近年來隨著衛星通訊及行動電話系統的快速發展，微波元件扮演非常重要的角色，元件之輕薄短小為其重要的研究目標。微波元件包括被動元件與主動元件。被動元件例如用於微小化濾波器、天線雙工器、發射機多工器及電壓控制振盪器的介電共振器，必須具有適當的介電常數、低的介電損失與小的共振頻率溫度係數。主動元件例如使用於射頻積體電路(RF-IC)中當作功率放大器的異質接面電晶體(HBT)，必須具有高速率與高功率的特性。
　　為達成這些要求，本論文針對上述兩類微波元件，分成兩大主題進行探討與研究：
一、 高品質因素，高溫度穩定性與高介電常數之微波介電共振陶瓷製備。
[1] 嘗試在MgTiO3材料中，加入BaO雜質，以改善介電特性。
[2] 摻雜NiO對Y2BaCuO5燒結行為與微波介電材料特性影響之研究。
[3] 在ZnO-TiO2材料中，加入Bi2O3雜質，以降低燒結溫度，並尋求較佳特性。
二、 InGaP/GaAs異質接面電晶體的製作及分析。
[1] 首先嘗試利用Ti與TiN薄膜來改善GaAs基材Cu金屬化製程的阻障性能。
[2] 研究利用不同的定電壓應力(constant period of voltage stress; CPVS)以找出消除HBT’s燒灼現象(burn-in effect)的最佳方法。
　　結果顯示，(一) 在不同的燒結條件下，於(1-x)MgO·xBaO·TiO2陶瓷材料中，可觀察到一些二次相，樣品的介電常數與Q×f值隨著添加比例x值的增加而增加，共振頻率溫度係數(τf.)可以藉由x值的適度增加而使之趨近於零。實際應用上，燒結溫度1330 oC，組成為0.97MgO·0.03BaO·TiO2陶瓷，具有較佳的微波介電特性：介電常數為20.6，Q×f值為32600GHz，而共振頻率溫度係數約為+4.47 ppm/oC。
　　(二) 當添加比例x值增加時，Y2Ba(Cu1-xNix)O5固溶體在分解溫度時分解成Y2O3與液相的量也會增加。由於燒結溫度必須低於分解溫度，故固溶體的εr與τf特性會嚴重地受到燒結條件的影響。以Ni取代Cu時，樣品的Q×f值可獲得到顯著地改善。在所有的製備組成中，Y2Ba(Cu1-xNix)O5陶瓷在溫度1330 oC做3小時燒結時可以展現較佳的微波介電特性：介電常數為13.8、Q×f 值為87200 GHz、而共振頻率溫度係數(τf )為–16.3 ppm/oC。
　　(三) ZnO-TiO2陶瓷掺雜有Bi2O3添加物時，由於添加物導致之液相燒結效應，故燒結溫度可以有效地降低到1000 oC。另外，適量的Bi2O3添加物可以有效地改善ZnO-TiO2陶瓷的密度與介電特性。共振頻率溫度係數(τf.)可以藉由燒結溫度的控制而變為零。燒結溫度在1000 oC時，掺雜有1wt%添加物的1ZnO-1TiO2陶瓷，可以獲得較好的微波介電特性：介電常數為29.3，操作於8.36 GHz頻率下的Q×f值為22000GHz，而共振頻率溫度係數約為+17.4 ppm/oC。
　　(四) 在初始沉積的Cu/GaAs結構中，銅就會擴散進入砷化鎵(GaAs)基材內，故需要擴散阻障層(diffusion barrier)以阻隔這種快速擴散現象。對於Cu/TiN/GaAs結構，TiN薄膜的柱狀結構提供高於450oC溫度時的擴散路徑。在GaAs基材上的Cu/TiN/Ti多層薄膜結構，溫度高達550 oC都還很穩定，不會有任何交互反應發生。這些結果顯示，TiN/Ti組成薄膜層對於砷化鎵基材的銅金屬化製程可以達成一種良好的擴散阻障作用。
　　(五) 在InGaP/GaAs異質接面電晶體的元件特性中,電流增益在固定偏壓下會顯現逐漸增大的燒灼現象,本研究利用改變射極(emitter)及基極(base)的間距,觀察電晶體的射極面積效應(emitter Size Effect),以及其他電性量測分析判斷造成燒灼現象之原因。經實驗證明，燒灼現象發生於Vbe > 1.75 V的區域，此時電流增益曲線會有第二次突然增加；基體復合電流(bulk recombination current)是主導燒灼現象的主要基極電流成份而不是表面復合電流(surface recombination current)、基極接觸復合電流(base contact recombination current)、或空間電荷復合電流(space-charge recombination current)。另外，利用定電壓應力(加五分鐘電壓Vbe = 2.0 V、Vce = 3.0 V)以改善電流增益的暫態現象。施加CPVS以後，燒灼現象被抑制，電流增益不再有第二次突然上升現象出現，同時提升了HBT’s的電氣性能，此種基-射極接面的電性改善主要歸因於施加CPVS後陷在基極區域的相關離子被消除。

　With the rapid growth of satellite communications and mobile radio systems, microwave devices play a very important role; miniaturization of microwave components for volume efficiency is a major research requirement. Microwave devices include passive components and active components. Passive components, such as microwave dielectric resonator for miniaturized filters, antenna duplexers, transmitter multiplexers and voltage controlled oscillators, must meet with a suitable dielectric constant (er) for possible size miniaturization (size of a dielectric resonator ～ 1/√er), a low dielectric loss (high Q value) for a stable resonant frequency, and a small temperature coefficient of resonant frequency (τf) for temperature stable circuits. Active components, such as heterojunction bipolar transistors for the power amplifiers in RF-IC circuit, require a high speed and high power characteristics.
