WO2015097897A1 - 半導体記憶装置およびその製造方法 - Google Patents
半導体記憶装置およびその製造方法 Download PDFInfo
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- WO2015097897A1 WO2015097897A1 PCT/JP2013/085222 JP2013085222W WO2015097897A1 WO 2015097897 A1 WO2015097897 A1 WO 2015097897A1 JP 2013085222 W JP2013085222 W JP 2013085222W WO 2015097897 A1 WO2015097897 A1 WO 2015097897A1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/80—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays
- H10B63/84—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays arranged in a direction perpendicular to the substrate, e.g. 3D cell arrays
- H10B63/845—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays arranged in a direction perpendicular to the substrate, e.g. 3D cell arrays the switching components being connected to a common vertical conductor
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- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0004—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising amorphous/crystalline phase transition cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/528—Geometry or layout of the interconnection structure
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/20—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/30—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having three or more electrodes, e.g. transistors
- H10B63/34—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having three or more electrodes, e.g. transistors of the vertical channel field-effect transistor type
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/80—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays
- H10B63/84—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays arranged in a direction perpendicular to the substrate, e.g. 3D cell arrays
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- G11C2213/75—Array having a NAND structure comprising, for example, memory cells in series or memory elements in series, a memory element being a memory cell in parallel with an access transistor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
- H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
- H01L21/82—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
- H01L21/822—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components the substrate being a semiconductor, using silicon technology
- H01L21/8232—Field-effect technology
- H01L21/8234—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type
- H01L21/823487—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type with a particular manufacturing method of vertical transistor structures, i.e. with channel vertical to the substrate surface
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- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
- H10N70/231—Multistable switching devices, e.g. memristors based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
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- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/821—Device geometry
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/821—Device geometry
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/881—Switching materials
- H10N70/882—Compounds of sulfur, selenium or tellurium, e.g. chalcogenides
- H10N70/8828—Tellurides, e.g. GeSbTe
Definitions
- the present invention relates to a selection transistor for selecting two directions in a semiconductor substrate surface, which reduces a dimension in a semiconductor substrate surface of a three-dimensional vertical semiconductor memory device.
- phase change memories using chalcogenide materials as recording materials have been actively studied.
- a phase change memory is a type of resistance change memory that stores information using the fact that recording materials between electrodes have different resistance states.
- the phase change memory stores information using the fact that the resistance value of a phase change material such as Ge 2 Sb 2 Te 5 is different between an amorphous state and a crystalline state.
- the resistance is high in the amorphous state and low in the crystalline state. Therefore, information is read from the memory cell by applying a potential difference to both ends of the element, measuring the current flowing through the element, and determining the high resistance state / low resistance state of the element.
- phase change memory data is rewritten by changing the electrical resistance of the phase change film to different states by Joule heat generated by current.
- the reset operation that is, the operation of changing to the high resistance amorphous state is performed by flowing a large current for a short time to dissolve the phase change material, and then rapidly decreasing the current and quenching.
- the set operation that is, the operation of changing to a low-resistance crystal state is performed by flowing a current sufficient to maintain the phase change material at the crystallization temperature for a long time.
- a phase change memory is suitable for miniaturization in principle because the current required to change the state of the phase change film decreases as the miniaturization progresses. For this reason, research is actively conducted.
- Patent Document 1 as a method for highly integrating a phase change memory, a plurality of through-holes penetrating all layers are collectively formed in a stacked structure in which a plurality of gate electrode materials and insulating films are alternately stacked.
- a configuration is disclosed in which a gate insulating film, a channel layer, and a phase change film are formed and processed inside a through hole.
- Each memory cell includes cell transistors and phase change elements connected in parallel, and a plurality of memory cells are connected in series in the vertical direction, that is, in the normal direction to the semiconductor substrate, to form a phase change memory chain.
- individual phase change memory chains are selected by vertical selection transistors.
- each select transistor has a structure separated for each phase change memory chain. Since the vertical selection transistor of Patent Document 1 forms a hole in which a channel is formed in a gate processed into a strip shape, the width of the gate needs to be larger than the minimum processing size.
- the gate pitch is about 3F, where F is the minimum processing dimension, and the pitch of the memory cells is also 3F.
- a technique for applying a similar vertical structure to a flash memory is disclosed in Patent Document 2.
- Patent Document 3 As a technique for reducing the gate pitch to 2F, the method of Patent Document 3 is disclosed. However, since it is necessary to form the selection transistors in two stages in order to perform selection in one direction within the semiconductor substrate surface, there is a disadvantage in that the degree of integration is improved but the number of processes is increased.
- Patent Document 4 discloses a technique for reducing the gate pitch to 2F with a single-stage selection transistor.
- a so-called gate last process is used in which after processing a semiconductor layer to be a channel, a gate insulating film and a gate are formed in a space portion of the processed channel semiconductor layer.
- the vertical selection transistor described in Patent Document 4 can be formed in one stage, the number of processes is small and the gate pitch can be reduced to 2F.
- this transistor is used as a selection transistor of a semiconductor memory device, it becomes impossible to independently operate memory cells connected to two channels that are turned on simultaneously.
- the thickness of the channel semiconductor layer is reduced to about the same as the thickness of the inversion layer, for example, about 5 nm, and the channel semiconductor layer to be turned off is gated. It is necessary to apply an off voltage to the gate on the opposite side that is in contact with the insulating film.
- the channel semiconductor layer having a thickness of about 5 nm is formed by extreme ultraviolet lithography (5 nm processing must be performed with high accuracy, whether using a gate first process or a gate last process. It is essential to use a high-cost lithography technique such as EUV), which increases the manufacturing cost of the semiconductor memory device. Furthermore, since the channel semiconductor layer processed to have a size of 5 nm comes into contact with the upper and lower electrodes with a width of 5 nm, the contact resistance between the electrode and the channel semiconductor layer is increased, and the on-current of the transistor is reduced.
- an object of the present invention is to provide a vertical selection transistor having a large on-current and a gate pitch of 2F in a simple process. As a result, the degree of integration of the memory cells can be improved, and the capacity and cost can be reduced.
- a semiconductor memory device includes a plate-like lower electrode formed above a semiconductor substrate, an upper electrode formed above the lower electrode, the lower electrode, and the upper electrode.
- a plurality of electrically rewritable memory cells disposed between the electrodes, and a plurality of memory chains connected in series; and a first selection transistor connected to one end of the memory chain;
- the memory chain has a longitudinal direction aligned with a normal direction of the semiconductor substrate, along a first direction in the semiconductor substrate surface and a second direction orthogonal to the first direction in the semiconductor substrate surface.
- the first selection transistors are arranged in a matrix, and are formed by extending in the second direction in parallel with the first direction at a pitch equal to the arrangement pitch of the memory chains in the first direction.
- a plurality of gates, a gate insulating film formed in contact with opposing sidewalls between the plurality of gates, and a first sandwiched between the plurality of gates via the gate insulating film Channel semiconductor layers, and the first channel semiconductor layer is formed on every other gate of the plurality of gates, and is formed on both sides of the gate via a gate insulating film.
- a layer is connected between the gate and the lower electrode or the upper electrode according to the result of the simultaneous film formation step, or a part of the result of the simultaneous film formation step is between the gate and the lower electrode or the upper electrode. Configured to remain in between.
- the memory cell is a phase change memory
- the second selection transistor further includes a second selection transistor connected in series with the first selection transistor, wherein the second selection transistor is parallel to the second direction at a pitch equal to the arrangement pitch of the memory chains in the second direction, and the first direction
- a plurality of gates formed to extend to each other, a gate insulating film formed in contact with opposing sidewalls between the plurality of gates, and between the plurality of gates via the gate insulating film
- a second channel semiconductor layer sandwiched between the second channel semiconductor layers, and the second channel semiconductor layer of the second select transistor is disposed on both sides in the second direction via a gate insulating film.
- the gate of the second selection transistor is present opposite to the gate of the second selection transistor, the gate of the second selection transistor is present opposite to the second channel semiconductor layer via the gate insulating film on both sides in the second direction,
- the gates of the second selection transistors are configured to have different shapes every other gate in the second direction.
- a method for manufacturing a semiconductor memory device in a method for manufacturing a semiconductor memory device, (a) a step of forming a metal film serving as a lower electrode on a semiconductor substrate via an interlayer insulating film; Forming a first insulating film on the lower electrode; (c) forming a first gate electrode layer and a second insulating film layer on the first insulating film; and (d) the second insulating film;
- the first gate electrode layer and the first insulating film layer are arranged in parallel with a predetermined width at a pitch twice the arrangement pitch of the memory chain array in the second direction in the semiconductor substrate surface.
