TW201810380A - Bonded SOI wafer manufacturing method - Google Patents

Abstract

The present invention comprises: a step for depositing a polycrystalline silicon layer on a base wafer; a step for obtaining a polished surface by polishing the polycrystalline silicon layer; a step for forming an insulating film on a bond wafer; a step for bonding the polished surface of the polycrystalline silicon layer and the bond wafer via the insulating film; and a step for thinning the bond wafer, wherein a silicon single crystal wafer of at least 100 [Omega]·cm is used as the base wafer, the step for depositing the polycrystalline silicon layer further includes a step for forming, in advance, an oxide film on a surface of the base wafer on which the polycrystalline silicon layer is to be deposited, the polycrystalline silicon layer is deposited by supplying, after being heated to a predetermined temperature of at least 1,000 DEG C, a source gas for the polycrystalline silicon layer at the predetermined temperature, and furthermore, even during heating to the predetermined temperature, the source gas for the polycrystalline silicon layer is supplied. Thus, provided is a bonded SOI wafer manufacturing method in which single crystallization of the polycrystalline silicon layer can be inhibited while high productivity is maintained.

Description

Method for manufacturing a bonded SOI wafer

The present invention relates to a method of fabricating a conformable SOI wafer.

As an SOI wafer corresponding to a radio frequency (RF) device, it has been solved in such a manner that the resistivity of the base wafer is increased. However, in order to gradually become more necessary for a higher radio frequency in response to further increase in speed, it has become increasingly impossible to use only conventional high-resistance wafers.

Then, as a countermeasure, it is proposed that a layer (carrier trap layer) having an effect of destroying the generated carrier is added immediately below the buried oxide film layer (BOX layer) of the SOI wafer, and it is necessary to use it. A high-resistance polysilicon layer in which the carriers generated in the high-resistance wafer are recombined is formed on the base wafer.

Patent Document 1 describes that a polycrystalline germanium layer or an amorphous germanium layer as a carrier trap layer is formed at the interface between the BOX layer and the base wafer.

On the other hand, Patent Document 2 also discloses that a polycrystalline layer as a carrier trap layer is formed at the interface between the BOX layer and the base wafer, and further, the heat treatment temperature after the formation of the polysilicon layer is restricted to prevent the polycrystalline layer. Recrystallization.

Further, in Patent Document 3, although a polycrystalline germanium layer or an amorphous germanium layer as a carrier trap layer is not described, it is described that the surface roughness of the surface of the base wafer bonded to the bonded wafer side is increased. Large, get the same effect as the carrier trap layer. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2007-507093 (Patent Document 2) Japanese Patent Publication No. 2013-513234 (Patent Document 3) Japanese Laid-Open Patent Publication No. 2010-278160 (Patent Document 4) JP-A-2015-211061 Bulletin

[Explanation of the Invention] However, if the growth temperature of the polycrystalline germanium layer is raised to a high temperature on the surface of the base wafer, the polycrystalline germanium layer is single-crystallized, and the function as a carrier trap layer is lost. The case where the characteristics are degraded. Further, although the single crystal of the polycrystalline germanium layer is suppressed by lowering the formation temperature of the polycrystalline germanium layer, there is a problem that the growth rate is lowered and the productivity is deteriorated.

Here, Patent Document 4 proposes a method of manufacturing a bonded SOI wafer including a first growth in which a polycrystalline germanium layer is deposited at a first temperature of 1010 ° C or lower, and a temperature higher than a first temperature. The second temperature is deposited thicker than the first growth. This manufacturing method can prevent the occurrence of single crystallization of the polycrystalline germanium layer and maintain the effect as a carrier trap layer. However, if the two-stage accumulation of such low-temperature deposition and high-temperature deposition is carried out in the stacking process, productivity is inevitably lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a bonded SOI wafer which can maintain high productivity while suppressing single crystal formation of a polysilicon layer. [Technical means to solve the problem]

In order to solve the above problems, the present invention provides a method for manufacturing a bonded SOI wafer, in which a bonded wafer and a base wafer each composed of a single crystal are bonded through an insulating film to produce a bonded SOI wafer. The manufacturing method includes the steps of: depositing a polysilicon layer on a bonding surface side of the base wafer; polishing a surface of the polysilicon layer to obtain a polishing surface; forming the insulating film on a bonding surface of the bonding wafer; and transmitting the insulating film through the bonding film Bonding the polished surface of the polysilicon layer of the base wafer to the bonded wafer; and thinning the bonded bonded wafer to form an SOI layer, wherein a single resistivity of 100 Ω ‧ cm or more is used As a step of depositing the polysilicon layer on the base wafer, the wafer wafer is further included in a stage in which an oxide film is formed on the surface of the base wafer on which the polysilicon layer is deposited, and the polycrystalline germanium layer is heated to 1000 ° C. The raw material gas of the polycrystalline germanium layer is supplied at the predetermined temperature up to the predetermined temperature, and the raw material gas of the polycrystalline germanium layer is also supplied when the temperature is raised to the predetermined temperature. .

