JP2720464B2 - Method and apparatus for forming metal thin film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to post-processing after forming a thin film.

2. Description of the Related Art With the recent high-density integration of VLSI, multilayer wiring technology has become indispensable. This high-density multilayer wiring requires connection of lower and upper metal wirings, and a thin film forming method capable of connecting a contact hole having a large aspect ratio (depth with respect to the diameter of the contact hole) is being developed. is there.

As a conventional example of this thin film forming method, a bias sputtering method will be described with reference to FIG.

An anode electrode 104 and a cathode electrode are provided in the chamber 101.
The cathode electrode 102 has an Al—Si (2%) target, and the anode electrode has a substrate 105. The two electrodes are connected to the RF power source (1) 103 and the RF
A power supply ((2) 106) is connected, and generally, a larger electric power is applied to the cathode electrode 102.

In the deposition method, an Ar gas is usually introduced into the chamber 101, and discharge is performed while maintaining a degree of vacuum at about several mTorr. A self-negative bias is induced on both electrodes to which the RF bias is applied, and sputtering by Ar ions occurs on the sheath on the electrode surface, and Al is removed on the target side, and the sputtered Al atoms are removed from the anode electrode 104 side. With substrate 1
Deposits on 05. Further, since deposition and sputtering are performed simultaneously on the anode electrode 104, Al on the substrate 105 is shaved and deposited, and is deposited while flattening.

According to this method, it is possible to embed a metal thin film in a contact hole of 0.8 μmφ, so that it may be used as a future VLSI technology with high density integration.

However, the conventional bias sputtering method described above directly hits the substrate 105 with ions in the plasma during the deposition of the thin film, thereby damaging a transistor formed on the substrate in advance and degrading its characteristics. In addition, the Al thin film deposited by bias sputtering has poor particle stability, the Al wiring often breaks after heat treatment, and it is difficult to align in the photolithography process. I have a problem.

The present invention has been made in view of the above problems, and proposes to provide a forming method for forming a thin film in a finer contact hole.

Means for Solving the Problems The method for forming a metal thin film of the present invention comprises: depositing a metal thin film on a substrate having a contact hole formed thereon, fixing the substrate on which the metal thin film is deposited to a holding table, and holding the holding table in a vacuum atmosphere. A circular motion is made toward the substrate surface of the substrate around a predetermined point, and a metal thin film is embedded in a concact hole by centrifugal force. A chamber, a means for evacuating the chamber, a holding table installed in the chamber and holding a substrate having a contact hole formed therein, and a holding table with the substrate surface of the substrate centered on a predetermined point. An apparatus having a means for performing a circular motion and a means for heating the inside of the chamber is used.

Function By centrifugal force, a part of the thin film flows into the contact hole having a high aspect ratio, thereby enabling the interlayer connection of the metal wiring.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, FIG. 2 shows a top view of the configuration of an example of an apparatus used in the present invention, and FIG. 3 shows a front view of the configuration of the same apparatus.

In the figure, a chamber 10 is made of a cylindrical stainless steel container and is set on legs 19. A lid 11 is provided on a part of the upper end surface of the chamber 10,
The sample is exchanged through this. An exhaust system 12 and a gas introduction system 13 are connected to the chamber 10, so that various gas atmospheres can be maintained in the chamber. From the center axis 14 at the center of the chamber 10, four arms 15
The substrate carrier 16 is attached to the end of the arm 15 at the end of the arm 15. The central shaft 14 is connected to a direct drive motor 17 located below the chamber 10, and can rotate the substrate transporter 16 at an arbitrary speed. A heater 18 surrounds the chamber 10 as a heating mechanism of the system, and can uniformly heat the inside of the chamber 10 to 450 ° C.

4 and 5 show details of the arm 15 and the substrate transporter 16 of the apparatus. FIG. 4 is a side view of the substrate carrier 16 and the arm 15 at rest. The arm 15 and the substrate carrier 16 are connected by an extension arm 20, and the substrate carrier 16 is moved by a movable shaft 21 on the extension arm 20.
Move around. When rotating, it moves in the direction of the arrow in the figure,
The arm 15 is in the radiation direction with respect to the bottom of the substrate carrier 16.

FIG. 5 is a top view of the substrate transporter 16 and the arm 15 during rotation. The substrate cassette 16 contains a wafer cassette 22. The wafer cassette 22 is detachable from the substrate carrier 16, and is set when preparing a wafer.

Next, an example of the thin film forming method of the present invention using this apparatus will be described with reference to FIG.

As a sample, a first aluminum wiring (0.8 μm thick) is formed after depositing a thermal oxide film 30 on a 6-inch Si substrate. Next, a planarization film is formed by a plasma SiO ₂ film 32 using an etch-back method, and a contact hole 33 is opened in the plasma SiO ₂ film 32 on a desired first aluminum wiring 31 by using photography and dry etching. . Thereafter, the Al deposited using the sputtering method is used as the second aluminum wiring 34 by using photography and dry etching.

