US-12620556-B2 - Plasma processing apparatus

US12620556B2US 12620556 B2US12620556 B2US 12620556B2US-12620556-B2

Abstract

A plasma processing apparatus includes: a processing chamber in which a sample is subjected to plasma processing, including, at an upper side therein, a dielectric plate, through which microwaves are transmitted; a radio frequency power supply which supplies radio frequency power for the microwaves; a cavity resonator which resonates microwaves transmitted from the radio frequency power supply through a waveguide and is placed above the dielectric plate; and a magnetic field forming mechanism which forms a magnetic field in the processing chamber. The plasma processing apparatus further includes: a ring-shaped conductor placed inside the cavity resonator; and a circular conductor which is placed inside the cavity resonator and placed in an opening at the center of the ring-shaped conductor.

Inventors

Tetsuo KAWANABE
Makoto Satake
Motohiro Tanaka

Assignees

HITACHI HIGH-TECH CORPORATION

Dates

Publication Date: 20260505
Application Date: 20210219

Claims (8)

1 . A plasma processing apparatus comprising: a processing chamber in which a sample is subjected to plasma processing, including, at an upper side therein, a dielectric plate through which a microwave is transmitted; a radio frequency power supply which supplies radio frequency power for the microwave; a cavity resonator which resonates the microwave transmitted from the radio frequency power supply through a waveguide and is placed above the dielectric plate; a magnetic field forming mechanism which forms a magnetic field in the processing chamber; a ring-shaped conductor disposed inside the cavity resonator; and a circular conductor which is disposed inside the cavity resonator in an opening formed at a center of the ring-shaped conductor, wherein the ring-shaped conductor and the circular conductor are constructed to form a slot disposed therebetween, wherein the circular conductor is configured to be independently moveable with respect to the ring-shaped conductor, and wherein the circular conductor has a convex tapered shape that fits to a concave tapered shape formed in the dielectric plate.
2 . The plasma processing apparatus according to claim 1 , wherein the slot has a width which suppresses diffraction of the microwave from occurring in a direction causing generation of plasma in a central portion of the processing chamber.
3 . The plasma processing apparatus according to claim 1 , wherein an upper surface and a side surface of the circular conductor are connected by a curved surface.
4 . The plasma processing apparatus according to claim 3 , wherein the circular conductor is a conductor which has a metal plate having a plurality of through openings, or a mesh structure.
5 . The plasma processing apparatus according to claim 1 , wherein a radius of the circular conductor is larger than a radius of a circular waveguide connected to a top of the cavity resonator.
6 . The plasma processing apparatus according to claim 2 , wherein a radius of the circular conductor is larger than a radius of a circular waveguide connected to a top of the cavity resonator.
7 . The plasma processing apparatus according to claim 2 , further including: a gas supply plate which has, at a central part thereof, a plurality of gas supply holes for supplying a gas to the processing chamber, and which is placed under the dielectric plate, wherein in the case where a height of the cavity resonator is denoted by HA, a thickness of the dielectric plate and the gas supply plate is denoted by HB, a relative permittivity of the dielectric plate and the gas supply plate is denoted by er, and a radius of the processing chamber is denoted by RB, a radius RC of the ring-shaped conductor satisfies a relational expression given below: RC≤RB−HB /(ε r (1+( HA/RB ) 2 )−1) (1/2) .
8 . The plasma processing apparatus according to claim 2 , further including: a gas supply plate which has, at a central part thereof, a plurality of gas supply holes for supplying a gas to the processing chamber, and which is placed under the dielectric plate, wherein in the case where the circular conductor and the gas supply plate are viewed in an axial direction of the circular conductor, a radius of the circular conductor is larger than a radius of a circle in contact with a gas supply hole positioned on an outermost circumference among the gas supply holes.

