JP2001098371A - Deposition of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To densify a thin film formed by a sputtering method. SOLUTION: In a state where a film deposition chamber 2 is grounded, a positive voltage and a negative voltage are alternately applied to a target holder 11 and a voltage being opposite in polarity to the voltage applied to the target holder 11 is applied to a substrate holder 9. When the negative voltage is applied to the target holder 11, Ar+ is allowed to sputter a target to deposit a thin film onto the surface of a substrate 10; when the negative voltage is applied to the substrate holder 9, Ar+ is allowed to sputter the surface of the substrate 10 to activate sputtered particles and densify the thin film. Accordingly, an ion assisted effect can be obtained without use of an ion source, and a thin film of high density can be deposited onto the surface of the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of a sputtering apparatus, and more particularly to a method for forming a high-density film.

[0002]

2. Description of the Related Art Conventionally, DC discharge sputtering has been used in many industrial fields because its structure is simple and a uniform film can be obtained on a wide substrate. Further, in order to cope with various film forming conditions and to increase the density of a formed film, a magnetron sputtering method, a high frequency method, and a dynamic mixing method are used as new sputtering methods.

The prior art dynamic mixing method is an improvement of the DC discharge method, and is denoted by reference numeral 101 in FIG.
Indicates a sputtering apparatus using a dynamic mixing method. The sputtering apparatus 101 has a vacuum chamber 102. A rotating mechanism 108 is provided on the ceiling of the vacuum chamber 102. A substrate holder 109 is arranged inside the vacuum chamber 102 and is connected to a rotation mechanism 108. A target holder 111 is disposed at the bottom of the vacuum chamber 102, and a target 112 is placed on the target holder 111.
Is arranged. A vacuum exhaust system 1 is provided outside the vacuum chamber 102.
03 and the gas introduction system 104 are arranged, and the vacuum chamber 10
2 are connected.

When sputtering is performed using this apparatus, the inside of a vacuum chamber 102 is evacuated by a vacuum evacuation system 103 to 10 ^-7 To
rr (1.33 × 10 ⁻⁵ Pa) or less, and the substrate 110 is placed on the substrate holder 109.
4 introduces Ar gas into the vacuum chamber 102.

Next, the substrate 110 is rotated in a horizontal plane by the rotation mechanism 108 and several tens of
A negative DC voltage of 0 V is applied, Ar gas introduced into the vacuum chamber 102 is ionized to be in a plasma state, and Ar ions
(Ar ⁺ ) is generated. Ar ⁺ flies in the direction of the target 112 to which the negative voltage is applied, sputters the surface of the target 112, and the sputtered particles collide with the substrate 110, and a thin film is formed on the substrate 110. Since the substrate 110 is rotating in a horizontal plane, sputtered particles uniformly collide with the surface of the substrate 110, and a thin film having a substantially uniform thickness can be formed on the substrate surface.

However, since the surface of the substrate 110 is not completely flat at the molecular level, if the sputtered particles only enter the surface of the substrate, the surface of the substrate 110 will be shallow at the shadow of the projection and the projection will grow thick at the projection. With the growth, voids and pores are formed on the surface and inside of the film, so that it is difficult to form a high-density film.

When the sputtered particles diffuse on the thin film or inside the thin film, voids and holes formed on the film surface and inside are filled, so that a dense film is formed.
Since about 90% of the active particles are low-active neutral particles having an energy amount of several eV to several tens eV, sputtered particles cannot sufficiently diffuse. In order to cause the sputtered particles to diffuse sufficiently, it is conceivable to raise the temperature of the substrate. However, an increase in the temperature of the substrate causes damage.

Therefore, in the film forming apparatus 101, the vacuum chamber 1
02, an ion source 105 is provided on the lower side wall. A mass flow controller 106 and a gas cylinder 107 are provided outside the vacuum chamber 102, and are connected to the ion source 105 in series in this order.

