JP2002319669A - Backside incident type photodiode and photodiode array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backside incident type photodiode, capable of suppressing the damage of a photodetector, without reducing the working efficiency at the time of assembling an optical fiber or the like. SOLUTION: According to the backside incident type photodiode, when the optical fiber F is inserted into a recess 1d of the photodiode 10 and mounted, since this component is abutted against a stepped part 1ds, a light-sensing region 1r disposed at a part deeper than the stepped part is protected against the component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a back illuminated photodiode and a photodiode array.

[0002]

2. Description of the Related Art As a photodetector which can be expected to have high sensitivity to short-wavelength light, for example, a back-illuminated CCD as disclosed in JP-A-6-29506 is known. In this CCD, etching is performed from the side (rear surface) of the substrate opposite to the side where the transfer electrode is present, and the thickness of the light receiving section is reduced from 15 μm to about 20 μm.

[0003] In this back-illuminated CCD, the thickness of the light receiving portion is extremely thin, so that even short-wavelength incident light is not absorbed by the semiconductor material before reaching the light receiving portion. The generated carriers reach the light receiving portion without being recombined in the substrate. Therefore, such a back-illuminated photodiode has sensitivity to light having a short wavelength of about 0.1 nm.

[0004]

However, when the thickness of the light receiving section is very small, the mechanical strength is weak. For example, in the field of optical communication, Japanese Patent Application Laid-Open No. 5-129938
As described in Japanese Patent Application Laid-Open Publication No. H10-209, an optical fiber and a photodiode are optically coupled and used. However, in the above-described back-illuminated photodiode, when the optical coupling with the optical fiber is performed, the fiber end comes into contact with the thinned light receiving portion, and the light receiving portion is easily damaged. Such a tendency to damage lowers the production yield.

It is possible to sharpen the tip of the fiber in accordance with the side surface shape of the opening from the back surface of the photodiode to the light receiving portion, that is, the cylindrical shape, to suppress the damage as described above. In such a case, work efficiency is reduced. As described above, the back illuminated photodiode has a problem that it has a very weak mechanical strength due to the presence of the thin plate portion and is easily damaged during assembly.

The present invention has been made in view of such a problem, and provides a back illuminated photodiode capable of suppressing damage to a light receiving portion without lowering work efficiency when assembling an optical fiber or the like. The purpose is to:

[0007]

In order to solve the above-mentioned problems, in a back illuminated photodiode according to the present invention, a photosensitive region is formed on a front surface side of a semiconductor substrate, and a photosensitive region is formed in a direction from the back surface side of the semiconductor substrate to the photosensitive region. In the back-illuminated photodiode in which light is incident on the photosensitive region via the concave portion, the side surface of the concave portion has a step.

According to the photodiode of the present invention, when a light-transmitting optical component such as an optical fiber is attached to the photodiode, the component comes into contact with the step, so that the light-sensitive region located deeper than this is protected. Will be done.

The step has a contact portion with which the peripheral portion of the end face of the optical fiber contacts, and extends from the periphery of the contact portion toward the rear surface so as to regulate the position of the side surface near the end face of the optical fiber. It preferably has a cylindrical surface. In this case, when the optical fiber is inserted into the concave portion, the optical fiber moves to the contact portion along the cylindrical surface, and at the contact portion, the movement of the optical fiber to the deep portion is restricted, and the optical surface is controlled by the cylindrical surface. Side position near the fiber end face (transverse movement)
Is regulated. Further, if an adhesive (resin) is filled between the cylindrical surface and the side surface of the optical fiber, the optical fiber can be more securely fixed. The diameter of the contact portion is desirably set to the cladding diameter of the optical fiber (125 μm).

An electrode for taking out carriers generated in the photosensitive region in response to the incidence of light is provided on the front side of the semiconductor substrate, and the front side of the semiconductor substrate is fixed to the supporting substrate via a resin material. Has a general ring shape,
This ring-shaped electrode is preferably partially cut off along the circumferential direction.

