TWI708279B - Method for manufacturing semiconductor epitaxial wafer - Google Patents

Abstract

The invention provides a method for manufacturing a semiconductor epitaxial wafer with higher gettering ability even if the cluster ion implantation conditions are the same. The method for manufacturing a semiconductor epitaxial wafer of the present invention includes: a first step of implanting multi-element cluster ions containing three elements of carbon, hydrogen and oxygen as constituent elements on the surface of the semiconductor wafer A modified layer formed by solid solution of the constituent elements of the multi-element cluster ions is formed; the second step, after the first step, is performed to enlarge the defects of black dot-like defects formed in the modified layer Density defect formation heat treatment; and a third step, following the second step, forming an epitaxial layer on the modified layer of the semiconductor wafer.

Description

Method for manufacturing semiconductor epitaxial wafer

The invention relates to a method for manufacturing a semiconductor epitaxial wafer. The present invention particularly relates to a method for manufacturing a semiconductor epitaxial wafer that exerts a higher gettering ability.

The main cause of deterioration of the characteristics of semiconductor devices can be metal contamination. For example, in a back-illuminated solid-state imaging device, metal mixed in a semiconductor epitaxial wafer serving as a substrate of the device becomes a main cause of an increase in dark current of the solid-state imaging device, and a defect called a white mark defect occurs. The backside-illuminated solid-state imaging device arranges the wiring layer and the like on the lower layer than the sensor part, and directly captures the light from the outside into the sensor, so that it can take clearer pictures in dark places. Images or moving images have been widely used in mobile phones such as digital video cameras and smart phones in recent years. Therefore, it is desired to minimize white mark defects.

The metal incorporation in the semiconductor device substrate is mainly generated in the manufacturing steps of semiconductor epitaxial wafers and the manufacturing steps of solid-state imaging devices (device manufacturing steps). It is believed that the metal contamination in the manufacturing process of the former semiconductor epitaxial wafer is caused by heavy metal particles originating from the constituent materials of the epitaxial growth furnace, or because chlorine-based gas is used as the furnace gas during epitaxial growth. Generate metal from its piping material Corrosion caused by heavy metal particles, etc. In recent years, the metal contamination has been improved to some extent by replacing the constituent material of the epitaxial growth furnace with a material excellent in corrosion resistance, but this is not sufficient. On the other hand, in the manufacturing steps of the latter solid-state imaging device, heavy metal contamination of the semiconductor epitaxial wafer is worrying during each process such as ion implantation, diffusion, and oxidation heat treatment.

Therefore, a gettering layer for capturing metal is usually formed on the semiconductor epitaxial wafer to avoid metal contamination of the semiconductor epitaxial wafer.

Here, as a technique for forming the gettering layer, there is a technique for irradiating cluster ions before forming the epitaxial layer. Patent Document 1 discloses a technique of implanting cluster ions containing carbon, hydrogen, and oxygen as constituent elements in a method of manufacturing a semiconductor epitaxial wafer. Moreover, Patent Document 1 also discloses that by implanting cluster ions containing three elements of carbon, hydrogen, and oxygen, black dot-like defects with a relatively large size presumably caused by lattice silicon are formed (Patent Document 1 The 2nd black dot defect in). According to the experimental results of Patent Document 1, it is suggested that the black dot-shaped defect functions as a strong gettering site.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2017-157613

By using the cluster ion implantation technique disclosed in Patent Document 1, a semiconductor epitaxial wafer with extremely excellent gettering ability can be obtained. However, using cluster ion implantation Although the formation mechanism and characteristics of the absorption point of entry are gradually understood to a certain extent, it is still in the research process. In particular, there are many unexplained aspects regarding multi-element cluster ions that include one or more other elements as constituent elements of cluster ions in addition to carbon and hydrogen. Hereinafter, in this specification, when the constituent element of the cluster ion contains three or more elements, it is referred to as "multi-element cluster ion".

Here, in order to further improve the gettering ability by the modified layer in Patent Document 1, for example, it is effective to increase the dose of cluster ions. However, if the dose is increased too much, a large number of epitaxial defects may be generated in the epitaxial layer formed on the modified layer. As such, there is a limit in improving the absorption ability by increasing the dose.

Therefore, from a viewpoint other than the cluster ion implantation conditions, it is expected to establish a new method to further improve the gettering ability.

