Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates
View Patent ↗The present invention provides apparatus for controlling the operation of plasma etching a semiconductor substrate by an alternating etching method, the apparatus comprising: a process chamber ( 1 ) in which said substrate ( 2 ) is processed, means for generating a plasma ( 6 ); at least one first window ( 7 ) formed in a first wall ( 8 ) of said chamber ( 1 ) facing the surface ( 2 a ) to be etched of said substrate ( 2 ); at least one second window ( 10 ) formed in a second wall ( 11 ) of said chamber ( 1 ) lying in a plane different from said first wall ( 8 ); first means ( 18 ) coupled to said second window ( 10 ) to detect a light signal ( 17 ) relating to a selected wavelength emitted by said plasma ( 6 ); means ( 13, 15 ) for emitting a monochromatic light signal ( 14 ) through said first window ( 7 ) towards said surface ( 2 a ) in a direction ( 9 ) substantially perpendicular to said surface ( 2 a ) in such a manner that said incident signal ( 14 a ) is reflected on said surface ( 2 a ); second means ( 16 ) for detecting said reflected signal ( 14 b ); and transformation means ( 19 ) coupled to said first means ( 18 ) and to said second means ( 16 ) to transform the signal detected by said second means ( 16 ) as a function of the signal detected by said first means ( 18 ).
1. A method of controlling the operation of plasma etching the surface of a semiconductor substrate by an alternating etching method, which comprises an etching portion and a deposition portion, the method comprising the following steps:
generating a monochromatic signal;
sending said signal to the substrate in a direction substantially perpendicular to the surface to be etched;
detecting said signal reflected on said substrate;
detecting a signal associated with the presence in the plasma of a species stemming from the reaction of an etching gas with said substrate, wherein the associated signal is detected simultaneously with the reflected signal; and
extracting from said reflected signal those portions of the signal that correspond to the presence of said species in order to obtain a curve representative of etching steps alone.
2. A method according to claim 1 , in which said substrate is made of silicon and said species is of the type SiF x .
3. A method according to claim 1 , in which said substrate is of silicon and said species is of the type CF x .
4. A method as in claim 1 , wherein the reflective signal is detected by an interferometer and the second signal is detected by an emission spectrometer.
5. A method as in claim 1 , wherein extracting a signal comprises retrieving a portion of the signal associated with the time that the second signal shows the etching process.
6. A method as in claim 1 , wherein the extracted signal provides information regarding at least one of an etch rate and an end of the etching process.
7. A method of controlling the operation of plasma etching in an alternating etching process, which comprises an etching portion and a deposition portion, comprising
receiving a first signal representative of the alternating etching process;
simultaneously detecting a second signal indicative of the etching portion of the alternating etching process; and
using the second signal to extract from the first signal a signal representative of the etching portion within the alternating etching process,
wherein extracting a signal comprises retrieving a portion of the signal associated with the time that the second signal shows the etching process.
8. A method as in claim 7 , wherein the first signal comes from a substrate that underwent the alternating etching process.
9. A method as in claim 7 , wherein the first signal is generated from a laser.
10. A method as in claim 7 , wherein the first signal is received through an interferometer.
11. A method as in claim 7 , wherein the second signal is detected by an emission spectrometer.
12. A method as in claim 7 , wherein the second signal indicative of the etching portion is associated with the plasma etching.
13. A method as in claim 7 , wherein the second signal indicative of the etching portion is associated with the species of the plasma stemming from the reaction of an etching gas with a substrate.
14. A method as in claim 7 , wherein the extracted signal provides information regarding at least one of an etch rate and an end of the etching process.
15. A method of controlling the operation of plasma etching of a substrate in an alternating etching process, which comprises an etching portion and a deposition portion, the method comprising
sending a first signal to the substrate;
receiving a signal reflective from the substrate;
simultaneously detecting a second signal associated with the etching portion of the alternating etching process; and
using the second signal to extract from the first signal a signal representative of the etching portion within the alternating etching process.
16. A method as in claim 15 , wherein the second signal indicative of the etching portion is associated with the plasma etching.
17. A method as in claim 15 , wherein the second signal indicative of the etching portion is associated with the species of the plasma stemming from the reaction of an etching gas with a substrate.
18. A method as in claim 15 , wherein extracting a signal comprises retrieving a portion of the signal associated with the time that the second signal shows the etching process.
19. A method as in claim 15 , wherein the extracted signal provides information regarding at least one of an etch rate and an end of the etching process.