JP2019201148A - Manufacturing method of bonded SOI wafer - Google Patents

Abstract

To provide a manufacturing method of a bonded SOI wafer that can suppress the deterioration of a SOI layer film thickness range due to flattening heat treatment without reducing the flattening effect by the flattening heat treatment.SOLUTION: In a manufacturing method of a bonded SOI wafer, an ion implantation layer is formed by ion implantation of at least one gas ion of hydrogen ions or rare gas ions from the surface of a bond wafer made of a silicon single crystal, and after the ion implanted surface of the bond wafer and the surface of a base wafer made of the silicon single crystal are bonded through a silicon oxide film, the bond wafer is peeled off with the ion implantation layer to manufacture the bonded SOI wafer having a BOX layer and an SOI layer on the base wafer, and flattening heat treatment on the bonded SOI wafer in an atmosphere containing an argon gas is performed. The flattening heat treatment is performed in a reduced-pressure atmosphere.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a bonded SOI wafer, and more particularly to a method for manufacturing an SOI wafer using an ion implantation separation method.

  An SOI (Silicon on Insulator) wafer manufacturing method, particularly a thin film SOI wafer manufacturing method capable of improving the performance of advanced integrated circuits, is a method of manufacturing an SOI wafer by peeling an ion-implanted wafer after bonding (ion) An injection peeling method: a technique called a smart cut method (registered trademark)) has attracted attention.

  In this ion implantation separation method, an oxide film is formed on at least one of two silicon wafers, and gas ions such as hydrogen ions or rare gas ions are implanted from the upper surface of one silicon wafer (bond wafer), An ion implantation layer (also referred to as a microbubble layer or an encapsulation layer) is formed inside the wafer. After that, the surface into which the ions are implanted is brought into close contact with the other silicon wafer (base wafer) through an oxide film, and then a heat treatment (peeling heat treatment) is applied to form a microbubble layer as a cleaved surface on one wafer (bond wafer). ) In the form of a thin film and bonded to produce a SOI wafer. In addition, there is a method of firmly bonding the peeled SOI wafer by applying a heat treatment (bonding heat treatment) (see Patent Document 1).

  At this stage, the cleaved surface (peeling surface) is the surface of the SOI layer, and an SOI wafer having a thin SOI layer thickness and high uniformity can be obtained relatively easily. However, a damaged layer due to ion implantation exists on the surface of the SOI wafer after peeling, and the surface roughness is larger than that of a normal mirror surface of a silicon wafer. Therefore, in the ion implantation separation method, it is necessary to remove such a damaged layer and surface roughness.

  One method for removing the surface roughness and damage layer on the SOI layer surface is an annealing method in which high-temperature heat treatment is performed in an argon-containing atmosphere. According to this annealing method, the film thickness uniformity of the SOI layer obtained by the ion implantation separation method can be kept high while the surface of the SOI layer is planarized (Patent Documents 1 and 2).

Republication publication WO2003 / 009386 Republication publication WO2011 / 027545

  However, in the batch type normal pressure high temperature Ar annealing heat treatment apparatus, etching proceeds by a redox reaction between the silicon surface of the SOI structure and the silicon oxide film interface on the surface, so that high temperature Ar annealing (hereinafter simply referred to as planarization heat treatment). The SOI layer thickness decreases before and after. At this time, there is a problem in that the uniformity of the SOI layer thickness after Ar annealing deteriorates because the reduction of the SOI layer thickness varies in the plane.

  The present invention has been made to solve the above-described problems. In the manufacture of bonded SOI wafers, the SOI layer thickness range is reduced by flattening heat treatment without reducing the flattening effect by flattening heat treatment. It is an object to provide a method for manufacturing a bonded SOI wafer that can be suppressed.

  In order to achieve the above object, in the present invention, an ion-implanted layer is formed by ion-implanting at least one gas ion of hydrogen ions or rare gas ions from the surface of a bond wafer made of a silicon single crystal, After bonding the ion-implanted surface of the wafer and the surface of the base wafer made of a silicon single crystal through a silicon oxide film, the bond wafer is peeled off by the ion-implanted layer, whereby the surface of the base wafer is removed. In a method for manufacturing a bonded SOI wafer, in which a bonded SOI wafer having a BOX layer and an SOI layer is manufactured, and the bonded SOI wafer is subjected to a planarizing heat treatment in an argon gas-containing atmosphere, the planarizing heat treatment is performed under a reduced pressure atmosphere. Provided is a method for manufacturing a bonded SOI wafer characterized by .

  Thus, by performing the planarization heat treatment in a reduced-pressure atmosphere, it is possible to suppress the deterioration of the SOI layer film thickness range due to the planarization heat treatment without reducing the planarization effect.

