JP5830255B2 - Manufacturing method of semiconductor substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor substrate provided with a germanium-based epitaxial film such as germanium (Ge) or silicon germanium (SiGe) on a heterogeneous substrate.

  The use of SOI (Silicon on insulator) substrates is conventionally known as a method for improving the processing speed by increasing carrier mobility in semiconductor devices, but in recent years, the use of GeOI (Germanium on insulator) substrates has been known. Has been proposed. This is because the carrier mobility in the Ge crystal is about twice as fast as the electron mobility and about four times as high as the hole mobility compared to the Si crystal, which is advantageous for designing a semiconductor device operating at high speed.

Epitaxial growth of Ge film on heterogeneous substrate is a method of depositing a number of Si _1-x Ge _x layers with slightly increasing Ge concentration on a Si substrate and finally obtaining a Ge layer that does not contain Si Is known (see, for example, Non-Patent Document 1). In this method, the Ge concentration in the Si _1-x Ge _x layer is gradually increased because Si and Ge have a lattice constant of about 4% different, so that a Ge film is directly epitaxially grown on the Si substrate. This is because lattice defects called misfit dislocations are introduced to suppress the occurrence of misfit dislocations.

  Then, hydrogen ions are implanted into the Ge layer thus obtained, bonded to a support substrate such as a silicon wafer with an oxide film, and subjected to heat treatment in a temperature range of about 400 to 600 ° C. A technique is known in which a minute hydrogen cavity called a microcavity is generated and thermally exfoliated to obtain a GeOI substrate.

However, this method increases the manufacturing cost because it is necessary to repeat the epitaxial growth of Si _1-x Ge _x many times, and above all, the lattice defects introduced into the Ge epitaxial layer are reduced to a sufficient level. It is difficult. Further, a post-peeling heat treatment is performed to increase the bond strength at the bonding interface between the support substrate and the Ge layer. The heat treatment temperature is relatively high, 800 to 900 ° C., and the melting point of Ge Is 918 ° C., it is difficult to say that this is a suitable method for industrial production.

However, if a Ge substrate is used as an epitaxial substrate, the above-mentioned problem does not occur, but the Ge substrate is extremely difficult to increase in diameter, and further, since Ge is a rare element, resulting in extremely high cost, The use of a Ge substrate is not practical.
R. People, “Physics and applications of GexSi1-x / Si strained layer structures,” IEEE Journal of Quantum Electronics, QE-22, 1696 (1986). M. Halbwax et al., “UHV-CVD growth and annealing of thin fully relaxed Ge films on (001) Si,” Optical Materials, 27 (2005), pp.822-825.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a semiconductor substrate manufacturing method for obtaining a high-quality Ge-based epitaxial film in a large area by a relatively simple technique. There is.

  In order to solve such a problem, a semiconductor substrate manufacturing method of the present invention includes a first step of epitaxially growing a silicon germanium (SiGe) film on a silicon (Si) substrate by a chemical vapor deposition method, and the SiGe A step of heat-treating the film in a temperature range of 700 to 1200 ° C., the second step of collecting dislocations of the SiGe film in the vicinity of the interface with the Si substrate by the heat treatment, and the surface side of the SiGe film A third step of implanting hydrogen ions to a predetermined depth in the SiGe film; a fourth step of subjecting at least one main surface of the SiGe film and the support substrate to a surface activation process; the SiGe film and the A fifth step of bonding the main surfaces of the support substrates together, and applying an external impact to the bonding interface between the SiGe film and the support substrate A sixth step of forming a SiGe thin film on the main surface of the supporting substrate by peeling off the SiGe crystal along a hydrogen ion implanted boundary of iGe film, characterized in that it comprises.

  Preferably, the Ge content of the SiGe film is 10% or more by molar ratio.

  Preferably, the third step includes a surface treatment step of setting the surface roughness of the SiGe film to an Rms value of 0.5 nm or less before the hydrogen ion implantation.

  The surface treatment process is performed by CMP polishing, for example.

  The bonding in the fifth step is preferably performed in a temperature range of 100 ° C. or higher and 400 ° C. or lower.

