JPH06340972A - Magnetron sputtering system and method therefor - Google Patents

Abstract

PURPOSE:To make the quality and thickness of a film uniform even if a target is thinned by adjusting the current of an electromagnet in accordance with the change of impedance and fixing the sputtering impedance. CONSTITUTION:The saturation magnetic flux density of a target 3 is decreased as the target 3 is thinned by successive sputtering, the leakage magnetic field strength is increased on the target 3 surface, and the sputtering impedance is lowered. In this case, the sputtering voltage value is outputted to a sputtering impedance arithmetic part 12 from a sputtering power source 4, and the calculated sputtering impedance is outputted to a corrected electromagnet current value arithmetic part 13. The calculated electromagnet current value is outputted to an electromagnet power source 10, the corrected current is applied to an outer coil 6, an intermediate coil 7 and an inner coil 8, and the sputtering impedance is fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron sputtering apparatus using an electromagnet and a magnetron sputtering method, and more particularly to a technique for controlling an electromagnet current in the magnetron sputtering apparatus.

[0002]

2. Description of the Related Art Generally, in a magnetron sputtering apparatus,
As the thickness of the target to be used becomes thinner due to the progress of erosion due to sputtering, the strength of the magnetic field leaking to the target surface becomes stronger, and when the strength of the leaking magnetic field becomes stronger, the sputtering impedance becomes smaller. As a result, the characteristics of the discharge change, and the quality of the film and the deposition rate of the film change. In order to deal with such a change, conventionally, as described in Japanese Patent Laid-Open No. 60-5878, the magnetic field strength is adjusted by changing the electromagnet current of a magnetron sputtering apparatus using an electromagnet, and the sputtering impedance is adjusted. Was always kept constant.

[0003]

By the way, in a magnetron sputtering apparatus using an electromagnet, the distribution of the magnetic field leaking to the target surface is changed by changing the electromagnet current to change the shape of the generated plasma. Then, there is a method which employs a method of obtaining a uniform film thickness by synthesizing film formation in each plasma shape. In the magnetron sputtering apparatus that employs the method of changing the plasma shape, the appropriate value of the sputtering impedance differs for each plasma shape.

However, since the prior art disclosed in the above-mentioned prior application aims to always keep the sputter impedance constant, the spatter in the sputter apparatus adopting the method of changing the plasma shape as described above. There was a problem that it was not possible to cope with changes in the appropriate value of impedance.

The present invention has been made in view of the above points,
The purpose is to achieve uniform film quality and film thickness regardless of the target thickness (regardless of the target thickness) even in the magnetron sputtering system that employs the method of changing the plasma shape. Another object of the present invention is to provide a magnetron sputtering apparatus that can be used.

[0006]

In order to achieve the above-mentioned object, the magnetron sputtering apparatus according to the present invention has a sputtering impedance for the same plasma shape that always has a constant value even if the target becomes thin.
In addition, the electromagnet current in each magnetic field distribution state is adjusted so that different sputtering impedance values are obtained for different plasma shapes.

[0007]

[Operation] Since each sputter impedance for each plasma shape is maintained at different proper values,
The discharge characteristics of each plasma shape can be individually made constant at all times. As a result, in the sputtering apparatus that employs the method of changing the plasma shape, it is possible to maintain uniform film quality and film thickness on a single substrate over a large number of substrates.

[0008]

The present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is an explanatory view (mainly showing a control system) showing a main structure of a magnetron sputtering apparatus according to a first embodiment of the present invention. In the figure, 1 is a vacuum chamber in which sputtering is performed, and the exhaust system of the vacuum chamber 1 is not shown. Reference numeral 2 denotes a substrate installed in the vacuum chamber 1. A target 3 is installed so as to face the substrate 2, and the target 3 is connected to a sputtering power source 4 which is a direct current constant power source. In the vacuum chamber 1,
A cylindrical electromagnet 5 is installed behind the target 3, and the electromagnet 5 is composed of an outer coil 6, a middle coil 7, an inner coil 8 and a yoke 9. The outer coil 6, the middle coil 7, and the inner coil 8 are connected to an electromagnet power source 10, which is a DC constant current power source. In FIG. 1, 11 is a reference electromagnet current value storage unit, 12 is a sputter impedance value calculation unit, 13 is a correction electromagnet current value calculation unit, 14 is a reference sputter power value storage unit, and 15 is a reference sputter impedance value storage unit. The operation of the control system that controls the storage / operation will be described in detail later.