- the semiconductor memory device of the present invention it is possible to manufacture a suitable memory cell array by increasing the density, and to realize a large capacity and low cost of the semiconductor memory device.
- the semiconductor memory device by applying a large-capacity, low-cost semiconductor storage device to an information processing device such as a storage or a server, the information processing device can use a large-capacity storage device at low cost, and can improve performance.
- FIG. 1 is an overall plan view of a semiconductor memory device of the present invention.
- 1 is a partial three-dimensional schematic diagram of a semiconductor memory device according to a first embodiment of the present invention.
- FIG. 3 is a three-dimensional schematic diagram of the memory cell array according to the first embodiment of the present invention. It is a figure explaining the reset operation
- FIG. 4 is a diagram for explaining a read operation of the memory cell array according to the first embodiment of the present invention. It is a figure explaining the setting operation
- FIG. 6 is an equivalent circuit diagram of the semiconductor memory device according to the second embodiment of the present invention. The voltage conditions for the read operation are shown. It is a three-dimensional schematic diagram of the memory cell array of the semiconductor memory device of Embodiment 3 of the present invention.
- A) is sectional drawing of the semiconductor memory device of Embodiment 3 of this invention.
- B) is a cross-sectional view of a memory cell.
- FIG. 6 is an equivalent circuit diagram of the semiconductor memory device according to the third embodiment of the present invention.
- FIG. 1 is an overall view showing a semiconductor memory device using a phase change memory according to Embodiment 1 of the present invention.
- the semiconductor memory device according to the first embodiment of the present invention is different from an I / O interface 1001 having an input / output buffer for exchanging data with the outside, and a memory cell array 1002.
- a plurality of voltage sources 1003 to 1006 for supplying a plurality of voltages, a voltage selector 1007 for selecting a voltage from the voltage sources 1003 to 1006, a connection destination of an output from the voltage selector 1007, and a bit line of the memory cell array 1002;
- a wiring selector 1008 selected from wirings such as word lines and a control unit 1009 for controlling the entire apparatus are provided.
- the wiring selector 1008 includes a reading unit 1010 having a sense amplifier and the like.
- the control unit 1009 selects a voltage for writing data with the voltage selector 1007, generates a voltage pulse with the power supplies 1003 to 1006, and uses the wiring selector 1008 with it.
- a voltage pulse is supplied to a predetermined wiring of the memory cell array 1002. Thereby, the input data is written to the phase change memory cell of the memory cell array.
- the control unit 1009 selects a data read voltage with the voltage selector 1007, generates voltage pulses with the power supplies 1003 to 1006, and A voltage pulse is supplied to a predetermined wiring of the memory cell array 1002 by the wiring selector 1008.
- the read current is read by the reading unit 1010, and the stored data is reproduced, and the read data is supplied to the external device via the control unit 1009 and the I / O interface 1001.
- FIG. 2 is a three-dimensional schematic diagram showing the configuration of the memory cell array portion of the semiconductor memory device according to the first embodiment of the present invention.
- Plate-shaped electrodes TEPLATE, BEPLATE, electrode 3 (MLR) extending in X direction, phase change memory chain (cell) PCMCHAIN, X selection transistor STTrX for realizing selection of PCMCHAIN in X direction by extending in X direction
- a Y selection transistor STTrY that realizes selection of PCMCHAIN in the Y direction in the extending and setting operation and resetting operation is shown.
- the gates of STTrX and STTrY are STTGX and STTGY, respectively. Further, FIG.
- 2 further includes wirings STTGXL and STTGY for supplying power to STTTGX via contacts STTGXC and STTGGXC that connect TEPLATE and BEPLATE to BEPLATE and BEPLATEC and STTGX to connect the circuit on the semiconductor substrate.
- Wiring STTGYL for supplying power to STTGY via contacts STTGYC and STTGYC leading to is shown.
- STTGYL is connected to the circuit on the semiconductor substrate by STTYC
- STTGXL is connected to the circuit on the semiconductor substrate by STTGXC, respectively, so that an appropriate potential can be supplied. Focusing on the elevations of STTGXL and STTGYL, a contact STTGYC is formed from the lower side and connected to STTGYL for STTGY extending in parallel below the read operation wiring MLR. On the other hand, for STTGX formed at the upper part of the MLR and orthogonal to the MLR, a contact STTGXC is formed from the upper side and connected to the STTGXL.
- the MLR is connected to the MLRL via the MLRC, and the MLRL is connected to the reading unit 1010.
- FIG. 3 shows a PCMCHAIN matrix-like array and its upper and lower parts extracted from FIG.
- a wiring STTGYL is also shown at the bottom.
- the electrode 3 (MLR) extends in the X direction and operates as a wiring MLR that selects the phase change memory chain PCMCHAIN in the Y direction in the read operation.
- MLR phase change memory chain
- STTrX that selects PCMCHAIN in the X direction is formed above the electrode 3 (MLR).
- the gate STTTGX of STTrX extends in the Y direction orthogonal to the electrode 3, and a channel semiconductor layer 51p is formed in the inter-gate space via a gate insulating film. As shown in FIG. 4, the channel semiconductor layer 51p is connected to the electrode 3 through the N-type semiconductor layer 42p.
- the channel semiconductor layer 51p is connected to the channel semiconductor layer 8p forming PCMCHAIN above.
- the channel semiconductor layer 51p is separated in the X direction and the Y direction for each PCMCHAIN.
- a phase change memory chain PCMCHAIN is formed above the X selection transistor STTrX.
- a diffusion layer made of an N-type semiconductor layer 25p is formed on the channel semiconductor layer 8p, and is connected to a plate-like electrode TEMPLATE serving as an upper electrode.
- PCMCHAIN is a stack in which gate polysilicon layers 21p, 22p, 23p, and 24p serving as cell gate electrodes and insulating films 11, 12, 13, 14, and 15 are alternately stacked. It is formed in a hole in the Z direction formed in the body. The detailed structure around PCMCHAIN will be described with reference to FIG.
- a Y selection transistor STTrY is formed that extends in the same X direction as the electrode 3 and selects PCMCHAIN in the Y direction during a set operation and a reset operation described later.
- the gate STTGY of STTrY extends in the X direction parallel to the electrode 3, and a channel semiconductor layer 50p is formed in the inter-gate space via a gate insulating film.
- the channel semiconductor layer 50p is connected to the electrode 3 through an N-type semiconductor layer 41p.
- the channel semiconductor layer 50p is connected to the plate electrode BEPLATE via the N-type semiconductor layer 40p.
- the length of the channel semiconductor layer 50p extending in the X direction is the channel width of STTrY.
- STTrY can drive a larger on-current as the channel width is larger.
- the channel semiconductor layer 50p may be separated in the X direction at an appropriate interval below the electrode 3 in accordance with the required on-current.
- the electrode wiring 3 extending in the X direction, the gate electrode STTGY of the Y selection transistor STTrY extending in the X direction, and the gate electrode STTGX of the X selection transistor STTrX extending in the Y direction are 2F pitches with a minimum processing dimension F Can be formed. That is, a memory cell having a projected area of 4F 2 in the XY plane can be formed.
- the structure of the selection transistors STTrX and STTrY will be described. Focusing on STTrY, a channel semiconductor layer 50p is formed on the side wall of the gate STTGY extending in the X direction and arranged in the Y direction at a 2F pitch via a gate insulating film.
- both sides in the Y direction are in contact with STTGY through the gate insulating film.
- both sides in the Y direction are in contact with the channel semiconductor layer 50p through the gate insulating film.
- the channel semiconductor layer 50p of the Y select transistor STTrY is thick in the Y direction (about 10 nm or more in the case of silicon)
- independent inversion layers are provided in two STTGYs that are in contact with the channel semiconductor layer via a gate insulating film. It is formed.
- the channel semiconductor layer 50p is turned on and conducts between the plate electrode BEPLATE and the electrode 3 (MLR).
- the channel semiconductor layer 50p When a turn-off voltage is applied to both gates, the channel semiconductor layer 50p is turned off to insulate between the plate electrode BEPLATE and the electrode 3 (MLR). In this case, when an ON voltage is applied to one STTGY, the two channel semiconductor layers 50p on both sides of the STTGY are necessarily turned on, and therefore, a selection operation for turning on only one of the channel semiconductor layers 50p cannot be performed.