When gas is introduced into the ion source 105 from the gas cylinder 107 via the mass flow controller 106 and plasma is generated in the ion source 105, the ion source 10
Ions are generated in 5. When these ions are irradiated onto the substrate 107 during film formation by sputtering, the sputtered particles are activated by the irradiated ions, and a thin film is easily formed even under low temperature conditions. Further, the activated particles cause diffusion movement on the surface of the thin film or inside the thin film, so that gaps and pores on the surface or inside the thin film are filled, and the formed thin film has a high density. When the ions of the sputtering gas collide with the side walls of the grooves on the surface of the thin film, the side walls are etched and the thin film is flattened. Such ion irradiation method is widely used in the field of thin film production because the energy control of irradiation ions is extremely easy.

It is generally known that the energy of irradiated ions is 100 eV or less for forming a high-density film. However, due to the nature of the ion source, low-energy ions of 100 eV or less are applied to the substrate. In the case of irradiation, since a large amount of ions cannot reach the substrate, there is a problem that the effect of ion assist cannot be sufficiently obtained.

In order to allow a large amount of ions to reach the substrate, the energy of the ions to be irradiated may be increased. However, if the energy of the ions is excessively large, the energy added to the sputtered particles becomes too large. There is a problem that the thin film is damaged.

As described above, in the above-described dynamic mixing method, the amount of ions incident on the substrate cannot always be sufficiently controlled, so that a sufficient ion assist effect cannot be obtained and a high-density thin film cannot be formed. Was difficult.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and has as its object to provide an effective ion assist effect to a substrate without irradiating ions. The purpose is to form a thin film.

[0014]

According to a first aspect of the present invention, there is provided a vacuum chamber, a substrate holder disposed in the vacuum chamber, and a substrate facing the substrate holder. Using a film forming apparatus having a target placed in a vacuum chamber, holding the substrate in the substrate holder, and applying a voltage to the target and the substrate holder in a state where a sputtering gas is introduced into the vacuum chamber. A thin film forming method for forming a thin film on the substrate surface by applying the ionized sputter gas to sputter the target with the ions of the sputter gas. And alternately applying voltages of opposite polarities to the substrate holder and the substrate holder.
The invention according to claim 2 is the thin film forming method according to claim 1, wherein the voltage value of the negative voltage applied to the substrate holder is different from the voltage value of the negative voltage applied to the target. It is characterized by having been made. The invention according to claim 3 is the thin film forming method according to claim 2, wherein a voltage value of the negative voltage applied to the substrate holder is smaller than a voltage value of the negative voltage applied to the target. It is characterized in that the absolute value is reduced.

In the method of forming a thin film according to the present invention, when the vacuum chamber is set to the ground potential, voltages having different polarities are alternately applied to the target and the substrate holder. In a state where a negative voltage (hereinafter referred to as a negative voltage) is applied to the target and a positive voltage (hereinafter referred to as a positive voltage) is applied to the substrate holder, ions of the sputtering gas flow in the direction of the target. The target jumps and collides with the target to be sputtered, and a thin film of sputtered particles is formed on the substrate surface.

On the other hand, when a positive voltage is applied to the target and a negative voltage is applied to the substrate holder, ions of the sputter gas fly toward the substrate, and energy is given to sputter particles near the substrate surface. The applied energy activates the sputtered particles and facilitates the formation of a thin film even under low temperature conditions. Further, the activated sputtered particles cause diffusion movement on the surface or inside the thin film, so that gaps and holes on the surface or inside the thin film are filled, and the formed thin film has a high density.

According to the present invention, when the vacuum chamber is set to the ground potential, voltages of opposite polarities are alternately applied to the target and the substrate holder. Ions can be ejected in both the target direction and the substrate direction, an ion assist effect can be obtained without the need for an ion source, and a high-density thin film can be formed.

The ion energy during sputtering is
It is almost proportional to the voltage value of the negative voltage applied to the target or the substrate, and if the voltage value of the negative voltage applied to the substrate and the voltage value applied to the target are the same, the case of flying in the target direction and the case of the substrate direction And the energy of the ion of the sputtering gas becomes the same.

In this case, if the energy of the ions of the sputtering gas flying in the direction of the target is increased, the energy of the ions of the sputtering gas flying in the direction of the substrate becomes excessively large, and the thin film on the substrate surface may be damaged. is there.

