Method for producing a semiconductor epiaxial wafer and method for producing a solid-state imaging device

Abstract

A method for producing a semiconductor epitaxial wafer (100), comprising: a first step of irradiating a surface (10A) of a semiconductor wafer (10) with cluster ions (16) containing hydrogen and carbon as constituent elements to form a modification layer (18, 18') formed from a constituent element of the cluster ions (16) containing hydrogen in a surface part of the semiconductor wafer (10) as a solid solution; a second step of irradiating the semiconductor wafer (10) with microwaves (W) of a frequency of 300 MHz or more and 300 GHz or less after the first step to heat the semiconductor wafer (10);and a third step of forming an epitaxial layer (20) on the modification layer (18, 18') of the semiconductor wafer (10) after the second step, wherein a beam current value of the cluster ions (16) in the first step is 50 µA or more and 5000 µA or less, and wherein the semiconductor wafer (10) is a silicon wafer.

Description

Technical field

[0001] The present disclosure relates to a method for producing a semiconductor epiaxial wafer and a method for producing a solid-state imaging device. background

[0002] A semiconductor epitaxial wafer, obtained by forming an epitaxial layer on a semiconductor wafer, is used as a component substrate for producing various semiconductor devices, such as a metal-oxide-semiconductor field-effect transistor (MOSFET), a dynamic random access memory (DRAM), a power transistor, and a back-illuminated solid-state imaging device.

[0003] For example, a back-illuminated solid-state imaging device can capture ambient light directly into a sensor to obtain a sharper image or video even in a dark place, by placing a wiring layer and the like beneath a sensor portion. Therefore, back-illuminated solid-state imaging devices have been widely used in digital video cameras and mobile phones, such as smartphones, in recent years.

[0004] With the increasing improvements and performance advancements of semiconductor devices in recent years, semiconductor epiaxial wafers used as device substrates are expected to be of higher quality to enhance device properties. To further improve device properties, crystal quality enhancement techniques such as oxygen precipitation heat treatment, getter techniques to prevent heavy metal contamination during epitaxial growth, and others have been employed.

[0005] For example, JP 2013-197373 A (PTL 1) describes a technique for controlling oxygen precipitation heat treatment conditions when oxygen precipitation heat treatment is performed on a silicon substrate and an epitaxial layer is then formed to produce an epitaxial wafer. Using the technique described in PTL 1, the leakage current of the epitaxial wafer after the formation of the epitaxial layer can be limited to 1.5E-10A or less.

[0006] Furthermore, we have proposed the following technique with reference to getters in WO 2012 / 157162 A1 (PTL 2): A method for producing a semiconductor epitaxial wafer comprises the following: a first step of irradiating a surface of a semiconductor wafer with cluster ions to form a modification layer formed from a constituent element of the cluster ions contained as a solid solution in a surface part of the semiconductor wafer; and a second step of forming an epitaxial layer on the modification layer of the semiconductor wafer. List of prior art patent literature PTL 1: JP 2013-197373 A PTL 2: WO 2012 / 157162 A1 Brief description (Technical problem)

[0007] As described in PTL 1 and PTL 2, various attempts have been made to improve the quality of semiconductor epitaxial wafers. During this time, the crystallinity within the epitaxial layer of the semiconductor epitaxial wafer was considered sufficiently high, and no technique for further improving this crystallinity had yet been proposed. Through the following research and experimental results, we have found that an improvement in device properties (for example, a reduction in white spot defects in the case of solid-state imaging devices) can very likely be achieved if the crystallinity within the epitaxial layer can be further increased.

[0008] It is known that even when hydrogen, a light element, is ion-implanted into a semiconductor wafer, it diffuses due to the heat treatment during the formation of an epitaxial layer. When the hydrogen concentration profile of a semiconductor epitaxial wafer, obtained by implanting hydrogen ions into the wafer under typical conditions and then forming an epitaxial layer on the wafer's surface where the hydrogen ion implantation area was formed, is actually observed, the hydrogen concentration is lower than the detection limit by secondary ion mass spectrometry (SIMS).

[0009] On the other hand, our research has newly demonstrated that if a surface of a semiconductor wafer is irradiated with hydrogen in the form of cluster ions to form a modification layer formed from the constituent element of the cluster ions contained as a solid solution in a surface part of the semiconductor wafer, the use of suitable irradiation conditions enables hydrogen to be localized in the modification layer, even after the formation of an epitaxial layer.

[0010] We observed the difference in crystallinity between an epitaxial layer of a semiconductor epitaxial wafer with hydrogen localized in a modification layer and an epitaxial layer of a semiconductor epitaxial wafer whose hydrogen concentration peak is defined by typical SIMS (e.g., hydrogen concentration detection limit: 7.0 × 10⁻⁶). 16 atoms / cm² 3) is not detectable by the cathode luminescence (CL) method. The CL method is a technique for measuring crystal defects by irradiating a sample with an electron beam to detect excitation light at a transition from near the bottom of the conduction band to near the top of the valence band.

[0011] In the first semiconductor epitaxial wafer, a peak in transverse optical (TO) line intensity was observed in the epitaxial layer. In the second semiconductor epitaxial wafer, a tendency was observed for the TO line intensity to gradually decrease in thickness from the interface between the semiconductor wafer and the epitaxial layer to the surface of the epitaxial layer. A TO line is a spectrum specific to a silicon element, corresponding to the band gap of silicon, and is observed using the chromatography (CL) method. Higher TO line intensity indicates higher crystallinity of silicon.

