TW201631793A - Flip-chip LED and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a flip-chip LED and a manufacturing method thereof; the transparent substrate has a light emitting surface having a plurality of bump structures integrally formed with the transparent substrate, thereby increasing the light emission area of the flip-chip LED, and reducing the ratio of light not emitting from ideal direction due to the total reflection occurring in the interface of the transparent substrate and the air, thereby increasing the brightness of the LED.

Description

Flip-chip type light-emitting diode and manufacturing method thereof

The present invention relates to a light-emitting diode and a method of manufacturing the same, and more particularly to a flip-chip light-emitting diode capable of exhibiting high brightness and a method of manufacturing the same.

A Light Emitting Diode (LED) is a solid-state light-emitting device made of a semiconductor material, which is generally a combination of III-V chemical elements such as gallium phosphide, gallium arsenide or gallium nitride. The compound semiconductor applies a voltage, so that the holes and electrons meet in the luminescent layer under the action of the electrode voltage to recombine, and the electrons will fall to a lower energy level, and at the same time, the photon mode is released, and the electric energy is converted into light. The effect of light.

In order to enhance the brightness of the light-emitting diode, a reflective structure such as a metallic silver film, a metal aluminum film, or a Bragg mirror is used to reflect the light generated by the light-emitting layer and concentrate toward an ideal light-emitting direction; or Finger or ring electrode configuration, transparent conductive layer or current blocking layer, etc., thereby improving the uniformity of current distribution and improving light extraction efficiency; or changing between layers of the light-emitting diode The interface structure is such that a particular optical effect occurs to increase the brightness of the product. These technical means have not been exhausted, and better brightness enhancement structures and manufacturing methods are still to be further developed, taking into account cost, yield and efficiency.

The main object of the present invention is to provide a flip chip type light emitting diode which is tied to The transparent substrate is used to form a plurality of bump structures on the light-emitting side, so that the surface area of the light-emitting surface is increased, and the possibility that the light is totally reflected on the light-transmitting substrate and the light cannot be emitted is reduced, thereby making the brightness of the flip-chip light-emitting diode Upgrade.

A further object of the present invention is to provide a flip-chip type light-emitting diode which is not only uniform in the structure of the bumps formed on the side of the light-transmitting substrate for light-emitting, but also can define a specific size range in the structure to ensure The effect of brightness enhancement can be achieved.

Another object of the present invention is to provide a method for fabricating a flip-chip light-emitting diode which does not remove the photoresist material used in the process of forming the bump structure by means of cleaning, but uses a dry etching method. The photoresist material is removed to prevent the epitaxial layer structure from being destroyed during the cleaning process.

Therefore, the present invention discloses a flip-chip type light-emitting diode and a manufacturing method thereof, which comprise, in a basic structure, a transparent substrate having a corresponding first surface and a second surface, the first surface The plurality of bumps are integrally formed with the transparent substrate, and each of the bumps has a bottom surface width W and a height H, and the aspect ratio (H/W) is greater than 0 and less than or equal to 0.33. An epitaxial layer is disposed on the second surface and has a first semiconductor layer, a light emitting layer and a second semiconductor layer. The two electrodes are electrically connected to the first semiconductor layer and the second semiconductor layer, respectively.

