Why increased capacitance density matter

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.