JPH06145972A - Bias sputtering method and its device - Google Patents

Abstract

PURPOSE:To form films having high quality by controlling the incident energy of the incident cations on a substrate. CONSTITUTION:The inside wall on the upper side of a vacuum vessel 8 is provided with a sputtering electrode 1 and the inside wall on the lower side is provided with a substrate electrode 2. A third electrode 3 is provided opposite to these electrodes near both side walls so as to include the space between the sputtering electrode 1 and the substrate electrode 2. Target materials 5a and 5b are fixed atop the sputtering electrode 1 and the third electrode 3. A substrate 6 to be formed with the films is fixed atop the substrate electrode 2. On the other hand, the DC electric power past a low-pass filter and the high- frequency electric power past a matching circuit are connected to the sputtering electrode 1. The DC electric power past the low-pass filter or the high-frequency electric power past the matching circuit is connected to the substrate electrode 2 so as to be switched by a switch 7. The DC electric power past the low-pass filter is connected to the third electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias sputtering method and apparatus for subjecting a substrate to film formation in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Conventionally, a sputtering method has been used as one method for forming a thin film on a substrate such as a semiconductor wafer. In a general sputtering method, a vacuum state of about 10 ⁻³ to 10 ⁻² [Torr] is formed in a vacuum container,
DC power or high frequency power is applied to the sputter electrode that holds the target material to cause plasma discharge, and cations are accelerated and impacted by the cathode drop voltage to the sputter electrode, which is the cathode, and this impact causes the target material placed on the sputter electrode. A thin film is formed by depositing the atoms released from the substrate on a substrate placed in a vacuum chamber.

The present invention relates to the bias sputtering method among them, and the conventional bias sputtering method will be described below.

FIG. 17 is a schematic block diagram of an apparatus using a conventional bias sputtering method. A magnetic field generating means 302 is provided in the upper side wall of the vacuum container 301, and a sputtering electrode 304,
Substrate electrodes 306 are provided on the lower sidewalls via insulators 303 and 305, respectively. A substrate 307 for forming a film is fixed on the upper surface of the substrate electrode 306, and a target material 308 is fixed on the upper surface of the sputter electrode 304. The substrate 307 is kept at a predetermined temperature by a suitable substrate temperature control means (not shown). The vacuum container 301 is evacuated to a high vacuum by an appropriate vacuum exhausting means (not shown), and then a sputtering gas such as argon is introduced by an appropriate gas introducing means (not shown) to obtain a pressure of several millitorr to several tens of millitorr. Maintained at. Sputtering electrode 3
A high frequency power source 309 having an oscillation frequency of 13.56 MHz is connected to the sputter electrode 304 as a sputter power source through a matching circuit so that the surface of the target material 308 attached to the upper surface of 04 becomes a negative high voltage. The target material 308 is generally made of a coating material formed on the substrate. When a high voltage is applied to the sputter electrode 304, a discharge occurs between the sputter electrode and the substrate electrode to generate plasma. Sputtering gas ions in this plasma, that is, argon ions in the normal case, are the target materials 3.
The target material 309 is accelerated and impacted by being attracted to the negative high voltage potential of 09. Therefore, the material to be formed into a film is knocked out from the target material 309 and deposited on the substrate 307.

A substrate bias power source 31 is used for the substrate electrode 306.
0 is connected. A DC power supply or a high frequency power supply is used as the substrate bias power supply. The purpose of the substrate electrode 306 and the substrate bias power supply 310 is to apply a desired potential to the substrate surface. In general, the substrate bias power source often keeps the DC component of the substrate surface potential at a certain potential during film formation. Since the substrate surface potential is lower than the plasma space potential, argon ions in the plasma also accelerate and impact the substrate surface with energy corresponding to the difference between the plasma space potential and the substrate surface potential. Therefore, by controlling the substrate surface potential, it is possible to control the energy of argon ions that accelerate and impact the substrate surface, and as a result, the film quality (hardness, crystallinity, etc.) of the thin film deposited on the substrate surface,
Adhesion with the substrate, step coverage, etc. can be improved.

Further, in addition to the sputtering electrode 401 and the substrate electrode 402 as in the conventional apparatus shown in FIG. 18, a third electrode 403 is newly installed near the target material 404 or the substrate 405, and between the electrode and the ground. There is known a method of forming a thin film with a DC voltage applied to the thin film.

[0007]

As the performance and the degree of integration of semiconductor devices have increased, the quality of the film (layer) for a semiconductor product obtained by a film forming technique such as a bias sputtering method has been improved. The requirements are more stringent.

However, the film formed by the conventional apparatus using the bias sputtering method has the following problems. 1) When depositing on a stepped portion, step breakage is likely to occur (poor step coverage). 2) A great number of stacking faults are mainly generated in the epitaxial film on the substrate having different conditions such as the Si (111) substrate.

The main cause of these problems is that the amount of irradiation of argon ions is small, the energy of the epitaxially growing atoms (eg Si) is still small, and the surface migration is insufficient.

Therefore, in order to increase the energy of the epitaxially grown atoms, the conventional 13.56 MH is used.
Attempts have been made to form a deposited film of higher quality by controlling the energy distribution and energy peak value of cations such as argon ions incident on the substrate by using high frequency power of 100 MHz or higher higher than the frequency of z.

However, even if an attempt is made to discharge between the target portion, which is the sputter electrode, and the substrate portion, which is the substrate electrode, the discharge by the high frequency power of 100 MHz or more spreads over the entire vacuum container and only lowers the efficiency of the input power. Instead, the plasma density near the wall of the vacuum container increases, causing a problem that impurities are mixed into the film due to sputtering of the vacuum container material itself.

Therefore, in order to prevent the spread of the discharge, the third electrode is installed so as to surround the sputter electrode and the substrate electrode as shown in FIG. 18, and a DC potential is applied to the third electrode. It was necessary to separate the vacuum chamber from the discharge space while preventing the sputtering of the electrode material. This FIG.
FIG. 19 shows the concentration of Fe contained in the deposited film on the substrate with respect to the third electrode potential application by the conventional device configuration shown in FIG. As shown in FIG. 19, by applying a positive potential as a direct-current potential to the third electrode, the concentration of Fe mixed in the film is reduced and sputtering of the vacuum chamber wall is prevented.

