JP2018049997A - Method of manufacturing silicon bonded wafer and silicon bonded wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing silicon bonded wafer in which a wafer for support substrate includes a gettering layer formed by transparent laser beam irradiation, and damage on an active layer due to transparent laser beam irradiation was suppressed, and to provide a silicon bonded wafer manufactured by that method.SOLUTION: A method of manufacturing silicon bonded wafer has a step of forming a gettering layer internally by irradiating a transparent laser beam from one side of a wafer for support substrate, a step of sticking one side of the wafer for support substrate and one side of a wafer for active layer by vacuum normal temperature bonding method, and a step of thinning the wafer for active layer as an active layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a silicon bonded wafer and a silicon bonded wafer.

  An epitaxial silicon wafer in which a silicon wafer and a silicon wafer are used as a substrate and a silicon epitaxial layer is provided on the substrate is used as a substrate material for semiconductor devices. In recent years, high-sensitivity CIS (CMOS Image Sensor) and high-performance semiconductor devices such as power devices are required to be defect-free and impurity-free in a device formation region of a substrate material.

  In general, a silicon epitaxial layer has sufficiently fewer defects and less impurities such as oxygen than a bulk silicon wafer serving as a substrate. Therefore, in the production of high-performance semiconductor devices, the silicon epitaxial layer of an epitaxial silicon wafer is widely used as an active layer.

  Here, in a semiconductor wafer manufacturing process or a device manufacturing process, if a heavy metal is mixed in a substrate of a semiconductor device, device characteristics such as a pause time failure, a retention failure, a junction leak failure, and an oxide dielectric breakdown are significantly adversely affected. However, in the semiconductor device manufacturing process, there is a concern that heavy metal contamination of the semiconductor substrate may occur during each process such as ion implantation, diffusion, and oxidation heat treatment. Therefore, in order to suppress the diffusion of heavy metals into the device formation area, which is the area where devices are formed, on the surface of a silicon wafer, which is a typical substrate, a gettering capability has been imparted to the silicon wafer by the gettering method. I have done it.

  The gettering method includes an intrinsic gettering method (IG method) in which oxygen is precipitated inside a silicon wafer and the formed oxygen precipitate (BMD) is used as a gettering site, There is known the extrinsic gettering method (EG method) that gives mechanical strain on the back surface using sandblasting, etc., or forms a polycrystalline silicon film or the like as a gettering site. Yes.

  In addition, an ion implantation method, that is, it is also known that carbon or the like is ion-implanted into a silicon wafer to form a modified region including an ion implanted region, and the modified region is used as a gettering site. For example, Patent Document 1 discloses a manufacturing method in which carbon ions are implanted from one surface of a silicon wafer to form a carbon ion implantation region, and then a silicon epitaxial layer is formed on the surface to form an epitaxial silicon wafer. Yes. In this technique, the carbon ion implantation region functions as a gettering site.

  For example, Patent Document 2 discloses a method of forming a gettering site by irradiation with a transmissive laser (hereinafter referred to as “laser gettering method”) as a gettering method instead of the ion implantation method. . That is, in Patent Document 2, the semiconductor laser substrate is irradiated with a transmissive laser beam with a focused point, and a modified region that has undergone a multiphoton absorption process is formed inside the semiconductor substrate. Let the region be a gettering site.

JP-A-6-338507 JP 2003-264194 A

  In the case of the laser gettering method described in Patent Document 2, the gettering layer is formed at a relatively free depth as compared with the restrictions associated with the ion implantation depth in the ion implantation method as in Patent Document 1. be able to. However, in the vicinity of the modified region formed by laser beam irradiation by the laser gettering method described in Patent Document 2, damage due to laser beam irradiation is inevitably received. It cannot be used as a defect-free active layer required for devices. Note that it is not appropriate to use a region on the side not subjected to laser beam irradiation as an active layer of a high-performance semiconductor device because the gettering site is too far from the device formation region.

  Therefore, the present inventor attempted to produce an epitaxial silicon wafer by applying a laser gettering method to a silicon wafer to form a modified region, and further epitaxially growing a silicon epitaxial layer on the surface subjected to laser beam irradiation. It was. However, in this case, the wafer itself may break due to the heat treatment during the formation of the epitaxial layer. In addition, even if cracking during the formation of the epitaxial layer can be avoided, there is a risk of cracking due to heat treatment in the subsequent device fabrication process. The present inventor considered that this is because secondary dislocation extends from the modified region. Furthermore, it was confirmed that the influence of the damage near the modified region formed by the laser beam irradiation extends to the epitaxial layer.

  As described above, when the laser gettering method is used as a gettering method at present, the defect-free and impurity-free requirements required for the active layer of the substrate material for high-performance semiconductor devices in recent years are sufficient. I can't respond.

  Therefore, in view of the above-mentioned problems, the present invention includes a new substrate material that includes a gettering layer formed by transmissive laser beam irradiation in a support substrate wafer, and that suppresses damage due to transmissive laser beam irradiation on an active layer, That is, it aims at providing the manufacturing method of a silicon bonded wafer, and the silicon bonded wafer manufactured by it.

  As a result of extensive studies by the inventor to solve the above problems, the following findings have been obtained. First, the present inventor forms a silicon epitaxial layer by epitaxial growth, and instead of using the layer as an active layer, a silicon wafer having an active layer is manufactured by bonding a support substrate wafer to an active layer wafer. Inspired to do. It has also been found that the support substrate wafer and the active layer wafer can be bonded together by a vacuum room temperature bonding method even after the support substrate wafer is subjected to the laser gettering method. The silicon bonded wafer thus produced has been found to be capable of imparting sufficient gettering capability to the support substrate wafer and suppressing damage to the active layer due to the transmissive laser beam irradiation.

The gist configuration of the present invention completed based on the above findings is as follows.
(1) A method for producing a silicon bonded wafer in which a support substrate wafer made of single crystal silicon and an active layer made of single crystal silicon are bonded,
A first step of forming a gettering layer inside the support substrate wafer by irradiating a transparent laser beam from one surface side of the support substrate wafer made of single crystal silicon to cause a multiphoton absorption process;
The one surface of the support substrate wafer made of single crystal silicon and the one surface of the active layer wafer are subjected to an activation treatment by irradiating an ionized neutral element at room temperature in a vacuum, A second step of bonding the support substrate wafer and the active layer wafer together by bringing one of the surfaces into an activated surface and subsequently contacting both of the activated surfaces at a vacuum room temperature;
A third step in which the active layer wafer is thinned and the thinned active layer wafer is an active layer;
A method for producing a silicon-bonded wafer, comprising:

  Hereinafter, the bonding method of the support substrate wafer and the active layer wafer in the present invention is referred to as “vacuum room temperature bonding method”. In the vacuum room temperature bonding method, the one surface of the support substrate wafer and the one surface of the active layer wafer are both bonded surfaces. In general, the other surface of the active layer wafer is a main surface that serves as a device formation surface of the silicon bonded wafer.

  (2) The method for producing a silicon bonded wafer according to (1), wherein an output of the transparent laser beam used in the first step is 4 μJ / pulse or less.

  (3) The silicon bonded wafer according to (1) or (2), wherein in the second step, bonding is performed so that misfit dislocations are formed in a bonded region between the support substrate wafer and the active layer wafer. Manufacturing method.

(4) The support substrate wafer and the active layer wafer each have a cutout portion indicating a crystal axis direction,
In the second step, the notch portions of the active layer wafer are bonded together in a state of being rotated in a circumferential direction from the notch portions of the support substrate wafer. Manufacturing method of silicon bonded wafer.

  (5) The method for producing a silicon-bonded wafer according to (3), wherein a surface orientation of the one surface of the support substrate wafer is different from a surface orientation of the one surface of the active layer wafer.

