3-D nonvolatile memory device and method of manufacturing the same

A three-dimensional (3-D) nonvolatile memory device includes a support protruded from a surface of a substrate and configured to have an inclined sidewall; channel structures each configured to comprise interlayer insulating layers and channel layers which are alternately stacked over the substrate including the support, bent along the inclined sidewall of the support, wherein each of the channel structures comprises a cell region and a contact region, and the channel layers are exposed in the contact region; select lines formed over the channel structures; and a pillar type channels coupled to respective channel layers at the contact region and penetrating the select lines.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. 119(a) to Korean patent application number 10-2011-0109487 filed on Oct. 25, 2011 in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety as set forth in full.

BACKGROUND

1. Field of the Invention

Embodiments of this disclosure relate to a semiconductor device and a method of manufacturing the same and, more particularly, to a three-dimensional (3-D) nonvolatile memory device and a method of manufacturing the same.

2. Description of the Related Art

A nonvolatile memory device retains data stored therein even though the supply of power is cut off. As the degree of integration of 2-D memory devices in which memory cells are formed in a single layer over a silicon substrate reaches a limit, there is proposed a 3-D nonvolatile memory device in which memory cells are vertically stacked in multiple layers from a silicon substrate.

The structure of a known 3-D nonvolatile memory device is described below.

FIG. 1is a perspective view showing the structure of a known 3-D nonvolatile memory device.

As shown inFIG. 1, the known 3-D nonvolatile memory device includes a plurality of channel structures C extended in parallel in a first direction I-I′, a plurality of vertical gates14each placed between the channel structures C adjacent to each other and vertically protruded from a substrate10, and a plurality of word lines WL coupled to the plurality of vertical gates14and extended in parallel in a second direction II-II′.

Each of the channel structures C includes a plurality of interlayer insulating layers11and a plurality of channel layers12which are stacked in an alternating manner over the substrate10. Furthermore, a tunnel insulating layer13A, a charge trap layer13B, and a charge blocking layer13C are interposed between the vertical gate14and the channel structure C.

In this structure, a plurality of strings is arranged in parallel to the substrate10and is stacked over the substrate10. Accordingly, the degree of integration of memory cells can be improved as compared with a 2-D memory device.

BRIEF SUMMARY

An example embodiment of this disclosure relates to a 3-D nonvolatile memory device and a method of manufacturing the same, which can reduce an area of a contact region.

In an aspect of this disclosure, a 3-D nonvolatile memory device includes a support protruded from a surface of a substrate and configured to have an inclined sidewall; channel structures each configured to comprise interlayer insulating layers and channel layers which are alternately stacked over the substrate including the support, bent along the inclined sidewall of the support, wherein each of the channel structures comprises a cell region and a contact region, and the channel layers are exposed in the contact region; select lines formed over the channel structures, and a pillar type channels coupled to respective channel layers at the contact region and penetrating the select lines.

In another aspect of this disclosure, a method of manufacturing a 3-D nonvolatile memory device includes forming a support protruded from a surface of a substrate and configured to have an inclined sidewall; forming channel structures each configured to comprise first interlayer insulating layers and channel layers which are alternately stacked over the substrate including the support, bent along the etched face of the support, wherein each of the channel structures comprises a cell region and a contact region, and the channel layers are exposed in the contact region; and forming select lines coupled to the respective channel layers at the contact region.

DESCRIPTION OF EMBODIMENTS

Hereinafter, some example embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The figures are provided to allow those having ordinary skill in the art an understanding of a scope of the embodiments of the disclosure.

FIG. 2Ais a cross-sectional view showing a structure of a 3-D nonvolatile memory device according to a first embodiment of this disclosure.

As shown inFIG. 2A, the memory device according to the first embodiment of this disclosure includes a plurality of channel structures C extended in the first direction (refer to I-I′ ofFIG. 1) and a plurality of word lines WL configured to cross the channel structures C and extended in parallel in the second direction (refer to II-II′ ofFIG. 1).

