JP4943820B2 - Method of manufacturing a GOI (Geon Insulator) substrate - Google Patents

Description

  The present invention relates to a method for growing a germanium-based epitaxial film such as germanium (Ge) or SiGe mixed crystal.

  In recent years, germanium (Ge) has attracted attention again as a useful semiconductor material. The reason is that the carrier mobility in the Ge crystal is about twice as fast as that of silicon (Si) in electron mobility and about four times in hole mobility, which is advantageous for designing a semiconductor device operating at high speed. is there. Also, when viewed as an optical device material, it has a high absorption coefficient at a wavelength of 1.6 μm or less compared to Si, so that it is a material for solar cells and a light receiving element for optical communication in the 1.55 μm band. As promising.

However, Ge differs from Si in that it is extremely difficult to obtain a large-diameter (single crystal) substrate and that Ge is a rare element. Against this background, there is also a method of depositing a number of Si _1-x Ge _x layers with a slightly changed (enhanced) Ge concentration on the Si wafer and finally epi-growing the Ge layer. It has been proposed (for example, Non-Patent Document 1). However, in such a method, it is necessary to repeat the epitaxial growth many times, and the resulting Ge crystal has to be extremely expensive.

In recent years, a method has also been proposed in which Ge is directly epitaxially grown on a Si wafer and heat treatment is applied to the Ge epitaxial film to reduce dislocation defects (Non-Patent Document 2). However, it is known that the defect density of the Ge epitaxial film obtained by this method is still high.
R. People, "Physics and applications of GexSi1-x / Si strained layer structures," IEEE Journal of Quantum Electronics, QE-22, 1696 (1986). Luan et. Al., "High efficiency specifics based on high quality epitaxial germanium grown on silicon substrate" Optical Materials, vol.17, pp.71-73, 2001. 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 technique for obtaining a high-quality Ge-based epitaxial film in a large area by a relatively simple technique.

  In order to solve such problems, the present invention provides a method for growing a germanium-based epitaxial film according to the present invention, comprising a step of growing a germanium (Ge) -based epitaxial film on a silicon (Si) substrate by a chemical vapor deposition method. A, a step B of performing a first heat treatment on the Ge-based epitaxial film in a temperature range of 700 to 900 ° C., a step C of implanting Ge from the surface side of the Ge-based epitaxial film, and a step after the ion implantation And a step D of performing a second heat treatment on the Ge-based epitaxial film in a temperature range of 700 to 900 ° C.

  Preferably, the step A includes a sub-step of previously growing a SiGe mixed crystal buffer layer having a thickness of 50 nm or less.

  Preferably, at least one of the atmospheric gases during the first and second heat treatments is either an inert gas or an oxygen gas, or a mixed gas thereof.

Furthermore, the dose during the ion implantation is preferably 1 × 10 ¹⁵ or more and 1 × 10 ¹⁷ atoms / cm ² or less.

  A method for manufacturing a GOI (Ge on Insulator) substrate according to the present invention includes a first step of implanting hydrogen ions from the surface side of a Ge-based epitaxial film obtained by the above-described method, the Ge-based epitaxial film, and an insulating material. A second step of subjecting at least one main surface of the support substrate to a surface activation process; and a third step of bonding the Ge-based epitaxial film and the main surfaces of the support substrate to each other at a temperature of 100 ° C. or higher and 400 ° C. or lower. And applying an external impact to the bonding interface between the Ge-based epitaxial film and the support substrate to peel off the Ge-based crystal along the hydrogen ion implantation interface of the Ge-based epitaxial film to form Ge on the main surface of the support substrate. And a fourth step of forming a system thin film.

  According to the present invention, a silicon having a large diameter is used as a substrate, a Ge-based crystal is epitaxially grown on the substrate, and the single crystal property of the surface region is maintained using an ion implantation method. Since the entire region of the Ge epitaxial film is recrystallized (single crystallized) by amorphizing the region near the interface and applying heat treatment, a high-quality Ge-based epitaxial film can be formed in a large area using a relatively simple method. Can be obtained.

  In addition, since the Ge-based epitaxial film obtained by the above method is transferred onto the insulating support substrate by the bonding method, a low-cost GOI substrate can be provided.

  In the following, an example of the process of the present invention will be described with reference to an example in which a Ge-based epitaxial film is a Ge film. However, the present invention is not limited to a Ge film, and a SiGe mixed crystal film can be used in the same process.

  1A to 1E are views for explaining a method for growing a germanium-based epitaxial film according to the present invention. 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 a CVD method using hydrogen gas as a carrier gas and introducing a high-purity germanium (GeH ₄ ) gas in a vacuum atmosphere. 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 3).

  Therefore, in the present invention, the Ge epitaxial film 11 is subjected to heat treatment in a temperature range of 700 to 900 ° 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, Ge is ion-implanted from the surface side of the Ge epitaxial film 11 at a dose of 1 × 10 ¹⁵ to 1 × 10 ¹⁷ atoms / cm ² , for example (FIG. 1C). By this Ge ion implantation, the Ge bonding state of the Ge epitaxial film 11 in the vicinity of the interface with the Si substrate 10 is broken and the amorphous region 13 is formed while maintaining the single crystallinity of the Ge epitaxial film surface region ( FIG. 1D).

