JP2008306210A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device that can reduce damage to crystal due to laser irradiation. <P>SOLUTION: Ions are implanted in a surface portion of a silicon substrate to make it amorphous. Impurities are implanted into the region made amorphous. A pulse laser beam of 400 to 650 nm in wavelength is made incident on the region where the impurities are implanted to activate the implanted impurities. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for activating an impurity implanted into a semiconductor substrate by laser irradiation.

  A technique is known in which impurities are implanted into a semiconductor substrate and irradiated with an excimer laser in the ultraviolet region, for example, an XeCl excimer laser with a wavelength of 308 nm or a KrF excimer laser with a wavelength of 248 nm. Hereinafter, a conventional activation method will be described.

  First, germanium (Ge) is doped into the surface layer portion of the silicon substrate to make the surface layer portion of the silicon substrate amorphous. Thereafter, desired impurity ions are implanted. By making the surface layer amorphous, the channeling phenomenon of impurity ions can be prevented.

  The surface of the semiconductor substrate is irradiated with an excimer laser to melt and recrystallize the amorphous part having a low melting point. Thereby, the implanted impurities are activated.

JP-A-6-69149 US Patent Application Publication No. 2001/0039063 US Patent Application Publication No. 2002/0086502

  In the above conventional method, the thermal history when the amorphous part is melted and then recrystallized damages the semiconductor crystal. Further, since the light absorption coefficient of silicon in the ultraviolet wavelength region is large, the energy of the laser beam is absorbed in an extremely thin region (region having a thickness of about 10 nm) of the silicon substrate. Since the deep region is heated by heat conduction from the surface layer portion, the temperature is hardly uniform in the thickness direction.

  Furthermore, since the excimer laser normally has a pulse energy fluctuation of about 7%, the activation rate varies from shot to shot.

  An object of the present invention is to provide a method for manufacturing a semiconductor device capable of reducing damage to a crystal caused by laser irradiation.

According to one aspect of the invention,
A process of implanting ions into the surface layer of the silicon substrate to make it amorphous;
Implanting impurities into the amorphized region;
There is provided a method for manufacturing a semiconductor device, which includes a step of irradiating a pulse laser beam having a wavelength of 400 to 650 nm into the region into which the impurity is implanted to activate the implanted impurity.

  By using a pulse laser beam having a wavelength of 400 to 650 nm, the amorphous region can be preferentially heated.

  FIG. 1 shows a schematic diagram of a laser annealing apparatus used in an embodiment of the present invention. The laser annealing apparatus includes a processing chamber 40, a transfer chamber 82, carry-in / out chambers 83 and 84, a laser light source 71, a homogenizer 72, a CCD camera 88, and a video monitor 89. A linear motion mechanism 60 including a bellows 67, coupling members 63 and 65, a linear guide mechanism 64, a linear motor 66, and the like is attached to the processing chamber 40. The linear motion mechanism 60 can translate the stage 44 disposed in the processing chamber 60.

  The processing chamber 40 and the transfer chamber 82 are connected via a gate valve 85, and the transfer chamber 82 and the carry-in / out chamber 83, and the transfer chamber 82 and the carry-in / out chamber 84 are connected via gate valves 86 and 87, respectively. . Vacuum pumps 91, 92, and 93 are attached to the processing chamber 40 and the carry-in / out chambers 83 and 84, respectively, so that the inside of each chamber can be evacuated.

  A transfer robot 94 is accommodated in the transfer chamber 82. The transfer robot 94 transfers the processing substrate between the processing chamber 40 and the loading / unloading chambers 83 and 84.

  A quartz window 38 for transmitting a laser beam is provided on the upper surface of the processing chamber 40. Note that visible optical glass such as BK7 may be used instead of quartz. The pulsed laser beam output from the laser light source 71 enters the homogenizer 72 through the attenuator 76. The homogenizer 72 makes the cross-sectional shape of the laser beam an elongated shape and makes the strength in the major axis direction uniform. The laser beam that has passed through the homogenizer 72 passes through an elongated quartz window 38 corresponding to the cross-sectional shape of the beam, and is incident on the processing substrate held on the stage 44 in the processing chamber 40. The relative position of the homogenizer 72 and the processing substrate is adjusted so that the surface of the substrate coincides with the homogenized surface.

  The direction in which the stage 44 is translated by the linear motion mechanism 60 is a direction orthogonal to the longitudinal direction of the quartz window 38. Thereby, it is possible to irradiate a wide area on the surface of the substrate with the laser beam. The substrate surface is photographed by a CCD camera 88, and the substrate surface being processed can be observed by a video monitor 89.

