JPH09331080A - Semiconductor device with photodetector and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photodiode structure having a high photoreceiving sensitivity and excellent frequency characteristics while optimizing characteristics of a bipolar element mounted in mixture on the same semiconductor substrate. SOLUTION: Since a P-N junction in an anode common type photodiode forming region 2 is formed of low concentration P<-> type epitaxial layer 12 and N<-> type epitaxial layer 17, a depletion layer has a sufficiently wide width, and can lower the capacity of the depletion layer. The layer 17 is disposed on a P<+> type embedded layer 13 via a P<-> type epitaxial layer 14. In a bipolar element forming region 4, the layer 17 is disposed directly on the N<+> type embedded layer 12. The epitaxial layers of suitable thicknesses can be respectively formed in the bipolar element and the photodiode, and the characteristics required for the element and the photodiode can be simultaneously satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device including at least a light receiving element such as a photodiode and a manufacturing method thereof.

[0002]

2. Description of the Related Art A photodiode, which is a light receiving element, is widely used as an optical sensor for converting an optical signal into an electric signal, such as a control optical sensor in various photoelectric conversion devices. Such a photodiode is often formed together with other elements such as a transistor, a resistor and a capacitor on the same chip, and is generally formed by a bipolar IC (In
It is often manufactured according to the manufacturing process of integrated circuit).

FIG. 13 shows a sectional structure of a conventional semiconductor device in which such a photodiode and a bipolar transistor are mounted together. This semiconductor device has an anode common type photodiode formation region 200 and a cathode common type photodiode formation region 30.
A photodiode forming region 100 of 0 and a bipolar element forming region 400 are included.

Of these, the anode common type photodiode forming region 200 is a P type silicon substrate 111.
High-concentration P-type buried layer (P ⁺ buried layer) formed on top
113 and a low-concentration N-type epitaxial layer (N ⁻ epitaxial layer) formed on the P ⁺ buried layer 113
117, a cathode lead-out portion 122a formed of a high-concentration N-type diffusion layer formed near the surface of the N ⁻ epitaxial layer 117, and an adjacent bipolar element formation region 400.
And the N ⁻ epitaxial layer 11 is formed in the region on the boundary side with the cathode common type photodiode forming region 300.
7 and a P ⁺ isolation layer 119 respectively formed so as to reach the P ⁺ buried layer 113 from the surface of the No. 7 surface. The cathode lead-out portion 122a is connected to the cathode lead-out wiring 124c, and the P ⁺ isolation layer 119 formed in the boundary region with the bipolar element formation region 400 is connected to the anode lead-out wiring 124d.

The cathode common type photodiode forming region 300 includes a high-concentration N type buried layer (N ⁺ buried layer) 112 formed on a P type silicon substrate 111.
An epitaxial layer 117, N ^{- -} N formed on the N ⁺ buried layer 112 and the anode was taken out portion 121a formed of a high concentration P-type diffusion layer formed in the vicinity of the surface of the epitaxial layer 117, N ^- epitaxial layer The N ⁺ plug-in layer 118 formed so as to reach the N ⁺ buried layer 112 from the surface of the 117 and the P ⁺ buried layer 113 from the surface of the N ⁻ epitaxial layer 117 at the boundary between the adjacent region. And the formed P ⁺ isolation layer 119. Anode take-out section 12
1a is connected to the anode lead-out wiring 124a, and the N ⁺ plug-in layer 118 is connected to the cathode lead-out wiring 1a.
24b.

The bipolar element forming region 400 is formed of an N ⁺ buried layer 112 formed on a P type silicon substrate 111.
And a base region 1 including an N ⁻ epitaxial layer 117 formed on the N ⁺ buried layer 112 and a P-type diffusion layer formed in the vicinity of the surface of the N ⁻ epitaxial layer 117.
20, an emitter 122b formed of a high-concentration N-type diffusion layer formed near the surface of the base region 120, a base extraction portion 121b formed of a high-concentration P-type diffusion layer formed near the surface of the base region 120, An N ⁺ plug-in layer 118 formed to reach the N ⁺ buried layer 112 from the surface of the N ⁻ epitaxial layer 117, and a high-concentration N-type diffusion layer formed near the surface of the N ⁺ plug-in layer 118. It includes a collector extraction portion 122c and a P ⁺ isolation layer 119 formed so as to reach the P ⁺ buried layer 113 at the boundary portion with the adjacent region. The emitter 122b is connected to the emitter lead-out wiring 124e, the base lead-out portion 121b is connected to the base lead-out wiring 124f, and the collector lead-out portion 122c is connected to the collector lead-out wiring 124g.

A silicon oxide film 125 as an insulating film is formed on the entire surface so as to cover the above element structure, and a second wiring layer 126 is further formed on the silicon oxide film 125 and patterned into a predetermined shape. . Further, a silicon nitride film 127 as an overpassivation film is formed so as to cover the entire structure described above.

As described above, the anode common type photodiode forming region 200 has an anode common structure in which the anode is short-circuited with the P type silicon substrate 111 and grounded in a circuit manner, and the cathode common type photodiode forming region is formed. 300 has a cathode common structure in which the cathode is connected to the power supply (Vcc) in a circuit manner.

Generally, the photosensitivity of a photodiode is determined by the number of carriers generated in the depletion layer and the number of carriers generated outside the depletion layer that reach the depletion layer by diffusion. Therefore, in order to improve the light receiving sensitivity, it is necessary to dispose a low-concentration diffusion layer in which a depletion layer easily spreads and a diffusion length of minority carriers is long in a portion where light is absorbed. On the contrary, disposing the high-concentration diffusion layer in the portion where the light is absorbed causes a decrease in the light-receiving sensitivity because the diffusion length of the minority carriers generated in the high-concentration diffusion layer is short.

