JP2002164528A - Semiconductor device and its manufacturing method, and solid-state image pickup device and solid-state image pickup system using semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve S/N by making a depletion layer not contact a bird's beak of a selectively oxidized film while maintaining sensitivity. SOLUTION: The MOS type image pickup element is equipped with the selectively oxidized film 103 which isolates a semiconductor element, and a channel stop layer 104 which is formed below the selectively oxidized film 103 and prescribes a spread of a channel stop layer, and the channel stop layer 104 is formed covering the bird's beak of the selectively oxidized film 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, a solid-state imaging device and a solid-state imaging system using the semiconductor device, and mainly relates to a semiconductor device used for a digital camera and the like, a method of manufacturing the same, and a semiconductor device. The present invention relates to a solid-state imaging device and a solid-state imaging system used.

[0002]

2. Description of the Related Art Conventionally, there are mainly two types of solid-state imaging devices, which are roughly classified according to the solid-state imaging device used. One uses a CCD image sensor,
The other uses a MOS type imaging device. MO
A solid-state imaging device using an S-type imaging device has an advantage of lower power consumption than a solid-state imaging device using a CCD imaging device. In general, a high S / N ratio, good linearity, a wide dynamic range (D range), and the like are required as the element performance of the solid-state imaging element.

In order to improve the S / N ratio, it is necessary to increase the signal strength or reduce the noise by improving the pixel aperture ratio. First, the structure of the MOS type image pickup device will be described below. Next, the mechanism of noise generation in the MOS type imaging device will be described.

FIG. 9 shows a conventional MOS image pickup device (CMO).
FIG. 3 is a schematic cross-sectional view of an (S sensor). In FIG. 9, 7
01 is a P-well region formed in a P-type semiconductor substrate or an N-type semiconductor substrate, 702 is a selective oxide film for performing element isolation, 703 is a channel stop layer formed below the selective oxide film 702, and 704 is a selective oxide film. A photodiode storage region (here, an N-type impurity region) which is formed in a self-aligned manner by the oxide film 702 and stores photocarriers;
Reference numeral 705 denotes a gate electrode for reading optical carriers accumulated in the accumulation region 704, and reference numeral 706 denotes a read region from which optical carriers are read.

Although not shown in FIG. 9, the read area 706 is connected to an amplifier, and the optical carrier read to the read area 706 is amplified by the amplifier and then read outside.

Further, when photocarriers are accumulated in the accumulation region 704 or during the readout period of the accumulated photocarriers, a reverse current of a photodiode other than the photocarriers is generated, thereby lowering the noise level of the sensor. .

In particular, there are many lattice defects near the edge (bird's beak) of the selective oxide film 702 where a large amount of stress is generated, where the depletion layer of the photodiode comes into contact and the current in the reverse direction increases sharply. Therefore, the following CMOS sensors have been proposed.

FIG. 10 is a schematic cross-sectional view of a CMOS sensor described in Japanese Patent Application Laid-Open Nos. 10-98176 and 10-308507. FIG.
At 0, the same parts as those in FIG. 9 are denoted by the same reference numerals. As shown in FIG. 10, the selective oxide film 702 side of the storage region 704 of the photodiode is narrowed by the distance L so that the depletion layer does not contact the edge of the selective oxide film 702.

[0009]

However, in the prior art, in order to prevent the depletion layer from contacting the edge of the selective oxide film 702, the selective oxide film 702 side of the photodiode accumulation region 704 is separated by a distance L. However, the size of the photodiode is reduced, and the sensitivity is reduced. As a technique for preventing the depletion layer from contacting the edge of the selective oxide film 702, it is necessary to reduce the distance L by the distance L. In order to minimize the reduction in sensitivity, the distance L should be minimized. Must be shorter.

Also, as shown in FIG.
Is formed, for example, using a resist. However, if there is a variation in the distance L for each pixel, the resulting image will vary, and correction between chips will be required.

Further, since the P well region 701 which is a low concentration region is formed in the region at the distance L, the depletion layer easily spreads in the region at the distance L. Therefore, the depletion layer is formed by the selective oxide film 702. To avoid touching the rim,
The distance L needs to be long enough, so that the area ratio of the accumulation region is reduced and the sensitivity is reduced. In order to prevent this, operations such as enlargement of the pixel pitch must be performed.