[0012] We have thus learned that the first semiconductor epitaxial wafer exhibits better crystallinity in the epitaxial layer than the second semiconductor epitaxial wafer. Next, assuming device formation using a semiconductor epitaxial wafer, we observed the TO line intensity under heat treatment simulating device formation. We consequently found that, even after the heat treatment simulating device formation, the epitaxial layer of the first semiconductor epitaxial wafer, although the TO line tip is retained, exhibits approximately the same level of TO line intensity as the epitaxial layer of the second semiconductor epitaxial wafer in regions other than the tip.It was accordingly demonstrated that the semiconductor epitaxial wafer with hydrogen localized in the modification layer exhibits a high overall crystallinity of the epitaxial layer after the formation of the epitaxial layer, compared to the semiconductor epitaxial wafer whose hydrogen concentration peak is not detectable. Based on the trend of changes in hydrogen concentration and TO line intensity between before and after the heat treatment simulating device formation, it can be considered that, as a result of performing the heat treatment simulating the device formation step, hydrogen present at a high concentration in the surface portion of the semiconductor wafer passivates point defects in the epitaxial layer, thereby improving the crystallinity of the epitaxial layer.

[0013] This led us to hypothesize that hydrogen localized in the semiconductor epitaxial wafer passivates defects in the epitaxial layer when the semiconductor epitaxial wafer undergoes the device manufacturing step, thereby improving device quality. If the peak hydrogen concentration in the surface portion of the semiconductor wafer can be increased, the passivation effect is likely to be stronger.

[0014] It could therefore be helpful to provide a semiconductor epitaxial wafer production process that can increase the peak concentration of hydrogen in a surface part of a semiconductor wafer after formation of an epitaxial layer. (Solution to the problem)

[0015] We conducted extensive research to solve the aforementioned problem. Since hydrogen is a light element, it diffuses considerably when an epitaxial layer is formed on the modification layer, because this formation involves high-temperature heat treatment, as previously mentioned. Accordingly, we carried out further research and conceived an idea in which the semiconductor wafer is irradiated with electromagnetic waves of a predetermined frequency after cluster-ion irradiation and before the formation of the epitaxial layer. This heating of the semiconductor wafer controls the diffusion of hydrogen localized in the modification layer.We discovered that the diffusion of hydrogen into the surface of the semiconductor wafer can be suppressed by this electromagnetic irradiation, even after epitaxial layer formation, and consequently the peak hydrogen concentration can be significantly increased compared to the case where no electromagnetic irradiation is performed. Accordingly, we provide the following.

[0016] A method for producing a semiconductor epitaxial wafer according to the present disclosure comprises the following: a first step of irradiating a surface of a semiconductor wafer with cluster ions containing hydrogen as a constituent element to form a modification layer formed from a constituent element of the cluster ions containing hydrogen in a surface part of the semiconductor wafer as a solid solution; a second step of irradiating the semiconductor wafer with electromagnetic waves of a frequency of 300 MHz or more and 3 THz or less after the first step to heat the semiconductor wafer; and a third step of forming an epitaxial layer on the modification layer of the semiconductor wafer after the second step.

[0017] The cluster ions preferably contain carbon as a constituent element.

[0018] Preferably, the beam current of the cluster ions in the first step is 50 µA or more. Preferably, the beam current of the cluster ions in the first step is 5000 µA or less.

[0019] Preferably, the semiconductor wafer is a silicon wafer.

[0020] A method for producing a solid-state imaging device according to the present disclosure comprises forming a solid-state imaging device on an epitaxial layer of a semiconductor epitaxial wafer produced by one of the above-mentioned methods for producing a semiconductor epitaxial wafer. (Beneficial effect)

[0021] According to the present disclosure, a semiconductor wafer is irradiated with electromagnetic waves of a predetermined frequency to heat the semiconductor wafer. Accordingly, a semiconductor epitaxial wafer production process can be provided which can increase the peak concentration of hydrogen in a surface portion of a semiconductor wafer after the formation of an epitaxial layer. List of characters

[0022] The following applies to the accompanying drawings: Fig. Figure 1 is a schematic section diagram illustrating a method for producing a semiconductor epiaxial wafer 100 according to one of the disclosed embodiments; Fig. 2A is a diagram in which a TEM section photograph of a silicon wafer after irradiation with cluster ions and a graph illustrating the concentration profile of both carbon, hydrogen and oxygen in the part corresponding to the TEM section photograph are superimposed in the reference experimental example 1; Fig. 2B is a diagram in which a TEM section photograph of a silicon wafer after microwave heating and a graph illustrating the concentration profile of both carbon, hydrogen and oxygen in the part corresponding to the TEM section photograph are superimposed in the reference experimental example 1; Fig. Figure 3A is a graph illustrating the concentration profile of a silicon epitaxial wafer according to Example 1; Fig. Figure 3B is a graph illustrating the concentration profile of a silicon epitaxial wafer according to comparison example 1; and Fig. Figure 4 is a graph comparing the peak concentration values ​​of the silicon epitaxial wafer according to Example 1 and the silicon epitaxial wafer according to Comparison Example 1. Detailed description