  A laser annealing method according to an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 2A, a resist film 2 is formed on the surface of the silicon substrate 1 to be annealed, and an opening is formed in the resist film 2 by performing exposure and development.

  As shown in FIG. 2B, germanium ions are implanted into the surface layer portion of the silicon substrate 1 through the opening 2a using the resist film 2 as a mask. Thereby, the surface layer part of the area | region corresponding to the opening 2a is amorphized, and the amorphous area | region 3 is formed. Note that the regions to be amorphized are, for example, MOSFET source and drain regions. In the case of making the source and drain regions amorphous, germanium ions are implanted into the regions to be the source and drain regions using the gate electrode of the MOSFET as a mask.

  The ions to be implanted are not limited to germanium, and ions of other group VI elements can also be used.

  As shown in FIG. 2C, impurities are implanted into the surface layer portion of the silicon substrate 1 using the resist film 2 as a mask. The impurity is, for example, the well-known boron (B), phosphorus (P), arsenic (As), or the like. Thereby, the impurity implantation region 4 is formed. Thereafter, the resist film 2 is removed.

  As shown in FIG. 2D, the silicon substrate 1 is held on the stage 44 of the laser annealing apparatus shown in FIG. 1, and the laser beam 5 is incident on the substrate surface. The laser beam 5 is a second harmonic of the Nd: YLF laser, and its wavelength is 527 nm.

As shown in FIG. 2E, the beam incident region 6 on the substrate surface has a linear shape that is long in one direction. For example, the width of the beam incident region 6 is 0.1 mm, the length is 17 mm, and the pulse width of the laser beam 5 is 110 ns. The energy density per pulse on the substrate surface is such a size that the surface layer portion of the substrate does not melt, and is 700 to 800 mJ / cm ² as an example. The laser beam 5 is irradiated on the entire surface of the substrate while moving the beam incident position in the minor axis direction of the beam incident region 6. At this time, the beam incident position is moved so that the incident area of the laser beam 5 partially overlaps the beam incident area in the previous shot.

  The energy density per pulse of the laser beam 5 is adjusted so that the temperature of the substrate surface does not exceed the melting point (1147 ° C.) of amorphous silicon. The substrate surface is heated by the irradiation of the laser beam 5, solid phase growth occurs, the amorphous region is recrystallized, and the impurities in the impurity implantation region 4 are activated.

  FIG. 3 shows a block diagram of an apparatus for adjusting the positional relationship between the silicon substrate 1 and the beam incident area and the relative position between the two. On the surface of the silicon substrate 1, lattice-like scribe lines 10X and 10Y are defined. Each of the scribe lines 10X extends in the horizontal direction of the drawing, and each of the scribe lines 10Y extends in the vertical direction of the drawing. A plurality of chips 11 are defined by grid-like scribe lines 10X and 10Y.

  The position sensor 45 detects the position in the translation direction and the rotation direction within the surface of the silicon substrate 1 held by the stage 44. The position detection result is input to the control device 46. The controller 46 drives the XY stage 44 so that the major axis direction of the beam incident area 6a is parallel to the scribe line 10Y and both ends thereof are positioned on the two scribe lines 10X adjacent to each other. To do. The length of the beam incident area 6a is adjusted in advance by the homogenizer 72 shown in FIG. 1 so as to be equal to the interval between the two scribe lines 10X. While irradiating the pulse laser beam, the silicon substrate 1 is moved so that both ends of the beam incident region 6a move on the scribe line 10X.

  Note that the length of the beam incident region may be an integral multiple of the interval between the scribe lines 10X. For example, both ends of the beam incident region 6b having a length twice as long as the interval between the scribe lines 10X may be moved on the scribe line 10X.

  In the above embodiment, since the surface layer portion of the substrate is not melted, the thermal load applied to the substrate is reduced, and the deterioration of crystallinity due to the thermal history can be prevented.

  Further, in the above embodiment, the linear beam incident area is moved in the minor axis direction while partially overlapping. When a laser beam having a square cross section on the substrate surface is used and the beam incident position is moved in a direction parallel to one side of the square, an annealing effect is produced at a portion corresponding to the side parallel to the moving direction. It tends to be uneven. In the above embodiment, since both ends of the beam incident areas 6a and 6b move on the scribe line 10X, the position where the annealing effect is non-uniformly coincides with the scribe line 10X. For this reason, the annealing effect can be made uniform in the chip 11.

  Next, a preferable range of the laser beam wavelength will be described.

FIG. 4 shows the wavelength dependence of the light absorption coefficient of amorphous silicon and single crystal silicon. The horizontal axis represents the wavelength in the unit “nm”, and the vertical axis represents the absorption coefficient in the unit “× 10 ⁷ cm ⁻¹ ”. Black circles and white circles in the figure indicate the absorption coefficient of single crystal silicon and the absorption coefficient of amorphous silicon, respectively.

