US20090001439A1 - Flash Memory Device and Method of Manufacturing the Same - Google Patents
Flash Memory Device and Method of Manufacturing the Same Download PDFInfo
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- US20090001439A1 US20090001439A1 US12/208,289 US20828908A US2009001439A1 US 20090001439 A1 US20090001439 A1 US 20090001439A1 US 20828908 A US20828908 A US 20828908A US 2009001439 A1 US2009001439 A1 US 2009001439A1
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- memory device
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Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/10—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the top-view layout
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B69/00—Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices
-
- 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
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/30—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the memory core region
Definitions
- the present invention relates to a flash memory device and a method of manufacturing the same.
- a flash memory device includes the advantages of EPROM having programming and erasing characteristics and EEPROM having electrically programming and erasing characteristics.
- This kind of flash memory device generally includes a thin tunnel oxide layer formed on a silicon substrate, a floating gate integrated on the oxide layer, an insulating layer, a control gate, and source and drain regions formed on the exposed portion of the substrate, in order to accomplish 1-bit storage using one transistor and to implement electrical programming and erasing.
- Such a flash memory device may include a source connecting layer for connecting the source of each unit cell to form a source line.
- the source connecting layer can be formed by using a metal contact method by which a contact is formed in the source of each unit cell.
- this method is not appropriate for the manufacture of a highly integrated device because a contact margin should be considered. Therefore, recently, a common source line formed as an impurity diffusion layer through a self aligned source (SAS) process has been used to realize a highly integrated device.
- SAS self aligned source
- the SAS process includes to an anisotropic etching process, in which a source region of a cell is opened by using a separate SAS mask after forming a gate electrode having a stacked structure, and then removing a field oxide layer to form a common source line relative to a neighboring cell.
- Such an SAS technique may shrink the size of a cell in the bit line (BL) direction, and so the gate to source space can be reduced. Therefore, this technique is a useful process for accomplishing a device having a line width of 0.25 ⁇ m level.
- Impurity ions such as arsenic (As) are implanted with high energy so as to form a junction having a predetermined depth on the common source line formed through the SAS process.
- the contact resistance of the source per cell is rapidly increased, in practice. This is because the length of the real surface resistance is increased due to the junction resistance formed along the surface profile of the trench region, so the specific resistance of the sidewall of the trench region is increased. That is, a relatively small amount of ions are implanted into the sidewall portion of the trench region during the ion implantation process, so the resistance may increase significantly.
- most memory cells having a line width of at least or about 0.25 ⁇ m or 0.18 ⁇ m employ a shallow trench isolation (STI) process as an isolation technique.
- the STI process can be a useful process to shrink the size of the cell along a word line (WL) direction, while the SAS process is essential to shrink the cell size along a bit line (BL) direction, depending on the orientation of the word lines and bit lines.
- WL word line
- BL bit line
- flash memory devices generally utilize an internal high voltage for programming and/or erasing operations, when the cell size is decreased, the depth of the trench should be increased, resulting in an increase in the length of the common source line, in turn adversely affecting the source resistance. In the case of an embedded flash memory device, potentially fatal product defects including degradation of programming characteristics and reading speed may result.
- the impurity ions are implanted with high energy, the surface of the common source line can be damaged, further increasing a surface resistance, thereby deteriorating the characteristics of a resulting semiconductor device.
- an object of the present invention is to provide a flash memory device and a method of manufacturing the same, capable of reducing or minimizing contact resistance of a common source line generated during an SAS process.
- the present invention provides a flash memory device comprising a plurality of trench lines in an isolation region of a semiconductor substrate, a common source region (formed by implanting impurity ions) along a word line (WL) direction under a surface portion of the semiconductor substrate, a plurality of gate lines in a vertical direction of the trench line, a drain region in a region of the substrate adjacent to the gate line and opposite to the common source region, a drain contact over the drain region, and a uniform by-product layer on the common source region.
- WL word line
- the present invention also provides a method of manufacturing a flash memory device including a common source region, the method comprising the steps of forming a gate line on a semiconductor substrate having an isolation layer, forming a self aligned mask on the semiconductor substrate and the gate line other than on the common source region, removing the isolation layer in the common source region using the self aligned mask and the gate line as a mask and uniformly depositing a by-product (generally produced during the removal of the isolation layer) onto the (exposed) common source region, and implanting impurity ions into the exposed common source region.