Therefore, the object of the present invention is to provide a method for manufacturing a semiconductor epitaxial wafer that has higher gettering ability even if the cluster ion implantation conditions are the same.

In order to solve the above-mentioned problems, the inventors conducted diligent studies. In addition, the inventors of the present invention conducted studies on whether the conditions for the growth of epitaxial crystals can be adjusted instead of the cluster ion implantation conditions to improve the gettering ability. Here, a general conceptual diagram of the heat treatment sequence (sequence) accompanying the epitaxial growth process will be explained using FIG. 1. The heat treatment sequence can be roughly divided into the following three processes: (i) After the semiconductor wafer is put into the epitaxial growth furnace, the temperature rise process until the epitaxial growth temperature is reached; (ii) the epitaxy is applied on the surface of the semiconductor wafer The epitaxial growth process of the growth of the epitaxial layer; (iii) After the epitaxial layer is formed, the temperature drop until the obtained semiconductor epitaxial wafer is taken out from the epitaxial growth furnace process.

The inventors conducted diligent studies, and as a result, it was found that the number of generation of black dot-like defects that serve as suction points greatly depends on the (i) heating process. Furthermore, the inventors learned that by performing a heating process that also serves as a defect formation heat treatment for increasing the defect density of black spot defects, even if the cluster ion implantation conditions are the same, the gettering ability can be further improved. The present invention was completed based on the above knowledge, and its gist structure is as follows.

(1) A method for manufacturing a semiconductor epitaxial wafer, which is characterized in that it comprises: a first step of implanting multi-element cluster ions containing three elements of carbon, hydrogen and oxygen as constituent elements into the surface of the semiconductor wafer. A modified layer formed by solid solution of the constituent elements of the multi-element cluster ions is formed on the surface layer of the wafer; the second step, after the first step, is performed to increase the blackness formed in the modified layer The defect formation heat treatment of the defect density of point defects; and the third step, following the second step, forming an epitaxial layer on the modified layer of the semiconductor wafer.

(2) The method for manufacturing a semiconductor epitaxial wafer as described in (1), wherein in the heat treatment conditions of the defect formation heat treatment in the second step, the heat treatment conditions are maintained in a first temperature region less than 800°C. The first holding time of the semiconductor wafer is 0 second or more and 45 seconds or less, and the second temperature region of the semiconductor wafer is maintained in the second temperature region of 800°C or more and less than 1000°C after the temperature rise from the first temperature region The holding time is more than 30 seconds.

(3) The method for manufacturing a semiconductor epitaxial wafer as described in (1) or (2), wherein the constituent elements of the multi-element cluster ion are composed of three elements: carbon, hydrogen, and oxygen.

(4) The method for manufacturing a semiconductor epitaxial wafer according to any one of (1) to (3), wherein the semiconductor wafer is a silicon wafer.

According to the present invention, it is possible to provide a method for manufacturing a semiconductor epitaxial wafer that has a higher gettering ability even if the cluster ion implantation conditions are the same.

10: Semiconductor wafer

10A: Surface of semiconductor wafer

16: cluster ion

18: modified layer

20: epitaxial layer

100: Semiconductor epitaxial wafer

D: Black spot defects

Fig. 1 is a conceptual diagram showing a general heat treatment sequence accompanying epitaxial growth.

2 is a diagram showing a cross-sectional view of a transmission electron microscope (Transmission Electron Microscope, TEM) in the vicinity of the substrate interface of the epitaxial silicon wafer in Reference Experimental Example 1. FIG.

3 is a diagram showing a TEM cross-sectional view near the substrate interface of the epitaxial silicon wafer in Reference Experimental Example 2. FIG.

4 is a schematic cross-sectional view illustrating an aspect of a heat treatment sequence accompanying epitaxial growth in an embodiment of the present invention.

(A) to (C) in FIG. 5 are schematic cross-sectional views illustrating a method of manufacturing a semiconductor epitaxial wafer 100 according to an embodiment of the present invention.

Before the detailed description of the embodiment, the experiment of the present invention (Refer to Experimental Example 1, Reference Experimental Example 2) for description.

