JP7377653B2 - Heat treatment method and heat treatment equipment - Google Patents

Description

The present invention relates to a heat treatment method and a heat treatment apparatus for heating a thin precision electronic substrate (hereinafter simply referred to as a "substrate") such as a semiconductor wafer by irradiating the same with flash light.

In the manufacturing process of semiconductor devices, flash lamp annealing (FLA), which heats semiconductor wafers in an extremely short period of time, is attracting attention. Flash lamp annealing is a process in which only the surface of a semiconductor wafer is extremely polished by irradiating the surface of the semiconductor wafer with flash light using a xenon flash lamp (hereinafter simply referred to as "flash lamp"). This is a heat treatment technology that raises the temperature in a short period of time (several milliseconds or less).

The radiation spectral distribution of a xenon flash lamp ranges from the ultraviolet region to the near-infrared region, which has a shorter wavelength than that of conventional halogen lamps and roughly matches the fundamental absorption band of silicon semiconductor wafers. Therefore, when a semiconductor wafer is irradiated with flash light from a xenon flash lamp, the amount of transmitted light is small and it is possible to rapidly raise the temperature of the semiconductor wafer. It has also been found that by irradiating flash light for an extremely short period of several milliseconds or less, it is possible to selectively raise the temperature only in the vicinity of the surface of the semiconductor wafer.

Such flash lamp annealing is used for processes that require very short heating times, such as typically for activating impurities implanted into semiconductor wafers. By irradiating the surface of a semiconductor wafer into which impurities have been implanted using the ion implantation method with flash light from a flash lamp, the surface of the semiconductor wafer can be heated to the activation temperature for a very short period of time, allowing the impurities to be deeply diffused. Therefore, only impurity activation can be performed without activating the impurity.

As an apparatus for performing flash lamp annealing, Patent Document 1 discloses that after preheating a semiconductor wafer by irradiating light from a halogen lamp, the surface of the semiconductor wafer is heated for 1 second or less by irradiating flash light from a flash lamp. A short-term heating device is disclosed. In the flash lamp annealing apparatus disclosed in Patent Document 1, after flash heating is completed and the temperature of the semiconductor wafer is lowered to a predetermined temperature or lower by natural cooling, the semiconductor wafer is taken out of the chamber.

Japanese Patent Application Publication No. 2018-195686

However, when the temperature of the semiconductor wafer is lowered by natural cooling, it takes a considerable amount of time for the temperature of the semiconductor wafer to drop below a predetermined temperature, which hinders improvement in throughput. Further, in the device disclosed in Patent Document 1, a small-diameter gas ring for supplying gas into the chamber is installed, but the inner wall surface of the gas ring is spaced apart from the wall surface of the chamber being cooled. For this reason, the cooling efficiency of the gas ring itself is low, and there has also been a problem that the gas ring is discolored by reaction products from the semiconductor wafer.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a heat treatment method and a heat treatment apparatus that can efficiently and quickly cool the inside of a chamber.

In order to solve the above problem, the invention according to claim 1 provides a heat treatment method for heating a substrate by irradiating the substrate with flash light, including a step of housing the substrate in a chamber, and a step of housing the substrate in the chamber. a preheating step of preheating the substrate by irradiating the substrate with light from a continuously lit lamp; and a flash heating step of heating the substrate by irradiating the substrate housed in the chamber with flash light from a flash lamp. and a cooling step of supplying a cooling gas having a higher thermal conductivity than nitrogen into the chamber, and stopping the supply of the cooling gas when the atmospheric temperature in the chamber drops to a predetermined temperature. It is characterized by

Moreover, the invention according to claim 2 is characterized in that in the heat treatment method according to the invention according to claim 1, the cooling gas is hydrogen or helium.

Further, the invention according to claim 3 is characterized in that in the heat treatment method according to the invention according to claim 1 or 2, supply of the cooling gas is started after the time when the flash light is irradiated onto the substrate.

Further, the invention according to claim 4 is characterized in that, in the heat treatment method according to the invention according to claim 3, supply of the cooling gas is started when the continuously lit lamp is turned off.

Further, the invention according to claim 5 provides a heat treatment apparatus for heating a substrate by irradiating the substrate with flash light, which includes a chamber for accommodating a substrate, and a chamber for irradiating the substrate accommodated in the chamber with light to heat the substrate. a continuously lit lamp that preheats the substrate; a flash lamp that irradiates the substrate housed in the chamber with flash light to heat the substrate; and a cooling gas that has a higher thermal conductivity than nitrogen in the chamber. and a gas supply unit that supplies the cooling gas, and the gas supply unit is characterized in that the gas supply unit stops supplying the cooling gas when the ambient temperature in the chamber drops to a predetermined temperature.

Moreover, the invention according to claim 6 is characterized in that in the heat treatment apparatus according to the invention according to claim 5 , the cooling gas is hydrogen or helium.

The invention of claim 7 is the heat treatment apparatus according to claim 5 or 6 , wherein the gas supply unit starts supplying the cooling gas after the flash light is irradiated onto the substrate. It is characterized by

In the heat treatment apparatus according to the seventh aspect of the present invention, the gas supply section starts supplying the cooling gas when the continuously lit lamp goes out.

According to the invention of claims 1 to 4 , since the cooling gas having a higher thermal conductivity than nitrogen is supplied into the chamber, the inside of the chamber can be efficiently and quickly cooled by the cooling gas having high cooling performance. I can do it. In addition, since the supply of cooling gas is stopped when the ambient temperature inside the chamber drops to a predetermined temperature, it prevents the components inside the chamber from being excessively cooled and makes the temperature history of the board uniform. I can do it.

