This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-039571, filed Mar. 6, 2018, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a semiconductor device and a manufacturing method of the semiconductor device.
A NAND-type flash memory in which memory cells are stacked three-dimensionally is known.
In general, according to one embodiment, a semiconductor device includes: a first transistor that includes: a first stacked body in which a first oxide, a first nitride, a first conductor, and a second nitride are subsequently stacked above a substrate; and first diffusion regions that are provided on the substrate and bracket the first stacked body; and a second transistor that includes: a second stacked body in which a second oxide, a second conductor, and a third nitride are subsequently stacked above the substrate; and second diffusion regions that are provided on the substrate and bracket the second stacked body, wherein the first transistor further includes: a third oxide provided on the first diffusion regions, and a fourth nitride consecutively provided on the third oxide and the second nitride, and wherein the second transistor further includes: a fourth oxide consecutively provided on the second diffusion regions and the third nitride, and a fifth nitride provided on the fourth oxide.
Hereinafter, the embodiment will be described with reference to the accompanying drawings. The drawings are schematic. Each embodiment is an example of an apparatus or a method to embody the technical idea of the invention. In the explanation that follows, constituent elements having the same functions and configurations will be denoted by the same reference symbols. The numbers after the letters constituting the reference symbols are used to discriminate elements which are denoted by the reference symbols that include the same letters and which have similar configurations. If there is no need of mutually distinguishing the elements which are denoted by the reference symbols that include the same letters, the same elements are denoted by the reference symbols that include only the same letters.
A semiconductor memory according to the first embodiment will be described.
1.1.1 Configuration of Semiconductor Memory
The memory cell array 10 includes a plurality of blocks BLK0 to BLKn (“n” is an integer equal to or greater than 1). A block BLK is a set of non-volatile memory cells, and is, for example, a unit of data erasure. In the memory cell array 10, a plurality of bit lines and a plurality of word lines are provided, and each memory cell is associated with one bit line and one word line. The configuration of the memory cell array 10 will be described later in detail.
The command register 11 retains a command CMD that is received by the semiconductor memory 1 from an external memory controller 2. The command CMD includes instructions to cause the sequencer 13 to execute a read operation and a write operation, for example.
The address register 12 retains address information ADD that is received by the semiconductor memory 1 from the memory controller 2. The address information ADD includes, for example, a block address BA and a page address PA. The block address BA is used to select a block BLK that includes a memory cell targeted for various types of operations. The page address PA is used to select a word line associated with a memory cell targeted for various types of operations.
The sequencer 13 controls the operation of the entire semiconductor memory 1 based on the command CMD retained in the command register 11. For example, the sequencer 13 controls the driver 14, the row decoder 15, and the sense amplifier 16 to perform a write operation for data DAT received from the memory controller 2.
The driver 14 generates a desired voltage under control of the sequencer 13. Subsequently, the driver 14 respectively applies, to corresponding signal lines, a voltage to be applied to a word line that is selected, for example, based on the page address PA retained in the address register 12, and a voltage to be applied to word lines that are not selected.
The row decoder 15 selects one block BLK based on the block address BA retained in the address register 12. The row decoder 15 thereafter applies the voltage applied to each signal line by the driver 14 to each of the selected word line and the unselected word lines, for example.
The sense amplifier 16 applies a desired voltage to each bit line in accordance with write data DAT received from the memory controller 2. The sense amplifier 16 determines data stored in a memory cell based on the voltage of the bit line, and transmits the determined read data DAT to the memory controller 2.
In the communications between the semiconductor memory 1 and the memory controller 2, the NAND interface standards, for example, are supported. For example, the memory controller 2 transmits a command latch enable signal CLE, an address latch enable signal ALE, a write enable signal WEn, and a read enable signal REn; receives a ready/busy signal REn; and transmits and receives an input/output signal I/O. The signal CLE is a signal notifying the semiconductor memory 1 that the received signal I/O is a command CMD. The signal ALE is a signal notifying the semiconductor memory 1 that the received signal I/O is address information ADD. The signal WEn is a signal instructing the semiconductor memory 1 to input the signal I/O. The signal REn is a signal instructing the semiconductor memory 1 to output the signal I/O. The signal RBn is a signal for notifying the memory controller 2 of whether the semiconductor memory 1 is in a ready state in which an instruction from the memory controller 2 can be received, or in a busy state in which an instruction from the memory controller 2 cannot be received. The signal I/O is, for example, an 8-bit signal, and may include a command CMD, address information ADD, write data DAT, and read data DAT, etc.
The semiconductor memory 1 and the memory controller 2 as described in the above may constitute one semiconductor device by a combination thereof. Examples of such a semiconductor device may include a memory card, such as an SD™ card, a solid state drive (SSD), etc.
1.1.2 Circuit Configuration of Memory Cell Array
A block BLK includes, for example, four string units, SU0 to SU3, as shown in
Each memory cell transistor MT is provided with a control gate and a charge storage layer, and stores data in a nonvolatile manner. Memory cell transistors MT0 to MT95 included in each NAND string NS are coupled in series between a source of the selection transistor ST1 and a drain of the selection transistor ST2. The control gates of the memory cell transistors MT0 to MT95 in the same block BLK are respectively coupled in common to the word lines WL0 to WL95 in common. A set of one-bit data that is stored in the plurality of memory cell transistors MT coupled in common to a word line WL in each string unit SU is referred to as a “page”.
