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在VLSI生产过程中接触孔的玻璃回流期间,当低温下即产生流动的BPSG在孔间距很小的情况下使用时,发现存在悬挂体(即凸出,其结果是在孔底部形成一个凹角),而且在极限情况下形成封闭孔。与回流有关的力和机理的详细研究表明,无论是玻璃的化学特性还是特殊的回流工艺参数均不是改变这种现象的因素。对一个理想几何形状的研究表明,如果玻璃厚度大于孔间距的临界值,则孔内的悬挂体出现在回流之后。已经计算出的临界值大约为0.4。对所有的玻璃厚度而言,一定数量的悬挂体将在回流中期形成。但是,对于亚临界玻璃厚度,该悬挂体将渐渐消失;而对于超临界玻璃厚度,该悬挂体将不断增大。在极限情况下,较大的悬挂体将会向玻璃/衬底界面扩展,从而导致孔的封闭。
During glass reflow of contact holes during VLSI production, when flowing at low temperatures, ie, BPSG, which is flowing, is found to have a hanging body (ie, bulging, with the result that a concave corner forms at the bottom of the hole) , But also forms a closed hole at the limit. A detailed study of the forces and mechanisms associated with reflow shows that neither the chemical properties of the glass nor the special reflow process parameters are factors that alter this phenomenon. Studies on an ideal geometry show that if the glass thickness is greater than the critical value of the hole spacing, the hanging body within the hole occurs after reflow. The calculated cut-off value is about 0.4. For all glass thicknesses, a certain number of suspensions will form mid-reflow. However, for subcritical glass thickness, the suspension will gradually disappear, whereas for supercritical glass thickness the suspension will continue to increase. In extreme cases, larger suspensions will spread to the glass / substrate interface, causing the hole to close.