According to the invention of claims 5 to 8 , since the cooling gas having a higher thermal conductivity than nitrogen is supplied into the chamber, the inside of the chamber can be efficiently and quickly cooled by the cooling gas having high cooling ability. I can do it. In addition, since the supply of cooling gas is stopped when the ambient temperature inside the chamber drops to a predetermined temperature, it prevents the components inside the chamber from being excessively cooled and makes the temperature history of the board uniform. I can do it.

1 is a longitudinal cross-sectional view showing the configuration of a heat treatment apparatus according to the present invention. It is a perspective view showing the whole appearance of a holding part. FIG. 3 is a plan view of a susceptor. It is a sectional view of a susceptor. It is a top view of a transfer mechanism. It is a side view of a transfer mechanism. FIG. 3 is a plan view showing the arrangement of a plurality of halogen lamps. 2 is a flowchart showing a procedure for processing a semiconductor wafer in the heat treatment apparatus of FIG. 1. FIG. FIG. 3 is a diagram showing changes in surface temperature of a semiconductor wafer.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the configuration of a heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 in FIG. 1 is a flash lamp annealing apparatus that heats a disk-shaped semiconductor wafer W as a substrate by irradiating the semiconductor wafer W with flash light. The size of the semiconductor wafer W to be processed is not particularly limited, but is, for example, φ300 mm or φ450 mm (φ300 mm in this embodiment). Impurities are implanted into the semiconductor wafer W before being carried into the heat treatment apparatus 1, and the implanted impurities are activated by heat treatment by the heat treatment apparatus 1. Note that in FIG. 1 and the subsequent figures, the dimensions and numbers of each part are exaggerated or simplified as necessary for easy understanding.

The heat treatment apparatus 1 includes a chamber 6 that accommodates a semiconductor wafer W, a flash heating section 5 that includes a plurality of flash lamps FL, and a halogen heating section 4 that includes a plurality of halogen lamps HL. A flash heating section 5 is provided on the upper side of the chamber 6, and a halogen heating section 4 is provided on the lower side. The heat treatment apparatus 1 also includes, inside the chamber 6, a holding part 7 that holds the semiconductor wafer W in a horizontal position, and a transfer mechanism 10 that transfers the semiconductor wafer W between the holding part 7 and the outside of the apparatus. Equipped with Further, the heat treatment apparatus 1 includes a control section 3 that controls the operating mechanisms provided in the halogen heating section 4, the flash heating section 5, and the chamber 6 to perform heat treatment on the semiconductor wafer W.

The chamber 6 is constructed by mounting quartz chamber windows on the upper and lower sides of a cylindrical chamber side part 61. The chamber side part 61 has a generally cylindrical shape with an open top and bottom, the upper opening is fitted with an upper chamber window 63 and is closed, and the lower opening is fitted with a lower chamber window 64 and closed. ing. The upper chamber window 63 configuring the ceiling of the chamber 6 is a disc-shaped member made of quartz, and functions as a quartz window that transmits the flash light emitted from the flash heating section 5 into the chamber 6 . Further, the lower chamber window 64 constituting the floor of the chamber 6 is also a disc-shaped member made of quartz, and functions as a quartz window that transmits light from the halogen heating section 4 into the chamber 6.

Further, a gas ring 90 is attached to the upper part of the inner wall surface of the chamber side part 61, and a reflection ring 69 is attached to the lower part. Both the gas ring 90 and the reflection ring 69 are formed in an annular shape. The inner space of the chamber 6, that is, the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side part 61, the reflection ring 69, and the gas ring 90 is defined as a heat treatment space 65.

By attaching the reflection ring 69 and the gas ring 90 to the chamber side portion 61, a recess 62 is formed in the inner wall surface of the chamber 6. That is, a recess 62 is formed that is surrounded by the center portion of the inner wall surface of the chamber side portion 61 where the reflection ring 69 and the gas ring 90 are not attached, the upper end surface of the reflection ring 69, and the lower end surface of the gas ring 90. Ru. The recess 62 is formed in an annular shape along the horizontal direction on the inner wall surface of the chamber 6, and surrounds the holding part 7 that holds the semiconductor wafer W.

Furthermore, a transfer opening (furnace opening) 66 is formed in the chamber side portion 61 to carry the semiconductor wafer W into and out of the chamber 6 . The transport opening 66 can be opened and closed by a gate valve 185. The conveyance opening 66 is connected to the outer peripheral surface of the recess 62 . Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W is carried into the heat treatment space 65 from the transfer opening 66 through the recess 62, and the semiconductor wafer W is carried out from the heat treatment space 65. It can be performed. Further, when the gate valve 185 closes the transfer opening 66, the heat treatment space 65 in the chamber 6 becomes a sealed space.

Further, the chamber side portion 61 is provided with a through hole 61a. A radiation thermometer 20 is attached to a portion of the 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 guiding infrared light emitted from the lower surface of a semiconductor wafer W held by a susceptor 74, which will be described later, to the radiation thermometer 20. The through hole 61a is provided so as to be inclined with respect to the horizontal direction so that the axis of the through hole 61a intersects with the main surface of the semiconductor wafer W held by the susceptor 74. A transparent window 21 made of barium fluoride material that transmits infrared light in a wavelength range that can be measured by the radiation thermometer 20 is attached to the end of the through hole 61a facing the heat treatment space 65.

