Embodiments described below relate to a semiconductor device, a semiconductor memory device, and a method of manufacturing a semiconductor device.
In recent years, miniaturization and higher levels of integration have been increasingly required in semiconductor devices. For example, in NAND type flash memory, there has been a rising demand not only for miniaturization of a memory region, but also for miniaturization of a peripheral circuit region thereof. However, miniaturization of the peripheral circuit region requires a different method from miniaturization of the memory region, hence it is not easy to effectively achieve miniaturization of the peripheral circuit region while suppressing an increase in the number of steps.
A semiconductor device according to an embodiment described below comprises: an active area where a transistor is provided; an element isolation insulating film that insulates and isolates that active area; and a gate electrode disposed sandwiching a gate insulating film, on the active area. The element isolation insulating film comprises: a first element isolation insulating film having a first width; and a second element isolation insulating film having a second width larger than the first width. The first element isolation insulating film includes in an surface thereof a first element isolation trench having a third width, and the second element isolation insulating film includes in an surface thereof a second element isolation trench having a fourth width larger than the third width. The first element isolation trench has disposed therein a third element isolation insulating film, and the second element isolation trench has disposed therein a fourth element isolation insulating film different from the third element isolation insulating film.
Next, a semiconductor device according to an embodiment will be described with reference to the drawings. A NAND type flash memory will be described below as an example of the semiconductor device, but the present invention is not limited to a NAND type flash memory, and an identical form may be applied also to another semiconductor device having a similar transistor.
First, a NAND cell type flash memory of an embodiment will be described with reference to
First, a configuration of a nonvolatile semiconductor memory device according to a first embodiment will be described with reference to
As shown in
The memory cell array 111 is configured having NAND cell units NU arranged in a matrix therein. Each of the NAND cell units NU includes, for example: a plurality of series-connected electrically rewritable nonvolatile memory cells MC (a memory string) ; and select transistors SG1 and SG2 for respectively connecting both ends of that memory string to a bit line BL and a common source line CELSRC.
Control gates of the memory cells MC in the NAND cell unit NU are connected to different word lines WL. Gates of the select transistors SG1 and SG2 are respectively connected to select gate lines SGD and SGS. A set of NAND cell units NU sharing one word line WL configures a memory block which is a unit of data erase.
Each of the bit lines BL is connected to the sense amplifier 112 shown in
As shown in
As shown in
Data transfer is performed between an external input/output port I/O and the sense amplifier 112, by the input/output buffer 115 and the data line 114. That is, page data read in the sense amplifier 112 is outputted to the data line 114, and is outputted, via the input/output buffer 115, to the input/output port I/O. Moreover, write data supplied from the input/output port I/O is loaded into the sense amplifier 112 via the input/output buffer 115.
Address data Add supplied from the input/output port I/O is supplied to the row decoder 113 and the column decoder 118 via the address register 117. Command data Com supplied from the input/output port I/O is decoded to be set in the control signal generating circuit 116.
Each of external control signals, that is, a chip enable signal/CE, an address latch enable signal ALE, a command latch enable signal CLE, a write enable signal/WE, and a read enable signal/RE are supplied to the control signal generating circuit 116. The control signal generating circuit 116, in addition to performing operation control of memory operations in general, controls the internal voltage generating circuit 119 to generate various kinds of internal voltages required in data read, write, and erase, based on the command Com and the external control signal. Moreover, the control signal generating circuit 116 is applied with a reference voltage from the reference voltage generating circuit 120. The control signal generating circuit 116 performs write from a selected memory cell M on a source line SL side and controls a read operation.
As shown in
One memory block BLKi is a set of memory cells configuring a minimum unit of a data erase operation, and details of structure of the memory block BLKi will be mentioned later. In
In each of the memory blocks BLKi, a plurality of the word lines WL are arranged with a certain pitch in the Y direction and having the X direction as their longer direction. In order to obtain a line width exceeding a resolution limit of lithography, wiring lines of the word lines WL or bit lines BL, and so on, are formed employing so-called sidewall transfer technology.
