KR20070071995A - Method of fabricating germanium-on-insulator substrate using a soi substrate - Google Patents

Abstract

A method for fabricating a germanium-on-insulator substrate using an SOI substrate is provided to reduce a fabricating cost by forming a GeOI substrate using a conventional SOI substrate. An SOI substrate is prepared which includes a substrate, an insulation layer formed on the substrate, and a silicon layer formed on the insulation layer(10). Germanium ions are implanted into at least a part of the silicon layer on the SOI substrate(20). While a thermal oxide layer is formed on the surface of the silicon layer on the SOI substrate, the implanted germanium ions are condensed to form a germanium layer or a silicon-germanium layer substantially having a germanium band gap characteristic under the thermal oxide layer(30). The silicon-germanium layer has a germanium content of 85 percent or higher, having a uniform germanium content along its thickness direction.

Description

Method of fabricating Germanium-On-Insulator Substrate Using A SOI substrate}

1 is a flow chart showing a method of forming a germanium-on-insulator substrate according to an embodiment of the present invention;

2, 3, 5, and 7 are cross-sectional views illustrating a process of forming a germanium-on-insulator substrate according to an embodiment of the present invention;

4 is a graph showing a germanium concentration profile in the depth direction of the structure of FIG. 3; And

6 is a graph showing a germanium concentration profile in the depth direction of the structure of FIG. 5.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor substrate, and more particularly, to a method for forming a germanium-on-insulator (GeOI) substrate having a germanium layer or a silicon-germanium layer having substantially germanium bandgap characteristics. will be.

The development of high speed and low power devices through conventional semiconductor substrates, such as silicon substrates, is facing limitations. Therefore, to overcome this limitation, a silicon-on-insulator (SOI) substrate or a GeOI substrate capable of forming a fully-depleted device has been developed as a virtual substrate.

Many methods for producing SOI substrates are known. For example, Electron. K. Izumi et al., "CMOS devices fabrication on buried SiO ₂ layers formed by oxygen implantation into silicon," published in Lett., 14, 593-594 (1978), also known as the Separation-by-Implanted Oxygen (SIMOX) method. A method for producing an SOI substrate is disclosed. As another example, US Patent No. 5,882,987 to Srikrishnan discloses a method of making an SOI substrate known as a smart-cut method.

GeOI substrates are advantageous in terms of high speed and low power characteristics compared to SOI substrates, and have the advantage of growing optical devices made of compound semiconductors on top. That is, a high speed device and an optical device may be simultaneously manufactured on one GeOI substrate. However, a method for producing a commercially available GeOI substrate is still unknown.

Accordingly, the technical problem to be achieved by the present invention is to provide a method for manufacturing a commercially available economical GeOI substrate.

A method of manufacturing a germanium-on-insulator (GeOI) substrate according to an aspect of the present invention for achieving the above technical problem includes the following steps. It provides a SOI substrate comprising a substrate, an insulator layer on the substrate and a silicon layer on the insulator layer. Germanium ions are implanted into at least a portion of the silicon layer of the SOI substrate. The thermal oxide layer is formed on the surface of the silicon layer of the SOI substrate and condensed with the implanted germanium ions to form a germanium layer or a silicon-germanium layer having substantially germanium bandgap characteristics under the thermal oxide layer.

According to an aspect of the present invention, the silicon-germanium layer may have a germanium content of 85% or more, and further, may have a uniform germanium content along the thickness direction.

According to another aspect of the present invention, implanting germanium ions amorphizes a portion of the silicon layer of the SOI substrate, and wherein the amorphous silicon layer portion is amorphous to the SOI substrate during the thermal oxide layer formation. The non-silicon layer portion can be recrystallized using the seed layer.

According to another aspect of the present invention, the step of forming the thermal oxide layer may be performed in an atmosphere of oxygen gas or a mixed gas containing oxygen gas.

According to another aspect of the present invention, the method of manufacturing the GeOI substrate may further include removing the thermal oxide layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to complete the scope of the invention. It is provided to inform you. In the drawings, the components may be exaggerated in size for convenience of description.

In embodiments of the present invention, a germanium-on-insulator (GeOI) substrate includes a substrate, an insulator layer on the substrate, and a germanium layer or silicon-germanium layer on the insulator layer. The silicon-germanium layer of the GeOI substrate does not have a bandgap characteristic of silicon, but substantially has a bandgap characteristic of germanium. For example, the silicon-germanium layer of a GeOI substrate may have a high germanium content. In this sense, the silicon-germanium layer structure having substantially the germanium bandgap characteristic formed on the insulator is referred to as GeOI structure in the present invention.

Hereinafter, a method of manufacturing a GeOI substrate according to an embodiment of the present invention will be described with reference to the cross-sectional views of FIGS. 2, 3, 5, and 7 in the order of the flowchart of FIG. 1.