- a by-product generally produced during the removal of the isolation layer
- FIG. 1 is a layout view showing a flash memory device according to a preferred embodiment of the present invention
- FIG. 2 is a cross-sectional view taken along line II-II′ of the flash memory device illustrated in FIG. 1 ;
- FIGS. 3 to 6 are cross-sectional views for explaining a method of manufacturing a flash memory device according to a preferred embodiment of the present invention
- FIG. 7 is a cross-sectional view showing a conventional flash memory device.
- FIG. 8 is a cross-sectional view showing a flash memory device according to a preferred embodiment of the present invention.
- FIG. 1 is a layout view showing a flash memory device according to a preferred embodiment of the present invention
- FIG. 2 is a cross-sectional view taken along line II-II′ shown in FIG. 1 .
- a flash memory device includes a plurality of trench lines 19 formed on a semiconductor substrate 100 corresponding to an isolation region.
- the trench lines 19 are formed in parallel with a bit line BL.
- the vertical dotted lines represent the border of the sidewall of the trench line 19 .
- the sidewall of the trench may be slanted, or have a characteristic angle (e.g., of from 75° to 88° with respect to a horizontal plane of the substrate).
- a common source region 12 is formed at and/or below the surface of the semiconductor substrate 100 by implanting dopants in the substrate.
- the long axis of the common source region 12 is generally in the direction of a word line WL.
- a plurality of gate lines 13 are formed.
- a drain region 15 is formed in a region of the substrate adjacent to the gate line 13 , but opposite to the common source region 12 .
- a drain contact 17 is formed in a portion of the drain region 15 , over the drain region 15 .
- an SAS mask 200 exposes a gap between a first gate line 13 and a neighboring gate line 13 , and a border or edge of the SAS mask 200 is arranged on the gate line 13 in parallel with the gate line 13 .
- ions 72 FIG. 2
- ions 61 implanted into the surface portion of the source region 51 are present.
- etching by-products 180 may remain on the common source region 12 .
- etching by-products 180 are uniformly located or distributed.
- etching by-products 180 form a uniform layer on the common source region 12 .
- the by-product 180 reduces or prevents the loss of a portion of the surface of the semiconductor substrate 100 during ion implantation onto the common source region 12 and reduces or prevents an increase in the surface resistance of the common source region 12 .
- a common source line 80 of the common source region 12 may be formed with a constant depth along the surface of the trench region 53 and the surface of the source region 51 , and so the resistance of the common source line 80 is reduced.
- FIGS. 3 to 6 are cross-sectional views illustrating the procedure for manufacturing a flash memory device according to an embodiment of the present invention.
- trench regions 53 and 54 are formed on a semiconductor substrate 100 and an isolation layer 60 is formed by filling the trench regions 53 and 54 with insulating material.
- the trench may be formed and filled by a conventional shallow trench isolation (STI) method.
- STI shallow trench isolation
- the trench regions 53 and 54 correspond to the trench lines 19 shown in FIG. 1 .
- the plurality of the trench lines 19 are formed in parallel with a bit line BL.
- a first oxide layer 110 is formed on the semiconductor substrate 100 except for the trench line 19 .
- the first oxide layer 110 may thus comprise silicon dioxide, and be grown by conventional wet or dry thermal oxidation of exposed silicon.
- a first polysilicon layer 120 is deposited on the semiconductor substrate 100 and the first oxide layer 110 .
- the first polysilicon layer 120 covering the common source region 12 is removed to expose the first oxide layer 110 (if the first oxide layer 110 is deposited, for example by chemical vapor deposition [CVD] and optional densification) or the isolation layer 60 in the trench if the first oxide layer 110 is grown by thermal oxidation).
- a second oxide layer 130 and a second polysilicon layer 140 are subsequently formed on the first polysilicon layer 120 and the first oxide layer 110 .
- the second polysilicon layer 140 , the second oxide layer 130 and the first polysilicon layer 120 are subsequently patterned and etched by photolithography and dry/plasma etching to expose a portion of the isolation layer 60 and the semiconductor substrate 100 .
- a plurality of gate lines 13 are formed in a direction perpendicular to the trench lines 19 and in parallel to the word line WL.
