JPS63136626A - Plasma processor - Google Patents

Abstract

PURPOSE:To prevent a material to be processed by charged particles in a plasma from being electrically damaged by separating and sealing the charged particles in the plasma from neutral radical. CONSTITUTION:A wafer 5 is placed on a stage 7 in which the bottom of a processing chamber 6 is grounded. Plasma gas inlet 8 and outlet 9 are formed near the bottom of the chamber 6. A microwave is introduced by a waveguide 2 to the chamber 6. The chamber 6 is filled in advance with plasma gas, and held in a predetermined vacuum pressure state. Thus, the interior gas is excited to a plasma state. In this case, a magnet coil 4 is energized, and excited to generate a magnetic field. The line of magnetic force is introduced perpendicularly to a wafer 5, and finely reduced and sealed simultaneously upon generation of the plasma by this pinch effect. Only the charged particles (ions and electrons) in the plasma are finely reduced and sealed, and neutral radical is not affected by the magnetic field, and not converged. The wafer 5 is not affected by the charged particles, and processed only by the neutral radical.

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to a plasma processing apparatus used, for example, in an etching process in a semiconductor manufacturing process, and in particular to a plasma processing apparatus for preventing electrical damage to a processed object due to charged particles in plasma. Regarding improvements.

[Prior Art] A plasma processing apparatus is used as one of resist dry etching techniques in pattern processing of semiconductor integrated circuits. Such plasma processing equipment excites a plasma state in which positive and negative charges are balanced by applying an electric field to a predetermined reduced pressure atmosphere, dissociating gas molecules in the plasma and generating active neutral radicals. Etching is performed by reacting chemical radicals with the substrate (wafer).

In conventional plasma processing apparatuses, charged particles such as ions and electrons in the plasma act on the object to be processed, causing electrical damage. Particularly in recent years, as the degree of integration of semiconductor integrated circuits has increased, the influence of such electrical damage on devices has become greater.For example, gate oxide films in MOS structures have become thinner; In the resist etching process, dielectric breakdown of the gate oxide film occurs due to the influence of charged particles in the plasma, resulting in deterioration of the characteristics of semiconductor devices and a decrease in yield.

[Object of the Invention] The present invention has been made in view of the drawbacks of the prior art, and provides a plasma processing apparatus that separates charged particles in plasma from neutral radicals to prevent electrical damage to the object to be processed. For the purpose of providing.

[Embodiments] FIGS. 1 to 4 show the configurations of different embodiments of the present invention.

In Fig. 1, 1 is a magnetron which is a microwave generator, 2 is a rectangular waveguide for guiding microwaves to the processing chamber, 4 is a magnet coil for generating a magnetic field to introduce plasma, and 5 is to be processed. 6 is a processing chamber, and 6a is a reaction vessel made of quartz that constitutes the processing chamber. This quartz minimizes contamination of the workpiece and efficiently achieves microwave transmission and magnetic field permeability. 8 is a plasma gas inlet, and 9 is an exhaust port connected to an exhaust pump (not shown). wafer 5
is mounted on the stage 7 at the bottom of the processing chamber 6. A plasma gas inlet 8 and an exhaust port 9 are provided near the bottom of the processing chamber 6.

The operation of the plasma processing apparatus having the above configuration will be explained.

Magnetron 1 generates 2.45 GHz microwaves. This microwave is introduced into the processing chamber 6 through the waveguide 2. The processing chamber 6 is filled with plasma gas from the introduction port 8 in advance, and the processing chamber 6 is maintained at a predetermined vacuum pressure state. By introducing the microwave into the processing chamber 6, the gas inside is excited and becomes a plasma state. At this time, the magnet coil 4 is energized and excited to generate a magnetic field. The magnetic lines of force are introduced perpendicularly to the wafer 5. Due to the pinch effect caused by this magnetic field, plasma is narrowed and sealed at the same time as it is generated.

Here, only the charged particles (ions and electrons) in the plasma are narrowed down and confined by the pinch effect, and the neutral radicals are not affected by the magnetic field and do not converge.The wafer 5 is the external ground for the confined charged particles. The process is performed using only neutral radicals without being affected by charged particles.

FIG. 2 is a block diagram of another embodiment of the present invention.

In this embodiment, a rectangular waveguide 3 with a movable short circuit is used as a microwave waveguide. Furthermore, in the embodiment shown in FIG. 1, since the waveguide 2 is disposed close to just above the wafer 5, the plasma generated directly above the wafer 5 is not affected by the confinement effect by the magnet coil 4, so that some The charged particles were having an electrical effect on the wafer 5. The embodiment shown in FIG. 2 is an improvement on this point. That is, the waveguide 3 is disposed at the top of the reaction vessel 6a, and the magnet coil 4 is provided between the microwave introduction section at the top and the wafer 5 at the bottom to prevent microwave leakage.

