Dry etching method and apparatus

Claim 2

A dry etching method comprising the steps of: placing a workpiece (11, 21) on an electrode (12, 22), said electrode being disposed in a processing chamber (14, 24); introducing an etching gas into said processing chamber; exciting said etching gas to generate a plasma; and applying a periodical voltage waveform V(t) to said electrode, said periodical voltage waveform V(t) having a first portion for allowing electrons to impinge the workpiece and a second portion for accelerating positive ions toward the workpiece, said second portion of the waveform including a first component for generating an accelerating field and a second component for cancelling the effect of charge-up at the workpiece surface.

Claim 3

A dry etching method comprising the steps of: placing a workpiece (11, 21) on an electrode (12, 22), said electrode being disposed in a processing chamber (14, 24); introducing an etching gas into said processing chamber; exciting said etching gas to generate a plasma; and applying a periodical voltage waveform V(t) to said electrode, said periodical voltage waveform V(t) having a first portion of a first polarity and a second portion of a second polarity, the first portion having a substantially constant first voltage-time product S 1 = |√V(t)dt| the second portion having a second voltage-time product S 2 = |√V(t)dt| which is greater than said first product S l , the time derivative of the voltage at said second portion being substantially constant, whereby particles of said first polarity in said plasma impinge on a surface of said workpiece in a period corresponding to said second portion of said voltage waveform, the magnitude of the voltage applied to said electrode in said period is increased with an increase in electric charge at said surface, to subject said particles to a substantially constant accelerating voltage, and said electric charge at said surface is neutralized by particles of said second polarity in a period corresponding to said first portion of said voltage waveform.

Claim 4

A dry etching method comprising the steps of: placing a workpiece (11, 21) on an electrode (12, 22), said electrode being disposed in a processing chamber (14, 24); introducing an etching gas into said processing chamber; exciting said etching gas to generate a plasma; and applying a periodical voltage waveform V(t) to said electrode, said periodical voltage waveform V(t) having a first portion of a first polarity and a second portion of a second polarity, the first portion having a substantially constant first voltage-time product S 1 = |√V(t)dt| the second portion having a second voltage-time product S 2 = |√V(t)dt| which is greater than said first product S l , the time derivative of the voltage at said second portion being substantially constant, whereby particles of said first polarity in said plasma impinge on a surface of said workpiece in a period corresponding to said second portion of said voltage waveform, the magnitude of the voltage applied to said electrode in said period is increased with an increase in electric charge at said surface, to subject said particles to a substantially constant accelerating voltage, and said electric charge at said surface is neutralized by particles of said second polarity in a period corresponding to said first portion of said voltage waveform.

Claim 5

A dry etching method according to Claim 2, wherein the magnitude of the voltage at said second portion of said periodical voltage waveform is not less than a first predetermined value (V AC ) '

Claim 6

A dry etching method according to Claim 3, wherein the magnitude of the voltage at said second portion of said periodical voltage waveform is not greater than a second predetermined value (V BO).

Claim 7

A dry ethcing method according to Claim 2,

Claim 8

further comprising a step of setting first and second values for indicating lower and upper limits of the magnitude of the voltage at said second portion of said periodical voltage waveform, respectively.

Claim 9

further comprising a step of setting first and second values for indicating lower and upper limits of the magnitude of the voltage at said second portion of said periodical voltage waveform, respectively.

Claim 10

A dry etching method according to Claim 5, further comprising a step of measuring the potential at a place equivalent to said surface of said workpiece placed on said electrode, and a step of determining the voltage at said second portion of said voltage waveform on the basis of the measured potential.

Claim 11

A dry etching method according to Claim 6, further comprising a step of detecting a time when the magnitude of said measured potential is reduced to zero, after said first portion of said voltage waveform has been applied, and a step of detecting a time when the magnitude of said measured potential reaches a value corresponding to said second value, after said second portion of said voltage waveform has been applied.

Claim 12

A dry etching method according to Claim 2, further comprising a step of determining and inputting said periodical voltage waveform by an input device (32).