- the channel semiconductor layer 50p is sufficiently thin (preferably 5 nm or less in the case of silicon), even if an on voltage is applied to one of STTGYs on both sides, a strong off voltage (in the case of NMOS, It can be turned off by applying a negative voltage (based on the source potential). This is because the depletion layer completely extends in the film thickness direction of the channel semiconductor 50p, and the carrier density of the inversion layer on the back surface side of the channel semiconductor 50p is controlled by the electric field from one STTGY.
- the channel semiconductor layers 50p on both sides thereof are not necessarily turned on, but by applying a strong off-voltage to another STTGY that is in contact via the gate insulating film. Can be turned off. Using this phenomenon, only one of the channel semiconductor layers can be selected and turned on. It is also possible to simultaneously turn on a plurality of channel semiconductor layers 50p continuous in the Y direction. However, a specific selection state such as turning on every other state is difficult. The same applies to STTGX.
- the channel semiconductor layers 50p and 51p are formed of silicon, and the thickness of the channel semiconductor layer 50p in the Y direction and the thickness of the channel semiconductor layer 51p in the X direction are set to about 5 nm or less.
- FIG. 4 is a diagram showing a part of the memory cell array according to the first embodiment (FIG. 4A). 2 and 3, PCMCHAIN parts omitted for the sake of clarity, that is, gate polysilicon layers 21p to 24p, insulating films 11 to 15, gate insulating film 9, channel polysilicon layer 8p, N-type polysilicon layer 25p, Phase change material 7 and insulating films 91 and 92 are also shown. In addition, gate insulating films GOX1_X and GOX2_X of STTrX are also shown. In addition, the cross-sectional view taken along the line A-A 'in one gate polysilicon layer 21p (FIG. 4B) and an equivalent circuit diagram corresponding to a part of the memory cell array (FIG. 4C) are shown.
- the operation of the memory cell can be performed as follows, for example. 0 V is applied to the gate line GL1 to which the selected cell SMC is connected, and the transistor whose channel is the channel polysilicon layer 8p is turned off. 7 V is applied to the gate lines GL2, GL3, and GL4 to which the non-selected cell USMC is connected, and the transistor is turned on. 0V is applied to TEMPLATE. During reset operation and set operation, STTrX and STTrY are turned on, and a reset voltage VRESET (for example, 5 V) and a set voltage (for example, 4 V) are applied to BEPLATE, respectively. The MLR is left floating.
- VRESET for example, 5 V
- a set voltage for example, 4 V
- the resistance of the channel is low when the transistor is ON, so that the current flows through the channel polysilicon layer 8p. Regardless of the state of the phase change material 7 in the USMC portion, substantially the same current can flow.
- SMC the current flows through the phase change material 7 because the transistor is in the OFF state.
- the operation is performed by changing the resistance value of the phase change material 7 by the current flowing through the phase change material 7 by SMC.
- STTrX is turned on, STTrY is turned off, and 1 V, for example, is applied to the MLR.
- the resistance of the channel is low when the transistor is ON, so that the current flows through the channel polysilicon layer 8p. Regardless of the state of the phase change material 7 in the USMC portion, substantially the same current can flow.
- SMC the current flows through the phase change material 7 because the transistor is in the OFF state.
- a current value flowing through the phase change material 7 is detected by SMC using a sense circuit connected to the MLR, and a read operation is performed.
- phase change material layer 7 for example, a material that stores information by utilizing the difference between the resistance value in the amorphous state and the resistance value in the crystalline state, such as Ge 2 Sb 2 Te 5, can be used.
- the phase change material in the amorphous state is heated above the crystallization temperature and held for about 10 ⁇ 6 seconds or longer. It implements by making it into a crystalline state.
- the phase change material in the crystalline state can be brought into an amorphous state by heating it to a temperature equal to or higher than the melting point to make it into a liquid state and then rapidly cooling it.
- FIG. 5 to FIG. 7 are equivalent circuit diagrams of the semiconductor memory device of FIG. 3, and explain the read operation / set operation / set operation / reset operation, respectively.
- the X selection transistor STTrX and the Y selection transistor STTrY are thin films of about 5 nm in the channel semiconductor layers 51p and 50p, they are turned on when an on voltage is applied to both gates, and an on voltage is applied to either one of them. When a strong off-voltage is applied to the other, the off state is established.
- each of the Y selection transistor STTrY and the X selection transistor STTrX is represented by two transistors connected in series, and the opposing transistors are described as being connected in series. did.
- FIG. 5 illustrates a read operation using an equivalent circuit diagram.
- the read operation all the Y selection transistors STTrY are turned off, and the plate electrode BEPLATE and the electrode 3 (MLR) are electrically insulated.
- MLR the plate electrode BEPLATE and the electrode 3
- Non-destructive reading can be performed by setting the current flowing at this time to a current that is small enough not to change the resistance state of the phase change memory, that is, sufficiently smaller than the set current and the reset current.
- the electrode wirings 3 are arranged in the Y direction at the same pitch as PCMCHAIN, and are connected to a resistance sense circuit on the semiconductor substrate. For example, by connecting the electrode wirings 3 to independent sense circuits, one cell can be selected from each of a plurality of PCMCHAINs arranged in the Y direction as shown in FIG. 5, and parallel reading can be performed.
- FIG. 6 illustrates the set operation using an equivalent circuit diagram.
- the electrode 3 and the sense circuit are insulated from each other by a peripheral circuit. That is, the electrode 3 is insulated from other than STTrX and STTrY that are in contact with each other at the top and bottom.
- the set operation is performed by generating Joule heat in PCMCHAIN by flowing a current between BEPLATE and TEPLATE via PCMCHAIN. Since current flows in parallel to a plurality of PCMCHAINs that are adjacent to each other, and all cells are selected simultaneously in each PCMCHAIN to generate heat (bundle erasure), heat is transferred between the PCMCHAIN.
- More cells can be set per unit power consumption than a method of selecting one cell at a time and performing a set operation or a method of performing a set operation by passing a current through PCMCHAIN one by one. That is, the erase transfer rate can be improved.
- FIG. 6 shows a case where a set operation is performed by passing a current through three PCMCHAINs continuous in the X direction and Y direction, that is, a total of nine PCMCHAINs.
- a method is used in which the set operation is collectively performed as a collective erase operation, and writing is performed to each cell by a reset operation described later.
- each memory cell has a configuration in which a phase change material layer and a cell transistor are connected in parallel, and each memory cell is connected in series. Therefore, during the set operation, the current flowing in the PCMCHAIN has a component flowing through the phase change material layer and a component flowing through the cell transistor.
- the set operation Since the set operation is performed in about 1 microsecond, Joule heat generated in the channel of the cell transistor is transmitted to the phase change material layer in contact with the channel.
- an appropriate on-voltage half-on voltage: VHON
- VHON half-on voltage
- the channel is adjusted to an appropriate on-resistance state, and a potential difference is applied between WLPLATE / BLPLATE, the Joule heat generated in the channel section changes in phase.
- the set operation can be carried out by being transmitted to the material layer. For this reason, even if the phase change material layer becomes too high resistance due to the reset operation, the set operation can be performed without applying a large voltage to the memory cell and causing a current to flow.
- VHON shown in FIG. 6 exemplifies this operation.
- FIG. 7 illustrates the reset operation using an equivalent circuit diagram.
- the electrode 3 and the sense circuit are insulated from each other by a peripheral circuit as in the set operation. That is, the electrode 3 is insulated from other than STTrX and STTrY that are in contact with each other at the top and bottom.
- the reset operation is performed by flowing a current between BEPLATE and TEMPLATE via PCMCHAIN.
- the set operation is a batch erase operation
- the reset operation is a data write operation, and is therefore selectively performed for each memory cell.
- the X selection transistor STTrX connected to the PCMCHAIN to be selected and the Y selection transistor STTrY connected via the electrode 3 are turned on, the off-voltage is applied to the cell transistor gate of the PCMCHAIN selected cell, and the PCMCHAIN unselected cell is selected.
- An on-voltage is applied to the cell transistor gate.
- a potential difference is applied between BEPLATE and TEPLATE
- a current flows through the phase change material layer of the selected cell SMC.
- the phase change material layer of SMC is changed from a low resistance crystal state (set state) to a high level like a normal phase change memory.
- the resistance can be changed to an amorphous state (reset state).
- amorphous state As in the set operation, only one PCMCHAIN can be selected between the plate electrodes BEPLATE and TEPLATE, but a plurality of PCMCHAIN can also be selected. This is because, unlike the read operation, it is not necessary to detect the current flowing through each PCMCHAIN. Since it is necessary to reduce the film thickness of the semiconductor channel layers 50p and 51p to about 5 nm, STTrX and STTrY are manufactured as follows. For STTrY, a contact is formed from the lower side with respect to the gate STTGY.
