JP3503410B2 - Optical sensor adjustment method and optical sensor adjustment device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical sensor.

[0002]

2. Description of the Related Art In an optical sensor, an optical sensor IC in which a light receiving element (photodiode or the like) and a signal processing circuit such as a transistor are formed on one chip is known (for example, Japanese Patent Laid-Open No. 63-116458). Gazette). However, this optical sensor IC has variations in output characteristics due to variations in sensitivity of the light receiving section and variations in circuit characteristics.

Therefore, by forming a thin film resistance element for adjustment on the chip and laser trimming the thin film resistance element, an accurate photosensor IC can be manufactured. As shown in FIG. 9, when adjusting the output characteristics at the time of light irradiation in an optical sensor in which the photoelectric conversion element, the signal processing circuit, and the circuit adjustment thin-film resistance element are integrated into one chip as described above, as shown in FIG. The thin film resistance element 52 is arranged so that the output of the signal processing circuit 51 reaches a predetermined value while irradiating 50 with light of the reference intensity.
Will be laser trimmed.

[0004]

However, in order to make the adjustment in this way, it is necessary to irradiate the light of the reference intensity from above the chip and at the same time to irradiate the laser light from directly above the chip, which is realized. Is difficult.
That is, it is necessary to provide a special device in which two kinds of light sources (a light source having a reference intensity and a laser oscillator) are arranged on a chip and which can irradiate a desired position with laser light. More specifically, equipment including a wafer test device with a light source and a laser trimming device is required.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical sensor adjustment method and an optical sensor which can easily perform adjustment in an optical sensor in which a photoelectric conversion element, a signal processing circuit, and a circuit adjusting thin film resistance element are integrated into one chip. An object is to provide a sensor adjusting device.

[0006]

According to a first aspect of the present invention, a current detector is provided at an output terminal of a photoelectric conversion element, and the photoelectric conversion element is irradiated with light having a reference intensity. A step of recording the detected current value, a current generation source is provided at the output terminal of the photoelectric conversion element, the photoelectric conversion element is not irradiated with light, and the recorded current value is signaled using the current generation source. And a step of performing laser trimming of the thin film resistance element so as to obtain a desired output value in a state where the thin film resistance element is supplied to the processing circuit.

By doing so, the light having the reference intensity is applied to the photoelectric conversion element, the current value at that time is detected by the current detector provided at the output terminal of the photoelectric conversion element, and the current value is recorded. . Then, a desired output value is obtained in a state where the recorded current value is supplied to the signal processing circuit by using the current generation source provided at the output terminal of the photoelectric conversion element without irradiating the photoelectric conversion element with light. Thus, the laser trimming of the thin film resistance element is performed.

With this arrangement, a general light source device can be used without using special equipment for arranging two kinds of light sources (a light source having a reference intensity and a laser oscillator) on a chip and irradiating laser light to a desired position. Then, it becomes possible to adjust the output characteristics at the time of light irradiation with a general trimming device.

When the adjustment is performed in a wafer state having a plurality of sensor formation regions as in the third aspect of the invention, it is practically preferable. Here, as an optical sensor adjustment device, as described in claim 4, a current detector provided at an output terminal of the photoelectric conversion element, and a light source for irradiating the photoelectric conversion element with light having a reference intensity, Storage means for storing a current value detected by the current detector when the photoelectric conversion element is irradiated with light having a reference intensity by the light source, a current generation source provided at an output terminal of the photoelectric conversion element, and photoelectric conversion The thin film resistance element is laser-trimmed so as to obtain a desired output value in a state where the element is not irradiated with light and the current value stored in the storage means is supplied to the signal processing circuit by using the current generation source. A device having a laser oscillator for

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a plan view of the optical sensor, and FIG. 2 shows a sectional view taken along line II-II of FIG.

The present optical sensor is used as an in-vehicle optical sensor such as a solar radiation sensor or a lighting control sensor.
That is, it is used as a solar radiation sensor used for controlling the air conditioning of a vehicle or a lighting control sensor that automatically turns on an illumination device when it gets dark and turns it off when it gets bright.