Each of the channel structures C includes a plurality of channel layers22and a plurality of interlayer insulating layers21stacked in an alternating manner. The channel structure C further includes cell regions in which a plurality of memory cells is formed and a contact region through which the plurality of channel layers22is exposed.

The contact region is patterned stepwise, and thus the plurality of channel layers22is exposed through the contact region. Accordingly, the channel layers22exposed in the contact region form respective contact pads. A plurality of contact plugs24is coupled to the respective contact pads of layers, that is, the respective channel layers22and is configured to penetrate a first insulating layer23. Furthermore, a plurality of select lines SL is coupled to the plurality of contact plugs24.

The plurality of select lines SL is extended in parallel in a direction to cross the channel structures C. A select transistor is provided in each region where the select lines SL cross the contact plugs24. Each of the select transistors includes a pillar type channel26, a gate electrode28configured to surround the pillar type channel26, and a gate insulating layer27interposed between the pillar type channel26and the gate electrode28. The pillar type channel26is coupled to the contact plug24.

Furthermore, a bit line BL is formed on a second insulating layer25including the select lines SL and is extended in the same direction as the channel structure C. Here, the bit line BL is coupled to the pillar type channels26of the plurality of select transistors.

In accordance with the first embodiment, an area of the contact region can be reduced by coupling the contact pads and the select lines through the respective contact plugs.

FIG. 2Bis a cross-sectional view showing the structure of a 3-D nonvolatile memory device according to a second embodiment of this disclosure.

As shown inFIG. 2B, the memory device according to the second embodiment of this disclosure includes supports31, channel structures C formed over the respective supports31, a plurality of select lines SL coupled to respective channel layers33via the pillar type channel36.

The support31includes an etched face which is protruded from a surface of a substrate30and is inclined. The etched face has a slant of a specific angle φ to the surface of the substrate30, and the angle φ of the incline plane may be 5 to 85°.

The support31may be a projecting part that forms a trapezoid or a triangle. If the projecting part of the support31forms a trapezoid, a width between the channel structures C adjacent to each other is determined by the width W of the flat top surface of the projecting part. Accordingly, the degree of integration of memory devices can be improved by reducing the width W of the top surface of the projecting part. It is preferred that the width W of the top surface be 1 μm or less.

The support31may be integrally formed with the substrate30or may be formed of an insulating layer. A method of forming the support31is described in detail later with reference toFIGS. 4 and 5.

The channel structure C includes a plurality of interlayer insulating layers32and a plurality of channel layers33which are alternately stacked over the substrate30. The channel structure C is formed on the substrate30including the support31, and an end of the channel structure C is formed along the etched face of the support31. Thus, a region of the channel structure C, formed along the etched face, is bent along the slant of the etched face.

In this structure, the channel structure C includes first regions formed flat on the substrate30and a second region formed with a slant along the etched face of the support31. The first regions may be used as cell regions where a plurality of memory cells is formed. The second region may be used as a contact region where the plurality of channel layers33and the plurality of select lines SL come in contact with each other. A plurality of word lines WL is arranged in the cell regions, and the plurality of channel layers33is exposed in the contact region. The channel layers33exposed in the contact region are used as respective contact pads.

The channel structure C has a generally flat top surface, and there is no step between the cell region and the contact region. That is, the cell region and the contact region may be formed to have the same top surface without a step, and thus the channel structure C may comprise a top surface having the contact region and the cell region having a substantially same height. An etch-stop layer34used to stop polishing in a chemical mechanical polishing (CMP) process may partially remain in the cell region of the channel structure C.

The plurality of select lines SL is extended in parallel in a direction to cross the channel structure C. The plurality of select lines SL is arranged at a substantially same height and may be coupled to the respective contact pads, that is, the respective channel layers33.

A select transistor is formed in each of the regions where the select lines SL cross respective channel layers33. Each of the select transistors includes a pillar type channel36, a gate electrode38configured to surround the pillar type channel36, and a gate insulating layer37interposed between the pillar type channel36and the gate electrode38. In particular, the pillar type channels36are formed to penetrate insulating layers35comprised of a first interlayer insulating layer35A and a second interlayer insulating layer35B and are directly coupled to the respective contact pads, that is, the channel layers33without additional contact plugs.