Further, generally, the arrival depth of the laser light penetrating into the silicon crystal depends on the wavelength of the light. For example CD
With a laser beam of wavelength 780 nm used for (compact disc), MD (mini disc), etc., the light absorption coefficient is about 1 × 10 ⁻³ / cm, and for the wavelength of 650 nm used for DVD (digital video disc) etc. , The light absorption coefficient is about 3 × 10 ⁻³ / cm, and further 45
At a wavelength of 0 nm, the light absorption coefficient is about 3 × 10 ⁻⁴ / cm. Correspondingly, the proportion of absorbed light is 1 /
The depth (absorption length of light) from the silicon-silicon oxide film interface that becomes e is about 10 μm at a wavelength of 780 nm, 65
It is about 3μm at 0nm and about 0.3μ at the wavelength of 450nm.
m. Under such a premise, in order to obtain sufficient light receiving sensitivity of the photodiode, it is necessary to take out carriers generated at a depth of at least twice the absorption length of light as a photocurrent.

On the other hand, in the bipolar transistor, in order to satisfy the requirement of high speed, it is desirable that the thickness of the N ⁻ epitaxial layer 17 on the N ⁺ buried layer 12 in FIG. In the case of a bipolar transistor that requires the operating frequency of
The thickness of the N ⁻ epitaxial layer 17 is generally about 1 μm.

Therefore, if it is attempted to mount a photodiode together with a high-speed bipolar transistor on a single chip, it will be 65 even if the wavelength of light is 450 nm.
With respect to light having a wavelength of 0 nm or 780 nm, it is necessary to allow carriers generated by light absorption to be output as a photocurrent at a position considerably deeper than the N ⁻ epitaxial layer 17. However, as shown in FIG. 13, since the high-concentration P ⁺ buried layer 13 exists below the N ⁻ epitaxial layer 17 of the photodiode (anode common type photodiode forming region 2), the P −
^{+ The} carriers generated in the buried layer 13 are recombined before reaching the depletion layer and cannot contribute to the light receiving sensitivity.

As a means for dealing with such a problem, a semiconductor device including a photodiode having a structure shown in FIG. 14, for example, has been conventionally known. In this figure, the same components as those of the above-mentioned conventional example (FIG. 13) are designated by the same reference numerals, and the description thereof will be omitted as appropriate. In this photodiode, after the P ⁺ buried layer 113 and the N ⁺ buried layer 112 are formed in the photodiode formation region 100 ', N is buried.
^- an epitaxial layer 114 was formed, then, N ⁺ buried layer 115 and P of the bipolar element forming region 400 '
^{After the +} buried layer 116 is formed, the N ⁻ epitaxial layer 117 in the bipolar element formation region 400 ′ is formed.

[0014]

However, in the structure of the photodiode (FIG. 14) described above, the P ⁺ buried layer 113, the N ⁺ buried layer 112 and the N ⁻ epitaxial layer 114 in the photodiode forming region 100 ′ are formed. later, the bipolar element forming region 400 'N ⁺ buried layer 115, P ⁺ buried layer 116 and N ^- so has been a structure of forming an epitaxial layer 117, a bipolar element forming region 400' N ⁺ buried layer 115 and P
^{+ By the} long-time high-temperature heat treatment when forming the buried layer 116, the P of the photodiode formation portion 100 'is
There is a problem that the ⁺ buried layer 113 and the N ⁺ buried layer 112 are diffused to a considerably upper portion (about 10 μm). For this reason, in order to increase the sensitivity of the photodiode, the thickness of the N ⁻ epitaxial layer 114 must be made considerably thick (20 μm or more), and the P ⁺ buried layer 113 depending on the target wavelength of light. It was also difficult to control the embedded position of the N ⁺ buried layer 112.

The present invention has been made in view of the above problems, and an object thereof is to optimize the characteristics of bipolar devices mixedly mounted on the same semiconductor substrate, and at the same time, to provide a photodetector having high light-receiving sensitivity and excellent frequency characteristics. It is an object of the present invention to provide a semiconductor device including a light receiving element capable of obtaining a diode structure and a manufacturing method thereof.

[0016]

A semiconductor device including a light receiving element according to the present invention includes at least a first conductivity type semiconductor and a second conductivity type semiconductor.
A semiconductor device including a light-receiving element having a junction with a conductive type semiconductor, wherein the first conductive type semiconductor is a first conductive type high concentration diffusion layer provided on a first conductive type semiconductor substrate, and the first conductive type high concentration diffusion layer.
A first conductivity type low concentration epitaxial layer provided on the conductivity type high concentration diffusion layer, and a second conductivity type semiconductor,
Second layer provided on the first conductivity type low concentration epitaxial layer
It is composed of a conductive type epitaxial layer and a second conductive type diffusion layer provided on the second conductive type epitaxial layer. This semiconductor device further includes a second-conductivity-type high-concentration diffusion layer provided in another region on the first-conductivity-type semiconductor substrate, and a second-conductivity-type high-concentration diffusion layer provided on the second-conductivity-type high-concentration diffusion layer. It is also possible to provide a bipolar device including a low concentration epitaxial layer.
Further, the first conductive type semiconductor is formed from the surface of the second conductive type epitaxial layer forming the second conductive type semiconductor.
It is also possible to divide the second conductivity type semiconductor into a plurality of parts by another first conductivity type high concentration diffusion layer which penetrates the conductivity type low concentration epitaxial layer and reaches the first conductivity type high concentration diffusion layer. is there.

