Substrate assembly, low emission implant mask, and method of implanting a substrate

Abstract

The present disclosure provides a substrate assembly, a low emission implantation mask, and a method of implanting a substrate. The substrate assembly can include a substrate base and a low emission implantation mask disposed on the substrate base. The low emission implantation mask can include a carbon-containing material including carbon isotopes formed from 12 C isotopically purified carbon formed from carbon isotope precursors.

Description

Technical Field

[0001] This disclosure generally relates to ion implantation, and more specifically to substrate assemblies, implantation masks for high-energy ion implantation, and methods for implanting ions into substrates. Background Technology

[0002] Ion implantation is a process of introducing dopants or impurities into a substrate through bombardment. An ion implantation system may include an ion source and a series of beamline components. The ion source may include a chamber for generating ions. The ion source may also include a power supply and an extraction electrode assembly disposed near the chamber. The beamline components may include, for example, a mass analyzer, a first accelerating or decelerating stage, a collimator, and a second accelerating or decelerating stage. Much like a series of optical lenses used to manipulate a beam, the beamline components can filter, focus, and manipulate ions or ion beams having specific types, shapes, energies, and / or other qualities. The ion beam passes through the beamline components and can be guided toward a substrate mounted on a platen or clamp.

[0003] Implantable devices capable of generating ion energies of approximately 1 MeV or greater are often referred to as high-energy ion implanters or high-energy ion implantation systems. One type of high-energy ion implanter employs a so-called tandem acceleration architecture, in which ions are accelerated to high energies through a first column, undergo charge exchange to change polarity, and are then accelerated to a second energy, which is approximately twice the first energy in a second column. Another type of high-energy ion implanter is called a linear accelerator (or LINAC), in which a series of electrodes arranged in tubes conducts and accelerates an ion beam along the series of tubes to increasingly higher energies, wherein the electrodes receive RF voltage signals under radio frequency (RF) conditions.

[0004] When high-energy ions collide with a workpiece (also known as a "substrate"), various types of particles are emitted from the workpiece, including secondary ions, electrons, and nuclear particles such as neutrons, in addition to ion implantation. In many cases, patterned implantation is performed, where areas of the substrate that will not be implanted are masked. Exemplary masking materials include photoresists (e.g., organic-based photoresists) and hard masking materials (including carbon, SiO2, SiC, or other materials). Most common masking materials contain a significant amount of carbon (C). Elemental carbon includes the dominant... 12 C isotopes, naturally occurring, constitute approximately 1.1% of the content. 13 C isotopes, and very small amounts 14 C isotopes. 13 When carbon isotopes are struck by ions with sufficient energy, they may undergo nuclear transformation, leading to radioactive decay through neutron emission mechanisms.

[0005] For example, carbon-based (organic) photoresists, SiC, carbon mask materials, and other mask materials tend to contain a fraction similar to that of naturally occurring materials, such as 1.1%. 13 C isotopes. Therefore, known carbon-based masking materials are susceptible to neutron emission when struck by high-energy ions, especially when the ion energy is above 1 MeV, and this likelihood increases as the ion energy increases from 2 MeV to 3 MeV.

[0006] To absorb the neutrons emitted during this radioactive process, it may be necessary to install a very thick cladding, such as a high-density polyethylene or borated polyethylene shield, in the ion implanter, which includes the implantation chamber containing the substrate. Furthermore, neutron radiation may persist for a considerable period, necessitating a long "cooling" cycle before the substrate is processed post-ion implantation.

[0007] This disclosure provides for these and other considerations. Summary of the Invention

[0008] In one embodiment, a substrate assembly may include: a substrate; and a low-emission implantation mask disposed on the substrate, the low-emission implantation mask comprising a carbon-containing material, the carbon material comprising... 12 Carbon isotope purified carbon formed from C carbon isotope precursors.

[0009] In another embodiment, a low-emission implantation mask may include: a photoresist layer having a thickness of 10 μm or greater, wherein the photoresist layer comprises a layer of... 12 Carbon isotope purified carbon formed from C carbon isotope precursors.

