BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section of one example of a Bragg reflector.
FIG. 2A is a block diagram of an ALD system including an ALD apparatus and a control system according to one embodiment.
FIG. 2B is an exploded perspective view of a reaction chamber of the ALD apparatus of FIG. 2A.
FIG. 3A is a timing diagram of a method of forming multiple thin films in an ALD apparatus according to one embodiment.
FIG. 3B is a timing diagram of a method of forming multiple thin films in an ALD apparatus according to another embodiment.
FIGS. 4A-4C are diagrams illustrating steps of supplying gases into reaction spaces in the method of FIG. 3A.
FIGS. 5A-5C are diagrams illustrating steps of supplying gases into reaction spaces in a method of forming an Al2O3 layer and a HfO2 layer according to another embodiment.
FIG. 6 is a flowchart illustrating a process for forming a triple layer of HfO2/Al2O3/HfO2 according to another embodiment.
FIGS. 7A-7C are diagrams illustrating steps of supplying gases into reaction spaces in a method of forming an Al2O3 layer and a tungsten (W) layer according to another embodiment.
FIG. 8 is a flowchart illustrating a process of forming a Bragg reflector multilayer stack of Al2O3/W according to another embodiment.
FIGS. 9A-9D are diagrams illustrating steps of supplying gases into reaction spaces in the method of FIG. 3B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The instant disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. Those skilled in the art will appreciate that the embodiments may be modified in various ways, all without departing from the spirit or scope of the instant disclosure.
Referring to FIGS. 2A and 2B, an ALD system 2 according to one embodiment will now be described in detail. Referring to FIG. 2A, the ALD system 2 includes an ALD reactor or apparatus 100 and a control system 200. The control system 200 serves to control the operation of the ALD apparatus 100. The control system 200 may include a computer which includes a processor and memory devices, which communicates with valves, temperature controllers and various mechanical moving parts, as will be better understood from the parts and sequences described below.
FIG. 2B illustrates an exemplary reaction chamber 110 of the ALD apparatus 100 of FIG. 2A. The illustrated reaction chamber 110 includes four separate reaction spaces 160, 170, 180, and 190. The reaction space 160 is excised to show a cross-section of the reaction chamber 110. The reaction spaces 160, 170, 180, and 190 are separated from one another. However, the reaction spaces 160, 170, 180, and 190 form a path along which a plurality of substrates can be sequentially transferred. In addition, the ALD apparatus 100 may further include a driver or driving mechanism to transfer the plurality of substrates from one reaction space to another. In the illustrated embodiments, the reaction spaces form a closed path or loop, such that the driver can move the substrates through the reaction spaces in multiple cycles without reversing direction. In other embodiments, the reaction spaces may form an open path, such that the driver can move the substrates through the reaction spaces in multiple cycles by switching directions at each end of the path.
The apparatus comprises a plurality of reaction spaces. The illustrated ALD apparatus 100 has first to fourth reaction spaces 160-190 and can process four substrates simultaneously. Each of the reaction spaces 160-190 may be in selective communication with one ALD reactant. For example, the first to fourth reaction spaces 160-190 may be in selective communication with first to fourth ALD reactants, respectively. However, none of the reaction spaces communicates with multiple mutually reactive ALD reactants. In the illustrated embodiment, the four substrates may be sequentially transferred from one reaction space to another until a thin film having a desired thickness is formed thereon. A skilled artisan will appreciate that the number of reaction spaces can vary widely depending on the design of the ALD apparatus. A skilled artisan will also appreciate that other ALD reactor designs may be suitable for deposition on multiple substrates in a space divisional manner and can also be used for the methods which will be described below. An example of such an ALD reactor is disclosed in U.S. patent application Ser. No. 11/376,817, filed Mar. 15, 2006, the disclosure of which is incorporated herein by reference. As will be clear to the skilled artisan in view of the '817 application, space-divisional or space-divided ALD involves keeping reactants separated in space, and moving the substrate(s) repeatedly into the each reactant space. In the illustrated embodiments of the present disclosure, reactant flow is kept constant rather than pulsed in each active reactant space during a given ALD process.
Each of the reaction spaces may be provided with at least one gas inlet and at least one gas source connected to the gas inlet(s). The gas inlet is configured to introduce a gas supplied from the gas source. In the context of this document, the terms “gas” and “reactant gas” encompass gas and vaporized reactant that is naturally liquid or solid under standard conditions. The illustrated embodiments provide both an ALD reactant vapor and a purge gas to each chamber, and mechanisms to switch flow between reactant and purge. For example, the ALD apparatus 100 may also include gas valves, each of which is used to control gas flow from the gas sources to the gas inlet(s). The gas valves may be electrically controllable. However, gases are not switched during ALD deposition of one material in multiple cycles.