- FIGS. 8 to 19 A method for manufacturing the semiconductor memory device according to the first embodiment will be described with reference to FIGS. 8 to 19, the BB ′ cross section (a) of the memory array portion on the lower electrode BEPLATE on the wiring STTGYL shown in FIG. 3 and the STTGYC portion for supplying power to the gate electrode STTGY shown in FIG. A CC ′ cross section (b) cut in a cross section is shown in parallel.
- An interlayer insulating film IDL is formed on a semiconductor substrate on which a circuit for driving a semiconductor memory device, a wiring STTGYL for supplying power to STTGY is formed, then BEPLATEC is formed, and a metal film that becomes BEPLATE, for example, tungsten And an N-type polysilicon layer 40p is formed on the titanium nitride.
- the deposited pattern is processed by known lithography and dry etching techniques to form a BEPLATE (FIG. 8).
- STTGYC that electrically connects STTGY and STTGYL formed in the upper portion of the BEPLATE space is formed (FIG. 9).
- insulating film 71 e.g., a silicon nitride film or a silicon oxide film
- STTGYC that electrically connects STTGY and STTGYL formed in the upper portion of the BEPLATE space is formed (FIG. 9).
- insulating film 71 e.g., a silicon nitride film or a silicon oxide film
- STTGYC that electrically connects STTGY and STTGYL formed in the upper portion of the BEPLATE space is formed (FIG. 9).
- CMP method chemical mechanical polishing
- N-type polysilicon layer 101p serving as STTGY and an insulating film 72 are formed on the insulating film 71, and then patterned (FIG. 10).
- the insulating film 72 and the N-type polysilicon layer 101p are processed simultaneously with the BEPLATE portion and the BEPLATE space portion.
- the insulating film 71 is processed, only the BEPLATE space portion is covered with a resist and only the BEPLATE portion is processed.
- 101p extending in the X direction is formed at a 4F pitch in the Y direction, where F is the minimum processing dimension.
- 101p is patterned with a Y-direction width of F and a space width of 3F.
- 101p formed with a pitch of 4F in the Y direction covers every other STTGYC formed with a pitch of 2F in the Y direction in the Y direction to form contacts.
- a gate insulating film for example, a silicon oxide film
- GOX1_Y is formed so as not to completely fill a space between 101p formed with a 4F pitch, and an amorphous silicon layer 201a as a protective film is subsequently formed.
- FIG. 11 The amorphous silicon layer 201a and the gate insulating film GOX1_Y at the pattern upper surface of the insulating film 72, the bottom of the groove of the 101p pattern, and the gate insulating film GOX1_Y are removed by etch back, and then the amorphous silicon layer 201a is removed by wet etching (FIG. 12).
- a silicon layer 50p serving as a channel semiconductor layer is formed so as not to completely fill the groove space between STTGY (FIG. 13).
- the thickness of 50p is preferably about 5 nm or less. A film thickness of 5 nm can be easily realized by single-layer silicon film formation. 50p is patterned, 50p is separated on the pattern upper surface of the insulating film 72, and 50p is removed on STTGYC not covered with 101p (FIG. 14).
- a gate insulating film for example, silicon oxide film
- an N-type polysilicon layer 102p that becomes a part of the gate STTGY is formed (FIG. 15).
- GOX2_Y and 102p covering STTGYC are removed by dry etching, for example, by covering the BEPLATE portion with a resist to expose STTGYC, and then an N-type polysilicon layer 103p that becomes a part of STTGYC is formed.
- 103p and STTGYC are connected (FIG. 16).
- the upper portions of 102p and 103p are removed by etch back, and the patterns of 102p and 103p are separated (FIG. 17).
- the same N-type polysilicon is used for 102p and 103p as for 101p, but a material different from 101p may be used for 102p and 103p.
- 102p and 103p can be silicided in a self-aligning manner using Ti, Ni, Co, etc. following the process of FIG. By doing so, the resistance of the gate electrode consisting of 102p and 103p can be lowered, so the dimensions of 102p and 103p in the X direction are reduced, the dimension of 101p in the X direction is increased, and the resistance of 101p is lowered. You can also.
- the gate insulating films GOX1_Y and GOX2_Y do not need to use the same material, and one can be a silicon oxide film and the other can be a High-K film. In addition, GOX1_Y and GOX2_Y can have different thicknesses.
- the thickness of 101p is the same on BEPLATE and STTGYC, but the thickness of 102p and 103p is different on BEPLATE and STTGYC and is thin on STTGYC. This is because the depth of the groove formed in the process of FIG. 10 is shallower than that on BEPLATE because the insulating film 71 was not removed on STTGYC. Although there is a concern that the resistance will increase, it can be solved by reducing the resistance by siliciding 102p and 103p, for example, as described above.
- the upper part is retracted to expose the upper part of the channel silicon layer 50p (FIG. 18).
- the gates STTGY (101p, 102p, 103p) of the Y selection transistor are formed with a pitch 2F in the Y direction.
- one consists of 101p and the other consists of two layers, 102p and 103p. Both gates are connected to STTGYC below.
- the width in the Y direction of the channel silicon layer 50p (the thickness sandwiched between the gate insulating films GOX1_Y and GOX2_Y) can be determined by the film thickness that does not depend on the minimum processing dimension, it is as in extreme ultraviolet lithography (EUV).
- EUV extreme ultraviolet lithography
- the thickness can be 5 nm without using a high-cost lithography technique.
- the channel silicon layers 50p on both sides of the gate composed of 102p and 103p are connected to each other via the lower portion of the gate composed of 102p and 103p.
- the N-type polysilicon layer 40p, which is the lower electrode, and the channel silicon layer 50p are in contact with each other. For this reason, the contact area between the N-type polysilicon layer 40p / channel silicon layer 50p can be ensured larger than in the case where the channel silicon layer 50p is separated below the gate composed of 102p and 103p. It is possible to reduce the contact resistance.
- the channel silicon layer 50p needs to be separated at the lower part of the gate composed of 102p and 103p, it is desirable to secure the contact area with the N-type polysilicon layer 40p by reducing the separation width as much as possible. .
- the later-described N-type polysilicon layer 41p which will be an upper electrode, also on the channel silicon layer 50p, a part of the channel polysilicon layer 50p is laid on the gate side made of 101p. It is desirable to increase the contact area with the upper electrode.
- an N-type polysilicon layer (42p) / titanium nitride layer / tungsten layer / titanium nitride layer / titanium layer / N-type polysilicon layer (41p) to be the readout wiring MLR are formed in this order from the lower layer to the X direction. Separated into a pattern that stretches. The pitch in the Y direction is 2F, the same as STTGY. After the space between the read wirings MLR is filled with the insulating film 81, the N-type polysilicon layer 42p is exposed by, eg, CMP (FIG. 19).
- an insulating film 74 for example, a silicon nitride film or a silicon oxide film
- an N-type polysilicon layer 104p that becomes STTGX and an insulating film 75 for example, a silicon nitride film or a silicon oxide film
- the N-type polysilicon layer 43p are formed, and then the insulating film layer 75, the N-type polysilicon layer 104p, the insulating film layer 74, and the N-type polysilicon layer 43p are patterned.
- the pattern extending in the Y direction is formed at a 4F pitch in the X direction, where F is the minimum processing dimension. For example, patterning is performed with the width in the X direction of 104p slightly larger than F and the width of the space slightly smaller than 3F (FIG. 20).
- a gate insulating film for example, a silicon oxide film
- GOX1_X is formed so as not to completely fill a space between 104p formed at 4F pitch, and then an amorphous silicon layer 202a serving as a protective film is formed.
- the amorphous silicon layer 202a and the gate insulating film GOX1_X at the top surface of the pattern of the insulating film 75 and the bottom of the groove between the 104p patterns are removed by etch back, and then the amorphous silicon layer 202a is removed by wet etching.
- the gate insulating film GOX1_X on the 104p sidewall is protected by the amorphous silicon layer 202a during the etch back, the reliability of the gate insulating film GOX1_X can be ensured as compared with the case where the amorphous silicon layer 202a is not provided.
- a silicon layer 51p serving as a channel is formed so as not to completely fill the space between STTTGX (104p).
- 51p is patterned, 51p is separated on the pattern of the insulating film 75, and 51p is further separated in the X direction at a pitch of 2F.
