Method of forming non-conformal layers

• US 20070026540A1
• Filed: 03/13/2006
• Published: 02/01/2007
• Est. Priority Date: 03/15/2005
• Status: Active Grant

• Current Assignee: ASM IP Holding B.V. (ASM International NV)
• Original Assignee: ASM America Incorporated (ASM International NV)
• Inventors: Elers, Kai-Erik, Marcus, Steven, Wilk, Glen, Raisanen, Petri, Maes, Jan, Nooten, Sebastian
• Granted Patent: US 7,608,549 B2
• Time in Patent Office: Days
• US Class Current: 438/5
• CPC Class Codes: C23C 16/045 Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
• CPC Class Codes: C23C 16/403 of aluminium, magnesium or beryllium
• CPC Class Codes: C23C 16/448 characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials
• CPC Class Codes: C23C 16/45519 Inert gas curtains
• CPC Class Codes: C23C 16/45525 Atomic layer deposition [ALD]
• CPC Class Codes: C23C 16/45542 Plasma being used non-continuously during the ALD reactions
• CPC Class Codes: C23C 16/45565 Shower nozzles
• CPC Class Codes: C23C 16/50 using electric discharges generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34
• CPC Class Codes: C23C 16/5096 Flat-bed apparatus
• CPC Class Codes: C23C 16/52 Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• 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 37/3244 Gas supply means
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01L 21/02164 the material being a silicon oxide, e.g. SiO2
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/3141 Deposition using atomic layer deposition techniques [ALD]
• CPC Class Codes: H01L 21/3162 on a silicon body
• CPC Class Codes: H01L 29/66181 Conductor-insulator-semiconductor capacitors, e.g. trench capacitors

Abstract

In one aspect, non-conformal layers are formed by variations of plasma enhanced atomic layer deposition, where one or more of pulse duration, separation, RF power on-time, reactant concentration, pressure and electrode spacing are varied from true self-saturating reactions to operate in a depletion-effect mode. Deposition thus takes place close to the substrate surface but is controlled to terminate after reaching a specified distance into openings (e.g., deep DRAM trenches, pores, etc.). Reactor configurations that are suited to such modulation include showerhead, in situ plasma reactors, particularly with adjustable electrode spacing. In another aspect, alternately and sequentially contacting a substrate, the substrate including openings, with at least two different reactants, wherein an under-saturated dose of at least one of the reactants has been predetermined and the under-saturated dose is provided uniformly across the substrate surface, deposits a film that less than fully covers surfaces of the openings, leading to depletion effects in less accessible regions on the substrate surface

Claims

1. A method for depositing a film on a semiconductor substrate, the method comprising:

providing a substrate with a surface comprising regions with different levels of accessibility;

providing a sequence of at least two different reactants in temporally separated and alternating reactant pulses, wherein at least one of the at least two different reactants is provided through a showerhead or otherwise provided in that it impinges vertically on the substrate;

selecting plasma-enhanced atomic layer deposition (PEALD) conditions to achieve self-saturation and self-limiting atomic layer deposition (ALD) mode deposition on the most accessible regions on the substrate surface and depletion effects in less accessible regions on the substrate surface; and

exposing the semiconductor substrate to the sequence of the reactant pulses with the selected temporal separations and durations to deposit the film.

2. The method of claim 1, wherein the regions comprise top surface regions.

3. The method of claim 2, wherein the regions further comprise trench regions that are less accessible than the top surface regions.

4. The method of claim 2, wherein the regions comprise pore regions that are less accessible than the top surface regions.

5. The method of claim 1, wherein the substrate comprises a DRAM trench and the film comprises, a collar extending only partially from a top surface of the substrate into the trench.

6. The method of claim 1, wherein selecting PEALD conditions comprises tuning at least one parameter selected from the group consisting of RF power on-time, RF power amplitude, frequency, reactant concentration, chamber pressure, total gas flow, reactant pulse durations and separations, and RF electrode spacing.

7. The method of claim 1, wherein providing a sequence of at least two different reactants in temporally separated and alternating reactant pulses comprises providing one reactant continuously and intermittently pulsing plasma power.

8. A method of controlling conformality of a deposited film on a semiconductor substrate, the method comprising:

providing a substrate with a plurality of openings at a surface thereof;

alternately and sequentially supplying pulses of at least two different reactants to the substrate; and

selectively activating at least one of the two different reactants in pulses, wherein selectively activating is controlled to have a depletion effect within the openings to less than fully cover surfaces of the openings.

9. The method of claim 8, wherein conformality of a deposited film is reduced in a controlled manner.

10. The method of claim 8, wherein selectively activating comprises activating a plasma within a deposition chamber directly over the surface.