However, when forming a high quality film, it is important to control the energy distribution and energy peak value of cations such as argon ions incident on the substrate according to the film material. In particular, it has been pointed out that it is important to clean the deposition environment and control the incident ion energy when the epitaxial growth on the Si wafer is performed by the sputtering method or the bias sputtering method. This incident ion energy control requires that low-energy ions be incident on the substrate, and there is a problem in how much this low-energy control range can be expanded.

Further, in the apparatus using the conventional bias sputtering method, the controllability of incident ion energy is poor,
That is, the energy of argon ions depends on the difference between the plasma space potential and the substrate surface potential. In the conventional bias sputtering method, the substrate space potential is kept at a certain value during film formation, and the plasma space potential has various causes ( When it fluctuates due to fluctuations in discharge parameters such as pressure, gas flow rate, power, fluctuations in target shape, fluctuations in temperature of target, vacuum container, matching circuit, etc., the energy of argon ions that accelerate and impact the substrate surface also fluctuate. . As a result, there is a problem in that the controllability of the film quality (hardness, crystallinity, etc.) of the thin film deposited on the substrate surface, the adhesion to the substrate, the step coverage, etc. becomes poor.

The present invention has been made in view of the above problems of the prior art, and a bias sputtering method and a bias sputtering method for forming a high quality film by controlling the incident energy of cations incident on a substrate. The purpose is to provide the device.

[0016]

According to the present invention for solving the above-mentioned problems, a sputtering electrode for holding a sputtering target material, a substrate electrode for holding a substrate, a sputtering electrode, and A third electrode including a plasma discharge space between substrate electrodes, wherein a plasma generation power source is connected to the sputtering electrode, and a DC power source or a high frequency power source is connected to the substrate electrode. A negative DC voltage is applied to the third electrode, and a target material is placed on the surface of the third electrode, or a ground electrode is provided in the plasma discharge space, and a discharge occupied by the ground electrode is provided. A ground electrode driving mechanism for driving the ground electrode to adjust the space area may be provided.

In a bias sputtering method of sputtering a target material by plasma discharge and depositing constituent atoms of the target material while irradiating the substrate with ions by the plasma discharge, sputtering of the target material while irradiating the substrate with ions. And a method of alternately depositing the step of depositing constituent atoms of the target material on the substrate and a step of irradiating the substrate with ions without performing sputtering of the target material, or a sputtering electrode holding the target material. In a bias sputtering apparatus that applies a high-frequency power and a DC voltage to a substrate electrode that holds a substrate to deposit a thin film on the substrate, an oscillation frequency of a high-frequency power source connected to the sputtering electrode is 50 MHz. The above is the spout Alternating means for alternately applying a DC voltage below the threshold value and a DC voltage above the threshold value at which the electrode target material is sputtered, and in synchronization with the change in the DC voltage applied alternately to the sputtering electrode, The one provided with a matching circuit control means for changing the circuit constant of the matching circuit, or applying high-frequency power to the sputtering electrode holding the target material and applying a DC voltage to the substrate electrode holding the substrate, In a bias sputtering apparatus for depositing a thin film, a floating potential detecting means for detecting a floating potential of a plasma discharge space, which is a high frequency power source connected to the sputtering electrode at a power frequency of 50 MHz or more, and a DC voltage applied to the substrate electrode. Potential control means for controlling the temperature based on the floating potential of the plasma discharge space In a bias sputtering apparatus for depositing a thin film on a substrate, which is provided with or applies high-frequency power to a sputtering electrode that holds a target material and applies a DC voltage to a substrate electrode that holds a substrate, the sputtering electrode Is a high frequency power source having a power source frequency of 50 MHz or more, and a high frequency current detecting means for detecting a current value flowing in the substrate between the substrate electrode and the DC power source; and the high frequency current detecting means based on the current value. A substrate potential control means for controlling the substrate DC voltage of the DC power supply may be provided.

[0018]

In the bias sputtering apparatus according to the present invention having the above-described structure, the substrate electrode driving mechanism drives the substrate electrode to increase the conductance of the plasma discharge space, and then the exhaust port of the vacuum container is brought to an ultrahigh vacuum state. Exhausted by. After reaching the ultra-high vacuum state, the substrate electrode is adjusted to a desired position by the substrate driving mechanism and the sputtering gas is introduced from the gas introduction port.

Next, a positive potential is applied to the substrate electrode on which the substrate is arranged, and a negative high potential is applied to the third electrode on which the target material is arranged, from a DC power source. Then, by applying high-frequency power from the high-frequency power supply and negative high potential from the direct-current power supply to the sputter electrode holding the target material, discharge is generated between the sputter electrode and the substrate electrode, and plasma is generated. Sputtering gas ions in the plasma are attracted to the negative high potentials of the substrate electrode and the third electrode and are accelerated and impacted on each target material. Therefore, the material forming the target material is knocked out from the target material and deposited on the substrate.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

The apparatus of this embodiment has a vacuum container 8, a sputtering electrode 1 is provided on the upper inner wall of the vacuum container 8, and a substrate electrode 2 is provided on the lower inner wall opposite to the sputtering electrode 1.
Further, in the vicinity of both side walls, a third electrode 3 is provided so as to face the space between the sputter electrode 1 and the substrate electrode 2 so as to include the space. Target materials 5a and 5b are fixed on the upper surfaces of the sputter electrode 1 and the third electrode 3, and a substrate 6 on which a film is to be formed is fixed on the upper surface of the substrate electrode 2. On the other hand, the sputter electrode 1 is connected to the DC power via the low pass filter and the high frequency power via the matching circuit, and the substrate power 2 is switched to the DC power via the low pass filter or the high frequency power via the matching circuit. It is connected so that it can be switched at 7. Then, DC power is connected to the third electrode 3 via a low-pass filter.