  It can be seen that the absorption coefficient of amorphous silicon is larger than that of single crystal silicon in a wavelength region of about 340 nm or more. By using light having a wavelength region where the absorption coefficient of amorphous silicon is larger than that of single crystal silicon, amorphous region 3 shown in FIGS. 2B and 2C can be preferentially heated. it can. Since heating of the single crystal silicon region is suppressed, impurities are less likely to diffuse into the single crystal silicon region, and a shallow PN junction can be easily formed.

  In addition, the absorption coefficient of amorphous silicon in a wavelength region of 400 nm or more is smaller than the absorption coefficient in the ultraviolet region. For this reason, light having a wavelength of 400 nm or more tends to reach a deep position in the amorphous silicon region. When an ultraviolet laser beam is used, only a very shallow region on the surface of the substrate is heated, and a deep region is indirectly heated by heat conduction. On the other hand, when a laser beam having a wavelength of 400 nm or more is used, a deep region is directly heated by the energy of the laser beam. For this reason, it becomes possible to make the temperature distribution in the thickness direction closer to each other. As a result, the activation rate of the impurities can be made uniform in the thickness direction.

  If the wavelength becomes too long, the absorption coefficient of amorphous silicon becomes small, and it becomes difficult to efficiently heat. Therefore, the wavelength of the laser beam for annealing the silicon substrate is preferably 400 to 650 nm. Since the laser beam in this wavelength region reaches a relatively deep region of the silicon substrate, it is suitable for laser annealing for forming a deep PN junction of the power semiconductor device.

Examples of the pulse laser having a wavelength of 400 to 650 nm include the second harmonic of the Nd: YAG laser, the second harmonic of the Nd: YVO ₄ laser, and the like, in addition to the second harmonic of the Nd: YLF laser. All solid-state lasers that excite these laser media with laser diodes have the characteristic that fluctuations in pulse energy are smaller than in excimer lasers. For this reason, in-plane uniformity of the annealing effect can be enhanced by using an all-solid-state laser as the laser light source.

  As described above, the surface layer portion of the semiconductor substrate is heated to a temperature not exceeding its melting point to activate the impurities, whereby the influence of the thermal history received by the semiconductor substrate can be reduced. By shaping the laser beam so that the beam cross section on the surface of the semiconductor substrate is long in one direction and moving the beam incident position in the short axis direction of the beam cross section, the substrate can be annealed uniformly. . In addition, by making the surface layer portion of the silicon substrate amorphous and using a laser beam having a wavelength of 400 to 650 nm, the amorphous portion can be preferentially heated. Thereby, diffusion of impurities into the single crystal region can be suppressed.

  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.

1 is a schematic plan view of an annealing apparatus used in a laser annealing method according to an embodiment of the present invention. FIG. 3 is a plan view of a substrate to be annealed for explaining a laser annealing method according to an embodiment of the present invention. 2 is a plan view showing a relative positional relationship between a semiconductor substrate annealed by a method according to an embodiment of the present invention and an incident position of a laser beam, and a block diagram of a position control device between the semiconductor substrate and the beam incident area. It is a graph which shows the wavelength dependence of the absorption coefficient of a single crystal silicon and an amorphous silicon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Resist film 2a Opening 3 Amorphous area | region 4 Impurity injection | pouring area | region 5 Laser beam 6, 6a, 6b Laser beam incident area | region 10X, 10Y Scribe line 11 Chip 38 Quartz window 40 Processing chamber 44 Stage 45 Position sensor 46 Controller 60 Direct Moving mechanism 63, 65 Coupling member 64 Linear guide mechanism 66 Linear motor 67 Bellows 71 Laser light source 72 Homogenizer 76 Attenuator 82 Transfer chamber 83, 84 Loading / unloading chamber 85, 86, 87 Gate valve 88 CCD camera 89 Video monitor 91, 92, 93 Vacuum pump 94 Transfer robot

Claims (2)

A process of implanting ions into the surface layer of the silicon substrate to make it amorphous;
Implanting impurities into the amorphized region;
A method of manufacturing a semiconductor device, comprising: irradiating a pulse laser beam having a wavelength of 400 to 650 nm into the impurity-implanted region to activate the implanted impurity. The beam cross section on the surface of the semiconductor substrate has a shape that is long in one direction,
Further, the incident position of the pulse laser beam is moved in the minor axis direction of the beam cross section, and the region where the pulse laser beam is irradiated and the incident region of the pulse laser beam partially overlap each other. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of irradiating a plurality of shots while moving the incident position.

Images