JP2008085355A - Ion implantation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an effective ion implantation method to constitute a low resistance and shallow pn junction. <P>SOLUTION: The ion implantation method comprises a step of first ion implantation by implanting ion of a first group III element, for forming a first region 82 with the first group III element distributed on the surface of a semiconductor substrate 81; and a step of second ion implantation by implanting ion of a second group III element, for forming a second region 83 including the first region 82 and being larger than the first region 82 on the surface of the semiconductor substrate 81 with the first group III element distributed thereon, and distributed with the second group III element and its compound having lighter mass than that of the first group III element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ion implantation method.

  As the integration of ULSI progresses and the element dimensions are reduced, the formation of shallow pn junctions has become increasingly important. The shallow pn junction is conventionally performed by a combination of ion implantation, which is one of doping techniques, and heat treatment (annealing).

  However, it is difficult to form a shallow pn junction using B (boron) as a p-type dopant. The reason for this is that B, which is a light element, has a remarkable channeling tail at the time of ion implantation and a large diffusion coefficient of B in Si. These cause the short channel effect of the p-channel MOS transistor.

  Such a problem of B ion implantation becomes more apparent as the device becomes finer. Therefore, various devices for suppressing channeling and suppressing diffusion at the time of ion implantation have been made with the aim of forming a shallow pn junction.

One of these is the use of BF ₂ as a p-type dopant. The reason is that in the case of ion implantation of molecules such as BF ₂ , shallower implantation than the simple substance B is possible with the same acceleration voltage. For example, the same range distance as that obtained when ion implantation of the simple substance B with an acceleration voltage of 200 eV is obtained with BF ₂ at an acceleration voltage of about 900 eV.

However, BF ₂ ion implantation has the following problems. That is, since the concentration of F (fluorine) is higher than that of B, the outward diffusion of B due to F after heat treatment or the immobilization of F due to the trapping of F in the implantation defect occurs. As a result, there is a problem that the activation rate of B is lowered and the resistance (sheet resistance, contact resistance) of the p-type diffusion layer is increased.

  As another method, there is a preamorphization method in which the Si substrate is amorphized in advance before introducing B by ion implantation. Amorphization of the Si substrate can be performed by ion implantation of an element belonging to the same group as the substrate element (Si) such as Si and Ge.

  Amorphization of the Si substrate can also be performed by ion implantation of n-type dopants such as As, P, and Sb. However, in this case, there is a problem that the carrier concentration of the p-type diffusion layer is lowered.

  Also, it is conceivable to use heavy elements such as In and Ga as p-type dopants. However, when this type of heavy element is ion-implanted at a high concentration, accelerated diffusion becomes obvious, and this is not a low-temperature process. There is a problem that it is difficult to use.

For the reasons described above, the Si substrate is generally amorphized by ion implantation of a substrate element such as Si or Ge and a family element. FIG. 12 shows the dependence of the p-type diffusion layer resistance (sheet resistance, contact resistance) obtained by Ge ion implantation and BF ₂ ion preamorphization on the acceleration voltage of Ge ions. FIG. 13 shows the impurity concentration distribution of the p-type diffusion layer obtained by the preamorphization method and the impurity concentration distribution of the p-type diffusion layer obtained by the single ion implantation method of BF ₂ . Each is shown.

  However, the pre-amorphization method in which ion implantation of an element similar to the substrate element has the following problems. That is, according to the study by the present inventors, as shown in FIG. 14, it has been found that the preamorphization method has a problem that the resistance of the p-type diffusion layer is higher than the ion implantation of B alone. . This is because the concentration of the electrically active dopant (B) decreases due to the presence of neutral ions (Si ions, Ge ions).

As described above, as a method for forming a shallow pn junction, a method using single ion implantation of BF ₂ or a method using two ion implantations using a pre-amorphization method has been known. There is a problem that the resistance of the mold diffusion layer is increased.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an effective ion implantation method for forming a pn junction having a low resistance of the p-type diffusion layer and a shallow junction depth. It is to provide.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

  An ion generator according to the present invention includes a container capable of holding therein a material plate containing a substance composed of a plurality of elements, and a gas having a physical etching and chemical etching action on the material plate. A gas introducing means for introducing the gas into the inside of the container, an ionizing means for ionizing the substance composed of the plurality of elements, and a gas deriving means for deriving the gas in the container to the outside of the container. To do.