(6) The active layer wafer is an epitaxial silicon wafer in which a silicon epitaxial layer is formed on a silicon wafer,
The method for producing a silicon-bonded wafer according to any one of (1) to (5), wherein the surface of the silicon epitaxial layer is the one surface of the wafer for active layer.

  (7) The method for manufacturing a silicon-bonded wafer according to (6), wherein in the third step, the active layer wafer is thinned from the side opposite to the silicon epitaxial layer, and the silicon wafer is ground and removed.

(8) The silicon substrate according to any one of (1) to (7), wherein the support substrate wafer includes a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (ASTM F121-1979) or less. Wafer manufacturing method.

  (9) The method for producing a silicon bonded wafer according to (8), wherein, in the first step, the gettering layer is formed inside the low oxygen region of the support substrate wafer.

  (10) The production of a silicon bonded wafer according to any one of (1) to (9), wherein the neutral element is at least one selected from the group consisting of argon, neon, xenon, hydrogen, helium and silicon. Method.

  (11) The silicon according to any one of (1) to (10), wherein the activation process in the second step is performed such that an amorphous layer having a thickness of 2 nm or more is formed on one of both surfaces. Manufacturing method of bonded wafer.

  (12) The activation process in the second step is performed according to any one of the above (1) to (10), wherein the activation process is performed so that an amorphous layer having a thickness of 10 nm or more is formed on one of both surfaces. Manufacturing method of silicon bonded wafer.

(13) A silicon bonded wafer in which a support substrate wafer made of single crystal silicon and an active layer made of single crystal silicon are bonded,
The bonding region for bonding the support substrate wafer and the active layer is amorphous,
The support substrate wafer includes a gettering layer in which gettering sites including modified regions having a diameter of 1 μm or more and 10 μm or less are periodically arranged in a radial direction.

  (14) The silicon bonded wafer according to (13), wherein misfit dislocations exist in a bonded region between the support substrate wafer and the active layer.

(15) The support substrate wafer and the active layer each have a cutout portion indicating a crystal axis direction,
The silicon bonded wafer according to (14), wherein the cutout portion of the active layer is located at a position rotated in the circumferential direction from the cutout portion of the support substrate wafer.

  (16) The silicon bonded wafer according to (14), wherein a surface orientation of a bonding surface of the support substrate wafer is different from a surface orientation of a bonding surface of the active layer.

  (17) The silicon bonded wafer according to any one of (13) to (16), wherein the active layer includes a silicon epitaxial layer.

(18) The support substrate wafer according to any one of (13) to (17), including a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (ASTM F121-1979) or less. Silicon bonded wafer.

  (19) The silicon bonded wafer according to (18), wherein the gettering layer is located in the low oxygen region of the support substrate wafer.

  According to the present invention, a method for manufacturing a silicon-bonded wafer in which a support substrate wafer includes a gettering layer formed by irradiating a transmissive laser beam and suppressing damage to the active layer by irradiating the transmissive laser beam, and thereby A manufactured silicon bonded wafer can be provided.

It is a schematic cross section explaining the manufacturing method of the silicon bonded wafer by a 1st embodiment of the present invention. It is a schematic cross-sectional enlarged view explaining the 1st process according to the manufacturing method of this invention. It is a schematic diagram which shows an example of the vacuum room temperature bonding apparatus used in the 2nd process according to the manufacturing method of this invention. It is a schematic cross section explaining the manufacturing method of the silicon bonded wafer by a 2nd embodiment of the present invention. It is a schematic cross section of the annealed wafer applicable to each of the wafer for support substrates and the wafer for active layers in embodiment of this invention. 4 is a photomicrograph showing the modified region of Invention Example 1-1 in Experimental Example 1. It is a graph which shows the TO line | wire intensity | strength by CL defect evaluation of the invention example 2-1 in the experiment example 2, and the comparative example 2-1. It is a microscope picture which shows the modified area | region after the heat processing of the reference example 1 in a reference experiment example.

(Silicon bonded wafer manufacturing method)
Hereinafter, an embodiment of a method for manufacturing a silicon bonded wafer in which a support substrate wafer and an active layer made of single crystal silicon are bonded according to the present invention will be described with reference to FIGS. First, as a first embodiment, a description will be given of an embodiment in which each of a support substrate wafer made of single crystal silicon and an active layer wafer made of single crystal silicon uses a bulk silicon wafer having no silicon epitaxial layer on the surface. To do. Next, as a second embodiment, an embodiment in which an epitaxial silicon wafer in which a silicon epitaxial layer is formed on a silicon wafer is used as an active layer wafer will be described.

(First embodiment)
FIG. 1 shows a flowchart of a method for manufacturing a silicon bonded wafer 100 according to the first embodiment of the present invention. In the method for manufacturing the silicon bonded wafer 100 according to the present embodiment, the multi-photon absorption process is caused by irradiating the transparent laser beam 80 from one surface 110A of the support substrate wafer 110 to generate a multiphoton absorption process. A first step of forming a gettering layer 114 inside is performed (FIGS. 1B and 2). Thereafter, a second step of bonding the support substrate wafer 110 and the active layer wafer by a vacuum room temperature bonding method is performed (FIGS. 1C to 1E). That is, in the second step, an activation treatment is performed by irradiating one surface 110A of the support substrate wafer 110 and one surface 120A of the active layer wafer 120 with the ionized neutral element 90 at room temperature in a vacuum. (FIG. 1 (C)), both one surfaces 110A and 120A are set as activation surfaces 141A and 142A (FIG. 1 (D)). Subsequently, both the activation surfaces 141A and 142A are brought into contact with each other at a vacuum room temperature, whereby the supporting substrate wafer 110 and the active layer wafer 120 are bonded together (FIG. 1E). After the second step, a third step is performed in which the active layer wafer 120 is thinned and the thinned active layer wafer 120 is used as the active layer 125 (FIG. 1F). In this way, the silicon bonded wafer 100 can be manufactured. Hereinafter, the details of each process will be described sequentially. In the vacuum room temperature bonding method, since the one surface 110A of the support substrate wafer and the one surface 120A of the active layer wafer are both bonded surfaces, they are hereinafter referred to as bonded surfaces.

  First, a support substrate wafer 110 made of single crystal silicon and an active layer wafer 120 made of single crystal silicon are prepared (FIG. 1A). Each of the support substrate wafer 110 made of single crystal silicon and the active layer wafer 120 made of single crystal silicon used in the first embodiment is a bulk single crystal silicon wafer having no epitaxial layer on the surface. Any thing can be used. Examples of known bulk single crystal silicon wafers include FZ silicon wafers, CZ silicon wafers, and annealed wafers. Hereinafter, these bulk single crystal silicon wafers are collectively referred to as “silicon wafers”.

<First step>
In the first step, a multi-photon absorption process is caused by irradiating a transparent laser beam 80 from the side of the bonding surface 110 A of the support substrate wafer 110 to form a gettering layer 114 inside the support substrate wafer 110. To do. A method for forming a gettering site by irradiation with the transmissive laser beam 80 will be described in detail with reference to FIG.

  FIG. 2A is an enlarged schematic cross-sectional view for explaining the vicinity of the focal position of the transmissive laser beam 80 immediately after the irradiation of the transmissive laser beam 80 on the support substrate wafer 110 is started. First, the converging lens 81 is used to irradiate the transmissive laser beam 80 with the focal position of the transmissive laser beam 80 at a predetermined depth d from the bonding surface 110 </ b> A of the support substrate wafer 110. By converging the transmissive laser beam 80 at a position of a predetermined depth d, a multiphoton absorption process is generated at the position to form the modified region 115. This modified region 115 is considered to be a region in which silicon is made amorphous by irradiation with the transmissive laser beam 80, and this modified region 115 serves as a gettering sink.

