berkley 半导体工艺讲义c_07--离子注入

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Ion Implantation+ y Blocking mask Si C(x) as-implant depth profile

x

Equal-Concentration contours

Depth x

Concentration Profile versus Depth is a single-peak functionReminder: During implantation, temperature is ambient. However, Reminder: During implantation, temperature is ambient. However, post-implant annealing step (>900ooC)is required to anneal out defects. post-implant annealing step (>900 C) is required to anneal out defects.Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Advantages of Ion Implantation Precise control of dose and depth profile Low-temp. process (can use photoresist as mask) Wide selection of masking materialse.g. photoresist, oxide, poly-Si, metal

Less sensitive to surface cleaning procedures Excellent lateral dose uniformity (< 1% variation across 12”wafer)

Application example: self-aligned MOSFET source/drain regionsAs+ As+ As+

Poly Si Gate

n+Professor N Cheung, U.C. Berkeley

p-Si

n+

SiO22

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Monte Carlo Simulation of 50keV Boron implanted into Si

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

(1) Range and profile shape depends on the ion energy (for a particular ion/substrate combination) (2) Height (i.e. Concentration) of profile depends on the implantation dose

C(x) in#/cm3

[Conc]=# of atoms/cm33[Conc]=# of atoms/cm[dose]=# of atoms/cm22[dose]=# of atoms/cm

doseφ

=∫

∞ C 0

( x )dx

Depth x in cmProfessor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Mask layer thickness can block ion penetration

photoresist SiO2, Si3N4, or others

Thick Mask

Thin mask Incomplete Blocking

Complete blocking

No blocking SUBSTRATE

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Ion Implantere.g. AsH3 As+, AsH+, H+, AsH2+ Ion source As+

$3-4M/implanterMagnetic Mass separation~60 wafers/hour

Accelerator Voltage: 1-200kV Dose~ 1011-1016/cm2 Accuracy of dose:<0.5% Uniformity<1% for 8” wafer Accelerator Column

waferTranslational wafer holder motion.

ion beam (stationary) spinning wafer holder6

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Eaton HE3 High Energy Implanter, showing the ion beam hitting the 300mm wafer end-station.

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Implantation DoseFor singly charged ions (e.g. As+)

Ion Beam Current in amps Implant× time q DoseΦ=[Implant area]=# cm 2Over-scanning of beam across wafer is common. Over-scanning of beam across wafer is common. In general,,Implant area> Wafer area In general Implant area> Wafer areaProfessor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Practical Implantation Dosimetryaperture for dose monitoring

Wafer holder wheel ions+ Faraday cup+V A+ bias applied to Faraday Cup to collect all secondary electrons. Cup current= Ion current

Secondary electron effect eliminated

e

* (Charge collected b

y integrating cup current )/ (cup area)= doseProfessor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Meaning of Dose and ConcentrationDose[#/area]: looking downward, how many fish per unit area for ALL depths?

Concentration[#/volume]: Looking at a particular location, how many fish per unit volume?

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Ion Implantation Energy Loss MechanismsNuclear stopping Si+ Crystalline Si substrate damaged by collision e+

+

Si

e Electronic stopping+ Si

Electronic excitation creates heatProfessor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Energy Loss and Ion PropertiesLight ions/at higher energy Heavier ions/at lower energy EXAMPLES Implanting into Si: more electronic stopping more nuclear stopping

H+ B+ As+

Electronic stopping dominates Electronic stopping dominates Nuclear stopping dominates13

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Stopping Mechanisms

B into Si P into Si As into Si

E1(keV) 3 17 73

E2(keV) 17 140 800

Professor N Cheung, U.C. Berkeley

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Sn≡ dE/dx|n Se≡ dE/dx|e

Depth x E~0 Se Substrate Se Sn

Surface E=Eo A+ Eo= incident kinetic energy

Sn

x~ Rp More crystalline damage at end of range Sn> SeProfessor N Cheung, U.C. Berkeley

Less crystalline damage S e> Sn15

半导体,工艺, 伯克利分校

EE143 F05

Lecture 7

Professor N Cheung, U.C. Berkeley