- a self aligned mask 160 is formed on the entire surface of the semiconductor substrate 100 except for the common source region 12 by using photoresist, and the isolation layer 60 remaining and/or exposed in the common source region 12 is removed to expose the semiconductor substrate 100 using the mask 160 and the gate line 13 as a self aligned mask to form a common source line 80 .
- a C x F y -based or C x F y H z -based by-product (which may comprise a fluorocarbon- and/or hydrofluoro-carbon-based polymer) is generated and a portion of the exposed semiconductor substrate 170 may be removed, or the sidewall of the second polysilicon layer 140 , the second oxide layer 130 , the first polysilicon layer 120 and the first oxide layer 110 may be damaged, thereby increasing a risk that the characteristics and reliability of the semiconductor device may deteriorate.
- a plasma etching process is performed to remove the isolation layer 60 .
- a plasma apparatus such as DRM (dipole ring magnetron) available from Tokyo Electron (TEL) Co., which generates a plasma in a MERIE (magnetic enhanced reactive ion etching) scheme, can be used.
- DRM dipole ring magnetron
- MERIE magnetic enhanced reactive ion etching
- the C x F y -based by-product generated during the etching process is deposited on the surface of the semiconductor substrate exposed after removing the isolation layer 60 in this embodiment of the present invention.
- the loss of the semiconductor substrate exposed after etching the isolation layer 60 during the removing process for the isolation layer 60 is minimized, and the generated by-product is uniformly formed or attached on the surface of the semiconductor substrate according to this embodiment of the present invention.
- the amount or the thickness of the by-product can be determined considering the time period of the etching process.
- the isolation layer can be removed by processing in the plasma apparatus for about 30 to 90 seconds, under typical processing conditions for removing such STI oxides.
- the processing time is less than 30 seconds, the amount of the by-product is too small and the isolation layer cannot be completely removed.
- the processing time exceeds 90 seconds the isolation layer may be overetched, and the depth of the trench in the semiconductor substrate may become too deep.
- the isolation layer can be removed by a plasma formed from C 5 F 8 gas and CH 2 F 2 gas, along with an inert gas to produce C x F y -based or C x F y H z -based by-product.
- the C 5 F 8 gas may be replaced with one or more gas-phase fluorocarbon etching agents (e.g., CF 4 , C 2 F 6 , C 3 F 8 , C 3 F 6 , cyclo-C 4 F 8 , C 4 F 10 , cyclo-C 5 F 10 , etc.), and the CH 2 F 2 gas may be replaced with one or more gas-phase hydrofluorocarbon etching agents (e.g., CHF 3 , C 2 F 5 H, 1,1,1,2- or 1,1,2,2-tetra-fluoroethane [C 2 F 4 H 2 ], C 3 F 6 H 2 , etc.).
- gas-phase fluorocarbon etching agents e.g., CF 4 , C 2 F 6 , C 3 F 8 , C 3 F 6 , cyclo-C 4 F 8 , C 4 F 10 , cyclo-C 5 F 10 , etc.
- gas-phase fluorocarbon etching agents e.g.,
- the isolation layer can be removed by etching the isolation layer 60 in a plasma generated by flowing C 5 F 8 (or other fluorocarbon) gas at a rate of about 5 sccm to 20 sccm, CH 2 F 2 (or other hydrofluorocarbon) gas at a rate of about 1 sccm to 20 sccm, and Ar (or other noble) gas at a rate of about 300 sccm to 500 sccm, while keeping an electric power of about 1,500 W to 2,000 W and a pressure of about 10 mT to 50 mT, thereby minimizing the loss of the semiconductor substrate after the etching process.
- the polymeric by-product can be uniformly distributed or attached to the surface of the semiconductor substrate.
- FIG. 7 is a cross-sectional view of a conventional flash memory device and FIG. 8 is a cross-sectional view of an exemplary flash memory device according to a preferred embodiment of the present invention.
- the depth of the trench is about 330 nm and the thickness of the by-product A, which is a deposited polymer created during the etching process of the isolation layer, is 17.2 nm.
- the by-product is irregularly formed on the sidewall portion and on the bottom portion of the isolation layer.
- the profile of the trench may become dull according to the conventional method.