However, in the present invention, the voltage value of the negative voltage applied to the target is made different from the voltage value of the negative voltage applied to the substrate holder. In particular, when the voltage value of the negative voltage applied to the substrate is made smaller than the voltage value of the negative voltage applied to the target, the energy of the ions of the sputtering gas that flies toward the substrate flies toward the target. It is smaller than the ion energy of the sputtering gas.

Accordingly, even when the energy of the ions of the sputtering gas flying toward the target increases and the sputtering is performed in a large amount, the energy of the ions of the sputtering gas flying toward the substrate is prevented from becoming excessively large. Therefore, a high-density thin film can be formed without damaging the thin film.

[0022]

Embodiments of the present invention will be described with reference to the drawings. Reference numeral 1 in FIG. 1 shows an example of a sputtering apparatus used in the thin film forming method of the present invention.

The sputtering apparatus 1 has a vacuum chamber 2.
A rotation mechanism 8 is provided on the ceiling of the vacuum chamber 2. A substrate holder 9 is arranged inside the vacuum chamber 2. The substrate holder 9 is connected to a rotation mechanism 8 so that the substrate holder 9 can be rotated in a horizontal plane by the rotation mechanism 8. At the bottom of the vacuum chamber 2, a target holder 11 attached to a support 13 is arranged, and a carbon target 12 is arranged on the target holder 11. A vacuum exhaust system 3 and a gas introduction system 4 are arranged outside the vacuum chamber 2 and are connected to the vacuum chamber 2.

The vacuum evacuation system 3 has a valve 31, a high vacuum pump 32, a valve 33, and a low vacuum pump 34, and is connected to the vacuum chamber 2 in this order. When the pump 32 and the low vacuum pump 34 are activated, the inside of the vacuum chamber 2 can be evacuated.

The gas introduction system 4 has a valve 43, a mass flow controller 42, and a gas cylinder 41. The gas introduction system 4 is connected to the vacuum chamber 2 in this order.
The gas can be introduced into the vacuum chamber 2 from the gas cylinder 41 via the mass flow controller 42.

A high-frequency power supply 25 is provided outside the vacuum chamber 2.
Are connected to the rotation mechanism 8 and the support 13. The rotating mechanism 8 and the support 13 are attached to the vacuum chamber 2 via insulating couplings 21 and 22, respectively, and are insulated from the vacuum chamber 2.

Although the vacuum chamber 2 and the gas introduction system 4 are grounded, the substrate holder 9 and the target holder 11 are mounted on the rotating mechanism 8 and the support 13, respectively, and are insulated from the vacuum chamber 2. When the high-frequency power supply 25 is started, a voltage described later can be applied to each of the substrate holder 9 and the target holder 11.

A method for forming a carbon thin film on the surface of the substrate 10 using the above-described sputtering apparatus will be described below. First, the inside of the vacuum chamber 2 is evacuated to 10 ⁻⁷ Torr by the vacuum evacuation system 3.
(1.33 × 10 ⁻⁵ Pa) or less, and while maintaining the vacuum state, Si is introduced into the vacuum chamber 2 by a transfer system (not shown).
The substrate 10 is loaded and held by the substrate holder 9, and the substrate 10
After facing the surface of the target 12 with the target 12, Ar gas is introduced into the vacuum chamber 2 by the gas introduction system 4.

When the pressure in the vacuum chamber 2 is 1 × 10 ⁻⁴ Torr (1.
33 × 10 ⁻² Pa), the rotation mechanism 8 rotates the substrate 10
Is rotated in a horizontal plane, the high-frequency power supply 25 is activated, and pulse voltages V _S and V _T described later are applied to the substrate holder 9 and the target holder 11, respectively.

FIG. 2 shows the voltage V applied to the substrate holder 9.
Shows the _S, a voltage waveform diagram of the voltage V _T applied to the target holder 11. First, the high frequency power supply 25 is connected to the substrate holder 9.
To a positive voltage + V _1, a negative voltage -V ₁ to the target holder 11, respectively applied (referred to as the period t ₁ the period of negative voltage -V ₁ to the target holder 11 side is applied in the following.). Here, the voltage values of + V ₁ and −V ₁ are respectively +
400V, -400V.

