Ion implantation method

Abstract

We provide ion implantation technology that can achieve the desired implantation profile. [Solution] The ion implantation method comprises: irradiating a wafer at a first temperature with a first ion beam set to an angle condition of the ion beam such that the incident angle is sufficiently smaller than the critical angle at which channeling occurs with respect to the crystal axis of the wafer, at a predetermined position on the surface of the wafer; and, after irradiation with the first ion beam, irradiating a wafer at a second temperature different from the first temperature with a second ion beam set to the same angle condition of the ion beam as the first ion beam at a predetermined position on the surface of the wafer. The angle condition of the ion beam is set by adjusting the angle of the wafer, thereby forming a desired implantation profile within the wafer.

Description

[Technical Field]

[0001] The present invention relates to an ion implantation method. [Background technology]

[0002] In semiconductor manufacturing processes, ion implantation (also called ion implantation) is a standard procedure for purposes such as altering the conductivity or crystal structure of a semiconductor. Ion implantation can be performed via a mask formed on the wafer surface, in which case ions are selectively implanted in areas corresponding to the mask's openings. Alternatively, ions may be selectively implanted using element structures such as gate electrodes formed on the wafer surface, in which case ions are implanted in source / drain regions adjacent to the gate electrode.

[0003] Furthermore, it is known that the interaction between the ion beam and the wafer changes depending on the angle of the ion beam irradiated onto the wafer, affecting the ion implantation process results. Therefore, precise control of the ion beam implantation angle is required to obtain a desired implantation profile. For example, by controlling the ion beam implantation angle to satisfy predetermined channeling conditions, it is possible to allow the beam to reach deeper positions, thereby achieving a deeper implantation profile. On the other hand, by controlling the ion beam implantation angle so as not to satisfy the channeling conditions, an implantation profile with a laterally spread distribution at shallower positions can be achieved (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-107751 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When attempting to implant ions into a specific location on the wafer surface using a mask or similar device, the implantation profile can change depending on the angle of incidence of the ion beam to the wafer surface, regardless of whether channeling is used. For example, if the beam is incident perpendicularly to the wafer surface, ions will be implanted mainly directly below the aperture region of the mask. However, if the beam is incident at an angle to the wafer surface, ions may be implanted mainly at a position obliquely shifted from the aperture region of the mask. Therefore, even if the implantation angle of the ion beam is precisely controlled, it is not always possible to form the desired implantation profile at the desired location.

[0006] One exemplary object of a certain aspect of the present invention is to provide an ion implantation technique capable of achieving a desired implantation profile. [Means for solving the problem]

[0007] An ion implantation method according to one aspect of the present invention comprises: irradiating a wafer at a first temperature with a first ion beam set to an angle condition of the ion beam such that the incident angle is sufficiently smaller than the critical angle at which channeling occurs with respect to the crystal axis of the wafer, at a predetermined position on the surface of the wafer; and, after irradiation with the first ion beam, irradiating a wafer at a second temperature different from the first temperature with a second ion beam set to the same angle condition of the ion beam as the first ion beam at a predetermined position on the surface of the wafer. The angle condition of the ion beam is set by adjusting the angle of the wafer, thereby forming a desired implantation profile within the wafer.

[0008] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an ion implantation technology that can achieve a desired implantation profile. [Brief explanation of the drawing]

[0010] [Figure 1] Figs. 1(a) and (b) are diagrams schematically showing the presence or absence of the channeling phenomenon of implanted ions. [Figure 2] Figs. 2(a) to (d) are diagrams schematically showing the angular characteristics of an ion beam incident on a wafer, and Figs. 2(e) to (h) are graphs schematically showing the angular components of the ion beam corresponding to (a) to (d). [Figure 3] It is a graph showing an example of the relationship between the implantation angle of an ion beam and the depth-direction implantation profile formed in a wafer. [Figure 4] It is a graph showing an example of the relationship between the implantation angle of an ion beam and the implantation concentrations at two peak positions. [Figure 5] It is a graph schematically showing an example of the distribution of implanted ions in a wafer. [Figure 6] It is a cross-sectional view schematically showing an example of a high-energy implantation process. [Figure 7] It is a graph showing an example of the relationship between the wafer temperature and the depth-direction implantation profile formed in a wafer. [Figure 8] It is a graph showing an example of the relationship between the wafer temperature and the implantation concentrations at two peak positions. [Figure 9] It is a graph showing an example of the implantation profile formed in a wafer when irradiated with phosphorus (P) ions. [Figure 10] It is a graph showing an example of the implantation profile formed in a wafer when irradiated with arsenic (As) ions. [Figure 11] Figs. 11(a) to (c) are cross-sectional views schematically showing an example of multi-stage implantation according to an embodiment. [Figure 12] Figs. 1(2)(a) to (c) are cross-sectional views schematically showing another example of multi-stage implantation according to an embodiment. [Figure 13] It is a top view showing the schematic configuration of an ion implantation apparatus according to an embodiment. [Figure 14] Figs. 14(a) and (b) are diagrams schematically showing the configuration of a lens device included in a beam shaper. [Figure 15] This graph schematically illustrates an example of controlling the focusing / divergence of an ion beam using a lens device. [Figure 16] This is a side view showing the configuration of the substrate transport processing unit in detail. [Figure 17] This is a schematic side view illustrating the process of placing a wafer into a wafer holding device. [Figure 18] Figures 18(a) and (b) schematically show the orientation of the wafer with respect to the direction of incidence of the ion beam. [Figure 19] Figures 19(a) and (b) schematically show wafers that are to be subjected to ion implantation. [Figure 20] Figures 20(a) to (c) schematically show the relationship between the orientation of the wafer and the atomic arrangement near the wafer surface. [Figure 21] This is a flowchart showing the flow of the ion implantation method according to the embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the configurations described below are illustrative and do not limit the scope of the present invention in any way.

[0012] Before describing the embodiments, an overview of the present invention will be given. The ion implantation method according to this embodiment involves heating or cooling a wafer to a predetermined temperature using a temperature control device, and irradiating the wafer at the predetermined temperature with an ion beam in such a way that predetermined channeling conditions are met. Here, "determined channeling conditions are met" means that the implantation process is performed such that the angular conditions for the occurrence of the channeling phenomenon are met by incidenting the ion beam along the crystal axis or crystal plane of the wafer. According to this embodiment, a desired implantation profile can be formed in the wafer by appropriately controlling both the angular conditions and temperature conditions of the wafer during ion implantation.

[0013] Figures 1(a) and 1(b) schematically illustrate the presence or absence of the channeling phenomenon of implanted ions 92. Figure 1(a) shows how implanted ions 92 channel within the crystal lattice 90. The implanted ions 92 have a relatively small angle of incidence θ1 with respect to the crystal axis C of the crystal lattice 90 and propagate within the crystal lattice 90 along the crystal axis C. Therefore, the implanted ions 92 are less affected by interactions with the atoms 91 that make up the crystal lattice 90 and can reach deeper into the crystal lattice 90 in a linear fashion.

[0014] Figure 1(b) shows how implanted ions 92 do not channel within the crystal lattice 90. The implanted ions 92 have a relatively large angle of incidence θ2 with respect to the crystal axis C of the crystal lattice 90, and they travel through the interior of the crystal lattice 90 intersecting the crystal axis C, interacting with the atoms 91 that make up the crystal lattice 90 and being scattered as they travel. As a result, the implanted ions 92 only reach shallower positions within the crystal lattice 90, and may reach positions shifted from their initial implantation position in directions perpendicular to the implantation direction (the vertical direction of the paper in Figure 1(b) and directions perpendicular to the paper).

[0015] In this book, the situation shown in Figure 1(a) is also referred to as "on-channeling," and the situation shown in Figure 1(b) is also referred to as "off-channeling." Whether the implanted ions 92 incident on the crystal lattice 90 are "on-channeling" or "off-channeling" is mainly determined by the incident angles θ1 and θ2 of the implanted ions 92. The incident angle that serves as the threshold for on-channeling and off-channeling is the critical angle θ C It is also said that the critical angle θ C This can be expressed, for example, by the following equation (1).

[0016]

number

[0017] For such a numerical critical angle θ C , if the incident angle θ of the implanted ion is sufficiently small (θ < θ C ), ions are implanted in the channeling state shown in Fig. 1(a). On the other hand, if the incident angle θ of the implanted ion is sufficiently large with respect to the critical angle θ C (θ > θ C ), ions are implanted in the off-channeling state shown in Fig. 1(b). Therefore, when irradiating a wafer with an ion beam to perform an implantation process, the depth of arrival and horizontal spread of the implanted ions constituting the ion beam change according to the angular characteristics of the ion beam, and the shape of the "implantation profile", which is the concentration distribution of the implanted ions in the wafer, may change. Therefore, in the ion implantation process, the tilt angle of the wafer with respect to the traveling direction of the ion beam is adjusted, and the implantation angle as the average value of the entire beam incident on the wafer is controlled.

[0018] In addition to the incident angle as the average value of the entire beam, the angular characteristics of the ion beam incident on the wafer include the angular distribution as a group of ion particles constituting the ion beam. The ion beam incident on the wafer is almost always slightly divergent or convergent, and the group of ion particles constituting the beam has an angular distribution with a certain spread. At this time, if the incident angle as the average value of the entire beam is the critical angle θ CEven if it is greater than the critical angle θ, the angular component of some ion particles is C If the angle is smaller, channeling phenomena will occur due to some of the ions. Conversely, the incident angle as an average value of the entire beam is the critical angle θ. C Even if it is smaller than the critical angle θ, the angular component of some ion particles is C If it is larger, some of the ions will be off-channeled.

[0019] Figures 2(a) to (d) schematically show the angular characteristics of the ion beam B incident on the wafer W. For ease of explanation, Figures (a) to (d) show the case where the orientation of the crystal axis C is perpendicular to the surface of the wafer W, and where the "off angle" of the wafer's main surface is 0 degrees. Note that the wafer W actually used does not need to have an off angle of exactly 0 degrees.

[0020] Figure 2(a) shows a "parallel beam" where ion beam B is incident parallel to the crystal axis C of wafer W, and almost all of the ion particles constituting ion beam B propagate parallel to the crystal axis C. Figure 2(b) is similar to (a) in that ion beam B is a parallel beam, but shows a "diagonal incident beam" where the incident angle of ion beam B is oblique to the crystal axis C. Figure 2(c) shows a "divergent beam" where the beam diameter of ion beam B widens and diverges towards wafer W, and Figure 2(d) shows a "converging beam" where the beam diameter of ion beam B narrows and converges towards wafer W. Thus, ion beam B may diverge or converge with respect to the overall direction of beam propagation, and in addition to the overall direction of beam propagation, it has an "angle distribution" that represents the variation in the angular component of each ion particle.

[0021] Figures 2(e) to (h) are schematic graphs showing the angular distribution of ion beam B corresponding to (a) to (d), respectively. The vertical axis of the graph represents the number of ion particles constituting ion beam B, and the horizontal axis represents the angle of incidence θ of the ion particles constituting ion beam B with respect to the crystal axis C. In the graph, the absolute value of the angle of incidence θ is the critical angle θ. CA smaller range is shown as the on-channeling region C1, where the absolute value of the incident angle θ is the critical angle θ. C A larger range is shown as the off-channeling region C2.

[0022] In Figure 2(e), the center of the angular distribution is 0 degrees, and because the spread of the angular distribution of ion beam B is small, the entire angular distribution is included in the on-channeling region C1. As a result, in Figure 2(e), the implanted ions that are on-channeling are dominant. On the other hand, in Figure 2(f), although the spread of the angular distribution of ion beam B is small, the center of the angular distribution is at the critical angle θ. C Because it is larger than the center angle, the entire angular distribution is contained within the off-channeling region C2. As a result, in Figure 2(e), the implanted ions that are off-channeling are dominant. In Figures 2(g) and (h), the angular distribution of ion beam B is large, and the center of the angular distribution is 0 degrees, so the entire angular distribution spans both the on-channeling region C1 and the off-channeling region C2. As a result, in Figures 2(g) and (h), both on-channeling and off-channeling are present in a mixed state. Note that the mixing ratio of on-channeling and off-channeling may change depending on the center angle and the size of the spread of the angular distribution.

[0023] Figure 3 is a graph showing an example of the relationship between the injection angle θ of ion beam B and the depth-direction injection profile formed in the wafer. This figure shows the simulation results when the injected ion is boron (B), the target of injection is the (100) plane of silicon (Si), and the injection energy is 1.5 MeV. The critical angle θ based on equation (1) above. CThe angle is approximately 0.9 degrees. Ion beam B is a divergent beam as shown in Figure 2(c), with a divergence angle (dispersion value) of approximately 0.4 degrees. The injection angles θ of ion beam B are set to 0 degrees, 0.2 degrees, 0.5 degrees, 1 degree, 2 degrees, and 5 degrees. The injection profile is distributed at deeper positions (right side of the graph) as the injection angle θ decreases. The injection profile also has roughly two peaks, with the first peak P1 at a depth of approximately 2.2 μm and the second peak P2 at a depth of approximately 3.1 μm. The first peak P1 tends to be lower as the injection angle θ decreases and higher as the injection angle θ increases, suggesting that it corresponds to injection ions based on off-channeling. On the other hand, the second peak P2 tends to be higher as the injection angle θ decreases and lower, suggesting that it corresponds to injection ions based on on-channeling.

[0024] Figure 4 is a graph showing an example of the relationship between the injection angle θ of ion beam B and the injection concentration at two peak positions P1 and P2, corresponding to the injection profile shown in Figure 3. The dashed line P1 shows the injection concentration at a depth d=2.2 μm corresponding to the first peak, and the solid line P2 shows the injection concentration at a depth d=3.1 μm corresponding to the second peak. As shown in the figure, the injection concentration at the first peak P1 tends to be lower as the injection angle θ is smaller and higher as the injection angle θ is larger. On the other hand, the injection concentration at the second peak P2 tends to be higher as the injection angle θ is smaller and lower as the injection angle θ is larger.

[0025] Figure 5 is a schematic graph showing an example of the distribution of implanted ions 92 in a wafer. This figure shows the calculation results from a simulation under the same implantation conditions as in Figure 3, with the implanted ions being boron (B), the implantation target being the (100) plane of silicon (Si), the implantation energy being 1.5 MeV, the implantation angle θ of ion beam B being 0 degrees, and the magnitude of the divergence angle of ion beam B being approximately 0.4 degrees. The vertical axis of the graph shows the depth position from the surface of wafer W, and the horizontal axis of the graph shows the position in the in-plane direction parallel to the surface of wafer W. In the example shown in this figure, implanted ions 92 are present in the range of depths from 2.0 μm to 3.5 μm. Ions 93 implanted at relatively deeper positions are on-channeling implanted ions and are present only near the center in the in-plane direction. On the other hand, ions 94 implanted at relatively shallow positions are off-channeling implanted ions and are distributed to spread out to positions away from the center in the in-plane direction. Thus, it can be seen that the implanted ions 93 and 94 based on on-channeling and off-channeling, respectively, also have different distributions in the in-plane direction perpendicular to the depth direction.

[0026] From the above, by precisely controlling the injection angle θ with respect to the crystal axis C of the wafer W, the shape of the injection profile formed inside the wafer W can be controlled. In particular, by selecting an angle condition in which on-channeling is dominant, an injection profile with less in-plane spread can be realized at a deeper location. On the other hand, by selecting an angle condition in which off-channeling is dominant, an injection profile with a larger in-plane spread can be realized at a shallower location. Furthermore, by changing the energy of the injected ions, the overall depth position of the injected ions can be controlled.

[0027] However, depending on the target of the ion implantation process, it may not be possible to freely change the implantation angle θ in order to control the implantation profile. In recent years, there has been a customer demand to implant ions to deeper positions in the depth direction from the wafer surface in order to further miniaturize semiconductor devices and improve their characteristics. In this case, a mask is formed on the wafer surface to implant ions only in a specific region in the in-plane direction. Furthermore, to implant ions to deeper positions, high-energy ion beams, such as 100 keV or more, or 1 MeV or more, are used.

[0028] Figure 6 is a schematic cross-sectional view illustrating an example of a high-energy injection process, showing how an ion beam B is irradiated through a thick mask 80 provided on the surface of a wafer W. As shown in the figure, in order to properly shield the high-energy ion beam B, the mask 80 on the wafer surface must be made thick, resulting in a high aspect ratio of the opening 82 of the mask 80. Therefore, when the ion beam is incident at an angle to the surface of the wafer W, the ion beam incident at an angle to the opening 82 is at least partially shielded by the side surface 81 of the opening 82 due to the high aspect ratio of the opening 82, making it difficult to properly irradiate the injection region 84 corresponding to the opening 82 with the ion beam. Consequently, when using a mask 80 with a high aspect ratio opening 82, the ion beam B must be incident almost perpendicular to the wafer W, and the incident angle θ of the ion beam B is constrained due to the mask shape. In this case, the incident angle θ of the ion beam B cannot be freely set for the purpose of controlling the injection profile.

[0029] Therefore, the inventors considered controlling the shape of the implantation profile formed within wafer W by controlling the temperature conditions of wafer W during irradiation with ion beam B. According to the inventors' findings, by increasing the wafer temperature during irradiation with ion beam B, ions can be implanted under conditions where channeling is relatively difficult (i.e., off-channeling). Conversely, by lowering the wafer temperature during irradiation with ion beam B, ions can be implanted under conditions where channeling is relatively easy (i.e., on-channeling).

[0030] Figure 7 is a graph showing an example of the relationship between wafer temperature T and the depth-direction injection profile formed within wafer W. Similar to Figure 3, this figure shows simulation results when the injected ion is boron (B), the injection target is the (100) plane of silicon (Si), the injection energy is 1.5 MeV, and the divergence angle of ion beam B is 0.4 degrees. However, in Figure 7, the injection angle θ of ion beam B is fixed at 0 degrees. The wafer temperature T during beam irradiation is -273°C, -196°C, -100°C, 27°C, 150°C, 414°C, and 450°C. As shown, the injection profile is generally distributed deeper (to the right of the graph) as the wafer temperature decreases. Furthermore, the first peak P1 of the injection profile tends to be smaller as the wafer temperature T decreases and larger as the wafer temperature T increases. Conversely, the second peak P2 tends to be larger as the wafer temperature T decreases and smaller as the wafer temperature T increases.

[0031] Figure 8 is a graph showing an example of the relationship between wafer temperature T and injection concentration at two peak positions P1 and P2, corresponding to the injection profile shown in Figure 7. The dashed line P1 represents the injection concentration at a depth d = 2.2 μm, corresponding to the first peak, and the solid line P2 represents the injection concentration at a depth d = 3.1 μm, corresponding to the second peak. As shown in the figure, the injection concentration at the first peak P1 tends to be lower as wafer temperature T decreases and higher as wafer temperature T increases. On the other hand, the injection concentration at the second peak P2 tends to be higher as wafer temperature T decreases and lower as wafer temperature T increases.

[0032] From the above, it can be seen that the injection profile can be controlled by changing the wafer temperature T during injection, similar to how the injection angle θ can be controlled. Specifically, by lowering the wafer temperature T, an on-channeling dominant state can be achieved. This is thought to be because lowering the wafer temperature W reduces the movement of the atoms constituting the crystal lattice of the wafer W, lowering the probability of the injected ions interacting with the crystal lattice of the wafer W, thus creating a state where channeling is more likely. Therefore, by lowering the wafer temperature T, an injection profile with less in-plane spread can be achieved at a deeper location. On the other hand, by raising the wafer temperature T, an off-channeling dominant state can be achieved, and an injection profile with greater in-plane spread can be achieved at a shallower location.

[0033] In this embodiment, a wafer W is heated or cooled to a predetermined temperature, and an ion beam B is irradiated onto the wafer W at the predetermined temperature to satisfy predetermined channeling conditions. This achieves a different implantation profile than when the ion beam B is irradiated at a temperature different from the predetermined temperature to satisfy predetermined channeling conditions. For example, by irradiating with ion beam B at a temperature lower than room temperature (27°C), an implantation profile with less in-plane spread at a deeper location can be achieved compared to when ion beam B is irradiated at room temperature. Conversely, by irradiating with ion beam B at a temperature higher than room temperature, an implantation profile with greater in-plane spread at a shallower location can be achieved compared to when ion beam B is irradiated at room temperature.

[0034] To reiterate, the "predetermined channeling conditions" here refer to the injection angle θ conditions under room temperature conditions where on-channeling is dominant. For example, the critical angle θ where most of the angular components of the irradiated ion beam B are calculated using equation (1). C This refers to the conditions that fall within a certain range. For example, a predetermined channeling condition is met when at least the full width at half maximum of the angular distribution of the irradiated ion beam B is included in the on-channeling region C1.

[0035] The ion implantation method according to this embodiment can be applied, for example, to isolation implantation and photodiode implantation during the manufacturing of CMOS image sensors. In isolation implantation, for example, the above-mentioned boron (B) can be used as the implanted ion species, and in photodiode implantation, phosphorus (P) or arsenic (As) can be used. This embodiment is applicable to high-energy implantation, and for example, implantation energies of 200 keV to 20 MeV can be used. The implantation depth that can be achieved in this case is approximately 0.1 μm to 10 μm.

[0036] When the target of injection is the (100) plane of silicon (Si), the critical angle θ of boron (B), phosphorus (P), and arsenic (As) based on equation (1) depends on the injection energy. C The following applies: When the injection energy is 200 keV, the critical angle θ of boron (B) C This is 2.47 degrees, and is the critical angle θ of phosphorus (P). C θ is 4.27 degrees, which is the critical angle θ of arsenic (As). C It is 6.34 degrees. The critical angle θ of boron (B) when the injection energy is 2 MeV. C θ is 0.78 degrees, which is the critical angle θ of phosphorus (P). C θ is 1.35 degrees, which is the critical angle θ of arsenic (As). C The critical angle θ of boron (B) is 2.00 degrees when the injection energy is 10 MeV. C θ is 0.35 degrees, which is the critical angle θ of phosphorus (P). C θ is 0.60 degrees, which is the critical angle θ of arsenic (As). C This is 0.90 degrees. Thus, the critical angle θ for on-channeling is 0.90 degrees. C Since this depends on the ion species and the implantation energy, it is preferable to set appropriate angular conditions for ion beam B according to the implantation conditions. For example, the angular conditions for ion beam B corresponding to a given channeling condition can be within 7 degrees, within 5 degrees, within 3 degrees, or within 1 degree relative to the crystal axis C.

[0037] Figure 9 is a graph showing an example of an implantation profile formed in a wafer when phosphorus (P) ions are irradiated. This figure is based on measurements performed by secondary ion mass spectrometry (SIMS). The target of implantation is the (100) plane of silicon (Si), and the implantation energy is 2.2 MeV. As shown in the figure, when the implantation angle θ is 0 degrees and the wafer temperature T is room temperature (27°C), the effect of on-channeling is prominent, resulting in a profile with high implantation concentration in the range of depths from 2 μm to 4 μm. On the other hand, when the wafer temperature T is increased to a high temperature (450°C) while the implantation angle θ is kept at 0 degrees, or when the implantation angle θ is set to 1 or 2 degrees while the wafer temperature T is kept at room temperature (27°C), a peak at a depth of about 2 μm based on off-channeling becomes clear, while the profile shows a low implantation concentration at a depth of about 3 μm to 4 μm. Therefore, even when injecting phosphorus (P), by increasing the wafer temperature T while keeping the injection angle θ fixed around 0 degrees, it is possible to achieve an injection profile similar to that when the injection angle θ is set to a critical angle (e.g., 1.29 degrees).

[0038] Figure 10 is a graph showing an example of an implantation profile formed in a wafer when arsenic (As) ions are irradiated. This figure is also a measurement result by SIMS. The target of implantation is the (100) plane of silicon (Si), and the implantation energy is 3.1 MeV. As shown in the figure, when the implantation angle θ is set to 0 degrees and the wafer temperature T is room temperature (27°C), the profile shows a gradual decrease in implantation concentration from a peak position at a depth of about 2 μm to a depth of 6 μm due to the effect of on-channeling. On the other hand, when the wafer temperature T is set to a high temperature (450°C) while the implantation angle θ is set to 1 or 2 degrees while the wafer temperature T is room temperature (27°C), the peak at a depth of about 2 μm due to off-channeling becomes more pronounced, and the profile shows a more pronounced decrease in implantation concentration in the range of depths greater than 2 μm. Therefore, even when injecting arsenic (As), by increasing the wafer temperature T while keeping the injection angle θ fixed near 0 degrees, it is possible to achieve an injection profile similar to that when the injection angle θ is set to a critical angle (e.g., 1.61 degrees).

[0039] Furthermore, this method can be applied to ionic species other than B, P, and As, such as nitrogen (N), aluminum (Al), gallium (Ga), indium (In), and antimony (Sb).

[0040] In the method according to this embodiment, it is preferable to set the dose of the irradiated ion beam B to a moderate or lower level, for example, a dose of 1 × 10⁻⁶ 14 cm -2 The following, or 1 × 10 13 cm -2 The following is preferable. Increasing the dose causes damage to accumulate in the area irradiated by the beam due to ion implantation, resulting in amorphous crystal structure and a change to a crystal state that is difficult to channel.

[0041] This embodiment is also applicable to multi-stage implantation, where ion beams with different implantation energies are irradiated to the same implantation region within the wafer surface. For example, by irradiating the same implantation region with three ion beams of high, medium, and low energy, ions can be implanted in areas centered on three different depth positions, forming an implantation profile in which regions of high implantation concentration are continuous in the depth direction. In this case, by performing multi-stage implantation while changing the wafer temperature T, the shape of at least one of the implantation profiles in the depth direction and the in-plane direction can be controlled more precisely.

[0042] Figures 11(a) to 11(c) are schematic cross-sectional views showing an example of multi-stage implantation according to an embodiment. First, in the first step shown in Figure 11(a), a high-energy first ion beam B11 is irradiated onto the first portion 86a, which is relatively deep within the implantation region corresponding to the opening 82 of the mask 80. Next, in the second step shown in Figure 11(b), a medium-energy second ion beam B12 is irradiated onto the second portion 86b, which is located at a moderate depth within the implantation region corresponding to the opening 82 of the mask 80. Subsequently, in the third step shown in Figure 11(c), a low-energy third ion beam B13 is irradiated onto the third portion 86c, which is relatively shallow within the implantation region corresponding to the opening 82 of the mask 80. As a result, an implantation region 86 is formed in which the first portion 86a, the second portion 86b, and the third portion 86c are continuous in the depth direction.

[0043] In the first to third steps shown in Figures 11(a) to (c), the injection angles of the ion beams B11 to B13 are the same, and the ion beams are incident almost perpendicular to the wafer surface so that predetermined channeling conditions are met. On the other hand, the wafer temperature T is changed in each of the first to third steps. In the first step, by setting the wafer temperature T relatively low, on-channeling is made the dominant injection condition, and the in-plane width w1 of the first portion 86a is reduced. In the second step, by setting the wafer temperature T to a moderate level, the contribution of off-channeling is increased, and the in-plane width w2 of the second portion 86b is made larger than the width w1 of the first portion 86a. In the third step, by setting the wafer temperature T relatively high, the contribution of off-channeling is further increased, and the in-plane width w3 of the third portion 86c is made larger than the width w2 of the second portion 86b. By performing the injection process in steps 1 to 3 while changing the temperature conditions in this way, a trapezoidal injection region 86 can be formed in which the in-plane width w3 to w1 sequentially decreases as it moves away from the wafer surface (i.e., as the injection position gets deeper). Such a trench-type injection profile can be used, for example, as an isolation injection region.

[0044] Figures 12(a) to 12(c) are schematic cross-sectional views showing another example of multi-stage implantation according to the embodiment. In this example as well, similar to Figures 11(a) to 11(c) described above, ion beams B21 to B23 with different energies are irradiated to the portion of the mask 80 corresponding to the opening 82. First, in the first step of Figure 12(a), the first portion 88a at a deep position is irradiated with a high-energy first ion beam B21. In the second step of Figure 12(b), the second portion 88b at a medium depth is irradiated with a medium-energy second ion beam B22. In the third step of Figure 12(c), the third portion 88c at a shallow position is irradiated with a low-energy third ion beam B23. As a result, an implantation region 88 is formed in which the first portion 88a, the second portion 88b, and the third portion 88c are continuous in the depth direction.

[0045] On the other hand, in the example shown in Figures 12(a) to (c), the temperature conditions of the wafer W are reversed compared to Figures 11(a) to (c) described above. Specifically, in the first step, the wafer temperature T is made relatively high to create injection conditions where off-channeling is dominant, and the in-plane width w1 of the first portion 88a is increased. In the second step, the wafer temperature T is set to a moderate level to increase the contribution of on-channeling, and the in-plane width w2 of the second portion 88b is made smaller than the width w1 of the first portion 88a. In the third step, the wafer temperature T is made relatively low to further increase the contribution of on-channeling, and the in-plane width w3 of the third portion 88c is made smaller than the width w2 of the second portion 88b. By performing the injection process in the first to third steps while changing the temperature conditions in this way, it is possible to form an injection region 88 with a shape in which the in-plane widths w3 to w1 increase sequentially as it moves away from the wafer surface (i.e., as the injection position gets deeper). Such a trench-type injection profile can be used, for example, as a photodiode injection region adjacent to the isolation injection region 86 shown in Figure 11(c).

[0046] In the example above, the number of multi-stage injection steps was set to three, but the number of multi-stage injection steps may be two, four or more, or the number of steps may be two or more. Furthermore, the injection angle of the ion beam irradiated in the multi-stage injection may be kept fixed while only the wafer temperature T and injection energy are changed, or the injection angle may be changed between steps.

[0047] When changing the wafer temperature T, for example, the temperature can be changed within the range of -200°C to 500°C. By setting the temperature change range to -100°C to 400°C, the wafer temperature T can be adjusted using a relatively simple temperature control device. When changing the wafer temperature T between multi-stage injection processes, it is preferable to set the temperature difference between processes to 50°C or more. By changing the wafer temperature T by 50°C or more, preferably 100°C or more, the proportion of contributions of on-channeling and off-channeling that occur in a single injection process can be significantly changed, and the shape of the injection profile in the depth direction and in-plane direction can be adjusted to achieve the desired injection profile.

[0048] Next, we will describe the ion implantation apparatus used to implement the ion implantation method described above.

[0049] Figure 13 is a schematic top view showing an ion implantation apparatus 100 according to an embodiment. The ion implantation apparatus 100 is a so-called high-energy ion implantation apparatus. The high-energy ion implantation apparatus is an ion implantation apparatus having a high-frequency linear acceleration type ion accelerator and a beamline for transporting high-energy ions. It accelerates ions generated in the ion source 10, transports the resulting ion beam B along the beamline to the workpiece (e.g., a substrate or wafer W), and implants ions into the workpiece.

[0050] The high-energy ion implantation apparatus 100 comprises an ion beam generation unit 12 that generates ions and separates their mass, a high-energy multi-stage linear acceleration unit 14 that accelerates the ion beam into a high-energy ion beam, a beam deflection unit 16 that performs energy analysis, energy dispersion control, and trajectory correction of the high-energy ion beam, a beam transport line unit 18 that transports the analyzed high-energy ion beam to the wafer W, and a substrate transport processing unit 20 that implants the transported high-energy ion beam into the semiconductor wafer.

[0051] The ion beam generation unit 12 comprises an ion source 10, an extraction electrode 11, and a mass spectrometer 22. In the ion beam generation unit 12, a beam is extracted from the ion source 10 through the extraction electrode 11 and simultaneously accelerated, and the extracted and accelerated beam is mass-analyzed by the mass spectrometer 22. The mass spectrometer 22 comprises a mass spectrometry magnet 22a and a mass spectrometry slit 22b. The mass spectrometry slit 22b may be placed immediately after the mass spectrometry magnet 22a, but in this embodiment, it is placed in the inlet of the next component, the high-energy multi-stage linear acceleration unit 14. As a result of the mass spectrometry by the mass spectrometer 22, only the ion species necessary for injection are selected, and the ion beam of the selected ion species is guided to the next component, the high-energy multi-stage linear acceleration unit 14.

[0052] The high-energy multi-stage linear acceleration unit 14 comprises multiple linear accelerators, i.e., one or more high-frequency resonators, for accelerating an ion beam. The high-energy multi-stage linear acceleration unit 14 can accelerate ions by the action of a high-frequency (RF) electric field. The high-energy multi-stage linear acceleration unit 14 includes a first linear accelerator 15a with a basic multi-stage RF resonator for high-energy ion implantation. The high-energy multi-stage linear acceleration unit 14 may additionally include a second linear accelerator 15b with an additional multi-stage RF resonator for ultra-high-energy ion implantation. The ion beam, further accelerated by the high-energy multi-stage linear acceleration unit 14, has its direction changed by a beam deflection unit 16.

[0053] The high-energy ion beam that exits the high-frequency multi-stage linear acceleration unit 14, which accelerates the ion beam to high energies, has an energy distribution within a certain range. Therefore, in order to irradiate a wafer with the high-energy ion beam downstream of the high-energy multi-stage linear acceleration unit 14 by beam scanning and beam parallelization, it is necessary to perform highly accurate energy analysis, trajectory correction, and beam focusing and divergence adjustments in advance.

[0054] The beam deflection unit 16 performs energy analysis, energy dispersion control, and trajectory correction of the high-energy ion beam. The beam deflection unit 16 comprises at least two high-precision deflection electromagnets, at least one energy width limiting slit, at least one energy analysis slit, and at least one transverse focusing instrument. The multiple deflection electromagnets are configured to perform energy analysis of the high-energy ion beam and precise correction of the ion implantation angle.

[0055] The beam deflection unit 16 includes an energy analysis electromagnet 24, a transverse focusing quadrupole lens 26 that suppresses energy dispersion, an energy analysis slit 28, and a deflection electromagnet 30 that provides steering (trajectory correction). The energy analysis electromagnet 24 is sometimes called an energy filter electromagnet (EFM). The high-energy ion beam is redirected by the beam deflection unit 16 and directed toward the wafer W.

[0056] The beam transport line unit 18 is a beamline device that transports the ion beam B emitted from the beam deflection unit 16, and includes a beam shaper 32 composed of a group of focusing / diverging lenses, a beam scanner 34, a beam parallelizer 36, and a final energy filter 38 (including a final energy separation slit). The length of the beam transport line unit 18 is designed to match the combined length of the ion beam generation unit 12 and the high-energy multi-stage linear acceleration unit 14, and is connected by the beam deflection unit 16 to form an overall U-shaped layout.

[0057] A substrate transport processing unit 20 is provided at the downstream end of the beam transport line unit 18. The substrate transport processing unit 20 includes an implantation processing chamber 60 and a substrate transport section 62. The implantation processing chamber 60 is provided with a platen drive device 40 that holds the wafer W during ion implantation and moves the wafer W in a direction perpendicular to the beam scanning direction. The platen drive device 40 is provided with a temperature control device 50 for adjusting the wafer temperature T during ion implantation. The substrate transport section 62 is provided with a wafer transport mechanism, such as a transport robot, for transporting the wafer W before ion implantation into the implantation processing chamber 60 and for transporting the ion-implanted wafer W out of the implantation processing chamber 60.

[0058] The beamline section of the ion implanter 100 is configured as a horizontal U-shaped folded beamline having two opposing long straight sections. The upstream long straight section consists of multiple units that accelerate the ion beam B generated by the ion beam generation unit 12. The downstream long straight section consists of multiple units that adjust the ion beam B, which has been redirected relative to the upstream long straight section, and implant it into the wafer W. The two long straight sections are configured to be approximately the same length. A workspace R1 of sufficient size for maintenance work is provided between the two long straight sections.

[0059] Figures 14(a) and (b) schematically show the configuration of the lens devices 32a, 32b, and 32c included in the beam shaper 32. The beam shaper 32 shown in Figure 13 includes, for example, three quadrupole lens devices 32a to 32c, which are arranged in the order of the first lens device 32a, the second lens device 32b, and the third lens device 32c from upstream to downstream of the beam trajectory. Figure 14(a) shows the configuration of the first lens device 32a and the third lens device 32c that focus the ion beam B in the vertical direction (y direction), and Figure 14(b) shows the configuration of the second lens device 32b that focuses the ion beam B in the horizontal direction (x direction).

[0060] The first lens device 32a in Figure 14(a) has a pair of horizontal opposing electrodes 72 facing each other in the lateral direction (x direction) and a pair of vertical opposing electrodes 74 facing each other in the vertical direction (y direction). A negative potential -Qy is applied to the pair of horizontal opposing electrodes 72, and a positive potential +Qy is applied to the vertical opposing electrodes 74. The first lens device 32a generates an attractive force between the negatively potential horizontal opposing electrodes 72 and the ion beam B, which is composed of a group of positively charged ion particles, and a repulsive force between the positively potential vertical opposing electrodes 74. As a result, the first lens device 32a shapes the ion beam B so that it diverges in the x direction and converges in the y direction. The third lens device 32c is configured similarly to the first lens device 32a, and the same potential as the first lens device 32a is applied to it.

[0061] The second lens device 32b in Figure 14(b) has a pair of horizontally opposed electrodes 76 facing each other in the lateral direction (x direction) and a pair of vertically opposed electrodes 78 facing each other in the vertical direction (y direction). The second lens device 32b is configured similarly to the first lens device 32a, but the positive and negative signs of the applied potentials are reversed. A positive potential +Qx is applied to the pair of horizontally opposed electrodes 76, and a negative potential -Qx is applied to the vertically opposed electrodes 78. The second lens device 32b generates a repulsive force with the positively charged horizontally opposed electrodes 76 and an attractive force with the negatively charged vertically opposed electrodes 78 for the ion beam B, which is composed of a group of positively charged ion particles. As a result, the second lens device 32b adjusts the beam shape so that the ion beam B is focused in the x direction and diverges in the y direction.

[0062] Figure 15 is a schematic graph showing an example of controlling the convergence / divergence of ion beam B by lens devices 32a to 32c, illustrating the relationship between the potentials Qx and Qy applied to the counter electrodes of lens devices 32a to 32c and the angular distribution of the shaped beam. The vertical convergence potential Qy on the horizontal axis represents the potential applied to the first lens device 32a and the third lens device 32c, while the horizontal convergence potential Qx on the vertical axis represents the potential applied to the second lens device 32b.

[0063] At point S, where predetermined potentials Qx0 and Qy0 are applied, the operating conditions result in a "parallel beam" with small spreads in both the x and y injection angle distributions, as shown in Figure 2(a) or (b). By changing the potentials Qx and Qy along the straight line Lx from point S, the beam can be adjusted to change only the injection angle distribution in the x direction, without changing the injection angle distribution in the y direction. As the transverse convergence potential Qx is increased from point S to point X1, the beam becomes a "convergent beam" that converges in the x direction, and the spread of the injection angle distribution in the x direction increases. On the other hand, as the transverse convergence potential Qx is decreased from point S to point X2, the beam becomes a "divergent beam" that diverges in the x direction, and the spread of the injection angle distribution in the x direction increases.

[0064] Similarly, by changing the potentials Qx and Qy along the straight line Ly from point S, the beam can be adjusted to change only the injection angle distribution in the y direction, without changing the injection angle distribution in the x direction. When the longitudinal convergence potential Qy is increased from point S to point Y1, it becomes a "converging beam" that converges in the y direction, and the spread of the injection angle distribution in the y direction increases. On the other hand, when the longitudinal convergence potential Qy is decreased from point S to point Y2, it becomes a "diverging beam" that diverges in the y direction, and the spread of the injection angle distribution in the y direction increases.

[0065] In this way, by changing the potentials Qx and Qy applied to each of the three-stage lens devices 32a to 32c under certain conditions, the injection angle distribution in the x and y directions of the ion beam irradiated onto the wafer W can be controlled independently. For example, if you want to adjust only the injection angle distribution in the x direction, you can change the potential in accordance with the slope of the line Lx while maintaining the relationship ΔQx = α·ΔQy. Similarly, if you want to adjust only the injection angle distribution in the y direction, you can change the potential in accordance with the slope of the line Ly while maintaining the relationship ΔQx = β·ΔQy. The values ​​of the slopes α and β of the lines Lx and Ly can be determined appropriately according to the optical characteristics of the lens device used. In this embodiment, the angle distribution of the ion beam B can be controlled with an accuracy of, for example, 0.1 degrees or less.

[0066] Figure 16 is a detailed side view of the substrate transport processing unit 20, showing the configuration downstream from the final energy filter 38. The ion beam B is deflected downward by the angular energy filter (AEF) electrode 64 of the final energy filter 38 and incident on the substrate transport processing unit 20. The substrate transport processing unit 20 includes an implantation chamber 60 in which the ion implantation process is performed, and a substrate transport section 62 equipped with a transport mechanism for transporting wafers W. The implantation chamber 60 and the substrate transport section 62 are connected via a substrate transport port 61.

[0067] The injection processing chamber 60 includes a platen drive device 40 for holding one or more wafers W. The platen drive device 40 includes a wafer holding device 42, a reciprocating motion mechanism 44, a twist angle adjustment mechanism 46, and a tilt angle adjustment mechanism 48. The wafer holding device 42 includes an electrostatic chuck for holding the wafer W. The reciprocating motion mechanism 44 causes the wafer holding device 42 to reciprocate in the y direction by causing the wafer holding device 42 to reciprocate in the y direction in a reciprocating motion direction (y direction) perpendicular to the beam scanning direction (x direction). In Figure 16, the arrow Y illustrates the reciprocating motion of the wafer W.

[0068] The twist angle adjustment mechanism 46 is a mechanism for adjusting the rotation angle of the wafer W. By rotating the wafer W around the normal to the wafer processing surface as an axis, it adjusts the twist angle between the alignment marks provided on the outer periphery of the wafer and the reference position. Here, the alignment marks of the wafer refer to notches or orientation flats provided on the outer periphery of the wafer, and are marks that serve as a reference for the angular position in the crystal axis direction and the circumferential direction of the wafer. The twist angle adjustment mechanism 46 is provided between the wafer holding device 42 and the reciprocating motion mechanism 44, and reciprocates together with the wafer holding device 42.

[0069] The tilt angle adjustment mechanism 48 is a mechanism for adjusting the inclination of the wafer W, and adjusts the tilt angle between the direction of travel of the ion beam B toward the wafer processing surface (z direction) and the normal to the wafer processing surface. In this embodiment, the tilt angle is adjusted as the angle of inclination of the wafer W with the x-axis as the central axis of rotation. The tilt angle adjustment mechanism 48 is provided between the reciprocating motion mechanism 44 and the wall surface of the injection processing chamber 60, and is configured to adjust the tilt angle of the wafer W by rotating the entire platen drive unit 40, including the reciprocating motion mechanism 44, in the R direction.

[0070] The injection chamber 60 is equipped with an energy slit 66, a plasma shower device 68, and a beam damper 63, which are positioned from upstream to downstream along the trajectory of the ion beam B.

[0071] The energy slit 66 is located downstream of the AEF electrode 64 and performs energy analysis of the ion beam B that is incident on the wafer W together with the AEF electrode 64. The energy slit 66 is an energy-defining slit (EDS) consisting of a horizontally elongated slit in the beam scanning direction (x direction). The energy slit 66 allows ion beam B with a desired energy value or energy range to pass towards the wafer W, while shielding other ion beams.

[0072] The plasma shower device 68 is located downstream of the energy slit 66. The plasma shower device 68 supplies low-energy electrons to the ion beam and the wafer processing surface in accordance with the beam current amount of the ion beam B, thereby suppressing the charge buildup of positive charge on the wafer processing surface caused by ion implantation. The plasma shower device 68 includes, for example, a shower tube through which the ion beam B passes and a plasma generator that supplies electrons into the shower tube.

[0073] The beam damper 63 is located at the downstream end of the beam trajectory, for example, mounted below the substrate transport opening 61. Therefore, when no wafer W is present in the beam trajectory, the ion beam B enters the beam damper 63. The beam damper 63 may be equipped with a beam measurement device for measuring the ion beam B.

[0074] The temperature control device 50 is attached to the wafer holding device 42 of the platen drive device 40. The temperature control device 50 heats or cools the wafer W held by the wafer holding device 42 to adjust the temperature T of the wafer W. The temperature control device 50 includes at least one of a heating device and a cooling device. The heating device includes, for example, a heating element and heats the wafer W by passing an electric current through the heating element to generate heat. The cooling device includes, for example, a cooling channel through which a refrigerant flows and cools the wafer W through the refrigerant flowing through the cooling channel. The temperature control device 50 may also include a temperature measuring instrument for measuring the temperature T of the wafer W and heats or cools the wafer W so that the temperature of the wafer W measured by the temperature measuring instrument is at a desired temperature.

[0075] The temperature control device 50 may be located at a different location from the wafer holding device 42. For example, a heating element may be placed near the outlet of the plasma shower device 68, and the wafer W may be heated using radiant heat from the heating element. Alternatively, the temperature control device 50 may be located along the wafer W transport path leading to the injection processing chamber 60, or it may be located in a preparation chamber different from the injection processing chamber 60. Furthermore, the temperature of the wafer W may be adjusted in combination with the temperature control device 50 located on the wafer holding device 42 and another temperature control device located at a different location from the wafer holding device 42.

[0076] Figure 17 is a schematic side view showing the process of loading a wafer W' into the wafer holding device 42. In Figure 17, the wafer W' positioned at the loading / unloading position for loading or unloading the wafer between the substrate transport unit 62 is shown by a solid line, and the wafer W positioned at the injection position where the wafer is irradiated with an ion beam B inside the injection processing chamber 60 is shown by a dashed line. The platen drive device 40 moves wafers W and W' between the injection position and the loading / unloading position by mainly combining rotational movement in the R direction by the tilt angle adjustment mechanism 48 and linear movement in the Y direction by the reciprocating motion mechanism 44. The wafer W' at the loading / unloading position is loaded or unloaded through the substrate transport opening 61 by the substrate transport robot 58 provided in the substrate transport unit 62.

[0077] Figures 18(a) and (b) schematically show the orientation of the wafer W with respect to the incident direction of the ion beam B. Figure 18(a) shows the state in which the tilt angle θ is set by tilting the wafer W with respect to the incident direction (z direction) of the ion beam B. The tilt angle θ is set as the rotation angle when the wafer W is rotated around the x-axis, as shown in the figure. The state in which the tilt angle θ = 0° is when the ion beam B is incident perpendicularly on the wafer W. Figure 18(b) shows the state in which the twist angle φ is set by rotating the wafer W around an axis perpendicular to the main surface of the wafer. The twist angle φ is set as the rotation angle when the wafer W is rotated around an axis perpendicular to the main surface of the wafer, as shown in the figure. The state in which the twist angle φ = 0° is when the line segment extending from the center O of the wafer W to the alignment mark M coincides with the y direction. By appropriately setting the tilt angle θ and twist angle φ as the arrangement of the wafer W relative to the ion beam B, predetermined channeling conditions can be achieved.

[0078] Figures 19(a) and (b) schematically show a wafer to be subjected to ion implantation. Figure 19(a) shows the crystal orientation of wafer W, and Figure 19(b) shows the atomic arrangement near the surface of wafer W. A single-crystal silicon substrate with a (100) plane as the wafer W to be implanted can be used. The alignment mark M of wafer W is <110> It is installed in a position that indicates direction.

[0079] Figures 20(a) to (c) schematically show the relationship between the orientation of wafer W and the atomic arrangement near the surface of wafer W. These figures schematically show the atomic arrangement near the surface of wafer W, and represent the atomic arrangement as seen from the ion beam B incident on wafer W. In these figures, the positions of silicon atoms are indicated by black circles. In addition, silicon atoms located at different positions in the depth direction (z direction) are drawn superimposed in the xy plane.

[0080] Figure 20(a) shows the atomic arrangement when the wafer W is positioned to satisfy the axial channeling conditions, specifically when the wafer W is positioned with a twist angle φ=23° and a tilt angle θ=0°. In the illustrated axial channeling conditions, multiple first crystal planes 96 formed by silicon atoms positioned on the solid line and multiple second crystal planes 97 formed by silicon atoms positioned on the dashed line intersect with each other in a lattice pattern, forming an "axial channel" 95, which is an axial gap extending one-dimensionally along the direction in which ions are implanted. As a result, in an ion beam having an angular distribution in at least one of the x and y directions, only ion particles traveling in a straight line in the z direction are channeled, while ion particles with angular components shifted to some extent from the z direction are blocked by one of the crystal planes and do not channel. Therefore, a wafer W positioned to satisfy the axial channeling conditions produces "axial channeling," which channels ion particles traveling axially along the incident direction of the ion beam B.

[0081] The arrangement that satisfies the axial channeling conditions is not limited to the twist angle and tilt angle settings described above; other twist and tilt angles may be used as long as the wafer arrangement achieves the atomic arrangement shown in the figure. To achieve the axial channeling conditions, for example, the twist angle φ of the wafer W may be set to substantially within the range of 15 to 30 degrees, and the tilt angle θ may be set to substantially 0 degrees.

[0082] Figure 20(b) shows the atomic arrangement when the wafer W is arranged to satisfy the planar channeling conditions, specifically when the wafer W is oriented with a twist angle φ=0° and a tilt angle θ=15°. Under the illustrated planar channeling conditions, multiple crystal planes 99 are formed by silicon atoms arranged in the yz plane, and a "planar channel" 98, a gap with two-dimensional extension, is formed between opposing crystal planes 99 in the x direction. As a result, an ion beam with an angular distribution in the x direction channels only some ion particles that travel in a straight line in the z direction, while ion particles with angular components shifted to some extent in the x direction are blocked by the crystal planes 99 and do not channel. On the other hand, an ion beam with an angular distribution in the y direction channels the gaps between crystal planes without being blocked by the crystal planes 99. Therefore, a wafer arranged to satisfy the planar channeling conditions produces "planar channeling," which primarily channels ion particles traveling along a reference plane defined by both the z and y directions along the incident direction of the ion beam B. Therefore, when an ion beam is irradiated onto a wafer arranged to satisfy the surface channeling conditions, a directional dependence occurs where ion particles with an angular component in the x-direction do not channel, while ion particles with an angular component in the y-direction do.

[0083] The arrangement that satisfies the surface channeling conditions is not limited to the above-described settings of the twist angle and tilt angle; other twist angles and tilt angles may be used as long as the atomic arrangement shown in the diagram can be realized in the wafer arrangement. To achieve the surface channeling conditions, for example, the twist angle φ of the wafer W may be set to substantially 0 degrees or 45 degrees, and the tilt angle θ may be set to substantially within the range of 15 degrees to 60 degrees.

[0084] Figure 20(c) shows the atomic arrangement when the wafer W described above is arranged to satisfy the off-channeling conditions, specifically when the wafer W is oriented with a twist angle φ = 23° and a tilt angle θ = 7°. Under the illustrated off-channeling conditions, no channels that serve as pathways for ion particles are visible, and the silicon atoms appear to be arranged without gaps in the x and y directions. As a result, when an ion beam is irradiated onto a wafer that satisfies the off-channeling conditions, an off-channeling state is achieved in which no channeling phenomenon occurs, regardless of whether the ion particles constituting the beam have angular components in the x and y directions.

[0085] The arrangement that satisfies the off-channeling conditions is not limited to the twist and tilt angles set above; other twist and tilt angles may be used as long as the wafer arrangement allows for the atomic arrangement shown in the diagram to be realized. More specifically, other angular conditions may be used as long as the wafer W is arranged in a direction such that the lower-order crystal planes of the wafer, such as the {100} plane, {110} plane, and {111} plane, intersect the reference orbit of the ion beam at an oblique angle. To achieve the off-channeling conditions, for example, the twist angle φ of the wafer W may be set substantially within the range of 15 to 30 degrees, and the tilt angle θ may be set substantially within the range of 7 to 15 degrees.

[0086] In this embodiment, the axial channeling conditions shown in Figure 20(a) can be used as the wafer arrangement that "satisfies predetermined channeling conditions". In the arrangement in Figure 20(a), since the tilt angle θ = 0°, even when a thick mask is formed on the wafer surface, the ion beam B can be incident in a direction perpendicular to the wafer surface, and ions can be accurately implanted at locations corresponding to the openings of the mask. Note that as an implantation process for semiconductor device manufacturing, only the implantation step using the axial channeling conditions shown in Figure 20(a) may be performed, or an implantation step using the surface channeling conditions shown in Figure 20(b) or an implantation step using the off-channeling conditions shown in Figure 20(c) may be additionally combined and performed.

[0087] Figure 21 is a flowchart showing the flow of the ion implantation method according to the embodiment. First, the energy of the ion beam B to be irradiated onto the wafer W is adjusted (S10). For example, the energy of the ion beam B can be adjusted by controlling the operation of the high-energy multi-stage linear acceleration unit 14. Next, the angular distribution of the ion beam B to be irradiated onto the wafer W is adjusted (S12). For example, the angular distribution of the ion beam B can be adjusted by changing the potentials Qx and Qy of the lens devices 32a to 32c of the beam shaper 32. At this time, the critical angle θ of channeling according to the energy of the ion beam B and the ion species is adjusted. C The beam's angular characteristics may be adjusted to achieve the following angular distribution.

[0088] Next, the wafer W to be injected is transported to the injection chamber 60 and fixed to the wafer holding device 42, and the temperature of the wafer W is adjusted using the temperature control device 50 (S14). At this time, the wafer W can be heated or cooled using the temperature control device 50 so that the wafer W reaches the desired temperature. Note that if the injection process is performed at room temperature or if the wafer W has already been adjusted to the desired temperature, it is not necessary to heat or cool the wafer W. Subsequently, the orientation of the wafer W is adjusted using the twist angle adjustment mechanism 46 and the tilt angle adjustment mechanism 48 so that the desired channeling conditions are met (S16). Note that the temperature adjustment step in S14 and the orientation adjustment step in S16 may be performed in any order, or they may be performed simultaneously.

[0089] Next, the wafer W, whose temperature and orientation have been adjusted, is irradiated with an ion beam B to perform ion implantation (S18). The temperature of the wafer W may be adjusted simultaneously during the execution of the ion implantation process in S18. For example, the wafer W may be heated or cooled while the ion beam B is irradiated onto the wafer W. Alternatively, the wafer W may be heated using the power supplied to the wafer W by the irradiation of the ion beam B. For example, when implanting high temperature into the wafer W, the wafer W may be heated using the temperature control device 50 before beam irradiation, and the wafer W may be heated using the power of the beam during beam irradiation. Heating by the temperature control device 50 may be used in combination with beam irradiation, and if the wafer W is excessively heated by the power of the beam, cooling by the temperature control device 50 may be used in combination. In addition, in order to suppress heating due to the power of the beam, the temperature of the wafer W may be kept constant throughout the beam irradiation through cooling by the temperature control device 50.

[0090] Next, if additional irradiation with ion beam B is required (Y in S20), the processes in S10 to S18 are executed again. For example, as illustrated in Figures 11(a) to (c) and 12(a) to (c), when multiple injection processes are performed by changing the energy of ion beam B and the temperature T of wafer W, the processes in S10 to S18 are executed with different injection conditions for each injection. The injection conditions that are changed at this time include the ion species, energy, dose amount, and angle distribution of ion beam B, as well as the tilt angle θ, twist angle φ, and temperature T of wafer W. On the other hand, if additional irradiation with ion beam B is not required (N in S20), this flow is terminated.