That is, since the thickness of the photosensitive region is thinner than that of the surroundings due to the presence of the concave portion, even when light of a short wavelength is incident, the carrier generated in the photosensitive region is applied to the electrode on the surface side. Can be removed via However, as described above, the mechanical strength of the photosensitive region has decreased due to the thinning of the photosensitive region. Therefore, the photosensitive region of the photodiode of the present invention is reinforced by fixing the front surface side of the semiconductor substrate to the support substrate via a resin material.

However, when the adhesion between the semiconductor substrate and the supporting substrate made of a resin material is low, sufficient reinforcement cannot be performed, so that the electrode has a substantially ring shape. Has been partially cut along the circumferential direction. In this case, at the time of bonding with the resin material, excess resin material or air bubbles are pushed to the outside through the cut portion of the ring-shaped electrode, and the adhesion between the semiconductor substrate and the support substrate by the resin material is improved. The strength of the sensitive area is improved. Note that, in the narrow sense, a ring refers to a shape that continuously surrounds the inside in the circumferential direction, and in the present invention, the case where a part is cut as described above is generally referred to as a ring shape. It shall be.

Preferably, the support substrate is a wiring substrate having a pattern wiring formed thereon, and the electrodes are electrically connected to the pattern wiring via bumps. That is, carriers generated in the photosensitive region in response to light incidence can be extracted through the bumps and the wiring patterns.

Further, the photodiode array of the present invention comprises:
A plurality of the above-mentioned back illuminated photodiodes are formed one-dimensionally or two-dimensionally in a semiconductor substrate. Such a photodiode array can capture a one-dimensional or two-dimensional image, but conventionally, the overall yield has been significantly reduced due to damage to individual photodiodes when an optical fiber is mounted. By using the photodiode of the present invention, it is possible to increase the production yield of the photodiode array without deteriorating the work efficiency at the time of mounting,
Further, since the frequency of defective photodiodes (pixels) can be significantly reduced, the number of pixels in one photodiode array can be increased.

An electrode is provided on the front surface side of the semiconductor substrate for taking out carriers generated in the photosensitive region in response to the incidence of light, and the electrode is located at a position deviating from the depth-extending region of the recess. The photosensitive region located on the region extending in the depth direction of the concave portion can be protected from the electrode.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A back illuminated photodiode according to an embodiment will be described below. The same elements will be denoted by the same reference symbols, without redundant description.

First, the structure will be described.

FIG. 1A is a plan view of a light receiving device in which a back illuminated photodiode 10 according to the embodiment is attached to a support substrate 20, and FIG. 1B is a light receiving device shown in FIG. FIG. 2 is an enlarged sectional view of a main part of a back-illuminated photodiode, taken along the line I (b) -I (b) of the device. In the sectional view shown in FIG. 1B, the lower side indicates the front surface of the back-illuminated photodiode 10, the upper side indicates the back surface, and
In order to easily explain the internal structure, in the plan view shown in FIG. 1A, the illustration of the protective film provided on the back surface side is omitted.

In this light receiving device, a back illuminated photodiode 10 is adhered to a support substrate (wiring board, printed circuit board) 20. The back illuminated photodiode 10 and the support substrate 20 are formed of a resin material interposed therebetween. (Underfill resin) Adhered by RSN. In order to electrically connect the back-illuminated photodiode 10 and the support substrate 20, a conductive bump (bump electrode) B is interposed between them. Instead of this, an insulating bump may be further provided as necessary.

More specifically, the support substrate 20 has a wiring pattern WP thereon, and is connected to electrodes (electrode pads) Ea and Ec on the front side of the back illuminated photodiode 10 via bumps B. .

The back-illuminated photodiode 10 has a light-sensitive region (light-receiving portion) as a light-receiving portion on the front surface side of the semiconductor substrate SB.
1r (1a, 1n, 1i, 1p) is formed, and the recess 1 extends in the direction of the photosensitive region 1r from the back surface side of the semiconductor substrate SB.
d, and light is incident on the photosensitive region 1r through the concave portion 1d.
Has a step 1ds.

