US20120080734A1

US20120080734A1 - Semiconductor memory device

Info

Publication number: US20120080734A1
Application number: US13/314,541
Authority: US
Inventors: Mitsunari Sukekawa
Original assignee: Elpida Memory Inc
Current assignee: PS4 Luxco SARL
Priority date: 2008-04-10
Filing date: 2011-12-08
Publication date: 2012-04-05
Also published as: US20090256182A1; US8093642B2; JP2009253208A

Abstract

A semiconductor memory device includes a memory cell portion and a peripheral circuit portion. The memory cell portion includes a pillar capacitor with a lower electrode, a dielectric film, and an upper electrode sequentially formed on a side surface of a first insulating portion which is parallel to a predetermined direction, and a transistor electrically connected to the lower electrode. The peripheral circuit portion includes a plate electrode, a cylinder capacitor with an upper electrode, a dielectric film, and a lower electrode sequentially formed on a side surface of the plate electrode which is parallel to the predetermined direction, and a transistor electrically connected to the lower electrode.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of co-pending application Ser. No. 12/421,049 filed Apr. 9, 2009, which claims foreign priority to Japanese patent application 2008-102556 filed Apr. 10, 2008. The entire content of each of these applications is hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a semiconductor memory device and a method of manufacturing the semiconductor memory device.
2. Description of the Related Art
A DRAM (Dynamic Random Access Memory) is composed of memory cells each made up of a transistor and a capacitor. The capacitor is composed of a lower electrode, a dielectric film, and an upper electrode. In recent years, with advanced semiconductor miniaturizing techniques, ensuring a required area for electrodes in the DRAM has been difficult.
Thus, to increase the area for the electrodes, Japanese Patent Laid-Open No. 2001-217406 discloses a technique of using an inner wall and an outer wall formed like crowns as an upper electrode and a lower electrode, respectively, to increase capacity. FIG. 11 shows a recessed lower electrode similar to the lower electrode in Japanese Patent Laid-Open No. 2001-217406.
In FIG. 11, the lower electrode is denoted by 105. The lower electrode in FIG. 11 is formed as follows. First, a transistor and a contact plug are formed such that the contact plug is electrically connected to one of a source region and a drain region of the transistor. Thereafter, an interlayer insulating film is formed all over the resulting surface. A mask pattern is then formed on a portion of the interlayer insulating film which is located on a region forming a memory cell portion.
Thereafter, by performing wet etching, the interlayer insulating film is removed except for the portion of the interlayer insulating film which is located under the mask pattern, to form an opening. A conductive material is then deposited on an inner wall of the opening to form a lower electrode. The interlayer insulating film is then removed. At this time, the internal surface (the interior of the recessed structure) of the lower electrode is exposed.
Efforts have been made to develop a method of preventing formation of a step between the memory cell portion and the peripheral circuit portion. Japanese Patent Laid-Open No. 2001-217406 and WO 97/019468 disclose methods of reducing a step that may be formed at the boundary between the memory cell portion and the peripheral circuit portion.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a semiconductor memory device including a memory cell portion and a peripheral circuit portion,
wherein the memory cell portion comprises:
a first insulating portion extending in a predetermined direction;
a capacitor including a lower electrode, a dielectric film, and an upper electrode sequentially formed on a side surface of the first insulating portion which is parallel to the predetermined direction;
