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EP-4737610-A1 - A METHOD OF PLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION

EP4737610A1EP 4737610 A1EP4737610 A1EP 4737610A1EP-4737610-A1

Abstract

There is provided a method of plasma-enhanced chemical vapor deposition comprising the steps of: supporting a wafer within a reactor chamber on a wafer support; generating a plasma from acetylene, hydrogen and argon gases using a high frequency RF power supply; and depositing an amorphous hydrogenated carbon film on the wafer; wherein during the deposition the reactor chamber pressure is within the range 1-6 Torr; and wherein during the deposition the wafer support temperature is between 200-350 degrees Celsius; such that the deposited amorphous hydrogenated carbon film provides a dielectric layer on the wafer exhibiting low leakage currents of less than 1.0E-07 A/cm 2 at an operating voltage of 2 MV/cm and a high breakdown voltage of more than 6 MV/cm.

Inventors

  • CROOK, KATHERINE
  • Royle, William
  • RUCINSKA, Emilia
  • PARFITT, Mollie

Assignees

  • SPTS Technologies Limited

Dates

Publication Date
20260506
Application Date
20250612

Claims (15)

  1. A method of plasma-enhanced chemical vapor deposition comprising the steps of: supporting a wafer within a reactor chamber on a wafer support; generating a plasma from acetylene, hydrogen and argon gases using a high frequency RF power supply; and depositing an amorphous hydrogenated carbon film on the wafer; wherein during the deposition the reactor chamber pressure is within the range 1-6 Torr; and wherein during the deposition the wafer support temperature is between 200-350 degrees Celsius; such that the deposited amorphous hydrogenated carbon film provides a dielectric layer on the wafer exhibiting low leakage currents of less than 1.0E-07 A/cm 2 at an operating voltage of 2 MV/cm and a high breakdown voltage of more than 6 MV/cm.
  2. A method according to claim 1, wherein during the deposition the wafer support temperature is in the range 225-325 degrees Celsius, optionally wherein during the deposition the wafer support temperature is in the range 250-300 degrees Celsius.
  3. A method according to any preceding claim, wherein the plasma is generated using a RF power supply at 13.56 MHz; and/or a RF power supply providing a power between 500-1500 W.
  4. A method according to any preceding claim, wherein the plasma is generated using a RF driven showerhead and an electrically grounded wafer support.
  5. A method according to any preceding claim, wherein the reactor chamber pressure is within the range 1.5-5 Torr.
  6. A method according to any preceding claim, undertaken in a capacitively coupled reactor.
  7. A method according to any preceding claim, wherein the acetylene gas is supplied to the reactor chamber at a flow rate in the range 100-600 sccm, optionally wherein the acetylene gas is supplied to the reactor chamber at a flow rate in the range 200-550 sccm.
  8. A method according to any preceding claim, wherein the hydrogen gas is supplied to the reactor chamber at a flow rate in the range 100-600 sccm, optionally wherein the hydrogen gas is supplied to the reactor chamber at a flow rate in the range 250-550 sccm.
  9. A method according to any preceding claim, wherein the argon gas is supplied to the reactor chamber at a flow rate in the range 200-1000 sccm, optionally wherein the argon gas is supplied to the reactor chamber at a flow rate in the range 300-900 sccm.
  10. A method according to any preceding claim, wherein the wafer is a 300 mm silicon wafer.
  11. A method according to any preceding claim, wherein the film deposited has a thickness between 150-1000 nm.
  12. A method according to any preceding claim, wherein the deposited amorphous hydrogenated carbon film has a density of 1.6-1.8 g/cc.
  13. A plasma-enhanced chemical vapor deposition system configured to undertake the method of any of claims 1-12, the system comprising: a reactor chamber; a gas inlet arranged to supply acetylene, hydrogen and argon gases to the reactor chamber; a wafer support configured to support a wafer within the reactor chamber; an RF power supply coupled to the reactor chamber.
  14. A system according to claim 13, wherein the wafer support is grounded and arranged to be resistively heated to thereby heat the wafer.
  15. A system according to claim 13 or 14, further comprising a cooling mechanism associated with the wafer support and configured to cool the wafer; and/or further comprising one or more flow control units configured to adjust the flow of the gases into and/or out of the reactor chamber.