A method of manufacturing a semiconductor device including a light receiving element according to the present invention includes at least a light receiving element having a junction between a first conductivity type semiconductor and a second conductivity type semiconductor, and a semiconductor substrate on which the light reception element is formed. A method of manufacturing a semiconductor device including a bipolar element provided in another region of
A step of selectively forming a second conductivity type high-concentration diffusion layer as a buried layer of the bipolar element in at least a bipolar element formation region on the conductivity type semiconductor substrate; and a first conductivity type high concentration layer as an element isolation layer of the bipolar element. Selectively forming a concentration diffusion layer, and selectively forming a first conductivity type high concentration diffusion layer as a buried layer of the light receiving element in at least the light receiving element formation region on the first conductivity type semiconductor substrate; After growing the first conductivity type low concentration epitaxial layer on the entire surface,
A step of selectively removing the first-conductivity-type low-concentration epitaxial layer other than the light-receiving element formation region; a step of growing a second-conductivity-type low-concentration epitaxial layer on the entire surface; And a step of forming at least a second conductivity type diffusion layer in the region near the surface of the epitaxial layer.

In the semiconductor device including the light receiving element of the present invention,
A junction (that is, a PN junction) between the first conductivity type semiconductor and the second conductivity type semiconductor in the light receiving element is a first conductivity type of the same conductivity type provided on the first conductivity type high concentration diffusion layer as a buried layer. The low-concentration epitaxial layer and the second conductivity type epitaxial layer provided below the second conductivity type diffusion layer as the surface diffusion layer of the second conductivity type semiconductor have a junction structure between the epitaxial layers. The width of the depletion layer can be sufficiently widened, and the depletion layer capacitance (parasitic capacitance) can be reduced. Further, a bipolar element including a second-conductivity-type high-concentration diffusion layer and a second-conductivity-type low-concentration epitaxial layer provided on the second-conductivity-type high-concentration diffusion layer is mixed and formed on the semiconductor device. In this case, by adopting the two-layer epitaxial structure in the light receiving element region, the diffusion length of the minority carriers is short and the light receiving sensitivity is high without being caught by the thickness of the second conductivity type low concentration epitaxial layer in the bipolar element region. It is possible to optimally set the depth of the buried layer (first conductivity type high-concentration diffusion layer) in the light-receiving element region which causes the decrease. Further, the second conductive semiconductor
The second conductivity type high concentration diffusion layer penetrates from the surface of the conductivity type epitaxial layer to the first conductivity type high concentration diffusion layer through the first conductivity type low concentration epitaxial layer forming the first conductivity type semiconductor. When the two-conductivity type semiconductor is divided into a plurality of parts, most of the carriers generated by the light incident on the opening of the adjacent light receiving element (photodiode) are used for the division. Since they are recombined in the high-concentration diffusion layer, crosstalk between adjacent light receiving elements is reduced.

In the method of manufacturing the semiconductor device including the light receiving element of the present invention, the epitaxial layer of the bipolar element is formed of only the second conductivity type low concentration epitaxial layer, while the epitaxial layer of the light receiving element is the first conductive layer. Since it is formed of two layers, the low-concentration epitaxial layer and the second-conductivity-type low-concentration epitaxial layer, the film thickness of the epitaxial layer required for each element can be controlled separately and arbitrarily.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a sectional structure of a semiconductor device including a light receiving element according to an embodiment of the present invention. This semiconductor device is a semiconductor device in which a photodiode and a bipolar transistor are mixedly mounted on the same substrate, and is formed according to a manufacturing process of a bipolar IC.

This semiconductor device includes a photodiode formation region 1 including an anode common type photodiode formation region 2 and a cathode common type photodiode formation region 3, and a bipolar element formation region 4.

Of these, the anode common type photodiode forming region 2 is a high-concentration P-type buried layer (P ⁺ buried layer) 13 formed on a P-type silicon substrate 11.
And a low concentration of P formed on the P ⁺ buried layer 13.
Type epitaxial layer (P ^- epitaxial layer) 14,
A low concentration of N formed on the P ⁻ epitaxial layer 14
Type epitaxial layer (N ⁻ epitaxial layer) 17,
A cathode lead-out portion 22a formed of a high-concentration N-type diffusion layer formed near the surface of the N ⁻ epitaxial layer 17,
P ⁺ isolations are formed in the region on the boundary side between the adjacent bipolar element forming region 4 and the cathode common type photodiode forming region 3 so as to reach the P ⁺ buried layer 13 from the surface of the N ⁻ epitaxial layer 17. And layer 19. The cathode lead-out portion 22a is connected to the cathode lead-out wiring 24c formed of the first wiring layer through a contact hole which is selectively opened in the silicon oxide film 23 formed so as to cover the element structure described above. There is. Further, the P ⁺ isolation layer 19 formed in the boundary region with the bipolar element formation region 4 is connected to the anode lead-out wiring 24d through a contact hole selectively opened in the silicon oxide film 23. Here, the P ⁺ buried layer 13 and the cathode extraction portion 22a are formed for the purpose of reducing parasitic resistance.

The cathode common type photodiode forming region 3 includes a high-concentration N-type buried layer (N ⁺ buried layer) 12 formed on a P-type silicon substrate 11 and the N ^+.
N ⁻ epitaxial layer 1 formed on the buried layer 12
7 and an anode lead-out portion 21 composed of a high-concentration P-type diffusion layer formed in the vicinity of the surface of the N ⁻ epitaxial layer 17.
a and, N ^- and N ⁺ plug layer 18 formed so as to reach from the surface of the epitaxial layer 17 to the N ⁺ buried layer 12, N at the boundary between the adjacent areas ^- P ⁺ buried from the surface of the epitaxial layer 17 And a P ⁺ isolation layer 19 formed to reach the layer 13.
The anode lead-out portion 21a is connected to the anode lead-out wiring 24a formed of the first wiring layer through a contact hole selectively opened in the silicon oxide film 23 formed so as to cover the above element structure. There is. Also, N
^{The +} plug-in layer 18 is connected to the cathode lead-out wiring 24b via a contact hole selectively opened in the silicon oxide film 23. Where N ⁺ buried layer 1
2 and the anode extraction portion 21a are formed for the purpose of reducing parasitic resistance.

