Source: http://www.google.de/patents/US7294582
Timestamp: 2013-12-10 03:10:33
Document Index: 419185790

Matched Legal Cases: ['arts 541', 'art 541', 'art 542', 'arts 541', 'art 541', 'art 1']

Patent US7294582 - Low temperature silicon compound deposition - Google PatenteSuche Bilder Maps Play YouTube News Gmail Drive Mehr » Erweiterte Patentsuche | Anmelden Erweiterte Patentsuche PatenteSequential processes are conducted in a batch reaction chamber to form ultra high quality silicon-containing compound layers, e.g., silicon nitride layers, at low temperatures. Under reaction rate limited conditions, a silicon layer is deposited on a substrate using trisilane as the silicon precursor....http://www.google.de/patents/US7294582?utm_source=gb-gplus-sharePatent US7294582 - Low temperature silicon compound deposition Ver�ffentlichungsnummerUS7294582 B2PublikationstypErteilung AnmeldenummerUS 11/213,449 Ver�ffentlichungsdatum13. Nov. 2007Eingetragen25. Aug. 2005 Priorit�tsdatum19. Juli 2002Geb�hrenstatusBezahltAuch ver�ffentlicht unterUS20060088985 Ver�ffentlichungsnummer11213449, 213449, US 7294582 B2, US 7294582B2, US-B2-7294582, US7294582 B2, US7294582B2 ErfinderRuben Haverkort, Yuet Mei Wan, Marinus J. De Blank, Cornelius A. van der Jeugd, Jacobus Johannes Beulens, Michael A. Todd, Keith D. Weeks, Christian J. Werkhoven, Christophe F. PomaredeUrspr�nglich Bevollm�chtigterAsm International, N.V.Zitat exportierenBiBTeX, EndNote, RefManPatentzitate (86), Nichtpatentzitate (6), Referenziert von (10), Klassifizierungen (25), Juristische Ereignisse (3) Externe Links: USPTO, USPTO-Zuordnung, EspacenetLow temperature silicon compound depositionUS 7294582 B2 Zusammenfassung Sequential processes are conducted in a batch reaction chamber to form ultra high quality silicon-containing compound layers, e.g., silicon nitride layers, at low temperatures. Under reaction rate limited conditions, a silicon layer is deposited on a substrate using trisilane as the silicon precursor. Trisilane flow is interrupted. A silicon nitride layer is then formed by nitriding the silicon layer with nitrogen radicals, such as by pulsing the plasma power (remote or in situ) on after a trisilane step. The nitrogen radical supply is stopped. Optionally non-activated ammonia is also supplied, continuously or intermittently. If desired, the process is repeated for greater thickness, purging the reactor after each trisilane and silicon compounding step to avoid gas phase reactions, with each cycle producing about 5-7 angstroms of silicon nitride.
Bilder(13) Anspr�che(44)
1. A method of fabricating integrated circuits, comprising:
depositing by chemical vapor deposition a silicon layer of a thickness of more than one monolayer on a plurality of substrates in a hot wall batch process chamber by exposing the substrates to a supply of trisilane;
interrupting the supply of trisilane;
forming a silicon compound layer by exposing the silicon layer to a reactive species after interrupting the supply, wherein the silicon compound layer has a thickness non-uniformity of about 5% or less and a step coverage of about 80% or greater; and
further comprising repeating depositing, interrupted and forming in a plurality of cycles.
2. The method of claim 1, wherein depositing the silicon layer comprises maintaining process conditions selected to achieve reaction rate limited deposition.
3. The method of claim 2, wherein depositing the silicon layer is performed at a temperature of about 600� C. or less.
4. The method of claim 3, wherein the temperature is about 500� C. or less.
5. The method of claim 4, wherein the temperature is about 400-450� C.
6. The method of claim 2, wherein exposing the substrates to the supply of trisilane comprises establishing a trisilane partial pressure of about 10 mTorr or less.
7. The method of claim 6, wherein the trisilane partial pressure is about 3-4 mTorr.
8. The method of claim 2, wherein exposing the substrates to the supply of trisilane comprises exposing the substrates to trisilane for about 30-120 seconds.
9. The method of claim 1, wherein forming the silicon compound layer comprises exposing the silicon layer to plasma-activated reactive species.
10. The method of claim 9, wherein forming the silicon compound layer comprises activating the reactive species in a remote microwave radical generator.
11. The method of claim 9, wherein forming the silicon compound layer comprises activating the reactive species within the batch process chamber.
12. The method of claim 11, wherein activating the reactive species within the batch process chamber comprises supplying current to a conductor coil within the batch process chamber.
13. The method of claim 12, wherein the conductor coil is housed within an evacuated insulating sleeve and reactive species are formed outside the insulating sleeve and within the batch process chamber.
14. The method of claim 9, wherein the plasma-activated reactive species comprises nitrogen radicals.
15. The method of claim 9, further comprising supplying ammonia into the process chamber.
16. The method of claim 15, wherein supplying ammonia comprises first intermixing the ammonia with the plasma-activated reactive species in the process chamber.
17. The method of claim 16, wherein intermixing the ammonia with the plasma-activated reactive species activates the ammonia to form nitrogen radicals from the ammonia.
18. The method of claim 1, wherein depositing the silicon layer comprises forming the silicon layer to a thickness equal to or greater than the nitridation saturation depth.
19. The method of claim 1, wherein the reactive species comprises a nitrogen species and the silicon-containing compound layer comprises silicon nitride.
20. The method of claim 19, wherein the silicon nitride layer is more uniform than a silicon nitride layer of substantially similar thickness deposited by chemical vapor deposition with silane.
21. A method of semiconductor processing, comprising:
establishing reaction rate limited chemical vapor deposition conditions in a hot wall batch reactor chamber;
depositing a silicon layer on each of a plurality of substrates in the chamber by exposing the substrates to a silicon source, wherein the silicon layer has a thickness between about 3 Å and about 30 Å, wherein the silicon source is trisilane;
interrupting flow of the silicon source and removing the silicon source from the batch reactor chamber; and
exposing the silicon layer to radicals to form a silicon compound layer having a thickness non-uniformity of about 5% or less and a step coverage of about 80% or greater,
wherein depositing the silicon layer is performed a plurality of times to deposit a plurality of silicon layers over each of the substrates, wherein trisilane is the silicon source used to deposit a first of the silicon layers.
22. The method of claim 21, wherein the radicals comprise nitrogen and the silicon compound is silicon nitride.
23. The method of claim 21, wherein exposing the silicon layer to radicals comprises exposing the silicon layer to ammonia and plasma-activated radicals.
24. The method of claim 23, wherein the plasma-activated radicals are nitrogen radicals.
25. The method of claim 23, wherein the plasma-activated radicals are one or more species chose from the group consisting of argon, hydrogen and helium radicals.
26. The method of claim 23, wherein exposing the silicon layer to radicals comprises generating the plasma-activated radicals in situ.
27. The method of claim 21, wherein exposing the silicon layer to radicals comprises remotely generating the plasma-activated radicals and supplying the plasma activated-radicals to the reactor chamber.
28. The method of claim 21, wherein exposing the silicon layer to radicals comprises exposing the silicon layer to plasma-activated nitrogen radicals and to one or more species chose from the group consisting of argon, hydrogen and helium radicals.
29. The method of claim 21, wherein depositing, interrupting and exposing comprises continuously flowing N2 into the batch reactor chamber, wherein exposing comprises providing power to a radical generator to generate radicals.
30. The method of claim 29, wherein depositing, interrupting and exposing comprises continuously flowing NH3 into the batch reactor chamber.
31. The method of claim 22, wherein the layer of an insulating silicon compound has a stoichiometry of about 45 silicon atoms per 56 nitrogen atoms.
32. The method of claim 21, wherein the radicals comprise oxygen and wherein the silicon compound is silicon oxide.
33. The method of claim 21, wherein the silicon source for depositing subsequent silicon layers after depositing the first silicon layer comprises one or more silicon precursors selected from the group consisting of silanes having a silane chemical formula SinH2n+2, where n=1 to 4, and halosilanes having a halosilane chemical formula R4-XSiHX, where R=Cl, Br or I and X=0 to 3.
34. The method of claim 33, wherein a first substrate temperature for depositing the first silicon layer is less than about 500� C.
35. The method of claim 21, wherein depositing, interrupting and exposing are performed at a temperature of less than about 600� C.
36. The method of claim 21, wherein depositing the silicon layer comprises providing trisilane through a gas injector.
37. The method of claim 36, wherein the gas injector has a plurality of openings along a height of the batch reactor chamber.
