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Complementary metal-oxide-semiconductor (CMOS) image sensors have widely been used in internet of thinking (IoT) devices such as smartphones, smart watch and personal computer tablets [1] . The consumer market strongly requires higher sensitivity and higher speed image data processing to realize high functional CMOS image sensors such as three dimensionally stacked back-side-illuminated CMOS image sensors (3D-CIS) [2] . However, there are some serious technological issues in the fabrication of advanced CMOS image sensors as shown in Fig. 1 .

We investigated the thermal behavior of dislocation loops formed in a CH3O-multielement-molecular-ion-implanted epitaxial silicon (Si) wafer by real-time cross-sectional TEM observation with in situ heating. We found that the CH3O-ion-implantation-induced faulted Frank dislocation loops (FDLs) shrink at a low rate at the beginning of heat treatment (1st stage), and then the shrinkage rate rapidly increased (2nd stage), resulting in the dissolution of the defects. The activation energies for the shrinkage of FDLs in the 1st and 2nd stages (E D-1 and E D-2) were found to be 2.94 ± 0.31 and 4.95 ± 0.25 eV, respectively. The shrinkage behavior in the 1st stage is the desorption of C and O atoms that segregated along the edge of an FDL because of the interaction between the CH3O-ion-implantation-induced FDL and the segregated impurities. On the other hand, the 2nd stage corresponds to the desorption of Si atoms from FDLs and its migration. Compared to our previous study on the shrinkage behavior of CH4N-ion-implantation-induced FDLs (J. Electrochem. Soc. 169, 047521 (2022)), E D-2 of the CH3O-ion-implantation-induced FDLs is almost the same as that of the CH4N-ion-implantation-induced FDLs, while the values of E D-1 are quite different. The difference between the E D-1 values of CH3O- and CH4N-ion-implantation-induced FDLs is suggested to be the difference of the kind of segregated impurities. Our experimental results suggest that thermal stability of the dislocation loop is determined by the kind of segregated impurities around the dislocation loop.

The gettering behavior in a hydrocarbon molecular (C3H5) ion implanted region was investigated using atom probe tomography (APT) with the aim of improving electrical properties of CMOS image sensors (CISs) and stacked CISs. APT clarified the formation of carbon atom agglomerates with copper and oxygen gettering capability in the C3H5 ion implanted region. However, there were no oxygen atoms near the copper atoms in the C3H5 ion implanted region. In addition, the copper gettering capability of each carbon atom agglomerates decreased with increasing ratio of the number of oxygen atoms to that of carbon atoms in the carbon atom agglomerates. The copper and oxygen gettering mechanism was considered to involve the formation of a complex with carbon-containing gettering sites. Oxygen degrades the copper gettering capability of carbon atom agglomerates by the formation of stable complexes with carbon-containing gettering sites, which can also act as copper gettering sites. Consequently, the oxygen concentration in the C3H5 ion implanted regions is an important factor in improving the electrical properties of CISs and stacked CISs.

We proposed the fabrication of the laminated wafer with the conductive diamond layer as an alternative SOI wafer for micro-electro mechanical systems (MEMS) sensors by chemical vapor deposition (CVD) and surface-activated bonding (SAB), in order to prevent the charge-up of devices on a BOX layer during plasma treatments. We demonstrated that the use of this laminated wafer could be deposited the boron-doped diamond layer and be bonded a silicon wafer (layer) at room temperature without a thermal stress. Therefore, we believe that this laminated wafer can contribute to the improvement of MEMS sensors as an alternative SOI wafer.

We investigated the recrystallization of discrete amorphous regions formed in a C3H5-molecular-ion-implanted silicon (Si) substrate surface in the rapid thermal annealing (RTA). The change in the crystalline fraction of the C3H5-molecular-ion-implanted substrate surface after the RTA was obtained from the chemical shifts of Si 2p spectra by X-ray photoelectron spectroscopy. We found that the crystalline fraction increases depending on the RTA temperature after an incubation period. The transformation from the amorphous phase to the crystalline phase was analyzed on the basis of the Johnson–Mehl–Avrami–Kolmogorov theory. It was revealed that recrystallization of discrete amorphous regions proceeded three-dimensionally and activation energy was estimated to be 2.74 ± 0.39 eV, which is approximately equal to 2.70 eV for the solid-phase epitaxy of the continuous amorphous layer in a Si crystal. Therefore, we believe that discrete amorphous regions are recrystallized via solid-phase epitaxy laterally and vertically from the amorphous/crystal interface around them.

