Patent Application
20080289575
1. Field of the Invention
The present invention relates to methods and apparatus for depositing a Group III-V film on a substrate by a hydride vapor phase epitaxy (HVPE) process.
2. Description of the Background Art
Exptaxial Group III-V layers are widely used in optoelectronics. In particular, intense blue to ultraviolet light emitting diodes (LED) are fabricated by gallium nitride (GaN) layers. Since nitrogen has high electronegaticity, GaN has a crystal structure of wurtzite in a stable state and has a crystal structure of zinc-blende in a metastable state. Additionally, GaN crystal includes a plurality of unit cells with predetermined lattice constant at room temperature, thereby assisting the GaN film to remain in a stable state while applying at ambient environment. The stable crystal structure and desired lattice constant make GaN film a promising candidate for manufacturing blue light emitting diodes (LED).
Several technologies have been developed to grow Group III-V semiconductors, such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and hydride vapor phase epitaxy (HVPE). Hydride vapor phase epitaxy (HVPE) process offers several advantages, such as high growth rate, simplicity, and low manufacturing cost compared to other conventional techniques. HVPE processes for growing Group III-V are generally performed in a reactor having a temperature controlled environment to assure the stability of Group III agent used in the process. Group III agents provided by a Group III source, such as Ga metal source, in the reactor reacts with HCl gas, forming Group III halide vapor. A Group V agent, such as ammonia (NH3), is subsequently transported vapor by a separate gas line to a reacting zone in the reactor where it may mix with the Group III halide vapor, such as GaCl. A carrier gas is used to carry Group III halide and Group V vapor towards the substrate within the reactor. The mixed Group III halide, such as GaCl, and Group V vapor, such as ammonia (NH3), carried by the carrier gas is subsequently eptaxial grown into a Group III-V layer (GaN) on the substrate surface. The film quality, uniformity and deposition rate may depend in part upon consistent mixing of precursors across the substrate.
Therefore, there is a need for an improved apparatus for growing a Group III-V film on a substrate by a hydride vapor phase epitaxy (HVPE) process.
The present invention provides improved methods and apparatus for depositing a Group III-V using a hydride vapor phase epitaxy (HVPE) process. In one embodiment, an apparatus for a hydride vapor phase epitaxy process may include an elongated body having a trough defined between a first and a second wall, a channel formed in the first wall configured to provide a gas to the trough, and an inlet port formed in the body coupled to the channel.
In another embodiment, an apparatus for a hydride vapor phase epitaxy process may include a chamber, a substrate support assembly adapted to receive a substrate disposed thereon, an elongated body having a trough defined between a first and second walls disposed in the chamber proximate the substrate support assembly, an outer inlet port formed in the elongated body, a gas dispense assembly attached to the elongated body, and an inlet port and an outlet port each formed above the first and the second wall of the trough.
In yet another embodiment, a method for a hydride vapor phase epitaxy process may include providing Group III metal liquid precursor in a container disposed in a chamber, flowing a halogen containing gas across the container to form a Group III metal halide vapor to a reacting zone in the chamber, and mixing the Group III metal halide vapor with Group V gas supplied in the chamber in the reacting zone.
So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.
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 invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention provides a method and apparatus for depositing a Group III-V film on a substrate surface using a hydride vapor phase epitaxy (HVPE) process. The invention provides a good control of a gas precursor mixture comprising Group III metal and Group V vapor, thereby enabling reliable and repeatable Group III-V film deposition with desired film properties and crystal structure on a substrate.
