JP2004140299A - Semiconductor integrated element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture with a high yield and at a low price a semiconductor integrated element having optical/electronic semiconductor elements, by suppressing Fe from diffusing from a β-FeSi<SB>2</SB>layer into an Si substrate, and by improving the performance of the electronic element. <P>SOLUTION: In the semiconductor integrated element, a plurality of optical semiconductor elements are formed on the same Si substrate, or optical and electronic semiconductor elements are formed on a single Si substrate. Further, in the active layers of the optical semiconductor element which contains Fe-Si compounds, a high-concentration p-type Si layer 8/a high-concentration p-type Si layer 9 are formed between an Fe-Si compound layer 2 and an Si substrate 1, and the concentration of acceptor of each high-concentration p-type Si layer is made not smaller than 5×10<SP>18</SP>cm<SP>-3</SP>. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor integrated device, and more particularly to an optical semiconductor integrated device in which a plurality of optical semiconductor devices are formed on the same Si substrate, or an optical / electronic semiconductor integrated device in which an optical semiconductor device and an electronic semiconductor device are formed. is there.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in manufacturing a phototransistor used as a light receiving element such as a photocoupler or a photointerrupter, for example, a P ⁺ -type base diffusion region is formed in advance around an emitter formation region, and then boron (B ⁺ ) and arsenic are formed. Two kinds of ions such as (As ⁺ ) are implanted, and a single heat treatment is performed to simultaneously form an emitter layer and a base layer immediately below the emitter layer (for example, see Patent Document 1).
[0003]
In a photodetector in which a waveguide and a photodetector are monolithically integrated, at least one of a p-type impurity diffusion layer and an n-type impurity diffusion layer is selectively provided near the photodetector, and an electrode is provided in each region. Is also known (for example, see Patent Document 2).
[0004]
On the other hand, beta iron silicide (hereinafter, β-FeSi ₂ ), which is an Fe—Si compound, is a direct transition semiconductor having a band gap of about 0.85 eV, and is a material for an active layer of a light emitting diode or laser having a wavelength band of 1.5 μm. Application is possible. This wavelength band has attracted attention as a device material for information systems using optical fibers since the loss of quartz optical fibers is minimized. In particular, β-FeSi ₂ has a small lattice constant difference from Si of about 5%, and single crystal Si can be epitaxially grown on the (100) plane. Therefore, an optical semiconductor device (light emitting device, light receiving device) using β-FeSi ₂ for an active layer, an optical semiconductor integrated device in which a Si-based optical semiconductor device and an electronic semiconductor device are monolithically integrated, and an optical / electronic semiconductor integrated device Is being actively developed. Further, β-FeSi ₂ is attracting attention as a semiconductor material having an extremely small load on the environment because β-FeSi ₂ is composed of a safe element such as Fe and Si without resource restrictions.
[0005]
FIG. 3 shows a simplified example of a conventional optical / electronic semiconductor integrated device in which an electronic circuit composed of a Si-based electronic device and a light receiving device using β-FeSi ₂ as an active layer are monolithically integrated. It is. The configuration of the optical / electronic semiconductor integrated circuit will be briefly described with reference to FIG.
[0006]
The light receiving element includes an n-type Si layer 2, an n-type β-FeSi ₂ layer 3, and a p-type β-FeSi ₂ layer 4 epitaxially grown on a Si substrate 1. The n-type β-FeSi ₂ layer 3 and the p-type β-FeSi ₂ layer 4 are active layers of the light receiving element, and can convert light having a wavelength shorter than 1.5 μm into an electric signal. An anode electrode 5 is formed on the p-type β-FeSi ₂ layer 4 and a cathode electrode 6 is formed on the n-type Si layer 2 in order to extract an electric signal of the light receiving element to the outside.
[0007]
Although not shown in detail, a region 7 shown by a two-dot broken line in the figure where the n-type Si layer 2, the n-type β-FeSi ₂ layer 3, and the p-type β-FeSi ₂ layer 4 are selectively removed is shown in FIG. , A Si-based electronic element, and an electronic circuit for processing an electric signal of the light receiving element. The surfaces of the electronic element and the light receiving element are covered with an insulating film not shown in the figure, and further, the electronic element and the light receiving element are electrically connected by metal wiring not shown in the figure. .