1‧‧‧Transparent substrate

11‧‧‧ first surface

12‧‧‧ second surface

13‧‧‧Bumps

130‧‧‧ bottom

15‧‧‧ Third Area

2‧‧‧ epitaxial layer

21‧‧‧First semiconductor layer

210‧‧‧First electrode

22‧‧‧Lighting layer

23‧‧‧Second semiconductor layer

230‧‧‧second electrode

3‧‧‧current conduction layer

4‧‧‧ boards

40‧‧‧Circuit contacts

41‧‧‧Circuit contacts

50‧‧‧Electrical bumps

51‧‧‧Electrical bumps

6‧‧‧ photoresist layer

61‧‧‧First area

62‧‧‧Second area

S1~S2‧‧‧ steps

S2-1~S2-3‧‧‧Steps

W‧‧‧Longest distance

H‧‧‧ Height

1 is a schematic cross-sectional view showing an embodiment of the present invention; FIG. 2 is a schematic structural view of an embodiment of the present invention, showing an application state FIG. 3 is a cross-sectional view showing a structure of an embodiment of the present invention for indicating an application aspect; FIG. 4A is a partial cross-sectional view showing an embodiment of the present invention for indicating Bumps; FIG. 4B is a graph showing the height and width of the corresponding bumps measured by data in an embodiment of the present invention; FIG. 4C is an embodiment of the present invention for transmitting an atomic force microscope (AFM) The image taken is used to indicate the appearance of the finished product of the bump, close to the image of the center of the transparent substrate (4C left) and the edge (4C right). Compared with the 4B, the bumps are distributed. Uniformity of the dimensions; 5A-5B is an image taken by a scanning electron microscope (SEM) according to an embodiment of the present invention, which is used to indicate that the surface of the transparent substrate has a bump structure; FIGS. 6A-6E: It is a schematic flow chart of a manufacturing method according to an embodiment of the present invention; and FIG. 7 is a light intensity distribution diagram of a practical measurement of a flip-chip light-emitting diode to indicate that the present invention (solid line) is transparent The surface of the substrate is made into a bump structure, and its performance in each light-emitting direction Both are superior to conventional flip-chip light-emitting diodes with a flat transparent substrate (dashed line)

In order to further understand and understand the features of the present invention and the effects achieved, the following examples and the detailed description are provided to illustrate the following:

First, please refer to FIG. 1 , which shows a flip-chip luminescence disclosed in an embodiment of the present invention. The diode body comprises a light-transmitting substrate 1, an epitaxial layer 2, a current conducting layer 3, a first electrode 210, a second electrode 230 and the like. The epitaxial layer 2 is disposed under the transparent substrate 1 , and the structure of the epitaxial layer 2 includes a first semiconductor layer 21 , a light emitting layer 22 , and a second semiconductor layer 23 . The current conducting layer 3 is sequentially stacked. The first electrode 210 and the second electrode 230 are electrically connected to the first semiconductor layer 21 and the current conducting layer 3, and are electrically connected to the second semiconductor. Layer 23.

Referring to FIG. 2 and FIG. 3 together, in the practical application, the first electrode 210 and the second electrode 230 are electrically connected to the circuit board 4 through the conductive bumps 50 and 51, respectively. Connected, the surface of the circuit board 4 has circuit contacts 40, 41, which can be connected with the aforementioned conductive bumps 50, 51.

In an embodiment of the present invention, the light-transmitting substrate has a bump structure for one side of the light-emitting surface; referring to FIG. 1 , the light-transmitting substrate 1 has a corresponding first surface 11 and second surface 12, wherein A surface 11 is a flip-chip light-emitting diode for emitting light, and the first surface 11 has a plurality of bumps 13 in the structure, and the bumps 13 are integrally formed with the transparent substrate 1 in the present embodiment. In the example, the shape of each bump is approximately a cone, and the width W and height H of the bottom surface thereof can increase the amount of light in order to reduce total reflection. The aspect ratio (H/W) of each bump is larger than 0 and less than or equal to 0.33. Since the transparent substrate 1 has a large number of bumps 13 present on the first surface 11 as a non-planar structure and under the same unit size, the non-planar structure can provide more surface area than a general planar structure, and thus The light-emitting diode has more light-emitting area, and the brightness thereof is increased, thereby increasing the light-emitting angle, and also reducing the total reflection of the light on the interface between the air and the light-transmitting substrate before leaving the light-transmitting substrate, thereby failing to smoothly emit light. possibility. In other embodiments of the invention, the approximate shape of at least a portion of the bumps includes a triangular pyramid, a quadrangular pyramid, and a polygonal pyramid. Body, hemisphere, partial hemisphere, semi-ellipsoid or partial semi-ellipsoid, but not limited to this.

In other embodiments of the present invention, the size of the bump on the transparent substrate can increase the amount of light emitted by the flip-chip light-emitting diode as long as it meets the above aspect ratio (H/W), and there is no size series. (dimension scale) restrictions. However, in order to enable the flip-chip light-emitting diode to uniformly increase light in all directions, the width W of the bottom surface of the bump on the transparent substrate is preferably set in a micron dimension, and the height H of the bump is higher. It is preferably set in a sub-micron dimension. Referring to FIG. 4A, in an embodiment of the invention, the width W of the bottom surface 130 of the bump 13 is 2.2 micrometers, and the height H of the bump 13 is 0.7 micrometer in this embodiment, and each bump 13 may also have The same height H. In another embodiment of the invention (not shown), the width W of the bottom surface of the bump is 2.2 microns and the height H of the bump is 0.27 microns. As shown in FIG. 4B and FIG. 4C, in one embodiment, the height of the bumps 13 is the same through a stable process, and the edges of the first surface are controlled (dotted lines) and the first surface. The height of the bump 13 at the center (solid line) can provide ideal uniformity and improve light extraction efficiency.