Further, a gas discharge port 81 for supplying processing gas to the heat treatment space 65 is formed in the upper part of the inner wall of the chamber 6 . The gas discharge port 81 is formed between the gas ring 90 and the upper chamber window 63. The gas discharge port 81 is connected to the gas supply pipe 83 through the internal space of the gas ring 90 . Gas supply pipe 83 is connected to processing gas supply source 85 . Further, a valve 84 is inserted in the middle of the gas supply pipe 83. When valve 84 is opened, processing gas is supplied from processing gas supply source 85 to gas ring 90 . A buffer space and a labyrinth structure are provided in the internal space of the gas ring 90. The processing gas supplied from the processing gas supply source 85 to the gas ring 90 passes through the internal space of the gas ring 90, whereby the flow velocity along the radial direction and circumferential direction of the chamber 6 is reduced, and the gas discharge port 81 The heat treatment space 65 is uniformly discharged from the heat treatment space 65. As the processing gas, for example, an inert gas such as nitrogen (N ₂ ), a reactive gas such as hydrogen (H ₂ ) or ammonia (NH ₃ ), or a mixed gas of these can be used. In the embodiment, nitrogen gas). The processing gas supply source 85 can also supply helium (He) or hydrogen as a cooling gas.

On the other hand, a gas exhaust hole 86 is formed in the lower part of the inner wall of the chamber 6 to exhaust the gas in the heat treatment space 65. The gas exhaust hole 86 is formed at a lower position than the recess 62 and may be provided in the reflective ring 69. The gas exhaust hole 86 is connected to a gas exhaust pipe 88 via a buffer space 87 formed in an annular shape inside the side wall of the chamber 6 . Gas exhaust pipe 88 is connected to exhaust section 190. Further, a valve 89 is inserted in the middle of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is discharged from the gas exhaust hole 86 through the buffer space 87 to the gas exhaust pipe 88 . Note that the processing gas supply source 85 and the exhaust section 190 may be a mechanism provided in the heat treatment apparatus 1, or may be a utility of a factory where the heat treatment apparatus 1 is installed.

Further, a gas exhaust pipe 191 for exhausting gas in the heat treatment space 65 is also connected to the tip of the transport opening 66 . Gas exhaust pipe 191 is connected to exhaust section 190 via valve 192. By opening the valve 192, the gas in the chamber 6 is evacuated via the conveying opening 66.

FIG. 2 is a perspective view showing the overall appearance of the holding section 7. As shown in FIG. The holding section 7 includes a base ring 71, a connecting section 72, and a susceptor 74. The base ring 71, the connecting portion 72, and the susceptor 74 are all made of quartz. That is, the entire holding portion 7 is made of quartz.

The base ring 71 is a quartz member having an arcuate shape with a portion missing from the annular shape. This missing portion is provided to prevent interference between the transfer arm 11 of the transfer mechanism 10 and the base ring 71, which will be described later. By being placed on the bottom of the recess 62, the base ring 71 is supported by the wall of the chamber 6 (see FIG. 1). A plurality of connecting portions 72 (four in this embodiment) are erected on the upper surface of the base ring 71 along the circumferential direction of the annular shape. The connecting portion 72 is also a quartz member and is fixed to the base ring 71 by welding.

The susceptor 74 is supported by four connecting parts 72 provided on the base ring 71. FIG. 3 is a plan view of the susceptor 74. Further, FIG. 4 is a cross-sectional view of the susceptor 74. The susceptor 74 includes a holding plate 75, a guide ring 76, and a plurality of substrate support pins 77. The holding plate 75 is a substantially circular flat plate member made of quartz. The diameter of the holding plate 75 is larger than the diameter of the semiconductor wafer W. That is, the holding plate 75 has a larger planar size than the semiconductor wafer W.

A guide ring 76 is installed at the upper peripheral edge of the holding plate 75. The guide ring 76 is an annular member having an inner diameter larger 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 has a tapered surface that becomes wider upward from the holding plate 75. The guide ring 76 is made of quartz like the holding plate 75. The guide ring 76 may be welded to the upper surface of the holding plate 75, or may be fixed to the holding plate 75 using a separately machined pin or the like. Alternatively, the holding plate 75 and the guide ring 76 may be processed as an integral member.

A region of the upper surface of the holding plate 75 inside the guide ring 76 is a planar holding surface 75a that holds the semiconductor wafer W. A plurality of substrate support pins 77 are provided upright on the holding surface 75a of the holding plate 75. In this embodiment, a total of 12 substrate support pins 77 are provided upright every 30° along a circumference concentric with the outer circumference of the holding surface 75a (inner circumference of the guide ring 76). The diameter of the circle in which the 12 substrate support pins 77 are arranged (the distance between the opposing substrate support pins 77) is smaller than the diameter of the semiconductor wafer W, and if the diameter of the semiconductor wafer W is φ300 mm, it is φ270 mm to φ280 mm (in this implementation). The shape is φ270mm). Each substrate support pin 77 is made of quartz. The plurality of substrate support pins 77 may be provided on the upper surface of the holding plate 75 by welding, or may be processed integrally with the holding plate 75.

Returning to FIG. 2, the four connecting parts 72 erected on the base ring 71 and the peripheral edge of the holding plate 75 of the susceptor 74 are fixed by welding. That is, the susceptor 74 and the base ring 71 are fixedly connected by the connecting portion 72. The holding part 7 is attached to the chamber 6 by supporting the base ring 71 of the holding part 7 on the wall surface of the chamber 6 . When the holding portion 7 is attached to the chamber 6, the holding plate 75 of the susceptor 74 is in a horizontal position (a position in which the normal line coincides with the vertical direction). That is, the holding surface 75a of the holding plate 75 is a horizontal surface.

The semiconductor wafer W carried into the chamber 6 is placed and held in a horizontal position on the susceptor 74 of the holding section 7 mounted in the chamber 6. At this time, the semiconductor wafer W is supported by twelve substrate support pins 77 erected on the holding plate 75 and held by the susceptor 74. More precisely, the upper ends of the twelve substrate support pins 77 contact the lower surface of the semiconductor wafer W to support the semiconductor wafer W. Since the height of the 12 substrate support pins 77 (the distance from the upper end of the substrate support pin 77 to the holding surface 75a of the holding plate 75) is uniform, the semiconductor wafer W is held in a horizontal position by the 12 substrate support pins 77. can be supported.