a plate electrode electrically connected to the upper electrode; and
a transistor including a source region and a drain region one of which is electrically connected to the lower electrode, and
the peripheral circuit portion comprises:
a plate electrode extending in the same direction as the predetermined direction;
a capacitor including an upper electrode, a dielectric film, and a lower electrode sequentially formed on a side surface of the plate electrode which is parallel to the predetermined direction; and
a transistor including a source region and a drain region one of which is electrically connected to the lower electrode.
In another embodiment, there is provided a method of manufacturing a semiconductor memory device, the method comprising:
forming a transistor and a contact plug in a memory cell portion forming region and a peripheral circuit portion forming region, the contact plug being electrically connected to one of a source region and a drain region of the transistor;
depositing an interlayer insulating film all over the memory cell portion forming region and the peripheral circuit portion forming region;
forming a plurality of first openings in the interlayer insulating film in the memory cell portion forming region such that the contact plug is exposed, and forming a second opening in the interlayer insulating film in the peripheral circuit portion forming region so as to enclose a predetermined region and to expose the contact plug;
depositing a conductive material on an inner wall of each of the first and second openings so as to leave an opening portion unfilled, to form a lower electrode;
filling an insulating material in each of the first openings with the lower electrode formed therein, to form a first insulating portion, and filling an insulating material into the second opening with the lower electrode formed therein;
removing the interlayer insulating film from the memory cell portion forming region and removing the interlayer insulating film composing the predetermined region in the peripheral circuit portion forming region to form a third opening;
depositing a dielectric film so as to cover a surface of the lower electrode in the memory cell portion forming region with the dielectric film and to cover an inner wall of the third opening in the peripheral circuit portion forming region with the dielectric film;
filling a conductive material, in the memory cell portion forming region, between the first insulating portions each formed with the dielectric film and the lower electrode, to form an upper electrode, and depositing a conductive material in the third opening so as to leave an opening portion unfilled in the peripheral circuit portion forming region to form an upper electrode; and
forming a plate electrode in the memory cell portion forming region such that the plate electrode is electrically connected to the upper electrode, and filling a conductive material into the opening portion of the third opening in the peripheral circuit portion forming region to form a plate electrode.
In another embodiment, there is provided a semiconductor memory device comprising:
a memory cell portion including a plurality of first capacitors, each of the first capacitors including a first lower electrode formed along a first insulating wall, a first upper electrode, and a first dielectric film formed between the first lower electrode and the first upper electrode; and
a peripheral circuit portion including at least one second capacitor, the second capacitor including a second lower electrode formed along a second insulating wall, a second upper electrode, and a second dielectric film formed between the second lower electrode and the second upper electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing a step of an example of a method of manufacturing a semiconductor memory device according to the present invention;