[0008]
[Patent Document 1]
JP-A-5-063282 (paragraph number 0012)
[0009]
[Patent Document 2]
JP-A-5-160430
[Problems to be solved by the invention]
However, in the manufacture of the optical / electronic semiconductor integrated device as shown in FIG. 3, a semiconductor device manufacturing process such as epitaxial growth and impurity diffusion is indispensable. In these steps, it is necessary to heat-treat the Si substrate for element formation at a temperature of about 800 ° C. to 900 ° C. for at least 30 minutes.
[0011]
On the other hand, in the epitaxial growth of the β-FeSi ₂ layer, it is inevitable that surplus Fe atoms are incorporated into the film, although the degree is different. These surplus Fe atoms diffuse into the Si substrate by heat treatment in the epitaxial growth or diffusion step. An Fe atom existing as an impurity in Si forms a deep level in the band cap and traps electrons and holes. These deep levels significantly reduce the performance of MOSFETs and bipolar transistors and cause problems such as poor switching operation, poor response characteristics, and reduced amplification factor. In order to avoid these problems, it is necessary to suppress the density of deep levels to the order of 10 ¹² cm ⁻³ .
[0012]
As a result of evaluating the region 7 of the opto-electronic semiconductor integrated device shown in FIG. 3 by DLTS (deep level transient spectroscopy), it was confirmed that a deep level of 10 ¹⁶ cm ⁻³ was present. Due to this high-density deep level, the electronic element exhibits poor switching operation, poor response characteristics, low amplification factor, and the like, and the desired performance as an optical / electronic semiconductor integrated element cannot be obtained.
[0013]
Therefore, an object of the present invention is to solve the above problems, suppress the diffusion of Fe from the β-FeSi ₂ layer into the Si substrate, improve the performance of the electronic device, and achieve a high yield of the optical / electronic semiconductor integrated device. And to provide it at low cost.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0015]
The semiconductor integrated device according to claim 1 is a semiconductor integrated device in which a plurality of optical semiconductor elements are formed on the same Si substrate, wherein the active layer of the optical semiconductor element includes an Fe-Si compound. And a high-concentration p-type Si layer between the Fe-Si compound layer and the Si substrate, and the high-concentration p-type Si layer has an acceptor concentration of 5 × 10 ¹⁸ cm ⁻³ or more.
[0016]
A semiconductor integrated device according to a second aspect of the present invention is a semiconductor integrated device in which an optical semiconductor device and an electronic semiconductor device are formed on the same Si substrate, wherein the active layer of the optical semiconductor device includes an Fe-Si compound. The device has a feature that a high-concentration p-type Si layer is provided between the Fe—Si compound layer and the Si substrate, and the high-concentration p-type Si layer has an acceptor concentration of 5 × 10 ¹⁸ cm ⁻³ or more. I do.
[0017]
A third aspect of the present invention is the semiconductor integrated device according to the first or second aspect, wherein the dopant of the high-concentration p-type Si layer is B or Al, or both B and Al.
[0018]
According to a fourth aspect of the present invention, in the semiconductor integrated device according to the first or second aspect, the high-concentration p-type Si layer includes two layers, a B-doped layer and an Al-doped layer.
[0019]
According to a fifth aspect of the present invention, in the semiconductor integrated device according to any one of the first to fourth aspects, a high-concentration p-type Si layer formed by doping B or Al is formed on the back surface of the Si substrate. I do.
[0020]
<The gist of the invention>
In the semiconductor integrated device according to the present invention, a p-type Si layer having a high carrier concentration is formed before epitaxially growing an Fe-Si compound layer, for example, β-FeSi ₂ . The p-type Si layer includes a B-doped p-type layer, an Al-doped p-type layer, or two layers of a B-doped p-type layer and an Al-doped p-type layer. The concentrations of B and Al as acceptors are both 5 × 10 ¹⁸ cm ⁻³ or more.
[0021]
Fe atoms easily move in Si by heat treatment, and the diffusion coefficient thereof is estimated to be about 1.1 × 10 ⁻³ exp (−0.66 / kT) cm ² s ⁻¹ . However, in the Si layer doped with B or Al at a high concentration, the apparent diffusion coefficient of Fe is reduced by about two orders of magnitude. This is because in a Si layer doped with B or Al at a high concentration, a B-Fe compound or an Al-Fe compound is formed in a short time, and the diffusion coefficient of these compounds becomes extremely small as compared with that of Fe alone. it is conceivable that.
[0022]
Therefore, by forming a Si layer doped with B or Al in a high concentration during the beta-FeSi ₂ layer and the Si substrate, it is possible to suppress the diffusion of Fe atoms into the Si substrate from the beta-FeSi ₂ layer become. As a result, the density of deep levels in the Si substrate can be kept low, and the performance of the electronic semiconductor element can be improved.