The chamber 100 generally includes a chamber body 102 having a processing region 116 defined therein. A substrate support assembly 104 is disposed in the processing region 116 having a substrate carrier 106 configured to receive a plurality of substrates 108 positioned thereon. A heating element (shown as 478 in
A metal precursor container 110 is disposed radially outward of the substrate support assembly 104 and configured to provide Group III metal agent for processing. Examples of Group III metals include gallium (Ga), aluminum (Al), indium (In) and the like. In one embodiment, the metal precursor container 110 may be fabricated by a corrosive resist material, such as quartz, glass, polymer, ceramic, or other materials substantially inert to halogen containing gas. Suitable examples of the material for fabricating the metal precursor container 110 include sapphire and quartz. In the embodiment depicted in
A gas inlet port 122 may be connected to the container 110 to supply a first reacting gas to the container 110. The gas inlet port 122 prevents the first reacting gases from pre-mixing or pre-reacting with other reacting gases from other sources supplied into the chamber 100 before entering into the processing region 116. The first reacting gases provided from the gas inlet port 122 flows across the container 110 to react with metal precursor disposed therein. In one embodiment, the first reacting gas is a halogen containing gas. Examples of halogen elements include chlorine (Cl), bromine (Br), and iodine (I). In the embodiment depicted in the present invention, the second reacting gas provided through the gas inlet port 122 is HCl gas.
A gas dispense assembly 112 is positioned adjacent to a sidewall of the metal precursor container 110 to supply the second reacting gas through a gas inlet port 114 to the processing region 116. The gas inlet port 114 formed in the gas dispense assembly 112 may supply the second reacting gas to the processing region 116 through a plurality of apertures 128 formed on a bottom side of the gas dispense assembly 112 (shown as 314 in
A metal precursor source 120 (also shown as 304 in
A gas manifold 126 may be disposed adjacent to each end of the container 110. Inert gas and/or purge gas are provided to the manifold 126 through inlet ports 118, 124 and flow into to the processing region 116 through outlet ports 138, 134 formed in the manifold 126. Different inert gas and/or purge gas may be supplied from the outlet ports 138, 134 to the chamber 100 to direct the gas flow from other gas inlet ports 114, 122 to desired regions of the chamber 100. In one embodiment, the ports, 138, 134 are coupled to a gas distribution plate positioned over the support 116 so that the vapor leaving the container 110 mixes with the second reacting gas over the substrates 108. Additionally, the inert gas and/or purge gas from the outlet ports 138, 134 may prevent the second gas flow entering the container 110, thereby preventing films from being formed on undesired regions in the chamber 100. In one embodiment, the inert gas and/or purge gas may include N2, H2, N2O, NO2, O3, He, Ar, and Kr among others.
At least one groove 210 is formed on an upper surface of the inner wall 214A to facilitate gas flow from the channel 216 to the trough 218. The grooves 210 create a restriction so the first reacting gas provided from the gas inlet port 122 uniformly distributed across the top of the channel 216. As the channel 216 is substantially filled with the reacting gas, the reacting gas flows through the grooves 210 to the trough 218. The configuration of the channel 216 provides a buffer zone or plenum for the reacting gas provided by the gas inlet port 122 to uniformly be provided to the grooves 210, thus resulting in a uniform and well-controlled flow of the first reacting gas to the trough 218. The numbers, shape, depth, distribution, and designs of the channel 216 and the grooves 210 may be varied to meet different process requirements.
In one embodiment, the bottom wall 208 of the body 212 extends beyond the second wall 204, thereby defining a recess 206 along the outer surface of the second wall 204. The recess 206 forms a slot when a container lid is disposed on the metal precursor container 110 to cover the trough 218 to direct the reacting gases to the processing region 116, as will be detail described below with reference to
The trough 218 may be filled with an amount of Group III metal precursor sufficient to react with the reacting gas from the gas supplying assembly 112. The Group III metal precursor filling in the trough 218 provides a source material that reacts with the first reacting gas and further forms a metal nitride layer on the substrate surface when mixed with the second reacting gas. In some embodiments, the metal precursor may be a solid metal material, such as bulk Ga. In some embodiments, the metal precursor may be in liquid form, such as liquid Ga metal. In some embodiments depicted in the present invention, the metal precursor may be in form of Ga-containing liquid. In some embodiments, the metal precursor may fill in the container 110 by the metal precursor source 120 to about between about 300 cubic centimeters and about 100 cubic centimeters or greater. In another embodiment, the metal precursor may fill in the container 110 by the metal precursor source 120 to about 1 mm or greater below the top of the second wall 204.
