JPH09176850A - Sputtering device and production of dielectric film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering device capable of controlling the compsn. of dielectric films and a process for producing the dielectric films. SOLUTION: An impedance circuit 5 having a prescribed quantity of impedance is connected to a substrate holder at the time of constituting the sputtering device by providing the inside of a vacuum chamber 9 constituted evacuatably to vacuum with the substrate holder 7 and a target holder 8. When a target 12 consisting of the dielectric compsn. is sputtered by impressing a high-frequency voltage on the target holder 8, currents flow to the substrate holder 7 via this impedance circuit 5 and, therefore, the potential of the substrate holder 7 may be controlled until the adequate potential is attained. Since the surface of the substrate 11 places or held on the substrate holder 7 is etched adequately by plasma, the dielectric films having a stoichiometric compsn. is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering apparatus for forming a dielectric film and a method for manufacturing a dielectric film,
In particular, the present invention relates to a sputtering apparatus for applying a high frequency voltage to a target holder to perform sputtering, and a dielectric film manufacturing method.

[0002]

2. Description of the Related Art Conventionally, an insulating film composed of an oxide thin film or the like has been widely used in manufacturing a semiconductor device. In recent years, among such insulating films, Pb (ZrTi) has been widely used.
A film having both a high dielectric constant and a ferroelectric property, represented by an O ₃ film and a SrBi ₂ Ta ₂ O ₉ film, is expected as a dielectric film applicable to a semiconductor memory device. These dielectric films are generally formed by a high frequency sputtering method in which a ceramic sintered target is sputtered. By using a target composed of a composition suitable for the dielectric film to be formed, the dielectric film of a desired material can be obtained. Body membrane formation is in progress.

However, the above-mentioned Pb (ZrTi) O
The metal oxide dielectric film such as ₃ film or SrBi ₂ Ta ₂ O ₉ film is composed of a composition containing a low melting point substance such as Pb or Bi and a high melting point substance such as Ta or Zr. Since the vapor pressure of the high melting point substance and the vapor pressure of the low melting point substance are greatly different, the composition ratio of the formed dielectric film may deviate from the composition ratio of the target used for sputtering. .

It is generally known that a low-melting point substance having a high vapor pressure is hard to be taken into a dielectric, and a dielectric film having a different composition ratio seriously affects the characteristics of a semiconductor device. In the prior art, a low melting point substance that is hard to be taken into the dielectric film was excessively taken into the target to prevent the composition ratio from being shifted.

However, even when the targets having the same composition ratio are used, the sputtering conditions such as the substrate temperature are different, or when the targets having the same composition ratio have the same sputtering conditions but different sputtering apparatuses, the dielectric There is a phenomenon that the composition ratio of the body membrane is different.

Particularly, when the sputtering apparatus is different, the distance between the target and the substrate is different, and due to the difference in the structure of the deposition preventive plate in the vacuum chamber, the shape of plasma formed in the apparatus is different. It will be different. As a result, the plasma density near the surface of the substrate becomes large, and the composition ratio of the formed dielectric film is greatly different even if a target of the same composition is sputtered. Even in such a case, there is a problem that a dielectric film having a stoichiometric composition cannot always be obtained.

This problem of the prior art is solved by Pb (Zr
Ti) O ₃ (lead zirconate titanate: hereinafter abbreviated as PZT) film A specific description will be given by taking the case of forming as a dielectric film. When performing this sputtering, Pb containing Pb in a 10% excess over the stoichiometric composition by adding PbO in consideration of deficiency of Pb which is a low melting point substance in advance.
A T ceramic target was used.

The sputtering conditions are Ar gas pressure 0.9P.
a, O ₂ gas pressure 0.1 Pa, substrate temperature 100 ° C.,
A deposition preventive plate disposed around the substrate is placed at a ground potential to serve as an anode electrode, and a frequency of 13.56 is applied to the cathode electrode on which the Pb-excessive PZT ceramic target is disposed.
Sputtering was performed by applying a high frequency voltage of MHz at an input power of 1 kW for 20 minutes.

This sputtering is carried out in two kinds of states, when the substrate holder on which the substrate is placed is placed at the ground potential and when the substrate holder is placed at a floating potential without being electrically connected to anywhere, A dielectric film was formed on each surface of the substrates placed on the substrate holder.

