TW201532300A - Photodetector and method of facricating the same - Google Patents

Abstract

The present invention provides a photodetector, which at least comprises a semiconductor substrates and a light absorbing layer (including metal layer, silicide layer). The semiconductor substrates comprise a plurality of contact structures, and the metal layer is formed on the semiconductor substrates and the contact structures. In addition, a method of fabricating the abovementioned photodetector is also disclosed in the present invention.

Description

Light detector and manufacturing method thereof

The present invention relates to a photodetector, and more particularly to a trench contact structure formed on a semiconductor substrate to increase the Schottky junction area between the light absorbing layer (including the metal, metal telluride layer) and the semiconductor substrate. A photodetector for infrared light detection and a method of fabricating the same.

Today's infrared light detectors use semiconductor materials to retain the characteristics of the band. When the material absorbs light, electrons and holes are separated, and the output of the electric signal is generated as a basis for judging the light intensity. . The semiconductor materials commonly used in infrared light detectors are germanium (Ge) and indium gallium arsenide (InGaAs). Photodetectors made of these materials have good photoelectric conversion efficiency in the infrared light band. However, this type of material is mostly costly, toxic, and difficult to integrate with today's semiconductor process technologies.

The use of bismuth (Si) wafers as a substrate is a very frequent and inexpensive material used in today's semi-conductive processes, and the corresponding process technology development is also very mature. However, the problem faced by tantalum substrates is that their energy band gap is only 1.12 eV at room temperature. That is to say, when the incident photon energy is lower than 1.12 eV, that is, the incident light wavelength is greater than 1100 nm, it will not be absorbed by the germanium substrate, thus severely limiting the Si-based light detection. The range of wavelengths that the device can detect.

In the prior art, it is seen that the metal nano-dot line structure is fabricated on the ruthenium substrate, and the surface plasmon decay is generated by absorbing light after using the metal nano-dot antenna structure (the structure size is less than 100 nm). In the past, the carrier is generated to cross the metal and the Schottky junction of the germanium substrate, and is used as a method of infrared detection. However, the localized Surface Plasma Resonance (LSPR) generated by such a metal nano-antenna structure is in the infrared band. Not significant, and severely limited by the polarization mode of the incident light, can only excite the local surface plasma phenomenon when the specific incident light is polarized, so the component of the metal nano-antenna structure finally presents the electrical signal The output is not ideal.

It can be seen that the manufacturing method of the conventional photodetector requires a long process time, a complicated process and a high cost, and is limited by the polarization mode of the incident light, which is also a major problem faced by the prior art. That is, the photodetector fabricated by the above method cannot convert the incident light source of any polarization direction into surface plasmons before considering the loss caused by the formation of the carrier by the surface plasmon, which is severely limited. The practicality of the actual operation causes an incident light source that will lose part of the polarization state.

In view of the above, the present invention provides a photodetector comprising at least a semiconductor substrate and a light absorbing layer (including a metal layer, a metal telluride layer). The semiconductor substrate includes a plurality of trench contact structures, and the light absorbing layer is formed on the semiconductor substrate and the plurality of trench contact structures.

In an embodiment of the invention, the light absorbing layer of the metal layer comprises: gold (Au), silver (Ag), aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni). , platinum (Pt), chromium (Cr), and cobalt (Co) and other materials.

In an embodiment of the present invention, the light absorbing layer of the metal telluride layer comprises: a platinum ruthenium compound (Pt _x Si), a nickel ruthenium compound (Ni _x Si), a titanium ruthenium compound (Ti _x Si), Materials such as cobalt ruthenium compound (Co _x Si), tungsten ruthenium compound (W _x Si), and molybdenum ruthenium compound (Mo _x Si), wherein x is an arbitrary number to indicate the ratio of metal to ruthenium.

In an embodiment of the invention, the contact trench structure is selected from the group consisting of a trench-like trench structure (eg, square, rectangular, circular, star, U-shape, irregular shape, etc.).

In one embodiment of the invention, a plurality of trench contact structures can use both periodic and aperiodic structures, all producing the same effect.

In an embodiment of the present invention, the trench contact structure may be the plurality of trench structures, and the depth of the plurality of trench structures and the thickness of the metal layer may be optimized according to a wavelength range to be detected. Processing.