  The modified region 115 formed through the multiphoton absorption process by irradiation with the transmissive laser beam 80 is different from a lattice defect formed through a normal laser light absorption process or a collection of minute defects due to dislocations. Has gettering ability. The multiphoton absorption process means that a large amount of photons are irradiated to a specific portion, that is, the focal point position of the transmissive laser beam 80 in a very short time, and a large amount of light is selectively selectively applied only to the focal point position. Energy is absorbed, thereby causing a reaction such as a change in crystal bonds in the irradiated region.

The gettering layer 114 can be formed inside the support substrate wafer 110 by repeatedly forming the modified region 115 on the entire surface of the wafer at a predetermined interval p (FIG. 2B). . The predetermined depth d is adjusted by condensing the transmissive laser beam 80 using a condensing lens 81 having excellent transmissivity in the near-infrared region and moving the position of the support substrate wafer 110 up and down to focus. Can be controlled by imaging. Further, the predetermined depth d may be appropriately designed according to the use of the silicon bonded wafer 100. Although not intended to be limited, the depth d of the focal point of the transmissive laser beam 80 can be about 1 μm to 50 μm, and preferably about 10 μm to 30 μm. Further, the density of the modified region 115 to be formed is determined according to the irradiation interval p of the transmissive laser beam 80, and the higher the density of the modified region 115, the stronger the gettering layer 114 has a gettering ability. It becomes. For example, the density of the modified region 115 to be formed may be 1.0 × 10 ⁵ pieces / cm ^{2 to} 1.0 × 10 ⁶ pieces / cm ² .

Note that it is preferable to use a low-power laser as the laser source of the transmissive laser beam 80, and it is more preferable to use an ultrashort pulse laser such as a femtosecond laser. An ultrashort pulse laser can make a laser wavelength into a suitable range by exciting a titanium sapphire crystal (solid laser crystal) using a semiconductor laser or the like. The ultrashort pulse laser can reduce the pulse width of the excitation laser beam to 1.0 × 10 ⁻¹⁵ (femto) seconds or less, and therefore can suppress the diffusion of thermal energy generated by excitation compared to other lasers. The light energy can be collected only in the vicinity of the focal point.

  Here, when irradiating the transmissive laser beam 80, the transmissive laser beam 80 is reliably obtained in the passage region 112 before the transmissive laser beam 80 forms an image at the focal position without modifying the passage region 112. It is assumed that laser irradiation is performed under conditions that allow the light to pass through. This laser irradiation condition is determined from 1.1 eV which is the energy band gap of silicon, and the incident wavelength is preferably 1000 nm or more from the viewpoint of transparency. On the other hand, when the wavelength exceeds 1200 nm, the photon energy (laser beam energy) is low because of the long wavelength region, and even if the transmissive laser beam 80 is condensed by the condensing lens 81, single crystal silicon is used. It is preferable that the thickness be 1200 nm or less because there is a possibility that sufficient photon energy for modification inside the support substrate wafer 110 may not be obtained.

  Here, the irradiation output of the transmissive laser beam 80 is preferably 4.0 μJ / pulse or less, and more preferably 3.0 μJ / pulse or less. When the irradiation output is 4.0 μJ / pulse or less, the size of the modified region 115 to be formed is in the range of 1 μm to 10 μm in diameter. Since the modified region 115 has such a size, the modified region 115 can be observed with an optical microscope. If the size of the modified region 115 is within this range, the gettering layer 114 having sufficient gettering capability can be formed. Further, when the gettering layer 114 is subjected to heat treatment, secondary dislocation extends from the modified region 115 as the crystal recovers. However, if the size of the modified region 115 is within this range, the amount of secondary dislocation extension can be suppressed. Therefore, there is almost no influence of the deterioration of crystallinity on the active layer 125. Note that the shape of the modified region 115 to be formed may be an ellipse or the like that is not a strict circle or a shape that cannot be considered a circle. In this case, the circumscribed circle having the smallest diameter that encloses the modified region 115 is approximated to a circle, and the size of the modified region 115 is determined by the diameter of the circumscribed circle.

  Therefore, in the gettering layer 114 thus formed by irradiation with the transmissive laser beam 80, gettering sites composed of the modified regions 115 having a diameter of 1 μm or more and 10 or less are periodically arranged in the radial direction. As described above, each of the modified regions 115 is considered to be a region where silicon is amorphized.

  In addition, it is preferable that the irradiation output of the transmissive laser beam 80 is 1.0 μJ / pulse or more. By doing so, the gettering layer 114 having sufficient gettering capability can be formed. Further, other irradiation conditions of the transmissive laser beam 80 can be general as long as a multiphoton absorption process occurs, for example, a beam diameter of 0.5 to 2.0 μm and a repetition frequency of about 1 kHz to 100 MHz. can do.

<Second step>
Subsequent to the first step of performing the laser gettering method, in the second step, the support substrate wafer 110 and the active layer wafer 120 are bonded together by a vacuum room temperature bonding method (FIGS. 1C to 1E). Specifically, the bonded surfaces 110A and 120A of the support substrate wafer 110 and the active layer wafer 120 are irradiated with ionized neutral elements 90 under vacuum to activate both bonded surfaces 110A and 120A. The activation surface. As a result, amorphous layers 141 and 142 are formed on the bonding surfaces 110A and 120A, respectively, and dangling bonds (bonding hands) inherent to silicon appear on the surfaces. Since this dangling bond is unstable in terms of energy, if both activated surfaces 141A and 142A are subsequently brought into contact with each other at a vacuum room temperature, the dangling bonds on both activated surfaces 141A and 142A are eliminated. Thus, the bonding force works instantaneously, and the two wafers are firmly bonded without any heat treatment or the like and without a non-bonded region (void).

  As an activation treatment method in the vacuum room temperature bonding method, an ionized neutral element accelerated by an ion beam apparatus is collided with both bonded surfaces, and both bonded surfaces are sputtered, or neutral elements ionized in a plasma atmosphere. Can be performed by performing a plasma etching process in which etching is performed by accelerating the two bonded surfaces.

  FIG. 3 shows an example of a vacuum room temperature bonding apparatus for bonding two wafers after activating both bonded surfaces of the support substrate wafer 110 and the active layer wafer 120 by plasma etching. The vacuum room temperature bonding apparatus 50 includes a plasma chamber 51, a gas introduction port 52, a vacuum pump 53, a pulse voltage application device 54, and wafer fixing bases 55A and 55B.

  First, the support substrate wafer 110 and the active layer wafer 120 are mounted and fixed on the wafer fixing bases 55A and 55B in the plasma chamber 51, respectively. Next, the inside of the plasma chamber 51 is depressurized by the vacuum pump 53, and then the source gas is introduced into the plasma chamber 51 from the gas inlet 52. Subsequently, a negative voltage is applied in a pulsed manner to the wafer fixing bases 55A and 55B (and the support substrate wafer 110 and the active layer wafer 120) by the pulse voltage application device 54. Accordingly, plasma of the source gas can be generated, and ions of the source gas contained in the generated plasma can be accelerated and irradiated toward both the wafers 110 and 120.

  The neutral element to be irradiated is preferably at least one selected from argon (Ar), neon (Ne), xenon (Xe), hydrogen (H), helium (He), and silicon (Si).

The chamber pressure (degree of vacuum) in the plasma chamber 51 is preferably 1 × 10 ⁻⁵ Pa or less. Thereby, it is possible to suppress activation of the elements sputtered on the surface of each wafer and perform the activation process without lowering the dangling bond formation rate.