[Reference experiment example 1]

Prepare a silicon wafer (diameter: 300mm, thickness: 725μm, dopant type: phosphorus, resistivity: 10Ω·cm) obtained from CZ single crystal silicon ingots. Then, using a cluster ion generator (manufactured by Nisshin Ion Instruments Co., Ltd., model: CLARIS (registered trademark)), the CH containing the cluster ionized diethyl ether (C ₄ H ₁₀ O) Multi-element cluster ions of ₃ O are injected into the surface of the silicon wafer under the conditions of an acceleration voltage of 80 keV/Cluster. In addition, the dose of the cluster ion is 1.0×10 ¹⁵ cluster/cm ² .

Secondly, the silicon wafer is transported to a high-speed thermal processing device (made by Hisol, model AccuThermo Aw610). Furthermore, in order to perform a heat treatment that simulates epitaxial growth at 1100° C. for 300 seconds (hereinafter, simulated growth heat treatment), the heat treatment is performed under the following conditions in a nitrogen atmosphere.

Input temperature in the furnace: 500℃

Heating rate until the simulated growth temperature: 60℃/s

(Sample 2~Sample 4)

Samples 2 to 4 were produced in the same manner as in sample 1, except that the heating rate of 60°C/s in sample 1 was changed to 15°C/s, 8°C/s, and 4°C/s.

For each sample of sample 1 to sample 4, TEM cross-sections before and after the simulated growth heat treatment were obtained. The results are shown in Figure 2.

[Reference experiment example 2]

(Sample 5)

Under the same conditions as the sample 1, a multi-element cluster containing CH ₃ O was ion implanted onto the surface of the silicon wafer. Then, in order to perform a simulated growth heat treatment at 800°C for 300 seconds, the silicon wafer after the cluster ion implantation was transferred to a high-speed heat treatment device (manufactured by Hisol) in the same manner as in Reference Experimental Example 1. The heat treatment is performed under the following conditions.

Input temperature in the furnace: 500℃

The heating rate until the simulated growth temperature: 8℃/s

(Sample 6~Sample 8)

Except that the heat treatment temperature of the simulated growth heat treatment in the sample 5 was changed from 800°C to 900°C, 1000°C, and 1100°C, samples 6 to 8 were produced in the same manner as in sample 5.

For each sample of Sample 5 to Sample 8, a TEM section after the heat treatment to simulate epitaxial growth was obtained. The results are shown in Figure 3.

<Review of Reference Experiment Example 1, Reference Experiment Example 2>

First, based on Fig. 2 according to Reference Experimental Example 1, it can be confirmed that the defect density of black dot-like defects formed before the simulated growth heat treatment at 1100°C for 300 seconds does not greatly depend on the heating rate. On the other hand, after the simulated growth heat treatment, although the defect density of black dot-like defects is reduced, the amount of reduction greatly depends on the heating rate.

Furthermore, based on Fig. 3 according to Reference Experimental Example 2, it can be confirmed that the amount of generation of black spot defects is relatively large by the simulated growth heat treatment at 800°C, 900°C, and 1000°C.

If the above results are considered comprehensively, it is considered as the following assumption: if a silicon wafer implanted with cluster ions is subjected to a heat treatment at 800°C or more and less than 1000°C, it will be black dots. Defects grow. On the other hand, if it is less than 800°C, the black spot-like defect species itself disappears, and if it is subjected to heat treatment at 1000°C or higher, the black spot-like defect is decomposed. The heat treatment sequence based on this assumption is shown in FIG. 4. In samples 1 to 3, although the passage time of the temperature zone where the black dot-shaped defect species disappeared less than 800°C was relatively short, the passage time of the temperature zone where the black dot-shaped defect grew was also relatively short. In Sample 4, although the passage time of the temperature zone where the black spot-shaped defect species of less than 800°C disappeared was relatively long, if it was subjected to a heat treatment of 800°C or higher and less than 1000°C, the black spot-shaped defect grew for a long time. Therefore, it is inferred that, as in the TEM cross-sectional photograph in the upper part of FIG. 2, in the state before the simulated growth heat treatment, the defect density of black dot-like defects is observed to the same degree. Moreover, as shown in the TEM cross-sectional photograph in the lower part of FIG. 2, after the simulated growth heat treatment, the defect density of the black dot-like defects has a non-incidental difference.

Therefore, the inventors learned that by performing defect formation heat treatment for increasing the defect density of black dot-shaped defects formed in the modified layer before forming the epitaxial layer, the gettering ability can be improved.