  An ion irradiation apparatus according to the present invention includes the ion generation apparatus according to the present invention, and an irradiation unit that irradiates a sample with ions of a substance composed of a plurality of elements generated by the ion generation apparatus. Features.

  An ion generation method according to the present invention includes a step of generating a gas having a physical etching and chemical etching action on a material plate including a substance composed of a plurality of elements, and the material plate with the gas. The method includes a step of physically and chemically etching to generate a substance composed of the plurality of elements from the material plate, and a step of ionizing the substance composed of the plurality of elements.

In the apparatus and method of the present invention, for example, a compound of a group 3 element such as GeB or GeB ₂ and a group 4 element (group 3 group 4 compound) is used as a material plate containing a substance composed of a plurality of elements. For example, by performing physical etching and chemical etching on the Group 3 and Group 4 compounds, the amount of ions of the Group 3 and Group 4 compounds necessary for ion implantation or ion irradiation can be easily generated.

  Here, the Group 4 element such as Ge is an element belonging to the same group as the Si substrate. Therefore, a group 4 element such as Ge is easily bonded to Si by heat treatment (annealing) after ion implantation of a group 3 group 4 compound into the Si substrate. In particular, Ge is desirable because it is a complete solid solution with respect to Si. Therefore, prevention of out-diffusion of group 3 elements such as B due to group 4 elements such as Ge after heat treatment and immobilization of group 4 elements due to trapping of group 4 elements such as Ge in implantation defects is prevented. it can.

  If the outward diffusion of the group 3 element such as B and the immobilization of the group 4 element such as Ge can be prevented in this way, the activation rate of the group 3 element such as B decreases, and the resistance of the p-type diffusion layer increases. The problem of doing does not happen. Further, the group 3 and group 4 compounds can make the range shorter than the ion implantation of the group 3 element alone. Therefore, it is possible to form a pn junction having a low resistance of the p-type diffusion layer and a shallow coupling depth.

  In addition, the ion implantation method according to the present invention includes a first ion implantation step of forming a first region in which a first group 3 element is distributed on the surface of a semiconductor substrate by ion implantation of the group 3 element, and the semiconductor substrate. A second group 3 element that includes a first region in which the first group 3 element is distributed on the surface thereof, and is wider than the first region and has a weight lower than that of the first group 3 element, or And a second ion implantation step of forming the second region in which the compound is distributed by ion implantation of the second group 3 element or compound thereof.

  The ion implantation method of the present invention expresses that the first group 3 element such as Ga is implanted more shallowly than the second group 3 element such as B. The reason why such ion implantation is performed is that the problem of enhanced diffusion in the conventional preamorphization method using Ga becomes noticeable when Ga is ion-implanted deeper than B. Therefore, according to the present invention, since the problem of the conventional preamorphization method using Ga can be solved, a pn junction having a low resistance of the p-type diffusion layer and a shallow coupling depth can be formed. .

  The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  According to the present invention, an ion generator, an ion irradiation apparatus, an ion generation method, and an ion implantation method that are effective for forming a pn junction having a low resistance of the p-type diffusion layer and a shallow junction depth can be realized. Become.

  In order to facilitate understanding of the ion implantation apparatus of the present invention, a conventional ion implantation apparatus will be briefly described first. Examples of the ion source arc chamber that is the heart of the ion implantation apparatus include a freeman type using a hot electrode, a burner type, and a microwave type using a magnetron.

  FIG. 4 shows a cross-sectional structure of a conventional Bernas ion source arc chamber. FIG. 4A shows a cross section parallel to the top surface of the chamber, and FIG. 4B shows a cross section parallel to the side surface of the chamber. Each of the cross sections is shown.

  A filament 54 is provided on one end face of the arc chamber 51 via an insulating support 52 and a reflector (spacer) 53, and a counter electrode 55 is provided on the other end face of the arc chamber 51 via an insulating support 52. It is.

For example, BF ₃ gas is supplied from the gas introduction port 56, the thermoelectrons are emitted from the filament 554, and the counter electrode 55 deflects the movement direction of the thermoelectrons in the opposite direction, thereby introducing the BF introduced into the arc chamber 21. Ionization is performed by increasing the collision probability with _three gases. Then, ions are taken out from an ion outlet 58 provided in the front plate 57.