  The pulse voltage applied to the support substrate wafer 110 and the active layer wafer 120 is set so that the acceleration energy of the irradiation element with respect to the wafer surface is 100 eV or more and 10 keV or less. When the acceleration energy is less than 100 eV, the irradiated neutral element is deposited on the wafer surface, and a dangling bond cannot be formed on the wafer surface. On the other hand, when the acceleration energy exceeds 10 keV, the irradiated element is injected into the wafer, and even in this case, dangling bonds cannot be formed on the wafer surface.

  The frequency of the pulse voltage determines the number of times that the support substrate wafer 110 and the active layer wafer 120 are each irradiated with ions. The frequency of the pulse voltage is preferably 10 Hz to 10 kHz. Here, by setting the frequency of the pulse voltage to 10 Hz or more, variations in ion irradiation can be absorbed and the ion irradiation amount is stabilized. Moreover, the plasma formation by glow discharge is stabilized by setting it as 10 kHz or less.

  The pulse width of the pulse voltage determines the time during which ions are irradiated to each of the support substrate wafer 110 and the active layer wafer 120. The pulse width is preferably 1 μsec or more and 10 ms or less. By setting it to 1 microsecond or more, the wafers 110 and 120 can be stably irradiated with ions. Moreover, the plasma formation by glow discharge is stabilized by setting it as 10 milliseconds or less.

  In the above-described processing, each of the support substrate wafer 110 and the active layer wafer 120 is not heated, so that the temperature is room temperature (usually 30 ° C. to 90 ° C.).

  Here, in this embodiment, the gettering layer 114 is formed on the support substrate wafer 110 by the laser gettering method in the first step, and the support substrate wafer on the side subjected to the transmission laser beam irradiation in the subsequent second step. The technical significance of bonding the bonding surface 110A (ie, the activation surface 141A) of the 110 and the bonding surface 120A (ie, the activation surface 142A) of the active layer wafer 120 will be described in detail below. .

  As described above, the modified region 115 formed by the laser gettering method is considered to be a region where silicon is amorphized. Even around the modified region 115, some damage is inevitably received due to the influence of laser irradiation. Further, when this modified region 115 is subjected to a heat treatment performed in a device manufacturing process or the like, secondary dislocations extend from the modified region 115 along with crystal recovery. First, in this embodiment, since the active layer wafer 120 and the support substrate wafer 110 are bonded together by a vacuum room temperature bonding method, damage due to laser irradiation does not reach the active layer wafer 120. Furthermore, the present inventor has found that the bonding region 140 after bonding the amorphous layers 141 and 142 has a function of suppressing secondary dislocation from the modified region 115 from extending to the active layer 125. . Therefore, when the silicon bonded wafer 100 is subjected to a heat treatment, the secondary dislocation extends from the modified region 115, but the extension of the secondary dislocation can be kept inside the support substrate wafer 110. Therefore, it is considered that the secondary dislocation extension due to the heat treatment hardly affects the active layer 125.

  Furthermore, the inventor has also found that the bonding region 140 has a function of suppressing oxygen diffusion from the support substrate wafer 110 to the active layer wafer 120. Therefore, it is experimentally clarified that the silicon bonded wafer 100 can extremely effectively suppress the adverse effect on the crystallinity on the active layer 125 while maintaining the gettering capability of the gettering layer 114 formed by the laser gettering method. became. In recent years, there has been a demand for a semiconductor substrate material having a low oxygen concentration, and if both the support substrate wafer 110 and the active layer wafer 120 are low oxygen concentration silicon wafers, the oxygen concentration of the active layer 125 remains low. It can also be.

  Note that the bonding region 140 after the amorphous layers 141 and 142 are bonded also functions as a gettering site for capturing heavy metals. Since the junction region 140 is directly under the active layer 125, it exhibits a high gettering capability and can sufficiently suppress heavy metal contamination of the active layer 125. As a result, it is also preferable that the characteristics of the device manufactured in the active layer 125 are not deteriorated.

  Here, the activation treatment is preferably performed so that the thicknesses of the amorphous layers 141 and 142 are both 2 nm or more. Thereby, the bonding region 140 after the amorphous layers 141 and 142 are bonded together can sufficiently function as a block layer that blocks thermal diffusion of impurities in the support substrate wafer 110 to the active layer 125, Further, the amorphous and gettering ability can be further enhanced. The thickness of the amorphous layers 141 and 142 can be adjusted by adjusting the acceleration voltage of ions.

  Moreover, in order to obtain the effect accompanying the thickness of the amorphous layers 141 and 142 more reliably, the activation treatment is preferably performed so that the thicknesses of the amorphous layers 141 and 142 are both 10 nm or more.

<Third step>
Following the second step of bonding by vacuum room temperature bonding, in the third step, the active layer wafer 120 is thinned, and the thinned active layer wafer is used as the active layer 125 (FIG. 1F). ). The thinning of the active layer wafer 120 can be suitably performed using well-known surface grinding and mirror polishing methods. In addition, this thinning may be performed using other techniques such as a known smart cut method.

  In the silicon bonded wafer 100 manufactured in this way, the support substrate wafer 110 and the active layer wafer 120 are bonded together by a vacuum room temperature bonding method, so that secondary dislocations from the modified region 115 extend to the active layer 125. It is also suppressed. Therefore, since the active layer 125 can take over a good defect state of the active layer wafer 120, if a defect-free silicon wafer is used as the active layer wafer 120, the active layer 125 has a defect-free quality of the silicon wafer. Can be maintained.

  As described above, the support substrate wafer 110 includes the gettering layer 114 formed by irradiation with the transmissive laser beam 80 by performing the first to third steps according to the present embodiment, and the defect-free active layer. A method of manufacturing a silicon bonded wafer 100 having 125 can be provided. The silicon bonded wafer 100 manufactured in this way can provide a sufficient gettering capability to the support substrate wafer 110 and can realize a defect-free active layer 125.

In addition, as described above in the second step, the bonding region 140 formed by the vacuum room temperature bonding method has a function of suppressing oxygen diffusion from the support substrate wafer 110 to the active layer wafer 120. Therefore, from the viewpoint of maintaining the oxygen concentration of the active layer 125 at a low oxygen concentration, the support substrate wafer 110 has an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (measurement conformity according to ASTM F121-1979; The same is true.) A single crystal silicon wafer including the following low-oxygen region is preferable, and the low-oxygen region is more preferably located on the surface layer portion of the support substrate wafer 110 on the bonding surface 110A side. The active layer wafer 120 is also preferably a single crystal silicon wafer including a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ or less, and the low oxygen region is a bonding surface of the active layer wafer 120. More preferably, it is located in the surface layer part on the 120A side.

Since the surface layer portion on the bonding surface 120A side of the active layer wafer 120 is a portion that becomes the active layer 125 of the silicon bonded wafer 100, a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ or less is used. Thus, an active layer 125 having a low oxygen concentration can be obtained. Moreover, since bonding is performed by the vacuum room temperature bonding method, it is sufficient that oxygen diffuses from the portion other than the surface layer portion of the active layer wafer 120 and the support substrate wafer 110 into the surface layer portion at the time of bonding. Can be suppressed.

Further, the surface layer portion on the bonding surface 110A side of the support substrate wafer 110 is a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ or less, thereby diffusing oxygen from the support substrate during the device manufacturing process. The active layer 125 can be maintained at a low oxygen concentration by being suppressed. In addition, since the bonding is performed by the vacuum room temperature bonding method, the low oxygen region can maintain the low oxygen concentration even after the bonding. Therefore, the surface layer portion of the support substrate wafer 110 can function as an oxygen diffusion suppression layer during the device manufacturing process.

  In this case, it is also preferable to form the gettering layer 114 in the low oxygen region of the support substrate wafer 110 in the first step. A silicon wafer with a low oxygen concentration is unlikely to form BMD even when subjected to a heat treatment, and therefore it is expected that the gettering capability will be insufficient. Therefore, by forming a gettering site in the low oxygen region, heavy metal contamination to the active layer 125 can be more reliably suppressed.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. Note that, in principle, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted. In the following, similarly, the same components are denoted by the same reference numerals in principle, and description thereof is omitted.

