【摘要】：非晶硅由于熱光系數(shù)高,成本低廉、易于集成等特點,被廣泛應(yīng)用于光學(xué)系統(tǒng)中。近年來,設(shè)計基于非晶硅薄膜熱光效應(yīng)的低損耗、高性能的光學(xué)器件成為半導(dǎo)體光學(xué)領(lǐng)域的研究重點,如熱光可調(diào)諧薄膜濾波器、熱光開關(guān)、紅外探測器等。在基于非晶硅熱光效應(yīng)設(shè)計的器件中,要求薄膜具有較高的熱光系數(shù)來實現(xiàn)器件設(shè)計功能。然而在其他情況下,非晶硅折射率隨溫度的變化可能會引起系統(tǒng)工作不穩(wěn)定及器件性能下降,因而要求其具有相對較小的熱光系數(shù)來避免這種熱誘導(dǎo)效應(yīng)。非晶硅材料具有連續(xù)不規(guī)則網(wǎng)格結(jié)構(gòu),這使得它的性質(zhì)在不同的工藝條件下具有很高的靈活性,因此研究薄膜熱光特性的工藝相關(guān)性具有相當(dāng)?shù)膶嵱脙r值。首先,通過理論分析得出極化率為影響熱光系數(shù)的主導(dǎo)因素并對其進行仿真。建立基于非晶硅內(nèi)部組分的氫團簇模型,通過改變晶胞內(nèi)不同硅氫基團的數(shù)量,研究了非晶硅帶邊770 nm及通信波段1330 nm和1550 nm處的極化率。結(jié)果表明,非晶硅熱光特性對H含量十分敏感。增加H含量,即提升SiH2和SiH3基團比例,能夠增強薄膜熱光效應(yīng),其中Si H3基團效果更優(yōu),而過量的H會降低對薄膜熱光系數(shù)的增幅,甚至?xí)斐杀∧峁庀禂?shù)下降。其次,為研究薄膜熱光特性工藝相關(guān)性,先重點解決非晶硅薄膜均勻制備工藝以及非晶硅薄膜熱光系數(shù)精確測量兩個亟需解決的關(guān)鍵性技術(shù)問題。本文從改善氣流場、溫度場、電磁場均勻性三個角度出發(fā)優(yōu)化反應(yīng)腔體設(shè)計,臺階儀測試結(jié)果顯示薄膜均勻性得到明顯改觀�？偨Y(jié)了國內(nèi)外熱光系數(shù)測量方法,結(jié)合熱光系數(shù)測量要求,設(shè)計出了基于FILMeasure-20的薄膜熱光系數(shù)測量平臺。最后,使用搭建的熱光系數(shù)精確測量平臺研究了不同工藝條件:射頻功率、沉積壓強、退火溫度處對薄膜性能及在1330 nm處熱光特性的影響。測試結(jié)果與現(xiàn)有理論值接近,證明了測試平臺的可靠性,并得出以下結(jié)論:(1)沉積時使用相對較高的射頻功率、適中的沉積壓強、對薄膜進行500℃短時間退火都是提高薄膜熱光系數(shù)的有效手段,其中500℃短時間退火可使熱光系數(shù)提升63.5%;(2)使用較低射頻功率、較高的沉積壓強、800℃以上高溫退火都是降低薄膜熱光系數(shù)的有效手段,其中900℃以上退火使薄膜熱光系數(shù)降低到10-5 K-1量級。在應(yīng)用中,可結(jié)合實際需要選擇合適的薄膜沉積參數(shù)。
[Abstract]:Amorphous silicon is widely used in optical systems because of its high thermo-optical coefficient, low cost and easy integration. In recent years, the design of low loss and high performance optical devices based on the thermo-optical effect of amorphous silicon thin films has become the focus of semiconductor optics, such as thermo-optical tunable thin film filters, thermo-optical switches, infrared detectors and so on. In the device based on the thermo-optical effect of amorphous silicon, the thin film is required to have a high thermo-optical coefficient to achieve the device design function. However, in other cases, the variation of the refractive index of amorphous silicon with temperature may lead to the instability of the system and the degradation of the device performance. Therefore, it is required that the amorphous silicon has a relatively small thermo-optical coefficient to avoid this thermal induction effect. The amorphous silicon material has a continuous irregular mesh structure, which makes its properties have high flexibility under different technological conditions, so it is of great practical value to study the process correlation of thermo-optical properties of thin films. Firstly, the polarizability is the main factor affecting the thermo-optical coefficient, and the simulation is carried out. The hydrogen cluster model based on the internal components of amorphous silicon is established. The polarizability of amorphous silicon band edge at 770 nm and communication band of 1330 nm and 1550 nm is studied by changing the number of different hydrosilyl groups in the crystal cell. The results show that the thermo-optical properties of amorphous silicon are sensitive to H content. Increasing H content, that is, increasing the ratio of SiH2 and SiH3 groups, can enhance the thermo-optical effect of the film, and the effect of Si H _ 3 group is better, while excessive H can decrease the increase of the thermo-optical coefficient and even cause the decrease of the thermo-optical coefficient of the film. Secondly, in order to study the correlation of thermo-optical properties of amorphous silicon thin films, two key technical problems which need to be solved urgently are the uniform preparation process of amorphous silicon films and the accurate measurement of thermo-optical coefficients of amorphous silicon films. In this paper, the design of the reaction cavity is optimized from three aspects of improving the airflow field, temperature field and electromagnetic field uniformity. The results of the step meter test show that the film uniformity has been improved obviously. The measurement methods of thermo-optical coefficient at home and abroad are summarized. According to the requirement of thermo-optical coefficient measurement, a measurement platform of film thermo-optical coefficient based on FILMeasure-20 is designed. Finally, the effects of different technological conditions, such as RF power, deposition pressure, annealing temperature on the film properties and thermo-optical properties at 1330 nm, were studied by using an accurate measurement platform for thermo-optical coefficient. The test results are close to the existing theoretical values, which proves the reliability of the test platform. The conclusions are as follows: (1) the relatively high RF power and moderate deposition pressure are used in deposition. Annealing at 500 鈩，

本文編號：2200411