Sidewall transfer technology will be simply described with reference to
First, a wiring line material 200 for forming a wiring line layer acting as the word line WL is deposited on a semiconductor substrate 100, and a hard mask 111 is formed on this wiring line material 200. As shown in STEP-1 of
Next, as shown in STEP-2, so-called slimming processing is performed by isotropic etching to thin a width of the hard mask 111. Then, a thin film acting as a sidewall transfer process-dedicated sidewall film is deposited on an entire surface including a sidewall of this hard mask 111. A part deposited on an upper surface of the hard mask 111 and an upper surface of the material film 200 of this thin film is removed by etching using anisotropic etching, or the like, and a sidewall process-dedicated sidewall film 112 is formed only on the sidewall of the hard mask 111.
The hard mask 111 may be configured from, for example, a BSG film. The sidewall film 112 is formed by a material having a high selection ratio with respect to the hard mask 111, and in the case that, for example, the hard mask 111 is configured from a BSG film, may be formed adopting, for example, a silicon nitride film as its material.
Next, as shown in STEP-3, the hard mask 111 is removed by etching by wet etching employing an alkaline-system solution, and only the sidewall film 112 having a high selection ratio with respect to the hard mask 111, is left. Then, as shown in STEP-4, the wiring line material 200 is etched to form a wiring line layer 200′ by anisotropic etching using this sidewall film 112 as a mask. The sidewall film 112 is formed so as to have a closed loop shape covering an outer periphery of the patterned hard mask 111, hence the wiring line layer 200′ also is formed in a closed loop shape along this sidewall film 112. The wiring line layer 200′ formed in the closed loop shape is cut at any (some, a certain) position and utilized as various kinds of wiring lines. In the case of a NAND type flash memory, the closed loop is cut at any two places of the closed loop shape, and two open loop state wiring lines are formed from one closed loop shaped wiring line. As a result, a line-and-space pattern of a wiring line width F and wiring line pitch 2F (spacing F) can be formed from a hard mask that has been formed with a wiring line pitch 4F by lithography of a resolution limit 2F.
Note that it is also possible that, after the hard mask 111 has been removed, a sidewall film is further formed on the sidewall of the sidewall film 112 and the sidewall film 112 is removed to leave said sidewall film, whereby further miniaturization is achieved.
Description of the present embodiment will be continued returning to
As mentioned above, in the case that sidewall transfer technology is employed, each of the word lines WL is configured as a closed loop state wiring line along a sidewall of a sacrifice film eventually removed by etching. Explaining this with reference to
Furthermore, this closed loop state wiring line is cut in two places by, for example, an insulating isolation film GR shown in
Next, a structure of the memory cell array of the NAND type flash memory according to the embodiment will be described with reference to the layout diagram of
Word lines WL extending in an X direction and bit lines BL extending in a Y direction are arranged intersecting each other, and a memory cell MC is formed at each of intersections of these word lines WL and bit lines BL. As shown in
A plurality (for example, M) of the memory cells MC (MC_0 to MC_M−1) aligned in the Y direction are connected in series via source/drain diffusion layers to configure one memory string MS. Sometimes, the memory cells at both ends of one memory string MS are configured as dummy cells not employed in data storage. Note that one memory string MS and select transistors SG1 and SG2 at both ends of that memory string MS configure one NAND cell unit NU. Moreover, a plurality of the NAND cell units NU aligned in the X direction are commonly connected by identical word lines WL and select gate lines SGS and SGD, and configure one memory block BLK. Although illustration thereof is omitted, the memory block BLK is formed in one well, whereby a minimum unit of a data erase operation is formed.
One end (a first end portion) of the memory string MS is connected to the bit line BL via the drain side select gate transistor SG1. The bit line BL and the drain side select gate transistor SG1 are connected via a contact not illustrated.
Moreover, the other end (a second end portion) of the memory string MS is connected to a source line CELSRC via the source side select gate transistor SG2. The source line CELSRC and the source side select gate transistor SG2 are connected via a contact not illustrated.