The selection transistors ST1 and ST2 are used to select a string unit SU at the time of various types of processing. The gates of selection transistors ST1 in the string units SU0 to SU3 in the same block BLK are respectively coupled in common to the selection gate lines SGD0 to SGD3. The drains of selection transistors ST1 in the same column in each block BLK are coupled in common to the corresponding bit line BL. The gates of selection transistors ST2 in the same block BLK are coupled in common to a selection gate line SGS. The sources of selection transistors ST2 in each block BLK are coupled in common to a source line SL between multiple blocks BLK.
The circuit configuration of the memory cell array 10 is not limited thereto. For example, the number of string units SU included in each block BLK and the number of memory cell transistors MT and selection transistors ST1 and selection transistors ST2 included in each NAND string NS may be discretionarily changed. The number of word lines WL and the number of selection gate lines SGD and SGS can be changed based on the number of memory cell transistors MT and the number of selection transistors ST1 and selection transistors ST2.
1.1.3 Configuration of Memory Cell Array
As shown in
A semiconductor pillar MH is provided from above a conductor 26 to penetrate conductors 23-26 to reach p-type well region 22. The semiconductor pillar MH includes, for example, a block insulation film 27, an insulation film 28, a tunnel oxide film 29, and a conductive semiconductor film 30. The block insulation film 27 is provided on an inner wall of a memory hole forming the semiconductor pillar MH, an insulation film 28 is provided on an inner wall of the block insulation film 27, the tunnel oxide film 29 is provided on an inner wall of the insulation film 28, and the semiconductor film 30 is embedded inside of the tunnel oxide film 29. A film of a different material may be additionally formed inside of the semiconductor film 30.
The semiconductor pillar MH includes a lower layer semiconductor pillar LMH, a higher layer semiconductor pillar HMH, and a semiconductor pillar junction MHJT. The lower layer semiconductor pillar LMH and the higher layer semiconductor pillar HMH are arranged at a lower position of the semiconductor pillar junction MHJT and at a higher position of the semiconductor pillar junction MHJT, respectively. Specifically, the lower layer semiconductor pillar LMH is provided on a lower surface of the semiconductor pillar junction MHJT to reach the upper surface of p-type well region 22. The higher layer semiconductor pillar HMH is provided from above conductor 26 to reach an upper surface of the semiconductor pillar junction MHJT.
On a junction surface between the semiconductor pillar junction MHJT and the lower layer semiconductor pillar LMH, the diameter of the semiconductor film 30 on the lower surface of the semiconductor pillar junction MHJT is greater than the diameter of the semiconductor film 30 on an upper surface of the lower layer semiconductor pillar LMH. On a junction surface between the semiconductor pillar junction MHJT and the higher layer semiconductor pillar HMH, the diameter of the semiconductor film 30 on the upper surface of the semiconductor pillar junction MHJT is greater than the diameter of the semiconductor film 30 on a lower surface of the higher layer semiconductor pillar HMH.
In the above-described configuration of the semiconductor pillar MH, the insulation film 28 functions as a charge storage layer of memory cell transistors MT, and a channel of the NAND string NS is formed in the semiconductor film 30. Portion in which the semiconductor pillar MH crosses conductor 23 function as selection transistor ST2; portions in which the semiconductor pillar MH crosses conductors 24 that function as word lines WL0 through WL47 function as memory cell transistors MT0 through MT47; portions in which the semiconductor pillar MH crosses conductors 25 that function as word lines WL48 through WL95 function as memory cell transistors MT48 through MT95; and portion in which the semiconductor pillar MH crosses conductor 26 function as selection transistor ST1.
The above-described configuration shown in
1.1.4 Peripheral Configuration of Memory Cell Array
The peripheral configuration of the memory cell array of the semiconductor memory according to the first embodiment will be described.
As shown in
In the hook-up area A2, conductors 23-26 and insulators 31-34 are formed in a stepwise manner having multiple steps. Conductors 23-26 are provided on an upper surface of each step of the stepwise structure. On the upper surface of each step of the stepwise structure, a non-illustrated contact plug is provided to be electrically coupled to each of conductors 23-26. Through this configuration, each of conductors 23-26 is hooked up via the corresponding contact plug.
In the peripheral area A3, the semiconductor substrate 20 is provided with insulators 36 that function as an element isolating region (STI: Shallow Trench Isolation). Insulator 36 forms, for example, a region which is insulated from p-type well region 22. N-type well region 35 (35_1 and 35_2) is formed on the region isolated from p-type well region 22 of the semiconductor substrate 20. That is to say, p-type well region 22 and n-type well regions 35_1 and 35_2 are formed with insulators 36 interposed therebetween on the semiconductor substrate 20 in the peripheral area A3.
P-type transistors TrP1 and TrP2 are respectively provided on n-type well regions 35_1 and 35_2. Specifically, p-type transistor TrP1 includes p+-type impurity diffusion regions 37_1 provided on n-type well region 35_1, and stacked body BYP1 provided above n-type well region 35_1 in an area interposed between p+-type impurity diffusion regions 37_1. Similarly, p-type transistor TrP2 includes p+-type impurity diffusion regions 37_2 provided on n-type well region 35_2, and stacked body BYP2 provided above n-type well region 35_2 in an area interposed between p+-type impurity diffusion regions 37_2. Each of p+-type impurity diffusion regions 37_1 and 37_2 functions as a source or a drain of p-type transistors TrP1 and TrP2. Each of stacked bodies BYP1 and BYP2 functions as a gate of p-type transistors TrP1 and TrP2. Contact plugs 39_1 and 39_2 are respectively provided above each of stacked bodies BYP1 and BYP2 so as to reach the gates of p-type transistors TrP1 and TrP2. Contact plugs 39_1 and 39_2 include, for example, tungsten (W).