The memory device further includes the plurality of bit lines BL extended in the same direction as the channel structure C and coupled to the pillar type channels36of the plurality of select transistors.

In accordance with the second embodiment, the contact region and the cell regions of the channel structure C can be formed without a step. Accordingly, a difference between the lengths of stacked strings can be reduced including the stepwise patterned contact region, thereby making uniform cell characteristics. Furthermore, the degree of integration of memory devices can be further improved because an area of the contact region can be reduced.

FIG. 2Cis a cross-sectional view showing the structure of a 3-D nonvolatile memory device according to a third embodiment of this disclosure.

As shown inFIG. 2C, the memory device according to the third embodiment of this disclosure includes select lines SL1and SL2coupled to a plurality of channel layers33, wherein the select lines SL1and SL2are placed at different levels and arranged in a staggered manner. That is, the plurality of select lines SL1and SL2are placed at several levels. For example, the first select lines SL1may be formed at a lower level, and the second select lines SL2may be formed at an upper level. In some embodiments, the select lines SL1and SL2may be arranged in two or more levels.

The remaining structures are the same as those of the second embodiment, and thus a description thereof is omitted.

In accordance with the third embodiment, the plurality of select lines SL1and SL2are placed at different levels and arranged in a staggered manner. Accordingly, an area of the contact region can be further reduced as compared with other structures in which the select lines SL are arranged in the same level.

FIG. 2Dis a cross-sectional view showing the structure of a 3-D nonvolatile memory device according to a fourth embodiment of this disclosure.

As shown inFIG. 2D, the memory device according to the fourth embodiment of this disclosure includes a plurality of select lines SL1and SL2placed at different levels and arranged in a staggered manner, wherein each of the select lines SL1and SL2is coupled to at least two adjacent channel layers33. Some of the select lines SL1and SL2adjacent to each other in a stack direction are coupled in common to some of the channel layers33. That is, the plurality of select lines SL1and SL2is placed at several levels. Each of the select lines SL1and SL2is coupled to at least two adjacent channel layers33. Furthermore, the first select line SL1disposed at a lower level and the second select line SL2disposed at an upper level are arranged in a staggered manner and partially overlapped with each other so that they are coupled in common to some of the channel layers33.

The remaining structures are the same as those of the second embodiment, and thus a description thereof is omitted.

In accordance with the fourth embodiment, a desired channel layer33, that is, a desired string can be selected by combining the first select line SL1and the second select line SL2.

FIGS. 3A to 3Dare cross-sectional views illustrating a method of manufacturing a memory device according to an example embodiment of this disclosure. A method of manufacturing the memory device according to the second embodiment described with reference toFIG. 2Bis described below.

As shown inFIG. 3A, a support41having etched faces that are inclined and protrude from a surface of a substrate40is formed. The end of the channel structure C is bent upwardly along the support41, and a contact region is formed at ends of the channel structure C. The support41is formed flat on a surface of the substrate40in cell regions where memory cells will be formed. The support41includes a projecting part having an incline plane of a specific angle φ in the contact region where contact pads will be formed. [look for contact region throughout]

A height H of the projecting part of the support31may be greater than a total sum of the thicknesses of a plurality of interlayer insulating layers42and a plurality of channel layers43which are formed in a subsequent process. In particular, the height H of the projecting part of the support31may be greater than the total sum of the thicknesses the plurality of interlayer insulating layers42, the plurality of channel layers43, and an etch stop layer44.

The plurality of interlayer insulating layers42and the plurality of channel layers43are alternately formed, i.e., formed in an alternating manner, over the substrate40on which the support41is formed. Here, if the support41is formed by etching the substrate40, the interlayer insulating layers42may be first formed. If the support41is formed by etching an insulating layer, the interlayer insulating layers42or the channel layers43may be first formed.

As a result, a stack body including the plurality of interlayer insulating layers42and the plurality of channel layers43is formed.

