Plasma etching method and plasma etching system for carrying out the same

• US 6,159,388 A
• Filed: 01/26/1998
• Issued: 12/12/2000
• Est. Priority Date: 02/18/1997
• Status: Expired due to Fees

• Current Assignee: Speedfam Co., Ltd
• Original Assignee: Speedfam Co., Ltd
• Inventors: Horiike, Yasuhiro, Yanagisawa, Michihiko, Iida, Shinya
• Primary Examiner(s): Mayekar, Kishor
• Application Number:
  US09/013,705
• Time in Patent Office: 1,051 Days
• Field of Search: 216/60, 156/345
• US Class Current: 216/60
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

Plasma etching method and apparatus for removing relatively thick portions from wafers by etching while measuring an actual etch quantity to thereby manufacture the wafers excellent in flatness quality on a mass-production basis. A conduit 20 of a plasma generator 2 is positioned above a relatively thick portion 111 of the wafer 110 to etch away a wafer material from the relatively thick portion 111 by ejecting a fluorine gas G. A laser beam L0 is emitted from a laser displacement meter 30 of a measuring apparatus 3 to detect an interference state between a reflected light beam L1 from the relatively thick portion 111 and a reflected light beam L2 form a reflecting plate 32 and count periodical changes of the interference state. When the count value m coincides with an integral value derived by dividing a desired etch quantity by a half wavelength of the laser beam L0, etching of the relatively thick portion 111 by the fluorine gas G is terminated.

Claims

1. A plasma etching method of removing a relatively thick portion from a surface of an article of concern to realize flatness thereof through an etching process by ejecting a gas of activated species onto to said relatively thick portion from a jet nozzle of a plasma generating means disposed substantially in opposition to said relatively thick portion,

said method comprising:

measuring an actual etched quantity of said relatively thick portion by using a laser light beam; and

terminating the etching process for said relatively thick portion when said actual etch quantity has attained a desired value.

2. A plasma etching method according to claim 1, wherein said measuring step includes the step of:

setting previously an integral value obtained by dividing an etch quantity desired for substantially flattening said surface of said article by removing said relatively thick portion by a half wavelength of said laser light;

irradiating a reflecting surface and a surface of said relatively thick portion, respectively, with said laser light beam; and

measuring a number of times an interference state between a reflected light beam from said reflecting surface and a reflected light beam from said surface of said relatively thick portion changes periodically in dependence on the etch quantity of said relatively thick portion; and

wherein said terminating step includes the step of;

terminating the etching process for said relatively thick portion when said number of times said interference state has changed coincides with said integral value.

3. A plasma etching method according to claim 1, wherein said first step includes the steps of:

setting previously an etched quantity desired for substantially flattening said surface of said article by removing said relatively thick portion through the etching process;

irradiating a reflecting surface and a surface of said relatively thick portion, respectively, with the laser light beam and converting an interference light beam produced by interference between a reflected light beam from said reflecting surface and a reflected light beam from the surface of said relatively thick portion into a corresponding electric signal;

setting a reference function representing a relation between said electric signal and said etch quantity and generating a shift function representing a predicted relation between said electric signal and the etch quantity by shifting said reference function on the basis of an initial value of said electric signal upon etching of said relatively thick portion and assigning values of said electric signal sequentially to said shift function; and

wherein said second step includes the step of;

terminating the etching process for said relatively thick portion when said actual etch quantity and said desired etch quantity substantially coincide with each other.

4. A plasma etching system, comprising:

plasma generating means including a jet nozzle for ejecting a gas of activated species produced through excitation to a plasma state onto a relatively thick portion of an article of concern;

measuring means for measuring an actual etch quantity of said relatively thick portion by using a laser light beam; and

control means for comparing said actual etch quantity as measured by said measuring means with a set value and terminating the etching process for said relatively thick portion when said actual etch quantity coincides with said set value.

5. A plasma etching system according to claim 4,

wherein said measuring means includes a laser light beam, having a wavelength, projected onto a reflecting surface and a surface of said relatively thick portion, respectively, said measuring means being configured to receive a reflected light beam from said reflecting surface and a reflected light beam reflected from the surface of said relatively thick portion and being further configured to detect a number of times an interference state between both the reflected light beams changes periodically in correspondence to said actual etch quantity of said relatively thick portion;

and

wherein said control means is configured to terminate said etching process when an integral value obtained by dividing an etch quantity desired for substantially flattening the surface of said article by removing said relatively thick portion by half a wavelength of said laser light beam coincides with said number of times the interference state has periodically changed.

