Apparatus and method to achieve continuous interface and ultrathin film during atomic layer deposition

Information

  • Patent Grant
  • 6503330
  • Patent Number
    6,503,330
  • Date Filed
    Wednesday, December 22, 1999
    24 years ago
  • Date Issued
    Tuesday, January 7, 2003
    21 years ago
Abstract
A method and apparatus for performing atomic layer deposition in which a surface of a substrate is pretreated to make the surface of the substrate reactive for performing atomic layer deposition.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to semiconductor technology and, more particularly, to a method and apparatus for the practice of atomic layer deposition.




2. Background of the Related Art




In the manufacture of integrated circuits, many methods are known for depositing and forming various layers on a substrate. Chemical vapor deposition (CVD) and its variant processes are utilized to deposit thin films of uniform and, often times conformal coatings over high-aspect and uneven features present on a wafer. However, as device geometries shrink and component densities increase on a wafer, new processes are needed to deposit ultrathin film layers on a wafer. The standard CVD techniques have difficulty meeting the uniformity and conformity requirements for much thinner films.




One variant of CVD to deposit thinner layers is a process known as atomic layer deposition (ALD). ALD has its roots originally in atomic layer epitaxy, which is described in U.S. Pat. Nos. 4,058,430 and 4,413,022 and in an article titled “Atomic Layer Epitaxy” by Goodman et al.; J. Appl. Phys. 60(3), Aug. 1, 1986; pp. R65-R80. Generally, ALD is a process wherein conventional CVD processes are divided into single-monolayer depositions, wherein each separate deposition step theoretically reaches saturation at a single molecular or atomic monolayer thickness or less and, then, self-terminates.




The deposition is an outcome of chemical reactions between reactive molecular precursors and the substrate (either the base substrate or layers formed on the base substrate). The elements comprising the film are delivered as molecular precursors. The desired net reaction is to deposit a pure film and eliminate “extra” atoms (molecules) that comprise the molecular precursors (ligands). In a standard CVD process, the precursors are fed simultaneously into the reactor. In an ALD process, the precursors are introduced into the reactor separately, typically by alternating the flow, so that only one precursor at a time is introduced into the reactor. For example, the first precursor could be a metal precursor containing a metal element M, which is bonded to an atomic or molecular ligand L to form a volatile molecule ML


x


. The metal precursor reacts with the substrate to deposit a monolayer of the metal M with its passivating ligand. The chamber is purged and, then, followed by an introduction of a second precursor. The second precursor is introduced to restore the surface reactivity towards the metal precursor for depositing the next layer of metal. Thus, ALD allows for single layer growth per cycle, so that much tighter thickness controls can be exercised over standard CVD process. The tighter controls allow for ultrathin films to be grown.




In practicing CVD, a nucleation step is assumed when a film of stable material is deposited on a stable substrate. Nucleation is an outcome of only partial bonding between the substrate and the film being deposited. Molecular precursors of CVD processes attach to the surface by a direct surface reaction with a reactive site or by CVD reaction between the reactive ingredients on the surface. Of the two, the CVD reaction between the reactive ingredients is more prevalent, since the ingredients have much higher affinity for attachment to each other. Only a small fraction of the initial film growth is due to direct surface reaction.




An example of nucleation is illustrated in

FIGS. 1-3

.

FIG. 1

shows a substrate


10


having bonding locations


11


on a surface of the substrate. Assuming that the CVD reaction involves a metal (M) and a ligand (L


x


) reacting with a non-metal (A) and hydrogen (H


z


), the adsorbed species diffuse on the surface and react upon successful ML


x


-AH


z


collisions. However, the reaction does not occur at all of the potential attachment (or bonding) locations


11


. Generally, defect sites (sites having irregular topology or impurity) are likely to trap molecular precursors for extended times and, therefore, have higher probability to initiate nucleation. In any event, as shown in

FIG. 1

, the bonding of the precursor to the surface occurs at only some of the bonding locations


12


.




Subsequently, as shown in

FIG. 2

, the initial bonding sites


12


commence to further grow the thin film material on the surface of the substrate


10


. The initial reaction products on the surface are the nucleation seed, since the attached products are immobile and diffusing molecular precursors have a high probability to collide with them and react. The process results in the growing of islands


13


on the substrate surface together with the continuous process of creating new nucleation sites


14


. However, as the islands


13


grow larger, the formation of new nucleation seeds is suppressed because most of the collisions occur at the large boundaries of the islands


13


.




As the islands


13


enlarge three-dimensionally, most of the adsorption and reaction processes occur on the island surfaces, especially along the upper surface area of the islands


13


. Eventually, this vertical growth results in the islands becoming grains. When the grains finally coalesce into a continuous film, the thickness could be on the order of 50 angstroms. However, as shown in

FIG. 3

, the separated nucleation sites can result in the formation of grain boundaries and voids


15


along the surface of the substrate, where potential bonding sites failed to effect a bond with the precursor(s). The grain boundaries and voids


15


leave bonding gaps along the surface of the substrate so that substantial film height will need to be reached before a continuous upper surface of the film layer is formed.




Although the results described above from nucleation is a problem with the standard CVD process, the effect is amplified with ALD. Since ALD utilizes one precursor at a time, the initial bonding will occur due to surface reaction of the initial precursor with sparse surface defects. Accordingly, seed nucleation sites


12


are very sparse (more sparse than CVD) and nucleation proceeds by growing ALD layers on these few seed sites. As a result, the nuclei grow three-dimensional islands


13


and coalesce only at thickness that are comparable to the distance between the nucleation seeds. That is, the voids


15


could be much larger in size, so that a much higher structure is needed to provide a continues upper surface for the film when only ALD is used.




Accordingly, if an ALD film can initiate growth on a substrate predominantly by nucleation, the film grows discontinuously for a much thicker distance. Ultimately a much thicker film is practically needed in the case of ALD to achieve continuous film, than that which can be obtained from CVD processes.




The present invention is directed to providing a technique to deposit ALD thin films of reduced thickness that has continuous interface and film.