- the N-type polysilicon layer 43p is also processed on the upper surface of the insulating film 75 (FIG. 21).
- the N-type polysilicon layer 43p functions as a source / drain diffusion layer of the channel semiconductor layer of the X selection transistor STTrX. Note that the N-type diffusion layer 43p is not necessarily formed.
- an N-type impurity may be doped on the channel semiconductor layer 51p, or an N-type polysilicon layer may be formed on the channel semiconductor layer 51p.
- the method for forming the N-type polysilicon layer 43p can also be used in the manufacture of the Y selection transistor STTrY.
- a gate insulating film for example, silicon oxide film
- GOX2_X is formed, and then an N-type polysilicon layer 105p that becomes the gate STTTGX is formed.
- the upper part of 105p is removed by etch back, and the pattern of 105p is separated.
- the insulating film 76 is formed, the upper part is retracted to expose the upper part of the channel silicon layer 51p (FIG. 22).
- STTGX is formed with a pitch of 2F in the X direction.
- one is composed of 104p
- the other is composed of 105p
- the shapes are different from each other.
- the width of the channel silicon layer 51p in the X direction can be determined by the film thickness that does not depend on the minimum processing dimension, it is as in extreme ultraviolet lithography (EUV).
- EUV extreme ultraviolet lithography
- the thickness can be 5 nm without using a high-cost lithography technique.
- the channel silicon layers 51p on both sides of the gate made of 105p are connected to each other through the lower part of the gate made of 105p, as in the description of FIG.
- the N-type polysilicon layer 42p which is the lower electrode
- the channel silicon layer 51p are in contact with each other. Therefore, compared with the case where the channel silicon layer 51p is separated at the lower part of the gate made of 105p, the contact area between the N-type polysilicon layer 42p / channel silicon layer 51p can be ensured, and thus the contact resistance. Can be reduced. Even when the channel silicon layer 51p needs to be separated at the lower part of the gate made of 105p, it is desirable to ensure the contact area with the N-type polysilicon layer 42p by reducing the separation width as much as possible.
- the STTGY formed after the STTGYL connected to the STTGYC and the contact STTGYC for supplying power to the STTGY is formed below the position where the STTGY is formed is formed by two layers of 102p and 103p. Since STTGXL connected to the contacts STTGXC and STTGXC is formed above STTGX, STTGX formed after STTGX formed by the 104p layer can be formed by a 105p single layer. It is of course possible to form a contact from the lower side by using the same process as STTGY for forming STTGX.
- the insulating films 11, 12, 13, 14, 15 and N-type polysilicon layers 21p, 22p serving as memory cell gates are formed.
- 23p, 24p and N-type polysilicon layers 25p serving as upper electrodes are alternately stacked to form a stacked body, and then memory cell formation, upper electrode formation, memory cell gate electrodes GATE1 (21p), GATE2 are formed by known techniques. (22p), GATE3 (23p), and GATE4 (24p) are processed.
- contacts STTGXC for supplying power to STTGX, STTGXL connected to STTGXC, memory cell gate electrodes GATE1, GATE2, GATE3, GATE4, and readout wiring MLR are formed, and peripheral circuits are formed.
- a wiring for connecting to is formed to complete the semiconductor memory device.
- the completed semiconductor memory device can form memory cells at a 2F pitch in both the X direction and the Y direction, so that the capacity can be increased and the bit cost can be reduced.
- the completed semiconductor storage device can use a large capacity storage device at low cost, so that performance can be improved.
- FIG. 23 is a bird's-eye view of a device structure of a flash memory using the selection transistor of the present invention
- FIG. 24 is a cross-sectional view in the XZ plane
- FIG. 25 is an equivalent circuit diagram.
- FIG. 25 shows voltage conditions for the read operation.
- the flash memory array is connected to electrodes at both ends via selection transistors.
- the operation method of the selection transistor is the same as that in the first embodiment.
- FIG. 23 shows a lower electrode BEPLATE, a lower selection transistor DSTTr extending in the Y direction, an upper selection transistor USTTr extending in the Y direction, and an upper electrode wiring BL extending in the X direction.
- the memory array will be described with reference to the following cross-sectional view. Note that the memory holes are formed at a 2F pitch in the X and Y directions. 24, the electrode layers 321p, 322p, 323p, and 324p to be gates and the insulating films 311, 312, 313, 314, and 315, which are omitted in FIG.
- a memory hole in the Z direction, an ONO film in the memory hole, that is, a silicon oxide film (331) / silicon nitride film (332) / silicon oxide film (333), and a channel semiconductor layer 308p are shown.
- DSTTr is formed of gate electrodes 301p and 302p, insulating films 371, 372, and 373, gate insulating films 361 and 362, and a channel semiconductor layer 350p.
- Two channel semiconductor layers 350p adjacent to each other in the X direction are connected to each other in the X direction below the gate electrode 302p via the gate insulating film 362, and in contact with the N-type semiconductor layer 340p which is a part of the lower electrode.
- the width in the X direction of the contact portion between 340p and 350p is larger than the film thickness of 350p, so that 340p and 350p can be brought into contact with each other over a wide area. The contact resistance can be reduced.
- An N-type semiconductor layer 341p is formed on the upper part of 350p, and is connected to the channel semiconductor layer 308p of the memory cell array.
- An N-type semiconductor layer 342p is formed on the channel semiconductor layer 308p and is connected to the channel semiconductor layer 351p of USTr.
- the USTr is formed of gate electrodes 303p and 304p, insulating films 374, 375 and 376, gate insulating films 363 and 364, and a channel semiconductor layer 351p.
- Two channel semiconductor layers 351p are connected to each other adjacent to each other in the X direction via an insulating film 375 above the gate electrode 303p, and in contact with the N-type semiconductor layer 343p which is a part of the upper electrode.
- the channel semiconductor layer 350p is separated from the altitude at which the side walls of at least the gate electrodes 301p and 302p are at an upper portion with a 2F pitch equal to the pitch of the memory holes in the Y direction.
- the channel semiconductor layers 351p are separated in the Y direction at the same 2F pitch as the pitch of the memory holes.
- the 351p separated in the Y direction is connected to the upper electrode BL extending in the X direction and formed at a 2F pitch in the Y direction.
- the channel semiconductor layers of the lower selection transistor DSTTr and the upper selection transistor USTTr including the selected cell are turned on.
- the on-voltage is applied to DSTm-2 and DSTm-1 among the gates DSTm-2, DSTm-1, DSTm, and DSTm + 1 of the DSTTr, and the off-voltage is applied to the remaining gates.
- An ON voltage is applied to USTm-2 and USTm-1 among the gates USTm-2, USTm-1, USTm, and USTm + 1 of the USTTr, and an off voltage is applied to the remaining gates. Thereby, one place in the X direction is selected.
- the potential Vthc at the threshold determination level is applied to the gate electrode including the selected cell, and the potential Vpass at which the channel semiconductor layer 308p of the cell is sufficiently turned on regardless of the threshold state of the cell (for example, other gate electrodes) 6V) is applied. Thereby, one place in the Z direction is selected. With one position selected in the X and Z directions, a potential of 0 V is applied to the lower electrode BEPLATE and 1 V is applied to the upper electrode BL. Since a plurality of BLs are formed at a 2F pitch in the Y direction, a plurality of BLs can be selected simultaneously in the Y direction. The current flowing through BL is detected, and information is read out depending on whether the threshold value Vth of the selected cell is higher or lower than Vthc.
- the write operation is performed after the erase operation described later is performed at once.
- the lower select transistor DSTTr is turned off, and the channel semiconductor layer of the upper select transistor USTTr connected to the selected cell is turned on. Thereby, one place in the X direction is selected.
- a write potential for example, +20 V
- the potential Vpass the cell channel semiconductor layer 308p of the cell is sufficiently turned on regardless of the threshold state of the cell
- the lower electrode BEPLATE is set to 0 V, for example.
- a potential corresponding to the data write pattern is applied to the upper electrode BL with one X direction and Z direction selected.
- a plurality of BLs are formed at a 2F pitch in the Y direction, a plurality of BLs can be selected simultaneously in the Y direction.
- 0 V is applied to BL, and 0 V is supplied from BL to the channel semiconductor layer 308p through the USTr. Since a potential difference of 20 V between +20 V of the selection gate and 0 V of the channel semiconductor layer 308p is applied to the ONO film of the selected cell, electrons are injected from the channel semiconductor layer 308p into the ONO film, and writing occurs.