A silicon substrate (silicon chip) 1 as a semiconductor substrate comprises a silicon substrate 1a and an N ^-- type epitaxial layer 1b formed thereon. At the center of the silicon substrate 1, a photodiode 3 as a photoelectric conversion element separated by a P ⁺ type region 2 is formed.
In the photo diode 3, N ^- is the surface portion of the type epitaxial layer 1b is formed a P ⁺ -type region 4 serving as a light receiving portion, an end portion of the P ⁺ -type region 4 is formed a P ⁺ -type region 5 . Further, in the photodiode 3, together with the buried N ⁺ -type region 6 is formed, N-type region 7 to reach the buried N ⁺ -type region 6 extends in the vertical direction is formed in an annular shape.

Photodiode on silicon substrate 1
A signal processing circuit 8 is formed around the area 3. signal
The processing circuit 8 is composed of a large number of semiconductor devices.
The device configures the signal amplification circuit, frequency conversion circuit, etc.
Has been. In FIG. 2, the NPN bipolar transistor is shown.
9 and the IIL element 10 are shown. That is, the silicon substrate 1
a and N^-Buried at the boundary with the epitaxial layer 1b
Included N⁺The mold region 11a is formed, and N^-Type epitaxial
N in the surface layer of layer 1b⁺Mold regions 12, 13 and P
⁺A mold region 14 is formed. Also, the silicon substrate 1a
And N^-Buried at the boundary with the epitaxial layer 1b
N⁺The mold region 11b is formed, and N^-Type epitaxial layer
P on the surface of 1b^-Mold area 15, P⁺Mold area 1
6,17, N⁺The mold region 18 is formed, and further on and below
Extension embedded N⁺N reaching the mold region 11b ⁺The mold area 19 is annular
Is formed in.

A silicon oxide film 20a is formed on the upper surface of the silicon substrate 1. In the photodiode 3, the silicon oxide film 20a has an opening, and a thin silicon oxide film 20b is formed in this region. A thermal oxide film is used as the silicon oxide film 20b and has a film thickness of 100 to 3
00 nm, and more specifically 300 nm. Also, in the photodiode 3, aluminum wiring 2
1, 22 are extended. The aluminum wiring 22 is electrically connected to the N-type region 7, and the aluminum wiring 21 is connected to the P ⁺ -type region 5.
Is electrically connected to. The aluminum wirings 21 and 22 are formed by patterning an aluminum thin film into a desired shape.

Further, in the signal processing circuit 8, the N ⁺ type region 12 is formed by the aluminum wiring 23 and the P ⁺ region is formed by the aluminum wiring 24.
The type region 14 and the N ⁺ type region 13 are electrically connected to each other by the aluminum wiring 25, and the impurity regions of the IIL element 10 are electrically connected to each other by the aluminum wiring.
Each aluminum wiring in this example is formed by patterning an aluminum thin film into a desired shape, and has a film thickness of 1.1 μm.

A TEOS oxide film 26 is formed on the aluminum wiring,
The SOG film 27 and the TEOS oxide film 28 are formed as an interlayer insulating film. Each film 2 in the photodiode 3
It is open without 6, 27 and 28. An aluminum thin film 29 as a light-shielding film is formed on the TEOS oxide film 28 in the signal processing circuit 8. The film thickness of the aluminum thin film 29 is 1.3 μm.

When light is incident from the outside toward the light receiving portion of the photodiode 3, the light passes through the thin silicon oxide film 20b and reaches the P ⁺ type region 4. When light enters near the PN junction between the N ⁻ type epitaxial layer 1 b and the P ⁺ type region 4, electron-hole pairs are generated. The generated minority carriers, that is, the electrons and holes generated in the P ⁺ type region 4 and the N ⁻ type epitaxial layer 1b move in opposite directions in both regions. At this time, a current flows from the N ⁻ type epitaxial layer 1b to the P ⁺ type region 4. This photocurrent is proportional to the amount of incident light. This photocurrent is sent to the signal processing circuit 8 through the aluminum wiring 21. In the signal processing circuit 8, the photocurrent is amplified and the frequency is converted. This signal is output to the outside through the pad 30a formed on the silicon oxide film 20a in FIG. That is, it is output to the outside via the pad 30a in FIG.