Another object of the present invention is to provide a method for fabricating the above photodetector, The following steps are rarely included: First, a semiconductor substrate is provided. Next, a plurality of patterns are formed on the semiconductor substrate, and the semiconductor substrate is patterned according to the patterns to form a plurality of trench contact structures. Finally, a light absorbing layer (such as a metal layer, a metal telluride layer) is formed on the semiconductor substrate and the plurality of trench contact structures.

In an embodiment of the invention, the step of forming the plurality of patterns on the semiconductor substrate is performed by a lithography process (I-line, g-line, E-beam, KrF, ArF, DUV, Extreme UV lithography). )To be done. In addition, in an embodiment of the invention, the step of patterning the germanium substrate according to the plurality of patterns to form the plurality of contact structures is performed by an etching process.

The features of the present invention and its advantages will be further understood from the following description. Refer to Figures 1 through 5D for reading.

100‧‧‧Photodetector

10‧‧‧Semiconductor substrate

20‧‧‧ trench contact structure

30‧‧‧Light absorbing layer (metal, metal telluride layer)

S102~S108‧‧‧Photodetector production steps

1 is a schematic view showing a manufacturing process of a photodetector according to an embodiment of the present invention; FIG. 2A is a cross-sectional view showing a periodic structure of a photodetector according to an embodiment of the present invention; and FIG. 2B is a view showing an embodiment of the present invention. A schematic diagram of a non-periodic structure of a photodetector; FIGS. 3A to 3E are diagrams showing a scanning electron microscope image of a photodetector according to an embodiment of the present invention; and FIG. 4A is a view showing a light field of a photodetector according to an embodiment of the present invention; Concentrated resonant cavity effect; FIG. 4B is a view showing the relationship between the groove structure adjustment of the photodetector and the absorbance of the metal layer in an embodiment of the present invention; FIG. 4C is a view showing the photodetector in an embodiment of the present invention; The light focusing effect of different incident light wavelengths and polarized light patterns; FIG. 5A shows the optical response spectrum of the photodetector under tungsten illumination in an embodiment of the present invention; FIG. 5B shows the optical detection in an embodiment of the present invention. The optical response spectrum of the detector under adjustable variable laser illumination; FIG. 5C is a view showing the relationship between the incident power of the photodetector and the output extra current when the incident light has a wavelength of 1310 nm (nm) according to an embodiment of the present invention; and FIG. 5D shows the present invention. In the embodiment, the relationship between the incident power of the photodetector and the output current of the output current at a wavelength of the incident light of 1550 nanometers (nm).

Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings, the same component symbols indicate the same components, and the size or thickness of the components may be exaggerated for clarity.

For the above, please refer to Figure 1, Figure 2A and Figure 2B at the same time. 1 is a schematic view showing a manufacturing process of a photodetector according to an embodiment of the present invention, FIG. 2A is a cross-sectional view showing a periodic structure of a photodetector according to an embodiment of the present invention, and FIG. 2B is a view showing a first embodiment of the present invention. A schematic diagram of the aperiodic structure of the photodetector in the embodiment.

First, as shown in FIG. 1, the photodetector provided by the present invention first provides a semiconductor substrate (such as a germanium substrate) as shown in step S102. In an embodiment of the invention, the semiconductor substrate can be a negative (n-type) doped germanium wafer and a thermal oxide is grown thereon, so that the subsequent photodetector is fabricated. Before the process begins, the window must be opened by etching on the thermal oxide layer. Furthermore, the thermal oxide layer can also be used as an etching mask for the subsequent lithography process. However, it should be noted that the above-described embodiments are for illustrative purposes only, and the present invention is not intended to be limited thereto.