Although not shown, each reaction space of the ALD apparatus 100 may be provided with a separate gas outlet. The gas outlets of the reaction spaces may be sufficiently separated from one another to prevent reactant gases from reacting with one another in the sequences of movement described below. This configuration prevents undesired particles, reactants or by-products from the various reaction spaces from being adsorbed or deposited on the surfaces of the gas outlets and then being exposed to the other reactants from the other reaction spaces.
In other embodiments, the gas outlet of each reaction space may be shared in order to simplify the design of the ALD apparatus. For example, the ALD apparatus of FIG. 2B may include two shared gas outlets. Every two reaction spaces may be connected to a common vacuum pump through one of the two shared gas outlets, instead of the four reaction spaces being connected to a common vacuum pump through one shared gas outlet.
In addition, a portion where the two outlets are connected to each other may be positioned far from each reaction space. This prevents the structures of the outlets from affecting the gas atmosphere in each reaction space, even if the ALD apparatus includes shared gas outlets. The ALD apparatus 100 may also include a gas curtain formed by a flowing inert gas. The gas curtain may be used to prevent gases supplied to the reaction spaces from mixing with one another.
As described above, the control system 200 of FIG. 2A serves to control the operation of the ALD apparatus 100. In the illustrated embodiment, the control system 200 is configured to control the reactant gases supplied to the ALD apparatus 100. The control system 200 may control the types of gases and the durations of gas supplies for each of the reaction spaces 160, 170, 180, and 190.
In one embodiment, the control system 200 may provide commands to the gas valves for controlling gas supplies to the reaction spaces. Each of the valves may be open for a predetermined period of time to supply a selected gas to each of the reaction spaces 160, 170, 180, 190. After such a step of supplying gases is completed, the control system 200 may provide other commands to the valves for supplying gases for the next step. Each substrate may be sequentially transferred from one reaction space to another during each step. The durations of supplying gases may be selected such that a thin film having a predetermined thickness is formed. The process described above may be repeated until thin films having a desired thickness are formed.
Referring to FIG. 3A and 3B, methods of supplying gases to the reaction spaces of a spatially divided ALD apparatus according to embodiments will now be described. FIG. 3A illustrates one embodiment of a method of forming thin films using an ALD apparatus including four reaction spaces. FIG. 3B illustrates another embodiment of a method of forming thin films using an ALD apparatus including six reaction spaces.
Referring to FIG. 3A, a method of depositing multiple layers according to one embodiment will now be described. In the illustrated embodiment, the multiple layers include two types of thin films: a first thin film and a second thin film. The method can be implemented in an ALD apparatus including first to fourth reaction spaces positioned in order. The first to fourth reaction spaces can form a closed or open path. Each of the reaction spaces is configured to process one substrate at a time. Thus, the four reaction spaces can process four substrates simultaneously. The configuration of the ALD apparatus can be as described above with respect to the reaction apparatus of FIG. 2B. The ALD apparatus may also be provided with a control system to control gas supplies to the reaction spaces, as described above with respect to the control system 200 of FIG. 2A.
In the illustrated embodiment, the ALD apparatus includes (1) a first set of inlets configured to introduce a first set of reactant gases for a first ALD process to the reaction spaces, and (2) a second set of inlets configured to introduce a second set of reactant gases for a second ALD process to the reaction spaces. In the illustrated embodiment, the first ALD process can be conducted for forming a first thin film AB whereas the second ALD process is conducted for forming a second thin film CD of a different composition. The first set of reactant gases can include a first reactant A and a second reactant B. The second set of reactant gases can include a third reactant C and a fourth reactant D.
In the embodiment, two of the four reaction spaces may form a first set of reaction spaces configured to receive the first set of reactant gases. The first set of reaction spaces can include the first and third reaction spaces. The other two of the four reaction spaces may form a second set of reaction spaces configured to receive the second set of reactant gases. The second set of reaction spaces can include the second and fourth reaction spaces. Each of the second set of reaction spaces can be interposed between the two of the first set of reaction spaces.
In the illustrated embodiment, before a first time period t1 starts, four substrates are loaded into the reaction spaces 160, 170, 180, 190. At that time, no reactant gases flow, although purge gases can optionally flow. Then, during the first time period t1, a first reactant gas A, a purge gas P, a second reactant gas B, and a purge gas P are simultaneously supplied into the reaction spaces 160, 170, 180, 190, respectively. The four substrates may be maintained in the reaction spaces 160, 170, 180, 190 for a predetermined period of time which lasts a portion of the first time period t1. In this manner, the first reactant gas A and the second reactant gas B are selectively supplied to the first and third reaction spaces 160, 180 (FIG. 2A), respectively, during the first time period t1.