Here, for example, Japanese Patent Application Laid-Open No. 10-10850
No. 7 describes that a deep p region is formed at the edge of the selective oxide film 702, but this can also be obtained if there is misalignment when forming this deep p region. Variations occur in the image, otherwise the number of manufacturing steps increases.

As described above, after all, in order to prevent the depletion layer from contacting the edge of the selective oxide film 702, the method of narrowing the selective oxide film 702 side of the storage region 704 of the photodiode by the distance L is used. Since various problems occur, it is necessary to prevent the depletion layer from contacting the edge of the selective oxide film 702 by another method.

In view of the above, the present invention is to prevent the depletion layer from contacting the edge of the selective oxide film 702 while maintaining the sensitivity.
It is an object to improve the N ratio.

[0015]

In order to solve the above problems, the present invention provides a selective oxide film for isolating a semiconductor device, and a channel stop layer formed under the selective oxide film and defining the extension of a channel region. Wherein the channel stop layer is formed so as to cover a bird's beak of the selective oxide film.

According to the present invention, there is also provided a solid-state image pickup device using the above-mentioned semiconductor device, wherein: a storage region for storing photocarriers formed between the selective oxide films; and a photocarrier stored in the storage region. And control means for controlling the reading of data.

Further, in the method of manufacturing a semiconductor device according to the present invention, a step of forming a nitride film on a well region of the first conductivity type; a step of performing ion implantation obliquely to a side wall of the nitride film; A step of forming a selective oxide film using the nitride film as a mask; and a step of forming a channel stop layer so as to cover the bird's beak of the selective oxide film by diffusing the implanted ions.

Further, the solid-state imaging system according to the present invention includes the above-described solid-state imaging device, an optical system that forms light on the solid-state imaging device, and a signal processing circuit that processes an output signal from the solid-state imaging device. It is characterized by having.

That is, according to the present invention, the selective oxide film is formed so as to cover the bird's beak of the selective oxide film, thereby preventing contact between the depletion layer and the bird's beak and preventing reverse current from flowing in the dark. I have.

[0020]

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

(Embodiment 1) FIG. 1 is a schematic sectional view of a solid-state imaging device in a solid-state imaging device according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 101 denotes a P-well region formed in a P-type semiconductor substrate or an N-type semiconductor substrate; 103, a selective oxide film for performing element isolation; The p ⁺ -type channel stop layer 107 formed in contact with the portion is formed in a self-aligned manner by the selective oxide film 103 and has a photodiode storage region (here, an N-type impurity region) for storing photocarriers. ), 106 are gate electrodes for reading the optical carriers accumulated in the accumulation region 107, 10
Reference numeral 8 denotes a reading area from which an optical carrier is read.

Although not shown in FIG. 1, the readout area 108 is connected to an amplifier, and the optical carrier read out to the readout area 108 is read out after being amplified by the amplifier. In addition, the polarity of the impurity region in each region in FIG. 1 may be a hole accumulation type solid-state imaging device in which the P-type and the N-type are opposite.

As shown in FIG. 1, in this embodiment, the channel stop layer 104 is formed so as to contact not only below the selective oxide film 103 but also a part of the storage region 107. The channel stop layer 104 formed in the vicinity prevents the depletion layer from contacting the edge of the selective oxide film 103.

FIG. 2 is a view showing a manufacturing process of the solid-state imaging device shown in FIG. As shown in FIG. 2, first, the P-well region 1
01, an SiN film 102 used as a mask pattern when forming a selective oxide film 103 in a later step.
To form Here, in the ion implantation step for forming the channel stop layer 104, ions are obliquely implanted into the P well region 101 to form an impurity region 109 below the SiN film 102, and also to form an impurity region 109 below the SiN film 102. The channel stop layer 104 can be formed (FIG. 2A).

Here, specifically, for example, the semiconductor substrate forming the P well region 101 is a silicon substrate, the ion species is boron, and the acceleration energy at the time of implantation is 3.
When the injection angle θ _{1 is set} to 60 ° and the implantation angle θ _{1 is set} to 60 °, the average ion range rp becomes 0.1 μm and the lateral penetration depth rpx is [average ion range rp × sin θ ₁ ]. 0.087 μm.

