JP3585519B2 - Sputtering apparatus and sputtering method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a sputtering apparatus and a sputtering method, and more particularly to a sputtering apparatus and a sputtering method for sputtering a target material using an RF power supply.
[0002]
[Prior art]
Sputtering technology has become indispensable in the modern high-tech industry and is widely known as a dry process with a wide range of applications. If the sputtering technique used for this sputtering technique is classified according to the type of voltage applied to the target electrode on which the target material is arranged, it can be broadly classified into DC sputtering technique and RF sputtering technique. It is considered that RF sputtering technology is indispensable.
[0003]
FIG. 4 shows a conventional sputtering apparatus used for this RF sputtering technique. Reference numeral 100 denotes a vacuum chamber in which a target material 101 is disposed. The target material 101 is connected to a high frequency power supply 108 via a matching box 109 for impedance matching.
[0004]
A substrate electrode 103 is placed at a position facing the target material 101. After a sputtered object 102 such as a silicon wafer or a glass substrate is placed on the substrate electrode 103, a vacuum state is applied by a vacuum pump (not shown). Then, the sputtering operation is started.
[0005]
A wraparound plate 105 and a shutter 104 are provided between the substrate electrode 103 and the object to be sputtered 102. Argon gas is introduced from a gas introduction hole 106 when a desired degree of vacuum is reached, and the target When the plasma generated by the application of the RF voltage to the material 101 is stabilized, the shutter 104 is opened to start sputtering, and a film is formed. If silicon is used for the target material 101 and a small amount of O ₂ gas is also introduced from the introduction hole 106 for sputtering, SiO ₂ can be formed on the object to be sputtered 102.
[0006]
[Problems to be solved by the invention]
However, in the RF sputtering apparatus of the prior art, as the sputtering power is increased, the surface of the target material, the surface of the target electrode, or the surface of the object between these and the earth shield, the surface of the object to be sputtered, or the surface of the electrode on which the object to be sputtered is disposed Abnormal discharge phenomenon occurs. Such an abnormal discharge can be observed at any place in the vacuum chamber, and when the abnormal discharge occurs, the film quality is deteriorated, and the sputtered object causes dielectric breakdown, which causes a product defect.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a sputtering apparatus and a sputtering method that do not generate abnormal discharge during sputtering.
[0008]
[Means for Solving the Problems]
Invention according to claim 1, wherein in order to solve the above problems, a target material, a target electrode which data Getto material is arranged, the plasma in the vicinity of the surface of the motor Getto material by applying an AC voltage to the motor Getto electrode in the sputtering apparatus having an AC power source for generating includes a positive voltage pulse power supply for applying a positive voltage pulse to the motor Getto electrode, AC power supply intermittently stop application to the target electrode of the AC voltage, a positive voltage pulse power supply Is connected to an AC power supply, and is synchronously set so as to apply a positive voltage pulse to the target electrode during a period in which the application of the AC voltage is stopped .
The method of the invention of claim 2, wherein includes a target material, a target electrode which data Getto material is disposed, and an AC power by applying an AC voltage to the motor Getto electrodes to generate plasma in the vicinity of the surface of the data Getto material a sputtering method using a sputtering apparatus, provided with a positive voltage pulse power supply further the sputtering apparatus, the AC voltage applied to the target electrode to intermittently stop, a positive voltage pulse to the motor Getto electrode outage It is characterized by applying .
[0009]
[Action]
The operation principle of the present invention will be described by taking an example of occurrence of abnormal discharge between the surface of a target material and the inner wall of a vacuum chamber when sputtering is performed by an RF magnetron sputtering method in which an abnormal discharge phenomenon is extremely large. Note that RF sputtering using a magnetron is generally widely used because high-power RF power can be applied to a target material, but the present invention is not limited to this RF magnetron sputtering method.
[0010]
It is known that this abnormal discharge often occurs when the target material 101 has a relatively low resistance and the film generated by sputtering is a relatively high resistance film such as an insulator. More specifically, the RF magnetron sputtering apparatus shown in FIG. 3 is used to place a Si target material 112 on the target electrode 111, and to introduce an Ar gas and an O ₂ gas to perform reactive sputtering, thereby performing sputtering (not shown). This is the case when an SiO ₂ film is formed on an object.
