JP2000164545A - Polishing method of platinum metal film and cell forming method of semiconductor storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a platinum metal film to be formed into a fine pattern and easily flattened in a short time by a method wherein a polished part of a platinum metal film provided to a work is converted into compound of high reactivity, and the converted part to be polished is polished through a chemical and mechanical polishing method. SOLUTION: An Ru film 16 except the inside of an opening 14 is chloridized into an RuClx, 17 by heating it at a temperature of approximately 500 deg.C or above in a Cl2 atmosphere. At this point, it is preferable that a protective film of SiO2 or the like is selectively deposited on an Ru surface inside the opening 14 so as to prevent a chloridizing reaction from occurring. Thereafter, the RuClx 17 and a TiN/Ti film 15 are polished through a chemical mechanical polishing method with slurry which contains hydrochloric acid as solvent that dissolves the RuClx 17 to be removed from a second interlayer insulating film 12, and the Ru film 16 and the TiN/Ti film 15 are left only inside the opening 14 to serve as a lower electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method for polishing a platinum group metal film by a chemical mechanical polishing method (hereinafter abbreviated as CMP method), and an electrode comprising the platinum group metal film. The present invention relates to a method for forming a cell of a semiconductor memory device.

[0002]

2. Description of the Related Art In recent years, high integration of integrated circuit elements has been progressing.
In memory cells, in particular, the progress of high integration has been remarkable in order to cope with an increase in storage capacity. Therefore, instead of the conventional silicon oxide (SiO ₂ ), PZT (Pd (Zr, Ti) O ₃ , which has a high dielectric constant and polarization characteristics, is used as a material for forming a capacitive insulating film forming a part of a memory cell. ) -Based ferroelectric thin films and BST ((Ba, Sr) TiO ₃ ) -based high-dielectric thin films, and studies on applying them to DRAM capacitors and nonvolatile memories are being actively conducted. In this nonvolatile memory, there is a disadvantage that the charge retention characteristics and the like of the film are deteriorated when rewriting data is repeated. This is called fatigue of the film. In order to prevent the deterioration of the film, improvements have been made to the high dielectric material and the ferroelectric material which constitute the film.

On the other hand, the improvement of the electrode material which is in contact with both surfaces of the film has been actively carried out. Since ferroelectrics and high dielectrics are metal oxides, they also tend to oxidize the metal of the electrode material in contact with both surfaces. for that reason,
A platinum group metal film having high oxidation resistance is used as an electrode. At present, platinum (Pt) and ruthenium (Ru) are used as platinum group metals used as electrodes, and the use of iridium (Ir) and the like is being studied.

[0004] Here, the cell used so far is a stack type, and a platinum group metal for a lower electrode has been patterned by dry etching using a chlorine-based gas. 4A to 4D are cross-sectional views showing a conventional process. After forming a wiring 43 by burying polysilicon as a wiring in a buried groove formed in the underlying silicon oxide film 41, a platinum-based metal film 42 serving as a lower electrode is deposited thereon by sputtering or CVD. Thereafter, the platinum-based metal film 42 is patterned by dry etching to form a lower electrode 44. And
A high dielectric film 4 composed of, for example, BST on a substrate
After depositing 5, an upper electrode film 46 is further deposited thereon to form a cell.

[0005]

However, the above-mentioned conventional method has the following problems.

In recent years, cells for 1 gigabit DRAMs have become extremely fine. In the conventional stacked cell structure, a pattern is formed from a platinum group metal film 42 for a base electrode to a lower electrode 44 by dry etching. Is difficult. For this reason, studies are being made toward a trench cell structure. In this trench type cell structure, an oxide film (for example, a silicon oxide film) which is an interlayer insulating film
In order to form an opening such as a buried groove, a conventional dry etching process can be applied. Further, since it is not necessary to dry-etch the platinum group metal film for the lower electrode, it is advantageous for forming a finer pattern than the conventional stacked cell structure.

However, in the process of forming the trench type cell, a platinum group metal film is deposited in the opening formed in the interlayer insulating film and on the interlayer insulating film, and then flattened by the CMP method to form the inside of the opening. Requires a step of embedding a platinum group metal film into the substrate, but at this time, there is a problem that the platinum group metal has poor chemical reactivity and is difficult to be planarized by the CMP method.

[0008] An object of the present invention is to form a fine pattern and use a conventional polishing slurry to form C
An object of the present invention is to provide a method of polishing a platinum group metal film and a method of forming a cell of a semiconductor memory device, which can easily perform planarization by the MP method in a short time.