Then, each of the substrates is transferred to the next reaction space while the first reactant gas A, the purge gas P, the second reactant gas B, and the purge gas P continue to be supplied into the reaction spaces 160, 170, 180, 190, respectively, still during the time period t1. Then, the four substrates are maintained in the reaction spaces 170, 180, 190, 160 adjacent to their original positions for another predetermined period of time which lasts a portion of the first time period t1.
In this manner, the four substrates are sequentially transferred repeatedly through the first to fourth reaction spaces during the first time period t1. Thus, by movement of the substrates from reaction space to reaction space during time period t1, the substrates are sequentially exposed to the first reactant gas A, the purge gas P, the second reactant gas B, and the purge gas P such that a first thin film AB is deposited on the surface of each substrate by ALD. The substrates may continue to be transferred through the reaction spaces, each making a plurality of cycles through the reaction spaces during the first time period t1. The first time period t1 can be selected such that first thin films AB having a desired thickness are deposited on the plurality of substrates during the first time period t1. While in the described sequence of movement the substrates pause in each reaction space, in other embodiments, the substrates may be substantially continuously moved through the reaction spaces 160, 170, 180, 190. Preferably each substrate spends sufficient time in each cycle in each of the first and third reaction spaces to allow ALD reactions to saturate the substrate surfaces.
Then, the control system controls or switches gas supplies for a second time period t2. During the second time period t2, all of the first to fourth reaction spaces are supplied with the purge gas P. The supply of the purge gas P into all the reaction spaces prevents any of the first reactant gas A remaining in the first reaction space and any of the second reactant gas B remaining in the third reaction space from flowing into the second and fourth reaction spaces positioned between the first and third reaction spaces. In one embodiment, the second time period t2 may be shorter than the first time period t1. In other embodiments, the second time period t2 may be omitted, particularly if other mechanisms prevent gas phase interactions between mutually reactive ALD reactants.
Next, as shown in FIG. 3A, the control system controls or switches gas supplies for a third time period t3. During this period, the purge gas P is supplied to the first reaction space. In addition, a third reactant gas C is supplied to the second reaction space while the purge gas P is supplied to the third reaction space. A fourth reactant gas D is supplied to the fourth reaction space. The substrates are sequentially transferred repeatedly in a plurality of cycles through the first to fourth reaction spaces during the third time period t3. Accordingly, each of the substrates is sequentially exposed to the purge gas P, the third reactant gas C, the purge gas P, and the fourth reactant gas D such that a second thin film CD is deposited on the surface of each substrate by ALD. In this manner, the third reactant gas C and the fourth reactant gas D are selectively supplied to the second and fourth reaction spaces 170, 190 (FIG. 2A), respectively, during the third time period t3.
Next, the control system controls or switches gas supplies for a fourth time period t4 such that the first to fourth reaction spaces are supplied with the purge gas P. In one embodiment, the fourth time period t4 may be shorter than the third time period t3. In other embodiments, the fourth time period t4 may be omitted, particularly if other mechanisms prevent gas phase interactions between mutually reactive ALD reactants.
As described above, the first time period t1 to the fourth time period t4 form a super cycle for sequentially forming the first thin film AB and the second thin film CD on a plurality of substrates. Each of these films are formed by multiple ALD cycles generated by moving substrates through separated reaction spaces, whereas each super cycle involves switching gases to conduct different ALD processes (e.g., to form film AB in time period t1 and to form film CD in time period t3). A multiple layer structure including a plurality of first and second thin films stacked upon one another may be formed by repeating the super cycle of the time periods t1 to t4. The control system may be configured to control the number of super cycles as well as the durations (number of ALD cycles) for each of the time periods t1-t4 so as to control the thickness of the multiple layers and the number of the thin films in the multiple layers.
In certain embodiments, the ALD apparatus may further include a gas activating device such as a radio frequency (RF) or microwave (MW) source for supplying RF or MW power. For example, the gas activating device may include an RF electrode, an RF coil, etc. The RF power may be applied during at least one time period, e.g., the first time period t1 and/or the third time period t3 of FIG. 3A such that at least one of the reactant gases A, B, C, and D is supplied in a plasma-activated state. The control system may serve to control activation of the reactant gases. As will be appreciated by the skilled artisan, other mechanisms can be used to activate or excite reactant gases.