11. The method of claim 10, wherein selectively activating comprises supplying the at least one of the reactants through a showerhead having openings extending across the substrate in face-to-face relation with the substrate.

12. The method of claim 11, wherein selectively activating comprises applying a first polarity to the showerhead and a second polarity to the substrate.

13. The method of claim 12, wherein the second polarity is ground.

14. The method of claim 8, wherein alternately and sequentially supplying pulses comprises supplying pulses of a first reactant, supplying a continuous feed of a second reactant, and selectively activating comprises pulsing plasma power to the second reactant between pulses of the first reactant.

15. The method of claim 8, wherein alternately and sequentially supplying pulses comprises alternating pulses of a first reactant with pulses of a second reactant, and selectively activating comprises pulsing plasma power during only portion of each pulse of the second reactant.

16. The method of claim 8, wherein the at least one of the two different reactants comprises a species non-reactive with the other of the two different reactants under deposition conditions in the absence of the selective activation.

17. The method of claim 16, wherein the at least one of the two different reactants comprises O₂.

18. The method of claim 16, wherein the at least one of the two different reactants comprises N₂.

19. The method of claim 8, wherein selectively activating comprises tuning at least one parameter selected from the group consisting of RF power on-time, RF power amplitude, frequency, reactant concentration, chamber pressure, total gas flow and RF electrode spacing.

20. The method of claim 8, wherein the openings comprise DRAM trenches and the deposited film comprises an insulating collar extending from the surface of the substrate into the trenches.

21. The method of claim 8, wherein the deposited film comprises a section having an end proximal to the substrate surface having a thickness greater than 90% of a thickness of the deposited layer at the substrate surface, the section having an end distal from the substrate surface having a thickness less than 10% of a thickness of the deposited layer at the substrate surface, the section having a length between the ends of less than about 1.0 μ

m.

22. The method of claim 21, wherein the section has a length between the ends of less than about 0.5 μ

m.

23. The method of claim 8, wherein the openings comprise trenches and pores in an insulating layer.

24. The method of claim 23, wherein the deposited film extends no more than about 3 pore depths into the insulating layer.

25. The method of claim 8, wherein the deposited film is an insulator.

26. The method of claim 8, wherein the deposited film is a conductor.

27. A method of controlling conformality of a deposited film on a semiconductor substrate comprising a plurality of openings at a surface thereof, the method comprising:

alternately and sequentially contacting a substrate with at least two different reactants, wherein an under-saturated dose of at least one of the reactants has been predetermined and the under-saturated dose is provided uniformly across the substrate surface such that the deposited film less than fully covers surfaces of the openings.

28. The method of claim 27, wherein the deposited film covers accessible regions of the substrate surface and not other regions.

29. The method of claim 27, wherein the under-saturated dose is provided perpendicularly to the substrate.

30. The method of claim 29, wherein the under-saturated dose is provided through a showerhead.

31. The method of claim 27, wherein at least one of the two different reactants is a non-radical reactant.

32. The method of claim 27, wherein at least one reactant is provided through a showerhead.

33. A method of partially lining a trench in a substrate in a reaction space by an atomic layer deposition (ALD) reaction, the method comprising:

contacting the substrate with a saturating dose of a first reactant to form a monolayer of the first reactant over the surfaces of the trench;

providing an under-saturating dose of a second reactant; and

contacting the substrate with the entire under-saturating dose of the second reactant, such that the second reactant reacts with a film formed by the first reactant to a desired depth within the trench.

34. The method of claim 33, additionally comprising repeating contacting the substrate with a saturating dose of a first reactant, providing an under-saturating dose of a second reactant and contacting the substrate with the entire under-saturating dose of the second reactant until a thin film of a desired thickness is formed to the desired depth in the trench.

35. The method of claim 33, wherein providing an under-saturating dose of a second reactant comprises filling a dosage chamber with second reactant at a particular temperature.

36. An apparatus for depositing a thin film on a substrate comprising a reaction chamber and a dosage control mechanism for providing a particular dose of a reactant to the reaction chamber, the dosage control mechanism comprising:

a reactant source vessel;

a dosage chamber with a controlled volume in communication with the reactant source vessel and the reaction chamber, wherein the dosage chamber has a first temperature and the reaction chamber has a second temperature; and

a control system configured to separately control the first temperature and the second temperature.

37. The apparatus of claim 36, wherein the reactant source vessel and dosage chamber are located within a temperature controlled environment.

38. The apparatus of claim 36, additionally comprising a first valve for controlling the flow of reactant from the reactant source vessel to the dosage chamber.

39. The apparatus of claim 38, additionally comprising a second valve for controlling the flow of reactant from the dosage chamber to the reaction chamber.

40. The apparatus of claim 36 additionally comprising a second dosage control mechanism.