JP2002158189A - Conductor thin film deposition method - Google Patents

Abstract

(57) Abstract: A ferroelectric memory exhibiting good ohmic contact characteristics is obtained by depositing a conductive thin film such as Ir or Pt while preventing oxidation of a buffer film such as ZrN or TiN. A single or a plurality of oxygen gettering materials 3 are fixed to portions of a target 1 made of a metal Ir or metal Pt outside an erosion region 2, and Ir or Pt particles generated by sputtering of the target are provided on a silicon substrate. Deposit on buffer film. As the oxygen gettering material 3, small pieces or ring pieces of Zr, Ti, Hf, Y, Al, Ce, Mg or the like are used. ZrN, Ti
N, TaSiN, Ti _1-x Al _x N, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for depositing a conductive thin film required for manufacturing electronic devices such as ferroelectric memories.

[0002]

2. Description of the Related Art A 1-transistor + 1-capacitor ferroelectric memory combining a semiconductor silicon and a ferroelectric thin film exhibits unique physical properties such as piezoelectricity, pyroelectricity, high dielectric constant, and Curie temperature phase transition rate. It is used in various fields for consumer and industrial use. When a ferroelectric thin film is directly deposited on a silicon substrate during the manufacture of a ferroelectric memory, the ferroelectric reacts with the Si of the substrate, and therefore a conductor for suppressing the reaction between the silicon substrate and the ferroelectric thin film. It is necessary to interpose a thin film.

It is desirable that the conductive thin film has low resistance and sufficient oxidation resistance, has good ohmic contact with the silicon substrate, and does not deteriorate the characteristics of the ferroelectric thin film. As long as the material exhibits low contact resistance, it can be used even if the material is slightly oxidized. Specifically, Ir / ZrN,
A two-layer structure of a conductive thin film such as Ir / TiN or Pt / TiN and a buffer film is known. Further, formation of a conductive thin film of Pt, Pd, or the like via a buffer film of Ti or W is introduced in Japanese Patent Application Laid-Open No. 6-57411.

[0004] Conductive thin films such as Ir and Pt deposited by a sputtering method can be used without deteriorating the ferroelectricity of ferroelectric thin films such as oxides such as PZT (lead zirconate titanate).
It is an electrode for suppressing the diffusion of oxygen into the lower buffer film and the silicon substrate Si. A buffer film such as ZrN or TiN interposed between a silicon thin film and a conductor thin film such as Ir or Pt
A reaction between a conductive thin film of Ir, Pt or the like and a silicon substrate is prevented, and a good ohmic contact is obtained between the two.

[0005]

However, Ir and Pt used as a conductive thin film material exhibit a strong catalytic action on oxygen. Therefore, when depositing Ir, Pt, or the like on a buffer film of TiN, ZrN, or the like by a sputtering method, even if the vacuum atmosphere is evacuated to a high degree of vacuum of about 4 × 10 ⁻⁶ Pa, a small amount remains. Oxygen and H
Oxygen-containing compounds such as ₂ O, CO and CO ₂ are activated and oxidize the buffer film. Oxidation of the buffer film increases the contact resistance,
This may slow down the device operation of the ferroelectric memory.

[0006] Oxidation of the buffer film is reduced by lowering the deposition temperature of the conductive thin film, but the oxidation cannot be suppressed to an extent necessary for securing good ohmic contact. Even if a conductive thin film is deposited by an electron beam evaporation method, an increase in the temperature of the entire system is unavoidable, and the oxygen partial pressure also increases. Further, the electron beam evaporation method requires an expensive ultra-vacuum apparatus, and has problems in workability and mass production.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem. A buffer film is formed by maintaining Zr, Ti, or the like having a strong oxygen gettering action in a reaction atmosphere. It is an object of the present invention to produce a high-performance ferroelectric memory by depositing a conductive thin film while preventing oxidation of the ferroelectric memory.

In order to achieve the object, the conductor thin film deposition method of the present invention fixes one or more oxygen gettering materials on a portion of the target made of metal Ir or metal Pt outside the erosion region, and sputters the target. Is characterized in that the Ir or Pt particles generated in the above are deposited on a buffer film provided on a silicon substrate. As the oxygen gettering material, Zr, Ti, Hf, Y, Al, Ce, M
g etc. are used. ZrN, TiN, Ta is used for the buffer film.
N, TaSiN, Ti _1-x Al _x N, and the like.

[0009]

The target used in the present invention has one or more oxygen gettering members 3 fixed in the vicinity of the periphery of the target 1 made of metal Ir or metal Pt. As the oxygen gettering material 3, a plurality of small pieces are arranged concentrically (FIG. 1a).
Or place a ring piece around the target 1 (see FIG. 1).
b). The target is not limited to the disk shape shown in FIG. 1, but a rectangular, square, or polygonal target can also be used. In any case, the fixing position of the oxygen gettering material 3 is selected at a position avoiding the erosion region 2 (FIG. 2) where the sputtering reaction is most active. Alternatively, the oxygen gettering material 3 can be mixed or alloyed with Ir or Pt constituting the target.

When the target 1 to which the oxygen gettering material 3 is fixed is sputtered, particles such as Ir and Pt are deposited on the buffer film on the silicon substrate to form a conductive thin film. The ring material 3 is sputtered. A small amount of Zr or Ti generated by sputtering the oxygen gettering material 3 captures residual oxygen in the sputtering atmosphere and prevents oxidation of buffer films such as ZrN and TiN. Zr and Ti trapped in residual oxygen may be mixed as oxides into the conductive thin film, but the mixed amount is 1%.
% And does not adversely affect the performance of the ferroelectric memory.

