Patent Application
20240006197
The present invention relates to a heat treatment apparatus irradiating a substrate with light, thereby heating the substrate. Examples of a substrate to be processed include a semiconductor wafer, a liquid crystal display apparatus substrate, a flat panel display (FPD) substrate, an optical disk substrate, a magnetic disk substrate, or a solar cell substrate.
A flash lamp annealing (FLA) heating a semiconductor wafer in an extremely short time attracts attention in a manufacturing process of a semiconductor device. The flash lamp anneal is a heat treatment technique of irradiating a surface of a semiconductor wafer with a flash of light using a xenon flash lamp (a simple term of “a flash lamp” means a xenon flash lamp hereinafter), thereby increasing a temperature of only the surface of the semiconductor wafer in an extremely short time (several milliseconds or less).
A radiation spectral distribution of the xenon flash lamp ranges from an ultraviolet region to a near-infrared region, thus a wavelength of the xenon flash lamp is shorter than that of a conventional halogen lamp, and almost coincides with a basic absorption band of a silicon semiconductor wafer. Thus, when the semiconductor wafer is irradiated with a flash of light emitted from the xenon flash lamp, the temperature of the semiconductor wafer can be rapidly increased with less transmitted light. It is also known that a flash light emission for the extremely short time of several milliseconds or less can selectively increase a temperature of only a region near the surface of the semiconductor wafer.
Such a flash lamp anneal is used for processing requiring a heating for an extremely short time, for example, typically an activation of impurity implanted into the semiconductor wafer. When the surface of the semiconductor wafer into which the impurity is implanted by an ion implantation method is irradiated with a flash of light from the flash lamp, the surface of the semiconductor wafer can be increased to an activation temperature only for the extremely short time, thus only an impurity activation can be executed without deeply diffusing the impurity.
Used typically as an apparatus for executing such a flash lamp anneal is a heat treatment apparatus in which a flash lamp is provided on an upper side of a chamber housing a semiconductor wafer and a halogen lamp is provided on a lower side thereof (for example, US 2011/0262115). In the apparatus disclosed in US 2011/0262115, the semiconductor wafer is preheated by light irradiation from the halogen lamp, and subsequently, the surface of the semiconductor wafer is irradiated with a flash of light from the flash lamp. The preheating is performed by the halogen lamp because the surface of the semiconductor wafer hardly reaches to a target temperature only by the flash light irradiation.
However, when the preheating is performed by the halogen lamp, it takes a certain period of time for the halogen lamp to reach a target output after being turned on, and a heat irradiation tentatively continues after the halogen lamp is turned off, thus there is a problem that a diffusion length of impurity implanted into the semiconductor wafer is relatively increased.
The halogen lamp mainly emits infrared light having a relatively long wavelength. With regard to a spectral absorption index of a silicon semiconductor wafer, an absorption index of infrared light having a long wavelength of 1 m or more is low in a low temperature range of 500° C. or less. That is to say, the semiconductor wafer having a temperature of 500° C. or less does not absorb infrared light emitted from the halogen lamp so much, thus an inefficient heating is performed in an initial stage of preheating.
It is considered to preheat the semiconductor wafer using a plurality of LED lamps as a method of solving these problems. The LED lamp has a high-speed rise and fall output compared with a halogen lamp. The LED lamp mainly emits visible light. Thus even in a case of a semiconductor wafer having a relatively low temperature of 500° C. or less, an absorption index of light emitted from the LED lamp is high, and the heating treatment can be efficiently performed even in an initial stage of preheating by using the LED lamp.
However, output of each LED lamp itself is relatively weak, thus intensity of light emitted to the semiconductor wafer is relatively weak. As a result, heating efficiency of heating the semiconductor wafer using the LED lamp is not sufficient. Considerably many LED lamps need to be disposed in a certain area to obtain high irradiation intensity.
The present invention is directed to a heat treatment apparatus irradiating a substrate with light, thereby heating the substrate.
According to one aspect of the present invention, a heat treatment apparatus includes: a chamber housing a substrate; a holder holding the substrate in the chamber; an auxiliary light source provided on one side of the chamber to irradiate the substrate held by the holder with light, the auxiliary light source including a plurality of vertical cavity surface emitting lasers; and a flash lamp provided on another side of the chamber to irradiate the substrate held by the holder with a flash of light.
The auxiliary light source includes the plurality of vertical cavity surface emitting lasers, thus intensity of light emitted to the substrate can be increased, and the substrate can be efficiently heated.
The auxiliary light source preferably includes a vertical cavity surface emitting laser emitting light having a different wavelength.
Even when apart of the substrate includes a portion having a low absorption index on light having a specific wavelength, a whole surface of the substrate can be uniformly heated.
It is preferable that the heat treatment apparatus further includes a homogenizer homogenizing light emitted from each of the plurality of vertical cavity surface emitting lasers between the chamber and the auxiliary light source.
An illuminance distribution in an irradiated surface of the substrate can be uniformed, and an in-plane temperature distribution of the substrate can be uniformed.
