FR3138732A1 - BONDED SILICON WAFER AND PRODUCTION METHOD - Google Patents

Abstract

The purpose of this disclosure is to provide a bonded silicon wafer of thin thickness and high infrared reflectance, and a method for producing the same. This disclosure provides a bonded silicon wafer comprising, a silicon wafer serving as a support substrate; a single-crystal silicon layer on the silicon wafer serving as a support substrate; and an infrared-reflecting silicon film provided between the silicon wafer serving as a supporting substrate and the single-crystal silicon layer; the infrared-reflective silicon film comprises amorphous silicon, and a thickness of the infrared-reflective silicon film is 16 nm or more. Abstract Figure: Figure 1

Description

BONDED SILICON WAFER AND PRODUCTION METHOD

The present invention relates to a bonded silicon wafer and a method for producing the same.

MEMS devices and semiconductor devices produced using the normal temperature bonding apparatus are known as bonded silicon wafers (see, e.g., PTL 1). In recent years, high-sensitivity infrared light-receiving sensors have been required in fields such as surveillance cameras and automobile anti-collision sensors, and efforts are required to utilize silicon wafers that are conventionally used as sensors. in the visible light range.

Patent Documents: PTL 1:2014/72249 A

Technical problem

Both monocrystalline silicon and silicon oxide are relatively transparent with low reflectance to infrared lights. Therefore, when silicon oxide or single crystal silicon is used as the infrared reflecting layer of the infrared light receiving sensor, the infrared reflecting layer requires a thickness of about 100 µm. If the thickness of the infrared reflecting layer can be made thinner, the infrared light receiving sensor can be made smaller. An object of this disclosure is therefore to provide a bonded silicon wafer of thin thickness and high infrared reflectance, and a method for producing the same.

The inventors of this disclosure have studied to solve the above problem and examined the use of amorphous silicon instead of silicon oxide, which has been commonly used as an infrared reflective silicon film in silicon-based devices. of silicon wafer. Since amorphous silicon has a higher infrared reflectance than silicon oxide and is formed using normal temperature bonding technology, they expected it to have an advantage over production process. However, the amorphous silicon film formed by the commonly used normal temperature bonding technology could not reflect infrared radiation sufficiently due to its thin thickness. The inventor of this disclosure further investigated the use of amorphous silicon and found that controlling the thickness of the amorphous silicon layer or combining it with a polycrystalline silicon layer significantly improves the above infrared reflectance. This disclosure has been completed on the basis of the above findings, and the spirit and configuration thereof are as follows.

<1> Bonded silicon wafer comprising: a silicon wafer serving as a support substrate; a layer of monocrystalline silicon on the silicon wafer serving as a support substrate; and an infrared-reflecting silicon film provided between the silicon wafer serving as a support substrate and the single-crystal silicon layer; the infrared-reflecting silicon film comprises amorphous silicon, and a thickness of the infrared-reflecting silicon film is 16 nm or more.

<2> Silicon wafer bonded according to <1>, in which the infrared-reflecting silicon film is made of amorphous silicon.

<3> Silicon wafer bonded according to <1>, in which the infrared-reflecting silicon film is formed by a laminated structure made of layer(s) of amorphous silicon and layer(s) of polycrystalline silicon.

<4> Silicon wafer bonded according to any of <1> to <3>, wherein the thickness of the infrared-reflecting silicon film is 25 nm or more.

<5> Silicon wafer bonded according to any of <1> to <3>, wherein the thickness of the single crystal silicon layer is 3 μm or more and 30 μm or less.

<6> Process for producing the silicon wafer bonded according to any one of <2>, <4>, or <5> comprising the steps of: a process of forming a layer(s) formed ( s) an amorphous silicon film forming a layer formed of an amorphous silicon film with a thickness of 15 nm or more on a surface of the silicon wafer for a support substrate; an activation treatment process subjecting a surface of the amorphous silicon film layer and a surface of a silicon wafer for a single crystal silicon layer to vacuum activation treatment at normal temperature to make both surfaces of activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

<7> Process for producing the silicon wafer bonded according to any one of <2>, <4>, or <5> comprising the steps of: a process of forming a layer(s) formed ( s) an amorphous silicon film forming a layer formed of an amorphous silicon film with a thickness of 15 nm or more on a surface of a silicon wafer for a single crystal silicon layer; an activation treatment process subjecting a surface of the layer formed of an amorphous silicon film and a surface of the silicon wafer for a support substrate to an activation treatment under vacuum at normal temperature to make the two surfaces of the activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

<8> Process for producing the silicon wafer bonded according to any one of <2>, <4>, or <5> comprising the steps of: a process of forming a layer(s) formed ( s) an amorphous silicon film forming layers formed of an amorphous silicon film with a total thickness of 16 nm or more on each surface of the silicon wafer for a support substrate and a silicon wafer for monocrystalline silicon layer; an activation treatment process subjecting each surface of the amorphous silicon film layers formed on each surface of the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer to activation treatment under vacuum at normal temperature to make both surfaces of the activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

<9> Process for producing the silicon wafer bonded according to any one of <3> to <5> comprising the steps of: a process of forming a layer(s) formed of a polycrystalline silicon film forming a layer formed of a polycrystalline silicon film with a thickness of 15 nm or more on a surface of the silicon wafer for a supporting substrate; an activation treatment process subjecting a surface of the polycrystalline silicon film layer and a surface of a silicon wafer for a monocrystalline silicon layer to vacuum activation treatment at normal temperature to make both surfaces of activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

<10> Process for producing the silicon wafer bonded according to any one of <3> to <5> comprising the steps of: a process of forming a layer(s) formed of a polycrystalline silicon film forming a layer formed of a polycrystalline silicon film with a thickness of 15 nm or more on a surface of a silicon wafer for monocrystalline silicon layer; an activation treatment process subjecting a surface of the layer formed of a polycrystalline silicon film and a surface of the silicon wafer for a support substrate to an activation treatment under vacuum at normal temperature to make the two surfaces of activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

<11> Process for producing the silicon wafer bonded according to any one of <3> to <5> comprising the steps of: a process of forming a layer(s) formed of a polycrystalline silicon film forming layers formed of a polycrystalline silicon film with a thickness of 16 nm or more on each surface of the silicon wafer for supporting substrate and a silicon wafer for monocrystalline silicon layer; an activation treatment process subjecting each surface of the polycrystalline silicon film layers formed on each surface of the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer to activation treatment under vacuum at normal temperature to make both surfaces of the activated zones; a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; and a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.

Hereinafter, the process of forming the activated zones on each of the silicon wafers for support substrate and the silicon wafer for monocrystalline silicon layer, then of bonding the activated zones of the two wafers together under vacuum at normal temperature is called “ vacuum bonding at normal temperature.

This disclosure provides a bonded silicon wafer of thin thickness and high infrared reflectance and a method for producing the same.

Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

Fig. 1

is a schematic cross-sectional view illustrating a bonded silicon wafer, in accordance with this disclosure;

Fig. 2A

is a schematic cross-sectional view illustrating a bonded silicon wafer, in accordance with this disclosure, wherein the infrared reflective silicon film is made of amorphous silicon;.