In the above structure, during sputtering, the vacuum chamber 1 is evacuated and the process gas A
Inject r. Further, a current is caused to flow through the outer coil 6, the middle coil 7, and the inner coil 8 by the electromagnet power source 10, and power is applied to the target 3 by the sputter power source 4 to apply a negative voltage. As a result, a magnetic field is generated from the electromagnet 5, a magnetron discharge is generated near the surface of the target 3, and Ar is excited and ionized. The target 3 is sputtered by these ions, and the substance of the sputtered target 3 adheres to the surface of the substrate 2 to form a thin film.

As is well known, generally, when sputtering is continued, the thickness of the target 3 becomes thin as shown in FIG. Accordingly, the saturation magnetic flux amount of the target 3 decreases as shown in FIG. 3, and the strength of the magnetic field leaking to the surface of the target 3 becomes stronger as shown in FIG. Therefore, the sputter impedance is lowered as shown in FIG. 5, and the sputter voltage is lowered as shown in FIG. As the sputtering voltage decreases due to the decrease in the thickness of the target 3, the ion sputtering energy decreases,
The quality and thickness of the film attached to the substrate 2 will change.

Therefore, in order to prevent changes in film quality and film thickness, the sputter impedance is kept constant. Therefore, the sputter power supply 4 outputs the sputter voltage value to the sputter impedance value calculation unit 12. Then, the sputter impedance value calculation unit 12 calculates the sputter impedance value based on the following equation (1) and outputs it to the corrected electromagnet current value calculation unit 13.

[0013]

[Equation 1]

However, in the equation (1), Z is the sputter impedance value, V is the sputter voltage value, and W is the sputter power value.

Here, in the magnetron sputtering apparatus which is the subject of the present embodiment (the present invention), as shown in FIG. 7, since the sputtering impedance increases as the electromagnet current decreases, the correction electromagnet current value computing unit is obtained. 13 calculates a corrected electromagnet current value based on the following equation (2) and outputs it to the electromagnet power source 10. Then, the electromagnet power supply 10 causes a current having the above-mentioned corrected electromagnet current value to flow through the outer coil 6, the middle coil 7, and the inner coil 8, thereby making the sputter impedance constant.

[0016]

[Equation 2]

However, in the equation (2), I: corrected electromagnet current value I ₀ : pre-correction electromagnet current value Z ₀ : reference sputtering impedance value.

Here, in the case of the sputtering apparatus which adopts the method of changing the plasma shape as in this embodiment, each coil (in this embodiment, the outer coil 6, the middle coil 7, the inner coil 8) is used. The distribution of the magnetic field leaking to the surface of the target 3 is changed by changing the value of the current flowing through the target 3. Normally, this change of the plasma shape is performed periodically. Therefore, for one cycle of the change in the plasma shape, each current value flowing through the outer coil 6, the middle coil 7, and the inner coil 8 is defined as a function of time, and this is stored in the reference electromagnet current value storage unit 11. From the reference electromagnet current value storage unit 11, the reference electromagnet current value of each coil corresponding to the current time is output to the correction electromagnet current value calculation unit 13. Then, the correction electromagnet current value calculation unit 13 takes in each data from the reference electromagnet current value storage unit 11 as the pre-correction electromagnet current value I _{0 in the above} equation (2), and based on the equation (2), Corrected electromagnet current values I of 6, 7, and 8 are calculated, and the calculated electromagnet current values I are output to the electromagnet power source 10. The electromagnet power source 10 has an outer coil 6, a middle coil 7, and an inner coil 8 according to the input corrected electromagnet current values I.
An electric current is applied to the plasma to change the plasma shape. Further, the correction electromagnet current value calculation unit 13 outputs each calculated correction electromagnet current value I to the reference electromagnet current value storage unit 11, and the reference electromagnet current value storage unit 11 sets it as a new reference electromagnet current value I _0. Update and memorize.