Further, the semiconductor wafer W is supported by a plurality of substrate support pins 77 at a predetermined distance from the holding surface 75a of the holding plate 75. The thickness of the guide ring 76 is greater than the height of the substrate support pin 77. Therefore, the guide ring 76 prevents the semiconductor wafer W supported by the plurality of substrate support pins 77 from shifting in the horizontal direction.

Further, as shown in FIGS. 2 and 3, an opening 78 is formed in the holding plate 75 of the susceptor 74 so as to pass through the holding plate 75 vertically. The opening 78 is provided so that the radiation thermometer 20 receives radiation light (infrared light) emitted from the lower surface of the semiconductor wafer W. That is, the radiation thermometer 20 receives the light emitted from the lower surface of the semiconductor wafer W through the transparent window 21 installed in the opening 78 and the through hole 61a of the chamber side part 61, and measures the temperature of the semiconductor wafer W. Measure. Furthermore, four through holes 79 are formed in the holding plate 75 of the susceptor 74, through which lift pins 12 of a transfer mechanism 10, which will be described later, pass through to transfer the semiconductor wafer W.

FIG. 5 is a plan view of the transfer mechanism 10. Further, FIG. 6 is a side view of the transfer mechanism 10. The transfer mechanism 10 includes two transfer arms 11. The transfer arm 11 has an arcuate shape along the generally annular recess 62 . Two lift pins 12 are provided upright on each transfer arm 11. The transfer arm 11 and lift pin 12 are made of quartz. Each transfer arm 11 is rotatable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 moves the pair of transfer arms 11 to a transfer operation position (solid line position in FIG. 5) in which the semiconductor wafer W is transferred to the holding part 7 and a semiconductor wafer W held by the holding part 7. It is horizontally moved between the retracted positions (positions indicated by two-dot chain lines in FIG. 5) where they do not overlap in plan view. The horizontal movement mechanism 13 may be one in which each transfer arm 11 is rotated by an individual motor, or one in which a pair of transfer arms 11 are rotated in conjunction with one motor using a link mechanism. It may be something that moves.

Further, the pair of transfer arms 11 are moved up and down together with the horizontal movement mechanism 13 by the lifting mechanism 14 . When the lifting mechanism 14 raises the pair of transfer arms 11 to the transfer operation position, a total of four lift pins 12 pass through the through holes 79 (see FIGS. 2 and 3) drilled in the susceptor 74, and the lift pins The upper end of 12 protrudes from the upper surface of susceptor 74. On the other hand, when the lifting mechanism 14 lowers the pair of transfer arms 11 at the transfer operation position and extracts the lift pin 12 from the through hole 79, and the horizontal movement mechanism 13 moves the pair of transfer arms 11 to open, each The transfer arm 11 moves to the retreat position. The retracted position of the pair of transfer arms 11 is directly above the base ring 71 of the holding section 7 . Since the base ring 71 is placed on the bottom surface of the recess 62, the retracted position of the transfer arm 11 is inside the recess 62. Note that an exhaust mechanism (not shown) is also provided near the parts where the drive parts (horizontal movement mechanism 13 and lifting mechanism 14) of the transfer mechanism 10 are provided, and the atmosphere around the drive parts of the transfer mechanism 10 is is configured so that the liquid is discharged to the outside of the chamber 6.

Returning to FIG. 1, the chamber 6 is provided with a radiation thermometer 20 and a temperature sensor 29. The radiation thermometer 20 is provided diagonally below the semiconductor wafer W held by the susceptor 74. The radiation thermometer 20 receives infrared light emitted from the lower surface of the semiconductor wafer W, and measures the temperature of the lower surface from the intensity of the infrared light. On the other hand, the temperature sensor 29 is configured using a thermocouple. The temperature sensor 29 is attached to the inner wall surface of the chamber 6. The temperature sensor 29 measures the atmospheric temperature within the chamber 6 .

The flash heating unit 5 provided above the chamber 6 includes a light source consisting of a plurality of (30 in this embodiment) xenon flash lamps FL and a light source provided inside the casing 51 so as to cover the upper part of the light source. and a reflector 52. Further, a lamp light emission window 53 is attached to the bottom of the casing 51 of the flash heating section 5. The lamp light emission window 53 constituting the floor of the flash heating section 5 is a plate-shaped quartz window made of quartz. By installing the flash heating unit 5 above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash lamp FL irradiates the heat treatment space 65 with flash light from above the chamber 6 through the lamp light emission window 53 and the upper chamber window 63.

The plurality of flash lamps FL are rod-shaped lamps each having an elongated cylindrical shape, and each of the flash lamps FL has its longitudinal direction along the main surface of the semiconductor wafer W held by the holding part 7 (that is, along the horizontal direction). They are arranged in a plane so that they are parallel to each other. Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane. The area where the plurality of flash lamps FL are arranged is larger than the planar size of the semiconductor wafer W.

The xenon flash lamp FL consists of a cylindrical glass tube (discharge tube) in which xenon gas is sealed and an anode and a cathode connected to a condenser at both ends. and an attached trigger electrode. Since xenon gas is an electrical insulator, no electricity will flow inside the glass tube under normal conditions even if a charge is stored in the capacitor. However, when a high voltage is applied to the trigger electrode to break down the insulation, the electricity stored in the capacitor instantly flows into the glass tube, and the excitation of xenon atoms or molecules at that time causes light to be emitted. In such a xenon flash lamp FL, the electrostatic energy previously stored in the capacitor is converted into extremely short light pulses of 0.1 milliseconds to 100 milliseconds, so it cannot be lit continuously like a halogen lamp HL. It has the characteristic of being able to emit extremely strong light compared to a light source. That is, the flash lamp FL is a pulsed light emitting lamp that emits light instantaneously in an extremely short period of less than one second. Note that the light emission time of the flash lamp FL can be adjusted by the coil constant of the lamp power supply that supplies power to the flash lamp FL.