Composition analysis was performed on the dielectric film formed by placing the substrate holder on which the substrate was placed at the ground potential and the dielectric film formed by placing the substrate holder at the floating potential, and the substrate holder was grounded. When placed at a potential, the composition of the dielectric film was insufficient because the Pb content was only about 80% of the stoichiometric composition.
On the other hand, when the floating potential is set, P
The b content is 140% of the stoichiometric composition,
It was excessive.

This difference is because the substrate holder placed at the ground potential serves as the counter electrode (anode electrode) of the cathode electrode, whereas the substrate holder placed at the floating potential does not serve as the cathode counter electrode. it seems to do. That is, when the substrate holder is placed at the ground potential, the amount of plasma incident on the substrate surface increases, and when the plasma etches the dielectric film being formed, the low melting point substance preferentially re-evaporates. The low melting point material is less than stoichiometric.

On the other hand, when the substrate holder is placed at a floating potential, the amount of etching on the surface of the substrate is small because the plasma is less likely to enter the surface of the substrate. Furthermore, the deposition preventive plate serves as an anode electrode and is etched by the plasma. When the attached low melting point substance is re-evaporated, it is taken into the dielectric film formed on the substrate surface, so that the low melting point substance becomes larger than the stoichiometric composition.

As described above, in the conventional sputtering technique, since the re-evaporation amount and the incorporation amount of the low melting point substance cannot be controlled, it is not possible to obtain a dielectric film having a composition according to the stoichiometric composition. It was rare.

[0014]

The present invention was created in order to solve the above-mentioned disadvantages of the prior art, and its purpose is to provide a sputtering apparatus capable of controlling the composition of a dielectric film,
Another object of the present invention is to provide a method for manufacturing a dielectric film.

[0015]

In order to solve the above-mentioned problems, the invention apparatus according to claim 1 is a vacuum tank configured to be capable of being evacuated, a substrate holder and a target holder provided in the vacuum tank. In the sputtering apparatus having, a substrate holder is connected to an impedance circuit having a predetermined amount of impedance, and when a high-frequency voltage is applied to the target holder, a current flows to the substrate holder through the impedance circuit. It is characterized by being configured to flow.

In that case, the impedance circuit may have a resistance component as in the invention device according to claim 2 or may have a capacitance component and an inductance component as in the invention device according to claim 3. .

In addition, like the invention device of claim 4,
The impedance circuit may be provided outside the vacuum chamber, and may be configured to be electrically connected to the substrate holder while maintaining an airtight state in the vacuum chamber.
According to a fifth aspect of the present invention, the substrate holder may be configured to be connected to the anode potential via the impedance circuit.

According to the sixth aspect of the present invention, a high frequency voltage is applied between a substrate holder and a target holder arranged in a vacuum chamber to sputter the dielectric target provided on the target holder. A dielectric film manufacturing method for forming a dielectric film, comprising connecting an impedance circuit to the substrate holder, adjusting an impedance of a current path flowing through the substrate holder, and controlling a composition of the dielectric film. And

According to the structure of the present invention, when a sputtering apparatus is constructed by providing a substrate holder and a target holder in a vacuum chamber which can be evacuated, a predetermined amount of impedance is applied to the substrate holder. Since the impedance circuit having is connected, when a high frequency voltage is applied to the target holder to sputter the target of the dielectric composition, a current will flow to the substrate holder through the impedance circuit,
The potential of the substrate holder can be controlled without providing a bias power source. Therefore, if the impedance value of the impedance circuit is set so that the substrate holder during sputtering has an appropriate potential, the surface of the substrate placed or held on the substrate holder will be appropriately etched. It is possible to control the composition of the dielectric film formed on the substrate surface.

Assuming that the impedance of the impedance circuit is a resistance component, by using a variable resistor,
It becomes easy to adjust the value. In that case, the current flowing in the impedance circuit is a high-frequency current, so if the impedance is configured by the capacitance component and the inductance component instead of the resistance component, or if the impedance component is configured by adding the capacitance component and the inductance component to the resistance component, the current path It becomes possible to more optimally adjust the substrate potential to various impedances of the high frequency power source.