Further, the aluminum thin film 2 as the light shielding film in FIG.
In the region where 9 is absent, a thin film resistance element 31 for laser trim adjustment is formed on the silicon oxide film 20a. More specifically, the thin film resistance element 31 for laser trim adjustment is made of CrSi or CrSiN, and the element 31 has a rectangular shape as shown in FIG. The laser trim adjustment resistance element 31 is a Cr-Si film or the like formed by a sputtering method and photoetched into a predetermined shape. The aluminum wiring 33 is connected to one end of the thin film resistance element 31 for laser trim adjustment, and the aluminum wiring 34 is connected to the other end. TEOS as an interlayer insulating film is formed on the thin film resistance element 31 for laser trim adjustment.
An oxide film 26, an SOG film 27, and a TEOS oxide film 28 are arranged, but this film can transmit a laser beam. A part of the laser trim adjustment thin-film resistance element 31 is laser-trimmed (the concave portion 3 shown in FIG. 1).
5).

As described above, the present optical sensor has a photodiode 3 as a photoelectric conversion element for receiving light and converting it into an electric signal, and a signal processing for inputting a current from an output terminal of the photodiode 3 to perform signal processing. The circuit 8 and the thin-film resistance element 31 for circuit adjustment are integrated into one chip.

Further, the silicon substrate 1 has a thickness of 1.6.
A surface protective film (silicon nitride film) 36 of μm is arranged. The thin film resistance element 31 for laser trim adjustment shown in FIG.
Together with N ⁺ -type region 32 is formed in the lower, N ⁺
The mold regions 32 are separated by the P ⁺ type regions 2.

Here, each device of the signal processing circuit 8 is formed on the silicon substrate 1 by diffusion or the like used in ordinary IC manufacturing. As devices, in addition to the bipolar transistor 9 and the IIL element 10, It includes elements such as diodes, diffused resistors and capacitors.

Next, the electrical configuration of the optical sensor thus configured, that is, the optical sensor in which the photodiode 3, the signal processing circuit 8 and the thin film resistance element 31 are integrated into one chip will be described.

FIG. 3 shows an electrical configuration diagram. The first terminal P1 of the signal processing circuit 8 is grounded, and a predetermined voltage (5 volts) is applied to the second terminal P2. Further, the photodiode 3 and the resistor R1 are connected in series, a predetermined voltage (5 volts) is applied to one terminal of this series circuit, and the other terminal (anode of the diode 3) is input to the signal processing circuit 8. It is connected to the terminal P3. A circuit adjusting thin film resistance element 31 is connected to the signal processing circuit 8. Further, the signal after the signal processing is output from the terminal P4 of the signal processing circuit 8.

When the photodiode 3 receives the light to be detected, a current I ₁ corresponding to the intensity of the received light flows through the photodiode 3 and is input to the signal input terminal P3 of the signal processing circuit 8. The signal processing circuit 8 converts the input signal into a voltage, amplifies the signal, and further
The frequency is converted and output from the terminal P4. Here, the resistance value of the circuit adjustment thin-film resistance element 31 is adjusted by laser trimming of the circuit adjustment thin-film resistance element 31, and signal amplification processing is performed with a gain according to this resistance value.

A control device (not shown) is connected to the terminal P4 of the signal processing circuit 8. In this control device, the headlight is turned on in response to the output signal from this frequency in accordance with the received light intensity of the detected light. Take actions.

The specifications of this sensor are that the power supply voltage is 5 V, the output of the signal processing circuit 8 is 500 H at an energizing current of 1 mA (milliamperes) with light of 1000 cruz (lx).
It is set to be z.