Based on the above experimental results, while referring to the heat treatment sequence in FIG. 4 and the schematic cross-sectional views of (A) to (C) in FIG. 5 showing the manufacturing process, the impurity of the epitaxial silicon wafer according to an embodiment of the present invention The spreading behavior prediction method is explained. In addition, in (A) to (C) in FIG. 5, for convenience of explanation, the ratio of the actual thickness is different, and the thickness of the modified layer 18 and the epitaxial layer 20 is exaggeratedly shown with respect to the semiconductor wafer 10 .

(Method of manufacturing semiconductor epitaxial wafer)

Method for manufacturing semiconductor epitaxial wafer 100 according to an embodiment of the present invention Including: the first step is to implant multi-element cluster ions 16 containing three or more elements as constituent elements into the surface 10A of the semiconductor wafer 10, and form the constituent element solids of the multi-element cluster ions 16 on the surface of the semiconductor wafer 10 The melted modified layer 18 (step A and step B of (A) to (C) in FIG. 5); the second step, after the first step, is performed to increase the inside of the modified layer 18 The formed black dot-shaped defects D are formed by the defect density of the defect formation heat treatment; and the third step, following the second step, is to form an epitaxial layer on the modified layer 18 of the semiconductor wafer ((A) to (A) to (C) Step C). Here, the constituent elements of the multi-element cluster ion 16 include carbon, hydrogen, and oxygen. Hereinafter, for simplification, the multi-element cluster ion containing carbon, hydrogen, and oxygen as constituent elements may be simply referred to as "CHO cluster". The CHO cluster may include elements other than carbon, hydrogen, and oxygen as constituent elements, or may be set to only three elements of carbon, hydrogen, and oxygen. Furthermore, step C from (A) to (C) in FIG. 5 is a schematic cross-sectional view of the semiconductor epitaxial wafer 100 obtained as a result of the manufacturing method. The epitaxial layer 20 serves as a device layer for manufacturing semiconductor elements such as back-illuminated solid-state imaging elements. The semiconductor wafer 10 is a silicon wafer, and the epitaxial silicon wafer with the epitaxial layer 20 being a silicon epitaxial layer is one of the preferred aspects of the semiconductor epitaxial wafer 100. Hereinafter, the details of each step will be described in order.

<Step 1>

In the first step of the present invention (step A and step B of (A) to (C) in FIG. 5), as described above, the surface 10A of the semiconductor wafer 10 is implanted with an element containing three or more elements as a constituent The multi-element cluster ions 16 of the element form a modified layer 18 in which constituent elements of the multi-element cluster ions 16 are solid-dissolved on the surface portion of the semiconductor wafer 10. The multi-element cluster ion 16 used in the first step contains carbon and hydrogen as described above. And oxygen as a constituent element.

<<Semiconductor Wafer>>

As the semiconductor wafer 10, for example, a bulk single crystal wafer containing silicon and compound semiconductors (GaAs, GaN, SiC) and having no epitaxial layer on the surface is mentioned. In the case of manufacturing a back-illuminated solid-state imaging device, a bulk single crystal silicon wafer is generally used. In addition, the semiconductor wafer 10 can be sliced by using a wire saw (Czochralski, CZ method) or a floating zone method (Floating Zone, FZ method) to slice a single crystal silicon ingot. (Slice) the resulting wafer. In addition, in order to obtain higher gettering ability, carbon and/or nitrogen may also be added to the semiconductor wafer 10. Furthermore, an arbitrary dopant at a predetermined concentration may be added to the semiconductor wafer 10 to form a so-called n+ type or p+ type, or n- type or p- type substrate.

In addition, as the semiconductor wafer 10, an epitaxial wafer having a semiconductor epitaxial layer formed on the surface of a bulk semiconductor wafer can also be used. For example, it is an epitaxial silicon wafer with a silicon epitaxial layer formed on the surface of a bulk single crystal silicon wafer. The silicon epitaxial layer can be formed by chemical vapor deposition (CVD) method under normal conditions. 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.

<<Cluster ion irradiation>>

Here, the so-called "cluster ion" in this specification is obtained by using the electron collision method to collide electrons with gaseous molecules to dissociate the bonds of the gaseous molecules, thereby making various atomic numbers Atom aggregates, and generate fragments (fragment) to ionize the atom aggregates, and perform ionized atoms of various atomic numbers The masses of the sub-aggregates are separated, and then the ionized atom aggregates of a specific mass number are extracted. That is, cluster ions are those obtained by imparting positive or negative charges to clusters formed by agglomerating a plurality of atoms and ionizing them, and can be clearly distinguished as monoatomic ions such as carbon ions or monomolecular ions such as carbon monoxide ions.