A cooling unit is provided on one of both side walls of the vacuum vessel 8 via a pipe, and an ultra-vacuum exhaust unit A is provided on the other side. A bellows 10 for moving the electrode substrate 2 in the vertical direction is provided on the lower side wall of the vacuum container 8, and a gas introduction / exhaust unit 9 and an ultra-vacuum exhaust unit B are provided on the lower side of the substrate electrode 2. There is.

FIG. 2 is a perspective view for explaining the structure of the gas introduction / exhaust unit 9. As shown in this figure, the gas inlet / outlet unit 9 has gas outlets 9b and outlets 9c alternately arranged on the upper surface thereof.
The gas introduced into the chamber is uniformly introduced and exhausted. The device configured as described above is controlled by a control device (not shown).

Next, the operation of this embodiment will be described.

In the apparatus of this embodiment, the support portion of the substrate electrode 2 is lowered through the bellows 10 to increase the conductance in the discharge air space, and then the vacuum vessel 8 is set in the ultra-high vacuum exhaust units A and B. Evacuate to below 10 ^-8 Torr. After reaching the ultra-high vacuum state, the support portion of the substrate electrode 2 is adjusted to a desired position by the bellows 10 and Ar gas adjusted to about 10 ⁻³ to 10 ⁻² [Torr] pressure is supplied from the gas inlet 9 a. Introduce.

Next, a third electrode having a positive potential (about 20 V) and a target material 5b is placed on the substrate electrode 2 on which the substrate 6 is placed.
Each of the electrodes 3 is applied with a DC power source of −100V. On the other hand, 100 MH is applied to the sputter electrode 1 holding the target 5a.
An electric power of 100 W from a high frequency power source of z and a negative potential of -200 V are applied from a direct current power source through a low pass filter to cause discharge, and a sputtering film is formed on the substrate 6.

The apparatus of the first embodiment of the present invention and FIG.
The experimental result which compared with the conventional apparatus shown in 8 is shown.

(Comparative Example 1) FIG. 3 shows data obtained by measuring the ion energy incident on the substrate by the Faraday cup method in the apparatus configuration of the first embodiment of the present invention. As shown in this result, applying a negative potential as in the present embodiment broadens the control range of the ions incident on the substrate on the low energy side, as compared with applying a positive potential to the third electrode 3 of the conventional device. I understand.

(Comparative Example 2) Apparatus of this Example (see FIG. 1)
18 and a conventional apparatus shown in FIG. 18, the target materials 5a and 5b are Si targets, and the substrate 6 is Si (1
00) Si film formation as a wafer (Si film thickness is 1000
The crystallinity in A) and electron mobility, which is one of the means for evaluating device characteristics, were compared. In order to compare crystallinity, Table 1 shows measurement data of RHEED (electron beam diffraction) of Si film formation at a substrate temperature of 210 ° C. to 350 ° C. for each device configuration.

[0031]

[Table 1] Electron beam diffraction image Si film thickness: 1000Å ◎: Kikuchi line ◯: Streak ×: halo The diffraction pattern by RHEED (electron beam diffraction) in this region shows sufficient epitaxialness, and the effect on the low energy side is not noticeable. . Next, Table 2 shows measured data of electron mobility by the Hall effect.

[0032]

[Table 2] No significant difference was observed in the RHEED (electron beam diffraction) pattern, but when the electrical characteristics of the actual film were measured,
It has been shown that lowering the energy of ions incident on the substrate forms a high quality film.

(Comparative Example 3) Table 3 shows the film forming rate when a positive potential is applied to the third electrode 3 in the conventional apparatus shown in FIG. 18 and when a negative potential of the present invention is applied.

[0034]

[Table 3] Regarding the film formation rate, when the −150 V voltage was applied to the third electrode of the present invention, the film formation rate was about twice as high as the positive potential application in the conventional apparatus.

(Second Embodiment) FIG. 4 is a schematic configuration diagram showing a second embodiment of the present invention.

Since the apparatus of this embodiment has almost the same structure as that of the above-mentioned first embodiment, only the structure different from that of the first embodiment will be described.

On the upper side wall of the vacuum container 18 of this embodiment, there is a bellows 2 as a ground electrode driving mechanism which is vertically movable.
1 is provided, and the bellows 21 has a third electrode 1
A ground electrode 14 as a ground electrode is attached so as to be interposed in a gap between the electrode 3 and the sputter electrode 11. Further, the device of this embodiment is controlled by a control device (not shown) as in the first embodiment.

Next, the operation of the apparatus of this embodiment will be described.

In the apparatus of this embodiment, the support portion of the substrate electrode 12 is lowered through the bellows 20 to increase the conductance in the discharge space, and then the vacuum container 18 is set in the ultra-high vacuum exhaust units A and B. Evacuate to below 10 ^-8 Torr. After reaching the ultra-high vacuum state, the support portion of the substrate electrode 12 is adjusted to a desired position by the bellows 20 and Ar gas adjusted to about 10 ⁻³ to 10 ⁻² [Torr] pressure is introduced from the gas introduction port. To do.

Next, after adjusting the earth area occupied in the discharge space by the earth electrode 14 via the bellows 21, the positive potential (20) is applied to the substrate electrode 12 on which the substrate 16 is installed.
V) and the third electrode 3 provided with the target material 15b are applied with a DC power source of −100V, respectively. On the other hand, a power of 100 W from a high frequency power supply of 100 MHz and a negative potential of −200 V are applied from a DC power supply through a low pass filter to the sputter electrode 11 holding the target 15a to cause discharge to form a sputtering film. This earth electrode 1
FIG. 5 shows the results of the ion energy incident on the substrate when 4 was inserted.

FIG. 5 is a diagram showing the minimum value of the substrate incident ion energy control range. By inserting the ground electrode 14, it is found that the minimum value of incident ion energy has a minimum value. This provides a means for expanding the control range of the ion energy incident on the substrate, particularly toward the low energy side.