In the illustrated embodiment, the reaction spaces are supplied with reactant gases and a purge gas in a manner to prevent different reactant gases from contacting each other while the multiple layers are deposited on the substrates. For example, the first reaction space may be supplied with the first reactant gas A during the first time period t1 while the second reaction space is supplied with the purge gas P. In addition, the first reaction space may be supplied with the purge gas P during the second time period t2 while the second reaction space is supplied with the third reactant gas C. In this manner, the reaction spaces are supplied with gases such that the gases do not react with one another, thereby preventing undesired deposition.
In FIG. 3A, the first to fourth time periods t1-t4 have the same duration. However, the durations of the first to fourth time periods t1, t2, t3, and t4 may be different from one another. For example, the second and fourth time periods t2 and t4, representing pauses between different ALD processes, may be shorter than the first and third time periods t1 and t3, or may be omitted. In addition, the first time period t1 and the third time period t3 may be selected to form first and second thin films having a desired thickness. In reality, for self-limiting ALD processes, “durations” of time periods t1 and t3 are merely proxies for numbers of ALD cycles caused by movement of the substrates, since in ALD only numbers of cycles affect thickness. In the ALD apparatus, the control system may serve to control the thickness of each thin films as well as the number of the thin films.
Referring to FIG. 3B, a method of depositing multiple layers according to another embodiment will be described below. In the illustrated embodiment, the multiple layers include three types of thin films: a first thin film, a second thin film, and a third thin film, each deposited by spatially separated ALD sequences. The method can be implemented in an ALD apparatus including six separate reaction spaces configured to process six substrates simultaneously. The six reaction spaces include a first to sixth reaction spaces positioned in order. The six reaction spaces may form a closed or open path. When described as a modification of FIG. 2B by the addition of fifth and sixth reaction spaces, the six reaction spaces may instead be described as first, second, fifth, third, fourth, sixth reaction spaces positioned in order while forming a closed path. A skilled artisan will appreciate that the numbered labels of the reaction spaces are arbitrary for the purpose of naming different reaction spaces. A skilled artisan will also appreciate that additional reaction spaces can be interposed between two of the six reaction spaces depending on the design of the ALD apparatus. In certain embodiments, the additional reaction spaces can be used for providing a purge gas between any two reaction spaces simultaneously supplying reactant gases for given ALD processes. The ALD apparatus may be provided with a control system for supplying gases for depositing multiple layers by ALD.
In the illustrated embodiment, the ALD apparatus includes (1) a first set of inlets configured to introduce a first set of reactant gases for a first ALD process to the reaction spaces, (2) a second set of inlets configured to introduce a second set of reactant gases for a second ALD process to the reaction spaces; and (3) a third set of inlets configured to introduce a third set of reactant gases for a third ALD process to the reaction spaces. In the illustrated embodiment, the first ALD process can be conducted for forming a first thin film AB whereas the second ALD process is conducted for forming a second thin film CD. The third ALD process may be conducted for forming a third thin film EF. The first set of reactant gases can include a first reactant A and a second reactant B. The second set of reactant gases can include a third reactant C and a fourth reactant D. The second set of reactant gases can include a third reactant C and a fourth reactant D. The third set of reactant gases can include a fifth reactant E and a sixth reactant F.
In the embodiment, two of the six reaction spaces may form a first set of reaction spaces configured to receive the first set of reactant gases. In the example of FIG. 3A, the first set of reaction spaces can include the first and fourth reaction spaces. Another two of the six reaction spaces may form a second set of reaction spaces configured to receive the second set of reactant gases. The second set of reaction spaces can include the second and fifth reaction spaces. Each of the second set of reaction spaces can be interposed between the two of the first set of reaction spaces. Yet another two of the six reaction spaces may form a third set of reaction spaces configured to receive the third set of reactant gases. The third set of reaction spaces can include the third and sixth reaction spaces. Each of the third set of reaction spaces can be interposed between one of the first set of reaction spaces and one of the second set of reaction spaces.
Referring to FIG. 3B, the control system controls gas supplies for a first time period t1. During the first time period t1, a first reactant gas A is supplied to a first reaction space while a second reactant gas B is supplied to a fourth reaction space. In addition, an inert purge gas P is supplied to second, third, fifth, and six reaction spaces. During the first time period t1, the substrates are each sequentially transferred through the first to sixth reaction spaces. Accordingly, the six substrates are each sequentially exposed to the first reactant gas A, the purge gas P, the purge gas P, the second reactant gas B, the purge gas P, and the purge gas P such that a first thin film AB is deposited on the surface of each substrate by ALD. The first time period t1 can be selected to have sufficient ALD cycles (e.g., movement through all six reaction spaces) such that first thin films AB having a desired thickness are deposited on the plurality of substrates during the first time period t1. In this manner, the first reactant gas A and the second reactant gas B are selectively supplied to the first and fourth reaction spaces, respectively, during the first time period t1.