Incidentally, in the sputtering device which applies a high frequency voltage with the target holder as the cathode electrode,
It is a general configuration to connect the deposition preventive plate provided around the substrate holder to the anode potential.
Since discharge occurs between the target holder and the deposition plate or vacuum chamber, if the substrate holder is connected to the anode potential via the impedance circuit, the target holder will pass the plasma, the substrate holder, and the impedance circuit to the anode potential. It becomes possible to form a current path reaching the potential. In this case, the anode potential on which the deposition preventive plate and the vacuum chamber are placed is usually the ground potential.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION 【Example】

<Example 1> An example of the sputtering apparatus of the present invention is shown in FIG.
It will be described together with the method 2 for producing a dielectric film of the present invention, which is indicated by reference numeral 2. The sputtering apparatus 2 has a vacuum chamber 9, a spacer 13 is provided on the bottom surface thereof, and a substrate holder 7 is provided on the spacer 13 via an insulator 14.

The substrate holder 7 is constructed so that the substrate 11 can be placed horizontally, and the target holder (backing plate) 8 is mounted on the ceiling of the vacuum chamber 9 above the substrate holder 7 via an insulator 19. Is airtightly attached. The back side of this target holder 8 is in the atmosphere,
The surface is located inside the vacuum chamber 9, and a target 12 formed by molding a ceramic sintered body, which is a material of the dielectric film, in a flat plate shape is substantially parallel to the substrate 11 on the surface portion. Is provided.

The back surface of the target holder 8 is connected to one end of a high frequency power source 17 for sputtering arranged outside the vacuum chamber 9, and the other end of the high frequency power source 17 and the vacuum chamber 9 are connected.
And are connected to ground potential. An adhesion-preventing plate 15 made of a metal material is provided on the bottom surface of the vacuum chamber 9 so as to surround the substrate holder 7 and has the same potential as the vacuum chamber 9.

The vacuum chamber 9 is provided with a gas introduction hole 23 and an exhaust hole 24. When performing sputtering, the substrate 11 is placed on the substrate holder 7 and a vacuum (not shown) connected to the exhaust hole 24 is provided. After the pump is started to bring the inside of the vacuum chamber 9 to a high vacuum state, Ar gas which is a sputtering gas is introduced from the gas introduction hole 23, the sputtering power source 17 is started, and the target holder 8 is used as a cathode electrode.
A high frequency voltage of 3.56 MHz is applied. Then, the deposition preventive plate 15 serves as an anode electrode for the target holder 8 and also serves as electrodes facing each other, and plasma is generated near the surface of the substrate 11. Target 12 by the plasma
When the surface is sputtered, the composition forming the target 12 is deposited on the substrate 11 to form a dielectric film.

One end of a copper wire 10 ₁ is connected to the substrate holder 7, and the other end of the copper wire 10 ₁ is connected to the vacuum tank 9 side of a current introducing terminal 16 airtightly provided on the bottom surface of the vacuum tank 9. The copper wire 10 ₂ is connected to the atmosphere side of the current introducing terminal 16
Is connected to one end of the impedance circuit 5 and the other end thereof is electrically connected to one end of the impedance circuit 5 located outside the vacuum chamber 9. The other end of the impedance circuit 5 is placed at the ground potential.

Therefore, a current path through the impedance circuit 5 is formed between the substrate holder 7 and the ground potential, and when electrons or ions are incident on the surface of the substrate 11, a current flows through the impedance circuit 5. At the time of sputtering, the substrate holder 7 has a potential according to the impedance of the impedance circuit 5 and the magnitude of the current flowing therethrough, and may not be in the floating potential state, but may be left at the anode potential. Absent.

This impedance circuit 5 includes a resistor 5 ₁
And a coil 5 ₂ and a capacitor 5 _3, and inside the impedance circuit 5, a resistor 5 ₁ and a coil 5 _{2 are provided.}
A capacitor 5 ₃ is connected in parallel to a circuit in which and are connected in series, and is configured to be inserted between the copper wire 10 ₂ and the ground potential. It is designed to have a fixed amount of impedance.

The resistance value of the resistor 5 ₁ is set to 500 kΩ, and the inductance value of the coil 5 ₂ is 1.2 μ.
Henry, set the capacitance value of condenser 5 ₃ to 10
Set it to 0 pF and set Pb to PZT on the target 12
Excessively added in the form of bO compound, the composition of Pb _1.1 (Zr
_A dielectric film was formed using a ceramic sintered target containing _0.5 Ti _0.5 ) O ₃ . The sputtering condition is 5 in the vacuum chamber 9.
After evacuating to × 10 ^-4 Pa or less, gas introducing hole 23
Ar gas mixed with 5% of O ₂ gas was introduced from
In an atmosphere of Pa, a high frequency voltage of 13.56 MHz was applied to the cathode 8 with an input power of 1 kW.