Description

TECHNICAL FIELD The present invention relates to a plasma processing apparatus. BACKGROUND ART In the manufacture of semiconductor devices, plasma processing such as plasma etching, plasma CVD (Chemical Vapor Deposition), and plasma aching is widely used. In an etching apparatus, which is one of plasma processing apparatuses, there is a demand that anisotropic processing and isotropic processing be performed by a single apparatus from the viewpoint of mass productivity of devices. The anisotropic processing can be achieved by ion-assisted reactions, which are dependent mainly on ions that are vertically incident on a wafer, and isotropic processing can be achieved by chemical reactions, which are dependent mainly on radicals isotropically diffusing and incident on a wafer. In general, at a low pressure, ion density increases and ion-based etching is promoted, and at a high pressure, radical density increases and radical-based etching is promoted. Therefore, it is desirable for such an etching apparatus to be capable of processing in a wide pressure range from a low pressure of approximately 0.1 Pa to a high pressure of several tens of Pa. Further, in order to ensure mass productivity of devices, it is necessary to perform uniform etching in a wafer surface over such a wide pressure range. As a plasma generation method, an ECR (Electron Cyclotron Resonance) method, an inductive coupling method, a capacitive coupling method, and the like are known. The ECR is a resonance phenomenon that occurs when there is a match between an electromagnetic wave frequency introduced from an electromagnetic wave generation source and a cyclotron frequency of electrons by a magnetic field formed by an electromagnetic coil. Plasma is generated when high-energy electrons accelerated by the ECR collide with gas molecules and are ionized. One advantage of the ECR method is that plasma can be efficiently and uniformly generated even in a low pressure range of 1 Pa or less, which is difficult to achieve by a plasma generation method such as the inductive coupling method or the capacitive coupling method. If the pressure in a discharge chamber is relatively low, the mean free path of electrons is long, so that electrons are sufficiently accelerated by ECR before colliding with gas molecules and becoming ionized, thus efficiently generating plasma in the vicinity of an isomagnetic field surface that satisfies ECR conditions. Normally, an isomagnetic field surface that satisfies the ECR conditions spreads out in a plane shape in a discharge chamber, so that an area where plasma is generated spreads out in a planar or ring shape in the discharge chamber. Consequently, relatively uniform plasma processing can be achieved. However, if the pressure in the discharge chamber is high, the mean free path of electrons is short, so that the electrons that receive energy from electromagnetic waves immediately collide with gas molecules and ionize or dissociate. Therefore, the area where plasma is generated will be localized in the vicinity of a central axis of the discharge chamber directly under a microwave introduction window, through which electromagnetic waves enter, and directly under a waveguide rather than in the vicinity of the isomagnetic field surface that satisfies the ECR conditions. This poses a problem in that, under a high-pressure condition, the distribution of an etching rate tends to be uneven, with a higher rate at a center. As a prior art for suppressing the localization of plasma generation at the central part of a discharge chamber, there is one disclosed in, for example, Patent Document 1. The plasma processing apparatus using the ECR method of Patent Document 1 has a microwave introduction window placed between a discharge chamber and an electromagnetic wave transmission unit, and an electromagnetic wave reflector and an auxiliary reflector placed under a microwave introduction window. Electromagnetic waves are emitted into the discharge chamber through a ring-shaped electromagnetic wave emission port, which is formed between the electromagnetic wave reflector and the auxiliary reflector, to cause ring-shaped plasma to occur on an ECR surface so as to form uniform plasma, thus achieving plasma processing with high uniformity. Further, Patent Document 2 relates to a plasma processing apparatus of a type that generates microwave plasma without a magnetic field. The plasma processing apparatus includes a waveguide, through which microwaves propagate, an introduction window of microwaves introduced into a processing container, an annular ring slot placed between the waveguide and the microwave introduction window, and a shielding plate that is placed on the processing container side of the microwave introduction window and shields the electric field of microwaves transmitted through the microwave introduction window. By providing the shielding plate, the plasma density at the central part in the processing container is reduced