky contact, form a high barrier area, and form a current blocking layer.

In this embodiment, the polygonal edge fingers can make the current distribution on the N-GaN surface more uniform, improve light emission and heat generation, and increase the luminous efficiency of the LED chip. Directly above the protective layer will not reduce the reflection efficiency of more mirrors.

Example 2

As shown in Figure 4, the arc-shaped N electrode of this embodiment includes an insertion finger and a pad 11; the pad is rectangular; the insertion finger is composed of a central area insertion finger and an edge polygonal insertion finger 12; The edge polygonal finger 12 is a square; the pad and the center region finger are located inside the edge polygon finger, both of which are left-right symmetrical structures, and the axis of symmetry is the left-right axis of symmetry of the edge polygon finger; the top of the center region finger It is in contact with the pad, and is perpendicular to the long side of the pad, and the bottom end is in contact with the edge polygonal finger.

The central area finger is composed of a vertical finger 23 and a parabolic finger 24 . The vertical fingers are located on the left and right symmetry axes of the edge polygon fingers, and the vertical fingers are connected to the parabolic fingers and the pads; the parabolic fingers are connected to the edge polygon fingers.

The width of the insert finger in this embodiment can range from 4 μm to 11 μm; the length of the long side of the pad ranges from 50 μm to 100 μm, and the length of the short side ranges from 30 um to 80 um; the graph of the wine glass-shaped insert finger is a curve is a parabola y ² =kx (0.5<k<2); the material of the N electrode is one or more of Al, Ti, Au, Ni or similar metals.

The vertical structure LED chip of this embodiment comprises a p-electrode protective layer, a reflective layer, a current blocking layer, an epitaxial layer, and an arc-shaped N electrode from bottom to top, and the shape of the current blocking layer is formed by the shape of the wine glass-shaped N electrode. Similar to the figure, the size of the flow blocking layer is 18%-25% larger than that of the wine glass-shaped N-electrode. Wherein, the epitaxial layer includes P-GaN, quantum well and N-GaN sequentially from bottom to top. The p-electrode protection layer sequentially includes a seed layer, a bonding layer, a doped silicon substrate layer, and an anti-oxidation layer from bottom to top.

The preparation method of the current blocking layer of the present embodiment is as follows:

Use PECVD to first grow a layer of SiO ₂ on the surface of P-GaN, and then evenly layer a layer of positive photoresist, use a positive photolithography plate to expose the photoresist corresponding to the vertical projection area of the arc-shaped N electrode pattern, and use BOE The solution washes away the SiO ₂ in the exposed area, uses the photoresist as a mask, and uses ICP to perform O ₂ plasma surface bombardment micro-treatment on the GaN in the exposed area, and then uses a fully automatic stripper to remove the remaining photoresist. A series of metal layers such as mirror and protective layer are grown on the surface of the mirror, and the mirror and P-GaN form a micro-processed area to form a Schottky contact, form a high barrier area, and form a current blocking layer.

In this embodiment, the polygonal edge fingers can make the current distribution more uniform on the N-GaN surface, improve light emission and heat generation, and increase the luminous efficiency of the LED chip. In addition, since the parabolic finger is formed on the electrode protection layer with strong reflection directly above, without degrading the reflection efficiency of more mirrors.

The above-mentioned embodiment is a preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the described embodiment, and any other changes, modifications, modifications, Substitution, combination, and simplification should all be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (9)

1. An arc-shaped N electrode, characterized in that, includes an insert finger and a pad; the pad is rectangular; the insert finger is composed of a center region insert finger and an edge polygon insert finger; The edge polygonal insert finger is a left-right symmetrical structure and an up-down symmetrical structure at the same time; The pad and the central area finger are located inside the edge polygonal finger, and both have left-right symmetrical structures, and the axis of symmetry is the left-right axis of symmetry of the edge polygonal finger; the top of the central area finger is in contact with the pad, and The long side of the pad is vertical, and the bottom end is in contact with the edge polygonal finger; The central area fingers include arc-shaped fingers and vertical fingers; the vertical fingers are located on the left and right symmetry axes of the edge polygon fingers. 2. The arc-shaped N-electrode according to claim 1, characterized in that, the central area finger is composed of two vertical fingers and a ring finger, and the ring finger is about the edge of the polygon finger. The left and right symmetry axes are symmetrical; the first vertical finger connects the ring finger and the pad; the second vertical finger connects the ring finger and the edge polygon finger. 3. The arc-shaped N-electrode according to claim 2, characterized in that, the radius range of the ring finger is 150um-250um. 4. The arc-shaped N electrode according to claim 1, characterized in that, the central area finger is composed of a vertical finger and a curved finger; the vertical finger connects the curved finger and the pad ; The curved finger is in contact with the edge polygonal finger; the curved finger is a parabola with an opening downward. 5 . The arc-shaped N electrode according to claim 4 , wherein the equation of the parabola is y ² =kx, where 0.5<k<2. 6. The arc-shaped N electrode according to claim 1, characterized in that, the width range of the insertion finger is 4 μm-11 μm; the length of the long side of the pad is 50 μm-100 μm, and the length of the short side is 50 μm-100 μm. The range is 30um-80um. 7. A LED chip with a vertical structure, characterized in that it comprises the arc-shaped N-electrode according to any one of claims 1-6. 8. The vertical structure LED chip according to claim 7, characterized in that it comprises a p-electrode layer, a reflective layer, a current blocking layer, an epitaxial layer, and an arc-shaped N electrode from bottom to top, and the shape of the current blocking layer is The shape of the curved N electrode is similar to that of the curved N electrode, and the size of the flow blocking layer is 18% to 25% larger than that of the curved N electrode; the epitaxial layer includes P-GaN, quantum wells and N-GaN. 9. The vertical structure LED chip according to claim 8, wherein the p-electrode layer comprises a seed layer, a bonding layer, a doped silicon substrate layer, and an anti-oxidation layer from bottom to top.