A gate of the drain side select gate transistor SG1 is connected to the drain side select gate line SGD arranged in parallel to the word line WL. Moreover, a gate of the source side select gate transistor SG2 is connected to the source side select gate line SGS arranged in parallel to the word line WL.
The silicon substrate 100 (p type well 10) sandwiched by the element isolation insulating films 11 constitutes an active area AA where the memory string (memory cell) is formed. That is, an surface of the silicon substrate 100 is electrically isolated into a plurality of active areas AA by the element isolation insulating film 11. The active areas AA are formed with a certain spacing in the X direction and extending having the Y direction as their longer direction, similarly to the element isolation insulating films 11.
As shown in
Furthermore, this memory cell MC comprises a charge accumulation film 25 disposed on the floating gate 24. This charge accumulation film 25 has a function of accumulating a charge injected into the floating gate 24 via the tunnel insulating film 23 by a write operation, and is formed by, for example, silicon nitride (SiN). A threshold voltage of the memory cell MC changes by an amount of charge accumulated in this charge accumulation film 25 and the floating gate 24, and data stored in the memory cell MC is determined based on this threshold voltage.
A film thickness of the charge accumulation film 25 may be set to about 2 nm, for example. Existence of the charge accumulation film 25 makes it possible for aspect ratio of the floating gate 24 to be reduced.
Formed on this charge accumulation film 25 is a block insulating film 26. This block insulating film 26 is, for example, configured by: a first insulating film 26A configured from hafnium oxide (HfOx); a second insulating film 26B configured from silicon oxide (SiO2); and a third insulating film 26C configured from hafnium oxide (HfOx). Deposited on this block insulating film 26 is a conductive film 28 acting as the word line WL. Film thicknesses of the first insulating film 26A, the second insulating film 26B, and the third insulating film 26C may each be set to about 5 nm, for example. In this example illustrated in
The conductive film 28 is formed by a metal such as tungsten (W). A stacked structure of a polycrystalline silicon film 13a and a metal silicide may be adopted in place of a metal film.
Deposited in a layer above this conductive film 28 is a cap insulating film 29. This cap insulating film 29 is configured from, for example, a silicon nitride film (SiN), and is formed so as to have a film thickness of about 20 nm, for example.
As shown in
A substantially identical gate electrode structure to that of the memory cell MC is formed also in a region of the select gate transistors SG1 and SG2. That is, the gate electrode of the select gate transistors SG1 and SG2 is configured from a stacked structure of a tunnel insulating film 23′, a floating gate 24′, a charge accumulation film 25′, an inter-gate insulating film 26′, a conductive film 28′, and a cap insulating film 29′, similar to that of the memory cell MC. The tunnel insulating film 23′, the floating gate 24′, the charge accumulation film 25′, the inter-gate insulating film 26′, and the conductive film 28′ have widths in a cross direction which are larger than, but film thicknesses which are substantially identical to, and are formed in steps which are identical to those of, respectively, the tunnel insulating film 23, the floating gate 24, the charge accumulation film 25, the inter-gate insulating film 26, and the conductive film 28 of the memory cell MC. However, in the select gate transistors SG1 and SG2, the inter-gate insulating film 26′ is removed by etching, whereby an opening EI is formed and the floating gate 24′ and the conductive film 28′ which is the control gate are configured to be in a short-circuited state via this opening EI.
The memory cell shown in
Next, a structure of a peripheral circuit region will be described. As previously mentioned, formed in the peripheral circuit region are, for example, the sense amplifier 112, the row decoder 113, the I/O buffer 115, the control signal generating circuit 116, the address register 117, the column decoder 118, the internal voltage generating circuit 119, or the reference voltage generating circuit 120, and so on, shown in
As shown in
A gate electrode 28P is formed so as to straddle each of a plurality of these active areas AA′. This gate electrode 28P functions as a gate electrode of the transistor formed in one active area AA′, and may be formed from, for example, n type or p type polysilicon.
