Patent Publication Number: US-11664215-B2

Title: High selectivity atomic later deposition process

Description:
BACKGROUND 
     Field 
     Embodiments generally relate to methods for selectively forming a metal containing material on certain locations of a semiconductor substrate. More specifically, embodiments relate to methods for selectively forming a metal containing material on certain locations of a semiconductor substrate by an atomic layer deposition process for semiconductor manufacturing applications. 
     Description of the Related Art 
     Reliably producing sub-half micron and smaller features is one of the key technology challenges for next generation very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of gate structures on the substrate is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die. 
     As the geometry limits of the structures used to form semiconductor devices are pushed against technology limits, the need for accurate formation with desired materials for the manufacture of structures having small critical dimensions and high aspect ratios and structures with certain desired materials has become increasingly difficult to satisfy. The conventional selective deposition process often cannot efficiently be confined to designated small areas of the substrate, resulting in undesired materials being formed on undesired locations of the substrate. Thus, deposited materials are generally globally formed across the entire surface of the substrate without selectivity or be deposited on undesired locations of the substrate, thus making the selective deposition processes difficult to achieve and often resulting in cross contamination on the substrate surface. 
     Thus, there is a need for improved methods for a deposition process suitable for advanced generation of semiconductor applications. 
     SUMMARY 
     Methods for depositing a metal containing material formed on a certain material of a substrate using an atomic layer deposition process for semiconductor applications are provided. In one embodiment, a method of forming a metal containing material on a substrate comprises pulsing a first gas precursor comprising a metal containing precursor to a surface of a substrate, pulsing a second gas precursor comprising a carboxylic acid to the surface of the substrate, and forming a metal containing material selectively on a first material of the substrate. 
     In another embodiment, a method of forming a metal containing material on a substrate includes performing an atomic layer deposition process by alternatively pulsing a first and a second gas precursor to a surface of a substrate, the surface of the substrate comprising a first and a second material, wherein the first gas precursor comprises a metal containing gas and the second gas precursor comprises a water free precursor, and selectively forming a metal containing material on the first material of the substrate. 
     In yet another embodiment, a method of forming a metal containing material on a substrate includes selectively forming a metal containing layer on a silicon material or a metal material on a substrate than on an insulating material on the substrate by an atomic layer deposition process by alternatively supplying a metal containing precursor and a water free precursor to the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG.  1    depicts an apparatus that may be utilized to perform an atomic layer deposition (ALD) process; 
         FIG.  2    depicts a flow diagram of an example of a method for selectively forming a metal containing material on certain locations on a substrate; 
         FIGS.  3 A- 3 F  depict one embodiment of a sequence for forming a metal containing material selectively on certain locations on the substrate during the manufacturing process according to the process depicted in  FIG.  2   ; and 
         FIGS.  4 A- 4 C  depict a process reaction occurred during the method of  FIG.  2   . 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
     DETAILED DESCRIPTION 
     Methods for selectively depositing a metal containing material at a certain location on a structure formed on the substrate are provided. The structure may include a back-end structure, front-end structure, interconnection structure, passivation structure, fin structure, a gate structure, a contact structure, or any suitable structure in semiconductor devices. In one example, an atomic layer deposition process may be utilized to form a metal containing material on a certain surface, e.g., selectively form a certain type of a material on a substrate comprising two or more different surfaces made from different materials. In one example, a titanium (Ti) containing material is formed by an atomic layer deposition (ALD) process. The titanium (Ti) containing material ALD deposition process utilizes a water free precursor to form the titanium (Ti) containing material with selected precursors. For example, the precursors selected to form the titanium (Ti) containing material comprises at least a Ti containing gas precursor and an acid agent at a selected process temperature greater than 150 degrees Celsius. 