[0023] One of the disclosed embodiments is described in detail below with reference to the drawings. Fig. 1 represents the thickness of a semiconductor wafer. 10 , a modification layer 18 (18') and an epitaxial layer 20 For the sake of simplicity, the figures are exaggerated and deviate from the actual thickness ratio. (Method for producing a semiconductor epiaxial wafer)

[0024] As in Fig. Figure 1 illustrates a method for producing a semiconductor epiaxial wafer. 100According to one of the disclosed embodiments, the following: a first step of irradiating a surface 10A of the semiconductor wafer 10 with cluster ions 16 , which contain hydrogen as a component element to form the modification layer 18 to form clusters consisting of a component element of the cluster ions 16 , which contains hydrogen, in a surface part of the semiconductor wafer 10 as a solid solution is formed (step A and step B in Fig. 1); a second step of irradiating the semiconductor wafer 10 with electromagnetic waves W a frequency of 300 MHz or more and 3 THz or less after the first step to process the semiconductor wafer 10 to warm up (step C and step D in Fig. 1); and a third step in the formation of the epitaxial layer 20 on the modification layer 18' of the semiconductor wafer 10after the second step (step E in Fig. 1) Step E in Fig. Figure 1 is a schematic cross-sectional diagram of the semiconductor epiaxial wafer. 100 , which is obtained as a result of this manufacturing process. The epitaxial layer 20 is a component layer used to fabricate a semiconductor device, such as a back-illuminated solid-state imaging device. We assume that the modification layer 18 as a result of the second step, it is altered in a certain way (described in more detail later). To distinguish between before and after the change, the modification layer that underwent the second step is referred to as "Modification Layer 18'".

[0025] The semiconductor wafer 10For example, a bulk single-crystal wafer made of silicon or a compound semiconductor (GaAs, GaN, SiC) lacks an epitaxial layer on any surface. A bulk single-crystal silicon wafer is typically used when fabricating a back-illuminated solid-state imaging device. When the semiconductor wafer 10 A single-crystal silicon ingot grown by the Czochralski process (CZ process) or the zone melting process (FZ process) and sliced ​​into wafers using a wire saw or similar device can be used. To achieve higher getter capability, carbon and / or nitrogen can be added to the semiconductor wafer 10. Furthermore, any dopant can be added to the semiconductor wafer. 10 added at a predetermined concentration to create an n + -Type- or a p + -Type- or an n - -Type- or p --Type substrate to obtain.

[0026] When the semiconductor wafer 10 An epitaxial semiconductor wafer, formed by creating an epitaxial semiconductor layer on the surface of a bulk semiconductor wafer, can be used. An example is a silicon epitaxial wafer obtained by creating an epitaxial silicon layer on the surface of a bulk single-crystal silicon wafer. This epitaxial silicon layer can be created under typical conditions using the CVD process. The thickness of the epitaxial layer is preferably in the range of 0.1 µm to 20 µm and more preferably in the range of 0.2 µm to 10 µm.

[0027] One of the characteristic steps of this revelation is the first step in step A from Fig. 1. In this description, “cluster ions” refers to a product obtained by applying a positive or negative charge to a cluster, which is an aggregate of several atoms or molecules, to ionize the cluster. A cluster is an aggregate of several (typically about 2 to 2000) atoms or molecules combined together.

[0028] If a silicon wafer, which is a type of semiconductor wafer, is irradiated with cluster ions consisting, for example, of carbon and hydrogen, the cluster ions reach 16When applied to the silicon wafer, the applied ions immediately generate a high-temperature state of approximately 1350 °C to 1400 °C due to the energy, and the silicon melts. The silicon then cools rapidly, and carbon and hydrogen form solid solutions in the silicon wafer near the surface. Accordingly, the "modification layer" in this description refers to a layer in which constituent elements of the applied ions form solid solutions at interstitial or substitution sites in the surface portion of the semiconductor wafer. The concentration profile of carbon in the depth direction of the silicon wafer, as determined by secondary ion mass spectrometry (SIMS), is sharper than that of monomer ions, although it depends on the accelerating voltage and the cluster size of the cluster ions. The thickness of the region (i.e., the modification layer) where the applied carbon is localized is approximately 500 nm or less (e.g.,approximately 50 nm to 400 nm). If constituent elements of the cluster ions . 16 The modification layer contains an element that contributes to gettering. 18 also as a getter location. Accordingly, the modification layer 18 , which consist of the component element (or elements) of the cluster ions 16 , which contains hydrogen, is formed as a solid solution by irradiation with the cluster ions 16 in the surface part of the semiconductor wafer 10 educated.

[0029] After the first step, that is, after the formation of the modification layer 18 , the second step of irradiating the semiconductor wafer 10 performed with electromagnetic waves of a frequency of 300 MHz or more and 3 THz or less to process the semiconductor wafer 10 to warm up (step C and step D in Fig. 1).