  The support substrate is, for example, a silicon wafer with an oxide film, quartz, glass, sapphire, silicon carbide (SiC), alumina, or aluminum nitride.

  According to the present invention, a silicon wafer or the like from which a large-diameter substrate can be obtained is used as an epitaxial growth substrate, and a film obtained by epitaxially growing a Ge-based crystal on this substrate is transferred onto an insulating support substrate by a bonding method. Therefore, it is possible to provide a low-cost GeOI substrate or SGOI substrate.

  Hereinafter, an example of a semiconductor substrate manufacturing process of the present invention will be described with reference to the drawings.

  In the following examples, the support substrate is described as a silicon wafer provided with an oxide film on the main surface, but not limited thereto, a quartz substrate, a glass substrate, a sapphire substrate, a silicon carbide (SiC) substrate, an alumina substrate, An aluminum nitride substrate or the like may be used.

(GeOI substrate)
1A to 1C and FIGS. 2A to 2D are diagrams for explaining an example of a manufacturing process of a semiconductor substrate of the present invention. In this embodiment, an example of a manufacturing process of a GeOI substrate is described. explain.

  In these drawings, reference numeral 10 denotes a silicon (Si) substrate for epitaxial growth of germanium (Ge) by chemical vapor deposition (CVD). This Si substrate 10 is a commercially available Si substrate grown by, for example, the CZ method (Czochralski method), and its electrical characteristics such as conductivity type and specific resistivity, crystal orientation, and crystal diameter are defined in the present invention. The Ge epitaxial film manufactured by this method is appropriately selected depending on the design value and process of the device provided.

A Ge film is epitaxially grown on the main surface of the Si substrate 10 by CVD using a high-purity gas of germane (GeH ₄ ) in a vacuum atmosphere using hydrogen gas as a carrier gas. High-density defects (threading dislocations) 12 are introduced into the Ge epitaxial film 11 from the interface with the Si substrate 10 (FIG. 1A), but suitable for the Ge epitaxial film 11 containing such threading dislocations. It is known that when energy for moving the threading dislocations 12 is applied by performing a proper heat treatment, the threading dislocations 12 change into loop dislocation defects near the Si substrate interface (see Non-Patent Document 2).

  Therefore, in the present invention, a temperature range of 650 to 900 ° C. (preferably 700 to 900 ° C.) is used to collect dislocations in the Ge epitaxial film 11 near the interface with the Si substrate 10 (reference numeral 12 ′ in the figure). In this case, heat treatment is performed (FIG. 1B). Note that the atmosphere gas at the time of the heat treatment is either an inert gas such as nitrogen or argon, an oxygen gas, or a mixed gas thereof.

  Subsequently, hydrogen ions are implanted from the surface side of the Ge epitaxial film 11 to form a hydrogen ion implanted layer in a region near the interface with the Si substrate 10 (FIG. 1C). By this hydrogen ion implantation, an ion implantation layer (damage layer) is formed at a predetermined depth (average ion implantation depth L) from the surface of the Ge epitaxial film 11, and an ion implantation interface 13 is formed.

The ion implantation conditions at this time are determined depending on the thickness of the Ge thin film to be peeled off. For example, the average ion implantation depth L is 0.5 μm or less, and the ion implantation conditions are the doses. The amount is 1 × 10 ^{16 to} 5 × 10 ¹⁷ atoms / cm ² , the acceleration voltage is 50 to 100 keV, and the like.

If a SiGe mixed crystal buffer layer having a thickness of 50 nm or less is grown in advance prior to epitaxial growth of Ge on the Si substrate 10, a Ge film having a lower defect level can be obtained. Such a buffer layer has a composition such as Ge _0.88 Si _0.12 so that the Ge epitaxial film grows coherently. In addition, prior to the implantation of hydrogen ions, if surface treatment is performed by a method such as CMP polishing so that the surface roughness of the Ge epitaxial film 11 is 0.5 nm or less in terms of Rms value, bonding in a later step will be performed. It is preferable because the adhesiveness of the bonding is increased.