[0023]
On the other hand, although the Fe concentration in the Si layer doped with B or Al at a high concentration becomes high, these layers are not active layers and do not affect the device characteristics.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples of the illustrated light emitting device.
[0025]
<First embodiment>
FIG. 1 simplifies an example of a semiconductor integrated device (optical / electronic semiconductor integrated device) in which a light receiving element using β-FeSi ₂ for an active layer and an electronic circuit composed of Si-based electronic elements are monolithically integrated. It is shown.
[0026]
First, a high carrier concentration p-type Si layer 8 was formed on a Si substrate 1 by Al doping by a diffusion method. The average Al concentration in this layer was 1 × 10 ¹⁹ cm ⁻³ . Next, a high carrier concentration p-type Si layer 9 doped with B was epitaxially grown on the high carrier concentration p-type Si layer 8 doped with Al. The B concentration of this layer was 1 × 10 ¹⁹ cm ⁻³ .
[0027]
After forming p-type Si layers 9 and 8 with high carrier concentration by B doping and Al doping, n-type Si layer 2, n-type β-FeSi ₂ layer 3 and p-type β-FeSi ₂ layer which are constituent layers of the light receiving element 4 was formed by an epitaxial growth method.
[0028]
The Si-based electronic device was mainly composed of a MOSFET and a bipolar transistor. Although not shown in detail in FIG. 1, these elements have high carrier concentration p-type Si layers 9 and 8, n-type Si layer 2, n-type β-FeSi ₂ layer 3 and p-type After the β-FeSi ₂ layer 4 was selectively removed, a β-FeSi ₂ layer 4 was formed in a region (Si-based electronic element formation region) 7 indicated by a two-dot broken line in the figure. In the process of forming the electrodes of the electronic device, the anode electrode 5 and the cathode electrode 6 of the light receiving device were also formed at the same time. Although not shown in FIG. 1, the surfaces of the electronic element and the light receiving element are covered with an insulating film, and the electronic element and the light receiving element are electrically connected by metal wiring.
[0029]
In the embodiment shown in FIG. 1, the p-type Si layer having a high carrier concentration for suppressing the diffusion of Fe atoms is composed of two layers of a B-doped layer 9 and an Al-doped layer 8, and the acceptor concentration is 1 ×. It was set to 10 ¹⁹ cm ⁻³ . In this configuration, when the density of the deep level in the region 7 was evaluated by the DLTS method, the value was as low as 2 × 10 ¹² cm ⁻³ . From this result, it was confirmed that the p-type Si layers 8 and 9 having a high carrier concentration effectively functioned as an Fe diffusion suppressing layer. Further, it was confirmed that the electronic element formed in the Si-based electronic element formation region 7 also operated almost as designed.
[0030]
Further, the case where the high carrier concentration p-type Si layer was constituted by a single layer of a B-doped layer or a single layer of an Al-doped layer was also evaluated. When the acceptor concentration was 5 × 10 ¹⁸ cm ⁻³ and the single layer of the B-doped layer was used, the density of deep levels in the region 7 was 8 × 10 ¹² cm ⁻³ . On the other hand, in the case of a single Al-doped layer having the same acceptor concentration, the value was 6 × 10 ¹² cm ⁻³ . In each case, the electronic device formed in the Si-based electronic device forming region 7 exhibited performance almost as designed. However, when the acceptor concentration was lower than 5 × 10 ¹⁸ cm ⁻³ , the density of the deep level rapidly increased to 2 × 10 ¹³ cm ⁻³ or more. In this case, in the electronic element formed in the region 7, defects such as a switching operation defect, a response characteristic defect, and a decrease in amplification rate occurred frequently, and the yield of the element was significantly reduced.
[0031]
<Second embodiment>
FIG. 2 shows a simplified example of a semiconductor integrated device (optical / electronic semiconductor integrated device) in which a light receiving element using β-FeSi ₂ for an active layer and an electronic circuit composed of Si-based electronic elements are monolithically integrated. It is shown in the form.
[0032]
As compared with the first embodiment shown in FIG. 1, a p-type Si layer 10 having a high carrier concentration by B doping or Al doping is formed on the back surface of a Si substrate 1. When this p-type Si layer is formed in the process of element formation and is heat-treated for about 30 minutes to 120 minutes in the temperature range of 400 ° C. to 700 ° C. after element formation, the deep level density in the Si substrate is further reduced, and 1 × It became 10 < ¹² > cm <^-3> or less. It is considered that this is because a very small amount of Fe atoms existing in the Si substrate were taken into the high carrier concentration p-type Si layer 10 during the heat treatment. The characteristics of the electronic device subjected to such a treatment were further improved, and the yield was also improved. The high carrier concentration p-type Si layer 10 can be removed after the heat treatment.