Further, in the case of changing the sputtering power according to the change of the plasma shape, the electric power applied to the target 3 is defined as a function of time for one cycle of the change of the plasma shape, and this is defined as the reference sputtering power value. Storage unit 1
Store in 4. The reference sputter power value storage unit 14 outputs the sputter power value corresponding to the current time to the sputter power source 4, and the sputter power source 4 applies power to the target 3 according to the sputter power value, thereby changing the sputter power. .

The purpose of changing the sputtering power as described above is to keep the sputtering power density constant.
The sputter power density is the sputter power per unit area of plasma on the target. Next, a second embodiment of the present invention which adopts another method of changing the sputtering power will be described with reference to FIG.
Will be explained. As shown in FIG. 8, in the magnetron sputtering apparatus of this embodiment, a sensor 16 for measuring the area of plasma on the target 3 is provided in the vacuum chamber 1 to obtain the plasma area, and the obtained plasma area data is used as the sputtering power value. It is sent to the calculation unit 17. In order to keep the sputtering power density constant, the sputtering power may be changed in proportion to the plasma area. Therefore, the sputtering power value calculation unit 1
7 obtains the sputter power value based on the following equation (3) and outputs it to the sputter power source 4 to change the sputter power.

[0021]

[Equation 3]

However, in the equation (3), W: sputter power value D ₀ : standard sputter power density A: plasma area.

Here, in the magnetron sputtering apparatus which employs the method of changing the plasma shape as in the first and second embodiments of the present invention, the appropriate value of the sputtering impedance is set for each plasma shape. different. On the other hand, the above-mentioned conventional technique aims to always keep the sputter impedance constant. Therefore, the conventional technique cannot cope with the change in the appropriate value of the sputtering impedance in the sputtering apparatus that employs the method of changing the plasma shape.

Therefore, in the first and second embodiments of the present invention, as shown in FIG. 1 and FIG. 8, the reference sputter impedance value storage unit 15 is provided so that the appropriate value of the sputter impedance according to the change of the plasma shape is obtained. To cope with the changes in. That is, the reference sputter impedance value Z ₀ is defined as a function of time for one cycle of the change in the plasma shape, and this is stored in the reference sputter impedance value storage unit 15. Then, the reference sputtering impedance value storage unit 15 outputs the reference sputtering impedance value Z ₀ corresponding to the current time to the correction electromagnet current value calculation unit 13, and the correction electromagnet current value calculation unit 13 is output.
Calculates the correction electromagnet current value I for each coil based on the equation (2) and outputs it to the electromagnet power supply 10. The electromagnet power source 10 has the outer coil 6, according to the corrected electromagnet current value I.
A current is passed through the middle coil 7 and the inner coil 8, respectively. This allows each sputter impedance for each plasma shape to be maintained at a different appropriate value.

Next, a third embodiment of the present invention will be described which adopts another method of maintaining the sputter impedance at different proper values.
This will be described with reference to FIG.

From the relationship of the state quantity of the sputtering process, the following equation (4) can be assumed as a model equation of the magnetron sputtering device.

[0027]

[Equation 4]

However, in the equation (4), Z is the sputtering impedance value I _{M is the} electromagnet current value k is the coefficient.

Further, the sputter impedance value Z is expressed by the above equation (1) using the sputter voltage value V and the sputter power value W, which are process state quantities that can be easily monitored. Therefore, instead of the sputter impedance value Z, the sputter voltage value V and the sputter power value W are used, and when the equation (1) is substituted into the equation (4), the following equation (5) is obtained.

[0030]

[Equation 5]

When this is solved for the electromagnet current value I _M , the following equation (6) is obtained.

[0032]

[Equation 6]

If the sputter impedance value Z matches the target value at a certain time n, the sputter voltage value V also matches the target value, and therefore the following equation (7) is established. .

[0034]

[Equation 7]

However, in the equation (7), V _g : target sputtering voltage value I _Mn : electromagnet current value at time n k _n : coefficient at time n

However, the coefficient k (coefficient k _n ) is a value that can change due to the change of the process state such as the progress of the target erosion and the change of the process gas pressure. Thus, at time n + 1 has elapsed unit time from the time n, the coefficient changes from k _n to k _{n + 1,} offset sputtering voltage value from the target value, as follows in equation (8).