- the by-product B is uniformly deposited on the side slope portion and the top and the bottom portion of the semiconductor substrate from which the isolation layer is removed in the flash memory device and method according to a preferred embodiment of the present invention, when compared with the conventional method, as shown in the cross-sectional SEM images of FIGS. 7-8 . Therefore, the formation of a non-uniform impurity diffusion layer during subsequent ion implantation can be reduced or prevented, and the damage to the semiconductor substrate due to injected ions during the ion impurity implantation also can be reduced or prevented.
- the profile of the trench also can be kept in a substantially vertical shape (e.g., along the plane of the gate and word line sidewall).
- high-density impurity ions 61 and 72 such as As (or, alternatively, P or B) are implanted onto the semiconductor substrate 100 to form a common source region 12 .
- the mask 160 is removed and high-density impurity ions 61 and 72 such as As (or, alternatively, P or B, depending on the ion implanted into the common source region 12 ) are implanted to form a drain region 15 .
- the by-product 180 remains on the exposed semiconductor substrate 100 , that is on the common source region 12 as illustrated in FIG. 2 .
- the loss of a (surface) portion of the semiconductor substrate 100 due to the impurity ions injected at a high energy can be reduced, minimized or prevented, and an increase of the surface resistance of the common source region 12 can be reduced, minimized or prevented to improve certain of the semiconductor device characteristics.
- the process of removing the isolation layer to form the common source line can be implemented in a plasma apparatus that forms plasma using a MERIE (magnetic enhanced reactive ion etching) technique, and the by-product generated during removing the isolation layer is substantially uniformly deposited on the surface of the exposed semiconductor substrate. Therefore, an increase in the surface resistance at the common source region can be reduced or prevented, and the characteristics and the reliability of the semiconductor device can be improved.
- MERIE magnetic enhanced reactive ion etching
- the etch profile of the trench can be kept in a substantially vertical shape according to the present invention.
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Abstract
Disclosed is a flash memory device. The flash memory device includes a plurality of trench lines in an isolation region of a semiconductor device, a common source region along a word line (WL) direction under a surface portion of the semiconductor substrate, a plurality of gate lines along a vertical direction of the trench line, a drain region on an opposite side of the gate line to the common source region, a drain contact over the drain region, and a uniform by-product layer on the common source region.
Description
- The present application is a divisional of U.S. patent application Ser. No. 11/638,077, filed Dec. 12, 2006, pending.
- 1. Field of the Invention
- The present invention relates to a flash memory device and a method of manufacturing the same.
- 2. Description of the Related Art
- In general, a flash memory device includes the advantages of EPROM having programming and erasing characteristics and EEPROM having electrically programming and erasing characteristics. This kind of flash memory device generally includes a thin tunnel oxide layer formed on a silicon substrate, a floating gate integrated on the oxide layer, an insulating layer, a control gate, and source and drain regions formed on the exposed portion of the substrate, in order to accomplish 1-bit storage using one transistor and to implement electrical programming and erasing.
- Such a flash memory device may include a source connecting layer for connecting the source of each unit cell to form a source line. The source connecting layer can be formed by using a metal contact method by which a contact is formed in the source of each unit cell. However, this method is not appropriate for the manufacture of a highly integrated device because a contact margin should be considered. Therefore, recently, a common source line formed as an impurity diffusion layer through a self aligned source (SAS) process has been used to realize a highly integrated device.
- In detail, the SAS process includes to an anisotropic etching process, in which a source region of a cell is opened by using a separate SAS mask after forming a gate electrode having a stacked structure, and then removing a field oxide layer to form a common source line relative to a neighboring cell.
- Such an SAS technique may shrink the size of a cell in the bit line (BL) direction, and so the gate to source space can be reduced. Therefore, this technique is a useful process for accomplishing a device having a line width of 0.25 μm level.
- Impurity ions such as arsenic (As) are implanted with high energy so as to form a junction having a predetermined depth on the common source line formed through the SAS process.
- However, since the common source line is formed along the profile of a trench in a memory cell formed through the SAS process, the contact resistance of the source per cell is rapidly increased, in practice. This is because the length of the real surface resistance is increased due to the junction resistance formed along the surface profile of the trench region, so the specific resistance of the sidewall of the trench region is increased. That is, a relatively small amount of ions are implanted into the sidewall portion of the trench region during the ion implantation process, so the resistance may increase significantly.