It is preferable that the auxiliary light source further includes a plurality of LED lamps, and the plurality of vertical cavity surface emitting lasers are circularly disposed to surround the plurality of LED lamps.
A peripheral part of the substrate where reduction in temperature easily occurs can be irradiated with light having high directionality from the vertical cavity surface emitting lasers to strongly heat the peripheral part, thus the in-plane temperature distribution of the substrate can be uniformed.
Accordingly, an object of the present invention is to efficiently heat a substrate.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Embodiments according to the present invention will now be described in detail with reference to the drawings. In the description hereinafter, unless otherwise noted, the expressions indicating relative or absolute positional relationships (e.g., “in one direction”, “along one direction”, “parallel”, “orthogonal”, “central”, “concentric”, and “coaxial”) include those exactly indicating the positional relationships and those where an angle or a distance is relatively changed within tolerance or to the extent that similar functions can be obtained. Unless otherwise noted, the expressions indicating equality (e.g., “same”, “equal”, and “uniform”) include those indicating quantitatively exact equality and those in the presence of a difference within tolerance or to the extent that similar functions can be obtained. Unless otherwise noted, the expressions indicating shapes (e.g., “circular”, “rectangular”, and “cylindrical”) include those indicating geometrically exact shapes and those indicating, for example, roughness or a chamfer to the extent that similar effect can be obtained. An expression “comprising”, “including”, or “having” a certain constituent element is not an exclusive expression for excluding the presence of the other constituent elements. An expression “at least one of A, B, and C” involves only A, only B, only C, arbitrary two of A, B, and C, and all of A, B, and C.
The heat treatment apparatus 1 includes a chamber 6 for housing the semiconductor wafer W, a flash heating part 5 including a plurality of built-in flash lamps FL, and an auxiliary heating part 4 including a plurality of vertical cavity surface emitting lasers (VCSELs) 45. The flash heating part 5 is provided over the chamber 6, and the auxiliary heating part 4 is provided under the chamber 6. The heat treatment apparatus 1 includes a holder 7 provided inside the chamber 6 and for holding the semiconductor wafer W in a horizontal attitude, and a transfer mechanism 10 provided inside the chamber 6 and for transferring the semiconductor wafer W between the holder 7 and the outside of the heat treatment apparatus 1. The heat treatment apparatus 1 further includes a controller 3 for controlling each operating mechanism provided to the auxiliary heating part 4, the flash heating part 5, and the chamber 6 to cause each operating mechanism to execute a heat treatment on the semiconductor wafer W.
The chamber 6 is configured such that upper and lower chamber windows made of quartz are mounted to the top and bottom, respectively, of a tubular chamber side portion 61. The chamber side portion 61 has a generally tubular shape having an open top and an open bottom. An upper chamber window 63 is mounted to block the top opening of the chamber side portion 61, and a lower chamber window 64 is mounted to block the bottom opening thereof. The upper chamber window 63 forming the ceiling of the chamber 6 is a disk-shaped member made of quartz, and serves as a quartz window that transmits a flash of light emitted from the flash heating part 5 therethrough into the chamber 6. The lower chamber window 64 forming the floor of the chamber 6 is also a disk-shaped member made of quartz, and serves as a quartz window that transmits light emitted from the auxiliary heating part 4 therethrough into the chamber 6.
An upper reflective ring 68 is mounted to an upper portion of the inner wall surface of the chamber side portion 61, and a lower reflective ring 69 is mounted to a lower portion thereof. Both of the upper and lower reflective rings 68 and 69 are in the form of an annular ring. The upper reflective ring 68 is mounted by being inserted downwardly from the top of the chamber side portion 61. The lower reflective ring 69, on the other hand, is mounted by being inserted upwardly from the bottom of the chamber side portion 61 and fastened with screws not shown. In other words, the upper and lower reflective rings 68 and 69 are removably mounted to the chamber side portion 61. An interior space of the chamber 6, i.e. a space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side portion 61, and the upper and lower reflective rings 68 and 69, is defined as a heat treatment space 65.
A recessed portion 62 is defined in the inner wall surface of the chamber 6 by mounting the upper and lower reflective rings 68 and 69 to the chamber side portion 61. Specifically, the recessed portion 62 is defined which is surrounded by a middle portion of the inner wall surface of the chamber side portion 61 where the reflective rings 68 and 69 are not mounted, a lower end surface of the upper reflective ring 68, and an upper end surface of the lower reflective ring 69. The recessed portion 62 is provided in the form of a horizontal annular ring in the inner wall surface of the chamber 6, and surrounds the holder 7 which holds the semiconductor wafer W. The chamber side portion 61 and the upper and lower reflective rings 68 and 69 are made of a metal material (e.g., stainless steel) with high strength and high heat resistance.