(Third Embodiment) FIG. 6 is a schematic configuration diagram showing a third embodiment of the present invention. In this figure, the apparatus of this embodiment has a vacuum container 31, and on each of the inner walls on both sides of the vacuum container 31, a sputter electrode 33 having a magnetism generating means on one side and a substrate electrode 35 having a heater built in on the other side. It is provided facing each other. A substrate 34 is fixed to the upper surface of the substrate electrode 35, and a low pulse filter 40 connected to a DC power supply 39 that determines the potential of the substrate 34 is connected to the outside of the vacuum container 31 from the substrate electrode 35. Further, the target material 32 is fixed on the upper surface of the sputter electrode 33, and the DC power 38 via the low pass filter 41 and the oscillation frequency via the matching circuit 37 are 50 MHz or more from the sputter electrode 33 to the outside of the vacuum container 31. Of the high frequency power, and the matching circuit 37 and the alternating application means 42 for alternately controlling the direct current 38 are connected.

FIG. 7 is a film formation time chart showing the characteristics of the sputtering method by the alternate applying means of this embodiment. As shown in FIG. 7A, the deposition rate repeats a certain value and zero, but the amount of ions incident on the substrate during that period is as shown in FIG.
It is kept constant as shown in (b). As a result, for example, in the film formation during the time T ₁ -T ₂ , the surface migration of the atoms deposited on the substrate is about the same as the conventional one, but during the time T ₂ -T ₃ , the deposition rate is zero. Therefore, the ions incident on the substrate can give energy to the deposited atoms that have flown to the substrate before time T ₂ and increase the surface migration.

Next, the operation of this embodiment will be described.

For example, A
While introducing the r gas, the target material 32 and the substrate 3
4, when a plasma discharge is generated by energization from a high frequency power source, Ar gas is ionized to generate Ar ⁺ ions,
A part of it is applied to the target material 32 and the substrate 34.
The energy of Ar ⁺ ions with which the substrate 34 is irradiated can be controlled by the DC power supply 39 connected to the substrate electrode 35 via the low pass filter 49. In addition, the target material 32
The energy of Ar ⁺ ions with which the target material 32 is irradiated can be controlled by the DC power supply 38 connected to the target material 32 via the low-pass filter 41.

The DC power source 38 alternately applies a DC bias below the threshold value at which the target material 32 is sputtered and a DC bias above the threshold value to the target material 32 according to the control signal from the alternate application means 42. Further, the matching circuit 37 by the matching circuit control means changes the matching circuit constant based on the control signal synchronized with the change of the DC bias from the alternate applying means 42 to maintain the plasma stably.

Next, the experimental results of this embodiment will be described below.

(Experiment 1) An Si film was formed by the film forming method shown in FIG. 7 using the bias sputtering apparatus shown in FIG.

The target material is n-type 5-inch Si, and the P concentration in the target material is 1.8 × 10 ¹⁸ cm ^−3.
Met.

The substrate is a P-type FZ (100) 4-inch Si wafer.
(B concentration 1.0 x 10¹⁵cm ^-3), And one side is
Bare silicon, one side of which is patterned thermal oxide film
Was used.

After this substrate was subjected to ordinary wet cleaning, it was introduced into a vacuum container and the substrate temperature was set to 250 ° C. The background vacuum degree at this time was 2 × 10 ⁻¹⁰ Torr. Next, Ar gas was introduced from the gas supply system, and the pressure in the vacuum container was set to 8 mTorr. Before forming the Si film, the substrate-side DC voltage and the target-material-side DC voltage were set to predetermined values, and high frequency power was applied to clean the substrate surface by Ar ⁺ ion irradiation. The substrate surface cleaning conditions are shown below.

Substrate surface cleaning conditions: High frequency power source oscillation frequency 80 MHz, High frequency power 10 W, Target material side DC voltage -15 V, Substrate side DC voltage +8 V, Substrate temperature 250 ° C, Ar gas pressure 8 mTorr, Time 5 minutes 250-500 ° C (250, 300,
(350, 400, 450, 500 ° C.), and the alternate application means is set such that the DC voltage on the target material side changes in the time chart shown in FIG. 8, and the other film forming conditions are as follows. I went.・ High frequency power supply oscillation frequency 80MHz ・ High frequency power 200W ・ Substrate side DC voltage + 3V ・ Ar gas pressure 8mTorr ・ Time 15 minutes When the target material side DC voltage is -20V, the deposition rate is 0 (Å / s) under the above conditions. I confirmed that there is. The deposition rate is 2.2 when the DC voltage on the target material side is -200V.
It was (Å / s).

The evaluation of the thin film is as follows. For the thin film on bare silicon, crystal analysis by electron beam diffraction, resistance measurement by the four-point probe method, step coverage by SEM observation from the patterning part, reverse current density of pn junction An evaluation was made. The evaluation results are shown in Table 4.

[0054]

[Table 4] As a comparative example of the above example, the DC voltage on the target material side during Si film formation was always -200 V, the film formation time was 7.5 minutes, and other Si film formation conditions and substrate surface cleaning conditions were the same as those of the above example. Si film formation was performed in the same manner. The evaluation results are shown in Table 5.

[0055]

[Table 5] From the above results, it has been found that the present invention is remarkably effective in improving the step coverage of the Si film, improving the crystallinity, and improving the electrical characteristics accordingly.

(Experiment 2) As a substrate, a P type (B 1 × 10
^The same apparatus was used as in Experiment 1, except that a ¹⁵ cm ⁻³ doped Si (111) FZ wafer was used.
A substrate on which a thin film was formed was obtained. The substrate surface cleaning conditions and film forming conditions are shown below.

Substrate surface cleaning Si film formation • High frequency power source oscillation frequency 80 MHz 80 MHz • High frequency power 10 W 200 W • Target material side DC voltage -15 V -200 V and -20 V repetitions • Substrate side DC voltage +8 V +3 V • Substrate temperature 250 ° C. 350 ° C. -Ar gas pressure 8mTorr 8mTorr-Time 5 minutes 15 minutes Regarding the physical properties and step coverage of the Si thin film,
A very good product having almost the same properties as that of the substrate temperature of 350 ° C. shown in Experiment 1 was obtained. S as a comparative example
Although the target material side DC voltage at the time of i film formation was -200 V and the film formation time was 7.5 minutes, Si film formation was performed by the conventional method.
No epitaxially grown film was obtained.

