JP6131179B2 - Manufacturing method of bonded SOI wafer - Google Patents

Description

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

  Conventionally, as an SOI wafer compatible with an RF (Radio Frequency) device, it has been dealt with by increasing the resistivity of the base wafer. However, in order to cope with further increase in speed, it has become necessary to cope with a higher frequency, and it has become impossible to cope only with the use of a conventional high-resistance wafer.

  As a countermeasure, it has been proposed to provide a layer (carrier trap layer) having an effect of eliminating generated carriers immediately under a buried oxide film layer (BOX layer) of an SOI wafer.

  Regarding the carrier trap layer, Patent Documents 1 and 2 describe forming an additional layer such as a polycrystalline silicon layer or an amorphous silicon layer as a carrier trap layer at the interface between the BOX layer and the base wafer. Has been.

  Patent Document 3 describes forming a rare gas ion implantation layer as a carrier trap layer.

Special table 2007-507093 Special table 2013-513234 gazette Special table 2012-517691 gazette

As described above, in order to manufacture a device corresponding to a higher frequency, it is essential to form a carrier trap layer under the BOX layer of the SOI wafer.
Further, as a method for manufacturing an SOI wafer having such a carrier trap layer, a hydrogen ion is mainly implanted into a bond wafer for forming an SOI layer to form an ion implantation layer for separation, and a base wafer and an insulating film are interposed therebetween. After bonding, a method (ion implantation peeling method) in which the film is peeled off by an ion implantation layer for peeling and thinned is mainly employed.
Therefore, as described in Patent Document 3, if the ion implantation for forming the carrier trap layer can be performed with the same hydrogen ions as the ion implantation for peeling, the ion species and the ion implantation apparatus are changed. Therefore, efficient manufacturing is possible.

  However, according to Patent Document 3, it is described that a rare gas ion implantation layer such as argon is formed as a carrier trap layer, but there is no mention of using hydrogen ions as a substitute for rare gas ions. .

  As a result of intensive investigations by the present inventors for this reason, the hydrogen ion implanted layer formed by implanting hydrogen ions less than the critical dose amount that does not cause peeling, has defects immediately after implantation, Defects caused by ion implantation disappear due to the heat treatment (bond strengthening heat treatment or heat treatment such as sacrificial oxidation for adjusting the SOI film thickness) during the bonded SOI wafer manufacturing process, so that it does not function as a carrier trap layer. It has been found.

  The present invention has been made in view of the above problems, and even an ion-implanted defect layer formed by hydrogen ion implantation can be sufficiently used as a carrier trap layer without being erased by heat treatment in a subsequent process. It is an object of the present invention to provide a method for manufacturing a bonded SOI wafer that can function.

In order to achieve the above object, the present invention includes a step of preparing a bond wafer and a base wafer each made of a silicon single crystal, and a first insulating film is formed on the surface of the base wafer. Forming a hydrogen ion implantation layer in the vicinity of the surface of the base wafer by implanting hydrogen ions less than a critical dose without causing separation through the insulation film; removing the first insulation film; by performing the reforming heat treatment on the base wafer in which the hydrogen ion implanted layer is formed, a step of modifying the hydrogen ion implanted layer in the ion implantation defect layer without peeling by the hydrogen ion implanted layer, the modified said base wafer subjected to quality heat treatment, after the said bond wafer was bonded via the second insulating film, to thin the bond wafer To provide a manufacturing method of a bonded SOI wafer characterized in that a step of forming an SOI layer Te.

  As described above, after the first insulating film is removed, the base wafer on which the hydrogen ion implanted layer is formed is subjected to heat treatment, whereby gas molecules in the heat treatment atmosphere are diffused into the hydrogen ion implanted layer, thereby repairing the defect. Therefore, the hydrogen ion implantation layer can be modified into an ion implantation defect layer that hardly disappears in a later process.

At this time, it is preferable to perform the modification heat treatment on the base wafer at a temperature of 500 ° C. or higher and 800 ° C. or lower.
By performing the reforming heat treatment at a temperature of 500 ° C. or higher, it is possible to prevent insufficient diffusion of gas molecules, and by performing the reforming heat treatment at a temperature of 800 ° C. or lower, ion implantation that does not easily disappear in the subsequent process. It is possible to more reliably prevent the defects from being crystallized and disappearing before the reforming to the defect layer proceeds.