[0037]

[Equation 8]

[0038] However, in equation (8), V _r: real sputtering voltage value I _{Mn + 1:} the electromagnet current at time n + 1 value k _{n + 1:} is a coefficient at time n + 1.

Therefore, at time n + 1 when a unit time has passed from time n, the electromagnet current value I _{Mn + 1} for making the sputter voltage value equal to the target value is given by the following equation (9).

[0040]

[Equation 9]

Transforming this equation (9), the following (10)
It becomes like a formula.

[0042]

[Equation 10]

Therefore, from the equations (8) and (10), the electromagnet current value I for making the sputter voltage value equal to the target value is obtained.
_{Mn + 1} is expressed by the following equation (11).

[0044]

[Equation 11]

Therefore, in this embodiment, as shown in FIG.
A reference sputtering voltage value storage unit 18 is provided in place of the reference sputtering impedance value storage unit 15, and the reference sputtering voltage value is defined as a function of time for one cycle of the change in the plasma shape. Remember. The reference sputtering voltage value storage unit 18 outputs the reference sputtering voltage value (target sputtering voltage value V _g ) corresponding to the current time to the correction electromagnet current value calculation unit 13.
Further, the sputter power source 4 also outputs the sputter voltage value (actual sputter voltage value V _r ) at the current time to the correction electromagnet current value calculation unit 13. Thereby, the correction electromagnet current value calculation unit 13 calculates the correction electromagnet current value I _{Mn + 1} based on the equation (11) and outputs it to the electromagnet power supply 10. Then, the electromagnet power source 10 supplies a current to the outer coil 6, the middle coil 7, and the inner coil 8 according to the corrected electromagnet current value I _{Mn + 1} . This allows each sputter impedance for each plasma shape to be maintained at a different appropriate value.

Next, as an example of application of this embodiment, the results of continuous sputtering under the following conditions when a magnetic thin film is formed on a magnetic disk substrate will be shown.

The plasma transfer control method is as follows, in which the position of plasma is switched in three steps for 5 seconds each in one cycle, and the electromagnet current and the sputtering power are switched in three steps. In the initial electromagnet current pattern setting, the current of the inner and outer coils 8 and 6 is set to 4 [A] for the first 5 seconds and 5 [A] for the subsequent 10 seconds, and the current of the middle coil is set to the first Five seconds was 5 [A], the next 5 seconds was 0 [A], and the subsequent 5 seconds was -5 [A]. Also, the sputtering power pattern setting is 1.
5 [kW], 1.0 [kW] for the next 5 seconds, then 5
The second was set to 0.5 [kW]. The target sputtering voltage was set to 550 [V], which was constant.

FIG. 10 shows changes in the sputtering voltage during sputtering.
Shown in. As described above, since the plasma position is switched in three stages, the first position is P1, the next position is P2,
The last position is set to P3, and the fluctuation of the sputtering voltage at each position is shown. The sputtering voltage converged within ± 2% (± 10 [V]) of the target sputtering voltage within 9 cycles, and then stabilized within the same range.

FIG. 11 shows changes in the sputtering voltage in the first cycle and the ninth cycle. In the first cycle, the distribution of the sputter voltage at three positions in the cycle was -38 [V] to +36 [V] with respect to the target sputter voltage. On the other hand, in the 9th cycle,
The sputter voltage at three positions in the cycle fell within a distribution of +6 [V] to +8 [V] with respect to the target sputter voltage.

From these results, it is understood that the apparatus of the present embodiment corrects the electromagnet current pattern with respect to the setting of the target sputtering voltage, whereby the sputtering voltage can be converged and stabilized, and the sputtering impedance can be maintained at different appropriate values.

[0051]

As described above, according to the present invention, it is possible to maintain the respective sputtering impedances for the respective plasma shapes at different proper values. Therefore, the discharge characteristic in each plasma shape can be always made constant individually. As a result, in the sputtering apparatus that employs the method of changing the plasma shape, it is possible to maintain uniform film quality and film thickness on a single substrate over a large number of substrates.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main configuration of a magnetron sputtering apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the change over time in the thickness of the target during sputtering.