38. The method of claim 21, wherein removing the silicon source comprises purging the process chamber with inert gas.
39. The method of claim 21, wherein removing the silicon source comprises performing one or more removal processes selected from the group consisting of evacuation of the silicon source, or displacement of the silicon source gas by a gas carrying radicals.
40. The method of claim 21, further comprising removing the radicals and exposing the substrates an other reactive species.
41. The method of claim 40, wherein the other reactive species is a dopant.
42. The method of claim 21, wherein exposing the silicon layer to radicals forms a gate dielectric layer.
43. The method of claim 42, further comprising forming a gate electrode over the gate dielectric layer.
44. The method of claim 21, wherein the reaction chamber is configured to accommodate a wafer boat, the wafer boat configured to accommodate the plurality of substrates.
REFERENCE TO RELATED APPLICATIONS This application claims the priority benefit of U.S. Provisional Application Ser. No. 60/605,068, BATCH SYSTEMS FOR LOW TEMPERATURE SILICON COMPOUND DEPOSITION, filed Aug. 27, 2004. This application is also a continuation-in-part of U.S. patent application Ser. No. 10/623,482, filed Jul. 18, 2003, which claims the priority benefit of U.S. Provisional Application Ser. No. 60/397,576, METHOD TO FORM ULTRA HIGH QUALITY SILICON-CONTAINING LAYERS, filed Jul. 19, 2002.
In addition, this application is related to: U.S. patent application Ser. No. 10/074,564, THIN FILMS AND METHODS OF MAKING THEM, filed Feb. 11, 2002; U.S. patent application Ser. No. 10/074,563, IMPROVED PROCESS FOR DEPOSITION OF SEMICONDUCTOR FILMS, filed Feb. 11, 2002; U.S. Provisional Application Ser. No. 60/659,454, HIGH STRESS NITRIDE AND METHOD FOR FORMATION THEREOF, filed Mar. 7, 2005; and U.S. patent application Ser. No. 11/212,503, REMOTE PLASMA ACTIVATED NITRIDATION, filed Aug. 24, 2005, all of which are hereby incorporated by reference in their entireties.
FIELD OF THE INVENTION This invention relates generally to forming silicon-containing layers during integrated circuit fabrication and, more particularly, to methods for forming uniform silicon compound layers by reaction rate limited processing.
In contrast to CVD, ALD molecular precursors used to produce a compound layer, i.e., a layer comprising two or more elements, are typically introduced into the ALD reactor in separate pulses. For example, a first precursor self-limitingly adsorbs on the substrate in a first pulse, with ligands of the adsorbed species preventing further adsorption. Between introduction of precursors, the reaction chamber is evacuated or purged with inert gas to prevent gas phase reactions between the different precursors. After purging of the first precursor, a second precursor can be introduced into the reaction chamber to react with the layer deposited by introduction of the first precursor, e.g., to strip the ligands or to replace the ligands. In this way, one cycle is completed and one thin compound layer is deposited on a substrate. After the layer is reacted with the second precursor, the second precursor (and any byproduct) can be removed by evacuation or inert gas purging. In addition to these precursors, other reactants can also be pulsed into the reaction chamber during each cycle. The cycle can then be repeated until a compound layer of a desired thickness is reached.
Nevertheless, high conformality and uniformity are important considerations as semiconductor fabrication currently involves depositing silicon-containing compound films during the process of making thousands or even millions of devices simultaneously on a substrate that is 200 millimeters (mm) in diameter. Moreover, the industry is transitioning to 300 mm wafers, and could use even larger wafers in the future. In addition, even larger substrates, in the form of flat panel displays, etc., are becoming increasingly common. Significant variations in the thickness and/or composition of the silicon-containing compound films during the manufacturing process can lead to lower manufacturing yields when the affected devices do not meet required performance specifications. Also, variations across the film within a particular device can reduce device performance and/or reliability. Thus, as substrate sizes increase to accommodate manufacture of larger numbers of microelectronic devices on a circuit, the problems created by the shortcomings of conventional CVD processes also increase.
SUMMARY OF THE INVENTION In accordance with one aspect of the invention, a method is provided for fabricating integrated circuits. The method comprises depositing a silicon layer on a plurality of substrates in a batch process chamber by exposing the substrates to a supply of trisilane. The supply of trisilane is interrupted. A silicon compound layer is formed by exposing the silicon layer to a reactive species after interrupting the supply of trisilane.
In accordance with yet another aspect of the invention, a method of semiconductor processing is provided. The method comprises establishing reaction rate limited deposition conditions in a reaction chamber. A silicon layer is deposited on each of a plurality of substrates in the reaction chamber by exposing the substrates to a silicon source. The silicon layer has a thickness between about 3 Å and about 30 Å. The silicon source is a polysilane. The flow of the silicon source is interrupted and the silicon source is removed from the reaction chamber. The silicon layer is exposed to radicals to form a silicon compound layer.
In another aspect of the invention, a semiconductor reactor is provided. The reactor comprises a process chamber and an evacuated tube inside the process chamber. The tube is formed by an insulating sleeve, which houses a coil of conductive material connected to a power source. The tube is configured to produce a plasma outside the sleeve but inside the process chamber.
FIG. 1 is a schematic cross-sectional side view of an elongated batch process tube with a gas injector, constructed in accordance with preferred embodiments of the invention;
FIG. 2 is a front view of a gas injector for use with the batch process tube of FIG. 1;
FIG. 3 is a horizontal cross-sectional view of the gas injector of FIG. 2;
FIG. 4 is a schematic side view of a batch reactor with a remote plasma generator for supplying plasma products to the process tube, in accordance with preferred embodiments of the invention;
FIG. 5 is a schematic cross section of an in situ plasma source within a batch reaction tube, in accordance with another embodiment of the invention;
FIG. 6 is an enlarged schematic cross section of the in situ plasma source of FIG. 5;
FIG. 7 is a flow chart showing steps for forming silicon-containing compound layers, in accordance with preferred embodiments of the invention;
FIG. 8A illustrates a substrate after wafer cleaning, in accordance with preferred embodiments of the invention;
FIG. 8B illustrates the substrate of FIG. 8A after formation of a silicon oxide layer, in accordance with preferred embodiments of the invention;
FIG. 8C illustrates a silicon nitride layer formed over the silicon oxide layer of FIG. 8B, in accordance with preferred embodiments of the invention;
FIG. 8D illustrates the silicon nitride layer of FIG. 8C made thicker by formation of subsequent silicon nitride layers over the silicon nitride layer of FIG. 8C, in accordance with preferred embodiments of the invention;
FIG. 8E illustrates a gate electrode formed after the silicon nitride layer of FIG. 8D has been formed to a preferred thickness, in accordance with preferred embodiments of the invention;
FIG. 9 is a flow chart showing a process for forming silicon nitride in a batch reactor, in accordance with some preferred embodiments of the present invention;
FIG. 10 is a graph illustrating thickness and refractive index (RI) for deposited silicon nitride layers, in accordance with some preferred embodiments of the present invention; and
FIG. 11 is a graph illustrating the thickness for silicon layers deposited in a batch reactor using four different nitridation conditions, in accordance with some preferred embodiments of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS International patent publication No. WO 04009861 A2, to Todd et al., which claims priority to the above-incorporated U.S. patent application Ser. No. 10/623,482, filed Jul. 16, 2002, discloses one method of depositing silicon nitride to form highly uniform and conformal films. Todd et al. teaches trisilane and nitrogen source pulses that are alternated with intervening purge steps. Todd et al., however, emphasizes the importance of the mass flow limited regime for such deposition.
It will be appreciated that high quality results in the mass flow limited regime is more easily achieved in the context of single substrate reactors than in batch systems. Batch systems, while advantageously allowing for increased throughput by simultaneously processing a plurality of substrates, can encounter difficulties in achieving an even distribution of precursor vapors across all substrates within the reaction chamber. Because the local deposition rate in a mass flow limited regime is dependent upon the local concentration of precursor, an uneven distribution of precursors can result in an uneven deposition rate across a substrate or across a batch of substrates. In turn, the uneven deposition rate can result in non-uniform layers. On the other hand, batch systems can often employ principles of hot wall reactors to achieve highly uniform temperature distributions. Accordingly, rather than the mass transport limited regime, depositions according to the preferred embodiments are preferably conducted under reaction rate limited conditions, also known as the kinetically limited reaction regime or kinetic regime, wherein deposition rates are sensitive to temperature changes but relatively insensitive to supplied reactant concentrations.
Depositions according to the preferred embodiments allow for the formation of highly uniform and conformal silicon-containing compound layers, particularly for batch processing. A silicon precursor is flowed into a batch process chamber to deposit a silicon layer. The silicon precursor is then removed from the chamber, e.g., by evacuation or by purging with another gas, such as a purge gas. Another precursor is flowed into the chamber to react with the silicon layer, thereby forming a silicon compound layer. The other precursor is then removed from the chamber. This sequence of flowing and removing precursors from the chamber can be repeated as desired to form a silicon-containing compound layer of a desired thickness. Deposition conditions are preferably chosen such that the formation of the silicon-containing compound layer occurs in the kinetic regime.