In the method of manufacturing such a bonded SOI wafer, a polycrystalline germanium layer is formed by placing a material gas of a polycrystalline germanium layer at a temperature rising stage from a low temperature to a high temperature, and a polycrystalline germanium layer is grown at a high temperature. Therefore, it is possible to manufacture a bonded SOI wafer in which single crystallization and high productivity of the polycrystalline germanium layer are suppressed.

At this time, it is preferable that the oxide film is formed by wet cleaning.

Since the oxide film is interposed between the base wafer and the polysilicon layer, the characteristics of the RF device may be affected. Therefore, the thickness of the oxide film is preferably thin, and is preferably, for example, 10 nm or less. As a method of forming an oxide film having such a thickness, wet cleaning is the easiest method.

Further, at this time, the predetermined temperature is preferably 1150 ° C or lower.

When the predetermined temperature for the temperature rise is 1150 ° C or lower, the possibility of single-crystalization of the polycrystalline germanium layer at a high temperature deposition can be reduced.

Further, at this time, the temperature at which the supply of the material gas of the polycrystalline germanium layer is started during the temperature rise to the predetermined temperature is preferably in the range of 600 ° C to 980 ° C.

When the temperature at which the supply of the material gas of the polycrystalline germanium layer is started is 980 ° C or less at the time of the temperature rise to the predetermined temperature, the oxide film is less likely to disappear during the temperature rise, so that the single crystal of the polycrystalline germanium layer is suppressed. Moreover, when it is 600 ° C or more, high productivity is ensured. [Compared with the efficacy of prior art]

In the method for producing a bonded SOI wafer of the present invention, when a polycrystalline germanium layer is deposited on a base wafer, a polycrystalline germanium layer is formed by placing a material gas of a polycrystalline germanium layer at a time of a temperature rising phase from a low temperature to a high temperature. And grow polycrystalline germanium layer at high temperature. Thereby, it is possible to manufacture a bonded SOI wafer in which both the single crystallization of the polycrystalline germanium layer and the high productivity are suppressed. Further, the method for producing a bonded SOI wafer of the present invention can be applied not only to the formation of a polycrystalline germanium layer but also to productivity improvement at the time of formation of a single crystal germanium layer, and has high versatility. [Simplified illustration]

Fig. 1 is a flow chart showing an example of a method of manufacturing a bonded SOI wafer of the present invention. Fig. 2 is a schematic view showing an example of a method of manufacturing a bonded SOI wafer of the present invention. Fig. 3 is a graph showing the deposition conditions of the polycrystalline germanium layer of the examples. Fig. 4 is a graph showing the deposition conditions of the polysilicon layer of Comparative Example 1. Fig. 5 is a graph showing the deposition conditions of the polysilicon layer of Comparative Example 2. Fig. 6 is a graph showing the productivity (production capacity) in Comparative Examples and Comparative Examples 1 and 2. Fig. 7 is a cross-sectional SEM photograph of a wafer in which a polycrystalline germanium layer was deposited in Examples and Comparative Examples 1 and 2.

Hereinafter, the present invention is described in detail with reference to the drawings, but the present invention is not limited thereto.

As described above, there is a need for a method of manufacturing a bonded SOI wafer capable of maintaining high productivity while suppressing single crystal formation of a polysilicon layer.

The present inventors have intensively studied the above-mentioned problems, and have considered a method of manufacturing a bonded SOI wafer in which single crystal formation of a polycrystalline germanium layer can be suppressed without deteriorating productivity in the formation of a polycrystalline germanium layer. In the conventional method for forming a polycrystalline germanium layer, the formation temperature of the polycrystalline germanium layer is lowered, and after the temperature is raised to a predetermined temperature, the raw material gas (germanium growth gas) of the polycrystalline germanium layer is introduced to grow the polycrystalline germanium layer to suppress single crystal formation of the polycrystalline germanium layer. However, in this method, there is a problem that the growth rate of the polycrystalline germanium layer is lowered and the productivity is deteriorated. On the other hand, in order to increase the productivity, the formation temperature of the polycrystalline germanium layer is raised to a high temperature, and although the growth rate of the polycrystalline germanium layer is increased, the problem of single crystal formation of the polycrystalline germanium layer is faced.

