# Patent

## Title
Stack type semiconductor memory device

## Abstract

A stack type memory device includes a semiconductor substrate; a plurality of bit lines arranged and stacked on the semiconductor substrate; a plurality of word lines formed on the plurality of bit lines; a plurality of interconnection units, each extending from a respective word line toward a respective one of the plurality of bit lines; and a plurality of memory cells connected between the plurality of bit lines and the interconnection units extending from the plurality of word lines, respectively.

## Background
CROSS-REFERENCES TO RELATED APPLICATION
The present application claims priority under 35 U.S.C. 119(a) to Korean application number 10-2011-0135698, filed on Dec. 15, 2011, in the Korean Patent Office, which is incorporated by reference in its entirety as if set forth in full.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to semiconductor integration circuit technology, and more particularly, to a stack type memory device having a three dimensional stack cell.
2. Related Art
With development in a mobile and digital information communication industry and an appliance industry, existing electron charge control-based devices are reaching their physical limits. Thus, new functional memory devices of a new configuration have developed. In particular, the development of next-generation memory devices with large capacity, ultra high-speed, and ultra lower-power consumption may include the features for large capacity of a memory in main information appliances.
Currently, resistive memory devices, which use a resistive device as a memory medium, have been suggested as the next-generation memory devices. These next-generation memory devices may include phase-change memory devices, resistive memory devices, and magnetoresistive memory devices.
The resistive memory device may include a switching device and a resistive device, and the resistive memory device stores data “0” or “1” according to a state of the resistive device.
In addition, the resistive memory devices may improve an integration density, and increasing the capacity in a limited area is important.
In addition, the phase-change memory device uses a diode connected to a word line as a switching device and forms a word line to have a linewidth as narrow as possible to reduce an integration density. Thus, a resistance of the word line is increased to cause word line bouncing, and a word line voltage may be unstable.
SUMMARY
According to one aspect of an exemplary embodiment, a stack type memory device includes a semiconductor substrate; a plurality of bit lines arranged and stacked on the semiconductor substrate; a plurality of word lines formed on the plurality of bit lines; a plurality of interconnection units, each extending from a respective word line toward a respective one of the plurality of bit lines; and a plurality of memory cells connected between the plurality of bit lines and the interconnection units extending from the plurality of word lines, respectively.
According to another aspect of an exemplary embodiment, a stack type memory device includes a semiconductor substrate; a plurality of active regions that each include a plurality of active layers that are stacked on the semiconductor substrate and insulated from one another; a plurality of gate electrodes that are formed in each of the plurality of active regions and the plurality of gate electrodes surround an upper portion of an uppermost active layer of the plurality of active layers and side portions of the plurality of active layers; a plurality of sources that are each formed in each of the plurality of active layers at a first side of the gate electrode; a plurality drains that are each formed in each of the plurality of active layers at a second side of the gate electrode; a plurality of bit lines that are each commonly connected to drains disposed in the same layer; a plurality of resistive device layers that are each connected to a respective one of the plurality of sources; and a common source line commonly connected to the resistive device layers.
According to still another aspect of an exemplary embodiment, a stack type memory device includes a semiconductor substrate; a plurality of active regions that each include a plurality of active layers that are stacked on the semiconductor substrate and insulated from one another; a plurality of gate electrodes that are formed in each of the plurality of active regions and the plurality of gate electrodes surround an upper portion of an uppermost active layer of the plurality of active layers and side portions of the plurality of active layers; a plurality of sources that are each formed in each of the plurality of active layers at a first side of the gate electrode; a plurality drains that are each formed in each of the plurality of active layers at a second side of the gate electrode; a plurality of resistive device layers that are each arranged at a first side of a respective one of the plurality of the drains; a plurality of bit lines that are each commonly connected to resistive device layers arranged in the same layer; a common source line commonly connected to the plurality of sources; and word lines that are each electrically connected to a respective one of the plurality of gate electrodes.
These and other features, aspects, and embodiments are described below in the section entitled “DESCRIPTION OF EXEMPLARY EMBODIMENT”.



BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and other advantages of the subject matter of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective view illustrating a stack type memory device according to an exemplary embodiment of the present invention;
FIGS. 2 to 9 are cross-sectional views for processes illustrating a method of manufacturing a stack type memory device according to an exemplary embodiment of the present invention;
FIGS. 10 and 17 are plan views for processes illustrating a method of manufacturing a stack type memory device according to an exemplary embodiment of the present invention;
FIG. 18 is a circuit diagram of a stack type memory device according to an exemplary embodiment of the present invention; and
FIGS. 19 to 21 are cross-sectional views illustrating stack type memory devices according to other exemplary embodiments of the present invention.