1 and 2, first, an SOI substrate 100 is prepared (step 10). The SOI substrate 100 includes a substrate 110, an insulator layer 120, and a silicon layer 130. Substrate 110 may be, for example, a bulk Si substrate or a bulk silicon-germanium substrate. The insulator layer 120 is formed on the substrate 110 and may include, for example, a silicon oxide film. The silicon layer 130 may be formed on the insulator layer 120 and include a single crystal epitaxial layer.

The SOI substrate 100 may be conventionally manufactured as known in the art. For example, Electron. The SIMOX method known from the paper by K. Izumi et al., Published in Lett., 14, 593-594 (1978), or the smart-cut method known from US Patent No. 5,882,987 to Srikrishnan, is known as SOI substrate 100. It can be used for the preparation of. Furthermore, SOI substrates 100 manufactured by the SIMOX method or the smart-cut method are commercially available.

For example, the insulator layer 120 may have a thickness in the range of 30 to 400 nm. The silicon layer 130 may be selected in consideration of the loss in the subsequent ion implantation step and the thickness of the final germanium layer or the silicon-germanium layer. For example, the silicon layer 130 may have a thickness in the range of 100 to 400 nm.

1 and 3, germanium ions 140 are implanted into at least a portion of the silicon layer 130 (step 20). Germanium ions 140 that are about 2.5 times heavier than silicon may collide with silicon of the silicon layer 130 to form an amorphous layer 145 in the silicon layer 130. The amorphous layer 145 indicates a case where silicon of a predetermined concentration or more is deviated from the original crystal lattice, and may be observed using an electron microscope.

The amorphous layer 145 may be formed to a predetermined depth within the silicon layer 130 or from the surface of the silicon layer 130. Thus, a portion of the amorphous silicon layer 130 of the amorphous structure remains between the amorphous layer 145 and the insulator layer 120, which may be referred to as the seed layer 150. The seed layer 150 may then be used as a seed when recrystallization of the amorphous layer 145.

Germanium ions 140 may be implanted at a high dose sufficient to amorphousize the silicon layer 130, such as a dose of 10 ¹⁷ to 10 ¹⁹ cm ⁻² . The implantation energy of the germanium ions 140 may be selected in consideration of the thickness of the silicon layer 130. For example, the implantation energy of germanium ions 140 may be adjusted so as not to amorphous the seed layer 150.

Referring to FIG. 4, a concentration profile according to the depth of germanium ions 140 implanted into the structure of FIG. 3 is shown. Germanium ions 140 have a Gaussian distribution in region A. Region A may correspond to silicon layer 130.

In another embodiment of the present invention, germanium ions may proceed at a high temperature in the range of 550 ~ 650 ℃. As such, when ion implantation proceeds at a high temperature, the amorphous layer 145 may be recrystallized simultaneously with generation. Therefore, in this case, the seed layer 150 may not need to remain in the silicon layer 130.

1 and 5, a silicon oxide having a germanium bandgap characteristic under the thermal oxide layer 170 while forming a thermal oxide layer 170 on a surface portion of the silicon layer 130 (FIG. 3). The germanium layer 160 is formed (step 30). The germanium ions (140 in FIG. 3) implanted in the formation of the thermal oxide layer 170 may be condensed under the thermal oxide layer 170 to form the silicon-germanium layer 160.

For example, the thermal oxide layer 170 may be formed by oxidizing the silicon layer 130 (in FIG. 3) in a furnace of oxygen gas or a mixed gas atmosphere containing oxygen. The mixed gas may further include an inert gas such as nitrogen or argon gas for controlling the atmosphere in addition to the oxygen gas. Oxidation may proceed for 10 minutes to 5 hours in the temperature range of 900 ~ 1400 ℃.

The thermal oxide layer 170 may include almost no germanium oxide layer and may include a silicon oxide layer. This is because, when silicon and germanium coexist, the oxidation of silicon is preferred because the oxidation energy of silicon is lower than that of germanium. Therefore, while the thermal oxide layer 170 is grown, silicon is oxidized to form a silicon oxide film, and germanium is evicted under the thermal oxide layer 170. The insulating layer 120 may serve to block diffusion of germanium into the substrate 110.

Accordingly, at the same time as the thermal oxide layer 170 is grown, germanium is condensed at a high concentration in the silicon layer 130 under the thermal oxide layer 170, thereby forming the silicon-germanium layer 160. By controlling the thickness of the thermal oxide layer 170, the thickness of the silicon germanium layer 160 and the germanium concentration may be adjusted. In other words, as the thickness of the thermal oxide layer 170 increases, the thickness of the silicon-germanium layer 160 may decrease and the germanium concentration of the silicon-germanium layer 160 may increase. When the thickness of the silicon germanium layer 160 is less than or equal to a predetermined value, as shown in FIG. 6, the germanium concentration may be uniform in the thickness direction in the region B displaying the silicon germanium layer 160. .

The thickness of the thermal oxide layer 170 may be adjusted such that the germanium concentration of the silicon-germanium layer 160 is 85% or more. When the germanium concentration is 85% or more, the silicon-germanium layer 160 may lose silicon bandgap characteristics and may have germanium bandgap characteristics substantially. Accordingly, the silicon germanium layer 160 may be substantially treated as a germanium layer. For the bandgap characteristics according to the germanium content of the silicon germanium layer 160, S. Wolf's "Silicon Processing for the VLSI Era", Volume 4, page 484, Figure 10-3 b).