Then, the control system controls or switches gas supplies for a second time period t2. During the second time period t2, the first to sixth reaction spaces may each be supplied with the purge gas P, as shown. All the reaction spaces may be supplied with the purge gas P to prevent the first reactant gas A (remaining in the first reaction space) and the second reactant gas B (remaining in the fourth reaction space) from flowing into the second and third reaction spaces and the fifth and sixth reaction spaces between the first reaction space and the fourth reaction space. The second time period t2 for supplying the purge gas P may be shorter than the first time period t1 for supplying the reactant gases A and B. In other embodiments, the second time period t2 may be omitted, particularly where other mechanisms prevent phase interactions between the mutually reactive ALD reactants.
Next, the control system controls or switches gas supplies for a third time period t3. During the third time period t3, a third reactant gas C is supplied to the second reaction space while a fourth reactant gas D is supplied to the fifth reaction space. During this time period, the purge gas P is supplied to the first, third, fourth, and sixth reaction spaces. In this manner, the third reactant gas C and the fourth reactant gas D are selectively supplied to the second and fifth reaction spaces, respectively, during the third time period t3.
During the third time period t3, the substrates are each sequentially transferred through the first to sixth reaction spaces. Accordingly, the substrates are each sequentially exposed to the purge gas P, the third reactant gas C, the purge gas P, the purge gas P, the fourth reactant gas D, and the purge gas P such that a second thin film CD is deposited on the surface of each substrate by ALD.
Next, the control system controls or switches gas supplies for a fourth time period t4. The first to sixth reaction spaces are supplied with the purge gas P during the fourth time period t4. The fourth time period t4 for supplying the purge gas P may be shorter than the third time period t3 for supplying the reactant gases C and D. In other embodiments, the fourth time period t4 may be omitted, particularly where other mechanisms prevent gas phase interactions between ALD reactants C and D.
Subsequently, the control system controls or switches gas supplies for a fifth time period t5. A fifth reactant gas E is supplied to the third reaction space while a sixth reactant gas F is supplied to the sixth reaction space for the fifth time period t5. The purge gas P is supplied to the first, second, fourth, and fifth reaction spaces during the fifth time period t5. The substrates are sequentially transferred repeatedly through the first to the sixth reaction spaces during the fifth time period t5. Thus, the substrates are sequentially exposed to the purge gas P, the purge gas P, the fifth reactant gas E, the purge gas P, the purge gas P, and the sixth reactant gas F such that a third thin film EF is deposited on the surface of each substrate by ALD. In this manner, the fifth reactant gas E and the sixth reactant gas F are selectively supplied to the third and sixth reaction spaces, respectively, during the fifth time period t3.
Next, the control system controls or switches gas supplies for a sixth time period t6. The first to sixth reaction spaces are supplied with the purge gas P during the sixth time period t6. The sixth time period t6 for supplying the purge gas P may be shorter than the fifth time period t5 for supplying the reactant gases E and F. In other embodiments, the sixth time period t6 may be omitted, particularly where other mechanisms prevent gas phase interactions between the mutually reactive ALD reactants E and F.
During the first to sixth time periods t1-t6, the first to third thin films AB, CD, and EF are formed over one another on the plurality of substrates. By repeating the process described above, additional layers including first to third thin films can be formed on the third thin film EF formed during the sixth time period t6. The method can be repeated until a desired number of layers are formed.
The control system may control the gas supplies such that each reaction space is supplied with one reactant gas or a purge gas in a manner to prevent different reactant gases from contacting each other while the multiple layers are deposited on each substrate.
In certain embodiments, the ALD apparatus may use RF or MW power during at least one time period, e.g., the first, third, and fifth time periods, t1, t3, and t5 shown in FIG. 3B. In such embodiments, at least one of the reactant gases A, B, C, D, E, and F is supplied in a state activated by plasma or other excitation means. The control system may also serve to control activation of the reactant gases.