  At this time, the reduced-pressure atmosphere is preferably set to 0.05 to 0.5 atm.

  In general, O-ring seals are often used in batch-type decompression systems, but organic substances from O-ring seals may be desorbed due to temperature rise and pressure reduction in the O-ring seal part of the heat treatment furnace. Therefore, it is preferable to set the pressure to 0.05 atm or higher because there is no fear that an organic substance (for example, methane) desorbed from the O-ring seal reacts with active silicon on the SOI surface to form SiC defects. On the other hand, the deterioration of the SOI layer thickness range can be sufficiently suppressed by setting the pressure to 0.5 atm or less.

  The argon gas-containing atmosphere may be a 100% argon gas atmosphere.

  Thus, even when the planarization heat treatment is performed in a 100% argon gas atmosphere, the method for manufacturing a bonded SOI wafer according to the present invention can be suitably used.

  As described above, according to the bonded SOI wafer manufacturing method of the present invention, it is possible to suppress deterioration of the SOI layer film thickness range due to the planarization heat treatment without reducing the planarization effect due to the planarization heat treatment.

It is the process flowchart which showed an example of the manufacturing method of the bonding SOI wafer of this invention.

  As described above, there has been a demand for the development of a method for manufacturing a bonded SOI wafer that can prevent deterioration in SOI layer film thickness uniformity after planarization heat treatment.

  As a result of intensive studies on the above problems, the inventors of the present invention contributed to the variation in the thickness reduction of the SOI layer by batch-type atmospheric high-temperature Ar annealing. Depending on the partial pressure, in the case of a batch boat, it is found that the SiO partial pressure at the center of the wafer is high and lower at the outer periphery, so that the etching rate at the outer periphery is increased. It was found that the uniformity of the SOI layer thickness after the planarization heat treatment can be improved by lowering the SiO partial pressure at the center of the wafer and reducing the difference from the outer peripheral portion.

  That is, the present invention forms an ion-implanted layer by ion-implanting at least one gas ion of hydrogen ions or rare gas ions from the surface of a bond wafer made of a silicon single crystal, and implants the ions of the bond wafer. After bonding the surface and the surface of the base wafer made of silicon single crystal through a silicon oxide film, the bond wafer is peeled off by the ion implantation layer, whereby a BOX layer and an SOI layer are formed on the base wafer. In a method for manufacturing a bonded SOI wafer, in which a bonded SOI wafer is manufactured and a planarized heat treatment is performed on the bonded SOI wafer in an argon gas-containing atmosphere, the planarized heat treatment is performed in a reduced-pressure atmosphere. This is a method for manufacturing a bonded SOI wafer.

Note that paragraph (0053) of JP2013-125909A describes that the SOI layer film thickness distribution deteriorates due to the planarization heat treatment, but in order to solve this, the pressure reduction is performed as in the present invention. There is no disclosure or suggestion of performing planarization heat treatment in an atmosphere.
Furthermore, Japanese Patent Application Laid-Open No. 2017-5201 describes that Ar annealing is performed as a heat treatment for planarizing the SOI layer surface, but there is no disclosure or suggestion of performing it in a reduced-pressure atmosphere.

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

FIG. 1 is a flowchart showing an example of a method for manufacturing a bonded SOI wafer according to the present invention. Hereinafter, a method for manufacturing a bonded SOI wafer according to the present invention will be described with reference to the flowchart of FIG.
In the bonded SOI wafer manufacturing method of the present invention, first, a bond wafer and a base wafer made of a silicon single crystal are prepared, and an ion implantation layer is formed on the bond wafer (FIG. 1A).

  Note that at least one of the bond wafer and the base wafer has a silicon oxide film formed on the surface.

  The ion-implanted layer in the bond wafer may be formed by injecting at least one kind of gas ion from hydrogen ions and rare gas ions from the surface of the bond wafer to form an ion-implanted layer inside the wafer. Just do it.

  Next, the ion-implanted surface of the bond wafer is bonded to the surface of the base wafer made of a silicon single crystal through a silicon oxide film (FIG. 1B). In this bonding, for example, the bond wafer and the base wafer are brought into contact with each other in a clean atmosphere at room temperature, whereby the wafers are bonded to each other without using an adhesive or the like.

  Next, an SOI wafer having a buried oxide film layer (BOX layer) and an SOI layer on the base wafer is manufactured by performing a peeling heat treatment to peel off the bond wafer with the ion implantation layer (FIG. 1C). As this peeling heat treatment, for example, the bond wafer can be peeled off by an ion implantation layer by applying a heat treatment in an atmosphere of an inert gas such as nitrogen, usually 400 ° C. or more and 700 ° C. or less for 30 minutes or more. Can be minutes. In addition, by performing plasma treatment on the bonding surface in advance, it is possible to perform peeling by applying an external force without performing heat treatment (or after performing heat treatment at a temperature that does not peel).