       FIG.  1    is a schematic cross-sectional view of one embodiment of an atomic layer deposition (ALD) processing chamber  100 . The ALD processing chamber  100  includes a gas delivery apparatus  130  adapted for cyclic deposition, such as ALD or chemical vapor deposition (CVD). The terms ALD and CVD as used herein refer to the sequential introduction of reactants to deposit a thin layer over a substrate structure. The sequential introduction of reactants may be repeated to deposit a plurality of thin layers to form a conformal layer to a desired thickness. The chamber  100  may also be adapted for other deposition techniques along with lithography processes. 
     The chamber  100  comprises a chamber body  129  having sidewalls  131  and a bottom  134 . A slit valve tunnel  133  formed through the chamber body  129  provides access for a robot (not shown) to deliver and retrieve a substrate  101 , such as a 200 mm, 300 mm or 450 mm semiconductor substrate or a glass substrate, from the chamber  100 . 
     A substrate support  192  is disposed in the chamber  100  and supports the substrate  101  during processing. The substrate support  192  is mounted to a lift  114  to raise and lower the substrate support  192  and the substrate  101  disposed thereon. A lift plate  116  is connected to a lift plate actuator  118  that controls the elevation of the lift plate  116 . The lift plate  116  may be raised and lowered to raise and lower pins  120  movably disposed through the substrate support  192 . The pins  120  are utilized to raise and lower the substrate  101  over the surface of the substrate support  192 . The substrate support  192  may include a vacuum chuck, an electrostatic chuck, or a clamp ring for securing the substrate  101  to the surface of the substrate support  192  during processing. 
     The substrate support  192  may be heated to heat the substrate  101  disposed thereon. For example, the substrate support  192  may be heated using an embedded heating element, such as a resistive heater, or may be heated using radiant heat, such as heating lamps disposed above the substrate support  192 . A purge ring  122  may be disposed on the substrate support  192  to define a purge channel  124  which provides a purge gas to a peripheral portion of the substrate  101  to prevent deposition thereon. 
     A gas delivery apparatus  130  is disposed at an upper portion of the chamber body  129  to provide a gas, such as a process gas and/or a purge gas, to the chamber  100 . A pumping system  178  is in communication with a pumping channel  179  to evacuate any desired gases from the chamber  100  and to help maintain a desired pressure or a desired pressure range inside a pumping zone  166  of the chamber  100 . 
     In one embodiment, the gas delivery apparatus  130  comprises a chamber lid  132 . The chamber lid  132  includes an expanding channel  137  extending from a central portion of the chamber lid  132  and a bottom surface  160  extending from the expanding channel  137  to a peripheral portion of the chamber lid  132 . The bottom surface  160  is sized and shaped to substantially cover the substrate  101  disposed on the substrate support  192 . The chamber lid  132  may have a choke  162  at a peripheral portion of the chamber lid  132  adjacent the periphery of the substrate  101 . The cap portion  172  includes a portion of the expanding channel  137  and gas inlets  136 A,  136 B. The expanding channel  137  has gas inlets  136 A,  136 B to provide gas flows from two similar valves  142 A,  142 B. The gas flows from the valves  142 A,  142 B may be provided together and/or separately. 
     In one configuration, valve  142 A and valve  142 B are coupled to separate reactant gas sources, but are coupled to the same purge gas source. For example, valve  142 A is coupled to a reactant gas source  138  and valve  142 B is coupled to reactant gas source  139 , which both valves  142 A,  142 B are coupled to purge a gas source  140 . Each valve  142 A,  142 B includes a delivery line  143 A,  143 B having a valve seat assembly  144 A,  144 B and includes a purge line  145 A,  145 B having a valve seat assembly  146 A,  146 B. The delivery line  143 A,  143 B is in communication with the reactant gas source  138 ,  139  and is in communication with the gas inlet  137 A,  137 B of the expanding channel  190 . The valve seat assembly  144 A,  144 B of the delivery line  143 A,  143 B controls the flow of the reactant gas from the reactant gas source  138 ,  139  to the expanding channel  190 . The purge line  145 A,  145 B is in communication with the purge gas source  140  and intersects the delivery line  143 A,  143 B downstream of the valve seat assembly  144 A,  144 B of the delivery line  143 A,  143 B. The valve seat assembly  146 A,  146 B of the purge line  145 A,  145 B controls the flow of the purge gas from the purge gas source  140  to the delivery line  143 A,  143 B. If a carrier gas is used to deliver reactant gases from the reactant gas source  138 ,  139 , the same gas may be used as a carrier gas and a purge gas (i.e., an argon gas may be used as both a carrier gas and a purge gas). 