  For the purpose of surface cleaning or surface activation on at least one main surface (bonding surface) of the Ge epitaxial film 11 in which the ion-implanted layer is formed in this way and the insulating support substrate 20 to be a handle wafer later. The plasma treatment and ozone treatment are performed (FIG. 2A). Such a surface treatment is performed for the purpose of removing the organic substances on the surface to be the bonding surface or increasing the OH group on the surface to achieve surface activation. The Ge epitaxial film 11 and the support substrate 20 are used. It is not always necessary to perform the treatment on both of the joint surfaces, and the treatment may be performed only on one of the joint surfaces.

  The Ge epitaxial film 11 subjected to such a surface treatment and the main surface of the support substrate 20 are adhered and bonded together as a bonding surface (FIG. 2B). As described above, since at least one main surface (bonding surface) of the Ge epitaxial film 11 and the support substrate 20 is activated by being subjected to surface treatment by plasma treatment, ozone treatment, or the like, even at the bonding at room temperature. It is possible to obtain a bonding strength that can sufficiently withstand mechanical peeling and mechanical polishing in the subsequent process. Therefore, it is not necessary to perform a high-temperature heat treatment (around 1000 ° C.) required by the so-called “SOITEC method”.

  However, when it is desired to have a higher bonding strength, the bonding may be performed at a temperature of 100 ° C. or higher and 400 ° C. or lower, and after bonding at room temperature, heating in a temperature range of 100 ° C. or higher and 400 ° C. or lower. It is good also as processing. The reason why the heat treatment temperature is set to 400 ° C. or lower in the present invention is that when heat treatment is performed at a temperature exceeding 400 ° C., a minute cavity called a microcavity is generated at the hydrogen ion implantation interface, and the Ge thin film after peeling is formed. This leads to rough surface.

When the support substrate 20 is a quartz substrate, the upper limit value of the heat treatment temperature is preferably set to 350 ° C. This is in consideration of the difference in thermal expansion coefficient between Si and quartz, the amount of strain resulting from the difference in thermal expansion coefficient, and the amount of strain and the thickness of the Si substrate 10 and the quartz substrate. When the thicknesses of the Si substrate 10 and the quartz substrate are approximately the same, there is a large difference between the thermal expansion coefficient of Si (2.33 × 10 ⁻⁶ ) and the thermal expansion coefficient of quartz (0.6 × 10 ⁻⁶ ). Therefore, when heat treatment is performed at a temperature exceeding 350 ° C., cracks due to thermal strain, peeling at the joint surface, etc. may occur due to the difference in rigidity between the two substrates. It may occur that the substrate or the quartz substrate is broken. For this reason, the upper limit of the heat treatment temperature is selected to be 350 ° C., and more preferably heat treatment is performed in a temperature range of 100 to 300 ° C.

  Subsequently, an external impact is applied to the bonding interface, and the Ge epitaxial film is peeled along the hydrogen ion implantation interface 13 to obtain a Ge thin film 14 (FIG. 2C). When surface treatment (CMP polishing or the like) is performed to remove damage caused by hydrogen ion implantation, a GeOI substrate having a Ge thin film 14 on its surface can be obtained (FIG. 2D).

(SGOI substrate)
The present embodiment is a process example of a method for manufacturing an SGOI substrate. Since the basic process is the same as that of the first embodiment, the description will be given with reference to FIGS. 1A to 1C and FIGS. 2A to 2D again. In this embodiment, reference numeral 11 in the figure is a SiGe epitaxial film obtained by epitaxially growing silicon germanium (SiGe) by chemical vapor deposition (CVD).

  High density defects (threading dislocations) 12 are also introduced into the SiGe epitaxial film 11 from the interface with the Si substrate 10 (FIG. 1A), but the dislocations in the SiGe epitaxial film 11 are exchanged with the Si substrate 10. In order to collect in the vicinity of the interface (reference numeral 12 'in the figure), heat treatment is performed in a temperature range of 650 to 1200 ° C. (preferably 700 to 1200 ° C.) (FIG. 1B). Note that the atmosphere gas at the time of the heat treatment is either an inert gas such as nitrogen or argon, an oxygen gas, or a mixed gas thereof.

