JP2003249640A - Manufacturing method of solid imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a solid imaging device having an exposure area larger than summarized exposure range of an aligned, inexpensively with a high accuracy. <P>SOLUTION: The whole exposure area of an imaging device 10 is divided into three sections of a pickup section, a left side peripheral circuit section and a right side peripheral circuit section. Then, in the initial exposure process, a first imaging section 20 comprising a main scale becoming the reference of a pattern mating mark 40B and a deviation of mating detecting mark 40A is formed. After the next exposure process, the exposure of the imaging section 20 after second exposure and the formation of respective marks 40A, 40B are effected based on the references of respective marks 40A, 40B formed in the first imaging section 20. Thereafter, the exposure of the left side area 310 and the right side area 320 of the peripheral circuit section 30 is effected sequentially. In this case, wafers aligned with the longitudinal summarized exposure range of the aligner are turned by 90° and the left side area 310 as well as the right side area 320 of the peripheral circuit section 30 are aligned longitudinally to effect the exposure. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image pickup device such as a CCD type image pickup device or a CMOS type image pickup device, and more particularly to a solid state having an exposure area larger than the collective exposure range of an exposure apparatus used in a photoresist process. The present invention relates to improvement of an exposure method when manufacturing an image pickup device.

[0002]

2. Description of the Related Art For example, in a general semiconductor device photoresist process, when simultaneously forming a pattern having a size exceeding the collective exposure range of an exposure apparatus, a plurality of reticles (circuit original plates) are used to form an entire pattern. It is necessary to obtain the entire pattern by dividing the exposure area of, exposing each divided area individually, and joining them. However, in such seam exposure, there is always a misalignment at the seam due to the alignment error of the exposure device,
Also, due to exposing multiple reticles separately,
Since a line width difference occurs between each exposure, there is a problem that a manufacturing error becomes large for a semiconductor device that fits within the collective exposure range. Therefore, when exposing a semiconductor device with a size that exceeds the collective exposure range, the target characteristics of the semiconductor device may not be achieved if the entire pattern is simply divided and stored in separate reticles, and they are jointly exposed. There is.

On the other hand, in the manufacturing process of a solid-state image sensor, market demand for a wide-angle solid-state image sensor has been increasing in recent years. In such a wide-angle solid-state image sensor, divisional stitch exposure is considered. I have no choice. Figure 4
FIG. 5 is a front view showing an appearance of a conventional CCD type image pickup device, and FIG. 5 is an explanatory view showing a division exposure region when the division type joint exposure is performed on the CCD type image pickup device shown in FIG. 4. In FIG. 4, an element chip 10 formed in a rectangular plate shape
An image pickup section 20 for picking up an image of a subject is provided in the central portion of the, and a peripheral circuit section 30 is provided in an area outside the image pickup section 20.

The image pickup section 20 has a plurality of photoelectric conversion elements (photosensors) for generating signal charges according to the amount of incident light.
A plurality of CCD vertical transfer units, which are arranged in a dimensional matrix and which vertically transfer the signal charges generated by each photoelectric conversion element for each column of each photoelectric conversion element, are further transferred by each CCD vertical transfer unit. One or a plurality of CCD horizontal transfer units that transfer the transferred signal charges in the horizontal direction, an output unit that converts the signal charges transferred by the CCD horizontal transfer units into electric signals, and outputs the signals as image pickup signals are provided. ing. Further, the peripheral circuit section 30 is provided with a signal processing circuit that performs a predetermined signal processing on the image pickup signal output from the output section, and further, each element such as a protection transistor, a bus line, and an electrode pad is arranged. There is.

