JPH0521428A - Formation method of conductive thin film - Google Patents

Abstract

PURPOSE:To enhance the orientation property of the conductive thin film by a method wherein the temperature of a semiconductor substrate and the deposition speed of a conductive material are set within a specific range when the conductive material is vapor-deposited and formed on the substrate via an amorphous film or a polycrystalline film. CONSTITUTION:The following are installed inside a vacuum chamber 1: a substrate 2 provided with a substrate temperature regulator 3; and a target 4 which is provided with an RF power supply 5, a low-pass filter 6 and a DC power supply 7. A sputtering gas is introduced into the vacuum chamber 1 from a sputtering-gas introduction port via a mass-flow controller 10 and a gas- temperature control device 9; it is discharged from an evacuation port 11. hen a conductive thin film is formed on the substrate via an amorphous film or a polycrystalline film by using this apparatus, the temperature of the substrate is set at 50 deg.C or lower and the deposition speed of a conductive material is set at 1.5X10<6> atoms/cm<2>.sec or higher and 1.0X10<18> atoms/cm<2>.sec or lower. Thereby, it is possible to form the conductive thin film whose orientation property and crystallinity are good.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a conductive thin film having good crystallinity.

[0002]

2. Description of the Related Art As a method for forming a conductive thin film on an amorphous insulating film or a polycrystalline insulating film on a semiconductor substrate,
Heretofore, physical vapor deposition methods such as sputtering methods and chemical vapor deposition methods such as CVD methods have been widely used.

However, a conductive thin film formed on an amorphous insulating film or a polycrystalline insulating film by a conventional method becomes a polycrystal having a low orientation by a heat treatment after the thin film is formed. When the thin film was applied to the wiring of a semiconductor device, many grain boundaries existed in this wiring.

By the way, in recent years, as the integration width of semiconductor devices has been improved and the wiring width has been narrowed, the disconnection of the wiring due to stress migration due to the stress of the thin film or electromigration due to the high current density will increase the reliability of the semiconductor device. It is a factor that lowers the price. This disconnection of the wiring is a serious problem in relation to the grain boundaries existing in large numbers in the thin film wiring. For example, the following reports have analyzed the phenomena of stress migration and electromigration in an aluminum thin film for wiring.

H.KANEKO et al. 27th Annual Proc.IRPS, pp1
In 94-199, stress migration (11
It has been reported that slit-like defects are generated at grain boundaries where (1) faces face each other, and it is clarified that such a grain boundary can be eliminated in a (111) oriented film, so that no wire breakage occurs. Regarding electromigration, S.VA
IDYA et al. Have reported that in Thin Solid Films, VOL.75 pp253-259, the orientation of the (111) plane is strong and the larger the grain size, the longer the life.

[0006] The above report shows that, for example, in the case of aluminum on an amorphous insulating film or a polycrystalline insulating film (1
11) It has been shown that if a conductive thin film with high orientation can be formed, resistance to stress migration and electromigration can be increased.

However, it has been difficult to form a highly oriented conductive thin film on an amorphous insulating film or a polycrystalline insulating film. In particular, when an alignment film is epitaxially formed on a single crystal film, a substrate having a high substrate temperature and a low deposition rate of vapor deposition particles is likely to be a thin film having low orientation.

[0008]

The present invention has been made to solve the above-mentioned conventional problems, and improves the orientation of a conductive thin film used for wiring or the like on an amorphous or polycrystalline film, An object is to provide a method for forming a highly reliable conductive thin film.

[0009]

The method for forming a conductive thin film according to the present invention is a method for forming a conductive thin film in which a conductive material is deposited on a substrate through an amorphous film or a polycrystalline film. Is 50 ° C. or lower, and the deposition rate of vapor-deposited particles of the conductive material is 1.5 × 10 ¹⁶ atoms / cm ² · sec or more and 1.0 × 10 ¹⁸ atoms / cm ² · sec or less.