In this structure, the generation of plasma directly above the wafer 5 is suppressed to a minimum, and the charged particles in the plasma found at the top of the reaction chamber 6 are completely sealed off by the action of the magnetic field of the magnet coil 4. Therefore, electrical damage to the wafer 5 is reliably prevented.

FIG. 3 shows yet another embodiment of the invention. In this embodiment, in order to improve plasma processing efficiency, a plasma gas inlet 8 is provided at the top of the reaction vessel 6a to smooth the flow of gas within the processing chamber 6. Other structures and functions are the same as those of the embodiment shown in FIG.

FIG. 4 shows yet another embodiment of the invention. This embodiment improves the controllability of the magnet coil 4. An electrically floating measuring element (floating probe) 10 for measuring ion density and electron density is provided near the wafer 5 in the processing chamber 6 .

This probe 10 is connected to a calculation unit 11 for calculating measurement results. The arithmetic unit 11 is further connected to a drive circuit (power supply) 12 for the magnet coil 4 to form a closed circuit. The current value obtained by the probe 10 is calculated by the calculation unit 11 to calculate the plasma state such as ion density and electron density. Based on this calculation result, the magnetic coil 4 is driven and controlled to control the strength of the magnetic field so as to minimize the ion density and electron density. Further, a double probe method is used to measure the ion density and electron density using the probe IO. This method allows stable measurements even when the plasma changes over time, and is not affected by changes in the plasma caused by gas generated from the workpiece being processed. It becomes possible to always maintain the ion density and electron density below a predetermined level regardless of the plasma state.

[Effects of the Invention] As explained above, in the plasma processing apparatus according to the present invention, by providing a magnetic field generating means such as a magnet coil, a magnetic field is introduced into plasma generated by microwaves, and charged particles in the plasma are removed. It becomes possible to separate and confine neutral radicals, preventing electrical damage to the processed object due to charged particles, stably improving product characteristics, and improving yield.

[Brief explanation of the drawing]

1 to 4 are configuration diagrams of different embodiments of the plasma processing apparatus according to the present invention. 1: magnetron, 2.3: waveguide, 4: magnet coil, 5: wafer, 6: processing chamber, 6a: reaction vessel, 7: stage, 8: inlet, 9: outlet, 10: probe, 11: Arithmetic unit. Patent applicant Canon Co., Ltd. Patent applicant Canon Sales Co., Ltd. Agent Patent attorney Tatsuo Ito Agent Patent attorney Tetsuya Ito Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] 1. A processing chamber having a plasma gas inlet and an outlet and accommodating an object to be processed therein, a microwave generating means, and generating plasma by introducing the microwave into the processing chamber. and a magnetic field generating means for separating and containing charged particles in the plasma generated in the processing chamber from neutral radicals and preventing them from scattering toward the object to be processed. plasma processing equipment. 2. The object to be processed is mounted on a grounded stage at the bottom of the processing chamber, and the plasma gas inlet and outlet are provided near the bottom of the processing chamber. The plasma processing apparatus according to item 1. 3. The object to be processed is mounted on a grounded stage at the bottom of the processing chamber, the plasma gas inlet is provided at the top of the processing chamber, and the outlet is provided near the bottom of the processing chamber. A plasma processing apparatus according to claim 1, characterized in that: 4. The plasma processing apparatus according to any one of claims 1 to 3, wherein the microwave generating means is a magnetron that generates microwaves of 2.45 GHz. 5. The plasma processing apparatus according to any one of claims 1 to 4, wherein the magnetic field generating means is a magnet coil disposed around the processing chamber. 6. Claims characterized in that a detection means for detecting the plasma state in the processing chamber is provided, and a control means is provided for controlling the magnetic field generation means according to the detection result of the detection means. Any one of paragraphs 1 to 5
The plasma processing apparatus described in Section 1. 7. The plasma processing apparatus according to claim 6, wherein the detection means comprises a measuring device that measures electron density, ion density, or both within the processing chamber. 8. The plasma processing apparatus according to claim 7, wherein the measuring device includes an electrically floating measurement probe disposed at the bottom of the processing chamber. 9. The plasma processing apparatus according to claim 7 or 8, wherein the control means comprises an arithmetic processing circuit that performs arithmetic processing on the electrical signal from the detection means. 10. Any one of claims 1 to 9, wherein the object to be processed is a semiconductor wafer.
The plasma processing apparatus described in Section 1.