This embodiment as described above is 50 MH.
Since the plasma is generated by the high frequency power source having the oscillation frequency of z or more, the self bias generated in the target material is small.

FIG. 9 is a diagram showing a conventional device configuration of the device of this embodiment shown in FIG. FIG. 10 shows a change in the self-bias of the target material when the oscillation frequency of the high frequency power source is changed at a high frequency power of 100 W and a discharge pressure of 8 mTorr in the apparatus having the same configuration as the conventional example shown in FIG. As shown in FIG. 10, when the oscillation frequency is 50 MHz or more, the magnitude of the DC bias applied to the target material can be easily controlled by appropriately selecting the high frequency power and the discharge pressure with respect to the sputtering threshold of the target material to be used. be able to. For this reason, the step of performing sputtering of the target material while irradiating the substrate with ions and depositing the constituent atoms of the target material on the substrate and the step of irradiating the substrate with ions without performing the sputtering of the target material are performed alternately. it can.

(Fourth Embodiment) FIG. 11 is a schematic diagram showing the fourth embodiment of the present invention. As shown in this figure, the apparatus of this embodiment has a vacuum container 51, and a sputter electrode 54 having a magnetism generating means 52 is provided on the lower side wall of the vacuum container 51 via an insulator 53. A substrate electrode 56 is provided on the upper side wall of the container 51 so as to face the sputter electrode 54 with an insulator 55 interposed therebetween. Sputter electrode 54
The target material 58 is held on the upper surface of the substrate, and the substrate 57 is held on the upper surface of the substrate electrode 56.

The substrate 57 is kept at a predetermined temperature by an appropriate substrate temperature control means (not shown). The vacuum container 51 is evacuated to a high vacuum by an appropriate vacuum exhausting means (not shown), and then an appropriate gas introducing means (not shown).
Argon gas is introduced to maintain the pressure of several millitorr to several tens of millitorr. A high frequency power supply 59 as a sputtering power supply is connected to the sputtering electrode 54 through a matching circuit so that the surface of the target material 58 attached to the front surface of the sputtering electrode 54 has a negative high voltage.

A substrate bias power source 60 is connected to the substrate electrode 56. As the substrate bias power source 60, a DC power source or a high frequency power source is used. Further, the substrate electrode 56 is connected to the substrate electrode 56 via the substrate surface potential detecting means 61.
Are connected. A vacuum container 5 is provided near the substrate electrode 56.
There is a floating potential measuring electrode 62 in the plasma space via 1 and the insulator 63. A substrate potential control means 65 is connected to the floating potential measurement electrode 62 via a floating potential detection means 64. The substrate potential control means 65 is connected to the substrate bias power source 60. The substrate potential control means 65 is configured to control the substrate bias power supply 60 based on signals from the substrate surface potential detection means 61 and the floating potential detection means 64.

Next, the operation of the apparatus of this embodiment will be described.

When a high voltage is applied to the sputter electrode 54, a discharge occurs between the sputter electrode and the substrate electrode to generate plasma. Argon ions in this plasma are attracted to the negative high voltage potential of the target material 58,
Accelerate and shock. For this reason, the material forming the target material 58 is knocked out and deposited on the substrate 57. Further, the argon ions in the plasma have an energy corresponding to the difference between the plasma space potential and the substrate surface potential, and also accelerate and impact the substrate surface. Substrate surface potential detection means 6
Based on 1 and the signal from the floating potential detection means 64, the substrate potential control means 65 controls the substrate bias power supply 60 so that the difference between the substrate surface potential and the floating potential becomes a desired constant value. Even if the plasma space potential fluctuates due to various causes (fluctuation of discharge parameters such as pressure, gas flow rate, power, temperature fluctuation of target material, vacuum vessel, matching circuit, etc.), the floating potential also fluctuates substantially. .

FIG. 12 shows the changes over time of the plasma space potential and the floating potential of the plasma space measured by the single probe electrostatic probe method, which is a general plasma measuring means, in the apparatus shown in FIG. It is a figure.

As shown in this figure, the floating potential also fluctuates in accordance with the fluctuation of the plasma space potential, and the difference is kept substantially constant. Therefore, if the substrate surface potential control means 65 controls the substrate bias power supply 60 so that the difference between the floating potential and the substrate surface potential becomes constant, the difference between the plasma space potential and the substrate surface potential can be kept constant. Therefore, it is possible to perform stable control in which the energy of the argon ions that are subjected to accelerated impact on the substrate surface is kept constant.

Although it is more direct to detect the plasma space potential and control the substrate bias power source so that the difference between the plasma space potential and the substrate surface potential is constant, it is a general plasma space potential detection means. In the single-probe electrostatic probe method, a metal needle is inserted into plasma, a voltage (V) between the plasma and a vacuum container in contact with the plasma is applied to measure a current (I) flowing through the metal needle, and V− Since the plasma space potential is calculated by calculating from the I characteristic, it is difficult to instantaneously detect the plasma space potential, and it is not practical because the measurement system is expensive. In comparison, the detection of the floating potential can be performed instantaneously, for example, by inserting a metal needle electrically insulated from the vacuum container into the plasma and simply measuring the potential of the metal needle. You can
The measuring system is also cheap and practical.

FIG. 13 shows the oscillation frequency of the high frequency power source 59 in the device shown in FIG. 11 from 13.56 MHz to 130.
Measure the energy distribution of argon ions incident on the surface of the substrate held at the ground potential with an electrostatic lens type ion energy measuring means when changing to MHz and discharging at a high frequency power of 100 W and an argon pressure of 7 mTorr. FIG. 7 is a diagram showing the relationship between the peak energy value of the energy distribution of argon ions, the half-value width of the energy distribution showing the spread of the energy distribution, and the relative number of argon ions having the peak energy value and the oscillation frequency, which are the results obtained.