The chamber side portion 61 is provided with a transport opening (throat) 66 for the transport of the semiconductor wafer W therethrough into and out of the chamber 6. The transport opening 66 is openable and closable by a gate valve 185. The transport opening 66 is connected in communication with an outer peripheral surface of the recessed portion 62. Thus, when the transport opening 66 is opened by the gate valve 185, the semiconductor wafer W is allowed to be transported through the transport opening 66 and the recessed portion 62 into and out of the heat treatment space 65. When the transport opening 66 is closed by the gate valve 185, the heat treatment space 65 in the chamber 6 is an enclosed space.
The chamber side portion 61 is further provided with a through hole 61a bored therein. A radiation thermometer 20 is mounted in a location of an outer wall surface of the chamber side portion 61 where the through hole 61a is provided. The through hole 61a is a cylindrical hole for directing infrared radiation emitted from a lower surface of a semiconductor wafer W held by a susceptor 74 to be described later therethrough to the radiation thermometer 20. The through hole 61a is inclined with respect to a horizontal direction so that a longitudinal axis (an axis extending in a direction in which the through hole 61a extends through the chamber side portion 61) of the through hole 61a intersects a main surface of the semiconductor wafer W held by the susceptor 74. Thus, the radiation thermometer 20 is provided obliquely lower side of the susceptor 74. A transparent window 21 made of barium fluoride material transparent to infrared radiation in a wavelength range measurable with the radiation thermometer 20 is mounted to an end portion of the through hole 61a which faces the heat treatment space 65.
At least one gas supply opening 81 for supplying a treatment gas therethrough into the heat treatment space 65 is provided in an upper portion of the inner wall of the chamber 6. The gas supply opening 81 is provided above the recessed portion 62, and may be provided to the upper reflective ring 68. The gas supply opening 81 is connected in communication with a gas supply pipe 83 through a buffer space 82 provided in the form of an annular ring inside the side wall of the chamber 6. The gas supply pipe 83 is connected to a treatment gas supply source 85. A valve 84 is inserted at some midpoint in the gas supply pipe 83. When the valve 84 is opened, the treatment gas is supplied from the treatment gas supply source 85 to the buffer space 82. The treatment gas which has flowed into the buffer space 82 flows in a spreading manner within the buffer space 82 which is lower in fluid resistance than the gas supply opening 81, and is supplied through the gas supply opening 81 into the heat treatment space 65. An inert gas such as nitrogen (N2), a reactive gas such as hydrogen (H2) and ammonia (NH3), or a gas mixture thereof, for example, can be used as the treatment gas (nitrogen gas in the present embodiment).
At least one gas exhaust opening 86 for exhausting a gas from the heat treatment space 65 is provided to a lower portion of the inner wall of the chamber 6. The gas exhaust opening 86 is provided below the recessed portion 62, and may be provided to the lower reflective ring 69. The gas exhaust opening 86 is connected in communication with a gas exhaust pipe 88 through a buffer space 87 provided in the form of an annular ring inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to an exhaust part 190. A valve 89 is inserted at some midpoint in the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is exhausted through the gas exhaust opening 86 and the buffer space 87 to the gas exhaust pipe 88. The at least one gas supply opening 81 and the at least one gas exhaust opening 86 may include a plurality of gas supply openings 81 and a plurality of gas exhaust openings 86, respectively, arranged in a circumferential direction of the chamber 6, and may be in the form of slits. The treatment gas supply source 85 and the exhaust part 190 may be mechanisms provided to the heat treatment apparatus 1 or be a utility in a factory in which the heat treatment apparatus 1 is installed.
The base ring 71 is a quartz member having an arcuate shape obtained by removing a portion from an annular shape. This removed portion is provided to prevent interference between transfer arms 11 of the transfer mechanism 10 to be described later and the base ring 71. The base ring 71 is supported by a wall surface of the chamber 6 by being placed on the bottom surface of the recessed portion 62 (with reference to
The susceptor 74 is supported by the four coupling portions 72 provided on the base ring 71.
The guide ring 76 is provided on a peripheral part of the upper surface of the holding plate 75. The guide ring 76 is an annular member having an inner diameter greater than the diameter of the semiconductor wafer W. For example, when the diameter of the semiconductor wafer W is 300 mm, the inner diameter of the guide ring 76 is 320 mm. The inner periphery of the guide ring 76 is in the form of a tapered surface which becomes wider in an upward direction from the holding plate 75. The guide ring 76 is made of quartz similar to that of the holding plate 75. The guide ring 76 may be welded to the upper surface of the holding plate 75 or fixed to the holding plate 75 with separately machined pins and the like. Alternatively, the holding plate 75 and the guide ring 76 may be machined as an integral member.
A region of the upper surface of the holding plate 75 which is inside the guide ring 76 serves as a planar holding surface 75a for holding the semiconductor wafer W. The substrate support pins 77 are provided upright on the holding surface 75a of the holding plate 75. In the present embodiment, a total of 12 substrate support pins 77 provided upright are spaced at intervals of 30 degrees along the circumference of a circle concentric with the outer circumference of the holding surface 75a (the inner circumference of the guide ring 76). The diameter of the circle on which the 12 substrate support pins 77 are disposed (the distance between opposed ones of the substrate support pins 77) is smaller than the diameter of the semiconductor wafer W, and is 270 to 280 mm (in the present embodiment, 270 mm) when the diameter of the semiconductor wafer W is 300 mm. Each of the substrate support pins 77 is made of quartz. The substrate support pins 77 may be provided by welding on the upper surface of the holding plate 75 or machined integrally with the holding plate 75.