The conductive material may be a metal or alloy having high conductivity and strong orientation. In particular, aluminum or an alloy containing aluminum as a main component or copper or an alloy containing copper as a main component is preferable. Both aluminum and copper (11
1) It has a face-centered cubic structure in which the plane is the densest plane.

Examples of the vapor deposition method of the conductive thin film according to the present invention include physical vapor deposition methods such as vacuum vapor deposition method, sputtering method, electron beam vapor deposition method and chemical vapor deposition methods such as CVD method. Among them, the sputtering method is a particularly preferable method because it has the advantages that it can form a thin film of a substance having a low vapor pressure and which is difficult to be vacuum-deposited, and has a high film deposition rate.

FIG. 1 shows a sputtering apparatus particularly preferable for use in the method for forming a conductive thin film of the present invention.

A substrate 2 provided with a substrate temperature controller 3 in a vacuum chamber 1, an RF power source 5, a low-pass filter 6 and D.
A target 4 having a C power source 7 is installed. The sputter gas is introduced into the vacuum chamber 1 through the sputter gas inlet 8 through the mass flow controller 10 and the gas temperature controller 9, and is exhausted through the exhaust port 11. The conductance of the exhaust port 11 is set low so that the gas pressure in the vacuum chamber 1 during sputtering can be kept high. The reason for this is that the mean free path of sputtered particles is reduced by increasing the density of gas atoms present in the plasma. Since the mean free path becomes smaller, the number of collisions between the sputtered particles and the gas atoms increases, so that the sputtered particles lose energy. In addition, the distance between the substrate 2 and the target 4 can be increased in order to increase the number of collisions between sputtered particles and gas atoms. The temperature of the sputtering gas can be set independently of the substrate temperature by the gas temperature control device 9. The inside of the gas temperature control device 9 is shown in FIG. Gas pipe 12
Has a loop shape inside the constant temperature chamber 13, and the sputtering gas reaches the set temperature while passing through the inside.

In the apparatus of FIG. 1, the sputtered particles have almost the same energy as the temperature of the sputter gas until reaching the substrate 2, and the phenomena such as temperature rise and damage of the substrate do not occur, and the energy is increased. Very uniform. The sputtering gas pressure for this is
1 × 10 ^-2 Torr or more is preferable. The distance between the substrate 2 and the target 4 is preferably 100 mm or more. The energy of sputtered particles can be changed by controlling the temperature of the sputtering gas.

The substrate temperature when depositing the conductive thin film is 50 ° C. or lower. The reason for this is that when the temperature exceeds 50 ° C., for example, when the conductive material is aluminum, a plane other than the (111) plane such as the (200) plane appears and the orientation decreases. The lower limit of the substrate temperature is
At the lowest temperature used in normal sputtering,
For example, -196 ° C.

The deposition rate of the vapor deposition particles of the conductive material is
1.5 × 10 ¹⁶ atoms / cm ² sec or more, 1.0 × 10 ¹⁸ atoms / cm ²
・ It is less than sec. If it is less than 1.5 × 10 ¹⁶ atoms / cm ² · sec, the (111) plane is preferentially oriented, but the crystallinity is not sufficient, and if it exceeds 1.0 × 10 ¹⁸ atoms / cm ² · sec, the energy of the vapor deposition particles is large. As a result, the temperature rise of the amorphous or polycrystalline insulating film becomes remarkable, which is not preferable.
A more preferable range of deposition rate is 1.0 × 10 ¹⁷ atoms / cm ² ·
sec ~ 8.0 × 10 ¹⁷ atoms / cm ² · sec. For this reason,
The sputtering apparatus uses 1.0 × 10 ¹⁶ atoms /
It must be able to be deposited at a rate of cm ² · sec or more.

The deposition rate of the vapor deposition particles is adjusted by changing the power applied to the target. For example,
1.5 × 10 ¹⁶ atoms / cm ² · sec or more, 1.0 × 10 ¹⁸ at
To obtain a deposition rate in the range of oms / cm ² · sec or less,
A target applied power of 0.1 to 10 W / cm ² is required.