- In particular, most memory cells having a line width of at least or about 0.25 μm or 0.18 μm employ a shallow trench isolation (STI) process as an isolation technique. The STI process can be a useful process to shrink the size of the cell along a word line (WL) direction, while the SAS process is essential to shrink the cell size along a bit line (BL) direction, depending on the orientation of the word lines and bit lines. However, if these processes are simultaneously applied, the source resistance can be remarkably increased.
- Since flash memory devices generally utilize an internal high voltage for programming and/or erasing operations, when the cell size is decreased, the depth of the trench should be increased, resulting in an increase in the length of the common source line, in turn adversely affecting the source resistance. In the case of an embedded flash memory device, potentially fatal product defects including degradation of programming characteristics and reading speed may result.
- Meanwhile, since the impurity ions are implanted with high energy, the surface of the common source line can be damaged, further increasing a surface resistance, thereby deteriorating the characteristics of a resulting semiconductor device.
- Accordingly, an object of the present invention is to provide a flash memory device and a method of manufacturing the same, capable of reducing or minimizing contact resistance of a common source line generated during an SAS process.
- To accomplish the above-described object, the present invention provides a flash memory device comprising a plurality of trench lines in an isolation region of a semiconductor substrate, a common source region (formed by implanting impurity ions) along a word line (WL) direction under a surface portion of the semiconductor substrate, a plurality of gate lines in a vertical direction of the trench line, a drain region in a region of the substrate adjacent to the gate line and opposite to the common source region, a drain contact over the drain region, and a uniform by-product layer on the common source region.
- The present invention also provides a method of manufacturing a flash memory device including a common source region, the method comprising the steps of forming a gate line on a semiconductor substrate having an isolation layer, forming a self aligned mask on the semiconductor substrate and the gate line other than on the common source region, removing the isolation layer in the common source region using the self aligned mask and the gate line as a mask and uniformly depositing a by-product (generally produced during the removal of the isolation layer) onto the (exposed) common source region, and implanting impurity ions into the exposed common source region.
-
FIG. 1 is a layout view showing a flash memory device according to a preferred embodiment of the present invention; -
FIG. 2 is a cross-sectional view taken along line II-II′ of the flash memory device illustrated inFIG. 1 ; -
FIGS. 3 to 6 are cross-sectional views for explaining a method of manufacturing a flash memory device according to a preferred embodiment of the present invention; -
FIG. 7 is a cross-sectional view showing a conventional flash memory device; and -
FIG. 8 is a cross-sectional view showing a flash memory device according to a preferred embodiment of the present invention. - Hereinafter, the flash memory device and the method of manufacturing the same according to preferred embodiments of the present invention will be described in detail with reference to the attached drawings.
- It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present.
-
FIG. 1 is a layout view showing a flash memory device according to a preferred embodiment of the present invention, andFIG. 2 is a cross-sectional view taken along line II-II′ shown inFIG. 1 . - Referring to
FIGS. 1 and 2 , a flash memory device according to a preferred embodiment of the present invention includes a plurality oftrench lines 19 formed on asemiconductor substrate 100 corresponding to an isolation region. Thetrench lines 19 are formed in parallel with a bit line BL. Here, inFIG. 1 , the vertical dotted lines represent the border of the sidewall of thetrench line 19. As shown inFIG. 2 , the sidewall of the trench may be slanted, or have a characteristic angle (e.g., of from 75° to 88° with respect to a horizontal plane of the substrate). - A
common source region 12 is formed at and/or below the surface of thesemiconductor substrate 100 by implanting dopants in the substrate. In a preferred embodiment, the long axis of thecommon source region 12 is generally in the direction of a word line WL. - Perpendicular to the direction of the
trench line 19, that is, parallel to the direction of the word line WL, a plurality ofgate lines 13 are formed. Adrain region 15 is formed in a region of the substrate adjacent to thegate line 13, but opposite to thecommon source region 12. Adrain contact 17 is formed in a portion of thedrain region 15, over thedrain region 15. - As illustrated in
FIG. 1 , anSAS mask 200 exposes a gap between afirst gate line 13 and a neighboringgate line 13, and a border or edge of theSAS mask 200 is arranged on thegate line 13 in parallel with thegate line 13. As illustrated inFIGS. 1 and 2 , at the common source region 12 (FIG. 1 ) formed by using theSAS mask 200, ions 72 (FIG. 2 ) implanted into the surface portion of thetrench region 53 are present, and at thesource region 51,ions 61 implanted into the surface portion of thesource region 51 are present. - On the
common source region 12, etching by-products 180 may remain. In one embodiment, etching by-products 180 are uniformly located or distributed. Alternatively, etching by-products 180 form a uniform layer on thecommon source region 12. The by-product 180 reduces or prevents the loss of a portion of the surface of thesemiconductor substrate 100 during ion implantation onto thecommon source region 12 and reduces or prevents an increase in the surface resistance of thecommon source region 12. - Accordingly, a
common source line 80 of thecommon source region 12 may be formed with a constant depth along the surface of thetrench region 53 and the surface of thesource region 51, and so the resistance of thecommon source line 80 is reduced. - Hereinafter, the method of manufacturing the flash memory device according to the preferred embodiment of the present invention will be described in detail with reference to attached drawings.