Since the residual oxygen is trapped by the oxygen gettering material 3, the effect of the residual oxygen contained in the sputtering atmosphere is eliminated, and a conductive thin film can be formed with a low contact resistance and good ohmic contact. In this respect, the conventional film forming method requires an ultra-vacuum degree to improve the ohmic contact, which has been a bottleneck in improving workability and film forming property. In fact, the ferroelectric memory manufactured according to the present invention does not require the ultra-vacuum used for electron beam evaporation or the like, and can reduce the conventional 1 Ω · cm ²
The contact resistance can be reduced to about 500 μΩ · cm ² which is smaller than the order by at least three orders of magnitude.

[0012]

[Embodiment] Ir was added to a ZrN buffer film provided on a silicon substrate.
The present invention will be specifically described by taking a case where a conductor thin film is deposited by a sputtering method as an example. In the present embodiment, a metal Ir target 1 having an outer diameter of 98 mm was used. Metal I
When the target 1 made of r was set and sputtering was performed, the erosion region 2 was a circumferential portion having an inner diameter of 50 mm to an outer diameter of 60 mm. Therefore, erosion area 2
A plurality of Zr small pieces 3 are arranged concentrically at equal intervals at positions spaced apart from the outer periphery.

A metal Ir target to which Zr small pieces 3 are fixed.
1 is set in the vacuum chamber, and the vacuum chamber is pressurized.
0.5Pa N_Two-4% H_TwoMaintain the atmosphere and output 100
W, discharge time 8 minutes, deposition rate 25 nm / min.
r was sputtered. The silicon substrate has a film thickness of 10
Epitaxially grown 0 nm (100) ZrN thin film
A (100) silicon substrate was used. For comparison,
Using the target 1 to which the Zr pieces 3 are not fixed,
Ambient: N _Two-4% H_Two, Pressure: 0.4 Pa, output: 100
W, discharge time: 8 minutes, deposition rate: 25 nm / min
Ir was similarly sputtered.

When each sample on which the Ir conductor thin film was deposited was subjected to X-ray diffraction, as shown in the diffraction pattern of FIG. 3, the thin film produced from the target 1 without Zr small pieces was compared before the Ir deposition. As a result, the peak intensity of ZrN was reduced by about 30% (FIG. 3a). The decrease in peak intensity is due to the residual oxygen activated during the deposition of Ir
This is presumed to be the result of oxidation of the N thin film. Actually, X-ray photoelectron spectroscopy (XPS) of the silicon substrate after the Ir deposition showed that a large amount of O was mixed in the ZrN thin film (FIG. 4).
a) It was confirmed that the oxidation of the ZrN thin film was progressing. When the interface resistance of the ZrN thin film / Ir thin film was measured, it showed a high value of 1 Ω · cm ² .

On the other hand, when an Ir conductor thin film was deposited from the target 1 to which the Zr small pieces 3 were fixed, the peak intensity of ZrN hardly changed before and after the deposition of Ir (FIG. 3B). This result indicates that oxygen remaining in the atmosphere is captured by the oxygen gettering action of the Zr small pieces 3 fixed to the target 1, and the oxidation of the ZrN thin film is suppressed. Further, the silicon substrate after the deposition of the Ir conductor thin film was subjected to X-ray photoelectron spectroscopy (XPS).
As a result, it was found that the level of oxygen contamination was kept low (FIG. 4B), and that the characteristics as a ferroelectric memory were not adversely affected. The interface resistance between the ZrN thin film / Ir thin film was also significantly reduced to 500 μΩ · cm ² .

[0016]

As described above, in the present invention, a target having an oxygen gettering material 3 such as Zr or Ti fixed thereto is used, and a small amount of Zr, Ti is used together with a conductive thin film material such as Ir or Pt. Sputtering Ti etc. Zr, Ti and the like generated by sputtering capture oxygen remaining in the sputtering atmosphere and prevent oxidation of buffer films such as ZrN and TiN. As a result, a thin film structure exhibiting good ohmic contact is obtained, and a ferroelectric memory which operates at high speed can be obtained.

[Brief description of the drawings]

FIG. 1 shows several examples of targets used in the present invention.

FIG. 2 shows a target made of metal Ir used in Examples.

FIG. 3 is a graph showing the effect of the presence or absence of small Zr pieces on the peak intensity of a ZrN buffer film before and after deposition of a conductive thin film.

FIG. 4 is a graph showing the effect of the presence or absence of small Zr pieces on the oxidation of a ZrN buffer film.

[Explanation of symbols]

 1: Target (Metal Ir target) 2: Erosion region 3: Oxygen gettering material (Zr small piece)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K029 AA06 BA02 BC03 BD01 CA05 DC03 4M104 BB04 BB06 DD40 GG16 5F083 FR02 GA02 JA15 JA38 JA40 PR22

Claims (2)

[Claims] At least one oxygen gettering material is fixed to a portion of a target made of metal Ir or metal Pt outside an erosion region, and Ir or Pt particles generated by sputtering the target are buffered on a silicon substrate. A method for depositing a conductive thin film, comprising depositing on a film. 2. Zr, Ti, Hf, Y, Al, Ce, M
2. The method according to claim 1, wherein one or more kinds selected from g are used as the oxygen gettering material.