PLASMA ETCHING PROCESS

• US 20150228495A1
• Filed: 01/30/2015
• Published: 08/13/2015
• Est. Priority Date: 01/31/2014
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Centre National De La Recherche Scientifique, Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: JOUBERT, Olivier, POSSEME, Nicolas, CUNGE, Gilles, DESPIAU-PUJO, Emilie, PARGON, Erwine
• Granted Patent: US 9,378,970 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

A method and system are provided for etching a layer to be etched in a plasma etching reactor, including: forming a reactive layer by injection of at least one reactive gas to form a reactive gas plasma, which forms, together with the layer to be etched, a reactive layer which goes into the layer to be etched during etching of said layer to be etched, wherein the reactive layer reaches a steady state thickness upon completion of a determined duration of said injection; said injection being interrupted before said determined duration has elapsed so that, upon completion of the forming of the reactive layer, the thickness of the reactive layer is smaller than said steady state thickness; and removing the reactive layer by injection of at least one inert gas to form an inert gas plasma, which makes it possible to remove only the reactive layer.

Claims

1. A method for etching a layer to be etched in a plasma etching reactor, with such method comprising:

an initial phase comprising;

at least one initial step of etching, with the initial step of etching comprising, for a duration D0, an injection into the reactor of at least one reactive gas to form a reactive gas plasma, with the reactive gas plasma forming, together with the layer to be etched, a reactive layer which goes into the layer to be etched, with the duration D0 of injection being longer than a determined duration Ds of injection upon completion of which the reactive layer reaches a steady state thickness which will be steady over time, so that the thickness of the reactive layer can reach said steady state thickness during said initial step of etching;

at least one step of removing the reactive layer, formed upon completion of the initial step of etching;

with the method comprising, after the initial phase, a subsequent phase including at least a sequence of steps, with each sequence including at least the following steps;

for a duration D1, an injection into the reactor of at least one reactive gas to form a reactive gas plasma, with the reactive gas plasma forming, together with the layer to be etched, a reactive layer which goes into the layer to be etched, with the duration D1 of injection being shorter than the determined duration Ds of injection upon completion of which the reactive layer would reach a steady state thickness, so that, during the subsequent phase, the thickness of the reactive layer remains smaller than said steady state thickness;

at least one step of removing the reactive layer, formed upon completion of the injection performed during the duration D1, with the removing step comprising injecting at least one inert gas into the reactor to form an inert gas plasma making it possible to remove the reactive layer only, formed upon completion of the injection performed during the duration D1.

2. The method according to claim 1, wherein the subsequent phase comprises a plurality of sequences of steps.

3. The method according to claim 1, wherein said layer to be etched is on the top of an underlying layer, and wherein the initial phase is interrupted and the subsequent phase is started when the layer to be etched has a thickness greater than the steady state thickness of the layer.

4. The method according to claim 3, wherein the initial phase is interrupted and the subsequent phase is started when the layer to be etched has a thickness greater than the steady state thickness of the layer and smaller than k times the steady state thickness of the layer, with k ranging from 8 to 2.

5. The method according to claim 4, wherein k ranges from 6 to 3.

6. The method according to claim 5, wherein k=4.

7. The method according to claim 1, wherein the duration D1 of injection of the reactive gas ranges from 50 to 500 ms.

8. The method according to claim 1, wherein the duration D1 of injection of the reactive gas is interrupted when the reactive layer has a thickness smaller than 2 nm and preferably smaller than 1 nm.

9. The method according to claim 1, wherein the layer to be etched is on the top of a barrier layer and the duration D1 of injection of the reactive gas is interrupted before the reactive layer has a thickness greater than the thickness of the barrier layer.

10. The method according to claim 1, wherein the duration of injection of the inert gas ranges from 50 to 500 ms and preferably from 100 to 500 ms.

11. The method according to claim 1, wherein during the step of forming a reactive layer during the subsequent phase, at least one of the following parameters is adjusted so as to control the forming of the reactive layer:

the duration D1 of injection of the reactive gas and the energy transmitted to the ions in the reactive gas plasma.