5A is an actual image observed using a scanning electron microscope, and it is seen that the transparent substrate 1 has a plurality of bumps 13 on its first surface 11; FIG. 5B is an enlarged representation of the portion of the first surface 11 .

The flip-chip light-emitting diode disclosed in the present invention is not particularly limited in other structures except for the characteristics of the transparent substrate on the surface; the current conducting layer 3 under the epitaxial layer 2 can be formed using indium tin oxide. A conductive film layer having high light transmittance, which can be a current which is dispersed from the second electrode 230 and introduced to the second semiconductor layer 230. The current conducting layer 3 may further comprise a reflecting function, which can travel the light generated from the light emitting layer 22 toward the light exiting direction, thereby effectively improving the light emitting efficiency of the light emitting diode.

The method for manufacturing a flip-chip type light-emitting diode according to the present invention includes the following steps: Step S1: growing an epitaxial layer on a transparent substrate, wherein the transparent substrate comprises a corresponding one a surface and a second surface, the epitaxial layer is grown on the second surface, having a first semiconductor layer, a light emitting layer, and a second semiconductor layer; and step S2: dry etching the first surface to make the first surface A surface has a plurality of bumps.

As described above, the flip-chip light-emitting diode disclosed in the present invention is characterized in that the surface of the transparent substrate has a bump structure, and the present invention is first used in the manufacture of the flip-chip light-emitting diode. The epitaxial layer is formed on one side of the transparent substrate, and then the other surface of the transparent substrate, that is, the first surface for light extraction, is dry-etched, so it is necessary to consider to avoid damage to the completed epitaxial layer. problem. Referring to the processes of FIG. 6A to FIG. 6E, in the step of dry etching the first surface, the method further comprises the step of: step S2-1: coating the photoresist material on the first surface to form a photoresist layer. Step S2-2: patterning the photoresist layer such that the photoresist layer has a plurality of first regions and a plurality of second regions having different thicknesses; and step S2-3: etching the photoresist layer using a dry etching method, Removing the photoresist material, and removing part of the transparent substrate together, and forming the bumps on the transparent substrate.

As shown in the figure, in one embodiment of the present invention, the photoresist layer 6 is patterned by a photomask, and the photoresist layer 6 is distinguished as a bump and a region not as a bump. The photoresist layer 6 has a plurality of first regions 61 and a plurality of second regions 62 having different thicknesses in the process, one of which is thick The degree can be zero. The first region 61 and the second region 62 are all removed by using a dry etching method such as Inductively Coupled Plasma (ICP) or Reactive Ion Etching (RIE). Since the thickness of the photoresist layer of the first region 61 and the second region 62 is different, after the photoresist material of the first region 61 is removed, the second region 62 still has a photoresist material, and thus continues to etch to the second region. The photoresist material of the region 62 is also removed, and at the same time, the transparent substrate 1 under the first region 61 is also partially removed during the etching process to form a recessed cavity and with the etching process. Continue and gradually deepen. The photoresist material of the second region 62 is removed, and the surface of the transparent substrate 1 exposed is the third region 15. The transparent substrate 1 has no or less influence on the third region 15 and is affected by etching. Compared with the region covered by the first region 61 of the photoresist layer 6 described above, the bump is a bump formed in the present invention, and the first region 61 is formed by the dry etching. The etch rate at the junction of the second region 62 has a slightly different effect and exhibits a characteristic of curvature, so that the bump approximately assumes the shape of the cone.