  FIG. 5 shows a cross-sectional structure of a conventional Freeman ion source arc chamber. FIG. 5A shows a cross section parallel to the upper surface of the chamber, and FIG. 5B shows a cross section parallel to the side surface of the chamber. Each of the cross sections is shown.

  Reflectors 63 are provided on the opposing surfaces of the arc chamber 61 via insulating support portions 62, and rod-shaped filaments 64 are provided between the opposing reflectors 63.

  Thermoelectrons are emitted from the filament 64 to generate plasma, and a magnetic field parallel to the filament 64 by the electromagnet 65 and a rotating magnetic field by the filament current are generated, and the thermoelectrons are complicated in the arc chamber 61 by the action of the reflector 63. By making it move, the collision probability between the thermoelectrons emitted from the filament 64 and the gas supplied from the gas inlet 66 is increased. Then, ions are taken out from an ion outlet 68 provided in the front plate 67.

  FIG. 6 shows a cross-sectional structure of a conventional microwave ion source arc chamber. In this method, the microwave generated in the magnetron 71 is guided to the discharge box 73 through the waveguide 72, plasma is generated in the discharge box 43, and ions are extracted through the extraction electrode 74.

  In a conventional ion implantation apparatus, generally, gas or solid is sublimated and the vapor is introduced into the various ion source arc chambers described above to perform ionization discharge.

However, in the conventional ion implantation apparatus, for example, in order to simultaneously ionize B (boron) and Ge (germanium), it is necessary to discharge two kinds of gases such as BF ₃ and GeF ₄ simultaneously. In this case, since B and Ge are ionized independently of each other, it is impossible to implant ions of B and Ge simultaneously.

(First embodiment)
FIG. 1 is a schematic diagram showing the overall configuration of an ion implantation apparatus. As will be described later, the present invention has a significant feature in an ion source arc chamber 1 which is an ion generator, and the other configuration shown in FIG. 1 is the same as the configuration of a conventional ion implantation apparatus.

  In the ion implantation apparatus shown in FIG. 1, ions are first generated in the ion source arc chamber 1 (details will be described later), and the ions are extracted by the extraction electrode 2 and mass-separated by the separation electromagnet 3.

  Subsequently, the ions of the group 3 element and the molecule containing the group 4 element (group 3 group 4 molecule) completely separated by the slit 4 have a predetermined final energy by acceleration / deceleration or no load by the accelerator 5. Be controlled. Then, the ion beam of the group 3 group 4 molecule is converged by the quadrupole lens 6 so as to have a convergence point on the surface of the sample 12 (for example, an n-type Si substrate).

  Subsequently, the ion beam is scanned by the scanning electrodes 7 and 8 so that the implantation amount is uniformly distributed over the entire sample surface. Then, in order to remove neutral particles generated by collision with the residual gas, the ion beam is bent by the deflection electrode 9 and the sample surface is irradiated with the ion beam through the mask 10. In the figure, 11 indicates ground.

  Hereinafter, details of the ion source arc chamber 1 (ion generator) shown in FIG. 1 and a method of using the same will be described with reference to FIGS. 2 and 3.

  FIG. 2 shows a cross-sectional structure of the Bernas-type ion source arc chamber of the present embodiment. FIG. 2A shows a cross section parallel to the upper surface of the chamber, and FIG. 2B shows a side surface of the chamber. FIG. 2C shows a cross section parallel to the longitudinal side surface of the chamber.

  The basic configuration is the same as the configuration of the conventional Bernas type ion source arc chamber shown in FIG. That is, a filament 24 made of tungsten is provided on one end face of an arc chamber 21 made of tungsten or graphite via an insulating support portion 22 and a reflector (spacer) 23, and the other end face of the arc chamber 21 is placed on the other end face. A counter electrode 25 is provided via the insulating support 22. Then, I (iodine) that has been heated in an oven to become vapor is supplied from the gas introduction port 26, and ions are extracted from an ion extraction port 28 provided in the front plate 27.

  In the ion generator in the present embodiment, a slit 29 is provided along the inner wall of the arc chamber 21, and a material plate 30 for taking out the Group 3 and Group 4 molecules is detachably held in the slit 29.