12. The method according to claim 1, wherein during the subsequent phase, the energy transmitted to the ions in the reactive gas plasma is less than 50 eV and preferably less than 25 eV, and the density of the reactive gas plasma ranges from 1010 and 5.1011 ions/cm3, and preferably from 1010 and 1011 ions/cm3.

13. The method according to claim 1, wherein during the step of removing the reactive layer during the subsequent phase, at least one of the following parameters is adjusted so as to remove the reactive layer without removing the layer to be etched not etched during the step of forming a reactive layer during the subsequent phase:

the duration of injection of the inert gas, the density of the inert gas plasma, the energy transmitted to the ions of the inert gas plasma.

14. The method according to claim 1, wherein the energy transmitted to the ions of the inert gas plasma is less than 50 eV and preferably less than 25 eV.

15. The method according to claim 1, wherein during the subsequent phase, the inert gas plasma formed during the step of removing the reactive layer is pulsed plasma and the energy transmitted to the ions of the inert gas plasma is less than 50 eV and preferably less than 25 eV.

16. The method according to claim 1, wherein the layer to be etched or a substrate supporting the layer to be etched is electrically polarized.

17. The method according to claim 1 wherein during the step of forming a reactive layer during the subsequent phase, an inert gas or a mixture of inert gases in addition to the reactive gas is injected.

18. The method according to claim 1, wherein the reactive gas is selected among Cl2, HBr, SF6, NF3, SiCl4, BCl3, H2, SiF4, O2, HCl, HI, CH2F2, CHF3, Ar, or is selected among CF4, CHF3, CH3F, C4F8, CH2F2, C4F6, C5F6, Ar, O2, He or a mixture of such gases.

19. The method according to claim 1, wherein the inert gas is a rare gas or a mixture of rare gases.

20. The method according to claim 1, wherein the inert gas is Argon (Ar), Xenon (Xe) or a mixture of such gases.

21. The method according to claim 1, wherein during the subsequent phase, said removing step comprising an injection of at least one inert gas into the reactor is executed continuously and simultaneously with a plurality of said injections of at least one reactive gas.

22. The method according to claim 1, wherein the layer to be etched is made of a semiconductor material selected among:

silicon (Si), germanium (Ge) or silicon-germanium (SiGe) or a thin III-V material-based layer or a metal layer or a layer of porous dielectric materials.

23. The method according to claim 1, wherein the layer to be etched is a layer of a MOSFET transistor.

24. The method according to claim 1, wherein said sequence of steps is executed several times.

25. The method according to claim 24, wherein the reactive gas and/or the inert gas is different between at least two sequences of steps.

27. A system for implementing the method according to claim 1 comprising:

one plasma etching reactor,

An injection device so configured as to inject at least two gases into the plasma etching reactor, with the injection device being so configured as to be able to inject at least one of the gases for a duration D1 of less than 1,000 milliseconds and preferably less than 500 milliseconds.

26. A method for etching a layer to be etched in a plasma etching reactor, with such method comprising at least:

a step of forming a reactive layer comprising an injection of at least one reactive gas into the reactor to form a reactive gas plasma able to etch the layer to be etched, with a reactive layer being formed on the surface of the layer to be etched under the effect of the reactive gas plasma, characterized in that;

the injection of the reactive gas is executed for a duration D1 shorter than 1,000 milliseconds, and in that;

the method comprises at least one step of removing the reactive layer, at least partly executed after the step of forming the reactive layer, with the removing step comprising injecting at least one inert gas into the reactor to form an inert gas plasma making it possible to remove the reactive layer;

and comprising the following step executed prior to the step of forming a reactive layer by injecting the reactive gas for a duration D1;

one initial step of etching, for a duration D0, an injection into the reactor of at least one reactive gas to form a reactive gas plasma, with the reactive gas plasma forming, together with the layer to be etched, a reactive layer which goes into the layer to be etched, with the duration D0 of injection being longer than a determined duration Ds of injection, upon completion of which the reactive layer reaches a steady state thickness, so that the thickness of the reactive layer can reach said steady state thickness during said initial step of etching.