JP6282128B2 - Plasma processing apparatus and FSV control method - Google Patents

Description

The present invention relates to a plasma processing apparatus and an FSV control method using the plasma processing apparatus.

In recent years, magnetoresistive memory (Magnetorescent Random Access Memory: MRAM) and ferroelectric memory (Ferroelectric Random Access Memory: FeRAM) using non-volatile materials have attracted attention as next-generation memories due to advantages such as power saving. .

  In the etching of the nonvolatile material, the productivity decreases due to the reaction product adhering in the chamber. Therefore, as a conventional plasma etching apparatus, for example, Patent Document 1 discloses an inductively coupled antenna 1 and a capacitively coupled antenna 8. The ratio of the plasma generated by the capacitively coupled discharge is adjusted by grounding to the earth via the load 17 whose impedance magnitude can be changed from between and adjusting the impedance magnitude of the load 17, A plasma etching apparatus that suppresses adhesion of reaction products to the inner wall of a vacuum vessel is disclosed.

  In Patent Document 2, high-frequency power is supplied to a vacuum processing chamber in which a sample is plasma-treated and a sample stage on which the sample is placed, an induction antenna provided outside the vacuum processing chamber, and the induction antenna. In a plasma processing apparatus comprising a Faraday shield that is capacitively coupled to a high-frequency power source and plasma and is applied with a high-frequency voltage from the high-frequency power source through a matching device, the matching device includes a series resonant circuit including a variable capacitor and an inductance. A plasma processing apparatus comprising: a motor control unit that controls a motor of a variable capacitor; and a high-frequency voltage detection unit that detects a high-frequency voltage applied to the Faraday shield, and feedback-controls the high-frequency voltage applied to the Faraday shield. Is disclosed.

JP 2000-323298 A JP 2012-129222 A

In the above-described plasma etching apparatus, during etching optimal for material processing and during plasma cleaning for removing reaction products on the inner wall of the vacuum vessel in order to prevent productivity degradation, a high-frequency voltage (hereinafter referred to as FSV) applied to the Faraday shield is removed. Therefore, it was necessary to control a wide range of FSV.

  However, in order to control a wide range of FSV with the above-described plasma etching apparatus, it is necessary to select a variable capacitor having a wide variable range as a means for adjusting the FSV and having a large change gradient, so that the control resolution is lowered. . As a result, there is a problem that the control accuracy of the FSV is deteriorated.

  Therefore, the present invention provides a plasma processing apparatus and an FSV control method that can stably control a wide range of FSVs with high accuracy.

The present invention includes a vacuum processing chamber in which a sample is subjected to plasma processing, an inductive coupling antenna disposed outside the vacuum processing chamber, a high frequency power source that supplies high frequency power to the inductive coupling antenna through a matching unit, and the vacuum processing A matching unit that includes a dielectric window that hermetically seals the upper portion of the chamber and a Faraday shield disposed between the inductively coupled antennas, and the high frequency voltage applied to the Faraday shield is FSV. A series resonance circuit including a capacitor and an inductance, a motor control unit that controls a motor that drives the variable capacitor, a detection unit that detects the FSV, and an FSV value detected by the detection unit is a desired FSV value. A control unit that controls the motor control unit so that the variable capacitor includes the first variable capacitor and the first variable capacitor. A second variable capacitor having a capacitance smaller than that of the variable capacitor, and if the deviation between the detected FSV and the desired FSV is larger than a predetermined value, the control device it is a plasma processing apparatus you and performs control such that the deviation becomes smaller with.

According to the present invention, a wide range of FSV can be stably controlled with high accuracy.

1 is a schematic cross-sectional view of a plasma etching apparatus according to the present invention. 2 is a diagram showing a configuration of an FSV detection / control circuit 19. FIG. It is a figure which shows the relationship between the electrostatic capacitance of a variable capacitor, and the position within a variable range. It is a figure which shows the concept of control of FSV which concerns on this invention. It is a flowchart which shows control of FSV of this invention.

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

  A schematic cross-sectional view of a plasma etching apparatus according to the present invention is shown in FIG. In this case, the vacuum vessel 2 is provided with a discharge part 2a made of an insulating material (for example, quartz, ceramic, etc.) that forms a plasma generation part, and a sample stage 5 on which a sample 13 that is, for example, a wafer is placed. And processing unit 2b. The processing unit 2b is grounded to the ground, and the sample stage 5 is attached to the processing unit 2b via an insulating material.

  A coil-shaped first inductively coupled antenna 1a and a coil-shaped second inductively coupled antenna 1b disposed below the first inductive antenna 1a are disposed outside the discharge portion 2a, which is a dielectric window. Yes. A Faraday shield 8 that is capacitively coupled with plasma and is a capacitively coupled antenna is disposed above the discharge part 2a. Further, the first inductively coupled antenna 1a, the second inductively coupled antenna 1b, and the Faraday shield 8 are connected in series to the first high frequency power supply 10 via the impedance matching circuit 12 in the matching box 3 that is a matching unit. ing.

