CN110571314B - Reverse voltage-stabilizing LED chip and preparation method thereof - Google Patents

Abstract

The invention discloses a reverse voltage-stabilizing LED chip, which comprises: the device comprises a substrate, an epitaxial layer, a first etching channel, a first light-emitting structure and at least one second light-emitting structure; the epitaxial layer is arranged on the substrate and is divided into a first area and a second area through a first etching channel etched to the substrate; the first light-emitting structure is arranged in the first area; the second light-emitting structure is arranged in the second area; the first light-emitting structure and the second light-emitting structure are mutually connected in series; and the current transmission directions of the first light-emitting structure and the second light-emitting structure are opposite. According to the invention, the plurality of second light-emitting structures are connected in series, so that the reverse breakdown voltage can be increased to 3n V (n is the number of the second light-emitting structures), the safety and the reliability of the LED chip are greatly improved when reverse current exists, and the LED chip can be applied to a plurality of different use occasions.

Description

A reverse voltage stabilizing LED chip and its preparation method

Technical Field

The invention relates to the technical field of light emitting diodes, and in particular to a reverse voltage stabilizing LED chip and a preparation method thereof.

Background technique

LED, also known as light-emitting diode, is a type of semiconductor diode with unidirectional conductivity. When the reverse voltage applied to the LED chip does not exceed a certain range, the current passing through the diode is the reverse current formed by the drift movement of minority carriers. This reverse current is very small and the diode is in the cut-off state. This reverse current is also called reverse saturation current or leakage current. However, when the applied reverse voltage exceeds a certain value, the reverse current will suddenly increase. This phenomenon is called electrical breakdown. The critical voltage that causes electrical breakdown is called the diode reverse breakdown voltage. During electrical breakdown, the diode loses its unidirectional conductivity. If the diode does not overheat due to electrical breakdown, the unidirectional conductivity may not be permanently destroyed. After the applied voltage is removed, its performance can still be restored. Otherwise, the diode will completely lose its unidirectional conductivity and be permanently damaged. Therefore, when using the diode, avoid applying too high a reverse voltage to it.

Since reverse voltage rarely occurs in existing use cases, existing LED chips are often not designed with reverse protection circuits. One situation where reverse current often occurs is when testing whether the chip is leaking. Since the leakage of the LED chip cannot be distinguished by applying a forward voltage, the reverse voltage is used for testing; but in this test situation, since the forward voltage of the LED is usually less than 4V, the reverse test voltage only needs to be slightly greater than the forward voltage, so the industry stipulates that a 5V voltage is used, but this 5V voltage does not refer to the reverse breakdown voltage. Therefore, simply satisfying the requirement of no leakage under a 5V reverse voltage is far from sufficient to prove its safety, making most existing LED chips unable to be used in situations with large reverse currents, and having low safety.

Summary of the invention

The technical problem to be solved by the present invention is to provide a reverse voltage-stabilized LED chip, which has a high reverse breakdown voltage and can effectively prevent the reverse current from damaging the LED chip, thereby improving the reliability of the LED chip.

Another technical problem to be solved by the present invention is to provide a method for preparing a reverse voltage-stabilized LED chip.

In order to solve the above technical problems, the present invention provides a reverse voltage-stabilized LED chip, which comprises: a substrate, an epitaxial layer, a first etched path, a first light-emitting structure and at least one second light-emitting structure; the epitaxial layer is arranged on the substrate and is divided into a first region and a second region by etching the first etched path to the substrate;

The first light emitting structure is disposed in the first region; the second light emitting structure is disposed in the second region; the first light emitting structure and the second light emitting structure are connected in series; and current transmission directions of the first light emitting structure and the second light emitting structure are opposite.

As an improvement of the above technical solution, it also includes a first secondary electrode and a second secondary electrode;

The first light emitting structure includes a first electrode and a second electrode, and the second light emitting structure includes a third electrode and a fourth electrode;

The first electrode and the fourth electrode are electrically connected via the second secondary electrode spanning the first etched path;

The second electrode and the third electrode are electrically connected via the first secondary electrode straddling the first etched street.

As an improvement of the above technical solution, the second region is further provided with a second etching path and a third secondary electrode; the second etching path is etched to the substrate;

Adjacent second light emitting structures are separated by the second etched path and are electrically connected through the third secondary electrode.

As an improvement of the above technical solution, the area of the first region: the area of the second region is (2-5): (0.5-1.5).

As an improvement of the above technical solution, the second region is provided with 2 to 8 second light-emitting structures and 1 to 7 second etching tracks.