Then, the Ar gas introduced into the vacuum chamber 2 is ionized to be in a plasma state, and Ar ions (Ar ⁺ ) are generated. Since Ar ⁺ is a positive ion, it receives an attractive force toward the target holder 11 to which the negative voltage −V ₁ is applied, flies toward the target 12, collides with the surface of the target 12, and sputters the target 12. When the sputtered carbon particles adhere to the surface of the substrate 10, a thin film is formed on the surface of the substrate 10. At this time, the substrate 1 is rotated by the rotation mechanism 8.
Since 0 rotates with the substrate holder 9 in the horizontal plane, sputter particles are uniformly sputtered on the surface of the substrate 10.

Next, the high frequency power supply 25 is connected to the substrate holder 9.
And the voltage applied to the target holder 11, respectively.
Is inverted, and a negative voltage −V is applied to the substrate holder 9._TwoTo
A positive voltage + V is applied to the target holder 11._Two, Respectively
(A negative voltage −V is applied to the substrate holder 9 side)._TwoIs applied
For the period t_TwoCalled. ). Here, + V_Two, -V _Two
Are +200 V and -200 V, respectively.

At this time, contrary to the period t ₁ , Ar ⁺ flies toward the substrate 10 by the attraction from the substrate 10 to which the negative voltage −V ₂ is applied, and collides with the thin film formed on the surface of the substrate 10. I do.

The sputtered particles on or near the surface of the substrate 10 are activated by receiving energy from Ar ⁺ , and grow even under a low temperature condition. Further, the activated sputtered particles cause diffusion movement on the surface or inside the thin film, so that gaps and pores on the surface or inside the thin film are filled, and the formed thin film has a high density.

Thereafter, the high-frequency power supply 25 reverses the polarity of the voltage applied to the substrate holder 9 and the polarity of the voltage applied to the target holder 11, and applies a positive voltage + V ₁ to the substrate holder 9 and a negative voltage −V to the target holder 11. ₁ is applied (period t ₁ ).

The high frequency power supply 25 repeats the above operation,
A negative voltage −V ₁ and a positive voltage + V ₁ are applied to the target holder 11 and the substrate holder 9 during the period t ₁ , respectively, and a positive voltage + is applied to the target holder 11 and the substrate holder 9 during the period t _2.
Alternately applying a negative voltage -V ₂ and V _2.

As described above, the high frequency power supply 25 alternately applies voltages having different polarities to the substrate holder 9 and the target holder 11, thereby causing Ar ⁺ to sputter the surface of the target 12 in the period t ₁ , At t ₂ , the sputtered particles on the surface of the substrate 10 can be activated.

As described above, a high-density thin film can be formed without using an ion source. In the present embodiment, the period t
_{When 1} was set to 60 μs and the period t ₂ was set to 40 μs, and the above-described voltage application was continued for 30 minutes, a 10 nm carbon thin film was formed on the surface of the substrate 10. The carbon thin film thus formed had a high density and a uniform thickness throughout the substrate.

It should be noted that the energy of Ar ⁺ is the negative voltage − applied to the target holder 11 and the substrate holder 9 respectively.
Since V _1, is substantially proportional to the absolute value of -V _2, in case of these negative voltages -V _1, the absolute value of -V ₂ the same size,
The energy of Ar ⁺ is substantially the same between the case of flying in the direction of the target 12 and the case of flying in the direction of the substrate 10.

For this reason, in order to sputter the target 12 in large quantities, when the energy of Ar ⁺ flying toward the target 12 is increased, the energy of Ar ⁺ flying toward the surface of the substrate 10 is also increased. Damage may occur.

However, in the above embodiment, the absolute values of the negative voltages −V ₁ and −V ₂ applied to the target holder 11 and the substrate holder 9 are different from each other, and the negative voltage −V ₁ applied to the substrate holder 9 is different. the absolute value of V ₂ (200V)
Is made smaller than the absolute value (400 V) of the negative voltage −V ₁ applied to the target holder 11.

For this reason, the energy of Ar ⁺ flying toward the substrate 10 becomes smaller than the energy of Ar ⁺ flying toward the target 12 and can be prevented from becoming excessively high. It becomes possible to form a dense thin film.