In the case of irradiating cluster ions to the silicon wafer as the semiconductor wafer 10, if the cluster ions are irradiated to the silicon wafer, the energy instantly becomes a high temperature state of about 1350°C to 1400°C, and the silicon melts. Thereafter, the silicon is rapidly cooled, and the constituent elements of cluster ions are dissolved in the vicinity of the surface of the silicon wafer. That is, the "modified layer" in this specification refers to a layer in which constituent elements of the irradiated ions are solid-dissolved in the crystal lattice positions or replacement positions of the crystals on the surface of the silicon wafer. As an example of a constituent element, for example, if the focus is on carbon, the concentration profile of carbon in the depth direction of a silicon wafer obtained by Secondary Ion Mass Spectrometry (SIMS) depends on cluster ions. The accelerating voltage and cluster size are sharper than in the case of single ions, and the thickness of the region where the irradiated carbon is locally present (that is, the modified layer) is approximately 500 nm or less (for example, about 50 nm to 400 nm) . Therefore, when the constituent element of the multi-element cluster ion 16 contains an element that contributes to absorption, such as carbon, the modified layer 18 functions as a strong absorption point.

In this embodiment, the implanted multi-element cluster ions 16 are CHO clusters, containing carbon, hydrogen, and oxygen as constituent elements. The covalent bond radius of the carbon atoms at the crystal lattice position is smaller than that of the silicon single crystal, and the contraction field of the silicon crystal lattice is formed. Therefore, the ability to attract impurities in the lattice gap becomes higher. Moreover, it is believed that by implanting carbon and oxygen in the form of CHO clusters, and then undergoing a heat treatment accompanying epitaxial growth, A black dot-shaped defect D is formed. Furthermore, hydrogen passivates the point defects of the silicon epitaxial layer (epitaxial layer 20), and contributes to improving the device characteristics when the semiconductor epitaxial wafer 100 obtained in this embodiment is used to manufacture a semiconductor device. Words are also favorable.

<Step 2>

After the first step, in the second step, a defect formation heat treatment for increasing the defect density of the black dot-shaped defects D formed in the modified layer 18 is performed. As described using Reference Experimental Example 1 and Reference Experimental Example 2, the defect density of the black dot-shaped defects D greatly depends on the temperature during the temperature rise process until reaching the epitaxial growth temperature. Therefore, by performing the heat treatment for forming defects before forming the epitaxial layer, the defect density of the black spot defects D in the semiconductor epitaxial wafer 100 finally obtained can be increased, and the gettering ability can be improved.

The heat treatment conditions of the defect formation heat treatment in the second step are not limited as long as the defect density of the black dot-shaped defects D can be increased, and it is preferable to maintain the first holding of the semiconductor wafer in the first temperature range less than 800°C. The time is 0 second or more and 45 seconds or less, and the second holding time for holding the semiconductor wafer in the second temperature region of 800° C. or more and less than 1000° C. after raising the temperature from the first temperature region is 30 seconds or more.

Referring to FIG. 4, as described above, the first temperature zone corresponds to the temperature zone where the defect species disappear, so the time to pass through this temperature zone is preferably as short as possible. Therefore, the first holding time is preferably 45 seconds or less, more preferably 30 seconds or less, still more preferably 10 seconds or less, and particularly preferably 5 seconds or less. In addition, as long as the furnace input temperature of the semiconductor wafer 10 into the epitaxial growth furnace is 800° C. or higher, the first holding time may be set to 0 seconds.

In addition, the second temperature zone corresponds to a temperature zone where defects grow, and therefore the time to pass through this temperature zone is preferably relatively long. Therefore, the second holding time is preferably 30 seconds or more, and more preferably 60 seconds or more. Although it is considered that the longer the second holding time is, the better, but in consideration of manufacturing efficiency, the upper limit of the second holding time can be set to 300 seconds.

In addition, in FIG. 4, the figure is shown in the aspect of maintaining at a fixed temperature in the second temperature range, but the present invention is not limited to this aspect at all. For example, in the second temperature zone, the heating rate can be set to a few degrees Celsius/second (for example, 1°C/sec to 3°C/second), or the temperature can be increased at a slower heating rate to achieve the second holding time. It is also possible to repeatedly increase the temperature and maintain the fixed temperature.