  The second inductively coupled antenna 1b is connected in series with a first variable capacitor 16 that can control the magnitude of the impedance to a desired value, and the Faraday shield 8 is connected in parallel with a second variable variable. The capacitor 17 and the third variable capacitor 26 and the coil 18 are connected to the ground. Further, the first inductively coupled antenna 1a and the second inductively coupled antenna 1b are connected to the antenna current ratio control circuit 15 via the first current sensor 14a and the second current sensor 14b, and the Faraday shield 8 Are connected to the FSV detection / control circuit 19.

  Further, the processing gas is supplied from the gas supply device 4 into the vacuum vessel 2, and the inside of the vacuum vessel 2 is evacuated to a predetermined pressure by the exhaust device 7. A second high frequency power supply 11 is connected to the sample stage 5.

  In the plasma etching apparatus configured as described above, a processing gas is supplied into the vacuum vessel 2 by the gas supply device 4, and the processing gas is generated by the first inductively coupled antenna 1a and the second inductively coupled antenna 1b. Plasma is generated by generating plasma by the induced magnetic field. The plasmaized gas is exhausted later by the exhaust device 7.

  The first high-frequency power source 10 supplies high-frequency power such as HF bands such as 13.56 MHz, 27.12 MHz, and 40.68 MHz and higher VHF bands to the first inductively coupled antenna 1a and the second induction. By supplying the coupled antenna 1b and the Faraday shield 8, an induction magnetic field and electric field for plasma generation are obtained. In order to suppress reflection of high-frequency power, the impedance matching circuit 12 is used to suppress the first inductively coupled antenna 1a. And the impedance of the second inductively coupled antenna 1b are made to match the output impedance of the first high frequency power supply 10.

  As the impedance matching circuit 12, a circuit using two variable capacitors that can change the capacitance, which is also called a general inverted L type, is used. The sample 13 to be processed is placed on the sample stage 5, and the second high frequency power supply 11 applies a bias voltage to the sample stage 5 in order to draw ions present in the plasma into the sample 13.

  Next, functions of the FSV detection / control circuit 19 will be described with reference to the drawings. As shown in FIG. 2, the FSV detection / control circuit 19 includes a control unit 23, an FSV detection circuit 24, a first stepping motor drive circuit 25, a second stepping motor drive circuit 27, a first stepping motor 28, and a second stepping motor. Stepping motor 29, first position detector 21 and second position detector 22 are provided. The FSV detection circuit 24 is a circuit that detects FSV. The first stepping motor 28 adjusts the capacity of the second variable capacitor 17, and the second stepping motor 29 adjusts the capacity of the third variable capacitor 26. Stepping motor for

  Further, the control unit 23 sets the first stepping motor 28 by the first stepping motor driving circuit 25 and the second stepping by the second stepping motor driving circuit 27 based on the FSV signal detected by the FSV detection circuit 24. Each motor 29 is driven to control to achieve a desired FSV. Note that the first position detector 21 and the second position detector 22 are located at which position in the variable range the capacitance of the second variable capacitor 17 and the capacitance of the third variable capacitor 26, respectively. Is transmitted to the control unit 23.

  Next, FIG. 3 shows the relationship between the capacitance of the second variable capacitor 17 and the position within the variable range, and the relationship between the capacitance of the third variable capacitor 26 and the position within the variable range. As shown in FIG. 3, the maximum capacitance of the second variable capacitor 17 is large and the gradient of the change in capacitance is large. On the other hand, the maximum capacitance of the third variable capacitor 26 is smaller than that of the second variable capacitor 17 and the inclination of the change in capacitance is smaller than that of the second variable capacitor 17.

  Next, the FSV control method will be described. First, FIG. 4 shows the relationship between the capacitance C and the FSV in a series resonance circuit composed of the second variable capacitor 17, the third variable capacitor 26, and the coil 18. The capacity of the capacitance C is a combined capacity of the second variable capacitor 17 and the third variable capacitor 26. Further, the FSV can be changed by increasing or decreasing the capacitance of any of the second variable capacitor 17 and the third variable capacitor 26. The case where the FSV is reduced from the ASV of FIG. 4 at the certain time and the set value (target value) of FSV from A in FIG. 4 to B in FIG. 4 will be described below with reference to FIG.

  First, in step 1, a setting signal for the target value (B) of the FSV is transmitted to the control unit 23, and the control of the FSV is started. Next, in step 2, the third variable capacitor 26 is adjusted from the signal from the second position detector 22 so that the capacitance of the third variable capacitor 26 becomes the capacitance at the center position of the variable range. This is because the FSV adjustment by the third variable capacitor 26 can be adjusted in either the increasing direction or the decreasing direction. In step 3, a deviation, which is a difference between the target value B and the current FSV monitor value, is calculated. Subsequently, in step 4, it is determined whether or not the deviation calculated in step 3 is within the allowable value of the target value (B) obtained in advance. If the deviation is within the allowable value of the target value (B), the process proceeds to step 8. The FSV control is terminated.