DESCRIPTION OF EXEMPLARY EMBODIMENT
Hereinafter, exemplary embodiments will be described in greater detail with reference to the accompanying drawings.
Exemplary embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of exemplary embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments should not be construed as limited to the particular shapes of regions illustrated herein but may be to include deviations in shapes that result, for example, from manufacturing. In the drawings, lengths and sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. It is also understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other or substrate, or intervening layers may also be present.
FIG. 1 is a perspective view illustrating a stack type memory device according to an exemplary embodiment of the present invention.
Referring to FIG. 1, a plurality of active layers 110 having line shapes are stacked on a semiconductor substrate 100, and insulating layers (not shown) are interposed between the plurality of active layers 110. The stacked active layers 110 are divided into unit active regions UNIT by insulating plugs 125 extending in the z direction.
A gate electrode G is formed in the central portion of each of the stacked unit active regions UNIT. A gate insulating layer (not shown) is interposed between the gate electrode G and the active layers 110. The gate electrode G may be formed in a “U”-shape to surround an upper surface of the uppermost unit active region of the stacked unit active regions UNIT and sidewalls of the stacked unit active regions UNIT. The gate electrode G is electrically connected to a word line 160. For example, the gate electrode includes a first portion g1 overlapped with a front side FS of the stacked unit active region UNIT structure, a second portion g2 overlapped with a back side BS of the stacked active region UNIT and a third portion g3 overlapped with the top side of the stacked active region UNIT.
A source S and a drain D are formed in each of the plurality of active layers at both sides of the gate electrode G so that a transistor is formed in each unit active region UNIT. A bit line 120 may extend in the z-direction and contact with a first side of the drains D. A resistive device layer 145 may be formed at a second side of each source S.
At this time, the bit line 120 may be commonly connected to drains D that are arranged to overlap the bit line 120 in a z-direction of FIG. 1 in a same layer (on a same plane). The bit lines extend in a direction that crosses the word line 160
In addition, the resistive device layer 145 is a storage medium configured to store a signal of the bit line 120 according to a switching operation of a transistor. The resistive device layer 145 may include any one selected from the group consisting of a praseodymium calcium manganese oxide (PCMO) layer, which is a material for a resistive random access memory (ReRAM), a chalcogenide layer, which is a material for a phase-change random access memory (PCRAM), a magnetic layer, which is a material for a magnetic random access memory (MRAM), a magnetization switching device layer, which is a material for a spin-transfer torque MRAM (STTMRAM), and a polymer layer, which is a material for a polymer random access memory (PoRAM).
The resistive device layers 145 may be commonly connected to a common source line 150, and for example, the common source line 150 may be a terminal for a ground voltage.
The stack type memory device is capable of integrating a plurality of memory cells in a limited area by a stacked arrangement of the active regions and bit lines.
FIGS. 2 to 9 are cross-sectional views for processes illustrating a method of manufacturing the stack type memory device of FIG. 1. FIGS. 10 to 17 are plan views for processes illustrating a method of manufacturing the stack type memory device of FIG. 1. Here, FIGS. 10 to 17 are plan views in an x-z plane. FIGS. 2 to 9 are cross-sectional views taken along line a-a′ of FIGS. 10 to 17.
Referring to FIGS. 2 and 10, an insulating layer 105 is formed on a semiconductor substrate 100. An active layer 110 and an interlayer insulating layer 115 are formed repeatedly so that a plurality of active layers 110 and a plurality of interlayer insulating layers 115 are alternately stacked, thereby forming a stacked active structure SA. The active layer 110 may include a semiconductor layer such as silicon (Si), a silicon germanium (SiGe), and gallium arsenide (GaAs), and the active layer 110 may be constituted of a single layer or multiple layers selected from the Si, SiGe, and GaAs. For example, the insulating layer 105 and the interlayer insulating layer 115 may include a silicon oxide material.
Referring to FIGS. 3 and 11, a first portion of the stacked active structure SA is patterned to expose the insulating layer 105. This patterning process forms a first hole H1. Subsequently, second holes H2 are formed through an etching process that pulls back the active layers 110 exposed through the first hole H1 from a lateral surface of the interlayer insulating layer 115. The first hole H1 is a hole for separating a bit line, and the second holes H2 are regions that define bit line regions. At this time, the stacked active structure SA is separated left and right along the z-direction by the first and second holes H1 and H2.