In addition, the defect formation heat treatment using this step is different from the recovery heat treatment for restoring crystallinity. The recovery heat treatment for restoring crystallinity is used to recover the amorphous state formed by cluster ion implantation. Compared with the defect formation heat treatment, a relatively high temperature heat treatment is required for a relatively long time.

<Step 3>

Immediately after the second step, the third step of forming the epitaxial layer 20 on the modified layer 18 of the semiconductor wafer 10 (step C of (A) to (C) in FIG. 5) is performed. The epitaxial layer 20 to be formed includes, for example, a silicon epitaxial layer, and it can be formed under normal conditions. In this case, for example, hydrogen is used as a carrier gas, and source gases such as dichlorosilane and trichlorosilane are introduced into the chamber. The growth temperature also varies depending on the source gas used, and can be in the range of 1000°C to 1200°C. The epitaxial growth is performed on the semiconductor wafer 10 by the CVD method at a temperature. The epitaxial layer 20 preferably has a thickness of 1 μm to 15 μm In the range. The reason is that in the case of less than 1 μm, the resistivity of the epitaxial layer 20 may change due to the outdiffusion of the dopant from the semiconductor wafer 10, and in the case of more than 15 μm, the solid-state imaging device may be affected. The spectral sensitivity characteristics may have an impact.

Although the defect density of the black dot-shaped defects D after the third step is lower than that of the black dot-shaped defects D immediately after the second step, the defect formation heat treatment using the second step is more than that of the previous ones. In terms of defect density, the resulting defect density becomes larger. Therefore, even if the cluster ion implantation conditions are set to be the same, the gettering ability of the obtained semiconductor epitaxial wafer 100 can be improved non-incidentally than before.

In addition, the so-called black dot-like defects D in this specification refers to the black dots observed in the modified layer 18 when the cleavage section of the semiconductor epitaxial wafer 100 is observed in bright mode by TEM Defects except for those with a small size of a few nanometers (nm) in diameter. The size of the black dot-shaped defect D is 15 nm or more and 100 nm or less, and the "size of the black dot-shaped defect" is the diameter of the defect in the TEM image. Furthermore, when the black point defect D is a shape that is not circular or can not be regarded as a circle, the circumscribed circle of the smallest diameter that contains the black point defect D is used, and the diameter is set to approximate a circle. In addition, the "defect density" of black dot-shaped defects refers to the number of defects per unit of a predetermined area in the area where black dot-shaped defects D exist in the TEM image based on the final result of the sample used in the TEM observation at this time. The thickness is defined.

Hereinafter, the irradiation state of the multi-element cluster ions of this embodiment will be explained Bright.

As long as the constituent elements of the irradiated multi-element cluster ion 16 contain carbon, hydrogen, and oxygen, other constituent elements are not particularly limited. The constituent elements of the multi-element cluster ion 16 may further include boron, phosphorus, arsenic, and antimony.

In addition, the ionized compound is not particularly limited. As the ionizable compound, for example, diethyl ether (C ₄ H ₁₀ O), ethanol (C ₂ H ₆ O), diethyl ketone (C ₅ H ₁₀ O) and so on. It is particularly preferable to use clusters C _n H _m O _l generated by diethyl ether, ethanol, etc. (l, m, and n are independent of each other, 1≦n≦16, 1≦m≦16, 1≦l≦16) . It is particularly preferable that the number of carbon atoms of the cluster ion is 16 or less, and the number of oxygen atoms of the cluster ion is 16 or less. The reason is that it is easy to control a cluster ion beam of a small size. In addition, for example, if trimethyl phosphite (C ₃ H ₉ O ₃ P) or the like is used, in addition to carbon, hydrogen, and oxygen, the constituent elements of the multi-element cluster ion 16 may include phosphorus.

The cluster size can be appropriately set in the range of 2 to 100, preferably 60 or less, and more preferably 50 or less. The cluster size can be adjusted by adjusting the gas pressure of the gas ejected from the nozzle, the pressure of the vacuum container, the voltage applied to the filament during ionization, and the like. Furthermore, the cluster size can be obtained by the following methods: obtain the distribution of the number of clusters by mass spectrometry using a quadrupole high frequency electric field or time-of-flight mass spectrometry, and take the average of the number of clusters .