As an improvement of the above technical solution, the side walls of the first etching path and the second etching path have an inclined angle.

As an improvement of the above technical solution, the inclination angle is ≤60 degrees.

As an improvement of the above technical solution, the first light-emitting structure and the second light-emitting structure further include a current blocking layer, a current diffusion layer and a passivation layer.

As an improvement of the above technical solution, the first light-emitting structure and the second light-emitting structure are arranged in parallel.

Correspondingly, the present invention also discloses a method for preparing the above-mentioned reverse voltage-stabilized LED chip, which comprises:

(1) providing a substrate and forming an epitaxial layer on the substrate;

(2) forming a first exposed region and a second exposed region on the epitaxial layer;

(3) forming a first etching path;

(4) forming a first light-emitting structure and a second light-emitting structure;

(5) The first light-emitting structure and the second light-emitting structure are connected in series to obtain a finished reverse voltage-stabilized LED chip.

The implementation of the present invention has the following beneficial effects:

The LED chip of the present invention is designed with two light-emitting structures with opposite current transmission directions on the substrate surface - a first light-emitting structure and a second light-emitting structure; wherein, multiple second light-emitting structures are connected in series, which can increase the reverse breakdown voltage to 3nV (where n is the number of second light-emitting structures), greatly improving the safety and reliability of the LED chip when reverse current exists, so that the LED chip of the present invention can be applied to a variety of different usage scenarios.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a reverse voltage-stabilized LED chip according to an embodiment of the present invention;

Fig. 2 is a cross-sectional view taken along the A-A direction in Fig. 1;

Fig. 3 is a cross-sectional view taken along the B-B direction in Fig. 1;

Fig. 4 is a cross-sectional view taken along the C-C direction in Fig. 1;

FIG5 is a schematic structural diagram of a reverse voltage-stabilized LED chip in another embodiment of the present invention;

Fig. 6 is a cross-sectional view taken along the A-A direction in Fig. 5;

Fig. 7 is a cross-sectional view taken along the B-B direction in Fig. 5;

Fig. 8 is a cross-sectional view taken along the C-C direction in Fig. 5;

FIG. 9 is a flow chart of a method for preparing a reverse voltage-stabilized LED chip according to the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. It is hereby stated that the directional terms such as up, down, left, right, front, back, inside, outside, etc. that appear or will appear in the text of the present invention are only based on the accompanying drawings of the present invention, and are not specific limitations of the present invention.

Referring to Figures 1 to 4, this embodiment provides a reverse voltage-stabilized LED chip, which includes: a substrate 1, an epitaxial layer 2, a first etching path 3, a first light-emitting structure 4, and at least one second light-emitting structure 5. Among them, the epitaxial layer 2 is arranged on the substrate 1, and the first etching path 3 is arranged on the epitaxial layer 2; the epitaxial layer 2 is divided into a first area 21 and a second area 22 by etching the first etching path 3 to the substrate 1. The first light-emitting structure 4 is arranged in the first area 21, and the second light-emitting structure 5 is arranged in the second area 22. The first light-emitting structure 4 and the second light-emitting structure 5 are connected in series; and the current transmission directions of the two are opposite. The present invention designs two light-emitting structures on the LED chip, and the current transmission directions of the two are opposite, which is equivalent to adding an additional protection circuit to the LED chip structure to avoid chip damage caused by reverse voltage.

Specifically, referring to FIG. 2 , the epitaxial layer 2 includes a first semiconductor layer 23, an active layer 24, and a second semiconductor layer 25 from bottom to top; the present invention does not impose any special restrictions on the specific type of the epitaxial layer, and those skilled in the art can select it according to the specific type of LED chip. Specifically, in this embodiment, the epitaxial layer 2 is a GaN-type semiconductor layer, the first semiconductor layer 23 is an N-GaN layer, and the second semiconductor layer is a P-GaN layer.

Specifically, referring to FIG. 2 and FIG. 3 , in this embodiment, the first light emitting structure 4 includes a first electrode 41 and a second electrode 43, wherein the first electrode 41 is connected to the first semiconductor layer 23, and the second electrode 43 is connected to the second semiconductor layer 24. The second light emitting structure 5 includes a third electrode 51 and a fourth electrode 52, wherein the third electrode 51 is connected to the first semiconductor layer 23, and the fourth electrode 52 is connected to the second semiconductor layer 24. The first light emitting structure 4 and the second light emitting structure 5 are separated by a first etching path 3 etched to the substrate 1, so that the first electrode 41 and the third electrode 51, and the second electrode 42 and the fourth electrode 52 are insulated on the epitaxial layer 2.

