在3D NAND 快閃記憶體晶片中的氮化矽層通常用熱磷酸來去除。然而，蝕刻氮化矽所產生的矽酸鹽產物所造成在二氧化矽層上異常的沉積行為將會對接下來的製程造成嚴重的影響。因此，我們製作了一個由兩個間隔80m的控片所形成的簡單系統來研究此沉積行為。為了瞭解此現象，不同因素的影響像是水含量(磷酸濃度)，以及攪拌程度的不同，將在此系統中被檢驗。我們發現，隨著水含量或者攪拌速率的增加，二氧化矽的沉積速率將隨之減少。實驗結果證實，在二氧化矽層的異常沉積現象是狹小空間中的化學沉積以及質傳兩個因素競爭所造成的結果。;The Si3N4 layers in a 3D NAND flash patterned wafer are generally removed by hot phosphoric acid. However, the abnormal deposition of silicate which is the byproduct from Si3N4 etching onto the neighboring SiO2 layers will cause a serious problem in the following process. In this work, the abnormal deposition phenomenon was investigated by a simple system containing a narrow gap (~80 um) between two blanket wafers. To understand the mechanism, the influences of various factors on the chemical etching dynamics were examined, including the water content and the extent of mechanical agitation. It is found that the growth rate of SiO2 decreases as the water content or the extent of agitation is increased. Our experimental results reveal that the abnormal growth on SiO2 layers is a consequence of the competition between chemical deposition and mass transfer in a confined space (reaction-diffusion system).
