KR100728983B1 - Phase change ram device and method of manufacturing the same - Google Patents

Abstract

A phase change RAM device and its fabricating method are provided to increase the effect of shielding heat radiation from a phase change layer by securing an empty space on a side and lower portion of the phase change layer. A lower electrode(53) is formed in a protruded plug shape in insulation layers(51) of a semiconductor substrate(50). A phase change layer(55) is formed on the lower electrode. An upper electrode(56) is formed in a pattern shape on the phase change layer, and has a size larger than the lower electrode. An interlayer dielectric(57) is formed on the insulation layers to cover the stack patterns, in which a spaces between the stack patterns are not buried.

Description

Phase change RAM device and method of manufacturing the same

1 to 3 are cross-sectional views showing conventional phase change memory elements.

4 is a cross-sectional view showing a phase change memory device according to an embodiment of the present invention.

5A through 5E are cross-sectional views illustrating processes of manufacturing a phase change memory device according to an embodiment of the present invention.

6 is a sectional view showing a phase change memory device according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

40: semiconductor substrate 41: insulating film

42: insulating film for etching stop 43: lower electrode

55: phase change film 46: upper electrode

47: interlayer insulating film 48: protective insulating film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change memory element, and more particularly, to a phase change memory element capable of suppressing thermal diffusion from a phase change film and reducing a current required for phase change, and a manufacturing method thereof.

The memory device is a volatile random access memory (RAM) device that loses input information when the power is cut off, and a read only memory (ROM) device that maintains the storage state of the input information even when the power is cut off. It is largely divided. The volatile RAM devices may include DRAM and SRAM, and the nonvolatile ROM devices may include flash memory devices such as EEPROM (Elecrtically Erasable and Programmable ROM). have.

However, although the DRAM has a very good memory device as is well known, high charge storage capability is required, and for this purpose, it is difficult to achieve high integration since the electrode surface area must be increased. In addition, the flash memory device requires a high operating voltage compared to a power supply voltage in connection with a structure in which two gates are stacked, and thus requires a separate boost circuit to form a voltage required for write and erase operations. Therefore, there is a difficulty in high integration.

Accordingly, many studies are being conducted to develop new memory devices having characteristics of the nonvolatile memory device and having a simple structure. For example, recently, a phase change RAM device has been developed. Was proposed.

The phase change memory device utilizes a difference in resistance between crystalline and amorphous phases due to the phase change of the phase conversion film interposed between the electrodes from the crystal state to the amorphous state through the current flow between the lower electrode and the upper electrode. It is a storage element for determining stored information. In other words, the phase conversion memory device uses a chalcogenide film as a phase conversion film. The chalcogenide film is a compound film made of germanium (Ge), stevidium (Sb), and tellurium (Te). A phase change occurs between an amorphous state and a crystalline state by heat generated by an applied current, that is, Joule heat, and at this time, the resistivity of the phase conversion film having an amorphous state is determined to be crystalline state. Since it is higher than the specific resistance of the phase change film having a value, the current flowing through the phase change film in the read mode is sensed to determine whether the information stored in the phase change memory cell is logic '1' or logic '0'.

On the other hand, in such a phase conversion memory device, the phase conversion film is in a crystalline state to an amorphous state, and a reset is called. In contrast, in the amorphous state to a crystalline state, a set is called. The lower the magnitude of the current for the / set (programming), the better. The magnitude of the current required for this phase change is closely related to the structure of the phase change memory device.

FIG. 1 is a partial cross-sectional view of a phase change memory device according to the related art. Referring to this, the phase change film 15 is connected to the lower electrode 13 through a small contact. When heat is transferred to the conversion film 15, a portion of the phase conversion film 15 of the contact region is changed. Unexplained reference numeral 10 denotes a semiconductor substrate, 11 denotes a first insulating layer, 12 denotes an electrical contact layer, 14 denotes a second insulating layer, 16 denotes an upper electrode, and 17 denotes a third insulating layer. Respectively.