-
FIGS. 3 to 6 are cross-sectional views illustrating the procedure for manufacturing a flash memory device according to an embodiment of the present invention. - According to an exemplary method of manufacturing a flash memory cell of the present invention, as shown in
FIG. 3 ,trench regions semiconductor substrate 100 and anisolation layer 60 is formed by filling thetrench regions - The
trench regions trench lines 19 shown inFIG. 1 . The plurality of thetrench lines 19 are formed in parallel with a bit line BL. In addition, afirst oxide layer 110 is formed on thesemiconductor substrate 100 except for thetrench line 19. Thefirst oxide layer 110 may thus comprise silicon dioxide, and be grown by conventional wet or dry thermal oxidation of exposed silicon. Afirst polysilicon layer 120 is deposited on thesemiconductor substrate 100 and thefirst oxide layer 110. - Then, the
first polysilicon layer 120 covering thecommon source region 12 is removed to expose the first oxide layer 110 (if thefirst oxide layer 110 is deposited, for example by chemical vapor deposition [CVD] and optional densification) or theisolation layer 60 in the trench if thefirst oxide layer 110 is grown by thermal oxidation). - After that, a
second oxide layer 130 and asecond polysilicon layer 140 are subsequently formed on thefirst polysilicon layer 120 and thefirst oxide layer 110. - Then, referring to
FIG. 4 , thesecond polysilicon layer 140, thesecond oxide layer 130 and thefirst polysilicon layer 120 are subsequently patterned and etched by photolithography and dry/plasma etching to expose a portion of theisolation layer 60 and thesemiconductor substrate 100. - Through the above-described processes, a plurality of
gate lines 13 are formed in a direction perpendicular to thetrench lines 19 and in parallel to the word line WL. - Then, referring to
FIG. 5 , a self alignedmask 160 is formed on the entire surface of thesemiconductor substrate 100 except for thecommon source region 12 by using photoresist, and theisolation layer 60 remaining and/or exposed in thecommon source region 12 is removed to expose thesemiconductor substrate 100 using themask 160 and thegate line 13 as a self aligned mask to form acommon source line 80. - By implementing the above-described processes, a CxFy-based or CxFyHz-based by-product (which may comprise a fluorocarbon- and/or hydrofluoro-carbon-based polymer) is generated and a portion of the exposed
semiconductor substrate 170 may be removed, or the sidewall of thesecond polysilicon layer 140, thesecond oxide layer 130, thefirst polysilicon layer 120 and thefirst oxide layer 110 may be damaged, thereby increasing a risk that the characteristics and reliability of the semiconductor device may deteriorate. - In order to solve this problem, according to the present invention, a plasma etching process is performed to remove the
isolation layer 60. - For example, a plasma apparatus such as DRM (dipole ring magnetron) available from Tokyo Electron (TEL) Co., which generates a plasma in a MERIE (magnetic enhanced reactive ion etching) scheme, can be used.