[0030] Electromagnetic waves with a frequency of 300 MHz or more and 3 THz or less are referred to as "microwaves" in a broader sense. Heating the semiconductor wafer 10 Irradiation with electromagnetic waves at a frequency of 300 MHz or higher and 3 THz or lower is referred to as "microwave heating" or "microwave annealing". In this description, the heating of the semiconductor wafer 10 by irradiation with electromagnetic waves of a frequency of 300 MHz or more and 3 THz or less, hereinafter referred to as "microwave heating". This step can be carried out using a commercially available microwave heating element and the constituent elements of the cluster ions 16 , which are in the modification layer 18These localized areas are excited by vibration through irradiation with electromagnetic waves, resulting in local heating that controls the diffusion of hydrogen. The modification layer 18 The surface is damaged by cluster ion irradiation. Depending on the irradiation conditions, an amorphous region may form within the modification layer. Microwave heating can repair the damage caused by cluster ion irradiation, restore crystallinity, and thus recover from surface roughness deterioration. 10A of the semiconductor wafer 10The conditions for electromagnetic irradiation to perform microwave heating are not limited, as long as the diffusion of hydrogen localized in modification layer 18 can be controlled. For example, electromagnetic irradiation can be performed in a range where the temperature of the semiconductor wafer is 50 °C or more and 1000 °C or less. The frequency of the applied electromagnetic waves can range from the millimeter wave to the infrared region. For example, the frequency of the applied electromagnetic waves can be 300 MHz or more and 300 GHz or less. The irradiation time of the electromagnetic waves can be, for example, 10 seconds or more and 30 minutes or less. The output of the applied electromagnetic waves can be, for example, 5 W or more and 12 kW or less.This step is one of the characteristic steps in this revelation, like the first step. Through this step, the modification layer is created. 18 to the modification layer 18'. The technical significance of carrying out these two steps will be described in detail later.

[0031] After the second step, the third step of forming the epitaxial layer begins. 20 on the modification layer 18' of the semiconductor wafer 10 performed (Step E in Fig. 1) The epitaxial layer 20For example, an epitaxial silicon layer can be formed under typical conditions. In this case, a source gas, such as dichlorosilane or trichlorosilane, can be introduced into the chamber using hydrogen as the carrier gas and epitaxially deposited onto the semiconductor wafer by the CVD process at a temperature in the range of approximately 1000 °C to 1200 °C, although the growth temperature varies depending on the source gas used. 10 The epitaxial layer is preferably between 1 µm and 15 µm thick. 20 If the concentration is less than 1 µm, there is a possibility that an outwardly directed doping concentration from the semiconductor wafer 10 a change in the specific resistance of the epitaxial layer 20 caused by the thickness of the epitaxial layer. 20If the difference is greater than 15 µm, there is a possibility that the spectral sensitivity characteristics of the solid-state imaging device may be affected.

[0032] The technical significance of carrying out the first and second steps in this revelation is described in more detail below.

[0033] Hydrogen ions diffuse because they are a light element, due to the heat treatment during the formation of the epitaxial layer. 20 or the like, easily move outwards and tend not to remain in the semiconductor wafer after the formation of the epitaxial layer. Considering this, the cluster ions 16 , which contain hydrogen as a constituent element, applied to the modification layer 18to form an epitaxial layer in which hydrogen is localized. We have experimentally discovered that by adjusting the cluster-ion irradiation conditions, hydrogen can be made to remain in the surface portion (i.e., in the modification layer) of the semiconductor wafer, even after the formation of the epitaxial layer. However, we have simultaneously discovered that if the epitaxial layer 20 Following cluster ion irradiation, the hydrogen peak concentration of the concentration profile in the depth direction (hereinafter simply referred to as "peak hydrogen concentration") decreases to approximately 0.5% of the peak hydrogen concentration immediately after cluster ion irradiation. Here, "remaining hydrogen" means that the peak hydrogen concentration after the formation of the epitaxial layer... 20such a level is detectable by SIMS. In this description, the "hydrogen concentration profile in the depth direction" refers to the hydrogen concentration distribution in the depth direction as measured by SIMS. For example, the peak concentration of hydrogen is detectable by magnetic sector SIMS if it is 7.0 × 10 16 atoms / cm² 3 or more.

[0034] We have experimentally discovered that the peak hydrogen concentration can be increased by performing the second step of this revelation even after the formation of the epitaxial layer. 20 compared to the case where the second step is omitted, the increase can be higher. More detailed research into the cause of this increase led us to believe that it stems from some kind of change, such as a phase transformation, in the modification layer. 18This results in the following: After performing cluster-ion irradiation on the silicon wafer under the same conditions (the details of the experimental conditions are described in more detail in the reference experimental examples), we obtained a diagram in which a TEM section photograph of the silicon wafer and a graph illustrating the concentration profile of carbon, hydrogen, and oxygen in the part corresponding to the TEM section photograph are superimposed ( Fig. 2A). We also received a diagram in which a TEM cross-sectional photograph of the silicon wafer after microwave heating and a graph illustrating the concentration profile of carbon, hydrogen, and oxygen in the part corresponding to the TEM cross-sectional photograph are superimposed ( Fig. 2B). The concentration profiles in Fig. 2A and Fig. 2B were detected by quadrupole SIMS. As shown in Fig. As can be seen in 2A, an amorphous region was formed near the cluster ion implantation area (at a depth of approximately 40 nm to 80 nm). As can be seen from Fig. As can be seen in Figure 2B, the crystallinity of the amorphous region was partially restored as a result of microwave heating. In Figure 2A, which does not include microwave heating, the hydrogen concentration decreases in a region deeper than the modification layer. 18 rapidly. In Figure 2B, which includes microwave heating, the rate of decrease in hydrogen concentration is gentler, demonstrating that hydrogen is trapped in the modification layer 18'. From these results and the difference in the peak hydrogen concentration after the formation of the epitaxial layer (and also with reference to Fig. 3A, Fig. 4B and Fig. 4, which are described later in the examples) we come to the assumption that the modified modification layer 18' has a higher hydrogen trapping function than the modification layer 18 exhibits, making it possible to increase the peak concentration of hydrogen after the formation of the epitaxial layer.

