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Micro-fabrication Process

Clean Room

Clean room classifications and applications

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

Micromachining Materials

Substrates: • Silicon • GaAs • Other elemental or compound semiconductors • Metals (bulk and foils) • Glasses • Quartz • Sapphire • Ceramics • Plastics, polymers and other organics

Micromachining Materials

Additive Materials: • Silicon (amorphous, polycrystalline, epitaxial) • Silicon compounds (oxides, nitrides, carbides, …) • Metals and metal compounds • Glass • Ceramics • Polymers and other organics • Biomaterials

Silicon Crystallography

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.

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

Si crystal structure

Si crystal= fcc +1/4(x,y,z)fcc

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>

c(214) plane

Planes and directions

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

晶圓製作流程

Czochralski Method

For growing single-crystalline ingot

CZ 晶體提拉過程

Floating Zone Method(FZ)

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。

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。

比較柴氏和浮動區長晶法

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。

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。

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).