JP3594418B2 - Light receiving element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light receiving element having an electromagnetic shielding effect suitable for an optical sensor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a light receiving element used for an infrared remote controller or an optical sensor constituting a receiving unit for short-range optical communication, for example, as shown in Japanese Utility Model Publication No. 5-36181, a metal mesh or a conductive film is provided in front of the element. They are arranged and connected to a ground potential, or the surface of the element is electromagnetically shielded with a transparent electrode or the like, and is housed in a metal case or resin-molded.
[0003]
On the other hand, when the light receiving element and the light receiving signal processing circuit are monolithically incorporated, as described in Japanese Patent Publication No. Hei 7-120762, the high density light is applied to the surface of the light receiving element at the same time when the gate and the source of the light receiving signal processing circuit are formed. In some cases, a layer is formed and this high-concentration layer attempts to shield simultaneously with wiring.
[0004]
[Problems to be solved by the invention]
However, when the electromagnetic shield is embedded in the light receiving element assembly, it is complicated to prevent misalignment and wiring of the mesh and film, and when a transparent electrode is provided on the element surface, a capacitor is placed between the shielding electrode and the element surface. Is formed, the electric capacity is increased, the receiving sensitivity is reduced, and in the case of optical communication, there is a disadvantage that the communicable range is significantly shortened.
[0005]
On the other hand, when the light receiving element and the light receiving signal processing circuit are monolithically integrated, the depth and impurity concentration of the layer corresponding to the photoelectric characteristics required for the light receiving element are different from the dopant and impurity concentration required for the circuit portion, or these light receiving elements It is theoretically possible to use the shield layer for the wiring, since the matching between the circuit and the circuit portion cannot be obtained. However, the attenuation of the optical signal and the decrease in the S / N ratio are caused. Further, in such a monolithic light receiving element, the response of the light receiving element is deteriorated because the manufacturing process is restricted to the circuit portion.
[0006]
[Means for Solving the Problems]
The present invention has been made in view of the above points, and uses a P-type conductive semiconductor substrate having a low impurity concentration, a P-type high-concentration layer provided on the back surface of the semiconductor substrate, and a semiconductor substrate having the same structure. N-type high-concentration layer provided as a light-receiving portion at a substantially central portion on the surface side of P, and a P-type low-sheet-resistance P-type layer provided on the surface of the N-type high-concentration layer with a larger area than the N-type high-concentration layer A PIN having a high-concentration thin layer and a P-type high-concentration layer surrounding the periphery of the P-type high-concentration thin layer on the surface of the semiconductor substrate. More preferably, a light receiving element is obtained, and the periphery of such an element is covered (enclosed) with a conductive material connected to the P-type high-concentration thin layer on the surface of the light receiving portion at the same potential.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic side view of a mounted state of a light receiving element according to an embodiment of the present invention, and FIG. 2 is a plan view of the light receiving element. In these figures, reference numeral 1 denotes a low-impurity-concentration semiconductor substrate having a resistance value of 500 Ωcm or more, which is an element substrate made of P-type Si having a thickness of 180 to 400 μm. The resistance value of the semiconductor substrate 1 is a value that is effective for maintaining a good reception sensitivity because the depletion layer spreads over the entire thickness of the layer when a bias voltage is applied, and is preferably 800 to 1200 Ωcm. Reference numeral 2 denotes an N-type high-concentration layer provided as a light receiving portion at a substantially central portion on the front surface side of the semiconductor substrate 1, and is provided in a substantially square shape in the example of FIG. An N-type ohmic electrode 21 is connected to a part of the surface of the N-type high-concentration layer 2 serving as a light-receiving portion. For example, the impurity concentration is 1 by diffusing phosphorus (P) to a depth of 1 to 5 μm. It is provided at about × 10 ²⁰ cm ⁻³ .
[0008]
Reference numeral 3 denotes a P-type high-concentration layer provided on the back surface of the semiconductor substrate 1, which is necessary when the P-type ohmic electrode 4 is provided, diffuses boron (B), and has an impurity concentration of about 1 × 10 ²⁰ cm. ^-3 . Therefore, the P-type high-concentration layer 3 is unnecessary when the P-type electrode is taken out from the surface side.
[0009]
