高介電常數金屬-絕緣層-金屬電容電性及其可靠度之研究

Abstract

在射頻積體電路中，其阻抗匹配電路、濾波器和類比頻率調節電路都會用到金氧金電容。而對於動態隨機存取記憶體來說，金氧金電容是為了用於儲存電荷，並且會影響到記憶體的一些參數，像是工作電壓、元件速度和資料保留的時間。然而不管是射頻積體電路還是動態隨機存取記憶體的電容，都會占掉大量的晶片面積。所以為了減少晶片面積和成本，我們必須縮小金氧金電容的尺寸。 在這次研究中，我們作出以高介電常數鈦鉭氧化物為介質層的金氧金電容。從元件的量測結果中，我們得到非常高的電容密度值為 23 fF/um2、從十萬赫茲（100K Hz）到一百億赫茲（10G Hz）只有1.8%的電容損耗。同時在十億赫茲頻率下（1G Hz），從量測的散射參數計算出低於550ppm的電壓相關電容值。由上述數據可知，此金氧金電容可適用於工作在射頻頻率的高精密積體電路上。同時，我們也研究了此電容在固定偏壓一段時間後的電容值、漏電流以及電壓相關的電容值。

In RF integrated circuits, MIM capacitors are used for impedance matching, filter and analog frequency tuning circuits. For DRAM, MIM capacitors are used to storage charges; they will influence some parameters of the memory, such as work voltage, device speed, and the data retention time. However, the capacitor area of above all usually consumes a large portion of the whole chip size. In order to reduce chip size and cost, we must continue scaling down the size of MIM capacitors. In this study, we have fabricated MIM capacitors using high-□ TiTaO dielectrics. From the measurement of devices, a very high capacitance density of 23 fF/um2 is obtained, with small capacitance reduction of 1.8 % from 100 KHz to 10GHz. And Small voltage dependence of capacitance < 550 ppm, mathematical derived from S-parameters, is obtained at 1 GHz, which ensures this MIM capacitor useful for high precision circuits operated at RF regime. We also have investigated the characteristic of capacitance, leakage, and VCC before and after constant-voltage stress.