[0010] In another embodiment, a method of implanting a substrate may include providing a low-emission implantation mask on the substrate, the low-emission implantation mask comprising isotope-purified... 12 Material C, the implantation mask includes an open region and a masked region, and has a first thickness. The method may include directing an ion species to the substrate with implantation energy, wherein the ion species is implanted into the substrate in the open region, but not into the substrate in the masked region. Therefore, the low-emission implantation mask produces a first neutron yield, which is lower than a second neutron yield when the ion species is implanted into a conventional implantation mask having the first thickness and comprising isotopically impure carbon material. Attached Figure Description

[0011] Figure 1 An exemplary substrate arrangement for low neutron emission is shown according to an embodiment of this disclosure.

[0012] Figure 2 An exemplary substrate arrangement for low neutron emission is shown according to some embodiments of the present disclosure.

[0013] Figure 3 Another substrate arrangement for low neutron emission is shown according to an additional embodiment of this disclosure.

[0014] Figure 4 An exemplary ion implanter arrangement is shown according to some embodiments of the present disclosure.

[0015] Figure 5 Exemplary process flows according to some embodiments of this disclosure are shown. Detailed Implementation

[0016] The accompanying drawings are not necessarily drawn to scale. They are schematic diagrams only and are not intended to depict specific parameters of this disclosure. The drawings are intended to illustrate exemplary embodiments of this disclosure and should therefore not be construed as limiting the scope. In the drawings, the same reference numerals denote the same elements.

[0017] In the following description, the apparatus, system, and method according to the present disclosure will be more fully illustrated with reference to the accompanying drawings, which illustrate embodiments of the system and method. The system and method may be implemented in many different forms and should not be considered as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.

[0018] For convenience and clarity, this document will use terms such as "top," "bottom," "upper," "lower," "vertical," "horizontal," "lateral," and "longitudinal" to describe the relative placement and orientation of the components and their constituent parts shown in the figures with respect to the geometry and orientation of the components of the semiconductor manufacturing apparatus. These terms will include specifically mentioned words, their derivatives, and words with similar meanings.

[0019] Elements or operations described herein in the singular and preceded by the word "a" (or "an") are understood to potentially include multiple elements or operations as well. Furthermore, references to "one embodiment" in this disclosure are not intended to exclude the existence of additional embodiments that also include the described features.

[0020] This document provides methods for improving mask materials and substrate assemblies, which exhibit lower neutron emission when exposed to high-energy implantation. In various embodiments, methods employing isotopically purified materials are provided. 12 Masking materials and substrate assemblies for carbon-based mask layers formed from C materials. The term "isotope-purified" is used in this paper. 12 "C-materials" can refer to carbon-containing materials, where the total carbon concentration is... 13 C concentration ( 13 C / ( 13 C+ 12 C)) is less than 0.5%, for example, less than 0.1%. In some cases, isotope purification... 12 Layer C may contain unmeasurable content. 13 C or containing less than one part per million (ppm) 13 C. It should be noted that any product with a significantly lower natural content ratio than 1.1% 13 The C concentration will proportionally reduce neutron emission and can therefore be described as "isotope purified". 12 C".

[0021] The inventors have recognized that, although many materials may exhibit neutron emission (including) when exposed to high-energy implantation, 12 C and 13 (C) Both, but the neutron emission cross section exhibits different energy dependencies for different materials. Specifically, embodiments of the present invention utilize 12 C and 13 Different energy dependencies of neutron emission between C in the MeV range.

[0022] As an example, when the proton energy is below 2 MeV, the energy from exposure to positive hydrogen ions (protons) 13 The neutron emission cross-section for C is expected to be less than 10 microbarns. Above 2.5 MeV, the neutron emission cross-section increases rapidly, reaching 50 to 100 millibarns for ion energies in the 3 to 10 MeV range, and remaining above 5 millibarns for ion energies up to 25 MeV. Similarly, for helium ions, 13 The neutron emission cross section of C is less than 1 microtarget at energies below 500 keV, but increases rapidly to 1 millitarget or greater at energies above 1 MeV. Specifically, for ion energies between 2 MeV and 25 MeV, it reaches tens to hundreds of millitargets.

[0023] In contrast, at proton energies below 2 MeV, the energy from exposure to positive hydrogen ions (protons) 12The neutron emission cross-section of C is expected to be less than 5 microtargets. This is from exposure to positive hydrogen ions (protons). 12 The neutron emission cross-section of C does not increase to the millitarget range until the ion energy is above 15 MeV, reaching a level between 50 and 100 millitargets for ion energies in the 20 to 100 MeV range. Similarly, for helium ions, 12 The neutron emission cross section of C is less than 1 microtarget at energies below 10 MeV, but increases rapidly above 11 MeV, reaching, for example, a level of about 10 millitargets between 11 MeV and 25 MeV.