The bipolar element forming region 4, the N ⁺ buried layer 12 formed on P-type silicon substrate 11, the N ⁺ N is formed on the buried layer 12 ^- epitaxial layer 17, N ^- epitaxial A base region 20 made of a P-type diffusion layer formed near the surface of the layer 17, an emitter 22b made of a high-concentration N-type diffusion layer formed near the surface of the base region 20, and a region near the surface of the base region 20. The base lead-out portion 21b formed of the high-concentration P-type diffusion layer formed, the N ⁺ plug-in layer 18 formed so as to reach the N ⁺ buried layer 12 from the surface of the N ⁻ epitaxial layer 17, and the N ⁺ plug-in A collector take-out portion 22 formed of a high-concentration N-type diffusion layer formed near the surface of the layer 18
c, and a P ⁺ isolation layer 19 formed so as to reach the P ⁺ buried layer 13 at the boundary with the adjacent region. The emitter 22b is connected to the emitter lead-out wiring 24e formed of the first wiring layer through a contact hole which is selectively opened in the silicon oxide film 23 formed so as to cover the above element structure. The base take-out portion 21b is provided with a base take-out wiring 2 through a contact hole selectively opened in the silicon oxide film 23.
It is connected to 4f. The collector take-out part 22c is
The collector lead-out wiring 24g is connected through a contact hole selectively opened in the silicon oxide film 23.

A silicon oxide film 25 as an insulating film is formed on the entire surface so as to cover the above element structure, and a second wiring layer 26 made of aluminum or the like is further formed thereon.
Are formed and patterned into a predetermined shape. Further, a silicon nitride film 27 as an overpassivation film is formed so as to cover the above entire structure.

As described above, in the anode common type photodiode formation region 2, the silicon substrate 1 is used.
1 is connected to the P ⁺ buried layer 13, further P ⁺ buried layer 13 is connected to the anode lead-out wires 24d by P ⁺ isolation layer 19. That is, this photodiode has an anode common structure in which the anode is short-circuited with the P-type silicon substrate 11 and is grounded in a circuit manner.

On the other hand, in the cathode common type photodiode forming region 3, the N ⁺ buried layer 12 is formed as N ^+.
The plug-in layer 18 is connected to the cathode lead-out wiring 22b which is connected to the power supply (Vcc). That is, this photodiode has a cathode common structure in which the cathode is connected to the power supply (Vcc) in a circuit manner.

Next, the operation of the semiconductor device including the light receiving element having the above structure will be described.

As shown in FIG. 1, the PN junction in the anode common type photodiode forming region 2 of this semiconductor device is a P ^- epitaxial layer 14 having a low concentration.
And N ⁻ epitaxial layer 17, the width of the depletion layer can be sufficiently widened and the capacity of the depletion layer can be reduced.

Further, as shown in FIG. 1, a low-concentration N ^- epitaxial layer 17 is not directly disposed on the P ⁺ buried layer 13 as in the conventional case, but an appropriate thickness is provided. Through the low concentration P ⁻ epitaxial layer 14 having
An N ⁻ epitaxial layer 17 is arranged thereon.
Therefore, in this region, the P ⁺ buried layer 13 is
Up to the depth of N ⁻ epitaxial layer 17 and P ⁻
It is determined by the sum of the depth of the epitaxial layer 14.

On the other hand, in the bipolar element forming region 4, the P ⁻ epitaxial layer 14 is formed on the N ⁺ buried layer 12.
Is not present, and the N ⁻ epitaxial layer 17 is directly arranged. Therefore, the depth from the surface to the N ⁺ buried layer 12 is determined only by the thickness of the N ⁻ epitaxial layer 17.

Therefore, in the bipolar element forming region 4, the depth of the N ⁻ epitaxial layer 17 is, for example, about 1 μm, considering only that the characteristics of the NPN bipolar transistor can be optimized. A relatively small value can be adopted. On the other hand, in the anode common type photodiode formation region 2,
Even if the N ⁻ epitaxial layer 17 is thin as described above, P
^- if the epitaxial layer 14 sufficiently thick, after all P
Since the N-junction surface is formed at a position sufficiently deep from the surface, it is possible to satisfy the condition for optimizing the characteristics of the common anode photodiode.

That is, in the anode common type photodiode forming region 2, since the diffusion length of the minority carriers is short, a high concentration of P which causes a decrease in the light receiving sensitivity is obtained.
⁺ Buried layer 13 or to place a sufficiently deep position, or it is also possible to arrange an optimal depth depending on the light-receiving wavelength, it is possible to obtain a high sensitivity and high-speed photodiode corresponding to the wavelength used. On the other hand, in the bipolar element formation region 4, since the N ⁻ epitaxial layer 17 on the N ⁺ buried layer 12 can be set sufficiently thin, the NPN
It is possible to sufficiently secure the high speed of the bipolar transistor.

As described above, in the present embodiment, the semiconductor device capable of simultaneously satisfying the formation condition required for the bipolar element formation region 4 and the formation condition required for the anode common type photodiode formation region 2 is provided. can get.