FIG. 3 is an explanatory diagram showing a change over time in a saturation magnetic flux amount of a target during sputtering.

FIG. 4 is an explanatory diagram showing a temporal change in magnetic field strength during sputtering.

FIG. 5 is an explanatory diagram showing a change over time in sputtering impedance during sputtering.

FIG. 6 is an explanatory diagram showing a time change of a sputtering voltage during sputtering.

FIG. 7 is an explanatory diagram showing a relationship between an electromagnet current and a sputtering impedance.

FIG. 8 is an explanatory diagram showing a main configuration of a magnetron sputtering apparatus according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a main configuration of a magnetron sputtering apparatus according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a measurement result of a sputtering voltage during sputtering performed using the magnetron sputtering apparatus according to the third embodiment of the present invention.

11 is an explanatory diagram showing changes in sputtering voltage in the first cycle and the ninth cycle of FIG.

[Explanation of symbols]

 1 vacuum chamber 2 substrate 3 target 4 sputter power supply 5 electromagnet 6 outer coil 7 middle coil 8 inner coil 9 yoke 10 electromagnet power supply 11 reference electromagnet current value storage unit 12 sputter impedance value calculation unit 13 correction electromagnet current value calculation unit 14 reference sputtering power Value storage unit 15 Reference sputter impedance value storage unit 16 Sensor 17 Sputter power value calculation unit 18 Reference spatter voltage value storage unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shinji Sasaki, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., Hitachi, Ltd. Hitachi Storage Systems Division (72) Inventor Kazutaka Iwakami 2880 Kozu, Odawara City, Kanagawa Stock Company Hitachi Storage Systems Division

Claims (11)

[Claims] 1. A magnetron sputtering apparatus using an electromagnet, characterized in that the electromagnet current is controlled so that the sputtering impedance for each plasma shape that changes depending on the electromagnet current is kept constant. 2. In a magnetron sputtering apparatus using an electromagnet, the area of the plasma target on each of the plasma shapes that change depending on the electromagnet current is measured, the sputtering power is changed accordingly, and the sputtering impedance of each is changed. The magnetron sputtering apparatus is characterized in that the electromagnet current is controlled so as to maintain a constant value. 3. The method according to claim 1, wherein the sputtering impedance is made constant by an electromagnet current in order to make the film quality uniform, and the plasma shape is made cyclic by the electromagnet current in order to make the film thickness uniform. A magnetron sputtering device characterized by varying. 4. The reference sputtering impedance value storage unit according to claim 1, wherein a sputtering impedance for each of the plasma shapes is stored, and a reference sputtering impedance value storage unit that outputs a reference sputtering impedance value corresponding to the current time is provided. A magnetron sputtering device characterized by. 5. The reference sputtering voltage value storage unit according to claim 1, which stores a sputtering voltage for each plasma shape and outputs a reference sputtering voltage value corresponding to a current time. A magnetron sputtering device characterized by. 6. A magnetron sputtering apparatus according to claim 1, which is used for forming a magnetic thin film on a magnetic disk substrate. 7. A magnetron sputtering method using an electromagnet, characterized in that the electromagnet current is controlled so that the sputtering impedance for each plasma shape that varies with the electromagnet current is kept constant. 8. In a magnetron sputtering method using an electromagnet, the area on the target of the plasma for each plasma shape that changes with the electromagnet current is measured, the sputtering power is changed accordingly, and the sputtering impedance of each is changed. The magnetron sputtering method is characterized in that the electromagnet current is controlled so as to maintain a constant value. 9. The plasma shape according to claim 7 or 8, wherein the sputtering impedance is made constant by an electromagnet current in order to make the film quality uniform, and the plasma shape is made cyclic by the electromagnet current in order to make the film thickness uniform. A magnetron sputtering method characterized by varying. 10. The reference sputter impedance value storage unit according to claim 7, which stores a sputter impedance for each plasma shape and outputs a reference sputter impedance value corresponding to a current time. And a magnetron sputtering method. 11. The reference sputtering voltage value storage unit according to claim 7, wherein a sputtering voltage for each of the plasma shapes is stored and a reference sputtering voltage value storage unit that outputs a reference sputtering voltage value corresponding to a current time is provided. And a magnetron sputtering method.