[0024] It should be noted that, to cite only one commercial implementation, an ion energy range of approximately 1 MeV to 10 MeV is characteristic of many implantation procedures for embedding hydrogen into silicon wafers. Therefore, by providing isotopically purified... 12 The C-formed masking material allows for the safe execution of ion implantation processes in the MeV range (e.g., 1 MeV to about 15 MeV for proton implantation and up to about 10 MeV for helium implantation), where the yield of neutrons is much lower.

[0025] According to various embodiments of this disclosure, organic (carbon-containing) materials can be used to prepare photoresist materials, wherein the carbon-containing materials can be purified from isotopes. 12 Carbon-containing chemicals are formed. Photoresist materials can be prepared using known processes, making them chemically identical to known photoresist materials, except that the carbon in the photoresist is only present in... 12 C isotopes (ignoring trace amounts (e.g., less than 1 ppm)) 14 C or 13 C (if present)). According to various embodiments, following known procedures, the isotope can then be purified. 12 C-type photoresist material is used as an implantation mask on a substrate.

[0026] According to other embodiments of this disclosure, a carbon-containing hard mask layer may be formed on a substrate, wherein the carbon-containing hard mask layer may be purified from isotopes. 12 C carbon is formed. In some embodiments where a hard mask layer is deposited via chemical vapor deposition (CVD), isotopically purified carbon can be used. 12 C precursor gas (e.g., 12 CH4 12 C2H6) is used to deposit a hard mask layer, wherein the superscript '12' indicates a given chemical or substance having the chemical formula, wherein the carbon material in the given chemical or substance contains only carbon. 12 C isotopes (ignoring trace amounts (e.g., less than 1 ppm)) 14C or 13 C (if present)). Therefore, isotope-purified [materials] can be deposited using known CVD methods. 12 Hard mask layer of C, such as Si 12 C 12 C, Si 12 CN, etc.

[0027] In other embodiments, isotope-purified materials can be used. 12 Hard mask layers are deposited on solid targets formed of carbon (C) using physical vapor deposition (PVD), including sputtering and evaporation. Therefore, hard mask layers, such as SiC, C, and SiCN, can be deposited using known PVD methods.

[0028] Isotopes can be purified according to known procedures. 12 C hard mask layers are patterned to form a hard mask.

[0029] Figure 1 An exemplary substrate arrangement for low neutron emission according to an embodiment of the present disclosure is shown. A substrate arrangement 100 is shown, wherein a substrate 102 supports an implantation mask 104. The implantation mask 104 defines an implantation pattern for ions to be implanted into the substrate 102. Therefore, when ions (generally shown as an ion beam 106) bombard the substrate arrangement 100, different portions of the implantation mask 104 (shown as portions 104A, 104B, and 104C) prevent the ion beam 106 from impacting the substrate 102 in regions directly beneath said different portions. The ion beam 106 is implanted into the substrate 102 in an open region 110 where no mask material is present. According to an embodiment of the present disclosure, as described above, the implantation mask 104 may be made of isotopically purified material. 12 A carbon-containing layer formed from material C. According to various embodiments, the implantation mask 104 is formed with a given mask thickness sufficient to prevent ions from the ion beam 106 from completely traveling through the implantation mask 104 and colliding with the substrate 102, as indicated by the arrows. The thickness of the implantation mask 104 can be set according to the ion energy and ion species to be implanted into the substrate 102. Exemplary thicknesses of the implantation mask 104 can range from a few micrometers to several hundred micrometers (μm) for use in implantation procedures, wherein the ion energy is set in the range of 1 MeV to 10 MeV, and wherein the ion species are protons or helium. The embodiments are not limited to this context. In some embodiments, the implantation mask 104 may be a photoresist mask, a stencil mask, or a hard mask. In some embodiments, the implantation mask 104 may be formed as a single layer, wherein the layer is purified from isotopes. 12 C material formation.