[0018]

When the substrate is a single crystal, it is widely practiced to raise the substrate temperature to some extent to activate the interaction between the surface of the substrate and the vapor-deposited particles and obtain an orientation similar to that of the substrate. However, when the substrate is amorphous, there is no interaction between the vapor-deposited particles that move freely and the plane orientation of the substrate, and the vapor-deposited particles tend to settle in a state where the interface energy with the substrate is low. For this reason, the (111) plane, which is the most stable plane in the face-centered cubic structure of aluminum, copper, or the like, is preferentially oriented, but when the substrate temperature is raised, the difference in interfacial energy between the planes becomes small and other planes ( For example, (200) plane appears.

Using the apparatus shown in FIG. 1, the substrate temperature when aluminum is sputtered on a silicon substrate having a thermal oxide film and the X-ray diffraction of the aluminum thin film (11)
The change in intensity of the 1) peak and the (200) peak is shown in FIG. As described above, when the substrate temperature is 50 ° C. or lower, only the (111) peak is observed, whereas when the substrate temperature is higher than 50 ° C. (20
0) The peak gradually appears.

When the substrate is a single crystal, the film deposition rate is usually set to a relatively low rate so that the vapor deposition particles move sufficiently on the substrate and interact with the substrate to deposit at a stable point. is there. For example, the film deposition rate is about 10 ¹² atoms / cm ² · sec in the conventional vacuum deposition method, and about 10 ¹⁴ atoms / cm ² · sec in the sputtering method.

On the other hand, according to the method of the present invention, it was found that the film deposition rate was several orders of magnitude higher and the orientation and crystallinity of the thin film were significantly improved.

FIG. 4 is a diagram showing the film deposition rate at room temperature and the intensity of the (111) peak by X-ray diffraction of the conductive thin film. In the region where the film deposition rate is smaller than 1.5 × 10 ¹⁶ atoms / cm ² · sec, the (111) peak is preferentially oriented, but the peak intensity is small due to poor crystallinity. Film deposition rate is 1.5
Under the condition of more than × 10 ¹⁶ atoms / cm ² · sec, the peak intensity also becomes large, and it can be seen that the orientation and crystallinity of the thin film are significantly improved. The reason for this is considered as follows.

The orientation of the thin film is determined at the time of forming the thin film, that is, at the time when the island grows into an island and the island is connected to form a continuous film.

When the base on which the film is deposited is amorphous, there are no sites where nuclei are generated, and nuclei are formed by collision of particles. When the film deposition rate is increased, the number of particles that reach the surface of the substrate per unit time is increased and the collision frequency is improved, so that the nucleus generation density is increased. These nuclei capture particles to form islands, and the islands consist of several tens of atoms, and crystals are present inside and tend to settle in a state of low interfacial energy. When the film deposition rate is several orders of magnitude higher as in the method for forming a conductive thin film of the present invention, the density of islands increases as the nucleus generation density increases, and crystalline islands are formed at high density from the early stage of the film formation step. To be done.

Further, according to the method of the present invention, since the islands are formed at a high density and the distance between the islands is reduced, a thin film having less surface irregularities and excellent in smoothness is obtained.

However, the film deposition rate is 1.0 × 10 ¹⁸ atoms / cm ²
・ If it exceeds sec, the temperature rise of the base becomes remarkable due to the energy of the vapor deposition particles, which is not preferable.

Further, even when the substrate is polycrystal, if the substrate temperature is set sufficiently low as described above, the film deposition rate can be increased and it can be treated in the same manner as amorphous.

[0028]

EXAMPLES Examples of the present invention will be described in detail below.

A conductive thin film was formed by the sputtering method using the apparatus shown in FIG. The substrate used was a 6-inch silicon substrate with a 1000 angstrom thick thermal oxide film on the surface. After performing a sufficient cleaning treatment to remove impurities on the surface, aluminum was sputtered as a conductive material under the following conditions.

