Semiconductor device buffer layer manufacturing method

Abstract

The present invention relates to the field of semiconductor device manufacture and in particular to a semiconductor device buffer layer manufacturing method. The semiconductor device comprises a semiconductor substrate, a first n-type buffer layer and a second n-type buffer layer. The first n-type buffer layer is formed by performing selenium implantation on the back surface of the semiconductor substrate and an annealing treatment after implantation. The second n-type buffer layer is formed by performing proton implantation or phosphorus implantation or a combination of proton implantation and phosphorus implantation on the back surface of the semiconductor substrate, and an annealing treatment after implantation. The method forms the first n-type buffer layer by implanting selenium elements capable of forming an n-type doping and having a high diffusion coefficient into the back surface of the semiconductor substrate, and forms a second n-type buffer layer by proton implantation witha small atomic mass or a common phosphorus implantation. Under a relative low-energy ion implantation condition, by the combination of the ion implantation of the above two elements and the annealingactivation, the depth of the n-type buffer layer is increased and the carrier concentration distribution of the n-type buffer layer and the device performance of the FS-IGBT are optimized.

Description

technical field [0001] The invention relates to the field of semiconductor device manufacturing, in particular to a method for manufacturing a semiconductor device buffer layer. Background technique [0002] In semiconductor devices such as diodes and insulated gate bipolar transistors (IGBTs), in order to reduce the thickness and loss of the device while ensuring the withstand voltage capability and switching performance of the device, it is necessary to dope the semiconductor substrate at a deeper position from the back of the device. , forming a buffer layer with a carrier concentration higher than that of the substrate. According to Poisson's equation, the electric field attenuation gradient is proportional to the charge concentration, so a buffer layer with a higher concentration can make the electric field rapidly decay and stop at this layer, preventing the depletion region from expanding to the back surface of the device and causing punchthrough, so the buffer layer ...

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Problems solved by technology

However, the above-mentioned technology has two disadvantages: 1. Limited by the atomic mass or the diffusion ability of ions in the semiconductor, for the above-mentioned commonly used doping elements, it is necessary to form a deep n-type buffer layer and optimize the current carrying capacity with a large space Sub-concentration distribution, by requiring a high-energy ion implanter above 500KeV, and the price of a high-energy ion implanter is very expensive, which will greatly increase the manufacturing cost of the device in the mass production of the device

2. If you choose low-cost low-energy ion implantation, then in the case of only phosphorus implantation or proton implantation, the carrier concentration distribution often drops too fast at the interface between the n-type buffer layer and the n-type drift region, forming a very small Steep concentration distribution, which will adversely affect the switching characteristics of the device and other performance

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