  Then, I gas is supplied to the material plate 30, and the material plate 30 is physically etched by I (specifically, sputter etching) and chemically etched. A substance containing an element is generated, and this substance is ionized by the thermoelectric emitted from the filament 24.

  The material plate 30 only needs to be installed on at least a part of the inner wall of the arc chamber. More preferably, the material plate 30 is a front surface provided with a pair of opposing surfaces to which the filament 24 and the counter electrode 25 are attached, and a lead-out port 28. Installed on 3 surfaces other than plate 27.

Further, as a constituent material of the material plate 30, a compound containing a Group 3 element and a Group 4 element such as GeB or GeB ₂ or a compound containing a Group 3 element and a Group 4 element such as an organic substance containing GeB or GeB ₂ is used. It is done. As the gas introduced from the gas inlet 26, a halogen simple substance gas such as F (fluorine), Cl (chlorine), Br (bromine) or 1 (iodine), or a gas containing halogen is used. These gases are in a gas state from the beginning, a halogen simple substance or a liquid containing a halogen substance, or a vapor obtained by vaporizing a halogen simple substance or a solid substance containing a halogen.

Hereinafter, a case will be described in which GeB ₂ is used as a constituent material of the material plate 30 and is installed on three surfaces of a pair of side wall surfaces and a bottom surface among the inner wall surfaces of the arc chamber 21.

In this case, when I is introduced into the arc chamber 21 from the gas inlet 26 and thermionic electrons are emitted from the filament 24, the sputtering effect and the etching reaction by I cause the Ge and B ions from the material plate 30 (GeB ₂ ). A simple substance and molecules of GeB and GeB ₂ are derived, and these are ionized by discharge.

The generated ions are extracted through the extraction port 28. Among these ions, only GeB ₂ ions are extracted by a mass separation magnet, and ions are implanted into the sample (Si). In this case, a beam current of about 2 mA was stably obtained at an acceleration voltage of 10 keV.

  In addition, ionization was performed using Xe (xenon), which is a rare gas that has a mass number close to that of iodine, that is, substantially equal in sputtering yield and is not a halogen, as a gas introduced from the gas inlet 26.

As a result, only a few hundred μA were obtained with Ge and B single ions, and only a few tens of μA were obtained with Group 3 and Group 4 molecular ions of GeB and GeB ₂ . This indicates that in order to derive a sufficient amount of Group 3 and Group 4 molecules from the material plate 30, not only the sputtering effect but also an etching reaction with halogen is required.

On the other hand, when ionization is performed by introducing BF ₃ and GeF ₄ gases from the gas inlet 56 at a flow rate of 1 sccm into the conventional ion source arc chamber shown in FIG. Although molecular ions such as GeF, GeF ₂ , BF, and BF ₂ were obtained, the presence of ions of Group 3 and Group 4 molecules such as GeB and GeB ₂ could not be confirmed. As long as ionization is performed using BF ₃ and GeF ₄ gases in this way, it is extremely difficult to generate ions such as GeB and GeB ₂ .

  On the other hand, if the material plate 30 is installed on the inner wall surface of the arc chamber and the halogen gas sputtering effect and etching reaction are used as in the present embodiment, a sufficient amount of Group 3 elements and 4 necessary for ion implantation are used. It becomes possible to easily generate molecular ions composed of group elements.

Further, by injecting ions of molecules such as GeB and GeB ₂ into a sample such as an n-type Si substrate, it becomes possible to introduce ions such as B into a shallower region even with the same acceleration voltage.

For example, in order to perform implantation corresponding to 1 keV with the simple substance B, ion implantation can be performed at a relatively high acceleration voltage of about 7.7 keV for GeB and about 8.7 keV for GeB ₂ .

When molecules such as GeB and GeB ₂ are used, ion implantation of Ge, which is a heavy element, simultaneously with B, which is a light element, is possible, and an amorphous layer can be formed by single ion implantation.

Further, by using GeB ₂ ions as the ion species, the ion transport amount can be halved and the implantation time can be shortened as compared with the case of using single B ions. As a result, the throughput of the ion implantation process can be increased.

In addition, in the pre-amorphization method in which B is implanted after the substrate is amorphized in advance, two steps are required. However, in GeB and GeB ₂ , an amorphous layer can be formed by one ion implantation. It can be shortened. This also leads to an improvement in throughput.