Next, a selective oxidation film 103 is formed by performing thermal oxidation. The channel stop layer 104 partially diffused so as to cover the bird's beak of the selective oxide film 103 is formed by the heat due to the thermal oxidation (FIG. 2B). Note that the ions implanted in the previous step are further diffused in the lateral direction by heat. That is, the penetration amount rpx increases.

[0027] If necessary, after the thermal oxidation treatment,
When heat treatment is further performed in an inert gas, the selective oxide film 10
No. 3 is not oxidized, so that the film thickness does not change, but the channel stop layer 104 further penetrates in the lateral direction.

Next, the SiN film 102 is transferred to the P well region 10.
Then, the gate oxide film 105 is formed (FIG. 2C). Then, polysilicon is deposited and patterned to form a gate electrode 106 (FIG. 2).
(D)). Next, the gate electrode 106 and the selective oxide film 10
2 is used as a mask to form a photodiode accumulation region 107 in a self-aligned (self-aligned) manner (FIG. 2).
(E)). Then, if the read area 108 is formed,
The solid-state imaging device shown in FIG. 1 is completed.

Actually, a single layer or a plurality of wiring layers and via holes are further formed, the wiring layers are electrically connected to the readout region 108 through the via holes, and the wiring layers are connected to the amplifier.

FIG. 3 is a plan view of FIG. In FIG. 3, reference numeral 501 denotes a bird's beak of the selective oxide film 103.
FIG. 1 is a sectional view taken along the line AA in FIG. In the present embodiment, ion implantation is performed at angles θ ₁ and θ ₂ , respectively.
The channel stop layer 104 is formed on the upper and lower sides of FIG. Thereby, an interface with the P-well region 101 is formed on the left and right sides of the accumulation region 107 in FIG. 3 by the mask pattern.

According to this embodiment, the depletion layer generated around the storage region 107 of the photodiode is isolated from the selective oxide film 103 by the channel stop layer 104 having a higher concentration than the P well region 101, so that the selective oxidation occurs. It does not come into contact with the bird's beak of the film 103. Therefore, the reverse current in the dark can be suppressed, and the noise level can be improved.

In the present embodiment, the read area 10
8, the same effect can be obtained, and the noise at the time of transfer after reading of the optical carrier can be improved. Further, in the present embodiment, the area of the storage region 107 is determined in a self-aligned manner by the selection pattern, thereby suppressing the variation in the area and making the characteristics uniform in the plane and between the chips.

Further, since the channel stop layer 104 is formed so as to cover the bird's beak 501, the generation of a reverse current in the bird's beak 501 can be suppressed, and the noise level of the solid-state imaging device is improved. further,
Since the accumulation region 107 is formed in a self-aligned manner with respect to the selective oxide film 103, the accumulation region 107 becomes large, thereby increasing the saturation charge, improving the S / N ratio and the D range, and increasing the sensitivity. Also improve.

(Embodiment 2) FIG. 4 is an explanatory view of a method of forming a SiN film according to a solid-state imaging device in a solid-state imaging device according to Embodiment 2 of the present invention. Referring to FIG.
Is an SiN film, which corresponds to 102 in FIG. 204-2
Reference numeral 06 denotes an impurity region, which corresponds to 109 in FIG.

As shown in FIG. 4, the SiN films 202, 20
3 are used as masks, and ion implantation is performed on the sidewalls of the SiN films 202 and 203 at an angle θ, thereby forming impurity regions 204 to 206 serving as channel stop layers.

Here, the impurity regions 204 to 206 are respectively formed when the interval between the SiN films 202 and 203 is small. That is, the SiN films 202 and 203
If the space between them is wide, the impurity regions 204 and 205 are not separately formed, but become one region.

In order to form an impurity region below the SiN films 202 and 203 without any leakage, a method described below is used.

FIG. 5 is a diagram showing a part of a schematic cross section of a solid-state imaging device in a solid-state imaging device according to Embodiment 2 of the present invention. As shown in FIG. 5, when the height of each of the SiN films 202 and 203 is H, the gap between the SiN films 202 and 203 is L, and the ion range is rp, the apparent penetration depth rpy is: rpy = rp × cos θ.

When the ion implantation is performed at an angle θ with respect to the side wall of the SiN film 203, the length in the cross section of the portion where the impurity region 304 is not formed with the SiN film 203 as a mask between the SiN films 202 and 203 is d. D = (rpy + H) × tan θ = (rp × cos θ +
H) × tan θ.