Claim 13

A dry etching apparatus comprising: an evacuatable processing chamber (14, 24); an electrode (12, 22) disposed in said processing chamber and applied with a voltage, a workpiece (11, 21) being placed on said electrode; gas feed means for introducing an etching gas into said processing chamber; plasma generating means (15, 16; 25, 26) for exciting said etching gas to generate a plasma in said processing chamber; and means (17, 27) for generating a periodic voltage waveform V(t) and applying the waveform V(t) to said electrode, the waveform V(t) having a first portion for allowing electrons to impinge the workpiece surface and a second portion for accelerating positive particles toward the workpiece, said second portion of the waveform including a first component for generating an accelerating field and a second component superposed on the first component for cancelling the effect of charge-up at the workpiece surface.

Claim 14

A dry etching apparatus comprising: an evacuatable processing chamber (14, 24); an electrode (12, 22) disposed in said processing chamber and applied with a voltage, a workpiece (11, 21) being placed on said electrode; gas feed means for introducing an etching gas into said processing chamber; plasma generating means (15, 16; 25, 26) for exciting said etching gas to generate a plasma in said processing chamber; and means (17, 27) for generating a periodic voltage waveform V(t) and applying the waveform V(t) to said electrode, the waveform V(t) having a first portion for allowing electrons to impinge the workpiece surface and a second portion for accelerating positive particles toward the workpiece, said second portion of the waveform including a first component for generating an accelerating field and a second component superposed on the first component for cancelling the effect of charge-up at the workpiece surface.

Claim 15

A dry etching apparatus comprising: an evacuatable processing chamber (14, 24); an electrode (12, 22) disposed in said processing chamber for applying a voltage and for accommodating a workpiece (11, 21) thereon; gas feed means for introducing an etching gas into said processing chamber; plasma generating means (15, 16; 25, 26) for exciting said etching gas to generate a plasma; and means (17, 27) for generating a periodical voltage waveform V(t) applied to said electrode, said periodical voltage waveform having a first portion of a first polarity and a second portion of a second polarity, a first substantially constant voltage-time product S 1 = |√V(t)dt| being obtained at said first portion, a second voltage-time product S 2 = |√V(t)dt| obtained at said second portion being greater than said first product, the derivative of the voltage at said second portion with respect to time being substantially constant, whereby a particle of said first polarity in said plasma impinges on a surface of said workpiece in a period corresponding to said second portion of said voltage waveform, the magnitude of the voltage applied to said electrode in said period is increased with an increase in electric charge at said surface, to subject said particle to a substantially constant accelerating voltage, and said electric charge at said surface is neutralized by particles of said second polarity in a period corresponding to said first portion of said voltage waveform.

Claim 16

A dry etching apparatus comprising: an evacuatable processing chamber (14, 24); an electrode (12, 22) disposed in said processing chamber for applying a voltage and for accommodating a workpiece (11, 21) thereon; gas feed means for introducing an etching gas into said processing chamber; plasma generating means (15, 16; 25, 26) for exciting said etching gas to generate a plasma; and means (17, 27) for generating a periodical voltage waveform V(t) applied to said electrode, said periodical voltage waveform having a first portion of a first polarity and a second portion of a second polarity, a first substantially constant voltage-time product S 1 = |√V(t)dt| being obtained at said first portion, a second voltage-time product S 2 = |√V(t)dt| obtained at said second portion being greater than said first product, the derivative of the voltage at said second portion with respect to time being substantially constant, whereby a particle of said first polarity in said plasma impinges on a surface of said workpiece in a period corresponding to said second portion of said voltage waveform, the magnitude of the voltage applied to said electrode in said period is increased with an increase in electric charge at said surface, to subject said particle to a substantially constant accelerating voltage, and said electric charge at said surface is neutralized by particles of said second polarity in a period corresponding to said first portion of said voltage waveform.

Claim 17

A dry etching apparatus according to Claim 10, wherein the magnitude of the voltage at said second portion of said periodical voltage waveform is not less than a first predetermined value.

Claim 18

A dry etching apparatus according to Claim 10, wherein said voltage waveform generating means (17, 27) includes an input device (32) for inputting various waveform parameters.

Claim 19

A dry etching apparatus according to Claim 12, wherein said voltage waveform generating means (17, 27) further includes memory means, an arithmetic and logic unit, and output means (36) for forming an output signal indicative of said voltage waveform.

Claim 20

A dry etching apparatus according to Claim 10, further comprising means (20A, 30A) for measuring a potential at a place in said processing chamber which is equivalent to said surface of said workpiece.

Claim 21

A dry etching apparatus according to Claim 14, wherein the result of the measurement made by said potential measuring means is supplied to said voltage waveform 1 generating means, to control said periodical voltage waveform.