Further, in the example shown in FIG. 5, CC shown in FIG.
The entire exposure area required for manufacturing the D-type image pickup device is divided into left and right (longitudinal direction) into two parts. Separate reticles are formed for the left-side exposure area 10A and the right-side exposure area 10B, and individually. By performing exposure and joining, it becomes possible to perform exposure of a solid-state imaging device having a large chip size with an exposure device having a small collective exposure range. A plurality of positioning marks 40A, 40B for positioning the divided exposure areas 10A, 10B at predetermined positions of the divided exposure areas 10A, 10B.
Are formed. The positioning marks 40A, 40
B is composed of a misalignment detection mark 40A provided at a corner of each of the divided exposure areas 10A and 10B and a pattern alignment mark 40B provided on the bottom side and the outer side of each of the divided exposure areas 10A and 10B. At
Pattern alignment mark 40B formed in the previous exposure step
The exposure position is determined with the target as, and the misalignment is corrected by the misalignment detection mark 40A.

[0006]

However, when the divisional stitching exposure according to the above-mentioned conventional example is used, a problem peculiar to the solid-state image pickup device is that the image pickup section having a great influence on the image characteristics has the above-mentioned division. The manufacturing error due to the use of seam exposure is unacceptable. Note that an exposure apparatus having a wider collective exposure range can be used to collectively expose such a large area. However, an exposure apparatus having such a large collective exposure range is generally used as a collective exposure range. Since the resolution is lower and the alignment error is larger than that of a narrow exposure apparatus, it is not possible to cope with recent miniaturization, and it is difficult to manufacture a high-quality wide-angle-angle solid-state imaging device. In the future, the batch exposure range will be wide,
At the same time, it is expected that an exposure apparatus with high resolution and high alignment accuracy will be developed. However, even if such an exposure apparatus is developed, it is expected to be an expensive apparatus and it cannot be easily introduced. Occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a solid-state image pickup device capable of manufacturing a solid-state image pickup device having an exposure area larger than the collective exposure range of an exposure apparatus with high accuracy and at low cost.

[0008]

In order to achieve the above object, the present invention provides an image pickup section including at least a plurality of photoelectric conversion elements that generate signal charges according to the amount of incident light, and is provided around the image pickup section. In the method for manufacturing a solid-state image sensor having a peripheral circuit section that processes a signal from the image-capturing section, in the case of producing a solid-state image sensor having an exposure area larger than the collective exposure range of an exposure apparatus used in a photoresist process, There is a divided exposure step of dividing the entire area of the solid-state image sensor into a plurality of areas, and exposing each divided area by a separate reticle. The method is characterized by including a first exposure step of forming a resist pattern.

According to the method of manufacturing a solid-state image pickup device of the present invention, when a solid-state image pickup device having an exposure region larger than the collective exposure range of the exposure apparatus used in the photoresist process is manufactured, a plurality of whole regions of the solid-state image pickup device are formed. Then, a divided exposure step is performed in which each divided area is exposed by an individual reticle. Then, in this divided exposure step, at least the entire image pickup section is collectively exposed to form a photoresist pattern. Therefore, at least for the image pickup section having a great influence on the image characteristics, it is possible to fabricate without exposing the inside of the image pickup section by forming the photoresist pattern by collectively exposing the entire image pickup section. As a result, it is possible to inexpensively manufacture a high-quality wide-angle-angle solid-state imaging device without causing deterioration in image quality of the solid-state imaging device and without using an expensive exposure device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

FIG. 1 is an explanatory view showing divided exposure areas used in the embodiment of the present invention. Note that the solid-state image sensor to be exposed in this embodiment is, for example, the CCD image sensor shown in FIG. 4, and the following description will be given using the reference numerals shown in FIG. Further, FIG. 2 is an explanatory view schematically showing a collective exposure range of an exposure apparatus used for the exposure work in the present embodiment example, and FIG. 3 is a plan view showing a specific example of the exposure work in the present embodiment example. is there.

First, the exposure apparatus used in this embodiment will be described. In a semiconductor device manufacturing process, an exposure apparatus used for forming a photoresist pattern is generally a structure in which a reticle pattern is reduced and projected at an appropriate magnification, and the entire surface of the wafer is exposed by sequentially moving a stage on which the wafer is placed. It has become. It should be noted that there is a method in which this exposure range is scanned by a slit type exposure means to finally obtain an exposure range as shown in FIG. 2, but this is essentially the same. As shown in FIG. 2, the optical system of the exposure apparatus has a circular imageable range 100 when viewed perpendicularly to the optical axis, and it is possible to collectively expose a rectangular range inscribed therein. Side arc portions 1 in the imageable range 100 of a microscope used for pattern matching of wafers and wafers
Since it is disposed at 20, only the rectangular range 110 avoiding the arc portions 120 on both sides can be used as the collective exposure range.