Next, a case where a Freeman ion source is used will be described. The basic configuration is the same as that of the conventional Freeman ion source arc chamber shown in FIG. That is, as shown in FIG. 3, reflectors 43 are provided on the opposing surfaces of the arc chamber 41 via insulating support portions 42, and rod-like filaments 44 are provided between the opposing reflectors 43. Then, BF ₃ gas is introduced from the gas inlet 45 and ions are taken out from the ion outlet 47 provided in the front slit 46.

In the ion generator according to the present embodiment, a slit 48 is provided along the inner wall of the arc chamber 41 as in the example shown in FIG. 2, and a material plate 49 containing a substance composed of a Group 3 element and a Group 4 element in the slit 48. Is detachably held. Then, thermoelectrons are emitted from the filament 44 to generate plasma, BF ₃ gas is introduced from the gas inlet 45, and ions are taken out from the ion outlet 47. At this time, the electromagnet 50 increases the collision probability between the thermal electrons and the BF ₃ gas.

  The material plate 49 may be provided on at least a part of the inner wall surface of the arc chamber 41. More preferably, the material plate 49 is provided with a pair of opposing surfaces to which the pair of reflectors 43 are attached, and an ion extraction port 47. It is installed on at least one of the three inner wall surfaces other than the front slit 46.

  In addition, as the constituent material of the material plate 49, a compound composed of a group 3 element and a group 4 element or a compound containing a group 3 element and a group 4 element is used.

Hereinafter, a case will be described in which GeB ₂ is used as a constituent material of the material plate 49 and is installed on three surfaces of a pair of side surfaces and a bottom surface of the inner wall of the arc chamber 41 made of molybdenum.

In this case, when the BF ₃ gas is introduced into the arc chamber 41 from the gas introduction port 45 and the thermoelectrons are emitted from the filament 44, the material plate 49 (GeB) is produced by the sputtering effect by the BF ₃ gas and the etching reaction by the F gas. ₂ ) Ge and B simple substances and GeB and GeB ₂ molecules are derived and ionized by discharge. Of the generated ions, only B ions were extracted by a separating electromagnet, and ions were implanted into the sample (Si) at an acceleration voltage of 1 keV.

  In the conventional ion generator shown in FIG. 5, the beam current of the single substance B at an acceleration voltage of 1 keV was about 200 μA.

  On the other hand, when the ion generator of this embodiment shown in FIG. 3 is used, the beam current amount of the single B at an acceleration voltage of 1 keV is about 600 μA, which is a current amount close to three times the conventional beam current.

  By installing the material plate 49 on the inner wall of the arc chamber 41 in this way, the amount of ion beam current for low acceleration ion implantation can be increased, and the implantation time (irradiation time) can be shortened. As a result, the throughput of the ion implantation process can be increased.

The ion implantation apparatus of the present invention described above is effective for forming a source / drain diffusion layer of a MOS transistor, for example. In this case, a low resistance and shallow p-type source can be obtained by introducing ions containing B into the surface of the Si substrate using the gate electrode or the gate electrode and the gate side wall insulating film as a mask using the ion implantation apparatus of the present invention. A drain diffusion layer can be formed. In particular, by introducing molecular ions such as GeB ₂ as ions containing B, the ion transport amount (dose) can be reduced to half of the dose amount (number of ions) during single B ion implantation. The effective injection time can be reduced very easily.

In the embodiment described above, GeB ₂ is used as the material plate. However, other compounds composed of Group 3 and Group 4 may be used.

In the embodiment described above, I and BF ₃ are used as the gases to be introduced. However, the other halogen single gas and the single gas or vapor are not necessarily used, and the halogen-containing gas or vapor is used. Can be used. Further, materials other than tungsten, molybdenum, and graphite can be used for the filament and the arc chamber.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to a method using a Freeman type and a Bernas type ion source arc chamber has been described, but the present invention can also be applied to other methods.

(Second Embodiment)
FIG. 7 is a process cross-sectional view illustrating a method of forming a pn junction according to the second embodiment of the present invention.

First, as shown in FIG. 7A, ion implantation of Ga (p-type dopant) is performed on the surface of the n-type silicon substrate 81. In the figure, reference numeral 82 denotes an amorphous region (first region) in which Ga on the substrate surface is implanted. The ion implantation conditions here are acceleration voltage: 1.5 KeV and implantation dose amount: 5 × 10 ¹⁴ cm ⁻² .

Next, as shown in FIG. 7B, ion implantation of BF ₂ is performed on the surface of the n-type silicon substrate 81. As shown in FIG. 8B and FIG. 8, the ion implantation at this time includes the first region 82 in the amorphous second region 83 into which BF ₂ is implanted, and the impurity concentration of Ga. Is made lower than the impurity concentration of BF ₂ . In order to satisfy these requirements, the ion implantation conditions here are ion species: BF ₂ , acceleration voltage: 0.9 KeV, and implantation dose amount: 1 × 10 ¹⁵ cm ⁻² . Note that B ion implantation may be performed instead of BF ₂ .

Finally, as shown in FIG. 7C, the impurities of Ga and BF ₂ are activated by 10 seconds of RTP (Rapid Thermal Process), and the p-type diffusion layer 84 is formed on the surface of the n-type silicon substrate 81. Form a shallow pn junction.

FIG. 9 is a diagram showing the heat treatment temperature dependence of the sheet resistance of the p-type diffusion layer 84 (Ga PAI (Pre-Amorphous Implantation)). In the figure, as a comparative example, when the first region is formed by Ge ion implantation (Ge PAI) and when the second region is not formed by single BF ₂ ion implantation (No PAI) The dependence of the sheet resistance of each of the p-type diffusion layers on the heat treatment temperature is also shown. From the figure, it can be seen that the sheet resistance of the p-type diffusion layer 84 is lower than those of the comparative example at any heat treatment temperature.

  FIG. 10 is a diagram showing the heat treatment temperature dependence of the hole mobility of the p-type diffusion layer 84. The figure also shows the heat treatment temperature dependence of the hole mobility of a p-type diffusion layer (Ge PAI, No PAI) formed by ion implantation similar to the two comparative examples of FIG. From the figure, Ga PAI (the present invention) is less temperature dependent than the comparative example of Ge PAI or No PAI, and the crystallinity is recovered even at a lower temperature (900 ° C. in this embodiment). I understand that.

  FIG. 11 is a diagram showing the heat treatment temperature dependence of the activation concentration of impurities in the p-type diffusion layer 84. The figure also shows the heat treatment temperature dependence of the activation concentration of impurities in p-type diffusion layers (Ge PAI, No PAI) formed by ion implantation similar to the two comparative examples of FIG. From the figure, it can be seen that the activation concentration of the p-type diffusion layer 84 (Ga PAI) of the present invention is higher than that of the comparative example of Ge PAI or No PAI.

The reasons for obtaining these results are as follows. First, in the case of the present invention, since Ga and BF ₂ ions are implanted so that the first region 82 is included in the second region 83, there are more Ga—B bonds than in the prior art. As a result, the electrical activation of B is promoted and the outward diffusion of B is suppressed. In addition, since the Ga—B bond is performed more quickly than the Si—B bond, the crystallinity of the p-type diffusion layer is improved even at a lower temperature.

From the above results, according to the present invention, even if BF ₂ which is a p-type dopant is used to form the first region 82, the depth of the first region 82 is formed by ion implantation of BF ₂ . By making it shallower than the depth of the second region 83, a pn junction having a low resistance of the p-type diffusion layer 84 and a shallow junction depth can be formed.

  In the present embodiment, the case where the pn junction is formed on the surface of the n-type silicon substrate 81 has been described. However, the present invention can also be applied to the case where the pn junction is formed on the surface of the n-type well.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the description has focused on the ion implantation apparatus / implantation method for selectively injecting a predetermined ion species among the plurality of ion species generated in the arc chamber into the sample. The present invention can also be applied to an ion irradiation apparatus / irradiation method in which ion species are collectively injected into a sample. The basic configuration of the ion irradiation apparatus is obtained by omitting the separation electromagnet 3 from the ion implantation apparatus of FIG.

  Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, if the problem described in the column of the problem to be solved by the invention can be solved, the configuration in which this constituent requirement is deleted Can be extracted as an invention. In addition, various modifications can be made without departing from the scope of the present invention.