After the completion of sputtering, the substrate 11 was taken out of the vacuum chamber 9 and the dielectric film formed on the surface was analyzed. The composition was the same as that of the sintering target used, and Pb _1.1 (Zr _0.5 It was Ti _0.5 ) O ₃ .

The impedance of the impedance circuit 5 can be changed by replacing the resistor 5 ₁ , the coil 5 ₂ , and the capacitor 5 ₃ and adjusting the resistance component, the inductance component, and the capacitance component. Even in a sputtering apparatus different from 2, the impedance film 5 having an appropriate impedance can be connected to the substrate holder to obtain a dielectric film having the same composition as the target provided.

<Comparative Example 1> The impedance circuit 5 and the copper wires 10 ₁ and 10 ₂ are removed from the sputtering apparatus 2, and the spacer 13 and the insulator 14 are replaced by a metal spacer 113 as shown in FIG. The substrate holder 7 was attached to the bottom of the vacuum chamber 9, and a sputtering apparatus 102 was constructed in which the potential of the substrate holder 7 was set to the ground potential via the vacuum chamber 9 as in the conventional technique. At this time, the target 12 was not replaced.

The substrate 11 was placed on the substrate holder 7 of the sputtering apparatus 102, and sputtering was carried out under the same sputtering conditions as in the above-mentioned Example 1. The composition of the dielectric film formed on the surface of the substrate 11 depends on the target 12 used.
The composition was Pb _0.7 (Zr _0.5 Ti _0.5 ) O ₃ , which was different from the composition No. ₁ , and the composition was an extremely small amount of Pb.

Comparative Example 2 Next, the impedance circuit 5
The metal spacer 113 is returned to the spacer 13 and the insulator 14 while being removed, and a sputtering device 112 in which the substrate holding plate 7 is placed at a floating potential as in the prior art is configured. At this time, the target 12 was not replaced.

The substrate 11 was placed on the substrate holder 7 of this sputtering apparatus 112, and the above-mentioned Example 1 and Comparative Example 1 were carried out.
Sputtering was performed under the same sputtering conditions. The composition of the dielectric film formed on the surface of the substrate 11 is the target 1
Unlike the composition of No. 2, it was Pb _1.5 (Zr _0.5 Ti _0.5 ) O ₃ , and the amount of Pb was extremely large.

[0036]

【Example】

<Embodiment 2> Next, an example of another sputtering apparatus of the present invention will be described with reference numeral 52 in FIG. In FIG. 2, the members of the sputtering apparatus 52 that are common to the above-described sputtering apparatus 2 are designated by the same reference numerals, and the description thereof will be omitted.

The sputtering device 52 has an impedance circuit 55 in place of the impedance circuit 5, one end of which is a copper wire 10 ₁ and a current introducing terminal 16 is provided.
If is electrically connected to the substrate holder 7 via the copper wire 10 _2, and the other end is connected to the ground potential. This impedance circuit 55 has a resistor 55 ₁ ,
The resistor 55 ₁ is configured to be inserted between the copper wire 10 ₂ and the ground potential inside the impedance circuit 55.

This resistor 55 ₁ is a variable resistor and is constructed so that the magnitude of the resistance value can be changed from 0Ω to 10 MΩ, and the target 12 having the same composition as that used in the sputtering apparatus 2 is used. Sputtering was performed under the same sputtering conditions as in Example 1 except that the impedance between the substrate holder 7 and the ground potential was different.

At this time, the impedance of the impedance circuit 55 was changed from 0Ω to about 2MΩ, a dielectric film was formed on the surface of the substrate placed on the substrate holder 7 having a different potential, and the composition was analyzed. The results are shown in FIG. 3 with the resistance value R (Ω) of the impedance circuit 55 as the horizontal axis and the Pb ratio x when the corresponding dielectric film Pb _X (Zr _0.5 Ti _0.5 ) O ₃ is taken as the vertical axis. Shown in the graph.

Impedance of impedance circuit 55
As the (resistance value R) increases, the Pb ratio X increases, and when the Pb ratio is R = 100 kΩ, the stoichiometric composition is x = 1.0.
And x = 1.1, which is the same as that of the sintered target used when R = 300 kΩ.