A heating element (shown as 524 in
A temperature detector 310 may be interfaced with to the metal precursor container 110 to monitor the container temperature and enable feed back for temperature control. In one embodiment, the temperature detector 310 may be a thermocouple coupled to the body 212, a remote pyrometric sensor, or other suitable temperature monitor device. In another embodiment, the temperature detect 310 may be in form of a device remote from the body having a detecting probe attaching to the body 212 through an aperture (not shown) formed in the body 212. The temperature detector 310 is coupled to a controller 316 to provide feed back loop for controlling the endpoint of the heating element, thereby enhancing temperature control.
In one embodiment, another configuration of a metal precursor source 304 different from the metal precursor source 120 of
In one embodiment, the trough 218 may be isolated by dividers 330 (shown in phantom in
The substrate carrier 106 is rotated by the power supply 480 so that each substrate 108 disposed around the substrate carrier 106 may be alternatively rotated into the reaction zone 450, thereby enhancing film growth and uniformity. Additionally, the heating elements 478 embedded in the substrate support assembly 104 maintain the substrate temperature at a desired processing temperature, thereby promoting the reacting rate for the deposition process.
During processing, a metal precursor 404 is disposed within the trough 218 of the elongated body 212. A container lid 408 is disposed on the metal precursor container 110 to confine the reacting gas flow in a desired flow path through the container 110. As the first reacting gas is supplied to the channel 216 of the container 110, the first reacting gas flows through an inlet port 420 defined between the groove 210 and the container lid 408, as shown by arrow 406. In some embodiments, at least one baffle 410 extends from a bottom surface of the container lid 408 toward the metal precursor 404 disposed in the elongated body 212. The baffle 410 extends into the upper region of the trough 218 and creates a tortuous path for the first reacting gas flowing through the body 212, thereby increasing the residence time and flow disturbance of the first reacting gas over the metal precursor 404. In some embodiments, a maze-lie wall, rows of tubes, spiral wire, coiled wire and other different types of configurations may be disposed in the upper region of the trough 218 above the metal precursor 404 to increase gas turbulence and extend the flow path. Alternatively, the baffle 410 and/or other types of flow path increasing elements may extend into a predetermined depth into the metal precursor 404 to create bubbles or foam that increases the surface area of the metal precursor 404 exposed to the first reacting gas. In yet another embodiment, the baffle 410 and/or other types of flow path increasing elements may be rotated to enhance the gas circulations in the upper region of the trough 218. In embodiments where the baffle 410 and/or other types of flow path increasing elements extends into the metal precursor 404, the baffle 410 may be moved and/or rotated so that the metal precursor 404 is agitated to increase exposed surface of the metal precursor to the first reacting gases.
The second wall 204 has a height slightly lower than the height of the first wall 202 of the elongated body 212. As the container lid 408 covers across the elongated body 212, an outlet port 422 is defined between the upper surface of the second wall 204 and the container lid 408 due to the height difference between the first wall 202 and the second wall 204. The height of the second wall 204 of the body 212 may be selected to assist in regulating the amount of first reacting gas flow, now in reacted with the metal to from a metal containing vapor, passing through the outlet port 422, thereby efficiently controlling the gas flow rate to the reacting zone 450.
The container lid 408 has an end 460 extending outwardly across the second wall 204 to a lip 412. The lip 412 extends downward adjacent the recess 206 defined in the second wall 204. A slot 462 is defined between the second wall 204 and an end 464 of lip 412 across the recess 206. The width of the slot 462 may be configured by selecting a length of the lip 412 of the container lid 408. In embodiments where a greater amount of metal containing vapor is desired, the width of the slot 462 may be larger to facilitate a greater volume of gas flow therethrough.