     Each valve  142 A,  142 B may be a zero dead volume valve to enable flushing of a reactant gas from the delivery line  143 A,  143 B when the valve seat assembly  144 A,  144 B of the valve is closed. For example, the purge line  145 A,  145 B may be positioned adjacent the valve seat assembly  144 A,  144 B of the delivery line  143 A,  143 B. When the valve seat assembly  144 A,  144 B is closed, the purge line  145 A,  145 B may provide a purge gas to flush the delivery line  143 A,  143 B. In the embodiment shown, the purge line  145 A,  145 B is positioned as slightly spaced from the valve seat assembly  144 A,  144 B of the delivery line  143 A,  143 B so that a purge gas is not directly delivered into the valve seat assembly  144 A,  144 B when open. A zero dead volume valve as used herein is defined as a valve which has negligible dead volume (i.e., not necessary zero dead volume.) Each valve  142 A,  142 B may be adapted to provide a combined gas flow and/or separate gas flow of the reactant gas from the sources  138 ,  139  and the purge gas from the source  140 . The pulses of the purge gas may be provided by opening and closing a diaphragm of the valve seat assembly  146 A of the purge line  145 A. The pulses of the reactant gas from the reactant gas source  138  may be provided by opening and closing the valve seat assembly  144 A of the delivery line  143 A. 
     A control unit  180  is coupled to the chamber  100  to control processing conditions. The control unit  180  comprises a central processing unit (CPU)  182 , support circuitry  184 , and memory  186  containing associated control software  183 . The control unit  180  may be one of any form of general purpose computer processors that can be used in an industrial setting for controlling various chambers and sub-processors. The CPU  182  may use any suitable memory  186 , such as random access memory, read only memory, floppy disk drive, compact disc drive, hard disk, or any other form of digital storage, local or remote. Various support circuits may be coupled to the CPU  182  for supporting the chamber  100 . The control unit  180  may be coupled to another controller that is located adjacent individual chamber components, such as the programmable logic controllers  148 A,  148 B of the valves  142 A,  142 B. Bi-directional communications between the control unit  180  and various other components of the chamber  100  are handled through numerous signal cables collectively referred to as signal buses  188 , some of which are illustrated in  FIG.  1   . In addition to the control of process gases and purge gases from gas sources  138 ,  139 ,  140  and from the programmable logic controllers  148 A,  148 B of the valves  142 A,  142 B, the control unit  180  may be configured to be responsible for automated control of other activities used in substrate processing, such as substrate transport, temperature control, chamber evacuation, among other activities, some of which are described elsewhere herein. 
       FIG.  2    is a flow diagram of one embodiment of a process  200  of forming a metal containing material by an atomic layer deposition (ALD) process. Such atomic layer deposition of the process  200  may be performed in the processing chamber  100  depicted in  FIG.  1   , or other suitable processing chamber. A structure containing the metal containing material formed by the ALD process  200  may be any suitable structure formed on a semiconductor substrate, such as interconnection structure with conductive and non-conductive areas, a fin structure, a gate structure, a contact structure, a front-end structure, a back-end structure or any other suitable structure utilized in semiconductor applications.  FIGS.  3 A- 3 F  and  FIG.  4 A- 4 C  are schematic cross-sectional views of portions of a composite substrate corresponding to various stages of the process  200 . The process  200  may be utilized to an interconnection structure both conductive and non-conductive areas formed on a substrate so as to form a metal containing material formed on certain locations of the structure with certain materials formed on the substrate. 