Referring again to
The semiconductor wafer W transported into the chamber 6 is placed and held in a horizontal attitude on the susceptor 74 of the holder 7 mounted to the chamber 6. At this time, the semiconductor wafer W is supported by the 12 substrate support pins 77 provided upright on the holding plate 75, and is held by the susceptor 74. More strictly speaking, the 12 substrate support pins 77 have respective upper end portions coming in contact with the lower surface of the semiconductor wafer W to support the semiconductor wafer W. The semiconductor wafer W can be supported in a horizontal attitude by the 12 substrate support pins 77 because the 12 substrate support pins 77 have a uniform height (distance from the upper ends of the substrate support pins 77 to the holding surface 75a of the holding plate 75).
The semiconductor wafer W supported by the substrate support pins 77 is spaced a predetermined distance apart from the holding surface 75a of the holding plate 75. A thickness of the guide ring 76 is greater than the height of the substrate support pins 77. Thus, the guide ring 76 prevents the horizontal misregistration of the semiconductor wafer W supported by the substrate support pins 77.
As illustrated in
The pair of transfer arms 11 are moved upwardly and downwardly together with the horizontal movement mechanism 13 by an elevating mechanism 14. As the elevating mechanism 14 moves up the pair of transfer arms 11 in their transfer operation position, the four lift pins 12 in total pass through the respective four through holes 79 (with reference to
Referring again to
The flash lamps FL, each of which is a rod-shaped lamp having an elongated cylindrical shape, are arranged in a plane so that the longitudinal directions of the respective flash lamps FL are in parallel with each other along a main surface of the semiconductor wafer W held by the holder 7 (that is, in the horizontal direction). Thus, a plane defined by the arrangement of the flash lamps FL is also a horizontal plane. A region in which the flash lamps FL are arranged has a size, as seen in plan view, greater than that of the semiconductor wafer W.
Each of the xenon flash lamps FL includes a cylindrical glass tube (discharge tube) containing xenon gas sealed therein and having positive and negative electrodes provided on opposite ends thereof and connected to a capacitor, and a trigger electrode attached to the outer peripheral surface of the glass tube. Because the xenon gas is electrically insulative, no current flows in the glass tube in a normal state even if electrical charge is stored in the capacitor. However, if high voltage is applied to the trigger electrode to produce an electrical breakdown, electricity stored in the capacitor flows momentarily in the glass tube, and xenon atoms or molecules are excited at this time to cause light emission. This xenon flash lamp FL has the property of being capable of emitting extremely intense light as compared with a light source that stays lit continuously such as a halogen lamp because the electrostatic energy previously stored in the capacitor is converted into an ultrashort light pulse ranging from 0.1 to 100 milliseconds. Thus, the flash lamps FL are pulsed light emitting lamps which emit light instantaneously for an extremely short time period of less than one second. The light emission time of the flash lamps FL is adjustable by the coil constant of a lamp light source which supplies power to the flash lamps FL.
The reflector 52 is provided over the plurality of flash lamps FL so as to cover all of the flash lamps FL. A fundamental function of the reflector 52 is to reflect the flash of light emitted from the plurality of flash lamps FL toward the heat treatment space 65. The reflector 52 is a plate made of an aluminum alloy. A surface of the reflector 52 (a surface which faces the flash lamps FL) is roughened by abrasive blasting.
The auxiliary heating part 4 provided under the chamber 6 includes a plurality of built-in VCSELs 45 in an enclosure 41. The auxiliary heating part 4 directs light from under the chamber 6 through the lower chamber window 64 toward the heat treatment space 65 to heat the semiconductor wafer W by means of the plurality of VCSELs 45.
As illustrated in
The VCSEL (vertical cavity surface emitting laser) 45 is a type of a semiconductor laser, and emits light to a surface of the semiconductor substrate in a vertical direction. The VCSEL 45 can emit light having higher intensity than the LED, and emits light having high directionality. The plurality of VCSELs 45 according to the first embodiment emit light having a wavelength of 940 nm. The VCSEL 45 is a continuous lighting lamp that emits light continuously for at least not less than one second.
Voltage is applied to each of the plurality of VCSELs 45 from a power supply part 49 (
The controller 3 controls the aforementioned various operating mechanisms provided to the heat treatment apparatus 1. The controller 3 is similar in hardware configuration to a typical computer. Specifically, the controller 3 includes a CPU that is a circuit for performing various computation processes, a ROM or read-only memory for storing a basic program therein, a RAM or readable/writable memory for storing various pieces of information therein, and a magnetic disk for storing control software, data and the like therein. The CPU in the controller 3 executes a predetermined treatment program, whereby the processes in the heat treatment apparatus 1 proceed.
