深空乏現象對超薄閘極氧化層金氧半電容元件光反應之影響

Abstract

本篇論文主要關注於超薄閘極氧化層金氧半電容元件之深空乏現象，為了深入瞭解此現象，引入各元件的光反應作為對照。首先，製造並加以量測具有簡單正方形圖案之金氧半電容元件。當少數載子的生成電流無法供給漏電流時，深空乏現象將會發生，且伴隨著閘極電流的飽和。側面不均勻性之加劇，如照光或氧化層厚度減少，均會強化邊緣電場，使得飽和電流更容易流經電容元件之邊緣。 接著，為了進一步探討邊緣區域的尺度，設計出變化邊緣相關參數之圖案。電極寬度大於10μm，且電極間距為30μm之元件的電容-電壓及電流-電壓曲線，與簡單正方形圖案的相近。然而，電極間距小於20μm，且電極寬度為30μm之元件的電流-電壓曲線，在電流飽和之過程中出現特別的過渡區；本文提出可能的解釋與圖例，認為此現象起因於兩臨近電極之邊緣空乏區耦合及少數載子共享。照光後，由於少數載子數量充足，此一過渡區將會消失。

In this thesis, deep depletion behavior of MOS capacitors with ultrathin oxides is of major concern, while the photoresponse of each sample is also included for better understanding of this behavior. First, MOS capacitors with simple square patterns are fabricated and measured. Accompanied by saturation of gate current, deep depletion behavior occurs when the generation current of minority carriers fails to supply the leakage current. Enhancement of lateral nonuniformity such as illumination or decrease in oxide thickness intensifies the fringing field at edge and makes the saturation current pass through the edge of MOS capacitors more likely. Subsequently, patterns with various changes in the edge-related parameters are designed so as to further recognize the approximate scales of edge regions. The capacitance-voltage and current-voltage curves of samples with electrode width lager than 10 μm and electrode separation of 30 μm are similar to those with simple square patterns. However, current-voltage curves of samples with electrode separation smaller than 20 μm and electrode width of 30 μm exhibit particular transition regions during the saturation of gate currents. Explanation and illustration are consequently proposed, supposing that the behavior originates from the coupling of edge depletion region and the sharing of minority charges between two adjacent electrodes. Under illumination, the transition regions disappear due to the abundant minority carriers.