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当砷扩散入硅中时,仅有一部分砷保留电活性。因为砷作为发射极掺杂剂是重要的,所以了解不活泼的砷的性质和它如何影响 As~+离子的溶解度和扩散是很必要的。提出了一个模型,在该模型中,当与〔VsiAs_2〕络合物形成准平衡时,As~+的扩散是通过一个简单的空位机构,游动的单质 As~+的通量根据〔VsiAs_2〕络合物形成的程度而作修正。讨论了缺陷的结构和它的形成能(≈1.8电子伏)。采用这一模型推导出一个有效扩散系数:D_As=2DiC_A/(1+8 K′_2C~3_A)式中 C_A 是 As~+浓度,K′_2是一个依赖于 As~+表面浓度和扩散温度的集合参数。给出了该方程的准确性的实验检验。这一定量分析的重要结果表明了 D_(AS)随砷浓度的增加而达到一个极大值,然后又单调地下降。出现 Dmax 的砷的浓度是依赖于总的砷表面掺杂和扩散温度。总的砷与电活性 As~+之比值在1300℃下下降到1。在1250℃下表明了As~+溶解度达到一极大值,在 P—Si 中是1.5×10~(21)原子/厘米~3,在n—Si 中是1.2×10~(21)原子/厘米~3。
When arsenic diffuses into silicon, only a portion of the arsenic retains its electrical activity. Because arsenic is important as emitter dopant, it is necessary to understand the nature of the inactive arsenic and how it affects the solubility and diffusion of the As ~ + ions. A model is proposed in which the diffusion of As ~ + is facilitated by a simple vacancy mechanism when the quasi-equilibrium with [VsiAs_2] complex is formed. The flux of the ascending As ~ + moves according to [VsiAs_2] The degree of complex formation is corrected. The structure of the defect and its formation energy (≈1.8 eV) are discussed. Using this model, an effective diffusion coefficient is derived: D_As = 2DiC_A / (1 + 8 K'_2C ~ 3_A) where C_A is the As ~ + concentration and K'_2 is a temperature that depends on the As ~ + surface concentration and diffusion temperature Collection parameters. The experimental verification of the accuracy of the equation is given. The important results of this quantitative analysis show that D_ (AS) reaches a maximum with the increase of arsenic concentration, and then decreases monotonically. The concentration of arsenic at which Dmax appears is dependent on the total arsenic surface doping and diffusion temperature. The total arsenic and electroactive As ~ + ratio dropped to 1 at 1300 ° C. At 1250 ℃, the As ~ + solubility reaches a maximum value of 1.5 × 10 ~ (21) atoms / cm 3 in P-Si and 1.2 × 10 ~ (21) atoms / cm 3 in n-Si. Cm ~ 3.