[0035] As described above, according to this embodiment the semiconductor epiaxial wafer 100 with an increased peak concentration of hydrogen in the surface portion of the semiconductor wafer after the formation of the epitaxial layer. A semiconductor device produced using such a semiconductor epitaxial wafer. 100 including the epitaxial layer 20 The product is manufactured and exhibits improved component properties.

[0036] After hydrogen diffusion control in the second step, the semiconductor wafer can 10Before the third step, the semiconductor wafer undergoes a recovery heat treatment to restore crystallinity. This recovery heat treatment can be performed, for example, by... 10 The material is held in an epitaxy unit at a temperature of 900 °C or higher and 1100 °C or lower for 10 minutes or more and 60 minutes or less, respectively, in an atmosphere of nitrogen gas, argon gas, or the like. The recovery heat treatment can be performed separately from an epitaxy unit, for example, using a rapid temperature rise / fall heat treatment unit, such as rapid thermal annealing (RTA) or rapid thermal oxidation (RTO).

[0037] The cluster ion irradiation mode in this disclosure is described below.

[0038] There are different types of clusters, depending on the combination method. For example, cluster ions can be generated by known methods described in the following documents: Gas cluster beam generation methods are described in (1) JP H9-41138 A and JP H4-354865 A. Ion beam generation methods are described in (1) Junzo Ishikawa, "Charged particle beam engineering", Corona Publishing, ISBN 978-4-339-00734-3, (2) The Institution of Electrical Engineers of Japan, "Electron / Ion Beam Engineering", Ohmsha, ISBN 4-88686-217-9, and (3) "Cluster Ion Beam - Basic and Applications", The Nikkan Kogyo Shimbun, ISBN 4-526-05765-7. Typically, a Nielsen ion source or a Kaufman ion source is used to generate positively charged cluster ions, and a high-current negative ion source using volume production is used to generate negatively charged cluster ions.

[0039] Regarding the constituent elements of the applied cluster ions 16, the other constituent elements are not restricted as long as hydrogen is present. Examples of constituent elements of cluster ions 16 besides hydrogen include carbon, boron, phosphorus, and arsenic. With regard to achieving a high getter capability, the cluster ions contain... 16 preferentially carbon as a constituent element. The modification layer 18 (The modification layer 18' after the second step) containing carbon as a solid solution acts as a strong getter site. This is because carbon atoms at a lattice site have a smaller covalent radius than silicon single crystals, thus forming a compression site in the silicon crystal lattice that attracts interstitial impurities. Furthermore, carbon containing a solid solution in the modification layer traps 18forms if the cluster ions 16 Carbon, as a constituent element, traps hydrogen. This trapping function is likely stronger in the 18' modification layer. Therefore, the trapping of carbon is also desirable with regard to increasing the peak hydrogen concentration.

[0040] It is also desirable for the constituent elements of the cluster ions to include one or more elements other than hydrogen and carbon. In particular, it is desirable to use one or more dopant elements selected from the group consisting of boron, phosphorus, arsenic, and antimony, in addition to hydrogen and carbon. Since the types of metals that can be efficiently gettered vary depending on the types of elements forming solid solutions, a wider variety of metal impurities can be addressed by incorporating several elements into solid solutions. For example, carbon enables efficient gettering of nickel, and boron enables efficient gettering of copper (Cu) and iron (Fe).

[0041] The compounds to be ionized are not limited. Ethane, methane, and the like can be used as ionizable carbon source compounds. Diborane and decaborone (B) can be used as ionizable boron source compounds. 10 H 14 ) and the like. For example, if mixed gas of dibenzyl and decaborane is used as the material gas, a hydrogen compound cluster can be produced in which carbon, boron, and hydrogen aggregate. If cyclohexane (C6H) 12 When used as a material gas, cluster ions composed of carbon and hydrogen can be produced. A cluster C is used in particular as a carbon source compound. n H m (3 ≤ n ≤ 16, 3 ≤ m ≤ 10), which is made from pyrene (C 16 H 10 ), Dibenzyl (C 14 H 14 ) and the like are preferably used because small cluster ion beams can be easily controlled.

[0042] The cluster size can be adjusted as required from 2 to 100, preferably to 60 or less, and more preferably to 50 or less. The cluster size can be adjusted by controlling the gas pressure of the gas discharged from a nozzle, the pressure of the vacuum vessel, the voltage applied to the filament during ionization, and the like. The cluster size can be determined by ascertaining the cluster number distribution by mass spectrometry based on an electric quadrupole radio frequency field or by time-of-flight mass spectrometry and calculating the average cluster number.