Further, the reflector 52 is provided above the plurality of flash lamps FL so as to cover them entirely. The basic function of the reflector 52 is to reflect the flash light emitted from the plurality of flash lamps FL toward the heat treatment space 65 side. The reflector 52 is formed of an aluminum alloy plate, and its surface (the surface facing the flash lamp FL) is roughened by blasting.

The halogen heating unit 4 provided below the chamber 6 includes a plurality of (40 in this embodiment) halogen lamps HL inside a housing 41. The halogen heating unit 4 is a light irradiation unit that heats the semiconductor wafer W by irradiating light from below the chamber 6 to the heat treatment space 65 through the lower chamber window 64 using a plurality of halogen lamps HL.

FIG. 7 is a plan view showing the arrangement of a plurality of halogen lamps HL. The 40 halogen lamps HL are arranged in two stages, upper and lower. Twenty halogen lamps HL are arranged in the upper stage near the holding part 7, and twenty halogen lamps HL are arranged in the lower stage farther from the holding part 7 than the upper stage. Each halogen lamp HL is a rod-shaped lamp having an elongated cylindrical shape. The 20 halogen lamps HL in both the upper and lower stages are arranged so that their longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holding part 7 (that is, along the horizontal direction). There is. Therefore, the plane formed by the arrangement of the halogen lamps HL in both the upper and lower stages is a horizontal plane.

Further, as shown in FIG. 7, the arrangement density of the halogen lamps HL in the region facing the peripheral portion of the semiconductor wafer W held by the holding portion 7 is higher than that in the region facing the center portion of the semiconductor wafer W held by the holding portion 7 in both the upper and lower stages. There is. That is, in both the upper and lower stages, the arrangement pitch of the halogen lamps HL is shorter at the periphery than at the center of the lamp array. Therefore, a larger amount of light can be irradiated onto the peripheral edge of the semiconductor wafer W, where the temperature tends to drop during heating by light irradiation from the halogen heating unit 4.

Further, a lamp group consisting of the upper stage halogen lamps HL and a lamp group consisting of the lower stage halogen lamps HL are arranged so as to intersect in a grid pattern. That is, a total of 40 halogen lamps HL are arranged so that the longitudinal direction of the 20 halogen lamps HL arranged in the upper stage and the longitudinal direction of the 20 halogen lamps HL arranged in the lower stage are orthogonal to each other. There is.

The halogen lamp HL is a filament-type light source that emits light by energizing a filament disposed inside a cylindrical glass tube to make the filament incandescent. The inside of the glass tube is filled with a gas made by introducing a small amount of halogen elements (iodine, bromine, etc.) into an inert gas such as nitrogen or argon. By introducing a halogen element, it becomes possible to set the temperature of the filament to a high temperature while suppressing breakage of the filament. Therefore, the halogen lamp HL has a longer lifespan than a normal incandescent light bulb and has the characteristics of being able to continuously emit intense light. That is, the halogen lamp HL is a continuously lit lamp that emits light continuously for at least one second or more. Further, since the halogen lamp HL is a rod-shaped lamp, it has a long life, and by arranging the halogen lamp HL along the horizontal direction, the radiation efficiency toward the semiconductor wafer W above becomes excellent.

Further, a reflector 43 is also provided in the housing 41 of the halogen heating section 4 below the two-stage halogen lamp HL (FIG. 1). The reflector 43 reflects the light emitted from the plurality of halogen lamps HL toward the heat treatment space 65 side.

The control unit 3 controls the various operating mechanisms described above provided in the heat treatment apparatus 1. The hardware configuration of the control unit 3 is similar to that of a general computer. That is, the control unit 3 includes a CPU, which is a circuit that performs various calculation processes, a ROM, which is a read-only memory that stores basic programs, a RAM, which is a readable and writable memory that stores various information, and control software and data. It has a magnetic disk for storing data. Processing in the heat treatment apparatus 1 progresses as the CPU of the control unit 3 executes a predetermined processing program.

In addition to the above configuration, the heat treatment apparatus 1 prevents an excessive temperature rise in the halogen heating section 4, flash heating section 5, and chamber 6 due to thermal energy generated from the halogen lamp HL and flash lamp FL during heat treatment of the semiconductor wafer W. Therefore, it is equipped with various cooling structures. For example, the wall of the chamber 6 is provided with a water cooling pipe (not shown). Further, the halogen heating section 4 and the flash heating section 5 have an air-cooled structure in which a gas flow is formed inside to exhaust heat. Furthermore, air is also supplied to the gap between the upper chamber window 63 and the lamp light emission window 53 to cool the flash heating section 5 and the upper chamber window 63.

Next, the processing procedure of the semiconductor wafer W in the heat processing apparatus 1 will be explained. FIG. 8 is a flowchart showing the processing procedure of the semiconductor wafer W in the heat treatment apparatus 1. The semiconductor wafer W to be processed here is a semiconductor substrate into which impurities (ions) have been added by ion implantation. Activation of the impurities is performed by flash light irradiation heat treatment (annealing) by the heat treatment apparatus 1. The processing procedure of the heat treatment apparatus 1 described below proceeds as the control unit 3 controls each operating mechanism of the heat treatment apparatus 1.