Next, a method of adjusting the output characteristics of the optical sensor having the above-described structure during light irradiation will be described. Specifically, an adjustment method for obtaining an output of 500 Hz with light of 1000 cruz (lx) which is the sensor specification will be described.

First, as shown in FIG. 5, a wafer 40 having a plurality of sensor forming regions is prepared. That is, as shown in FIG. 4, a wafer having a laser trim adjustment thin-film resistance element 31 before laser trimming (a state without the recess 35 shown in FIG. 1) is prepared. Then, a probe 41 (see FIG. 4) is applied to the pad 30b of FIG. 1, and the anode terminal of the photodiode 3 is grounded via the ampere meter 42 as shown in FIG. Ampere meter 42
A computer 43 is connected to. The computer 43 is provided with a memory 43a as a storage means.

From this state, as shown in FIGS. 4 and 6, the light source 45 is used to cause the photodiode 3 to emit light (1
000 lux). The computer 43 stores (records) the current value detected by the amp meter 42 at that time in the memory 43a. This measured current value is I ₂ .

That is, light is radiated from directly above the wafer 40 using a light source device having a prescribed brightness, and the current flowing between the anode of the photodiode 3 and the ground (GND) at this time is measured to measure the chips in the wafer. It is stored in the memory 43a of the computer 43 together with the position (position of the sensor formation area).

Subsequently, the ampere meter 42 is removed, and the variable constant current circuit (current source) 44 is arranged for the anode terminal of the photodiode 3 as shown in FIG. Then, in a state where the photodiode 3 is not irradiated with light and the current value I ₂ recorded in the memory 43a using the variable constant current circuit 44 is supplied to the signal processing circuit 8, as shown in FIGS. First, the laser trimming thin film resistance element 31 is laser trimmed so as to obtain a desired output value of 500 Hz. That is, the recess 35 shown in FIG. 1 is formed by the laser beam of the laser oscillator 46.

That is, in the laser trimming device, the previously stored current value I ₂ is supplied to the terminal P3 of the signal processing circuit 8 and trimming is performed so that a desired output value is output in this state. Lasers used for trimming are YAG laser and YLF laser (both having a wavelength of 1.06 μm
Degree) can be used.

Hereinafter, similar output adjustment is performed for other sensors on the wafer. Then, the wafer is diced and cut into each sensor chip. By doing so, it is possible to adjust the output characteristics at the time of light irradiation with a general light source device and a general trimming device without using a special device. Further, according to this method, adjustment in a wafer state is possible. Therefore, the cost can be reduced without causing defective chips to flow out to the subsequent process during adjustment. In addition, if you try to make the same adjustment after assembling the chip to a package etc., it is necessary to take out the terminal for adjustment to the outside by a bonding wire, etc. Therefore, the parts and process can be simplified.

As described above, the present embodiment has the following features. (A) An ampere meter 42 as a current detector is provided at the output terminal of the photodiode 3 as a photoelectric conversion element,
The photodiode 3 is irradiated with light having a reference intensity, and the current value detected by the ampere meter 42 at that time is recorded. Then, the output terminal of the photodiode 3 is provided with a constant current circuit 44 as a current source,
The thin film resistance element 31 is laser-trimmed so as to obtain a desired output value in a state in which the recorded current value is supplied to the signal processing circuit 8 by using the constant current circuit 44 without irradiating light on the light. I chose By doing so, a general light source device and a general light source device can be used without using special equipment for arranging two types of light sources (light source of reference intensity and laser oscillator) on a chip and irradiating laser light to a desired position. It is possible to adjust the output characteristics at the time of light irradiation with a conventional trimming device. (B) Since the adjustment is performed in a wafer state having a plurality of sensor formation regions, it is practically preferable. (C) The photodiode 3 is used as an adjusting device for the optical sensor.
Ampere meter 42 provided at the output terminal of the light source 45 and a light source 45 for irradiating the photodiode 3 with light of the reference intensity.
And the light source 45 emits light having a reference intensity to the photodiode 3
Memory 43a as a storage means for storing the current value detected by the ampere meter 42 when the laser beam is radiated to the constant current circuit 44 provided at the output terminal of the photodiode 3.
And a thin film resistance element for obtaining a desired output value in a state where the photodiode 3 is not irradiated with light and the current value stored in the memory 43a using the constant current circuit 44 is flown to the signal processing circuit 8. An apparatus having a laser oscillator 46 for laser trimming 31 is preferably used.

