Electrohydrodynamic ejection printing and electroplating for photoresist-free formation of metal features

Patent metadata

Field	Value
Publication number	US-2023340686-A1
Application number	US-202117759673-A
Country	US
Kind code	A1
Filing date	Jan 27, 2021
Priority date	Feb 3, 2020
Publication date	Oct 26, 2023
Grant date	—

Abstract

Methods, inks, apparatus, and systems for forming metal features on semiconductor substrates are provided herein. Advantageously, the techniques herein do not require the use of photoresist, and can be accomplished without many of the processes and apparatuses used in the conventional process flow. Instead, electrohydrodynamic ejection printing is used to deposit an ink that includes an electroplating additive such as accelerator or inhibitor. The printed substrate can then be electroplated in a preferential deposition process that achieves a first deposition rate on areas of the substrate where the ink is present and a second deposition rate on areas of the substrate where the ink is absent, the first and second deposition rates being different from one another. After electroplating, chemical etching may be used to spatially isolate the preferentially grown metal features from one another.

First claim

What is claimed is:

1 . A method of depositing metal on a substrate, the method comprising:
a) receiving a substrate comprising a seed layer, wherein the seed layer is conductive and is exposed on a surface of the substrate; b) printing an ink in a pattern on the seed layer through electrohydrodynamic ejection printing, wherein the ink comprises an electroplating additive dissolved in a solvent, wherein the electroplating additive comprises an accelerator or an inhibitor, and wherein the electroplating additive adsorbs onto the seed layer; and c) electroplating metal on the substrate through a preferential deposition that provides a first deposition rate at locations where the electroplating additive from the ink is present and a second deposition rate at locations where the electroplating additive from the ink is absent, wherein the first deposition rate is different from the second deposition rate.

2 . The method of claim 1 , wherein the electroplating additive comprises an accelerator, and wherein the first deposition rate is greater than the second deposition rate such that the metal is preferentially deposited at locations where the accelerator from the ink is present.

3 . The method of claim 2 , wherein the accelerator comprises an alkane chain with at least one mercapto- and one sulfonic acid group, or an acid-salt.

4 . The method of claim 3 , wherein the accelerator comprises mercaptopropane sulfonic acid or mercaptoethane sulfonic acid.

5 . The method of claim 3 , wherein the solvent in the ink comprises at least one material selected from the group consisting of: water, terpineol, ethylene carbonate, propylene carbonate, dimethylsulfoxide (DMSO), ethylene glycol, and propylene glycol.

6 . The method of claim 2 , further comprising chemically etching the substrate to remove a portion of the metal deposited in (c) and a portion of the seed layer, thereby forming metal features at locations where the accelerator from the ink is present, the metal features being spatially isolated from one another.

7 . The method of claim 6 , wherein the substrate is electroplated in (c) in an electrolyte comprising:
between about 10-1000 ppm plating suppressor additive, between about 10-60 g/L copper ions, between about 5-180 g/L acid, and between about 30-80 ppm halide ions.

8 . The method of claim 7 , wherein the electrolyte is either free of accelerator or has only trace amounts of accelerator.

9 . The method of claim 1 , wherein the electroplating additive comprises an inhibitor, and wherein the first deposition rate is lower than the second deposition rate such that the metal is preferentially deposited at locations where the inhibitor from the ink is absent.

10 . The method of claim 9 , wherein the inhibitor comprises at least one material selected from the group consisting of: 6-mercaptohexanol and benzotriazole.

11 . The method of claim 9 , further comprising chemically etching the substrate to remove a portion of the metal deposited in (c), the ink printed in (b), and a portion of the seed layer, thereby forming metal features at locations where the inhibitor from the ink was absent, the metal features being spatially isolated from one another.

12 . The method of claim 9 , wherein the substrate is electroplated in (c) in electrolyte comprising:
between about 0-1000 ppm accelerator, between about 10-60 g/L copper ions, and between about 5-180 g/L acid.

13 . The method of claim 12 , where the electrolyte is either free of the inhibitor or has only a trace amount of the inhibitor.

14 . The method of claim 1 , wherein the substrate further comprises an adhesion barrier layer positioned under the seed layer, the method further comprising:
d) chemically etching the substrate to remove a portion of the metal deposited in (c) and a portion of the seed layer, thereby forming metal features, the metal features being spatially isolated from one another; and e) electroplating a second metal onto the substrate, wherein the second metal selectively deposits on the metal features formed in (d), without substantially forming on the adhesion barrier layer.

15 . The method of claim 14 , wherein the second metal forms a diffusion barrier layer, the method further comprising:
f) electroplating solder material onto the diffusion barrier layer, wherein the solder material selectively deposits on the diffusion barrier layer formed in (e), without substantially forming on the adhesion barrier layer.

16 . The method of claims 1 , wherein the electroplating additive in the ink reacts with and chemically binds to the seed layer on the substrate.

17 . A system for processing a substrate, the system comprising:
an electrohydrodynamic ejection printing apparatus comprising:
a nozzle having an opening that has a diameter between about 50-5000 nm.
an ink reservoir fluidically connected with the nozzle,
a substrate support for supporting the substrate during printing, and
a power supply configured to apply a potential between the nozzle and the substrate support or between the nozzle and the substrate;
an electroplating apparatus comprising:
a chamber for holding electrolyte,
a substrate holder configured to hold the substrate during electroplating,
an anode, and
a power supply configured to apply potential between the anode and the substrate during electroplating; and
a controller configured to cause:
printing ink in a pattern on the substrate using the electrohydrodynamic ejection printing apparatus, wherein the ink comprises an electroplating additive dissolved in a solvent, the electroplating additive comprising an accelerator or an inhibitor, and
after printing the ink on the substrate, electroplating metal on the substrate using the electroplating apparatus, wherein the electroplating occurs through a preferential deposition that provides a first deposition rate at locations where the electroplating additive from the ink is present and a second deposition rate at locations where the electroplating additive from the ink is absent, and wherein the first deposition rate is different from the second deposition rate.

18 . The system of claim 17 , further comprising an apparatus configured to deposit a seed layer on the substrate, wherein the controller is configured to cause depositing the seed layer on the substrate before the ink is printed on the substrate.

19 . The system of claim 18 , further comprising a chemical etching apparatus configured to remove metal from the substrate, wherein the controller is configured to cause removing a portion of the metal electroplated onto the substrate and removing a portion of the seed layer on the substrate.

20 . The system claim 17 , wherein the electrohydrodynamic ejection printing apparatus and the electroplating apparatus are provided together in a single tool.

21 . An ink for electrohydrodynamic ejection printing, the ink comprising:
a) an electroplating additive comprising an accelerator or an inhibitor, wherein the electroplating additive is present at a concentration between about 0.1-10 g/L; and b) a solvent having:
i. a vapor pressure when at 25° C. that is equal to or less than about 24 Torr, and
ii. a dielectric constant between about 40-90,
wherein the ink has a viscosity between about 0.7-20 cP, and wherein the electroplating additive is completely dissolved in the solvent.

22 . The ink of claim 21 , wherein a concentration of oxygen in the ink is about 1 ppm or

Assignees

• Lam Res Corp

Inventors

• Mayer Steven T
• Thorkelsson Kari

Classifications

• H10W72/29

  Bond pads specially adapted therefor · CPC title

• H10W72/952

  comprising metals or metalloids, e.g. PbSn, Ag or Cu · CPC title

• H10W72/923

  Bond pads having multiple stacked layers · CPC title

• H10W72/019

  of bond pads · CPC title

• H10W72/01971

  Cleaning, e.g. oxide removal · CPC title