The light emitting angle of a light-emitting diode is defined as the angle of the light exiting the maximum light intensity. Figure 7 is a light intensity distribution diagram (solid line) of the above-described embodiment (the width W of the bottom surface of the bump is 2.2 μm and the height is 0.27 μm) of the present invention, which is similar to the conventional flip-chip light-emitting diode ( Compared with the light intensity distribution map (dashed line) of the non-bump structure, it can be confirmed that the light-efficiency can be improved after the bump structure is formed on the light-transmitting substrate, and the light-emitting intensity is improved in each light-emitting direction, thereby effectively increasing the light-emitting intensity. Angle, and achieve the purpose of improving light efficiency. In the embodiment of the present invention, the light exit angle is extended to 135 degrees by 131 degrees (a conventional flip chip type light emitting diode).

In summary, the present invention discloses a flip-chip type light-emitting diode and a manufacturing method thereof, and the light-transmitting substrate has a plurality of bump structures on one side for light-emitting, and thus is relatively flat. The structure has more light-emitting area, which can improve the brightness and light-emitting angle of the flip-chip light-emitting diode; further, the invention also considers the problem of bump fabrication and protection of the epitaxial layer when fabricating the light-emitting diode. Therefore, the dry etching method is used, and the step of directly etching and removing the photoresist material is omitted to omit the use of the cleaning liquid to prevent the epitaxial layer from being damaged by the cleaning liquid. The invention not only has the advantages of improving the brightness, but also comprehensively considers the feasibility and the maintenance of the yield in the production, and is undoubtedly a highly crystalline flip-chip light-emitting diode and a manufacturing method thereof.

The above is only the embodiment of the present invention, and is not intended to limit the scope of the present invention, and the variations, modifications, and modifications of the shapes, structures, features, and spirits described in the claims of the present invention are It should be included in the scope of the patent application of the present invention.

1‧‧‧Transparent substrate

11‧‧‧ first surface

12‧‧‧ second surface

13‧‧‧Bumps

2‧‧‧ epitaxial layer

21‧‧‧First semiconductor layer

210‧‧‧First electrode

22‧‧‧Lighting layer

23‧‧‧Second semiconductor layer

230‧‧‧second electrode

3‧‧‧current conduction layer

Claims (10)

A flip-chip type light emitting diode comprising: a transparent substrate having a corresponding first surface and a second surface, the first surface having a plurality of bumps, the bumps being integrated with the transparent substrate Forming, each bump has a bottom surface width W and a height H, and an aspect ratio (H/W) is greater than 0 and less than or equal to 0.33; an epitaxial layer is disposed on the second surface and has a first semiconductor a layer, a light emitting layer and a second semiconductor layer; and two electrodes electrically connected to the first semiconductor layer and the second semiconductor layer, respectively. The flip-chip light-emitting diode according to claim 1, wherein the approximate shape of at least part of the bumps comprises a cone, a triangular pyramid, a quadrangular pyramid, a polygonal pyramid, a hemisphere, and a partial hemisphere. , semi-ellipsoid or partial semi-ellipsoid. The flip-chip type light emitting diode according to claim 1, wherein the light transmissive substrate is a sapphire substrate. The flip-chip light-emitting diode according to claim 1, wherein the width of the bumps is a micron size. The flip-chip light-emitting diode according to claim 4, wherein the height of the bumps is a sub-micron size. The flip-chip light-emitting diode according to claim 1, wherein the bumps have the same height. A method for manufacturing a flip-chip light-emitting diode, comprising the steps of: providing a transparent substrate, wherein the transparent substrate comprises a corresponding one of the first surface and a second surface; and growing an epitaxial layer On the second surface of the light substrate, the epitaxial layer has a first semiconductor a body layer, a light-emitting layer and a second semiconductor layer; and etching the first surface such that the first surface has a plurality of bumps, each bump having a bottom width W and a height H, an aspect ratio (H/ W) is greater than 0 and less than or equal to 0.33. The method for manufacturing a flip-chip type light-emitting diode according to claim 7, wherein the step of etching the first surface comprises the steps of: coating a photoresist material on the first surface to form a a photoresist layer; the photoresist layer is patterned such that the photoresist layer has a plurality of first regions and a plurality of second regions having different thicknesses; and the photoresist layer and a portion of the transparent substrate are etched using a dry etching method, And the formation of the bumps. The method for manufacturing a flip-chip type light emitting diode according to claim 8, wherein the dry etching method comprises an inductively coupled plasma etching and/or reactive ion etching. The method for manufacturing a flip-chip type light emitting diode according to claim 8, wherein the photoresist layer of the first region or the second regions has a thickness of zero.