Motorola Corporation

Kuo-Tung Chang

Ko-Min Chang

Craig T Swift

Bruce L Morton

Umesh Sharma

Erwin J Prinz

Danny P Shum

Wei-Ming Chen

Jack Higman

Marius K Orlowski

Jon T Fitch

Keith E Witek

Chung-You Hu

Chi Nan Brian Li

Douglas R Roberts

George L Espinor

Craig A Cavins

David Burnett

Wei-Hua Liu

Lee Z Wang

Yangming Su

Keith Forbes

A first plurality of memory cells ( ) connected in series lies within a first well ( ) that is separated and electrically isolated ( ) from a second plurality of memory cells ( et al.) connected in series lying within a second well ( ). In one embodiment, the first and second wells ( ) are doped p-type and are contained within an n-well ( ) and a substrate ( ). Applying a negative voltage to its corresponding bit line and a positive voltage to its corresponding word line programs a predetermined memory cell within the first plurality. A lesser positive voltage than that applied to the predetermined memory cell's word line is applied to all other bit lines and word lines of non-selected memory cells. By utilizing a negative voltage while programming a memory cell, the magnitude of programming voltages is reduced, thereby, removing the need for an elaborate charge pump to generate a much higher programming voltage.

Non-volatile memory with a serial transistor structure with isolated well and method of operation

A semiconductor device includes a non-volatile memory, such as an electrically erasable programmable read only memory (EEPROM) array of memory cells. The memory is arranged as an array of cells in rows and columns. P-well regions of the array are spaced apart and electrically isolated by shallow trench features. The cells of each column are positioned within a respective isolated p-well region. Control gates of sequentially corresponding memory cells in columns of the array are electrically coupled by common wordlines. Bitlines electrically couple drain regions of each memory cell in the respective columns of the memory cell array. Source lines electrically couple source regions of each memory cell in the respective columns of the array. The source lines and at least one memory cell in each column of the array are electrically coupled to the p-well region corresponding to the column of the source line and cell. Each column of the array is therefore located within an isolated well, common to the cells in the column but isolated from other wells of other columns. The array is programmed by pulsing potentials as to each column, with isolation of results for each column.

Non-volatile memory, method of manufacture, and method of programming

A split-gate EEPROM transistor includes a channel region ( ) formed in a vertically disposed semiconductor body ( ) and residing intermediate to a drain region ( ) and a source region ( ). A select gate electrode ( ) is horizontally disposed on a semiconductor substrate ( ). A floating gate electrode ( ) resides adjacent to the channel region ( ) and overlies the select gate electrode ( ). A control gate electrode ( ) resides adjacent to the control gate electrode ( ) and also overlies the select gate electrode ( ). In operation, the select gate electrode ( ) regulates the flow of electrical charge from the source region ( ) into the channel region ( ), and provides a field plate electrical isolation for adjacent memory cells in an EEPROM array.

Split-gate vertically oriented EEPROM device and process

A semiconductor device (,) includes a memory cell having a select transistor (,) and a storage transistor (,) having a relatively uniform tunnel dielectric thickness under both the floating gate (,) of the storage transistor and the select gate (,) of the select transistor (,). The select transistor (,) is adjacent to the drain region (,) for the memory cell to nearly eliminate a drain disturb problem. During programming, the control gate (,) is at a negative potential, and the drain region (,) is at a positive potential. The drain potential is sufficiently low to not degrade the tunnel dielectric layer (,) of the select transistor (,). During erase, a positive potential is applied to the control gate (,). The relatively uniform tunnel dielectric layer (,) thickness of the select transistor (,) allows for a faster operating device by increasing the read current of the memory device.

Semiconductor device and method of operating it

A nonvolatile memory includes five transistors. The memory has an MOS transistor in series with two pairs of transistors, where each pair includes a floating gate transistor and a metal-oxide-semiconductor transistor electrically connected in parallel. The memory structure may be formed with three levels of silicon-containing or metal-containing layers. The memory structure is less susceptible to read disturb errors compared to a prior art dual-bit nonvolatile memory structure.

Nonvolatile memory circuit and structure

A semiconductor device (70) includes a memory cell having a select transistor (67) and a storage transistor (65) having a relatively uniform tunnel dielectric thickness under both the floating gate (651) of the storage transistor and the select gate (671) of the select transistor (67). The select transistor (67) is adjacent to the drain region (68) for the memory cell to nearly eliminate a drain disturb problem. During programming, the control gate (652) is at a negative potential, and the drain region (68) is at a positive potential. The drain potential is sufficiently low to not degrade the tunnel dielectric layer (42) of the select transistor (67). During erase, a positive potential is applied to the control gate (652). The relatively uniform tunnel dielectric layer (42) thickness of the select transistor (67) allows for a faster operating device by increasing the read current of the memory device.

Method of building an EPROM cell without drain disturb and reduced

An EEPROM device includes a split-gate FET (10) having a source (36), a drain (22), a select gate (16) adjacent the drain (22), and a control gate (32) adjacent the source (36). When programming the split-gate FET (10), electrons are accelerated in a portion of a channel region (38) between the select gate (16) and the control gate (32), and then injected into a nitride layer (24) of an ONO stack (25) underlying the control gate (32). The split-gate FET (10) is erased by injecting holes from the channel region (38) into the charge nitride layer (24). When reading data from the split-gate FET (10), a reading voltage is applied to the drain (22) adjacent the select gate (16). Data is then read from the split-gate FET (10) by sensing a current flowing in a bit line coupled to the drain (22).