However, in the structure as shown in FIG. 1, since the lower electrode 13 in the form of a plate is used as a heating film, the heat supplied to the phase conversion film 15 through the lower electrode 13 is again lowered. The problem is that the programming current is high because it is easily diffused through.

Accordingly, in order to compensate for the shortcomings of the phase change memory device employing the plate-shaped lower electrode, a technology of forming the lower electrode in the form of a plug rather than the plate is minimized to minimize the diffusion of heat supplied to the phase conversion film. It became.

As shown in FIG. 2, in the phase change memory device having a plug type lower electrode, the lower electrode 23 is formed in a plug shape in the first insulating film 21, and the phase change film 25 and the upper electrode ( Since the stacked pattern of 26 is formed on the first insulating layer 21 to be in contact with the lower electrode 23, the diffusion of heat is suppressed rather than the structure employing the plate-shaped lower electrode described above. Unexplained reference numeral 20 denotes a semiconductor substrate and 27 denotes a second insulating film.

However, even if the lower electrode is formed as a plug as shown in FIG. As in the structure of FIG. 1, the contact area between the phase change film and the upper electrode is relatively wider than the contact area between the phase change film and the lower electrode, and heat dissipation from the phase change film is easily performed. The problem is still high.

Accordingly, in order to reduce the contact area between the phase change film and the upper electrode and to suppress heat emission from the phase change film, a phase change memory device as shown in FIG. 3 has been proposed.

In the phase change memory device shown in FIG. 3, the phase change material film and the upper electrode conductive film are successively patterned, and at the edge of the upper electrode conductive film, that is, at the edge of the upper electrode 36, patterned when the phase change material film is patterned. After the phase change material film is under-cut, the second insulating film 37 is formed by a process having poor step coverage such as PVD (Physical Vaporization Deposition). 36) reduces the contact area between the phase conversion film 35 and suppresses the diffusion of heat through the under-cut space.

As illustrated, before forming the second insulating layer 37, a step such as atomic layer deposition (ALD) on the surface of the first insulating layer 31 including the phase change layer 35 and the upper electrode 36 is formed. A protective insulating film 38 having a uniform thickness may be additionally formed through a process having excellent coating property. Meanwhile, reference numeral 30 denotes a semiconductor substrate and 33 denotes a lower electrode, respectively.

When the phase change memory device having the structure shown in FIG. 3 is manufactured, the size of the phase change layer 35 is reduced while the size of the upper electrode 36 remains the same as in the prior art. Since the contact area of the phase conversion film 35 can be secured by forming an empty space around the phase conversion film 35, the current required for programming can be reduced.

However, in the phase change memory device having the structure as shown in FIG. 3, empty spaces are formed only in the lateral direction of the phase change film 35, and the lower surfaces of the phase change film 35 are the lower electrode 33 and the first insulating film 31. Since both are covered by), thermal diffusion is prevented to some extent in the lateral direction of the phase conversion film 35, while thermal diffusion is easily performed in the downward direction, thereby limiting the programming current.

On the other hand, as another embodiment of the proposed invention of the structure of FIG. 3, the structure of making the size of the phase conversion film 35 smaller than that of the lower electrode 33 is also presented, but the plug-type lower electrode having a diameter of 100 nm or less ( 33) It is practically difficult to leave the phase change material film below 100 nm on the surface. This is because the position of the phase change film 35 remaining when the etching rate of the phase change material film is not uniform even along the direction is deviated from the lower electrode 35 of the plug type. When patterning the conductive film for the upper electrode, if a mis-alignment occurs due to inaccuracy in the exposure process, the probability of occurrence is higher.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, the phase that can reduce the current required for the phase change by reducing the contact area between the phase conversion film and the electrode and suppress the thermal diffusion from the phase conversion film It is an object of the present invention to provide a conversion memory device and a method of manufacturing the same.