At this time, it is preferable to set a dose amount in hydrogen ion implantation to the base wafer within a range of 1 × 10 ¹⁶ / cm ² or more and 1 × 10 ¹⁷ / cm ² or less.
By setting the dose of hydrogen ion implantation to 1 × 10 ¹⁶ / cm ² or more, the function as a carrier trap layer can be prevented from becoming insufficient, and the dose of hydrogen ion implantation can be set to 1 × 10 ¹⁷ / cm. ^By setting it to ² or less, peeling can be prevented from occurring in the reforming heat treatment.

At this time, the second insulating film is formed on the surface of the bond wafer, and at least one of hydrogen ions or rare gas ions having a critical dose amount or more is formed in the vicinity of the surface of the bond wafer via the second insulating film. It is preferable that the thinning is performed by forming an ion implantation layer for peeling and bonding the base wafer to the base wafer, followed by peeling with the ion implantation layer for peeling.
In this manner, the bond wafer can be thinned using the ion implantation separation method.

At this time, the first and second insulating films are preferably silicon oxide films.
As the first and second insulating films, silicon oxide films can be suitably used.

  As described above, according to the method for manufacturing a bonded SOI wafer of the present invention, an ion implantation layer formed by hydrogen ion implantation is modified into an ion implantation defect layer, and the defects are not eliminated by a heat treatment in a subsequent process. It can function sufficiently as a carrier trap layer.

It is a figure which shows the flow of the manufacturing method of the bonding SOI wafer of this invention. It is a figure which shows the evaluation flow corresponding to the flow of the manufacturing method of the bonding SOI wafer of this invention. It is a figure which shows the cross-sectional TEM observation result of the wafer of Experimental example 1-4.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
As described above, in order to manufacture a device corresponding to a higher frequency, it has become essential to form a carrier trap layer under the BOX layer of the SOI wafer.
However, a hydrogen ion implanted layer formed by implanting hydrogen ions less than the critical dose that does not cause peeling has defects immediately after the implantation, but heat treatment during the subsequent bonded SOI wafer manufacturing process ( There is a problem that defects caused by ion implantation disappear due to bond strengthening heat treatment or heat treatment such as sacrificial oxidation for adjusting the SOI film thickness, and the film does not function as a carrier trap layer.

  Therefore, the present inventors have made it possible to sufficiently function as a carrier trap layer even if an ion implantation layer formed by hydrogen ion implantation less than the critical dose is not eliminated by heat treatment in a subsequent process. We intensively studied a method for manufacturing a bonded SOI wafer that can be bonded.

As a result, the present inventors, thereby removing the formed insulating film in front of the hydrogen ion implantation step, by performing a modified heat treatment a base wafer hydrogen ion implanted layer is formed in an oxidizing atmosphere, modification It has been found that gas molecules in the heat treatment atmosphere can diffuse into the hydrogen ion implanted layer and hinder the repair of defects, and that the hydrogen ion implanted layer can be modified into an ion implanted defect layer that does not easily disappear in a later process. Invented the invention.

Hereinafter, an SOI wafer manufacturing method of the present invention will be described with reference to FIG.
First, a base wafer and a bond wafer made of silicon single crystal are prepared (see steps S1-0 and S2-0 in FIG. 1).
For RF devices, the resistivity of the base wafer is preferably 1000 Ω · cm or more, and more preferably 3000 Ω · cm or more.

Next, a first insulating film is formed on the base wafer (see step S1-1 in FIG. 1).
As the first insulating film, a silicon oxide film is preferably formed by thermal oxidation.
Further, a second insulating film (buried oxide film) is formed on the bond wafer (see step S2-1 in FIG. 1).
The first insulating film and the second insulating film are preferably formed using a silicon oxide film by thermal oxidation.

Next, hydrogen ions less than the critical dose that do not cause separation are implanted through the first insulating film into the base wafer to form a hydrogen ion implanted layer near the surface of the base wafer (S1 in FIG. 1). -See step 2).
The dose amount of hydrogen ion implantation into the base wafer is preferably set in the range of 1 × 10 ¹⁶ / cm ² or more and 1 × 10 ¹⁷ / cm ² or less, 3 × 10 ¹⁶ / cm ² or more, 6 × More preferably, it is set within the range of 10 ¹⁶ / cm ² or less.
By setting the dose of hydrogen ion implantation to 1 × 10 ¹⁶ / cm ² or more, the function as a carrier trap layer can be prevented from becoming insufficient, and the dose of hydrogen ion implantation can be set to 1 × 10 ¹⁷ / cm. ^By setting it to ² or less, it is possible to reliably prevent peeling in the reforming heat treatment.

  Further, through the second insulating film, at least one of hydrogen ions or rare gas ions having a critical dose amount or more that causes separation is implanted into the bond wafer to form an ion implantation layer for separation near the surface of the bond wafer (FIG. 1 S2-2 step).