  Thereafter, in order to increase the bonding strength of the bonded interface between the SOI layer after peeling and the base wafer, bonding heat treatment in an oxidizing atmosphere may be performed (FIG. 1D). The bonding heat treatment conditions are not particularly limited, but can be performed, for example, in an oxidizing atmosphere at a temperature of 900 ° C. or higher for 10 minutes to several hours (for example, 2 hours).

  A planarization heat treatment is performed on the manufactured SOI wafer in an atmosphere containing argon gas. In the present invention, this planarization heat treatment is performed in a reduced pressure atmosphere (FIG. 1E). The range of the pressure is not particularly limited, but is preferably 0.05 to 0.5 atm. In general, an O-ring seal is often employed in a batch-type decompression system, and an organic substance may be desorbed from the O-ring seal due to temperature increase and pressure reduction in a heat treatment furnace. Therefore, by setting the pressure in such a range, it is possible to prevent the organic substance (for example, methane) desorbed from the O-ring seal from reacting with active silicon on the SOI surface to form SiC defects, and to form the SOI layer. Degradation of the film thickness range can be sufficiently suppressed.

In the present invention, the planarization heat treatment is performed in an argon gas-containing atmosphere, but may be performed in a 100% argon gas atmosphere, or a mixed gas atmosphere such as argon and hydrogen (for example, Ar: H ₂ by volume ratio = 50: 50). ).

  In the present invention, the temperature and time of the planarization heat treatment are not particularly limited, and can be performed at a known temperature and time. For example, the temperature may be from 1,100 ° C. to 1,300 ° C. and from several minutes to several hours, and in particular, from 1,150 ° C. to 1,250 ° C. and from 5 minutes to 3 hours.

  As described above, in the method for manufacturing a bonded SOI wafer according to the present invention, since the planarization heat treatment is performed in a reduced-pressure atmosphere, the SiO partial pressure at the center of the wafer can be lowered to reduce the difference from the outer peripheral portion. Thereby, the deterioration of the SOI layer film thickness range due to the planarization heat treatment can be suppressed without reducing the planarization effect due to the planarization heat treatment.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited to these.

(Examples 1-2)
In accordance with the manufacturing conditions shown in Table 1 below along the flow chart of FIG. 1, the oxide-bonded bond wafer with the oxide film and the base wafer are bonded together, and the bond wafer is peeled off with the ion-implanted layer. Flattening heat treatment was performed under reduced pressure in an atmosphere containing argon gas. Here, the planarization heat treatment was performed by changing the gas atmosphere and the atmospheric pressure.
The SOI layer film thickness before and after the planarization heat treatment is measured on the entire surface at a pitch of 1 mm using an optical film thickness measuring instrument (Acumap manufactured by ADE). Value). Moreover, the surface roughness (1 μm square RMS) of the SOI layer before and after the planarization heat treatment was measured using an AFM (atomic force microscope). The results are shown in Table 1.

(Comparative example)
A bonded SOI wafer was manufactured in the same manner as in Example 1 except that the planarization heat treatment was performed at normal pressure and not performed in a reduced pressure atmosphere, and the SOI layer thickness range and the SOI layer surface roughness were measured. The results are shown in Table 1.

  As shown in Table 1, in Example 1 and Example 2 in which the planarization heat treatment was performed in a reduced pressure atmosphere, the SOI layer film after the planarization heat treatment was compared with the comparative example in which the planarization heat treatment was not performed in the reduced pressure atmosphere. The thickness range was good, and the SOI layer thickness uniformity after the planarization heat treatment was good. In particular, the improvement of the SOI layer film thickness range was based on the fact that the difference between the central portion and the peripheral portion became smaller.

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

Claims (3)

An ion-implanted layer is formed by ion implantation of at least one gas ion of hydrogen ions or rare gas ions from the surface of a bond wafer made of a silicon single crystal, and the ion-implanted surface of the bond wafer and a silicon single crystal A bonded SOI wafer having a BOX layer and an SOI layer on the base wafer by peeling the bond wafer with the ion-implanted layer after bonding the surface of the base wafer made of silicon via a silicon oxide film In the method for manufacturing a bonded SOI wafer, the planarized heat treatment is performed in an argon gas-containing atmosphere on the bonded SOI wafer.
A method for producing a bonded SOI wafer, wherein the planarizing heat treatment is performed in a reduced-pressure atmosphere.   The method for producing a bonded SOI wafer according to claim 1, wherein the reduced-pressure atmosphere is set to 0.05 to 0.5 atm.   The method for producing a bonded SOI wafer according to claim 1 or 2, wherein the argon gas-containing atmosphere is a 100% argon gas atmosphere.

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