EE 5611 Introduction to Microelectronic Technologies Fall Tuesday, September 04, 2012 Lecture 01

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1 EE 5611 Introduction to Microelectronic Technologies Fall 2012 Tuesday, September 04, 2012 Lecture 01 1

2 Instructor: Jing Bai Contact hone: (218) , Office: MWAH 255 Webpage: Office hours: 1:00-2:00M on Monday and Wednesday or by appointment 2

3 Course Information Textbook Stephen A. Campbell Fabrication Engineering at the Micro- and Nanoscale Course Assessment Homework: 10% Quizzes: 10% Two projects: 15% Two midterms: 20% each Final: 25% 3

4 Administrative Issues Course assignment Homework will be assigned every two weeks on average Two projects during the semester (One for photovoltaic device testing the other one is the transistor testing) Homework and project due date will be posted when assigned For each assignment, 10% will be deducted for each late day; assignment will not be accepted over 3 late days Attendance Class attendance sign-in is required 4

5 Microelectronic Technologies The collection and ordering of those unit processes for making a useful product are called a technology. Microelectronics is normally associated with integrated circuits (IC). However, the microelectronics technologies could also be applied to make other types of solid-state devices. The unit processes for making ICs include photolithography, oxidation, doping, thin film deposition, and etching. The technology required to built the IC is independent of the density of transistors on the wafer. The density of transistors is defined by the photomask. One of the most fundamental changes in the fabrication process that allows the technology evolution is the minimum feather size that can be printed on the chip. 5

6 Major Milestones in Microelectronic Technologies Very pure silicon and germanium were manufactured N junction diodes was invented The junction transistor was invented at Bell Lab by Bardeen, Brattain and Schockley Integrated circuits (ICs) were invented by Kilby at TI First commercial integrated circuits Semiconductor industry surpasses $1-billion in sales First MOS IC CMOS invented Moore s law invented by Intel co-founder Gordon E. Moore Microprocessor invented Semiconductor Industry passes $10-billion Intel 80386DX mm silicon wafers introduced Mbit DRAM Mbit DRAM Intel 80486DXTM 1990 s-2000 s Intel entium Series Intel demonstrated the first working 32 nm processor Intel demonstrated the 22 nm tri-gate transistor 6

7 Moore s Law Number of transistors on a chip roughly double every 18 months Has been true since 1970 and shows no sigh of slowing World's first 2-billion transistor microprocessor (Intel Itanium processor) is announced in February

8 Device Becomes Ever Smaller Smaller feather size leads to more transistors per unit area (high density) and higher speed Intel announced the 22 nm tri-gate transistor in

9 Scope of This Course Microelectronic fabrication processes Diffusion Oxidation Ion implantation hotolithography Thin film deposition Etching rocess integration Overview on optical devices hotovoltaic devices Overview of current development of photovoltaic devices Operation principle of p-n junction solar cells Reflection, absorption, recombination and carrier lifetime in semiconductor solar cells Efficiency limit and loss mechanisms in solar cells Semiconductor solar cells design and production Thin film and polymer solar cells Overview on MEMS and nanoscale devices Two projects on device measurement V cells Transistors 9

10 Semiconductor Manufacture rocess Design Fabrication (Semiconductor Foundry) An example of packaged Semiconductor chip ackage Testing 10

11 Introduction on Semiconductor Materials Semiconductor material properties Crystal structure of semiconductor materials Growth of semiconductor materials 11

12 Semiconductors, Metals and Insulators Semiconductors: a material having conductivity between those of metals and insulators (e.g., Si, Ge). Metal: a conductors of electricity (e.g., Cu, Fe) Insulators: a material that resists the flow of current (e.g., SiO 2 ). free electrons at 0K? Yes No No conduction band valence band Electron Energy overlap Metal Semiconductor Insulator Bandgap Eg Electronic band-structure 12