The electrodes Ea and Ec are electrodes for taking out carriers generated in the photosensitive region in response to the incidence of light, and the electrodes Ea and Ec are displaced from the region extending in the depth direction of the concave portion 1d. The light-sensitive region 1r, which is provided at the position and is located on the region extending in the depth direction of the concave portion 1d, can be protected from the urging force applied to the electrodes Ea and Ec at the time of attachment.

According to this structure, when a light-transmitting optical component such as an optical fiber is inserted and mounted in the concave portion 1d of the photodiode 10, the component comes into contact with the step portion 1ds.
The light-sensitive region 1r located deeper than this is protected from the component. In addition, even when the optical fiber is attached, it is not necessary to process the tip of the optical fiber with a point. In addition, it can also process.

Therefore, the back illuminated photodiode 1
According to 0, damage to the photosensitive region 1r can be suppressed without lowering the working efficiency at the time of assembling an optical fiber or the like.

The photosensitive region 1 at the deepest part of the concave portion
The thickness of r is reduced to about 10 to 15 μm.

In the following description, the opening on the back side of the step 1ds in the recess 1d is referred to as a first opening, and the opening on the front side is referred to as a second opening.

The diameter of the first opening is approximately 125 μm, and the first opening is located on the surface side of the step 1ds via a flat shelf (intermediate bottom) having a plane perpendicular to the substrate thickness at the step 1ds. And these are located concentrically.

The diameter of the second opening is approximately 10 μm. In addition, although the shape of these openings is circular, it may be a shape along a crystal plane of the semiconductor material, such as a square or a hexagon.

The semiconductor substrate SB includes a high-concentration N-type semiconductor substrate 1b serving as a base, and a low-concentration epitaxial layer 1i epitaxially grown on the surface side of the N-type semiconductor substrate 1b.
A region immediately below the bottom surface of the concave portion 1d (the bottom surface of the second opening: a thin plate portion)
The accumulation layer 1a formed on the back side of the epitaxial layer 1i, and the accumulation layer 1a
And a p-type semiconductor layer (P ⁺ -type diffusion layer) 1p formed on the surface side of the epitaxial layer 1i in a region immediately below the recess 1d.
And

The conductivity type of the low-concentration epitaxial layer 1i is I-type or low-concentration N-type.
It is assumed that it is a low concentration N-type having an impurity concentration of ¹³ / cm ³ or less. Therefore, the I-type indicates a low impurity (carrier) concentration.

To explain the above structure in detail, an N-type semiconductor layer 1n, an I-type epitaxial layer 1i, and a P-type semiconductor layer 1p are sequentially stacked from the back side in a region immediately below the concave portion 1d of the semiconductor substrate SB. These constitute a PIN photodiode. If the concentration of the N-type impurity in the epitaxial layer 1i is increased, it functions as a normal PN junction type photodiode. In any case, the resistance value of the N-type semiconductor layer 1n is set relatively low,
This contributes to efficient formation of a depletion layer in the epitaxial layer 1i.

The high-concentration N-type semiconductor substrate 1b has a high-concentration conductive layer 1b 'having a high concentration on the exposed surface in the recess 1d and on the back surface of the substrate located outside the recess 1d. , Which may be highly concentrated throughout.

The high-concentration N-type substrate 1b is physically and electrically connected to a high-concentration N-type semiconductor layer for contact (referred to as a connection layer (N ⁺ layer diffusion layer)) 1bb 'crossing the epitaxial layer 1i in the thickness direction. It is connected.

The connection layer 1bb 'is physically and electrically connected to the cathode electrode Ec provided on the substrate surface.

The thickness (depth) of the lattice-like high-concentration N-type semiconductor layer 1n is larger than that of the accumulation layer 1a. This N-type semiconductor layer 1n is connected to the N ⁺ -type substrate 1b at the peripheral portion.

Therefore, when a predetermined potential is applied to the cathode electrode Ec, this potential can be applied to the lattice-like high-concentration N-type semiconductor layer 1n via the connection layer 1bb 'and the N ⁺ -type substrate 1b.