[0030] It should be noted that in various application scenarios, the substrate arrangement 100 can be deployed in a high-energy implanter (e.g., a tandem ion implanter or a linear accelerator (LINAC) implanter), wherein the ions of the ion beam 106 can bombard the substrate with energies in the MeV range. For example, in various non-limiting embodiments, the ion energy of the ion beam 106 can be from 1 MeV to 10 MeV. When bombarding the implantation mask 104, since the carbon species in the implantation mask 104 are not present... 13 C, therefore, the neutron yield produced by ions from ion beam 106 can be suppressed. It should be noted that for positive hydrogen ions (protons) of 1 MeV to 10 MeV or helium ions of 1 MeV to 10 MeV, neutron emission through implanted mask 104 can be suppressed relative to known masks having the same chemical composition as implanted mask 104, where, in known masks, 13 C isotopes exist in carbon species at a natural abundance of approximately 1.1%.

[0031] Figure 2 Another exemplary substrate arrangement for low neutron emission according to an embodiment of this disclosure is shown. A substrate arrangement 200 is shown, wherein a substrate 102 supports an implanted mask 204. Figure 1 As shown, the implantation mask 204 is used to define the implantation pattern for ions to be implanted into the substrate 102. Therefore, when ions (generally shown as ion beam 206) bombard the substrate arrangement 200, different portions of the implantation mask 204 (shown as portions 204A, 204B, and 204C) block the ion beam 206 from impacting the substrate 102 in the area directly below said different portions.

[0032] According to embodiments of this disclosure, the implantation mask 204 may be formed of multiple layers, said multiple layers including, generally as described above, isotopically purified. 12 At least one carbon-containing layer is formed from C material. For example... Figure 2 As shown, the implantation mask 204 may include two layers, namely an outer layer shown as an upper layer 208 and a lower layer 210. The upper layer 208 may have an upper interface with the environment, at which the ion beam 206 is implanted into the upper layer 208. Therefore, the upper layer 208 may be purified from isotopes. 12A carbon-containing layer formed from material C. Similar to the implantation mask 104, the thickness of the upper layer 208 can be set according to the type and energy of the ions in the ion beam 206, so that the ion beam 206 is contained within the upper layer 208. In this way, the lower layer 210 can be formed from a different material than the upper layer 208. For example, the implantation mask 204 can be a chemically homogeneous set of layers, such as a set of two carbon-containing photoresist layers, wherein the upper layer 208 and the lower layer 210 have the same chemical composition. The difference between the lower layer 210 and the upper layer 208 may be that the lower layer 210 is formed from... 13 C 12 The C ratio is similar to or the same as that of naturally occurring carbon species, which have an abundance of 1.1%. Therefore, when irradiated with ions (e.g., protons or helium) in the 1 MeV to 10 MeV range, the lower layer 210 can exhibit significantly higher neutron emission than the upper layer 208. Using the lower layer 210 in the implantation mask 204 helps to provide a relatively thick mask, wherein only a portion of the mask is made of relatively expensive, isotopically purified carbon. 12 C forms a layer. In other words, isotope purification... 12 C mask materials can be very expensive, making isotope purification only possible on top of the mask. 12 C can save costs, while the lower part of the mask is made of chemically identical but naturally occurring materials. 13 The mask is made of a material composed of carbon isotopes. The advantage of this arrangement is that the two layers of the mask can be photolithographically processed together in the same process (exposure, development, hard baking, etc.), while reducing the neutron emission of the mask with minimal additional cost.

[0033] Specifically, the thickness of the upper layer 208 allows some ions from the ion beam 206 to completely penetrate the upper layer 208 and into the lower layer 210 for the target implantation energy, while the ions from the ion beam 206 do not penetrate into the substrate 102 (as shown by arrow 206A). The thickness of the upper layer 208 can also be arranged such that, for the target implantation energy, the ion energy of the ion beam 206 will be lower than that from the substrate 102. 13 C produces a large number of neutrons at a threshold energy, for example, below 2.5 MeV for a proton ion beam. In other words, the presence of an upper layer 208 with sufficient thickness allows the lower layer 210 to be composed of a large number of neutrons. 13 The formation of C isotopes is impure carbon because the energy of any ion that can completely penetrate the upper 208 layer is sufficiently reduced to produce neutrons.

[0034] Figure 3 Another exemplary substrate arrangement for low neutron emission according to an embodiment of this disclosure is shown. A substrate arrangement 300 is shown, wherein a substrate 102 supports an implanted mask 304. Figure 1 and Figure 2As shown, the implantation mask 304 is used to define the implantation pattern for ions to be implanted into the substrate 102. Therefore, when ions (generally shown as ion beam 306) bombard the substrate, different portions of the implantation mask 304 (shown as portions 304A, 304B, and 304C) block the ion beam 306 from impacting the substrate 102 in the area directly below the different portions.