[0043] To determine the peak concentration of hydrogen in the surface part of the semiconductor wafer 10 to increase further, even after the formation of the epitaxial layer 20 , is the beam flux value of the cluster ions 16 preferably 50 µA or more. If the cluster ions 16, which contain hydrogen, when applied under this current value condition, forms hydrogen that is in the constituent elements of the cluster ions 16 is contained, more reliably a solid solution in the surface part of the semiconductor wafer. 10 above an equilibrium concentration. To further ensure this effect, the beam current is preferably 100 µA or more, and more preferably 300 µA or more. The beam current of the cluster ions 16 This can be adjusted, for example, by changing the source gas decomposition conditions in the ion source.

[0044] If the beam current value is excessively high, there is a possibility of excessive epitaxial defects in the epitaxial layer. 20 Therefore, the beam current value is preferably 5000 µA or less.

[0045] The accelerating voltage of the cluster ions, together with the cluster size, influences the peak position of the concentration profile in the depth direction of the constituent elements of the cluster ions. In this disclosure, the accelerating voltage of the cluster ions can be greater than 0 keV / cluster and less than 200 keV / cluster, preferably 100 keV / cluster or less, and more preferably 80 keV / cluster or less. Two methods are typically used to adjust the accelerating voltage: (1) electrostatic acceleration and (2) radio frequency acceleration. An example of the former method is a technique of arranging several electrodes at regular intervals and applying the same voltage between them to form a constant electric acceleration field in the axial direction.An example of the latter method is a linear acceleration (Linac) method of accelerating ions using radio frequency while they are moved linearly.

[0046] The dose of cluster ions can be adjusted by controlling the ion irradiation time. In this disclosure, the dose of hydrogen can be 1 × 10 13 up to 1 × 10 16 atoms / cm² 2 and preferably 5 × 10 13 atoms / cm² 2 or more. If the dose of hydrogen is less than 1 × 10 13 atoms / cm² 2 If the dose of hydrogen is greater than 1 × 10⁻⁶, there is a possibility that hydrogen diffuses during the formation of the epitaxial layer. 16 atoms / cm² 2 If so, there is a possibility that the surface of the epitaxial layer 20 is significantly damaged.

[0047] In the case of using cluster ions containing carbon as a constituent element, the dose of carbon is preferably 1 × 10 13 up to 1 × 10 16 atoms / cm² 2 and preferred 5 × 10 13 atoms / cm² 2 or more. If the dose of carbon is less than 1 × 10 13 atoms / cm² 2 If the carbon dose is greater than 1 × 10⁻⁶, the getter capability is insufficient. 16 atoms / cm² 2 If so, there is a possibility that the surface of the epitaxial layer 20 is significantly damaged.

[0048] A preferred embodiment of a semiconductor epiaxial wafer produced by the production method according to this disclosure is described below.

[0049] It is preferred that the peak of the hydrogen concentration profile is located in a region at a depth of 150 nm from the surface. 10A of the semiconductor wafer10 in the depth direction. This region can be defined in this description as the surface portion of the semiconductor wafer. Preferably, the peak of the hydrogen concentration profile lies at a depth of 100 nm from the surface. 10A of the semiconductor wafer 10 in the depth direction. Since it is physically impossible for the peak position of the hydrogen concentration profile to be at the outermost surface (a depth of 0 nm from the surface). 10A of the semiconductor wafer 10 ) of the semiconductor wafer, which is equipped with the cluster ions 16 When irradiated, the tip is located at a depth of 5 nm or more.

[0050] The peak concentration of the hydrogen concentration profile is preferably 1.0 × 10 17 atoms / cm² 3 or more and preferably 1.0 × 10 18 atoms / cm² 3 or more.

[0051] The full width at half maximum (FWHM) of the peak of the carbon concentration profile in the depth direction of the semiconductor wafer. 10 in the modification layer 18 preferably 100 nm or less. Such a modification layer 18 This is a region where carbon is localized as a solid solution at interstitial or substitution sites in the surface portion of the semiconductor wafer and can act as a strong getter site. To achieve high getter capability, the full width at half maximum (FWHM) is preferably 85 nm or less. The lower limit can be set at 10 nm. In this description, the "carbon concentration profile in the depth direction" refers to the concentration distribution in the depth direction as measured by SIMS.

[0052] With regard to achieving high getter capability, it is desirable that, in addition to the hydrogen and carbon mentioned above, one or more elements other than the main material of the semiconductor wafer (silicon in the case of a silicon wafer) are present in a solid solution in the modification layer. 18 form.

[0053] To achieve a higher getter capability, the semiconductor epiaxial wafer features 100 Furthermore, the peak of the carbon concentration profile is preferentially located in a region at a depth of 150 nm from the surface. 10A of the semiconductor wafer 10 in the depth direction. The peak concentration of the carbon concentration profile is preferably 1 × 10 15 atoms / cm² 3 or more, preferably in a range of 1 × 10 17 up to 1 × 10 22 atoms / cm² 3 and especially preferably in a range of 1 × 10 19 up to 1 × 10 21 atoms / cm²

[0054] The thickness of the modification layer 18 is defined as an area in which the concentration profile of the component element of the cluster ions 16 is detected locally in the concentration profile mentioned above, and can, for example, lie in a range of 30 nm to 400 nm. (Method for producing a solid-state imaging device)