Referring to FIGS. 4 and 12, a conductive material fills the second holes H2 to form bit lines 120, which are in contact with the stacked active layers, respectively. The conductive material for the bit lines 120 may include at least one selected from the group consisting of a metal layer such as tungsten (W), copper (Cu), titanium (Ti), molybdenum (Mo), and tantalum (Ta), a metal nitride layer such as titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), molybdenum nitride (MoN), niobium nitride (NbN), titanium silicon nitride (TiSiN), titanium aluminum nitride (TiAlN), titanium boron nitride (TiBN), zirconium silicon nitride (ZrSiN), tungsten silicon nitride (WSiN), tungsten boron nitride (WBN), zirconium aluminum nitride (ZrAlN), molybdenum silicon nitride (MoSiN), molybdenum aluminum nitride (MoAlN), tantalum silicon nitride (TaSiN), and tantalum aluminum nitride (TaAlN), a metal silicide layer such as titanium silicide (TiSi), an heterometal layer such as titanium tungsten (TiW), and a metal oxynitride layer such as a titanium oxynitride (TiON), tungsten oxynitride (WON), and tantalum oxynitride (TaON). In addition, the bit line 120 is commonly connected to active layers 110 arranged on the same plane. Next, an insulating layer fills the first hole H1 to form an insulating plug 125. The bit lines 120 stacked in a y-direction and disposed in the same layer in the x-direction are separated from one another by the stacked interlayer insulating layers 115 and the insulating plug 125.
Referring to FIGS, 5 and 13, a second portion of the stacked active structure SA is etched to expose the insulating layer 105 so that the stacked active structure SA is separated in the x-direction of FIG. 13. An area P in FIG. 13 denotes an area in which the stacked active structure SA is etched to be separated in the x-direction. Through this etching process, the stacked active structure SA is divided into a plurality of stacked active patterns SAP having a rectangular shape extending in the x-direction. Here, each of the stacked active patterns may be referred to as a stacked active region, and one layer constituting the stacked active region may be a unit active region in which one memory cell is formed.
A gate insulating layer 130 and a gate electrode layer 135 are formed on a resultant structure of the semiconductor substrate 100 in which the plurality of stacked active patterns SAP are formed. Like the bit line, the gate electrode layer 135 may include any one selected from the group consisting of a metal layer such as tungsten (W), copper (Cu), titanium (Ti), molybdenum (Mo), and tantalum (Ta), a metal nitride layer such as titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), molybdenum nitride (MoN), niobium nitride (NbN), titanium silicon nitride (TiSiN), titanium aluminum nitride (TiAlN), titanium boron nitride (TiBN), zirconium silicon nitride (ZrSiN), tungsten silicon nitride (WSiN), tungsten boron nitride (WBN), zirconium aluminum nitride (ZrAlN), molybdenum silicon nitride (MoSiN), molybdenum aluminum nitride (MoAlN), tantalum silicon nitride (TaSiN), and tantalum aluminum nitride (TaAlN), a metal silicide such as titanium silicide, an heterometal layer such as titanium tungsten (TiW), and a metal oxynitride layer such as a titanium oxynitride (TiON), tungsten oxynitride (WON), and tantalum oxynitride (TaON).
The gate electrode layer 135 and the gate insulating layer 130 are first patterned to surround each stacked active pattern SAP.
Referring to FIGS. 6 and 14, the first patterned gate electrode layer 135 and gate insulating layer 130 are additionally etched to form gate electrodes G on the stacked active patterns SAP. Each of the gate electrodes G is formed on each of the stacked active patterns SAP. More specifically, when viewed in FIG. 14, each of the gate electrodes G is arranged in a direction perpendicular to the extending direction (x-direction) of each of the stacked active patterns SAP. However, the gate electrode G is substantially formed to surround an upper surface and side surfaces of the stacked active pattern SAP as shown in FIG. 1. Therefore, although the gate electrode G is arranged in a one-to-one correspondence with the stacked active patterns SAP, the gate electrode G substantially serves as a shared gate electrode to the unit active regions constituting each of the stacked active patterns SAP.
Next, a source and a drain are formed in each of the unit active regions using the gate electrode G as a mask. The source S and drain D may be formed in each of the stacked unit active layers 110 through a stepwise ion implantation process. In this process, the drain D may be formed to be in contact with the bit line 120. The source S may have a larger width than the drain D so that a space where a resistive device layer (not shown) is to be formed in a subsequent process is ensured.