In the second embodiment, as shown in FIG. 2A, an epitaxial silicon wafer in which a silicon epitaxial layer 122 is formed on a silicon wafer 121 is used as the active layer wafer 120. This means that an epitaxial silicon wafer is used as the active layer wafer 120 having the low oxygen region described above. The surface 122A of the silicon epitaxial layer 122 is used as a bonding surface 120A of the active layer wafer 120. In other processes, the silicon bonded wafer 200 in which the active layer 125 is formed of the silicon epitaxial layer 122 can be manufactured in the same manner as in the first embodiment. The oxygen concentration of the silicon epitaxial layer 122 is generally two orders of magnitude lower than the oxygen concentration of the bulk silicon wafer 121 serving as the substrate, and has an oxygen concentration below the detection limit of 3 × 10 ¹⁶ atoms / cm ³ or less. An epitaxial layer can be formed. According to the present embodiment, the silicon epitaxial layer 122 can be used as the active layer 125 of the silicon bonded wafer 200.

  In the second embodiment, it is preferable that in the third step, the active layer wafer 120 is thinned from the surface opposite to the silicon epitaxial layer 122 and the silicon wafer 121 is ground and removed. In this case, in addition to grinding and removing the silicon wafer 121, it is also preferable to partially remove the silicon epitaxial layer 122 by grinding. Although impurities may diffuse from the silicon wafer 121 in the portion of the silicon epitaxial layer 122 on the silicon wafer 121 side during epitaxial growth, the influence of impurity diffusion can be suppressed by doing so.

<Epitaxial silicon wafer>
When an epitaxial silicon wafer is used as the active layer wafer 120, the thickness of the epitaxial layer can be appropriately determined in consideration of the target thickness of the active layer 125, but should be thicker than the target thickness of the active layer. Is preferred. In other words, the predetermined thickness portion from the silicon wafer interface of the epitaxial layer is affected by the diffusion of oxygen from the silicon wafer in the epitaxial layer formation process, but by removing the portion in the thinning step, the active layer and This is because the resulting epitaxial layer can have a low oxygen concentration.

The epitaxial layer can be formed under general conditions. For example, hydrogen (H) is used as a carrier gas, and a source gas such as dichlorosilane (H ₂ Cl ₂ Si) or trichlorosilane (HCl ₃ Si) is introduced into the chamber, and the growth temperature differs depending on the source gas used. The silicon epitaxial layer can be epitaxially grown by a CVD (Chemical Vapor Deposition) method at a temperature in the range of approximately 1000 to 1200 ° C.

<Missfit dislocation formation in the bonding area>
Incidentally, misfit dislocations are not usually formed in the bonding region 140 of the silicon bonded wafer 100 in which the support substrate wafer 110 and the active layer wafer 120 are bonded together by the vacuum room temperature bonding method. This is because, in general, silicon wafers of the same type having the same plane orientation are bonded together so that the notches indicating the crystal axis direction are aligned. However, in the present embodiment, in the second step of performing vacuum room temperature bonding, it is preferable to perform bonding so that misfit dislocations are formed at the interface between the support substrate wafer 110 and the active layer wafer 120.

  Since the bonding region 140 is amorphous, recrystallization proceeds gradually by the heat treatment. Therefore, there is a possibility that the secondary dislocation extension suppressing function from the modified region 115 is gradually lost. However, by forming misfit dislocations in the bonding region 140, the bonding region 140 can maintain the function of suppressing secondary dislocation extension even after recrystallization has progressed.

  In order to form such misfit dislocations at the interface, for example, the support substrate wafer 110 and the active layer wafer 120 each have a notch portion indicating the crystal axis direction, and in the bonding step, the support substrate It is preferable that the bonding is performed in a state in which the notch portion of the wafer for wafer 110 is in a position rotated in the circumferential direction from the notch portion of the wafer for active layer 120. The rotation angle is not particularly limited, but misfit dislocations can be formed sufficiently if the rotation angle is rotated by 2 ° or more, and it is preferable to rotate the rotation angle by 5 ° or more. The upper limit of the rotation angle is not particularly limited, but can be 358 °. Such a shift of the rotation angle may be adjusted before the activation process, but considering the stability of the activation process, it is preferable to adjust the rotation angle immediately before the bonding after the activation process. The notch may be a notch or an orientation flat (sometimes referred to as “orientation flat”) that is generally provided in a silicon wafer.

  Since the notch portion of the support substrate wafer 110 and the notch portion of the active layer wafer 120 are joined while being shifted in the circumferential direction, a crystal orientation shift occurs, so that the support substrate wafer 110 and the active layer wafer Misfit dislocations are formed at the interface with the wafer 120.

  In addition, when the plane orientation of the bonding 110A of the support substrate wafer 110 and the plane orientation of the bonding 120A of the active layer wafer 120 are different from each other, misfit dislocations may be formed at the bonding interface between the two. it can. For example, if the plane orientation of the bonding 110A of the support substrate wafer 110 is the (111) plane and the plane orientation of the bonding 120A of the active layer wafer 120 is the (100) plane, misfit dislocations are formed at the interface. be able to. Of course, this combination may be reversed, and the combination of plane orientations is not limited to the above example, and may be the (110) plane. When the surface orientations of the two bondings are different from each other, the notch portions of the support substrate wafer 110 and the notch portions of the active layer wafer 120 may be aligned and bonded.

  Hereinafter, various silicon wafers that can be used in the first and second embodiments described above will be described in more detail.

  Examples of the bulk single crystal silicon wafer used for the support substrate wafer 110 and the active layer wafer 120 include an FZ silicon wafer, a CZ silicon wafer, and an annealed wafer. About a CZ silicon wafer, it is more preferable that a surface layer part is a low oxygen concentration.

<FZ silicon wafer>
The FZ silicon wafer is a wafer obtained by slicing a single crystal silicon ingot grown by a floating zone (FZ) method with a wire saw or the like. The wafer has an oxygen concentration over the entire direction of 3 × 10 ¹⁶ atoms / cm ³ or less and below the detection limit. Therefore, it is suitable for use as the support substrate wafer 110 and the active layer wafer 120 in the present invention.

<CZ silicon wafer>
The CZ silicon wafer is a wafer obtained by slicing a single crystal silicon ingot grown by the Czochralski (CZ) method with a wire saw or the like, and the oxygen concentration is 1 × 10 ¹⁷ atoms / cm ³ to. A silicon wafer of 18 × 10 ¹⁷ atoms / cm ³ is obtained. In the present invention, for example, a CZ silicon wafer manufactured by using the MCZ (Magnetic field applied Czochralski) method or the like and having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ or less in the entire thickness direction is used as the supporting substrate wafer 110 and More preferably, the active layer wafer 120 is used.

<Annealed wafer>
An annealing wafer in which a silicon wafer is heat-treated in a non-oxidizing atmosphere or a reducing atmosphere and oxygen in the surface layer portion of the silicon wafer is diffused outward to reduce the oxygen concentration in the surface layer portion is used for a support substrate. It is also preferable to use as the wafer 110 and the active layer wafer 120. FIG. 5 shows a schematic cross-sectional view of the annealed wafer 60. When used in the present invention, the DZ layer 60B, which is the surface layer portion, can have an oxygen concentration of 3 × 10 ¹⁶ atoms / cm ³ or less. As a result, when the annealed wafer 60 is used as the support substrate wafer 10, the effect of suppressing the diffusion of oxygen to the active layer 125 during the device fabrication process can be sufficiently obtained, and the annealed wafer 60 can be used as the active layer wafer 120. In this case, an active layer 125 having a low oxygen concentration can be obtained.