In order to achieve the above object, the present invention provides a semiconductor substrate including an insulating film; A plug type lower electrode formed in the insulating film and having an upper end protruded; A phase conversion film formed on the lower electrode; An upper electrode formed on the phase conversion layer and having a pattern size larger than that of the lower electrode; And an interlayer insulating film formed on the insulating film to cover the stacked pattern without filling a space between the stacked pattern of the phase conversion film and the upper electrode and the insulating film.

Here, the phase change film and the upper electrode are the same size, or the upper electrode has a size larger than the phase change film.

In addition, the phase conversion memory device of the present invention for achieving the above object, the insulating protective film formed in a uniform thickness on the insulating film including the protruding upper end surface of the lower electrode and the surface of the phase conversion film and the upper electrode. It includes more.

Meanwhile, a method of manufacturing a phase change memory device of the present invention for achieving the above object includes the steps of sequentially forming a first insulating film, an etch stop film and a second insulating film on a semiconductor substrate; Etching the second insulating layer, the etch stop layer and the first insulating layer to form a contact hole; Forming a plug type lower electrode in the contact hole; Sequentially forming a phase change material film and a conductive film on the second insulating film; Etching the conductive layer and the phase change material layer to form a stacked pattern of the phase change layer and the upper electrode having a size larger than that of the lower electrode; Etching an edge portion of the phase change film to form a first empty space between an upper electrode and an etch stop film; Etching the second insulating layer until the etch stop layer is exposed to form a second void space between the phase change layer and the etch stop layer; And forming an interlayer insulating layer on the etch stop layer to cover the stacked pattern of the phase change layer and the upper electrode without filling the first and second empty spaces.

Here, after forming the second empty space and before forming the interlayer insulating film, a protective insulating film having a uniform thickness is formed on the etch stop layer including the surface of the stacked pattern of the phase change film and the upper electrode. It further comprises the step.

In addition, a method of manufacturing a phase change memory device of the present invention for achieving the above object comprises the steps of sequentially forming a first insulating film, an etch stop film and a second insulating film on a semiconductor substrate; Etching the second insulating layer, the etch stop layer and the first insulating layer to form a contact hole; Forming a lower electrode in the contact hole; Sequentially forming a phase change material film and a conductive film on the second insulating film; Etching the conductive layer and the phase change material layer to form a stacked pattern of the phase change layer and the upper electrode having a size larger than that of the lower electrode; Etching the second insulating layer until the etch stop layer is exposed to form an empty space between the phase change layer and the etch stop layer; And forming an interlayer insulating layer on the etch stop layer to cover the stacked pattern of the phase change layer and the top electrode without filling the empty space between the top electrode and the etch stop layer.

The second insulating layer may be etched until the etch stop layer is exposed to form an empty space between the phase change layer and the etch stop layer, and before the forming of the interlayer insulating layer, before the phase change layer and the upper electrode. The method may further include forming a protective insulating film having a uniform thickness on the etch stop film including the stacked pattern surface of the film.

(Example)

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

4 is a cross-sectional view of a phase change memory device according to an embodiment of the present invention. Referring to this, the phase change memory device of the present invention is a predetermined substructure (not shown) such as a gate and a junction region (source / drain region). And an insulating film 41 made of an oxide film to cover the lower structure (not shown), and a semiconductor substrate 40 having an insulating film 42 for etching stop of nitride material formed on the insulating film 41; And a lower electrode 43 having a plug shape formed in the etch stop insulating film 42 and the insulating film 41 and having an upper end protruding therefrom, a phase conversion film 45 formed on the lower electrode 43, and the phase conversion. The upper electrode 46 having a pattern shape formed on the film 45 and having a size larger than that of the lower electrode 43 and the phase conversion layer 45, and the phase conversion layer 45 and the upper electrode 46 are stacked. The stacked pattern is covered without filling the empty space between the pattern and the etch stop insulating film 42. The interlayer insulating film 47 formed on the etch stop insulating film 42 is included.