The silicon-germanium layer 160 may be recrystallized at the growth stage. Recrystallization of the silicon-germanium layer 160 may be nucleated and grown from the seed layer (150 in FIG. 3). Although the silicon-germanium layer 160 has been described as being recrystallized, it may be described that the silicon layer (130 of FIG. 3) is recrystallized and subsequently phase transformed into the silicon-germanium layer 160.

In another embodiment of the present invention, a germanium layer may be formed under the thermal oxide layer 170. That is, when all of the silicon of the silicon layer (130 of FIG. 3) is oxidized so that the thermal oxide layer 170 is no longer grown, a germanium layer without silicon may be formed under the thermal oxide layer 170.

In another embodiment of the present invention, the silicon-germanium layer 160 and the germanium layer are distinguished, but in embodiments of the present invention, the silicon-germanium layer 160 having substantially germanium bandgap characteristics includes a germanium layer. It may be understood that. In this case, the germanium content of the silicon germanium layer may range from 85 to 100%.

1 and 7, the thermal oxide layer 170 may be removed. For example, the thermal oxide layer 170 may be removed using an etchant including HF (step 40). Accordingly, a GeOI substrate having a structure of the substrate 110, the insulating layer 120, and the silicon-germanium layer 160 may be manufactured. Here, the silicon-germanium layer 160 may have a germanium band gap characteristic and may include a germanium layer. GeOI substrate can be used as a substrate for manufacturing the optical device.

In another embodiment of the present invention, the thermal oxide layer 170 is not removed and may be used as a layer for manufacturing an optical device.

In embodiments of the present invention, GeOI substrates can be economically manufactured using conventional semiconductor manufacturing apparatus. Thus, GeOI substrates can be easily produced commercially using conventional SOI substrates and conventional semiconductor manufacturing apparatus.

The foregoing description of specific embodiments of the invention has been presented for purposes of illustration and description. Therefore, the present invention is not limited to the above embodiments, and various modifications and changes are possible in the technical spirit of the present invention by combining the above embodiments by those skilled in the art. It is obvious.

GeOI substrate according to the present invention can be manufactured using a conventional SOI substrate, it is possible to lower the manufacturing cost. The manufacturing step of the GeOI substrate uses the germanium ion implantation and heat treatment steps commonly used in the semiconductor manufacturing process. Therefore, GeOI substrates can be economically manufactured using a conventional semiconductor manufacturing apparatus. Thus, GeOI substrates can be easily produced commercially using conventional SOI substrates and conventional semiconductor manufacturing apparatus.

Claims (12)

Providing an SOI substrate comprising a substrate, an insulator layer on the substrate, and a silicon layer on the insulator layer; Implanting germanium ions into at least a portion of the silicon layer of the SOI substrate; And Forming a thermal oxide layer on the surface of the silicon layer of the SOI substrate and condensing the implanted germanium ions to form a germanium layer or a silicon-germanium layer having substantially germanium bandgap characteristics under the thermal oxide layer. Method of manufacturing a germanium-on-insulator substrate comprising a. The method of claim 1, wherein the silicon-germanium layer has a germanium content of 85% or more. The method of manufacturing a germanium-on-insulator substrate according to claim 2, wherein the silicon-germanium layer has a uniform germanium content along the thickness direction. The method of claim 1, wherein the germanium ions are implanted at a dose of 10 ¹⁷ to 10 ¹⁹ cm ⁻² . 5. The germanium-on-insulator substrate of claim 4, wherein the silicon layer of the SOI substrate has a thickness in the range of 100 to 400 nm, and the insulator layer of the SOI substrate has a thickness in the range of 30 to 400 nm. Manufacturing method. 2. The method of claim 1 wherein implanting germanium ions amorphizes a portion of the silicon layer of the SOI substrate, and wherein the amorphous silicon layer portion is amorphous of the amorphous silicon layer of the SOI substrate during the thermal oxide layer formation. A method of manufacturing a germanium-on-insulator substrate, wherein the layer portion is recrystallized using the seed layer. 7. The method of claim 6, wherein the seed layer is a portion of a silicon layer adjacent to an insulator layer of the SOI substrate. The method of claim 1, wherein the injecting the germanium ions is performed at a temperature in a range of 550 ° C. to 650 ° C. 7. The method of claim 1, wherein the forming of the thermal oxide layer is performed at a temperature in the range of 900 to 1400 ° C. The method of claim 1, wherein the forming of the thermal oxide layer is performed in an atmosphere of oxygen gas or a mixed gas containing oxygen gas. The method of claim 10, wherein the mixed gas comprises nitrogen gas or argon gas. The method of manufacturing a germanium-on-insulator substrate according to any one of claims 1 to 11, further comprising removing the thermal oxide layer.

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