Composite substrate structure and fabrication method thereof

Abstract

The invention relates to a composite substrate structure and a fabrication method thereof. The composite substrate structure comprises a first substrate layer, an opaque interlayer and a second substrate layer, the first substrate layer, the opaque interlayer and the second substrate layer are sequentially arranged from bottom to top, the opaque interlayer is integrated with the first substrate layer and the second substrate layer, the thermal expansion coefficient of the first substrate layer is identical to that of the second substrate layer, when the first substrate layer is placed on a heating element, the opaque interlayer is used for absorbing the thermal radiation emitted by the heating element, the absorbed heat is used for heating the inner side surfaces of the first substrate layer and the second substrate layer, and the temperature of the outer side surface of the second substrate layer can meet the requirement of the growth temperature of an epitaxial material by the aid of the heating of the opaque interlayer for the second substrate inner side surface. By means of the composite substrate structure and the fabrication method thereof, the warping problem of substrates such as sapphire at the high temperature can be eliminated or alleviated, the substrate material is saved, the thinning operation for the substrate can be simplified during the fabrication process of a chip, the fabricating cost of light-emitting diode (LED) chips can be lowered, and the yield of the LED chips can be improved.

Description

technical field [0001] The invention relates to an LED epitaxial chip in the field of photoelectric technology, in particular to an LED chip epitaxial substrate with a composite structure and a manufacturing method thereof. Background technique [0002] When making GaN-based LED chips, the epitaxial layer structure of InGaN, GaN and other materials and devices is mainly grown on sapphire, SiC, Si and other substrates. Sapphire has many advantages, for example: firstly, the production technology of sapphire substrate is mature, the cost is low, and the crystal quality is good; secondly, sapphire has good stability and can be used in high temperature growth process; finally, sapphire has high mechanical strength Easy to handle and wash. However, using sapphire as a GaN-based LED epitaxial substrate also has some problems, such as lattice mismatch and thermal stress mismatch, the inability to fabricate devices with vertical structures, and difficulties in thinning and cutting ...

AI Technical Summary

Problems solved by technology

However, using sapphire as a GaN-based LED epitaxial substrate also has some problems, such as lattice mismatch and thermal stress mismatch, the inability to make devices with vertical structures, and difficulties in thinning and cutting operations, etc.

A particularly prominent problem is that the sapphire substrate has poor thermal conductivity, and it will warp due to the difference in surface tension between the upper and lower surfaces or the internal stress accumulation after depositing different films on the upper surface when it is heated at a high temperature (see figure 1 ), if a sapphire substrate with a small thickness is used, the degree of warpage will be even worse, which will cause the epitaxial growth of InGaN, GaN layers, etc. due to the uneven temperature distribution along the radial direction of the epitaxial wafer during growth, which will affect the photoelectric parameters, such as light Inhomogeneity in wavelength, brightness or voltage, etc., resulting in low yield

[0003] In order to overcome this problem, the industry has developed a variety of technical solutions. For example, one of the trial solutions is to improve the structure of the substrate heating equipment to achieve uniform heating of the entire sapphire substrate, but this solution often leads to The structure of the device becomes very complicated, the manufacturing cost is greatly increased, and the heating of the sapphire substrate is limited, and the sapphire substrate still has the problem of warping; another common solution is to use a thicker substrate, such as a thickness of A 2-inch sapphire wafer of about 430 μm and above or a 4-inch sapphire wafer of about 600 μm and above is used as the substrate to keep the substrate as flat as possible during the epitaxial growth process, but this requires the substrate to be cleaned after the epitaxial layer is formed. Additional thinning will not only increase the production cost, but also increase the difficulty and workload of the thinning operation of the substrate, which will also greatly increase the manufacturing cost of the LED chip, and lead to a significant decrease in the yield of the chip

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