- In particular, the CxFy-based by-product generated during the etching process is deposited on the surface of the semiconductor substrate exposed after removing the
isolation layer 60 in this embodiment of the present invention. - In addition, the loss of the semiconductor substrate exposed after etching the
isolation layer 60 during the removing process for theisolation layer 60 is minimized, and the generated by-product is uniformly formed or attached on the surface of the semiconductor substrate according to this embodiment of the present invention. - At this time, the amount or the thickness of the by-product can be determined considering the time period of the etching process.
- For example, the isolation layer can be removed by processing in the plasma apparatus for about 30 to 90 seconds, under typical processing conditions for removing such STI oxides. When the processing time is less than 30 seconds, the amount of the by-product is too small and the isolation layer cannot be completely removed. When the processing time exceeds 90 seconds, the isolation layer may be overetched, and the depth of the trench in the semiconductor substrate may become too deep.
- In the present invention, the isolation layer can be removed by a plasma formed from C5F8 gas and CH2F2 gas, along with an inert gas to produce CxFy-based or CxFyHz-based by-product. Alternatively, the C5F8 gas may be replaced with one or more gas-phase fluorocarbon etching agents (e.g., CF4, C2F6, C3F8, C3F6, cyclo-C4F8, C4F10, cyclo-C5F10, etc.), and the CH2F2 gas may be replaced with one or more gas-phase hydrofluorocarbon etching agents (e.g., CHF3, C2F5H, 1,1,1,2- or 1,1,2,2-tetra-fluoroethane [C2F4H2], C3F6H2, etc.).
- For example, the isolation layer can be removed by etching the
isolation layer 60 in a plasma generated by flowing C5F8 (or other fluorocarbon) gas at a rate of about 5 sccm to 20 sccm, CH2F2 (or other hydrofluorocarbon) gas at a rate of about 1 sccm to 20 sccm, and Ar (or other noble) gas at a rate of about 300 sccm to 500 sccm, while keeping an electric power of about 1,500 W to 2,000 W and a pressure of about 10 mT to 50 mT, thereby minimizing the loss of the semiconductor substrate after the etching process. Thus, the polymeric by-product can be uniformly distributed or attached to the surface of the semiconductor substrate. -
FIG. 7 is a cross-sectional view of a conventional flash memory device andFIG. 8 is a cross-sectional view of an exemplary flash memory device according to a preferred embodiment of the present invention. - Referring to
FIG. 7 , the depth of the trench is about 330 nm and the thickness of the by-product A, which is a deposited polymer created during the etching process of the isolation layer, is 17.2 nm. The by-product is irregularly formed on the sidewall portion and on the bottom portion of the isolation layer. - In addition, the profile of the trench may become dull according to the conventional method.
- However, referring to
FIG. 8 , it is confirmed that the by-product B is uniformly deposited on the side slope portion and the top and the bottom portion of the semiconductor substrate from which the isolation layer is removed in the flash memory device and method according to a preferred embodiment of the present invention, when compared with the conventional method, as shown in the cross-sectional SEM images ofFIGS. 7-8 . Therefore, the formation of a non-uniform impurity diffusion layer during subsequent ion implantation can be reduced or prevented, and the damage to the semiconductor substrate due to injected ions during the ion impurity implantation also can be reduced or prevented. - According to the present invention, the profile of the trench also can be kept in a substantially vertical shape (e.g., along the plane of the gate and word line sidewall).
- After that, high-
density impurity ions semiconductor substrate 100 to form acommon source region 12. - Then, referring to
FIG. 6 , themask 160 is removed and high-density impurity ions drain region 15. At this time, as described above, the by-product 180 remains on the exposedsemiconductor substrate 100, that is on thecommon source region 12 as illustrated inFIG. 2 . - As a result, the loss of a (surface) portion of the
semiconductor substrate 100 due to the impurity ions injected at a high energy can be reduced, minimized or prevented, and an increase of the surface resistance of thecommon source region 12 can be reduced, minimized or prevented to improve certain of the semiconductor device characteristics. - According to the inventive flash memory device and the method of manufacturing the same, the process of removing the isolation layer to form the common source line can be implemented in a plasma apparatus that forms plasma using a MERIE (magnetic enhanced reactive ion etching) technique, and the by-product generated during removing the isolation layer is substantially uniformly deposited on the surface of the exposed semiconductor substrate. Therefore, an increase in the surface resistance at the common source region can be reduced or prevented, and the characteristics and the reliability of the semiconductor device can be improved.