[0011]
When performing sputtering with this RF magnetron system, the order between the magnets 115 ₁ and the magnet 115 _{and second} Si target material 112 is strongly sputtered, only that portion will be dug deeply, the erosion 113 is formed Is common.
[0012]
On the other hand, the non-erosion portion 116 _1, 116 _2, may sputtered particles conversely thin film is deposited to come back by the scattering, this O ₂ reactive gas is also incorporated together when the thin film 117 ₁ , 117 ₂ becomes a SiO ₂ film having a high resistance. When the surface is hit with Ar ions, electrons are extracted or secondary electrons are emitted, and the surface is positively charged.
[0013]
Meanwhile, electrons present in the plasma, the order to be confined in a magnetic field to make the magnet ₁₁₅ 1, 115 _2, only enter a small amount in the non-erosion portion ₁₁₆ 1, 116 _2. Therefore, when the thin films 117 ₁ and 117 ₂ begin to be charged by sputtering, almost all electrons are emitted, and the potential of the thin films 117 ₁ and 117 ₂ continues to rise, so that a creeping discharge phenomenon occurs at the end. If the potential difference exceeds the withstand voltage of the thin films 117 ₁ and 117 ₂ , an abnormal discharge is caused, for example, a dielectric breakdown discharge occurs on the target material 112.
[0014]
According to the present invention, since a positive voltage pulse is applied to the target electrode 111,
Electrons come from the plasma toward the target electrode 111. Then, if the target material 112 is disposed on the range, electrons enter this target material and discharge positive charges accumulated in the target material 112 by charging.
[0015]
Therefore, the non-erosion portion 116 _1, 116 ₂ potential such on the target electrode 111 are not rise above a certain limit, abnormal discharge does not occur.
[0016]
During sputtering, the thin films 117 ₁ and 117 ₂ deposited on the surface of the target material 112 are charged to a positive potential, but the target material 112 or the target electrode 111 disposed in the vicinity of the target material 112 is charged with the positive potential. Is at the opposite negative potential VDC. The present invention includes not only a case where a positive voltage pulse is applied to the target electrode 111 and the potential becomes a positive potential higher than the ground potential, but also a case where a negative voltage lower than the ground potential is applied even when the positive voltage pulse is applied. This includes the case where the potential remains.
[0017]
【Example】
Embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a block diagram of a first embodiment of the apparatus of the present invention, and a silicon plate 12 as a target material is disposed on a target electrode 11. An RF power source 14 as an AC power source is connected to the target electrode 11 via a matching box 13 for impedance matching. A pulse power supply 15 is connected to the target electrode 11 so that a positive voltage pulse can be applied to the target electrode 11 and the silicon plate 12.
[0018]
FIG. 2A shows an AC voltage VRF output from the RF power supply 14, a positive voltage pulse VP1 output from the pulse power supply 15, and the AC voltage VRF and the positive voltage pulse VP1 of the first embodiment. 4 is a graph showing a voltage waveform of the target electrode 11 shown in FIG.
[0019]
The voltage VDC in FIG. 2A is a voltage called a self-bias voltage. When the AC voltage VRF is applied to the target electrode 11, positive Ar ions in plasma existing in the vacuum chamber and negative Ar ions This appears on the target electrode 11 due to the difference in mobility due to the mass difference between the electrons. When the positive voltage pulse VP1 is superimposed from the pulse power supply 15 on the target electrode 11 to which the AC voltage VRF is applied. , And an AC voltage waveform VT1. Although the peak voltage of the voltage waveform VT1 when the positive voltage pulse VP1 is applied exceeds 0 V, the present embodiment includes a case where the peak voltage does not exceed 0 V as long as the voltage is equal to or higher than the self-bias voltage VDC.
[0020]
FIG. 1B is a block diagram of a second embodiment of the apparatus of the present invention. A silicon plate 22 is disposed on a target electrode 21, and a pulse RF power supply 24 serving as an AC power supply is provided via a matching box 23. It is connected. A pulse power supply 25 for applying a positive voltage pulse to the target electrode 21 is connected to the target electrode 21, and the pulse RF power supply 24 and the pulse power supply 25 are connected to each other so as to be synchronized.
