[Air Bubbles free artificial dielectric material fabrication in specified molds for ultra wide band antenna miniaturization]

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TABLE OF CONTENT

CHAPTER 4: RESULTS AND ANALYSIS1

DRIE of Alignment Holes1

Backside Etch5

Metallization for Antenna and Feedline10

Platform Release13

Platform Release Method Results18

Wafer Dicing19

SMA Connector Adhesion20

FZP and ordinary lens antennas for microwave and terahertz frequencies21

Optimization Of FZP Lens Design For Removal Of Maximum Gain Frequency Shift23

Electromagnetic Bandgap (Ebg) Material24

Analysis Of EBG Material27

DRA Theory And Analysis30

CHAPTER 5: CONCLUSION41

Electrostatic Actuation during Antenna Measurements43

REFERENCES51

CHAPTER 4: RESULTS AND ANALYSIS

DRIE of Alignment Holes

The MEMS antenna platform required features on both sides of the silicon wafer. For this work, a double-sided alignment tool was not available at the HiDEC facility. To ensure accurate alignment of the features on both sides, through-holes were utilized and achieved by the DRIE method. Similar schemes were utilized prior to the development of double-sided aligners for fabrication of accelerometers and similar devices . An array of alignment holes ranging in size from 25~m to 300~m were used to ensure that alignment holes would be present on the opposite side of the wafer and that accurate alignment could be achieved. Figure 3.5 shows a portion of the alignment array with the smallest and larges alignment mark present prior to DRIE (Baek, 2003).

The DRIE process was conducted using an STS 5922 machine, shown in Figure 3.6, which utilized the Bosch, or time-multiplexed, process. The machine alternated between standard plasma etch containing sulfur hexafluoride (SF 6) and the deposition of a chemically inert passivation layer of octafluorocyclobutane (C4F s) which was controlled by mechanical hardware. The SF 6 ions attacked the target wafer at a near vertical orientation due to the large induced electric potential perpendicular to the surface, minimizing any horizontal etching. The passivation step coated the entire wafer with a thin layer of C4Fs which is similar to Teflon. The passivation layer was quickly etched away on surfaces perpendicular to the incident bombarding ions, but etched on the sidewalls much more slowly.

Each step lasted on the order of 10 seconds, which resulted in a large number of isotropic etch steps and allowed high aspect ratio etches. The STS 5922 generated the plasma with a lkW RF generator with an additional RF generator attached to the platen, or wafer holder. The two generator setup allowed independent bias control to the substrate. The wafer was held in place electrostatically and a helium back cooling system was used to keep the wafer temperature below 800 C.

The pressure inside the system was critical and was controlled by a butterfly valve which could be operated in either a fixed or automatic mode. In fixed mode, the valve position was constant and the process gas flows determined the pressure in the chamber. In automatic mode, the valve position changed in response to the gas flow to maintain a particular pressure. The system was connected to a personal computer (PC) with software to fully control the process recipe and ramp rates of various processing parameters. The SF 6 etches silicon isotropically by first dissociating into ...