SUMMARY OF THE INVENTION




A method and apparatus for performing atomic layer deposition in which a surface of a substrate is pretreated to make the surface of the substrate reactive for performing atomic layer deposition (ALD). As a result, the ALD process can start continuously without nucleation or incubation, so that continuous interfaces and ultrathin films are formed.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a cross-sectional diagram showing a problem encountered with prior art CVD processes, in which sparse seed nuclei are formed to initiate film growth by non-continuous nucleation.





FIG. 2

is a cross-sectional diagram showing the start of nucleation emanating from the chemical attachment shown in

FIG. 1

, in which the spacing between the nucleation sites results in the formation of separated islands as the deposition process progresses.





FIG. 3

is a cross-sectional diagram showing the result of further growth of the deposited layer of

FIG. 2

, in which the formation of grain boundaries and voids requires more than desirable thickness to be deposited to obtain a continuous layer at the surface.





FIG. 4

is a cross-sectional diagram showing an embodiment of the present invention in pretreating a surface of a substrate to activate the surface, prior to performing atomic layer deposition to grow an ultra thin film layer.





FIG. 5

is a cross-sectional diagram showing the presence of many more active sites on the surface of the substrate after surface pretreatment shown in

FIG. 4

is performed.





FIG. 6

is a cross-sectional diagram showing a first sequence for performing ALD when a first precursor is introduced to the prepared surface of FIG.


5


.





FIG. 7

is a cross-sectional diagram showing a formation of ligands on the substrate surface of

FIG. 6

after the first precursor reacts with the pretreated surface and the subsequent introduction of a second precursor.





FIG. 8

is a cross-sectional diagram showing the restoration of the substrate surface of

FIG. 7

so that the first precursor can be reintroduced to repeat the ALD cycle for film growth and, in addition, a continuous interface layer of the desired film is deposited on the substrate by the sequences of

FIGS. 5-7

.





FIG. 9

is a cross-sectional diagram showing a formation of a next ALD monolayer atop the first monolayer shown in

FIG. 8

to further grow the layer above the substrate one atomic/molecular layer at a time.





FIG. 10

is a cross-sectional diagram showing an alternative pretreatment technique in which an intermediate layer is formed to provide activation sites on the surface of the substrate prior to performing ALD.





FIG. 11

is a block diagram showing one reactor apparatus for performing ALD, as well as pretreating the surface by practicing the present invention.











DETAILED DESCRIPTION OF THE INVENTION




The practice of atomic layer deposition (ALD) to deposit a film layer onto a substrate, such as a semiconductor wafer, requires separately introducing molecular precursors into a processing reactor. The ALD technique will deposit an ultrathin film layer atop the substrate. The term substrate is used herein to indicate either a base substrate or a material layer formed on a base substrate, such as a silicon substrate. The growth of the ALD layer follows the chemistries associated with chemical vapor deposition (CVD), but the precursors are introduced separately.




In an example ALD process for practicing the present invention, the first precursor introduced is a metal precursor comprising a metal element M bonded to atomic or molecular ligand L to make a volatile molecule ML


x


(the x, y and z subscripts are utilized herein to denote integers 1, 2, 3, etc.). It is desirable that the ML


x


molecule bond with a ligand attached to the surface of the substrate. An example ligand is a hydrogen-containing ligand, such as AH, where A is a nonmetal element bonded to hydrogen. Thus, the desired reaction is noted as AH+ML


x


→AML


y


+HL, where HL is the exchange reaction by-product.




However, in a typical situation as noted in the Background section above, the substrate surface does not possess ample bonding sites for all the potential locations on the surface. Accordingly, the ML


x


precursor bonding to the surface can result in the formation of islands and grains which are sufficiently far apart to cause the problems noted above. In order to grow continuous interfaces and films, the present invention is practiced to pretreat the surface of the substrate prior to ALD in order to have the surface more susceptible to ALD. In the preferred embodiment the substrate surface is first treated to make the surface more reactive. This is achieved by forming reactive termination on the surface which will then react with the first ALD precursor.





FIG. 4

shows one embodiment for practicing the present invention. In

FIG. 4

, a substrate


20


(again, substrate is used herein to refer to either a base substrate or a material layer formed on a base substrate) is shown upon which ALD is performed. Instead of applying the ML


x


precursor initially onto the substrate


20


, one or more radical specie(s), including such species as oxygen, hydrogen, OH, NH


2


, Cl and F, is introduced to react with a surface


21


of the substrate


20


. The species can be remote plasma generated and carried to the processing chamber. The reactive species can be selected to react with most surfaces, however, the particular specie selected will depend on the surface chemistry. A given specie is utilized to modify the surface


21


. The reactive specie typically will modify the surface by exchanging other surface species and/or attaching to previously reconstructed sites.




For example, SiO


2


surface with approximately 100% siloxane SiOSi bridge is generally inert. OH, H or O radical exposure can efficiently insert HOH into the SiOSi to generate


2


Si—OH surface species that are highly reactive with ML


x


molecular precursor. In

FIG. 4

, a generic AH


z


reaction is shown to treat the surface


21


of the substrate


20


. A number of example reactions using a particular species to treat various surfaces is described later below.




The introduction of the pretreatment plasma into the processing chamber containing the substrate


20


results in the formation of surface species at various desired bonding sites. Thus, as shown in

FIG. 5

, the surface is shown containing AH sites. It is desirable to have the AH species at many of the potential bonding sites. Subsequently, as shown in

FIG. 6

, the first precursor ML


x


is introduced to start the ALD process for growing a film layer having the composition MA.




It should be noted that the prior art practice of performing ALD commences by the introduction of ML


x


. Since the prior art does not pretreat the surface


21


, there is a tendency for the surface to have lot less potential bonding sites. That is, there are lot less AH sites on non-treated surfaces versus the number available for the pretreated surface


21


shown in FIG.


6


. Accordingly, with less bonding sites on the surface, the earlier described problems associated with nucleation can occur. However, the pretreated surface


21


allows for many more bonding sites to be present on the surface to reduce the above-noted problem.