[0035] According to embodiments of this disclosure, the implantation mask 304 may be formed of multiple layers, said multiple layers including those purified from isotopes as described above. 12 At least one carbon-containing layer is formed from C material. For example... Figure 3 As shown, the implantation mask 304 may include two layers: an upper layer 308 and a lower layer 310. The upper layer 308 may have an upper interface with the environment, at which the ion beam 306 is implanted into the upper layer 308. Therefore, the upper layer 308 may be purified from isotopes. 12 A carbon-containing layer formed from material C. Like the upper layer 208, the thickness of the upper layer 308 can be set according to the type and energy of the ions in the ion beam 306, so as to contain the ion beam 306 within the upper layer 308, or to sufficiently decelerate the ion beam 306 so that it cannot generate neutrons even when colliding with the lower layer 310. Thus, the lower layer 310 can be formed from a different material than the upper layer 308. It should be noted that in some embodiments, the lower layer 310 can be formed from a different material and / or a different process than the upper layer 308. For example, the lower layer 310 can be a hard mask material, while the upper layer 308 is a photoresist material.

[0036] Figure 4 An ion implantation system 400 arranged according to an embodiment of the present disclosure is shown. The ion implantation system 400 may include an ion source chamber 404 capable of generating an ion beam 412 and an extraction assembly 406. The ion implantation system 400 may also include known components (including a mass analyzer 408) for providing a mass-analyzed beam by deflecting and filtering the ion beam 412. Figure 4As shown, the ion implantation system 400 may include a high-energy acceleration component 410. The high-energy acceleration component 410 may represent a known tandem accelerator or a known linear accelerator, wherein the high-energy acceleration component 410 is capable of accelerating the ion beam 412 to ion energies of 1 MeV or greater, for example up to 10 MeV, or up to 20 MeV in some embodiments. The ion implantation system 400 may also include a collimator 414 (which may include a corrector magnet) and a terminal station 422, wherein a substrate assembly 416 is disposed in the terminal station 422. The substrate assembly 416 is shown as a substrate 418, including a low-emission implantation mask 420 disposed on the substrate 418. The low-emission implantation mask 420 is typically arranged as a carbon-containing mask according to any of the foregoing embodiments, wherein at least the upper layer of the low-emission implantation mask 420 is isotopically purified. 12 C material formation.

[0037] In operation, when the ion beam 412 collides with the substrate assembly 416 at an energy of, for example, 1 MeV to 10 MeV, the implantation mask includes components with a considerably large... 13 C score (e.g., at 1.1%) 13 Compared to a known arrangement of carbon (the fraction naturally occurring within the C range), neutron emission from substrate assembly 416 was suppressed.

[0038] Figure 5 An exemplary process flow 500 according to some embodiments of the present disclosure is illustrated. At block 502, a substrate is provided in the implantation chamber of a high-energy ion implanter. At block 504, a low-emission implantation mask is provided on the substrate. In various embodiments, as described above, the low-emission implantation mask comprises isotopically purified... 12 A carbon-containing layer formed by C. In some embodiments, the low-emission implantation mask may be a single layer, while in other embodiments it may include multiple layers.

[0039] At block 506, an ion beam is generated in a high-energy ion implanter and accelerated to high ion energies along the beamline. In various non-limiting embodiments, the high ion energies can be in the range of above 1 MeV, above 3 MeV, above 5 MeV, and up to 10 MeV. As an example, the ion implanter can be a tandem accelerator arranged to accelerate hydrogen ions, helium ions, or other ions. The embodiments are not limited to this context. In additional embodiments, the ion implanter can be a linear accelerator capable of accelerating ions to ion energies in the range of 1 MeV to 10 MeV. Therefore, after acceleration by a tandem accelerator or a linear accelerator, the ion beam can appear at high energies in the range of 1 MeV to 10 MeV in the downstream portion of the beamline.

[0040] At block 508, high-energy ions are directed to the substrate, whereby the high-energy ions are implanted into the substrate within an open region of the low-emission implantation mask, and whereby the high-energy ions are trapped within the low-emission implantation mask. Therefore, during the implantation process, the neutron yield can be suppressed compared to scenarios using known implantation masks that are chemically similar to low-emission implantation masks, where known implantation masks may contain a large number of... 13 The formation of carbon isotopes of C (e.g., in the range of 1.1 atomic percent).