- the erasing operation first, about 0 V is applied to the gates 303p and 304p of the USTTr and the gates 301p and 302p of the DSTTr, and about 5 V is applied to the BEPLATE and BL, and hot holes are generated at the BEPLATE side end of the DSTTr and the BL side end of the USTR. Then, appropriate potentials are applied to the gates 303p and 304p of the USTTr and the gates 301p and 302p of the DSTTr in the block to be erased to inject hot holes generated by turning on the USTTr and DSTTr into the channel semiconductor layer 308p.
- the semiconductor memory device of the second embodiment since memory cells can be formed at a 2F pitch in both the X direction and the Y direction, the capacity can be increased and the bit cost can be reduced.
- the completed semiconductor storage device to an information processing apparatus such as a storage or a server, the information processing apparatus can use a large capacity storage device at low cost, so that performance can be improved.
- the phase change memory and the flash memory are used, respectively, but the selection transistor of the present invention can also be used for other memories.
- a case where a vertical cross-point memory is used is shown. 26 is a bird's-eye view of a device structure of a vertical cross-point memory using the selection transistor of the present invention, FIG. 27 is a cross-sectional view in the XZ plane, and FIG. 28 is an equivalent circuit diagram.
- the vertical cross-point memory array is connected to the electrode via a selection transistor on the lower side.
- the operation method of the selection transistor is the same as in the first and second embodiments.
- FIG. 26 shows a lower electrode wiring BTL extending in the X direction and formed at a 2F pitch in the Y direction, a selection transistor STTr extending in the Y direction, conductive film layers 421p, 422p, 423p, and 424p to be electrodes, and formed in a stacked body.
- a Z-direction memory hole, a resistance change material film 407 and a conductive film layer 408p in the memory hole are shown.
- the memory holes are formed at a 2F pitch in the X direction and the Y direction.
- FIG. 27A is a cross-sectional view taken along the XZ plane of FIG.
- insulating films 411, 412, 413, 414, and 415 which are omitted are also shown.
- Diodes are formed on the inner walls of the memory holes of the conductive film layers 421p, 422p, 423p, and 424p. This diode can be realized by forming the conductive films 421p, 422p, 423p, and 424p with N-type silicon and forming 405p with a P-type semiconductor layer in FIG. 27A, for example.
- FIG. 27B shows a part of FIG. 27A extracted.
- a diode composed of an N-type silicon layer 421p and a P-type semiconductor layer 405p, a memory cell composed of a resistance change material film 407, and an electrode 408p extending in the Z direction are shown.
- a memory cell including a diode and a resistance change memory is formed.
- the STTr is formed of gate electrodes 401p and 402p, insulating films 471, 472 and 473, gate insulating films 461 and 462, and a channel semiconductor layer 450p.
- Two channel semiconductor layers 450p are connected to each other adjacent to each other in the X direction via a gate insulating film 462 below the gate electrode 402p, and are in contact with 440p which is a part of the lower electrode at the connection portion.
- the 440p and 450p can be brought into contact with each other over a wide area. The contact resistance can be reduced.
- An N-type semiconductor layer 441p is formed over 450p and is connected to the conductive layer 408p of the memory cell array.
- the channel semiconductor layer 450p of the lower select transistor STTr including the selected cell is made conductive.
- the STTr gates STXm-2, STXm-1, STXm, and STXm + 1 an on-voltage is applied to STXm-2 and STXm-1, and an off-voltage is applied to the remaining gates.
- one place in the X direction is selected.
- VREAD for example, 1 V
- 0 V is applied to the other BTLs.
- 0 V is applied to the electrode layer including the selected cell
- VREAD is applied to the other electrode layers.
- a current flows because a voltage is applied to the diode in the forward direction.
- no voltage flows because a voltage is applied to the diode at 0 V or in the reverse direction. Therefore, since a current flows only in the selected cell, reading can be performed by determining the resistance of the selected cell by detecting with a reading circuit connected to the current BTL.
- the channel semiconductor layer 450p of the lower select transistor STTr including the selected cell is made conductive.
- the STTr gates STXm-2, STXm-1, STXm, and STXm + 1 an on-voltage is applied to STXm-2 and STXm-1, and an off-voltage is applied to the remaining gates. Thereby, one place in the X direction is selected.
- the VTL connected to the selected cell via the STTr is set to VSET (for example, 3 V) for the set operation, VRESET (for example, 2 V) for the reset operation, and others. 0 V is applied to the BTL.
- 0 V is applied to the electrode layer including the selected cell
- VSET for example, 3 V
- VRESET for example, 2 V
- a current flows because a voltage is applied to the diode in the forward direction.
- a voltage does not flow because a voltage is applied to the diode in the reverse direction. Therefore, since a current flows only in the selected cell, a set operation and a reset operation can be selectively performed.
- the completed semiconductor memory device can form memory cells at a 2F pitch in both the X direction and the Y direction, so that the capacity can be increased and the bit cost can be reduced.
- the completed semiconductor storage device can use a large capacity storage device at low cost, so that performance can be improved.
- insulating films 11, 12, 13, 14, and 15, N-type polysilicon layers 21p, 22p, 23p, and 24p that serve as memory cell gates, and an N-type polysilicon layer 25p that serves as an upper electrode are alternately stacked.
- the protective amorphous was formed in the same manner as the formation of the STTGY and STTGX gate insulating films GOX1_Y and GOX2_X and the channel silicon layers 50p and 51p. Silicon layers 201a and 202a can also be used.
- the lower side of the stacked body is configured with the X selection transistor STTrX of the first embodiment.
- This is a configuration in which the N-type polysilicon layer 43p (see FIG. 20) is not used on the channel semiconductor layer 51p of the X selection transistor STTrX.
- the invention of the fourth embodiment does not depend on the structure of the base. Insulating films 11, 12, 13, 14, 15, N-type polysilicon layers 21 p, 22 p, 23 p, 24 p serving as memory cell gates and N-type polysilicon layers 25 p serving as upper electrodes are alternately stacked to form a stacked body.
- a hole HOLE reaching the diffusion layer formed on the channel silicon layer 51p is formed in the stacked body.
- the gate insulating film 9 and the protective amorphous silicon layer 203a after forming the gate insulating film 9 and the protective amorphous silicon layer 203a, the gate insulating film 9 and the protective amorphous silicon layer 203a on the top surface of the stacked body and the bottom of the HOLE are removed by etch back (FIG. 29).
- the protective amorphous silicon layer 203a is removed by wet etching to form a channel semiconductor layer 8p (FIG. 30).
- the channel semiconductor layer 8p can be formed, for example, by forming a single silicon layer.
- the gate insulating film 9 on the side wall of the stacked body is protected by the amorphous silicon layer 203a during the etch back, the reliability of the gate insulating film 9 can be ensured as compared with the case where there is no amorphous silicon layer 203a.
- the phase change material 7 is formed on the surface of the channel silicon layer 8p by using the CVD method.
- the phase change material 7 is formed so as not to completely embed HOLE, and the remaining holes are completely filled with an insulating film 91.
- the insulating film 91 and the phase change material 7 are removed to the altitude of the insulating film 15 in HOLE by etch back.
- the insulating film 92 is formed, the insulating film 92 on the N-type polysilicon layer 25p is removed by etch back, and the upper surface of 25p is exposed by removing 8p or 8p on the upper surface of 25p. In 8p on 25p, the N-type impurities in 25p are diffused, and N-type impurities are contained at a high concentration.
- the upper electrode is processed (FIG. 31).
- the gate electrodes GATE1, GATE2, GATE3, and GATE4 of the memory cell are processed by a known technique.
- contacts STTGXC for supplying power to STTGX, STTGXL connected to STTGXC, memory cell gate electrodes GATE1, GATE2, GATE3, GATE4, and readout wiring MLR are formed, and peripheral circuits are formed.
- a wiring for connecting to is formed to complete the semiconductor memory device.
- the insulating film 9 can be formed thin. For this reason, the diameter of HOLE can be reduced and high integration can be achieved. Therefore, the bit cost can be reduced.