  Next, the first insulating film formed on the base wafer is removed (see step S1-3 in FIG. 1). When the first insulating film is a silicon oxide film, the first insulating film can be removed by HF cleaning (see step S1-3 in FIG. 1).

Next, the base wafer from which the first insulating film has been removed is subjected to a heat treatment, for example, in an oxidizing gas atmosphere or an inert gas atmosphere, thereby reforming the hydrogen ion implanted layer into a hydrogen ion implanted defect layer (FIG. 1). S1-4 step).
At this time, the heat treatment for reforming is preferably performed at a temperature of 500 ° C. or higher and 800 ° C. or lower. By performing at a temperature of 500 ° C. or higher, it is possible to prevent the atmospheric gas from being insufficiently diffused, and by performing the temperature at a temperature of 800 ° C. or lower, reforming into an ion implantation defect layer that hardly disappears in a subsequent process proceeds. It is possible to more reliably prevent defects from becoming single crystal and disappearing before.

Next, pre-bonding cleaning of the modified heat-treated base wafer and bond wafer is performed (see step S3 in FIG. 1). The pre-bonding cleaning can be performed using, for example, a cleaning liquid composed of an NH ₄ OH / H ₂ O ₂ aqueous solution and an HCl / H ₂ O ₂ aqueous solution.

  Next, the second insulating film is formed such that the surface of the base wafer on which the hydrogen ion implantation defect layer is formed and the surface of the bond wafer on which the peeling ion implantation layer is formed are in contact with each other. (See S4 in FIG. 1).

Next, the bonded wafer is subjected to a peeling heat treatment and peeled off by a peeling ion implantation layer formed on the bond wafer, whereby the bond wafer is thinned to form an SOI layer (see S5 in FIG. 1).
This exfoliation heat treatment can be performed, for example, in an Ar atmosphere at 500 ° C. for 30 minutes.

  Next, a heat treatment is performed on the bonded wafer that has been thinned from the bond wafer (see S6 in FIG. 1). This heat treatment is, for example, bonding heat treatment, sacrificial oxidation, or the like. The bonding heat treatment can be performed, for example, in an oxidizing atmosphere at 1000 ° C. for 4.5 hours, and the sacrificial oxidation can be performed, for example, at 1050 ° C. for 1.5 hours.

In the above description, the bond wafer is thinned using the ion implantation separation method. However, the bond wafer can be thinned using chemical mechanical polishing (CMP) or etching.
In the above description, the second insulating film is formed on the bond wafer side. However, the second insulating film can be formed on the base wafer side after the modifying heat treatment in step S1-4. You may make it form in.
Moreover, although the process of step S1-0-step S1-4 was demonstrated above so that a process of step S2-0-step S2-2 may be advanced in parallel above, these are performed before bonding of step S4. As long as it is performed, the process may be individually performed.

(Experimental example)
As an alternative evaluation of the flow for manufacturing the bonded SOI wafer of the present invention shown in FIG. 1, a base wafer was produced according to the evaluation flow shown in FIG.
In the evaluation flow of FIG. 2, the “cleaning process before bonding” (step S3), the “bonding process” (step S4), and the “peeling heat treatment process” (step S5) of FIG. 1 are omitted.
Further, in the evaluation flow of FIG. 2, instead of the “heat treatment process” (step S6) of FIG. 1, step S6 ′ which is a heat treatment process for evaluation (heat treatment assuming heat treatment of the SOI wafer manufacturing process: 1000 ° C., 4.5 hours + 1050 ° C., 1.5 hours).
After the heat treatment step (Step S6 ′), the cross section of the base wafer was observed with a transmission electron microscope (TEM).
Table 1 shows the experimental conditions for each step of the evaluation flow.

The TEM observation result of Experimental Example 1-4 is shown in FIG.
As can be seen from FIG. 3, in Experimental Examples 3 and 4 (an oxide film is formed on the base wafer, hydrogen ions are implanted, the formed oxide film is removed with HF, and a modification heat treatment is performed), A high-density defect layer (continuous defect layer) was formed over the entire surface near the surface of the base wafer below the oxide film.
However, in the case where the oxide film formed on the base wafer is not removed, the reforming heat treatment after hydrogen ion implantation is performed at a high density in both cases of Ar atmosphere (Experiment 1) and O ₂ atmosphere (Experiment 2). No defective layer was observed.
In addition, although the same experiment was conducted by changing the reforming heat treatment temperature in step S1-4 to 500 ° C., the same result as in the case of 800 ° C. was obtained.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
A silicon single crystal wafer having a diameter of 300 mm, a crystal orientation <100>, and a resistivity of 3000 Ωcm is used as the base wafer, and a silicon single crystal wafer having a diameter of 300 mm, a crystal orientation <100>, and a resistivity of 10 Ωcm is used as the bond wafer. A bonded SOI wafer was manufactured according to the manufacturing flow shown in FIG.
Here, Table 2 shows conditions for each step of Example 1-4 and Comparative Example 1-2.