FIGS. 7-9

show the remaining sequence for performing ALD. After the ML


x


precursor is introduced, the AH+ML


x


→AML


y


+HL reaction occurs, wherein HL is exchanged as the reaction by-product. As shown in

FIG. 7

, the surface of the substrate


21


now contains the MA-L combination, which then reacts with the second precursor comprising AH


z


. The second precursor, shown here comprising a nonmetal element A and hydrogen reacts with the L terminated sites on the surface


21


. The hydrogen component is typically represented by H


2


O, NH


3


or H


2


S. The reaction ML+AH


z


→MAH+HL results in the desired additional element A being deposited as AH terminated sites and the ligand L is eliminated as a volatile by-product HL. The surface


21


now has AH terminated sites, as shown in FIG.


8


.




At this point of the process, the first precursor has been introduced and deposited by ALD, followed by the second precursor, also by ALD. The sequence of surface reactions restores the surface


21


to the initial condition prior to the ML


x


deposition, thereby completing the ALD deposition cycle. Since each ALD deposition step is self-saturating, each reaction only proceeds until the surface sites are consumed. Therefore, ALD allows films to be layered down in equal metered sequences that are identical in chemical kinematics, deposition per cycle, composition and thickness. Self-saturating surface reactions make ALD insensitive to transport non-uniformity either from flow engineering or surface topography, which is not the case with other CVD techniques. With the other CVD techniques, non-uniform flux can result in different completion time at different areas, resulting in non-uniformity or non-conformity. ALD, due to its monolayer limiting reaction, can provide improved uniformity and/or conformity over other CVD techniques.





FIG. 9

illustrates the result of a subsequent ALD formation of the MA layer when the next ML


x


sequence is performed to the surface of the substrate shown in FIG.


8


. Thus, additional ALD deposition cycles will further grow the film layer


22


on the surface


21


, one atomic or molecular layer at a time, until a desired thickness is reached. With the pretreatment of the surface


21


, nucleation problems noted earlier are inhibited, due to ample bonding sites on the surface. Thus, the initial ALD layers, as well as subsequent ALD layers, will have ample bonding sites on the surface to attach the reactive species. Continuous ultrathin film layers of 50 angstroms and under can be deposited with acceptable uniformity and conformity properties when practicing the present invention.




It is appreciated that the pretreatment of the surface


21


can be achieved to deposit enough radical species to exchange with the surface. In this instance, these radical species (shown as AH in the example illustrated) provide termination sites for bonding to the ML


x


precursor. However, in some instances, it may be desirable to actually deposit an intermediate layer above the surface


21


. In this instance, an actual intermediate layer


23


is formed above the surface


21


and in which the termination sites are actually present on this layer


23


. This is illustrated in FIG.


10


. Again, this layer can be deposited by a plasma process, including ALD. Then, the ALD process sequence, commencing with the deposition of ML


x


can commence.




An intermediate layer may be required in some instances when the substrate cannot be made reactive with either of the ALD molecular precursors by a simple attachment or exchange of surface species. The ultra thin intermediate layer


23


is deposited as part of the pretreatment process. The intermediate layer


23


provides a new surface that is reactive to one or both precursors. The layer


23


is formed having a thickness which is kept minimal, but sufficient for activation. The intermediate layer


23


may be conductive, semiconductive or insulating (dielectric). Typically, it will match the electrical properties of either the substrate


20


or the overlying film being grown. For example, layer


23


is needed as a transition layer when W or WN


x


films are deposited on SiO


2


. In this instance, Al


2


O


3


(which is an insulator) or TiN, Ti, Ta or Ta


x


N (which are conductors) can be used for the intermediate layer


23


.




It is to be noted further, that the intermediate layer


23


can be deposited by ALD for the pretreatment of the surface. Additionally, the surface


21


of the substrate


20


can be pretreated first by the first method described above to prepare the surface


21


for the deposition of the intermediate layer


23


. Although this does require additional process, it may be desirable in some instances.




It is appreciated that the pretreatment of surface


21


is achieved by a plasma process in the above description, including the use of ALD. However, other techniques can be used instead of a plasma process to pretreat the surface


21


. Thus, the surface


21


can be treated, even the intermediate layer


23


grown, by other techniques. Furthermore, a leaching process an be utilized. Since some surfaces are quite inert, a process other than reactive exchange or attachment may be desirable. For example, hydrocarbon and fluorocarbon polymers are utilized for low-k dielectrics. Adhesion of films, for sealing (insulating) or for forming a barrier (metals, metal nitrides), is difficult to achieve. In these instances, leaching hydrogen or fluorine from the top layer of the polymer can activate the surface for ALD.




Thus, a number of techniques are available for pretreating a surface of a substrate so that the surface is more active for ALD. The present invention can be implemented in practice by a number of chemistries and chemical reactions. A number of examples are provided below with relevant equations. It is to be understood that the examples listed below are provided as examples and in no way limit the invention to just these examples.




EXAMPLE 1




ALD deposition of Al


2


O


3


on silicon. A silicon substrate is first activated (pretreated) by forming thin layers of silicon oxide (SiO


2


) or silicon oxinitride, in which OH and/or NH


x


groups form the terminations. The process involves O


2


/H


2


/H


2


O/NH


3


remote plasma that includes different ratios of the constituents to form the terminations prior to the introduction of the first precursor to grow the Al


2


O


3


thin film layer on silicon.




Si—H—OH.+H.+NH


x


.→Si—OH+Si—NH


x


(where “.” defines a radical)




Si—OH+Al(CH


3


)


3


→Si—O—Al(CH


3


)


2


+CH


4






Si—NH


x


+Al(CH


3


)


3


→Si—NH


x−1


—Al(CH


3


)


2


+CH


4






EXAMPLE 2




ALD deposition of AL


2


O


3


on silicon. The silicon substrate is activated by forming thin layers of SiO


2


that is hydroxilated by exposing HF cleaned (H terminated) silicon to a pulse of H


2


O at temperatures below 430° C. This process results in a self-saturated layer of SiO


2


that is approximately 5 angstroms thick.




Si—H+H


2


O→Si—O—Si—OH+H


2






Si—OH+Al(CH


3


)


3


→Si—O—Al(CH


3


)


2


+CH


4






EXAMPLE 3




ALD deposition of Al


2


O


3


on WN


x


. NH


3


/H


2


/N


2


plasma is used to leach fluorine from the top layers of the WN


x


film and terminate the surface with NH


x


species. These species are reacted with trimethyl aluminum (TMA) to initiate deposition of Al


2


O


3


on WN


x


.