FIG. 1A shows a cross-sectional shape of this sample. left
A small amount of Al
Deposition is recognized, but adhesion of Al is discriminated in the 0.7 μmφ contact hole, and it is hard.

The sample is processed by the device. Before using the apparatus, the inside of the chamber 10 is kept at a constant atmosphere of 450 ° C., and N ₂ gas is flown at 2 l / min from the gas introduction system 13. The sample is placed in a wafer cassette 22, the lid 11 is opened, and inserted into the substrate transporter 16. The wafer cassette 22 is placed in another substrate transporter 16 in advance for balancing. The lid 11 is closed, the rotary pump attached to the exhaust system 12 is turned on, and the inside of the chamber 10 is evacuated. The rotation speed is increased to 200 rpm in 30 seconds, and then to 6000 rpm in 2 minutes and 30 seconds. Continue running for 30 minutes while maintaining 6000 rpm. At this time, the gravitational acceleration applied on the wafer surface is a = ω ² r = (2π × 6000/60) ² × 0.5 = 32800 m / s ² a: gravitational acceleration ω: angular velocity r: arm length, ie, gravity of 3350 g Will be added.

Next, decelerate in 5 minutes and turn off the rotary pump (OF
F) to return the system to atmospheric pressure, open the lid 11, take out the wafer cassette 22, and take out the wafer. FIG. 1B shows a cross-sectional structural view of the SEM of the wafer subjected to the above processing. The structure of the element is the same as that of FIG. 1.2μmφ, 0.7
Al was completely depressed in both the contact holes of μmφ, and no cavity was formed.

This is because the gravitational acceleration during rotation is approximately 33% of the weight of Al.
50 times the weight and the atmosphere is the melting point of Al (663 ℃)
Since the temperature is 450 ° C., which is close to, the grain of Al is in a fluid mode, which is considered to be caused by migration (movement) in the contact hole.

The result of electrically measuring this contact hole is 0.7
At μmφ, the resistance between the first aluminum and the second aluminum changed from 0.8Ω to 0.01Ω as compared with before the treatment. Also,
Thereafter, a P-SiN film (stress 5 × 10 ⁹ dyn / cm) is deposited as a passivation film, and subjected to a thermal stress test (150 ° C. 50 dyn / cm).
0 hour), no disconnection was observed in the contact connection.

In particular, the advantages in comparison with the bias sputtering method described above are as follows: 1. There is no damage to the underlying transistor.

2. High thermal stability during film processing. 3. Even after performing the processing of the present invention, there is no roughness on the AL surface, and alignment in subsequent photolithography is extremely easy.

4. The grain growth of Al wiring is equivalent to high temperature storage at 450 ° C., and no abnormal disconnection such as that observed during bias sputtering occurs.

5. The required sintering process can be performed simultaneously after Al wiring. Effect of the Invention The above effects can be obtained by using the method of forming a thin film according to the present invention. 1. A predetermined metal is placed in a contact hole having a high aspect ratio. It can be completely buried and can be connected with low resistance between the upper and lower metal wirings.

2. The characteristics of the transistor formed in advance on the substrate are not changed.

3. The reliability of metal wiring does not decrease after the processing of the metal thin film.

4. This process according to the present invention can be performed during or after the process is completed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process of the thin film forming method of the present invention, FIG. 2 is a top view of the external appearance of the apparatus according to the present invention, FIG. 3 is a front view of the external appearance of the apparatus, and FIG. FIG. 5 is a side view of the substrate transporter and the arm at the time of rotation, FIG. 5 is a side view of the substrate transporter and the arm at the time of rotation of the apparatus, and FIG. 6 is a conceptual view of the configuration of a general bias sputtering apparatus. 30 ... thermal oxide film, 31 ... first aluminum, 32 ... SiO ₂ , 33 ...
... contact hole, 34 ... second aluminum.

Claims (2)

(57) [Claims] A metal thin film is deposited on a substrate on which a contact hole is formed, and the substrate on which the metal thin film is deposited is fixed to a holder, and the holder is placed in a vacuum atmosphere around a predetermined point. A method for forming a metal thin film, wherein a circular motion is performed toward a surface, and the metal thin film is embedded in the contact hole by centrifugal force. 2. A chamber, means for evacuating the chamber, means for holding a substrate provided in the chamber and having a contact hole formed therein, and means for holding the substrate on a predetermined point with respect to the holding table. An apparatus for forming a metal thin film, comprising: means for performing a circular motion toward the center of the substrate surface; and means for heating the inside of the chamber.