KR101069420B1 - Nand flash memory array having pillar type single crystal channel and virtual source/drain and fabrication method of the same - Google Patents

Abstract

The present invention relates to a NAND flash memory array having a virtual source / drain by a columnar single crystal channel and fringing field, and a method of manufacturing the same, wherein the active region is composed of kxn single crystal silicon pillars formed by etching a substrate. By forming m word lines and control means (common source region, lower select gate, and upper select gates) vertically, the degree of integration can be increased in three dimensions by a simple process. The body of the cell is connected to the substrate to enable the normal erase operation, and has the effect of increasing the charge carrier mobility by the single crystal channel.

Pillar, Monocrystalline Channel, Fringe Field, NAND, Flash, Memory, Array

Description

NAND flash memory array with columnar single crystal channel and virtual source / drain and manufacturing method thereof

The present invention relates to a NAND flash memory array and a method of manufacturing the same, and more particularly, to a NAND flash memory array having a virtual source / drain by columnar single crystal channels and fringing fields. will be.

Recently, due to various demands such as large-capacity memory, various methods for increasing memory density have been studied.

Among them, three-dimensional flash memory has been proposed. Toshiba Corp. recently proposed a memory array in which word lines are stacked in a vertical direction (International Publication No. WO 2008/096802).

The structure according to the prior art has an advantage that the effective cell size can be proportionally reduced as the number of layers of the word line increases (6F ² / n, n = number of layers).

However, according to the prior art, after depositing amorphous silicon and silicon dioxide in order to form a word line, the portion to be a channel is drilled in a 'punch' manner. Since the channel is filled with poly silicon and used as a channel, the mobility of charge carriers in the channel is very low.

In addition, since the prior art has a floating body structure, it is necessary to use a method of erasing by generating holes through GIDL to increase body potential (that is, conventional erase is impossible), and erase speed The problem is that the erase time is also long.

In order to solve the problems of the prior art as described above, a plurality of single crystal silicon pillars are formed by etching a silicon substrate, and an insulating layer and a conductive material are repeatedly stacked thereon, and a plurality of word lines as well as upper and lower selection gate lines are formed. It is an object of the present invention to provide a NAND flash memory array having a virtual source / drain by a single crystal silicon channel and fringing field, and a method of manufacturing the same.

In order to achieve the above object, the NAND flash memory array according to the present invention comprises a p-type single crystal silicon substrate; Pillars spaced at a predetermined distance on the substrate with the same material as the substrate and formed with k x n pillars; A common source region formed of an n-type impurity doping layer on the substrate between the pillars; A lower selection gate formed on the common source region and each of the pillars with a first insulating film interposed therebetween; M word lines formed by repeatedly stacking a second insulating film and a conductive layer m times on the lower selection gate and each pillar; K upper select gates formed to match k rows of the pillars with a third insulating layer interposed between the conductive layer and the pillars forming the highest word line among the m word lines; A fourth n-type impurity doping layer is formed on each of the pillars exposed to the upper selection gates, and a fourth n-type impurity doping layer is formed on each of the pillars on which each of the upper selection gates and the second n-type impurity doping layers are formed. And n bit lines formed to be electrically connected to an upper end of each of the pillars on which the second n-type impurity doping layer is formed in accordance with the n columns of the pillars with the insulating layer interposed therebetween. They are connected to each other by a single p-type body integrally with the substrate located below the common source region.