[0033]
The present invention relates not only to a semiconductor integrated device in which an optical semiconductor device and an electronic semiconductor device are formed on the same Si substrate (optical / electronic semiconductor integrated device), but also to a semiconductor in which a plurality of optical semiconductor devices are formed on the same Si substrate. The present invention can be applied to an integrated device. These semiconductor integrated devices can be used as devices for information systems and communication systems using silica-based optical fibers.
[0034]
Further, the present invention can be applied to a remote control system used in a television, an air conditioner, and the like. Conventionally, a GaAs LED and a SiIC for driving the GaAs LED had to be constituted by discrete elements. By applying the present invention, an infrared LED and a driving IC can be monolithically constituted.
[0035]
【The invention's effect】
As described above, according to the present invention, a semiconductor integrated device in which a plurality of optical semiconductor devices are formed on the same Si substrate or a semiconductor integrated device in which an optical semiconductor device and an electronic semiconductor device are formed on the same Si substrate. Therefore, in a semiconductor integrated device in which the active layer of the optical semiconductor device includes an Fe-Si compound, a high-concentration p-type Si layer is provided between the Fe-Si compound layer and the Si substrate. Since the acceptor concentration is set to 5 × 10 ¹⁸ cm ⁻³ or more, it is possible to suppress the diffusion of Fe, which is an obstructive factor when monolithically integrating the β-FeSi ₂ -based light emitting / receiving element and the Si-based semiconductor element. it can. Therefore, according to the present invention, it is possible to greatly improve the yield of Si-based semiconductor devices, and to integrate optical / electronic semiconductor devices using β-FeSi ₂ -based devices with extremely low environmental load. Can be supplied at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic view of a cross-sectional structure of an optical / electronic semiconductor integrated device in which a β-FeSi ₂ -based light receiving device and a Si-based electronic device are monolithically integrated according to a first embodiment of the present invention.
FIG. 2 is a schematic view of a cross-sectional structure of an optical / electronic semiconductor integrated device in which a β-FeSi ₂ -based light receiving device and a Si-based electronic device are monolithically integrated according to a second embodiment of the present invention.
FIG. 3 is a schematic view of a cross-sectional structure of a conventional optical / electronic semiconductor integrated device in which a conventional β-FeSi ₂ -based light receiving device and a Si-based electronic device are monolithically integrated.
[Explanation of symbols]
Reference Signs List 1 Si substrate 2 n-type Si layer 3 n-type β-FeSi ₂ layer 4 p-type β-FeSi ₂ layer 5 anode electrode 6 cathode electrode 7 Si-based electronic element forming region 8 Al-doped high carrier concentration p-type Si layer 9 B-doped High carrier concentration p-type Si layer 10 High carrier concentration p-type Si layer by Al or B doping

Claims (5)

A semiconductor integrated device in which a plurality of optical semiconductor elements are formed on the same Si substrate, wherein the active layer of the optical semiconductor element includes an Fe-Si compound.
A semiconductor integrated circuit having a high-concentration p-type Si layer between an Fe-Si compound layer and a Si substrate, wherein the high-concentration p-type Si layer has an acceptor concentration of 5 × 10 ¹⁸ cm ⁻³ or more. element. A semiconductor integrated device in which an optical semiconductor element and an electronic semiconductor element are formed on the same Si substrate, wherein the active layer of the optical semiconductor element includes an Fe-Si compound.
A semiconductor integrated circuit having a high-concentration p-type Si layer between an Fe-Si compound layer and a Si substrate, wherein the high-concentration p-type Si layer has an acceptor concentration of 5 × 10 ¹⁸ cm ⁻³ or more. element. The semiconductor integrated device according to claim 1, wherein
A semiconductor integrated device, wherein the dopant of the high-concentration p-type Si layer is B or Al, or both B and Al. The semiconductor integrated device according to claim 1, wherein
A semiconductor integrated device, wherein a high-concentration p-type Si layer is composed of two layers, a B-doped layer and an Al-doped layer. The semiconductor integrated device according to claim 1,
A semiconductor integrated device, wherein a high-concentration p-type Si layer formed by doping B or Al is formed on a back surface of a Si substrate.

Images