The plurality of interlayer insulating layers42and the plurality of channel layers43are formed along a profile of the support41so that a step according to the support41is incorporated. Furthermore, the interlayer insulating layers42may be formed of oxide layer, such as SiO2, and the channel layers43may be formed of semiconductor layers, such as polysilicon layers.

Next, the etch stop layer44is formed on top of the highest interlayer insulating layer42or channel layer43depending on which forms the top layer of the channel structure C. The etch stop layer44is used for an etch stop in a subsequent etch process. The etch stop layer44may be formed of a combination of SiN and SiO2.

As shown inFIG. 3B, channel structures C are formed by performing a planarizing process on the interlayer insulating layers42A and the channel layers43A until a surface of the support41is exposed. For example, the etch stop layer44A formed in the contact region is removed. chemical mechanical polishing (CMP) process using the etch stop layers44A, remaining in the cell regions, as a polishing stop layer. As a result, the plurality of interlayer insulating layers42A and the plurality of channel layers43A which are stacked in the projecting part of the support41A are etched, thereby defining the contact region in which the plurality of channel layers43A is exposed.

In some embodiments, after forming a polishing oxide layer on the etch stop layer44A, the etch stop layer44A formed in the contact region may be removed by an etch-back process. In some embodiments, in the process of performing the CMP process, part of the top of the projecting part of the support41A may be etched.

InFIG. 3B, the etched support is indicated by ‘41A’, the etched interlayer insulating layers are indicated by ‘42A’, and the etched channel layers are indicated by ‘43A’.

The channel layers43A that are exposed in the contact region become respective contact pads, and the contact pads are coupled to the respective pillar type channels of select transistors which are formed in a subsequent process. An area of the contact pad may be determined by the angle φ of the incline plane of the support41A and the thickness of the interlayer insulating layer42A and the channel layer43A. For example, given that the sum of the thicknesses of the interlayer insulating layer42A of one layer and the channel layer43A of one layer may be ‘z’ and the angle of the incline plane of the support41A may be ‘φ’. Here, a width necessary to form one contact pad, that is, a contact pitch a, is expressed by Equation 1 below, and the contact pitch ‘a’ is greater than the sum ‘z’.

Referring to Equation 1, when the angle φ of the incline plane of the support41is 45°, an interval between the channel layers43that are exposed in the contact region is about 1.4 times the sum ‘z’. That is, a contact pad having a sufficient area can be formed in a narrow area by forming the contact region using the inclined support.

Next, although not shown, a plurality of channel structures C extended in parallel in one direction is formed by patterning the stack body in which the plurality of contact pads is formed. In some embodiments, the channel structures C may be formed by patterning the stack body before forming the contact region.

Next, a process of forming a plurality of memory cells is performed. For example, a tunnel insulating layer, a charge trap layer, and a charge blocking layer may be formed on the entire surface where the plurality of channel structures C is formed. A vertical gate disposed between the channel structures C adjacent to each other and a plurality of word lines WL extended in a direction to cross the channel structures C may be formed.

As shown inFIG. 3C, a first interlayer insulating layer45is formed on the resulting structure in which the plurality of contact pads is formed. A plurality of select lines SL is formed on the first interlayer insulating layer45. The plurality of select lines SL is spaced apart from one another and may be formed at respective positions over a position where the contact pads are formed.

As shown inFIG. 3D, a second interlayer insulating layer46is formed on the first interlayer insulating layer45A on which the plurality of select lines SL is formed. A plurality of contact holes through which the respective contact pads are exposed is formed by etching the second interlayer insulating layer46, the select lines SL, and the first interlayer insulating layer45A. InFIG. 3D, the first interlayer insulating layer etched in the process of forming the contact holes is indicated by ‘45A’.

A gate insulating layer48is formed on the inner wall of each of the contact holes. A pillar type channel layer47is formed within the contact hole on which the gate insulating layer48is formed. As a result, the select transistor, including the pillar type channel layer47, a gate electrode49configured to surround the pillar type channel layer47, and the gate insulating layer48disposed between the pillar type channel layer47and the gate electrode49, is formed. The select transistor has a gate all-around structure in which the pillar type channel layer47is surrounded by the gate electrode49for 360° such that the gate electrode49substantially forms a ring around the pillar type channel layer47with the gate insulating layer48disposed between the gate electrode49and the pillar type channel layer47.