We propose the use of a laminated wafer with a conductive diamond layer for forming cavities as an alternative silicon-on-insulator wafer for micro-electro mechanical system (MEMS) sensors. Since this wafer has no insulator such as a buried oxide (BOX) layer but a conductive layer, it is not charged during plasma treatment in MEMS sensor fabrication processes. The conductive diamond layer was formed on a base wafer doped with boron of more than 2 × 1021 atoms cm−3 by microwave-plasma-enhanced chemical vapor deposition. The resistivity of this layer was 0.025 Ω cm, and this layer can be selectively etched to a base wafer made of silicon crystal, such as a BOX layer. In addition, a silicon wafer can be bonded to its layer without voids with gaps of more than 2 nm by surface-activated bonding. Therefore, we believe that the laminated wafer studied here is useful for the fabrication processes for MEMS sensors that may otherwise be damaged by plasma treatment.

The thermal stability of end-of-range (EOR) defects formed in a CH4N-molecular-ion-implanted epitaxial silicon (Si) wafer was studied by transmission electron microscopy (TEM) observation. By plan-view TEM observation, we found that the density and size of the CH4N-ion-implantation-induced EOR defects negligibly changed upon heat treatment at temperatures below 1000 °C, whereas the EOR defect density was drastically reduced by heating at 1100 °C. This result suggests that almost all CH4N-ion-implantation-induced EOR defects were sufficiently thermally stable to maintain their size at temperatures below 1000 °C, and that above 1100 °C, most of the EOR defects lost their stability, shrank and finally dissolved. Additionally, by in situ cross-sectional TEM observation during heat treatment, we found a large difference in the shrinkage rates of the EOR defects between at the beginning of heat treatment and the last minute of just before defect disappearance. We found that the EOR defects began to gradually shrank at the beginning of heat treatment (1st stage), and then the shrinkage rate rapidly increased (2nd stage), finally resulting in the dissolution of the defects. The activation energies for the shrinkage of EOR defects in the 1st and 2nd stages (E D-1 and E D-2) were found to be 7.55 ± 1.03 and 4.57 ± 0.32 eV, respectively. The shrinkage behavior in the 1st stage is likely to be due to the thermally activated desorption of C and N species that segregated along the edge of an EOR defect. On the other hand, from the E D-2 value, the shrinkage behavior in the 2nd stage is deduced to be due to the desorption of interstitial Si atoms. These findings suggest that this two-stage shrinkage behavior is peculiar to the EOR defects formed in the CH4N-ion-implanted epitaxial Si wafer, and that the interaction between the EOR defect and the impurities segregated at the edge of the defect affects the thermal robustness of the molecular-ion-implantation-induced EOR defects.

Three-dimensional (3D) stacked complementary metal oxide semiconductor (CMOS) image sensors require reduction in leakage current due to interface state defects at the SiO2/Si interface. Hydrocarbon molecular ion implanted silicon wafers have identified the hydrogen termination effect of such wafer, contributing to high performance of CMOS image sensors. However, recently, low-temperature heat treatment during a device process has been shown to reduce the concentration of hydrogen diffusing from the hydrocarbon-molecular-ion-implanted region. Thus, a new method of molecular ion implantation with phosphorus added has been developed. In this paper, we present the results of our analysis of the diffusion behavior of hydrogen in a hydrocarbon molecule with phosphorus (CH2P) by reaction kinetic analysis and TCAD simulation. The results of reaction kinetic analysis show binding energies of 0.76 eV (C–H2 binding state) and 0.45 eV (P–H binding state). TCAD simulation results show that the 0.76 eV binding energy indicates that hydrogen is adsorbed in a carbon and silicon self-interstitial cluster (C/I cluster). On the other hand, the binding energy of 0.45 eV indicates that hydrogen is trapped in phosphorus complexes. Hydrogen in the CH2P-implanted region diffuses owing to the difference in between these binding states. Thus, a reduction in the interface state density of Si/SiO2 can be expected.

