JP2014195004A - Process of manufacturing semiconductor element and manufacturing apparatus of semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a semiconductor element capable of shortening an annealing time by enlarging a beam spot area without raising output power of a laser light source.SOLUTION: Dopant ions are injected into a surface layer part of a semiconductor substrate. By, after injecting the dopant ions, injecting the same element as a constituting element of the semiconductor substrate into the surface layer part of a semiconductor substrate, density of crystal defects in the surface layer part of a semiconductor substrate is raised. By, after raising the density of crystal defects, making a laser beam incident on a surface of the semiconductor substrate, the dopants are activated.

Description

  The present invention relates to a method for manufacturing a semiconductor element that performs laser annealing, and a semiconductor element manufacturing apparatus that performs laser annealing.

  Generally, heating using an electric furnace, rapid thermal annealing (RTA), and the like are applied to heat treatment of a semiconductor substrate, for example, a silicon wafer. The heating time when applying RTA is on the order of milliseconds. In recent years, laser annealing, which has a heating time shorter than that of RTA, has been applied (Patent Documents 1 and 2). As a laser light source for laser annealing, for example, a solid-state laser such as an Nd: YAG laser is used.

  A technique for performing annealing using a pulse laser beam having a pulse width of 1 μs to 100 μs is known (Patent Document 3). In this method, a semiconductor laser (laser diode) is used as a laser light source.

JP 2011-060868 A JP 2011-119297 A JP 2012-134228 A

  When performing activation annealing of the dopant implanted into the semiconductor substrate, the output power of the laser light source and the size of the beam spot on the surface of the semiconductor substrate are determined in order to ensure a sufficient pulse energy density for activation. Is done. By scanning the surface of the semiconductor substrate with a pulsed laser beam, an annealing process is performed on the entire area of the semiconductor substrate. The annealing time can be shortened by increasing the area of the beam spot. However, when the beam spot is enlarged, the output power of the laser light source must be increased in order to ensure a sufficient pulse energy density.

  An object of the present invention is to provide a method of manufacturing a semiconductor device capable of increasing the area of a beam spot and shortening the annealing time without increasing the output power of a laser light source. Another object of the present invention is to provide a semiconductor device manufacturing apparatus for manufacturing a semiconductor device by applying the laser annealing method.

According to one aspect of the invention,
Implanting dopant ions into the surface layer of the semiconductor substrate;
A step of increasing the density of crystal defects in the surface layer portion of the semiconductor substrate by implanting ions of the same element as the constituent elements of the semiconductor substrate into the surface layer portion of the semiconductor substrate after implanting the dopant ions; ,
After increasing the density of crystal defects, a method of manufacturing a semiconductor device is provided which includes a step of activating the dopant by irradiating a laser beam on the surface of the semiconductor substrate.

According to another aspect of the invention,
A first ion implantation apparatus for implanting ions of the same element as a constituent element of the semiconductor substrate into the semiconductor substrate;
A laser annealing apparatus that performs annealing by applying a laser beam to the semiconductor substrate;
A transfer device for transferring the semiconductor substrate from the first ion implanter to the laser annealing device;
A control device for controlling the first ion implantation device, the laser annealing device, and the transfer device;
The control device controls the first ion implantation device, the laser annealing device, and the transfer device,
Implanting ions of the same element as the constituent elements of the semiconductor substrate into the surface layer portion of the semiconductor substrate carried into the first ion implantation apparatus under the condition that the crystal defect density of the surface layer portion of the semiconductor substrate is high;
Thereafter, transferring the semiconductor substrate from the first ion implantation apparatus to the laser annealing apparatus;
Thereafter, there is provided a semiconductor device manufacturing apparatus for performing a laser annealing process by making a laser beam incident on the semiconductor substrate.

  If the density of crystal defects is increased before laser annealing, the absorption rate of the laser beam is increased. For this reason, the pulse energy density for obtaining a desired annealing effect can be lowered.

FIG. 1A to FIG. 1C are cross-sectional views of a semiconductor device in the course of manufacturing a semiconductor device manufacturing method according to an embodiment. FIG. 1D to FIG. 1E are cross-sectional views of a semiconductor element in the course of manufacturing a semiconductor element manufacturing method according to an embodiment. FIG. 1F to FIG. 1G are cross-sectional views of a semiconductor device in the course of manufacturing a semiconductor device manufacturing method according to an embodiment. FIG. 2 is a schematic diagram of a semiconductor device manufacturing apparatus according to an embodiment. FIG. 3 is a schematic view of a laser annealing apparatus used in the semiconductor device manufacturing apparatus according to the embodiment.

  With reference to FIGS. 1A to 1G, a method for manufacturing a semiconductor device according to an embodiment will be described. Hereinafter, the manufacture of an insulated gate bipolar transistor (IGBT) will be described as an example.

