Gate-All-Around FET

choi

I am a biologist. But for years I can not understand finFET. Today, I did a short research because the preceding Bloomberg says, "A shift in technology could also help Rapidus, Shimizu added. The 2-nanometer chips it envisages will use a Gate-All-Around transistor structure instead of the current FinFET structure, making it easier for newcomers to break in, Shimizu said."

(a)
(i) from the Web: "The first GAAFET was showcased in 1988 by Toshiba which was a vertical nanowire GAAFET, and was called a Surrounding Gate Transistor (SGT) [which was the initial name for GAA]. A Gate-All-Around Field Effect Transistor (GAAFET) technology is similar in function to a FinFET transistor but the gate material surrounds the channel from all sides. Generally, based on design, GAAFETs can have two or four gates. Gate-All-Around Field Effect Transistor (GAAFET) technology is believed to be the successor to FinFETs, as it provides better device performance at smaller sizes such as below 7 nm."
(ii) Sander Hofman, What Is a Gate-All-Around Transistor?  And how will it change the semiconductor industry?  ASML, undated.
https://www.asml.com/en/news/sto ... l-around-transistor

For an outsider like me, I did not appreciate this sentence ("These gates turn on and off, either allowing or preventing current from passing through") in this Web page, until I read more on the topic.
(iii) Gate-All-Around (GAA). Applied Materials, undated
https://www.appliedmaterials.com ... nced-logic/gaa.html
("Gate-All-Around (GAA) is a transistor architecture that overcomes the challenges of the FinFET architecture. GAA takes the FinFET design and turns it sideways so that the channels are horizontal instead of vertical. Instead of surrounding the channel on three sides as in the FinFET architecture, GAA surrounds it on all four sides, to allow better control of the transistor switch")


(b) What is a gate?
(i) A planar transistor, of the first generation, is MOSFET, which stands for metal–oxide–semiconductor field-effect transistor.
https://en.wikipedia.org/wiki/MOSFET
("The basic principle of the field-effect transistor was first patented by Julius Edgar Lilienfeld in 1925. * * * The 'metal' in the name MOSFET is sometimes a misnomer, because the gate material can be a layer of polysilicon (polycrystalline silicon). Similarly, 'oxide' in the name can also be a misnomer, as different dielectric materials are used with the aim of obtaining strong channels with smaller applied voltages")

In that design, a gate is made up of "metal."
(ii)
(A) What is a MOSFET? It's Types, Working, Circuit, and Application. Electronicsforu.com, Aug 24, 2023
https://www.electronicsforu.com/ ... orking-applications
("The charge carriers enter the channel at the source and exit via the drain. The width of the channel is controlled by the voltage on an electrode called Gate which is located between the source and the drain. It is insulated from the channel near an extremely thin layer of metal oxide" which is not shown in figures)

Pay attention to the third figure, under the heading "N-Channel MOSFET." The base (excluding source, drain, gate and maybe channel, that is; jargon for base is "substrate") of the transistor is made of silicon.

For simplicity, you accept "charge carriers" as electronics. But if they are really electronics, this is n-type semiconductor, where n stands for negative and means electronics (flowing from source to drain, through the FLEETING channel that comes about and disappear in no time and that was controlled by a gate).
(B) extrinsic semiconductor
https://en.wikipedia.org/wiki/Extrinsic_semiconductor

Please read paragraph 1 of introduction carefully. P stands for positive, which is a hole (devoid of electron).
(iii) How Does a Logic Gate in a Microchip Work? A gate seems like a device that must swing open and closed, yet microchips are etched onto silicon wafers that have no moving parts. So how can the gate open and close? Scientific American, Oct 28, 1999
https://www.scientificamerican.c ... es-a-logic-gate-in/

Quote:

(A) "Larry Wissel, ASIC Applications Engineer at IBM Microelectronics, replies: Those of us who design logic gates for computers seldom reminisce on how the terms we use to describe technology came into use. The vision of a gate swinging back and forth clearly does not literally represent the structures on a silicon chip. But the reason for the usage of the term 'gate' for computer logic can be appreciated by examining the basic function of a gate: to control a flow.   On a farm, gates may be used to control the 'flow' of sheep or goats between pens.* * *

He did not get to the point. So read the next and last speaker.
(B) "Tak Ning of the IBM TJ Watson Research Center adds some complementary details:"

Please read it carefully.

"The source and drain regions of a MOSFET are fabricated to be full of electrons [this is about n-type semiconductor that constitutes the transistor] which are ready to carry current. The channel region, on the other hand, is designed to be empty of electrons under normal condition" when NO positive voltage is applied to gate.

(c) In 3-D finFET, source, channel and drain all stick up to form a "fin."

(d)
(i) Julius Edgar Lilienfeld  
https://en.wikipedia.org/wiki/Julius_Edgar_Lilienfeld
was a Jew born in present-day City of Lviv, western Ukraine, in the Austrian part of the Austro-Hungarian Empire. He received PhD in 1905 from what is present-day Humboldt University of Berlin. He came to US in 1921.
(ii) https://en.wikipedia.org/wiki/MOSFET
(section 1 History: "In 1955 Carl Frosch and L Derick accidentally grew a layer of silicon dioxide over the silicon wafer")

After Lilienfeld were three physicists of three Bell Labs: William Shockley, John Bardeen and Walter Houser Brattain who together were awarded Nobel Prize for Physics in 1956. But they (all four of them) could not make it (transistor) work in reality. Carl Frosch and Lincoln Derick did (make it work).
(iii)
(A) Carl Frosch
https://en.wikipedia.org/wiki/Carl_Frosch
("was a Bell Labs researcher who discovered that silicon could be protectively coated with silicon dioxide by the right exposure to oxygen when hot. Such protective coating overcame a problem of surface states found in active silicon circuit elements. The discovery also revealed the potential for the process of silicon etching.   This discovery process was akin to that of penicillin in that an accidental event led to the discovery of the solution to a major problem")
(B) 1955: Development of Oxide Masking. Computer History Museum, undated.
https://www.computerhistory.org/ ... t-of-oxide-masking/

This silicon oxide is the oxide in MOSFET's name.
(iv) After the duo's discovery, silicon oxide is always an insulation between gate and channel, be it MOSFET (planar), finFET or GAAFET.

Figure 3 Transistor evolution from single-gate and double-gate to nanowire transistor. In MK Md Arshad, N Othman and U Hashim, Fully Depletion of Advanced Silicon on Insulator MOSFETs. Critical Reviews in Solid State and Materials Sciences, 40: 182-196 (2015)
https://www.researchgate.net/fig ... 0-21_fig2_272827614
, where oxide is blue.