As shown in
Along with demands for miniaturization of the peripheral circuit region, it is being required that a spacing between these gate electrodes 28P is further reduced. In the present embodiment, an element isolation trench TGR1 is formed in part of an surface of the element isolation insulating film 11P positioned between the active areas AA′. The gate electrode 28P is insulated and isolated by an element isolation insulating film 32 implanted in this element isolation trench T. This element isolation trench TGR1 is formed simultaneously to, and by an identical step to that of the element isolation trench TGR for cutting the loop state word line WL formed by the previously mentioned sidewall transfer technology. The element isolation insulating film 32 is deposited inside the element isolation trench TGR1 and above an inter-layer insulating film 31 formed on an upper surface of the gate electrode 28P. This element isolation insulating film 32 is implanted and formed inside the element isolation trench TGR1 by an identical material, and in an identical step, to that of an insulating film implanted in the element isolation trench TGR acting as a loop cut insulating film.
As shown in
Note that the element isolation insulating film 32 may be formed adopting a silane film (SiH4) as its material, for example. In the case of the element isolation insulating film 32 being formed by a silane film, because implanting characteristics of the silane film are low, the inside of the element isolation trench TGR1 is not completely filled by the silane film, and an air gap 32G of the kind shown in
Furthermore, formed on an upper surface of this element isolation insulating film 32 is an inter-layer insulating film 34 formed by, for example, a dTEOS film (a TEOS film generated by a plasma CVD method). Deposited above the inter-layer insulating film 34, via a later-to-be-described liner film 35 (for example, a silicon nitride film), is an inter-layer insulating film 36. Disposed above the inter-layer insulating film 36 is a metal wiring line M1. The metal wiring line M1 is a metal wiring line for connecting to an external circuit the gate electrode 28P or a source/drain diffusion layer of a transistor not illustrated. For example, as shown in
Note that in the semiconductor device of this first embodiment, it is only in the surface of the narrow-width element isolation insulating film 11P (11Pn) that the element isolation trench TGR1 is formed and has its inside implanted with the element isolation insulating film 32. On the other hand, in the element isolation insulating film 11P (11Pw) of broader width than the element isolation insulating film 11Pn, an element isolation trench TGR2 of broader width than the element isolation trench TGR1 is formed. A width D2 of this element isolation trench TGR2 is larger than a width Dl of the element isolation trench TGR1. Moreover, formed inside the element isolation trench TGR2 is an element isolation insulating film different from the element isolation insulating film 32, for example, a sidewall film SM, the liner film 35, and the inter-layer insulating film 36. The sidewall film SM is formed on a sidewall of the element isolation trench TGR2, and is configured from, for example, a silicon oxide film. The liner film 35 is formed on a sidewall of this sidewall film SM and on an upper surface of the inter-layer insulating film 34. The liner film 35 may be configured from, for example, a silicon nitride film (SiN).
Next, a method of manufacturing a semiconductor device of the first embodiment will be described with reference to the process drawings of
First, as shown in
Then, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Then, as shown in
Then, as shown in
Subsequently, as shown in
Note that as shown in
As described above, due to the semiconductor device of the first embodiment, transistors formed in active areas AA′ facing each other sandwiching the narrow-width element isolation insulating film 11Pn are divided by the element isolation trench TGR1 formed along the longer direction of the element isolation insulating film 11Pn. By having this element isolation trench TGR1 implanted with the element isolation insulating film 32, the gate electrode 28P can be insulated and isolated by a narrow spacing. Therefore, a contribution can be made to miniaturization of the peripheral circuit region.
Moreover, this element isolation trench TGR1 can be formed simultaneously to a cutting trench when cutting a loop state wiring line formed by sidewall transfer technology, hence miniaturization of the peripheral circuit region can be achieved while also reducing the number of steps.
Next, a semiconductor device according to a second embodiment will be described with reference to
As shown in
Similar advantages to those of the first embodiment can be displayed also by this second embodiment.
Next, a semiconductor device according to a third embodiment will be described with reference to
As shown in
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
This application is based on and claims the benefit of priority from prior U.S. Provisional Patent Application No. 62/129,424, filed on Mar. 6, 2015, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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62129424 | Mar 2015 | US |