A method of manufacturing a semiconductor device including the light receiving element shown in FIG. 1 will be described with reference to FIGS.

First, as shown in FIG. 2A, a silicon oxide film 41 having a thickness of, for example, about 100 nm is formed on the surface of a P-type silicon substrate 11 by a normal thermal oxidation method, and then a photoresist is formed. Is used as a mask, phosphorus (P) is selectively ion-implanted into the bipolar element formation region 4 and the cathode common type photodiode formation region 3,
Ion implantation layer 1 as a source of N ⁺ buried layer 12 described later
2'is formed. In this case, the implantation energy is, for example, 50 keV, and the dose amount is, for example, 8 × 10 ¹⁴ / cm ^2.
And Further, using the photoresist as a mask, boron (B) is selectively ion-implanted into the anode common type photodiode formation region 2 to form an ion-implanted layer 13 'which becomes a source of a P ⁺ buried layer 13 described later. In this case, the implantation energy is, eg, 30 keV, and the dose amount is, eg, 2.5 × 10 ¹⁵ / cm ² .

Next, for example, nitrogen (N ₂ ) at 1200 ° C.
Annealing (heat treatment) is performed for about 80 minutes in the atmosphere to activate the impurity ions implanted in the above step, and then annealing (heat treatment) is performed for about 20 minutes in a wet oxygen (O ₂ ) atmosphere at 1200 ° C., for example. ) Is performed to remove lattice defects caused by damage at the time of ion implantation. Then, the silicon oxide film 41 is removed using hydrofluoric acid. As a result, as shown in FIG. 2B, N ⁺
Buried layer 12 and P ⁺ buried layer 13 are formed.

Next, as shown in FIG.
P over the entire surface under the forming conditions of μm and resistivity of 20 Ω · cm.
^- the epitaxial layer 14 is deposited. At this time, as shown in the same figure, the N ⁺ burying layer 12 and the P ⁺ burying layer 13 are diffused (auto-doped) to the inside of the P ⁻ epitaxial layer 14 by the heat applied during the epitaxial growth.

Next, as shown in FIG. 4, anisotropic etching such as RIE (reactive ion etching) is carried out using the photoresist as a mask, and the P ^- pitaxial layer 14 other than the anode common type photodiode formation region 2 is formed.
Is removed. At this time, the P ^- pitaxial layer 1 in the region other than the anode common type photodiode forming region 2 is formed.
4 does not have to be completely removed, and may be removed up to the vicinity of the N ⁺ buried layer 12. This is N
^- heat treatment of the thermal processing and bipolar isolation in the formation of the epitaxial layer 17, N ⁺ buried layer 1
P remaining on the 2 ^- epitaxial layer 14 is because incorporated in a portion of N ⁺ buried layer 12 by diffusion from the N ⁺ buried layer 12.

Next, as shown in FIG. 4, an N ^- epitaxial layer 17 is formed on the entire surface. The formation conditions at this time are, for example, a film thickness of 1.5 μm and a resistivity of 1.0 Ω · cm.

Next, as shown in FIG. 5, a silicon oxide film (not shown) having a thickness of about 10 nm is formed by a thermal oxidation method.
Of the N ⁺ buried layer by selectively ion-implanting phosphorus into the collector extraction portion of the bipolar element formation region 4 and the cathode extraction portion of the cathode common type photodiode formation region 3 using the photoresist as a mask. An N-type high-concentration diffusion layer reaching 12 is formed, and this is used as an N ⁺ plug-in layer 18. in this case,
The implantation energy is, for example, 70 keV, and the dose amount is, for example, 5 × 10 ¹⁵ / cm ² .

Next, as shown in FIG. 5, boron is selectively ion-implanted into the isolation portion of the bipolar element formation region 4 and the anode extraction portion of the common anode type photodiode formation region 2 using the photoresist as a mask. Then, the P ⁺ isolation layer 19 composed of the high-concentration P-type diffusion layer is formed. At that time, the implantation energy is, for example, 50 keV, and the dose amount is, for example, 1 × 1.
It is set to 0 ¹⁵ / cm ² . Then, for example, annealing is performed in a nitrogen atmosphere at 1100 ° C. for about 80 minutes to activate the implanted impurity ions.

Next, as shown in FIG. 6, boron is selectively ion-implanted into the N ⁻ epitaxial layer 17 in the bipolar element formation region 4 using the photoresist as a mask,
Further, the base region 20 of the NPN bipolar transistor is formed by annealing in a nitrogen atmosphere at 900 ° C. for about 30 minutes. At that time, the implantation energy is, for example, 35 keV, and the dose amount is, for example, 1 ×.
10 ¹⁴ / cm ² .

Next, as also shown in FIG. 6, using the photoresist as a mask, the N ⁻ epitaxial layer 17 in the cathode common type photodiode forming region 3 and the base region 20 of the NPN bipolar transistor are formed.
Boron difluoride (BF ₂ ) which is a P-type impurity is selectively ion-implanted to form the anode extraction portion 21a of the cathode common type photodiode and the base extraction portion 21b of the NPN bipolar transistor. At that time, the implantation energy is, for example, 60 keV, and the dose amount is, for example, 1 × 10 ¹⁵ / cm ² .

Next, as also shown in FIG. 6, using the photoresist as a mask, the N ⁻ epitaxial layer 17 in the anode common type photodiode forming region 2, the base region 20 in the bipolar element forming region 4 and the N ⁺ plug-in are formed. Arsenic (As), which is an N-type impurity, is selectively ion-implanted into the layer 18 to form a cathode extraction portion 22a of an anode common type photodiode, an emitter 22b and a collector extraction portion 22c of an NPN bipolar transistor. At that time, the implantation energy is, for example, 70 keV, and the dose amount is, for example, 1 × 10 ¹⁵ / cm 3.
^{Assume 2} . After that, CVD (Chemical Vapor Depositio)
By the method n), a silicon oxide film 23 is deposited to a thickness of about 500 nm and is annealed for about 20 minutes in a nitrogen atmosphere at 950 ° C. for activation.