Fig. 2B

is a schematic cross-sectional view illustrating the first aspect of a silicon wafer bonded according to this disclosure, wherein the infrared reflective silicon film is formed by a laminated structure of an amorphous silicon layer and a layer of polycrystalline silicon;

Fig. 2C

is a schematic cross-sectional view illustrating the second aspect of a silicon wafer bonded according to this disclosure, wherein the infrared reflective silicon film is formed by a laminated structure of an amorphous silicon layer and a layer of polycrystalline silicon;

Fig. 2D

is a schematic cross-sectional view illustrating the third aspect of a silicon wafer bonded according to this disclosure, wherein the infrared reflective silicon film is formed by a laminated structure of an amorphous silicon layer and polycrystalline silicon layers ;

Fig. 3

[Fig. 3 is a schematic cross-sectional view illustrating the first embodiment of the method for producing a bonded silicon wafer according to this disclosure;

Fig. 4

is a schematic cross-sectional view illustrating the second embodiment of the process for producing a bonded silicon wafer according to this disclosure;

Fig. 5

is a schematic cross-sectional view illustrating the third embodiment of the method for producing a bonded silicon wafer according to this disclosure;

Fig. 6

is a schematic cross-sectional view illustrating the fourth embodiment of the method for producing a bonded silicon wafer according to this disclosure;

Fig. 7

is a conceptual diagram illustrating an example of an apparatus used for vacuum bonding at normal temperature in one embodiment of the method for producing a bonded silicon wafer according to this disclosure; And

Fig. 8

is a cross-sectional view of a bonded silicon wafer to illustrate a method of measuring the reflectance of infrared lights on a bonded silicon wafer according to one embodiment of this disclosure.

(1. Overview)

Before describing the embodiments according to this disclosure, the correspondence between each drawing will be explained. There is a schematic cross-sectional view of a bonded silicon wafer 1 in accordance with this disclosure. Here, an infrared reflective silicon film 30 may be made of amorphous silicon or be formed by a laminated structure of amorphous silicon layer(s) and polycrystalline silicon layer(s). There illustrates a bonded silicon wafer 2 in which the infrared reflecting silicon film 30 is made of amorphous silicon. Figures 2B to 2D illustrate three different aspects of the infrared-reflecting silicon films 30 in bonded silicon wafers 3 to 5 in which the infrared-reflecting silicon films 30 are in particular formed by a laminated structure of layer(s) of amorphous silicon and polycrystalline silicon layer(s), and are hereinafter referred to as first, second and third aspects, respectively.

There is a schematic cross-sectional view illustrating an embodiment of the method for producing the bonded silicon wafer 2 when the infrared-reflecting silicon film is made of amorphous silicon (hereinafter referred to as the first embodiment). In the first embodiment illustrated in , a layer formed of an amorphous silicon film 131 is formed on a silicon wafer for support substrate 110, however, the layer formed of an amorphous silicon film can be formed on a silicon wafer for monocrystalline silicon layer 120 instead.

There is a schematic cross-sectional view illustrating one embodiment of the process for producing the bonded silicon wafer 2 when the infrared-reflecting silicon film is made of amorphous silicon and provides the amorphous silicon film layer 231 on both the support substrate silicon wafer 210 and the single crystal silicon layer silicon wafer 220 (hereinafter referred to as the second embodiment).

There is a schematic sectional view illustrating an embodiment of the process for producing the bonded silicon wafer 3 when the infrared-reflecting silicon film is formed by a laminated structure of an amorphous silicon layer and a silicon layer polycrystalline and having the infrared-reflecting silicon film according to the first aspect (hereinafter referred to as the third embodiment). In the third embodiment illustrated in , the polycrystalline silicon film layer 335 is formed on the support substrate silicon wafer 310, however, the polycrystalline silicon film layer can be formed on the monocrystalline silicon layer silicon wafer 320 instead, and in this case, the bonded silicon wafer 4 having the infrared-reflecting silicon film according to the second aspect can be produced.

There is a schematic sectional view illustrating an embodiment of the process for producing the bonded silicon wafer 5 when the infrared-reflecting silicon film 430 is formed by a laminated structure of a layer of amorphous silicon and layers of polycrystalline silicon and having the infrared reflective silicon film 430 according to the third aspect (hereinafter referred to as the fourth embodiment).

One or more embodiments of this disclosure are described in detail below with reference to the drawings. First of all, an overview of the bonded silicon wafers 1 to 5 according to this disclosure is given with reference to the and in Figures 2A to 2D. Here, the infrared-reflecting silicon film 30 in the bonded silicon wafer 1 described in may be made of amorphous silicon or be formed by a layered structure of amorphous silicon layer(s) and polycrystalline silicon layer(s). Next, the method for producing a bonded silicon wafer according to the first to fourth embodiments to obtain bonded silicon wafers 2 to 5 will be described, and the details of each configuration will also be explained. The specific aspects applicable to this disclosure are then described. In each drawing, the thickness of each component is exaggerated for purposes of explanation. Therefore, the thickness of each component differs from the actual thickness ratio.

(2. Bonded silicon wafer)

In reference to the , the bonded silicon wafer 1 according to this disclosure comprises a support substrate silicon wafer 10, a single crystal silicon layer 21 made of single crystal silicon on the support substrate silicon wafer 10, and an infrared reflecting silicon film 30 provided between the silicon wafer for support substrate 10 and the monocrystalline silicon layer 21. The infrared reflecting silicon film 30 comprises amorphous silicon. In the linked silicon wafer 2 of the , the infrared-reflecting silicon film 30 is made of amorphous silicon, and in the linked silicon wafers 3 to 5 of Figures 2B in the , the infrared-reflecting silicon film 30 is formed by a laminated structure of amorphous silicon layer(s) and polycrystalline silicon layer(s). Here, monocrystalline silicon as the material of the supporting substrate silicon wafer 10 and the monocrystalline silicon layer 21 is transparent to infrared light, while amorphous silicon and polycrystalline silicon as the material of the reflective silicon film infrared 30 is opaque to infrared light. By making the thickness of the infrared reflective silicon film 30 which is made of amorphous silicon alone or amorphous and polycrystalline silicon 16 nm or more, the bonded silicon wafers of thin thicknesses and high infrared reflectance can be obtained. The infrared reflecting silicon film 30 may be made of amorphous silicon or may be formed by a laminated structure of amorphous silicon layer(s) and polycrystalline silicon layer(s), however if the thickness thereof is below 16nm, it will not reflect infrared lights sufficiently. The thickness of the infrared reflecting silicon film 30 is preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more. Although infrared reflective silicon film 30 approaches 100% reflectance the thicker it is, it generally saturates at 25 nm. For this reason, although there is no particular limit to the upper limit, it is possible to set the upper limit to 40 nm for the purpose of making the bonded silicon wafer 1 smaller. The thickness of the single crystal silicon layer 21, into which the infrared lights penetrate, is preferably 3 μm or more and 30 μm or less, although there is no particular limit. Depending on the application of the bonded silicon wafer 1, the thickness of the single crystal silicon layer 21 may be 5 μm or more, 10 μm or more, 20 μm or less, or 15 μm or less.

There schematically illustrates the bonded silicon wafer when the infrared reflecting silicon film 30 is made of amorphous silicon.

Figures 2B to 2D each schematically illustrate the first to third aspects in which the infrared-reflecting silicon films 30 are formed by a laminated structure of amorphous silicon layer(s) and layer(s) ) of polycrystalline silicon.

In the first aspect of the infrared reflecting silicon film 30 illustrated in , the polycrystalline silicon layer 35 is provided on a surface side of the supporting substrate silicon wafer 10, and the amorphous silicon layer 32 is provided on the surface side of the single crystal silicon layer 21.

In the second aspect of the infrared reflecting silicon film 30 illustrated in , the polycrystalline silicon layer 35 is provided on a surface side of the single crystal silicon layer 21, and the amorphous silicon layer 32 is provided on the surface side of the supporting substrate silicon wafer 10.

In the third aspect of the infrared reflecting silicon film 30 illustrated in , the infrared reflective silicon film 30 has a polycrystalline silicon layer 35a and a polycrystalline silicon layer 35b provided on the surface side of both the support substrate silicon wafer 10 and the single crystal silicon layer 21 , respectively. The amorphous silicon layer 32 is provided between the polycrystalline silicon layer 35a and the polycrystalline silicon layer 35b.