Schematic diagram showing the overall configuration of the ion implanter The figure which shows the cross-section of the Bernas type ion source arc chamber of 1st Embodiment The figure which shows the cross-section of the Freeman type ion source arc chamber of 1st Embodiment Diagram showing the cross-sectional structure of a conventional Bernas-type ion source arc chamber The figure which shows the section structure of the conventional Freeman type ion source arc chamber Diagram showing the cross-sectional structure of a conventional microwave ion source arc chamber Process sectional drawing which shows the formation method of the pn junction which concerns on the 2nd Embodiment of this invention It shows the concentration distribution in the substrate surface of the Ga and BF ₂ The figure which shows the heat processing temperature dependence of the sheet resistance of the p-type diffused layer of this invention (Ga PAI) and a comparative example (Ge PAI, No PAI) The figure which shows the heat treatment temperature dependence of the hole mobility of the p-type diffused layer of this invention (Ga PAI) and a comparative example (Ge PAI, No PAI) The figure which shows the heat treatment temperature dependence of the activation concentration of the impurity in the p-type diffused layer of this invention (Ga PAI) and a comparative example (Ge PAI, No PAI) The figure which shows the acceleration voltage dependence of Ge ion of the sheet resistance and contact resistance of the p-type diffused layer obtained by the conventional preamorphization method The figure which shows concentration distribution of each impurity of the p-type diffused layer obtained by the conventional pre-amorphization method and the single ion implantation method of BF ₂ Diagram for explaining problems of conventional pre-amorphization method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ion source arc chamber, 2 ... Extraction electrode, 3 ... Separation electromagnet, 4 ... Slit, 5 ... Accelerator, 6 ... Quadrupole lens, 7, 8 ... Scan electrode, 9 ... Deflection electrode, 10 ... Mask, 11 ... Ground, DESCRIPTION OF SYMBOLS 21 ... Arc chamber, 22 ... Insulation support part, 23 ... Reflector (spacer), 24 ... Filament, 25 ... Counter electrode, 26 ... Gas introduction port, 27 ... Front plate, 28 ... Ion extraction port, 29 ... Slit, 30 ... Material plate 41... Arc chamber 42. Insulation support part 43. Reflector 44. Filament 45. Gas inlet 46. Front slit 47. Ion outlet 48. Slit 49. Material plate 50. Electromagnet 51... Arc chamber 52. Insulating support 53 53 Reflector 54 Filament 55 Counter electrode 5 ... gas inlet, 57 ... front plate, 58 ... ion outlet, 61 ... arc chamber, 62 ... insulation support, 63 ... reflector, 64 ... filament, 65 ... electromagnet, 66 ... gas inlet, 67 ... front plate, 68 ... Ion extraction port, 71 ... Magnetron, 72 ... Waveguide, 73 ... Discharge box, 74 ... Extraction electrode, 81 ... N-type silicon substrate, 82 ... Region into which ion implantation of Ga (first region), 83 ... BF ₂ ion-implanted region (second region), 84 ... p-type diffusion layer.

Claims (5)

A first ion implantation step of forming a first region in which a first group 3 element is distributed on a surface of a semiconductor substrate by ion implantation of the group 3 element;
A first region in which the first group 3 element is distributed, the second group 3 element having a lighter mass than the first group 3 element or a compound thereof distributed on the surface of the semiconductor substrate; and A second region in which a second group 3 element or a compound thereof having a lighter mass than the first group 3 element and having a smaller mass is distributed than the first region is represented by the second group 3 element or a compound ion thereof. And a second ion implantation step formed by implantation. The concentration of the first group 3 element in the first region in the first ion implantation step is the second group 3 element in the second region in the second ion implantation step or its 2. The ion implantation according to claim 1, wherein ion implantation of the first group 3 element and ion implantation of the second group 3 element or a compound thereof are performed so as to be lower than a concentration of the compound. Method. The dose amount of the first group 3 element in the first ion implantation step is less than the dose amount of the second group 3 element or compound thereof in the second ion implantation step. The ion implantation method according to claim 2. 3. The ion implantation method according to claim 1, further comprising a heat treatment step for activating impurities in the first and second regions after the second ion implantation step. 4. 5. The ion implantation method according to claim 1, wherein the first group 3 element is Ga or In, and the second group 3 element is B. 6.

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