Next, as shown in FIG. 7, the silicon oxide film 23 is selectively etched by anisotropic etching such as RIE, and the silicon substrate side (anode extraction portion 21a, N ⁺ plug-in layer). 18, cathode extraction portion 22a, P ⁺ isolation layer 19, emitter 22
b, base take-out portion 21b, and collector take-out portion 22c) are formed. Next, titanium (Ti) for making ohmic contact with the silicon substrate side is formed on the entire surface by about 30 nm, titanium oxynitride (TiON) which is a refractory metal is formed by about 70 nm, and further, silicon (Si) is formed. ) Is formed as a low melting point metal aluminum (Al) with a thickness of about 600 nm, and the first wiring layer 2
Get 4. Each of these metal films is formed by, for example, a sputtering method. After this, the first wiring layer 2
By removing the unnecessary portion of 4 by etching by an anisotropic etching method such as RIE method, the anode lead-out portion 21a, the N ⁺ plug-in layer 18, the cathode lead-out portion 22a, the P ⁺ isolation layer 19, the emitter Wirings 24a to 24g are respectively connected to 22b, the base take-out portion 21b, and the collector take-out portion 22c.

Next, as shown in FIG. 8, an interlayer insulating film 25 between the upper and lower wiring layers is formed on the entire surface. This interlayer insulating film 2
For SOG, for example, first, a silicon oxide film is formed to a thickness of about 1 μm by a plasma CVD method or the like, and then SOG is performed.
(Spin-on-glass) is used for flattening, and the silicon oxide film is further reduced to 1.0 by plasma CVD or the like.
It is performed by forming the film with a thickness of about μm.

Next, as also shown in FIG. 8, RIE is performed.
Method, etc., a contact hole (not shown) for connecting the upper and lower wiring layers is opened in the interlayer insulating film 25, and then Ti and AlSi are deposited to about 100 nm and 1000 nm, respectively, by a sputtering method or the like to form the second layer. The first wiring layer 26 is formed, and the portion of the second wiring layer that covers the anode extraction portion 21a and the cathode extraction portion 22a of the photodiode formation region 1 is etched and removed by the RIE method or the like. The second wiring layer covers a region other than the photodiode and plays a role of shielding light.

Finally, as shown in FIG. 1, plasma C
A silicon nitride film 27 as an overpassivation film is formed on the entire surface to a thickness of about 700 nm by the VD method or the like, and the silicon nitride film 27 at the bonding pad portion is removed by etching by the RIE method or the like, and then, for example, 400 Sintering is performed by performing heat treatment for about 30 minutes in an atmosphere of Fo gas (mixed gas of 95% N ₂ and 5% H ₂ ) at ° C. This completes the main manufacturing process of the semiconductor device.

As described above, in the method of manufacturing a semiconductor according to the present embodiment, after the P ⁺ buried layer 13 and the N ⁺ buried layer 12 are formed on the P type silicon substrate 11, P is buried over the entire surface.
^- epitaxial layer 14 is formed only on the anode common type photodiode formed region 2 P ^- leaving epitaxial layer 14 in the other region P ^- epitaxial layer 14
Since the N ^- epitaxial layer 17 is formed after the removal of P by etching, the film thickness of the P ^- epitaxial layer 14 is set to the optimum thickness for the characteristics of the photodiode, and the film thickness of the N ^- epitaxial layer 17 is set. It is easy to control the thickness to be optimum for the characteristics of the bipolar transistor.

Next, another embodiment of the present invention will be described.

FIG. 9 shows a sectional structure of a main part of a semiconductor device including a light receiving element according to another embodiment of the present invention. This figure is an enlarged view of only the anode common type photodiode formation region 2'corresponding to the anode common type photodiode formation region 2 of the semiconductor device shown in FIG. The structures of the region 3 and the bipolar element formation region 4) are the same as those in FIG. In this figure, the same components as those of the above-described embodiment (FIG. 1) are designated by the same reference numerals, and the description thereof will be appropriately omitted.

[0054] In this embodiment, the anode-common type photodiode formed region 2 ', P ⁺ isolation layer 19a reaching the P ⁺ buried layer 13 is formed,
As a result, the photodiodes 2a 'and 2b' are separated. Further, the second wiring layer 26 for light shielding is left between the photodiodes 2a 'and 2b'. Other configurations are the same as those in FIG.

[0055] In the structure shown in FIG. 9, P isolation portion ^- epitaxial layer 14 is etched away, between the photodiodes are separated by P ⁺ isolation layer 19a reaching the P ⁺ buried layer 13. That is,
There is no low-concentration diffusion layer (P ⁻ epitaxial layer 14) having a long minority carrier diffusion length in the isolation portion, and a high-concentration diffusion layer (P ⁺ buried layer 13) having a short minority carrier diffusion length is not present.
Only exists. Therefore, when light is incident on the photodiode 2a ', it is extremely unlikely that carriers generated there will reach the adjacent photodiode 2b', and good crosstalk characteristics are exhibited. Note that the crosstalk between photodiodes refers to a phenomenon in which when a photodiode is irradiated, photocurrent is also detected from an adjacent photodiode.