In the first to third aspects where the infrared-reflecting silicon film 30 is formed by a laminated structure of amorphous silicon layer(s) and polycrystalline silicon layer(s), the following cases are determined due to the embodiments of the production method: the case where the polycrystalline silicon layer and the amorphous silicon layer are laminated in this order from the side of the silicon wafer for supporting substrate 10 in the film of infrared-reflecting silicon 30; the case where the amorphous silicon layer and the polycrystalline silicon layer are laminated in this order from the side of the supporting substrate silicon wafer 10 into the infrared reflective silicon film 30; and the case where the polycrystalline silicon layer, the amorphous silicon layer and the polycrystalline silicon layer are laminated in this order from the side of the supporting substrate silicon wafer 10 into the infrared reflective silicon film 30. Additionally, in the first to third illustrated aspects, although not shown, the layered structure may further comprise a layered structure formed by one or each of the amorphous silicon layer(s) and polycrystalline silicon layer(s). additional(s). In either case, for bonded silicon wafers 2 to 5 according to this disclosure, the layered structure of the amorphous silicon layer(s) and the polycrystalline silicon layer(s) will also function as a film infrared-reflecting silicon. The following is a sequential description of the embodiments for producing bonded silicon wafers 2 to 5.

(3. First method embodiment for producing a bonded silicon wafer)

In reference to the , the method for producing a bonded silicon wafer 100 according to the first embodiment is described. This embodiment is a process for producing the bonded silicon wafer 2 in , and is an embodiment of the silicon wafer linked 1 in where the infrared reflecting silicon film 30 is made of amorphous silicon.

The method of manufacturing the bonded silicon wafer 100 comprises the following steps: a process of forming layer(s) formed of an amorphous silicon film (see S110 and S120 in ) forming the layer formed of an amorphous silicon film 131 with a thickness of 15 nm or more on the surface of the silicon wafer for support substrate 110; an activation processing process (see S130 and S140 in ) subjecting the surface of the layer formed of an amorphous silicon film 131 and the surface of the silicon wafer for monocrystalline silicon layer 120 to a vacuum activation treatment at normal temperature to make the two surfaces of the activated zones 132a , 132b; a binding process (see S150 in ), following this activation treatment process, bringing the two activated zones 132a, 132b into contact with one another under vacuum at normal temperature, thus bonding the two activated zones 132a, 132b together to form the film of infrared-reflecting silicon 130; and a thickness reduction process (see S160 in ), after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer 120, thereby obtaining the single crystal silicon layer 121. The details of each process are described sequentially below.

<Process of formation of layer(s) formed of an amorphous silicon film>

In the process of forming layer(s) formed of an amorphous silicon film (see S110 and S120 in ), the amorphous silicon film layer 131 made of amorphous silicon is formed on the surface of the support substrate silicon wafer 110. The amorphous silicon film layer 131 can be formed by methods generally known. The thickness of the amorphous silicon film layer 131 formed here is 15 nm or more so that the amorphous silicon area will function as an infrared reflective silicon film when made into a wafer. silicon bonded. During activation processing, activated areas made of amorphous silicon are formed from surfaces of each silicon wafer to a depth position of about 1 nm, therefore, when the silicon wafers are bonded together, an infrared reflective silicon film 130 with a thickness of 16 nm or more is formed. The thickness of the amorphous silicon film layer 131 formed in this process is preferably 19 nm or more, more preferably 24 nm or more, and even more preferably 29 nm or more. The upper limit of the thickness of the layer formed from amorphous silicon film 131 is not particularly limited, but the upper limit is about 40 nm for industrial productivity.

<<Formation of a layer formed from an amorphous silicon film by CVD process>>

The amorphous silicon film layer 131, which is made of amorphous silicon, can be formed on the surface of the supporting substrate silicon wafer 110 using a CVD method such as plasma CVD. If the layer is formed while the temperature of the supporting substrate silicon wafer 110 is between 500°C and 600°C, the layer formed of an amorphous silicon film made of amorphous silicon can be caused to grow.

<Activation processing process>

Then, in the activation processing process (see S130 and S140 in ), activation treatment is carried out for vacuum bonding at normal temperature. In other words, the surface of the layer formed of an amorphous silicon film 131 of the silicon wafer for support substrate 110 and the surface of the silicon wafer for monocrystalline silicon layer 120 are subjected to an activation treatment by irradiation of ion beams or beams of neutral atoms 910 under vacuum at normal temperature to form activated zones 132a, 132b on each surface of the silicon wafer for support substrate 110 and of the silicon wafer for silicon layer monocrystalline 120. As described below, on the surface of each silicon wafer, an activated zone made of amorphous silicon is formed at a depth position of about 1 nm from the surface of the side irradiated by the beam, although the depth depends on the injected energy.

Binding process

In the binding process (see S150 in ), following the above activation processing process, by bringing into contact the activated areas 132a, 132b of both the silicon wafer for support substrate 110 and the silicon wafer for monocrystalline silicon layer 120 each other under vacuum at normal temperature, the two silicon wafers are bonded together via the layer formed of an amorphous silicon film 131. At this time, the amorphous silicon is formed not only in the activated zone 132a on the surface of the layer formed of an amorphous silicon film 131 on the silicon wafer for support substrate 110, but also in the activated zone 132b on the surface of the silicon wafer for monocrystalline silicon layer 120, where the layer formed of an amorphous silicon film 131 has not been formed, at a depth position of approximately 1 nm. Therefore, at the time of bonding, the activated area 132b and the amorphous silicon film layer 131 together form the infrared reflecting silicon film 130 made of amorphous silicon with a thickness of 16 nm or more.

<<Vacuum bonding at normal temperature>>

In reference to the and to the , the bonding method using normal temperature vacuum bonding to carry out the activation treatment process and the above bonding process is described. Normal temperature vacuum bonding is a method of bonding the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 to each other at normal temperature without heating. In this embodiment, the surface of the amorphous silicon film layer 131 of the silicon wafer for support substrate 110 and the surface of the silicon wafer for monocrystalline silicon layer 120 are each subjected to treatment. activation by irradiation of ion beams or beams of neutral atoms under vacuum at normal temperature, and the two surfaces above are transformed into activated zones 132a, 132b, respectively (see also S130 and S140 in ). As a result, dangling connections appear in the activated areas 132a, 132b. Therefore, when the above two activated areas are brought into contact under vacuum at normal temperature, a bonding force is instantly activated and the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 are firmly bonded with the activated areas 132a, 132b above as bonding surfaces (see also S150 in ).

Activation processing methods include accelerating ionized elements in a plasma atmosphere toward the substrate surface and accelerating ionized elements accelerated from an ion beam device toward the substrate surface. In reference to the , the activation processing method is explained using a conceptual diagram illustrating an example of a device which implements this method. The normal temperature vacuum bonding apparatus 930 has a plasma chamber 931, a gas inlet 932, a vacuum pump 933, an impulse voltage application device 934 and wafer supports 935a, 935b .

Firstly, the supporting substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 are placed on the wafer holder(s) 935a, 935b in the plasma chamber 931, respectively, and fixed. Then, the interior of the plasma chamber 931 is depressurized by the vacuum pump 933, and then the source gas is introduced into the plasma chamber 931 from the gas inlet 932. Then, a negative voltage is applied by pulses to the wafer supports 935a, 935b (as well as to the silicon wafer for support substrate 110 and the silicon wafer for monocrystalline silicon layer 120) by the pulse voltage application device 934. This allows to generate a plasma of the raw material gas, and accelerates and irradiates the ions of the raw material gas contained in the generated plasma towards the surface of the layer formed of an amorphous silicon film 131 formed on the silicon wafer to support substrate 110 and the surface of the silicon wafer for monocrystalline silicon layer 120.

