Wednesday, October 17, 2012

The memory resistor patent thicket

Patent thickets are overlapping patent rights controlled by different corporations which often act as an impedance to commercialization of new technology. One area which seems to have a big problem with patent thickets is memory resistor technology (e.g. ReRAM, CBRAM, phase change memory) in which over 3300 US patents have already issued (more information on the patent statistics available at this link). Despite this large number of patents there has been almost no indication of significant commercial development yet (other than HP's memristor hype).

At this point the large number of patents seem to indicate problems in terms of patent thickets for any start-up company interested in developing applications of memory resistor materials. I thought it might be a good idea to point out some of the broad patents which do not seem to meet the requirements for patentability (i.e. novelty or obviousness) based on uncited prior art and which may be some of the more stickier thorns of this patent thicket. A brief summary of these patents is organized below based on the listed assignee. I filed more thorough explanations with the USPTO under 37 CFR 1.501 (linked here).

AMD
US 6864522 - This patent filed in 2003 claims an ionic memory resistor with an active and passive layer. Some of the claims are broad enough to be anticipated by a chalcogenide ionic memory resistor patent filed by Micron in 2001 (US 6348365).

Axon Technology
US 6635914 and US 6985378 - These patents filed in 2001 claims an ionic memory resistor with an oxidizable electrode. The basic claimed structure was already described back in 1988 by a company called Maxdem Inc. (US 4945257).

US 7675766, US 7728322, US 7929331, and US 8022384 - These patents with priority going back to 2000 includes claims to ionic memory resistors. The basic claimed structure was already described back in 1988 by a company called Maxdem Inc. (US 4945257) and by NASA in 1991 (US 5278636).

Hewlett Packard
US 6456525 - This patent filed in 2000 includes claims to a crosspoint array of memory resistors with a serial linear resistor. The claimed structure was already described by Caltech researchers in US 4839859 in 1987.

US 6518156 and US 6891744 - These patents filed in 2000 claims memory resistor crossbar structure with nanoscale lines. The basic memory resistor crossbar structure was already described in 1983 by Energy Conversion Devices (US 4677742). Scaling to nanoscale dimensions would have been obvious using techniques such as nanoimprint lithography (US 5772905) to improve device density.

US 6625055 - This patent filed in 2002 claims storing multibit data in individual memory resistance cells. Multibit memory resistor storage was earlier described by Energy Conversion Devices such as in US 4646266 filed in 1984.

US 6870751 - This patent filed in 2002 claims a memory resistor crosspoint array with a current concentrating feature. This was earlier described by Energy Conversion Devices in US 5687112 filed in 1997.

US 7034332 - This patent filed in 2004 claims a nanoscale memory resistor array with self-aligned rectifying elements. This was earlier described by Macronix in 2002 for phase change materials (US 6579760).

US 7443711 - This patent filed in 2004 claims a nanoscale memory resistor with tunable impedance. This was earlier described by Unity Semiconductor in 2003 (US 7038935). It is notable that the attorney arguments in this case were based on misunderstanding of the definition of electrical impedance versus electrical reactance which may also affect the validity of the patent.

US 7741638 - This patent filed in 2005 for a control layer of a memory resistor for controlling electrochemical or electrophysical reaction paths. The claimed structure was earlier described by Macronix in 2003 (US 6873541) and by Sharp in 2003 (US 6972238).

US 7763880 - This patent filed in 2007 claims a 3-terminal ionic memory resistor but this concept was earlier described by NEC in 2004 (US 2006/0164880).

US 7902869 and US 7982504 - These patents filed in 2010 claim a 3D crossbar memory resistor circuit. The claimed structure was earlier described by Toshiba in 2003 for 3D phase change memory resistor crossbars (US 7335906).

US 7985962 - This patent filed in December of 2008 claims a memory resistor structure with a metal oxide electrode. This was earlier described by Samsung in US 7417271 filed in the US in January of 2007.