     The process  200  begins at operation  202  by providing a substrate, such as the substrate  101 , as shown in  FIG.  3 A . In one embodiment, the substrate  101  may have a structure  350  formed on the substrate  101 . In one example, the structure  350  may be utilized for forming semiconductor devices. In the example depicted in  FIG.  3 A , the structure  350  may include at least two different materials, such as a first material  304  and a second material  306 . In one example, the first material  304  may be a silicon material or a metal material and the second material  306  may be an insulating material, such as SiO 2 , SiON, SiN, SiOC, SiCOH, and the like. In the example wherein the first material  304  is a silicon material, the silicon material of the first material  304  may be the material from the substrate  101 . Thus, the substrate  101  may be patterned to form openings that allow the second material  306  to be filled therein. The second material  306  is an insulating material comprising oxide or other suitable materials, such as SiO 2 , SiON, SiOC, SiCOH or SiN. 
     In one example, the substrate  101  may include materials selected from a group consisting of crystalline silicon (e.g., Si&lt;100&gt; or Si&lt;111&gt;), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers and patterned or non-patterned wafers silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire. The substrate  101  may have various dimensions, such as 200 mm, 300 mm, 450 mm or other diameter, as well as, being a rectangular or square panel. Unless otherwise noted, embodiments and examples described herein are conducted on substrates with a 200 mm diameter, a 300 mm diameter, or a 450 mm diameter substrate. In the embodiment wherein a SOI structure is utilized for the substrate  101 , the substrate  101  may include a buried dielectric layer disposed on a silicon crystalline substrate. In the embodiment depicted herein, the substrate  101  may be a crystalline silicon substrate. Moreover, the substrate  101  is not limited to any particular size or shape. The substrate  101  may be a circular, polygonal, square, rectangular, curved or otherwise non-circular workpiece, such as a polygonal glass substrate used in the fabrication of flat panel displays. 
     Although the example depicted in  FIG.  3 A  shown that the structure  350  is formed on the substrate  101 , it is noted that there may be further structures formed between the interconnection structure  350  and the substrate  101  as needed. In one example, a front-end structure, such as a gate structure and/or a contact structure may be formed between the structure  350  and the substrate  101  to enable functions of the semiconductor devices. 
     In one example, the insulating material for the second material  306  included in the structure  350  may be a dielectric material, such as silicon oxide, doped silicon materials, or low-k materials, such as carbon containing materials. Suitable carbon containing materials include amorphous carbon, SiC, SiOC, doped carbon materials or any suitable materials. Suitable examples of the low-k insulating dielectric material include SiO containing materials, SiN containing materials, SiOC containing materials, SiC containing materials, carbon based materials, or other suitable materials. 
     The insulating material may be formed by a plasma enhanced chemical vapor deposition (CVD), a flowable chemical vapor deposition (CVD), a high density plasma (HDP) chemical vapor deposition (CVD) process, atomic layer deposition (ALD), cyclical layer deposition (CLD), physical vapor deposition (PVD), or the like as needed. 
     At operation  204 , a first pulse of a first gas precursor is supplied onto the substrate surface in a processing chamber, such as the processing chamber  100  depicted in  FIG.  1   , to form a first monolayer  308   a  selectively on the first material  304  of the substrate  101 , as shown in  FIG.  3 A . The first monolayer  308   a  may be a part of the metal containing material eventually desired to be formed on the substrate  101 . The first monolayer  308   a  is selected to predominantly form the first material  304  (e.g., a silicon material or a metal material) with compatible film qualities and characteristics to the first monolayer  308   a , but not to the second material  306  (e.g., an insulating material), so that the first monolayer  308   a  may be selectively formed on the surface  309  of the first material  304  of the substrate  101 , rather than globally formed across the substrate  101 , including the surfaces  310  of the second material  306 . 