On the other hand, in the annealed wafer 60, the oxygen concentration of the silicon wafer before annealing, that is, the oxygen concentration other than the surface layer portion (the central portion 60A) of the annealed wafer 60 is 1 × 10 ¹⁷ atoms / cm ³ or more and 16 × 10 ^17. It is preferable to be atoms / cm ³ or less. In the case of 1 × 10 ¹⁷ atoms / cm ³ or more, there is no possibility of occurrence of slip at the time of annealing, and in the case of exceeding 16 × 10 ¹⁷ atoms / cm ³ , the influence of oxygen precipitates formed at the time of annealing on the active layer region This is because even when the photolithography process is performed during the device manufacturing process, no pattern processing abnormality occurs.

When the annealed wafer 60 is used as the support substrate wafer 110, the thickness of the DZ layer 60B at which the oxygen concentration is 3 × 10 ¹⁶ atoms / cm ³ or less is not particularly limited, but is preferably 5 to 30 μm. When the thickness is 5 μm or more, the effect of suppressing the diffusion of oxygen to the active layer 125 can be sufficiently obtained during the device fabrication process. When the thickness exceeds 30 μm, slip is unlikely to occur during annealing, and the annealing time becomes longer and produced. This is because there is no loss of sex.

On the other hand, when the annealed wafer 60 is used as the active layer wafer 120, the thickness of the DZ layer having an oxygen concentration of 3 × 10 ¹⁶ atoms / cm ³ or less can be appropriately determined in consideration of the target thickness of the active layer 125. Good.

  Although the heat treatment conditions for obtaining the DZ layer having the above thickness depend on the oxygen concentration of the silicon wafer before annealing, for example, in a temperature range of 1200 ° C. to 1350 ° C. using a batch heat treatment furnace, It can be 2 hours or more. The gas atmosphere during the heat treatment can be an inert gas atmosphere such as argon gas.

  As the support substrate wafer 110 and the active layer wafer 120, any combination of the above-described various wafers can be used. When an epitaxial silicon wafer is used as the active layer wafer 120, it is also preferable that the bulk silicon wafer 121 serving as the base substrate is the above-described various wafers.

  Each wafer can be made to be n-type or p-type by adding an arbitrary impurity, and the resistivity can be adjusted by adjusting the concentration of the impurity.

<Silicon wafer not containing dislocation clusters and COP>
In addition, in the manufacture of a single crystal silicon ingot by the CZ method, which is a material of a silicon wafer, the distribution of defects formed in the single crystal differs depending on the thermal history received by the growing single crystal ingot, and the single crystal ingot It is known that crystal regions such as dislocation clusters due to interstitial silicon, vacancy-caused vacancy agglomerated defects (COP: Crystal Originated Particles), and defect-free regions where no dislocation clusters or COP exist are formed. In the present embodiment, it is also preferable to use a silicon wafer that does not contain dislocation clusters and vacancy agglomerated defects (COP: Crystal Originated Particles) as the support substrate wafer 110 and the active layer wafer 120. In particular, it is more preferable to use a silicon wafer containing no dislocation clusters and COPs for the active layer wafer 120 that becomes the active layer 125 after thinning. As a result, an active layer 125 that does not contain dislocation clusters and COPs can be obtained, and generation of dark current in the photodiode formation region (space charge region) can be suppressed.

  Here, the “silicon wafer not containing COP” in the present invention means a silicon wafer in which COP is not detected by observation and evaluation described below. That is, first, a silicon wafer cut out from a single crystal silicon ingot grown by the CZ method is subjected to SC-1 cleaning (that is, ammonia water, hydrogen peroxide water, and ultrapure water are 1: 1: 15). The surface of the silicon wafer after cleaning was observed and evaluated using Surfscan SP-2 as a surface defect inspection device as a surface defect inspection device. (LPD: Light Point Defect) is specified. At this time, the observation mode is set to Oblique mode (oblique incidence mode), and surface pits are estimated based on the detection size ratio of the Wide Narrow channel. The LPD thus identified is evaluated as to whether it is a COP by using an atomic force microscope (AFM). By this observation and evaluation, a silicon wafer in which COP is not observed is referred to as a “silicon wafer not including COP”.

  On the other hand, dislocation clusters are large (about 10 μm) defects (dislocation loops) formed as an aggregate of excess interstitial silicon, and are manifested by etching such as seco-etching or Cu decoration. By doing so, the presence or absence of dislocation clusters can be easily confirmed on a visual level.

(Silicon bonded wafer)
The silicon bonded wafer 100 according to one embodiment of the present invention can be manufactured according to the first embodiment described above. That is, as shown in FIG. 1F, the silicon bonded wafer 100 is formed by bonding a support substrate wafer 110 made of single crystal silicon and an active layer 125 made of single crystal silicon. The bonding region 140 for bonding the support substrate wafer 110 and the active layer 125 is amorphous, and the support substrate wafer 110 has a gettering site including a modified region 115 having a diameter of 1 μm or more and 10 or less in the radial direction. It includes gettering layers 114 arranged periodically. This silicon bonded wafer 100 includes a gettering layer 114 formed by irradiation with a transmission laser beam and having a sufficient gettering capability, and the support substrate wafer 110 includes damage to the active layer 125 due to irradiation with the transmission laser beam. Is suppressed.

  In the silicon bonded wafer 100, it is preferable that misfit dislocations exist in the bonded region 140 between the support substrate wafer 110 and the active layer 125. Here, the support substrate wafer 110 and the active layer 125 each have a cutout portion indicating the crystal axis direction, and the cutout portion of the active layer 125 rotates in the circumferential direction from the cutout portion of the support substrate wafer 110. It is preferable that it exists in the position made to do. On the other hand, it is also preferable that the surface orientation of the bonding surface of the support substrate wafer 110 and the surface orientation of the bonding surface of the active layer 125 are different from each other. Note that the bonding surface corresponds to the bonding surface described above in the embodiment of the method for manufacturing the silicon bonded wafer 100.

  In addition, as shown in FIG. 4F, in the silicon bonded wafer 200, the active layer 125 is preferably made of a silicon epitaxial layer.

The support substrate wafer 110 preferably includes a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (ASTM F121-1979) or less, and a gettering layer is formed in the low oxygen region of the support substrate wafer 110. It is also preferred that 114 is located.

[Experimental Example 1]
(Invention Example 1-1)
A silicon bonded wafer according to Invention Example 1-1 was manufactured according to the procedure shown in FIG. First, as a support substrate wafer, an n-type CZ silicon wafer having a diameter of 200 mm and a thickness of 725 μm (oxygen concentration: 0.3 × 10 ¹⁸ atoms / cm ³ , dopant: phosphorus, dopant concentration: 4.4 × 10 ¹⁴ atoms) / Cm ³ , target resistivity: 10 Ω · cm). Further, as an active layer wafer, an n-type CZ silicon wafer having a diameter of 200 mm and a thickness of 725 μm (oxygen concentration: 0.3 × 10 ¹⁸ atoms / cm ³ , dopant: phosphorus, dopant concentration: 1.4 × 10 ¹⁴ atoms) / cm ^3, the target resistivity: the 30 [Omega · cm) on the silicon epitaxial layer having a thickness of 8 [mu] m (dopant: phosphorus dopant ^{concentration: 4.4 × 10 14 atoms / cm} 3, the target resistivity: 10 [Omega · cm) epitaxial growth An epitaxial silicon wafer was prepared.

  Next, under the irradiation conditions of beam wavelength: 1064 nm, laser spot length: 1 μm, pulse energy: 1.50 μJ / pulse, pulse width 30 nm, repetition period: 100 kHz, a transparent laser beam is irradiated onto the support substrate wafer, A gettering layer was formed. The depth position d of the focal spot was set to 30 μm.