FIG. 2 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 3 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 4 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 5 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 6 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 7 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 8 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 9 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention;

FIG. 10 is a diagram showing a step of the example of the method of manufacturing the semiconductor memory device according to the present invention; and

FIG. 11 is a diagram showing a related semiconductor memory device.

In the drawings, numerals have the following meanings. 1: interlayer insulating film, 2: tungsten plug, 3: silicon nitride film, 4: interlayer insulating film, 5: photo resist, 6: capacitance pattern, 7: groove pattern, 8: capacitance pattern, 9: capacitive lower electrode TiN film, 10: silicon nitride film, 11: photo resist, 12: memory cell portion wet cutting pattern, 13: peripheral circuit portion wet cutting pattern, 14: peripheral circuit portion capacitive lower electrode, 15: capacitive film, 16: capacitive upper electrode, 17: capacitive plate electrode, 18: photo resist, 19: capacitive electrode pattern, 23: first opening, 24: second opening, 26: predetermined region, 27: third opening, 101: interlayer insulating film, 102: tungsten plug, 103: silicon nitride film, 104: interlayer insulating film, 105: capacitive lower electrode, 106: wet damage, 107: pattern collapse, 200: silicon substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes.
FIG. 10 is a diagram showing an example of a semiconductor memory device including a DRAM. FIG. 10A is a top view of a semiconductor memory device. FIG. 10B is a sectional view of the semiconductor memory device taken along direction A-A′ in FIG. 10A. The semiconductor memory device in the present example includes a transistor electrically connected to a capacitor. However, in FIG. 10, the transistor is omitted.
As shown in FIG. 10A, the left side, in the figure, of the semiconductor memory device in the present example corresponds to a memory cell portion. The right side corresponds to a peripheral circuit portion. Dummy groove pattern 7 is formed at the boundary between the memory cell portion and the peripheral circuit portion so as to enclose the memory cell portion. Dummy groove pattern 7 forms a boundary portion.
A plurality of pillar capacitors 6 are formed in the memory cell portion. As shown in FIG. 10B, each of capacitors 6 is composed of first insulating portion 30 extending in predetermined direction 28, and lower electrode 9, dielectric film 15, and upper electrode 16 sequentially formed on a side surface of the first insulating portion which is parallel to predetermined direction 28, and plate electrode 17 electrically connected to upper electrode 16. The first insulating portion is shaped like a pillar. The pillar shape of the first insulating portion allows dielectric film 15 and upper electrode 16 to be easily formed on the side surface thereof. The pillar shape also enables an increase in the contact area between the first insulating portion and dielectric film 15.
A plurality of first insulating portions 30 each with lower electrode 9, dielectric film 15, and upper electrode 16 sequentially formed on the side surface thereof are arranged at regular intervals in particular direction 20. A plurality of first insulating portions 30 compose array of first insulating portions 30. The memory cell portion has a plurality of arrays of first insulating portions 30. The adjacent arrays are arranged such that the first insulating portions in one array are staggered with respect to the first insulating portions in the other array. A conductive material is filled between the first insulating portions each with the lower electrode and the dielectric film formed on the side surface thereof to make up upper electrode 16. Arranging the first insulating portions in this manner allows the capacitors to be formed at a high density per unit area. This allows for refinement.
Furthermore, one of a source region and a drain region of a transistor (not shown in the FIGS) is electrically connected to lower electrode 9. The transistor may be a planar-type transistor or a Fin-type transistor. A semiconductor substrate 200 is formed under the lower electrode 9. One transistor and one capacitor make up one memory cell in a DRAM (Dynamic Random Access memory). In the DRAM, information can be stored in capacitor 6 by expressing a state in which charge is accumulated and a state in which no charge is accumulated, as two values.