Reference numeral 5 denotes a P-type high-concentration thin layer further provided on the surface of the N-type high-concentration layer 2, which has a larger area than the N-type high-concentration layer 2 so as to cover most of the surface side of the N-type high-concentration layer 2. It is shallower than the N-type high concentration layer 2 and has a depth of, for example, 0.5 to 2 μm. Such a P-type high-concentration thin layer 5 is obtained by diffusing boron (B), and has a surface resistance of, for example, 30 Ω / b in order to obtain conductivity. Preferably, the sheet resistance is set to be 20 KΩ / b or less. The P-type high-concentration thin layer 5 is in ohmic contact with the shield electrode 51.
[0010]
Reference numeral 6 denotes a P-type high-concentration layer surrounding the periphery of the P-type high-concentration thin layer 5 on the surface of the semiconductor substrate 1, which is separated from the P-type high-concentration thin layer 5 on the light-receiving portion surface, and has an impurity concentration of about 1 × 10 ^20. It is preferable that the depth is 1-7 μm at cm ⁻³ , which is deeper than the P-type high-concentration thin layer 5. Above the surrounding P-type high-concentration layer 6, the above-mentioned shield electrode 51 is arranged in a square shape so as to cover the P-type high-concentration layer 6. An insulating film 11 made of silicon dioxide or silicon nitride is provided on the surface for protecting the surface and preventing undesired reflection. In a portion where the electrodes 21 and 51 take ohmic contact, a photolithography technique or the like is used. A through hole is provided.
[0011]
Such a light receiving element is fixed to a frame 8 using a conductive adhesive 7, but in order to prevent noise incident from the side of the element, the side of the element is surrounded by a conductive material 9 such as a metal frame. It is most preferable that the shield electrode 51 of the P-type high-concentration thin layer 5 on the light receiving section surface and the conductive material 9 are connected by a wire bond wire or the like to form an equipotential surface.
[0012]
In such a configuration, the light receiving element forms a so-called PIN photodiode, and is configured to have high light receiving sensitivity, and can provide an effective electromagnetic shielding effect. FIG. 3 is a correlation diagram between the surface resistance value of the P-type high-concentration thin layer 6 on the light-receiving portion surface and the signal reach when the light-receiving element is incorporated in the infrared light receiving module. The surface resistance value of the thin concentration layer 6 is 10 KΩ / b or less, which indicates that there is a particularly excellent effect. In addition, the TV receiver and the inverter fluorescent lamp were arranged as noise sources, and the noise resistance was examined. As a result, when the light-receiving element of the present invention was used as it was, the influence of noise appeared on the output of the light-receiving module at a location 16 mm away from the noise source on a lot average, but the conductive material 9 was provided around the light-receiving element. In this case, even when the light receiving module was brought into contact with the noise source case (outer box), the output did not show any influence of noise.
[0013]
【The invention's effect】
As described above, the present invention maintains high-sensitivity light-receiving element characteristics as a PIN photodiode, and has an electromagnetic shield layer, an electromagnetic shield ring electrode, an opposing ring layer, etc. on its surface, so that it does not hinder assembly and is efficient. Electromagnetic shielding was successfully performed.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a mounted state of a light receiving element according to an embodiment of the present invention.
FIG. 2 is a plan view of a light receiving element according to an embodiment of the present invention.
FIG. 3 is a correlation diagram between a surface resistance value of a P-type high-concentration thin layer 6 and a signal reaching distance.
[Explanation of symbols]
1 semiconductor substrate 2 N-type high concentration layer (light receiving section)
3 P-type high concentration layer 4 P-type ohmic electrode 5 P-type high concentration thin layer 6 P-type high concentration layer 7 Conductive adhesive 8 Frame 9 Conductive material

Claims (1)

A P-type conductive semiconductor substrate having a low impurity concentration is used, a P-type high concentration layer provided on the back surface of the semiconductor substrate, and an N-type light-receiving portion provided substantially at the center on the front surface side of the semiconductor substrate. -Type high-concentration layer, a P-type high-concentration thin layer having a lower sheet resistance provided on the surface of the N-type high-concentration layer over a larger area than the N-type high-concentration layer, and a P-type high-concentration layer on the surface of the semiconductor substrate. A surrounding P-type high-concentration layer surrounding the thin layer; and a shield electrode in contact with the P-type high-concentration thin layer. The shield electrode is arranged to cover the surrounding P-type high-concentration layer. receiving element, characterized in that.

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