W


x


N+H.+NH


x


.→W—NH


x






W—NH


x


+Al(CH


3


)


3


→W—NH


x−1


—Al(CH


3


)


2


+CH


4






EXAMPLE 4




ALD deposition of Al


2


O


3


on TiN. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species. These species are reacted with TMA to initiate Al


2


O


3


ALD.




TiN+H.+NH


x


.→Ti—NH


x






TiNH


x


+Al(CH


3


)


3


→TiNH


x−1


—Al(CH


3


)


2


+CH


4






EXAMPLE 5




ALD deposition of Al


2


O


3


on Ti. NH


3


/H


2


/N


2


plasma is used to nitridize the surface and terminate the surface with NH


x


species. Maintain conditions to avoid extensive nitridization into the Ti film. The NH


x


species are reacted with TMA to initiate Al


2


O


3


ALD.




Ti+NH


x


.+H.→TiNH


x






TiNH


x


+Al(CH


3


)


3


→TiNH


x −1


—Al(CH


3


)


2


+CH


4






EXAMPLE 6




ALD deposition of Al


2


O


3


on W. NH


3


/H


2


/N


2


plasma is used to nitridize the surface and terminate the surface with NH


x


species. Maintain conditions to avoid extensive nitridization into the W film. The NH


x


species are reacted with TMA to initiate Al


2


O


3


ALD.




W+NH


x


.+H.→WNH


x






W—NH


x


+Al(CH


3


)


3


→W—NH


x−1


—Al(CH


3


)


2


+CH


4






EXAMPLE 7




ALD deposition of Al


2


O


3


on Ta. NH


3


/H


2


/N


2


plasma is used to nitridize the surface and terminate the surface with NH


x


species. Maintain conditions to avoid extensive nitridization into the Ta film. The NH


x


species are reacted with TMA to initiate Al


2


O


3


ALD.




Ta+NH


x


.+H.→TaNH


x






TaNH


x


+Al(CH


3


)


3


→TaNH


x−1


—Al(CH


3


)


2


+CH


4






EXAMPLE 8




ALD deposition of Al


2


O


3


on Ta


x


N. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species. The NH


x


species are reacted with TMA to initiate Al


2


O


3


ALD.




Ta


x


N+NH


x


.+H.→TaNH


x






TaNH


x


+Al(CH


3


)


3


→TaNH


x−


—Al(CH


3


)


2


+CH


4






EXAMPLE 9




ALD deposition of Ta


2


O


5


on Al


2


O


3


. The process involves O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents. This plasma is used to terminate the surface with OH species that are reactive with TaCl


5


.




Al


2


O


3


+OH.+O.+H.→Al


2


O


3


—OH




Al


2


O


3


−OH+TaCl


5


→Al


2


O


3


—O—TaCl


4


+HCl




EQUATION 10




ALD deposition of Al


2


O


3


on Ta


2


O


5


. The process involves O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents. This plasma is used to terminate the surface with OH species that are reactive with TaCl


5


.




Ta


2


O


5


+O.+H.+OH.→Ta


2


O


5


—OH




Ta


2


O


5


—OH+Al(CH


3


)


3


→Ta


2


O


5


—O—Al(CH


3


)


2


+CH


4






EXAMPLE 11




ALD deposition of TiO


x


on Al


2


O


3


. The process involves O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents. This plasma is used to terminate the surface with OH species that are reactive with TMA.




Al


2


O


3


+O.+H.+OH.→Al


2


O


3


—OH




Al


2


O


3


—OH+TiCl


4


→Al


2


O


3


—O—TiCl


3


+HCl




EXAMPLE 12




ALD deposition of Al


2


O


3


on TiO


x


. The process involves O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents. This plasma is used to terminate the surface with OH species that are reactive with TiCl


4


.




TiO


2


+O.+H.+OH.→TiO


2


—OH




TiO


2


—OH+Al(CH


3


)


3


→TiO


2


—O—Al(CH


3


)


2


+CH


4






EXAMPLE 13




ALD deposition of TiO


x


on TiN. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species. The NH


x


species are reacted with TiCl


4


to initiate TiO


x


ALD.




TiN+H.+NH


x


.→Ti—NH


x






Ti—NH


x


+TiCl


4


→TiNH


x−1


—TiCl


3


+HCl




EXAMPLE 14




ALD deposition of W on TiN. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species. The NH


x


species are reacted with TiCl


4


to initiate TiN ALD.




TiN+H.+NH


x


.→Ti—NH


x






Ti—NH


x


+WF


6


→TiNH


x−1


—WF


5


+HF




EXAMPLE 15




ALD deposition of WN


x


on TiN. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species. The NH


x


species are reacted with TiCl


4


to initiate WN


x


ALD.




TiN+H.+NH


x


.→Ti—NH


x






Ti—NH


x


+WF


6


→TiNH


x−1


—WF


5


+HF




EXAMPLE 16




ALD deposition of WN


x


on SiO


2


. O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents is used to terminate the surface with OH species that are reactive with TiCl


4


. The TiCl


4


species is used to grow an intermediate layer of Ti or TiN. The final layer is terminated with NH


x


species (from the TiN ALD) which reacts with WF


6


to initiate the WN


x


ALD process.




SiO


2


+H.+O+OH.→Si—OH




Si—OH+TiCl


4


→SiO—TiCl


3


+HCl




SiO—TiCl


3


+NH


3


→SiO—TiN—NH


x


+HCl




SiO—TiN—NH


x


+WF


6


→SiO—TiN—NH


x−1


WF


5


+HF




EXAMPLE 17




ALD deposition of W on SiO


2


. O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents is used to terminate the surface with OH species that are reactive with TiCl


4


. The TiCl


4


species is used to grow an intermediate layer of Ti or TiN. The final layer is terminated with NH


x


species (from the TiN ALD) which reacts with WF


6


to initiate the W ALD process.