Example 1
A bonded SOI wafer was produced under the conditions shown in Table 2. The HF cleaning process in step S1-3 was performed using a 10% HF aqueous solution, and the reforming heat treatment process in step S1-4 was performed at 100% O 2, 700 ° C. for 2 hours.

(Example 2)
A bonded SOI wafer was produced under the conditions shown in Table 2. The HF cleaning process in step S1-3 was performed using a 10% HF aqueous solution, and the reforming heat treatment process in step S1-4 was performed at 100% O 2, 600 ° C. for 3 hours.

(Example 3)
A bonded SOI wafer was produced under the conditions shown in Table 2. The HF cleaning process in step S1-3 was performed using a 10% HF aqueous solution, and the reforming heat treatment process in step S1-4 was performed at 100% O2, 500 ° C. for 4 hours.

Example 4
A bonded SOI wafer was produced under the conditions shown in Table 2. The HF cleaning process in step S1-3 was performed using a 10% HF aqueous solution, and the reforming heat treatment process in step S1-4 was performed at 100% Ar, 800 ° C. for 2 hours.

(Comparative Example 1)
A bonded SOI wafer was produced under the conditions shown in Table 2. Note that the HF cleaning process in step S1-3 was performed using a 10% HF aqueous solution, and the reforming heat treatment process in step S1-4 was not performed.

(Comparative Example 2)
A bonded SOI wafer was produced under the conditions shown in Table 2. Note that the HF cleaning process in step S1-3 was not performed, and the reforming heat treatment process in step S1-4 was performed at 100% O 2, 700 ° C. for 2 hours.

The cross section of the bonded SOI wafer produced under the conditions of Example 1-4 and Comparative Example 1-2 was observed by TEM.
As a result, the surface of the base wafer below the buried oxide film (BOX film) of the SOI wafer of Example 1-4 that was subjected to HF cleaning to remove the thermal oxide film and subjected to the reforming heat treatment at 500 ° C. to 800 ° C. It was found that a high-density defect layer (that is, a continuous defect layer) was formed in the vicinity.
On the other hand, in Comparative Example 1 in which the modified heat treatment was not performed and in Comparative Example 2 in which the HF cleaning was not performed, a defect layer was sparsely observed in the vicinity of the surface of the base wafer below the buried oxide film. A high-density defect layer was not formed, and the level was insufficient to function as a carrier trap layer.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Claims (5)

Each of them prepares a bond wafer and a base wafer made of silicon single crystal,
A first insulating film is formed on the surface of the base wafer, and hydrogen ions are implanted in the vicinity of the surface of the base wafer by implanting hydrogen ions less than the critical dose without causing separation through the first insulating film. Forming a layer;
Removing the first insulating film;
Modifying the hydrogen ion implantation layer into an ion implantation defect layer without peeling off the hydrogen ion implantation layer by performing a modification heat treatment on the base wafer on which the hydrogen ion implantation layer is formed;
And a step of forming an SOI layer by thinning the bond wafer after bonding the base wafer subjected to the reforming heat treatment and the bond wafer through a second insulating film. A manufacturing method of a bonded SOI wafer, which is characterized. The bonded SOI wafer production according to claim 1, wherein the modified heat treatment for the base wafer is performed at a temperature of 500 ° C or higher and 800 ° C or lower in an oxidizing gas atmosphere or an inert gas atmosphere. Method. The dose amount in hydrogen ion implantation to the base wafer is set within a range of 1 × 10 ¹⁶ / cm ² or more and 1 × 10 ¹⁷ / cm ² or less. Manufacturing method of bonded SOI wafer. The second insulating film is formed on the surface of the bond wafer, and at least one of hydrogen ions or rare gas ions having a critical dose amount or more that causes separation near the surface of the bond wafer through the second insulating film. 2. The thin film is formed by implanting to form an ion implantation layer for separation and bonding the base wafer to the base wafer, and then performing separation heat treatment with the separation ion implantation layer. The manufacturing method of the bonding SOI wafer as described in any one of claim | item 3.   5. The method for manufacturing a bonded SOI wafer according to claim 1, wherein the first and second insulating films are silicon oxide films. 6.

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