In addition, a method of manufacturing a NAND flash memory array according to the present invention includes a first step of sequentially stacking an oxide film and a nitride film on a p-type single crystal silicon substrate and etching the substrate to form k x n single crystal silicon pillars; A second step of forming a common source region as an n-type impurity doped layer on the etched substrate exposed through the pillars by ion implantation perpendicular to the substrate; Forming an insulating film on a lower selection gate by forming an oxide film on the common source region and each of the pillars; Depositing and etching a gate material over the substrate to form a lower selection gate; Removing the insulating film of the lower select gate exposed on the lower select gate and forming a tunneling oxide film / nitride film / blocking oxide film on the lower select gate and each pillar; A sixth step of forming m word lines by repeatedly laminating a conductive layer and an oxide film on the entire surface of the substrate; Depositing and etching a gate material on the entire surface of the substrate again to form k top select gates so that the pillars arranged in the same row in accordance with the k rows of the pillars are wrapped with a single gate; ; An eighth step of filling an oxide film over the entire surface of the substrate and planarizing the same by using a CMP process, and then etching the oxide film and the nitride film to expose an upper portion of each pillar; A ninth step of forming an n-type impurity doping layer on the exposed silicon pillar by ion implantation into the substrate; Forming a conductive layer on the entire surface of the substrate and etching the upper end of the pillars arranged in the same row according to the n columns of the pillars to form n bit lines such that one bit line is electrically connected Characterized in that configured to include.

The NAND flash memory array according to the present invention forms an active region with kxn single crystal silicon pillars formed by etching a substrate, and vertically m word lines and control means (common source region, lower select gate, and upper select gate). 3) can increase the degree of integration three-dimensionally, as well as the body of each cell is connected to the substrate to enable the normal erase operation, to increase the charge carrier mobility by the single crystal channel It is effective.

In addition, in the method of manufacturing a NAND flash memory array according to the present invention, a plurality of gates are vertically stacked by simply etching a substrate to form a plurality of single crystal silicon pillars, and then repeatedly depositing and etching an insulating film and a conductive material. There is an effect that can implement (wordlines).

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a perspective view showing an embodiment configuration of a NAND flash memory array according to the present invention, FIG. 2 is a plan view from above of FIG. 1, and FIGS. 3 to 18 are cross-sectional views taken along line AA of FIG. 1. A cross-sectional view of the process showing how the shape is created. In FIG. 2, reference numeral 1 denotes a memory region, and 100 denotes a single crystal silicon pillar.

 First, the NAND flash memory array according to the present invention includes a single crystal silicon substrate 10, as shown in Figs. Pillars (12; 100) spaced at a predetermined distance from the same material as the substrate and formed with k x n; A common source region 40 formed as a first impurity doping layer on the substrate between the pillars; A lower select gate 52 formed on the common source region and each of the pillars 12 with a first insulating layer 24a therebetween; M word lines formed by repeatedly stacking a second insulating layer (60, 64a, 65a, 66a) and a conductive layer (71, 72, 73, 74) m times on the lower selection gate and each pillar; K rows of the pillars 100 with a third insulating layer 67 interposed between the conductive layer 74 and the pillars 12 forming the most significant word line among the m word lines. K top select gates 75 formed in conformity with; A second impurity doped layer 42 is formed on each of the pillars exposed to the upper select gates, and each of the upper select gates 75 and the second impurity doped layer 42 is formed on each pillar. 4 formed to be electrically connected to an upper end of each of the pillars 12 in which the second impurity doping layer 42 is formed in accordance with n columns of the pillars 100 with the insulating film 82 interposed therebetween. It characterized in that it comprises a number of bit lines (90).

As described above, an active region is formed of kxn pillars 100 by the same single crystal silicon as the substrate 10, and m m lines and control means (common source region, lower select gate, and upper select vertically) are vertically formed. By forming the gates), the degree of integration can be increased in three dimensions, and the body 12 of each cell is connected to the substrate 10 to enable a normal erasing operation. There is an advantage to increase the charge carrier mobility (mobility).

In the above embodiment, the single crystal silicon pillars 12 and 100 may be formed by etching a p-type single crystal silicon substrate with a circular column (described in detail in the embodiment of the manufacturing method), and the first impurities. The doping layer 40 and the second impurity doping layer 42 may be formed of an n-type impurity doping layer.