[0021]
FIG. 2B shows the pulse RF voltage VRFpulse output from the pulse RF power supply 24, the positive voltage pulse VP2 output from the pulse power supply 25, and the pulse VRF voltage and the positive voltage pulse VP2 of the second embodiment. 5 is a graph showing a voltage waveform of the target electrode 21 applied. The voltage VDC in FIG. 2B appears on the target electrode 21 for the same reason as the self-bias voltage in FIG. 2A, and the self-bias voltage VDC includes the pulse RF voltage VRFpulse and the When the positive voltage pulse VP2 is superimposed, an AC voltage waveform VT2 is obtained.
[0022]
The pulse RF power supply 24 is set to perform a synchronous operation for stopping the output of the output voltage VRFpulse while the pulse power supply 25 outputs the positive voltage pulse VP2.
[0023]
Note that the AC voltage VRF and the pulse RF voltage VRFpulse are high frequencies, and a frequency of 13.56 MHz is frequently used in a commercially available RF sputtering apparatus due to restrictions in laws and regulations. The present invention is not limited to this, and can be widely applied to frequencies where an abnormal discharge phenomenon can occur.
[0024]
As described above, abnormal discharge can be prevented by intermittently applying the positive voltage pulse to the target electrode.
[0025]
The specific experimental results are as follows: Ar gas pressure 6.7 × 10 ⁻¹ Pa (5.0 × 10 ⁻³ Torr), O ₂ gas pressure 1.3 × 10 ⁻¹ Pa (1 × 10 ⁻³ Torr). ), Target material Si, 5 ″ × 8 ″ (thickness 4 mm), RF power 1000 W, sputtering time 10 minutes, sputtering was performed, and the number of abnormal discharges was measured.
[0026]
In the sputtering according to the prior art, as shown by the plot on the y-axis of the graph of FIG. 6A, abnormal discharge was observed 20 times (■) on the surface of the target material and 5 times (●) on the inner wall of the vacuum chamber. .
[0027]
In contrast, when the present invention was applied, the following experimental results were obtained.
[0028]
(1) First, experimental results in the first embodiment will be described.
[0029]
{Circle around (1)} The sputtering was performed under the same film forming conditions as the film forming conditions, and the self-bias voltage VDC of the target electrode was measured to be −400 V.
[0030]
The AC voltage VRF was applied to the target electrode, the pulse application period Tpulse of the positive voltage pulse Vpulse was set to 200 μsec, and the pulse application time tpulse was set to 10 μsec, and the positive voltage pulse VP1 was superimposed to perform sputtering. The results at that time are shown in the graph of FIG. 5A, where the number of abnormal discharges N is plotted on the vertical axis, and the potential Vtarget of the target electrode when the positive voltage pulse VP1 is applied is plotted on the horizontal axis. In this graph, the number of abnormal discharges on the target material surface is represented by a curve 171 connecting plots of white squares (□), and the number of abnormal discharges on the inner wall of the vacuum chamber is represented by a curve 172 connecting plots of white circles (（). is there.
[0031]
It can be seen that the number of abnormal discharges decreases when the voltage value of the potential Vtarget of the target electrode becomes -200 V or more.
[0032]
In FIGS. 5B, 5C, and 6A to 6C, the number of discharges on the surface of the target material is plotted by a white square (□), and the number of discharges on the inner wall of the vacuum chamber is indicated by a white circle. It is represented by the plot (（).
[0033]
{Circle around (2)} Among the above conditions, the pulse application time tpulse is set to 10 μsec, the voltage of the positive voltage pulse Vpulse is set so that the potential Vtarget of the target electrode becomes +40 V, and the value of the pulse application cycle Tpulse is varied. And the number N of abnormal discharges was measured. The result is shown in FIG. At this time, the number of discharges on the surface of the target material is indicated by a curve 175, and the number of discharges on the inner wall of the vacuum chamber is indicated by a curve 176. It can be seen that the pulse application cycle Tpulss is effective at 200 μsec or less.
[0034]
{Circle around (3)} This time, the voltage value of the positive voltage pulse Vpulse is maintained so that the potential Vtarget of the target electrode becomes +40 V, the pulse application period Tpulse is set to 200 μsec, and the value of the pulse application time tpulse is variously set. The number N of abnormal discharges was measured by shaking. The results are shown in FIG. 5C, where the number of discharges on the target material surface is indicated by a curve 177 and the number of discharges on the inner wall of the vacuum chamber is indicated by a curve 178. It can be seen that the pulse application time tpulse is effective at 10 μsec or more.