     The atomic layer deposition (ALD) process as performed for process  200  is a chemical vapor deposition (CVD) process with self-terminating/limiting growth. The ALD process yields a thickness of only a few angstroms or in a monolayer level. The ALD process is controlled by distribution of a chemical reaction into two separate half reactions which are repeated in cycles. The thickness of the metal containing material formed by the ALD process depends on the number of the reaction cycles. 
     The first reaction of the operation  204  provides the first monolayer  308   a  being absorbed on the first material  304  on the substrate  101  and a second reaction (e.g., which will be performed at operation  208 ) provide a second monolayer being absorbed on the first monolayer  308   a . As the ALD process is very sensitive to the substrate conditions, the first monolayer  308   a  that forms on the first material  304  where the silicon material (or metal material) is located may not be able to adhere or form on the oxide material, such as the insulating material from the second material  306 , formed on the substrate  101 . Thus, by utilizing the differences of the material properties at different locations from the substrate, a selective ALD deposition process is enabled to allow the precursors from the ALD deposition process to nucleate and grow on the nucleate sites provided from the silicon elements (or metal elements) from the first material  304 , while inert to the surfaces  310  from oxide material from the second material  306 . 
     In one example, the first gas precursor is a metal containing precursor, which is utilized to provide metal elements to form a metal containing material on the substrate  101 . Thus, the first monolayer  308   a  as formed on the first material  304  is a metal material. The metal elements sourced from the first gas precursors are selected to be easily absorbed and attached to the silicon elements (or metal elements) from the first material  304  from the substrate  101 . Thus, the selective ALD deposition process selectively grow the first monolayer  308   a  comprising metal elements only on designated sites, i.e., the silicon materials or metal materials, from the first material  304 , without forming on the non-silicon or non-metal material (e.g., oxide material or insulating material) from the second material  306 . 
     During the ALD deposition process, a pulse of a first gas precursor (e.g., a first reactant) is supplied into the processing chamber, such as the processing chamber  100  depicted in  FIG.  1   , to form the first monolayer  308   a . It is believed that the first monolayer  308   a  is absorbed onto the first material  304  by a chemical reaction that allows the metal atoms from the first monolayer  308   a  to be securely adhered on the silicon or metal atoms from the first material  304 . Since the metal elements from the first monolayer  308   a  may have chemical properties different from the oxide material from the second material  306 , the molecules from the second material  306  may not be able to successfully adhere the metal atoms from the first monolayer  308   a , thus selectively allowing the metal atoms from the first monolayer  308   a  to be adhered on the silicon or metal atoms of the first material  304 . In this way, the subsequently formed second monolayer (e.g.,  312   a  shown in  FIG.  3 C ) may selectively deposit on the first monolayer  308   a , thus enabling a continuing selective deposition of an ALD process. In some examples, it is noted that the Ti precursor may physisorbs on second material  306  without undergoing a chemical reaction. This non-selective physisorption is subsequently removed by controlling the substrate temperature and purge time at operation  206  before co-reactant dose at operation  208 . 
     In one example, the first gas precursor (e.g., a first reactant) utilized in the first pulse of reaction to form the first monolayer  308   a  includes metal containing gas precursor, such as a metal alkoxide, particularly, such as a titanium (Ti) containing gas precursor or hafnium (Hf) containing gas precursor. Suitable examples of the titanium (Ti) containing gas precursor include titanium (IV) isopropoxide (Ti(OCH(CH 3 ) 2 ) 4 , titanium n-butoxide (n-C 4 H 9 O) 4 Ti), titanium t-butoxide (t-C 4 H 9 O) 3 Ti), titanium chloride (TiCl 4 ), tetrakis(diethylamido)titanium(IV) and tetrakis(dimethylamido)titanium(IV), and the like. In one example, the titanium (Ti) containing gas precursor is titanium (IV) isopropoxide (Ti(OCH(CH 3 ) 2 ) 4 . Suitable examples of the hafnium (Hf) containing gas precursor include Hf(OCH(CH 3 ) 2 ) 4 , (t-C 4 H 9 O) 3 Hf, is(cyclopentadienyl) hafnium (IV) dimethyl (Cp 2 HfMe 2 ), tetrakis(diethylamido) hafnium (TDEAH) and tris(dimethylamido) silane (Tris-DMAS). 