The lip 412 may have a length less the length of the second wall 204, thereby defining an opening 424 between the end 464 of the lip 412 and the body 212. The dimension and/or shape of the opening 424 may be varied according to different process requirements by increasing or decreasing the length of the lip 412. Alternatively, the dimension of the opening 424 may be varied in accordance with different ends 464 of the lip 412 as described further below with reference to
In embodiments where a first reacting gas is HCl and the metal precursor 404 is liquid Ga metal, the HCl gas may be supplied to the channel 216 through the inlet port 420 to the trough 218 of the elongated body 212. The HCl gas reacts with Ga metal, forming GaCl vapor. The GaCl vapor is subsequently transported through the outlet port 422 into the slot 462 defined in the recess 206. The GaCl vapor exits the body 212 through to the opening 424. A second reacting gas, such as a Group V gas, for example, NH3 gas, is supplied from a gas port 416, located out of the container 100. The second reacting gas flows below the metal precursor container 110, as shown in phantom by arrow 416, to the reacting zone 450 above the substrate surface 418. In one embodiment, a first carrier gas may be optionally used to transport the first and/or the second reacting gas to the reacting zone 450. A second carrier gas 498, such as N2, H2, Ar He, supplied from the ports 138, 134, or other source, such as from the gas distribution plate 402, is supplied to the chamber 100. The second carrier gas directs the GaCl vapor and NH3 gas toward the substrate surface. The NH3 gas reacts with the GaCl vapor to form a GaN film on the substrate surface 418. The growth rate of the GaN film may be determined by reacting temperature, reacting vapor concentration, gas flow rate, and ratio of gas vapor mixing. The process may be terminated as a desired thickness of GaN is reached. In one embodiment, the GaN film is deposited to a thickness between about 0.5 μm and about 100 μm.
During processing, several process parameters may be regulated. In one embodiment, HCl gas supplied from the gas supplying assembly 122 to the metal precursor container 110 may have a flow rate at between about 5 sccm and about 1 slm. The second carrier gas supplied from the gas distribution plate 402 into the processing region 116 may have a flow rate at between about 0 sccm and about 5 slm. Suitable examples of the carrier gas include H2, N2, Ar, He and combinations thereof. Optionally, the first carrier gas may be supplied with the NH3 or HCl into the reacting region 450 at a flow rate between about 0 and about 20 slm.
The substrate temperature may be controlled between about 700 degrees Celsius and about 1400 degrees Celsius. The metal precursor container 110 may be controlled at a temperature between about 900 degrees Celsius and about 1200 degrees Celsius.
A heating element 524 may be interfaced with the body 554 of the container 500 to control the temperature of metal precursor 522 disposed therein. A lamp assembly 528 may be optionally disposed around and/or below the metal precursor container 500 to enhance control of the container temperature, thereby substantially preventing temperature gradients across the metal precursor container 500. Alternatively, the lamp assembly 528 may be disposed below the container lid 542 to provide radiant heat to the metal precursor. A temperature detector 552 similar to the temperature detector 112 of
The container lid 542 includes a lip 544 having the end 546 facing downwardly toward an upper surface 550 of a recess 540. The end 546 may have a sloped surface 516 to direct the flow of vapor exit the body 554. Alternatively, the end 546 may have a flat, horizontal surface 515, as shown in
A blocking wall 606 is disposed on an end 658 of the bottom leg 650 and below the container lid 604. The blocking wall 606 is spaced from the second wall 606 so that a slot 628 is defined therebetween. The blocking wall 606 may be part of the lid 606, the support 602, or be a separate component. The blocking wall 606 has a substantially horizontal slot or plurality of openings 630 to facilitate vapor flowing out of the container 600 into a reacting zone 660 defined over a substrate surface 662. The plurality of openings 630 may elevated above from the substrate surface, thereby allowing the reacting gas flowing therethrough to be injected on a desired region 634 on the substrate surface 662. The trajectory of the vapor exiting the opening 630 may be controlled and be selected at an appropriate injection angle 638. Alternatively, a plurality of openings 632 formed in the blocking wall 606 may be located at different heights and/or different injection angles 640 to create different reacting region 636. Similar to the configuration described above in
As the openings 630, 632 formed on the blocking wall 606 may be formed at different heights on the blocking wall 606, gave different configuration, angle, distribution, and number, the adjustable profile, thickness and uniformity of the deposited Group III nitride film may be tailored to meet specific design requirements. The configuration of the openings 630, 632 formed in the blocking wall 606 may be readily changed by switching to another blocking wall.
Thus, an improved method and apparatus for depositing a Group III nitride using a hydride vapor phase epitaxy (HVPE) process are provided. The improved apparatus advantageously facilitates reproducible and robust Group III nitride film deposition, thereby enhancing film to film crystal structure reproduction.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
