TWI553696B - Plasma processing device and its substrate DC bias voltage measurement method - Google Patents

Description

Plasma processing device and substrate DC bias voltage measuring method thereof

The present invention relates to the field of plasma processing technologies, and in particular, to a technical field of monitoring a DC bias voltage on a surface of a substrate.

In the plasma processing process, Electro Static Chuck (ESC) is often used to fix, support and transfer the substrate (Wafer) to the workpiece. The electrostatic chuck is disposed in the reaction chamber, and the electrostatic chucking method is used instead of mechanically fixing the substrate, which can reduce the possible mechanical loss to the substrate and completely contact the electrostatic chuck with the substrate, thereby facilitating heat conduction. . During the reaction, a reaction gas is introduced into the reaction chamber, and RF power is applied to the reaction chamber. Usually, the RF power is applied to the conductor base under the electrostatic chuck. The RF power mainly includes the RF source power and the RF bias power, and the RF The source power and the RF bias power work together to ionize the reaction gas to generate a plasma, and the plasma and the substrate undergo a plasma reaction to complete the processing of the substrate. In this process, due to the characteristics of the plasma and some parameter conditions in the reaction chamber, a DC bias voltage is generated on the surface of the substrate. The magnitude of the DC bias represents some states of the plasma, and the magnitude of the DC bias changes. This means that the state of the plasma in the reaction chamber changes and therefore needs to be monitored.

Under normal conditions, the output of the RF power source and the RF bias power source is constant, and the DC bias voltage on the surface of the substrate is relatively stable. The signal can be directly collected to monitor the DC bias voltage on the surface of the substrate. However, in some applications, RF power sources need to be set up. Or the output of the RF bias power source is a pulse output, and the DC bias voltage of the surface of the substrate changes according to the output of the RF source power or the RF bias power, in order to monitor the DC bias voltage. The plasma reaction device needs to increase the sampling frequency of the DC bias voltage, which is a waste of a large data space for the device that needs to record data in units of years, and increases the difficulty of monitoring. Adding a burden to existing plasma processing equipment.

In order to solve the above problems, the present invention provides a plasma processing apparatus including a vacuum reaction chamber, an electrostatic chuck supporting a substrate is disposed under the vacuum reaction chamber, and a susceptor is disposed under the electrostatic chuck. The pedestal serves as a lower electrode of the vacuum reaction chamber, the lower electrode is connected to a radio frequency power source, the radio frequency power source outputs pulse power, and a DC bias voltage detecting pin is disposed under the substrate, and the probe pin is connected. A clock trigger switch, the back end of the clock trigger switch is respectively connected to a high potential integration circuit and a low potential integration circuit.

Preferably, the radio frequency power comprises radio frequency source power and radio frequency bias power, and the radio frequency source power or radio frequency offset power is at least one output pulse power.

Preferably, the pulse frequency of the radio frequency power is the same as the clock frequency of the clock trigger switch.

Preferably, the output of the radio frequency source power is a pulse signal, and the pulse signal is used as a clock signal of the clock trigger switch. When the output pulse signal of the radio frequency power is a rising edge, the clock triggers the switch and the back end. The low potential integration circuit is connected, and when the output signal is a falling edge, the clock trigger switch is connected to the high potential integration circuit at the back end.

Preferably, when the output of the radio frequency offset power is a pulse signal, the pulse signal is used as a clock signal of the clock trigger switch, and the output pulse signal of the radio frequency power is At the rising edge, the clock trigger switch is connected to the high potential integration circuit of the back end, and when the output signal is a falling edge, the clock trigger switch is connected to the low potential integration circuit of the back end.

Preferably, when the output of the radio frequency source power and the radio frequency offset power are both pulse signals, the pulse signal is used as a clock signal of the clock trigger switch, and the output pulse signal of the radio frequency power is a rising edge. The clock trigger switch is connected to a high potential integration circuit at the back end. When the output signal is a falling edge, the clock trigger switch is connected to a low potential integration circuit at the back end.

Preferably, the frequency of the radio frequency bias power ranges from 400 kHz to 13.56 MHz, and the frequency of the radio frequency source power ranges from 27 MHz to 120 MHz.

Preferably, the radio frequency offset power and the radio frequency source power have a pulse frequency ranging from 50 Hz to 10 KHz, and the working ratio ranges from 10% to 90%.

Further, the present invention also discloses a method for measuring a DC bias voltage of a surface of a substrate in a plasma processing apparatus, comprising the steps of: placing a probe for detecting a DC bias voltage on a surface of the substrate, the detecting a clock trigger switch is connected to the rear end of the pin, and a high potential integration circuit and a low potential integration circuit are respectively connected to the rear end of the clock trigger switch; the output pulse signal frequency of the RF power is adjusted; and the pulse output signal frequency is used as a The clock trigger switch adjusts the frequency. When the output pulse signal of the RF power is a rising edge or a falling edge, the clock trigger switch is respectively connected to the high potential integration circuit or the low potential integration circuit, and the high potential integration The circuit or the low potential integration circuit respectively integrates the high potential pulse and the low potential pulse of the DC bias voltage detected by the probe, and obtains an average value of the DC bias voltage at a high potential and an average value at a low potential. Then separately collect signals to realize the monitoring of the DC bias voltage on the surface of the substrate.

Preferably, the sampling time interval between the average value of the DC bias voltage at a high potential and the average value at a low potential is greater than or equal to 0.1 s.

The invention has the advantages that the DC bias voltage in the pulse on-off state is separated by a pulse trigger switch, and the clock trigger switch is connected to a high potential integration circuit and a low potential integration circuit, and the clock trigger switch is The rising edge and the falling edge of the clock signal switch the signal, and are respectively connected with the high-potential integration circuit or the low-potential integration circuit at the back end to realize the integration of the DC bias voltage at a higher value and a lower value respectively. Continuous analog signal to monitor the DC bias voltage on the substrate surface. By adopting the technical solution described in the present invention, the sampling frequency can be greatly reduced, and the sampling circuit can be simplified.

10‧‧‧ probe needle

20‧‧‧clock trigger switch

30‧‧‧High potential integration circuit

40‧‧‧Low potential integration circuit

60‧‧‧Support substrate

100‧‧‧vacuum reaction chamber

110‧‧‧Electrostatic chuck

130‧‧‧RF source power

140‧‧‧RF bias power

Fig. 1 is a schematic view showing the structure of a plasma processing apparatus according to the present invention.

Fig. 2 is a schematic diagram showing the pulse of the DC bias voltage when the power of the RF source is pulse output according to the present invention.

Fig. 3 is a schematic diagram showing the pulse of the DC bias voltage when the RF bias power is a pulse output according to the present invention.

Fig. 4 is a schematic diagram showing the pulse of the DC bias voltage when the RF source power and the RF bias power are pulse output according to the present invention.

Fig. 5 is a schematic view showing the detecting device of the DC bias voltage of the present invention.

The present invention discloses a plasma processing apparatus and a method for measuring a DC bias voltage of a substrate. The above objects, features and advantages of the present invention can be more clearly understood. The specific embodiments of the present invention are described below with reference to the accompanying drawings and embodiments. The embodiment will be described in detail.

1 is a schematic view showing the structure of a plasma processing apparatus according to the present invention. The plasma processing apparatus includes a vacuum reaction chamber 100. An electrostatic chuck 110 supporting a substrate 60 is disposed under the vacuum reaction chamber 100. A susceptor 120 is disposed under the electrostatic chuck 110. The susceptor 120 serves as the vacuum reaction chamber at the same time. The lower electrode of the 100 is connected to a radio frequency power source. The radio frequency power includes a radio frequency source power 130 and a radio frequency bias power 140. The radio frequency source power 130 and the radio frequency bias power 140 have at least one output pulse power. The reaction gas in the reaction gas source enters the vacuum reaction chamber 100 through the upper electrode as a gas shower head, dissociates the generated plasma under the action of the radio frequency power, and performs plasma treatment on the substrate to complete the etching process. When the plasma is processed on the substrate, due to the characteristics of the plasma, a DC bias voltage is generated on the surface of the substrate, and the magnitude of the DC bias voltage reflects some parameter states of the plasma, if the DC bias voltage occurs. The change indicates that the plasma state in the reaction chamber has changed and needs to be adjusted to avoid affecting the plasma process. In addition, the DC bias voltage on the surface of the substrate 60 also determines the magnitude of the DC voltage applied to the electrostatic chuck 110. The magnitude of the DC voltage determines the electrostatic attraction of the electrostatic chuck to the substrate 60, and the electrostatic chuck. The DC voltage is offset by the DC bias voltage on the surface of the substrate. If the DC bias voltage is not monitored and the DC voltage on the electrostatic chuck 110 is fed back, the electrostatic chuck of the electrostatic chuck 110 will be insufficient. The piece is detached from the electrostatic chuck. Cause process accidents.

Under normal conditions, the output of the RF power source and the RF bias power source is constant, and the DC bias voltage on the surface of the substrate is relatively stable. The signal can be directly collected to monitor the DC bias voltage on the surface of the substrate. However, in the application of the present invention, the output of the RF power source or the RF bias power source needs to be set as a pulse output, and the DC bias voltage of the substrate surface at the corresponding time changes with the pulse change of the RF output, when the pulse The frequency is 50Hz to 10kHz, if the direct current bias of the substrate surface corresponding to the RF output in the frequency range is directly Sampling requires very high sampling frequency. Since the plasma processing device is always in working state, the sampling result needs to be recorded all the time. It is a waste of a large data space for the etching equipment that needs to record data in units of years. At the same time, it increases the difficulty of monitoring. Adding a burden to existing plasma processing equipment.

The inventors of the present application have found through a large amount of data acquisition that the DC bias voltage periodically changes with the change of the RF power pulse output, and FIG. 2 to FIG. 4 show the DC bias voltage with the source power of the RF power. Schematic diagram of the bias power variation, as can be seen from Figure 2, when the RF source power is pulse output and the RF bias power is constant output, the DC bias voltage on the substrate surface is also pulsed, and when the RF source When the output pulse signal of the power is a rising edge, the magnitude of the DC bias voltage is a falling edge. When the output pulse signal of the RF source power is a falling edge, the magnitude of the DC bias voltage is a rising edge. It can be seen from Fig. 3 that when the RF source power is constant output and the RF bias power is pulse output, the DC bias voltage of the substrate surface is also pulsed, and when the RF bias power output pulse signal is On the rising edge, the magnitude of the DC bias voltage is the rising edge. When the output pulse signal of the RF bias power is the falling edge, the magnitude of the DC bias voltage is the falling edge. It can be seen from Fig. 4 that when the RF source power and the RF bias power are both pulse outputs, the DC bias voltage on the surface of the substrate is also pulsed, and the output pulse signal of the RF bias power is a rising edge. When the magnitude of the DC bias voltage is a rising edge, when the output pulse signal of the RF bias power is a falling edge, the magnitude of the DC bias voltage is a falling edge. As can be seen from the above figures, the pulse change frequency of the DC bias voltage on the surface of the substrate is the same as the pulse output frequency of the RF power. With this feature, FIG. 5 shows a technical solution for detecting the DC bias voltage of the present invention.

Figure 5 is a schematic view showing the detecting device of the DC bias voltage of the present invention, A DC bias voltage detecting pin 10 is disposed above the substrate 60. The detecting pin 10 is connected to a clock triggering switch 20. The rear end of the clock triggering switch 20 is connected to a high potential integrating circuit 30 and a low potential integrating circuit 40, respectively. 20 is controlled by a clock signal 50, the frequency of which is the same as the frequency of the pulse signal of the radio frequency power. Under the control of the clock signal 50, when the pulse signal is at the rising edge or the falling edge, the clock trigger switch 20 switches, and is connected to the high potential integrating circuit 30 or the low potential integrating circuit 40, respectively. The corresponding high-potential integration circuit 30 and low-potential integration circuit 40 start to integrate and average the DC bias voltage in the period at the high potential and the low potential, respectively, because the high-potential integration circuit 30 and the low-potential integration circuit 40 For the analog circuit, the DC bias voltage value measured by the probe pin 10 can be instantaneously integrated, and the sampling device can be used to perform high and low potential sampling on the basis of the average value calculated by the high potential integration circuit 30 and the low potential integration circuit 40. The sampling frequency can be greatly reduced, the storage space of the plasma processing device is saved, and the processing efficiency of the plasma processing device is improved.

Specifically, considering that the high and low potentials of the RF source power pulse output signal in the same period are opposite to the high and low potentials of the DC bias voltage, when the RF source power output is a pulse signal, when the pulse signal is used as the clock trigger switch a pulse signal, when the output pulse signal of the RF source power is a rising edge, the clock trigger switch is connected to a low potential integration circuit at the back end, and when the output signal is a falling edge, the clock triggers a high potential of the switch and the back end The integration circuit is connected.

Since the high-low potential of the RF bias power pulse output signal is the same as the high-low potential of the DC bias voltage in the same period, when the output of the RF bias power is a pulse signal, regardless of whether the output of the RF source power is a pulse output, When the output pulse signal of the RF bias power is a rising edge, the clock trigger switch is connected to a high potential integration circuit at the back end, When the output signal is a falling edge, the clock trigger switch is connected to the low potential integration circuit at the back end.

The present invention is disclosed in the above preferred embodiments, but it is not intended to limit the present invention, and any one skilled in the art can make possible variations and modifications without departing from the spirit and scope of the invention. The scope of protection should be determined by the scope defined by the claims of the present invention.

10‧‧‧ probe needle

60‧‧‧Support substrate

100‧‧‧vacuum reaction chamber

110‧‧‧Electrostatic chuck

130‧‧‧RF source power

140‧‧‧RF bias power

Claims (6)

A plasma processing apparatus includes a vacuum reaction chamber, an electrostatic chuck supporting a substrate is disposed under the vacuum reaction chamber, a pedestal is disposed under the electrostatic chuck, and the pedestal serves as the vacuum reaction chamber simultaneously a lower electrode, the lower electrode is connected to a radio frequency power source, and the radio frequency power source outputs a pulse power, wherein: a constant current bias voltage detecting pin is disposed above the substrate, and the detecting pin is connected to a clock trigger switch. The rear end of the clock-triggered switch is respectively connected to a high-potential integration circuit and a low-potential integration circuit, and the radio frequency power includes a radio frequency source power and a radio frequency offset power, and the radio frequency source power or the radio frequency bias power is at least one output pulse power. The pulse frequency of the radio frequency power is the same as the clock frequency of the clock trigger switch. A plasma processing apparatus includes a vacuum reaction chamber, an electrostatic chuck supporting a substrate is disposed under the vacuum reaction chamber, a pedestal is disposed under the electrostatic chuck, and the pedestal serves as the vacuum reaction chamber simultaneously a lower electrode, the lower electrode is connected to a radio frequency power source, and the radio frequency power source outputs a pulse power, wherein: a constant current bias voltage detecting pin is disposed above the substrate, and the detecting pin is connected to a clock trigger switch. The rear end of the clock-triggered switch is respectively connected to a high-potential integration circuit and a low-potential integration circuit, and the radio frequency power includes a radio frequency source power and a radio frequency offset power, and the radio frequency source power or the radio frequency bias power is at least one output pulse power. The output of the RF source power is a pulse signal, and the pulse signal is used as a clock signal of the clock trigger switch. When the output pulse signal of the RF power is a rising edge, the clock triggers a low potential integration of the switch and the back end. The circuit is connected, and when the output signal is a falling edge, the clock trigger switch is connected to the high potential integration circuit at the back end. A plasma processing apparatus includes a vacuum reaction chamber, an electrostatic chuck supporting a substrate is disposed under the vacuum reaction chamber, a pedestal is disposed under the electrostatic chuck, and the pedestal serves as the vacuum reaction chamber simultaneously a lower electrode, the lower electrode is connected to a radio frequency power source, and the radio frequency power source outputs a pulse power, wherein: a constant current bias voltage detecting pin is disposed above the substrate, and the detecting pin is connected to a clock trigger switch. The rear end of the clock-triggered switch is respectively connected to a high-potential integration circuit and a low-potential integration circuit, and the radio frequency power includes a radio frequency source power and a radio frequency offset power, and the radio frequency source power or the radio frequency bias power is at least one output pulse power. When the output of the RF bias power is a pulse signal, the pulse signal is used as a clock signal of the clock trigger switch, and when the output pulse signal of the RF power is a rising edge, the clock trigger switch and the back end are high. The potential integration circuit is connected, and when the output signal is a falling edge, the clock trigger switch and the low potential integration circuit at the back end . A plasma processing apparatus includes a vacuum reaction chamber, an electrostatic chuck supporting a substrate is disposed under the vacuum reaction chamber, a pedestal is disposed under the electrostatic chuck, and the pedestal serves as the vacuum reaction chamber simultaneously a lower electrode, the lower electrode is connected to a radio frequency power source, and the radio frequency power source outputs a pulse power, wherein: a constant current bias voltage detecting pin is disposed above the substrate, and the detecting pin is connected to a clock trigger switch. The rear end of the clock-triggered switch is respectively connected to a high-potential integration circuit and a low-potential integration circuit, and the radio frequency power includes a radio frequency source power and a radio frequency offset power, and the radio frequency source power or the radio frequency bias power is at least one output pulse power. When the output of the RF source power and the RF bias power are both pulse signals, the pulse signal serves as a clock signal of the clock trigger switch, and an output pulse signal of the RF power When the rising edge is the rising edge, the clock triggering switch is connected to the high potential integrating circuit of the back end, and when the output signal is the falling edge, the clock triggering switch is connected to the low potential integrating circuit of the back end. A method for measuring a DC bias voltage of a substrate, comprising: placing a probe for detecting a DC bias voltage on a surface of the substrate, and connecting a rear end of the probe to a clock trigger switch, a rear end of the clock trigger switch is respectively connected to a high potential integration circuit and a low potential integration circuit; adjusting an output pulse signal frequency of a radio frequency power; using the pulse output signal frequency as an adjustment frequency of the clock trigger switch, when the radio frequency When the output pulse signal of the power is a rising edge or a falling edge, the clock triggering switch is respectively connected to the high potential integrating circuit or the low potential integrating circuit, and the high potential integrating circuit or the low potential integrating circuit respectively respectively pairs the detecting pin The high-potential pulse and the low-potential pulse of the detected DC bias voltage are integrated, and the average value of the DC bias voltage at the high potential and the average value at the low potential are obtained, and then the signal is separately collected to realize the substrate. Monitoring of surface DC bias voltage. The method for measuring a DC bias voltage of a substrate according to claim 5, wherein the sampling time interval of the average value of the DC bias voltage at a high potential and the average value at a low potential is greater than or equal to 0.1s.