1. Field of the Invention
The present invention relates to a light emitting diode (LED) and a manufacturing method thereof, and more particularly, to a manufacturing method capable of reducing stresses between materials.
2. Description of the Prior Art
LEDs are widely used in lighting and display technology due its advantages of low power consumption, environment friendliness, small size, and easy installment. In the LED technology, group III-nitride compounds such as GaN, AlGaN InGaN and AlInGaN are particularly important because it exhibit excellent features such as wide energy gap, high luminous efficiency and a superior light emission characteristic: it covers almost the entire visible light spectrum.
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Therefore, the prior art developed methods to reduce the problems caused by stress accumulation in the epitaxial layers. For example, metal-organic chemical vapor deposition (MOCVD) is introduced to form the buffer layer 104 of AlN or GaN in awareness of the feature of heterogenerous growth of the buffer layer 104. Another approach is provided to form the active layer 104 having superlattice structure. Or, as shown in
It is found the lattice dismatch is increased when aluminum content in the epitaxial layer such as AlxGa1-xN is increased, that means where if the quantity of X is higher, the lattice mismatch is larger. Therefore the methods provided by the prior art still cannot effectively solve the problem while those methods further increase process complexity and cost. It is also observed that the bar-like substances 118 and the crack preventive layer deteriorate the optical performance of the LED. Thus, it is a difficult issue for fabrication that how to reduce the strain stress, avoid the cracking in the epitaxial layers and improve the performance of the device without further complicating the manufacturing methods for the LED.
One aspect of the present invention is to provide a manufacturing method of LED that effectively reduces the strain stress without complicating the manufacturing method.
According to one aspect of the present invention, a LED is provided. The LED comprises a substrate, a protrusive patterned layer positioned on the substrate and exposing portions of the substrate to form a plurality of exposed regions, and a plurality of individual island semiconductor multi-layer respectively positioned in each exposed region.
According to another aspect of the present invention, a manufacturing method of an LED is provided. The method comprises steps of providing a substrate, forming a protrusive patterned layer exposing portions of the substrate to form a plurality of exposed regions on the substrate, and forming an individual island semiconductor multi-layer respectively in each exposed regions.
According to the LED provided by the present invention, the surface of the substrate, on which the semiconductor layers are formed, is divided by the protrusive patterned layer, resulting in the plurality of exposed regions. And the individual island semiconductor multi-layer is respectively formed in each of the exposed regions. Consequently, the ratio of strain release boundary in per unit area is increased and thus efficiency of stress release is improved and the semiconductor multi-layer of high quality is obtained without cracking.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
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With consideration of temperatures for forming other layers of the LED in the subsequent steps, the protrusive patterned layer 204 is required to endure temperature higher than 1000° C. Therefore the protrusive patterned layer 204 in the preferred embodiment includes a high-temperature endurable material, preferably a dielectric material such as silicon oxide (SiO), silicon nitride (SiN), or silicon oxynitride (SiON) formed by chemical vapor deposition (CVD), low-pressure chemical vapor deposition (LPCVD), or plasma-enhanced chemical vapor deposition (PECVD). With conventional patterning method that omitted herein for the sake of brevity, the protrusive patterned layer 204 is formed on the substrate 202.
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According to the manufacturing method of an LED provided by the present invention, the surface of the substrate 202 is divided into the plurality of exposed regions 206 by the protrusive patterned layer 204, and the island semiconductor multi-layer 220 is individually formed in each of the exposed regions 206. Therefore the protrusive patterned layer 204 serves as the boundary between the island semiconductor multi-layers 220 for forming the LED device after the cutting process. As mentioned above, since the strain stress is released at the strain release boundary which is often formed on the edge of the semiconductor layers, the strain stress are effectively released when the ratio of strain release boundary in per unit area is increased. In the case that the semiconductor layers are in bulk before cutting process in the prior art, the ratio of the strain release boundary of the bulk semiconductor layers before the cutting process is about 78%. However the ratio of the strain release boundary to the island semiconductor multi-layers 220 before the cutting process is improved to 112.6% according to the method provided by the present invention. In other words, by breaking up the whole semiconductor layer into parts, that are the island semiconductor multi-layers 220 before the cutting process, the ratio of the strain release boundary in per unit area is greatly increased. Consequently, the strain stress accumulated in the semiconductor layers is effectively released and thus semiconductor layers of high quality are obtained.
Furthermore, different from the prior art that introducing bar-like substances or crack preventive layer, the method of manufacturing LED provided by the present invention improves both of the stress release efficiency and the LED performance without adding any layers or other structure in the essential semiconductor layers or complicating the method it self. Accordingly, the provide method is more preferable for forming AlxGa1-xN with the quantity of X larger than 0.25.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
Number | Date | Country | Kind |
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200910208519.8 | Oct 2009 | CN | national |