Contact plug 39_1 includes a lower layer contact plug LCSP1, a higher layer contact plug HCSP1, and a contact plug junction CSJTP1. Lower layer contact plug LCSP1 and higher layer contact plug HCSP1 are placed at a lower position of contact plug junction CSJTP1 and at a higher position of contact plug junction CSJTP1, respectively. Specifically, lower layer contact plug LCSP1 is provided on a lower surface of contact plug junction CSJTP1 to reach the upper surface of p-type transistor TrP1. Higher layer contact plug HCSP1 is provided from the layer in which insulator 34 is provided to reach an upper surface of contact plug junction CSJTP1. Contact plug junction CSJTP1 is provided on the same layer as the layer where insulator 32 is provided, similar to the semiconductor pillar junction MHJT, for example.
On a junction surface between contact plug junction CSJTP1 and lower layer contact plug LCSP1, the diameter (area) of the lower surface of contact plug junction CSJTP1 is greater than the diameter (area) of an upper surface of lower layer contact plug LCSP1. On a junction surface between contact plug junction CSJTP1 and higher layer contact plug HCSP1, the diameter of the upper surface of contact plug junction CSJTP1 is greater than the diameter of a lower surface of higher layer contact plug HCSP1.
Similarly, contact plug 39_2 includes a lower layer contact plug LCSP2, a higher layer contact plug HCSP2, and a contact plug junction CSJTP2. The relationships between lower layer contact plug LCSP2, contact plug junction CSJTP2, and higher layer contact plug HCSP2 in contact plug 39_2 are the same as the relationships between lower layer contact plug LCSP1, contact plug junction CSJTP1, and higher layer contact plug HCSP1 in contact plug 39_1.
N-type transistor TrN is provided on p-type well region 22. Specifically, n-type transistor TrN includes n+-type impurity diffusion regions 38 provided on p-type well region 22, and stacked body BYN provided above p-type well region 22 in an area interposed between n+-type impurity diffusion regions 38. N+-type impurity diffusion regions 38 function as a source or drain of n-type transistor TrN. Stacked body BYN functions as a gate of n-type transistor TrN. Contact plug 40 is provided above stacked body BYN so as to reach the gate of the n-type transistor TrN. Contact plug 40 includes, for example, tungsten (W).
Contact plug 40 includes a lower layer contact plug LCSN, a higher layer contact plug HCSN, and a contact plug junction CSJTN. Lower layer contact plug LCSN and higher layer contact plug HCSN are placed at a lower position of the contact plug junction CSJTN and at a higher position of contact plug junction CSJTN, respectively. Specifically, lower layer contact plug LCSN is provided on a lower surface of contact plug junction CSJTN to reach the upper surface of n-type transistor TrN. Higher layer contact plug HCSN is provided from the layer in which insulator 34 is provided to reach an upper surface of contact plug junction CSJTN. Contact plug junction CSJTN is provided on the same layer as the layer where insulator 32 is provided, similar to the semiconductor pillar junction MHJT, for example.
On a junction surface between contact plug junction CSJTN and lower layer contact plug LCSN, the diameter of the lower surface of contact plug junction CSJTN is greater than the diameter of an upper surface of lower layer contact plug LCSN. On a junction surface between contact plug junction CSJTN and higher layer contact plug HCSN, the diameter of the upper surface of contact plug junction CSJTN is greater than the diameter of a lower surface of higher layer contact plug HCSN.
In
1.1.5 Configuration of Transistor
Next, the configuration of the transistors formed in the peripheral area of the semiconductor memory according to the first embodiment will be described with reference to
First, the configuration of p-type transistor TrP1 will be described with reference to
As shown in
Oxide 41 functions as a gate insulation film, and includes, for example, silicon dioxide (SiO2).
Nitride 42 is provided on a part of an upper surface of oxide 41, and includes, for example, silicon nitride (SiN). Nitride 42 functions as a gate insulation film in combination of oxide 41, and functions to prevent the diffusion of p+-type impurities doped by conductor 43 in n-type well region 35_1 via oxide 41.
As stated above, in order to activate p-type transistor TrP1 with a small threshold voltage, the total EOT of oxide 41 and nitride 42 is preferably less than 4 nm. A preferable example of the total EOT of oxide 41 and nitride 42 is, for example, approximately 3 nm.
Conductor 43 functions as a gate, and includes, for example, a polysilicon (polycrystalline silicon) in which boron (B) is doped as p+-type impurities. Conductor 44 functions as an electrode that is capable of coupling conductor 43 and lower layer contact plug LCSP1 with a low contact resistance, and includes, for example, tungsten silicide (WSi). Namely, conductors 43 and 44 form a polycide structure in which a metal silicide is stacked on a polycrystalline silicon in which a p+-type impurity is doped.
Nitride 45 functions as a cap layer, and includes, for example, silicon nitride (SiN).
A film of oxide 46 is formed on a side surface of nitride 42, conductor 43, conductor 44, and nitride 45, and on an upper surface of oxide 41 (except an area in which nitride 42 is provided). In addition, oxide 47 is provided to cover the top of oxide 46. Oxide 46 and oxide 47 function as a sidewall, and include, for example, silicon dioxide (SiO2).