As shown in this figure, as the oscillating frequency increased, both the peak energy value and the full width at half maximum became smaller, and the energy distribution became lower and sharper. In particular, the energy distribution became remarkably sharp when the oscillation frequency was 50 MHz or higher. Therefore, in the apparatus shown in FIG. 11, a high frequency power source with an oscillation frequency of 50 MHz or more is connected to the target material, and the difference between the substrate surface potential and the floating potential of the plasma space is maintained at a desired constant value so that the target material is incident on the substrate. The energy control range of incoming argon ions can be greatly improved, and stable acceleration impact of low-energy argon ions with a sharp energy distribution is possible, and high-quality with very little ion damage. Film deposition became possible. It should be noted here that, even if a high frequency power source with an oscillation frequency of 50 MHz or more is connected to the target material, the conventional control device that keeps the substrate surface potential constant during film formation changes the plasma space potential. In the case of occurrence, there is a risk that high-energy argon ions having a sharp distribution are incident on the substrate surface, and it is difficult to deposit a stable film with less ion damage.

In the apparatus shown in FIG. 11, a Si target is used as a target material, a Si substrate is used as a substrate, a high frequency power source having an oscillation frequency of 90 MHz is used as a sputtering power source, and the substrate surface potential is substrate surface potential-floating potential = 10V. And S on the Si substrate under the following film forming conditions.
The i-film was deposited.

Substrate temperature 300 ° C. High frequency power 400 W Argon gas pressure 8 mTorr Time 60 minutes The crystallinity of the deposited Si film was evaluated by electron beam diffraction to find that it was a single crystal film. The substrate surface potential at the initial stage of film formation is 1
It was 2 V, and the substrate surface potential at the time of film formation completion was 19 V.

FIG. 14 is a diagram showing a conventional device configuration of the device of this embodiment shown in FIG.

As a comparative example of the above Si film formation, in the conventional apparatus shown in FIG. 14, a DC power supply was used as the substrate bias power supply, the substrate surface potential was fixed at 12 V, and the other film formation conditions were the same as those in the above embodiment. When the film was formed and the crystallinity of the Si film was evaluated, it was an amorphous film.

The crystallinity of the Si film formed by the bias sputtering method is characterized in that it greatly changes from an amorphous film to a single crystal film in response to a change in the number eV of argon ions acceleratingly impacting the substrate surface. Is
In particular, it has a remarkable effect in improving the controllability of the crystallinity of the Si film.

(Fifth Embodiment) FIG. 15 is a schematic structural view showing a fifth embodiment of the present invention.

In this embodiment, the structure of the vacuum container, which is the main body of the apparatus, is almost the same as that of the fourth embodiment. Therefore, only the structure of the control means provided outside the vacuum container will be described.

As shown in FIG. 15, a substrate bias power source 80 is connected to the substrate electrode 76. As the substrate bias power supply 80, a DC power supply with good controllability is used. Substrate electrode 7
A low-pass filter 83 is connected between the substrate bias power source 80 and the substrate bias power source 80 to prevent high frequency leakage to the substrate bias power source 80 side. Between the substrate electrode 76 and the low pass filter 83, a high frequency current detecting means 82 for detecting a current of plasma flowing through the substrate 77 is provided.
The substrate potential control means 84 is configured to control the substrate bias power supply 80 based on the signal from the high frequency current detection means 82.

Next, the operation of the apparatus of this embodiment will be described.

When a high voltage is applied to the sputter electrode 74,
Electric discharge occurs between the sputter electrode 74 and the substrate electrode 76 to generate plasma. Argon ions in the plasma are attracted to the negative high-voltage potential of the target material 78 and are accelerated and impacted on the target material 78. Therefore, the material forming the target material 78 is knocked out and deposited on the substrate 77. Further, the argon ions in the plasma have an energy corresponding to the difference between the plasma space potential and the substrate surface potential, and also accelerate and impact the substrate surface. Based on the signal from the high frequency current detection means 82, the substrate potential control means 84 is controlled so that the ratio of the ion current and the electron current becomes a desired constant value.
Controls the substrate bias power supply 80. Even if the plasma space potential fluctuates due to various causes (fluctuation of discharge parameters such as pressure, gas flow rate, electric power, temperature fluctuation of target material, vacuum container, matching circuit, etc.), ion current and electrons incident on the substrate 77 The current ratio does not change.

FIG. 16 shows the substrate bias power supply voltage at a constant ion-electron current ratio by the plasma space potential and the high frequency current power supply by the single probe electrostatic probe method which is a general plasma measuring means in the device shown in FIG. It is a figure showing change over time.

As shown in this figure, the high-frequency current detecting means 82 follows the ion-
Ion energy incident on the substrate by changing the voltage of the substrate bias power supply 80 controlled to keep the electron current ratio constant (= plasma space potential-substrate surface potential)
Is kept almost constant. Therefore, if the substrate bias power supply 80 is controlled so that the ratio of the ion current and the electron current detected by the high frequency current detecting means 82 becomes a desired constant value, the difference between the plasma space potential and the substrate surface potential becomes constant. Therefore, it is possible to perform stable control in which the energy of the argon ions acceleratingly impacting the substrate surface is kept constant.

In this embodiment as well, as shown in FIG. 13 of the fourth embodiment, as the oscillation frequency increases, both the peak energy value and the half value width become smaller and the energy distribution becomes
It became low energy and sharpened. In particular, the energy distribution became remarkably sharp when the oscillation frequency was 50 MHz or higher. Therefore, in the device shown in FIG. 15, by connecting a high frequency power source having an oscillation frequency of 50 MHz or more to the target material and maintaining the ratio of the ion current and the electron current detected by the high frequency current detecting means at a desired constant value, The energy control range of argon ions incident on the substrate can be greatly improved, and stable acceleration impact of low energy argon ions with a sharp energy distribution is possible, resulting in very little ion damage. It has become possible to deposit high quality films. It should be noted here that, even if a high frequency power source with an oscillation frequency of 50 MHz or more is connected to the target material, the conventional control device that keeps the substrate surface potential constant during film formation changes the plasma space potential. In the case of occurrence, there is a risk that high-energy argon ions having a sharp distribution are incident on the substrate surface, and it is difficult to deposit a stable film with less ion damage.