Sputtering method: RF magnetron method Target: 140 mmφ aluminum (Al) plate Substrate temperature: room temperature (25 ° C.) Substrate-target distance: 150 mm Sputtering gas: Argon (Ar) gas pressure: 1 × 10 ^-2 Torr target Bias: 200 V Target applied power: 5 W / cm ² Film thickness: 4000 Å The film deposition rate was controlled by changing the RF power applied to the target while keeping the target bias constant. When the target applied power is 5 W / cm ² , the film deposition rate is 1.
It was 0 × 10 ¹⁷ atoms / cm ² · sec. The sputtering time was chosen so that the film thickness was 4000 Å. When the orientation and crystallinity of the conductive thin film thus prepared were evaluated by X-ray diffraction, only the (111) plane was oriented.

This electroconductive thin film was actually processed into wiring and an electromigration test was conducted. The test piece was prepared by the following steps. The aluminum thin film formed on the oxide film is subjected to a series of operations such as resist coating on a predetermined portion, exposure using a mask, development, and etching, as shown in FIG.
A test substrate 17 having an anode 14, a cathode 15, and a wiring portion 16 having a wiring width of 0.8 μm connecting the respective electrodes as shown in FIG. With respect to the wiring portion 16 of the test board 17, the test temperature is set to 200 ° C. and the current density is set to 2
A current corresponding to × 10 ⁶ A / cm ² was passed and the average failure time was measured. The results are shown in FIG. 6 together with a comparative example in which the film deposition rate at the time of forming a thin film was changed. From this figure, it can be seen that the average failure time becomes longer under the condition that the film deposition rate is higher than 1.5 × 10 ¹⁶ atoms / cm ² · sec, and the effect of improving the orientation and the crystallinity appears.

[0032]

As described in detail above, according to the present invention,
A conductive thin film having good orientation and crystallinity can be formed on an amorphous film or a polycrystalline film, and such a conductive thin film has excellent resistance to deterioration phenomena such as stress migration and electromigration, It can be applied to highly reliable wiring even in submicron wiring. Further, the conductive thin film formed by the method of the present invention also has improved surface smoothness.

[Brief description of drawings]

FIG. 1 is a diagram showing a sputtering apparatus used in the present invention.

FIG. 2 is a diagram showing the inside of a gas temperature control device 9.

FIG. 3 is a diagram showing a substrate temperature at the time of forming a thin film and the intensities of a (111) peak and a (200) peak by X-ray diffraction of the thin film.

FIG. 4 is a diagram showing a film deposition rate at room temperature and an intensity of a (111) peak by X-ray diffraction of a thin film.

FIG. 5 is a diagram showing a test substrate on which a wiring portion is formed by the method of the present invention.

FIG. 6 is a diagram showing a relationship between a film deposition rate and a mean failure time when forming a thin film.

[Explanation of symbols]

1 ... Vacuum chamber, 2 ... Substrate, 3 ... Substrate temperature controller, 4 ... Target, 5 ... RF power supply, 6
……… Low-pass filter, 7 ……… DC power supply, 8 ………
Sputtering gas inlet, 9 ... Gas temperature control device, 10
……… Mass flow controller, 11 ……… Exhaust port, 1
2 ... Gas pipe, 13 ... Inside constant temperature bath, 14 ...
… Anode, 15 ………… Cathode, 16 ………… Wiring section, 17 ……
… Test board

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Kawanoue, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki City, Kanagawa Prefecture, Toshiba Research Institute Ltd. (72) Inventor Naofumi Kaneko Komukai, Kawasaki-shi, Kanagawa Prefecture Toshiba Town No. 1 Inside Toshiba Research Institute, Inc.

Claims (1)

Claim: What is claimed is: 1. A method of forming a conductive thin film, comprising depositing a conductive material on a substrate through an amorphous film or a polycrystalline film, wherein the temperature of the substrate is 50 ° C. or lower, Deposition rate of vapor-deposited particles of a conductive material is 1.5 × 10 ¹⁶ atoms / cm ² · se
A method of forming a conductive thin film, characterized in that it is not less than c and not more than 1.0 × 10 ¹⁸ atoms / cm ² · sec.