A film of oxide 48 that functions as a protection film of the semiconductor substrate 20 is formed on upper surfaces of p+-type impurity diffusion regions 37_1. Oxide 48 is formed, for example, by performing substrate oxidation to the semiconductor substrate 20, and includes, for example, silicon dioxide (SiO2).
On an upper surface of nitride 45, oxide 47, and oxide 48, a film of nitride 49 is consecutively formed. Nitride 49 includes, for example, silicon nitride (SiN).
Although hatching is omitted, a film of insulator 50 that functions as an interlayer insulation film is formed on an upper surface of nitride 49 above p+-type impurity diffusion region 37_1 to fill a space around stacked body BYP1. Insulator 50 includes, for example, NSG (Non-doped silicate glass).
A film of nitride 51 is formed on an upper surface of insulator 50 and an upper surface of nitride 49 formed on the upper surface of stacked body BYP1.
Nitride 51 includes, for example, silicon nitride (SiN), and functions as a stopper when etching is performed to form contact holes in which contact plugs (not shown in the drawings) electrically coupled with the source and the drain of p-type transistor TrP1, respectively, and lower layer contact plug LCSP1 are provided. A film of oxide 52 is formed on an upper surface of nitride 51. Oxide 52 includes, for example, silicon dioxide (SiO2).
Although hatching is omitted, a film of insulator 53 that functions as an interlayer insulation film is formed on an upper surface of oxide 52. Insulator 53 includes, for example, dTEOS (silicon oxide formed of TEOS (Tetraethyl ortho-silicate) by plasma CVD (Chemical vapor deposition)).
Lower layer contact plug LCSP1 is provided to penetrate insulator 53, oxide 52, nitride 51, nitride 49, and nitride 45 to reach conductor 44. Lower layer contact plug LCSP1 is in contact with conductor 44, nitride 45, nitride 49, and nitride 51 at a position lower than the layer of oxide 52. Namely, lower layer contact plug LCSP1 is provided not to be in contact with oxide at a position lower than the layer of oxide 52.
Next, the configuration of p-type transistor TrP2 will be described with reference to
As shown in
Oxide 61p functions as a gate insulation film, and includes, for example, silicon dioxide (SiO2). As stated above, oxide 61p is formed to have the EOT greater than the total EOT of oxide 41 and nitride 42, to be activated with a greater threshold voltage than p-type transistor TrP1. Specifically, the EOT of oxide 61p is preferably 5 nm or more, for example. A preferable example of the EOT of oxide 61p is, for example, approximately 7 nm.
Conductor 62p functions as a gate, and includes, for example, a polysilicon in which phosphorus (P) is doped as n+-type impurities. Conductor 63p functions as an electrode that is capable of coupling conductor 62p and lower layer contact plug LCSP2 with a low contact resistance, and includes, for example, tungsten silicide (WSi). Namely, conductors 62p and 63p form a polycide structure in which metal silicide is stacked on a polycrystalline silicon in which n+-type impurities are doped.
Nitride 64p functions as a cap layer, and includes, for example, silicon nitride (SiN).
A film of oxide 65p is formed on a side surface of nitride conductor 62p, conductor 63p, and nitride 64p, and on an upper surface of oxide 61p (except an area in which conductor 62p is provided). In addition, oxide 66p is provided to cover the top of oxide 65p. Oxide 65p and oxide 66p function as a sidewall, and includes, for example, silicon dioxide (SiO2).
On upper surfaces of p+-type impurity diffusion regions 37_2, nitride 64p, and oxide 66p, a film of oxide 67p is consecutively formed. Oxide 67p includes, for example, silicon dioxide (SiO2).
A film of nitride 68p is formed on an upper surface of oxide 67p. Nitride 68p includes, for example, silicon nitride (SiN).
Although hatching is omitted, a film of insulator 69p that functions as an interlayer insulation film is formed on an upper surface of nitride 68p above p+-type impurity diffusion regions 37_2 to fill a space around stacked body BYP2. Insulator 69p includes, for example, NSG.
A film of nitride 70p is formed on an upper surface of insulator 69p and the upper surface of nitride 68p formed above stacked body BYP2. Nitride 70p includes, for example, silicon nitride (SiN), and functions as a stopper when etching is performed to form contact holes in which contact plugs (not shown in the drawings) electrically coupled with the source and the drain of p-type transistor TrP2, respectively, and lower layer contact plug LCSP2 are provided. A film of oxide 71p is formed on an upper surface of nitride 70p. Oxide 71p includes, for example, silicon dioxide (SiO2).
Although hatching is omitted, a film of insulator 72p is formed on an upper surface of oxide 71p. Insulator 72p includes, for example, dTEOS.
Lower layer contact plug LCSP2 is provided to penetrate insulator 72p, oxide 71p, nitride 70p, nitride 68p, oxide 67p, and nitride 64p to reach conductor 63p. Lower layer contact plug LCSP2 is in contact with conductor 63p, nitride 64p, oxide 67p, nitride 68p, and nitride 70p at a position lower than the layer of oxide 71p. Namely, lower layer contact plug LCSP2 may be in contact with oxide 67p at a position lower than the layer of oxide 71p.