Referring to FIGS. 7 and 15, an upper insulating layer 140 is formed on a resultant structure of the semiconductor substrate 100 including the gate electrode G. Next, the upper insulating layer 140 and the stacked active patterns SAP are etched to expose sidewalls of the sources S of the stacked active patterns SAP to form a third contact hole H3. Portions of the exposed source S are pulled back by a designated length to form a fourth hole H4. Here, a depth of the fourth hole H4 is determined to be substantially equal to a width of the drain D.
Referring to FIGS. 8 and 16, a resistive material fills the fourth hole H4 to form a resistive device layer 145. The resistive device layer 145 may include any one selected from the group consisting of a praseodymium calcium manganese oxide (PCMO) layer, which is a material for a resistive random access memory (ReRAM), a chalcogenide layer, which is a material for a phase-change random access memory (PCRAM), a magnetic layer, which is a material for a magnetic random access memory (MRAM), a magnetization switching device layer, which is a material for a spin-transfer torque MRAM (STTMRAM), and a polymer layer, which is a material for a polymer random access memory (PoRAM). By forming the resistive device layer 145, a transistor connected to the resistive device layer 145 is formed.
A conductive material fills the third hole H3 to form a common source line 150 that is commonly connected to the resistive device layers 145 connected to the respective sources S.
Referring to FIGS. 9 and 17, an interlayer insulating layer 155 is formed on a resultant structure of the semiconductor substrate 100 including the common source line 150, and subsequently, a conductive plug 157, which is in contact with the gate electrodes G, is formed within the interlayer insulating layer 155. A word line 160 is formed on the interlayer insulating layer 155 to be in contact with the conductive plug 157. The word line 160 may extend in the same direction as an extending direction of the active layer 110. A contact CT shown in FIG. 17 is a contact between the word line 160 and the conductive plug 157.
The stack type memory device according to the above-described exemplary embodiment may be implemented with a circuit shown in FIG. 18.
Referring to FIG. 18, a stack type memory device 1000 includes a plurality of word lines WL0, WL1, and WL2, a plurality of bit lines BL0, BL1, and BL2, and a plurality of memory cells mc.
The plurality of bit lines BL0, BL1, and BL2 are stacked and extend in a first direction. The plurality of word lines WL0, WL1, and WL2 include interconnection units L extending toward the stacked bit lines BL0, BL1, and BL2. Here, the interconnection units L may correspond to the contact plugs 157 of FIG. 9.
The plurality of memory cells mc are connected between the interconnection units L extending from the plurality of word lines WL0, WL1, and WL2 and the bit lines BL0, BL1, and BL2. Each of the plurality of memory cells mc may be constituted of a transistor Tr and a variable resistor Rv. In the transistor Tr, a gate is connected to a corresponding interconnection unit L, a drain is connected to a corresponding bit line, and a source is connected to the variable resistor Rv. The variable resistor Rv may be connected to the common source line 150 and correspond to the resistive device layer 145 of the exemplary embodiment.
Bit lines BL3, BL4, and BL5 are bit lines arranged in adjacent stacked active regions.
The stack type memory device is configured to stack the plurality of memory cells and stack the bit lines to improve an integration density. Accordingly, a word line formation area is ensured and the word line may be prevented from being bounced.
FIG. 19 is a cross-sectional view illustrating a stack type resistive memory device according to another exemplary embodiment. In the exemplary embodiment, an NMOS transistor is used as a transistor. A source and a drain of the NMOS transistor may be formed by implanting a high concentration n type impurity.
In addition, as shown in FIG. 20, silicide layers 118 may be used as a source and a drain of a transistor. By using silicide layers, a junction resistance of the transistor can be improved.
In addition, as shown in FIG. 21, a resistive device layer 146 may be disposed between a drain D and a bit line 120. Through this embodiment, the same features as in the above-described exemplary embodiments can be obtained.
Although not described in detail in the above-described exemplary embodiments, a source and a drain of a transistor may be formed in a general lightly doped drain (LDD) type.
As described above in detail, according to the exemplary embodiments, the resistive memory device is configured in a three dimensional structure, and thus, an integration density may be improved and a word line bouncing can be prevented.
While certain embodiments have been described above, it will be understood that the embodiments described are by way of example only. Accordingly, the devices and methods described herein should not be limited based on the described embodiments. Rather, the systems and methods described herein should only be limited in light of the claims that follow when taken in conjunction with the above description and accompanying drawings.