  On the other hand, if the deviation is larger than the allowable value in step 4, the process proceeds to step 5 and subsequent steps, and the FSV is adjusted by changing the capacitance of the second variable capacitor 17 or the third variable capacitor 26. Specifically, in step 5, it is determined whether the FSV control is performed by the variable capacitor of either the second variable capacitor 17 or the third variable capacitor 26. When the threshold value C set in advance and the deviation calculated in step 3 are compared and the deviation is larger than the threshold value C, the second variable capacitor 17 is used in advance to determine the deviation in step 7. After changing the FSV by the drive amount of the first stepping motor 28, the process returns to step 3. If the second stepping motor 29 is driven in step 7, the driving of the second stepping motor 29 is stopped. That is, in step 7, the FSV is controlled using only the second variable capacitor 17.

  On the other hand, if the threshold value preset in step 5 is compared with the deviation calculated in step 3, and the deviation is determined to be less than or equal to the threshold value C, the third variable is determined in step 6. After changing the FSV by a predetermined driving amount of the second stepping motor 29 using the capacitor 26, the process returns to step 3. If the first stepping motor 28 is driven in step 6, the driving of the first stepping motor 28 is stopped. That is, in step 6, the FSV is controlled using only the third variable capacitor 26. Thereafter, Step 3 to Step 7 are repeated until the FSV monitor value falls within the allowable value of the FSV target value (B).

  As described above, a wide range of FSV control by the second variable capacitor 17 having a large capacitance variable range and a high precision FSV control by the third variable capacitor 26 having a small capacitance variable range are combined. According to the present invention which is the control of the FSV, the FSV can be controlled over a wide range and with high accuracy.

  Further, the threshold value C of the present embodiment is larger than the allowable value of the target value (B), and is a value used as a reference when selecting either the second variable capacitor 17 or the third variable capacitor 26. .

  Furthermore, the present invention can stably control a desired FSV with high accuracy even when the control range of the FSV is widened. Further, according to the present invention, since the control of FSV is controlled by a plurality of variable capacitors, the operating range of the single variable capacitor is narrowed, and the burden on the variable capacitor is reduced. This prolongs the lifetime of the variable capacitor.

  In addition, the present invention is an invention for controlling a wide range of FSV with high accuracy by performing FSV control step by step using a plurality of variable capacitors having different capacitances.

DESCRIPTION OF SYMBOLS 1a 1st inductive coupling antenna 1b 2nd inductive coupling antenna 2 Vacuum vessel 2a Discharge part 2b Processing part 3 Matching box 4 Gas supply apparatus 5 Sample stand 7 Exhaust apparatus 8 Faraday shield 10 1st high frequency power supply 11 2nd high frequency Power supply 12 Impedance matching circuit 13 Sample 14a First current sensor 14b Second current sensor 15 Antenna current ratio control circuit 16 First variable capacitor 17 Second variable capacitor 18 Coil 19 FSV detection / control circuit 21 First position Detector 22 Second position detector 23 Control unit 24 FSV detection circuit 25 First stepping motor drive circuit 26 Third variable capacitor 27 Second stepping motor drive circuit 28 First stepping motor 29 Second stepping motor

Claims (2)

A vacuum processing chamber in which the sample is plasma treated;
An inductively coupled antenna disposed outside the vacuum processing chamber;
A high frequency power source for supplying high frequency power to the inductively coupled antenna through a matching unit;
A dielectric window that hermetically seals the upper portion of the vacuum processing chamber and a Faraday shield disposed between the inductively coupled antennas;
When the high-frequency voltage applied to the Faraday shield is FSV, the matching unit includes a series resonant circuit composed of a variable capacitor and an inductance, a motor control unit that controls a motor that drives the variable capacitor, and the FSV. And a control unit that controls the motor control unit so that the FSV value detected by the detection unit becomes a desired FSV value,
The variable capacitor comprises a first variable capacitor and a second variable capacitor having a smaller capacitance than the first variable capacitor,
When the deviation between the detected FSV and the desired FSV is larger than a predetermined value, the control device performs control such that the deviation is reduced using the first variable capacitor. Plasma processing equipment. A vacuum processing chamber in which the sample is plasma treated;
An inductively coupled antenna disposed outside the vacuum processing chamber;
A high frequency power source for supplying high frequency power to the inductively coupled antenna through a matching unit;
A dielectric window that hermetically seals the upper portion of the vacuum processing chamber and a Faraday shield disposed between the inductively coupled antennas;
When the high-frequency voltage applied to the Faraday shield is FSV, the matching unit includes a series resonant circuit composed of a variable capacitor and an inductance, a motor control unit that controls a motor that drives the variable capacitor, and the FSV. And a control unit that controls the motor control unit so that the FSV value detected by the detection unit becomes a desired FSV value,
In the FSV control method for controlling the FSV using a plasma processing apparatus comprising a first variable capacitor and a second variable capacitor having a smaller capacitance than the first variable capacitor,
When the deviation between the detected FSV and the desired FSV is larger than a predetermined value, the FSV is controlled using the first variable capacitor so that the deviation is reduced. Control method.