The accumulation layer 1a is formed to have a uniform depth so that photoelectrons generated in a shallow region near the back surface of the epitaxial layer 1i can efficiently reach the detection region on the front surface without recombination. To work.

It should be noted that the connection layer 1bb 'is a P-type semiconductor layer 1p
, And the P-type semiconductor layer 1p is provided with the concave portion 1d.
Extends to a region outside the bottom surface (thick plate portion). In other words, the P-type semiconductor layer 1p is the thin plate portion 1 of the semiconductor substrate.
r and extends to the thick plate portion. Since the P-type semiconductor layer 1p is set to have an area larger than the area of the bottom surface defined by the second opening of the concave portion 1d, the electrode Ea is connected to the pattern wiring WP of the wiring board 20 via the bump B. In addition, the impact can be absorbed by the thick plate portion of the semiconductor substrate, and the impact on the thin plate portion can be suppressed to a minimum.

It is more desirable that the P-type semiconductor layer 1p is set to have an area larger than the opening area defined by the first opening of the recess 1d.

As an electrical effect of such a structure, an improvement in the arrival rate of carriers to the electrodes can be mentioned. That is, the area of the P-type semiconductor layer 1p is at least the area of the bottom surface of the recess 1d, preferably the first area of the recess 1d.
Since the area is larger than the area defined by the opening, most of the carriers can reach the P-type semiconductor layer 1p even if carriers generated by light incident from the opening diffuse.

The P-type semiconductor layer 1p is connected to an anode electrode Ea provided on the substrate surface side. Therefore,
When a predetermined potential is applied to the anode electrode Ea, this potential can be applied to the P-type semiconductor layer 1p. A voltage is applied between these electrodes Ec and Ea so that the voltage applied to the photodiode becomes reverse bias.

As described above, the electrodes Ec and Ea are connected to the wiring pattern WP of the support substrate 20 via the bumps B. Therefore, if the above-described voltage is applied to the wiring pattern WP, a drive voltage can be applied to the photodiode of this example.

Each of the semiconductor layers located on the electric path leading to the N-type and P-type layers has a low resistance, and the lattice-type N-type high-concentration semiconductor layer 1n also has a low resistance. The photodiode can realize complete depletion even at a low bias voltage operation of about 2 V or less, and can realize high-speed response. Moreover, since the accumulation layer 1a is formed in the N-type high-concentration semiconductor layer 1n, recombination near the surface of the carrier can be prevented.

The exposed surfaces of the P-type semiconductor layer 1p, the connection layer 1bb 'and the epitaxial layer 1i are covered with a front-side protective film PLf. Accumulation layer 1a, N
The exposed surfaces of the mold semiconductor layer 1n, the recess 1d and the back surface of the substrate are covered with a back surface side protective film PLb. Thereby, it is possible to suppress intrusion of foreign matter into the semiconductor material covered with the protective films PLf and PLb.

The back surface protective film PLb covers the lower bottom of the second opening, that is, the surface of the photosensitive region 1r, and functions as an anti-reflection film.

The entire surface of the exposed surface of the protective film PLb on the back surface of the step portion 1ds and the back surface of the substrate 1b is covered by a back electrode Eb also having a light shielding function. In addition,
The high-concentration conductive layer 1b 'on the rear surface of the substrate located outside the concave portion 1d is electrically and physically connected to the rear electrode Eb provided on the rear surface of the substrate, and applies a fixed potential such as a ground potential to the rear electrode Eb. By doing so, the substrate potential can be grounded. Therefore, the back-illuminated photodiode 1
Light incident on a portion other than the light receiving surface at the bottom of the lower opening of electrode 0
, And can reduce electromagnetic noise emitted to portions other than the light receiving surface 1r.

The materials, thicknesses, impurity concentrations or specific resistances of the above components are as follows.