     Strong adherence of atoms in each layers and absorbability of the layers of atoms onto the surface of substrate provide compact and secured bonding structures so as to render a film property with a high film density and high selectivity (as compared to a chemical vapor deposition process). 
     The first pulse of reaction sourced from the first gas precursor at operation  204  lasts for a predetermined time interval. The term pulse as used herein refers to a dose of material injected into the process chamber. During pulsing of the first gas precursor, several process parameters are also regulated. In one embodiment, the process pressure is controlled at between about 0.01 Torr and about 20 Torr. 
     The processing temperature is maintained greater than 150 degrees Celsius, such as between about 150 degrees Celsius and about 300 degrees Celsius, such as about 250 degrees Celsius. It is believed that the relatively higher deposition temperature, such as greater than 150 degrees Celsius, may assist reacting the metal compound from the first gas precursor efficiently so as to assist adsorption of the metal elements onto the substrate surface. Furthermore, the relatively high deposition temperature, such as greater than 150 degrees Celsius, can assist the metal containing precursor, such as the titanium (IV) isopropoxide (Ti(OCH(CH 3 ) 2 ) 4 , to react with a surface having a certain type of the terminal group (e.g., Si—H) from the surface  309 , thus rendering a selective deposition process. Furthermore, the relatively high deposition temperature, such as greater than 150 degrees Celsius, can assist with desorption of physically adsorbed metal containing precursor from surface  310 . It is believed that deposition temperatures greater than 150 degrees Celsius but below 300 degrees Celsius may prevent non-selective decomposition of the metal containing precursor which would lead to deposition on all surfaces. 
     For example, in the example depicted in  FIG.  4 A  wherein the first gas precursor is titanium (IV) isopropoxide (Ti(OCH(CH 3 ) 2 ) 4  and while pulsing the first gas precursor onto the substrate surface, the first gas precursor reacts under the relatively high temperature environment, undergoing ligand exchange with the reactive surface (e.g., such as Si—H terminal surface) from the surface  309  of the first material  304 . Thus, the reactive titanium (IV) isopropoxide (Ti(OCH(CH 3 ) 2 ) 4  is attached via oxygen to the first material  304 , forming the first monolayer  308   a , as shown in  FIG.  3 B  with a byproduct, such as propane, desorbed to the gas phase. In contrast, the surface  310  of the second material  306 , which often has an alkyl terminal group (e.g., —C x H y ) sourced from the ambient or from the film bonding structure, would not actively react (e.g., or relatively inert to) with the titanium terminal group, thus avoiding the first monolayer  308   a  being formed on the second material  306 . Thus, by selecting different temperature range of the process with the desired type of the first gas precursor, a selective deposition process is enabled and enhanced. 
     Thus, the first monolayer  308   a  shown in  FIG.  3 B  may include Ti elements, after the first pulse of the first gas precursor. Each pulse of the first reaction may deposit a layer of the first monolayer  308   a  having a thickness between about 1 Å and about 5 Å. 
     At operation  206 , after pulsing of the first gas precursor, a purge gas may be supplied to the substrate surface. Between each pulse of the first precursor or/and a second precursor (which will be later performed at operation  208 ) and/or a reactive gaseous species, a purge gas or a purge gas mixture, such as a nitrogen gas, an inert gas (e.g., He or Ar) or the like, may be pulsed into the processing chamber in between each or multiple pulses of the first precursor or/and a second precursor and/or a reactive gaseous species to remove the by-products, impurities or residual precursor gas mixture which is unreacted/non-absorbed by the substrate surface (e.g., unreacted impurities from the reactant gas mixture or others) so they can be pumped out of the processing chamber. 