Here, if d <L / 2, one unseparated impurity region 304 is formed below the SiN films 202 and 203 as shown in FIG. That is, the thickness H of the SiN films 202 and 203, the ion implantation angle θ, the L between the SiN films 202 and 203, and the ion range rp may be selected so as to satisfy L> 2 × (rp × cos θ + H) × tan θ. .

(Embodiment 3) FIG. 6 is a view showing a part of a schematic cross section of a solid-state imaging device in a solid-state imaging device according to Embodiment 3 of the present invention. , S
The state after ion implantation is shown in parallel with the side surface of the iN film 202.

In the second embodiment of the present invention, the method of forming one impurity region 304 which is not separated by changing various conditions has been described with reference to FIG. 5. For example, in the case where various conditions cannot be changed, As shown in FIG.
Then, ions are implanted between the SiN films 202 and 203 in parallel with the side surfaces of the SiN film 202 from the state shown in FIG.
The impurity region 207 may be formed.

(Embodiment 4) As described with reference to FIG. 4, Embodiment 1 shows a state where ions are implanted, for example, by rotating the wafer four times every 90 degrees. In contrast, in Embodiment 4 of the present invention,
For example, as shown in FIG.
The following effects can be obtained by implanting ions twice every 0 degree. Note that, in FIG. 7, the same parts as those shown in FIGS. 1 and 4 are denoted by the same reference numerals.

That is, in the present embodiment, the channel width below the gate electrode 106 of the transistor is effectively widened because there is no channel stop layer 104 in this portion, and good transfer characteristics are secured and the transfer speed is increased. Be faster. Further, it is possible to miniaturize the MOS transistor in design.

The ion implantation described with reference to FIG. 4 may be performed not only four times but also plural times or while rotating the wafer.

(Embodiment 5) FIG. 8 is a configuration diagram of a solid-state imaging system according to Embodiment 5 of the present invention. In FIG.
Reference numeral 1 denotes a barrier that functions both as protection of the lens and a main switch. Reference numeral 2 denotes a lens that forms an optical image of a subject on the solid-state imaging device 4. Reference numeral 3 denotes an aperture for varying the amount of light passing through the lens. A solid-state image sensor that captures the subject as an image signal, an image signal processing circuit that performs various types of correction, clamping, and other processing on the image signal output from the solid-state image sensor 4; An A / D converter for performing analog-digital conversion of an image signal; 7 a signal processing unit for performing various corrections and the like on image data output from the A / D converter 6; 8 a solid-state imaging device 4; A circuit 5, an A / D converter 6, a timing generating section which is a driving means for outputting various timing signals to the signal processing section 7, and a general control / operation section 9 for performing various operations and controlling the entire still video camera. 10 includes a memory unit for temporarily storing image data, a recording medium control interface unit for performing recording or reading the recording medium 11, 1
Reference numeral 2 denotes a detachable recording medium such as a semiconductor memory for recording or reading image data, and reference numeral 13 denotes an external interface (I / F) for communicating with an external computer or the like.
Department.

Next, the operation of FIG. 8 will be described. When the barrier 1 is opened, the main power is turned on, the power of the control system is turned on, and the power of the imaging system circuit such as the A / D converter 6 is also turned on. then,
In order to control the exposure amount, the overall control / arithmetic unit 9 controls the aperture 3
Is opened, and the signal output from the solid-state imaging device 4 is output to the A / D converter 6 through the imaging signal processing circuit 5. The A / D converter 6 A / D converts the signal,
Output to the signal processing unit 7. The signal processing unit 7 performs an exposure calculation based on the data in the overall control / calculation unit 9.

The brightness is determined based on the result of the photometry, and the overall control / arithmetic unit 9 controls the aperture according to the result. Next, based on the signal output from the solid-state imaging device 4, high-frequency components are extracted, and the distance to the subject is calculated by the overall control / calculation unit 9. Thereafter, the lens is driven to determine whether or not the lens is in focus. If it is determined that the lens is not in focus, the lens is driven again to perform distance measurement.