Specifically, referring to FIG. 1 , FIG. 3 , and FIG. 4 ; in this embodiment, a first secondary electrode 6 and a second secondary electrode 7 are further included. The first secondary electrode 6 crosses the first etching path 3 and connects the first electrode 41 and the fourth electrode 52 ; the second secondary electrode 7 crosses the first etching path 3 and connects the second electrode 42 and the third electrode 51 ; through the connection between the first secondary electrode 6 and the second secondary electrode 7 , the first light emitting structure 4 and the second light emitting structure 5 are connected in series with each other; and the current transmission directions of the two are opposite.

Specifically, in the present invention, n second light-emitting structures 5 are provided on the surface of the LED chip, specifically, 2≤n≤8; the reverse breakdown voltage of the LED chip can be increased to 3n V by n second light-emitting structures. Preferably, 2≤n≤5; further preferably, n＝3. The present invention does not impose any special restrictions on the number of the second light-emitting structures 5, and those skilled in the art can select according to the specific application occasion.

Specifically, referring to FIG. 2 , in this embodiment, two second light-emitting structures 5 are provided on the surface of the LED chip; the second light-emitting structures 5 pass through the second etching path 8 that penetrates the substrate 1, so that different second light-emitting structures are not mutually conductive on the epitaxial layer 2. Furthermore, a third secondary electrode 9 is provided on the surface of the LED chip, which spans the second etching path 8 and connects the third electrode 51 of the adjacent second light-emitting structure 5 with the fourth electrode 52, so as to realize the mutual series connection of the adjacent second light-emitting structures 5.

It should be noted that although setting an opposite light-emitting structure on the surface of the LED chip can increase the reverse breakdown voltage of the LED chip and improve its safety. However, the reverse light-emitting structure will also occupy the surface area of the LED chip, resulting in a reduction in the light-emitting area and a decrease in the LED light efficiency. Therefore, in order to balance the light efficiency and the reverse voltage stabilization effect, it is necessary to control the area occupied by the two light-emitting structures. Specifically, in the present invention, the area of the first region 21: the area of the second region 22 is controlled to be (2~5): (0.5~1.5); wherein the first region 21 is used to form a first light-emitting structure 4, which is mainly used for emitting light under forward conduction; the second region 22 is used to form a second light-emitting structure 5, which is mainly used to increase the reverse breakdown voltage under reverse conduction. Controlling the ratio of the first region to the second region can effectively improve the brightness of the LED chip. Preferably, the area of the first region: the area of the second region is (2~5):1.

Furthermore, in order to improve the brightness of the LED chip, the first light-emitting structure and the second light-emitting structure are arranged in parallel to achieve full utilization of the surface area of the LED chip.

Furthermore, in order to improve the brightness of the LED chip, the side walls of the first etching path 3 and the second etching path 8 are provided with an inclined angle, which can improve the side light extraction efficiency of the LED chip and improve the brightness. Specifically, the inclined angle is ≤60 degrees, preferably 30 to 50 degrees.

In addition, referring to Figures 4 to 8, in another embodiment of the present invention, in order to improve the overall performance of the LED chip, the first light-emitting structure 4 and the second light-emitting structure 5 further include a current blocking layer 43/53, a transparent conductive layer 44/54, and a passivation layer 45/55. Among them, the current blocking layer 43/53 is arranged between the first electrode 41, the third electrode 51 and the second semiconductor layer 25, which can effectively prevent breakdown and current crowding when the current or chip area is too large. The transparent conductive layer 44/54 is arranged between the second semiconductor layer 25, the current blocking layer 43/53 and the first electrode 41, the third electrode 51, which can play a role in expanding the current distribution. The passivation layer 45/55 is arranged on the entire surface of the LED chip, and holes are provided in the first electrode, the second electrode, the third electrode, and the fourth electrode regions to expose the electrodes.

Correspondingly, referring to FIG. 9 , the present invention further discloses a method for preparing the above-mentioned reverse voltage-stabilized LED chip, which comprises the following steps:

S100: providing a substrate, and forming an epitaxial layer on the substrate;

Specifically, the substrate 1 may be made of sapphire, silicon carbide or silicon, or other semiconductor materials. Preferably, the present invention uses a sapphire substrate.

Specifically, the first semiconductor layer 23, the active layer 24 and the second semiconductor layer 25 are sequentially formed on the substrate by metal organic chemical vapor deposition (MOCVD) to obtain the epitaxial layer 2; but the method is not limited to the above method.