Subsequently, the support substrate wafer and the active layer wafer were bonded together by a vacuum room temperature bonding method. Specifically, the support substrate wafer and the active layer wafer are introduced into the vacuum room temperature bonding apparatus shown in FIG. 3, the temperature in the chamber is 25 ° C., and the pressure in the chamber is 1.0 × 10 ⁻⁵ Pa. Then, an activation treatment is performed to irradiate the surface of the epitaxial layer, which is a surface layer portion of each wafer, with Ar ions under conditions of acceleration voltage: 600 eV, frequency: 150 Hz, pulse width: 50 × 10 ⁻⁶ seconds, Amorphous layers having a thickness of 5 nm were formed on both surfaces. Then, the wafer for support substrates and the wafer for active layers were bonded together through the amorphous layer of both surfaces.

  Finally, the active layer wafer is ground and polished from the side opposite to the silicon epitaxial layer to remove part of the active layer wafer in the thickness direction of the silicon wafer and the epitaxial layer. As a result, the epitaxial layer was thinned to leave a thickness of 4 μm to obtain a silicon bonded wafer according to Invention Example 1-1.

(Comparative Example 1-1)
Similar to the support substrate wafer of Invention Example 1-1, an n-type CZ silicon wafer having a diameter of 200 mm and a thickness of 725 μm (oxygen concentration: 0.3 × 10 ¹⁸ atoms / cm ³ , dopant: phosphorus, dopant concentration: 4. 4 × 10 ¹⁴ atoms / cm ³ and target resistivity: 10 Ω · cm) were prepared. Next, a transparent laser beam was irradiated onto the silicon wafer under the same conditions as in Invention Example 1-1. Furthermore, a silicon epitaxial layer (dopant: phosphorus, dopant concentration: 4.4 × 10 ¹⁴ atoms / cm ³ , target resistivity: 10 Ω · cm) having a thickness of 4 μm is formed as an active layer, and the example according to Comparative Example 1-1 An epitaxial silicon wafer was produced.

(Comparative Example 1-2)
In Comparative Example 1-1, an epitaxial silicon wafer according to Comparative Example 1-2 was produced in the same manner as Comparative Example 1-1 except that the transparent laser beam was not irradiated onto the silicon wafer.

  Each sample produced in Invention Example 1-1 and Comparative Examples 1-1 and 1-2 was evaluated for epitaxial defect evaluation, oxygen concentration analysis, and gettering ability evaluation. Furthermore, about invention example 1-1, the cross-sectional photograph and TEM cross-sectional photograph by an optical microscope were acquired. The respective micrographs are shown in FIGS. 6 (A) and 6 (B).

<Epitaxial defect evaluation>
Each sample was measured in Normal mode using Surfscan SP1 (manufactured by KLA-Tencor), and defects having a size of 0.2 μm or more were detected as LPD. The results are shown in Table 1.

<Oxygen concentration analysis>
For each sample, the oxygen concentration distribution in the depth direction of the active layer was measured by secondary ion mass spectrometry (SIMS). Table 1 shows the oxygen concentration at a depth of 3 μm from the surface of the active layer.

<Evaluation of gettering ability>
The surface of the active layer of each sample was intentionally contaminated by spin coating using Ni contamination liquid (1 × 10 ¹² atoms / cm ² ), and then heat-treated at 800 ° C. for 1 hour in a nitrogen atmosphere. . Next, after immersing in the light solution for 3 minutes, the surface of the active layer was observed with an optical microscope, and the presence or absence of generation of pits (surface pits caused by nickel silicide: Ni pits) observed on the surface of the active layer was investigated. The results are shown in Table 1.

  First, from FIG. 6A, it is confirmed that the modified region is formed and the bonding region is amorphous. Further, all of the modified regions were in the range of 1 μm to 8 μm. FIG. 6B corresponds to an enlarged view of a TEM cross-sectional photograph of this modified layer, suggesting that the modified region is an amorphous region.

  In Table 1, in Example 1-1 and Comparative Example 1-2, the number of LPDs is about several, whereas in Comparative Example 1-1, the number of LPDs is larger than that of Invention Example 1-1 and Comparative Example 1-2. There are extremely many. This is presumably because damage caused by laser irradiation also affects the epitaxial layer. Moreover, in Table 1, the oxygen concentration of Invention Example 1-1 is sufficiently smaller than Comparative Example 1-1 and Comparative Example 1-2. This is thought to be because the bonding region suppressed oxygen diffusion from the support substrate wafer. Furthermore, from Table 1, it can also be confirmed that the invention example 1-1 and the comparative example 1-1 that were irradiated with the transparent laser beam have gettering ability.

  From the above, in Invention Example 1-1 that satisfies the production conditions of the present invention, the support substrate wafer includes a gettering layer formed by irradiating a transmissive laser beam, and the transmissive laser to the active layer It was confirmed that a silicon bonded wafer in which damage caused by beam irradiation was suppressed could be manufactured. On the other hand, in Comparative Example 1-1, since many epitaxial defects exist, the epitaxial layer cannot be used as an active layer. In Comparative Example 1-2, there is no gettering capability.

[Experiment 2]
(Invention Example 2-1)
A silicon bonded wafer according to Invention Example 2-1 was manufactured according to the procedure shown in FIG. First, the support substrate wafer and the active layer wafer were the same as those in Invention Example 1-1. Then, an epitaxial silicon wafer obtained by epitaxially growing a 15 μm thick silicon epitaxial layer (dopant: phosphorus, dopant concentration: 4.4 × 10 ¹⁴ atoms / cm ³ , target resistivity: 10 Ω · cm) on the active layer wafer is obtained. Prepared.

  Next, a gettering layer was formed by irradiating the support substrate wafer with a transparent laser beam in the same manner as in Example 1-1 except that the depth of the focal spot was 3 μm.

  Subsequently, in the same manner as in Example 1-1, the support substrate wafer and the active layer wafer were bonded together by a vacuum room temperature bonding method. Then, the active layer wafer is ground and polished from the side opposite to the silicon epitaxial layer, and a part of the active layer wafer in the thickness direction of the silicon wafer and the epitaxial layer is removed as an active layer. The epitaxial layer was thinned to leave a thickness of 10 μm to obtain a silicon bonded wafer according to Invention Example 2-1.

(Comparative Example 2-1)
Similar to the support substrate wafer of Invention Example 2-1, an n-type CZ silicon wafer having a diameter of 200 mm and a thickness of 725 μm (oxygen concentration: 0.3 × 10 ¹⁸ atoms / cm ³ , dopant: phosphorus, dopant concentration: 4. 4 × 10 ¹⁴ atoms / cm ³ and target resistivity: 10 Ω · cm) were prepared. Next, a transparent laser beam was irradiated onto the silicon wafer under the same conditions as in Invention Example 2-1. Further, a silicon epitaxial layer having a thickness of 10 μm (dopant: phosphorus, dopant concentration: 4.4 × 10 ¹⁴ atoms / cm ³ , target resistivity: 10 Ω · cm) is formed as an active layer, and the method according to Comparative Example 2-1 An epitaxial silicon wafer was produced.

  Each evaluation of CL evaluation, secondary dislocation observation, and device characteristic evaluation was implemented with respect to each sample produced in Invention Example 2-1 and Comparative Example 2-1.

<CL evaluation>
The CL method (Cathode Luminescence: cathode luminescence) was performed from the cross-sectional direction on the sample obtained by obliquely polishing each sample, and the TO line intensity was obtained from the CL spectrum in the thickness (depth) direction of the active layer. The TO line is a spectrum peculiar to the Si element corresponding to the Si band gap observed by the CL method. The stronger the TO line, the higher the Si crystallinity. As measurement conditions, an electron beam was irradiated at 20 keV under 33K. The measurement result of CL intensity | strength of the thickness direction of Example 2-1 and Comparative Example 2-1 is shown in FIG. The TO line intensity at the outermost surface of the epitaxial layer is 100%.

