Post on 05-Feb-2016
description
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Micro-fabrication Process
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Clean Room
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Clean room classifications and applications
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Clear room classification
Class 1000: fewer than 1,000 particles (>0.5μm) in 1 cubic foot of air
Class 100: fewer than 1,00 particles (>0.5μm) in 1 cubic foot of air
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Micromachining Materials
Substrates: • Silicon • GaAs • Other elemental or compound semiconductors • Metals (bulk and foils) • Glasses • Quartz • Sapphire • Ceramics • Plastics, polymers and other organics
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Micromachining Materials
Additive Materials: • Silicon (amorphous, polycrystalline, epitaxial) • Silicon compounds (oxides, nitrides, carbides, …) • Metals and metal compounds • Glass • Ceramics • Polymers and other organics • Biomaterials
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Silicon Crystallography
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Cubic Lattices
• Simplest arrangements of atoms in three dimension in which the unit cell is a cubic volume
• Simple Cubic (sc) structure has an atom located at each corner of the unit cell
•Body Centered Cubic (bcc) has an additional atom at the center of the cube
• Face Centered Cubic (fcc) unit cell has atoms at the eight corners and on the six faces.
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Cubic Lattices
sc bcc fcc
• How is the arrangement of atoms in Silicon?
• Silicon has fcc + (1/4x, 1/4y, 1/4z) fcc structure
a is lattice constant
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Si crystal structure
Si crystal= fcc +1/4(x,y,z)fcc
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Planes and directionsLattice vector R= r*a+ s*b+ t*c, r, s & t are integers
We can define a plane in a crystal lattice with three integer, called Miller indices
1. Find the intercepts of the plane in terms of integral multiples of the basis vectors
[Fig2, 4, 1]
2. Take the reciprocal of the integers and reduce to smallest set of integers h, k, l, in this case 2,1,4
3. Label the plan (214) & direction is <214>
a
b
c(214) plane
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Planes and directions
a
b
c
a
b
c
a
b
cBlue is (100) plane, yellow arrow is <100> dirn
Blue is (010) plane, yellow arrow is <010> dirn
Blue is (110) plane, yellow arrow is
<110> dirn
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晶圓製作流程
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Czochralski Method
For growing single-crystalline ingot
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CZ 晶體提拉過程
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Floating Zone Method(FZ)
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懸浮帶區法 (FZ 法 )
因CZ法缺點，乃因坩鍋內的氧原子會滲入單晶錠長晶過程中。 FZ法可以生產含氧量非常低的單晶錠。 先以模子鑄出含摻雜物多晶矽棒。 種晶被熔融並接合於棒的下端。 射頻(RF)加熱線圈沿軸向上移動，多晶棒熔融，原子排成種晶方向。 缺點 –無法生成大直徑晶錠。 –差排 (dislocation) 密度較高。 生成的晶錠以製造 –功率晶體 (thyristor) 。 –大功率整流元件(rectifier) 等為主要目的。
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比較柴氏和浮動區長晶法兩法之比較 柴氏法 (Czochralski) – 較普遍、便宜。 – 較大晶圓尺寸 (300 mm in production) 。 – 原料可再度使用。 懸浮帶區法 (FZ 法 ) – 純矽晶 ( 無坩堝 ) 。 – 較昂貴，晶圓尺寸較小 (150 mm) 。 – 主要用來製造分離式功率元件所需晶圓。
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比較柴氏和浮動區長晶法
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晶圓的備製 去除末端：用鋸將晶錠的兩端 ( 頸及尾 ) 切除。 研磨直徑尺寸：用無心研磨機 (centerless grinder) 。 檢測結晶方向、導電形式，以及阻抗性結晶方向檢測方法 -X 光繞射 (diffraction) 、平行 (collimate
d) 光束折射。 晶錠刻意偏移主方向 (off-orientation) 幾度：離子植入。
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晶塊修整 “裁切”錐形的晶塊與錐體末端。 驗證程序控制以控制小塊金屬或雜質。
晶塊本體研磨至所需直徑，並加上平的或槽口記號。
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Silicon Wafer Cuts
Miller indices indicated by ground edges called “flats”. “n”-type and “p”-type refer to “doping”. N means “negative” (phosphorous) and P means “positive” (boron).
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Photolithography
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Lithography devices
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Lithography process
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Lithography process-cont.
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Positive/negative resist
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Positive/negative resist-cont.
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Positive/negative resist-cont.
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Masking and Exposure
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Mask fabrication process
M ASK 10um〈 〉
PATTERNTRANSFER
4000dpiPL OTTER
M ASK 2um〈 〉
DEVEL OPEPATTERN
L ASERWRITER
M ASK 1um〈 〉
DEVEL OPEPATTERN
E-BEAMWRITER
Auto-CADL -edit, etc.
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Lithographic masks
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Lithographic light source
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Exposure Light Source (UV)
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Development
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Developing the pattern (C)
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Oven Baking
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Lithographic processing: Repeat process
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Etching
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Etching Mechanism
Etching type Wet etching Dry etching Etching steps Oxidation Reaction Remove products
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Factors in Wet Etching
• Limited• Reaction limited• Diffusion limited
• Factors• Concentration• Temperature• Stirring
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Anisotropic Wetting Etching
HNA system
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Anisotropic Etch
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Anisotropic Etchants
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Wet anisotropic etching
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Etch the material
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Dry Etching
Ion bombardment Plasma reactor
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Bulk machining using dry etch
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Lithographic processing: Final release
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Micro device integration: Packaging
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Commercial micro devices: sensors and actuators