  As shown in FIG. 1A, a p-type base region 33, an n-type emitter region 34, a gate electrode 35, a gate are formed on one surface (hereinafter referred to as a first surface) of a semiconductor substrate 31 made of n-type silicon. An insulating film 36 and an emitter electrode 37 are formed. These are formed by a general semiconductor manufacturing process.

  As shown in FIG. 1B, the semiconductor substrate 31 is thinned by grinding the other surface of the semiconductor substrate 31 (hereinafter referred to as the second surface). If the semiconductor substrate 31 is thinned at the stage of forming the element structure on the first surface, it is inconvenient for handling the semiconductor substrate 31. Moreover, it is preferable to make the semiconductor substrate 31 thin in order to reduce the element resistance of the IGBT. In order to facilitate handling at the stage of forming the element structure on the first surface and reduce the element resistance, after forming the element structure on the first surface and before processing the second surface, The semiconductor substrate 31 is ground. In the process after grinding, the second surface of the semiconductor substrate 31 is processed.

  As shown in FIG. 1C, phosphorus (P) ions are implanted into the surface layer portion of the semiconductor substrate 31. Thereby, an n-type buffer layer 39 is formed. As shown in FIG. 1D, boron (B) ions are implanted into the surface layer portion of the semiconductor substrate 31. Thereby, a p-type collector layer 38 is formed. The boron ion implantation depth is shallower than the phosphorus ion implantation depth in the ion implantation step shown in FIG. 1C. Therefore, the n-type buffer layer 39 remains in a region deeper than the p-type collector layer 38.

  As shown in FIG. 1E, silicon (Si) ions are implanted into the surface layer portion of the semiconductor substrate 31. Silicon ions are implanted under conditions that increase crystal defects 41 in the surface layer portion of the semiconductor substrate 31. It is preferable that the elements implanted to increase the crystal defects 41 are the same as the constituent elements of the semiconductor substrate 31. In the embodiment, since the semiconductor substrate 31 is a silicon substrate, silicon is used as an implantation element. When the semiconductor substrate 31 is a SiC substrate, silicon and carbon (C) are used as an implantation element. By making the implanted element the same as the constituent element of the semiconductor substrate 31, the crystal defects 41 can be increased without affecting the dopant concentration in the surface layer portion of the semiconductor substrate 31.

As shown in FIG. 1F, a laser beam 45 is incident on the second surface of the semiconductor substrate 31, that is, the surface on which the buffer layer 39 and the collector layer 38 are formed, and activation annealing is performed. For example, a pulse laser beam is used as the laser beam 45, the wavelength thereof is in the range of 690 nm to 950 nm, the pulse width is in the range of 10 μs to 100 μs, and the pulse energy density on the surface of the semiconductor substrate 31 is 250 kW / It is in the range of cm ^{2 to} 750 kW / cm ² . As a light source of such a pulse laser beam, for example, a laser diode array can be used. By this laser annealing, phosphorus and boron in the buffer layer 39 and the collector layer 38 are activated, and at the same time, the crystal defects 41 (FIG. 1E) are recovered. After the laser annealing, a collector electrode 40 is formed on the collector layer 38 as shown in FIG. 1G.

  In the above embodiment, before the laser annealing shown in FIG. 1F, the crystal defects 41 in the surface layer portion of the semiconductor substrate 31 are increased in the silicon ion implantation step shown in FIG. 1E. As the crystal defect density increases, the absorption rate of the laser light increases. For this reason, even if the pulse energy density is lowered, a sufficient annealing effect can be obtained.

  Since the pulse energy density required for the activation annealing may be low, the beam spot can be enlarged under the condition that the laser power is unchanged. When the beam spot is increased, the annealing time can be shortened. Under the condition that the size of the beam spot is unchanged, the laser power can be reduced. When the laser power is lowered, deterioration of the laser light source can be suppressed and the life can be extended.

  Activation annealing using a laser may be performed under a condition that the surface of the semiconductor substrate 31 is melted or may be performed under a condition that the surface is not melted. When activation annealing is performed under melting conditions, the melting depth is preferably shallower than the collector layer 38 in order to maintain the dopant concentration distribution in the depth direction. In the molten region, the dopant is activated when recrystallizing. In the region that does not melt, the dopant is activated by solid phase diffusion. When activation annealing is performed under conditions that do not melt, the dopant is activated by solid phase diffusion throughout the entire region.

In the implantation of silicon ions for increasing the crystal defect density (FIG. 1E), if the crystal defect is caused to an excessively deep region, it becomes difficult to recover the defect. In order to sufficiently recover crystal defects caused by silicon ion implantation, it is preferable to make the depth of silicon ion implantation shallower than the depth of boron implanted in the ion implantation step shown in FIG. 1D.