[0009]

According to a first aspect of the present invention, there is provided a method for polishing a platinum group metal film, comprising: converting a polished portion of a platinum group metal film provided on a workpiece into a highly reactive compound; Characterized by being polished by a mechanical polishing method.

[0010] Examples of highly reactive compounds include halogenated metal halides, sulfurized metal sulfides, and oxidized metal oxides.

According to the method for polishing a platinum group metal film according to any one of the first to fourth aspects of the present invention, the polishing portion of the platinum group metal film provided on the workpiece is made of a highly reactive compound (metal halide, metal sulfide, The conversion to (metal oxide) facilitates polishing, and planarization by the CMP method can be easily performed in a short time using a commercially available polishing slurry.

According to a fifth aspect of the present invention, in the method of polishing a platinum group metal film, a polishing slurry is supplied between the polishing pad and a portion to be polished of the platinum group metal film, and the polishing slurry is supplied between the polishing pad and the workpiece. The method is characterized in that a polishing pad and a workpiece are relatively rotated while applying pressure to polish a portion to be polished of a platinum group metal film.

According to the method for polishing a platinum group metal film according to the fifth aspect, a commercially available polishing slurry can be obtained by converting a platinum group metal film having poor chemical reactivity into a compound having higher reactivity. By using it, the platinum group metal film can be easily and quickly removed.

According to a sixth aspect of the present invention, in the method for polishing a platinum group metal film, the polishing of the platinum group metal film may be performed by polishing all the polished portions of the platinum group metal film, and the polishing rate may be different. Is terminated when the image is exposed.

According to the method for polishing a platinum group metal film according to claim 6, when the platinum group metal film converted into a highly reactive compound is completely polished, the platinum group metal having a low polishing rate is removed. Exposure will cause CMP to end spontaneously.

According to a seventh aspect of the present invention, in the polishing method for a platinum group metal film according to the fifth or sixth aspect, the platinum group metal film converted into a highly reactive compound is soluble in the polishing slurry. It is characterized by using a suitable solvent.

According to the method for polishing a platinum group metal film according to the present invention, the platinum group metal film is converted into a compound having a higher reactivity, so that after the conversion without using a special polishing slurry. By using a commercially available polishing slurry in which a solvent in which the compound is soluble is used, the platinum group metal film can be easily and quickly removed.

According to a eighth aspect of the present invention, in the method of forming a cell of a semiconductor memory device, an interlayer insulating film is deposited on a substrate having a conductor portion,
An opening reaching at least a part of the conductor is formed in the interlayer insulating film, a platinum group metal film is deposited in the opening and on the interlayer insulating film, and the platinum group metal film other than the inside of the opening is reactive. And remove the platinum group metal film converted to a highly reactive compound until the interlayer insulating film is exposed by chemical mechanical polishing, and leave the platinum group metal film in the opening. A lower electrode is formed, a dielectric film is deposited on the lower electrode, and an upper electrode film is deposited on the dielectric film.

According to the method of forming a cell of a semiconductor memory device of the present invention, a trench type cell having a platinum group metal film as a lower electrode is formed, and a fine pattern of the platinum group metal film can be formed. Thus, a cell of a semiconductor memory device suitable for high integration can be formed.

According to a ninth aspect of the present invention, in the method of forming a cell for a semiconductor memory device according to the eighth aspect, a solvent in which a platinum group metal film converted into a highly reactive compound is soluble is used as the polishing slurry. It is characterized by the following.

According to the method for forming a cell of a semiconductor memory device according to the ninth aspect, the platinum group metal film is converted into a compound having a higher reactivity, so that the converted metal can be used without using a special polishing slurry. By using currently commercially available polishing slurries in which a solvent in which the compound is soluble is used,
The platinum group metal film can be easily and quickly removed.

[0022]

1 to 3 show a method of polishing a platinum group metal film and a method of forming a cell of a semiconductor memory device according to the present invention.
This will be described with reference to FIG.

FIGS. 1 (a) to 1 (d) and FIGS. 2 (a) to 2 (c)
FIG. 4 is a cross-sectional view showing a step of forming a trench cell having a lower electrode composed of a platinum group metal film.