<Secondary dislocation observation>
Each sample was heat-treated at 1100 ° C. for 8 hours. This corresponds to heat treatment simulating a device manufacturing process. The amount of secondary dislocation extension after heat treatment from the modified region was measured from the TEM cross-sectional view. The results are shown in Table 2.

<Device characteristics evaluation>
A pn junction diode was prepared from each sample, and the leakage current value of each pn junction diode was measured. The results are shown in Table 2.

  First, from FIG. 7, in Comparative Example 2-1, on the support substrate side of the epitaxial layer, a decrease in TO line intensity was observed. This is considered to be due to the influence of defects generated in the transmission region of the transmission laser beam. On the other hand, in the invention example 2-1, since the active layer is formed by the vacuum room temperature bonding method, the influence of the defect generated in the transmission region of the transmission laser beam is not recognized. Note that, at the position of 13 μm deep from the wafer surface, which is the focal point position of the transmissive laser beam, the comparative example 2-1 has higher TO line intensity than the invention example 2-1. This is considered to be due to partial crystal recovery of the modified region due to the heat treatment during epitaxial layer growth.

  Next, from Table 2, regarding the amount of secondary dislocation extension, in Invention Example 2-1, it is 2.4 μm or less, which means that the secondary dislocation does not extend to the active layer. On the other hand, since it is 7.2 μm in Comparative Example 2-1, it is confirmed that secondary dislocation extends to the active layer during the device manufacturing process in Comparative Example 2-1. In addition, since the inventive example 2-1 has a much smaller leakage current than the comparative example 2-1, the silicon bonded wafer according to the inventive example 2-1 is suitable for use in a high-performance semiconductor device.

[Reference experiment example]
A silicon bonded wafer according to Reference Example 1 was manufactured under the same conditions as in Invention Example 1-1. This sample was heat-treated at 1100 ° C. for 2 hours. And the cross-sectional photograph and TEM cross-sectional photograph by an optical microscope were acquired similarly to Experimental example 1. FIG. The respective micrographs are shown in FIGS. 8 (A) and 8 (B). Note that in FIG. 8A, a two-dot chain line is attached in order to clarify the position of the joining region.

  Comparing FIG. 6 (A) and FIG. 8 (A), it is confirmed that the modified region has crystal recovered. Further, when FIG. 6B is compared with FIG. 8B, it is also confirmed that secondary dislocation extends as the modified region recovers from the crystal.

  According to the present invention, a method for manufacturing a silicon-bonded wafer in which a support substrate wafer includes a gettering layer formed by irradiating a transmissive laser beam and suppressing damage to the active layer by irradiating the transmissive laser beam, and thereby A manufactured silicon bonded wafer can be provided.

100, 200 Silicon bonded wafer 110 Support substrate wafer 114 Gettering layer 115 Modified region 120 Active layer wafer 121 Silicon wafer 122 Silicon epitaxial layer 125 Active layer 140 Bonded region 141, 142 Amorphous layer 50 Vacuum room temperature bonding apparatus 51 Plasma chamber 52 Gas introduction port 53 Vacuum pump 54 Pulse voltage application device 55A, 55B Wafer fixing table 60 Annealed wafer 60A Center portion 60B DZ layer (first low oxygen region or second low oxygen region)
80 Transmitted laser beam 90 Neutral element

Claims (19)

A method for producing a silicon bonded wafer in which a support substrate wafer made of single crystal silicon and an active layer made of single crystal silicon are bonded,
A first step of forming a gettering layer inside the support substrate wafer by irradiating a transparent laser beam from one surface side of the support substrate wafer made of single crystal silicon to cause a multiphoton absorption process;
The one surface of the support substrate wafer made of single crystal silicon and the one surface of the active layer wafer are subjected to an activation treatment by irradiating an ionized neutral element at room temperature in a vacuum, A second step of bonding the support substrate wafer and the active layer wafer together by bringing one of the surfaces into an activated surface and subsequently contacting both of the activated surfaces at a vacuum room temperature;
A third step in which the active layer wafer is thinned and the thinned active layer wafer is an active layer;
A method for producing a silicon-bonded wafer, comprising:   2. The method of manufacturing a silicon bonded wafer according to claim 1, wherein an output of the transparent laser beam used in the first step is 4.0 μJ / pulse or less.   3. The method for manufacturing a silicon bonded wafer according to claim 1, wherein in the second step, bonding is performed so that misfit dislocations are formed in a bonded region between the support substrate wafer and the active layer wafer. The support substrate wafer and the active layer wafer each have a cutout portion indicating a crystal axis direction,
4. The silicon according to claim 3, wherein, in the second step, bonding is performed in a state where the notch portion of the active layer wafer is in a position rotated in a circumferential direction from the notch portion of the support substrate wafer. Manufacturing method of bonded wafer.   The method for producing a silicon-bonded wafer according to claim 3, wherein a surface orientation of the one surface of the support substrate wafer is different from a surface orientation of the one surface of the active layer wafer. The active layer wafer is an epitaxial silicon wafer in which a silicon epitaxial layer is formed on a silicon wafer,
The method for producing a silicon-bonded wafer according to claim 1, wherein the surface of the silicon epitaxial layer is the one surface of the active layer wafer.   The method for producing a silicon-bonded wafer according to claim 6, wherein in the third step, the active layer wafer is thinned from the side opposite to the silicon epitaxial layer, and the silicon wafer is ground and removed. The method for producing a silicon bonded wafer according to claim 1, wherein the support substrate wafer includes a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (ASTM F121-1979) or less. .   9. The method for manufacturing a silicon bonded wafer according to claim 8, wherein in the third step, the gettering layer is formed inside the low oxygen region of the support substrate wafer.   The method for producing a silicon bonded wafer according to claim 1, wherein the neutral element is at least one selected from the group consisting of argon, neon, xenon, hydrogen, helium, and silicon.   11. The silicon bonded wafer manufacture according to claim 1, wherein the activation process in the second step is performed such that an amorphous layer having a thickness of 2 nm or more is formed on one of both surfaces. Method.   The manufacturing of the silicon bonded wafer according to any one of claims 1 to 10, wherein the activation process in the second step is performed such that an amorphous layer having a thickness of 10 nm or more is formed on one of both surfaces. Method. A silicon bonded wafer in which a support substrate wafer made of single crystal silicon and an active layer made of single crystal silicon are bonded,
The bonding region for bonding the support substrate wafer and the active layer is amorphous,
The support substrate wafer includes a gettering layer in which gettering sites including modified regions having a diameter of 1 μm or more and 10 μm or less are periodically arranged in a radial direction.   The silicon bonded wafer according to claim 13, wherein misfit dislocations exist in a bonded region between the support substrate wafer and the active layer. The support substrate wafer and the active layer each have a notch portion indicating a crystal axis direction,
The silicon bonded wafer according to claim 14, wherein the cutout portion of the active layer is at a position rotated in a circumferential direction from the cutout portion of the support substrate wafer.   The silicon bonded wafer according to claim 14, wherein the surface orientation of the bonding surface of the support substrate wafer is different from the surface orientation of the bonding surface of the active layer.   The silicon bonded wafer according to claim 13, wherein the active layer is formed of a silicon epitaxial layer. 18. The silicon bonded wafer according to claim 13, wherein the support substrate wafer includes a low oxygen region having an oxygen concentration of 3 × 10 ¹⁷ atoms / cm ³ (ASTM F121-1979) or less.   The silicon bonded wafer according to claim 18, wherein the gettering layer is located in the low oxygen region of the support substrate wafer.