  FIG. 2 is a schematic plan view of a semiconductor device manufacturing apparatus according to the embodiment. The semiconductor device manufacturing apparatus according to the embodiment includes a phosphorus implantation apparatus 51, a boron implantation apparatus 52, a silicon implantation apparatus 53, a laser annealing apparatus 54, a transfer apparatus 55, and a control apparatus 50 for controlling these apparatuses. The phosphorus implantation apparatus 51 implants phosphorus ions into the semiconductor substrate 31 that has been carried in (FIG. 1C). The boron implantation device 52 implants boron ions into the semiconductor substrate 31 that has been carried in (FIG. 1D). The silicon implantation apparatus 53 increases crystal defects by implanting silicon ions into the semiconductor substrate 31 that is carried in (FIG. 1E).

  The transfer device 55 receives the semiconductor substrate 31 from the wafer carrier 60 and carries it into the phosphorus implantation device 51. Further, the semiconductor substrate 31 is transferred from the phosphorus implantation device 51 to the boron implantation device 52, from the boron implantation device 52 to the silicon implantation device 53, and from the silicon implantation device 53 to the laser annealing device 54. Further, the semiconductor substrate 31 is unloaded from the laser annealing apparatus 54 and returned to the wafer carrier 60.

  FIG. 3 shows a schematic diagram of the laser annealing apparatus 54 (FIG. 2). The laser light source 10 includes a driver 11 and a laser oscillator 12. When a trigger signal is input from the control device 50, the laser light source 10 emits a laser pulse corresponding to a pulse width defined by the trigger signal. For the laser oscillator 12, for example, a laser diode having an oscillation wavelength of 690 nm to 950 nm is used.

  The laser oscillator 12 has a plurality of light emitting points arranged in a line. Each of the light emitting points has a shape that is long in the arrangement direction, and the ratio of the dimension between the major axis direction and the minor axis direction is, for example, 100: 1. The dimension of the light emitting point in the major axis direction is approximately equal to the interval between two light emitting points adjacent to each other. In other words, the light emitting points and the non-light emitting regions are alternately arranged at equal intervals.

  The driver 11 includes a capacitor and a pulse waveform shaping circuit. The pulse waveform shaping circuit shapes the current waveform so that the discharge current from the capacitor becomes, for example, a top flat pulse current. A top flat pulse current is supplied to the laser oscillator 12. The pulse waveform shaping circuit can be configured by using a power semiconductor element such as a power MOSFET or IGBT and a control circuit, for example. When a pulse current is supplied from the driver 11, the laser oscillator 12 oscillates and emits a laser pulse.

  A pulse laser beam emitted from the laser light source 10 enters the workpiece 30 via the shutter 13, the half-wave plate 15, the beam homogenizer 16, the beam splitter 17, the quarter-wave plate 20, and the condenser lens 21. To do. The workpiece 30 is, for example, a silicon wafer into which a dopant has been implanted, and is held on the stage 22.

  Opening and closing of the shutter 13 is controlled by the control device 50. The half-wave plate 15 changes the polarization direction of the pulse laser beam by changing the direction of the slow axis. The change in the direction of the slow axis of the half-wave plate 15 is controlled by the control device 50.

  The beam splitter 17 reflects a part of the incident pulse laser beam toward the beam damper 18 and advances the remaining component straight. The ratio of the component that travels straight through the beam splitter 17 can be controlled by changing the direction of the slow axis of the half-wave plate 15 to change the polarization direction. For this reason, by changing the direction of the slow axis of the half-wave plate 15, the pulsed laser beam that reaches the workpiece 30 can be attenuated.

  The pulsed laser beam that has traveled straight through the beam splitter 17 passes through the quarter-wave plate 20 and the condenser lens 21 and enters the workpiece 30. The beam homogenizer 16 and the condensing lens 21 make the beam cross section on the surface of the workpiece 30 elongated in one direction, and the light intensity in the major axis and the direction (width direction) perpendicular to the major axis is uniform. (The spatial profile is made top flat). As the beam homogenizer 16, for example, a kaleidoscope, an optical fiber, an array lens, a fly-eye lens, or the like can be used. The stage 22 is controlled by the control device 50 to move the workpiece 30 in two directions perpendicular to the optical axis of the pulse laser beam, specifically in the major axis direction and the width direction of the beam cross section.

  The reflected light reflected from the surface of the workpiece 30 passes through the condenser lens 21 and the quarter wavelength plate 20 and enters the beam splitter 17. By passing through the quarter-wave plate 20 twice in the forward path and the return path, the polarization direction changes by 90 °. Therefore, the reflected light is reflected by the beam splitter 17 and enters the beam damper 19.