Preferably, the silicon precursor is a silane, more preferably, a polysilane (a silane having the chemical formula SinH2n+2, where n=2 to 4) and, most preferably, the polysilane is trisilane. To form silicon nitride, the other precursor is a nitrogen species, e.g., an excited nitrogen species, including nitrogen radicals. The excited nitrogen species can be generated by a remote or in situ plasma. In some preferred embodiments, the flow of excited nitrogen species is intermixed with a flow of ammonia. In other preferred embodiments, the flow of ammonia is intermixed with a flow of an excited species which is not a nitrogen species. Unexpectedly, combining ammonia with an excited species has been found to advantageously increase the quality, especially the uniformity, of deposited films.
Thus, depositions according to the preferred embodiments advantageously allow for the formation of very uniform and conformal films, as discussed further below.
FIGS. 1-6 illustrate two different versions of an exemplary batch reactor, commercially available under the trade name Advance 412� or A412� from ASM International N.V. of Bilthoven, The Netherlands. The illustrated reactor is a vertical furnace type of reactor, which has benefits for efficient heating and loading sequences, but the skilled artisan will appreciate that the principles and advantages disclosed herein will have application to other types of reactors.
With reference to FIG. 1, a schematic cross-sectional side-view is shown of an exemplary elongated furnace with a gas injector. The process tube or chamber 526 is preferably surrounded by a heating element (not shown). A liner 528, delimiting the outer perimeter of the reaction space 529, is preferably provided inside the process chamber 526. Preferably, at the bottom of the process chamber 526, a wafer load 550 may enter and exit the process chamber 526 by a door 530. Precursor source gas is injected through a gas injector 540, preferably via a gas feed conduit 544. The gas injector 540 is provided with a pattern of holes 548, preferably extending substantially over the height of the wafer load 550. Note that, because gases are first introduced into the reaction space 529 from the holes 548 of the gas injector 540, the interior of gas delivery devices, such as the gas injector 540, through which gases travel is not part of the reaction space 529 and is, in a sense, outside of the reaction space 529. Consequently, the reaction space 529 comprises the interior volume of the process chamber 526, excluding the volume occupied by gas delivery devices such as the gas injector 540.
In a preferred embodiment, inside the process chamber 526, gas is flowed in a generally upward direction 552 and then removed from the reaction space 529 via an exhaust space 554 between the process chamber 526 and the liner 528, where gas flows in a downward direction 556 to the exhaust 558, which is connected to a pump (not shown). The gas injector 540 preferably distributes process gases inside the process chamber 526 over the entire height of the reaction space 529. The gas injector 540 itself acts as a restriction on the flow of gas, such that the holes 548 that are closer to the conduit 544 tend to inject more gas into the reaction space than those holes 548 that are farther from the conduit 544. Preferably, this tendency for differences in gas flows through the holes 548 can be compensated to an extent by reducing the distance between the holes 548 (i.e., increasing the density of the holes 548) as they are located farther away from the conduit 544. In other embodiments, the size of individual holes making up the holes 548 can increase with increasing distance from the conduit 544, or both the size of the holes 548 can increase and also the distance between the holes 48 can decrease with increasing distance from the conduit 544. Advantageously, however, the preferred embodiments are illustrated with holes 548 of constant size so as to minimize the surface area of the sides of the gas injector 540 containing the holes 548.
The gas injector 540 in accordance with one illustrative embodiment of the invention is shown in FIG. 2. The gas injector 540 preferably comprises two gas injector parts 541 and 542, each preferably provided with separate gas feed conduit connections 545 and 546, respectively. The first part 541 injects gas into the lower volume of the reaction space 529 (FIG. 1) and the second part 542 injects gas into the upper volume of the reaction space 529 (FIG. 1). The parts 541 and 542 are connected by linkages 549 and 551. At its top end, the gas injector 540 can be provided with a hook 553, to secure the top end of the gas injector 540 to a hook support inside the chamber 526 (FIG. 1).
The cross-section shown in FIG. 3 is taken through the lower end of the gas injector 540 and straight through a pair of injection holes 548 provided in gas injector part 541, for injecting the gas into the lower end of the process chamber 526. Preferably, in each gas injector part, the holes 548 are provided in pairs, at the same height. In addition, the two holes 548 preferably inject the precursor gas in two directions 566 and 568 forming an angle 570 of between about 60 and 120 degrees, illustrated at about 90 degrees, to improve the radial uniformity. Moreover, as shown, the tubes comprising the gas injector 540 preferably have an oblong shape, as viewed in horizontal cross-section. Preferably, the longer dimension of the oblong shape faces the center of the process chamber 526, i.e., the side of the oblong shape with the longer dimension is perpendicular to an imaginary line extending radially from the center of the process chamber 526.
In a preferred embodiment, in a CVD mode, two precursor source gases, providing the two constituting elements of a binary film, are mixed in the gas supply system (not shown) prior to entering the gas injector 540 via feed conduit connections 545 and 546 (FIG. 2). Pre-mixing the precursor gases in the gas supply system is one way to ensure a homogeneous composition of injected gas over the height of the boat. However, the gases can be flowed into the process chamber 526 (FIG. 1) without pre-mixing. In another embodiment, the two precursor source gases can each be injected via their own separate gas injectors 540 (not shown), so that they are first mixed after being injected into the reaction space 529. Consequently, it will be appreciated that more than one gas injector 540 may be located inside the process chamber 526.
With reference to FIG. 4, a process tube 526 is shown in relation to a remote plasma generator. The illustrated remote plasma unit comprises a microwave radical generator (MRG) commercially available from MKS Instruments of Wilmington, Mass., USA, and includes a microwave power generator 580 coupled to a plasma cavity or applicator 582 through which a source of reactant flows during operation. Microwave power is coupled from the power generator 580 through a waveguide 584 to the plasma cavity 582. The reactant source, preferably a source of nitrogen in the illustrated embodiments and, most preferably, diatomic nitrogen gas (N2), flows through the plasma cavity 582 during operation and plasma products are carried to the process chamber 526 by way of a conduit 586. The conduit materials and length are preferably optimized to maximize the delivery of neutral nitrogen species (N) while minimizing recombination into N2 and minimizing delivery of ions, as will be appreciated by the skilled artisan. The conduit can lead to a gas injector of the type illustrated in FIGS. 1-3, or can lead to a more conventional gas inlet, such as in the bottom flange of the process tube 526 from which plasma products (and other reactants) flow upwardly and diffuse laterally across the substrate surfaces.
The use of a remote MRG unit is particularly applicable to the pulsed silicon precursor process of the preferred embodiments. Unlike most batch processes, the nitridation (or other compound forming step) of the preferred embodiments is a self-limiting process in the kinetic regime, such that uniformity of radical distribution within the process chamber 526 is not essential. Over-reaction is not a concern from a result point of view. Nevertheless, non-uniformity of radical distribution is disadvantageous because it will prolong the nitridation process; nitridation would be conducted for a longer time to ensure complete nitridation across each wafer at every vertical position within the process chamber 526. Furthermore, aside from uniformity issues, the distance traversed from the plasma cavity 582 to the process chamber 526, and within the process chamber 526 to reach each wafer, leads to a relatively low radical survival rate due to collisions en route that cause recombination.
With reference to FIG. 5, an in situ plasma source 590 can be provided within the process chamber 526 to improve distribution of radicals across the wafers 550. Preferably the plasma source extends more than about half the height of the process chamber 526 (FIG. 1), more preferably extending at least about 90% of the height of the wafer stack 550 within the process chamber 526.
With reference to FIG. 6, the plasma source 590 includes a conductor coil 592, formed of, e.g., copper, sealed within an insulating sleeve 594, formed of, e.g., quartz or, more preferably, sapphire. Optionally, a conductive core 596, formed of, e.g., iron or ferrite, is also included. The volume (FIG. 1) defined by the insulating sleeve 594 is preferably evacuated to avoid plasma generation within the insulating sleeve 594.
In operation, a current is applied to the coil. A readily available radio frequency (RF) power source, e.g., 13.56 MHz, can be employed for this purpose. Process gases surrounding the plasma source 590, outside the insulating sleeve 594, but inside the process chamber 526 (FIG. 1), are ignited in an annulus surrounding the plasma source 590. Due to the proximity to the wafers 550, lower power can be employed, compared to use of a remote plasma generator. Symmetry of distribution across the wafers can be provided by rotating the wafer boat during operation.