The heat treatment apparatus 1 further includes, in addition to the aforementioned components, various cooling structures to prevent an excessive temperature rise in the auxiliary heating part 4, the flash heating part 5, and the chamber 6 because of the heat energy generated from the VCSELs 45 and the flash lamps FL during the heat treatment of the semiconductor wafer W. As an example, a water cooling tube (not shown) is provided to the walls of the chamber 6. Also, the auxiliary heating part 4 and the flash heating part 5 have an air cooling structure for forming a gas flow therein to exhaust heat. Air is supplied to a gap between the upper chamber window 63 and the lamp light radiation window 53 to cool down the flash heating part 5 and the upper chamber window 63.
A treatment operation in the heat treatment apparatus 1 is described next. A typical heat treatment operation performed on a normal semiconductor wafer (product wafer) W which becomes a product is described herein. The semiconductor wafer W to be treated is a silicon (Si) semiconductor substrate into which impurity is implanted by ion implantation as a preceding process. The impurity is activated by an anneal processing performed by the heat treatment apparatus 1. The process procedure in the semiconductor wafer W described hereinafter proceeds when the controller 3 controls each operation mechanism of the heat treatment apparatus 1.
Firstly, the valve 84 for air supply is opened and the valve 89 for air exhaust are opened to start air supply and exhaust within the chamber 6 prior to the treatment of the semiconductor wafer W. When the valve 84 is opened, nitrogen gas is supplied from the gas supply opening 81 into the heat treatment space 65. Also, when the valve 89 is opened, the gas within the chamber 6 is exhausted through the gas exhaust opening 86. This causes the nitrogen gas supplied from an upper portion of the heat treatment space 65 in the chamber 6 to flow downwardly and then to be exhausted from a lower portion of the heat treatment space 65.
Subsequently, the gate valve 185 is opened to open the transport opening 66. A transport robot outside the heat treatment apparatus 1 transports the semiconductor wafer W to be processed through the transport opening 66 into the heat treatment space 65 in the chamber 6. At this time, there is a possibility that the atmosphere outside the apparatus is carried into the heat treatment space 65 as the semiconductor wafer W is transported into the heat treatment space 65, however, the nitrogen gas is continuously supplied into chamber 6, thus the nitrogen gas flows through the transport opening 66 and it is possible to minimize an outside atmosphere carried into the heat treatment space 65.
The semiconductor wafer W transported into the heat treatment space 65 by the transport robot is moved forward to a position lying immediately over the holder 7 and is stopped thereat. Then, the pair of transfer arms 11 of the transfer mechanism 10 is moved horizontally from the retracted position to the transfer operation position and is then moved upwardly, whereby the lift pins 12 pass through the through holes 79 and protrude from the upper surface of the holding plate 75 of the susceptor 74 to receive the semiconductor wafer W. At this time, the lift pins 12 move upwardly to above the upper ends of the substrate support pins 77.
After the semiconductor wafer W is placed on the lift pins 12, the transport robot moves out of the heat treatment space 65, and the gate valve 185 closes the transport opening 66. Then, the pair of transfer arms 11 moves downwardly to transfer the semiconductor wafer W from the transfer mechanism 10 to the susceptor 74 of the holder 7, so that the semiconductor wafer W is held in a horizontal attitude from below. The semiconductor wafer W is supported by the substrate support pins 77 provided upright on the holding plate 75, and is held by the susceptor 74. The semiconductor wafer W is held by the holder 7 in such an attitude that the front surface thereof where a pattern is formed and the impurity is implanted is the upper surface. A predetermined distance is defined between a back surface (a main surface opposite from the front surface) of the semiconductor wafer W supported by the substrate support pins 77 and the holding surface 75a of the holding plate 75. The pair of transfer arms 11 moved downwardly below the susceptor 74 is moved back to the retracted position, i.e. to the inside of the recessed portion 62, by the horizontal movement mechanism 13.
After the semiconductor wafer W is held in the horizontal attitude from below by the susceptor 74 of the holder 7 formed of quartz, the plurality of VCSELs 45 in the auxiliary heating part 4 emit light and preheating (or assist-heating) is started. Light emitted from the plurality of VCSELs 45 is transmitted through the lower chamber window 64 and the susceptor 74 both made of quartz, and impinges on the lower surface of the semiconductor wafer W. By receiving light irradiation from the VCSELs 45, the semiconductor wafer W is preheated, so that the temperature of the semiconductor wafer W increases. It should be noted that the transfer arms 11 of the transfer mechanism 10, which are retracted to the inside of the recessed portion 62, do not become an obstacle to the heating using the VCSELs 45.