The acceleration voltage of the cluster ion and the cluster size affect the peak position of the concentration distribution of the constituent elements of the cluster ion in the depth direction. In this embodiment, the acceleration voltage of the multi-element cluster ion 16 can be set to exceed 0 keV/Cluster and less than 200 keV/Cluster, preferably set to 100 keV/Cluster or less, and more preferably set Below 80keV/Cluster. Furthermore, regarding the adjustment of the acceleration voltage, two methods (1) electrostatic acceleration and (2) high frequency acceleration are usually used. In the former method, a plurality of electrodes are arranged at equal intervals, an equal voltage is applied between the electrodes, and an equal acceleration electric field is created in the axial direction. In the latter method, there is a linear linear accelerator (linac) method in which ions are accelerated by high frequency while traveling in a straight line.

In addition, the dose of cluster ions can be adjusted by controlling the ion irradiation time. The dose of each element of carbon, hydrogen, and oxygen is determined by the cluster ion species and the cluster ion dose (Cluster/cm ² ). In this embodiment, the dose of the multi-element cluster ion 16 can be adjusted such that the dose of carbon is 1×10 ¹³ atoms/cm ² to 1×10 ¹⁷ atoms/cm ² , and it is preferable to set the dose of carbon to 5×10 ¹³ atoms/cm ² or more and 5×10 ¹⁶ atoms/cm ² or less. The reason is that when the dose of carbon is less than 1×10 ¹³ atoms/cm ² , there is a case where sufficient absorption capacity cannot be obtained, and when the dose of carbon exceeds 1×10 ¹⁶ atoms/cm ² , there is The surface of the epitaxial layer 20 may be severely damaged.

In addition, the beam current value of the multi-element cluster ion 16 may be 50 μA or more and 5000 μA or less. Furthermore, the beam current value of the cluster ions can be adjusted by changing the decomposition conditions of the source gas in the ion source, for example.

The representative embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.

[Example]

(Trial Example 1)

Prepare a silicon wafer (diameter: 300mm, thickness: 725μm, dopant type: phosphorus, resistivity: 10Ω·cm) obtained from CZ single crystal silicon ingots. Then, using a cluster ion generator (manufactured by Nisshin Ion Instruments Co., Ltd., model: CLARIS (registered trademark)), the CH containing the cluster ionized diethyl ether (C ₄ H ₁₀ O) Multi-element cluster ions of ₃ O are injected into the surface of the silicon wafer under the conditions of an acceleration voltage of 80 keV/Cluster. In addition, the dose of the cluster ions is 1.0×10 ¹⁵ cluster/cm ² (the dose of carbon is also 1.0×10 ¹⁵ atoms/cm ² ).

Next, the silicon wafer is transferred to a wafer-by-wafer epitaxial growth device (manufactured by Applied Materials) with a furnace temperature of 600°C. Next, set the temperature rise time to 800°C to 5 seconds (heating rate 40°C/s), and set the temperature rise time from 800°C to 1000°C to 5 seconds (heating rate 40°C/s) and increase to 1000°C . Immediately afterwards, the temperature in the device was raised to 1120°C. After the hydrogen baking treatment was carried out at this temperature for 30 seconds, hydrogen was used as the carrier gas, and trichlorosilane was used as the source gas. The silicon crystal was deposited at 1120°C by the CVD method. A silicon epitaxial layer (thickness: 5μm, dopant type: phosphorus, resistivity: 50Ω·cm) was grown epitaxially on the round surface on the side where the modified layer was formed to produce the epitaxial crystal of Trial Example 1. Silicon wafer.

(Trial Example 2~Trial Example 25)

As shown in Table 1 below, set the heating time up to 800°C to 5 seconds (heating rate 40°C/s), 10 seconds (heating rate 20°C/s), 30 seconds (heating rate 6.7°C/s), 45 seconds (heating rate 4.4°C/s), 60 seconds (heating rate 3.3°C/s), set the heating time from 800°C to 1000°C to 5 seconds (heating rate 40°C/s), 10 seconds (heating rate) 20°C/s), 30 seconds (heating rate of 6.7°C/s), 60 seconds (heating rate of 3.3°C/s), 300 seconds (heating rate of 0.67°C/s), except for this, it was produced in the same way as Trial Example 1 The epitaxial silicon wafers of Trial Example 2 to Trial Example 25.