13 Semiconductor Materials Elements: Si, Ge III-V compounds: AlAs, GaAs, InAs, In II-VI compounds: CdS, CdSe, ZnS, Si is today s most important semiconductor material Low cost easily oxidized to form SiO 2 insulating layer High Eg, can be used in high temperature eriodic table of semiconductors GaAs and In are popular for optoelectronic applications 13

14 Types of Solids Three general types 1. Amorphous with order only within a few atomonic and molecular dimensions (Fig. (a)) 2. olycrystalline with multiple sing-crystal regions (called grains) separated by grain boundary (Fig.(b)) 3. Single crystal with geometric periodicity throughout the entire material (Fig. (c)) (a) (b) (c) 14

15 Basic Crystal Structures Three common types: a) Simple cubic b) Body-centered cubic (bcc) c) Face-centered cubic (fcc) a a b c and = b = c = lattice constant (a) (b) (c) 15

16 Examples of Lattice lanes in Cubic Lattices (100) lane with normal direction [100] (110) lane with normal direction [110] (111) lane with normal direction [111] 16

17 Silicon Wafer roduction Technique Czochralski Growth Raw material olysilicon nuggets purified from sand Si crystal ingot Crystal pulling A silicon wafer fabricated with microelectronic circuits Final wafer product after polishing, cleaning and inspection Slicing into Si wafers using a diamond saw 17

18 Identification of Wafer Surface Crystallization Flats can be used to denote doping and surface crystallization Dopants (impurities) for Si: n-type dopant (donor): hosphors (), Arsenic (As) p-type dopant (acceptor): Boron (B) 18

19 The Diamond Structure Materials possess diamond structure: Si, Ge 8 atoms per unit cell Any atom within the diamond structure will have 4 nearest neighboring atoms 19

20 The Zincblende Structure Difference with the diamond structure: two different types of atoms (e.g., GaAs) Each Ga atom has four nearest As neighbors and each As atom has four nearest Ga neighbors 20

21 Typical N-well CMOS Manufacturing rocess Step #1: Oxidation (a) -type substrate cleaning SiO 2 (b) Oxidation After wafer cleaning, SiO 2 is deposited by wet oxidation and dry oxidation 21

22 Step #2: hotolithography Defining N-well R (a) Deposit photoresist (R) (c) Develop R UV-light Mask #1 (b) Exposure under the UV light (d) Etch SiO 2 and remove R 22

23 Step #3: Diffusion to Form N-well (a) N-well predeposition n-well (b) N-well drive in The above diffusion process could also be replaced by ion implantation. 23

24 Step #4: Formation of Gate Structure n-well (a) Strip off remaining oxide using hydrogen fluoride (HF) n-well olysilicon Thin gate oxide (b) Deposit thin layer of gate oxide and polysilicon. n-well (c) attern poly-si and oxide layers using photolithography process. 24

25 Step #5: Formation of N-type Diffusion Regions n-well (a) Deposit oxide layer to pattern the diffusion regions n+ n+ n+ n-well (b) attern oxide layer to define the n-type diffusion regions and create diffusion regions n+ n+ n+ n-well (c) Strip off the oxide layer 25

26 Step #6: Formation of -type Diffusion Regions p+ n+ n+ p+ p+ n+ n-well Similar process as Step #5 is used to create p-type diffusion regions 26

27 Step #7: Formation of Insulation Layer with Metal Contacts p+ n+ n+ p+ p+ n+ n-well Nitride (a) Deposit nitride layer p+ n+ n+ p+ p+ n+ n-well (b) Etch nitride layer to leave metal contact cuts 27

28 Step #8: Formation of Metal Contacts Metal p+ n+ n+ p+ p+ n+ (a) Deposit metal layer n-well p+ n+ n+ p+ p+ n+ n-well (b) attern metal layer and form metal contacts 28

29 Summary of Fabrication rocesses Oxidation Diffusion Ion implantation hotolithography Etching Thin film deposition (non-metal and metal layers) 29