SiO


2


+H.+O.+OH.→Si—OH




Si—OH+TiCl


4


→SiO—TiCl


3


+HCl




SiO—TiCl


3


+NH


3


→SiO—TiN—NH


x


+HCl




SiO—TiN—NH


x


+WF


6


→SiO—TiN—NH


x−1


WF


5


+HF




Alternatively, TaCl


5


can be used for growing an intermediate Ta


x


N layer.




EXAMPLE 18




ALD deposition of WN


x


on hydrocarbon polymer (low-k dielectric layer). NF


3


remote plasma generates fluorine atoms that leach out hydrogen from the hydrocarbon. The leached surface is reacted with TiCl


4


and followed by TiN or Ti/TiN ALD of a thin intermediate layer. The NH


x


terminated surface that is prepared during the TiN ALD is reacted with WF


6


to initiate WN


x


ALD.




C


n


H


m


+F.→C


p


H


q


C.




C


p


H


q


C.+TiCl


4


→C


p


H


q−1


CTiCl


3


+HCl




C


p


H


q−1


CTiCl


3


+NH


3


→C


p


H


q−1


CTiN—NH


x


+HCl




C


p


H


q−1


CTiN—NH


x


+WF


6


→C


p


H


q−1


CTiN—N


x−1


—WF


5


+HF




EXAMPLE 19




ALD deposition of WN


x


on perfluorocarbon polymer (low-k dielectric layer). H


2


/NH


3


remote plasma generates H atoms and NH


x


radicals that leach out fluorine from the hydrocarbon. The leached surface is reacted with TiCl


4


and followed by TiN or Ti/TiN ALD of a thin intermediate layer. The NH


x


terminated surface that is prepared during the TiN ALD is reacted with WF


6


to initiate WN


x


ALD.




C


m


F


n


+H.+NH


x


.→C


p


F


q


C.+HF




C


p


F


q


C.+TiCl


4


→C


p


F


q


C—TiN—NH


x






C


p


F


q


C—TiN—NH


x


+WF


6


→C


p


F


q


C—TiNH


x−1


—NWF


5


+HF




EXAMPLE 20




ALD deposition of oxide on another oxide. The surface of the first oxide is activated by O


2


/H


2


/H


2


O remote plasma that includes different ratios of the constituents. This process is used to terminate the surface with OH species that are reactive with a metal precursor for the next oxide layer.




M


1


O


x


+O.+H.+OH.→M


1


O


x


—OH




M


1


O


x


—OH+M


2


L


y


→M


1


O


x


—O—M


2


L


y−1


+HL




EXAMPLE 21




ALD deposition of oxide on metal, semiconductor or metal nitride. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species that are reactive with a metal precursor for initiating ALD.




M


1


+H.+NH


x


.→M


1


→NH


x






M


1


NH


x


+M


2


L


y


→M


1


NH


x−1


M


2


L


y−1


+HL




EXAMPLE 22




ALD deposition of metal, semiconductor or conductive metalnitride on oxide. NH


3


/H


2


/N


2


plasma is used to terminate the surface with NH


x


species or O


2


/H


2


/H


2


O plasma generated radicals are used to terminate the surface with OH species. The species are reactive with a metal precursor for initiating ALD.




M


1


O


x


+O.+H.+OH.→M


1


O


x


—OH




M


1


O


x


—OH+M


2


L


y


→M


1


O


x


—O—M


2


L


y−1


+HL




Again, it is appreciated that the above are described as examples only and that many other ALD reactions and pretreatment procedures are available.




Referring to

FIG. 11

, an apparatus for practicing the present invention is shown. An ALD reactor apparatus


30


is shown as one embodiment. It is appreciated that a variety of other devices and equipment can be utilized to practice the invention. Reactor


30


includes a processing chamber


31


for housing a wafer


32


. The wafer


32


comprises the substrate


20


described in the earlier Figures. Typically, the wafer


32


resides atop a support (or chuck)


33


. A heater


34


is also coupled to the chuck to heat the chuck


33


and the wafer


32


for plasma deposition. The processing gases are introduced into the chamber


31


through a gas distributor


35


located at one end of the chamber


31


. A vacuum pump


36


and a throttling valve


37


are located at the opposite end to draw and regulate the gas flow across the wafer surface.




A mixing manifold


38


is used to mix the various processing gases and the mixed gases are directed to a plasma forming zone


39


for forming the plasma. A variety of CVD techniques for combining gases and forming plasma can be utilized, including adapting techniques known in the art. The remotely formed plasma is then fed into gas distributor


35


and then into the chamber


31


.




The mixing manifold


38


has two inlets for the introduction of gases and chemicals. A carrier gas is introduced and the flow split at the mixing manifold


38


. The carrier gas is typically an inert gas, such as nitrogen. The mixing manifold


38


also has two inlets for the chemicals. In the example diagram of

FIG. 11

, chemical A and chemical B are shown combined with the carrier gas. Chemistry A pertains to the first precursor and chemistry B pertains to the second precursor for performing ALD for the two precursor process described above. Chemical selection manifold


40


and


41


, comprised of a number of regulated valves, provide for the selecting of chemicals that can be used as precursors A and B, respectively. Inlet valves


42


and


43


respectively regulate the introduction of the precursor chemistries A and B into the mixing manifold


38


.




The operation of the reactor for performing ALD is as follows. Once the wafer is resident within the processing chamber


31


, the chamber environment is brought up to meet desired parameters. For example, raising the temperature of the wafer in order to perform ALD. The flow of carrier gas is turned on so that there is a constant regulated flow of the carrier gas as the gas is drawn by the vacuum created by the pump


36


. When ALD is to be performed, valve


42


is opened to allow the first precursor to be introduced into the carrier gas flow. After a preselected time, valve


42


is closed and the carrier gas purges any remaining reactive species. Then, valve


43


is opened to introduce the second precursor into the carrier gas flow. Again after another preselected time, the valve


43


is closed and the carrier gas purges the reactive species form the chambers of the reactor. The two chemicals A and B are alternately introduced into the carrier flow stream to perform the ALD cycle to deposit a film layer.