Then, the inventors of the present invention have found that the bottom of the polycrystalline germanium layer is formed by adding a cerium growth gas at a temperature rising stage from a low temperature to a high temperature, and the polycrystalline germanium layer is grown at a high temperature, thereby achieving both suppression of single crystal formation and high productivity. The accumulation of polycrystalline germanium layers completes the present invention.

Hereinafter, an example of an embodiment of a method for manufacturing a bonded SOI wafer of the present invention will be described with reference to FIGS. 1 and 2, and an example of a method for manufacturing a bonded SOI wafer will be described below. Although the manufacturing method of the ion implantation peeling method is demonstrated, this invention is not limited to this.

First, a bonded wafer 1 made of a single crystal germanium is prepared (refer to step S11 and Fig. 2 (a) of Fig. 1).

Then, an insulating film 3 (for example, an oxide film) to be buried in the insulating film layer is formed on the bonding surface of the bonded wafer 1 by, for example, thermal oxidation or CVD (refer to step S12 and FIG. 2 of the first drawing). (b)). In this case, the formation of the insulating film 3 can be formed not only on the bonding surface but also on the entire bonding wafer.

Next, the bonding wafer 1 is implanted with an ion implantation layer 4 in the bonding wafer 1 by implanting at least one kind of gas ions of hydrogen ions and rare gas ions from the upper surface of the insulating film 3 by the ion implanter. Refer to step S13 and FIG. 2(c) of Fig. 1 .

Here, in order to remove the particles bonded to the bonding surface of the wafer 1, the cleaning before bonding is performed (refer to step S14 of FIG. 1).

On the other hand, in addition to the above, the base wafer 2 composed of single crystal germanium is prepared (refer to step S21 and Fig. 2 (d) of Fig. 1). At this time, a single crystal germanium wafer having a specific resistance of 100 Ω ‧ cm or more is prepared as the base wafer 2 .

When the specific resistance of the base wafer 2 is 100 Ω··cm or more, it can be suitably used for the manufacture of a radio frequency device, and more preferably 1000 Ω··cm or more and more preferably 3,000 Ω··cm or more. Although the upper limit of the specific resistance is not particularly limited, it can be, for example, 50,000 Ω ‧ cm.

Next, an oxide film (base oxide film) 5 is formed on the base wafer 2 (refer to step S22 and FIG. 2(e) of FIG. 1). Although the thickness of the oxide film 5 is not particularly limited, it may affect the characteristics of the RF device by interposing an oxide film between the base wafer and the polysilicon layer, so that the thickness of the oxide film is preferably thin, for example, 0.3. The thickness of nm or more and 10 nm or less is preferable.

As a method of forming an oxide film having such a thickness, wet cleaning can be mentioned as the most convenient method. Specifically, by using SC1 (a mixed aqueous solution of NH ₄ OH and H ₂ O ₂ ), SC ₂ (a mixed aqueous solution of HCl and H ₂ O ₂ ), and hydrogen peroxide water (H ₂ SO ₄ and H ₂ O _{2 )} The mixed aqueous solution), ozone water, or the like is washed, or a combination of these solutions is washed to form an oxide film having a thickness of 0.5 to 3 nm.

Next, the polysilicon layer 6 is deposited on the oxide film (base oxide film) 5 (refer to step S23 and FIG. 2(f) of FIG. 1). Here, the deposition of the polycrystalline germanium layer is performed by raising the temperature to a predetermined temperature of 1000 ° C or higher, supplying the material gas of the polycrystalline germanium layer at a predetermined temperature, and further supplying the polycrystalline silicon at the time of raising the temperature to a predetermined temperature. The raw material gas of the layer.

Further, in the present invention, it is necessary to raise the temperature to a predetermined temperature of 1000 ° C or higher. When the predetermined temperature of the temperature rise is less than 1000 ° C, the single crystal of the polycrystalline germanium layer can be suppressed, but the growth rate is lowered and the productivity is deteriorated. Further, the upper limit of the predetermined temperature for the temperature rise is preferably 1150 ° C or lower. When the predetermined temperature of the temperature rise is 1150° C. or lower, the polycrystalline germanium layer is deposited thinly by introducing the material gas of the polycrystalline germanium layer at a temperature rise to the predetermined temperature, and the oxide film is deposited at a predetermined temperature of the high temperature. Since it does not easily disappear, the possibility of single crystallization of the polycrystalline germanium layer can be reduced.