In FIG. 3B, the first to sixth time periods t1, t2, t3, t4, t5, and t6 have substantially the same duration. In other embodiments, the durations of the first to sixth time periods t1, t2, t3, t4, t5, and t6 may be different from one another. Particularly, the second time period t2, the fourth time period t4, and the sixth time period t6 may be shorter than the other time periods t1, t3, and t5. In other embodiments, the second, fourth, and sixth time periods t2, t4, t6 may be omitted. In addition, the first time period t1, the third time period t3, and the fifth time period t5 may be varied in terms of numbers of cycles each wafer takes in movement through the reaction spaces by the control system 200, depending on the desired thicknesses of the first to third thin films.
Note that the examples of FIGS. 3A and 3B each involve two-reactant ALD processes, but the skilled artisan can readily adapt the sequences to incorporate more complicated (e.g., three-reactant or four-reactant) ALD sequences.
With reference to FIG. 4A to FIG. 9C, methods of depositing multiple layers including a plurality of different thin films according to embodiments will now be described in detail. In the methods, each reaction space is supplied with either a single reactant gas and/or a purge gas to prevent two or more reactants from reacting with one another. The drawings include designations of either purge gases (“P”) or reactants (“A,” “B,” “C,” “D,” “E,” “F,” “Al,” “O,” “Hf,” “WF6,” “SiH4,”) within reaction spaces at different stages of the sequences.
First, as shown in FIG. 4A, the reaction space 180 is supplied with a first reactant gas A while the reaction space 160 is supplied with a second reactant gas. The reaction space 170 is supplied with an inert gas P. The reaction space 190 is supplied with the inert gas P. The substrates are sequentially transferred repeatedly through the reaction spaces 160 to 190 such that the surface of each of the substrates is sequentially exposed to the second reactant gas B, the inert gas P, the first reactant gas A, and the inert gas P. In this manner, a first thin film AB is deposited on the surface of each of the substrates by ALD. The gas supply scheme shown in FIG. 4A and movement of the substrates may be used for the first time period t1 of FIG. 3A.
Referring to FIG. 4B, the reaction space 160 is supplied with the inert gas P while reaction space 170 is supplied with a fourth reactant gas D. The reaction space 180 is supplied with the inert gas P. The reaction space 190 is supplied with a third reactant gas C. The substrates are sequentially transferred repeatedly through the reaction spaces 160 to 190 so that the surface of each of the substrates is sequentially exposed to the inert gas P, the fourth reactant gas D, the inert gas P, and the third reactant gas C. In this manner, a second thin film CD is deposited on the surface of each of the substrates by ALD. The gas supply scheme shown in FIG. 4B and movement of the substrates may be used for the third time period t3 of FIG. 3B.
Referring to FIG. 4C, all the reaction spaces may be supplied with an inert purge gas. This configuration can prevent the reactant gases A, B, C, and D from flowing into adjacent reaction spaces. The gas supply scheme shown in FIG. 4C may be used for the second and fourth time periods t2, t4 of FIG. 3B, between deposition of the first thin film AB and the second thin film CD. This manner of use involves supplying each reaction space with either a reactant gas or a purge gas while substrates move from chamber to chamber, thereby avoiding interactions in the gas phase between reactants.
Referring to FIG. 5A to 5C, a method of depositing multiple layers including one or a plurality of Al2O3 layers and one or a plurality of HfO2 layers will now be described. In the method, reaction spaces are supplied with gases or vapors such as trimethylaluminum (Al(CH3)3, TMA), tetrakisethylmethylamido hafnium (Hf[N(CH3)(C2H5)]4, TEMAHf), ozone (O3), and argon (Ar). In the illustrated embodiment, TMA, ozone, ozone, and TEMAHf can serve to be the first, second, third, and fourth reactant gases, respectively, of FIGS. 4A-4C. In other embodiments, nitrogen (N2) gas or helium (He) may be used as an inert gas instead of argon (Ar) gas.
Referring to FIG. 5A, for depositing an Al2O3 layer on a plurality of substrates, the reaction space 160 is supplied with the ozone (O3) gas as an O precursor. The reaction space 170 is supplied with the argon (Ar) gas. The reaction space 180 is supplied with the TMA gas as an Al precursor. The reaction space 190 is supplied with the argon (Ar) gas. Rotating or moving substrates through these spaces causes ALD of Al2O3.
Referring to FIG. 5B, for depositing an HfO2 layer on the substrates, the reaction space 160 is supplied with the argon (Ar) gas. The reaction space 170 is supplied with the TEMAHf gas as an Hf precursor. The reaction space 180 is supplied with the Ar gas. The reaction space 190 is supplied with the ozone (O3) gas as an O precursor. In the illustrated embodiment, the TMA gas or the TEMAHf gas has a lower vapor pressure. Thus, the TMA gas or the TEMAHf gas may be supplied together with a carrier gas. The ozone (O3) gas may each be supplied with oxygen (O2) gas. For purging all reaction spaces, the reaction spaces 160, 170, 180, and 190 may be supplied with Ar gas or other inactive purge gas as shown in FIG. 5C. As noted previously, this stage may represent purging between ALD depositions of different films, or during loading/unloading.