[0048]

[Table 1]

FIG. 3 is a plan view of the photodiode as viewed from the front side (in the direction of arrow III in FIG. 2). The cathode electrode Ec and the anode electrode Ea are formed in a divided pattern as shown in FIG. In the back-illuminated photodiode 10 of this example, the thickness of the photosensitive region 1r is smaller than that of the surroundings due to the presence of the concave portion 1d.
Even when light of a short wavelength is incident, generated carriers can be extracted through the electrodes Ec and / or Ea. That is, the electrodes Ec and / or Ea are provided on the front surface side of the semiconductor substrate SB in order to take out carriers generated in the photosensitive region 1r in response to the incidence of light, and the front surface side of the semiconductor substrate SB is made of a resin material. Support substrate 2 via RSN
It is fixed to 0.

However, the mechanical strength of the photosensitive region 1r has been reduced by the thinning of the photosensitive region 1r. In this example, the front side of the semiconductor substrate SB is supported on the support substrate 2 via the resin material RSN.
By fixing to 0, the photosensitive region 1r is reinforced.

However, when the adhesion between the semiconductor substrate SB and the support substrate 20 by the resin material RSN is low, sufficient reinforcement cannot be performed.

Therefore, the electrodes Ec and Ea have a substantially ring shape, and the ring-shaped electrodes Ec and Ea
Has been partially cut along the circumferential direction. In this case, when bonding with the resin material RSN, the excess resin material R passes through the cut portions of the ring-shaped electrodes Ec and Ea.
SN or bubbles are pushed out, and the adhesion between the semiconductor substrate SB and the support substrate 20 by the resin material RSN is improved,
Therefore, the intensity of the photosensitive region 1r is improved.

Note that, in a narrow sense, a ring is a shape that continuously surrounds the inside in the circumferential direction, and in the description, a part that is partially cut is generally called a ring shape. And

To describe the electrode structure in detail, the width of the cathode electrode Ec along the circumferential direction is about 200 μm, and the pitch (interval) between the electrodes Ec is about 200 μm. This dimension is effective for facilitating the flow of the resin material RSN when filling the gap between the circuit board 20 and the back-illuminated photodiode 10 with the resin material RSN, and for filling the entire gap with the resin material RSN. Resin material RSN
Since the thin plate portion of the back illuminated photodiode 10 is protected (supported) rather than spreading over the entire gap including the thin plate portion, the mechanical strength thereof can be sufficiently increased. The anode electrode Ea is arranged inside the cathode electrode Ec, and its shape and arrangement are the same as those of the cathode electrode Ec.

FIG. 4 is a longitudinal sectional view of the light receiving device in which the optical fiber F is fixed in the concave portion. The optical fiber F has a concave portion 1
d is in contact with the step 1ds. The step portion 1ds has a contact portion ABT with which the peripheral portion of the end surface of the optical fiber F contacts, and extends from the periphery of the contact portion ABT to the rear surface so that the position of the side surface Fs near the end surface of the optical fiber is regulated. It has a cylindrical surface 1dc.

In this case, when the optical fiber F is inserted into the concave portion 1d in order to perform optical connection (coupling) between the photodiode 10 and the optical fiber F, the optical fiber F is brought into contact with the contact portion ABT along the cylindrical surface 1dc. (Automatic alignment function), the movement of the optical fiber F to the deep portion of the substrate is restricted (functions as a stopper) at the contact portion ABT, and the side surface F near the optical fiber end surface is defined by the cylindrical surface 1dc.
The position of s (lateral movement) is regulated (position regulation function). These function as means for aligning the optical axis of the optical fiber F with the light receiving portion (detection region) 1r of the back-illuminated photodiode 10.

Further, the cylindrical surface 1dc and the optical fiber side surface Fs
If an unillustrated adhesive (resin) is filled in between, the optical fiber F can be fixed more reliably (resin accommodation function).

It is desirable that the first opening is set to the cladding diameter (125 μm) of the optical fiber F.

The second opening is formed by etching the step 1ds (intermediate bottom) of the first opening, which is sufficiently smaller than the diameter of the optical fiber F to be connected. And are formed substantially concentrically. In this example, since the diameter of the second opening is smaller than the diameter of the optical fiber, the optical fiber does not come into contact with the light receiving portion 1r, which is the substrate thin plate portion, and damage to the thin plate portion is prevented.