First, the air supply valve 84 is opened, and the exhaust valves 89 and 192 are opened to start supplying and exhausting air into the chamber 6. When the valve 84 is opened, nitrogen gas as a processing gas is supplied from the processing gas supply source 85 to the gas ring 90 , and the nitrogen gas that has passed through the internal space of the gas ring 90 enters the heat treatment space 65 from the gas discharge port 81 . It is discharged. Further, when the valve 89 is opened, the gas in the chamber 6 is exhausted from the gas exhaust hole 86. As a result, the nitrogen gas supplied from the upper part of the heat treatment space 65 in the chamber 6 flows downward and is exhausted from the lower part of the heat treatment space 65.

Further, by opening the valve 192, the gas in the chamber 6 is also exhausted from the transfer opening 66. Further, the atmosphere around the drive section of the transfer mechanism 10 is also exhausted by an exhaust mechanism (not shown).

Subsequently, the gate valve 185 is opened to open the transfer opening 66, and the ion-implanted semiconductor wafer W is carried into the heat treatment space 65 in the chamber 6 via the transfer opening 66 by a transfer robot outside the apparatus ( Step S1). At this time, there is a risk that the atmosphere outside the apparatus will be drawn in as the semiconductor wafer W is carried in. However, since nitrogen gas continues to be supplied to the chamber 6, the nitrogen gas may flow out from the transfer opening 66, causing such a situation. Entrainment of external atmosphere can be suppressed to a minimum.

The semiconductor wafer W carried in by the transfer robot advances to a position directly above the holding section 7 and stops. When the pair of transfer arms 11 of the transfer mechanism 10 horizontally move from the retracted position to the transfer operation position and rise, 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. and receives the semiconductor wafer W. At this time, the lift pins 12 rise above the upper ends of the substrate support pins 77.

After the semiconductor wafer W is placed on the lift pins 12, the transfer robot leaves the heat treatment space 65, and the transfer opening 66 is closed by the gate valve 185. Then, by lowering the pair of transfer arms 11, the semiconductor wafer W is transferred from the transfer mechanism 10 to the susceptor 74 of the holding section 7, and is held from below in a horizontal position. The semiconductor wafer W is supported by a plurality of substrate support pins 77 erected on the holding plate 75 and held by the susceptor 74 . Further, the semiconductor wafer W is held by the holding unit 7 with the patterned and impurity-injected surface facing upward. A predetermined distance is formed between the back surface (main surface opposite to the front surface) of the semiconductor wafer W supported by the plurality of substrate support pins 77 and the holding surface 75a of the holding plate 75. The pair of transfer arms 11 that have descended below the susceptor 74 are moved to a retracted position, that is, inside the recess 62, by the horizontal movement mechanism 13.

FIG. 9 is a diagram showing changes in the surface temperature of the semiconductor wafer W. At time t1 after the semiconductor wafer W is held from below in a horizontal position by the susceptor 74 of the holding section 7 formed of quartz, the 40 halogen lamps HL of the halogen heating section 4 are turned on all at once to provide a backup. Heating (assisted heating) is started (step S2). The halogen light emitted from the halogen lamp HL passes through the lower chamber window 64 and the susceptor 74 formed of quartz, and is irradiated onto the lower surface of the semiconductor wafer W. By receiving light irradiation from the halogen lamp HL, the semiconductor wafer W is preheated and its temperature increases. Note that since the transfer arm 11 of the transfer mechanism 10 is retracted inside the recess 62, it does not interfere with the heating by the halogen lamp HL.

When performing preheating with the halogen lamp HL, the temperature of the semiconductor wafer W is measured by the radiation thermometer 20. That is, the radiation thermometer 20 receives infrared light emitted from the lower surface of the semiconductor wafer W held by the susceptor 74 through the opening 78 through the transparent window 21 to measure the temperature of the wafer being heated. The measured temperature of the semiconductor wafer W is transmitted to the control section 3. The control unit 3 controls the output of the halogen lamp HL while monitoring whether the temperature of the semiconductor wafer W, which is heated by light irradiation from the halogen lamp HL, has reached a predetermined preheating temperature T1. That is, the control unit 3 feedback-controls the output of the halogen lamp HL based on the measured value by the radiation thermometer 20 so that the temperature of the semiconductor wafer W becomes the preheating temperature T1. The preheating temperature T1 is set to about 200° C. to 800° C., preferably about 350° C. to 600° C. (600° C. in this embodiment), at which there is no fear that impurities added to the semiconductor wafer W will be diffused by heat. .

After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the control section 3 maintains the semiconductor wafer W at the preheating temperature T1 for a while. Specifically, at time t2 when the temperature of the semiconductor wafer W measured by the radiation thermometer 20 reaches the preheating temperature T1, the control unit 3 adjusts the output of the halogen lamp HL to bring the temperature of the semiconductor wafer W almost to the preheating temperature T1. The heating temperature is maintained at T1.

By performing preheating using the halogen lamp HL, the entire semiconductor wafer W is uniformly heated to the preheating temperature T1. At the stage of preheating by the halogen lamps HL, the temperature at the periphery of the semiconductor wafer W, where heat radiation is more likely to occur, tends to be lower than that at the center, but the density of the halogen lamps HL in the halogen heating section 4 is The area facing the peripheral edge of the substrate W is higher than the area facing the center. Therefore, the amount of light irradiated onto the peripheral edge of the semiconductor wafer W, where heat radiation is likely to occur, increases, and the in-plane temperature distribution of the semiconductor wafer W during the preheating stage can be made uniform.

At time t3 when the temperature of the semiconductor wafer W reaches the preheating temperature T1 and a predetermined time has elapsed, the flash lamp FL of the flash heating section 5 irradiates the surface of the semiconductor wafer W held by the susceptor 74 with flash light (step S3). At this time, a part of the flash light emitted from the flash lamp FL goes directly into the chamber 6, and the other part is once reflected by the reflector 52 and then heads into the chamber 6. Flash heating of the semiconductor wafer W is performed by the irradiation.