In the apparatus shown in FIG. 15, a Si target is used as the target material, a Si substrate is used as the substrate, a high frequency power source with an oscillation frequency of 90 MHz is used as the sputtering power source, and the substrate surface electrode is the current value of the high frequency current detecting means. The current was set to 1: 2, and the Si film was deposited on the Si substrate under the following film forming conditions.

Substrate temperature 300 ° C. High frequency power 400 W Argon gas pressure 8 mTorr Time 60 minutes The crystallinity of the deposited Si film was evaluated by electron diffraction to find that it was a single crystal film. The substrate surface potential at the initial stage of film formation is 1
It was 2 V, and the substrate surface potential at the time of film formation completion was 19 V.

As a comparative example of the above Si film formation, in the conventional apparatus shown in FIG. 17, a DC power supply was used as the substrate bias power supply, the substrate surface potential was fixed at 19 V, and the other film formation conditions were the same as in the above embodiment. When the film was formed and the crystallinity of the Si film was evaluated, it was an amorphous film.

Next, in the apparatus shown in FIG. 15, an Al target often used as a target material for metal wiring,
Si substrate as the substrate, the transmission frequency of the sputtering power source is 60 MH
Using a high frequency power source of z, the substrate surface potential is set so that the current value of the high frequency current detecting means is ion current: electron current = 3: 1, and an Al film is deposited on the Si substrate under the following film forming conditions. did.

Substrate temperature 300 ° C. High frequency power 250 W Argon gas pressure 8 mTorr Time 15 minutes Annealing at 450 ° C. for 30 minutes after film formation
When the surface of the 1 film was confirmed by SEM (scanning electron microscope), no abnormal protrusion (hill rock) was observed. The substrate surface potential at the beginning of film formation was -15V, and the substrate surface potential at the end of film formation was -20V.

As a comparative example of the above Al film formation, a DC power supply was used as the substrate bias power supply in the conventional apparatus shown in FIG. When the film was formed and the same annealing was performed, protrusions were observed everywhere on the surface of the Al film.

Although the effects of the sputtering apparatus of the present invention have been shown for Si and Al in the present embodiment, the apparatus of the present invention has similar effects for other metal films and semiconductor films.

[0090]

The bias sputtering apparatus according to the present invention described above has the following effects.

In the apparatus according to the present invention described in claims 1 and 2, the target material is provided on the electrode surface of the third electrode provided so as to include the plasma discharge space in which the sputter electrode and the substrate electrode face each other. Since a negative DC potential is applied to the third electrode, a positive DC potential is applied to the substrate electrode to positively remove positive ions in the plasma discharge space like the sputter electrode, and an electron current to the substrate electrode is applied. Even if the inflow is increased, the neutral state of the plasma is sufficiently maintained, and the control range (particularly in the low energy direction) of the positive ion incident energy on the substrate can be widened. In addition, the increase in impurities such as Fe mixed in the film due to the application of the negative potential to the third electrode can also be achieved by using the target material for depositing the surface of the electrode itself on the substrate. It is possible to prevent impurities from being mixed by the outer wall portion sputtering, and it is possible to improve the deposition rate of film formation.

According to a third aspect of the present invention, there is provided a step of performing target sputtering while irradiating a substrate with ions, depositing constituent atoms of the target on the substrate, and performing target sputtering without performing target sputtering. By alternately repeating the step of irradiating the substrate with the substrate, the substrate is more effectively formed than the method of forming a thin film by only the step of sputtering the target while irradiating the substrate with the ions and depositing the constituent atoms of the target on the substrate. It is possible to increase the ratio of the ions to be irradiated on the substrate and the deposited atoms (ions / deposited atoms), and it is possible to improve the step coverage and the crystallinity by increasing the surface migration of the deposited atoms.

In the apparatus according to the present invention described in claim 4, the oscillation frequency of the high frequency power source connected to the sputter electrode is 50H.
Alternating means for alternately applying a DC voltage equal to or higher than Mz and lower than a threshold value and a DC voltage equal to or higher than the threshold value at which the target material of the sputter electrode is sputtered; Since the matching circuit control means for changing the circuit constant of the matching circuit of the high frequency power supply is provided, plasma is generated by the high frequency power supply having an oscillation frequency of 50 MHz or more, and thus the self-bias generated in the target material is small. Therefore, if the oscillation frequency is 50 MHz or more, it is possible to easily control the magnitude of the DC voltage applied to the target material by appropriately selecting the high frequency power and the discharge pressure with respect to the sputtering threshold of the target material to be used. A step of performing sputtering of a target material while irradiating ions to deposit constituent atoms of the target material on the substrate and a step of irradiating the substrate with ions without performing sputtering of the target can be performed.

Further, when the DC voltage applied to the target material is changed, the plasma impedance also changes. Therefore, a matching circuit control means for changing the circuit constant of the matching circuit of the high frequency power source in synchronization with the change of the DC voltage is provided. By providing the plasma, the plasma can be stably maintained.

According to a fifth aspect of the present invention, there is provided a floating potential detecting means for detecting a floating potential in the plasma space, and a substrate potential control for controlling a bias potential applied to the substrate based on the floating potential in the plasma space. Since the bias potential applied to the substrate can be controlled based on the floating potential of the plasma space by including the means, even if the plasma space potential fluctuates due to various causes, the floating potential of the plasma space almost follows up. Since it fluctuates, it is possible to stably control the energy value of gas ions that accelerate and impact the substrate surface.