The element to be irradiated is chosen from at least one of Ar, Ne, Xe, H, He and Si.

With reference to S140 in . As mentioned above, the activation treatment in vacuum bonding at normal temperature forms an amorphous silicon area in each of the amorphous silicon film layer 131 and the silicon wafer for single crystal silicon layer 120 at a depth position of about 1 nm from the surface, on the side where the beam is irradiated, and dangling bonds are formed. In this embodiment, since the amorphous silicon film layer 131 is made of amorphous silicon, the activated zone 132a is formed on the silicon wafer for support substrate 110 without changing the thickness of the silicon zone amorphous, and the activated zone 132b made of amorphous silicon is formed on the silicon wafer for monocrystalline silicon layer 120. It should be noted that these zones made of amorphous silicon formed on the two silicon wafers also function as trap layers gas (in English “gettering layers”). For example, the activated zone 132a, which is made of amorphous silicon, is useful in that it can suppress the outward diffusion of oxygen and impurities contained in the support substrate silicon wafer 110 toward the silicon wafer for monocrystalline silicon layer 120.

- Specificities of vacuum bonding at normal temperature -

The chamber pressure in the plasma chamber 931 may be 1 x10-5 Pa or less. If the value is 1 × 10-5 Pa or less, there is no risk that the rate of dangling bond formation will be reduced due to reattachment of the sputtered elements to the substrate surface.

The pulse voltage applied to the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 can be set such that the acceleration energy of the irradiated elements relative to the substrate surface falls between 100 eV and 10 keV. If the value is 100 eV or more, there is no risk that the irradiated elements will be deposited on the substrate surface, and if the value is 10 keV or less, there is no risk that the irradiated elements are injected inside the substrate, thus allowing stable formation of dangling bonds.

The frequency of the pulse voltage determines the number of times the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 are irradiated with neutral ions or atoms. The frequency of the pulse voltage can be between 10 Hz and 10 kHz. If the frequency of the pulse voltage is 10 Hz or more, the irradiation variations of ions or neutral atoms can be absorbed, thereby stabilizing the irradiation of ions or neutral atoms. If the frequency of the pulse voltage is 10 kHz or less, the formation of plasma by glow discharge is stable.

The pulse width of the pulse voltage determines the time during which the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 are irradiated with neutral ions or atoms. The pulse width is preferably between 1 µsec and 10 msec. If the pulse width is 1 μsec or more, the ions or neutral atoms can be stably irradiated to the support substrate and the single crystal silicon layer substrate. If the pulse width is 10 ms or less, the glow discharge plasma formation is stable.

As mentioned above, the support substrate silicon wafer 110 and the single crystal silicon layer silicon wafer 120 are not heated. Therefore, the temperature of each cake is room temperature (typically 30°C to 90°C).

<Thickness reduction process of a silicon wafer for monocrystalline silicon layer>

After the activation treatment process and the normal temperature vacuum bonding process described above, the thickness reduction process of the silicon wafers for single crystal silicon layer 120 is carried out (see S160 in ). In this process, the thickness of the silicon wafer for single crystal silicon layer 120 is reduced from the opposite side of the laminated surface, thereby obtaining the single crystal silicon layer 121 made of single crystal silicon. To reduce the thickness, for example, the silicon wafer for single crystal silicon layer 120 can be ground and polished. In this way, a silicon wafer bonded with a single crystal silicon layer 121 of the desired thickness can be obtained. The thickness of the monocrystalline silicon layer 121 can be determined depending on the device to be formed there, and is preferably 3 μm or more and 30 μm or less, or may be 5 μm or more, 10 μm or more. , 20 μm or less, or 15 μm or less. It should be noted that for such grinding and polishing, any known or given grinding and polishing process may be suitably used, and specific examples include surface grinding and mirror polishing.

The resulting bonded silicon wafer 100 comprises the support substrate silicon wafer 110, the single crystal silicon layer 121 on the support substrate silicon wafer 110, and the infrared reflective silicon film 130 made of amorphous silicon , provided between the support substrate silicon wafer 110 and the single crystal silicon layer 121. The amorphous silicon of the infrared reflecting silicon film 130 essentially consists of the layer formed of an amorphous silicon film 131 on the surface side of the silicon wafer for support substrate 110 and the activated zone 132b formed on the surface of the silicon wafer for monocrystalline silicon layer 120, and the layer formed of an amorphous silicon film 131 comprises the activated zone 132a formed at the surface of the layer formed of an amorphous silicon film 131.

The first embodiment of the process for producing the bonded silicon wafer is described above with reference to the . In the first embodiment, the amorphous silicon film layer 131 was formed on the support substrate silicon wafer 110. However, as a variation of the first embodiment, the bonded silicon wafer 100 illustrated in can also be produced by the same process as in the first embodiment above, except that the layer formed of an amorphous silicon film 131 is formed on the silicon wafer for single crystal silicon layer 120. This is- that is, the bonded silicon wafer 100 can be produced by the following steps: a process of forming layer(s) formed of an amorphous silicon film forming the layer formed of a film amorphous silicon 131 made of amorphous silicon on the surface of the silicon wafer for the monocrystalline silicon layer 120; an activation treatment process subjecting the surface of the silicon wafer for support substrate 110 and the surface of the layer formed of an amorphous silicon film 131 on the silicon wafer for monocrystalline silicon layer 120 to an activation treatment activation having to irradiate the ion beams or the beams of neutral atoms 910 under vacuum at normal temperature, thus forming the activated zones 132a, 132b on each of the silicon wafer for support substrate 110 and the silicon wafer for layer monocrystalline silicon 120; a bonding process, following this activation treatment process, bringing the two activated zones 132a, 132b into contact under vacuum at normal temperature, thus bonding the silicon wafer for support substrate 110 and the silicon wafer for silicon layer monocrystalline 120 via the layer formed of an amorphous silicon film 131; and a thickness reduction process reducing the thickness of the silicon wafer for the single crystal silicon layer 120 from the opposite side of the laminated surface, to make the single crystal silicon layer 121. Since the same techniques as described herein -above in the first embodiment can be used for the formation of the layer formed from an amorphous silicon film 131, vacuum bonding at normal temperature, and grinding and polishing for thickness reduction, the descriptions redundant are omitted.

(4. Second embodiment of method for producing a bonded silicon wafer)

In reference to the , the production method of the bonded silicon wafer 200 according to the second embodiment is described. The bonded silicon wafer 200 produced in this embodiment is, like the bonded silicon wafer 100 produced in the first embodiment, a bonded silicon wafer in which the infrared reflective silicon film 30 illustrated in is made of amorphous silicon. For the sake of brevity, the same components and steps as in the first embodiment are, in principle, marked with the same reference numbers to the units and tens, and the detailed description as to the configuration is omitted, and the same applies below.

The method of manufacturing the bonded silicon wafer 200 comprises the following steps: a process of forming a layer formed of an amorphous silicon film (see S210 and S220 in ) forming layers formed of an amorphous silicon film 231a, 231b with a thickness of 16 nm or more on each surface of the silicon wafer for support substrate 210 and the silicon wafer for single crystal silicon layer 220; an activation processing process (see S230 and S240 in ) subjecting each surface of the layers formed of an amorphous silicon film 231a, 231b formed on each surface of the silicon wafer for support substrate 210 and of the silicon wafer for monocrystalline silicon layer 220 to an activation treatment under vacuum at normal temperature to make the two surfaces of the activated zones 232a, 232b; a binding process (see S250 in ), following the activation treatment process, bringing the two activated zones 232a, 232b into contact with each other under vacuum at normal temperature, thus bonding the two activated zones 232a, 232b together to form the film of infrared-reflecting silicon 230; and a thickness reduction process (see S260 in ), after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer 220, thereby obtaining the single crystal silicon layer 221.