Gettering sinks for metallic impurities formed by carbon-cluster ion implantation in epitaxial silicon wafers have been investigated using technology computer-aided design and atom probe tomography (APT). We found that the defects formed by carbon-cluster ion implantation consist of carbon and interstitial silicon clusters (carbon-interstitial clusters). Vacancy-type clusters are not dominant gettering sinks for metallic impurities in the carbon-cluster ion implanted region. APT data indicated that the distribution of oxygen atoms in the defects differs between Czochralski-grown silicon and epitaxial silicon wafers. The high gettering efficiency observed in carbon-cluster ion implanted epitaxial silicon wafers in comparison with Czochralski-grown silicon wafers is due to the distribution of oxygen atoms in the defects. Defects not containing O atoms provide strong gettering sinks for metallic impurities. These defects are formed by only carbon-interstitial clusters. Oxygen atoms inside the defects modify the amount of carbon-interstitial cluster formation on the defects. It is suggested that the gettering efficiency for metallic impurities in carbon-cluster ion implanted epitaxial silicon wafer is determined by the amount of carbon-interstitial clusters.

We developed a novel hybrid-molecular-ion-implantation technique for proximity gettering to reduce the carbon dose. In this molecular-ion-implantation technique, a molecular ion beam with a mixture of silicon hydride and hydrocarbon-molecular-ions is used. We found that 150 nm silicon {111} extrinsic Frank-type dislocation loops in the ion-implanted region are formed by this technique after epitaxial growth. Nickel and copper gettering test results showed that the ion-implanted region can getter Ni and Cu contaminants that diffused from the wafer surface at a carbon dose lower than those in hydrocarbon-molecular-ion-implanted wafers. We determined by energy dispersive x-ray (EDX) observation that end of range defects (EOR) act as gettering sites. We speculate two types of gettering induced by this technique: the relaxation-type gettering caused by EOR defects and the segregation-type gettering caused by the high concentration of carbon around EOR defects.

We developed silicon epitaxial wafers with high gettering capability by using hydrocarbon&ndash, molecular&ndash, ion implantation. These wafers also have the effect of hydrogen passivation on process-induced defects and a barrier to out-diffusion of oxygen of the Czochralski silicon (CZ) substrate bulk during Complementary metal-oxide-semiconductor (CMOS) device fabrication processes. We evaluated the electrical device performance of CMOS image sensor fabricated on this type of wafer by using dark current spectroscopy. We found fewer white spot defects compared with those of intrinsic gettering (IG) silicon wafers. We believe that these hydrocarbon&ndash, ion&ndash, implanted silicon epitaxial wafers will improve the device performance of CMOS image sensors.

We proposed the fabrication of an SOI wafer for customized power devices by chemical vapor deposition (CVD) of a BOX layer and surface-activated bonding (SAB). We demonstrated that the use of this SOI wafer can form an extra thick BOX layer of $10 ^{\circ }\mu \mathrm {m}$ and can be fabricated at temperature below 500 °C without thermal stress. Therefore, we believe that this SOI wafer can contribute to the improvement of customized power devices with breakdown voltages of over 500V.

We propose a fabrication process for a silicon on insulator (SOI) wafer with an extremely thick buried oxide (BOX) layer for custom micro-electro mechanical systems (MEMS) devices. A BOX layer is generally formed by thermal oxidation above 800 °C. It is limited for this method to form an extremely thick layer of more than 10 μm. Thus, we attempted to deposit the BOX layer by chemical vapor deposition at 300 °C for a short time, followed by annealing at above 300 °C to make it denser. In addition, a silicon layer was bonded to the BOX layer at room temperature by surface activated bonding not to receive thermal stress. As a result, the bonding interface had no voids. The breakdown electric field of the BOX layer in the accidental B mode was improved by annealing. Therefore, SOI wafers fabricated by our method will be beneficial to next-generation MEMS device fabrication.