The peripheral circuit portion includes at least one cylinder capacitor. FIG. 10A shows an example in which the peripheral circuit portion includes two capacitors. Each of the capacitors includes plate electrode 17 extending in the same direction as predetermined direction 28, and upper electrode 16, dielectric film 15, and lower electrode 9 sequentially formed on a side surface of plate electrode 17 which is parallel to predetermined direction 28. The capacitors and transistors in the peripheral circuit portion can be used as, for example, a miniaturized voltage compensating circuit for stabilizing voltage.
Plate electrode 17 is shaped like a rectangular parallelepiped. The rectangular parallelepipedic shape of plate electrode 17 allows the areas of upper electrode 16 and lower electrode 9 to be increased, while ensuring sufficient miniaturization. Furthermore, lower electrode 9 is formed on an inner wall of an opening formed so as to cover dielectric film 15. Lower electrode 9 makes up a recessed structure. A part of lower electrode 9 is in contact with dielectric film 15. Insulating material 10 is filled in the recessed structure making up the lower electrode. Moreover, one of the source and drain regions of the transistor (not shown in the FIGS) is electrically connected to lower electrode 9. The transistor may be a planar-type transistor or a Fin-type transistor. A semiconductor substrate 200 is formed under the lower electrode 9.
Boundary portion 7 is formed between the memory cell portion and the peripheral circuit portion. Boundary portion 7 includes conductive material film 21 formed on an inner wall of an opening extending in the same direction as predetermined direction 28, and second insulating portion 22 filled in the opening.
A constituent material for the first insulating portion of the memory cell portion, insulating material 10 of the peripheral circuit portion, and the second insulating portion of the boundary portion is not particularly limited provided that the material offers an insulating property. However, silicon nitride is preferably used. A constituent material for upper electrode 16 and lower electrode 9 in the memory cell portion and peripheral circuit portion is not particularly limited provided that the material is conductive. However, TiN is preferably used.
Thus, in the semiconductor memory device in the present example, the pillar capacitor is formed in the memory cell portion. The cylinder capacitor is formed in the peripheral circuit portion. In the memory cell portion and the peripheral circuit portion, after lower electrode 9 is formed, insulating material 10 is filled inside lower electrode 9 (the interior of the recessed structure). This enables problems that may occur during the subsequent steps to be avoided: for example, during wet etching, an etchant may permeate the inside of lower electrode 9 to etch an unexpected region. As a result, the memory cell portion and the peripheral circuit portion can be prevented from being improperly formed.
Furthermore, the first insulating portion is present inside the lower electrode of the memory cell portion. Thus, the first insulating portion serves as a support to improve the strength of the lower electrode. As a result, the lower electrode can be prevented from being collapsed. Moreover, in the peripheral circuit portion, the lower electrode, the dielectric film, and the upper electrode are sequentially formed on the side surface of the plate electrode. This enables an increase in the areas of the lower and upper electrodes, while enabling a reduction in the area occupied by the capacitor to ensure sufficient miniaturization.
Now, with reference to FIGS. 1 to 10, an example of a method of manufacturing a semiconductor memory device according to the present exemplary embodiment will be described.
First, a transistor (not shown in the FIGS) was formed in a memory cell portion forming region and a peripheral circuit portion forming region. Then, interlayer insulating film 1 was formed all over the resulting surface. Then, as shown in FIG. 1, a semiconductor substrate was prepared. The contact plugs 2 were formed in interlayer insulating film 1 so as to be electrically connected to one of the source and drain regions of the transistor. Silicon nitride film 3 was then deposited to a thickness of 30 nm to 100 nm by an LP-CVD method. Silicon oxide film 4 was deposited to a thickness of 0.5 μm to 1.5 μm as an interlayer insulating film by a plasma CVD method. A photo resist was then formed on silicon oxide film 4. Photo resist pattern 5 was thereafter formed using a lithography method.
Then, as shown in FIG. 2, a plasma dry etching technique was used to form a plurality of cylindrical first openings 23 in interlayer insulating film 4 in the memory cell portion forming region through photo resist pattern 5 as a mask so that contact plugs 2 were exposed in interlayer insulating film 4 in the memory cell portion forming region. At this time, the first openings were formed such that a plurality of arrays of the first openings were arranged at regular intervals in a particular direction and such that the first openings in one of the adjacent arrays were staggered with respect to the first openings in the other array. Simultaneously with the formation of the first openings, second opening 24 was formed in interlayer insulating film 4 in the peripheral circuit portion forming region so as to enclose rectangular parallelepipedic predetermined region 26 and to expose the contact plug. In this step, the first and second openings were formed to extend in predetermined direction 28. Thereafter, photo resist pattern 5 was removed.