Next, as shown in step S104, a plurality of patterns are formed on the germanium substrate, and a plurality of trenches are formed in step S106 based on the plurality of patterns. In the preferred embodiment, step S104 is performed by using a lithography process (I-line, g-line, E-beam, KrF, ArF, DUV, Extreme UV lithography), which can reduce the process cost and exceed the output. The purpose. The step S106 is performed by a dry etching process, and the depth of the plurality of trenches formed is preferably 1.2 micrometers (μm), but the invention is not limited thereto. Finally, a metal layer is formed on the inner surface of the plurality of trenches by using a metal sputtering process. In a preferred embodiment, the light absorbing layer (such as a metal layer) is made of gold (Au), silver (Ag), aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), platinum (Pt). ), selected from the group of chromium (Cr) and cobalt (Co); and the light absorbing layer (such as metal halide layer) is composed of platinum ruthenium compound (Pt _x Si), nickel ruthenium compound (Ni _x Si), titanium ruthenium Selected from the group consisting of compound (Ti _x Si), cobalt ruthenium compound (Co _x Si), tungsten ruthenium compound (W _x Si), and molybdenum ruthenium compound (Mo _x Si) (where x is any number to indicate metal and ruthenium The ratio is between 1 nanometer (nm) and 10,000 nanometers (nm), but the invention is not limited thereto. That is, in a preferred embodiment of the invention, a plurality of deep trench/thin metal structures are formed on a semiconductor substrate. However, as described above, the present invention is directed to fabricating a plurality of contact structures on a germanium substrate for forming a Schottky junction between a large-area metal-germanium substrate, and thus the plurality of contact structures are not intended to be deep trenches. For the sake of limitation, structures including holes (eg, square, rectangular, circular, star, 卍, irregular, etc.) are also feasible. Furthermore, the plurality of trench contact structures may be a periodic array structure, and will be described later in a periodic trench array structure, but the invention is not intended to be limited thereto, and the present invention is not limited thereto. In an embodiment, the same effect is produced if a non-periodic structure is used. In other words, the plurality of trench contact structures of the present invention are selected from the group of periodic structures and non-periodic structures. Explain first.

In the above, the photodetector produced by the method provided by the present invention is shown in FIGS. 2A and 2B, and FIG. 2A shows the periodic cross section of the photodetector 100 in an embodiment of the present invention. FIG. 2B is a schematic diagram showing the aperiodic structure of the photodetector 100 in an embodiment of the present invention. As shown, the present invention is formed on a semiconductor substrate 10 to form a plurality of contact structures 20, and then form a thin (such as the aforementioned, for example, 30 nm) metal layer 30 to cover the semiconductor substrate 10 and the plurality of contact structures. 20 side walls and bottom. Moreover, the size of the plurality of contact structures and the periodicity of the arrangement thereof can also be adjusted by the I-line lithography process of the above step S104 as follows: For example, the table labeled H065P13, that is, the contact structure has a dimension of 0.65 micrometers (μm) and the periodicity is 1.3 micrometers (μm) (that is, the distance between the two contact structures). At this time, the scanning electron microscope image of the photodetector is as shown in FIGS. 3A to 3E.

Next, please refer to FIGS. 4A to 4C for the optical characteristic portion of the photodetector provided by the present invention. First, under the top surface of the above contact structure (ie, deep trench), 0 nm (nm), 30 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm Settings A detecting element is used to observe the light field focusing effect of the photodetector provided by the present invention. At this time, as shown in FIG. 4A, the photodetector provided by the preferred embodiment of the present invention (ie, having an array structure of deep trenches/thin metal) has a strong light field aggregating effect, which can make incident After the infrared light source encounters the periodic metal structure, the coupling generates surface plasmons into the deep trench, which produces the effect of light field gathering, so that a large part of the light is confined to the metal structure and is thinned by the thin layer. The metal is absorbed.

Furthermore, as shown in FIG. 4B, adjusting the size and arrangement periodicity of the contact structure 20 in accordance with the aforementioned table can regulate the absorption of the strongest wavelength position by the metal layer 30. Therefore, the present invention can further adapt the measurement band to be targeted by adjusting the structural parameters.

Finally, please refer to FIG. 4C. FIG. 4C is a diagram showing the light focusing effect of the photodetector on different incident light wavelengths and polarized light patterns according to an embodiment of the present invention. The table marked as H07P14). As shown, the previously fabricated structure (ie, an array structure with deep trenches/thin metal) has an excellent electric field at a wavelength of 1420 nm (nm) regardless of whether the incident light is X-axis polarized or Y-axis polarized. In addition, not only at a wavelength of 1420 nm (nm), the above structure is excellent in surface plasma phenomenon and cavity effect at a wavelength of incident light of 1310 nm (nm) and 1550 nm (nm). The electric field strength. That is to say, the above structure is not sensitive to the polarization mode of the incident light, and an excellent light field agglomeration effect can be produced regardless of the wavelength or the polarization mode incident on the structure.

In order to prove that the photodetector provided by the present invention has a good infrared photoelectric photoelectric conversion response, the optical detector is further measured for the optical detector. It must be noted that in order to achieve low energy consumption considerations, no bias is applied during the measurement of the electrical signal.