FIG. 10 shows a cross-sectional structure of a main part of a semiconductor device including a light receiving element in another example for comparison with the semiconductor device including the light receiving element shown in FIG. This figure shows only an anode common type photodiode formation region 2 ″ corresponding to the anode common type photodiode formation region 2 of the semiconductor device shown in FIG. 1 in an enlarged manner, and the structure of the other regions is the same as FIG. In this figure, the same components as those of the above-described embodiment (FIG. 9) are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

In this example, the P ⁻ epitaxial layer 14 is formed in the anode common type photodiode formation region 2 ″.
P ⁺ isolation layer 19b is formed, which reaches a plurality of photodiodes 2a ″, 2
It is separated into b ″. Other configurations are the same as in FIG.

In the structure shown in FIG. 10, P ^{+ in} the separated portion
Since the low concentration P ⁻ epitaxial layer 14 having a long minority carrier diffusion length is present under the isolation layer 19b, when light is incident on the photodiode 2a ″, the carriers generated therein are generated in the P ⁻ epitaxial layer 14. Photodiode 2 that has moved and is slightly adjacent
It reaches up to b ″. Therefore, the crosstalk characteristic between the adjacent photodiodes separated is not good.

FIG. 11 shows the output characteristics of the photodiode shown in FIG. In this figure, the horizontal axis represents the position of the photodiode in the plane direction, and the vertical axis represents the output of the photodiode. As shown in this figure, when the photodiodes 2a 'and 2b' are exposed to light, their outputs are output to their own openings (areas where the second wiring layer 26 is removed in FIG. 9). While it becomes maximum when exposed to light, in the region between the photodiode 2a 'and the photodiode 2b', the second wiring layer 26
Ideally, the output will always be 0 because the light is blocked. However, actually, even when the light hits a portion other than its own opening, the carriers may slightly diffuse to the PN junction portion of its own photodiode, resulting in a minute output. However, in this photodiode, the P ⁺ isolation layer 19a reaches the P ⁺ buried layer 13, and the carriers generated by the light incident on the adjacent photodiode enter the PN junction portion of its own photodiode. The output waveform shows a relatively sharp dip with the peak at the opening, as indicated by the broken line, because the ratio of the peaks is extremely small. Therefore, the leakage amount A from the adjacent photodiode can be suppressed to a low level.

On the other hand, the photodiode shown in FIG. 10 exhibits different characteristics as shown in FIG. In this figure, the horizontal axis and the vertical axis represent the same as in the case of FIG. As shown in this figure, in the photodiode shown in FIG. 10, carriers generated by the light incident on the adjacent photodiode and penetrating into the PN junction portion of the photodiode of its own through the P ⁻ epitaxial layer 14. Is larger than in the case of FIG. 9, the output waveform has a shape with a relatively gentle skirt with a peak at the opening, as shown by the broken line. Therefore, the leakage amount A ′ from the adjacent photodiode becomes a high level.

As described above, in the photodiode (FIG. 9) according to the present embodiment, the crosstalk characteristic between the photodiodes can be improved when the photodiode region is divided into a plurality of regions.

Although the present invention has been described above with reference to some embodiments, the present invention is not limited to these embodiments, and various modifications can be made within the equivalent range. For example, in the above embodiment, the bipolar transistor has been described as having an ion-implanted emitter structure, but other structures such as a polysilicon emitter structure or a double polysilicon structure may be used.

[0063]

As described above, according to the semiconductor device including the light receiving element according to any one of claims 1 to 3, the first conductivity type semiconductor and the second conductivity type semiconductor in the light receiving element are provided. Is a first conductivity type low concentration epitaxial layer of the same conductivity type provided on the first conductivity type high concentration diffusion layer as a buried layer, and the surface diffusion of the second conductivity type semiconductor. Since it has a junction structure between the epitaxial layers including the second conductive type epitaxial layer provided under the second conductive type diffusion layer as a layer, the depletion layer width can be sufficiently widened, and the depletion layer The capacity can be reduced.

Particularly, as in the semiconductor device including the light-receiving element according to the second aspect, the second-conductivity-type high-concentration diffusion layer and the second-conductivity-type low-concentration epitaxial layer provided on the second-conductivity-type high-concentration diffusion layer. Even when a bipolar element including a layer is formed by being mixedly mounted, by adopting the two-layer epitaxial structure in the light receiving element region, the thickness of the second conductivity type low-concentration epitaxial layer in the bipolar element region is caught. It is possible to optimally set the depth of the buried layer (first-conductivity-type high-concentration diffusion layer) in the light-receiving element region, which has a short minority carrier diffusion length and causes a decrease in light-receiving sensitivity. Therefore, the thickness of the epitaxial layer in the bipolar element region and the thickness of the epitaxial layer in the light receiving element region can be optimized separately. Therefore, it is possible to achieve high sensitivity and high speed of the photodiode and the like while ensuring high speed of the bipolar transistor and the like.

Further, according to the semiconductor device including the light receiving element of the third aspect, the first conductivity type low-constant constituting the first conductivity type semiconductor is formed from the surface of the second conductivity type epitaxial layer constituting the second conductivity type semiconductor. Since the second conductivity type semiconductor is divided into a plurality of parts by another first conductivity type high concentration diffusion layer which penetrates the concentration epitaxial layer and reaches the first conductivity type high concentration diffusion layer, the adjacent light receiving element ( Most of the carriers generated by the light incident on the opening of the photodiode will be recombined in the first-conductivity-type high-concentration diffusion layer provided for the division, and the crosstalk between the adjacent light-receiving elements is effective. Can be reduced. Furthermore, the width of the first-conductivity-type high-concentration diffusion layer for separation is narrow, which is advantageous in terms of chip space.