- In addition, the etch profile of the trench can be kept in a substantially vertical shape according to the present invention.
- Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (8)
1. A flash memory device comprising:
a plurality of trench lines in an isolation region of a semiconductor substrate;
a common source region in a word line (WL) direction under a surface portion of the semiconductor substrate;
a plurality of gate lines perpendicular to the trench line;
a drain region on an opposite side of the gate line from the common source region;
a drain contact over a portion of the drain region; and
a uniform by-product layer on the common source region.
2. The flash memory device as claimed in claim 1 , wherein ions implanted into a surface portion of the trench region are also present in the common source region.
3. The flash memory device as claimed in claim 1 , wherein the by-product layer is configured to prevent a loss of a portion of the surface of the semiconductor substrate during ion implantation into the common source region and/or prevent a surface resistance from increasing in the common source region.
4. The flash memory device as claimed in claim 1 , wherein a common source line in the common source region has a substantially constant depth.
5. The flash memory device as claimed in claim 1 , wherein the trench lines are parallel with a bit line (BL).
6. The flash memory device as claimed in claim 1 , wherein the gate line is parallel with a word line (WL).
7. The flash memory device as claimed in claim 1 , wherein the by-product layer comprises a fluorocarbon- and/or hydrofluorocarbon-based polymer.
8. The flash memory device as claimed in claim 1 , wherein the by-product layer is on a sidewall, a bottom wall and an upper wall portion of the isolation region in the semiconductor substrate.
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US12/208,289 US20090001439A1 (en) | 2005-12-13 | 2008-09-10 | Flash Memory Device and Method of Manufacturing the Same |
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KR1020050122506A KR100650899B1 (en) | 2005-12-13 | 2005-12-13 | Method of manufacturing flash memory cell |
KR10-2005-0122506 | 2005-12-13 | ||
US11/638,077 US7439143B2 (en) | 2005-12-13 | 2006-12-12 | Flash memory device and method of manufacturing the same |
US12/208,289 US20090001439A1 (en) | 2005-12-13 | 2008-09-10 | Flash Memory Device and Method of Manufacturing the Same |
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CN103801413A (en) * | 2012-11-07 | 2014-05-21 | 财团法人工业技术研究院 | Magnetic droplet processing apparatus |
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KR101016518B1 (en) * | 2008-07-15 | 2011-02-24 | 주식회사 동부하이텍 | Semiconductor memory device and manufacturing method of semiconductor memory device |
US20120094450A1 (en) * | 2010-10-19 | 2012-04-19 | Eon Silicon Solution Inc. | Manufacturing method of multi-level cell nor flash memory |
CN111323443B (en) * | 2020-03-04 | 2023-12-01 | 武汉新芯集成电路制造有限公司 | SONO etching sample preparation and detection method |
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US20020039843A1 (en) * | 2000-09-29 | 2002-04-04 | Takenobu Ikeda | Method of manufacturing a semiconductor integrated circuit device |
US20020132427A1 (en) * | 2001-01-24 | 2002-09-19 | Rudeck Paul J. | Modified source/drain re-oxidation method and system |
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- 2005-12-13 KR KR1020050122506A patent/KR100650899B1/en not_active IP Right Cessation
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US20040248413A1 (en) * | 2000-04-27 | 2004-12-09 | Micron Technology, Inc. | Etchant and method of use |
US20020039843A1 (en) * | 2000-09-29 | 2002-04-04 | Takenobu Ikeda | Method of manufacturing a semiconductor integrated circuit device |
US20020132427A1 (en) * | 2001-01-24 | 2002-09-19 | Rudeck Paul J. | Modified source/drain re-oxidation method and system |
US7195977B2 (en) * | 2003-10-01 | 2007-03-27 | Dongbu Electronics Co., Ltd. | Method for fabricating a semiconductor device |
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CN103801413A (en) * | 2012-11-07 | 2014-05-21 | 财团法人工业技术研究院 | Magnetic droplet processing apparatus |
CN103801413B (en) * | 2012-11-07 | 2015-09-30 | 财团法人工业技术研究院 | Magnetic droplet processing apparatus |
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KR100650899B1 (en) | 2006-11-27 |
US20070131973A1 (en) | 2007-06-14 |
US7439143B2 (en) | 2008-10-21 |
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