After the in-focus state is confirmed, the main exposure starts. When the exposure is completed, the image signal output from the solid-state imaging device 4 is corrected in an imaging signal processing circuit 5, further A / D-converted by an A / D converter 6, and passed through a signal processing unit 7 to perform overall control. The data is stored in the memory unit 10 by the operation 9. Thereafter, the data stored in the memory unit 10 is
Under the control of the overall control / arithmetic unit 9, the data is recorded on a removable recording medium 12 such as a semiconductor memory through a recording medium control I / F unit. Further, the image may be processed by inputting it directly to a computer or the like through the external I / F unit 13.

[0050]

As described above, according to the present invention,
Since the channel stop layer is formed so as to cover the bird's beak of the selective oxide film, it is possible to prevent the depletion layer from contacting the bird's beak of the selective oxide film while maintaining the sensitivity, and to improve the S / N. it can.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a solid-state imaging device in a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of the solid-state imaging device shown in FIG.

FIG. 3 is a plan view of FIG. 1;

FIG. 4 is an explanatory diagram of a method of forming a SiN film according to a solid-state imaging device in a solid-state imaging device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a part of a schematic cross section of a solid-state imaging device in a solid-state imaging device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a part of a schematic cross section of a solid-state imaging device in a solid-state imaging device according to a third embodiment of the present invention.

FIG. 7 is a schematic plan view of a solid-state imaging device in a solid-state imaging device according to Embodiment 4 of the present invention.

FIG. 8 is a configuration diagram of a solid-state imaging system according to a fifth embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a conventional MOS image sensor.

FIG. 10 is a schematic cross-sectional view of a conventional MOS image sensor.

[Explanation of symbols]

101, 701 P-well region 102, 202, 203, 302, 303 SiN film 103, 702 Selective oxide film 104, 703 Channel stop layer 105 Gate oxide film 106, 705 Gate electrode 107, 704 Storage region 108, 706 Read-out region 204- 207, 304, 305 Impurity region serving as channel stop layer 501 Bird's beak

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/76 S (72) Inventor Tetsuro Asaba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F term (reference) 4M118 AA05 AB01 BA14 CA03 CA19 EA03 EA07 EA08 EA16 FA06 FA26 FA28 FA33 5C024 CX03 CX41 CY47 GY31 5F032 AA14 AC01 BA01 BB01 CA03 CA15 CA17 DA43 DA53 DA77

Claims (8)

[Claims] 1. A semiconductor device comprising: a selective oxide film for isolating a semiconductor element; and a channel stop layer formed under the selective oxide film and defining the extension of a channel region, wherein the channel stop layer is formed by the selective oxidation. A semiconductor device formed so as to cover a bird's beak of a film. 2. A solid-state imaging device using the semiconductor device according to claim 1, wherein the semiconductor element is a photoelectric conversion element having a storage region for storing optical carriers, and the storage region is provided in the channel stop layer. A solid-state imaging device, which is formed adjacently. 3. The storage region is a semiconductor region of a first conductivity type, the channel stop layer is a semiconductor region of a second conductivity type, and the storage region and the channel stop layer are well regions of a second conductivity type. The solid-state imaging device according to claim 2, wherein: 4. A step of forming a nitride film on the well region, and a step of obliquely ion-implanting a side wall of the nitride film so that a channel stop layer can be formed also under a part of the nitride film. Forming a selective oxide film using the nitride film as a mask, and forming a channel stop layer so as to cover the bird's beak of the selective oxide film by diffusing the implanted ions. Device manufacturing method. 5. The method according to claim 4, wherein the step of forming the channel stop layer is a step of heating in an inert gas. 6. The step of performing ion implantation obliquely to the side wall of the nitride film includes performing ion implantation from a plurality of directions or performing ion implantation while relatively rotating an ion implantation apparatus and the well region side. 6. The method for manufacturing a semiconductor device according to claim 4, wherein: 7. An angle at which the ions are implanted with respect to a side wall of the nitride film is θ, an average range of the implanted ions is rp, a height of the nitride film is H, and an interval L between the nitride films is L. 7. The method of manufacturing a semiconductor device according to claim 4, wherein: L> 2 × (rp × cos θ + H) × tan θ is satisfied. 8. A solid-state imaging device according to claim 2, comprising: an optical system that forms light on the solid-state imaging device; and a signal processing circuit that processes an output signal from the solid-state imaging device. Characterized solid-state imaging system.