In addition, the temperature at which the supply of the material gas of the polycrystalline germanium layer is started at the time of the temperature rise to the predetermined temperature is preferably in the range of 600 ° C to 980 ° C. When the temperature at which the supply of the raw material gas of the polycrystalline germanium layer is started is 980 ° C or less at the time of the temperature rise to the predetermined temperature, the oxide film is less likely to disappear during the temperature rise, so that the single crystal of the polycrystalline germanium layer can be suppressed. Moreover, when it is 600 ° C or more, high productivity can be ensured.

In addition, the supply of the material gas in the polycrystalline silicon layer at the time of the temperature rise to the predetermined temperature may be started simultaneously with the start of the temperature rise until the temperature rises to the predetermined temperature, or may be performed until the temperature is raised to the predetermined temperature. It can be started.

Next, the surface of the polysilicon layer 6 deposited on the base wafer 2 is polished to obtain a polished surface (refer to step S24 and FIG. 2(g) of FIG. 1).

Here, in order to remove the particles on the surface of the polished polycrystalline germanium layer 6, the particles are washed before bonding (refer to step S25 of Fig. 1).

Further, either the steps S11 to S14 of the first drawing of the bonding wafer and the steps S21 to S25 of the first drawing of the base wafer may be performed either first or both.

Next, the base wafer 2 on which the polycrystalline germanium layer 6 is formed is bonded to the surface of the base wafer 2 on which the polycrystalline germanium layer 6 is formed (the polished surface) and the surface on which the implanted wafer 1 is implanted on the ion side. The bonded wafer 1 on which the insulating film 3 is formed is in close contact with each other (refer to step S31 and FIG. 2(h) of FIG. 1).

Next, a heat treatment (peeling heat treatment) for causing the ion implantation layer 4 to generate a microbubble layer is applied to the bonded wafer, and the wafer 1 is peeled off by the ion implantation layer 4 (microbubble layer) to be thinned. The bonded SOI wafer 8 on which the insulating film 3 and the SOI layer 7 are formed on the base wafer 2 is produced (refer to step S32 and FIG. 2(i) of FIG. 1).

Thereafter, in order to increase the bonding strength of the bonding interface, a bonding heat treatment is applied to the bonded SOI wafer 8 (refer to step S33 of Fig. 1).

As described above, a bonded SOI wafer can be manufactured. Further, the thinned film of the bonded bonded wafer 1 can be formed by polishing, polishing, etching, or the like in addition to the ion implantation stripping method.

According to the method for producing a bonded SOI wafer of the present invention as described above, it is possible to maintain high productivity and suppress single crystal formation of the polysilicon layer. Further, the method for producing a bonded SOI wafer of the present invention is not limited to the formation of a polycrystalline germanium layer, and can be applied to an increase in productivity at the time of formation of a single crystal germanium layer, and has high versatility. [Examples]

Hereinafter, the present invention will be described more specifically by showing examples and comparative examples, but the present invention is not limited to these examples.

[Examples] A bonded SOI wafer was produced by using the method of manufacturing a bonded SOI wafer described in Figs. 1 and 2 . In this case, a single crystal germanium wafer having a diameter of 200 mm, a crystal orientation of <100>, a resistivity of 1300 Ω·cm, and a p-type is used as the base wafer, and the formation of the oxide film on the base wafer and the deposition of the polysilicon layer are as follows. Conditions are carried out.

Oxide film formation conditions SC1+SC2 cleaning The thickness of the oxide film is about 1 nm

Stacking conditions of polycrystalline germanium layer (as shown in Fig. 3) Input temperature: 850 °C 850 °C ~ 1070 °C one-stage deposition (feeding raw material gas at the same time of temperature rise) Normal pressure film thickness 3.0 μm (after grinding) The film thickness was 2.0 μm. Carrier gas: H ₂ gas source gas: trichlorohydroquinone gas (TCS gas) At this time, the deposition rate at 1070 ° C was 3.0 μm / min.

Further, it takes time (the elapsed time of the process step) to measure the deposition of the polycrystalline germanium layer, and the productivity (production capacity) is determined based on the time (seconds/piece) required to produce a wafer in which a polycrystalline germanium layer is deposited in Comparative Example 1 to be described later. ). Further, the single crystallized state of the deposited polycrystalline germanium layer was confirmed by observing the cross-sectional SEM. These results are shown in Table 1, Figure 6, and Figure 7. The polycrystalline germanium layer is deposited on the base wafer in this manner, and the subsequent process is further performed to fabricate the bonded SOI wafer.