US 8063395 - This patent filed in 2009 claims an ionic memory resistor with an electrode formed of amorphous material. This was earlier described by AMD in US 6838720 filed in 2003.

IMEC
US 7960775 - This patent filed in 2008 claims a metal oxide memory resistor with an oxygen gradient. This was earlier described by Sharp in 2003 (US 6972238), IBM in 2006 (US 7569459), and Samsung in 2007 (US 7417271).

Micron Technology
US 6891749 - This patent filed in 2002 claims a memory resistor structure having electrodes with different electrochemical potential. This was earlier described by AMD in 2002 (US 6781868).

Panasonic
US 7369431 and US 7826247 - These patents filed in 2004 claims determining a relationship between voltage polarity and increase/decrease of resistance in a memory resistance cell. This was earlier described in 1994 for a synaptic memory resistance cell (US 5541869).

US 7577022 - This patent filed in 2005 claims a memory resistor structure having both variable resistance and diode characteristics. This was earlier described in Energy Conversion Devices in 1984 (US 4646266), Micron in 2002 (US 6891749), and Spansion in 2004 (US 7157732).

Samsung
US 7085154 and  US 7180771, - These patents filed in 2004 claims a method for setting the pulse width duration for programming a memory resistor. The claimed method was earlier described in 1994 for a synaptic memory resistance cell (US 5541869).

US 7400027 - This patent filed in 2005 claims a multilayer memory resistor cell with a resistance changing layer and a threshold switching layer. This was earlier disclosed by Energy Conversion Devices in 1985 (US 4597162) and again by Unity Semiconductor in 2003 (US 6870755).

US 7417271 - This patent filed in 2007 claims a multilayer oxide memory resistance cell. This was earlier described by Sharp in 2003 (US 6972238).

US 7656696 - This patent filed in 2006 claims a memory resistor with a resistor to control a switching window. The claimed structure was already described by Caltech researchers in US 4839859 in 1987.

US 7935952 - This patent filed in 2008 claims a memory resistor including a threshold switching resistor, an intermediate electrode, and a resistance changing layer. This was earlier described by Unity Semiconductor in 2002 (US 6753561) and by Sharp in 2003 (US 6849564).

US 8054672 - This patent filed in 2007 claims a chalcogenide memory resistor operating without phase change and with a limited electrode contact region. This was earlier described by Axon Technology in 2002 (US 6798692).

Sandisk
US 7733685 - This patent filed in 2008 claims a memory resistor structure sandwiched between distributed diodes. This was earlier described in 2006 (US 7378870).

US 8208282 - This patent with priority going back to 1998 claims a memory resistor cell including a vertically aligned steering element (e.g. diode) and state change element. This was earlier described by Energy Conversion Devices in 1991 (US 5296716).

Sony
US 7583525 - This patent filed in 2007 claims a method of driving a memory resistor by applying multiple voltage pulses to change the resistance state. The claimed method was earlier described in 1994 for a synaptic memory resistance cell (US 5541869).

Spansion
US 7183141 - This patent filed in 2004 claims a method of reversibly programming a memory resistor. This was earlier described by researchers at CalTech in 1990 (US 5272359).

US 7564708 - This patent filed in 2006 claims an ionic memory resistor including an active and passive layer. This was earlier described by Micron Technology in 2001 (US 6348365) and by AMD in 2003 (US 6864522).

US 7646624 - This patent filed in 2006 claims selecting an electrode material of a memory resistor to determine the on-state resistance. This was earlier described by Micron Technology in 2002 (US 6891749).

Unity Semiconductor
US 6870755 - This patent filed in 2003 claims a reversibly writable memory resistor. This was earlier described by Energy Conversion Devices such as in US 4597162 filed in 1985.

US 6906939 - This patent filed in 2003 claims a 3D stacked memory resistor array. This was earlier described by Energy Conversion Devices such as in US 5912839 filed in 1998.