Referring to FIGS. 5A-5C and 6, a process of depositing multiple layers on four substrates will now be described in detail. The multiple layers may include a triple-layer of HfO2/Al2O3/HfO2 on multiple substrates using the apparatus of FIGS. 5A-5C.
Referring to FIG. 6, each reaction space is supplied with an inert gas such as argon (Ar) (S100) as shown in FIG. 5C. Then, four substrates are loaded into the reaction spaces (S110). Next, the reactant gases are supplied as shown in FIG. 5B (S120) while the four substrates are sequentially transferred through the four reaction spaces 160, 170, 180, and 190 repeatedly until a HfO2 layer having a desired thickness is formed (S130).
Next, all the reaction spaces are supplied with the inert gas such as argon (Ar) as shown in FIG. 5C (S140). Then, the reactant gases are supplied as shown in FIG. 5A (S150) while the four substrates are sequentially transferred through the four reaction spaces 160, 170, 180, and 190 repeatedly until an Al2O3 layer having a desired thickness is formed (S160).
Next, all the reaction spaces are supplied with the inert gas such as argon (Ar) as shown in FIG. 5C (S170). Subsequently, the reactant gases are supplied as shown in FIG. 5B (S180) while the four substrates are sequentially transferred through the four reaction spaces 160, 170, 180, and 190 repeatedly until another HfO2 layer having a desired thickness is formed (S190). Next, all the reaction spaces are supplied with the inert gas such as argon (Ar) as shown in FIG. 5C (S200). After triple-layers of HfO2/Al2O3/HfO2 having the desired thickness are deposited, the substrates are unloaded from each reaction space (S210).
Referring to FIG. 7A to FIG. 7C, a method of forming a Bragg reflector layer including an Al2O3 layer and a tungsten (W) layer will now be described in detail. In the method, reaction spaces are supplied with gases such as TMA, ozone (O3), hexafluorotungsten (WF6), silane (SiH4), and argon (Ar). In the illustrated embodiment, TMA, ozone, SiH4, and WF6 can serve to be the first, second, third, and fourth reactant gases, respectively, of FIGS. 4A-4C. In other embodiments, nitrogen (N2) gas or helium (He) may be used as an inert gas instead of the argon (Ar) gas.
Referring to FIG. 7A, for depositing an Al2O3 layer on a plurality of substrates, the reaction space 160 is supplied with ozone (O3) gas. The reaction space 170 is supplied with argon (Ar) purge gas. The reaction space 180 is supplied with TMA gas. The reaction space 190 is supplied with argon (Ar) purge gas. ALD is conducted in this state while substrates are cycled through these reaction spaces.
Referring to FIG. 7B, for depositing a tungsten (W) layer, the reaction space 160 is supplied with argon (Ar) gas. The reaction space 170 is supplied with WF6 gas. The reaction space 180 is supplied with argon (Ar) gas. The reaction space 190 is supplied with SiH4 gas, which serves as a reducing agent to strip halides from the adsorbed tungsten complex. In the illustrated embodiment, the WF6 gas and the SiH4 gas may each be supplied mixed with an inert gas or hydrogen (H2) gas. ALD is conducting in this state while substrates are cycled through these reaction spaces. For purging all the reaction spaces, the reaction spaces 160, 170, 180, and 190 are supplied with Ar gas, as shown in FIG. 7C.
Referring to FIGS. 7A-7C and 8, a process of forming a Bragg reflector layer including a plurality of double-layers of Al2O3/W on four substrates using the ALD apparatus of FIGS. 7A-7C will be described in detail. Referring to FIG. 8, each reaction space is supplied with an inert gas such as argon (Ar) (T100) as shown in FIG. 7C. Then, four substrates are loaded into the reaction spaces (T110).
The reactant gases are supplied as shown in FIG. 7A while the four substrates are sequentially transferred through the four reaction spaces 160, 170, 180, and 190 repeatedly until an Al2O3 layer having a desired thickness is formed (T130). Then, for purging all the reaction spaces, the reaction spaces 160, 170, 180, and 190 are supplied with Ar gas (T140), as shown in FIG. 7C. Next, the reactant gases are supplied (T150), as shown in FIG. 7B while the four substrates are sequentially transferred through the four reaction spaces 160, 170, 180, and 190 repeatedly until the W layer having a desired thickness is formed (T160).