Then, as shown in FIG. 3, TiN film 9 was deposited all over the resulting surface to a thickness of 5 nm to 30 nm by a thermal CVD method using a TiCl₄gas. At this time, TiN film 9 was formed in each of the first and second openings so as to leave an opening portion unfilled. Thereafter, the TiN film on interlayer insulting film 4 was removed by the dry etching technique to form lower electrode 9 on an inner wall of each of the first and second openings.
Then, as shown in FIG. 4, silicon nitride film 10 was deposited all over the resulting surface to a thickness of 10 to 50 nm by the LP-CVD method. Silicon nitride 10 was thus buried inside the first and second openings. At this time, first insulating portion 30 was formed in each of the first openings. Then, a photo resist was formed on silicon nitride film 10.
Thereafter, photo resist pattern 11 was formed using the lithography method so that the memory cell portion forming region had cutting pattern 12, whereas the peripheral circuit portion forming region had cutting pattern 13. FIG. 5A is a top view showing this condition. FIG. 5B is a sectional view showing a cross section taken along direction A-A′ in FIG. 5A. FIGS. 6 to 9 also show cross sections taken along the direction A-A′ in FIG. 5A.
As shown in FIG. 5, the cutting pattern 12 was formed in the peripheral circuit portion forming region. In the subsequent steps, the exposed silicon nitride 10 was etched by film thickness thereof using the photo resist pattern 11 as a mask, to form the first insulating portions 30. This etching simultaneously leaved a beam made of the silicon nitride 10 connecting a plurality of capacitors 6 on upper surface of the lower electrode 9 in the memory cell portion forming region. As a result, the capacitor 6 can be prevented from being collapsed when the silicon oxide 4 in the memory cell portion forming region is removed in the subsequent steps.
Then, as shown in FIG. 6, silicon nitride film 10 was removed through photo resist pattern 11 as a mask by the plasma dry etching method, to expose silicon oxide film 4.
Thereafter, as shown in FIG. 7, wet etching using a diluted hydrofluoric acid was performed, which exhibits a higher etching rate for silicon oxide film 4 than for silicon nitride film 10. That is, in the memory cell portion forming region, silicon oxide film 4 was removed. In the peripheral circuit portion forming region, silicon oxide film 4 making up predetermined region 26 was removed to form a third opening (reference numeral 27). As a result, in the memory cell portion forming region, an outer wall of each of lower electrodes 9 was exposed. In the peripheral circuit portion forming region, the third opening enclosed by lower electrodes 9 was exposed.
Then, as shown in FIG. 8, dielectric film 15 was sequentially deposited all over the resulting surface. As a result, dielectric film 15 was formed to cover the surfaces of the lower electrodes in the memory cell portion forming region, while covering lower electrode 9 making up an inner wall of the third opening in the peripheral circuit portion forming region. Thereafter, TiN film 16 was deposited all over the resulting surface to a thickness of 10 nm to 30 nm. At this time, in the memory cell portion forming region, TiN was filled between the first insulating portions each formed with dielectric film 15 and lower electrode 9, to form upper electrode 16. At the same time, in the peripheral circuit portion forming region, a TiN film was deposited on the inner wall of the third opening so as to leave an opening portion unfilled, to form the upper electrode.
Thereafter, as shown in FIG. 9, tungsten film 17 was deposited all over the resulting surface. As a result, in the memory cell portion forming region, plate electrode 17 was formed on upper electrode 16. In the peripheral circuit portion forming region, plate electrode 17 was formed so as to fill the opening portion of predetermined region 26. Photo resist pattern 18 with a predetermined pattern was thereafter formed on tungsten film 17.
Then, as shown in FIG. 10, plasma dry etching was performed through photo resist pattern 18 as a mask to process plate electrode 17 and upper electrode 16 so as to prevent the communication between plate electrode 17 and upper electrode 16, between the memory cell portion forming region and the peripheral circuit portion forming region.
Thus, the semiconductor memory device in the present example was successfully formed.
It is apparent that the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention.