[Comparative Example 1] A bonded SOI wafer was produced in the same manner as in the example. Except for the deposition conditions of the polycrystalline germanium layer, the conditions shown in Fig. 4 are ascertained. In other words, when the temperature is raised, the TCS gas is not supplied, and the TCS gas is supplied under two-stage conditions of 900 ° C and 1070 ° C to deposit the polycrystalline germanium layer, and the deposition rate at 900 ° C is 0.3 μm / min. The deposition rate at 1070 ° C was 3.0 μm / min.

Further, in the same manner as in the examples, the measurement of the elapsed time of the process step in the deposition process of the polycrystalline germanium layer and the state of single crystal formation of the polycrystalline germanium layer after deposition were confirmed. In Comparative Example 1, the productivity was 1 because the time required to produce a wafer in which a polycrystalline germanium layer was deposited was used as a reference. These results are shown in Table 1, Figure 6, and Figure 7.

[Comparative Example 2] A bonded SOI wafer was produced in the same manner as in the example. However, the deposition conditions of the polycrystalline germanium layer are as shown in Fig. 5. In other words, the TCS gas was not supplied at the time of temperature rise, and the polycrystalline germanium layer was deposited by supplying the TCS gas only at one stage of 1020 °C. Further, the deposition rate was 2.2 μm/min.

In the same manner as in the examples, the measurement of the elapsed time of the process step in the deposition process of the polycrystalline germanium layer, the calculation of the productivity based on Comparative Example 1, and the state of single crystal formation of the polycrystalline germanium layer after deposition were confirmed. These results are shown in Table 1, Figure 6, and Figure 7.

【Table 1】

As shown in Table 1, Figure 6, and Figure 7, the productivity of a wafer in which a polycrystalline germanium layer is stacked in an embodiment of manufacturing a bonded SOI wafer by the method of manufacturing a bonded SOI wafer of the present invention (production) The ability is high, and no single crystal of the polysilicon layer occurs. Further, it is clear that the single crystal of the polysilicon layer does not occur in the production of the bonded SOI wafer, and the overall productivity of the bonded SOI wafer is improved.

On the other hand, in Comparative Example 1 in which the raw material gas of the polycrystalline germanium layer was not supplied and the polycrystalline germanium layer was deposited under the two-stage condition, the single crystal of the polycrystalline germanium layer did not occur, but the productivity was low. In addition, in Comparative Example 2 in which the raw material gas of the polycrystalline germanium layer was not supplied and the polycrystalline germanium layer was deposited under one-stage conditions, the productivity was low and the polycrystalline germanium layer was single-crystallized.

Further, the present invention is not limited by the foregoing embodiments. The above-described embodiments are exemplified, and have substantially the same configuration as the technical idea described in the patent application scope of the present invention, and all of the same effects are included in the technical scope of the present invention.

1‧‧‧ Bonded wafer
2‧‧‧Substrate wafer
3‧‧‧Insulation film
4‧‧‧Ion implantation layer
5‧‧‧Oxide film
6‧‧‧Polysilicon layer
7‧‧‧SOI layer
8‧‧‧Fixed SOI Wafer

Claims (5)

A method for manufacturing a bonded SOI wafer, wherein a bonded wafer and a base wafer each composed of a single crystal are bonded through an insulating film to produce a bonded SOI wafer, the manufacturing method comprising the following steps: Depositing a polycrystalline germanium layer on the bonding surface side of the bonded base wafer; polishing the surface of the polycrystalline germanium layer to obtain a polished surface; forming the insulating film on the bonding surface of the bonded wafer; and transmitting the underlying crystal through the insulating film The polished surface of the circular polycrystalline germanium layer is bonded to the bonded wafer; and the bonded bonded wafer is thinned to form an SOI layer, wherein single crystal twin crystal having a resistivity of 100 Ω·cm or more is used. The step of depositing the polysilicon layer as the base wafer further includes a step of depositing an oxide film on the surface of the base wafer on which the polysilicon layer is deposited, and the deposition of the polysilicon layer is increased to 1000 ° C or higher. The raw material gas of the polycrystalline germanium layer is supplied at a predetermined temperature until the predetermined temperature is reached, and the raw material gas of the polycrystalline germanium layer is also supplied while the temperature is raised to the predetermined temperature. The method of manufacturing a bonded SOI wafer according to claim 1, wherein the oxide film is formed by wet cleaning. The method of manufacturing a bonded SOI wafer according to claim 1, wherein the predetermined temperature is 1150 ° C or lower. The method of manufacturing a bonded SOI wafer according to claim 2, wherein the predetermined temperature is 1150 ° C or lower. The method for producing a bonded SOI wafer according to any one of claims 1 to 4, wherein, when the temperature is raised to the predetermined temperature, the temperature of the source gas supplied to the polysilicon layer is 600 ° C to 980 Temperature in the range of °C.