  Hereinafter, the control of the control device 50 (FIG. 2) will be described. First, the control device 50 controls the transfer device 55 to take out the semiconductor substrate 31 (FIG. 1A) to be processed from the wafer carrier 60 (FIG. 2) and carry it into the phosphorus implantation device 51. At this stage, the semiconductor substrate 31 stored in the wafer carrier 60 is the one after grinding shown in FIG. 1B. After carrying the semiconductor substrate 31 into the phosphorus implantation apparatus 51, the control apparatus 50 controls the phosphorus implantation apparatus 51 to implant phosphorus ions into the semiconductor substrate 31 (FIG. 1C).

  After injecting phosphorus, the following procedure is executed under the control of the control device 50. First, the transfer device 55 transfers the semiconductor substrate 31 from the phosphorus injection device 51 to the boron injection device 52. Boron implanter 52 implants boron ions into semiconductor substrate 31 (FIG. 1D). The transfer device 55 transfers the semiconductor substrate 31 implanted with boron ions from the boron implanter 52 to the silicon implanter 53. The silicon implanter 53 implants silicon ions into the semiconductor substrate 31 (FIG. 1E). Thereby, crystal defects in the surface layer portion of the semiconductor substrate 31 are increased. The transfer device 55 transfers the semiconductor substrate 31 implanted with silicon ions from the silicon injection device 53 to the laser annealing device 54. The laser annealing device 54 performs laser annealing to activate boron and phosphorus and recover crystal defects (FIG. 1F).

  The ion implantation and activation annealing shown in FIGS. 1A to 1G can be efficiently performed by the semiconductor device manufacturing apparatus shown in FIGS.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 Laser light source 11 Driver 12 Laser oscillator 13 Shutter 15 Half wave plate 16 Beam homogenizer 17 Beam splitter 18, 19 Beam damper 20 1/4 wavelength plate 21 Condensing lens 22 Stage 30 Semiconductor substrate 31 Semiconductor substrate 33 P type base region 34 n Type emitter region 35 gate electrode 36 gate insulating film 37 emitter electrode 37
38 n-type buffer layer 39 p-type collector layer 40 collector electrode 41 crystal defect 45 laser beam 50 control device 51 phosphorus implantation device 52 boron implantation device 53 silicon implantation device 54 laser annealing device 55 transfer device 60 wafer carrier

Claims (5)

Implanting dopant ions into the surface layer of the semiconductor substrate;
A step of increasing the density of crystal defects in the surface layer portion of the semiconductor substrate by implanting ions of the same element as the constituent elements of the semiconductor substrate into the surface layer portion of the semiconductor substrate after implanting the dopant ions; ,
And a step of activating the dopant by irradiating a laser beam on the surface of the semiconductor substrate after increasing the density of crystal defects.   The method of manufacturing a semiconductor device according to claim 1, wherein an implantation depth in the step of increasing the density of crystal defects is shallower than an implantation depth in the step of implanting the dopant ions. A first ion implantation apparatus for implanting ions of the same element as a constituent element of the semiconductor substrate into the semiconductor substrate;
A laser annealing apparatus that performs annealing by applying a laser beam to the semiconductor substrate;
A transfer device for transferring the semiconductor substrate from the first ion implanter to the laser annealing device;
A control device for controlling the first ion implantation device, the laser annealing device, and the transfer device;
The control device controls the first ion implantation device, the laser annealing device, and the transfer device,
Implanting ions of the same element as the constituent elements of the semiconductor substrate into the surface layer portion of the semiconductor substrate carried into the first ion implantation apparatus under the condition that the crystal defect density of the surface layer portion of the semiconductor substrate is high;
Thereafter, transferring the semiconductor substrate from the first ion implantation apparatus to the laser annealing apparatus;
And a step of performing laser annealing by applying a laser beam to the semiconductor substrate. A second ion implanter for implanting dopant ions into the semiconductor substrate;
The transfer device further transfers the semiconductor substrate from the second ion implanter to the first ion implanter,
The control device controls the first ion implantation device, the second ion implantation device, the laser annealing device, and the transfer device,
Before implanting ions into the semiconductor substrate with the first ion implanter, implanting dopant ions into the semiconductor substrate carried into the second ion implanter;
The apparatus for manufacturing a semiconductor device according to claim 3, wherein the semiconductor substrate is transferred from the second ion implanter to the first ion implanter.   The control device controls the first ion implantation device and the second ion implantation device to determine the depth of ion implantation by the first ion implantation device to determine the ion implantation depth by the second ion implantation device. The apparatus for manufacturing a semiconductor device according to claim 4, wherein the depth is less than a depth of implantation of the semiconductor element.

Images