In addition, the phase change memory device of the present invention has a uniform thickness on the etch stop insulating film 42 including the protruding upper surface of the lower electrode 43 and the surface of the phase conversion film 45 and the upper electrode 46. The insulating protective film 48 is further included.

Here, the insulating protective film 48 is a film formed by an ALD or CVD process having excellent step coverage, and is usually formed of a nitride film material to form the phase conversion film 45 and the upper and lower electrodes 43 and 45 when the interlayer insulating film 47 is formed. It serves to prevent the interfacial properties of the deterioration.

In addition, the insulating protective film 48 may be formed to a thickness of about 200 μm or less so that the empty space between the stacked pattern of the phase conversion film 45 and the upper electrode 46 and the etch stop insulating film 42 is not filled.

Meanwhile, in FIG. 4, the phase conversion film 45 is larger than the lower electrode 43 but smaller than the upper electrode 46. However, the present invention is not limited thereto, and the phase conversion film and the upper electrode are the same size. It can also be made to have However, when the phase conversion film and the upper electrode have the same size, since the empty space is secured only toward the lower surface of the phase conversion film, the size of the empty space which serves to suppress heat emission is larger than that of the structure shown in FIG. 4. Becomes smaller.

Hereinafter, a method of manufacturing a phase change memory device according to an embodiment of the present invention will be described with reference to FIGS. 5A to 5E.

5A through 5E are cross-sectional views illustrating processes of manufacturing a phase change memory device according to an exemplary embodiment of the present invention.

Referring to FIG. 5A, a predetermined substructure (not shown) such as a gate and a junction region (source / drain region) is formed, and a first insulating layer 51 is formed to cover the substructure (not shown). A semiconductor substrate 50 in which an etch stop insulating film 52 and a second insulating film 54 are sequentially stacked is formed on the first insulating film 51. The first and second insulating layers 51 and 54 may be formed of an oxide film, and the etch stop insulating layer 52 may be formed of a nitride film.

Referring to FIG. 5B, after forming the contact hole H by etching the second insulating film 54, the etch stop insulating film 52, and the first insulating film 51, a conductive film is buried in the contact hole H. Thus, the lower electrode 52 in the form of a plug is formed.

Then, a phase change material film and a conductive film are sequentially formed on the second insulating film 54, and the phase change film 55 having a size larger than that of the lower electrode 53 is etched by etching the conductive film and the phase change material film. A stack pattern of the upper electrode 56 is formed.

Referring to FIG. 5C, the edge portion of the phase conversion layer 55 is etched to form a first empty space V1 between the upper electrode 56 and the etch stop insulating layer 52.

Referring to FIG. 5D, the second insulating layer is etched until the etch stop insulating layer 52 is exposed to form a second empty space V2 between the phase change layer 55 and the etch stop insulating layer 52.

Referring to FIG. 5E, a protective insulating film 58 having a uniform thickness is formed on the etch stop insulating film 52 including the surface of the stacked pattern of the phase change film 55 and the upper electrode 56.

Here, the protective insulating film 58 is preferably formed of a nitride film, and is formed to a thickness not filling the first and second empty spaces (V1, V2).

Then, the interlayer insulating film (ie, covering the stacked pattern of the phase conversion film 55 and the upper electrode 56 without filling the first and second voids V1 and V2 on the protective insulating film 58). 57).

As described above, the present invention not only forms an empty space in the lateral direction of the phase conversion film 55 by etching the edge portion of the patterned phase conversion film, but also allows the upper end of the plug type lower electrode 53 to protrude. By making an empty space also in the lower direction of 55, it is possible to increase the heat dissipation blocking effect by the empty space, thereby lowering the programming current.