Further, in vertically stacking the conductive layers 71, 72, 73, and 74 for forming m word lines, the second insulating layers 64a and 65a are spaced apart from each other by a predetermined distance between upper and lower conductive layers. , 66a) It is preferable to make thickness into 2-50 nm. This is to form a source / drain electrically by a neighboring conductive layer up and down, i.e., as a fringing field of the upper and lower conductive layers, instead of forming a source / drain as an impurity doped layer in each single crystal silicon pillar. to be.

However, the thickness of the second insulating films 64a, 65a, and 66a between the conductive layers may vary depending on the dielectric constant of the second insulating film and the V _pass voltage to be applied to the word line.

The first insulating film 24a is a conventional silicon oxide film, and the second insulating film formed on the lower selection gate 52 and the pillars 12 among the second insulating films is a tunneling oxide film 61 / nitride film ( 62) / blocking oxide films 63 and 60, and the third insulating film formed on the pillars 12 among the third insulating films is a tunneling oxide film 61 / nitride film 62 / blocking oxide film 63. And an oxide film of the same material as that of the blocking oxide film 63 is formed in the third insulating film 67 on the conductive layer, and the fourth insulating film formed on the pillars 12 among the fourth insulating films. The insulating film is formed in the order of tunneling oxide film 61 / nitride film 62 / blocking oxide film 63 and 60, and the fourth insulating film 82 on the upper selection gate 75 is preferably filled with an oxide film.

By the configuration as described above, as shown in FIG. 18, the ONO layer 60 of the tunneling oxide film 61, the nitride film 62, and the blocking oxide film 63 is formed to surround the single crystal silicon pillars 12, and the ONO The gate material or the conductive material layer is stacked with the oxide layer interposed therebetween, covering the layer 60, and a memory cell having a gate-all-around structure having the nitride layer 62 as the charge storage layer is formed in each pillar ( 12, 100) to form a plurality.

Meanwhile, in the NAND flash memory array according to the above embodiment, the external connection of the memory region 1 composed of the single crystal silicon pillars 100 may be made as shown in FIG. 1 or 2.

That is, the common source region 40 is a common source line CSL, the lower select gate 52 is a lower select gate line LSGL, and the m conductive layers 71, 72, 73, and 74 are formed. Are connected to word lines WL1, WL2, ..., WLm, respectively, by predetermined contacts 110, and the k top select gates 75 are each top select gate lines USGL1, USGL2,. .., USGLk) is connected by a predetermined contact 120, the top of the single-crystal silicon pillars 100 is located in the same column n is formed perpendicular to each of the upper select gate line so that it is connected to the same bit line The bit lines BL1, BL2, ..., BLn are respectively connected.

Next, referring to Figs. 3 to 18, a manufacturing method of the NAND flash memory array according to the embodiment will be described.

First, as shown in FIG. 3, the oxide film 20 and the nitride film 30 are sequentially stacked on the p-type single crystal silicon substrate 10 through a normal thermal oxidation process and a CVD process, and as shown in FIG. 4, the substrate ( 10) is etched to form kxn single crystal silicon pillars 12 (100) having a predetermined height (first step).

Subsequently, as shown in FIG. 4, the common source region is formed of an n-type impurity doped layer 40 on the etched substrate exposed between the pillars 12 by ion implantation perpendicular to the substrate 10 (second step).

Thereafter, as shown in FIG. 5, an oxide film 24 is formed on the common source region 40 and the pillars 12 to form an insulating film of the lower selection gate (third step).

Subsequently, as shown in FIG. 6, the gate material 50 is deposited on the entire surface of the substrate, and planarized through a chemical mechanical polishing (CMP) process, and then the gate material 50 is etched by a dry recess method. The lower select gate 52 is formed (fourth step).

The gate material 50 may be a silicon-based material (eg, polysilicon, amorphous silicon, etc.) or metal doped with impurities.