Split-gate memory device and method for accessing the same

A non-volatile memory having a control gate (14) and a sidewall select gate (28) is illustrated. The sidewall select gate (28) is formed in conjunction with a semiconductor doped oxide (20) to form a non-volatile memory cell (7). The semiconductor element used to dope the oxide layer (20) will generally include silicon or germanium. The non-volatile memory cell (7) is programmed by storing electrons in the doped oxide (20), and is erased using band-to-band tunneling.

Method of making and accessing split gate memory device

A non-linear charge pump (1120) provides various voltages for use in a nonvolatile memory (400) and operates at low power supply voltages. The non-linear charge pump (1120) includes at least two non-linear voltage doubling stages (1132, 1134), which allows a capacitor formed with relatively thin gate oxide in a first stage (1132) to be made larger than a capacitor formed using relatively thick gate oxide in a second stage (1134). An output of a last voltage doubling stage (1136) is then input to a linear stage (1150) to generate a precise voltage. Another charge pump (1140) including non-linear stages (1142, 1144) followed by a linear stage (1146) is used to generate a reference voltage for the main non-linear charge pump (1130). The nonlinear stage (1130) includes a special bulk biasing circuit to bias the bulk of a transistor (1285) on the output side of the charging circuit (1284, 1285, 1286, 1287) continuously to prevent forward biasing the parasitic drain-bulk diode.

Non-linear charge pump

A memory array (25) having a selected memory cell (10) and an unselected memory cell (30) is programmed and read. Each memory cell in the memory array (25) contains an isolation transistor (22) and a floating gate transistor (23). To program the selected memory cell (10), programming voltages are applied to a control gate line (21), a drain line (14), an isolation line (19), and a source line (12). To reduce the effects of the drain disturb problem, a gate terminal (32) of the unselected memory cell (30) is held at a positive voltage. To read selected memory cell (10), a read voltage is applied to an isolation gate line (31) of unselected memory cell (30) which insures that the unselected memory cell (30) does not conduct or contribute to leakage current and power consumption during the read operation.

Method for operating a memory array

An EEPROM cell (40) includes a floating gate transistor (47) and an isolation transistor (45). Both a floating gate (48) and an isolation gate (46) are formed on a tunnel dielectric (44) within the cell. The isolation gate is coupled to a doped source region (52) of the floating gate transistor. The isolation transistor is not biased during a program operation of the cell, enabling a thin tunnel dielectric (less than 120 angstroms) to be used beneath all portions of both gates within the cell. Thus, the need for both a conventional tunnel dielectric and a gate dielectric is eliminated. The cell tolerates over-erasure, can be programmed at low programming voltages, and has good current drive due to the thin tunnel dielectric throughout the cell.

Method for making an EEPROM cell with isolation transistor

A method for fabricating a 1-transistor EEPROM device, which can be programmed and erased by Fowler-Nordheim tunneling includes the formation of a memory gate (28) overlying a tunneling region (22), and aligning source (32) and drain (34) regions in a semiconductor substrate (10), such that a vertically oriented electric field (46) is created in the tunneling region (22). The memory gate (28) is coupled to a contact region (30) by a connecting portion (31). A select gate (14) controls a portion of the channel region in the substrate (10) adjacent to the tunneling region (22). The EEPROM device is programmed by applying a voltage of a first polarity memory gate (28), while applying a voltage of a second polarity to the source region (32), the drain region (34), and to the substrate (10). Under the applied voltages, charge carriers tunnel through a tunnel oxide layer (40) and into a silicon nitride layer (42), located intermediate to the memory gate (28) and the tunnel region (22). To erase the EEPROM device, the polarity of the applied voltages is reversed, and charge carriers of an opposite conductivity type tunnel into the silicon nitride layer (42).

Fabrication process for a 1-transistor EEPROM memory device capable of

Flash EEPROM cells having merged select/control gates may be formed, so that the portions of the channel regions that correspond to select transistors are formed after spacers are formed but prior to patterning a merged select/control gate layer. Because the portions of the channel regions that correspond to the select transistors are not determined by the patterning of the merged select/control gate layer, misalignment of the mask used to pattern the merged select/control gate layer does not affect the size of the select transistor portion of the channel region. The spacers may be left on over the substrate in the finished devices thereby saving at least one processing step. The memory structure may also be used in other EPROM-type memory cells, such as individually erasable EEPROMs and EPROMs that are not electrically erasable.

Electrically programmable read-only memory array

Method of making a nonvolatile memory device with five transistors

An EEPROM memory array includes a plurality of memory cells having a floating gate electrode (22) formed as a sidewall spacer adjacent to a control gate electrode (20). Source and drain regions (12, 14) reside in a semiconductor substrate (10) and define a segmented channel region (16) therebetween. A select gate electrode (18) overlies a first channel region (24) and separates the floating gate electrode (2) from the source region (12). The control gate electrode (20) overlies a third channeI region (28) and separates the floating gate electrode (22) from the drain region (14). The floating gate electrode (22) overlies a second channel region (26) and is separated therefrom by a thin tunnel oxide layer (42). The EEPROM device of the invention can be programmed by either source side injection, or by Fowler-Nordheim tunneling. Additionally, a process is provided for the fabrication of an EEPROM array utilizing adjacent select gate electrodes (18, 18') as a doping mask.

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Austin, TX, United States of America

Kuo-Tung Chang