When the pretreatment of the surface is to be performed by plasma, the pretreating species can be introduced into the mixing manifold through either or both of the chemical selection routes through selection manifold(s)


40


,


41


to mix with the carrier gas. Again, the pretreatment is performed prior to the initial introduction of the first ALD precursor used to deposit the film. Accordingly, the introduction of the pretreatment chemistry can be achieved from adapting designs of a standard ALD reactor.




Thus, an apparatus and method to achieve continuous interface and ultrathin film during atomic layer deposition is described. The present invention allows an ALD process to start continuously without nucleation or incubation and allows ultrathin film layers of 50 angstroms or less in thickness to be deposited having continuous uniformity and/or conformity.



Claims
  • 1. An apparatus comprising:a mixing manifold having a common carrier gas inlet and a split flow of carrier gas after the carrier gas inlet, said mixing manifold having a first chemical inlet to introduce a first precursor chemical in one flow path of the split flow of the carrier gas and having a second chemical inlet to introduce a second precursor chemical in a second flow path of the split flow of the carrier gas; a reactor coupled to said mixing manifold to receive the first precursor chemical during a first time period and the second precursor chemical during a second time period to perform atomic layer deposition.
  • 2. The apparatus of claim 1 wherein the carrier gas flows at a constant regulated flow to said reactor.
  • 3. The apparatus of claim 1 wherein the carrier gas flows at a constant regulated flow to introduce the first precursor chemical into said reactor during the first time period and to purge the first precursor chemical from said reactor after the first time period, but prior to the second time period.
  • 4. The apparatus of claim 3 wherein the carrier gas introduces the second precursor chemical into said reactor during the second time period and to purge the second precursor chemical from said reactor after the second time period.
  • 5. The apparatus of claim 1 further including a plasma source coupled to said mixing manifold and said reactor to introduce plasma into said reactor.
  • 6. The apparatus of claim 1 further including a plasma source coupled between said mixing manifold and said reactor to vertically introduce the first and second precursor chemicals and plasma into said reactor.
  • 7. The apparatus of claim 1 further including a gas distributor disposed on said reactor to distribute the carrier gas entering said reactor.
  • 8. The apparatus of claim 1 further including a downstream vacuum pump and throttle valve to regulate the carrier gas to have a constant regulated flow.
  • 9. An apparatus comprising:a mixing manifold having a common carrier gas inlet and a split flow of carrier gas after the carrier gas inlet, said mixing manifold having a first chemical inlet to introduce a first precursor chemical into a first flow path of the split flow of the carrier gas and having a second chemical inlet to introduce a second precursor chemical into a second flow path of the split flow of the carrier gas, the carrier gas having a constant regulated flow; a reactor coupled to said mixing manifold to receive the first precursor chemical during a first time period and the second precursor chemical during a second time period to perform atomic layer deposition to deposit a film layer on a wafer.
  • 10. The apparatus of claim 9 wherein the carrier gas purges the first precursor chemical from said reactor after the first time period, but prior to the second time period.
  • 11. The apparatus of claim 10 wherein the carrier gas purges the second precursor chemical from said reactor after the second time period.
  • 12. The apparatus of claim 11 further including a plasma source coupled to said mixing manifold and said reactor to introduce plasma into said reactor.
  • 13. The apparatus of claim 11 further including a plasma source coupled between said mixing manifold and said reactor to vertically introduce the first and second precursor chemicals and plasma into said reactor.
  • 14. The apparatus of claim 11 further including a gas distributor disposed on said reactor to distribute the carrier gas entering said reactor.
  • 15. The apparatus of claim 10 further including a downstream vacuum pump and throttle valve to regulate the carrier gas to have the constant regulated flow.
Government Interests

The United States Government has rights in this invention pursuant to Contract No. F33615-99-C-2961 between Genus, Inc. and the U.S. Air Force Research Laboratory.