Next, the configuration of n-type transistor TrN will be described with reference to
In
As shown in
Oxide 61n functions as a gate insulation film, and includes, for example, silicon dioxide (SiO2). As stated above, n-type transistor TrN may have a similar value of breakdown voltage to p-type transistor TrP1, or may have a similar value of breakdown voltage to p-type transistor TrP2. Accordingly, the EOT of oxide 61n may be less than 4 nm, or may be 5 nm or more. A preferable example of the EOT of oxide 61n is, for example, approximately 3 nm when oxide 61n has a similar value of breakdown voltage to p-type transistor TrP1. A preferable example of the EOT of oxide 61n is, for example, approximately 7 nm when oxide 61n has a value of a breakdown voltage similar to p-type transistor TrP2.
Conductor 62n functions as a gate, and includes, for example, a polysilicon in which phosphorus (P) is doped as n+-type impurities. Conductor 63n functions as an electrode that is capable of coupling conductor 62n and lower layer contact plug LCSN with a low contact resistance, and includes, for example, tungsten silicide (WSi). Namely, conductors 62n and 63n form a polycide structure in which metal silicide is stacked on a polycrystalline silicon in which n+-type impurities are doped.
Nitride 64n functions as a cap layer, and includes, for example, silicon nitride (SiN).
A film of oxide 65n is formed on a side surface of nitride conductor 62n, conductor 63n, and nitride 64n, and on an upper surface of oxide 61n (except an area in which conductor 62n is provided). In addition, oxide 66n is provided to cover the top of oxide 65n. Oxide 65n and oxide 66n function as a sidewall, and includes, for example, silicon dioxide (SiO2).
On upper surfaces of the N+-type impurity diffusion regions 38, nitride 64n, and oxide 66n, a film of oxide 67n is consecutively formed. Oxide 67n includes, for example, silicon dioxide (SiO2).
A film of the nitride 68n is formed on an upper surface of the oxide 67n. Nitride 68n includes, for example, silicon nitride (SiN).
Although hatching is omitted, a film of insulator 69n that functions as an interlayer insulation film is formed on an upper surface of nitride 68n above the N+-type impurity diffusion regions 38 to fill a space around stacked body BYN. Insulator 69n includes, for example, NSG.
A film of nitride 70n is formed on an upper surface of insulator 69n and an upper surface of nitride 68n formed above stacked body BYN. Nitride 70n includes, for example, silicon nitride (SiN), and functions as a stopper when etching is performed to form contact holes in which contact plugs (not shown in the drawings) electrically coupled with the source and the drain of n-type transistor TrN, respectively, and lower layer contact plug LCSN are provided. A film of oxide 71n is formed on an upper surface of the nitride 70n. Oxide 71n includes, for example, silicon dioxide (SiO2).
Although hatching is omitted, a film of insulator 72n that functions as an interlayer insulation film is formed on an upper surface of oxide 71n. Insulator 72n includes, for example, dTEOS.
Lower layer contact plug LCSN is provided to penetrate insulator 72n, oxide 71n, nitride 70n, nitride 68n, oxide 67n, and nitride 64n to reach conductor 63n. Lower layer contact plug LCSN is in contact with conductor 63n, nitride 64n, oxide 67n, nitride 68n, and nitride 70n at a position lower than the layer of oxide 71n. Namely, lower layer contact plug LCSN may be in contact with oxide 67n at a position lower than the layer of oxide 71n.
Next, a manufacturing method of the semiconductor memory according to the first embodiment will be described.
1.2.1 Method of Manufacturing Transistor
The manufacturing method of the transistor TrP and TrN formed in the peripheral area A3 of the semiconductor memory according to the first embodiment will be described with reference to
As shown in
As stated above, the total EOT of oxide 41 and nitride 42 of stacked body BYP1 is set to be smaller than the EOT of oxide 61p of stacked body BYP2. Stacked body BYP1 is formed to include nitride 42 between oxide 41 and conductor 43; stacked bodies BYP2 and BYN do not include nitride between oxide 61p and conductor 62p, or between oxide 61n and conductor 62n. Boron (B) is doped in conductor 43 of stacked body BYP1, and phosphorus (P) is doped in conductor 62p of stacked body BYP2 and in conductor 62n of stacked body BYN.
Subsequently, a film of oxide 67 (67p or 67n) is formed on the entire surface of the peripheral area A3, as shown in
Subsequently, as shown in
Subsequently, as shown in
As stated above, oxide 67 is formed on p+-type impurity diffusion regions 37_2, and n+-type impurity diffusion regions 38; however, oxide 48 is formed by performing oxidation to the upper portions of p+-type impurity diffusion regions 37_1. Accordingly, the boundary between p+-type impurity diffusion regions 37_1 and oxide 48 is positioned lower than the boundary between oxide 67 and p+-type impurity diffusion regions 37_2 or n+-type impurity diffusion regions 38.
Subsequently, as shown in
Subsequently, as shown in
A film of nitride 51 (or 70p or 70n) is formed on the upper surface of insulator 50, and on the upper surface of nitride 49 (except an area where insulator 50 is provided). Oxide 52 (or 71p or 71n) is provided on the upper surface of nitride 51.