The dimensions of the first and second openings are 125 μm and 10 μm, respectively.

In this example, since the optical fiber F has a cladding diameter of 125 μm and a core diameter of 10 μm, by adopting the above dimensions, the alignment function at the first opening can be sufficiently achieved, and moreover, the optical fiber F can be applied to a thin plate. Contact can be prevented.
Although the optical fiber F is located in the first opening, these are fixed by a resin adhesive or the like.

Next, a method for manufacturing the light receiving device will be described. In this light receiving device, step (1) is performed in the following order.
To (12).

(1) The epitaxial layer 1i is formed.
That is, the semiconductor substrate 1b is prepared, and the epitaxial layer 1i is grown on the surface of the semiconductor substrate 1b. The semiconductor substrate 1b has a thickness of about 385 μm and a specific resistance of 0.02Ω · cm.
The following substrate. The epitaxial layer 1i has a thickness of 10 to 10.
15 μm, and the specific resistance is several hundred Ω · cm or more. CV
Method D or the like can be used.

(2) The connection layer 1bb 'for the cathode is formed. That is, after forming a mask having an opening in a predetermined region on the surface of the epitaxial layer 1i, an N-type impurity (phosphorus) is diffused through the opening to form a connection layer 1bb 'reaching the substrate 1b.

(3) The anode P-type semiconductor layer 1p is formed inside the connection layer 1bb '. That is, a mask having an opening in a region where this layer is to be formed is placed on the epitaxial layer 1.
Formed again on the i surface and P-type impurities (boron) from the surface side
To spread. The impurity concentration of the P-type semiconductor layer 1p is 1 × 1
The thickness is set at about 0 ¹⁹ / cm ³ or more and about 0.5 μm in thickness.
As a result, the connection layer 1bb 'having an impurity concentration of 1 × 10 ¹⁹ / cm ³ or more and a thickness of about 10 to 15 μm is
This means that it is formed so as to surround p.

(4) A front-side protective film PLf is formed. That is, the surface-side protective film PLf is formed by oxidizing the exposed surfaces of the P-type semiconductor layer 1p and the epitaxial layer 1i. This oxidation is thermal oxidation, and the surface side protective film PL
SiO ₂ is formed as f.

(5) The back surface of the substrate is etched to form a concave portion 1d having a two-step concave structure. First, a mask is formed on the back surface of the semiconductor substrate 1b in which only the first opening formation region is exposed. Using this mask, a first opening is formed by dielectrically coupled plasma (ICP) etching.

After the formation of the first opening, the etching is temporarily stopped. Next, the bottom (middle bottom) of the formed first opening
Is formed on the bottom portion in which only the second opening formation scheduled region is exposed. Using this mask, a second opening is again formed by dielectrically coupled plasma (ICP) etching. The step of forming the second opening includes the epitaxial layer 1
The process ends when i is exposed. In this example, the first opening is 1
It is about 25 μmφ, and the second opening is about 10 μmφ.

(6) A patterned semiconductor layer 1n is formed. That is, a mask (lattice shape) having a predetermined pattern is formed on the bottom surface of the concave portion 1d, and an N-type impurity (phosphorus) is diffused into the epitaxial layer 1i through the mask. This impurity concentration is set to about 2 × 10 ¹⁸ / cm ³ .

(7) An accumulation layer is formed on the exposed surface in the same region as the patterned semiconductor layer 1n.

In general, when accumulating, phosphorus may be ion-implanted into the N-type silicon substrate. However, the ion-implanted layer becomes amorphous, and is recrystallized and ion-implanted phosphorus atoms by a subsequent heat treatment. Must be activated. Usually this heat treatment (annealing)
For example, so-called two-step annealing in which heat treatment at about 600 ° C. and about 1000 ° C. are continuously performed is performed.

(8) A backside protective film PLb is formed. That is, the protective film PLb is formed on the exposed surface of the substrate 1b including the concave portion 1d and the back surface and the exposed surface of the epitaxial layer 1i.
To form When SiNx (silicon nitride) is used as the protective film PLb, a CVD method is used for the formation.