<Process of formation of layer(s) formed of an amorphous silicon film>

While in the first embodiment, the layer formed of an amorphous silicon film 131 was formed only on the silicon wafer for support substrate 110, the second embodiment differs in that the layers formed of a amorphous silicon film 231a, 231b are formed on each of the silicon wafer for support substrate 210 and the silicon wafer for monocrystalline silicon layer 220. The method of forming the layers formed of an amorphous silicon film 231a, 231b made of amorphous silicon is the same as in the first embodiment, and a CVD process or the like can be applied. The total thickness of the amorphous silicon film layers 231a, 231b formed here is 16 nm or more to ensure that the infrared reflective silicon film 230 effectively reflects infrared light when made into the wafer. bonded silicon 200. The thickness of each of the layers formed from an amorphous silicon film 231a, 231b may be the same or different. In the production method of the second embodiment, since the two surfaces to be activated are made of amorphous silicon, the thickness of the infrared-reflecting silicon film 230 obtained after bonding and the total thickness of the layers formed of a silicon film amorphous 231a, 231b formed before bonding are the same. The total thickness of the layers formed from amorphous silicon 231a, 231b is preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more. The upper limit to the total thickness of the layer formed from amorphous silicon film 231 is not particularly limited, but the upper limit is about 40 nm for industrial productivity.

<Activation processing process and binding process>

In the second embodiment, the activation treatment activates the surfaces of the layers formed from amorphous silicon film 231a, 231b to form the activated zones 232a, 232b on the surfaces of the two silicon wafers. Then, in the bonding process, the activated zones 232a, 232b are bonded together under vacuum at normal temperature as in the first embodiment.

<Thickness reduction process>

The thickness reduction process can also be carried out in the same way as in the first embodiment.

The resulting bonded silicon wafer 200 comprises the support substrate silicon wafer 210, the single crystal silicon layer 221 on the support substrate silicon wafer 210, and the infrared reflective silicon film 230 made of amorphous silicon , provided between the silicon wafer for support substrate 210 and the monocrystalline silicon layer 221. The amorphous silicon of the infrared-reflecting silicon film 230 essentially consists of the layer formed of an amorphous silicon film 231a provided on the surface of the silicon wafer for support substrate 110 and the layer formed of an amorphous silicon film 231b provided on the surface of the silicon wafer for monocrystalline silicon layer 220. The layer formed of an amorphous silicon film 231a comprises the activated zone 232a formed on the surface of the amorphous silicon film layer 231a, and the amorphous silicon film layer 231b comprises the activated zone 232b formed on the surface of the film layer of amorphous silicon 231b.

(5. Third embodiment of method for producing a bonded silicon wafer)

In reference to the , the production method of the bonded silicon wafer 300 according to the third embodiment is described. This embodiment is a process for producing bonded silicon wafers 2, 3 in the aspects illustrated in and in . Unlike the first and second embodiments, the infrared-reflecting silicon wafer film 330 in this embodiment is formed by a laminated structure of an amorphous silicon layer and a polycrystalline silicon layer.

The method of manufacturing the bonded silicon wafer 300 comprises the following steps: a process of forming layer(s) formed of a polycrystalline silicon film (see S310 and S320 in ) forming a layer formed of a polycrystalline silicon film 331 with a thickness of 5 nm or more on the surface of the silicon wafer for support substrate 310; an activation processing process (see S330 and S340 in ) subjecting the surface of the layer formed of a polycrystalline silicon film 331 and the surface of a silicon wafer for monocrystalline silicon layer 320 to a vacuum activation treatment at normal temperature to make the two surfaces of the activated zones 332a, 332b; a binding process (see S350 in ), following this activation treatment process, bringing the two activated zones 332a, 332b into contact with each other under vacuum at normal temperature, thus linking the two activated zones 332a, 332b together to form the film of infrared-reflecting silicon 330; and a thickness reduction process (see S360 in ), after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer 320, thereby obtaining the single crystal silicon layer 321.

<Process of formation of layer(s) formed of a polycrystalline silicon film>

In the process of forming layer(s) formed of a polycrystalline silicon film (see S310 and S320 in ), a polycrystalline silicon film layer 335 made of polycrystalline silicon is formed on the surface of the support substrate silicon wafer 310. The polycrystalline silicon film layer 335 can be formed by methods generally known. The thickness of the polycrystalline silicon 335 film layer formed here should be 15 nm or more so that the area formed by the layered structure of polycrystalline silicon and amorphous silicon functions as an infrared reflective silicon film when transformed into the bonded silicon wafer 300. Since the activated zone made of amorphous silicon is formed from the surface of each silicon wafer to a depth position of about 1 nm during processing of activation, an infrared-reflective silicon film 330 with a thickness of 16 nm or more is formed when the silicon wafers are bonded together. The thickness of the polycrystalline silicon layer 335 formed in this process is preferably 19 nm or more, more preferably 24 nm or more, and even more preferably 29 nm or more. The upper limit of the thickness of the layer formed by a 335 polycrystalline silicon film is not particularly limited, but the upper limit is about 40 nm for industrial productivity.

<<Formation of a layer formed from a polycrystalline silicon film by CVD process>>

The polycrystalline silicon film layer 335, which is made of polycrystalline silicon, can be formed on the surface of the support substrate silicon wafer 310 using a CVD method such as plasma CVD. If the layer is formed while the temperature of the supporting substrate silicon wafer 310 is between 700°C and 900°C, the layer formed of a polycrystalline silicon film made of polycrystalline silicon can be caused to grow.

<Activation processing process>

The activation processing can be performed in the same manner as the first and second embodiments described above. In other words, referring to S330 and S340 in , the surface of the layer formed of a polycrystalline silicon film 335 of the silicon wafer for support substrate 310 and the surface of the silicon wafer for monocrystalline silicon layer 320 are subjected to activation treatment by irradiation of beams of ions or beams of neutral atoms 910 under vacuum at normal temperature to form activated zones 332a, 332b on the respective surfaces of the silicon wafer for support substrate 310 and of the silicon wafer for monocrystalline silicon layer 320. As described below, on the surface of each silicon wafer, an activated zone made of amorphous silicon is formed at a depth position of about 1 nm from the surface of the side irradiated by the beam.

Binding process

In the binding process (see S350 in ), following the activation processing process, by bringing into contact the activated areas 332a, 332b of both the silicon wafer for support substrate 310 and the silicon wafer for monocrystalline silicon layer 320 l one another under vacuum at normal temperature, the two silicon wafers are bonded together via the layer formed of a 335 polycrystalline silicon film. At this time, at least 1 nm of amorphous silicon is also formed at the surface of the silicon wafer for monocrystalline silicon layer 320, where the layer formed of a polycrystalline silicon film 335 has not been formed. Therefore, at the time of bonding, together with the layer formed of polycrystalline silicon film 335, an infrared-reflecting silicon film 330 made of polycrystalline silicon and amorphous silicon will be formed with a thickness of 16 nm or more.

<Thickness reduction process>

The subsequent thickness reduction process can be carried out in the same way as in the first and second embodiments.

The bonded silicon wafer 300 thus obtained comprises the silicon wafer for support substrate 310, the single crystal silicon layer 321 on the silicon wafer for support substrate 310, and the infrared reflecting silicon film 330 provided between the wafer of silicon for support substrate 310 and the monocrystalline silicon layer 321. The infrared reflecting silicon film 330 comprises a layer formed of a polycrystalline silicon film 335 made of polycrystalline silicon and the activated zone 332. The activated zone 332 is derived from the activated zones 332a, 332b described above.