According to the method for manufacturing a semiconductor device including the light receiving element of the fourth aspect, after the first and second conductivity type high-concentration diffusion layers (buried layers) are formed on the first conductivity type semiconductor substrate, Since the first-conductivity-type low-concentration epitaxial layer is formed and the first-conductivity-type low-concentration epitaxial layer in regions other than the light-receiving element region is removed by etching, the second-conductivity-type epitaxial layer is formed. 4. The structure of a semiconductor device including the light-receiving element according to claim 1, wherein the film thickness of the epitaxial layer of the bipolar element and the film thickness of the epitaxial layer of the light-receiving element can be separately and arbitrarily controlled. There is an effect that can be easily obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a semiconductor device including a light receiving element according to an embodiment of the present invention.

2A to 2D are cross-sectional process charts showing a method of manufacturing a semiconductor device including the light receiving element of FIG.

FIG. 3 is a sectional process drawing following FIG. 2;

FIG. 4 is a sectional process drawing following FIG. 3;

FIG. 5 is a sectional process drawing following FIG. 4;

FIG. 6 is a sectional process drawing following FIG. 5;

FIG. 7 is a sectional process drawing following FIG. 6;

FIG. 8 is a sectional process drawing following FIG. 7;

FIG. 9 is a cross-sectional view showing a structure of a semiconductor device including a light receiving element according to another embodiment of the present invention.

10 is a cross-sectional view showing a structural example of a semiconductor device including another light receiving element for comparison with the semiconductor device including the light receiving element in FIG.

11 is a diagram showing crosstalk characteristics of a photodiode in the semiconductor device including the light receiving element shown in FIG.

12 is a diagram showing a crosstalk characteristic of a photodiode in the semiconductor device including the light receiving element shown in FIG.

FIG. 13 is a sectional view showing a structure of a semiconductor device including a conventional light receiving element.

FIG. 14 is a cross-sectional view showing a structure of a semiconductor device including another conventional light receiving element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photodiode formation area, 2, 2 '... Anode common type photodiode formation area, 3 ... Cathode common type photodiode formation area, 4 ... Bipolar element formation area, 11 ... Silicon substrate (1st conductivity type semiconductor substrate), 12 ... N ⁺ buried layer (second conductivity type high-concentration diffusion layer), 13 ... P ⁺ buried layer (first conductivity type high-concentration diffusion layer), 14 ... P ⁻ epitaxial layer (first conductivity type low-concentration epitaxial layer) , 17 ... N ^- epitaxial layer (second conductivity type low concentration epitaxial layer), 18 ... N ⁺ plug-in layer, 19 ... P ⁺ isolation layer, 19a ... P ⁺
Isolation layer (first for isolation between photodiodes)
Conductivity type high-concentration diffusion layer), 20 ... Base region, 21a ... Anode extraction portion, 21b ... Base extraction portion, 22a
... Cathode extraction part (second conductivity type diffusion layer), 22b ...
Emitter, 22c ... collector take-out part, 23, 25 ...
Silicon oxide film, 24 ... First wiring layer, 26 ... Second wiring layer, 27 ... Silicon nitride film

Claims (4)

[Claims] 1. A semiconductor device including a light-receiving element having at least a junction between a first conductivity type semiconductor and a second conductivity type semiconductor, wherein the first conductivity type semiconductor is provided on a first conductivity type semiconductor substrate. And a first conductivity type low concentration epitaxial layer provided on the first conductivity type high concentration diffusion layer, wherein the second conductivity type semiconductor is the first A light receiving device comprising a second conductivity type epitaxial layer provided on the conductivity type low concentration epitaxial layer and a second conductivity type diffusion layer provided on the second conductivity type epitaxial layer. A semiconductor device including an element. 2. A second-conductivity-type high-concentration diffusion layer provided in another region on the first-conductivity-type semiconductor substrate, and a second-conductivity provided on the second-conductivity-type high-concentration diffusion layer. A semiconductor device including a light-receiving element according to claim 1, further comprising a bipolar element configured to include a low-concentration epitaxial layer. 3. The second-conductivity-type semiconductor penetrates the first-conductivity-type low-concentration epitaxial layer that constitutes the first-conductivity-type semiconductor from the surface of the second-conductivity-type epitaxial layer that constitutes the second-conductivity-type semiconductor. Another first-conductivity-type high-concentration diffusion layer reaching the first-conductivity-type high-concentration diffusion layer is provided, and the second-conductivity-type semiconductor is divided into a plurality of parts by the other first-conductivity-type high-concentration diffusion layer. A semiconductor device including the light receiving element according to claim 1. 4. A light receiving element having at least a junction between a first conductivity type semiconductor and a second conductivity type semiconductor, and a bipolar element provided in another region on a semiconductor substrate on which the light reception element is formed. A method of manufacturing a semiconductor device, comprising: a step of selectively forming a second conductivity type high concentration diffusion layer as a buried layer of a bipolar element in at least a bipolar element formation region on a first conductivity type semiconductor substrate; And selectively forming a first-conductivity-type high-concentration diffusion layer as an element isolation layer of the first-conductivity-type semiconductor substrate, and at least a first-conductivity-type high-concentration diffusion layer as a buried layer of the light-receiving element on at least the light-receiving element formation region on the first-conductivity-type semiconductor substrate A step of selectively forming a diffusion layer and, after growing a first-conductivity-type low-concentration epitaxial layer on the entire surface, selecting the first-conductivity-type low-concentration epitaxial layer other than the light-receiving element forming region Step of removing the second conductive type low concentration epitaxial layer over the entire surface, and at least a second conductive type diffusion layer in a region near the surface of the second conductive type low concentration epitaxial layer in the light receiving element formation region. A method of manufacturing a semiconductor device including a light receiving element, the method including: