Ion implantation system and method thereof

Abstract

The present disclosure provides an ion implantation system and a method thereof. The ion implantation system may include: an ion source that generates an ion beam; a substrate platform disposed downstream of the ion source; a deceleration stage that includes components for deflecting the ion beam, the deceleration stage being disposed between the ion source and the substrate platform; and a gas source that is directly coupled to the deceleration stage to supply hydrogen or helium gas to the deceleration stage, wherein high-energy neutral species generated from the ion beam do not scatter onto the substrate platform. The ion implantation system of the present disclosure can provide the advantages of conveniently and safely reducing energy contamination caused by high-energy neutral species.

Description

[0001] This invention is a divisional application of the patent application for invention with the application number 201880018810.6, originally filed on March 12, 2018, and the original invention name being "Device and Technology for Decelerating Ion Beams without Energy Pollution". Technical Field

[0002] Embodiments of the present invention relate to a beam line ion implanter, and more particularly to electrodes, an ion implantation system, and a method thereof in an ion implanter for accelerating an ion beam. Background Art

[0003] Currently, a beam line ion implanter uses multiple components to guide an ion beam from an ion source to a substrate. To properly process the substrate, the ion beam can be accelerated or decelerated to a target ion energy, and can have a trajectory and shape of the ion beam, and the trajectory and shape of the ion beam are manipulated by various beam line components to produce a set of target characteristics of the ion beam at the substrate. In many types of ion implanters (including medium energy ion implanters and low energy ion implanters), the ion source can generate an ion beam, which is guided downward along the beam line at a relatively high energy and is decelerated to the final energy just before hitting the substrate. This procedure is used because the best way to generate a high current beam (with a current greater than ≈1 mA) at a low energy (below ≈10 kiloelectron volts (keV)) is to transport the ion beam at a relatively high energy through ion extraction, mass analysis, and other beam line elements before decelerating to the final energy at the latest possible stage before hitting the substrate. Since the space charge force causes the ions to repel each other, such low energy high current beams cannot be transported over a long distance in the beam line. In known ion implanters, the architecture of decelerating near the wafer introduces a risk of energy pollution caused by high energy substances hitting the substrate. Specifically, ions that are neutral in volume before or during deceleration will continue to propagate because their energy does not change, and can therefore hit the wafer (substrate) at a higher energy than expected.

[0004] In some ion implanters, this problem is solved by providing a bend within a component (such as a deceleration stage) so that the neutral matter traveling through the deceleration stage can be shielded from the substrate by the bend in the deceleration stage. Although the neutral matter traveling in a straight direction may not reach the substrate, energy pollution is still found in ion implanters that have a bend in the deceleration stage.

[0005] In view of these and other considerations, the present disclosure is provided. Summary of the Invention

[0006] In one embodiment, an ion implantation system may include: an ion source that generates an ion beam; a substrate platform disposed downstream of the ion source; and a deceleration stage that includes components that deflect the ion beam, wherein the deceleration stage is disposed between the ion source and the substrate platform. The ion implantation system may further include a hydrogen source that supplies hydrogen to the deceleration stage, wherein energetic neutrals generated from the ion beam do not scatter onto the substrate platform.

[0007] In another embodiment, an ion implantation method may include: generating an ion beam; decelerating the ion beam in a deceleration stage; changing the trajectory of the ion beam during the deceleration; and directing hydrogen into the deceleration stage during the deceleration.

[0008] In yet another embodiment, a deceleration stage for processing an ion beam may include: a housing that houses the ion beam; and a deceleration assembly that decelerates the ion beam, wherein the deceleration assembly is disposed upstream of a substrate platform and the deceleration assembly includes a first plurality of electrodes disposed within the housing. The deceleration stage may further include a deflection assembly that deflects the ion beam, wherein the deflection assembly includes a second plurality of electrodes disposed within the housing, wherein the trajectory of the ion beam is changed. The deceleration stage may further include a hydrogen source that supplies hydrogen within the housing, wherein the partial pressure of hydrogen within the housing is greater than 10 -6 Torr. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A block diagram illustrating an ion implanter 100 in accordance with an embodiment of the present disclosure.

[0010] Figure 2 A detailed view illustrating an embodiment of a deceleration stage 116 in accordance with an embodiment of the present disclosure.

[0011] Figure 3 Illustrates the variation of the scattering probability of several different gases for 20 keV boron species with the scattering angle.

[0012] Figure 4 Illustrates a process flow in accordance with other embodiments of the present disclosure.

[0013] The drawings are not necessarily to scale. The drawings are merely representations and are not intended to depict specific parameters of the present disclosure. The drawings are intended to illustrate exemplary embodiments of the present disclosure and should not be construed as limiting the scope. In the drawings, like numerals represent like elements.

[0014] In addition, for clarity of illustration, some elements in some of the figures may be omitted or not shown to scale. For clarity of illustration, cross-sectional views may be in the form of "slice" or "near-sighted" cross-sectional views to omit some background lines that would otherwise be visible in a "true" cross-sectional view. In addition, for clarity, some reference numerals may be omitted in some of the figures. Detailed Description

[0015] Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings in which some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, the same reference numerals refer to the same elements throughout.

[0016] Embodiments of the present invention relate to an ion beam processing apparatus (e.g., a beam line implanter). Various embodiments may be applicable to beam line ion implanters where the ion energy can be in a range up to approximately 500 keV and in certain embodiments the ion energy can be less than 50 keV. The embodiments are not limited in this context. As detailed below, embodiments of the present invention facilitate operating an ion implanter at a relatively low energy (e.g., less than 50 keV) while preventing energy contamination associated with conventional ion implanters.

[0017] Figure 1A block diagram of an ion implanter 100 in accordance with an embodiment of the present disclosure is shown. The ion implanter 100 includes an ion source 102 for generating an ion beam 104, an analyzer magnet 106, a vacuum chamber 108, a collimator 110, and a substrate stage 112 shown for supporting a substrate 114. The ion implanter 100 further includes a deceleration stage 116 disposed downstream of the collimator 110. For simplicity, the ion beam 104 is only shown as the central ray trajectory of the ion beam. In various embodiments, the ion source 102 may be an indirectly heated cathode (IHC) ion source, a radio frequency (RF) ion source, a microwave ion source, or other ion sources. Like in a conventional analyzer magnet, the analyzer magnet 106 can change the trajectory of ions extracted from the ion source 102. The vacuum chamber 108 may include a mass resolving slit, which can be used as a conventional mass resolving slit for screening out ions with undesired mass. In various embodiments, the ion beam 104 may be provided as a static ribbon beam, a spot beam, or a scanned spot beam, where the scanned spot beam is generated by an electrostatic scanner or a magnetic scanner; and may include multiple components or stages. The collimator 110 may be a magnetic collimator or an electrostatic collimator for at least generating a collimated ion beam that will be conducted to the substrate 114. The ion implanter 100 may include other beamline components including apertures, a dithering component, additional acceleration / deceleration components, and the operation of these other components is well known. For clarity, further discussion of such components is omitted herein.

[0018] As Figure 1 As further shown, the ion implanter 100 may include a hydrogen source 118, where the hydrogen source 118 is arranged to supply hydrogen gas to the deceleration stage 116. As described below, in combination with the deceleration stage 116, the hydrogen source 118 can help reduce the energy contamination of the material implanted into the substrate 114. In a particular embodiment, the hydrogen source 118 may directly supply hydrogen gas into the deceleration stage 116, where the hydrogen gas helps with the beam delivery of the ion beam 104 while reducing or eliminating energy contamination.

[0019] Now turning to Figure 2, showing a detailed view of an embodiment of deceleration stage 116. Deceleration stage 116 may include a deceleration assembly 201 that includes a deceleration power supply 232 and deceleration electrodes 202 for changing the energy of ion beam 104, and in particular for reducing the energy of ion beam 104 from a higher energy ion beam 104A (e.g., 10 keV) to a lower energy ion beam 104B (e.g., 2 keV). Deceleration stage 116 may further include a deflection assembly 203 that includes a deflection power supply 234 and deflection electrodes 204 and deflects the path of ion beam 104 such that the direction of propagation of ion beam 104 changes when ion beam 104 exits deceleration stage 116 and impinges on substrate 114. Although shown as separate components, in various embodiments, deflection assembly 203 and deceleration assembly 201 may share common electrodes for changing the direction and energy of ion beam 104.

[0020] As Figure 2 Further shown, deceleration stage 116 can be used to shield potential contaminants from impinging on substrate 114. As shown, deceleration stage 116 has a curved shape where the deceleration stage does not provide a line of sight path for ion beam 104 from the entrance 220 to the exit 222 of deceleration stage 116. Since ion beam 104 is made up of charged particles, ion beam 104 can be deflected via the electric field generated by deflection assembly 203.

[0021] It should be noted that any neutral species (such as high-energy neutral species 206) entering deceleration stage 116 may potentially create a source of high-energy contamination at substrate 114. Such potential contamination is because high-energy neutral species that do not carry a net charge are not decelerated by deceleration assembly 201 and can thus travel through deceleration stage 116 at an energy higher than the energy of the lower energy ion beam 104B. Thus, any high-energy neutral species leaving deceleration stage 116 may have an energy higher than the target energy for implantation, where the target energy is imparted to the ions decelerated by deceleration stage 116 and corresponds to the energy of the lower energy ion beam 104B. For example, the target energy for ion implantation carried by lower energy ion beam 104B may be 2 keV, while high-energy neutral species 206 may enter deceleration stage 116 carrying 10 keV of energy. By providing a curved shape, deflection assembly 203 can capture high-energy neutral species because the trajectory of high-energy neutral species 206 is not changed by the field generated by deflection assembly 203, enabling high-energy neutral species 206 to travel in a straight trajectory towards the wall of deflection assembly 203.

[0022] To provide proper beam control of the ion beam 104, a background gas may be provided to the ion implanter (including to the deceleration stage 116). The background gas may be provided by a hydrogen source 118 and may flow into the housing 117 of the deceleration stage 116 to form an appropriate partial pressure of hydrogen gas 210 in the deceleration stage 116. After allowing the hydrogen gas 210 to flow into the deceleration stage 116, the hydrogen gas 210 may be ionized by interaction of its electrons with the ions in the ion beam 104. The ionization of the hydrogen gas 210 (to produce positive ions) may thus release electrons that are trapped in the ion beam 104, thereby reducing the space charge potential and improving the ion beam properties (e.g., maintaining a compact ion beam) by reducing the mutual repulsion between the positive ions. For example, this reduction in the space charge potential is particularly beneficial for low energy ions having an energy below 50 keV. The background gas ions have low energy (e.g., a few eV or less) after being ionized, are repelled by the beam potential, and may be attracted to the walls of the components of the beam line (e.g., the housing 117). In this way, the background gas may improve the beam optics for a low energy ion beam without interfering with the implantation process.

[0023] Advantageously, providing the hydrogen gas 210 to the deceleration stage 116 at an appropriate partial pressure may provide proper beam control by reducing the space charge while also reducing energy contamination (compared to known ion implanters). In known ion implanters using nitrogen or inert gases (such as argon or xenon), energy contamination has been observed in substrates implanted with dopant ions (such as boron). Specifically, a high energy tail of the depth distribution of the dopant may be observed within the implanted substrate, indicating the effect of high energy neutrals that are not properly decelerated and attempt to traverse the deceleration stage. Even for ion implanters having a curved deceleration stage such that neutrals traveling in a straight line trajectory into the deceleration stage can be intercepted by the walls of the deceleration stage, this contamination still occurs.

[0024] Without being limited to a particular theory, the energy contamination observed in known ion implanters may be caused, at least in part, by Rutherford scattering of high energy neutrals by the background gas present in the ion implanter. Specifically, a Rutherford scattering model may be used to analyze the interaction between a projectile ion (or high energy neutral) and a residual gas atom. The geometric characteristics of the scattering of the ions in the ion beam caused by interaction with the background gas atoms are summarized in Table I. As shown in Table I, when using a conventional background gas (such as nitrogen) in an ion implanter, the dopant ions may be scattered within a relatively large scattering angle. In the case of B + ions, even if the deceleration stage is as Figure 2Shown in a bent configuration, boron ions can still be scattered by the nitrogen background gas by up to 180 degrees, thus providing an explanation for the reason why high-energy neutral species can be emitted from the deceleration stage. In other words, the high-energy neutral species entering the deceleration stage 116 can be reflected by the background gas species, thus redirecting the high-energy neutral species out of the deceleration stage 116 towards the substrate 114. This situation is particularly applicable when using nitrogen or a gas of higher mass, in which case the deflection angle of the ions can be very large, especially for P + ions or B + ions. When using nitrogen (m = 14 amu) as the background gas as in a known ion implanter, boron ions (or high-energy neutral species) can be scattered by any angle up to 180°. Such a scattering event will cause some kinetic energy to be transferred from the boron ions (or high-energy neutral species) to the nitrogen atoms, but even at a scattering angle θ of 30°, the scattered boron atoms will still have 80% of their initial energy before scattering. Assuming that the trajectory of the high-energy neutral species scattered at 30 degrees enables the high-energy neutral species to be emitted from the deceleration stage, and assuming that 80% of the energy of the scattered high-energy neutral species does not match the expected energy of the implanted ions, such a scattering event will cause energy contamination when the scattered neutral species reaches the wafer.

[0025] It should be noted that in an embodiment of the present invention in which the hydrogen source 118 is used to direct hydrogen to the deceleration stage 116, the maximum scattering angle when the B + species encounters hydrogen is only 5 degrees, which means that high-energy boron neutral species having substantially the same mass as the B + will be deflected in a similar manner. Therefore, when the high-energy boron neutral species collides with the hydrogen species, its trajectory will substantially not change, thus reducing the probability that the reflected high-energy boron neutral species is emitted from the bent deceleration stage whose curvature can be 30 degrees or greater than 30 degrees.

[0026] [Table I]

[0027]

[0028] In addition, for example, using hydrogen 210 in the deceleration stage 116 will greatly reduce the probability of scattering-type collisions compared to nitrogen. It should be noted that in order to provide optimal beam delivery for the ion beam (especially beam delivery at a beam energy of less than 50 keV), for example, a gas pressure of approximately 5×10 -6 torr, 1×10 -5 torr or 3×10 -5 torr can be used to provide sufficient ionization events to reduce the space charge in the ion beam while not introducing an excessive total pressure in the beam line. Within this pressure range, the probability of gas-phase collisions can be estimated for a given species in the ion beam. Figure 3shows the variation of the scattering probability of several different gases on 20 keV boron species with the scattering angle under a background gas pressure of 1×10 -5 Torr. As shown in the figure, at an approximate scattering angle of 4 degrees, the scattering probability for hydrogen is nearly two orders of magnitude lower than that for nitrogen, and the absolute value is 10 -5 , which means that even at very low angles, the chance of a given boron atom being scattered by a hydrogen species is still only 10 -5 . These probabilities have been estimated using Transport of Ions in Matter (TRIM), a well-known Monte Carlo simulation program.

[0029] Referring again to Figure 2 , in some embodiments, the hydrogen source 118 can be coupled to the hydrogen port 119 to directly deliver the gas into the deceleration stage 116. In this way, hydrogen can be directly provided in the environment required in the following situations: optimizing beam delivery by providing an appropriate background gas pressure, while minimizing energy contamination by greatly reducing the probability of high-energy neutral species being reflected through the outlet of the deceleration stage.

[0030] In various additional embodiments, the hydrogen source that supplies hydrogen to the deceleration stage can be a local hydrogen source. It should be noted that in known ion implanters, hydrogen is not used for the purpose of supplying the background gas. Among the reasons for not using hydrogen in ion implanters include safety considerations (such as flammability). Generally, when using a hazardous gas to provide the source of the implanted species in a known ion implanter, dedicated gas cartridges can be used to contain the hazardous gas, where these dedicated gas cartridges are placed in a housing at high voltage to match the voltage of the ion source.

[0031] In one embodiment, to minimize safety issues, instead of a gas cylinder or gas tank, the local hydrogen source can be a source that generates hydrogen locally as needed. The local source of supplying hydrogen does not need to be placed at the high electrical potential of the ion source and does not need to be activated during the implantation process. Therefore, when hydrogen is not used in the ion implanter, there is no hydrogen in the beam line of the ion implanter. In a specific embodiment, an electrolytic hydrogen generator can be located near the deceleration stage to produce hydrogen for the deceleration stage during ion implantation while generating and guiding the ion beam through the deceleration stage.

[0032] Figure 4Illustrate process flow 400 according to other embodiments of the present disclosure. In step 402, an ion beam is generated at an ion source. In various embodiments, the ion source 102 can be an indirectly heated cathode (IHC) ion source, a radio frequency ion source, a microwave ion source, or other ion sources. In step 404, the ion beam is decelerated in a deceleration stage. For example, in one instance, the energy of the ion beam can be reduced from 10 keV to 2 keV. In step 406, the ion beam is deflected in the deceleration stage to change the trajectory of the ion beam. For example, when the ion beam leaves and goes to the substrate, the ion beam can be deflected by an angle of 15 degrees, 30 degrees, 45 degrees, or an angle greater than 45 degrees from the initial trajectory when entering the deceleration stage. In step 408, hydrogen is introduced into the deceleration stage during the deceleration and deflection of the ion beam. In some embodiments, hydrogen can form a pressure of at least 5×10 -6 Torr. Thus, hydrogen can provide optimal suppression of the space charge effect in the ion beam without scattering the high-energy neutral species entering the deceleration stage, thereby preventing the high-energy neutral species from deflecting towards the substrate.

[0033] Embodiments of the present invention provide several advantages. The first advantage relates to the ability to reduce energy contamination in medium-energy ion implanters and low-energy ion implanters without having to redesign the accelerator column. Embodiments of the present invention also provide the additional advantage of conveniently and safely reducing energy contamination caused by high-energy neutral species.

[0034] The scope of the present disclosure is not limited to the specific embodiments described herein. In fact, from the foregoing description and drawings, various other embodiments and modifications other than the embodiments of the present disclosure described herein will be apparent to those of ordinary skill in the art. Accordingly, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Additionally, the present disclosure has been described herein in the context of a particular implementation manner for a particular purpose in a particular environment, and those of ordinary skill in the art will recognize that its applicability is not limited thereto, and the present disclosure can be beneficially implemented for any number of purposes in any number of environments. Accordingly, the claims set forth above should be construed in accordance with the full breadth and spirit of the present disclosure described herein.

Claims

1. An ion implantation system, characterized in that, Comprising: An ion source that generates an ion beam; A substrate platform disposed downstream of the ion source; A deceleration stage that includes a component for deflecting the ion beam, the deceleration stage being disposed between the ion source and the substrate platform; And A gas source that is directly coupled to the deceleration stage to supply helium gas to the deceleration stage, Wherein high-energy neutral species generated from the ion beam do not scatter onto the substrate platform.

2. The ion implantation system according to claim 1, characterized in that, The deceleration stage includes a curved shape, wherein the deceleration stage does not provide a line-of-sight path for the ion beam from an inlet of the deceleration stage to an outlet of the deceleration stage.

3. The ion implantation system according to claim 1, characterized in that, Including a port that directly delivers the helium gas into the deceleration stage.

4. The ion implantation system according to claim 1, characterized in that, The deceleration stage includes at least 5×10 -6 helium partial pressure of the support.

5. The ion implantation system according to claim 1, characterized in that, The gas source includes a plurality of ports for supplying helium gas to the ion beam, wherein at least one of the plurality of ports is disposed in the deceleration stage.

6. The ion implantation system according to claim 1, characterized in that, The ion beam includes boron ions having an ion energy of 50 keV or less than 50 keV.

7. An ion implantation method, characterized in that, Comprising: Generating an ion beam; Decelerating the ion beam in a deceleration stage; During deceleration, changing the trajectory of the ion beam; And During deceleration, directly guiding helium gas from a gas source into the deceleration stage.

8. The ion implantation method according to claim 7, characterized in that, The helium gas is guided through a port in the deceleration stage.

9. The ion implantation method according to claim 7, characterized in that, The air pressure in the deceleration stage is at least 5×10 -6 Torr.

10. An ion implantation system, characterized in that, Comprising: A beam line that includes an ion source to generate an ion beam that includes an implant material; A substrate platform disposed downstream of the ion source; A deceleration stage disposed between the ion source and the substrate platform; And A gas source that is directly coupled to the deceleration stage to supply hydrogen gas to the beam line at a specified partial pressure, Wherein the implant material scatters at an angle of no more than 5 degrees during collision with the hydrogen gas.

11. The ion implantation system according to claim 10, characterized in that, Including a port that directly delivers the hydrogen gas into the deceleration stage.

12. The ion implantation system according to claim 10, characterized in that, The deceleration stage includes a curved shape, wherein the deceleration stage does not provide a line-of-sight path for the ion beam from an inlet of the deceleration stage to an outlet of the deceleration stage.

13. The ion implantation system according to claim 10, wherein, The gas source includes a local hydrogen generator.

14. An ion implantation method, characterized in that, Comprising: Generating an ion beam that includes an implant material; Conducting the ion beam along a beam line using a plurality of beam line components; Decelerating the ion beam in a deceleration stage; And Directly guiding hydrogen gas into the deceleration stage at a specified partial pressure, wherein the implant material scatters at an angle of no more than 5 degrees during collision with the hydrogen gas.

15. The ion implantation method according to claim 14, wherein, The deceleration stage includes a curved shape, wherein the deceleration stage does not provide a line-of-sight path for the ion beam from an inlet of the deceleration stage to an outlet of the deceleration stage.

16. The ion implantation method according to claim 14, wherein, Including generating the hydrogen gas using a local hydrogen generator.

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