## Claims

1. A stack type memory device, comprising:
a semiconductor substrate;
a first stack structure and a second stack structure, each of the first and second stack structures including a plurality of memory cells stacked on the semiconductor substrate, wherein the first stack structure and the second stack structure are divided by an insulating plug;
a plurality of bit lines formed at one side of the plurality of memory cells of the first and second stack structures, respectively, and stacked on the semiconductor substrate; and
a plurality of word line structures, each of the word line structures including:
a gate insulating layer formed over the plurality of memory cells,
first and second gate electrodes, wherein each of the first and second gate electrodes has a U-shape and directly contact the gate insulating layer, wherein the U-shape is formed of a first portion for covering a front side of each of the corresponding memory cells of the first or second stack structures, a second portion for covering a back side of each of the corresponding memory cells of the first or second stack structures and a third portion for covering a top side of the corresponding memory cell of the first and second stack structures, wherein the gate insulating layer is interposed between the first and second gate electrodes and the corresponding memory cells of the first and second stack structures, and the first to third portions are electrically connected with one another,
a word line formed on the stack structures and the plurality of bit lines, wherein the word line is configured to select one of the gate electrodes of the plurality of word lines, and
an interconnection unit electrically connected between the third portion of the gate electrode and the word line,

wherein the plurality of memory cells constituting the first and second stack structures are connected in parallel.

2. The stack type memory device of claim 1, wherein each of the plurality of memory cells includes:
a switching transistor electrically connected to a corresponding bit line and the word line; and
a variable resistor electrically connected to the switching transistor.

3. The stack type memory device of claim 2, wherein the variable resistors of the plurality of memory cells are commonly connected to a common source line.

4. A stack type memory device, comprising:
a semiconductor substrate;
a stack structure, wherein the stack structure includes a plurality of active layers stacked on the semiconductor substrate and insulated from one another;
a gate insulating layer formed over the plurality of active layers,
a gate electrodes having a U-shape and that directly contacts the gate insulating layer, wherein the U-shape is formed of a first portion overlapped with a front side of the corresponding active layers of the stack structure, a second portion overlapped with a back side of the corresponding active layers of the stack structure and a third portion overlapped with a top side of the corresponding active layer of the stack structure, wherein the gate insulating layer is interposed between the gate electrodes and the corresponding active layers of the stack structure, and the first to third portions are electrically connected with one another;
a plurality of sources that are each formed in each of the plurality of active layers at a first side of the first and second portions of the gate electrode;
a plurality drains that are each formed in each of the plurality of active layers at a second side of the first and second portions of the gate electrode;
a plurality of bit lines that are each commonly connected to drains disposed in the same layer;
a plurality of resistive device layers that are each connected to a respective one of the plurality of sources; and
a common source line connected to the resistive device layers in common.

5. The stack type memory device of claim 4, wherein the plurality of active regions are arranged and stacked on the semiconductor substrate in parallel and separated from each other.

6. The stack type memory device of claim 5, wherein the bit lines are stacked and extended in a first direction so that the bit lines are one-to-one corresponding to the active layers.

7. The stack type memory device of claim 6, wherein the bit line is formed at a first side of the drains.

8. The stack type memory device of claim 4, further comprising a plurality of word lines formed on the gate electrodes to be electrically connected to the gate electrodes.

9. The stack type memory device of claim 8, wherein the plurality of word lines extend in a second direction that crosses the bit line.

10. The stack type memory device of claim 4, wherein the source and drain include high concentration n type impurity regions.

11. The stack type memory device of claim 4, wherein the source and drain include silicide layers.

12. The stack type memory device of claim 4, wherein the resistive device layer includes any one selected from the group consisting of a praseodymium calcium manganese oxide (PCMO) layer, a chalcogenide layer, a magnetic layer, a magnetization switching device layer, and a polymer layer.

13. The stack type memory device of claim 12, wherein the resistive device layer is formed at a first side of each source.