Preferred Silicon Precursor
Preferably, a polysilane is used as the silicon precursor to form the silicon layer, discussed below. As used herein, a �polysilane� has the chemical formula SinH2n+2, where n=2 to 4. Preferably, the polysilane is disilane or trisilane. Most preferably, the polysilane is trisilane. Consequently, while the invention is described in the context of particularly preferred embodiments employing CVD cycles with trisilane, the skilled artisan will appreciate, in view of the present disclosure, that certain advantages of the described processes can be obtained with other precursors and/or other deposition techniques.
Trisilane (H3SiSiH2SiH3 or Si3H8) offers substantial benefits when used as a silicon precursor, as disclosed in U.S. application Ser. No. 10/623,482, filed Jul. 18, 2003; U.S. application Ser. No. 10/074,564, filed Feb. 11, 2002; and published PCT Application WO 02/064,853, published Aug. 2, 2002, the disclosures of which are hereby incorporated by reference in their entireties. For example, films can be deposited with trisilane at substantially lower temperatures than with other silicon precursors, such as silane (SiH4). Moreover, deposition rates with trisilane are relatively insensitive to substrate material and thickness. Also, trisilane has an extremely short film nucleation time, which reduces the size of localized crystalline deposits of silicon. As a result, deposited silicon films can be made thinner, while still being uniform. Moreover, the films will show reduced surface roughness due to the reduced size of the localized silicon deposits.
As described in greater detail below, in forming a silicon-containing compound layer, a thin silicon layer is first deposited on a substrate by exposing the substrate to a silicon precursor. The silicon layer can then be reacted with another reactive species to form a silicon-containing compound layer. Multiple sequential cycles of these depositions and reactions can be performed to build up a silicon-containing compound layer to a desired thickness.
FIG. 7 shows a general process sequence in accordance with preferred embodiments of the invention. A substrate is provided in a process chamber and all sequence steps are preferably performed in situ in that process chamber. �Substrate� is used herein in its usual sense to include any underlying surface onto which a silicon-containing material is deposited or applied in accordance with the preferred embodiments of the present invention. Preferred substrates can be made of virtually any material, including without limitation metal, silicon, germanium, plastic, and/or glass, preferably silicon compounds (including Si�O�C�H low dielectric constant films) and silicon alloys. Substrates can also have in them physical structures such as trenches or steps, as in a partially fabricated integrated circuit.
In step 100, a silicon layer is deposited on a substrate by exposing the substrate to a silicon precursor. The silicon precursor is preferably a silane, more preferably, a polysilane and, most preferably, trisilane. The silicon precursor is preferably introduced into the process chamber in the form of a feed gas or as a component of a feed gas. The feed gas can include gases other than the silicon precursor, such as inert carrier gases. The carrier gas can comprise carrier gases known in the art, such as nitrogen, hydrogen, helium, argon, or various combinations thereof. Preferably, nitrogen is used as the carrier gas. Where the silicon precursor is trisilane, the trisilane is preferably introduced into the chamber by way of a bubbler used with a carrier gas to entrain trisilane vapor, more preferably, a temperature controlled bubbler is utilized.
In forming 100 the silicon layer, deposition from a silicon precursor can be conducted according to various deposition methods known to those skilled in the art, but the greatest benefits are obtained when deposition is conducted according to the CVD methods taught herein. The disclosed methods can be practiced by employing CVD, including plasma-enhanced chemical vapor deposition (PECVD) or, more preferably, thermal CVD.
It will be appreciated that a reaction kinetics limited regime is primarily achieved by use of a relatively low temperature. This results in a reduced film deposition rate that is preferable in a batch furnace. Because of the large batch size, an adequate throughput can still be achieved at a deposition rate that results from temperatures shifted down into the reaction rate limited regime. Advantageously, trisilane enables acceptable deposition rates at very low temperatures, allowing a considerably reduced consumption of thermal budgets. As the skilled artisan will readily appreciate, thermal budgets are constantly reduced as critical dimensions are scaled down, tolerances for diffusion are reduced, and new materials with lower resistance to thermal processing are introduced. The process is preferably operated at a temperature below about 600� C. and, more preferably, at a temperature below about 500� C., and, even more preferably, at a temperature between about 300� C. and about 500� C.
The thickness of the film formed in Step 100 can be varied according to the intended application, as known in the art, by varying the deposition time and/or gas flow rates for a given set of deposition parameters (e.g., total pressure and temperature). For a particular set of deposition conditions, the duration of silicon deposition for silicon layer formation 100 is preferably chosen so that a thin silicon layer is formed. By forming thin and uniform silicon layers, the layers can be easily fully reacted, allowing for the formation of uniform silicon-containing compound layers. Preferably, the thickness of the silicon layer is more than a monolayer of silicon, but is less than about 20 Å and, more preferably, less than about 10 Å.
With continued reference to FIG. 7, after silicon layer formation 100, any excess silicon precursor and byproduct is removed 110 from the process chamber. Silicon precursor removal 110 can occur by any one, or any combination of removal processes, including the following: purging of the process chamber with inert gas, evacuation of the silicon precursor, or displacement of the silicon precursor gas by a gas carrying a reactive species. Where silicon precursor gas removal 110 is performed by purging, the process chamber is preferably purged for a duration long enough to replace the atmosphere in the chamber at least once.
It will be appreciated that silicon precursor gas removal 110 is preferably performed such that the quantity of a particular reactant in the process chamber is at a level sufficiently low as to minimize unwanted side reactions with the next reactant to enter the chamber. This, in turn, minimizes undesirable incorporation of impurities in the silicon-containing compound layers that are formed. Such a low level of reactants can be achieved by, for example, optimizing the duration of a purge or evacuation of the reaction chamber. At such a level, the process chamber can be said to be substantially free of a particular reactant.
With continued reference to FIG. 7, after silicon precursor gas removal 110, the silicon layer can be reacted 120 with a reactive species to form a silicon-containing compound layer. The silicon-containing compound layer can be formed by introduction of the reactive species into the process chamber. Preferably, the reaction conditions are chosen to completely react the silicon layer and to avoid damage to underlying structures, e.g., as discussed in more detail herein with respect to the formation of silicon nitride layers. The reactive species can include, as noted, a reactive nitrogen species for forming silicon nitride layers, or a reactive oxygen species for forming silicon oxide layers. Exemplary reactive nitrogen species include chemical species such as (H3Si)3N (trisilylamine), ammonia, atomic nitrogen, hydrazine (H2N2), hydrazoic acid (HN3), NF3, mixtures of the foregoing and dilutions of the foregoing with inert gases (e.g., H2, N2, Ar, He). More preferably, nitrogen radicals and/or ammonia are the reactive nitrogen species, as discussed below.
With continued reference to FIG. 7, after formation of the silicon-containing compound layers 120, reactant removal 130 can be performed using any of the methods described above for silicon precursor removal 110. It will be appreciated, however, that Steps 110 and 130 need not occur by exactly the same methods, e.g., one step can involve purging, while the other can involve evacuating.
Accordingly, performance of the steps 100, 110, 120, and 130 comprises one cycle 140 and deposits one layer of a silicon-containing compound on a substrate. The cycle 140 can then be repeated until the silicon-containing compound layers are built up to a desired thickness.
It will be appreciated that various other layers can be formed over the deposited silicon compound layer. For example, where the silicon compound layer is a silicon nitride which forms a gate dielectric, a gate electrode can be formed over the gate dielectric, by methods known in the art.
Referring to FIGS. 8A through 8E, the result of the above-described process, applied to forming a gate dielectric, is shown in stylized illustrations. FIG. 8A illustrates a substrate 400 after wafer cleaning. It will be appreciated that wafer cleaning prior to a deposition can be performed by various ex situ and in situ methods known in the art. FIG. 8B illustrates an interfacial layer 410 is formed over the substrate 400 to improve electrical performance of the deposited layers. The interfacial layer 410 can be, e.g., a silicon oxide layer, which is formed ex situ or in situ according to methods known in the art, including but not limited to thermal or chemical oxidation or other methods involving exposing the substrate to oxidant. FIG. 8C illustrates a silicon nitride layer 420 formed by performing a first cycle 140 (FIG. 7) over the interfacial layer 410. FIG. 8D illustrates the silicon nitride layer 420 made thicker by subsequent additional performances of cycles 140 (FIG. 7). FIG. 8E illustrates a subsequently formed gate electrode 430.
