In a press release, we announced that Smoltek Semi has devel­oped a new dielec­tric stack that increas­es capac­i­tance den­si­ty by 230 per­cent and reduces leak­age cur­rent by 50 per­cent. But what the heck is a dielec­tric stack? And how does it ben­e­fit you as a share­hold­er and investor?

CNF-MIM capacitors are needed

Car­bon nanofibers are the core of what we do. We use them to tack­le com­plex mate­r­i­al chal­lenges across var­i­ous indus­tries, such as cre­at­ing ultra-thin capac­i­tors with suf­fi­cient capacitance.

Capac­i­tors are essen­tial for sta­bi­liz­ing the pow­er fluc­tu­a­tions caused when tran­sis­tors inside an appli­ca­tion proces­sor switch between ones and zeros bil­lions of times per sec­ond. They quick­ly absorb excess ener­gy and release stored ener­gy when need­ed. The catch is that these capac­i­tors must be placed very close to the tran­sis­tors to be effective—ideally, right under the chip itself.

This requires capac­i­tors small enough to fit between the sol­der balls on the under­side of the chip. These capac­i­tors need to be thin­ner than the diam­e­ter of the sol­der balls yet still pro­vide enough capac­i­tance to han­dle the task.

Smoltek Semi address­es this chal­lenge with its CNF-MIM capacitors.

Three things that increase capacitance

Fun­da­men­tal­ly, a capac­i­tor con­sists of two met­al plates with an insu­lat­ing mate­r­i­al between them. Its abil­i­ty to store ener­gy, capac­i­tance, is pri­mar­i­ly deter­mined by three factors:

• The area of the met­al plates’ sur­face. The larg­er the area, the high­er the capacitance.
• The dis­tance between the met­al plates. The short­er the dis­tance, the high­er the capacitance.
• The abil­i­ty of the insu­la­tion mate­r­i­al to store ener­gy. The high­er this abil­i­ty (expressed as the dielec­tric con­stant, κ), the high­er the capacitance.

CNF-MIM capac­i­tors are just met­al-insu­la­tion-met­al (MIM) capac­i­tors where we cre­ate a large area in a small vol­ume using car­bon nanofibers (CNF).

CNF as area multiplier

Grow­ing car­bon nanofibers on a sur­face increas­es the sur­face area tens of thou­sands of times. To under­stand why this is so, con­sid­er a car­bon nanofiber as a ver­ti­cal­ly stand­ing cylin­der of height h and radius r. The cylinder’s man­tle sur­face is 2πrh, and its base sur­face is πr². So you could say that the car­bon nanofiber takes up a sur­face of πr² but cre­ates a new sur­face of 2πrh. Since h is much larg­er than r, the new sur­face is also much larg­er, more pre­cise­ly 2πrh /​ πr² = 2h/​r. A car­bon nanofiber with r = 20 nm and h = 20 µm thus increas­es the area by a whop­ping fac­tor of 1,000.

It is this capac­i­ty, as an area mul­ti­pli­er, that car­bon nanofiber is used in Smoltelk’s CNF-MIM capac­i­tor. They mul­ti­ply the sur­face area, which we then cov­er lay­er by lay­er with met­al, insu­la­tion, and more metal.

Sim­ply put, we start with a sub­strate on which we grow a for­est of car­bon nanofibers. Each car­bon nanofiber is then coat­ed in met­al. Next, we add a lay­er of insu­la­tion over the met­al-coat­ed nanofibers. Final­ly, we place anoth­er met­al lay­er on top of the insu­la­tion. This cre­ates a large met­al-insu­la­tion-met­al sur­face area rel­a­tive to its small volume.

Because a capacitor’s abil­i­ty to store ener­gy is pro­por­tion­al to its sur­face area, the capac­i­tance per unit vol­ume of CNF-MIM capac­i­tors is extreme­ly high. This allowed Smoltek to show­case a lab pro­to­type of the world’s thinnest capac­i­tor already in 2021.

Meaning of the press release

Hafni­um oxide was used as insu­la­tion in the first batch­es of CNF-MIM capac­i­tors. Hafni­um oxide is a mate­r­i­al with high dielec­tric con­stant κ.

What the press release says is that Smoltek Semi’s researchers have devel­oped a brand new insu­la­tion that alone increas­es capac­i­tance den­si­ty by 230 per­cent com­pared to hafni­um oxide.

On the same sur­face area as before, we can now get more than three times the capac­i­tance. This means that Smoltek puts fur­ther dis­tance between itself and its competitors.

More­over, as icing on the cake, Smoltek’s engi­neers have reduced the inevitable leak­age cur­rent by 50 percent.

Dielectric stack

The new insu­la­tion con­sists of lay­er upon lay­er of two mate­ri­als. One mate­r­i­al has a very high dielec­tric con­stant κ, which means it can store a lot of ener­gy. The oth­er mate­r­i­al is a very good elec­tri­cal insu­la­tor, which means it acts as a bar­ri­er to leak­age current.

We call the new mate­r­i­al a dielec­tric stack, because it is a stack of lay­ers of the two mate­ri­als, and it has a high dielec­tric con­stant κ.

Yageo is testing

To bet­ter under­stand the prop­er­ties of the new dielec­tric stack, we began by using it in the sim­plest type of capac­i­tors: par­al­lel plate capac­i­tors. As the name sug­gests, these con­sist of two par­al­lel met­al plates with the dielec­tric stack between them. This design lets us study the dielec­tric stack’s char­ac­ter­is­tics with­out inter­fer­ence from oth­er factors.

We have man­u­fac­tured these capac­i­tors and sent them to Yageo for reli­a­bil­i­ty test­ing and fur­ther char­ac­ter­i­za­tion. Mean­while, we’ve already moved on to the next phase: inte­grat­ing the new dielec­tric stack into CNF-MIM capacitors.

As Yageo car­ries out its test­ing and the first CNF-MIM capac­i­tors are pro­duced using the new dielec­tric stack, Smoltek’s CTO, Farzan Gha­vani­ni, reviews the ini­tial results with sat­is­fac­tion and enthu­si­asm. With a 230 per­cent increase in capac­i­tance, a 50 per­cent reduc­tion in leak­age cur­rent, and a flaw­less 100 per­cent fab­ri­ca­tion yield, he is gen­uine­ly thrilled by this breakthrough.

What does this mean to you?

So, what does this mean for you as a share­hold­er and investor?

This means that Smoltek is not just keep­ing up in a com­pet­i­tive indus­try but also active­ly pulling ahead. With a 230 per­cent increase in capac­i­tance and a 50 per­cent reduc­tion in leak­age cur­rent, Smoltek has set a new bench­mark in per­for­mance. This break­through strength­ens our mar­ket posi­tion and makes our tech­nol­o­gy even more attrac­tive to major play­ers in the semi­con­duc­tor indus­try. It’s not just a tech­ni­cal achievement—it’s a com­mer­cial advan­tage that could lead to new part­ner­ships and a faster path to mar­ket adoption.