In the above embodiment, the case of forming a carbon thin film has been described. However, the present invention is not limited to this, and in particular, a heteroepitaxial film or a
This is effective in a film forming process that requires a dense thin film structure, such as when a DLC (Diamond like carbon) thin film is formed.

[0044] Further, in the above embodiment, a negative voltage is applied -V ₁ to the target 12 in the period t _1, but by applying a negative voltage -V ₂ to the substrate holder 9 in the period t _2, the present invention will now However, for example, as shown in FIG.
2 negative voltage -V ₂ is applied in the period t ₁ to a substrate holder 9
A negative voltage −V ₂ is applied in a period t ₂ ,
The target 12 may be configured to apply the same magnitude of the negative voltage −V ₂ to both the substrate holder 9 and the target 12.

Further, the absolute value of the negative voltage -V ₁ is applied to the target holder 11 and 400V, the substrate holder 9
While the 200V negative absolute value of the voltage -V ₁ is applied to, the present invention is not limited to this, the absolute value of -V ₁ 10
It may be a 1MV following range of 0V, the absolute value of -V ₂ may be any 1MV following range of 10V.

Further, in the present embodiment, the periods t ₁ and t ₂ are set to 60 μs and 40 μs, respectively, and the pulse voltages V _S and V _T
(T ₁ + t ₂ ) is 100 μs and the frequency is 10 kHz.
z, but the periods t ₁ and t _{2 of} the present invention and the frequencies of the pulsed voltages V _S and V _T are not limited to these.
For example, the periods t ₁ and t ₂ may be in a range from 1 ps to 1 s. Further, a pulsed voltage V _S, the frequency of the V _T is 0.5H
What is necessary is just to be in the range of z or more and 1 THz or less. Although Ar gas is used as a sputtering gas, the present invention is not limited to this, and an inert gas such as Xe gas or Ne gas may be used.

[0047]

As described above, a high-density thin film can be formed without damaging the thin film.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a sputtering apparatus used for a thin film forming method of the present invention.

FIG. 2 is a voltage waveform diagram illustrating an example of voltages respectively applied to a target and a substrate holder in the thin film forming method according to the embodiment of the present invention.

FIG. 3 is a voltage waveform diagram illustrating an example of voltages respectively applied to a target and a substrate holder in a thin film forming method according to another embodiment of the present invention.

FIG. 4 is a view for explaining a sputtering apparatus which performs a conventional dynamic mixing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sputter apparatus 2 ... Vacuum tank 3 ... Vacuum exhaust system 4 ... Gas introduction system 9 ... Substrate holder 1
0: substrate 11: target holder 12: target 25: high frequency power supply

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiro Yamamoto 2500 Hagizono, Chigasaki-shi, Kanagawa Japan Vacuum Engineering Co., Ltd. (72) Masato Kiuchi 1-81-31 Midorioka, Ikeda-shi, Osaka Industrial Technology Osaka Industrial Co., Ltd. Within the Technical Research Institute (72) Inventor Satoshi Sugimoto 1-5-14, Shichijo 1-chome, Nara City, Nara Prefecture (72) Inventor Katsutoshi Tanaka 1-3-6, Higashiizumioka, Toyonaka City, Osaka Prefecture 3-2-1, Furuedai, Suita-shi, Fu-ku 508 F-term (reference) 4K029 BA34 DC05 DC35 JA02

Claims (3)

[Claims] 1. A substrate holder, comprising: a film forming apparatus having a vacuum chamber, a substrate holder arranged in the vacuum chamber, and a target arranged in the vacuum chamber so as to face the substrate holder. In a state where the sputtering gas is introduced into the vacuum chamber, a voltage is applied to the target and the substrate holder to ionize the sputtering gas, and the target is sputtered with the ions of the sputtering gas. A thin film forming method for forming a thin film on the substrate surface, wherein when the vacuum chamber is set to a ground potential, voltages of opposite polarities are alternately applied to the target and the substrate holder. Thin film forming method. 2. The thin film according to claim 1, wherein a voltage value of the negative voltage applied to the substrate holder is different from a voltage value of the negative voltage applied to the target. Forming method. 3. The voltage value of the negative voltage applied to the substrate holder is smaller in absolute value than the voltage value of the negative voltage applied to the target. Item 3. The method for forming a thin film according to Item 2.