  Subsequently, hydrogen ions are implanted from the surface side of the SiGe epitaxial film 11 to form a hydrogen ion implanted layer in a region near the interface with the Si substrate 10 (FIG. 1C), and a predetermined amount is formed from the surface of the SiGe epitaxial film 11. The ion implantation interface 13 is formed at a depth (average ion implantation depth L).

  In order to keep the level of dislocation generation in the region near the interface with the Si substrate 10 low, the composition of the SiGe epitaxial film is preferably set so that the Ge content is 10% or more in terms of a molar ratio. Further, as already described in Example 1, prior to the implantation of hydrogen ions, surface treatment is performed by a technique such as CMP so that the surface roughness of the SiGe epitaxial film 11 is 0.5 nm or less in terms of Rms. It is preferable that the adhesiveness of the bonding in the subsequent process is increased.

  For the purpose of surface cleaning, surface activation, etc. on at least one main surface (bonding surface) of the SiGe epitaxial film 11 in which the ion-implanted layer is formed in this way and the insulating support substrate 20 to be a handle wafer later. The plasma treatment and the ozone treatment are performed (FIG. 2A), and the main surfaces are bonded together (FIG. 2B).

  In addition, when it is desired to have a higher bonding strength, the bonding may be performed at a temperature of 100 ° C. or more and 400 ° C. or less. The processing may be performed as described above.

  Subsequently, external impact is applied to the bonding interface, the SiGe epitaxial film is peeled along the hydrogen ion implantation interface 13 to obtain a SiGe thin film 14 (FIG. 2C), and finally the surface of the SiGe thin film 14 is formed. When surface treatment (CMP polishing or the like) is performed to remove damage caused by hydrogen ion implantation, an SGOI substrate having the SiGe thin film 14 on its surface can be obtained (FIG. 2D).

  The present invention makes it possible to provide a semiconductor substrate having a high-quality Ge-based epitaxial film with a large area by a relatively simple technique.

It is a figure for demonstrating the manufacturing method of the semiconductor substrate of this invention. It is a figure for demonstrating the manufacturing method of the semiconductor substrate of this invention.

10 Si substrate 11 Ge or SiGe epitaxial film 12 Defect 13 Ion implantation interface 14 Ge or SiGe thin film 20 Support substrate

Claims (4)

A first step of epitaxially growing a silicon germanium (SiGe) film on a silicon (Si) substrate by chemical vapor deposition;
Performing a heat treatment on the SiGe film in a temperature range of 700 to 1200 ° C., and collecting dislocations of the SiGe film in the vicinity of the interface with the Si substrate by the heat treatment;
A third step of implanting hydrogen ions from the surface side of the SiGe film to a predetermined depth in the SiGe film;
At least one main surface of the SiGe film and the support substrate, which is a quartz substrate, is subjected to a surface activation treatment for surface activation by removing organic substances on the main surface and increasing OH groups on the main surface by ozone treatment. A fourth step to apply;
A fifth step of bonding the SiGe film and the main surfaces of the support substrate together;
An external impact is applied to the bonding interface between the SiGe film and the support substrate to peel the SiGe crystal along the hydrogen ion implantation interface of the SiGe film, thereby forming a SiGe thin film on the main surface of the support substrate. And comprising the steps of
The method of manufacturing a semiconductor substrate, wherein the bonding in the fifth step is performed in a temperature range of 100 ° C. or more and 300 ° C. or less.   The method for manufacturing a semiconductor substrate according to claim 1, wherein a Ge content of the SiGe film is 10% or more by molar ratio.   3. The semiconductor substrate according to claim 1, wherein the third step includes a surface treatment step in which the surface roughness of the SiGe film is set to 0.5 nm or less in terms of Rms before the hydrogen ions are implanted. Production method. The method for manufacturing a semiconductor substrate according to claim 3, wherein the surface treatment step is performed by CMP polishing.

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