It will be appreciated that in some embodiments, the silicon-containing compound layer can subsequently be reacted after step 130 (FIG. 7) in each cycle 140, or after completing all cycles 140. For example, silicon-containing compound layers that serve as semiconductors (e.g., SiGe) can subsequently be doped. In another example, a silicon oxynitride (SiOxNy) layer can be formed from a silicon nitride layer by introducing an oxygen source to oxidize the silicon nitride, to form silicon oxynitride. It will be appreciated that such a silicon oxynitride layer can be used as an interfacial layer for forming dielectric layers in place of the silicon oxide layer described above with reference to FIGS. 8A to 8E. Silicon carbide nitride (SiCxNy) or silicon oxycarbide (SiOxCy) can similarly be formed by a subsequent carbonization, nitridation or oxidation step.
In some embodiments, different silicon sources can be used in different cycles 140 (FIG. 7). For example, trisilane can be used as the silicon precursor for one cycle, and disilane can be used for another cycle. Preferably, trisilane is used to form at least the first silicon layer deposited on a substrate in the first performance of cycles 140 (FIG. 7). Subsequent silicon layers can be formed using, e.g., halosilanes (i.e., silicon compounds having the chemical formula R4−XSiHX, where R=Cl, Br or I and X=0 to 3) or other silanes (SinH2n+2 where n=1 to 4, with n≧2 preferred). It will also be appreciated that combinations of silicon precursors can be used, e.g., trisilane and disilane can be used simultaneously after forming the first silicon layer.
It will be further appreciated that the temperatures for Steps 100 (FIG. 7) for each cycle 140 is preferably isothermal, but can also vary for different cycles 140. For example, a silicon layer formation 100 can occur at a first temperature that is less than about 525� C., preferably less than about 500� C., and most preferably less than about 475� C. Preferably, the layer is then allowed to stand for several seconds to allow for complete elimination of the hydrogen from the as-deposited silicon layer, prior to forming a silicon-containing compound layer 120 (FIG. 7). Preferably, the layer is allowed to stand for more than 10 seconds. For formation of the silicon-containing compound layer 120 (FIG. 7), the temperature is then increased to a second temperature that is higher than the first temperature. Preferably, subsequent cycles 140 (FIG. 7) are performed isothermally at this second higher temperature to deposited a silicon-containing compound layer of a desired thickness. Such a process is particularly useful for silicon nitride film deposition on substrate surfaces other than crystalline silicon (e.g., SiO2, low dielectric constant spin on glass materials, metal oxides, metal silicates and metals), as the low temperature and hydrogen elimination period give a film with low hydrogen content at the interface with the substrate surface. Advantageously, the higher temperatures for subsequent deposition cycles allows for faster depositions and increased throughput after formation of the low hydrogen interface.
It will also be appreciated that any of the steps or combinations of the steps 100-130 in a cycle 140 can be performed a plurality of times before progressing to the next step. For example, a plurality of silicon precursor pulses, each followed by a silicon precursor source removal, can be performed to form a silicon layer, before the silicon layer is reacted to form a silicon-containing compound layer. Similarly, a plurality of reactive species pulses, each followed for a reactive species removal, can be performed to react the silicon layer to form a silicon-containing compound layer, before or without forming another silicon layer.
Deposition of Silicon Nitride Films
FIG. 9 illustrates a process for the deposition of silicon nitride layers, in a manner more particular in certain aspects to the use of radicals for reacting with the trisilane-enabled silicon layer and for forming the silicon compound layer.
With reference to FIG. 9, a silicon layer is first deposited 690 by flowing trisilane. As noted, process conditions are arranged for deposition in the kinetic regime. The process is preferably operated at a temperature below about 600� C. and, more preferably, at a temperature below about 500� C., and, even more preferably, at a temperature between about 400-450� C. In addition, the reactant supply or partial pressure of trisilane is set at a sufficiently low level to maintain the deposition in the kinetic regime. As long as the reaction rate is slower than the rate at which reactant is supplied, uniformity in a properly tuned batch furnace (in which uniform temperatures can be maintained) is excellent. Reference is made to Sze, VLSI TECHNOLOGY, pp. 240-41 (1988), the disclosure of which is incorporated herein by reference. In the illustrated batch reactors, process pressure is maintained at about 10 Torr or below and more preferably about 1 Torr or below. In order to maintain reaction rate limited deposition, trisilane preferably is supplied at less than about 100 sccm trisilane, and, more preferably, at less than about 20 sccm. The trisilane is typically diluted with a flow of a non-reactive or inert gas such as N2, H2, Ar or He. The trisilane partial pressure is thus preferably below about 10 mTorr, more preferably, about 3-4 mTorr. Preferably, the trisilane step 690 has a duration of about 30-120 seconds. Preferably, about 3-30 Å of silicon are deposited in the deposition step 690, more preferably, about 3-8 Å and, most preferably, about 4-5 Å.
Preferably, the thickness of the deposited silicon layer thickness is chosen based upon nitridation conditions in the step 694, discussed below. This is because, during nitridation of a silicon layer, atomic nitrogen can diffuse through the silicon layer and into the underlying silicon substrate. The depth of this nitrogen diffusion can be measured, as known in the art, and is related to various process conditions, including nitridation temperature and duration of nitridation. Thus, for a given set of process conditions, atomic nitrogen will diffuse into, and possibly through, the silicon layer to a particular depth, called the nitridation saturation depth. When nitridation occurs for less than about one minute, the nitridation saturation depth can be termed the short-term nitridation saturation depth.
The nitridation of the underlying substrate has been found to result in silicon nitride layers with dielectric properties which are inferior to what is theoretically expected. Thus, to improve the dielectric properties of deposited silicon nitride films, nitridation of the underlying substrate is preferably minimized, preferably by depositing the first silicon layer formed over a substrate to a thickness equal to or greater than the nitridation saturation depth. It will be appreciated that subsequently deposited layers will typically be spaced farther from the substrate than the nitridation saturation depth, as a consequence of being deposited over this first silicon layer. As a consequence, the thickness of silicon layers deposited after the first layer preferably are less than or equal to the nitridation saturation depth.
For a given set of nitridation conditions, however, after forming the first silicon layer, silicon layers formed in subsequent cycles can be thinner since the nitridation saturation depth remains relatively constant while the silicon nitride layer thickness increases. For example, the first silicon layer can be deposited to about the nitridation saturation depth, e.g., about 8 to 20 Å, and subsequent layers can be deposited to a thinner thickness, e.g., about 3 Å to 10 Å per cycle. In addition to varying the thickness of the silicon layer, it will be appreciated that other process conditions, such as the nitridation temperature and/or the duration of nitridation, can be varied so that the nitridation saturation depth is not deeper than the thickness of the silicon layer.
After the deposition step 690, trisilane flow is interrupted. In the illustrated embodiment the reactor is purged 692, preferably for 10 seconds to 5 minutes, and most preferably for about 20-40 seconds. Purging 692 avoids interaction between the trisilane and the subsequent radicals, which can undesirably cause gas phase reactions and particles. An exemplary purge flow for a batch reactor is 5 slm N2. While other non-reactive gases can be used, N2 has particular advantages for efficiency in the nitridation process described herein.
Subsequently activated species are supplied to react with the thin silicon layer left by the deposition step 690. In the illustrated embodiment, nitrogen gas (N2) has been flowing in prior purge step 692. Accordingly, the activated species can be supplied by simply continuing the N2 flow and turning on plasma power 694 to activate nitrogen radicals. The skilled artisan will appreciate that the same can be true of many other reactants that are non-reactive under the very low temperature conditions that are preferred for the trisilane deposition, but that can be activated by turning on plasma power to form radicals that react with the silicon layer and form a silicon compound. Additionally, the plasma power can be turned on for a remote plasma generator (FIG. 4) or for an in situ plasma source (FIGS. 5-6).
In a preferred embodiment, the nitrogen radicals are generated by the application of high frequency electrical power. In a preferred embodiment, this high frequency is in the GHz range. In one example, the nitrogen radicals are generated in a remote microwave radical generator (MRG) from MKS Instruments by flowing 1 to 5 slm N2 through the MRG under the application of 3 kW microwave power at 2.45 GHz. Optionally, the remotely generated radicals can be distributed over the entire wafer load by the use of one or more gas injectors. Alternatively, the nitrogen radicals can also be generated inside the furnace chamber, preferably over the entire length of the vertically elongated chamber. This can be achieved by the coupling of high frequency electrical power into the process tube. In the embodiment of FIGS. 5 and 6, this coupling occurs through a coil 592 that is inserted into the process chamber 529 (FIG. 1). As noted above, the coil 592 is preferably placed inside a protective sleeve 594 of electrically insulating material, and this sleeve 594 is preferably evacuated to pressures below about 100 mTorr to avoid the generation of plasma inside the sleeve 594.
During radical reaction step 694, the pressure is typically about 1 Torr. For N radicals generated from N2 gas, for example, the nitridation time is typically 5 to 10 minutes. Depending upon the thickness of the silicon formed by the deposition step 690, the thickness of the silicon compound (nitride in this case) formed is preferably about 5-40 Å, more preferably, about 5-11 Å, and, most preferably, about 5-7 Å.