[0055] A method for manufacturing a solid-state imaging device according to one of the disclosed embodiments comprises forming a solid-state imaging device on a semiconductor epitaxial wafer produced according to the above-mentioned method for producing a semiconductor epitaxial wafer, i.e., on the epitaxial layer. 20 , which are located on the surface of the semiconductor epiaxial wafer 100The solid-state imaging device obtained through this production process adequately suppresses white spot defects compared to solid-state imaging devices obtained through conventional methods. EXAMPLES

[0056] A detailed description is given below using examples, although the present disclosure is not limited to these examples. (Reference experimental example)

[0057] First, the following reference experimental examples were carried out to determine the difference in the silicon wafer surface area depending on whether microwave heating was performed after cluster ion irradiation or not. <Referenzbeispiel 1>

[0058] A p-type silicon wafer (diameter: 300 mm, thickness: 775 µm, doping type: boron, resistivity: 20 Ω·cm) obtained from a CZ single crystal was prepared. One surface of the silicon wafer was then irradiated with cluster ions of C3H5, which were generated by cluster ionization of cyclohexane (C6H). 12 ) under irradiation conditions of an accelerating voltage of 80 keV / cluster (accelerating voltage per hydrogen atom: 1.95 keV / atom, accelerating voltage per carbon atom: 23.4 keV / atom, distance between hydrogen atoms: 40 nm, distance between carbon atoms: 80 nm) using a cluster ion generator (CLARIS, manufactured by Nissin Ion Equipment Co., Ltd.). A silicon wafer according to Reference Example 1 was obtained accordingly. The dose when using cluster ions was 6.67 × 10 14 Cluster / cm 2 This is 3.3 × 10 15 atoms / cm² 2regarding the number of hydrogen atoms and 2.0 × 10 15 atoms / cm² 2 with regard to the number of carbon atoms. The beam current of the cluster ions was set to 800 µA. <Referenzbeispiel 2>

[0059] A silicon wafer was irradiated with cluster ions under the same conditions as in Reference Example 1. Subsequently, the silicon wafer was subjected to microwave heating using a microwave heating element (DSG) manufactured by Hitachi Kokusai Electric Inc. to obtain a silicon wafer according to Reference Example 2. The electromagnetic irradiation conditions during microwave heating were as follows: Microwave power: 10 W Estimated wafer temperature: 750 °C Treatment time: 300 s Frequency: 2.45 GHz. <Referenzauswertung 1: Beobachtung mit TEM-Schnittfotografie>

[0060] For each of the silicon wafers according to reference examples 1 and 2, a section around the modification layer was observed after cluster ion irradiation using a transmission electron microscope (TEM). Fig. Figure 2A illustrates a TEM sectional view of Reference Example 1 and Fig. Figure 2B illustrates a TEM section view of Reference Example 2. In each TEM section photograph, areas with black contrast are regions of particularly severe damage, and areas that appear white are amorphous regions. Fig. 2A and Fig. 2B is a concentration profile obtained by SIMS, mentioned below, superimposed on the TEM slice view. Fig. 2B parts have been created where in Fig. 2A amorphous regions had changed to black. It appears that some kind of change, such as a phase transformation, occurred while crystallinity was restored. <Referenzauswertung 2: Auswertung eines Konzentrationsprofils eines Siliziumwafers durch Quadrupol-SIMS>

[0061] For each of the silicon wafers according to reference examples 1 and 2, the concentration profile of carbon, hydrogen and oxygen was measured in the depth direction by quadrupole SIMS (depth resolution: 2 nm, lower detection limit of hydrogen: 4.0 × 10 17 atoms / cm² 3 ). Fig. 2A illustrates the concentration profile of reference example 1 and Fig. Figure 2B illustrates the concentration profile of reference example 2. As shown Fig. 2A and Fig. As can be seen in 2B, the peak concentration of hydrogen decreased as a result of microwave heating, however, hydrogen remained in the outermost surface and carbon implantation area of ​​the silicon wafer even after microwave heating. <Referenzauswertung 3: Messung von Haze-Niveau>

[0062] For each of the silicon wafers according to reference examples 1 and 2, the silicon wafer surface was observed in DWN mode using Surfscan SP-1 (manufactured by KLA-Tencor Corporation), and the mean of the obtained haze values ​​was evaluated as a haze level. For reference example 1, the haze level was 0.42 ppm. For reference example 2, the haze level was 0.03 ppm. It was found that the haze level in reference example 2 recovered to approximately the same level as immediately before cluster ion irradiation. (Experimental example 1)<Beispiel 1>

[0063] A silicon wafer was irradiated with C3H5 cluster ions under the same conditions as in Reference Example 2 and then microwaved. The silicon wafer was then transferred to a single-wafer epitaxial growth unit (manufactured by Applied Materials, Inc.) and hydrogen annealed at 1120 °C for 30 seconds. An epitaxial silicon layer (thickness: 5 µm, doping type: boron, resistivity: 10 Ω·cm) was then epitaxially grown onto the surface of the silicon wafer on the side where the modification layer was formed by CVD at 1150 °C using hydrogen as the carrier gas and trichlorosilane as the source gas. A silicon epitaxial wafer according to Example 1 was thus produced. <Vergleichsbeispiel 1>