Description

Introduction This invention relates to a method of plasma-enhanced chemical vapor deposition (PECVD), in particular, a method of depositing an amorphous hydrogenated carbon thin film on a wafer that has excellent electrical isolation properties. This invention also relates to a PECVD apparatus configured to undertake such a method. Background Plasma-enhanced chemical vapor deposition (PECVD) techniques can be used to deposit carbon thin films for various purposes where carbon coatings are required. The films can include for example diamond-like carbon films, 2D carbon layer films and polymer films. It will be appreciated that a "thin film" is a film having a thickness of no more than a few micrometres. The films tend to be disordered or amorphous over most practical process parameters. They are commonly defined as amorphous carbon (a-C) or amorphous hydrogenated carbon (a-C:H) films. Dense amorphous hydrogenated carbon films (i.e. with a density above 1.8 g/cc) can be used for example to provide a hard diamond-like carbon (DLC) protective layer on a substrate for advanced patterning applications, providing improved etch selectivity over conventional SiO2 or SiN masks. It is preferable for reasons of efficiency and ease of manufacture, to deposit films at low temperatures, below 350 degrees Celsius. It will be appreciated that the temperature being referred to is the wafer temperature/ wafer support temperature. It would be advantageous to develop suitable methods of depositing an amorphous hydrogenated carbon film to be used as a dielectric film in an interconnect scheme. This would provide an alternative to conventional films such as SiO2, SiN, SiC and SiCN films. The film should be deposited at a low temperature, and at an acceptable deposition rate, for economic reasons. Summary In a first aspect of the invention there is provided a method of plasma-enhanced chemical vapor deposition. The method comprises the steps of: supporting a wafer within a reactor chamber on a wafer support; generating a plasma from acetylene, hydrogen and argon gases using a high frequency RF power supply; and depositing an amorphous hydrogenated carbon film on the wafer. During the deposition the reactor chamber pressure is within the range 1-6 Torr and the wafer support temperature is between 200-350 degrees Celsius such that the deposited amorphous hydrogenated carbon film provides a dielectric layer on the wafer exhibiting low leakage currents of less than 1.0E-07 A/cm2 at an operating voltage of 2 MV/cm and a high breakdown voltage of more than 6 MV/cm. The inventors have recognised that the electrical isolation properties of the deposited film must be adequate for use as a dielectric film in an interconnect scheme. As such a PECVD process has been devised using acetylene, hydrogen and argon gases to deposit, at a sufficiently fast deposition rate, an amorphous hydrogenated carbon film displaying low leakage currents and a high breakdown voltage. This has been achieved with a high frequency power supply, a reactor chamber pressure within the range 1-6 Torr and wafer temperature between 200-350 degrees Celsius. A lower platen/ wafer support temperature (<350 degrees Celsius) has been found to enable a fast deposition rate, however beneath a certain temperature, the electrical performance of the film has been found to deteriorate. A suitable temperature for the platen to enable an acceptable deposition rate and still provide suitable electrical properties has been found to be 200-350 degrees Celsius. Without being bound by any conjecture it is proposed that amorphous hydrogenated carbon film deposited below 200 degrees Celsius and above 350 degrees Celsius using the C2H2/Ar/H2 chemistry and a high frequency RF plasma result in structural changes in the film which degrade the dielectric properties of the film. At lower temperatures higher density films are deposited which contain excess sp2 bonding (determined from FTIR sp3/sp2 ratios) which result in degraded dielectric properties, while at high temperatures insufficient hydrogen can be incorporated into the film to adequately passivate dangling bonds in the low density a-C matrix, once again producing degraded dielectric properties when compared to the present films. Optionally, the wafer temperature is in the range 225-325 degrees Celsius, more preferably in the range 250-300 degrees Celsius. The density of the film has been found to depend on temperature, and furthermore the density of the film has been found to impact the electrical performance of the film. A narrow range of densities corresponding to temperatures between 225-325, more optimally 250-300 has been found to provide optimal electrical properties. The plasma is generated using a high frequency RF supply i.e. a power supply in excess of 1 MHz, typically greater than 2MHz. Optionally, the plasma is generated using a RF power supply at 13.56 MHz. It has been found that varying the power results in films having dif