First, in the step shown in FIG. 1A, a first interlayer insulating film 11 made of a silicon oxide film is formed on a silicon substrate (not shown) to a thickness of 700 nm by thermal oxidation. A contact hole having a diameter of about 0.16 μm is formed at the position. Then, a thickness of about 1 μm is formed in the contact hole and on the first interlayer insulating film 11 by the CVD method.
Is deposited, and phosphorus is diffused to lower the resistance. After that, the first interlayer insulating film 11 is formed by using the CMP method.
Unnecessary portions of the polysilicon are removed until the surface of the substrate is exposed, and the entire upper surface of the substrate is planarized. As a result, the polysilicon is buried only in the contact hole, and the polysilicon wiring 13 is formed.

Next, a second interlayer insulating film 12 made of a silicon oxide film having a thickness of about 1 μm is deposited on the substrate, and FIG.
In the step shown in FIG. 2B, an opening 14 (for example, having a diameter of about 0.28) having a columnar pattern is formed in the second interlayer insulating film 12.
μm) is formed using a conventional dry etching technique for an oxide film. At this time, the opening 14 is formed such that the polysilicon wiring 13 is exposed at any part of the bottom surface of the opening 14.

Next, in the step shown in FIG.
A TiN / Ti film 15 is deposited as an adhesion layer and a barrier metal layer in the inside 4 and on the second interlayer insulating film 12. At this time,
The thickness of the TiN film is about 20 nm, and the thickness of the Ti film is about 10 nm. Further, in succession, TiN / Ti
On the film 15, a Ru film 16, which is a platinum group metal film, is deposited to a thickness of 30 nm by sputtering or CVD.

Next, in the step shown in FIG.
The surface of the Ru film 16 other than the portion to be polished is chlorinated by chlorine gas to be converted into RuClx (a halogenated platinum group metal film) 17.

Further, in the step shown in FIG. 2A, planarization is performed by a CMP method in order to remove the TiN / Ti film 15 and the RuClx 17 other than in the opening 14.

FIG. 3 is a perspective view showing an example of the structure of a polishing machine used for the CMP used in this step. CMP
The polishing machine is a disk-shaped platen 3 that rotates around a central axis.
1 (platen), a platen shaft 32 supporting the platen 31 at the center, and a polishing pad 33 made of a closed-cell urethane resin or a non-woven fabric adhered on the platen 31
A disc-shaped carrier 34 on which a wafer 36 is mounted;
A carrier shaft 35 that supports the carrier 34 at a central portion;
A polishing liquid supply device 37 for supplying a slurry-like polishing liquid 38; Here, both the platen shaft 32 and the carrier shaft 35 are forcibly rotated by a servomotor or the like, and their rotation speeds are variably controlled independently of each other.

As a result of the polishing by the CMP method, FIG.
As shown in FIG. 3A, RuCl on the second interlayer insulating film 12 is formed.
The x film 17 and the TiN / Ti film 15 are removed, the Ru film 16 and the TiN / Ti film 15 remain only in the opening 14, and the lower electrode 18 is formed.

Next, in the step shown in FIG. 2B, a high dielectric constant dielectric thin film having a thickness of about 20
nm of (Ba0.5, Sr0.5) a TiO ₃ film 19 MOC
It was deposited by the VD method.

Next, in the step shown in FIG.
5, on the Sr0.5) TiO ₃ film 19, the Ru film 20 as an upper electrode film, the opening 14 is deposited by sputtering or CVD to be buried all.

The polysilicon wiring 13 buried in the first interlayer insulating film 11 is used as a capacity storage contact connected to the source region of the silicon substrate, and the lower electrode 18 buried in the opening 14 is used as a capacity storage electrode. , (Ba0.5
, Sr0.5) TiO ₃ film 19 as a capacitance insulating film, and Ru
By using the film 20 as a plate electrode, a capacitor serving as a DRAM cell is formed. The cells formed in the manufacturing process of the present embodiment are not limited to DRAM memory cells, but can be applied to nonvolatile memory cells.

[0034] The cell of the semiconductor memory device formed by the above steps, oxidizing a strong high dielectric film as a capacitor insulating film ((Ba0.5, Sr0.5) TiO ₃ film) while using the 19, the lower electrode Since the 18 and the upper electrode 20 are made of a platinum group metal (Ru) having high oxidation resistance, it is possible to prevent deterioration of the rewriting characteristics and the like due to fatigue deterioration of the capacitor insulating film.

In particular, according to the forming method of this embodiment,
A lower electrode 18 made of a platinum group metal (Ru) is buried in the opening 14 by a CMP method, and a highly oxidizable high dielectric film (Ba0.5, Sr0.5) TiO is further formed thereon.
₃ film 19 and R which is a platinum-based metal film constituting the upper electrode.
Since the u film 20 is deposited, a trench cell suitable for miniaturization can be formed while using a platinum-based metal, which is difficult to form a fine pattern by dry etching, as the lower electrode film.