     It is that the time of the purging at operation  206  may impact on the removal efficiency of the amount of the residuals left on the second material  306 . Thus, a sufficient time period for the purge process at operation  206  is desired so as to remove the surface residuals or byproduct from the substrate surface. 
     The process parameters controlled during the operation  206  for pulsing the purge gas and/or purge gas mixture may be controlled similar to or the same as the pulsing of the first gas mixture at operation  204 . 
     At operation  208 , after the first reaction and a pump/purge process, a second gas precursor (e.g., a second reactant or called a co-reactant) is supplied to initiate a second reaction, forming a second monolayer  312   a  on the first monolayer  308   a , as shown in  FIG.  3 C . The second precursor may be supplied with or without additional reactive gaseous species as needed. The second precursor is a gas precursor comprising a carboxylic acid (e.g., R—COOH, R stands for any suitable molecule). Suitable examples of the carboxylic acid include acetic acid (CH 3 COOH), benzoic acid (C 6 H 5 COOH), formic acid (HCOOH), chloroacetic acid (CH 2 ClCOOH), dichloroacetic acid (CHCl 2 COOH), oxalic acid (HO 2 CCOOH), trichloroacetic acid (CCl 3 CO 2 H), and trifluoroacetic acid (CF 3 COOH). The second gas precursor is a water free co-reactant so as to avoid breakdown of self-assembled monolayer, which often occurred in a conventional chemical reaction. In one example, the carboxylic acid selected for the second gas precursor is acetic acid (CH 3 COOH). The pulse of the second gas precursor initiates a second reaction which may deposit the second monolayer  312   a  having a thickness between about 1 Å and about 3 Å. 
     It is believed that acetic acid (CH 3 COOH) may be reactive towards the adsorbed metal precursor ligands due to the relatively high processing temperature present during the reaction. As a result, the acidic hydrogen undergoes ligand exchange with the adsorbed Ti active species from the first monolayer,  308   a . As shown in  FIG.  4 B , the thermal energy assists reacting the carboxylic acid with the isopropoxide terminals of the Ti complex agent resulting in —OC(═O)R termination of the Ti and isopropanol desorbed to the gas phase. In the example depicted in  FIG.  4 B , three bonding branches from the Ti complex agent are bonded with the oxygen terminals (—OC(═O)R) from the carboxylic acid attached thereto. It is noted that the degree of decomposition of the carboxylic acid and the reaction to the Ti complex agent from the first monolayer  308   a  may be in any form or may be controlled by different temperature settings, pulse dose ratio, pulse frequency, or pulse dose concentration as needed. Thus, after the oxygen terminals (—OC(═O)R) from the carboxylic acid are attached to the Ti complex agent, a Ti and oxide containing material (e.g., TiO2) is selectively formed on the first material  304 . 
     The second reaction lasts for a predetermined time interval to form the second monolayer  312   a , as shown in  FIG.  3 C . During pulsing of the second precursor comprising carboxylic acid, a reactive gaseous specie may be supplied simultaneously with, alternatively, or sequentially with the second precursor (e.g., the Si containing precursor as one example) as needed prior to, during or after the pulsing of the second gas precursor. 
     During supplying of the second precursor with or without the reactive gaseous species (e.g., the reactive gaseous species supplied after the first precursor), several process parameters are also regulated. In one embodiment, the process pressure is controlled at between about 0.01 Torr and about 20 Torr. 