S200: forming a first exposed region and a second exposed region on the epitaxial layer;

Specifically, S200 includes:

S201: forming a first photoresist on the surface of the epitaxial layer;

Wherein, the first photoresist may be a positive photoresist or a negative photoresist;

S202: exposing the first photoresist to form a first exposure area;

Specifically, the pattern on the original film is transferred to the photosensitive plate through exposure via the light source, and then the photoresist in the exposed area or the unexposed area is removed.

Photolithography forms a first pattern photolithography area, forms a first light-emitting structure exposed area and a second light-emitting structure exposed area, and checks the positive and negative electrodes of the two light-emitting structures to ensure reverse arrangement;

S203: etching the first exposed area to form a first exposed area and a second exposed area;

Among them, dry etching can be used to etch the epitaxial layer. Dry etching can form good control over key dimensions and ensure uniformity, but is not limited to the above etching process.

S204: removing the first photoresist.

S300: forming a first etching path;

Specifically, step S300 includes:

S301: forming a second photoresist on the surface of the epitaxial layer;

S302: exposing the second photoresist to form a second exposure area;

S303: etching the second exposure area;

Specifically, the epitaxial layer may be etched by dry etching, which can form good control over key dimensions and ensure uniformity, but is not limited to the above etching process.

Specifically, in order to improve the connection stability between the first light-emitting structure 4 and the second light-emitting structure 5 in the present invention, the side wall of the first etching path 3 has a certain inclination angle. The first etching path 3 of this structure can also improve the side light extraction efficiency of the light-emitting structure and improve the light extraction efficiency of the chip. Preferably, the inclination angle is ≤60 degrees. When the angle is too large, the metal film is difficult to form and is prone to breakage during the subsequent evaporation of the secondary electrode. Preferably, the inclination angle is 30-50 degrees. This angle can ensure that the electrode is not broken during evaporation and at the same time greatly improve the light extraction efficiency of the chip.

Furthermore, in order to ensure the connection stability between the first light-emitting structure 4 and the second light-emitting structure 5, the width of the first etching path 3 is set to 10-20μm; if the width of the deep etching path is too narrow, the tilt angle will be too large and the wire will be easily broken; if the deep etching path is too wide, the light-emitting area will be reduced and the chip light extraction efficiency will be reduced. Preferably, the width of the first etching path 3 is set to 12-18μm; further preferably, it is 16μm. The first etching path 3 with this width can ensure that the LED chip has a high light extraction efficiency and ensure the connection stability between the first light-emitting structure 4 and the second light-emitting structure 5.

S304: removing the second photoresist.

S400: forming a first light-emitting structure and a second light-emitting structure;

Specifically, S400 includes:

S410: forming a current blocking layer on the surface of the epitaxial layer;

Specifically, S410 includes:

S411: depositing a current blocking layer;

Specifically, silicon dioxide can be selected as the current blocking layer, which has good light transmittance; but it is not limited to silicon dioxide.

S412: forming a third photoresist on the surface of the current blocking layer;

S413: exposing the third photoresist to form a third exposure area;

S414: etching the exposure area;

S415: removing the third photoresist; obtaining a finished current blocking layer.

Specifically, when designing the current blocking layer, a hole can be opened under the primary electrode to prevent the electrode from falling off due to silicon oxide. The periphery of the current blocking layer should be 5um larger than the primary electrode, so that it can play the role of current blocking without affecting the transmission of light in other places.

S420: forming a transparent conductive layer;

Specifically, S420 includes:

S421: depositing a transparent conductive layer;

Specifically, indium tin oxide can be used as the transparent conductive layer, but is not limited thereto;

S422: forming a fourth photoresist on the surface of the transparent conductive layer;

S423: exposing the fourth photoresist to form a fourth exposure area;

S424: etching the exposure area;

Specifically, wet etching is used to etch the transparent conductive layer. Specifically, a mixed solution of ferric chloride and hydrochloric acid is used to etch the transparent conductive layer, and the etching time is 150-220s. This etching time can not only fully etch the current diffusion layer, but also ensure that the overall thickness of the ITO layer is not greatly reduced, which affects the current expansion of the chip.

S425: removing the fourth photoresist to form a transparent conductive layer.

Specifically, when designing the transparent conductive layer, the transparent conductive layer is set to shrink by at least 2 μm according to the specific width of the second semiconductor layer; this can not only play a role in current diffusion, but also prevent the transparent conductive layer from contacting the side wall, causing leakage of the LED chip;

S430: forming a first electrode, a second electrode, a third electrode and a fourth electrode;

Specifically, S430 includes:

S431: forming a fifth photoresist on the surface of the epitaxial layer;

S432: exposing the fifth photoresist to form a fifth exposure area;

S433: performing electrode evaporation on the fifth exposure area;

The primary electrode is deposited by electron beam evaporation, thermal evaporation or magnetron sputtering, but is not limited thereto.