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Abstract
Description
ここで選択トランジスタSTTrX、STTrYの構造について説明する。STTrYに注目すると、X方向に延伸し2FピッチでY方向に並ぶゲートSTTGYの側壁にゲート絶縁膜を介してチャネル半導体層50pが形成されている。1つのチャネル半導体層50pに注目すると、そのY方向の両面がゲート絶縁膜を介してSTTGYと接している。また、1つのSTTGYに注目すると、そのY方向の両面がゲート絶縁膜を介してチャネル半導体層50pと接している。Y選択トランジスタSTTrYのチャネル半導体層50pのY方向の厚さが厚い(シリコンの場合10nm程度以上)場合には、チャネル半導体層にゲート絶縁膜を介して接する2つのSTTGYでそれぞれ独立な反転層が形成される。その結果、2つのゲートのどちらか一方、あるいは両方にオン電圧が印加されている場合にはチャネル半導体層50pはオン状態となり、プレート状電極BEPLATEと電極3(MLR)の間を導通させる。2つのゲートにともにオフ電圧が印加された場合にチャネル半導体層50pはオフ状態となりプレート状電極BEPLATEと電極3(MLR)の間を絶縁させる。この場合、1つのSTTGYにオン電圧を印加するとその両側にある2つのチャネル半導体層50pが必ずオン状態となるため、チャネル半導体層50pの1つだけをオン状態にする選択動作ができない。
半導体チャネル層50p、51pの膜厚を5nm程度にまで薄くする必要があるため、STTrX、STTrYの製造は、以下のように行う。また、STTrYについては、ゲートSTTGYに対して下側からコンタクトを形成する。
この段階で、Y選択トランジスタのゲートSTTGY(101p,102p,103p)はY方向にピッチ2Fで形成される。ただし、Y方向に連続する2本に注目すると、一方は101pからなり、他方は102pと103pの2層からなる。そしてどちらのゲートも下方でSTTGYCと接続される。チャネルシリコン層50pのY方向の幅(ゲート絶縁膜GOX1_YとGOX2_Yで挟まれた膜厚)は、最小加工寸法に依らない成膜膜厚で定めることができるので、極端紫外線リソグラフィ(EUV)のような高コストなリソグラフィ技術を用いなくても、例えば5nmとすることができる。
なお、チャネルシリコン層50pを102pと103pからなるゲートの下部で分離する必要が生じた場合でも、その分離幅は極力小さくして、N型ポリシリコン層40pとの接触面積を確保することが望ましい。
チャネルシリコン層50pの上部でもチャネルシリコン層50pと上部電極となる後述のN型ポリシリコン層41pとの接触抵抗を低減するため、チャネルポリシリコン層50pの一部を101pからなるゲート側に乗り上げる構造として、上部電極との接触面積を大きくすることが望ましい。
この段階で、STTGXはX方向にピッチ2Fで形成される。ただし、X方向に連続する2本に注目すると、一方は104pからなり、他方は105pからなり、形状は互いに異なる。チャネルシリコン層51pのX方向の幅(ゲート絶縁膜GOX1_X、GOX2_Xで挟まれた膜厚)は、最小加工寸法に依らない成膜膜厚で定めることができるので、極端紫外線リソグラフィ(EUV)のような高コストなリソグラフィ技術を用いなくても、例えば5nmとすることができる。
なお、チャネルシリコン層51pを105pからなるゲートの下部で分離する必要が生じた場合でも、その分離幅は極力小さくして、N型ポリシリコン層42pとの接触面積を確保することが望ましい。
図23に、本発明の選択トランジスタを用いたフラッシュメモリのデバイス構造の鳥瞰図、図24にXZ平面での断面図、図25に等価回路図を示す。図25には、読み出し動作の電圧条件が示されている。
フラッシュメモリアレイは両端で選択トランジスタを介して電極と接続されている。選択トランジスタの動作方法は、実施の形態1と同じである。
図24は、図23で省略した、ゲートとなる電極層321p、322p、323p、324p、と絶縁膜311、312、313、314、315が交互に積層された積層体、積層体に形成されたZ方向のメモリホールとメモリホール内のONO膜すなわちシリコン酸化膜(331)/シリコン窒化膜(332)/シリコン酸化膜(333)、チャネル半導体層308p、が示されている。
チャネル半導体層351pは、Y方向にメモリホールのピッチと同じ2Fピッチで分離されている。Y方向に分離された351pは、X方向に延伸しY方向に2Fピッチで形成された上部電極BLに接続されている。
図26に、本発明の選択トランジスタを用いた縦型クロスポイントメモリのデバイス構造の鳥瞰図、図27にXZ平面での断面図、図28に等価回路図を示す。縦型クロスポイントメモリアレイは下部側で選択トランジスタを介して電極と接続されている。選択トランジスタの動作方法は、実施の形態1、2と同じである。
エッチバックの際に、アモルファスシリコン層203aで積層体側壁のゲート絶縁膜9が保護されているので、アモルファスシリコン層203aが無い場合と比較してゲート絶縁膜9の信頼性を確保できる。
次に、公知の技術によって、メモリセルのゲート電極GATE1、GATE2、GATE3、GATE4の加工を行う。層間絶縁膜を成膜後、STTGXに給電するためのコンタクトSTTGXC、STTGXCと接続されるSTTGXL、メモリセルのゲート電極GATE1、GATE2、GATE3、GATE4、読み出し用配線MLRへのコンタクトを形成し、周辺回路と接続する配線を形成して半導体記憶装置を完成させる。
完成した半導体記憶装置は、メモリセルのゲート絶縁膜9の信頼性が確保できるため、絶縁膜9を薄く形成できる。このためHOLEの直径を縮小し高集積化することができる。従って、ビットコストの低減が可能である。
8p、50p、51p:チャネル半導体層
9:ゲート絶縁膜
11、12、13、14、15:絶縁膜層
21p、22p、23p、24p:ゲートポリシリコン層
25p、40p、41p、42p:N型半導体層
71、72、73、74、75、76:絶縁膜層
81:絶縁膜層
91、92:絶縁膜層
101p、102p、103p、104p、105p:ゲートポリシリコン層
201a、202a、203a:保護アモルファスシリコン層
301p、302p、303p、304p:ゲート電極層
308p:チャネル半導体層
311、312、313、314、315:絶縁膜層
321p、322p、323p、324p:ゲート電極層
331、333:シリコン酸化膜層
332:シリコン窒化膜層
340p、341p、342p、343p:N型半導体層
350p、351p:チャネル半導体層
361、362、363、364:ゲート絶縁膜層
371、372、373、374、375、376:絶縁膜層
401p、402p:ゲート電極層
405p:P型半導体層
407:抵抗変化材料層
408p:導電膜層
411、412、413、414、415:絶縁膜層
421p、422p、423p、424p:N型半導体層
440p、441p:N型半導体層
450p:チャネル半導体層
461、462:ゲート絶縁膜層
471、472、473:絶縁膜層
1001:I/Oインタフェース
1002:メモリセルアレイ
1003、1004、1005、1006:電圧源
1007:電圧セレクタ
1008:配線セレクタ
1009:制御部
1010:読み取り部
1011:管理領域
GOX1_X、GOX2_X、GOX1_Y、GOX2_Y:ゲート絶縁膜
ILD:層間絶縁膜
BEPLATE:プレート状下部電極
MLR、MLRn-1、MLRn、MLRn+1:読出し動作用配線
MLRC:MLRに給電するためのコンタクト
MLRL:MLRに給電するための配線
TEPLATE:プレート状上部電極
F:最小加工寸法
ARRAY:相変化メモリチェインアレイ
PCMCHAIN:相変化メモリチェイン
SPCMCHAIN:選択相変化チェイン
USPCMCHAIN:非選択相変化チェイン
STTrX:X方向の選択を行う選択トランジスタ
STTrY:Y方向の選択を行う選択トランジスタ
STTrX1、STTrX2:X方向の選択を行う選択トランジスタ
STTrY1、STTrY2:Y方向の選択を行う選択トランジスタ
STTGX:X方向の選択を行う選択トランジスタのゲート
STTGY:Y方向の選択を行う選択トランジスタのゲート
STTGXC:STTGXへのコンタクト
STTGYC:STTGYへのコンタクト
STTGXL:STTGXへの給電用の配線
STTGYL:STTGYへの給電用の配線
STTGXLC:STTGXへのコンタクト
STTGYLC:STTGYへのコンタクト
BELC:BEPLATEと周辺回路を接続するコンタクト
TELC:TEPLATEと周辺回路を接続するコンタクト
GATE1、GATE2、GATE3、GATE4:トランジスタのゲート電極
GL1、GL2、GL3、GL4:ゲートに給電する端子
STXm-1、STXm、STXm:選択トランジスタゲート
STYn-2、STYn-1、STYn、STYn+1、STYn+2:選択トランジスタゲート
SMC:選択メモリセル
USMC:非選択メモリセル
VREAD:読出し電圧
VSET:セット電圧
VRESET:リセット電圧
X、Y、Z:方向
VON:トランジスタのオン電圧
VOFF:トランジスタのオフ電圧
