Rebirth: Dominate The World, Starting From The School Network

no doubt.

The insulating layer is the most critical of all components of the transistor.

Its function is to isolate the gate and channel.

Because the gate switches the channel through the electric field~.

The electric field is generated by applying a certain voltage to the gate.

If current flows from the gate into the channel, then the current leaks and the gate cannot function as a switch.

Through Ohm's law we can know that if there is voltage, there will be current.

If the current flows from the gate into the channel, what's the point of talking about switching?

It’s all leaked a long time ago!

Why is the insulating layer called oxide and not insulator?

Because the earliest insulating layer was silicon dioxide, which coexists very naturally with silicon.

Its relative dielectric constant (a measure of insulation, the higher, the better for transistor performance) is about 3.9.

A good insulating layer is the lifeline of a transistor. Silicon naturally has such a property: a super good insulating layer is a matter of historical significance for the semiconductor industry.

Therefore.

At the 65nm process node, the principle of the Ge-strained channel introduced is to penetrate the silicon into the silicon by discharging impurities in appropriate places.

The lattice constants of germanium and silicon are different, thus causing the silicon lattice shape to change.

According to energy band theory, this change can increase the mobility of electrons in the direction of the channel.

A high mobility will increase the operating current of the transistor.

Someone once lamented.

It is said that God is helping mankind to invent integrated circuits. First, he gave so much sand (the raw material of silicon wafers) and then gave him a perfect natural insulation layer.

So far.

Silicon is extremely difficult to replace.

An important reason is that as a material for manufacturing transistors, its overall performance is perfect.

"Silicon dioxide is good, but when the size of transistors shrinks to a certain limit, problems begin to occur."

"During its shrinking process, the electric field intensity remains unchanged."

"In this case, from the perspective of the energy band, because of the volatility of electrons, if the insulating layer is too narrow, there is a certain probability that the electrons will tunnel through and cross the energy band barrier of the insulating layer, resulting in leakage current. ."

"The size of the current is negatively related to the thickness of the insulating layer, as well as the 'barrier height' of the insulating layer."

"So the smaller the thickness, the lower the potential barrier, the greater the leakage current, which is more detrimental to the transistor."

Another scientist at the meeting also spoke.

"so."

"On the other hand, the switching performance, operating current, etc. of the transistor require a large insulating layer capacitance."

“According to the fact that capacitance is equal to the dielectric constant divided by the thickness of the insulating layer.”

"The smaller the thickness, the greater the dielectric constant, which is better for the transistor."

"Actually, if the capacitance is infinite, the SS index will reach the ideal 60."

Having said this, the scientist paused, and then changed the subject.

"but!"

"There has been a contradiction in the design goals here, that is, whether the thickness of the insulation layer should continue to be reduced."

"In fact, before this node, silicon dioxide has shrunk to a thickness of less than two nanometers, which is a thickness of more than a dozen atomic layers, and the problem of leakage current has replaced the problem of performance."

Speaking of which.

All the experts and scholars in the conference room fell silent.

Those sitting here are all the smartest people. If there is a problem, of course they start to think of a solution.

Human beings are greedy.

They are neither willing to give up the performance enhancement of large capacitors, nor are they willing to take the risk of leakage.

0…Please give me flowers…

To put it in more popular terms, whatever choice adults make, they need both!

at present.

Pangu Semiconductor has reached a bottleneck in the search for dielectric materials.

The high-k material is really great.

but.

High-k materials have two side effects.

One is that the operating current will be reduced inexplicably.

Second, it will change the threshold voltage of the transistor.

The threshold voltage is the minimum voltage required to open the channel of the transistor. This value is a very important parameter of the transistor.

....00

The main reason for this problem is.

High-k materials will reduce the channel carrier mobility in the trench and affect the position of the Fermi level at the interface.

The lower the carrier mobility, the lower the operating current.

The so-called Fermi level is an analytical method to explain the distribution of semiconductor electrons from the image of energy band theory.

Simply put, its location affects the threshold voltage of the transistor.

The occurrence of these two problems is related to the dipole distribution inside the high-k material.

A dipole is a pair of charge systems with a positive charge on one end and a negative charge on the other.

It can change its distribution according to the direction of the external electric field.

The reason why the dielectric constant of high-k materials is high has a lot to do with the internal dipoles.

so.

This is a double-edged sword.

In academia.

In recent years, various imaginative new designs have been proposed.

For example.

Negative capacitance effect transistors, carbon nanotubes, tunneling transistors, etc.

But in fact, all these involve basically four directions.

Materials, mechanisms, processes, and structures. .