We propose to use a bonding wafer as an alternative epitaxial wafer with an extra thick epitaxial layer of more than 100 μm thickness to fabricate vertical time-of-flight (TOF) complementary metal-oxide-semiconductor (CMOS) imaging sensors that can detect infrared (IR) radiation of wavelength greater than 1120 nm. This bonding wafer comprises a floating zone (FZ)-grown silicon wafer bonded to a Czochralski (CZ)-grown silicon substrate by room-temperature surface-activated bonding. Because the device-fabricating region is formed by bonding the FZ-grown wafer to the CZ-grown silicon substrate at room temperature, the oxygen concentration in this region is decreased to less than that in an epitaxial wafer. In addition, our bonded wafer can have a strong gettering capability for oxygen and transition metals (nickel, copper, and iron) in the bonding interface. Furthermore, the bonded wafer can inhibit out-diffusion of oxygen or transition metal to the device-fabricating region from the CZ-grown silicon substrate, and the device-fabricating region can have fewer impurities after fabricating the devices in the bonded wafer. Therefore, we consider that this bonded wafer can be fabricated by the simple processes of bonding and grinding (polishing) at room temperature without thermal stress, and this method is effective for decreasing the dark currents and white-spot defects generated owing to the presence of oxygen or transition metal, which are undesirable in advanced TOF-CMOS imaging sensors of a vertical structure.

The reduction in the density of SiO2/Si interface state (D it) in the isolation region and transfer transistor gate oxide is necessary to improve the performance of complementary metal-oxide semiconductor (CMOS) image sensors. In this study, we demonstrated that a hydrocarbon-molecular-ion-implanted epitaxial silicon wafer can reduce the D it and Pb0 center density in SiO2/Si interface regions analyzed by quasi-static capacitance–voltage and electron spin resonance measurements, respectively. The D it and Pb0 center density of wafers without hydrocarbon molecular ions increased after annealing at 700 °C. On the other hand, the D it and Pb0 center density of wafers implanted with hydrocarbon molecular ions decreased after annealing at 700 °C. We also estimated the activation energy to be 1.67 eV for the hydrogen termination reactions with hydrogen molecules and Si dangling bonds at the SiO2/Si interface. The termination effects of the hydrocarbon-molecular-ion-implanted epitaxial silicon wafers can contribute to the high electrical performance of CMOS image sensors.

We propose a process for the fabrication of a silicon-on-insulator (SOI) wafer with a silicon carbide (SiC) insulator layer by combining plasma-enhanced chemical vapor deposition and surface-activated bonding without thermal stress to obtain sufficient thermal conductivity for self-heating power and high-frequency device applications. The thermal conductivity of the deposited SiC layer is twice that of a silicon dioxide (SiO2) layer, and the breakdown electric field of this layer is 10–11 MV cm−1, the same as that of a SiO2 layer. In addition, the bonding interface between the silicon layer and the deposited SiC insulator layer has no voids or punch-out dislocations. Therefore, the SOI wafer with a SiC layer has high thermal conductivity and breakdown electric field; this SOI wafer and its fabrication process will be important for the realization of next-generation self-heating devices such as power and high-frequency devices.

We investigate the amorphous formation behavior on hydrocarbon molecular ion implantation conditions such as hydrocarbon molecular ion size by X-ray photoelectron spectroscopy (XPS). The cross-sectional radius of the amorphous region was obtained from the peak intensity of the amorphous component in Si 2p spectra analyzed by XPS, and using columnar formula for a model. We confirmed that the cross-sectional radius of the amorphous region formed by hydrocarbon molecular ions differs greatly from that formed by monomer carbon ions, and increases by 0.078 nm as the number of carbon atoms composing the hydrocarbon molecular ion increases. The dependence of amorphous formation on the hydrocarbon molecular size is related to the C–C binding distance, and the ratio of increase in the amorphous cross-sectional radius corresponds to half of the C–C binding distance. Therefore, the collision behavior of hydrocarbon molecular ions during implantation predominantly influence the size of hydrocarbon molecular ions.

Using proton (H+)-implanted silicon (Si) substrates, we clarified the effect of dangling bond termination by hydrogen on the interfacial strain in the silicon dioxide (SiO2)/Si system. The variations of the SiO2/Si interface structure caused by H+ implantation into a SiO2/Si sample and by hydrogen out-diffusion heat treatment were analyzed by high-resolution synchrotron radiation photoemission spectroscopy. We found that H+ implantation into the SiO2/Si sample [intentional generation of the interfacial dangling bonds] can increase the intensity of the strained-Si peaks in the Si 2p photoemission spectrum. In addition, our study revealed that the strained Si atom amount and dangling bond density are reduced by hydrogen out-diffusion heat treatment. These findings suggest that the increase/decrease in the dangling bond density by H atoms results in the increase/decrease in local strain field around a dangling bond, thereby changing the length of the Si–Si bonds beneath the SiO2/Si interface. Out-diffused hydrogen seems to play roles to not only reduce the dangling bond density but also relax the local strain at the SiO2/Si interface. The hydrogen termination effect is expected to have an advantage in structural stability in the SiO2/Si system as compared with the pure thermal termination effect.

