JPS629543A - Optical pickup device - Google Patents

Abstract

PURPOSE:To attain miniaturization of the entire device and to improve the S/N by forming a photodetector and an amplifier circuit for the output signal on a single semiconductor substrate. CONSTITUTION:Islands 26, 27 are formed to the major face of the semiconductor substrate 25, drain regions 28-33 are formed to each island and source-drain regions 34, 35 are formed to the regions between the islands. Further, gate oxide films 36, 37 and gate electrodes 38, 39 are provided to the regions 32, 33 and the regions 34, 35 of the island 27 while being overlapped on each region. Then the photodetector and the amplifier circuit for the output signal are formed on the signal semiconductor substrate as semiconductor devices to miniaturize the entire device and to improve the S/N.

Description

[Detailed Description of the Invention] [Industrial Application W] The invention of Part B relates to an optical pickup device that uses laser light to read information from an information recording medium in which information is recorded in the form of tracks.

[Prior Art] Figure 5 is a schematic diagram of a conventional 3-beam optical pickup device. With an optical pickup that reads the recorded information on this disc,
laser light source 3, diffraction grating, beam splitter 4,
An optical system that includes an objective l/lens, etc. and irradiates the track with the light beam from the laser light source 3, and a photodetector IJIFB that receives the reflected light beam from the information track guided by the optical system and outputs an electric signal. Although not shown, there are two components for focusing the light flux on the information track and for ensuring that the light flux accurately follows the information track.
It is equipped with two drive mechanisms.

Light detection! ! As shown in FIG. 6, #8 is at least four light receiving sections 6 arranged symmetrically with respect to mutually orthogonal axes.
a-9d, and two light receiving sections 6e and (3f) arranged to face each other with this light receiving section in between.

) is a current-voltage conversion circuit using a CMOS inverter connected to the external terminal of the photodetector 8 corresponding to each of the light receiving sections 6a to 6f, which converts the output current of the light receiving section into voltage and supplies it to the subsequent amplifier circuit. .

FIG. 8 shows a structural diagram of the photodetector 6, in which a high concentration p-type diffusion layer (hereinafter referred to as a p+ diffusion layer) is formed on a low concentration n-type impurity substrate 8 (hereinafter referred to as an n- substrate). Each detection section 9a-6
f.

On the other hand, FIG. 7 shows the CMOS that constitutes the current-voltage conversion circuit.
A structural diagram of an inverter is shown, and 9 is an n-substrate electrode.

Next, the operation will be explained. The laser beam emitted from the laser light source 3 is split into one main beam and two sub beams by a diffraction grating, and is irradiated onto the track of the disk 1 through the objective lens 5, while the reflected light from the disk 1 is reflected by the objective lens. The light enters from the beam splitter 5 and is separated by the beam splitter 4 and irradiated onto the photodetector 8.

That is, as shown in FIG. 6, the main beam is irradiated on the central detection parts 6a to 6d of the photodetector 6, and the sub-beams are irradiated on the other opposing detection parts (3e, 9f, respectively).

Therefore, each of the detection parts 6a to 6f of the photodetector 6 receives a photocurrent corresponding to the amount of light from the external terminal to the current-voltage conversion circuit 7.
Figure 8 shows the electrical circuit at this time, where the input signal is input to a voltage signal and is converted into a voltage signal.The detection section of the photodetector Wi6 is equipped with a resistor of 1 day and 1 day, so that the output signals of each detection section do not interfere with each other. A bias power source is connected through a circuit including a capacitor 20, and when a light beam hits the detection section, a photocurrent is generated.

[Problem 3 to be solved by the invention As described above, according to the conventional optical pickup device,
Since the current-voltage conversion circuit is connected to the photodetector through the external terminal of the pickup, the assembly work is complicated, the size increases, and the cost increases.In particular, the SN/N of the reproduced signal is reduced due to the routing of the lead wires. There was a problem that the ratio decreased.

This invention was made to solve the above-mentioned problems, and aims to provide an optical pickup device in which the pickup itself is miniaturized to reduce costs and improve the S/N ratio.