  Subsequently, when a second heat treatment is performed in a temperature range of 700 to 900 ° C., the single crystal portion near the surface of the Ge epitaxial film 11 becomes a seed, and the amorphous region 13 becomes a single crystal (FIG. 1E). ). 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. The thus obtained Ge epitaxial film 11 is a high-quality Ge film having a low density of both threading dislocations and loop dislocations.

If a SiGe mixed crystal buffer layer having a film thickness of 50 nm or less is grown in advance prior to epitaxial growth of Ge on the Si substrate, 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 can be coherently grown.

  The present embodiment relates to a method for manufacturing a GOI (Ge on Insulator) substrate using a Ge epitaxial film obtained by the method for growing a germanium epitaxial film of the present invention.

  FIG. 2 is a diagram for explaining a method of manufacturing a GOI substrate according to the present invention. The substrate shown in FIG. 2A is a Si substrate having the Ge epitaxial film 11 produced in Example 1 as a main surface. 10.

  First, 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. 2A). By this hydrogen ion implantation, an ion implantation layer (damage layer) 14 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 15 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.

  For the purpose of surface cleaning, surface activation, etc. on at least one main surface (bonding surface) of the Ge epitaxial film 11 in which the ion implantation layer 14 is formed in this way and the insulating support substrate 20 to be a handle wafer later. The plasma treatment and ozone treatment described above were performed (FIG. 2B). 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 surface treatment and the main surface of the support substrate 20 are brought into close contact with each other as a bonding surface, and heat treatment is performed at a temperature of 100 ° C. or higher and 400 ° C. or lower (FIG. 2C). 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, the relatively low temperature described above. Even in this heat treatment, it is possible to obtain a bonding strength of a level that can sufficiently withstand mechanical peeling and mechanical polishing in the subsequent process. When it is desired to give higher bonding strength, if necessary, the temperature is once lower than 100 ° C. after bonding, and the Ge epitaxial film 11 and the support substrate 20 are bonded again to 100 ° C. or higher. The heat treatment at a temperature of 400 ° C. or lower is repeated.

  The reason why the above 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 this is thermally separated. This is because, as a result of this phenomenon, surface roughness of the Ge thin film after peeling and substrate cracking are caused.

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 20. When the thicknesses of the Si substrate 10 and the quartz substrate 20 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 ). Due to the difference, when heat treatment is performed at a temperature exceeding 350 ° C., cracks due to thermal strain or peeling at the joint surface may occur due to the difference in rigidity between the two substrates. It may occur that the Si 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, external impact is applied to the bonding interface, and the Ge epitaxial film is peeled along the hydrogen ion implantation interface 15 to obtain a Ge thin film 16 (FIG. 2D). If a surface treatment (CMP polishing or the like) is performed to remove damage caused by hydrogen ion implantation, a GOI substrate having a Ge thin film 16 on its surface can be obtained (FIG. 2E).

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

It is a figure for demonstrating the growth method of the germanium type epitaxial film of this invention. It is a figure for demonstrating the manufacturing method of the GOI board | substrate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Si substrate 11 Ge epitaxial film 12 Defect 13 Ge amorphous region 14 Ion implantation layer 15 Ion implantation interface 16 Ge thin film 20 Support substrate

Claims (5)

A step A of growing a germanium (Ge) -based epitaxial film on a silicon (Si) substrate by chemical vapor deposition;
Applying a first heat treatment to the Ge-based epitaxial film in a temperature range of 700 to 900 ° C .;
Step C of ion-implanting Ge from the surface side of the Ge-based epitaxial film;
Applying a second heat treatment to the Ge-based epitaxial film after the ion implantation in a temperature range of 700 to 900 ° C .;
A first step of implanting hydrogen ions from the surface side of the Ge-based epitaxial film obtained by the epitaxial film growth method comprising:
A second step of performing a surface activation process on at least one main surface of the Ge-based epitaxial film and the insulating support substrate;
A third step of bonding the Ge-based epitaxial film and the main surfaces of the support substrate to each other at a temperature of 100 ° C. or higher and 400 ° C. or lower;
An external impact is applied to the bonding interface between the Ge-based epitaxial film and the support substrate, the Ge-based crystal is peeled along the hydrogen ion implantation interface of the Ge-based epitaxial film, and a Ge-based thin film is formed on the main surface of the support substrate. A fourth step of forming
A method of manufacturing a GOI (Ge on Insulator) substrate. 2. The method of manufacturing a GOI substrate according to claim 1, wherein the step A includes a sub-step of previously growing a SiGe mixed crystal buffer layer having a thickness of 50 nm or less . 3. The method of manufacturing a GOI substrate according to claim 1, wherein the atmosphere gas at the time of the first heat treatment is either an inert gas, an oxygen gas, or a mixed gas thereof . The method for manufacturing a GOI substrate according to any one of claims 1 to 3, wherein the atmosphere gas at the time of the second heat treatment is any one of an inert gas and an oxygen gas, or a mixed gas thereof . 5. The method of manufacturing a GOI substrate according to claim 1, wherein a dose during the ion implantation is 1 × 10 ¹⁵ or more and 1 × 10 ¹⁷ atoms / cm ² or less .

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