We have developed hydrocarbon molecular ion implanted epitaxial wafers for advanced CMOS image sensors. The hydrocarbon molecular ion implanted region has the highest gettering capability for metallic impurities and plays a barrier role for-diffused oxygen atoms from CZ grown Si substrate. In addition, implanted hydrogen atoms diffuse out and passivate process-induced defects in device process. It is previously reported that high-dose hydrocarbon molecular ion implantation enhances these characteristics even more. However in high-dose implantation condition, stacking faults are formed in epitaxial layer. In this study, the flash lamp annealing is investigated as recovery annealing after high-dose implantation. The flash lamp annealing is expected to change the re-crystallization behavior of amorphous layer and suppress the formation of stacking faults in epitaxial layer without diffusion of hydrogen atoms from implanted region. Consequently, by the flash lamp annealing after high-dose implantation the stacking faults in epitaxial layer are perfectly suppressed. Furthermore, high concentration hydrogen remains in implanted region after FLA and epitaxial growth process due to change of defect morphology. Without recovery annealing after high-dose implantation, amorphous layer is re-crystallized in ramp-up time of epitaxial growth process and clamshell type defects are formed. Conversely, by flash lamp annealing high density small defect are formed. These high density small defects are contributed to remain hydrogen atoms in implanted region.

The metallic impurity gettering capability of hydrocarbon molecular ion-implanted silicon wafers was demonstrated by using a complementary metal-oxide-semiconductor (CMOS) image sensor that provides floating diffusion amplifier voltage (V dark ) output signals under dark conditions. It was found that the V dark output signals of hydrocarbon molecular ion implanted p/p− and p/p+ silicon wafers did not increase after intentional contamination with Fe, Cu, Ni and Co metallic impurities. This indicates that the hydrocarbon molecular ion implanted silicon wafers were able to getter metallic impurities in the projection range of hydrocarbon molecular ion implantation during CMOS device fabrication. It was also found that the hydrocarbon-molecular-ion-implanted silicon wafers had improved electrical device performance factors, such as pn-junction leakage current, in actual device process lines. This gettering technique has no dependence on the silicon wafer substrates such as whether it is composed of bulk por p+ boron doped silicon crystals. We believe that the hydrocarbon-molecular-ion-implanted silicon wafers will be advantages for advanced CMOS image sensor fabrication.

The difference in agglomerate defects formed by carbon-cluster-ion-implanted Czochralski (CZ)-Si and epitaxial Si has been investigated using atom probe tomography. In the previous work, we reported on the strong gettering capability in implanted epitaxial Si. We found that the distribution of O and C atom concentrations on agglomerates differs between CZ-Si and epitaxial Si. This suggests that a C agglomerate, which grows without including O atoms, results in strong gettering efficiency for Fe.

We describe the effect of microwave heating on C 3 H 5 carbon cluster ion implanted epitaxial wafers using a high dose amount of carbon cluster ion implantation condition. A high dose amount condition of C 3 H 5 carbon cluster ion implantation generates implantation-related defects, such as stacking faults, after epitaxial growth. Therefore, we investigated the control and reduction of stacking faults using the microwave heating technique. We revealed that this technique can control and reduce stacking faults by selectively heating of the carbon cluster ion implantation projection range.

CMOS image sensor has been widely used for ubiquitous devices. However, CMOS image sensor devices performance is dramatically influenced by process induced defects such as metallic impurities contamination at devices active region during CMOS devices process. Thus, it is extremely important to study metallic impurities influence on CMOS image sensor devices performance and to develop effectiveness metallic impurities gettering techniques. We introduce our new proximity gettering technique for advanced CMOS image sensor using carbon cluster ion implantation technique. Furthermore, we demonstrated that the carbon cluster ion implanted silicon wafer has high gettering capability of metal, oxygen and hydrogen impurity during CMOS image sensor devices fabrication process.