Preferably, nitridation of the silicon layers is complete and results in a substantially perfect stoichiometry in the reaction of the silicon layer with the reactive nitrogen species. Such a complete reaction allows less incorporated impurities, denser films, and improved thickness control and step coverage. In addition, the deposited silicon nitride layers have improved insulating properties, and can be made thicker than conventional insulating thin films, increasing the effectiveness of these deposited layers as diffusion barriers.
After complete reaction of the thin silicon layer to form a compound silicon layer, the plasma power is switched off 696. In the case of N2 gas, switching off the plasma power while continuing the N2 flow leads to purging, and the radicals die off rapidly without the power on, such that reaction with any subsequent trisilane step 690 can be readily avoided.
Optionally, the steps 690-696 can be repeated 698 as many times as desired, with each cycle depositing 690 a layer of silicon thin enough that it can be quickly and fully reacted by radicals in step 696. For trisilane pulses of 1.5 min, a film thickness of 5-6 Å nitride is created in one cycle of silicon deposition and nitridation.
It will be appreciated that formation 594 of the silicon-compound layer can include reaction of the silicon layer with more than one reactive species, even where the atomic species of interest for the different reactive species is the same. For example, for nitridation, a beneficial effect was observed by the use of an NH3 flow in addition to a nitrogen radical flow. This NH3 was fed directly into the process tube, rather than via the radical generator. Although non-activated NH3 hardly reacts with silicon at temperatures below 500� C., it was noted that the addition of non-activated NH3 to the nitrogen radicals resulted in a more fully nitridized amorphous silicon layer. Without wishing to limited by theory, it is believed that the nitrogen radicals from a remote plasma generator activate the ammonia within the process chamber. In contrast, N radicals alone leave a slightly silicon-rich silicon nitride film. Interestingly, ammonia provided through the remote MRG actually decreased the nitridation effect, even relative to N radicals alone.
FIG. 10 illustrates the results of experiments, in a batch A412� reactor from ASM International N.V. of Bilthoven, The Netherlands, in which substrates were maintained at about 435� C. and the wafer boat was rotated at 5 rpm. Reaction rate limited deposition conditions were established. In silicon deposition pulses of 1.5 minutes, trisilane was provided through the inlet at the bottom of the reactor to produce a trisilane partial pressure of about 3.3 mTorr. N2 was provided through an MRG at a rate of 5 slm. After trisilane flow was interrupted and purged for about 30 seconds, remote plasma power was turned on at a level of 3,000 W for about 10 minutes. In addition, a flow of 1 slm NH3 was provided through the bottom of the process chamber. During the nitridation step, the pressure in the reaction chamber is typically 1 Torr. Fifty cycles were performed to form a silicon nitride layer having a thickness of about 257 Å.
The flow of nitrogen radicals is applied alternatingly with the flow of trisilane. When the nitrogen radicals are flowing simultaneously with the trisilane, gas phase reactions tend to occur resulting in the undesirable formation of particles and non-uniform films. The flow of NH3, if any, can be applied alternatingly with the flow of trisilane or can be applied in a continuous fashion, so that the NH3 is also flowing during the trisilane pulses. As noted, since N2 and NH3 are non-activated when the plasma power is off (purge steps and silicon deposition steps), neither gas reacts very much under the preferred temperature conditions in the absence of plasma power, and benefits can be obtained by a constant supply of the gases, such as avoidance of pressure fluctuation.
While in the experiments all gases were provided through the bottom of the vertical reactor and exhausted from the top, it will be understood in view of the present disclosure that benefits can be obtained by other injection arrangements. Optionally, the process gases can also be injected via gas injection tubes or multiple hole injectors (see FIGS. 2-3) to improve the uniformity over the entire batch. In the case where trisilane is provided through such injectors, N2 can also be provided through the same injectors, acting as a carrier gas during trisilane pulses and as a reactant (whether remotely activated or activated in situ) during nitridation (or other reaction) pulses, and as a purge gas between the trisilane and the nitrogen pulses. Under the low temperatures of the preferred embodiments, ammonia can also be provided simultaneously or intermittently (with plasma power) through the injector or through the bottom inlet.
As noted above, although the process is described using a nitride film deposition process as an example, it will be clear that other silicon compound layers can be deposited in this manner such as silicon carbide, silicon oxide, silicon oxynitride and silicon germanium layers. In such embodiments, the deposited silicon film from a trisilane step is carbonized, oxidized, oxynitrided or exposed to germanium precursors in between successive trisilane pulses. For example, silicon oxides can also be formed by introducing an oxygen source during formation of a silicon-containing compound layer 120 (FIG. 7), rather than introducing a nitrogen source. The oxygen source can include oxidants known in the art including, but not limited to, atomic oxygen, water, ozone, oxygen, nitric oxide, and nitrous oxide.
One skilled in the art will appreciate that further modifications to the batch reactor, or to the way of operating the batch reactor, known in the art, can be applied to improve the performance of this process. For example, it is possible to use a holder boat or ring boat to improve the uniformity of film deposition over each wafer.
Desirably, preferred silicon-containing compound films according to the preferred embodiments have a thickness that is highly uniform across the surface of the film. Film thickness uniformity is preferably determined by making multiple-point thickness measurements, e.g., by ellipsometry or cross-sectioning, determining the mean thickness by averaging the various thickness measurements, and determining the rms thickness variability. To enable comparisons over a given surface area, the results can be expressed as percent non-uniformity, calculated by dividing the rms thickness variability by the average thickness and multiplying by 100 to express the result as a percentage. Preferably, the thickness non-uniformity is about 20% or less, more preferably about 10% or less, even more preferably about 5% or less, most preferably about 2% or less.
The silicon compound layer films formed according to the preferred embodiments also show excellent stoichiometry and purity. These advantages are evident in the results shown in FIG. 10 for the silicon nitride layers in which trisilane was used as the silicon source and activated NH3 and N2 were used as the nitrogen sources.
Analysis of the films indicates a substantially stoichiometric silicon nitride film, as the silicon nitride was found to have a stoichiometry of about Si45N56, or a ratio of about 1.25 nitrogen atoms per silicon atom, approximately equal to perfectly stoichiometric silicon nitride, Si3N4, which has a ratio of about 1.33 nitrogen atoms per silicon atom. In addition, the silicon nitride film showed excellent compositional purity, with the hydrogen concentration within the film at less than about 0.8 atomic percent. Thus, analysis of the silicon nitride films showed the films to have excellent purity and stoichiometry.
Advantageously, the high conformality and physical and chemical uniformity of silicon-containing compound layers formed in accordance with the preferred embodiments have improved physical properties relative to similar layers formed by conventional processes. For example, it has been found that insulating layers of silicon compounds, e.g., silicon nitride and silicon oxide, have worse than theoretically expected insulating properties due in part to reaction of the underlying substrate when forming the silicon compound and also due to incorporated impurities, such as incorporated hydrogen. Desirably, the preferred insulating layers have low incorporated hydrogen and minimized reactions of the underlying substrate, resulting in improved insulating properties.
While conventional silicon nitride films, by virtue of the higher dielectric constant of silicon nitride itself, has theoretically appeared to fit this need, in practice, silicon nitride films formed by conventional CVD processes have not exhibited the physical and electrical properties required for gate dielectric applications. Typically, these films have exhibited leakage currents only marginally better than that of SiO2 at comparable physical thicknesses. It is believed that this has been due in part to the chemical composition of the films, i.e., the presence of impurities incorporated into the silicon-nitride layers. Elements such as hydrogen, carbon and oxygen are believed to be the principal impurities responsible for film properties that do not meet theoretical predictions. It is also believed that the unintentional presence of nitrogen at the interface with a crystalline silicon surface, �below� the silicon nitride layer itself, contributes to the worse than expected electrical performance. This nitrogen within the underlying bulk semiconductor is thought to be present as a by-product of the silicon nitride deposition process.
EXAMPLE 1 A silicon nitride layer was formed in a batch A412� reactor from ASM International N.V. of Bilthoven, The Netherlands. A batch of wafers was loaded into a boat and the boat loaded into the reaction chamber and prepared for trisilane deposition. The temperature of the wafers is allowed to stabilize such that the temperature across each wafer is uniform at about 435� C. The boat was rotated about a vertical axis within the reaction chamber at the rate of 5 rpm. The pressure was set to about 1.3 Torr. Trisilane diluted with inert gas was flowed into the reaction chamber with a trisilane partial pressure of 3.3 mTorr for 1.5 minutes. A thin layer of amorphous silicon results. Trisilane flow was interrupted. Nitridation was then performed by providing 5 slm N2 through an MKS remote microwave radical generator (MRG) for 10 minutes, with power set to 3000 W. The cycle was repeated about 50 times.