It is determined whether sufficient deposition has occurred (T180). The cycle of supplying gases is repeated (T185) until a desired number of the double-layers of Al2O3/W are formed on the substrates. After the multiple layers including a plurality of double-layers of Al2O3/W and having a desired thickness are deposited, the substrates are unloaded from each reaction space (T190).
The multiple layers including three or more different layers may be also deposited using the ALD apparatus and the method of supplying gases according to another embodiment. Referring to FIG. 9A to FIG. 9D, a method of depositing multiple layers including three different types of layers will now be described below. The method can be implemented in an ALD apparatus including six separate reaction spaces through which substrates move in each of the three ALD depositions.
As described above, each reaction space may be selectively supplied with one reactant gas or an inert gas at any given time period during the process. For example, the reaction space 140 may be supplied with one of a second reactant gas B and an inert gas. The reaction space 150 may be supplied with one of a fourth reactant gas D and an inert gas. The reaction space 160 may be supplied with one of a sixth reactant gas F and an inert gas. The reaction space 170 may be supplied with one of a first reactant gas A and an inert gas. The reaction space 180 may be supplied with one of a third reactant gas C and an inert gas. The reaction space 190 may be supplied with one of a fifth reactant gas E and an inert gas.
As shown in FIG. 9A, during a time period, the reaction space 140 is supplied with the second reactant gas B. The reaction space 150 is supplied with an inert or purge gas P. The reaction space 160 is supplied with the inert gas P. The reaction space 170 is supplied with the first reactant gas A. The reaction space 180 is supplied with the inert or purge gas P. The reaction space 190 is supplied with inert or purge gas P. During this time period, the surface of each substrate sequentially transferred through the six reaction spaces 140 to 190 is exposed to the second reactant gas B, the inert gas P, the inert gas P, the first reactant gas A, the inert gas P, and the inert gas P in sequence such that a first thin film AB is deposited on the surface of each substrate by ALD. The gas supplying scheme shown in FIG. 9A can be used for the first time period t1 of FIG. 3B.
Referring to FIG. 9B, during another time period, the reaction space 140 is supplied with the inert gas P. The reaction space 150 is supplied with the fourth reactant gas D. The reaction space 160 is supplied with the inert gas P. The reaction space 170 is supplied with the inert gas P. The reaction space 180 is supplied with the third reactant gas C. The reaction space 190 is supplied with the inert gas P. During this time period, the surface of each substrate sequentially transferred through the six reaction spaces 140 to 190 is exposed to the inert gas P, the fourth reactant gas D, the inert gas P, the inert gas P, the third reactant gas C, and the inert or purge gas P such that a second thin film CD is deposited on the surface of each substrate by ALD. The gas supplying scheme shown in FIG. 9B can be used for the third time period t3 of FIG. 3B.
As shown in FIG. 9C, during yet another time period, the reaction space 160 is supplied with the sixth reactant gas F, while the reaction space 190 is supplied with the fifth reactant gas E. During this time period, the other reaction spaces 140, 150, 170, 180 are supplied with the inert gas P. The surface of each substrate sequentially transferred through the six reaction spaces 140 to 190 is exposed to the inert gas P, the inert gas P, the sixth reactant gas F, the inert gas P, the inert gas P, and the fifth reactant gas E in sequence such that a third thin film EF is deposited on the surface of each substrate by ALD. The gas supplying scheme shown in FIG. 9C can be used for the fifth time period t5 of FIG. 3B.
Referring to FIG. 9D, during yet another time period, all the reaction spaces 140-190 may be supplied with a purge gas. The gas supplying scheme shown in FIG. 9D can be used for the second, fourth, and sixth time periods t2, t4, t6 of FIG. 3B. The gas supply schemes shown in FIG. 9A to 9D may be combined to deposit multiple layers including three thin films AB, CD, and EF overlying one another in a desired order.
As described above, multiple layers including at least two layers of different materials may be deposited on a plurality of substrates in a relatively short period of time. In addition, the configurations of the ALD apparatuses of the embodiments reduce undesired deposition by reaction between reactant gases. In addition to purge curtains and whole reactant spaces separating reactant spaces that have reactant flowing, each reactant space is subject to only one reactant, despite use in deposition of multiple materials. This minimizes risk of interaction between mutually reactive reactants, except for on the substrate surfaces. Nevertheless, multiple types of deposition can be conducted in the same apparatus without unloading the substrates.
While this invention has been described in connection with what is presently considered to be certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Patent Application
20080075858
