活性離子蝕刻技術於磷化銦鎵鋁/砷化銦鎵通道摻雜場效應電晶體元件之製作與分析; Reactive Ion Etching Technology for the Realization of AlGaInP/InGaAs Doped-Channel HFETs

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Title:	活性離子蝕刻技術於磷化銦鎵鋁/砷化銦鎵通道摻雜場效應電晶體元件之製作與分析;Reactive Ion Etching Technology for the Realization of AlGaInP/InGaAs Doped-Channel HFETs
Authors:	楊世丞;Shih-Cheng Yang
Contributors:	電機工程研究所
Keywords:	活性離子蝕刻;磷化銦鎵鋁;通道摻雜場效應電晶體;功率元件;Reactive Ion Etching;AlGaInP;DCFET;Power Device
Date:	2003-09-26
Issue Date:	2009-09-22 11:38:28 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	隨著無線通訊的蓬勃發展，射頻電路模組如功率放大器模組等，在無線通訊模組系統中的地位愈來愈重要。而國內對於射頻功率放大器模組之需求性日益增加，故如何成功設計並製作射頻功率模組，實為一重要的議題，而在射頻功率放大器模組中，元件的選擇成了很重要的課題。一個電子元件，具有高輸出功率、好的線性度以及大的工作範圍，在於功率電路設計上的應用是必要的。而本論文的主要目的即是開發新型結構之場效應電晶體，配合活性離子蝕刻技術的高度均勻性，研製出符合高頻、高功率以及高線性度的之電子元件。 (AlxGa1-x)0.5In0.5P (0? x ?1)，與GaAs晶格相互匹配的四元異質結構材料，由於其本身材料的優越特性，深具潛力取代傳統AlGaAs或GaInP材料，成為高速場效應電晶體中的蕭特基層。以(Al0.3Ga0.7)0.5In0.5P為例，相較於AlGaAs與GaInP材料，此四元材料擁有較大能隙(Eg=2.03 eV)，較高的蕭特基能位障(Φb=1.0 eV)，以及在場效應電晶體中，所形成AlGaInP/InGaAs接面時，造成的導帶不連續性較大(△Ec=0.28 eV)，這些材料特性，將使得製作出的AlGaInP/InGaAs場效應電晶體，擁有一些AlGaAs或GaInP所無法達到的特性，例如較大的元件崩潰電壓、較小的閘極漏電流，以及較好的元件線性度，而這些元件特性將主宰在高功率應用上的設計。此外由於此材料的低表面復合速度以及對GaAs 的高蝕刻選擇性，更進一步確定AlGaInP / InGaAs此材料系統的重要性。在本論文中，首先著重於活性離子蝕刻技術的開發方面，基於選擇性的考量，我們採用BCl3+CHF3與BCl3+CF4兩種混和氣體當作蝕刻源，針對磷化銦鎵鋁四元化合物作蝕刻特性的分析。藉由改變混和氣體之間的流量比例，對GaAs/AlGaInP異質材料的選擇性可高達40~50。在表面破壞分析方面，我們則分別利用物性(AFM)，電性(IV、TLM)及光學特性(PL)，證明BCl3+CHF3混和氣體所產生的破壞較小。在第三章中，由於通道摻雜場效應電晶體(DCFET)具有優越的電流推動能力與高崩潰電壓特性，相當適用於高功率元件之設計，故在本章節中，我們結合AlGaInP四元材料的優越特性，配合在第二章節開發的活性離子蝕刻技術，開發出(AlxGa1-x)0.5In0.5P/In0.15Ga0.85As通道摻雜場效應電晶體。不論從元件的直流、高頻或功率特性，甚至是可靠度測試，皆證明了(Al0.3Ga0.7)0.5In0.5P/In0.15Ga0.85As DCFETs深具潛力成為未來射頻功率放大器模組之關鍵性零組件。在第四章中，為了觀察比較不同閘極長度在元件特性上的差異，我們利用電子束微影設備及三層電子束光阻，製作出0.2、0.4、0.8、1.0微米???型閘極GaInP/InGaAs通道摻雜場效應電晶體，其中0.2微米元件可將元件電流增益截止頻率及功率增益截止頻率大幅增加為34 GHz以及50 GHz。除此之外，我們也針對不同閘極長度的元件作小訊號分析，並分析其元件內部傳輸效應，可得電子在0.2微米GaInP/InGaAs通道摻雜場效應電晶體之平均傳輸速度為1.1 x 107 cm/sec. In recent years, microwave power devices play an important role in wireless communication systems. An electronic device with high linearity, high output power, and high-speed performance is essential for power application. Extensive studies have been focused on the AlGaAs/InGaAs and GaInP/InGaAs HFET devices, which demonstrated superior millimeter-wave performances. However, the conduction band offset (∆Ec) of AlGaAs/GaAs heterojunction is limited by the aluminum composition, which must be kept below 23%, to prevent the presence of donor complex (DX) center and ineffective donor activation. (AlxGa1-x)0.5In0.5P quaternary compounds, lattice matched to GaAs, are expected to substitute AlGaAs or GaInP materials as a Schottky layer, due to its wider bandgap and larger Schottky barrier height. Because of a larger conduction band discontinuity versus InGaAs channel, it provides a better carrier confinement for electrons and also a higher current density. In