According to a sixth aspect of the present invention, there is provided a high frequency power source having a power source frequency of 50 MHz or more connected to the sputter electrode, and a current value flowing through the substrate between the substrate electrode and the DC power source. By providing a high-frequency current detection means for detecting the voltage and a substrate potential control means for controlling the substrate DC voltage of the DC power source based on the current value, a discharge is generated at an oscillation frequency of 50 MHz or more, and the substrate surface is discharged. Since the energy distribution of the arriving ions can be narrowed and the DC potential applied to the substrate can be controlled by the current value of the ions entering the substrate, the substrate surface is accelerated even if the plasma space potential fluctuates due to various causes. The energy value of the bombarding gas ions can be controlled stably.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a perspective view for explaining the configuration of a gas introduction / exhaust unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing data obtained by measuring ion energy incident on a substrate using the Faraday cup method in the device configuration of the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a minimum value of a substrate incident ion energy control range.

FIG. 6 is a schematic configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a film formation time chart showing the characteristics of the sputtering method by the alternate control means of the third embodiment of the present invention.

FIG. 8 is a time chart of the target material side DC voltage used in Experiment 1 of the third embodiment of the present invention.

9 is a diagram showing a conventional device configuration of the device of the third embodiment shown in FIG.

FIG. 10 is a diagram showing changes in the self-bias of the target material when the oscillation frequency of the high frequency power source is changed as shown in the third embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing a fourth embodiment of the present invention.

FIG. 12 shows the plasma space potential and the floating potential of the plasma space measured by the single-probe electrostatic probe method, which is a general plasma measuring means, in the device of the fourth embodiment of the present invention, and shows the change over time. It is a figure.

FIG. 13 shows the peak energy value of the energy distribution of argon ions in the device showing the fourth embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the relative number of argon ions having a half-width of the energy distribution showing the spread of the energy distribution and the peak energy value, and the oscillation frequency.

14 is a diagram showing a conventional device configuration of the device of the fourth embodiment shown in FIG.

FIG. 15 is a schematic configuration diagram showing a fifth embodiment of the present invention.

FIG. 16 is a substrate bias power supply voltage at a constant ion-electron current ratio by a plasma space potential and a high frequency current power supply by a single probe electrostatic probe method which is a general plasma measuring means in the device of the fifth embodiment of the present invention. It is a figure showing the change over time.

FIG. 17 is a schematic configuration diagram showing a conventional bias sputtering apparatus.

FIG. 18 is a schematic configuration diagram showing a conventional bias sputtering apparatus.

FIG. 19 is a diagram showing the concentration of Fe contained in a deposited film on a substrate with respect to application of a third electrode potential in the conventional bias sputtering apparatus shown in FIG. 18.

[Explanation of symbols]

1, 11, 33, 74 Sputtering electrode 2, 12, 35, 56, 76 Substrate electrode 3, 13 Third electrode 5a, 5b, 15a, 15b, 32, 58, 78 Target material 6, 16, 34, 57,77 substrate 7,17 switch 8,18,31,51,71 vacuum container 9,19 gas inlet / outlet unit 9a gas inlet 9b gas outlet 9c exhaust outlet 10 bellows 14 earth electrode 20,21 -36, 59, 79 High frequency power supply 37 Matching circuit 38, 39 DC power supply 40, 41, 83 Low pass filter- 42 Alternate application control means 52, 72 Magnetomagnetism generation means 53, 55, 63, 73, 74, 75 Insulator 54 Sputtering electrode 60,80 Substrate bias power supply 61 Substrate surface potential detecting means 62 Floating potential measuring electrode 64 Floating potential detecting means 65,84 Substrate potential control means 81 Gas introduction means 82 High frequency current detection means

Claims (6)

[Claims] 1. A vacuum vessel, a sputtering electrode holding a sputtering target material, a substrate electrode holding a substrate, and a third electrode including a plasma discharge space between the sputtering electrode and the substrate electrode. In a bias sputtering apparatus having a plasma generation power source connected to the sputter electrode and a DC power source or a high frequency power source connected to the substrate electrode, a negative DC voltage is applied to the third electrode,
A bias sputtering apparatus in which a target material is placed on the surface of the third electrode. 2. A ground electrode is provided in the plasma discharge space,
2. The bias sputtering apparatus according to claim 1, further comprising a ground electrode driving mechanism that drives the ground electrode to adjust a discharge space area occupied by the ground electrode. 3. A bias sputtering method in which a target material is sputtered by plasma discharge and constituent atoms of the target material are deposited while irradiating the substrate with ions by the plasma discharge, wherein the target material is irradiated with ions on the substrate. And a step of depositing constituent atoms of the target material on the substrate and a step of irradiating the substrate with ions without performing sputtering of the target material are alternately repeated. . 4. A bias sputtering apparatus for applying a high frequency power and a direct current voltage to a sputtering electrode holding a target material and applying a direct current voltage to a substrate electrode holding a substrate to deposit a thin film on the substrate, Alternating voltage applying means that has an oscillation frequency of a high frequency power source connected to the sputter electrode of 50 MHz or more, and that can alternately apply a DC voltage equal to or lower than a threshold value and a DC voltage equal to or higher than the threshold value for sputtering the target material of the sputter electrode; A bias sputtering apparatus comprising matching circuit control means for changing the circuit constant of the matching circuit of the high frequency power source in synchronization with a change in the DC voltage applied alternately to the. 5. A bias sputtering apparatus for applying a high frequency power to a sputtering electrode holding a target material and applying a DC voltage to a substrate electrode holding a substrate to deposit a thin film on the substrate, comprising: A high-frequency power supply having a power supply frequency of 50 MHz or more is connected, and a floating potential detecting means for detecting a floating potential in the plasma discharge space, and a DC voltage applied to the substrate electrode are controlled based on the floating potential in the plasma discharge space. A bias sputtering apparatus comprising a substrate potential control means. 6. A bias sputtering apparatus for applying a high frequency power to a sputtering electrode holding a target material and applying a DC voltage to a substrate electrode holding a substrate to deposit a thin film on the substrate. A high-frequency power supply having a power supply frequency of 50 MHz or more to be connected, and high-frequency current detection means for detecting a current value flowing in the substrate between the substrate electrode and the direct-current power supply; and the direct current based on the current value. A bias sputtering apparatus, comprising: a substrate potential control means for controlling a substrate DC voltage of a power source.