ADJUSTMENT OF VUV EMISSION OF A PLASMA VIA COLLISIONAL RESONANT ENERGY TRANSFER TO AN ENERGY ABSORBER GAS

• US 20160135274A1
• Filed: 11/12/2014
• Published: 05/12/2016
• Est. Priority Date: 11/12/2014
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Fischer, Andreas, Lill, Thorsten
• Granted Patent: US 9,609,730 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32091 the radio frequency energy being capacitively coupled to the plasma
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32449 Gas control, e.g. control of the gas flow
• CPC Class Codes: H01J 37/32972 Spectral analysis
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32
• CPC Class Codes: H05G 2/003 the plasma being generated from a material in a liquid or gas state

Abstract

Disclosed are methods of adjusting the emission of vacuum ultraviolet (VUV) radiation from a plasma in a semiconductor processing chamber. The methods may include generating a plasma in the processing chamber which includes a VUV-emitter gas and a collisional energy absorber gas, and adjusting the emission of VUV radiation from the plasma by altering the concentration ratio of the VUV-emitter gas to collisional energy absorber gas in the plasma. In some embodiments, the VUV-emitter gas may be helium and the collisional energy absorber gas may be neon, and in certain such embodiments, adjusting VUV emission may include flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma. Also disclosed are apparatuses which implement the foregoing methods.

Claims

1. A method of adjusting the emission of vacuum ultraviolet (VUV) radiation from a plasma in a semiconductor processing chamber, the method comprising:

generating a plasma in the processing chamber, the plasma comprising a VUV-emitter gas and a collisional energy absorber gas, the plasma emitting VUV radiation; and

adjusting the emission of VUV radiation from the plasma by altering the concentration ratio of the VUV-emitter gas to collisional energy absorber gas in the plasma.

2. The method of claim 1, wherein the VUV-emitter gas is helium.

3. The method of claim 2, wherein the collisional energy absorber gas is neon.

4. The method of claim 3, wherein adjusting the emission of VUV radiation from the plasma comprises flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma.

5. The method of claim 4, wherein the emission of VUV radiation from the plasma is adjusted upward by flowing helium into the processing chamber so as to increase the ratio of helium to neon in the plasma.

6. The method of claim 4, wherein the emission of VUV radiation from the plasma is adjusted downward by flowing neon into the processing chamber so as to decrease the ratio of helium to neon in the plasma.

7. The method of claim 4, further comprising:

measuring a property of the plasma and/or the substrate; and

setting the flow of helium and/or neon into the processing chamber in response to the measured property.

8. The method of claim 7, wherein the property is the emission intensity from an emission band of an excited state species of the plasma.

9. The method of claim 8, wherein the measured emission band is the emission band of neon centered at 632.8 nm.

10. The method of claim 7, wherein the property is the profile of an etched feature of a semiconductor substrate measured with a metrology tool, the feature having been etched in the processing chamber.

11. The method of claim 10, wherein the flow of helium is decreased and/or the flow of neon is increased in response to a measured bowing of the sidewalls of the etched feature.

12. The method of claim 3, wherein the plasma is a capacitively-coupled plasma.

13. The method of claim 12, wherein the semiconductor processing chamber in which the plasma is generated is part of a capacitively coupled plasma reactor, the reactor having an upper plate, the reactor configured such that the gap between the upper plate and the substrate is between about 1.5 cm and 2.5 cm.

14. The method of claim 3, wherein the plasma is an inductively-coupled plasma, wherein the semiconductor processing chamber in which the plasma is generated is part of an inductively coupled plasma reactor having a gap region within which the plasma is generated, and wherein the reactor comprises one or more components located within the gap region which provide a structure against which neon atoms may collide and be collisionally de-excited.

15. The method of claim 14, wherein the one or more components which provide said structure for the de-excitation of neon comprise a set of concentric cylinders oriented with their central axes perpendicular to the plane of the substrate.

16. A method of etching a feature on the surface of a semiconductor substrate, the method comprising:

(a) adsorbing an etchant onto the surface of a semiconductor substrate such that the etchant forms an adsorption-limited layer on the surface;

(b) after (a), removing unadsorbed and/or desorbed etchant from the volume surrounding the adsorbed etchant;

(c) after (b), generating a plasma in the processing chamber, the plasma comprising helium and neon, the plasma emitting VUV radiation;

(d) contacting the adsorbed etchant with the plasma to etch the surface of the substrate; and

(e) repeating (a)-(d) multiple times and adjusting the emission of VUV radiation from the plasma in (d) by altering the concentration ratio of helium to neon in the plasma, thereby altering the anisotropy of the etching of the surface of the substrate.

17. The method of claim 16, wherein the etchant comprises chlorine.

18. The method of claim 16, wherein adjusting the emission of VUV radiation from the plasma comprises flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma.

19. The method of claim 18, further comprising:

measuring the profile of the etched feature of the semiconductor substrate with a metrology tool; and

setting the flow of helium and/or neon into the processing chamber in response to the measured profile.

20. A semiconductor processing apparatus comprising:

a processing chamber;

a plasma generator;

one or more gas flow inlets configured for flowing helium and neon into the processing chamber; and

a controller comprising machine readable instructions for;

operating the plasma generator to generate a plasma in the processing chamber, the plasma comprising helium and neon, the plasma emitting VUV radiation; and

operating the one or more gas flow inlets to adjust the emission of VUV radiation from the plasma by flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma.

21. The semiconductor processing apparatus of claim 20:

wherein the apparatus further comprises an optical detector; and

wherein the machine readable instructions of the controller further comprise instructions for;

operating the optical detector to measure an emission intensity of an emission band of the plasma; and

operating the one or more gas flow inlets to set the flow rate of helium and/or neon into the processing chamber in response to the measured emission intensity.

22. The semiconductor processing apparatus of claim 20:

wherein the one or more gas flow inlets are further configured for flowing an etchant gas into the processing chamber;

wherein the apparatus further comprises;

a vacuum pump;

a valve-controlled conduit to the vacuum pump; and

a metrology tool for measuring an etch profile of a feature of a semiconductor substrate; and

wherein the machine readable instructions of the controller further comprise instructions for;

operating the one or more gas flow inlets to flow etchant gas into the processing chamber;

setting conditions within the processing chamber such that the etchant adsorbs onto the surface of the semiconductor substrate forming an adsorption-limited layer of etchant;

operating the valve-controlled conduit and vacuum pump to remove unadsorbed and/or desorbed etchant from the volume surrounding the adsorbed etchant;

operating the plasma generator, after absorption of etchant and removal of unadsorbed and/or desorbed etchant, to etch a feature on the semiconductor substrate;

operating the metrology tool to measure an etch profile of the etched feature on the semiconductor substrate; and

operating the one or more gas flow inlets to set the flow rate of helium and/or neon into the processing chamber in response to the measured etch profile.