The temperature of the semiconductor wafer W which is on the increase by the irradiation with light from the VCSELs 45 is measured with the radiation thermometer 20. The measured temperature of the semiconductor wafer W is transmitted to the controller 3. The controller 3 controls the power supply part 49 to adjust the output from the VCSELs 45 while monitoring whether or not the temperature of the semiconductor wafer W which is on the increase by the irradiation with light from the VCSELs 45 reaches a predetermined preheating temperature T1. In other words, the controller 3 effects feedback control of the output from the VCSELs 45 so that the temperature of the semiconductor wafer W is equal to the preheating temperature T1, based on the value measured with the radiation thermometer 20. The preheating temperature T1 is set to be approximately 200° C. to 800° C., and is preferably set to be approximately 350° C. to 600° C., so that there is no possibility of diffusion of the impurity added to the semiconductor wafer W caused by the heat (600° C. in the present embodiment).
After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the controller 3 maintains the temperature of the semiconductor wafer W at the preheating temperature T1 for a short time. Specifically, at the point in time when the temperature of the semiconductor wafer W measured with the radiation thermometer 20 reaches the preheating temperature T1, the controller 3 adjusts the output from the VCSELs 45 to maintain the temperature of the semiconductor wafer W at approximately the preheating temperature T1.
The flash lamps FL in the flash heating part 5 irradiate the front surface of the semiconductor wafer W held by the susceptor 74 with a flash of light at a time when a predetermined time period has elapsed since the temperature of the semiconductor wafer W reaches the preheating temperature T1. At this time, part of the flash of light emitted from the flash lamps FL travels directly toward the interior of the chamber 6. The remainder of the flash of light is reflected once from the reflector 52, and then travels toward the interior of the chamber 6. The irradiation of the semiconductor wafer W with such a flash of light achieves the flash heating of the semiconductor wafer W.
The flash heating, which is achieved by the emission of a flash of light from the flash lamps FL, is capable of increasing the temperature of the front surface of the semiconductor wafer W in a short time. Specifically, the flash of light emitted from the flash lamps FL is an intense flash of light emitted for an extremely short period of time ranging from about 0.1 to about 100 milliseconds as a result of the conversion of the electrostatic energy previously stored in the capacitor into such an ultrashort light pulse. The temperature of the front surface of the semiconductor wafer W is increased instantaneously to a treatment temperature T2 of 1000° C. or more by the flash light irradiation from the flash lamps FL, and after the impurity implanted into the semiconductor wafer W is activated, the temperature of the front surface decreases rapidly. In this manner, the heat treatment apparatus 1 can increase and decrease the temperature of the front surface of the semiconductor wafer W in the extremely short time, thus the diffusion of the impurity implanted into the semiconductor wafer W caused by the heat can be suppressed and the impurity can be activated. The time required for the activation of the impurity is extremely shorter than the time required for a heat diffusion, thus the activation is completed in a short time of approximately 0.1 milliseconds to 100 milliseconds in which the diffusion does not occur.
When the flash heating treatment is finished, the VCSELs 45 are turned off after an elapse of a predetermined time. Accordingly, the temperature of the semiconductor wafer W decreases rapidly from the preheating temperature T1. The radiation thermometer 20 measures the temperature of the semiconductor wafer W which is on the decrease. The result of measurement is transmitted to the controller 3. The controller 3 monitors whether the temperature of the semiconductor wafer W is decreased to a predetermined temperature or not, based on the result of measurement with the radiation thermometer 20. After the temperature of the semiconductor wafer W is decreased to the predetermined temperature or below, the pair of transfer arms 11 of the transfer mechanism 10 is moved horizontally again from the retracted position to the transfer operation position and is then moved upwardly, so that the lift pins 12 protrude from the upper surface of the susceptor 74 to receive the heat-treated semiconductor wafer W from the susceptor 74. Subsequently, the transport opening 66 which has been closed is opened by the gate valve 185, and the transport robot outside the heat treatment apparatus 1 transports the semiconductor wafer W placed on the lift pins 12 out of the chamber 6. Thus, the heating treatment of the semiconductor wafer W is completed.
In the first embodiment, the semiconductor wafer W is preheated to the preheating temperature T1 by the irradiation with light from the VCSELs 45, and subsequently the temperature of the front surface of the semiconductor wafer W is increased to a treatment temperature T2 by irradiating the front surface thereof with a flash of light from the flash lamps FL. The VCSEL 45 can emit light having relatively higher intensity than the LED. Thus, when light irradiation from the plurality of VCSELs 45 is performed, intensity of light emitted to the substrate W can also be increased at the time of preheating, and the semiconductor wafer W can be efficiently heated. The VCSELs 45 emits light having relatively high intensity, thus the number of VCSELs 45 disposed in the auxiliary heating part 4 can be reduced compared with a case where the auxiliary heating part 4 is made up of LED lamps.
In the first embodiment, the plurality of VCSELs 45 emit light having a single wavelength of 940 nm, however, in place of it, the plurality of VCSELs 45 may emit light having a plurality of different wavelengths. That is to say, plural types of VCSELs 45 each having a wavelength of emitting light different from each other may be provided to the auxiliary heating part 4. When light having a single wavelength is emitted from the plurality of VCSELs 45, in a case where a film having a low absorption index to the light having such a wavelength is formed in a part of the semiconductor wafer W, a temperature of only the part of the semiconductor wafer W is relatively low and in-plane uniformity of a temperature distribution may not be achieved. When light having a plurality of wavelengths is emitted from the plurality of VCSELs 45, a whole surface of the semiconductor wafer W can be uniformly heated to increase in-plane uniformity of a temperature distribution even in a case where a film having a low absorption index to the light having a specific wavelength is formed in a part of the semiconductor wafer W.