In this case, in order to polish the Ru film 16, which is a platinum group metal film having poor chemical reactivity, using a CMP method, the RuC is heated to a high temperature in a chlorine gas atmosphere.
Since it is converted to 1 × 17, the region near the surface of the Ru film 16 is chlorinated. The chlorinated region is easily removed by the CMP method using the polishing slurry. At this time, the chlorination is performed by a thickness corresponding to the thickness of the film deposited on the portion other than the opening 14 so that the Ru film 16 in the opening 14 is not subjected to a chemical change. Since RuClx17 is soluble in hydrochloric acid, a trench cell can be formed using a commercially available polishing slurry containing hydrochloric acid in a short time (for example, one minute) suitable for a mass production process.

In this embodiment, the polished portion of the platinum group metal film is halogenated to form a metal halide.
The present invention is not limited to this, and for example, it may be sulfided to metal sulfide or oxidized to metal oxide.

Although the polysilicon wiring 3 is formed as a wiring on the silicon substrate, a wiring made of another conductive material such as a TiN wiring or a W wiring may be formed.

Further, the capacitor insulating film of the cell is constituted by a BST film which is a high dielectric film, but is not limited to this.

Further, although the opening 14 formed in the second interlayer insulating film 12 is formed in a columnar shape, the present invention is not limited to this, and openings of various patterns are provided to form lower electrodes of various patterns. be able to.

Next, FIG. 1 (c) (d), FIG. 2 (a)
Specific examples of the surface treatment method and the polishing method in the steps shown in (1) will be described.

Example 1 By heating in a Cl ₂ atmosphere to 500 ° C. or more for 30 minutes, the Ru film 16 other than the inside of the opening was salified, and RuClx
17 is assumed. At this time, the Ru surface inside the opening is SiO ₂
It is desirable to selectively deposit and protect such a protective film as to prevent a chloride reaction from occurring.

For example, CVD-SiO _{2 is formed} on the Ru film 16.
After forming a film with a thickness not less than the thickness that fills the inside of the opening,
-SiO ₂ film is etched back to form a CVD-SiO ₂ film serving as a protective film inside the opening. This CVD-Si
After salifying the Ru film 16 using the O ₂ film as a protective film, the CV
The D-SiO ₂ film is selectively removed.

Thereafter, RuClx17 and TiN / T
By performing CMP of the i-film 15 with a commercially available slurry using a hydrochloric acid solvent in which RuClx is soluble, for 1 minute,
RuClx film 17 on second interlayer insulating film 12 and TiN
/ Ti film 15 is removed, and Ru film 16 is formed only in the holes.
The TiN / Ti film 15 remains, and the lower electrode 18 is formed.

After the lower electrode is formed, R
The protective film deposited for protection of the u surface is removed.

Example 2 By heating in an H ₂ S atmosphere at a temperature of 800 ° C. or more for 45 minutes, the Ru film 16 other than the inside of the opening is sulfided to obtain RuS. At this time, it is desirable to prevent a sulfurization reaction from occurring by selectively depositing and protecting a protective film such as SiO _{2 on} the Ru surface inside the opening by the method as in the first embodiment.

Thereafter, RuSx and TiN / Ti film 1
5 is performed for 1 minute with a commercially available slurry using a hydrochloric acid solvent in which RuSx is soluble, whereby the RuSx film and the TiN / Ti film 15 on the second interlayer insulating film 12 are removed, and the inside of the hole is removed. Only the Ru film 16 and TiN /
The Ti film 15 remained, and the lower electrode 18 was formed.

After the lower electrode is formed, R
The protective film deposited for protection of the u surface is removed.

[0049]

According to the method for polishing a platinum group metal film according to any one of the first to fourth aspects, the polishing portion of the platinum group metal film provided on the workpiece is treated with a highly reactive compound (metal halide, sulfide). Metal, metal oxide), it becomes easier to polish,
Using a commercially available polishing slurry, planarization by the CMP method can be easily performed in a short time.

According to the method for polishing a platinum group metal film according to claim 5, a commercially available polishing slurry can be obtained by converting a platinum group metal film having poor chemical reactivity into a compound having higher reactivity. By using it, the platinum group metal film can be easily and quickly removed.