US Referenced Citations (57)
Number Name Date Kind
4058430 Suntola et al. Nov 1977 A
4389973 Suntola et al. Jun 1983 A
4413022 Suntola et al. Nov 1983 A
4416933 Antson et al. Nov 1983 A
4533410 Ogura et al. Aug 1985 A
4533820 Shimizu Aug 1985 A
4689247 Doty et al. Aug 1987 A
4828224 Crabb et al. May 1989 A
4836138 Robinson et al. Jun 1989 A
4846102 Ozias Jul 1989 A
4867952 Baumann et al. Sep 1989 A
4907862 Suntola et al. Mar 1990 A
4913929 Moslehi et al. Apr 1990 A
4975252 Nishizawa et al. Dec 1990 A
4976996 Monkowski et al. Dec 1990 A
4993360 Nakamura Feb 1991 A
5000113 Wang et al. Mar 1991 A
5015503 Varrin, Jr. et al. May 1991 A
5077875 Hoke et al. Jan 1992 A
5078851 Nishihata et al. Jan 1992 A
5119760 McMillan et al. Jun 1992 A
5156820 Wong et al. Oct 1992 A
5194401 Adams et al. Mar 1993 A
5204314 Kirlin et al. Apr 1993 A
5270247 Sakuma et al. Dec 1993 A
5281274 Yoder Jan 1994 A
5294778 Carman et al. Mar 1994 A
5304247 Kondo et al. Apr 1994 A
5320680 Learn et al. Jun 1994 A
5336327 Lee Aug 1994 A
5484484 Yamaga et al. Jan 1996 A
5582866 White Dec 1996 A
5616208 Lee Apr 1997 A
5693139 Nishizawa et al. Dec 1997 A
5702530 Shan et al. Dec 1997 A
5711811 Suntola et al. Jan 1998 A
5749974 Habuka et al. May 1998 A
5788447 Yonemitsu et al. Aug 1998 A
5851849 Comizzoli et al. Dec 1998 A
5876503 Roeder et al. Mar 1999 A
5879459 Gadgil et al. Mar 1999 A
5916365 Sherman Jun 1999 A
5935338 Lei et al. Aug 1999 A
6007330 Gauthier Dec 1999 A
6015590 Suntola et al. Jan 2000 A
6042652 Hyun et al. Mar 2000 A
6050216 Szapucki et al. Apr 2000 A
6077775 Stumborg et al. Jun 2000 A
6090442 Klaus et al. Jul 2000 A
6124158 Dautartas et al. Sep 2000 A
6139700 Kang et al. Oct 2000 A
6143659 Leem Nov 2000 A
6174377 Doering et al. Jan 2001 B1
6200893 Sneh et al. Mar 2001 B1
6270572 Kim et al. Aug 2001 B1
6305314 Sneh et al. Oct 2001 B1
20010045187 Uhlenbrock Nov 2001 A1
Foreign Referenced Citations (9)
Number Date Country
0 442 490 Aug 1991 EP
0 442 490 May 1995 EP
0 511 264 Aug 1995 EP
60-10625 Jan 1985 JP
2-152251 Jun 1990 JP
5-152215 Jun 1993 JP
8-236459 Sep 1996 JP
10-102256 Apr 1998 JP
WO-9110510 Jul 1991 WO
Non-Patent Literature Citations (60)
Entry
Bedair, S.M. et al., “Atomic Layer Epitaxy of III-V Binary Compounds”, Appl. Phys. Lett. (1985) 47(1): 51-3.
Ozeki, M. et al., “Kinetic Processes In Atomic-Layer Epitaxy of GaAs and A1As Using A Pulsed Vapor-Phase Method”, J. Vac. Sci. Technol. (1987) B5(4): 1184-86.
O'Hanlon, J. “Gas Release From Solids”, A Users Guide to Vacuum Technology (1989) Chap. 4: 56-71.
Watanabe, A. et al., “The Mechanism of Self-Limiting Growth of Atomic Layer Epitaxy of GaAs By Metalorganic Molecular Bean Epitaxy Using Trimethylgallium and Arsine”, Jpn.J. of Appl. Phys. (1989) 28(7): L 1080-82.
Suntola, T. “Atomic Layer Epitaxy”, Material Science Reports (1989) 4: 261-312.
Higashi, G. et al., “Sequential Surface Chemical Reaction Limited Growth of High Quality Al2O3 Dielectrics”, Appl. Phys. Lett. (1989) 55(19): 1963-5.
Colas, E. et al., “Atomic Layer Epitaxy of Device Quality GaAs”, Appl. Phys. Lett. (1989) 55(26): 2769-71.
Nishizawa, J. et al., “Molecular Layer Epitaxy of Silicon”, J. Cryst. Growth (1990) 99:502-5.
Sakaue, H. et al., “Digital Chemical Vapor Deposition of SiO2 Using A Repetitive Reaction of Triethysilane/ Hydrogen and Oxidation”, Jpn. J. of Appl. Phys. (1990) 30(. L124-7.
Roth, A. “The Vacuum”, Vacuum Technology (1990) Chap. 1: 1-7 and Chap. 2: 28-45.
McDermott, B. et al., “Ordered GaInP by Atomic-Layer Epitaxy”, J. Cryst. Growth (1991) 107(1-4): 96-101.
Yokoyama, H. et al., “Atomic Layer Epitaxy of GaAs Using Nitrogen Carrier Gas”, Appl. Phys. Lett. (1991) 59(17): 2148-49.
Yamaga, S. and Yoshikawa, A. “Atomic Layer Epitaxy of ZnS by a New Gas Supplying System in Low-Pressure Metalorganic Vapor Phase Epitaxy”, J. Cryst. Growth (1992) 117: 152-155.
Gotoh, J. et al., “Low-Temperature Growth of ZnSe-Based Pseudomorphic Structures By Hydrogen-Radical-Enhanced Chemical Vapor Deposition”, J. Cryst. Growth (1992) 117: 85-90.
Suntola, T. “Cost Effective Processing by Atomic Layer Epitaxy”, Thin Solid Films (1993) 225: 96-8.
Ritala, M. et al., “Growth of Titanium Dioxide Thin Films By Atomic Layer Epitaxy”, Thin Solid Films, (1993) 225: 288-95.
Kattelus, H. et al., “Layered Tantalum-Aluminum Oxide Films Deposited By Atomic Layer Epitaxy”, Thin Solid Films (1993) 225: 296-98.
Koleske, D. et al., “Surface Morphology of Si on Si (100) Grown Below 500 Degrees C Using H/C1 Exchange Chemistry”, J. Appl. Phys. (1993) 74(6): 4245-7.
Fujiwara, H. et al., “Low Temperature Grown of ZnSxSe1-x Alloys Fabricated by Hydrogen Radical Enhanced Chemical Vapor Deposition in an Atomic Layer Epitaxy Mode”, J. Appl. Phys. (1993) 74(9): 5510-5.
Somorjai, G. “An introduction to surface Chemistry and Catalysis” (1994) Chap. 1: 12-7.
Ritala, M. et al., “Surface Roughness Reduction in Atomic Layer Epitaxy Growth of Titanium Dioxide Thin Films”, Thin Solid Films (1994) 249: 155-62.
Imai, S. et al., “Hydrogen Atom Assisted ALE of Silicon”, Appl. Surf. Sci. (1994) 82-83: 322-6.
Sugahara, S. et al., “Atomic Layer Epitaxy of Germanium” Appl. Surf. Sci. (1994) 82-83: 380-6.
