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在MEMS器件中,浓硼掺杂层通常为器件的结构层.但由于受表面固溶度及浓度梯度影响,该掺杂层(硼原子浓度≥5×1019cm-3)厚度越大所需的扩散时间越长.为了能在同等扩散工艺条件下,制备出更厚的浓硼掺杂层以满足器件要求,提出了多步扩散法.即在保证总的累计扩散时间不变的前提下,将传统的扩散过程分为两个相对短的扩散周期.并且这两个周期连续进行,每个周期各包含一次预扩散和再分布.与传统的两步扩散相比,多步扩散法可为硅基底引入更大量的硼杂质,并且具有一定能力使硼杂质留在一定深度范围内.因此该方法可以获得更大的有效节深.实验中采用该方法成功制备出21μm厚的浓硼掺杂层.然而在文献中提到的采用传统两步法在同样条件下得到的厚度则小于15μm.从而验证了该方法可在同等扩散工艺条件下,可以制备出更厚的浓硼掺杂层.
In MEMS devices, the heavily-doped boron layer is usually the structural layer of the device, but due to the influence of surface solid solubility and concentration gradient, the greater the thickness of the doped layer (boron atoms concentration ≥5 × 1019cm-3) The longer the diffusion time.In order to be able to produce thicker thick boron doping layer under the same diffusion process conditions to meet the requirements of the device, a multi-step diffusion method is proposed.In the premise of ensuring the total cumulative diffusion time constant, The traditional diffusion process is divided into two relatively short diffusion cycles, and the two cycles are continuous, each cycle contains a pre-diffusion and redistribution compared with the traditional two-step diffusion, multi-step diffusion can be The silicon substrate introduces a larger amount of boron impurity and has the ability to leave the boron impurity within a certain depth range, so that the method can obtain a greater effective nodal depth.In this experiment, a 21 μm-thick concentrated boron doping However, in the literature, the traditional two-step method is used to obtain the thickness less than 15μm under the same conditions, thus verifying that the method can produce thicker thick boron-doped layers under the same diffusion process conditions.