<Evaluation 1: Observation using TEM section photographs>

Regarding each of the epitaxial silicon wafers of Trial Example 1 to Trial Example 25, a cross-section near the substrate interface was observed with a TEM (Transmission Electron Microscope), and the defect density of black spot defects was determined. Furthermore, the size of the defect observed within the depth of 300nm from the substrate interface is 15 Defects below nm to 100 nm are regarded as black dot-shaped defects. The observed defect density is shown in Table 1 together.

<Evaluation 2: Evaluation of Absorption Ability>

For each of the epitaxial silicon wafers of Trial Example 1 to Trial Example 25, the gettering ability was evaluated. First, use Ni contamination solution (1.0×10 ¹³ atoms/cm ² ) and use spin-coating contamination method to contaminate the surface of the epitaxial layer of each epitaxial silicon wafer forcibly, and then implement it at 900°C in a nitrogen atmosphere. Minutes of diffusion heat treatment. Thereafter, for each epitaxial silicon wafer, SIMS measurement was performed, and the distribution of the Ni concentration in the cluster ion implantation region (in this evaluation, 300 nm from the substrate interface for simplicity) was measured. Then, the trapped amount of Ni in the ion implantation region (corresponding to the integrated value of the Ni concentration in the SIMS distribution) is obtained. The captured amount of Ni is classified as follows and used as an evaluation criterion. The evaluation results are shown in Table 1 together.

◎: 9.7×10 ¹² atoms/cm ² or more

○: 9.5×10 ¹² atoms/cm ² or more and less than 9.7×10 ¹² atoms/cm ²

△: 9.0×10 ¹² atoms/cm ² or more and less than 9.5×10 ¹² atoms/cm ²

×: less than 9.0×10 ¹² atoms/cm ²

<Examination of Evaluation Results>

First, according to Table 1, it can be confirmed that the level of the sucking ability has a clear correlation with the defect density of black dot-shaped defects, and it can be confirmed that the higher the defect density of black dot-shaped defects, the higher the sucking ability. It was also confirmed that the shorter the passage time of the temperature zone estimated to be the disappearance of the defect species, and the longer the passage time of the temperature zone estimated to be the growth of the defect, the higher the defect density of black dot-shaped defects. Therefore, even if cluster ion implantation Under the same conditions, by performing defect formation heat treatment to increase the defect density of black dot-shaped defects, the absorption ability can also be improved.

[Industrial availability]

According to the present invention, it is possible to provide a method for manufacturing a semiconductor epitaxial wafer that has a higher gettering ability even if the cluster ion implantation conditions are the same.

10‧‧‧Semiconductor Wafer

10A‧‧‧Semiconductor wafer surface

16‧‧‧Cluster ion

18‧‧‧Modified layer

20‧‧‧Epitaxial layer

100‧‧‧Semiconductor epitaxial wafer

D‧‧‧Black dot defect

Claims (4)

A method for manufacturing a semiconductor epitaxial wafer, which is characterized by comprising: The first step is to implant multi-element cluster ions containing three elements of carbon, hydrogen and oxygen as constituent elements into the surface of the semiconductor wafer, and form solid solution of the constituent elements of the multi-element cluster ions on the surface of the semiconductor wafer The modified layer; In the second step, after the first step, a defect formation heat treatment is performed to increase the defect density of the black dot-shaped defects formed in the modified layer; and In the third step, following the second step, an epitaxial layer is formed on the modified layer of the semiconductor wafer. The method for manufacturing a semiconductor epitaxial wafer according to the first item of the patent application, wherein in the heat treatment conditions of the defect formation heat treatment in the second step, the semiconductor is maintained in a first temperature region less than 800°C The first holding time of the wafer is 0 second or more and 45 seconds or less, and the second holding time for holding the semiconductor wafer in the second temperature region of 800°C or more and less than 1000°C after the temperature rise from the first temperature region For more than 30 seconds. According to the method for manufacturing a semiconductor epitaxial wafer described in the first item of the patent application, the constituent elements of the multi-element cluster ion are composed of three elements: carbon, hydrogen and oxygen. According to the method for manufacturing a semiconductor epitaxial wafer according to any one of items 1 to 3 of the scope of patent application, the semiconductor wafer is a silicon wafer.

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