The third embodiment of the process for producing the bonded silicon wafer 300 in accordance with the first aspect is described above with reference to the . In this embodiment, the layer formed of a polycrystalline silicon film 335 is formed on the silicon wafer for support substrate 310, however, as an alternative variant of the third embodiment, the same process as in the third embodiment. above embodiment can be followed except that the polycrystalline silicon layer 335 is formed on the silicon wafer for monocrystalline silicon layer 320; by this process, the bonded silicon wafer 4 according to the second aspect illustrated in can be produced. In other words, the bonded silicon wafer 4 according to the second aspect can be produced by the following steps: a process of forming a layer(s) formed of a polycrystalline silicon film forming the polycrystalline silicon film layer 335 made of polycrystalline silicon on the surface of the silicon wafer for monocrystalline silicon layer 320; an activation treatment process subjecting the surface of the silicon wafer for support substrate 310 and the surface of the silicon wafer for single crystal silicon layer 320 to vacuum activation treatment at normal temperature to produce the activated areas 332a, 332b on each surface of the support substrate silicon wafer 310 and the single crystal silicon layer silicon wafer 320; a bonding process, following this activation treatment process, bringing the two activated zones 332a, 332b into contact with each other under vacuum at normal temperature, thus bonding both the silicon wafer for support substrate 310 and the silicon wafer for monocrystalline silicon layer 320 together via the polycrystalline silicon film layer 335; and a thickness reduction process, reducing the thickness of the silicon wafer for single crystal silicon layer 320 from the opposite side of the laminated surface, thereby obtaining the single crystal silicon layer 321 made of single crystal silicon. Formation of the polycrystalline silicon 335 film layer, vacuum bonding at normal temperature, and grinding and polishing for thickness reduction can be accomplished using the same techniques as described above in the third embodiment, so that redundant descriptions are omitted.

(6. Fourth embodiment of method for producing a bonded silicon wafer)

In reference to the , a method for producing the bonded silicon wafer 400 according to the fourth embodiment is described. This embodiment is intended for the production of the bonded silicon wafer 5 of the third aspect illustrated in . The infrared-reflecting silicon film 430 in this embodiment is made of polycrystalline silicon and amorphous silicon, as in the third embodiment.

The method of manufacturing the bonded silicon wafer 400 comprises the following steps: a process of forming a layer formed of a polycrystalline silicon film (see S410 and S420 in ) forming layers formed of a polycrystalline silicon film 435a, 435b with a thickness of 16 nm or more on each surface of the silicon wafer for support substrate 410 and the silicon wafer for monocrystalline silicon layer 420; an activation processing process (see S430 and S540 in ) subjecting each surface of the layers formed of a polycrystalline silicon film 435a, 435b formed on each surface of the silicon wafer for support substrate 410 and of the silicon wafer for monocrystalline silicon layer 420 to an activation treatment under vacuum at normal temperature to make the two surfaces of the activated zones 432a, 432b; a binding process (see S450 in ), following this activation treatment process, bringing the two activated zones 432a, 432b into contact with each other under vacuum at normal temperature, thus linking the two activated zones 432a, 432b together to form the film of infrared-reflecting silicon 430; and a thickness reduction process (see S460 in ), after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer 420, thereby obtaining the single crystal silicon layer 421.

<Process of formation of layer(s) formed of a polycrystalline silicon film>

While in the third embodiment, the layer formed of a polycrystalline silicon film 335 was formed only on the silicon wafer for support substrate 310, the fourth embodiment differs in that the layers formed of a polycrystalline silicon film 435a, 435b are formed on each of the silicon wafer for support substrate 410 and the silicon wafer for monocrystalline silicon layer 420. The method of forming the layers formed of a polycrystalline silicon film 435a, 435b made of amorphous silicon is the same as in the third embodiment, and a CVD process or the like can be applied. The total thickness of the polycrystalline silicon film layers 435a, 435b formed here is 16 nm or more to ensure that the infrared reflective silicon film 430 effectively reflects infrared light when made into the wafer. bonded silicon 400. The thickness of each of the layers formed from an amorphous silicon film 435a, 435b may be the same or different. In the production method of the fourth embodiment, since the two surfaces to be activated are made of polycrystalline silicon, the thickness of the infrared-reflecting silicon film 430 obtained after bonding and the total thickness of the layers formed of a silicon film polycrystalline 435a, 435b formed before bonding are the same. The total thickness of the layers formed of polycrystalline silicon 435a, 435b is preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more. The upper limit for the total thickness of the layer formed of a polycrystalline silicon 430 film is not particularly limited, but the upper limit is about 40 nm for industrial productivity. Note that, in the fourth embodiment, the layer formed of a polycrystalline silicon film is formed on each of the silicon wafer for support substrate 410 and the silicon wafer for monocrystalline silicon 420, however the layer formed of A polycrystalline silicon film can be formed on one side and the layer formed of an amorphous silicon film can be formed on the other side.

<Activation processing process and binding process>

In the fourth embodiment, the activation treatment activates the surfaces of the layers formed from polycrystalline silicon film 435a, 435b to form activated zones 432a, 432b on the surfaces of the two silicon wafers. Then, in the bonding process, the activated zones 432a, 432b are bonded together under vacuum at normal temperature as in the third embodiment.

<Thickness reduction process>

The thickness reduction process can also be carried out in the same way as in the third embodiment.

The bonded silicon wafer 400 thus obtained comprises the silicon wafer for support substrate 410, the single crystal silicon layer 421 on the silicon wafer for support substrate 410, and the infrared reflecting silicon film 430 provided between the wafer of silicon for support substrate 410 and the monocrystalline silicon layer 421. The infrared reflecting silicon film 430 is formed by the laminated structure made of the amorphous silicon layer and the polycrystalline silicon layers. Further, the layered structure of the amorphous silicon layer and the polycrystalline silicon layers comprises the polycrystalline silicon film layer 435a and the polycrystalline silicon film layer 435b provided on the surface side of both the support substrate silicon wafer 410 and the single crystal silicon layer silicon wafer 421, respectively; the layer formed of a polycrystalline silicon film 435a comprises polycrystalline silicon and the activated zone 432a made of amorphous silicon on the surface thereof, and the layer formed of a polycrystalline silicon film 435b comprises polycrystalline silicon and a activated zone 432b made of amorphous silicon on the surface thereof.

In the first to fourth embodiments, it is also preferable to flatten the surfaces of the amorphous silicon film layer and the polycrystalline silicon film layer before the activation treatment. In other words, it is preferable to planarize the layers formed of an amorphous silicon film 131, 231 in the first and second embodiments, respectively, and the layers formed of a polycrystalline silicon film 335, 435 in the third and fourth embodiments, respectively.

Although the planarization conditions are not restricted, the layer formed of an amorphous silicon film or the layer formed of a polycrystalline silicon film is preferably planarized so that their surface roughness Ra is less than 3 nm; and it is better to contain the polishing tolerance under 30 nm. In fact, planarization allows a more secure connection after activation. For planarization, the known process of chemical mechanical polishing (CMP), etc. can be used appropriately. The surface roughness Ra here follows the definition of the arithmetic average roughness Ra specified in JIS B 0601 (2001).

The production method of the first to fourth embodiments described above can be used to produce the bonded silicon wafer according to this disclosure.

(7. Specific aspects)

In the following, the specific aspects of silicon wafers applicable to the silicon wafer for the support substrate 10 and the silicon wafer for single crystal silicon layer 20 (single crystal silicon layer 21) which can be used in this disclosure are described.