[Means for solving the problem] The optical pickup device according to the present invention integrates a photodetector and an amplification circuit for an electric signal output from the photodetector on a single semiconductor substrate. It was formed.

[Effect]

In this invention, the output signal of the photodetector is effectively processed by an amplifier circuit formed on a single semiconductor substrate with a thickness of 1/4 ml.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a cross-sectional view of a semiconductor device forming an amplifier circuit and a photodetector, in which two n- islands 26 and 27 are formed on the main surface side of a p- semiconductor substrate 25, and each island has a p+ source. Drain regions 28 to 33 are formed by impurity diffusion, and n+ resource drain regions 34 and 35 are formed in regions between the islands by impurity diffusion.

Furthermore, the p″ source/drain region 3 of one island 27
Gate oxide films 38, 37 and gate electrodes 38, 39 are provided in the n+ resource rain regions 34, 35 and 2.33 so as to partially overlap with each region. In other words, the p↑ source/drain regions 28 to 31 in this semiconductor device correspond to the respective detection parts 6a to 6f of the photodetector 6, and the tpty north drain 1i regions 32, 33 where the gate electrode is provided, The n+ resource rain region 34 constitutes the current-voltage conversion circuit 7 as a complementary field transistor.

FIG. 3 is a diagram illustrating the manufacturing process of such a semiconductor device. First, n- islands 26 and 27 are formed on the main surface side of the semiconductor substrate 25 by impurity diffusion.
? Resource rain regions 34 and 35 are formed by impurity diffusion.

Next, p''' source/drain regions 28 to 33 are formed on the n-island 28.27 by impurity diffusion, and some p''
Gate oxide films 3B and 3F are deposited on + resource rain regions 32 and 33 and n+ resource rain regions 34 and 35 so as to partially overlap with each region, and a conductive gate is deposited on the gate oxide film B. Form electrodes 38.38.

Therefore, the p+ source drain regions 28-31 become the anodes of the photodetector 6, and the pt source drain regions 32.33 provided with electrodes e< n± source drain FIG. 4 shows another embodiment of the invention, namely n - This is a diagram illustrating the manufacturing process of a semiconductor device using a substrate. First, a p- island 4141 is formed on the main surface side of an n- semiconductor substrate 40 by impurity diffusion, and pt source/drain regions 42 to 43 are formed. is formed by impurity diffusion.

Next, the p- island 41 is connected to the source/drain region 4.
5,4Ei are formed by impurity diffusion, and n↑ source/drain regions 45, 4B and p↑ source/drain regions 43
, 44 are deposited with gate oxide films 47, 48 so as to partially overlap with these regions, and conductive gate electrodes pi 49, 50 are formed on the gate oxide films.

Therefore, according to this embodiment, the p-soil source drain 42
is a photodetector and one node thereof, and the substrate 40 directly serves as a cathode.

[Effects of the Invention] As explained above, in this invention, since the photodetector and the amplification circuit for its output signal are formed as a semiconductor device on a single semiconductor substrate, it is possible to achieve overall miniaturization. This also has the effect of improving the S/N ratio.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an optical pick one-tub device showing one embodiment of the explanation in Part B, Fig. 2 is a sectional view of a semiconductor device, Fig. 3 is a sectional view showing the manufacturing process of the semiconductor device, and Fig. 4 is a sectional view showing the manufacturing process in another embodiment, FIG. 5 is a schematic diagram showing a conventional optical pickup device, FIG. 6 is a configuration diagram of a photodetector, and FIG. 7 is a sectional view of the photodetector. FIG. 8 is a sectional view of a semiconductor device constituting an amplifier circuit, and FIG. 9 is a circuit diagram. 6 is a photodetector, 7 is an amplifier circuit, and 25 is a semiconductor substrate. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 3 Figure 4 4゜

Claims (1)

[Claims] In a device that converts information into an electrical signal and outputs it by irradiating an information recording medium with a laser beam and receiving the reflected laser beam with a photodetector, the amplification circuit of the electrical signal is connected to the photodetector. An optical pickup device characterized by being formed on a single semiconductor substrate.