Claims

1. A device comprising:

an insulating pillar that includes an upper surface, a bottom surface and a side surface between the upper and bottom surfaces;

a first conductive film including a first portion formed on the bottom surface of the insulating pillar and a second portion continuously elongated from the first portion to cover the side surface of the insulating pillar;

an insulating film formed on the second portion of the first conductive film; and

a second conductive film formed on the insulating film;

the first and second conductive films and the insulating film therebetween serving as first and second electrodes and a dielectric film therebetween of a capacitor, respectively.

2. The device as claimed in claim 1, wherein the insulating film is elongated over the upper surface of the insulating pillar beyond a tip portion of the second portion to provide an elongated portion, and the second conductive film extends over the elongated portion of the insulating film.

3. The device as claimed in claim 1, further comprising a conductive plug selectively formed in a first insulating layer, the first portion of the first conductive film being in contact with the conductive plug.

4. The device as claimed in claim 3, further comprising a second insulating film formed between the insulating film and a portion of the first insulating layer around the conductive plug.

5. The device as claimed in claim 4, wherein the insulating pillar is same in material with the second insulating film.

6. A device comprising:

an interlayer insulating layer;

a plurality of conductive plugs formed in the interlayer insulating layer apart from one another; and

a plurality of capacitors each formed in contact with an associated one of the conductive plugs;

wherein each of the capacitors comprises:

a lower electrode including a bottom portion and a pipe portion, the bottom portion including a first main surface and a second main surface opposite to the first main surface, the first main surface being in contact with a part of the associated one of the conductive plugs, the second main surface including a first part and a second part surrounding the first part, the pipe portion protruding upwardly from the second part of the second main surface of the bottom portion;

an insulating pillar protruding upwardly from the first part of the second main surface of the bottom portion of the first electrode to fill an inside of the pipe portion of the first electrode;

a dielectric film formed on an outside surface of the pipe portion of the first electrode; and

a second electrode formed on the dielectric film.

7. The device as claimed in claim 6, wherein the second electrodes of the capacitors are in contact with one another to form a plate electrode.

8. The device as claimed in claim 7, wherein the insulating pillars of the capacitors are formed separately from one another.

9. The device as claimed in claim 6, wherein the dielectric film of each of the capacitors is elongated over a top portion of the insulating pillar beyond a tip end of the pipe portion of the first electrode to form an elongated portion; and the second electrode extends to cover the elongated portion of the dielectric film.

10. The device as claimed in claim 9, wherein the insulating pillars of the capacitors are formed separately from one another, and the second electrodes of the capacitors are in contact with one another to form a plate electrode.

11. The device as claimed in claim 6, wherein the dielectric films of the capacitors are formed continuously with one another to form a continuous dielectric film and the second electrodes of the capacitors are formed continuously with one another to form a plate electrode.

12. The device as claimed in claim 11, further comprising an etching stopper film formed around the bottom portions of the first electrodes of the capacitors to intervene between the interlayer insulating layer and the continuous dielectric layer, the etching stopper film and the continuous dielectric layer intervening between the interlayer insulating layer and the plate electrode.

13. A device comprising:

a substrate;

an interlayer insulating layer over the substrate; and

a memory cell array comprising a plurality of word lines, a plurality of bit lines, a plurality of memory cells each disposed a different one of intersections of the word and bit lines, a plate electrode, and a plurality of conductive plugs selectively formed in the interlayer insulating layer, each of the memory cells comprising a transistor and a capacitors:

wherein the transistor of each of the memory cells comprises:

a first diffusion region connected to an associated one of the bit lines,

a second diffusion region connected to an associated one of the conductive plugs, and

a gate electrode connected an associated one of the word lines; and

wherein the capacitor of each of the memory cells comprises:

an insulating pillar extending vertically,

a lower electrode including a first portion sandwiched between the insulating pillar and an associated one of the conductive plugs in contact with the insulating pillar and the associated one of the conductive plugs, and a second portion elongated from the first portion vertically along the insulating pillar, and

a dielectric film formed between the second portion of the lower electrode and the plate electrode.

14. The device as claimed in claim 13, wherein the first and second portions of the lower electrode cooperate with each other to continuously surround a substantial whole of a side surface of the insulating pillar with keeping a top portion of the insulating pillar uncovered.

15. The device as claimed in claim 14, wherein the dielectric films of the capacitors are formed continuously with one another to cover the top portion of the insulating pillar of each of the capacitors.

16. The device as claimed in claim 15, further comprising an insulating film formed on portions of the interlayer insulating layer among the first portions of the first electrodes of the capacitors to intervene between the dielectric film and the portions of the interlayer insulating layer.

17. The device as claimed in claim 16, wherein the insulating film is same in material with the insulating pillar.

18. The device as claimed in claim 17, wherein the insulating film comprises a silicon nitride film and the insulating pillar also comprises a silicon nitride film.