The orientation of the plane of the silicon wafer is arbitrary; a pancake (100) or a pancake (110), etc. can be used.

The thickness of the silicon wafer can be determined depending on the application, and can be from 300 µm to 1.5 mm. It has already been mentioned that the thickness of the single crystal silicon layer made of single crystal silicon obtained from the silicon wafer for single crystal silicon layer is determined in the range of 100 nm to 1 mm as appropriate.

The silicon wafer can be doped with dopants such as boron (B), phosphorus (P), arsenic (As) and antimony (Sb); or to obtain the desired characteristics, with carbon (C) or nitrogen (N).

The diameter of the silicon wafer is not limited in any way. This disclosure can be applied to silicon wafers with a typical diameter of 300 mm or 200 mm, etc. Of course, this disclosure can be applied to silicon wafers with a diameter greater than 300 mm, as well as to silicon wafers with a diameter less than 300 mm.

The term "silicon wafer" as used herein may refer to a so-called "in-bulk" silicon wafer, which does not have an epitaxial layer or other layer such as an infrared-reflecting silicon film made of silicon oxide or the like which is formed on the surface; or an epitaxial silicon wafer with another layer, such as an epitaxial layer, formed separately on its surface. Although a natural oxide film a few Å thick may be formed on the surface of the silicon wafer, such a natural oxide film may be present, or if necessary, may be removed using known cleaning methods, etc.

Examples

This disclosure is described in more detail below using examples, however this disclosure is in no way limited to the following examples.

[Experimental Example 1]

(Example 1-1)

The n-type CZ silicon wafers (dopant: phosphorus) with a diameter of 8 inches (203.2 mm) and a thickness of 500 μm were prepared to be the silicon wafer serving as the supporting substrate and the monocrystalline silicon layer. Then, the silicon wafer serving as the supporting substrate was introduced into the plasma CVD system, and the vacuum degree in the system was maintained at 1 × 10-5 Pa or less. Then, with the stage temperature maintained at 500°C, 55 cm3STP/min (in English “sccm”) of silane gas (CH3SiH3) as source gas and 110 cm3STP/min of H2 gas as carrier gas were put into circulation, to form a layer formed of an amorphous silicon film with a thickness of 15 nm on the surface of the silicon wafer for support substrate by plasma CVD process.

Then, the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer were both introduced into the chamber, and the vacuum degree was maintained at 1 × 10-5 Pa or less. Then, the activation treatment was applied to the surface of the silicon wafer for support substrate and to the surface of the wafer for active layer by irradiating argon ions at 1.4 keV to form activated zones ( amorphous silicon) on the surface of the two silicon wafers. Then, the two substrates were linked by bringing the activated zones of the two wafers into contact together under vacuum at normal temperature.

Then, the silicon wafer for the single crystal silicon layer was ground and polished from the opposite side of the bonded surface so as to leave a thickness of 10 μm, and the bonded silicon wafer for Example 1-1 was obtained.

Observation by TEM of the bonding interface of the bonded silicon wafer thus obtained confirmed the formation of amorphous silicon with a thickness of 16 nm. In other words, it was found that an activated zone with a thickness of 1 nm was formed when the surface of the silicon wafer for single crystal silicon layer was subjected to the activation treatment.

(Example 1-2)

In Example 1-1, a layer formed of an amorphous silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 1-2, the bonded silicon wafer for Example 1-2 was produced under the same conditions as Example 1-1, except that the thickness of the layer formed of an amorphous silicon film formed was 20 nm.

(Example 1-3)

In Example 1-1, a layer formed of an amorphous silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 1-3, the bonded silicon wafer for Example 1-3 was produced under the same conditions as Example 1-1, except that the thickness of the layer formed of an amorphous silicon film formed was 25 nm.

(Example 1-4)

In Example 1-1, a layer formed of an amorphous silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 1-3, the bonded silicon wafer for Example 1-3 was produced under the same conditions as Example 1-1, except that the thickness of the layer formed of an amorphous silicon film formed was 30 nm.

(Conventional Example 1)

The same silicon wafer serving as support substrate and the same silicon wafer for monocrystalline silicon layer as in Example 1-1 were prepared. Then, without forming a layer formed of an amorphous silicon film or any other layer on one or the other of the substrates, the two substrates were subjected to the vacuum activation treatment at normal temperature to form activated zones on both cakes, and the activated areas of the two cakes were linked together.

Then, the silicon wafer for the single crystal silicon layer was ground and polished from the opposite side of the bonded surface so as to leave a thickness of 10 μm, and the bonded silicon wafer for Conventional Example 1 was obtained. .

(Comparative Example 1)

The same silicon wafer serving as support substrate and the same silicon wafer for monocrystalline silicon layer as in Example 1-1 were prepared. In Example 1-1, a layer formed of an amorphous silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Comparative Example 1, the bonded silicon wafer was produced under the same conditions as Example 1-1, except that the thickness of a layer formed from an amorphous silicon film formed was of 10nm.

(Evaluation: Infrared reflectance)

To evaluate the infrared reflectivity of the infrared-reflecting silicon film, infrared light was incident on the surfaces of the bonded silicon wafers using a film thickness measuring device (CHRocodile IT500, manufactured by Presitec). , and the signal intensity of the reflected light was detected. In reference to the , the principle of measuring infrared reflectance using the Fourier Transform Infrared (FTIR) method with this instrument is briefly explained. The laser light source that serves as incident light for this instrument is a super luminescent diode. Using this instrument, the reflected light L2 and the reflected light L3 obtained when the near-infrared light L1 was irradiated on the bonded silicon wafer were detected, and the infrared reflectance L2/L3 was obtained. Here, the reflected light L2 is the light reflected from the surface 528A of the bonded silicon wafer 500, and the reflected light L3 is the light reflected from the interface of the single crystal silicon layer 521 and the region 530 formed of silicon amorphous. The non-reflected infrared light will then flow towards the 510 region of the single crystal silicon on the supporting substrate side.

The results are listed in Table 1 below. From the results of this evaluation, it was confirmed that the amorphous silicon areas in Examples 1-1 to Example 1-4 function sufficiently as infrared-reflecting silicon films, while the amorphous silicon areas formed in the Conventional Example and Comparative Example 1 are insufficient to function as infrared reflecting silicon films.

Sample Conventional Example 1 Comparative Example 1 Example 1-1 Example 1-2 Example 1-3 Example 1-4 IR reflective silicon film Amorphous silicon Amorphous silicon Amorphous silicon Amorphous silicon Amorphous silicon Amorphous silicon Thickness of IR-reflecting silicon film 6 11 16 21 26 31 Reflection intensity of reflected light 4214 7862 11700 14879 18262 19394 Reflectance (%) 23.7 44.3 65.9 83.8 100 100

[Experimental Example 2]

(Example 2-1)

The n-type CZ silicon wafers (dopant: phosphorus) with a diameter of 8 inches (203.2 mm) and a thickness of 500 μm were prepared to be the silicon wafer serving as the supporting substrate and the monocrystalline silicon layer. Then, the silicon wafer serving as the supporting substrate was introduced into the plasma CVD system, and the vacuum degree in the system was maintained at 1 × 10-5 Pa or less. Then, with the stage temperature maintained at 800°C, 55 cm3STP/min (in English “sccm”) of silane gas (CH3SiH3) as source gas and 110 cm3STP/min of H2 gas as carrier gas were put into circulation, to form a layer formed of a polycrystalline silicon film with a thickness of 15 nm on the surface of the silicon wafer for support substrate by plasma CVD process.