EXAMPLE 2 A silicon nitride layer was formed using the process of Example 1, except that during nitridation, in addition to 5 slm N2 through the microwave radical generator (MRG), NH3 was additionally provided separately to the reaction chamber.
The deposited films were analyzed and the results shown in FIG. 10, and discussed above, were obtained.
EXAMPLE 3 A silicon nitride layer was formed in a batch A412� reactor from. ASM International N.V. of Bilthoven, The Netherlands. A batch of wafers was loaded into a boat, vertically separated and with major surfaces horizontally oriented, and the boat was loaded into the reaction chamber and prepared for trisilane deposition. The temperature of the wafers was allowed to stabilize such that the temperature across each wafer was uniform at about 435� C. The boat was rotated about a vertical axis within the reaction chamber at a rate of 5 rpm. The process conditions were as specified in Table 1. Four different nitridation conditions were investigated: 1�no nitridation; 2�nitridation with N2; 3�nitridation with N2+90 sccm NH3; 4-nitridation with N2+180 sccm NH3. In all cases, an amorphous silicon film was deposited using 50 cycles of trisilane exposure steps, each trisilane exposure step alternated with a purge step. During the amorphous silicon deposition step, trisilane and N2 were injected through a first multiple hole injector. During the nitridation step, N2 (and NH3) was (were) injected through a second multiple hole injector in proximity of an in-situ radical generator having a pair of electrodes extending over the vertical height of the furnace and driven by high frequency electrical power at a frequency of 2.45 GHz. For the plasma ignition, higher flows and a higher pressure were selected to facilitate the ignition of the plasma. During the subsequent plasma exposure step, lower flows and a lower pressure were used to increase the diffusion length of the radicals so that they could more easily penetrate between the vertically stacked wafers.
The addition of NH3 to the N2 flow had a beneficial effect on the film uniformity of the nitride films, as shown in FIG. 11. The variation in average film thickness was advantageously low at about 1.5 Å. In comparison, the variation for the silicon nitride film nitrided using N2 alone was about 13 Å, and the variation for an amorphous silicon film deposited without nitridation was about 5 Å.
The addition of NH3 also resulted in an average nitride film thickness that was lower than for nitridation with activated N2 alone flow. The average thickness decreased with the addition of higher levels of NH3. The lower nitride film thickness may indicate a more complete nitridation of the film, or a longer inhibition time for the silicon deposition after each nitridation step or may indicate a combination of both.
Trisilane flow during deposition
N2 flow during deposition
Tube pressure during trisilane deposition
Deposition time/cycle
In-situ radical generator power
N2 flow at Plasma ignition
NH3 flow at Plasma ignition
Tube pressure at Plasma ignition
Plasma ignition step time
N2 flow during stable plasma
NH3 flow during stable plasma
Tube pressure during stable plasma
Stable Plasma step time
50 (dep only,
50 (both dep
no plasma)
It will be appreciated that other additions to N2 during the plasma nitridation step may have a similar beneficial effect. For example, Ar, H2, He, or mixtures thereof can be added to the N2 flow, whether or not in combination with NH3. Without being limited by theory, the beneficial effect may be caused by an improved uniformity of the plasma, an improved efficiency of the plasma, the creation of more reactive radical species, or the creation of radical species having a longer lifetime or a combination of these effects.
Patentzitate Zitiertes PatentEingetragen Ver�ffentlichungsdatum Antragsteller TitelUS436382812. Dez. 197914. Dez. 1982International Business Machines Corp.Method for depositing silicon films and related materials by a glow discharge in a disiland or higher order silane gasUS449521822. Sept. 198322. Jan. 1985Hitachi, Ltd.Process for forming thin filmUS458567115. Nov. 198329. Apr. 1986Mitsui Toatsu Chemicals, IncorporatedFormation process of amorphous silicon filmUS468454211. Aug. 19864. Aug. 1987International Business Machines CorporationLow pressure chemical vapor deposition of tungsten silicideUS472039525. Aug. 198619. Jan. 1988Anicon, Inc.Low temperature silicon nitride CVD processUS52140023. Dez. 199125. Mai 1993Agency Of Industrial Science And TechnologyProcess for depositing a thermal CVD film of Si or Ge using a hydrogen post-treatment step and an optional hydrogen pre-treatment stepUS522732930. Aug. 199113. Juli 1993Hitachi, Ltd.Method of manufacturing semiconductor deviceUS535667318. M�rz 199118. Okt. 1994Jet Process CorporationEvaporation system and method for gas jet deposition of thin film materialsUS535682112. Aug. 199318. Okt. 1994Kabushiki Kaisha ToshibaMethod for manufacturing semiconductor integrated circuit deviceUS538939814. Jan. 199414. Febr. 1995Hoya CorporationMethod of manufacturing magnetic recording medium for contact recordingUS538957018. Aug. 199214. Febr. 1995Kabushiki Kaisha ToshibaMethod of forming boron doped silicon layer and semiconductorUS54538583. Febr. 199526. Sept. 1995Semiconductor Energy Laboratory Co., Ltd.Electro-optical device constructed with thin film transistorsUS547133029. Juli 199328. Nov. 1995Honeywell Inc.Polysilicon pixel electrodeUS559149412. Febr. 19967. Jan. 1997Applied Materials, Inc.Deposition of silicon nitrides by plasma-enhanced chemical vapor depositionUS560772428. Apr. 19954. M�rz 1997Applied Materials, Inc.Low temperature high pressure silicon deposition methodUS561425718. Mai 199525. M�rz 1997Applied Materials, IncLow temperature, high pressure silicon deposition methodUS564829322. Juli 199415. Juli 1997Nec CorporationMethod of growing an amorphous silicon filmUS565653115. Dez. 199512. Aug. 1997Micron Technology, Inc.Method to form hemi-spherical grain (HSG) silicon from amorphous siliconUS56958192. Mai 19969. Dez. 1997Applied Materials, Inc.Method of enhancing step coverage of polysilicon depositsUS569877130. M�rz 199516. Dez. 1997The United States Of America As Represented By The United States National Aeronautics And Space AdministrationVarying potential silicon carbide gas sensorUS570052019. Juni 199623. Dez. 1997Applied Materials, Inc.Low temperature, high pressure silicon deposition methodUS57860277. Juli 199728. Juli 1998Micron Technology, Inc.Method for depositing polysilicon with discontinuous grain boundariesUS578903018. M�rz 19964. Aug. 1998Micron Technology, Inc.Method for depositing doped amorphous or polycrystalline silicon on a substrateUS583758023. Apr. 199717. Nov. 1998Micron Technology, Inc.Method to form hemi-spherical grain (HSG) siliconUS584960122. Apr. 199415. Dez. 1998Semiconductor Energy Laboratory Co., Ltd.Electro-optical device and method for manufacturing the sameUS587412910. Dez. 199623. Febr. 1999Applied Materials, Inc.Low temperature, high pressure silicon deposition methodUS58767978. Okt. 19972. M�rz 1999Applied Materials, Inc.Low temperature high pressure silicon deposition methodUS588586914. Sept. 199523. M�rz 1999Micron Technology, Inc.Method for uniformly doping hemispherical grain polycrystalline siliconUS59593267. Mai 199728. Sept. 1999Nec CorporationCapacitor incorporated in semiconductor device having a lower electrode composed of multi-layers or of graded impurity concentrationUS602770530. Nov. 199822. Febr. 2000Showa Denko K.K.Method for producing a higher silaneUS60838105. Dez. 19964. Juli 2000Lucent TechnologiesIntegrated circuit fabrication processUS610360024. Sept. 199815. Aug. 2000Sharp Kabushiki KaishaMethod for forming ultrafine particles and/or ultrafine wire, and semiconductor device using ultrafine particles and/or ultrafine wire formed by the forming methodUS61598288. Dez. 199812. Dez. 2000Micron Technology, Inc.Semiconductor processing method of providing a doped polysilicon