An example in which the pillar type channel layer47and the gate insulating layer48penetrate the first interlayer insulating layer45, the select lines SL, and the second interlayer insulating layer46is illustrated inFIG. 3D. In some embodiments, the gate insulating layer48may be selected only in a location where the pillar type channel layer47and the gate electrode49come in contact with each other. To this end, an interlayer insulating layer under the select lines SL, an interlayer insulating layer in which the select lines are filled, and an interlayer insulating layer over the select lines are formed.

Next, bit lines BL extended in the same direction as the channel structures C and coupled to the pillar type channel layers47of the select transistors are formed on the result structure in which the plurality of select transistors is formed. The bit lines BL may be formed by forming a conductive layer and patterning the conductive layer or using a damascene method.

The method of forming the memory device according to the second embodiment has been described above. The memory devices according to the third and the fourth embodiments may also be manufactured using a substantially same method as described above.

A method of forming the select lines SL1and SL2of the memory device according to the third embodiment is described below.

As shown inFIG. 2C, after forming the channel structure C including the plurality of contact pads, a first interlayer insulating layer35A. The first select lines SL1are formed on the first interlayer insulating layer35A. The first select lines SL1are formed at the positions of some of the plurality of contact pads.

A second interlayer insulating layer35B is formed on the first interlayer insulating layer35A on which the first select lines SL1are formed. The second select lines SL2are formed on the second interlayer insulating layer35B. The second select lines SL2are formed at the positions of the remaining contact pads of the plurality of contact pads. Accordingly, the first select lines SL1and the second select lines SL2are formed at different heights from each other and may be arranged at different positions of the plurality of contact pads.

A third interlayer insulating layer35C is formed on the second interlayer insulating layer35B on which the second select lines SL2are formed. First contact holes through which some of the plurality of contact pads is exposed are formed by etching the third interlayer insulating layer35C, the second interlayer insulating layer35B, the first select lines SL1, and the first interlayer insulating layer35A. At the same time, second contact holes through which the remaining contact pads of the plurality of contact pads are exposed are formed by etching the third interlayer insulating layer35C, the second select line SL2, the second interlayer insulating layer35B, and the first interlayer insulating layer35A.

After forming a gate insulating layer37on the inner walls of the first contact holes and the second contact holes, a plurality of pillar type channel layers36is formed.

A method of forming the select line SL1and SL2of the memory device according to the fourth embodiment is described below.

As shown inFIG. 2D, after forming the channel structure C including the plurality of contact pads, a first interlayer insulating layer35A is formed. The first select lines SL1are formed on the first interlayer insulating layer35A. Each of the first select lines SL1are formed to cover at least two adjacent channel layers at a position where the at least two adjacent channel layers are formed.

A second interlayer insulating layer35B is formed on the first interlayer insulating layer35A on which the first select lines SL1are formed. The second select lines SL2are formed on the second interlayer insulating layer35B. Each of the second select lines SL2are formed to cover at least two adjacent channel layers at a position where the at least two adjacent channel layers are formed, and staggered with the first select line SL1. In particular, the first select line SL1and the second select line SL2adjacent to each other in the stack direction overlap with each other so that they cover some of the channel layers.

A third interlayer insulating layer35C is formed on the second interlayer insulating layer35B on which the second select lines SL2are formed. A plurality of contact holes through which the plurality of contact pads is exposed is formed by etching the third interlayer insulating layer35C, the second select lines SL2, the second interlayer insulating layer35B, the first select lines SL1, and the first interlayer insulating layer35A.

After forming a gate insulating layer37on the inner walls of the plurality of contact holes, a plurality of pillar type channel layers36is formed.

FIGS. 4 and 5are cross-sectional views illustrating a method of forming the support according to an example embodiment of this disclosure.