Next, as shown in FIG. 7, the insulating layer 24 of the lower select gate exposed on the lower select gate 52 is removed by wet etching, and as shown in FIG. 8, the lower select gate 52 and the respective angles are removed. The tunneling oxide film 61, the nitride film 62, and the blocking oxide film 63, 60 are sequentially formed on the pillar 12 through a CVD process or the like (fifth step).

9 to 15, the conductive layers 71, 72, 73, and 74 and the oxide layers 64a, 65a, 66a, and 67 are repeatedly stacked m times on the entire surface of the substrate to form m word lines. (Step 6).

Here, the sixth step will be described in more detail as follows.

First, as shown in FIG. 9, the conductive material 70 is deposited on the entire surface of the substrate and planarized by a CMP process (Step 6-1). In this case, the nitride layer 32 serves as an etch stopper. In addition, like the gate material 50, the conductive material 70 may be a silicon-based material (eg, polysilicon, amorphous silicon, etc.) or metal doped with an impurity.

Subsequently, as shown in FIG. 10, the conductive material 70 is etched in a recessed manner by dry etching to form the conductive layer 71 (step 6-2).

Thereafter, as shown in FIG. 11, the blocking oxide film 63 of each pillar 12 exposed on the conductive layer 71 is removed by wet etching (Step 6-3).

Next, as shown in FIG. 12, a blocking oxide film is formed again on the conductive layer 71 and the pillars 12 (step 6-4).

Subsequently, as shown in FIGS. 13 to 15, the deposition, the etching, and the etching of the blocking oxide layer 63 are performed on the m-1 through the steps 6-1 to 6-4. Repeating to form m word lines (step 6-5).

Subsequently, as shown in FIG. 15, the blocking oxide layer 63 is formed on the uppermost conductive layer 74 and the pillars 12, and the gate material is again deposited and etched on the entire surface of the substrate to form the pillars. The pillars arranged in the same row in accordance with k rows form k top select gates 75 so as to be wrapped around a single gate (seventh step).

Next, as shown in FIG. 16, the oxide film 80 is filled on the entire surface of the substrate and planarized by a CMP process to expose the nitride film 32, and as shown in FIG. 17, the oxide film ( 80) and the nitride film 32 are etched (eighth step).

Thereafter, as illustrated in FIG. 17, an n-type impurity doping layer 42 is formed on the exposed silicon pillar 12 by ion implantation into the substrate (ninth step).

Next, a conductive layer is formed of metal or the like on the entire surface of the substrate and is etched. As shown in FIG. 18, one bit line is electrically connected to an upper end of pillars arranged in the same row according to n columns of the pillars. N bit lines 90 are formed (step 10).

After that, as shown in FIGS. 1 and 2, a contact and wiring process for connecting the memory region 1 is performed.

As described above, in the method of manufacturing a NAND flash memory array according to the above embodiment, a plurality of single crystal silicon pillars are formed by etching a substrate, and then a plurality of vertically stacked vertically by repeating deposition and etching of an insulating film and a conductive material. The advantage is that control gates (word lines) can be implemented.

1 is a perspective view showing an embodiment of a NAND flash memory array according to the present invention.

FIG. 2 is a layout with a plan view from above of FIG. 1.

3 to 18 are process cross-sectional views showing a process of making a cross-sectional shape cut along the line AA of FIG.

