Breaking News
News & Analysis

ReRAM Startup Bets on Silver

8/5/2013 11:02 AM EDT
65 comments
NO RATINGS
1 saves
Page 1 / 3 Next >
More Related Links
View Comments: Newest First | Oldest First | Threaded View
<<   <   Page 2 / 7   >   >>
Ron Neale
User Rank
Author
Re: CBRAM? ECM or EM good question
Ron Neale   10/2/2013 9:52:03 AM
NO RATINGS
PhyandEE: I was not trying to minimize the potential problems of mixing Ag and the silicon fab process but I think it should be possible to create an Ag based memory pore structure that keeps the silver isolated, in the same way as in the case of copper-silicon. However, I think the fact that silver is a fast diffuser in silicon raises a potential reliability problem at the memory cell level. The filament represents a silver concentration gradient in the a-Si so I would think there is a distinct possiblility that with the device in its on state the filament might just diffuse away in a radial direction with time-temperature, resulting in failure. If that is what you were trying to imply then I agree with you. When we see the reliability test results for representative devices (20nm) that should give us a good idea of the magnitude of the problem, "big" or otherwise.

 

PhyandEE
User Rank
Author
Re: CBRAM? ECM or EM good question
PhyandEE   10/2/2013 8:47:48 AM
NO RATINGS
Copper might be a different story. To solve this problem, for example, additional diffusion barriers are used. 

But in their work, they seem to use silver as the conducting bridge (filament). The silver atoms diffuse through the amorphous silicon and form the filament for switching. The problem comes. Silver atoms can diffuse through the whole silicon layer. The silicon layer can not be perfect. With the electrical field applied, with the heat generated, and with the time, it is a big problem. 

Ron Neale
User Rank
Author
Re: CBRAM? ECM or EM good question
Ron Neale   10/2/2013 5:26:27 AM
NO RATINGS
PHYandEE: I think you will find I made the same point in my comment to Peter Clarke that you will find in the last page of his piece above. I think the fact that silver is a fast diffuser in silicon and needs very little encouragement (electric field, current, heat) to move is the very reason the Crossbar device "works".

However, remember there was a time, for similar resons, when if you suggested that you wanted to use copper as a conductor on silicon people would have advised you it was not a wise step, they might have used stronger language, now its use is common.

 

PhyandEE
User Rank
Author
Re: CBRAM? ECM or EM good question
PhyandEE   10/1/2013 11:50:12 PM
NO RATINGS
I don't quite understand why they use Ag in a circuit. Silver is known for its serous migration effects under an electrical field. The heat by current makes this even worse. I don't know how they solve the reliablity issue using such a material.

Ron Neale
User Rank
Author
Re: CBRAM? ECM or EM good question
Ron Neale   10/1/2013 2:59:10 PM
NO RATINGS
Resistion-I went back and had a look at K-H Kim's thesis. It states "..movement of Ag ions in the a-Si matrix..." Suggesting a belief that those were ions moving towards the cathode, with a positive charge. Belief because there was not much evidence provided to prove the point; perhaps I missed it. It is not clear to me what elements provide for the oxidation-reduction prcess to form a ECM cell and provide the positive charged ions that you suggested need to be neutralized. Describe that for me with the elements available and you can have your positively charged Ag ion.

The thesis also states ".. Current can only flow through the device with a positve bias.." By that I think it is the current for programming to the low resistance state making the Ag electrode positive. The reason for that is because of the non-linear element that is somewhere in structure.  Current does flow in the reverse direction for erase.

resistion
User Rank
Author
Re: CBRAM? ECM or EM good question
resistion   9/30/2013 1:00:58 PM
NO RATINGS
So it's neutral Ag that's moving?

Ron Neale
User Rank
Author
Re: CBRAM? ECM or EM good question
Ron Neale   9/30/2013 9:13:43 AM
NO RATINGS
Resistion-Not so much a complication, for me more a process of elimination of all possibilities. I tried to look at all the possible ways in which an electrochemical cell might be formed from the elements available in the Crossbar memory structure.

resistion
User Rank
Author
Re: CBRAM? ECM or EM good question
resistion   9/29/2013 9:00:24 PM
NO RATINGS
I see, so the presence of mobile hydrogen could be an electrochemical complication.

Ron Neale
User Rank
Author
Re: CBRAM? ECM or EM good question
Ron Neale   9/29/2013 2:03:30 PM
NO RATINGS
Resistion- Hydrogen should be the only other element that is available in a-Si and would have the possiblity of being mobile. (Remember a-Si is a sub hydride of silicon). I am not sure  if it possible to make a silver-hydrogen ECM cell where oxidation-reduction takes place in the OIL RIG* sense. I did look at the possibilty that the movement of Ag into the a-Si lattice would displace hydrogen into the void at the depleted surface of the Ag electrode. I would think that would most likely trigger the crystalization of the a-Si and that would not be reversible.

For an Ag-aSi-xtalSi  Crossbar memory structure I also looked at the possibility that solid state epitaxy on the single crystal surface might account for the diode/non-linear element (or even be a way of creating one). In the the distant past I did use palladium as a catalyst for low temperature solid state epitaxy of a-Si on xtal crystal after switching for use as a PROM. Some of the details are in my US patent No 4,174,521.

Sorry *OIL-RIG Oxidation Is Loss-Reduction Is Gain, of electrons

resistion
User Rank
Author
Re: CBRAM? ECM or EM good question
resistion   9/29/2013 9:34:19 AM
NO RATINGS
Thanks I would be interested. Earlier I meant the Ag+ ions might be neutralized in silicon instead of at the electrode. But the other effects you mentioned also could play a role.

<<   <   Page 2 / 7   >   >>
Most Recent Comments
michigan0
 
SteveHarris0
 
realjjj
 
SteveHarris0
 
SteveHarris0
 
VicVat
 
Les_Slater
 
SSDWEM
 
witeken
Most Recent Messages
9/25/2016
4:48:30 PM
michigan0 Sang Kim First, 28nm bulk is in volume manufacturing for several years by the major semiconductor companies but not 28nm FDSOI today yet. Why not? Simply because unlike 28nm bulk the LDD(Lightly Doped Drain) to minimize hot carrier generation can't be implemented in 28nm FDSOI. Furthermore, hot carrier reliability becomes worse with scaling, That is the major reason why 28nm FDSOI is not manufacturable today and will not be. Second, how can you suppress the leakage currents from such ultra short 7nm due to the short channel effects? How thin SOI thickness is required to prevent punch-through of un-dopped 7nm FDSOI? Possibly less than 4nm. Depositing such an ultra thin film less then 4nm filum uniformly and reliably over 12" wafers at the manufacturing line is extremely difficult or not even manufacturable. If not manufacturable, the 7nm FDSOI debate is over!Third, what happens when hot carriers are generated near the drain at normal operation of 7nm FDSOI? Electrons go to the positively biased drain with no harm but where the holes to go? The holes can't go to the substrate because of the thin BOX layer. Some holes may become trapped at the BOX layer causing Vt shift. However, the vast majority of holes drift through the the un-dopped SOI channel toward the N+Source,...

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed