JP3038828B2 - Plasma processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method for etching or depositing an object to be processed, such as a semiconductor substrate, with plasma.

<Conventional technology> If a device using low-temperature plasma is roughly classified, in a vacuum, a counter electrode method, for example, 10 KHz to 30 K is applied to one of parallel plate electrodes.
There is a technique using a technique of generating a plasma by applying a high frequency voltage of about Hz, and a technique using a technique of generating a plasma by introducing a microwave of 2.45 GHz into a vacuum chamber. Conventionally, the technique using parallel plate electrodes has been mainly used among them.

On the other hand, with the miniaturization of semiconductor devices, there has been a problem that the device characteristics are affected by the impact of ions generated during plasma processing. Further, there is a demand for increasing the processing speed in order to improve the processing capacity.

When increasing the processing speed, simply increasing the density of the plasma or the concentration of radicals (active particles immediately before ionization) is not sufficient. In dry etching by plasma processing and plasma CVD, ion energy plays an important role. In the case of dry etching, if the energy of the ions is too large, the underlying film is shaved or affects the crystal structure, and the device characteristics are degraded. On the other hand, if it is too small, the polymer formed on the etched surface is not sufficiently removed, and the etching rate is reduced. On the other hand, the polymer protective film is not formed, and the side surface of the pattern is etched, resulting in a problem that the dimensional accuracy of the pattern deteriorates.

In plasma CVD, too, the ion energy affects the film formation such that the film composition becomes coarse when the energy of the ions is weak, and becomes dense when the energy is strong.

Therefore, proper control of ion energy is essential for future plasma processing.

FIG. 2 is a schematic view of a conventional plasma processing apparatus for etching by high-frequency discharge. In a processing chamber 1, an anode electrode 2 and a cathode electrode 3 of a parallel electrode type, for example, a parallel plate are arranged to face each other. The cathode electrode 3 has C, L
A variable output high-frequency power supply 5 which is a power supply for generating plasma of 13.56 MHz is connected via a matching box 4 of the circuit network, and a processing substrate 6 is placed thereon. When an etching gas is introduced while exhausting the processing chamber 1 and a high-frequency voltage is applied to the cathode electrode 3 by the high-frequency power supply 5, plasma 7 is generated between the processing chamber 1 and the anode electrode 2. The ions in the plasma are accelerated by the electric field between the plasma 7 and the cathode electrode 3 and are incident on the processing substrate 6 with a direction, so that a fine pattern can be etched.

The incident energy of the ions is such that when a high frequency is applied, a sine wave voltage in which a DC voltage component VDC is superimposed is generated on the cathode electrode 3 as shown in FIG. 3, and largely depends on the DC voltage component VDC at this time. It has been known. Therefore, the ion energy is controlled by the DC voltage VDC
By measuring the output voltage of the matching box 4 in which is detected and controlling the high-frequency power supply 5 by the control device 8 which inputs the measurement result, it is possible to generate desired ion energy.

<Problems to be Solved by the Invention> However, when controlling the true ion energy, the plasma potential, which is the DC potential difference between the plasma 7 and the cathode electrode 3, must be measured. As described above, the DC voltage component VDC generated at the cathode electrode 3 is measured, which means that the DC potential difference between the processing chamber 1 and the cathode electrode 3, which is normally set to the ground potential, is measured. Therefore, there is an important problem that the ion energy in the plasma with respect to the object to be processed, which greatly affects the etching characteristics and the like, is not accurately controlled.

<Means for Solving the Problems> In order to solve the above problems, in the present invention,
In a plasma processing method of generating plasma by electron cyclotron resonance using high frequency power or microwave power in a processing chamber and performing etching or deposition processing on an object to be processed, the plasma and a cathode electrode on which the object to be processed is mounted are formed. A bias voltage applying power supply for applying a bias voltage to the electrodes and a plasma for generating plasma so that a plasma potential, which is a DC potential difference, is directly measured and a predetermined ion energy is generated based on the measured result. It is characterized by controlling at least one of a power supply for generation and a power supply for generating a magnetic field for causing electron cyclotron resonance. Further, an emissive probe is preferably used for measuring the plasma potential, and a Langmuir probe is used for measuring the plasma potential when the power supply for generating a magnetic field is not operated.