6. A plasma etching system according to claim 5, wherein said measuring means comprises:

a first laser displacement meter for sending and receiving said laser light beams, wherein said first laser displacement is configured to measure the number of times said interference state between said received laser light beams changes periodically;

a half mirror interposed between said first laser-displacement meter and said jet nozzle of said plasma generating means for directing said laser light beam onto said relatively thick portion by way of said jet nozzle, said half mirror being configured to direct the reflected light beam from said relatively thick portion to said first laser displacement meter by way of said jet nozzle; and

a reflecting plate disposed in opposition to said first laser displacement meter with said half mirror being interposed between said reflecting plate and said first laser displacement meter.

7. A plasma etching system according to claim 6, further comprising:

displacing means for moving one of said article of concern and said jet nozzle relative to the other;

wherein said control means includes;

a recording medium for storing data concerning said integral values corresponding to individual relatively thick portions and positions thereof; and

a controller for reading the position data and positioning said jet nozzle in opposition to the relatively thick portion located at the position corresponding to said position data and put into operation said measuring means, whereupon said controller compares said integral value with said number of times outputted from said measuring means and stops said measuring means when said comparison results in coincidence.

8. A plasma etching system according to claim 5, further comprising:

displacing means for moving one of said article of concern and said jet nozzle relative to the other;

wherein said control means includes;

a recording medium for storing data concerning said integral values corresponding to individual relatively thick portions and positions thereof; and

a controller for reading the position data and positioning said jet nozzle in opposition to the relatively thick portion located at the position corresponding to said position data and put into operation said measuring means, whereupon said controller compares said integral value with said number of times the interference state has changed as outputted from said measuring means and stops operation of said measuring means when said comparison results in coincidence.

9. A plasma etching system according to claim 4, wherein said measuring means includes a laser light beam, having a wavelength, projected onto a reflecting surface and the surface of said relatively thick portion, said measuring means being configured to convert an interference light resulting from interference between a reflected light beam from said reflecting surface and a reflected light beam from the surface of said relatively thick portion into a corresponding electric signal, and generate a shift function representing an expected relation between said electric signal and said etch quantity by shifting by a quantity a reference function representing a present relation between said electric signal and the etch quantity on the basis of an initial value of said electric signal in the etching process, wherein said actual etch quantity is determined by assigning values of said electric signal obtained sequentially to said shift function;

and

wherein said control means terminates the etching process for said relatively thick portion when said actual etch quantity substantially coincides with said value.

10. A plasma etching system according to claim 9, wherein said measuring means includes:

photoelectric transducer means for converting the interference light beam between said reflected laser light beams as received into said electric signal;

reference function storage means for storing said reference function representing the relation between said electric signal and said etch quantity,

a shift function generating unit for generating the relation expected between said electric signal and said etch quantity by shifting said reference function by a phase on the basis of said electric signal outputted from said photoelectric transducer means, and

a second laser displacement meter for determining the actual etch quantity by assigning values of said electric signal outputted from said photoelectric transducer means to said shift function;

a half mirror interposed between said second laser displacement meter and said jet nozzle of said plasma generating means for directing said laser light beam onto said relatively thick portion by way of said jet nozzle, said half mirror being so arranged as to direct the reflected light beam from said relatively thick portion to said second laser displacement meter by way of said jet nozzle; and

a reflecting plate disposed in opposition to said second laser displacement meter with said half mirror being interposed between said reflecting plate and said second laser displacement meter.

11. A system for planarizing a surface of an article comprising:

a plasma generator including a conduit, said conduit configured to direct a gas toward a portion of the article;

a measuring apparatus including a laser displacement meter having a laser beam, said apparatus configured to direct said laser beam toward the portion through said conduit and receive said laser beam from the portion through said conduit.

12. The system according to claim 11, further comprising a mechanism to move the article relative to said conduit.

13. A method of planarizing a surface of an article, said method comprising the steps of:

measuring the thickness of a film at a plurality of locations on the surface of the article;

determining relatively thick portions of said film;

storing said thickness information for said relatively thick portions and corresponding position information on a recording medium;

placing a first thick portion proximate a plasma etch source, wherein said etch source includes a jet nozzle; and

etching said first thick portion while simultaneously measuring a thickness of said film by directing a light beam through said jet nozzle.

14. The method according to claim 13, further comprising the steps of:

recalling said thickness and position information;

moving said plasma etch source proximate a second thick position; and

etching said film at said second thick position.

15. The method according to claim 13, further comprising the step of determining an amount of material to remove by irradiating a reflecting surface and a surface of said thick portion, respectively, with the light beam and converting an interference light beam produced by interference between a reflected light beam from said reflecting surface and a reflected light beam from the surface of said thick portion into a corresponding electric signal.