Electro-oxidative metal removal in through mask interconnect fabrication

Patent metadata

Field	Value
Publication number	US-10692735-B2
Application number	US-201816040407-A
Country	US
Kind code	B2
Filing date	Jul 19, 2018
Priority date	Jul 28, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

In one implementation a wafer processing method includes filling a plurality of through-resist recessed features with a metal, such that a ratio of fill rate of a first feature to a fill rate of a second feature is R1; followed by electrochemically removing metal such that a ratio of metal removal rate from the first feature to the metal removal rate from the second feature is greater than R1, improving the uniformity of the fill. In some embodiments the method includes contacting an anodically biased substrate with an electrolyte such that the electrolyte has a transverse flow component in a direction that is substantially parallel to the working surface of the substrate. The method can be implemented in an apparatus that is configured for generating the transverse flow at the surface of the substrate. In some implementations the method makes use of distinct electrochemical regimes to achieve improvement in uniformity.

First claim

The invention claimed is:

1. A method for processing a semiconductor substrate, the method comprising:
(a) providing a semiconductor substrate having a working surface, wherein the working surface comprises a plurality of through mask metal features, into an apparatus configured for electrochemical metal removal;
(b) selecting a regime for the electrochemical metal removal from the group consisting of an electroetching below a critical potential, electropolishing above the critical potential, and electroetching below the critical potential followed by electropolishing above the critical potential; and
(c) electrochemically removing a portion of the metal from the through mask metal features in the selected regime while improving the uniformity of the metal, wherein the apparatus configured for electrochemical metal removal comprises:
(i) a vessel configured for holding an electrolyte and a cathode during electrochemical metal removal from the semiconductor substrate;
(ii) a semiconductor substrate holder configured to hold the semiconductor substrate such that the working surface of the semiconductor substrate is immersed into the electrolyte and is separated from the cathode during the electrochemical removal of metal from the semiconductor substrate;
(iii) a mechanism configured to provide a transverse flow of electrolyte contacting the working surface of the semiconductor substrate in a direction that is substantially parallel to the working surface of the semiconductor substrate, wherein the mechanism is different from a mechanism for rotating the semiconductor substrate; and
(iv) a reference electrode for measuring a potential proximate the semiconductor substrate or an equivalent potential.

2. The method of claim 1 , wherein electrochemically removing the portion of the metal comprises electroetching the metal below the critical potential under current-controlled conditions.

3. The method of claim 1 , wherein electrochemically removing the portion of the metal comprises electropolishing the metal above the critical potential under potential-controlled conditions.

4. A method for processing a semiconductor substrate, the method comprising:
(a) providing a semiconductor substrate having a working surface, wherein the working surface comprises an exposed metal, into an apparatus configured for electrochemical metal removal;
(b) anodically biasing the semiconductor substrate and immersing the working surface of the semiconductor substrate into an electrolyte; and
(c) electrochemically removing a portion of the metal while improving the uniformity of the metal by removing metal in an electroetching regime below a critical potential, followed by removing metal in an electropolishing regime above the critical potential, wherein the apparatus configured for electrochemical metal removal comprises:
(i) a vessel configured for holding an electrolyte and a cathode during electrochemical metal removal from the semiconductor substrate;
(ii) a semiconductor substrate holder configured to hold the semiconductor substrate such that the working surface of the semiconductor substrate is immersed into the electrolyte and is separated from the cathode during the electrochemical removal of metal from the semiconductor substrate;
(iii) a mechanism configured to provide a transverse flow of electrolyte contacting the working surface of the semiconductor substrate in a direction that is substantially parallel to the working surface of the semiconductor substrate, wherein the mechanism is different from a mechanism for rotating the semiconductor substrate; and
(iv) a reference electrode for measuring a potential proximate the semiconductor substrate or an equivalent potential.

5. A method for processing a semiconductor substrate, the method comprising:
(a) providing a semiconductor substrate having a plurality of through mask metal features, into an apparatus configured for electrochemical metal removal;
(b) anodically biasing the semiconductor substrate and immersing the working surface of the semiconductor substrate into the electrolyte;
(c) electrochemically removing a portion of the metal from the through mask metal features, such that metal thickness variation within individual through mask features is reduced, wherein the apparatus configured for electrochemical metal removal comprises:
(i) a vessel configured for holding an electrolyte and a cathode during electrochemical metal removal from the semiconductor substrate;
(ii) a semiconductor substrate holder configured to hold the semiconductor substrate such that the working surface of the semiconductor substrate is immersed into the electrolyte and is separated from the cathode during the electrochemical removal of metal from the semiconductor substrate;
(iii) a mechanism configured to provide a transverse flow of electrolyte contacting the working surface of the semiconductor substrate in a direction that is substantially parallel to the working surface of the semiconductor substrate, wherein the mechanism is different from a mechanism for rotating the semiconductor substrate; and
(iv) a reference electrode for measuring a potential proximate the semiconductor substrate or an equivalent potential.

6. An apparatus for electrochemically removing metal from a semiconductor substrate, the apparatus comprising:
(a) an anode chamber configured to house an anodically biased semiconductor substrate during electrochemical metal removal from the semiconductor substrate, wherein the anode chamber has at least one inlet for introducing a fluid to the anode chamber;
(b) a cathode chamber configured to house a cathode, wherein the cathode chamber has at least one inlet for introducing a fluid into the cathode chamber; and
(c) an ionically permeable separator between the anode chamber and the cathode chamber, wherein the apparatus further comprises a reference electrode for measuring a potential proximate the semiconductor substrate or an equivalent potential, wherein the reference electrode is positioned to reside within about 5 cm from the surface of the semiconductor substrate, or, is positioned at a location, where a potential is equivalent to a potential measured within about 5 cm of the semiconductor substrate.

7. The apparatus of claim 6 , wherein the inlet to the cathode chamber is positioned proximate the cathode, and wherein the cathode chamber further comprises an outlet positioned proximate the ionically permeable separator.

8. The apparatus of claim 6 , wherein the ionically permeable separator is configured to block or inhibit transfer of hydrogen bubbles and/or metal particles from the cathode chamber to the anode chamber.

9. The apparatus of claim 6 , further comprising a catholyte recirculation loop and an anolyte recirculation loop.

10. The apparatus of claim 6 , further comprising a cathode having a plurality of through-holes, wherein the apparatus is configured to pass the fluid from the at least one inlet in the cathode chamber through the holes of the cathode.

11. The apparatus of claim 6 , wherein the apparatus is configured to process data from the reference electrode, and maintain electrochemical removal process in a selected regime.

12. The apparatus of claim 6 , wherein the apparatus further comprises a controller comprising program instructions for causing an electrochemical metal removal from the semiconductor substrate in an electroetching regime below a critical potential.

13. The apparatus of claim 6 , wherein the apparatus further comprises a controller comprising program instructions for causing an electrochemical metal removal from the semiconductor substrate in an electropolis

Assignees

• Lam Res Corp

Inventors

• Thorkelsson Kari
• Abraham Richard G
• Mayer Steven T

Classifications

• H10P72/0476

  comprising at least one plating chamber · CPC title

• H10P72/0422

  for wet etching · CPC title

• H10P50/667

  by liquid etching only · CPC title

• H10P14/46

  using a liquid · CPC title

• H10W70/05

  of insulating or insulated package substrates, or of interposers, or of redistribution layers (manufacture or treatment of leadframes H10W70/04) · CPC title