Although the photodiode 3 is used as the photoelectric conversion element in the above description, a phototransistor or the like may be used.

[Brief description of drawings]

FIG. 1 is a plan view of an optical sensor according to an embodiment.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an electrical configuration diagram of an optical sensor.

FIG. 4 is a cross-sectional view of an optical sensor for explaining adjustment.

FIG. 5 is a plan view of a wafer.

FIG. 6 is a circuit configuration diagram for explaining adjustment.

FIG. 7 is a circuit configuration diagram for explaining adjustment.

FIG. 8 is a cross-sectional view of an optical sensor for explaining adjustment.

FIG. 9 is a circuit configuration diagram for explaining adjustment according to a conventional method.

[Explanation of symbols]

3 ... Photodiode, 8 ... Signal processing circuit, 31 ... Laser trim adjustment thin film resistance element, 40 ... Wafer, 42 ... Ampere meter, 43 ... Computer, 43a ... Memory,
44 ... Variable constant current circuit, 45 ... Light source, 46 ... Laser oscillator

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-106536 (JP, A) JP-A-10-284707 (JP, A) JP-A-63-116458 (JP, A) JP-A-1- 205462 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 27/14

Claims (6)

(57) [Claims] 1. A photoelectric conversion element for receiving light and converting it into an electric signal, a signal processing circuit for inputting a current from an output terminal of the photoelectric conversion element for signal processing, and a thin film resistance element for circuit adjustment. And is a method of adjusting a photosensor integrated into one chip, the output terminal of the photoelectric conversion element is provided with a current detector, the photoelectric conversion element is irradiated with light having a reference intensity, and the current detector at that time is used. A step of recording the detected current value, providing a current generation source at the output terminal of the photoelectric conversion element, without irradiating the photoelectric conversion element with light, and the recorded current value using the current generation source And a step of performing laser trimming of the thin film resistance element so as to obtain a desired output value in a state in which the signal is supplied to the signal processing circuit. 2. The method of adjusting an optical sensor according to claim 1, wherein the photoelectric conversion element is a photodiode, and the output terminal is an anode. 3. The optical sensor adjustment according to claim 1, wherein the adjustment is performed in a wafer state having a plurality of sensor formation regions.
Way . 4. A photoelectric conversion element for receiving light and converting it into an electric signal, a signal processing circuit for inputting a current from an output terminal of the photoelectric conversion element for signal processing, and a thin film resistance element for circuit adjustment. Is a one-chip optical sensor adjustment device, a current detector provided at the output terminal of the photoelectric conversion element, a light source for irradiating the photoelectric conversion element with light of reference intensity, the light source Storage means for storing a current value detected by the current detector when the photoelectric conversion element is irradiated with light having a reference intensity, a current generation source provided at an output terminal of the photoelectric conversion element, and the photoelectric conversion The thin film resistance element is laser-trimmed so as to obtain a desired output value in a state where the element is not irradiated with light and the current value stored in the storage means is supplied to the signal processing circuit by using the current generation source. Do Adjusting apparatus for an optical sensor, characterized in that a laser oscillator of the fit. 5. The optical sensor adjustment device according to claim 4, wherein the photoelectric conversion element is a photodiode, and the output terminal is an anode. 6. The optical sensor adjustment device according to claim 4, wherein the adjustment is performed in a wafer state having a plurality of sensor formation regions.