We have characterized CH3O ion-implanted epitaxial wafers in device fabrication processes. We confirmed that the CH3O ion-implanted wafers can reduce the density of white spot defects in CMOS image sensors. Evaluation of the CH3O ion-implanted region before and after device fabrication processes which included heat treatment and ion implantation, showed that two types of defects, namely stacking faults and carbon-related defects, exist in the CH3O ion implantation region getter the metallic impurities during device fabrication processes. In particular, it was clarified that stacking fault defects existing in the CH3O ion-implanted region are powerful gettering sinks for oxygen. Thus, it was considered that two types of gettering sink formed by CH3O ion implantation contribute to the reduction in the density of white spot defects. We believe that these characteristics can contribute to the improvement of fabrication processes for advanced CMOS image sensors.

We propose a fabrication process for a silicon on insulator (SOI) wafer with a diamond buried oxide (BOX) layer by combining nanodiamond-seeding deposition and a surface-activated bonding technique for high-frequency and power device applications. The diamond layer was deposited on a base wafer by the spin-coating of nanodiamonds and microwave-plasma-enhanced chemical vapor deposition. The thermal conductivity of this deposited diamond layer was three times that of a conventional SiO2 layer. A silicon wafer was then bonded to the diamond layer at room temperature in ultrahigh vacuum without forming any voids. Additionally, this SOI wafer was used to fabricate devices at 1000 °C. Therefore, we believe that this SOI wafer with a diamond BOX layer and its fabrication process are important for the realization of self-heating devices such as next-generation high-frequency and power devices.

Complementary metal oxide semiconductor (CMOS) image sensors have become widely used ubiquitous devices such as smart phone and personal computer type tablets. Consumer markets strongly demands more high sensitivity imaging and more high speed image data processing for achieving advanced CMOS image sensor fabrication. However, there are some serious improvement technical issues in CMOS image sensor fabrication process. Extremely important technical issue is metallic impurity contaminated device active region during device fabrication process such as high temperature rapid thermal annealing, dry etching and plasma heat treatment. Metallic impurities formed deep energy level defects in the silicon band-gap. Thus, these deep energy level defects strongly affects electrical device characteristic such as pn-junction leakage current, recombination lifetime and gate oxide breakdown voltage. Another technical issue is oxygen impurity out-diffused to the device active region from a Czochralski (CZ) grown silicon substrate during device heat process. Oxygen impurity formed oxygen related deep energy level defects in the device active region of photo-diode space charge region and transfer transistor gate channel region. These oxygen related defects strongly influenced on electrical device performance such as image lag. Therefore, in recent years, CMOS image sensor manufacturers have strongly demanded silicon wafers with the highest metal and oxygen impurities gettering capability during CMOS device processes. In response, we have developed a novel gettering wafer production concept using a hydrocarbon molecular ion implantation technique for advanced CMOS image sensors [1][2][3]. This technique can implant a silicon wafer surface simultaneously with carbon and hydrogen elements that form the projection range using a hydrocarbon compound molecular gas source. In our previous study, it was found that a hydrocarbon molecular ion implanted silicon wafer had three unique characteristics for high performance of advanced CMOS image sensors. First, a hydrocarbon molecular ion projection range has high gettering capability of metallic impurities [1][2][4]. Second, this projection range also has a diffusion barrier effect for oxygen impurities out-diffusing to the device active region from a CZ grown silicon wafer substrate [5]. Third, it is expected that diffusing hydrogen to the device active region from the hydrogen of hydrocarbon molecular ions gettered in the projection range during the device fabrication process will have a passivation effect on unreconstructed surface dangling bonds and Si/SiO2 interface state densities such as local oxidation of silicon or shallow trench isolation [6][7]. Moreover, we achieved more improvement for gettering capability of hydrocarbon molecular ion implanted silicon wafer which formed epitaxial layer without epitaxial growth process using room temperature direct bonding technique. In this presentation, we demonstrate that a hydrocarbon molecular ion implanted silicon wafers using room temperature direct bonding technique has high gettering capability characteristics for transition metal and light element impurities such as oxygen, and hydrogen during the CMOS image sensor fabrication process. References [1] K.Kurita, et al , Jpn. J. Appl. Phys. 55,121301(2016)/DOI.org/10.7567/JJAP.55.121301. [2] K.Kurita, et al , Phys.Status.Solidi A, 1700216(2017)/DOI 10.1002/pssa.201700216. [3] R.Okuyama, et al: Jpn. J. Appl. Phys. 57,011301(2018)/DOI.org/10.7567/JJAP.57.011301. [4] A.Onaka, et al: Jpn. J. Appl. Phys. 57,021304(2018)/DOI.org/10.7567/JJAP.57.021304. [5] K.Kurita, et al , J. Surf. Sci. Soc. Jpn.,Vol.37,p104(2016)/DOI.org/10.1380/jsssj.37.104. [6] R.Okuyama, et al: Jpn. J. Appl. Phys. 56,025601(2017)/DOI.org/10.7567/JJAP.56.02560. [7] R.Okuyama, et al , Phys.Status.Solidi C, 1700036(2017)/DOI 10.1002/pssc.201700036.