layerUS616149830. Juni 199719. Dez. 2000Fuji Electric Co., Ltd.Plasma processing device and a method of plasma processUS617166210. Dez. 19989. Jan. 2001Mitsubishi Denki Kabushiki KaishaMethod of surface processingUS619766915. Apr. 19996. M�rz 2001Taiwan Semicondcutor Manufacturing CompanyReduction of surface defects on amorphous silicon grown by a low-temperature, high pressure LPCVD processUS619769431. Juli 19966. M�rz 2001Applied Materials, Inc.In situ method for cleaning silicon surface and forming layer thereon in same chamberUS622818128. Sept. 19988. Mai 2001Shigeo YamamotoMaking epitaxial semiconductor deviceUS632631129. M�rz 19994. Dez. 2001Sharp Kabushiki KaishaMicrostructure producing method capable of controlling growth position of minute particle or thin and semiconductor device employing the microstructureUS638502019. Jan. 20007. Mai 2002Samsung Electronics Co., Ltd.Methods of forming HSG capacitors from nonuniformly doped amorphous silicon layers and HSG capacitors formed therebyUS645589215. Sept. 200024. Sept. 2002Denso CorporationSilicon carbide semiconductor device and method for manufacturing the sameUS6503846 *20. Juni 20017. Jan. 2003Texas Instruments IncorporatedTemperature spike for uniform nitridization of ultra-thin silicon dioxide layers in transistor gatesUS6551893 *27. Nov. 200122. Apr. 2003Micron Technology, Inc.Atomic layer deposition of capacitor dielectricUS661369531. Aug. 20012. Sept. 2003Asm America, Inc.Surface preparation prior to depositionUS682182511. Febr. 200223. Nov. 2004Asm America, Inc.Process for deposition of semiconductor filmsUS696285911. Febr. 20028. Nov. 2005Asm America, Inc.Thin films and method of making themUS712558230. Juli 200324. Okt. 2006Intel CorporationLow-temperature silicon nitride depositionUS717279220. Dez. 20026. Febr. 2007Applied Materials, Inc.Method for forming a high quality low temperature silicon nitride filmUS719262624. Sept. 200320. M�rz 2007L'Air Liquide, Soci�t� Anonyme � Directoire et Conseil de Surveillance pour l'Etude et l'Exploitation des Proc�d�s Georges ClaudeMethods for producing silicon nitride films and silicon oxynitride films by thermal chemical vapor depositionUS2001003298621. Juni 200125. Okt. 2001Seiko Epson CorporationFabrication method for a thin film semiconductor device, the thin film semiconductor device itself, liquid crystal display, and electronic deviceUS2002009862731. Aug. 200125. Juli 2002Pomarede Christophe F.Surface preparation prior to depositionUS20030059535 *25. Sept. 200127. M�rz 2003Lee LuoCycling deposition of low temperature films in a cold wall single wafer process chamberUS2004009658214. Nov. 200220. Mai 2004Ziyun WangComposition and method for low temperature deposition of silicon-containing films such as films including silicon nitride, silicon dioxide and/or silicon-oxynitrideUS2005007969214. Mai 200414. Apr. 2005Applied Materials, Inc.Methods to fabricate MOSFET devices using selective deposition processUS2005008028617. Juni 200414. Apr. 2005Ziyun WangComposition and method for low temperature chemical vapor deposition of silicon-containing films including silicon carbonitride and silicon oxycarbonitride filmsUS2005011883718. Juli 20032. Juni 2005Todd Michael A.Method to form ultra high quality silicon-containing compound layersUS2006008428320. Okt. 200420. Apr. 2006Paranjpe Ajit PLow temperature sin deposition methodsEP0368651A29. Nov. 198916. Mai 1990Fujitsu LimitedEpitaxial growth process and growing apparatusEP0486047A215. Nov. 199120. Mai 1992Seiko Epson CorporationThin film semiconductor device, process for fabricating the same, and silicon filmEP0747974A229. Mai 199611. Dez. 1996Canon Kabushiki KaishaPhotovoltaic element and fabrication process thereofEP1065728A221. Juni 20003. Jan. 2001Matsushita Electric Industrial Co., Ltd.Heterojunction bipolar transistor and method for fabricating the sameGB2298313A Titel nicht verf�gbarGB2332564A Titel nicht verf�gbarJPH0391239A Titel nicht verf�gbarJPH0521378A Titel nicht verf�gbarJPH0562911A Titel nicht verf�gbarJPH01217956A Titel nicht verf�gbarJPH01268064A Titel nicht verf�gbarJPH02155225A Titel nicht verf�gbarJPH03185817A Titel nicht verf�gbarJPH03187215A Titel nicht verf�gbarJPH03292741A Titel nicht verf�gbarJPH04323834A Titel nicht verf�gbarJPH07249618A Titel nicht verf�gbarJPH08242006A Titel nicht verf�gbarJPH11317530A Titel nicht verf�gbarJPS633414A Titel nicht verf�gbarJPS633463A Titel nicht verf�gbarJPS5978918A Titel nicht verf�gbarJPS5978919A Titel nicht verf�gbarJPS6043485A Titel nicht verf�gbarJPS6276612A Titel nicht verf�gbarJPS57209810A Titel nicht verf�gbarJPS61153277A Titel nicht verf�gbarWO2002064853A212. Febr. 200222. Aug. 2002Asm IncThin films and methods of making them using trisilaneWO2004009861A218. Juli 200329. Jan. 2004Asm IncMethod to form ultra high quality silicon-containing compound layers* Vom Pr�fer zitiertNichtpatentzitateReferenz1Ikoma et al., Growth of Si/3C-SiC/Si(100) hetrostructures by pulsed supersonic free jets, Applied Physics Letters, vol. 75, No. 25, pp. 3977-3979, Dec. 1999.2International Search Report and Written Opinion for International Application No. PCT/US2006/047805. May 8, 2007.3International Search Report dated Nov. 13, 2003 for international patent application No. PCTUS02/02921, filed on Feb. 1, 2002.4Ishihara et al., "Low-temperature chemical-vapor-deposition of silicon-nitride from tetra-silane and hydrogen azide," Materials Research Society Symposium Proceedings, vol. 284, pp. 3-8 (1983).5Olivares, J. et al., "Solid-phase crystallization of amorphous SiGe films deposed by LPCVD on SiOs and glass," Thin Solid Films 337 (1999), pp. 51-54.6Yeh et al., "Low-temperature chemical-vapor-deposition of silicon-nitride film from hexachloro-disilane and hydrazine," Jpn. J. Appl. Phys. vol. 35, part 1, No. 2B, pp. 1509-1512 (Feb. 1996). Referenziert von Zitiert von PatentEingetragen Ver�ffentlichungsdatum Antragsteller TitelUS7465669 *12. Nov. 200516. Dez. 2008Applied Materials, Inc.Method of fabricating a silicon nitride stackUS791941621. Jan. 20095. Apr. 2011Asm Japan K.K.Method of forming conformal dielectric film having Si-N bonds by PECVDUS797298012. Mai 20105. Juli 2011Asm Japan K.K.Method of forming conformal dielectric film having Si-N bonds by PECVDUS7994070 *30. Sept. 20109. Aug. 2011Tokyo Electron LimitedLow-temperature dielectric film formation by chemical vapor depositionUS8119544 *6. Jan. 200921. Febr. 2012Tokyo Electron LimitedFilm formation method and apparatus for semiconductor processUS81428623. Sept. 200927. M�rz 2012Asm Japan K.K.Method of forming conformal dielectric film having Si-N bonds by PECVDUS828273526. Nov. 20089. Okt. 2012Asm Genitech Korea Ltd.Atomic layer deposition apparatusUS852461221. Jan. 20113. Sept. 2013Novellus Systems, Inc.Plasma-activated deposition of conformal filmsUS854594030. Aug. 20121. Okt. 2013Asm Genitech Korea Ltd.Atomic layer deposition apparatusCN101481794B12. Jan. 20096. M�rz 2013东京毅力科创株式会社Film formation method and apparatus for semiconductor process* Vom Pr�fer zitiertKlassifizierungen US-Klassifikation438/763, 257/E21.102, 438/786, 438/775, 257/E21.192, 257/E21.268, 257/E21.267, 438/791, 257/E21.293Internationale KlassifikationH01L21/31, H01L21/469 UnternehmensklassifikationC23C16/4408, C23C16/45523, C23C16/24, H01L21/3185, H01L21/2053, C23C16/56, H01L21/3144, C23C16/345 Europ�ische KlassifikationC23C16/56, C23C16/34C, C23C16/24, H01L21/318B, C23C16/44A10, C23C16/455FJuristische Ereignisse DatumCodeEreignisBeschreibung14. Apr. 2011FPAYFee paymentYear of fee payment: 420. Mai 2008CCCertificate of correction23. Jan. 2006ASAssignmentOwner name: ASM INTERNATIONAL N.V., NETHERLANDSFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HAVERKORT, RUBEN;WAN, YUET MEI;DE BLANK, MARINUS J.;AND OTHERS;REEL/FRAME:017493/0425;SIGNING DATES FROM 20051021 TO 20051215DrehenOriginalbildGoogle-Startseite - Sitemap - USPTO-Bulk-Downloads - Datenschutzerkl�rung - Nutzungsbedingungen - �ber Google Patente - Feedback gebenDaten bereitgestellt von IFI CLAIMS Patent Services.© 2012 Google