[0064] A silicon epitaxial wafer according to comparison example 1 was produced under the same conditions as example 1, except that no microwave heating was performed. <Auswertung 1: Auswertung des Konzentrationsprofils des Epitaxialwafers durch Magnetsektor-SIMS>

[0065] For each of the silicon epitaxial wafers according to Example 1 and Comparative Example 1, the concentration profile of hydrogen, carbon, and oxygen in the wafer depth direction was determined by a magnetic sector SIMS measurement (depth resolution: 30 nm, lower detection limit of hydrogen: 4.0 × 10⁻⁶). 16 atoms / cm² 3 ) measured. Fig. 3A illustrates the concentration profile of Example 1 and Fig. Figure 3B illustrates the concentration profile of comparison example 1. Fig. 3A and Fig. Figure 3B specifies the depth along the horizontal axis, with the surface of the epitaxial layer of the silicon epitaxial wafer defined as 0. A depth of up to 5 µm corresponds to the epitaxial layer, and a depth of 5 µm or more corresponds to the silicon wafer. When the epitaxial wafer is measured by SIMS, the thickness of the epitaxial layer inevitably has a measurement error of approximately ±0.1 µm. Accordingly, 5 µm in the drawing is not a precise boundary between the epitaxial layer and the silicon wafer.

[0066] As from Fig. 3A and Fig. As can be seen in 3B, the peak concentrations of each of the elements hydrogen, carbon and oxygen in the silicon wafer surface portion were higher in Example 1 than in Comparative Example 1. Fig. Figure 4 is a graph illustrating the ratio of the peak concentration of each of the elements hydrogen, carbon, and oxygen in Example 1 to the peak concentration of the corresponding element in Comparative Example 1, which was set to 1. The peak concentration of hydrogen, in particular, was higher in Example 1 than in Comparative Example 1.

[0067] The peak concentrations of both carbon and hydrogen, which are constituents of the cluster ions, are elevated. Assuming that the rate of increase of hydrogen, which tends to diffuse outwards, is higher than that of carbon, it is more likely that hydrogen and a constituent of the cluster ions other than hydrogen interact to induce some kind of change, such as a phase transformation, in the cluster ion irradiation region than that hydrogen diffusion was simply suppressed. This appears to lead, in particular, to an increase in the peak concentration of hydrogen.

[0068] Furthermore, as from Fig. 3A, Fig. 3B and Fig.As can be seen in section 4, the carbon and oxygen concentrations in Example 1 are higher than in Comparison Example 1. This indicates an improved getter capability in Example 1 compared to Comparison Example 1.

[0069] Furthermore, the haze level from reference evaluation 3 for reference experimental example 1 was lower (improved) after the formation of the epitaxial layer in example 1 than in comparison example 1. INDUSTRIAL APPLICABILITY

[0070] According to the present disclosure, a semiconductor epitaxial wafer production process can be provided which can increase the peak hydrogen concentration in a surface portion of a semiconductor wafer after the formation of an epitaxial layer. A semiconductor device produced using such a semiconductor epitaxial wafer exhibits improved device properties. Reference symbol list 10 semiconductor wafers 10A Surface of the semiconductor wafer 16 cluster ions 18 (18') Modification layer 20 Epitaxial layer 100 semiconductor epiaxial wafers W electromagnetic waves QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2013197373 A [0005, 0006] WO 2012 / 157162 A1

[0006] JP H941138 A

[0038] JP H4354865 A

[0038] Cited non-patent literature

[0000] unzo Ishikawa, „Charged particle beam engineering“, Corona Publishing, ISBN 978-4-339-00734-3, (2) The Institution of Electrical Engineers of Japan, „Electron / Ion Beam Engineering“, Ohmsha, ISBN 4-88686-217-9 und (3) „Cluster Ion Beam - Basic and Applications“, The Nikkan Kogyo Shimbun, ISBN 4-526-05765-7

[0038]

Claims

[1] Method for producing a semiconductor epiaxial wafer, the method comprising: a first step of irradiating a surface of a semiconductor wafer with cluster ions containing hydrogen as a constituent element to form a modification layer formed from a constituent element of the cluster ions containing hydrogen in a surface part of the semiconductor wafer as a solid solution; a second step of irradiating the semiconductor wafer with electromagnetic waves of a frequency of 300 MHz or more and 3 THz or less after the first step to heat the semiconductor wafer; and a third step of forming an epitaxial layer on the modification layer of the semiconductor wafer after the second step. [2] Method for producing a semiconductor epiaxial wafer according to claim 1, wherein the cluster ions further contain carbon as a constituent element. [3] Method for producing a semiconductor epiaxial wafer according to claim 1 or 2, wherein the beam current value of the cluster ions in the first step is 50 µA or more. [4] Method for producing a semiconductor epiaxial wafer according to any one of claims 1 to 3, wherein the beam current value of the cluster ions in the first step is 5000 µA or less. [5] Method for producing a semiconductor epitaxial wafer according to any one of claims 1 to 4, wherein the semiconductor wafer is a silicon wafer. [6] Method for manufacturing a solid-state imaging device, the method comprising: Forming a solid-state imaging device on an epitaxial layer of a semiconductor epitaxial wafer produced by the method for producing a semiconductor epitaxial wafer according to any one of claims 1 to 5.