Next, a second embodiment according to the present invention will be described.
The homogenizer 48 is a quartz planar member provided between the plurality of VCSELs 45 and the lower chamber window 64 of the chamber 6. Although the homogenizer 48 is the planar member, it is not a single plate, but has a planar form as a result of bundling a plurality of diffraction optical elements 48a.
As illustrated in
The light emitted from the plurality of VCSELs 45 and passing through the homogenizer 48 is emitted to the semiconductor wafer W, thus illuminance unevenness in the irradiated surface of the semiconductor wafer W is resolved and the illuminance distribution is uniformed. As a result, an in-plane temperature distribution of the semiconductor wafer W at the time of preheating is also ununiformed.
The configuration of the heat treatment apparatus 1a in the second embodiment is the same as the heat treatment apparatus 1 in the first embodiment except that the homogenizer 48 is provided. A procedure of processing the semiconductor wafer W in the heat treatment apparatus 1a according to the second embodiment is also similar to that in the first embodiment.
In the second embodiment, the homogenizer 48 homogenizing the light emitted from each of the plurality of VCSELs 45 is provided between the chamber 6 and the plurality of VCSELs 45. Accordingly, a uniform illuminance distribution can be obtained in an upper surface of the homogenizer 48. Thus, a illuminance distribution in the irradiated surface of the semiconductor wafer W is also uniformed, and the in-plane temperature distribution of the semiconductor wafer W can also be uniformed.
Next, a third embodiment according to the present invention will be described.
The auxiliary heating part 4 according to the third embodiment includes the plurality of VCSELs 45 and the plurality of LED lamps 47. The LED lamp 47 includes a light emitting diode. The light emitting diode is a type of a diode, and emits light by electroluminescence effect when voltage is applied in a forward direction.
In the third embodiment, the plurality of LED lamps 47 are arranged in a center part of the auxiliary heating part 4, and the plurality of VCSELs 45 are arranged in a peripheral part thereof. That is to say, the plurality of VCSELs 45 are arranged to face the peripheral part of the semiconductor wafer W where the temperature easily decreases at the time of preheating, and the plurality of LED lamps 47 are arranged to face the center part of the semiconductor wafer W. Accordingly, the light having high directionality can be emitted from the VCSELs 45 to the peripheral part of the semiconductor wafer W where the temperature easily decreases at the time of preheating to relatively increase illuminance of the peripheral part thereof. As a result, the peripheral part of the semiconductor wafer W where the temperature easily decreases is strongly heated, thus reduction in temperature of the peripheral part is resolved, and the in-plane temperature distribution of the semiconductor wafer W at the time of preheating can be uniformed.
The configuration of the heat treatment apparatus 1b according to the third embodiment is the same as the heat treatment apparatus 1 according to the first embodiment except that the VCSELs 45 and the LED lamps 47 are provided to the auxiliary heating part 4. A procedure of processing the semiconductor wafer W in the heat treatment apparatus 1b according to the third embodiment is also similar to that according to the first embodiment.
In the third embodiment, the LED lamps 47 are provided to the auxiliary heating part 4 as the auxiliary light source in addition to the VCSELs 45, and the plurality of VCSELs 45 are circularly disposed to surround the plurality of LED lamps 47. Accordingly, light having high directionality is emitted from the VCSELs 45 to the peripheral part of the semiconductor wafer W where the temperature easily decreases at the time of preheating, thus the peripheral part can be strongly heated, and the in-plane temperature distribution of the semiconductor wafer W at the time of preheating can be uniformed.
A unit price of the VCSELs 45 is higher than that of the LED lamps 47. The VCSELS 45 are provided to only the peripheral part of the semiconductor wafer W where the temperature easily decreases, and the inexpensive LED lamps 47 are provided to the other portion, thus uniformity of the in-plane temperature distribution of the semiconductor wafer W can be achieved while suppressing increase in cost.
The plurality of VCSELs 45 and/or the plurality of LED lamps 47 may emit light having a plurality of different wavelengths. That is to say, plural types of VCSELs 45 each having a wavelength of emitting light different from each other and/or plural types of LED lamps 47 each having a wavelength of emitting light different from each other may be provided to the auxiliary heating part 4. In the manner similar to the first embodiment, when light having a plurality of wavelengths is emitted from the plurality of VCSELs 45 and/or the plurality of LED lamps 47, the whole surface of the semiconductor wafer W can be uniformly heated to increase in-plane uniformity of the temperature distribution even in a case where a film having a low absorption index to the light having a specific wavelength is formed in a part of the semiconductor wafer W.
Next, a fourth embodiment according to the present invention will be described.