As shown inFIG. 4, a support51may be formed by etching a substrate50. For example, a trench T may be formed in a region where a memory block will be formed by etching the substrate50. A projecting part for separating the trenches T is used as the support51according to an example embodiment of this disclosure. Accordingly, the support51is integrally formed with the substrate50.

In order for the support51to be inclined and have an etched face, a process condition is controlled in the process of etching the trenches T. For example, the support51being inclined and having an etched face may be formed by etching the substrate50using a combination of isotropic etching and isotropic etching.

If the support51is formed by etching the substrate50as described above, it is preferred that the interlayer insulating layer be first formed and the channel layers then be formed when forming the stack body in order to electrically isolate the channel structure C and the substrate50from each other.

In some embodiments, after forming an insulating layer on the substrate, the support may be formed by etching the insulating layer. In this case, when forming the stack body, the channel layers may be formed and the interlayer insulating layer may be then formed.

As shown inFIG. 5, a dummy structure5is formed on the substrate50. An insulating layer may be formed on the entire surface of the substrate50on which the dummy structure5is formed, thereby forming the support51.

The dummy structure5is used to form the projecting part of the support51which is protruded from a surface of the substrate50. The dummy structure5may be formed by an additional process or by using part of a process of manufacturing the memory device.

For example, the dummy structure5may be a dummy transistor formed when the transistor of a peripheral circuit region is formed. In this case, the transistor formed in the peripheral circuit region and the dummy transistor placed in the support region are formed at the same time. The dummy structure5, in this example, includes a gate insulating layer1and a gate electrode2, and it may further include spacers3on its sidewalls. The dummy structure5may further include a tunnel insulating layer, a floating gate, a charge blocking layer, and a control gate or may include a tunnel insulating layer, a charge trap layer, a charge blocking layer, and a control gate depending on the type of device.

If it is difficult to form the incline plane of the projecting part of the support51because a height of the dummy structure5is low or the top of the dummy structure5is flat, an additional structure4may be further formed at the top of the dummy structure5. For example, the additional structure4having a section of a triangle or trapezoid may be formed at the top of the dummy transistor so that the projecting part has a sufficient incline plane. The additional structure4may be formed of an insulating layer.

FIG. 6shows a construction of a memory system according to an example embodiment of this disclosure.

As shown inFIG. 6, the memory system100according an example embodiment of this disclosure includes a nonvolatile memory device120and a memory controller110.

The nonvolatile memory device120is formed to have the above-described contact structure. Furthermore, the nonvolatile memory device120may be a multi-chip package including a plurality of flash memory chips.

The memory controller110is configured to control the nonvolatile memory device120, and it may include SRAM111, a central processing unit (CPU)112, a host interface (I/F)113, an error correction code (ECC) block114, and a memory I/F115. The SRAM111is used as the operating memory of the CPU112. The CPU112performs an overall operation for the exchange of data of the memory controller110. The host I/F113is equipped with a data exchange protocol between the memory system100and a host. Furthermore, the ECC block114detects errors in data read from the nonvolatile memory device120and corrects the detected errors. The memory interface115performs as an interface with the nonvolatile memory device120. The memory controller110may further include RCM for code data for an interface with the host.

The memory system100configured as above may be a memory card or a Solid State Disk (SSD) in which the nonvolatile memory device120and the memory controller110are combined. For example, if the memory system100is an SSD, the memory controller110may communicate with the outside (for example, the host) through one of various interface protocols, such as a USB, MMC, PCI-E, SATA, PATA, SCSI, ESDI, and IDE.

FIG. 7shows a construction of a computing system according to an example embodiment of this disclosure.

As shown inFIG. 7, the computing system200according to an example embodiment of this disclosure may include a CPU220, RAM230, a user interface240, a modem250, and a memory system210all of which are electrically coupled to a system bus260. If the computing system200is a mobile device, the computing system200may further include a battery for supplying operating voltages to the computing system200. The computing system200may further include application chipsets, a camera image processor (CIS), mobile DRAM, and so on.

The memory system210may include a nonvolatile memory device212and a memory controller211, such as those shown inFIG. 6.