VHON:トランジスタのハーフオン電圧
HOLE:メモリホール
DSTTr、USTTr:選択トランジスタ
DSTm-2、DSTm-1、DSTm、DSTm:選択トランジスタゲート
USTm-2、USTm-1、USTm、USTm:選択トランジスタゲート
Vthc:閾値判定レベルの電位
Vpass:非選択セルのゲートへの印加電位
Vth:閾値電位
STTr:選択トランジスタ
BTL:電極配線
Claims (15)
- 半導体基板の上方に形成されたプレート状の下部電極と、前記下部電極の上方に形成された上部電極と、前記下部電極と前記上部電極の間に配置された、電気的に書き換え可能な複数のメモリセルが直列に接続された複数のメモリチェインと、前記メモリチェインの一端に接続された第1選択トランジスタとを有し、
前記複数のメモリチェインは、その長手方向を前記半導体基板の法線方向と合わせて、前記半導体基板面内の第1方向と、第1方向と前記半導体基板面内で直交する第2方向とに沿ってマトリックス状に配置され、
前記第1選択トランジスタは、前記第1方向のメモリチェインの配列ピッチと等ピッチで第1方向に並列に、前記第2方向に延伸して形成されている複数のゲートと、前記複数のゲートの間の対向する各側壁に接して形成されたゲート絶縁膜と、及び前記ゲート絶縁膜を介して前記複数のゲートの間に挟まれて形成された第1のチャネル半導体層とを有し、
前記第1のチャネル半導体層は、前記複数のゲートのうち1つおきのゲートにおいて、該ゲートの両隣りにゲート絶縁膜を介して形成されている両チャネル半導体層が、同時成膜工程の結果により該ゲートと前記下部電極または上部電極との間で接続されている、または同時成膜工程の結果の一部が該ゲートと前記下部電極または上部電極との間に残されていることを特徴とする半導体記憶装置。 - 前記メモリセルが相変化メモリであることを特徴とする請求項1に記載の半導体記憶装置。
- 前記第1選択トランジスタのゲートは、前記第1選択トランジスタのゲートの下方側から形成されたコンタクト孔を介して給電されることを特徴とする請求項2に記載の半導体記憶装置。
- 前記第1選択トランジスタのゲートは、2つ以上の材料層で形成されていることを特徴とする請求項2に記載の半導体記憶装置。
- 前記下部電極と前記メモリチェインアレイの間に前記第1選択トランジスタに加えて、前記第1選択トランジスタと直列に接続される第2選択トランジスタを更に備え、
前記第2選択トランジスタは、前記第2方向のメモリチェインの配列ピッチと等ピッチで第2方向に並列に、前記第1方向に延伸して形成されている複数のゲートと、前記複数のゲートの間の対向する各側壁に接して形成されたゲート絶縁膜と、及び前記ゲート絶縁膜を介して前記複数のゲートの間に挟まれて形成された第2のチャネル半導体層とを有し、
前記第2選択トランジスタの第2チャネル半導体層は、前記第2方向の両側でゲート絶縁膜を介して前記第2選択トランジスタのゲートと対向して存在し、前記第2選択トランジスタのゲートは前記第2方向の両側で前記ゲート絶縁膜を介して前記第2のチャネル半導体層と対向して存在し、前記第2選択トランジスタのゲートは第2方向に1つおきに形状が異なることを特徴とする請求項2に記載の半導体記憶装置。 - 前記第1選択トランジスタと前記第2選択トランジスタの間に、前記第2方向に延伸し、前記第1選択トランジスタの第1チャネル半導体層および前記第2選択トランジスタの第2チャネル半導体層と電気的に接続された金属配線を更に備えていることを特徴とする請求項5に記載の半導体記憶装置。
- 前記第1選択トランジスタの第1チャネル半導体層は、単層の半導体層で形成されていることを特徴とする請求項1に記載の半導体記憶装置。
- 前記第1チャネル半導体層の上部に形成されるソース/ドレイン拡散層は、前記第1選択トランジスタのゲートの1つおきの上方に、前記第1チャネル半導体層と接して形成されていることを特徴とする請求項1に記載の半導体記憶装置。
- 前記メモリセルがフラッシュメモリであることを特徴とする請求項1に記載の半導体記憶装置。
- 前記メモリセルが縦型クロスポイントメモリであることを特徴とする請求項1に記載の半導体記憶装置。
- 前記第1選択トランジスタの前記第1のチャネル半導体層の前記第1方向の厚みは、5nm以下とすることを特徴とする請求項1乃至10のいずれかの請求項に記載の半導体記憶装置。
- 前記第2選択トランジスタの前記第2のチャネル半導体層の前記第2方向の厚みは、5nm以下とすることを特徴とする請求項5または請求項6に記載の半導体記憶装置。
- (a)半導体基板上に層間絶縁膜を介して下部電極となる金属膜を形成する工程と、
(b)前記下部電極上に第1絶縁膜を形成する工程と、
(c)前記第1絶縁膜上に第1ゲート電極層と第2絶縁膜層を形成する工程と、
(d)前記第2絶縁膜、前記第1ゲート電極層、及び前記第1絶縁膜層を、メモリチェインアレイの前記半導体基板面内の第2方向の配列ピッチの2倍のピッチで所定の幅で並列に、前記半導体基板面内の第1方向に延伸するようにパターニングする工程と、
(e)前記工程(d)で形成されたスペースが完全には埋め込まれないように第1ゲート絶縁膜層を形成する工程と、
(f)前記工程(e)で形成されたパタンの上表面と、及びスペース部の下部電極上の前記第1ゲート絶縁膜層を除去する工程と、
(g)前記工程(f)で形成されたスペースが完全には埋め込まれないように第1チャネル半導体を成膜する工程と、
(h)前記工程(g)で形成されたスペースが完全には埋め込まれないように第2ゲート絶縁膜を成膜する工程と、
(i)第2ゲート電極層を成膜する工程と、
(j)前記工程(i)で形成した前記第2ゲート電極層をエッチバックにより前記工程(d)で形成された溝ごとに分離する工程と、
を含むことを特徴とする半導体記憶装置の製造方法。 - 請求項13に記載の半導体記憶装置の製造方法において、
前記工程(b)と前記工程(c)の間に、
(b1)前記第1絶縁膜にコンタクト孔を形成する工程と、
前記工程(i)と前記工程(j)の間に、
(i1)前記工程(d)で形成されたスペース部に存在する前記コンタクト孔を覆う前記第1ゲート絶縁膜と前記第2ゲート電極層を、コンタクト孔上で除去する工程と、
(i2)第3ゲート電極層を形成する工程と、
(i3)前記工程(i2)で形成した前記第3ゲート電極層をエッチバックにより前記工程(d)で形成された溝ごとに分離する工程と、
を更に含むことを特徴とする半導体記憶装置の製造方法。 - 請求項13に記載の半導体記憶装置の製造方法において、
前記工程(e)と前記工程(f)の間に、
(e1)第1ダミー層を形成する工程と、
前記工程(f)と前記工程(g)の間に、
(f1)前記工程(e1)で形成した前記第1ダミー層を除去する工程と、
を更に含むことを特徴とする半導体記憶装置の製造方法。
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US15/106,133 US20170040379A1 (en) | 2013-12-27 | 2013-12-27 | Semiconductor memory device and method for manufacturing same |
JP2015554475A JP6180549B2 (ja) | 2013-12-27 | 2013-12-27 | 半導体記憶装置およびその製造方法 |
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US9472281B1 (en) * | 2015-06-30 | 2016-10-18 | HGST Netherlands B.V. | Non-volatile memory with adjustable cell bit shape |
CN110071136A (zh) * | 2018-01-21 | 2019-07-30 | 成都海存艾匹科技有限公司 | 三维纵向电编程存储器 |
US9679913B1 (en) * | 2016-11-04 | 2017-06-13 | Macronix International Co., Ltd. | Memory structure and method for manufacturing the same |
US10936201B2 (en) * | 2019-02-21 | 2021-03-02 | Intel Corporation | Low latency mirrored raid with persistent cache |
US11665908B2 (en) | 2019-03-22 | 2023-05-30 | Kioxia Corporation | Semiconductor memory device incorporating hafnium oxide insulative portions |
TWI720547B (zh) * | 2019-03-22 | 2021-03-01 | 日商東芝記憶體股份有限公司 | 半導體記憶裝置 |
CN112992784B (zh) * | 2019-12-02 | 2024-01-12 | 长鑫存储技术有限公司 | 半导体结构及其形成方法 |
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