Then, the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer were both introduced into the chamber, and the vacuum degree was maintained at 1 × 10-5 Pa or less. Then, the activation treatment was applied to the surface of the silicon wafer for support substrate and to the surface of the wafer for active layer by irradiating argon ions at 1.4 keV to form an activated zone ( amorphous silicon) on the surface of the two silicon wafers. Then, the two substrates were bonded by bonding the activated areas of the two wafers together under vacuum at normal temperature.

Then, the silicon wafer for the single crystal silicon layer was ground and polished from the opposite side of the bonded surface so as to leave a thickness of 10 μm, and the bonded silicon wafer was obtained.

Observation by TEM of the bonding interface of the bonded silicon wafer thus obtained confirmed the formation of an amorphous silicon zone with a thickness of 1 nm in addition to the layer formed of a polycrystalline silicon film with a thickness of 15 nm. In other words, it was found that an activated zone with a thickness of 1 nm was formed when the surface of the silicon wafer for single crystal silicon layer was subjected to the activation treatment.

(Example 2-2)

In Example 2-1, a layer formed of a polycrystalline silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 2-2, the bonded silicon wafer for Example 2-2 was produced under the same conditions as Example 2-1, except that the thickness of the layer formed of A polycrystalline silicon film formed was 20 nm.

(Example 2-3)

In Example 2-1, a layer formed of a polycrystalline silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 2-3, the bonded silicon wafer for Example 2-3 was produced under the same conditions as Example 2-1, except that the thickness of the layer formed of A polycrystalline silicon film formed was 25 nm.

(Example 2-4)

In Example 2-1, a layer formed of a polycrystalline silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Example 2-3, the bonded silicon wafer for Example 2-3 was produced under the same conditions as Example 2-1, except that the thickness of the layer formed of A polycrystalline silicon film formed was 30 nm.

(Comparative Example 2)

In Example 2-1, a layer formed of a polycrystalline silicon film with a thickness of 15 nm was formed on the surface of the silicon wafer serving as a support substrate by the plasma CVD process. Here, in Comparative Example 2, the bonded silicon wafer was produced under the same conditions as Example 2-1, except that the thickness of the layer formed of a polycrystalline silicon film formed was 10nm.

(Evaluation: Infrared reflectance)

In the evaluation of the infrared reflectance in Example 2, as in Example 1, the above-mentioned film thickness measuring device was used to determine the infrared reflectance. Here, in Experimental Example 2, the reflected light L2 is the light reflected from the surface 528A of the bonded silicon wafer 500, and the reflected light L3 is the light reflected from the interface of the single crystal silicon layer 521 and of region 530 formed of polycrystalline silicon.

The results are listed in Table 2 below. From the results of this evaluation, it was confirmed that the areas formed from amorphous silicon and polycrystalline silicon in Examples 2-1 to Example 2-4 function as infrared reflective silicon films, while the areas of amorphous silicon and polycrystalline silicon formed in Comparative Example 2 are insufficient to function as infrared reflective silicon films.

Sample Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5 IR reflective silicon film Polycrystalline Silicon + Amorphous Silicon Polycrystalline Silicon + Amorphous Silicon Polycrystalline Silicon + Amorphous Silicon Polycrystalline Silicon + Amorphous Silicon Polycrystalline Silicon + Amorphous Silicon Thickness of IR-reflecting silicon film 16 21 26 31 11 Reflection intensity of reflected light 11993 15962 18434 18534 8936 Reflectance (%) 67.5 89.9 100 100 50.3

According to this disclosure, the bonded silicon wafer with low thickness and high infrared reflectance can be obtained.

Claims (11)

Bonded silicon wafer comprising:
a silicon wafer serving as a support substrate;
a layer of monocrystalline silicon on the silicon wafer serving as a support substrate; And
an infrared-reflecting silicon film provided between the silicon wafer serving as a support substrate and the single-crystal silicon layer;
Or
the infrared reflective silicon film comprises amorphous silicon, and
a thickness of the infrared reflecting silicon film is 25 nm or more. The bonded silicon wafer of claim 1, wherein the infrared reflective silicon film is made of amorphous silicon. Bonded silicon wafer according to claim 1, wherein the infrared reflecting silicon film is formed by a laminated structure made of amorphous silicon layer(s) and polycrystalline silicon layer(s). A bonded silicon wafer according to any of claims 1 to 3, wherein the thickness of the infrared reflecting silicon film is 25 nm or more. A bonded silicon wafer according to any of claims 1 to 3, wherein the thickness of the single crystal silicon layer is 3 μm or more and 30 μm or less. Process for producing the bonded silicon wafer according to claim 2 comprising the steps of:
a process of forming layer(s) formed of an amorphous silicon film forming a layer formed of an amorphous silicon film having a thickness of 15 nm or more on a surface of the wafer silicon for support substrate;
an activation treatment process subjecting a surface of the amorphous silicon film layer and a surface of a silicon wafer for a single crystal silicon layer to vacuum activation treatment at normal temperature to make both surfaces of activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer. Process for producing the bonded silicon wafer according to claim 2 comprising the steps of:
a process of forming a layer(s) formed of an amorphous silicon film forming a layer formed of an amorphous silicon film having a thickness of 15 nm or more on a surface of a silicon wafer for monocrystalline silicon layer;
an activation treatment process subjecting a surface of the layer formed of an amorphous silicon film and a surface of the silicon wafer for a support substrate to an activation treatment under vacuum at normal temperature to make the two surfaces of the activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer. Process for producing the bonded silicon wafer according to claim 2 comprising the steps of:
a process of forming a layer formed of an amorphous silicon film forming layers formed of an amorphous silicon film having a thickness of 16 nm or more on each surface of the silicon wafer for a support substrate and d a silicon wafer for a monocrystalline silicon layer;
an activation treatment process subjecting each surface of the amorphous silicon film layers formed on each surface of the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer to activation treatment under vacuum at normal temperature to make both surfaces of the activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer. Process for producing the bonded silicon wafer according to claim 3 comprising the steps of:
a process of forming a layer(s) formed of a polycrystalline silicon film forming a layer formed of a polycrystalline silicon film with a thickness of 15 nm or more on a surface of the wafer silicon for support substrate;
an activation treatment process subjecting a surface of the polycrystalline silicon film layer and a surface of a silicon wafer for a monocrystalline silicon layer to vacuum activation treatment at normal temperature to make both surfaces of activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer. Process for producing the bonded silicon wafer according to claim 3 comprising the steps of:
a process of forming layer(s) formed of a polycrystalline silicon film forming a layer formed of a polycrystalline silicon film having a thickness of 15 nm or more on a surface of a silicon wafer for monocrystalline silicon layer;
an activation treatment process subjecting a surface of the layer formed of a polycrystalline silicon film and a surface of the silicon wafer for a support substrate to an activation treatment under vacuum at normal temperature to make the two surfaces of activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer. Process for producing the bonded silicon wafer according to claim 3 comprising the steps of:
a process of forming layer(s) formed of a polycrystalline silicon film forming layers formed of a polycrystalline silicon film having a thickness of 16 nm or more on each surface of the wafer silicon for support substrate and a silicon wafer for monocrystalline silicon layer;
an activation treatment process subjecting each surface of the polycrystalline silicon film layers formed on each surface of the supporting substrate silicon wafer and the single crystal silicon layer silicon wafer to activation treatment under vacuum at normal temperature to make both surfaces of the activated zones;
a bonding process, following the activation treatment process, bringing the two activated zones into contact with each other under vacuum at normal temperature, thus bonding the two activated zones together to form the silicon film reflecting the infrared; And
a thickness reduction process, after the bonding process, reducing the thickness of the silicon wafer for single crystal silicon layer, thereby obtaining the single crystal silicon layer.