Through the above process, the structures of p-type transistors TrP1 and TrP2, and n-type transistor TrN shown in
1.2.2 Method of Manufacturing Contact Plug
The manufacturing method of a contact plug coupled to a gate of a transistor formed in the peripheral area of the semiconductor memory according to the first embodiment will be described with reference to
As shown in
Specifically, insulator 31 and replacement material 81 or 82 are alternately stacked on p-type well region 22 in the memory area A1 and the hook-up area A2. More specifically, replacement material 81 is provided on the upper surface of insulator 31 at the lowermost layer, and insulator 31 and replacement material 82 are alternately stacked on the replacement material 81. Replacement materials 81 and 82 include, for example, silicon nitride (SiN). Insulator 32 is provided above the replacement material 82 at the uppermost layer. In the hook-up area A2, the stacked body including insulators 31 and 32 and replacement materials 81 and 82 is formed in a stepwise manner so that replacement material 81 or 82 is placed on the upper surface of each step. Specifically, a non-illustrated mask is provided on the upper surface of insulator 32 over the memory area A1, the hook-up area A2, and the peripheral area A3. Subsequently, after a pattern is formed in the mask by lithography, anisotropic etching of the lower side stacked structure is performed based on the obtained pattern, and slimming of the mask pattern is performed to eliminate a part of the mask pattern. The processes are repeated sequentially. Through these processes, etching can be performed to make the lower side stacked structure to be stepwise. Thereafter, insulator 53 (or 72p or 72n) is provided on oxide 52, up to the level so that the periphery of the lower side stacked structure is filled (for example, the same layer in which insulator 32 is provided).
In the memory area A1, lower layer memory hole LH is formed in an area of the lower side stacked structure where the lower layer semiconductor pillar LMH and the semiconductor pillar junction MHJT are to be formed.
Subsequently, as shown in
Specifically, when forming lower layer contact holes LCSPH1, LCSPH2, and LCSNH, the lower layer memory hole LH is pre-filled with a non-illustrated mask. Thereafter, a non-illustrated mask, for example, is formed on the upper surfaces of insulators 53 and 32. The parts of mask on insulator 53 is eliminated by lithography, for example, and accordingly, areas where lower layer contact plugs LCSP1, LCSP2, and LCSN are to be provided are exposed. Thereafter, in areas of insulator 53 where the mask is eliminated, lower layer contact holes LCSPH1, LCSPH2, and LCSNH are formed by anisotropic etching by RIE (reactive ion etching). Lower layer contact holes LCSPH1, LCSPH2, and LCSNH penetrate insulator 53 to respectively reach the upper surface of nitride 45 of stacked body BYP1, the upper surface of nitride 64p of stacked body BYP2, and the upper surface of nitride 64n of stacked body BYN. The mask filled in the lower memory hole LH is eliminated as appropriate.
When forming lower layer contact holes LCSPH1, LCSPH2, and LCSNH, lower layer contact holes (not illustrated) to provide contact plugs coupled respectively to sources and drains of p-type transistors TrP1, TrP2, and n-type transistor TrN may be formed at the same time. In this case, in the aforementioned etching process, nitride 51 (or 70p or 70n) functions as a stopper against forming of the lower layer contact holes. Accordingly, when the etching to lower layer contact hole LCSPH1 is performed to reach the upper surface of nitride 45, it is possible to prevent etching to a lower layer contact hole corresponding to a contact plug coupled to each of the source and the drain of p-type transistor TrP1 from reaching to oxide 48.
Thus, in the process described below, when a sacrificial material is filled in the lower layer contact hole corresponding to the contact plug coupled to each of the source and the drain of p-type transistor TrP1, physical coupling between the sacrificial material and nitride 42 through oxide 48 and 41 is prevented.
Subsequently, as shown in
Specifically, lower layer contact holes LCSPH1, LCSPH2, LCSNH, and lower layer memory hole LH are completely filled with sacrificial materials 91_1, 91_2, 92, and 93, and thereafter, the sacrificial materials 91_1, 91_2, 92, and 93 are etched back to the level where contact plug junctions CSJTP1, CSJTP2, and CSJTN, and semiconductor pillar junction MHJT are to be formed.
Through this process, nitrides 45, 64p, and 64n may be physically coupled with the lower side stacked structure through the sacrificial materials 91_1, 91_2, and 92 (and insulator 53).
Subsequently, as shown in
Specifically, after a non-illustrated mask is provided on the upper surface of insulators 53 and 32, wet etching that can be selectively eliminate insulators 53 and 32 is performed. Through this process, insulators 53 and 32 are eroded in the horizontal direction from portions exposed by etching back to sacrificial materials 91_1, 91_2, 92, and 93. Accordingly, the diameter of openings of lower layer contact holes LCSPH1, LCSPH2, LCSNH, and lower layer memory hole LH (namely, areas where contact plug junction CSJTP1, CSJTP2, CSJTN and semiconductor pillar junction MHJT are to be formed) is widened.
Thereafter, sacrificial materials 91_1, 91_2, 92, and 93 are respectively filled in the portions in which the shapes of contact plug junctions CSJTP1, CSJTP2, CSJTN, and semiconductor pillar junction MHJT are formed.
Subsequently, as shown in
Namely, p-type transistors TrP1 and TrP2 and n-type transistor TrN can be physically coupled to the upper side stacked structure respectively through sacrificial materials 91_1, 91_2, and 92.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Specifically, a non-illustrated mask is provided, for example, by CVD, on the upper surface of insulators 53 and 34 over the memory area A1, the hook-up area A2, and the peripheral area A3. The mask on insulator 53 is eliminated by lithography, for example, and accordingly, areas where higher layer contact plugs HCSP1, HCSP2, and HCSN are to be provided are exposed. Thereafter, in the areas of insulator 53 where the mask is eliminated, higher layer contact holes HCSPH1, HCSPH2, and HCSNH are formed by anisotropic etching by RIE. Each of higher layer contact holes HCSPH1, HCSPH2, and HCSNH reaches the upper surfaces of respective sacrificial materials 91_1, 91_2, and 92.