[0041]

【Example】

 <Example 3> The following composition,

K _1.2 NbO ₃ (potassium niobate) Pb _1.1 TiO ₃ (lead titanate) (Pb _1.1 La _0.04 ) (Zr _0.5 Ti _0.5 ) O ₃ (lanthanum lead zirconate titanate / PLZT) Li _1.2 NbO ₃ ( Lithium niobate) Li _1.2 TaO ₃ (lithium tantalate) Sr _1.1 Bi _2.5 T ₂ O ₇ (strontium bismuth titanate) Bi _4.5 Ti ₃ O ₁₂ (bismuth titanate). The targets are held one by one on the target holder 8 of the sputtering device 52, and sputtering is performed under the same sputtering conditions as those in the above-described first and second embodiments to form a dielectric film of a composition corresponding to each target on the substrate surface. Formed and subjected to compositional analysis. The results are shown in Table 1 below.

[0043]

[Table 1]

In any case, it is understood that the composition of the dielectric film formed is different if the impedance of the impedance circuit 55 is different even under the same target and the same sputtering condition. Further, it was found that there are impedance values at which a dielectric film having the same composition as each target can be obtained and impedance values at which a dielectric film having a stoichiometric composition can be obtained, similarly to the PZT target.

As described above in detail, the present invention is effective when the composition of the dielectric target contains metal substances having different melting points (high melting point substance and low melting point substance).

As is widely known, the melting point of the metal substance contained in each composition described above is 1 atm.

K: 63.5 ° C. Li: 179 ° C. Bi: 271.4 ° C. Pb: 327.5 ° C. Sr: 769 ° C. La: 920 ° C. Ti: 1675 ° C. Zr: 1852 ° C. Nb ...... 2467 ° C. Ta ・ ・ ・ 2996 ° C., and both compositions contain a high melting point substance having a melting point of 1000 ° C. or higher and a low melting point substance having a melting point of less than 1000 ° C. It can be seen that the difference in melting point between the high melting point substance and the low melting point substance contained therein is at least 500 ° C. or more. The present invention is particularly effective for a dielectric target containing in its composition two or more kinds of substances having a melting point difference of 500 ° C. or more.

[0048]

Since the substrate holder during sputtering can be set to an appropriate potential, the composition ratio of the low melting point substance in the dielectric film can be controlled, and a dielectric film having a stoichiometric composition can be obtained. You can By changing the impedance value, it is possible to obtain a dielectric thin film having a constant composition ratio even when the sputtering apparatus and the sputtering conditions are different or the composition ratio of the target is changed. Therefore, manufacturing variations can be reduced, and the quality of the dielectric thin film becomes stable.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a sputtering apparatus of the present invention.

FIG. 2 is a sectional view of another example of the sputtering apparatus of the present invention.

FIG. 3 shows resistance values R and P when a dielectric film is formed using the sputtering apparatus and a PZT sintered target.
Graph showing the relationship with b ratio

FIG. 4 An example of a sputtering device in which the substrate holder is placed at ground potential

FIG. 5: An example of a sputtering device in which the substrate holder is placed at a floating potential

[Explanation of symbols]

2, 52 ...... Sputtering device 5, 55 ...... Impedance circuit 7 ...... Substrate holder 8 ...... Target holder 9 ...... Vacuum chamber 11 ...... Substrate 12 ...... Target

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials (72) Inventor Michio Ishikawa 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Materials Research

Claims (6)

[Claims] 1. A sputtering apparatus comprising a vacuum chamber configured to be evacuated, and a substrate holder and a target holder provided in the vacuum chamber, wherein the substrate holder has an impedance having a predetermined amount of impedance. A sputtering apparatus, characterized in that a circuit is connected so that when a high frequency voltage is applied to the target holder, a current flows through the substrate holder through the impedance circuit. 2. The sputtering apparatus according to claim 1, wherein the impedance circuit has a resistance component. 3. The sputtering apparatus according to claim 1, wherein the impedance circuit has a capacitance component and an inductance component. 4. The impedance circuit is provided outside the vacuum chamber, and is electrically connected to the substrate holder while maintaining an airtight state in the vacuum chamber. The sputtering apparatus according to any one of 1. 5. The substrate holder according to claim 1, wherein the substrate holder is configured to be connected to an anode potential via the impedance circuit.
The sputtering apparatus according to the item. 6. A dielectric film for forming a dielectric film by applying a high frequency voltage between a substrate holder and a target holder arranged in a vacuum chamber to sputter a dielectric target provided on the target holder. A method of manufacturing a dielectric film, comprising connecting an impedance circuit to the substrate holder, adjusting impedance of a current path flowing through the substrate holder, and controlling a composition of the dielectric film.