In the fourth embodiment, additional VCSELs 45 are further arranged around the auxiliary heating part 4 according to the third embodiment. The plurality of additional VCSELs 45 are obliquely provided in a region on an outer side of the semiconductor wafer W held by the holder 7. More specifically, the plurality of LED lamps 47 are arranged with a uniform density in a circular region in the manner similar to the third embodiment. The plurality of VCSELs 45 are arranged with a uniform density in annular region surrounding the circular region where the plurality of LED lamps 47 are arranged. Furthermore, the plurality of additional VCSELs 45 are arranged around the annular region where the plurality of VCSELs 45 are arranged. The plurality of additional VCSELs 45 provided to the region on the outer side of the semiconductor wafer W are obliquely arranged so that an illuminance direction thereof is directed to the peripheral part of the lower surface of the semiconductor wafer W. A configuration and a process procedure according to the fourth embodiment are the same as those according to the third embodiment except that the plurality of additional VCSELs 45 are provided.
In the fourth embodiment, light having high directionality is emitted from the VCSELs 45 to the peripheral part of the semiconductor wafer W where the temperature easily decreases at the time of preheating, thus the peripheral part can be strongly heated in the manner similar to the third embodiment, and the in-plane temperature distribution of the semiconductor wafer W at the time of preheating can be uniformed. Furthermore, in the fourth embodiment, an additional light irradiation is performed on the surface of the semiconductor wafer W by the additional VCSELs 45, thus the semiconductor wafer W can be heated more efficiently.
Next, a fifth embodiment according to the present invention will be described.
The heat treatment apparatus 100 includes an upper portion heating part 150 on an upper side of a chamber 110 housing the semiconductor wafer W and a lower portion heating part 140 on a lower side of the chamber 110. A quartz susceptor 170 is provided in the chamber 110. The semiconductor wafer W to be processed is supported by the susceptor 170 in the chamber 110. A quartz window (not shown) that transmits light is provided to a top and bottom of the chamber 110 in the manner similar to the first embodiment.
The lower portion heating part 140 includes the plurality of VCSELs 45 in the manner similar to the auxiliary heating part 4 according to the first embodiment. Similarly, the upper portion heating part 150 also includes the plurality of VCSELs 45. The heat treatment apparatus 100 performs light irradiation from the top and bottom of the chamber 110 to heat the semiconductor wafer W by the plurality of VCSELs 45.
The light irradiation using the plurality of VCSELs 45 is performed from the top and bottom, thus the temperature of the semiconductor wafer W increases at a speed of 100° C. to 200° C. per second. The temperature of the semiconductor wafer W reaches a peak temperature T3 at a time when several seconds have elapsed since the plurality of VCSELs 45 starts light irradiation. The peak temperature T3 is 900° C. to 1000° C., for example. The plurality of VCSELs 45 stop light irradiation at a time when the temperature of the semiconductor wafer W reaches the peak temperature T3, and the temperature of the semiconductor wafer W rapidly decreases. Alternatively, the temperature of the semiconductor wafer W may be kept at the peak temperature T3 for a certain period of time (for example, several seconds).
In the fifth embodiment, the semiconductor wafer W is heated by light irradiation by the VCSELs 45 which can emit light relatively having higher intensity than the LEDs. Thus, the semiconductor wafer W can be efficiently heated.
While the embodiments according to the present invention have been described hereinabove, various modifications of the present invention are possible in addition to those described above without departing from the scope and spirit of the present invention. In the first embodiment, the plurality of VCSELs 45 are concentrically disposed, however, the configuration is not limited thereto, thus the plurality of VCSELs 45 may be disposed in a lattice pattern at regular intervals, for example.
In the third embodiment and the fourth embodiment, a homogenizer as described in the second embodiment may be provided on an upper side of the plurality of VCSELs 45 annularly provided. Accordingly, an illuminance distribution in the peripheral part of the semiconductor wafer W can be further uniformed.
In the third embodiment and the fourth embodiment, the plurality of VCSELs 45 are annularly disposed around the plurality of LED lamps 47, however, the configuration is not limited thereto, thus it is sufficient that the VCSELs 45 are provided to face a part of the semiconductor wafer W where reduction in temperature easily occurs at the time of the heating treatment.
In the fifth embodiment, a heating part including the plurality of VCSELs 45 may be provided to only one of an upper side and a lower side of the chamber 110. A homogenizer as described in the second embodiment may be provided to the plurality of VCSELs 45 according to the fifth embodiment. Furthermore, in the fifth embodiment, a rapid heating treatment of the semiconductor wafer W may be performed using the plurality of VCSELs 45 and the plurality of LED lamps as described in the third embodiment and the fourth embodiment.
Although the 30 flash lamps FL are provided to the flash heating part 5 according to the aforementioned embodiment, the present invention is not limited thereto. Any number of flash lamps FL may be provided. The flash lamps FL are not limited to the xenon flash lamps, but may be krypton flash lamps.
While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-107017 | Jul 2022 | JP | national |