(9) Cathode and anode electrodes Ec, E
a is formed. That is, a contact hole is formed in a region corresponding to the n-type connection layer 1bb 'and the P-type semiconductor layer 1p in the front side protective film PLf, and the n-type connection layer 1bb' and the P-type semiconductor are formed through the contact hole. Aluminum is deposited on the layer 1p to form electrodes Ec and Ea, respectively. Note that S is further added on these by CVD or the like.
An iO ₂ protective film may be formed.

(10) The back surface electrode Eb for shading and grounding is formed. That is, after a contact hole is formed in a predetermined region of the back surface side protective film PLb, the surface of the substrate 1b exposed by the protective film PLb and the contact hole is covered with the electrode Eb. Aluminum can be used as an electrode material. The high concentration layer 1 to which the electrode Eb is connected
b 'is formed at an appropriate time before step (8).

(11) The circuit board 20 and the back illuminated photodiode 10 are electrically connected. That is, the substrate S
If there is a protective film (not shown) covering the surface of B, the portions corresponding to the electrodes Ea and Ec are removed, and then a conductive bump B is formed on the anode and cathode electrodes Ea and Ec. The wiring pattern WP on the circuit board 20 and the electrodes Ea and Ec are connected by the bumps B. The bump B is made of Ni / Au. In addition, the circuit board 20
If necessary, a circuit such as an amplifier for amplifying the output signal from the photodiode 10 may be provided.

(12) The gap between the back illuminated photodiode 10 and the printed circuit board 20 connected by the bumps is filled with a resin material RSN and cured to complete the light receiving device shown in FIG.

Next, the back illuminated photodiode 10
Will be described. This photodiode array is formed in a single semiconductor substrate, and the one photodiode 1 is attached to a wiring pattern WP formed on a single wiring substrate 20.
The connection is made via a bump in the same manner as 0.

FIG. 5 shows a plurality of back-illuminated photodiodes 1.
FIG. 6 is a plan view of a light receiving device in which a back-illuminated photodiode array in which 0s are two-dimensionally arranged is attached to a wiring board 20, and FIG. 6 is a cross-sectional view taken along the line IV-IV of the light receiving device shown in FIG. is there.

The array type back illuminated photodiode is
A plurality of optical fibers F are formed at predetermined intervals on the same substrate, and are optically connected to the respective openings (recesses 1d). Each of the concave portions 1d is formed in a double concave shape as in the above embodiment, and the optical fiber F is located in each of the first openings, and these are fixed by a resin adhesive or the like.

According to the back-illuminated photodiode array, a two-dimensional image incident through the optical fiber F can be obtained. The back-illuminated photodiode 10 may be arranged one-dimensionally. In this case, the back illuminated photodiode array can obtain a one-dimensional image. In other words, this photodiode array is formed by forming a plurality of one-dimensional or two-dimensional back-illuminated photodiodes 10 in the semiconductor substrate SB.

Conventionally, the yield as a whole has been significantly reduced due to the damage of individual photodiodes at the time of mounting an optical fiber. However, by using the above-described photodiode 10, the photodiode array can be mounted without lowering the work efficiency at the time of mounting. Since the manufacturing yield can be increased and the frequency of defective photodiodes (pixels) can be significantly reduced, the number of pixels in one photodiode array can be increased.

Further, the conductivity type of the semiconductor can be reversed. That is, N-type and P-type are interchangeable.

The anode and cathode electrodes E
The shapes of a and Ec are roughly disk-shaped and may be divided.

FIG. 7 is a diagram showing another planar pattern of the N-type semiconductor layer 1n. Although the above-described N-type semiconductor layer 1n has a lattice shape, it may have a ring shape, a substantially ring shape, a concentric double ring shape, or the like as shown in FIG.