[0091] In multiple injection processes, the wafer temperature T may be set to include a range around room temperature (27°C, 300K). Alternatively, the conditions may be set so that the wafer temperature T is below room temperature in all multiple injection processes; for example, the temperature conditions may be varied within the range of -200°C to 27°C. As a specific example, temperatures of approximately -196°C (77K), -123°C (150K), -73°C (200K), -23°C (250K), and 27°C (300K) may be set. On the other hand, the conditions may be set so that the wafer temperature T is above room temperature in all multiple injection processes; for example, the temperature conditions may be varied within the range of 27°C to 500°C. For example, you could set temperatures of around 27°C (300K), 127°C (400K), 227°C (500K), 327°C (600K), 427°C (700K), and 500°C (773K). You could also include temperatures below and above room temperature, and vary the temperature conditions within the range of -200°C to 500°C.

[0092] In multiple injection processes, the injection profile may be controlled not only by adjusting the wafer temperature T but also by fine-tuning the angular distribution of the ion beam B, or at least one of the mean value (mean angle) and variance value (divergence / convergence angle) of the angular distribution of the ion beam B may be fine-tuned. For example, in multiple injection processes, the mean value of the angular distribution of the ion beam B with respect to the crystal axis C of the wafer W may be set to the critical angle θ. C Less than or critical angle θ C Within the above range, the angle may be changed by 0.1 degrees or more. For example, it may be set to 0.1 degrees, 0.3 degrees, 0.5 degrees, 0.8 degrees, 1 degree, 1.5 degrees, 2 degrees, 2.5 degrees, 3 degrees, 3.5 degrees, 5 degrees, 7 degrees, etc. The average value of the angle distribution with respect to the wafer W can be adjusted by the tilt angle adjustment mechanism 48. In addition, the dispersion value of the angle distribution of the ion beam B may be adjusted in 0.1-degree increments. The dispersion value of the angle distribution of the ion beam B can be adjusted by the beam shaper 32.

[0093] Furthermore, when performing multiple implantation processes by changing the energy of the ion beam B or the temperature T of the wafer W, it is not necessary to perform multiple implantation processes consecutively on a single wafer W. For example, when multiple implantation processes under the same conditions are performed on a large number of wafers W for mass production, the first implantation process using the first condition may be performed consecutively on multiple wafers, and then the settings of the ion implantation apparatus 100 may be changed from the first condition to the second condition, and the second implantation process using the second condition may be performed consecutively on multiple wafers.

[0094] Furthermore, the process of adjusting the temperature of the wafer W may be performed in the middle of the wafer W transport process. For example, as explained in Figure 17, the wafer W' brought into the implantation chamber 60 needs to be moved from the loading / unloading position to the implantation position by driving the platen drive device 40. In addition, the wafer W placed at the implantation position also needs to have its tilt angle θ and twist angle φ adjusted. By heating or cooling the wafer W to the desired temperature during the execution of such preparation processes in the implantation chamber 60, the additional work time required for temperature adjustment can be reduced or eliminated, and a decrease in the throughput of the ion implantation process can be suppressed.

[0095] Furthermore, the process of adjusting the temperature of the wafer W may be performed in a preparation room different from the injection processing chamber 60. For example, a preparation room for temperature adjustment may be provided in the substrate transport unit 62, and the wafer W may be heated or cooled using a temperature adjustment device installed in the preparation room. Alternatively, a temperature adjustment device may be provided in the substrate transport robot 58, etc., so that the wafer W is heated or cooled while being transported by the substrate transport robot 58. The wafer W may be heated or cooled only in a location different from the injection processing chamber 60, or the temperature adjustment of the wafer W in a location different from the injection processing chamber 60 may be combined with the temperature adjustment within the injection processing chamber 60. Furthermore, instead of actively cooling the wafer W using the temperature adjustment device 50, the temperature of the wafer W may be adjusted by utilizing heat dissipation from the wafer W due to the temperature difference with the surrounding environment.

[0096] Although the present invention has been described above with reference to the embodiments described above, the present invention is not limited to the embodiments described above, and the present invention also includes combinations and substitutions of the configurations of each embodiment as appropriate. Furthermore, it is possible to appropriately rearrange the combinations and processing order in each embodiment or to make various design changes and other modifications to the embodiments based on the knowledge of those skilled in the art, and such modified embodiments may also be included in the scope of the present invention.

[0097] In the above-described embodiment, an example was given of performing isolation implantation or photodiode implantation by irradiating an ion beam B onto a mask 80 with a large thickness t. This embodiment is not limited to the above-described applications and can also be applied to, for example, the formation of trench-type pn junction structures used in power devices, or the formation of trench-type or planar-type pn junction structures used in logic circuits, etc. In this case, ion implantation may be performed using an electrode layer or insulating layer provided on the wafer surface as a mask.

[0098] The above-described embodiment explains the control of the implantation profile of the implanted ions. This embodiment can also be similarly applied to the control of the profile of damage (defects) within the wafer caused by ion implantation. [Explanation of Symbols]

[0099] 10...Ion source, 12...Ion beam generation unit, 14...High-energy multi-stage linear acceleration unit, 18...Beam transport line unit, 20...Substrate transport processing unit, 40...Platen drive device, 42...Wafer holding device, 44...Reciprocating motion mechanism, 46...Twist angle adjustment mechanism, 48...Tilt angle adjustment mechanism, 50...Temperature control device, 60...Impregnation processing chamber, 62...Substrate transport section, 100...Ion implantation device, W...Wafer.

Claims

1. For a wafer at a first temperature, a first ion beam is irradiated at a predetermined position on the surface of the wafer, with the angle of incidence set to an ion beam angle condition that is sufficiently smaller than the critical angle at which channeling occurs with respect to the crystal axis of the wafer. The method comprises, after irradiation with the first ion beam, irradiating the wafer, which is at a second temperature different from the first temperature, with a second ion beam set to the same ion beam angle conditions as the first ion beam at a predetermined position on the surface of the wafer, The angle condition of the ion beam is set by adjusting the angle of the wafer. A desired injection profile is formed within the wafer. Ion implantation method.

2. The ion species of the first ion beam are the same as the ion species of the second ion beam. The ion implantation method according to claim 1.

3. The energy of the second ion beam is lower than the energy of the first ion beam. The ion implantation method according to claim 1 or 2.

4. The angle adjustment of the wafer includes adjusting the twist angle of the wafer. The ion implantation method according to any one of claims 1 to 3.

5. The twist angle of the wafer is set within the range of 15 to 30 degrees. The ion implantation method according to claim 4.

6. The angle adjustment of the wafer includes adjusting the tilt angle of the wafer. The ion implantation method according to any one of claims 1 to 5.

7. The tilt angle of the wafer is set within the range of 7 to 15 degrees. The ion implantation method according to claim 6.

8. The first temperature and the second temperature are between -200°C and 500°C. The ion implantation method according to any one of claims 1 to 7.

9. The difference between the first temperature and the second temperature is 50°C or more. The ion implantation method according to any one of claims 1 to 8.

10. The first ion beam is adjusted by a beam shaper to have a first angular distribution, The second ion beam is adjusted by the beam shaper to have a second angular distribution. When the first ion beam and the second ion beam are irradiated onto the wafer under the angle conditions of the ion beams, the conditions are met such that at least the full width at half maximum component of the first angular distribution and the second angular distribution are on-channeling. The ion implantation method according to any one of claims 1 to 9.

11. The first angular distribution is adjusted by the beam shaper by converging or diverging the first ion beam in a first direction perpendicular to the direction of incidence of the ion beam to the wafer surface, and by converging or diverging the first ion beam in a second direction perpendicular to both the incidence direction and the first direction. The second angular distribution is adjusted by the beam shaper by converging or diverging the second ion beam in the first direction and converging or diverging the second ion beam in the second direction. The ion implantation method according to claim 10.

12. The absolute value of the incident angle at which the first ion beam and the second ion beam are on-channeling is smaller than the critical angle θc shown in the following equation (1). [Math 1] Z １ This is the atomic number of the implanted ion, and Z ２ This is the atomic number of the substance to be injected, E １ is the energy of the implanted ion, and d is the interatomic interval of the crystal of the substance to be implanted. The ion implantation method according to claim 10 or 11.

13. At least one of the first ion beam and the second ion beam has an energy of 1 MeV or more when accelerated by an accelerator. The ion implantation method according to any one of claims 1 to 12.

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