S444: tear off the gold and remove the fifth photoresist to obtain a first electrode, a second electrode, a third electrode and a fourth electrode.

S450: forming a passivation layer;

Specifically, S450 includes:

S451: depositing a passivation layer;

Specifically, metal organic chemical vapor deposition (MOCVD) is used to deposit the passivation layer. The material of the passivation layer is selected from silicon dioxide or silicon nitride, but is not limited thereto, preferably silicon dioxide. The thickness of the passivation layer is 80-500nm, preferably 100-300nm.

S452: forming a sixth photoresist;

S453: exposing the sixth photoresist to form a sixth exposure area;

Specifically, the sixth exposure region needs to form an area smaller than 5 um of the primary electrode region above the primary electrode region for etching the passivation layer.

S454: etching the sixth exposure area;

Specifically, wet etching is used for etching, and a solution of ammonium fluoride and hydrofluoric acid in a ratio of 15 to 1 can be used for etching to ensure that the etching reaches the surface of the primary electrode, so as to form an opening in the primary electrode.

S455: removing the sixth photoresist; forming a passivation layer.

S500: Connecting the first light-emitting structure and the second light-emitting structure in series to obtain a finished reverse voltage-stabilized LED chip.

Specifically, S500 includes:

S501: forming a seventh photoresist;

S502: exposing the seventh photoresist to form a seventh exposure area;

S503: performing vapor deposition on the seventh exposure area;

Wherein, electron beam evaporation, thermal evaporation or magnetron sputtering process is used for evaporation of secondary electrodes. Please refer to Figures 4 and 8 to evaporate the first secondary electrode 6, the second secondary electrode 7 and the third secondary electrode 9 so that the first light-emitting structure and the second light-emitting structure are connected in series, and the adjacent second light-emitting structures are connected in series.

S504: tear off the gold and remove the seventh photoresist to form the first secondary electrode, the second secondary electrode, and the third secondary electrode finished products, and then obtain the reverse stabilization LED chip finished product.

The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims (5)

1. A reverse voltage-stabilized LED chip, characterized in that it comprises: a substrate, an epitaxial layer, a first etching path, a first light-emitting structure, 2 to 8 second light-emitting structures, 1 to 7 second etching paths, a first secondary electrode, a second secondary electrode and a third secondary electrode; the epitaxial layer is arranged on the substrate and is divided into a first region and a second region by etching the first etching path to the substrate; the area of the first region: the area of the second region is (2 to 5): (0.5 to 1.5); The first light-emitting structure is disposed in the first region; the second light-emitting structure is disposed in the second region; the first light-emitting structure and the second light-emitting structure are connected in series; the first light-emitting structure and the second light-emitting structure are disposed in parallel, and current transmission directions of the first light-emitting structure and the second light-emitting structure are opposite; The epitaxial layer comprises a first semiconductor layer, an active layer and a second semiconductor layer sequentially arranged on a substrate; The first light emitting structure includes a first electrode and a second electrode, and the second light emitting structure includes a third electrode and a fourth electrode; the first electrode and the third electrode are connected to the first semiconductor layer, and the second electrode and the fourth electrode are connected to the second semiconductor layer; The first electrode and the fourth electrode are electrically connected via the second secondary electrode spanning the first etched path; The second electrode and the third electrode are electrically connected via the first secondary electrode spanning the first etched path; The second etching path and the third secondary electrode are arranged in the second region; the second etching path is etched to the substrate; adjacent second light emitting structures are separated by the second etching path and are electrically connected through the third secondary electrode. 2 . The reverse-stabilized LED chip according to claim 1 , wherein the side walls of the first etched path and the second etched path have an inclined angle. 3 . The reverse-stabilized LED chip according to claim 2 , wherein the tilt angle is ≤ 60 degrees. 4 . The reverse-stabilized LED chip according to claim 1 , wherein the first light-emitting structure and the second light-emitting structure further comprise a current blocking layer, a current diffusion layer and a passivation layer. 5. The method for preparing a reverse-stabilized LED chip according to any one of claims 1 to 4, characterized in that it comprises: (1) providing a substrate and forming an epitaxial layer on the substrate; (2) forming a first exposed region and a second exposed region on the epitaxial layer; (3) forming a first etching path; (4) forming a first light-emitting structure and a second light-emitting structure; (5) The first light-emitting structure and the second light-emitting structure are connected in series to obtain a finished reverse voltage-stabilized LED chip.