[0041] In view of the foregoing, at least the following advantages are achieved through the embodiments disclosed herein. The first advantage is that by providing isotopically purified [material] on the substrate... 12 Low-emission implantation masks for C reduce neutron emission during ion implantation at energies in the MeV range (e.g., between approximately 1 MeV and 10 MeV). A second advantage is improved substrate handling after high-energy implantation by avoiding a post-implantation "cooling" cycle, where post-implantation neutron emission is avoided, for example, during high-energy implantation to approximately 1% fraction of neutron emission. 13 The emission that occurs later in the carbon-containing mask formed by C isotopes.

[0042] While certain embodiments of this disclosure have been set forth herein, this disclosure is not limited thereto, as the scope of this disclosure has the broadest range permitted by the art and indicated in this specification. Therefore, the foregoing description should not be considered restrictive. Other modifications within the scope and spirit of the appended claims will be apparent to those skilled in the art.

Claims

1. A substrate assembly comprising: a substrate base; and 4. The substrate assembly of claim 1, the low emission implant mask comprising a thickness of at least 10 μιη. a low emission implantation mask disposed on the substrate base, the low emission implantation mask comprising a carbon-containing material, the carbon-containing material including carbon isotopes formed from 12 isotopically purified carbon formed from C carbon isotopes precursors, wherein the "isotopically purified carbon" refers to a carbon-containing material wherein the concentration of 13 C concentration 13 C concentration 13 C concentration 12 C concentration is less than 0.5%.

2. The substrate assembly of claim 1, the low emissivity implant mask characterized by 13 C Carbon isotope concentration less than 0.1%.

3. The substrate assembly of claim 1, the low emission implant mask comprising an outer layer formed from isotopically purified 12 C, and an underlying layer formed from isotopically impure carbon beneath the outer layer.

5. The substrate assembly of claim 3, the outer layer comprising a thickness of at least 10 μιη.

6. The substrate assembly of claim 1, the low emission implant mask comprising a photoresist material or a hard mask material.

7. A low emission implant mask comprising:

10. A method of implanting a substrate comprising: a photoresist layer having a layer thickness of 10 μm or more than 10 μm, wherein the photoresist layer comprises a compound selected from the group consisting of 12 isotopically purified carbon formed from a carbon isotope precursor, wherein the "isotopically purified carbon" refers to a carbon-containing material wherein the concentration of 13 C concentration 13 C / ( 13 C+ 12 C) is less than 0.5%.

8. The low emission implantation mask of claim 7, the photoresist layer characterized by 13 C Carbon Isotope Concentration less than 0.1%.

9. The low emission implantation mask of claim 7, the photoresist layer comprising an outer layer formed from isotopically purified 12 C, and an underlying layer formed from isotopically impure carbon beneath the outer layer. directing an ion species toward the substrate at an implant energy, providing a low emission implant mask on the substrate, the low emission implant mask comprising isotopically purified 12 C material, the low emission implant mask including an open region and a masked region, and having a first thickness; and wherein the ion species implants into the substrate in the open regions and not in the masked regions, and wherein the low emission implant mask produces a first neutron yield that is lower than a second neutron yield when the ion species is implanted into a normal implant mask having the first thickness and comprising isotopically impure carbon material.

13. The method of claim 10, the low emission implant mask comprising a photoresist material or a hard mask material. wherein said "isotopically enriched" means that the concentration of the isotope is greater than 50% of the total concentration of the element. 12 "C material" means a carbon-containing material, wherein the concentration of carbon is greater than 50% of the total concentration of the element. 13 C concentration 13 C / ( 13 C+ 12 C) is less than 0.5%.

11. The method of claim 10, the low emissivity implant mask characterized by 13 C Carbon isotope concentration less than 0.1%.

12. The method of claim 10, the low emission implantation mask comprising an outer layer formed from isotopically purified 12 C, and an underlying layer formed from isotopically impure carbon beneath the outer layer.

14. The method of claim 10, wherein the implant energy is between 100 keV and 10 MeV.

15. The method of claim 10, wherein the implant energy is higher than 1 MeV.

16. The method of claim 10, the implanting comprising: accelerating the ion species as an ion beam to a high ion energy along a beamline of an ion implanter.

17. The method of claim 16, the ion implanter comprising a linear accelerator or a tandem accelerator. ​

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