Subsequently, as shown in
In the above process, the process may be performed to form a lower layer contact hole corresponding to a contact plug coupled to each of the source and the drain of respective transistors, and to expose a diffusion region.
Subsequently, as shown in
Through the aforementioned process, the gate of each of p-type transistors TrP1 and TrP2 and n-type transistor TrN is hooked up through contact plugs 39_1, 39_2, and 40.
According to the first embodiment, deterioration of transistor characteristics can be prevented. The advantageous effect will be explained below.
As shown in
Hydrogen ion H* can cleave SiN bonds used for nitride. Thus, hydrogen ion H* affects nitride 42 to lower the function of nitride 42 which is to prevent diffusion of boron (B) doped in conductor 43 to n-type well region 35_1. If boron (B) is diffused in n-type well region 35_1, a threshold voltage of p-type transistor TrP1 may vary in an unexpected range, and accordingly, characteristics of p-type transistor TrP1 may be deteriorated. Thus, it is preferable that a path that allows hydrogen ion H* to enter nitride 42 is blocked when manufacturing p-type transistor TrP1.
According to the first embodiment, nitride 49 is provided on the upper surface of nitride 45 of p-type transistor TrP1 without oxide intervention. With this structure, sacrificial material 91_1 is not in contact with oxide physically coupled with nitride 42 at a position lower than the layer of oxide 52. Accordingly, it is possible to prevent hydrogen ion H* propagated to the upper position of p-type transistor TrP1 through sacrificial material 91_1 from reaching nitride 42. Therefore, it is possible to prevent bonds of nitride 42 from being cleaved, and also to prevent the threshold voltage of p-type transistor TrP1 from varying.
A film of oxide 48 is formed on upper portion of p+-type impurity diffusion regions 37_1 by substrate oxidation. Through this process, oxide 48 can be provided between p+-type impurity diffusion regions 37_1 and nitride 49 without forming a film of oxide on the upper surface of nitride 45. Accordingly, it is possible to prevent crystal defects from being produced in p+-type impurity diffusion regions 37_1 due to the stress of nitride 49. Therefore, it is possible to prevent bonds of nitride 42 from being cleaved while protecting p+-type impurity diffusion regions 37_1.
A film of oxide 67 is consecutively formed over the peripheral area A3 after stacked bodies BYP1, BYP2, and BYN are formed. Thereafter, oxide 67 is eliminated from the upper surfaces of nitride 45 of stacked body BYP1 and p+-type impurity diffusion regions 37_1. Through this process, oxide 67 can be provided for p-type transistor TrP2 and re-type transistor TrN, without the need of substrate oxidation. Accordingly, it is possible to prevent a loss of the upper portion of p+-type impurity diffusion regions 37_2 and n+-type impurity diffusion regions 38 due to substrate oxidation. Therefore, it is possible to prevent a deterioration in withstand voltage in p-type transistor TrP2 and n-type transistor TrN (especially, for transistors with high breakdown voltage).
As an example of an aspect where sacrificial material 91_1 is filled in contact plug 39_1, the case is assumed where contact plug 39_1 is formed in three steps: firstly in lower layer contact plug LCSP1, secondly in contact plug junction CSJT1, and finally in higher layer contact plug HCSP1.
According to the first embodiment, the stepwise stacked structure is formed step-by-step, i.e., separately in the lower side stacked structure and the upper side stacked structure, in the memory area A1 and the hook-up area A2. Accordingly, the semiconductor pillar MH is formed step-by-step formation of the lower layer semiconductor pillar LMH, the semiconductor pillar junction MHJT, and the higher layer semiconductor pillar HMH. Contact plugs 39_1, 39_2, and 40 are formed in accordance with the formation of the lower layer semiconductor pillar LMH, the semiconductor pillar junction MHJT, and the higher layer semiconductor pillar HMH by step-by-step formation of lower layer contact plugs LCSP1, LCSP2, and LCSN; contact plug junctions CSJTP1, CSJTP2, and CSJTN; and higher layer contact plugs HCSP1, HCSP2, and HCSN.
It is known that characteristics of tungsten (W), used for contact plugs 39_1, 39_2, and 40, are easily deteriorated by being influenced by the manufacturing process of other parts of the semiconductor memory 1. For example, tungsten (W) may easily cause boundary exfoliation of a film by receiving heat due to thermal processing. In addition, tungsten (W) may easily cause corrosion by a chemical solution used for wet etching. According to the first embodiment, after forming lower layer contact holes LCSPH1, LCSPH2, and LCSNH, sacrificial materials 91_1, 91_2, and 92 are respectively filled in lower layer contact holes LCSPH1, LCSPH2, and LCSNH as a replacement of tungsten (W) until higher layer contact holes HCSPH1, HCSPH2, and HCSNH are formed. By using sacrificial materials 91_1, 91_2, and 92, deterioration of contact plugs 39_1, 39_2, and 40 due to various types of processing in the manufacturing method of the semiconductor memory 1 can be prevented.
The process of filling sacrificial materials 91_1, 91_2, and 92 respectively in lower layer contact holes LCSPH1, LCSPH2, and LCSNH is performed simultaneously with the process of filling sacrificial material 93 in the lower layer memory hole LH. The process of forming the shapes of contact plug junctions CSJTP1, CSJTP2 and CSJTN is performed simultaneously with the process of forming the shape of the semiconductor pillar junction MHJT. Accordingly, it is possible to prevent an increase of the processes required for forming contact plugs 39_1, 39_2, and 40.