We propose a fabrication process for silicon wafers by combining carbon-cluster ion implantation and room-temperature bonding for advanced CMOS image sensors. These carbon-cluster ions are made of carbon and hydrogen, which can passivate process-induced defects. We demonstrated that this combination process can be used to form an epitaxial layer on a carbon-cluster ion-implanted Czochralski (CZ)-grown silicon substrate with a high dose of 1 × 1016 atoms/cm2. This implantation condition transforms the top-surface region of the CZ-grown silicon substrate into a thin amorphous layer. Thus, an epitaxial layer cannot be grown on this implanted CZ-grown silicon substrate. However, this combination process can be used to form an epitaxial layer on the amorphous layer of this implanted CZ-grown silicon substrate surface. This bonding wafer has strong gettering capability in both the wafer-bonding region and the carbon-cluster ion-implanted projection range. Furthermore, this wafer inhibits oxygen out-diffusion to the epitaxial layer from the CZ-grown silicon substrate after device fabrication. Therefore, we believe that this bonding wafer is effective in decreasing the dark current and white-spot defect density for advanced CMOS image sensors.

The effect of oxygen (O) concentration on the Fe gettering capability in a carbon-cluster (C3H5) ion-implanted region was investigated by comparing a Czochralski (CZ)-grown silicon substrate and an epitaxial growth layer. A high Fe gettering efficiency in a carbon-cluster ion-implanted epitaxial growth layer, which has a low oxygen region, was observed by deep-level transient spectroscopy (DLTS) and secondary ion mass spectroscopy (SIMS). It was demonstrated that the amount of gettered Fe in the epitaxial growth layer is approximately two times higher than that in the CZ-grown silicon substrate. Furthermore, by measuring the cathodeluminescence, the number of intrinsic point defects induced by carbon-cluster ion implantation was found to differ between the CZ-grown silicon substrate and the epitaxial growth layer. It is suggested that Fe gettering by carbon-cluster ion implantation comes through point defect clusters, and that O in the carbon-cluster ion-implanted region affects the formation of gettering sinks for Fe.

Polycrystalline anatase TiO2 films have been successfully deposited on Si(100) substrates at a temperature of 250 °C at growth rates of higher than 10 A/s by atmospheric chemical vapor deposition with titanium tetraisopropooxide as a precursor and H2O2 vapor as an oxidant. The H2O2 vapor enhances the crystallization of the TiO2 amorphous network in the grown films. We also show that TiO2 film obtained by low-temperature deposition with the H2O2 vapor exhibits a photocatalytic activity for the naturally adsorbed carbon impurity on its surface, indicating the applicability of the present technique to the field of photocatalyst coating. The present technique is also applicable to the deposition of anatase TiO2 films on flexible polyimide tapes.

We investigated the gettering efficiency of iron and nickel in Czochralski (CZ) silicon wafers depending on crystalline nature such as interstitial-silicon-dominant or vacancy-dominant crystal growth. After a typical heat treatment for dynamic random access memories (DRAMs), the density of silicon oxide precipitates in the vacancy-dominant crystal regions was approximately two orders higher than interstitial-silicon-dominant crystal regions. After a DRAM heat treatment, irons were preferably gathered at vacancy-dominant crystal region while nickels were selectively at only an interstitial-silicon-dominant crystal region. Silicon wafers designed with extreme gettering ability via rapid thermal annealing (RTA) at 1150 °C for 10 s using NH 3 and Ar gas mixture produced the “M” shape of oxygen precipitates in which the peak density of the precipitates was in the range of ∼3 × 10 10 cm −3 while the bulk density was in the range of ∼2 × 10 9 cm −3 . The RTA silicon wafer completely eliminated irons and nickels from the wafer surface that are gathered at oxygen precipitates in silicon bulk during a DRAM heat treatment.