     The processing temperature is maintained greater than 150 degrees Celsius, such as between about 150 degrees Celsius and about 300 degrees Celsius, such as about 250 degrees Celsius. It is believed that the relatively high deposition temperature, such as greater than 150 degrees Celsius, may assist reacting the carboxylic acid with adsorbed metal ligands so as to assist adsorption of the oxygen elements onto the substrate surface, thus rendering a selective deposition process. 
     Thus, the first monolayer  308   a  and the second monolayer  312   a  as shown in  FIG.  3 C  may include Ti elements as well as oxygen elements, after the second pulse of the second precursor. 
     In one example, the dose concentration and/or the dose pulse numbers may be varied between the first gas precursor and the second gas precursor supplied at operation  204  and  208 . In one example, the first gas precursor is pulsed at a dosing concentration greater than the second gas precursor in the respective operation  204 ,  208 . For example, approximately 20 doses/pulses of Ti containing gas are performed for each cycle of the deposition at operation  204  while approximately 1 dose/pulse of carboxylic acid for each cycle of the deposition at operation  208 . Thus, the dose concentration/gas concentration ratio between the Ti containing gas and the carboxylic acid between each cycle of the operation  204  and  208  is controlled between about 15:1 to about 30:1, for example about 20:1. 
     At operation  210 , after pulsing of the second gas precursor, a purge gas may be supplied to the substrate surface. Between each pulse of the first precursor or/and a second precursor and/or a reactive gaseous species, a purge gas or a purge gas mixture, such as a nitrogen gas, an inert gas (e.g., He or Ar) or the like, may be pulsed into the processing chamber in between each or multiple pulses of the first precursor or/and a second precursor and/or a reactive gaseous species to remove the by-products, impurities or residual precursor gas mixture which is unreacted/non-absorbed by the substrate surface (e.g., unreacted impurities from the reactant gas mixture or others) so they can be pumped out of the processing chamber. 
     The process parameters controlled during the operation  210  for pulsing the purge gas and/or purge gas mixture may be controlled similar to or the same as the pulsing of the first gas precursor or the second gas precursor at operation  204  and  208 , respectively. 
     It is noted that the first reaction at operation  204  and the second reaction at operation  208  (and the purge processes at operation  206  and  210 ) may be repeatedly performed, as indicated by the loop  212 , forming an additional first monolayer  308   b , as shown in  FIG.  3 D  and yet another additional second monolayer  312   b , as shown in  FIG.  3 E , until a desired thickness of the overall metal containing layer  320  is reached, as shown in  FIG.  3 F . It is noted that the element/atom scale shown in in  FIGS.  3 B- 3 E  is exaggerated for ease of explanation. 
     Furthermore, for the bonding mechanism during the second cycle of operation  204  and  208 , a second loop of providing the first gas precursor (performed at operation  204 ) may supply a second round of the Ti containing gas to the substrate surface. As discussed above, the relatively weak bonding structure from the —OC(═O)R bonding may be reacted, as shown in  FIG.  4 C , with the ligands from the Ti complex, allowing additional Ti terminal to be attached to the oxygen elements, thus forming the desired TiO 2  on the first material  304 , as shown in  FIG.  4 C . 
     At operation  214 , as discussed above, when a desired thickness (e.g., after a predetermined number of cycles of operations  204  to  210 ) is reached, the metal containing layer  320  is selectively formed on the first material  304 , as shown in  FIG.  3 F . The metal containing layer  320  has a thickness having a range from 10 Å and about 100 Å. As discussed above, based on the number of the cycles of the selected operations, the composition of the resultant metal containing layer  320 , such as a TiO 2  layer, may be varied. For example, the metal containing layer  320  may be a Ti rich or oxygen rich TiO 2  layer as determined by the different selection of pulses, doses, gas concentration provided during each loop or each cycle of the deposition process. 
     Thus, a selective deposition process is provided to form a metal containing layer on different surfaces, e.g., different portions, of a substrate by a selective ALD process. Thus, a structure with desired different type of materials formed on different locations of the substrate may be obtained. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.