　To achieve these requirements, this thesis major focuses on the above-mentioned two microwave devices including two objects:
1. Preparation for microwave dielectric resonator with high quality factor, excellent temperature and high dielectric constant.
[a1] Try to add BaO dopant into MgTiO3 materials and improve microwave dielectric properties.
[a2] To study the influence of Ni substitution on the sintering behavior and the microwave dielectric properties of Y2Ba(Cu1-xNix)O5 ceramics.
[a3] ZnO-TiO2 ceramics with Bi2O3 addition was investigated to reduce the sintering temperature and find better microwave dielectric properties.
2. Fabrication and analysis of InGaP/GaAs heterojunction bipolar transistors.
[b1] Try to use Ti and TiN (titanium nitride) as a diffusion barrier for Cu metallization of GaAs substrate and improve the barrier performance.
[b2] InGaP/GaAs HBTs was studied to find the optimum condition to annihilate the burn-in effect by applying the constant period of voltage stress (CPVS).
Some minor phases were observed in (1-x)MgO·xBaO·TiO2 under different sintering conditions. The dielectric constant and Q×f of the specimens increased with an increase in x. In the (1-x)MgO·xBaO·TiO2 system, the temperature coefficient of resonant frequency could be controlled by varying x and can lead to a zero τf. For practical applications, 0.97MgO·0.03BaO·TiO2 ceramics sintered at 1320oC have excellent microwave dielectric properties:εr = 20.6, Q×f = 32600 GHz and τf = +4.47 ppm/oC.
　As the x values increased, the decomposition temperatures at which Y2Ba(Cu1-xNix)O5 solid solutions decomposed into Y2O3 and liquid phases also increased. Since the sintering temperatures needed to be performed below the decomposition temperatures, the εr and τf properties of Y2Ba(Cu1-xNix)O5 solid solutions were significantly affected by the sintering conditions. The Q×f values of the samples improved remarkably upon Ni substitution for Cu. Among the prepared compositions, Y2Ba(Cu00.2Ni0.8)O5 ceramics sintered at 1330oC for 3 h exhibit optimum microwave dielectric properties: εr = 13.8, Q×f = 87200 GHz and τf = –16.3 ppm/oC.
The sintering temperature of ZnO-TiO2 ceramics with Bi2O3 addition could be effectively reduced to 1000 oC due to the liquid phase effects resulted from the additives. A proper amount of Bi2O3 addition could effectively improve the densification and dielectric properties of ZnO-TiO2 ceramics. The temperature coefficient of resonant frequency could be controlled by varying the sintering temperature and lead to a zero τf value. At 1000 oC, 1ZnO-1TiO2 ceramics with 1wt% addition gave a better microwave dielectric propertiesεr of 29.3, a Q×f value of 22000GHz at 8.36 GHz and a τf value of +17.4 ppm/ oC.
In the as-deposited Cu/GaAs structure, copper diffused into GaAs substrate, and a diffusion barrier was required to block the fast diffusion. For the Cu/TiN/GaAs structure, the columnar grain structure of TiN films provided paths for diffusion at higher temperatures above 450°C. The Cu/TiN/Ti films on GaAs substrate were very stable up to 550°C without any interfacial interaction. 　　These results show that a TiN/Ti composite film forms a good diffusion barrier for copper metallization with GaAs.
Two significantly abrupt increase of dc current gains (β) at the opposite extremes of base-emitter voltages (Vbe) linked by a relatively slight increase of β in the range of 1.25 V ≦ Vbe ≦ 1.75 V are found in InGaP/GaAs heterojunction bipolar transistors (HBT’s). The burn-in effect directly arises the second abrupt increase of β occurred at Vbe > 1.75 V instead of elsewhere. Besides, choosing Vbe > 1.75 V, higher base-emitter voltage results in faster increase rate with better current gain transient improvement. Based on these observations, constant period of voltage stress (CPVS with Vbe = 2.0 V and Vce = 3.0 V for 5 minutes) with specific choice of Vbe > 1.75 V (the voltage range corresponding to the second abrupt increase of β), is thus applied to promote the electrical performance of HBT’s. After applying CPVS, the burn-in effect is substantially suppressed without showing any second abrupt increase of current gain. Although the current measured under both reverse and forward biases is greatly reduced for the base-emitter junction, CPVS slightly degrades the electrical properties of base-collector junction. The bulk recombination other than the surface recombination current, the base contact recombination and the space-charge recombination, is the dominant base current component to arise the burn-in effect. The electrical improvement of base-emitter junction should be due to the annihilation of H-related traps in the base region after CPVS. Once H- ions form, we propose that these ions are too fast to drift towards the base-collector junction under reverse bias of base-collector voltage. After migration through the extrinsic base region, H- ions are supposed to be trapped near the base-collector space region, which results in the degradation of base-collector junction after CPVS.

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