Since flash heating is performed by irradiating flash light from the flash lamp FL, the surface temperature of the semiconductor wafer W can be raised in a short time. In other words, the flash light emitted from the flash lamp FL is generated by converting electrostatic energy stored in a capacitor in advance into an extremely short light pulse, and the irradiation time is extremely short, ranging from 0.1 milliseconds to 100 milliseconds. It's a strong flash. Then, the surface temperature of the semiconductor wafer W, which is flash-heated by the flash light irradiation from the flash lamp FL, instantaneously rises to the processing temperature T2 of 1000° C. or more, and the impurities implanted into the semiconductor wafer W are activated. After that, the surface temperature drops rapidly. In this way, the heat treatment apparatus 1 can raise and lower the surface temperature of the semiconductor wafer W in an extremely short time, so that the impurity can be activated while suppressing the diffusion of the impurity implanted into the semiconductor wafer W due to heat. Can be done. Note that the time required for the activation of impurities is extremely short compared to the time required for their thermal diffusion, so activation is not possible even during a short period of time, such as 0.1 to 100 milliseconds, in which no diffusion occurs. Complete.

After the flash heating process is completed, the halogen lamp HL is turned off at time t4 after a predetermined period of time (for example, 2 seconds) has elapsed. At the same time that the halogen lamp HL is turned off, the supply of cooling gas is started (step S4). Specifically, helium gas is supplied as a cooling gas from the processing gas supply source 85 to the gas ring 90 at time t4 when the halogen lamp HL is turned off. The helium gas supplied to the gas ring 90 is supplied from the gas discharge port 81 to the heat treatment space 65 in the chamber 6 . Furthermore, exhaust from the gas exhaust hole 86 continues.

Helium gas has high thermal conductivity (approximately 0.144 W/m·K at 0°C). Therefore, helium gas has high cooling ability. By supplying helium gas into the chamber 6 at the same time as the halogen lamp HL is turned off, the semiconductor wafer W, which is at a relatively high temperature immediately after flash heating, is rapidly cooled and its temperature is quickly lowered.

Further, although the wall of the chamber 6 is cooled by the water cooling pipe, the inner wall of the gas ring 90 which is spaced apart from the wall is not sufficiently cooled. Therefore, the inner wall surface of the gas ring 90 is likely to become high in temperature due to light irradiation from the halogen lamp HL and the flash lamp FL, and may be discolored by reaction products originating from the film of the semiconductor wafer W that has been heated. In this embodiment, since helium gas having a high cooling capacity is supplied into the chamber 6 after flash heating, not only the semiconductor wafer W but also the components of the chamber 6 including the gas ring 90 are rapidly cooled. That will happen. Thereby, discoloration of the gas ring 90 can also be prevented.

The atmospheric temperature within the chamber 6 is measured by a temperature sensor 29. The supply of helium gas is continued until the atmospheric temperature within the chamber 6, as measured by the temperature sensor 29, falls to a predetermined temperature (for example, 200° C. to 250° C.) (step S5). Then, at time t5 when the atmospheric temperature within the chamber 6 measured by the temperature sensor 29 has decreased to a predetermined temperature, the process proceeds from step S5 to step S6, and the supply of cooling gas is stopped.

After the supply of cooling gas is stopped, the pressure inside the chamber 6 is reduced (step S7). Specifically, the valve 84 is closed to stop the gas supply to the chamber 6, and only the exhaust from the chamber 6 is executed to reduce the pressure inside the chamber 6. By reducing the pressure inside the chamber 6, the helium gas used for cooling is discharged from the chamber 6.

After the pressure inside the chamber 6 is reduced to a predetermined pressure (for example, about 100 Pa), nitrogen gas is supplied into the chamber 6 to restore the pressure inside the chamber 6 to atmospheric pressure (step S8). At this time, the valve 84 is opened again, nitrogen gas is supplied from the processing gas supply source 85, and nitrogen gas is supplied into the chamber 6 from the gas discharge port 81. As a result, the inside of the chamber 6 becomes a nitrogen atmosphere again.

Next, the cooled semiconductor wafer W is carried out from the chamber 6 (step S9). After the inside of the chamber 6 is restored to a nitrogen atmosphere, the pair of transfer arms 11 of the transfer mechanism 10 moves horizontally again from the retracted position to the transfer operation position and rises, so that the lift pins 12 move toward the susceptor 74. It protrudes from the upper surface and receives the cooled semiconductor wafer W from the susceptor 74. Subsequently, the transfer opening 66 that had been closed by the gate valve 185 is opened, and the semiconductor wafer W placed on the lift pins 12 is carried out by a transfer robot outside the apparatus, and the processing of the semiconductor wafer W in the heat treatment apparatus 1 is completed. Complete.

In this embodiment, after the flash heat treatment is completed, helium gas having a high cooling ability is supplied into the chamber 6 as a cooling gas. Thereby, the inside of the chamber 6 including the semiconductor wafer W and the gas ring 90 can be efficiently and quickly cooled. By rapidly cooling the semiconductor wafer W after flash heating, the cooling time of the semiconductor wafer W can be shortened compared to natural cooling, and throughput can be improved. Further, by efficiently cooling the gas ring 90, discoloration of the gas ring 90 can be prevented.

Furthermore, in this embodiment, the supply of cooling gas is stopped when the atmospheric temperature within the chamber 6 drops to a predetermined temperature. If the cooling gas is continued to be supplied for a long period of time, the components of the chamber 6 will be excessively cooled. Then, when processing a subsequent new semiconductor wafer W, the semiconductor wafer W will be held by the excessively cooled susceptor 74, resulting in a problem that the temperature history of the plurality of semiconductor wafers W will become uneven. occurs. Therefore, to prevent the inside of the chamber 6 from being excessively cooled, the supply of cooling gas is stopped when the atmospheric temperature inside the chamber 6 falls to a predetermined temperature.

