Plasma processing method and apparatus

Abstract

A plasma processing method is arranged to supply a predetermined process gas into a plasma generation space in which a target substrate is placed, and turn the process gas into plasma. The substrate is subjected to a predetermined plasma process by this plasma. The spatial distribution of density of the plasma and the spatial distribution of density of radicals in the plasma are controlled independently of each other relative to the substrate by a facing portion opposite the substrate to form a predetermined process state over the entire target surface of the substrate.

1 . A capacitive coupling parallel-plate plasma etching apparatus for subjecting a target substrate to a plasma etching process, the apparatus comprising;
 a process container configured to have a vacuum atmosphere therein;   an upper electrode and a lower electrode disposed inside the process container to face each other such that the lower electrode is configured to support the target substrate and a plasma generation space is present between the upper electrode and the lower electrode;   a focus ring disposed to surround the target substrate to improve uniformity of the plasma etching process on the target substrate;   an RF (radio frequency) power supply mechanism configured to apply an RF power to the upper electrode;   a gas distribution cell disposed inside the upper electrode and configured to distribute a process gas to be supplied into the process container; and   a process gas supply mechanism configured to supply the process gas into the gas distribution cell,   wherein the upper electrode comprises outer and inner upper electrodes electrically insulated from each other and disposed on a peripheral side and a central side, respectively, in a radial direction relative to a center through which a vertical line extending from a center of the target substrate passes, such that outer and inner RF discharge regions are defined by the outer and inner upper electrodes, respectively,   the inner upper electrode comprises an electrode plate facing the plasma generation space essentially all over the target substrate,   the outer upper electrode comprises an electrode member surrounding the electrode plate of the inner upper electrode and facing the plasma generation space at a position radially outside an outer peripheral edge of the target substrate and opposite to the focus ring,   the RF power supply mechanism comprises a common RF power supply connected to the outer and inner upper electrodes and a variable capacitor disposed between the RF power supply and at least one of the outer and inner upper electrodes, and is configured to use adjustment of the variable capacitor to cause the RF power to be discharged toward the plasma generation space from the outer and inner RF discharge regions at a predetermined ratio, so as to control spatial distribution of density of the plasma relative to the target substrate,   the gas distribution cell is disposed only at a position directly above the electrode plate of the inner upper electrode and internally divided by an annular partition member into outer and inner gas supply cells on a peripheral side and a central side, respectively, in the radial direction,   the inner upper electrode has a number of gas delivery holes formed therein and communicating with the outer and inner gas supply cells, such that an outer gas delivery region is defined by part of the gas delivery holes communicating with the outer gas supply cell and an inner gas delivery region is defined by part of the gas delivery holes communicating with the inner gas supply cell, and thus the outer and inner process gas delivery regions are present on a peripheral side and a central side, respectively, in the radial direction on the inner RF discharge region,   the outer upper electrode has no gas delivery holes formed therein, and thus the outer RF discharge region includes no process gas delivery region, and   the process gas supply mechanism comprises a common process gas supply source connected to the outer and inner gas supply cells and a flow rate control valve disposed between the process gas supply source and at least one of the outer and inner gas supply cells, and is configured to use adjustment of the flow rate control valve to cause the process gas to be delivered toward the plasma space from the outer and inner process gas delivery regions at a predetermined ratio, so as to control spatial distribution of density of radicals in the plasma relative to the target substrate independently of the spatial distribution of density of the plasma.   
   
   
       2 . The apparatus according to  claim 1 , wherein the electrode member of the outer upper electrode has a planar area of set to be ¼ to 1 times a planar area of the electrode plate of the inner upper electrode. 
   
   
       3 . The apparatus according to  claim 1 , wherein the outer upper electrode is separated from the inner upper electrode by an annular gap of 0.25 to 2.0 mm, in which a dielectric body is disposed to electrically insulate the outer upper electrode from the inner upper electrode. 
   
   
       4 . The apparatus according to  claim 1 , wherein the inner upper electrode comprises a conductive electrode support that detachably supports the electrode plate and the gas distribution cell is formed in the electrode support. 
   
   
       5 . The apparatus according to  claim 1 , wherein the flow rate control valve comprises two flow rate control valves respectively disposed between the process gas supply source and the outer and inner gas supply cells. 
   
   
       6 . The apparatus according to  claim 1 , wherein the variable capacitor is disposed between the RF power supply and the inner upper electrode. 
   
   
       7 . The apparatus according to  claim 1 , wherein the apparatus further comprises an additional RF power supply mechanism connected to the lower electrode and configured to supply the lower electrode with an RF power having a frequency lower than that of the RF power supplied to the upper electrode. 
   
   
       8 . The apparatus according to  claim 7 , wherein a low-pass filter is connected to the inner upper electrode and is not connected to the outer upper electrode, the low-pass filter being configured to prevent the RF power supplied from the common RF power supply from passing through and allow the RF power supplied from the additional RF power supply mechanism to pass through to ground.