<Operation> A plasma potential measurement method is used to measure a DC potential difference between a plasma and a cathode electrode on which an object to be processed is placed. As a specific example of this measurement means, an emissive probe is inserted into the plasma. By doing so, the potential of the plasma can be directly measured, and by controlling each power supply based on the measured plasma potential, a predetermined ion energy can be generated, which greatly affects the etching characteristics and the like. The ion energy for the object to be processed can be accurately and appropriately controlled.

Embodiment FIG. 1 is a schematic view of an embodiment in which the method of the present invention is applied to an ECR (Electron Cyclotron Resonance) type plasma processing apparatus for etching. In the figure, 21 is a processing chamber, 23
Is a cathode electrode, 24 is a power supply for applying a bias voltage, 25 is a microwave power supply for generating plasma, 26 is a processing substrate, 27 is plasma, 28 is a control device, 29 is a waveguide, 30 is a coil, and 31 is a magnetic field. DC power supply. 32 is an emissive probe that can directly measure the plasma potential,
32a and a current source 32b.
With a inserted into the plasma 28, the emissive probe is placed insulated from all electrodes.

A microwave power supply 25 with variable output is attached to one end of the waveguide 29, and the other end covers the processing chamber 21. There is a coil 30 around it, and a processing substrate 26
A cathode electrode 23 for mounting the
23 is connected to a bias voltage applying power supply 24 for generating a variable output DC or high-frequency voltage.

In the processing chamber 21, the filament 32a of the emissive probe 32 is attached so as not to enter the ion sheath generated between the plasma and the cathode electrode 23.

The plasma 27 is generated by electron cyclotron resonance caused by the microwave generated by the microwave power supply 25 and the magnetic field of the coil 30. In the control of the ion energy of the plasma, when the heating current of the probe 32 inserted into the plasma is increased, the amount of emitted thermoelectrons from the filament 32a increases, and the apparent ion saturation current increases. As a result, the floating potential at which the probe current becomes zero becomes equal to the potential of the plasma. Therefore, by measuring the potential difference between one end of the current source 32b and the cathode electrode 23, the plasma potential, which is the DC potential difference between the plasma 27 and the cathode electrode 23, can be directly measured. By controlling at least one of the bias voltage application power supply 24, the plasma generation microwave power supply 25, and the magnetic field generation DC power supply 31 singly or simultaneously by the control device 28 which receives the measurement result as an input, Can be generated accurately and appropriately at a predetermined value.

In addition, as another application example of the method of the present invention, there is a plasma processing apparatus in which a bias voltage applying power supply is provided on a cathode of a parallel plate electrode type, and a plasma processing apparatus without a bias voltage applying power supply in an ECR method. is there.

An emissive probe that is not affected by a magnetic field is suitable as a probe, and a Langmuir probe is suitable when a power supply for generating a magnetic field is not operated.

<Effects of the Invention> As described above, according to the present invention, by directly measuring the plasma potential, which is the DC potential difference between the plasma and the cathode electrode on which the object is placed, the ion energy with respect to the object can be reduced in advance. Since it can be accurately and appropriately controlled to the determined value, it is possible to provide a plasma processing method having good etching characteristics or deposition characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of an apparatus for performing the method of the present invention. FIG. 2 is a schematic diagram of a conventional high-frequency discharge plasma processing apparatus. FIG. 3 is a diagram showing a voltage waveform generated at a cathode electrode on which an object to be processed is placed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 21/31 H01L 21/302 D (56) References JP-A-62-40386 (JP, A) JP-A-58-171822 ( JP, A) JP-A-61-241921 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 16/00-16/56 C23C 1/00-4/04 H01L 21 / 205 H01L 21/302 H01L 21/31 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A plasma processing method in which plasma is generated in a processing chamber by electron cyclotron resonance using high-frequency power or microwave power, and etching or deposition processing is performed on an object to be processed. A bias voltage for applying a bias voltage to the electrode so as to directly measure a plasma potential which is a DC potential difference from a cathode electrode to be mounted, and to generate a predetermined ion energy based on the measurement result. A plasma processing method for controlling at least one of a power supply, a plasma generation power supply for generating the plasma, and a magnetic field generation power supply for causing the electron cyclotron resonance. 2. The plasma processing method according to claim 1, wherein an emissive probe is used for measuring the plasma potential. 3. The plasma processing method according to claim 1, wherein a Langmuir probe is used for measuring the plasma potential when the power supply for generating a magnetic field is not operated.