<Description of the symbols for the main parts of the drawings>

10: single crystal silicon substrate 12: single crystal silicon pillar

20, 24a, 64a, 65a, 66a, 67, 80, 82: insulating film (oxide film)

30, 32: nitride film 40, 42: n-type impurity doping layer

52: lower select gate 60: ONO layer

71, 72, 73, 74: conductive layer (word line)

75: upper select gate 90: bit line

Claims (8)

a p-type single crystal silicon substrate; Pillars spaced at a predetermined distance on the substrate with the same material as the substrate and formed with k x n pillars; A common source region formed of an n-type impurity doping layer on the substrate between the pillars; A lower selection gate formed on the common source region and each of the pillars with a first insulating film interposed therebetween; M word lines formed by repeatedly stacking a second insulating film and a conductive layer m times on the lower selection gate and each pillar; K upper select gates formed to match k rows of the pillars with a third insulating layer interposed between the conductive layer and the pillars forming the highest word line among the m word lines; A fourth n-type impurity doping layer is formed on each of the pillars exposed to the upper selection gates, and a fourth n-type impurity doping layer is formed on each of the pillars on which each of the upper selection gates and the second n-type impurity doping layers are formed. And n bit lines formed to be electrically connected to an upper end of each of the pillars having the second n-type impurity doping layer formed thereon, with an insulating layer interposed therebetween. And the pillars are connected to each other by a single p-type body integrally with a substrate positioned below the common source region. The method of claim 1, The second insulating film, On the lower selection gate and each pillar, tunneling oxide, nitride, and blocking oxide are formed in this order. And an oxide film of the same material as the blocking oxide film is formed between the conductive layers. The method of claim 2, The first insulating film is a silicon oxide film, The third insulating film is formed on the pillars in the order of tunneling oxide film / nitride film / blocking oxide film, an oxide film of the same material as the blocking oxide film is formed on the conductive layer, And the fourth insulating film is formed on the pillars in the order of tunneling oxide film / nitride film / blocking oxide film, and is filled with an oxide film on the upper selection gate. 4. The method according to any one of claims 1 to 3, And a thickness of the second insulating layer between the conductive layers is 2 to 50 nm. In the method of manufacturing a NAND flash memory array according to claim 4, a first step of sequentially stacking an oxide film and a nitride film on a p-type single crystal silicon substrate and etching the substrate to form k x n single crystal silicon pillars; A second step of forming a common source region as an n-type impurity doped layer on the etched substrate exposed through the pillars by ion implantation perpendicular to the substrate; Forming an insulating film on a lower selection gate by forming an oxide film on the common source region and each of the pillars; Depositing and etching a gate material over the substrate to form a lower selection gate; Removing the insulating film of the lower select gate exposed on the lower select gate and forming a tunneling oxide film / nitride film / blocking oxide film on the lower select gate and each pillar; A sixth step of forming m word lines by repeatedly laminating a conductive layer and an oxide film on the entire surface of the substrate; Depositing and etching a gate material on the entire surface of the substrate again to form k top select gates so that the pillars arranged in the same row in accordance with the k rows of the pillars are wrapped with a single gate; ; An eighth step of filling an oxide film over the entire surface of the substrate and planarizing the same by using a CMP process, and then etching the oxide film and the nitride film to expose an upper portion of each pillar; A ninth step of forming an n-type impurity doping layer on the exposed silicon pillar by ion implantation into the substrate; Forming a conductive layer on the entire surface of the substrate and etching the upper end of the pillars arranged in the same row according to the n columns of the pillars to form n bit lines such that one bit line is electrically connected Method of manufacturing a NAND flash memory array comprising a. The method of claim 5, The m word lines may be formed in the sixth step. A 6-1 step of depositing a conductive material on the entire surface of the substrate and planarization by a CMP process; Step 6-2 of forming a conductive layer by etching the conductive material in a recessed manner by dry etching; A step 6-3 of removing the blocking oxide films of the pillars exposed on the conductive layer; A step 6-4 of forming a blocking oxide film on the conductive layer and each pillar again; And a sixth to sixth step of repeating the sixth to sixth steps m-1 to the sixth to sixth steps. The method of claim 6, And removing the insulating film of the lower selection gate of the fifth step and removing the blocking oxide film of the sixth to third steps by wet etching. The method of claim 6, The gate material and the conductive material are silicon-based materials or metals doped with impurities, And the conductive layer forming the n bit lines is a metal.

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