[0035]
(2) Next, an experimental result in the second embodiment will be described under the same film forming conditions as the film forming conditions.
[0036]
{Circle around (1)} At this time, the self-bias voltage VDC of the target electrode is also −400 V. During the sputtering, the application period TRF (on) of the pulse RF voltage VRFpulse is 200 μsec, the pulse RF voltage is stopped, and the positive voltage pulse VP2 is stopped. The pulse RF voltage VRFpulse was applied to the target electrode with a positive voltage pulse application time tP2 of 10 μsec applied. Then, sputtering was performed while varying the voltage value of the positive voltage pulse VP2, and the number N of abnormal discharges was measured.
[0037]
The experimental results at that time are shown in FIG. A curve 202 indicates the number of abnormal discharges on the surface of the target material, and a curve 203 indicates the number of abnormal discharges on the inner wall of the vacuum chamber. It can be seen that when the voltage value of the positive voltage pulse VP2 becomes 80 V or more, abnormal discharge is no longer observed.
[0038]
{Circle around (2)} The voltage value of the positive voltage pulse VP2 and the application cycle tP2 (μsec) are set to 80 V and 10 μsec, and the value of the application cycle TRF (on) (μsec) of the pulse RF voltage VRFpulse is varied to change the number of discharges. Was measured. The results are shown in the graph of FIG. At this time, the number of discharges on the target material surface is represented by a curve 206, and the number of discharges on the inner wall of the vacuum chamber is represented by a curve 207. It is effective when the period TRF (on) of the pulse RF voltage VRFpulse is 200 μsec or less. You can see that there is.
[0039]
(3) Without changing the voltage value of the positive voltage pulse VP2 (80 V), the application period TRF (on) of the pulse RF voltage VRFpulse is reset to 200 μsec, and the application of the pulse RF voltage VRFpulse is stopped. The number N of abnormal discharges was measured by variously changing the value of the time tp2 (μsec) for applying the voltage pulse VP2. The results are shown in a graph of FIG. It can be seen that it is effective when the application time tp2 of the positive voltage pulse VP2 is 10 μsec or more.
[0040]
(3) In the above experiment, the positive voltage pulses VP1 and VP2 were applied at a constant period. However, the present invention includes a case where the intervals between the positive voltage pulses are different.
[0041]
【The invention's effect】
According to the present invention, since abnormal discharge does not occur during sputtering, a high-quality thin film can be formed.
[Brief description of the drawings]
FIG. 1A shows a first embodiment of the apparatus of the present invention. FIG. 2B shows a second embodiment. FIG. 2 shows a relationship between an AC voltage and a positive voltage pulse. FIG. FIG. 4 shows a conventional sputtering apparatus. FIG. 5 shows experimental values of the first embodiment of the present invention. FIG. 6 shows experimental values of the second embodiment of the present invention.
12, 22 target material 11, 21 target electrode 15, 25 pulse power supply VRF, VRFpulse AC voltage VP1, VP2 positive voltage pulse

Claims (2)

Target material,
A target electrode to which the target material is disposed,
In a sputtering apparatus having an AC power supply for applying an AC voltage to the target electrode to generate plasma near the surface of the target material,
A positive voltage pulse power supply for applying a positive voltage pulse to the target electrode,
The AC power supply intermittently stops applying the AC voltage to the target electrode,
The sputtering apparatus is characterized in that the positive voltage pulse power supply is connected to the AC power supply, and is synchronously set so as to apply a positive voltage pulse to the target electrode during a period in which the application of the AC voltage is stopped. Target material,
A target electrode to which the target material is disposed,
A sputtering method using a sputtering apparatus having an AC power source to generate plasma in the vicinity of the surface of the target material by applying an AC voltage to the target electrode,
A sputtering method, further comprising: providing a positive voltage pulse power supply to the sputtering apparatus, intermittently stopping an AC voltage applied to the target electrode, and applying a positive voltage pulse to the target electrode during a stop period. .

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