As described above, in the above-mentioned back illuminated photodiode, the low-concentration first conductivity type (N +) is formed on the first surface (front surface) side of the first conductivity type (N + type) semiconductor substrate 1b.
^- -type) epitaxial layer 1i is formed, the substrate 1b opposed to the surface of the first conductive type epitaxial layer 1i (first
A high-concentration second conductivity type (P ⁺ -type) diffusion layer 1p is formed in a predetermined region (surface: front surface), and a first concentration is formed in a region facing the high-concentration second conductivity type diffusion layer 1p on the exposed surface side of the semiconductor substrate 1b. A back-illuminated semiconductor photodiode having an opening (1d) formed so as to expose a conductive type epitaxial layer (1i), and detecting light incident from the opening (1d).
Is formed in a double concave shape including a first opening and a second opening. The first opening has a larger diameter than the second opening and is formed substantially concentrically.

[0086]

According to the back illuminated photodiode of the present invention, it is possible to provide a back illuminated photodiode capable of suppressing damage to the light receiving portion without lowering the working efficiency at the time of assembling an optical fiber or the like.

[Brief description of the drawings]

FIG. 1A is a plan view of a light receiving device in which a back-illuminated photodiode 10 according to an embodiment is attached to a support substrate 20, and FIG. 1B is a light receiving device shown in FIG. It is I (b) -I (b) arrow line sectional drawing of an apparatus.

FIG. 2 is an enlarged sectional view of a main part of a back illuminated photodiode.

FIG. 3 is a plan view of the photodiode as viewed from the front side (the direction of arrow III in FIG. 2).

FIG. 4 shows I (b) -I (b) of an optical fiber and a light receiving device.
It is arrow sectional drawing.

FIG. 5 is a plan view of a light receiving device in which a back-illuminated photodiode array in which a plurality of back-illuminated photodiodes 10 are arranged two-dimensionally is mounted on a wiring board 20.

FIG. 6 is a sectional view taken along the line IV-IV of the light receiving device shown in FIG.

FIG. 7 is a diagram showing a plane pattern of an N-type semiconductor layer 1n.

[Explanation of symbols]

10: back-illuminated photodiode, SB: semiconductor substrate,
1r: photosensitive region, 1d: concave portion, 1ds: step portion.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 BA06 CA02 CA32 GA02 GA09 HA14 HA31 5F049 MA04 NA09 NA10 NB03 NB05 QA06 QA20 RA02 SS02 SZ20 TA14 5F088 AA01 BA16 BB02 BB03 DA17 EA03 EA04 EA20 GA07 GA08 GA10 JA14

Claims (6)

[Claims] 1. A photosensitive region is formed on a front surface side of a semiconductor substrate, and has a concave portion extending from the rear surface side of the semiconductor substrate toward the photosensitive region. Light is transmitted to the photosensitive region through the concave portion. In the back-illuminated photodiode, the side surface of the concave portion has a step portion. 2. The stepped portion has a contact portion with which the peripheral portion of the end face of the optical fiber is in contact, and is positioned from the periphery of the contact portion so that the position of the side surface near the end surface of the optical fiber is regulated. 2. The back illuminated photodiode according to claim 1, wherein the photodiode has a cylindrical surface extending in the back direction. 3. An electrode for taking out carriers generated in the light-sensitive region in response to the incidence of light on a front side of the semiconductor substrate, wherein the front side of the semiconductor substrate is a support substrate via a resin material. 3. The back-illuminated photodiode according to claim 2, wherein the electrode has a substantially ring shape, and the ring-shaped electrode is partially cut along a circumferential direction. 4. . 4. The substrate according to claim 3, wherein the support substrate is a wiring substrate having a pattern wiring formed thereon, and the electrodes are electrically connected to the pattern wiring via bumps. 2. The back-illuminated photodiode described in 1. above. 5. A photodiode array comprising a plurality of one-dimensional or two-dimensional back-illuminated photodiodes according to claim 1 formed in said semiconductor substrate. 6. An electrode on a surface side of the semiconductor substrate for taking out carriers generated in the light-sensitive region in response to the incidence of light, the electrode being displaced from the depth-extending region of the concave portion. 2. The back illuminated photodiode according to claim 1, wherein the photodiode is provided at an inclined position.