When forming lower layer contact holes LCSPH1, LCSPH2, and LCSNH, a lower layer contact hole corresponding to a contact plug to be coupled with each of the source and the drain may be simultaneously formed. According to the first embodiment, nitride 51 is formed on the upper surface of nitride 49 and above p+-type impurity diffusion regions 37_1. With this structure, when lower layer contact hole LCSPH1 reaches nitride 45 by etching, it is possible to prevent the lower layer contact hole corresponding to the contact plug coupled to each of the source and the drain from reaching oxide 48. Accordingly, it is possible to prevent a possibility that the sacrificial material filled in the lower layer contact hole is coupled to nitride 42 through oxide 48 and 41. Therefore, it is possible to prevent hydrogen ion H* from being propagated to nitride 42 through the sacrificial material filled in the contact plug coupled to each of the source and the drain.
Next, a semiconductor memory according to a second embodiment will be explained. The second embodiment differs from the first embodiment in that a diffusion region of p-type transistors TrP1 and TrP2 and n-type transistor TrN is raised to a higher level relative to the channel region. In the explanation that follows, configurations and manufacturing processes different from those of the first embodiment will be mainly described, and the explanation of similar configurations and manufacturing processes will be omitted.
First, the configuration of p-type transistor TrP1 will be described with reference to
As shown in
The other configurations such as stacked body BYP1 of p-type transistor TrP1 according to the second embodiment are the same as those of p-type transistor TrP1 according to the first embodiment explained with reference to
Next, the configuration of p-type transistor TrP2 will be described with reference to
As shown in
The other configurations such as stacked body BYP2 of p-type transistor TrP2 according to the second embodiment are the same as those of p-type transistor TrP2 according to the first embodiment explained with reference to
Next, the configuration of n-type transistor TrN will be described with reference to
As shown in
The other configurations such as stacked body BYN of n-type transistor TrN according to the second embodiment are the same as those of n-type transistor TrN according to the first embodiment explained with reference to
Next, the manufacturing method of transistors formed in the peripheral area of the semiconductor memory according to the second embodiment will be explained with reference to
First, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
As stated above, oxide 67 is formed above p+-type impurity diffusion regions 37_2A, and n+-type impurity diffusion regions 38A; however, oxide 48 is formed by performing oxidation to the p+-type impurity diffusion regions 37_1A. Accordingly, the boundary between p+-type impurity diffusion regions 37_1A and oxide 48 is positioned lower than the boundary between oxide 67 and p+-type impurity diffusion regions 37_2A or n+-type impurity diffusion regions 38A.
In addition, as stated above, p+-type impurity diffusion regions 37_1A are raised by epitaxial growth. Accordingly, even after the oxide 48 is formed by substrate oxidation, the boundary between p+-type impurity diffusion regions 37_1A and oxide 48 can be positioned higher than the boundary between the channel region of p-type transistor TrP1 and oxide 41.
Subsequently, as shown in
Subsequently, as shown in
A film of nitride 51 is formed on the upper surface of insulator 50 and the upper surface of nitride 49. Oxide 52 is provided on the upper surface of nitride 51.
Through the above process, the structures of p-type transistors TrP1 and TrP2, and n-type transistor TrN shown in
According to the second embodiment, areas where p+-type impurity diffusion regions 37_1A and 37_2A, and n+-type impurity diffusion regions 38A are to be formed are raised by epitaxial growth. Through this process, the boundary between p+-type impurity diffusion regions 37_1A and oxide 48 is positioned higher than the boundary between oxide 41 and n-type well regions 35_1. Accordingly, the amount of the diffusion region of p-type transistor TrP1 reduced by substrate oxidation can be compensated by the amount built up by epitaxial growth. Therefore, the sufficient thickness of p+-type impurity diffusion regions 37_1A is ensured, and deterioration of the characteristics of p-type transistor TrP1 can be prevented.
The above-described first and second embodiments can be modified as in the following, for example.
In the first and second embodiments, the semiconductor memory 1 has the structure where memory cell transistors MT having charge storage layers are three-dimensionally arranged, but the structure is not limited thereto. The configurations and manufacturing process regarding the hook-up area A2 and the peripheral area A3 explained in the above embodiments can be adopted in other semiconductor memory devices. For example, the configurations and manufacturing process regarding the hook-up area A2 and the peripheral area A3 explained in the above embodiments may be adopted to semiconductor memory devices having the structure where phase change memory cells are three-dimensionally arranged, or to semiconductor memory devices having the structure where memory cells using ferroelectric thin film materials are three-dimensionally arranged.
In addition, in the above embodiments, the method for manufacturing the memory area A1 includes alternately stacking insulator 31 or 32 and replacement 81 or 82 including silicon nitride (SiN) on the p-type well region 22 to form a first stacked body, alternately stacking insulator 33 or 34 and replacement 83 or 84 including silicon nitride (SiN) to form a second stacked body above the first stacked body, and replacing the replacements 81, 82, 83, and 84 with conductors 23, 24, 25, and 26, but the method is not limited thereto. For example, material including a metal or silicon etc. may be used instead of silicon nitride (SiN) to form a stacked structure of conductive materials and insulators 31-34 on the p-type well region 22, and the conductive materials of the stacked structure may function as selection gate line SGS, SGD, and word lines WL0 through WL95, without replacing the conductive materials to other materials.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the embodiments. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
Number | Date | Country | Kind |
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2018-039571 | Mar 2018 | JP | national |