addition to these advantages, due to the nature of doped-channel design where a high linearity and a high current density can be achieved, this (AlxGa1-x)0.5In0.5P quaternary heterostructure devices are very promising for microwave power application. In this thesis, a systematic approach for studying the etching characteristics of the quaternary (AlxGa1-x)0.5In0.5P compounds, using chlorine and fluorine mixing plasma, was applied. By adjusting the dry etching parameters, a high GaAs / AlGaInP etching selectivity ratio of 45 and 52 can be achieved for BCl3+CHF3 and BCl3+CF4 plasma systems, respectively. Based on the I-V, TLM, PL and AFM damage evaluations, BCl3+CHF3 gas system has been evidenced that it has a lower damage compared with the case using BCl3+CF4 system, and is suitable for the fabrication of heterojunction field electron transistor (HFETs) where the critical gate recess is involved. . In chapter 3, the (AlxGa1-x)0.5In0.5P / In0.15Ga0.85As doped-channel FETs (DCFETs) were successfully fabricated and characterized, where the optimized RIE-recessed process was applied. Based on the experimental results, we conclude that for the aluminum content of (Al0.3Ga0.7)0.5In0.5P, i.e. x=0.3, is the best composition to realize DCFETs in terms of device characteristics. Its high Schottky barrier height (ΦB=1.0 eV) and large conduction-band discontinuity (△Ec= 0.27 eV versus GaAs) suppress the gate leakage current and enhance the current drive capability, and therefore increase the device operation dynamic range. From the reliability test, it could be more confirmed its superior quality of the Schottky performance in (Al0.3Ga0.7)0.5In0.5P layers. These remarkable properties indeed reveal that the studied device structure has a good potentiality for the high-power device applications. In chapter 4, submicron Ga0.51In0.49P / In0.15Ga0.85As DCFETs with variable gate-lengths (0.2, 0.4, 0.6, and 1.0 μm) were developed by the e-beam lithography. Because the depletion region beneath the gate and the electric filed distribution along the channel are more uniform in the highly doped channel design, the short-channel effects in our 0.2 ?m gate-length devices can be eliminated. An excellent linearity of our 0.2 ?m gate-length devices also reveals that the GaInP / InGaAs doped-channel device developed in this work have a great potential candidate as a microwave power device in portable digital phone applications. Furthermore, in order to investigate the intrinsic transport characteristics of devices, a detailed delay time analysis was also performed on our 0.2 ?m gate-length devices. The 0.2 ?m GaInP / InGaAs DCFET demonstrates an electron transit time ?e.t of 1.88 psec, which is corresponding to an average saturated velocity ?s of 1.1 x 107 cm/sec.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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