Please refer to Figure 5A. First, the wavelength of any polarized light is incident on the tungsten light source in the range of 1200 nm (nm) to 1650 nm (nm). At this time, as shown in Fig. 5A, the photon energy of 1.12 eV below the energy gap of 矽 can be measured, and a good photoelectric conversion response can be provided. Furthermore, a tunable laser can also be used as a light source incident element, and the wavelength range is from 1450 nm to 1590 nm (nm), as shown in Fig. 5B, even if The photodetector provided by the present invention also has a good photoresponse effect under illumination of different light source incident elements.

Next, please refer to FIG. 5C to inject the photodetector provided by the present invention with different light intensities under the condition of fixing the wavelength of the incident light. As shown in the figure, when the wavelength of the incident light is 1310 nanometers (nm), the output of the optical signal has a good linearity (R ² = 0.9982) at a weak light intensity. As shown in Fig. 5D, when the wavelength of the incident light is 1550 nanometers (nm), the output of the optical signal has a good linearity regardless of weak or strong light intensity (its R ² =0.9998). Therefore, the photodetector provided by the present invention is a wide-band, high photoelectric conversion efficiency and low-energy 矽-based infrared photodetector.

In summary, the present invention is formed on a tantalum substrate after a plurality of cycles, and then covered with a periodic (or non-periodic) contact structure of the metal layer to form a continuous metal film structure. Then, the Schottky junction formed by the resonant cavity effect formed by the continuous metal film structure and the surface plasma phenomenon and the contact of the large-area metal-ruthenium substrate can effectively generate heat through the surface plasma decay. Hot electrons, which in turn enhance the photoelectric conversion of the sigma-based infrared photodetector. At the same time, through the design of the upper graphic, the photodetector is further restricted from being incident on any polarized light, and the infrared light source of any polarization type can be effectively collected. Such a non-toxic, low-cost photodetector that is compatible with current semiconductor processes, in addition to reducing the cost and time required for the process, can also break through the inherent barrier of the substrate by 1.12 eV, which is currently An effective breakthrough technology for detecting infrared light using a krypton-based photodetector. In the same way, after using the present invention on any semiconductor substrate, the limitations of the natural energy barrier can be broken, and the wavelength range detectable by the original semiconductor material can be broken.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the present invention should be included in the following. Within the scope of the patent application. .

100‧‧‧Photodetector

10‧‧‧Semiconductor substrate

20‧‧‧ trench contact structure

30‧‧‧Light absorbing layer

Claims (10)

A photodetector includes at least: a semiconductor substrate including a plurality of trench contact structures; and a light absorbing layer formed on the semiconductor substrate and the plurality of trench contact structures. The photodetector of claim 1, wherein the light absorbing layer comprises a metal layer. The photodetector of claim 2, wherein the metal layer is selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), copper (Cu), titanium. Selected in the group of (Ti), nickel (Ni), platinum (Pt), chromium (Cr), and cobalt (Co). The photodetector of claim 1, wherein the light absorbing layer comprises a metal telluride layer. The photodetector of claim 4, wherein the metal telluride layer is composed of a platinum rhodium compound (Pt _x Si), a nickel antimony compound (Ni _x Si), a titanium germanium compound (Ti _x Si), The cobalt ruthenium compound (Co _x Si), the tungsten ruthenium compound (W _x Si), and the molybdenum ruthenium compound (Mo _x Si) group are selected, wherein x is an arbitrary number to indicate the ratio of metal to ruthenium. The photodetector of claim 1, wherein the plurality of trench contact structures are selected from a group of holes and a group of trench structures. The photodetector of claim 6, wherein the hole structure is selected from the group consisting of a square, a rectangle, a circle, a star, a U shape, an irregular shape, and a groove structure. The photodetector of claim 1, wherein the plurality of contact structures comprise the plurality of trench structures. The photodetector of claim 1, wherein the plurality of trench contact structures are selected from a periodic structure and a non-periodic structure group. A method of forming a photodetector, comprising at least the steps of: providing a semiconductor substrate; forming a plurality of patterns on the semiconductor substrate; patterning the semiconductor substrate according to the plurality of patterns to form a plurality of contact structures; and forming a light An absorbing layer is on the semiconductor substrate and the plurality of contact structures.