According to the method for polishing a platinum group metal film according to the sixth aspect, when the platinum group metal film converted into a highly reactive compound is completely polished, the platinum group metal having a low polishing rate is removed. Exposure will cause CMP to end spontaneously.

According to the method for polishing a platinum group metal film according to claim 7, the platinum group metal film is converted into a compound having a higher reactivity, so that the post-conversion can be performed without using a special polishing slurry. By using a commercially available polishing slurry in which a solvent in which the compound is soluble is used, the platinum group metal film can be easily and quickly removed.

According to the method for forming a cell of a semiconductor memory device of the present invention, a trench type cell having a platinum group metal film as a lower electrode is formed, and a fine pattern of the platinum group metal film can be formed. Thus, a cell of a semiconductor memory device suitable for high integration can be formed.

According to the method for forming a cell of a semiconductor memory device according to the ninth aspect, the platinum group metal film is converted into a compound having a higher reactivity, so that the converted metal can be used without using a special polishing slurry. By using currently commercially available polishing slurries in which a solvent in which the compound is soluble is used,
The platinum group metal film can be easily and quickly removed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a step of forming a trench cell having a lower electrode composed of a platinum group metal film according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a step of forming a trench cell having a lower electrode composed of a platinum group metal film according to the embodiment of the present invention.

FIG. 3 is a perspective view showing a structure of a CMP polishing machine used in a CMP step according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a step of forming a stacked cell having a lower electrode composed of a conventional platinum group metal film.

[Explanation of symbols]

REFERENCE SIGNS LIST 11 first interlayer insulating film 12 second interlayer insulating film 13 polysilicon wiring 14 opening 15 TiN / Ti film 16 Ru film (platinum group metal film) 17 RuClx film (halogenated platinum group metal film) 18 lower electrode 19 (Ba0.5, Sr0.5) TiO ₃ film (dielectric film) 20 Ru film (upper electrode film) 31 the platen 32 platen shaft 33 the polishing pad 34 the carrier 35 carrier shaft 36 wafer 37 polishing liquid supply device 38 polishing solution

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 27/108 H01L 27/10 651 21/8242

Claims (9)

[Claims] 1. A method for polishing a platinum group metal film, comprising: converting a portion to be polished of a platinum group metal film provided on a workpiece to a highly reactive compound; and polishing the compound by a chemical mechanical polishing method. . 2. A polishing method for a platinum-group-based metal film, wherein a portion to be polished of the platinum-group-based metal film provided on a workpiece is halogenated to be converted into a metal halide and polished by a chemical mechanical polishing method. Method. 3. A method for polishing a platinum group metal film, comprising: sulphidizing a polished portion of a platinum group metal film provided on a workpiece to convert it to a metal sulfide; and polishing by a chemical mechanical polishing method. . 4. A method for polishing a platinum group metal film, comprising: oxidizing a portion to be polished of a platinum group metal film provided on a workpiece, converting the polished portion into a metal oxide, and polishing by a chemical mechanical polishing method. . 5. A polishing slurry is supplied between a polishing pad and a portion to be polished of a platinum group metal film, and a pressure is applied between the polishing pad and a workpiece while the polishing pad and the workpiece are being applied. 2. The method for polishing a platinum group metal film according to claim 1, wherein the polishing portion of the platinum group metal film is polished by relatively rotating a workpiece. 6. The platinum-based metal film according to claim 5, wherein the polishing of the platinum-based metal film is completed by polishing all the polished portions of the platinum-based metal film and exposing metals having different polishing rates. A method for polishing a group III metal film. 7. The platinum group metal according to claim 5, wherein a solvent in which the platinum group metal film converted into a highly reactive compound is soluble is used for the polishing slurry. Polishing method of the film. 8. A step of depositing an interlayer insulating film on a substrate having a conductor portion, a step of forming an opening in the interlayer insulating film to reach at least a part of the conductor portion, A step of depositing a platinum group metal film on the insulating film, a step of converting the platinum group metal film other than the inside of the opening to a highly reactive compound, and exposing the interlayer insulating film by chemical mechanical polishing. Removing the platinum-group-based metal film converted to the highly reactive compound until forming a lower electrode by leaving the platinum-group-based metal film in the opening, and forming a dielectric on the lower electrode. A cell forming method for a semiconductor memory device, comprising: depositing a body film; and depositing an upper electrode film on the dielectric film. 9. The method according to claim 8, wherein a solvent in which the platinum group metal film converted into a highly reactive compound is soluble is used as the polishing slurry.