The embodiments of the present invention have been described above, but the present invention can be modified in various ways other than those described above without departing from the spirit thereof. For example, in the above embodiment, helium gas is used as the cooling gas, but the invention is not limited to this, and the cooling gas may be any gas having a higher thermal conductivity than nitrogen. That is, the thermal conductivity of nitrogen gas is approximately 0.024 W/m·K at 0° C., and a gas having a higher thermal conductivity than that may be supplied into the chamber 6 as a cooling gas. An example of a gas other than helium that has a higher thermal conductivity than nitrogen is hydrogen (approximately 0.168 W/m·K at 0° C.). Even if hydrogen gas is supplied as a cooling gas into the chamber 6 after the flash heat treatment is completed, the same effects as in the above embodiment can be obtained.

Further, in the above embodiment, the supply of cooling gas was started at the same time as the halogen lamp HL was turned off, but the timing of supplying the cooling gas is not limited to this, and flash light was irradiated from the flash lamp FL. Any time after that time (after time t3) is sufficient. Therefore, for example, the supply of cooling gas may be started at the same time as the flash lamp FL emits light. However, the halogen lamp HL is on for a predetermined period of time after irradiating the flash light (period from time t3 to time t4), and even if the supply of cooling gas is started at the same time as the flash lamp FL emits light, the halogen lamp Heating by HL and cooling by cooling gas are performed simultaneously, which is not efficient. Therefore, the inside of the chamber 6 can be cooled more efficiently by starting the supply of cooling gas at the same time as the halogen lamp HL goes out, as in the above embodiment. Furthermore, it is prohibited to supply cooling gas before irradiating the flash light. This is because if the cooling gas is supplied before the flash light is irradiated, there is a risk that the temperature of the semiconductor wafer W will fall below the preheating temperature T1 during the flash light irradiation.

Furthermore, the flow rate of the cooling gas within the chamber 6 may be increased by controlling the supply flow rate of the cooling gas from the gas ring 90 and the exhaust pressure from the gas exhaust hole 86. The cooling gas supply flow rate can be up to 150 l/min. By increasing the flow rate of the cooling gas within the chamber 6, the cooling efficiency within the chamber 6 can be increased.

Further, in the above embodiment, the flash heating section 5 is equipped with 30 flash lamps FL, but the number is not limited to this, and the number of flash lamps FL can be any number. . Further, the flash lamp FL is not limited to a xenon flash lamp, but may be a krypton flash lamp. Further, the number of halogen lamps HL provided in the halogen heating section 4 is not limited to 40, but may be any number.

Further, in the above embodiment, the semiconductor wafer W is preheated using a filament type halogen lamp HL as a continuously lit lamp that emits light continuously for 1 second or more, but the present invention is not limited to this. Instead of the halogen lamp HL, a discharge type arc lamp (for example, a xenon arc lamp) may be used as a continuously lit lamp to perform preheating.

Further, the substrate to be processed by the heat treatment apparatus 1 is not limited to a semiconductor wafer, but may be a glass substrate used for a flat panel display such as a liquid crystal display device or a substrate for a solar cell.

1 Heat treatment device 3 Control unit 4 Halogen heating unit 5 Flash heating unit 6 Chamber 7 Holding unit 10 Transfer mechanism 65 Heat treatment space 74 Susceptor 75 Holding plate 77 Substrate support pin 81 Gas discharge port 86 Gas exhaust hole 90 Gas ring FL Flash lamp HL Halogen lamp W Semiconductor wafer

Claims (8)

A heat treatment method for heating a substrate by irradiating the substrate with flash light, the method comprising:
a housing step of housing the substrate in the chamber;
a preheating step of preheating the substrate by irradiating the substrate housed in the chamber with light from a continuously lit lamp;
a flash heating step of heating the substrate by irradiating the substrate housed in the chamber with flash light from a flash lamp;
a cooling step of supplying a cooling gas having a higher thermal conductivity than nitrogen into the chamber;
Equipped with
A heat treatment method characterized in that the supply of the cooling gas is stopped when the ambient temperature in the chamber falls to a predetermined temperature . The heat treatment method according to claim 1,
A heat treatment method characterized in that the cooling gas is hydrogen or helium. In the heat treatment method according to claim 1 or 2,
A heat treatment method characterized in that supply of the cooling gas is started after the time when the flash light is irradiated onto the substrate. The heat treatment method according to claim 3,
A heat treatment method characterized in that the supply of the cooling gas is started when the continuously lit lamp is turned off. A heat treatment apparatus that heats a substrate by irradiating the substrate with flash light,
a chamber containing a substrate;
a continuously lit lamp that irradiates light onto the substrate housed in the chamber to preheat the substrate;
a flash lamp that irradiates the substrate housed in the chamber with flash light to heat the substrate;
a gas supply unit that supplies a cooling gas having a higher thermal conductivity than nitrogen into the chamber;
Equipped with
The heat treatment apparatus is characterized in that the gas supply unit stops supplying the cooling gas when the atmospheric temperature in the chamber drops to a predetermined temperature. The heat treatment apparatus according to claim 5 ,
A heat treatment apparatus characterized in that the cooling gas is hydrogen or helium. The heat treatment apparatus according to claim 5 or 6 ,
The heat treatment apparatus is characterized in that the gas supply unit starts supplying the cooling gas after the flash light is irradiated onto the substrate. The heat treatment apparatus according to claim 7 ,
The heat treatment apparatus is characterized in that the gas supply unit starts supplying the cooling gas when the continuously lit lamp goes out.

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