Meanwhile, in the above-described exemplary embodiment of the present invention, the edge portion of the patterned phase conversion film is etched to form the first empty space V1 in the lateral direction of the phase conversion film 55, and then the plug type lower electrode 53. Although protruding the upper end of the to form a second empty space (V2) in the lower direction of the phase conversion film 55, in another embodiment of the present invention by skipping the edge portion etching step of the phase conversion film, Figure 6 As illustrated, a phase change memory device may be manufactured in which an empty space is formed only in the downward direction of the phase change film 55. At this time, the process after protruding the upper end of the lower electrode 54 and the conditions thereof are the same as those of the above-described embodiment. However, when the empty space is made only in the downward direction of the phase change film 55 as shown in FIG. 6, the volume of the empty space is reduced than that of FIG.

Hereinbefore, the present invention has been described with reference to some examples, but the present invention is not limited thereto, and a person having ordinary skill in the art to which the present invention belongs does not depart from the essential idea of the present invention. It will be appreciated that it can be implemented in a modified form.

As described above, according to the present invention, in the manufacture of the phase conversion memory element, the void space is secured not only in the side direction of the phase conversion film but also in the downward direction, thereby preventing the heat emission blocking effect from the phase conversion film due to the empty space. It can be increased to reduce the amount of current required during programming.

Claims (7)

A semiconductor substrate on which an insulating film is formed; A plug type lower electrode formed in the insulating film and having an upper end protruded; A phase conversion film formed on the lower electrode; An upper electrode formed on the phase conversion layer and having a pattern size larger than that of the lower electrode; And An interlayer insulating film formed on the insulating film to cover the stacked pattern without filling a space between the stacked pattern of the phase conversion film and the upper electrode and the insulating film; Phase change memory device comprising a. The method of claim 1, And the upper electrode has the same size, or the upper electrode has a larger size than the phase converting film. The method of claim 1, And an insulating protective film having a uniform thickness on an insulating film including a protruding upper end surface of the lower electrode, a phase conversion film, and a surface of the upper electrode. Sequentially forming a first insulating film, an etch stop film, and a second insulating film on the semiconductor substrate; Etching the second insulating layer, the etch stop layer and the first insulating layer to form a contact hole; Forming a plug type lower electrode in the contact hole; Sequentially forming a phase change material film and a conductive film on the second insulating film; Etching the conductive layer and the phase change material layer to form a stacked pattern of the phase change layer and the upper electrode having a size larger than that of the lower electrode; Etching an edge portion of the phase change film to form a first empty space between an upper electrode and an etch stop film; Etching the second insulating layer until the etch stop layer is exposed to form a second void space between the phase change layer and the etch stop layer; And Forming an interlayer insulating layer on the etch stop layer to cover the stacked pattern of the phase change layer and the upper electrode without filling the first and second empty spaces; A method for manufacturing a phase change memory device comprising a. The method of claim 4, wherein Forming a protective insulating film having a uniform thickness on the etch stop layer including the surface of the stacked pattern of the phase change film and the upper electrode after the forming of the second empty space and before forming the interlayer insulating film. The method of manufacturing a phase conversion memory device characterized in that it further comprises. Sequentially forming a first insulating film, an etch stop film, and a second insulating film on the semiconductor substrate; Etching the second insulating layer, the etch stop layer and the first insulating layer to form a contact hole; Forming a lower electrode in the contact hole; Sequentially forming a phase change material film and a conductive film on the second insulating film; Etching the conductive layer and the phase change material layer to form a stacked pattern of the phase change layer and the upper electrode having a size larger than that of the lower electrode; Etching the second insulating layer until the etch stop layer is exposed to form an empty space between the phase change layer and the etch stop layer; And Forming an interlayer insulating layer on the etch stop layer to cover the stacked pattern of the phase change layer and the top electrode without filling the empty space between the top electrode and the etch stop layer; A method for manufacturing a phase change memory device comprising a. The method of claim 7, wherein The second insulating layer is etched until the etch stop layer is exposed to form an empty space between the phase change layer and the etch stop layer, and before the forming of the interlayer insulating layer, the phase conversion layer and the upper electrode are stacked. And forming a protective insulating film having a uniform thickness on the etch stop film including the pattern surface.

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