Dillon, A.C. et al., “Surface Chemistry of A12O3 Deposition Using A1(CH3)3 and H2O in a Binary Raction Sequence”, Surf. Sci. (1995) 322(1-3): 230-42.
Ott, A. W. et al., “Modification of Porous Alumina Membranes Using Al3O3 Atomic Layer Controlled Deposition”, Chem. Of Materials (1997) 9(3): 707-14.
Bedair, S.M. Atomic Layer Epitaxy Deposition Processes, J. Vac. Sci. Technol. B 12(1), Jan./Feb. 1994 pp. 179-185.
Colter, P.C. et al. Atomic Layer Epitaxy of Device Quality GaAs with a 0.6 um/h Growth Rate, Appl. Phys. Lett., vol. 59, No. 12, Sep. 16, 1991.
Hukka, T. et al. Novel Method for Chemical Vapor Deposition and Atomic Layer Epitaxy Using Radical Chemistry, Thin Solid Films 225 (1993) 212-218.
Kodama, K. et al. In situ x-Ray Photoelectron Spectroscopic Study of GaAs Grown by Atomic Layer Epitaxy Appl. Phys. Lett., vol. 54, No. 7, Feb. 13, 1989.
Koleske, D.D. et al. Atomic Layer Epitaxy of Si on Ge(100) Using Si2C16 and Atomic Hydrogen, Appl. Phys.Lett. 64 (7), Feb. 14, 1994.
Lubben, D. et al. UV Photostimulated Si Atomic-Layer Epitaxy, Mat. Res. Soc. Symp. Proc. vol. 222. 1991 Material Reseach Society 177-187.
Sneh, O. et al. Proceedings of 4th Internat. Sympos on Atomic Layer Epitaxy, Linz, Austria, Jul. 1996, Appl. Surf. Sci. 112 (1997).
Suntola, T. Atomic Layer Epitaxy, Handbook of Crystal Growth, vol. 3 1994, pp., 605-663.
Yarmoff, J.A. et al. Atomic Layer Epitaxy of Silicon by Dichlorosilane Studies with Core Level Spectroscopy, J.Vac. Sci. Technol. A 10(4), Jul./Aug. 1992.
George, S.M. et al., Surface Chemistry for Atomic Layer Growth, J. Phys. Chem. 1996, pp. 13121-13131:100.
Imai, Shigeru, et al., Atomic Layer Epitaxy of Si Using Atomic H, Thin Solid Films, 225, 168 (1993).
Ott, A.W. et al. AI303 Thin Film Growth on Si (100) Using Binary Reaction Sequence Chemistry, Thin Solid Films, 292 (1997) pp. 135-144.
Ott, A.W. et al. Proceedings of 4th Internat. Sympos on Atomic Layer Epitaxy, Linz, Austria, Jul. 1996, Appl. Surf. Sci. 112 pp. 205-215 (1997).
Sneh, O. et al. Atomic Layer Growth of Si02 on Si (100) Using SiCI4 and H20 in a Binary Reaction Sequence, Surf. Sci. 334 pp. 135-152 (1995).
Suntola, T., Atomic Layer Epitaxy, Thin Solid Films, 216, (1992) pp. 84-89.
Suntola, T., Surface Chemistry of Materials Deposition of Atomic Layer Level, Appl. Surf, Sci. 100/101 (1996) 391-398.
Tischler, M.A. et al., Growth and Characterization of Compound Semiconductors by Atomic Layer Epitaxy, J. Cryst. Growth 77, 89 (1986).
Farrell, J.T. et al., High Resolution Infrared Overtone Spectroscopy of N2-HF: Vibrational Red Shifts and Predissociation Rate as a Function of HF Stretching Quanta, J. Phys. Chem. 1994, pp. 6068-6074: 98.
George, S.M. et al, Atomic Layer Controlled Deposition of SiO2 and AI203 Using ABAB . . . Binary Reaction Sequence Chemistry, Applied Surface Science, 1994, pp. 460-467: 82/83.
Klaus, J.W. et al. Atomic Layer Deposition of SiO2 Using Catalyzed and Uncatalyzed Self-Limiting Surface Reactions, Surface Review and Letters, 1999, pp. 435-448: vol. 6, Nos. 3 & 4.
Klaus, J.W. et al. Growth of SiO2 at Room Temperature with the Use of Catalyzed Sequential Half Reactions, Science, Dec. 1997, pp. 1934-1936: vol. 278.
Sneh, O. et al. Adsorption and Desorption Kinetics of H20 on a Fully Hydroxylated Si02 Surface, Surface Science 1996, pp. 61-78: vol. 364.
Sneh, O. et al. Atomic Layer Growth of SiO2 on Si(100) Using SiCI4 and H20 in a Binary Reaction Sequence, Surface Science, 1995, pp. 135-152: vol. 334.
Sneh, O. et al. Atomic Layer Growth of Si02 on Si (100) Using the Sequential Deposition of SiCI4 and H20, Mat. Res. Symp. Proc. 1994, pp. 25-30: vol. 334.
Sneh, O. et al. Atomic Layer Showing Its Metal, European Semiconductor, Jul. 2000, pp. 33-36.
Sneh, O. et al. Diffusion of XE on a Stepped Pt(11,119) Surface, American Chemical Society, Abstract of Papers, Mar. 1993 Part 2 (235).
Sneh, O. et al. Sample Manipulator Employing a Gas-Thermal Switch Designed for High Pressure Experiments in an Ultrahigh Vacuum Apparatus, J. Vac. Sci. Technol, Mar./Apr. 1995, pp. 493-496. vol. A 13(2).
Sneh, O. et al. Thermal Stability of Hydroxyl Groups on a Well-Defined Silica Surface, J. Phy. Chem. 1995, pp. 4639-4647: vol. 99.
Sneh, O. et al. Xenon Diffusion on a Stepped Pt (11,11,9) Surface, J. Chem,. Phys., Aug. 1994, pp. 3287-3297: vol. 101 (4).
Wise, M.L. et al. Adsorption and Decomposition of Diethyldiethoxysilane on Silicon Surfaces: New Possibilities for Si02 Deposition, J.Vac. Sci, Technol., May/Jun. 1995, pp. 865-875, vol. B 13(3).
Wise, M.L. et al. Diethyldiethoxysilane as a New Precursor for Si02 Growth on Silicon, Mat. Res. Soc. Symp. Proc., 1994, pp. 37-43: vol. 334.
Wise, M.L. et al. Reaction Kinetics of H20 with Chlorinated Si(111)-(7×7) and Porous Silicon Surfaces, Surface Science, 1996, pp. 367-379: vol. 364.
Wise, M.L. et al. H20 Adsorption Kinetics on Si(111) 7×7 and Si(111) 7×7 Modified by Laser Annealing, J. Vac. Sci. Technol. Jul./Aug. 1995, pp. 1853-1860: vol. A 13(4).
Atomic Layer Epitaxy. T. Suntola and M. Simpson. Blackie and Son Ltd. 1990. pp. 1-39.
Atomic Layer Epitaxy. Collin H. L. Good man and Markus V. Pessa. J. Appl. Phys. 60(3), Aug. 1, 1986. The American Institute of Physics. pp. R65-R81.