For example, in a general exposure apparatus having an exposure area of 22 mm square, the actual imageable area has a diameter of 31.1.
mm circular shape, long side 25.2 mm, short side 18.2 m
It is possible to obtain a rectangular exposure range of m. Note that this numerical value is an example and does not limit the present invention. Then, in order to obtain a solid-state imaging device having a size exceeding the unique collective exposure range determined by such an exposure device, the above-described divisional exposure is required. For example, as shown in FIG. 5, if the whole is divided into two, a solid-state imaging device having a maximum size of 25.2 mm × 36.4 mm can be obtained in the above example. However, since each of the two divided areas is separately exposed by using the pattern alignment mark 40B described above, it is necessary to separately perform the alignment error correction with the previous process pattern using the alignment error detection mark 40A. , It is not possible to optimize the deviation correction between the divided areas. Further, since the exposure energies of the divided areas are not always the same, there is a problem that a line width difference between the divided areas is likely to occur.

Therefore, in the present embodiment, by devising the dividing method as follows, the exposure of the entire image pickup section, which has a particularly important influence on the image quality characteristic, is collectively performed, and a defect for splicing is performed. Is lost. That is,
It is impossible to completely eliminate the above-mentioned problems of positional deviation and line width difference by dividing exposure using a plurality of reticles,
By the following division method, it is possible to eliminate the splicing of the image pickup units and almost ignore the influence of the above problem. Specifically, as shown in FIG. 1, the image pickup section 20 serves as a collective exposure area 210 as a whole, and the peripheral circuit section 3 other than that is provided.
0 is divided into the left side and the right side and
By setting 0 and 320, the entire pattern is jointly exposed in a total of three divided areas.

Next, the seaming exposure process will be described with reference to FIG. First, as shown in FIG.
In the first exposure process, the pattern alignment mark 40B
The first imaging unit 20 including the main scale that serves as a reference for the misalignment detection mark 40A is formed. At this time, FIG.
As shown in (A), the horizontally long imaging unit 20 is mounted on the wafer 60.
Is rotated by 90 ° and set, and exposure is performed in a state of being aligned with the collective exposure range 110 of the above-described exposure apparatus.

After the next exposure step, the marks 40A and 40B formed on the first image pickup unit 20 are used as a reference, and the exposure of the second and subsequent image pickup units 20 and the marks 40A and 40A are performed.
40B is formed (first exposure step), and then FIG.
As shown in (B) and (C), the left side region 310 and the right side region 320 of the peripheral circuit section 30 are sequentially exposed (second).
Exposure process). At this time, the vertically oriented wafer is rotated 90 ° in FIG.
0, the right side region 320 is exposed vertically. Even when the peripheral circuit section 30 is exposed, the marks 40A and 40B formed in the first exposure step can be used as a reference for exposure.

According to such a divided exposure process, the same misalignment and line width difference as in the conventional case occur between the image pickup section 20 and the peripheral circuit section 30, but the unit element exists only in the image pickup section 30. Since only a single circuit exists in the peripheral circuit section, strict pattern matching between the two areas is not necessary as compared with that in the imaging area. Further, by utilizing such a property, in the exposure step of the peripheral circuit section, the marks 40A and 40B used only in each peripheral circuit section 30 are formed during the exposure of each divided area of the peripheral circuit section 30, and The marks 40A and 40B formed on these peripheral circuit portions 30 may be used in the subsequent exposure process.

By the method as described above, a solid-state image pickup device having a size exceeding the collective exposure range of the exposure device can be manufactured without investing new equipment. Further, although conventional splicing exposure causes an unacceptable error in product characteristics, the method of this example can obtain product characteristics equivalent to those of a normal batch exposure product.

In the above example, 3 work steps are required.
Although the case of performing one split stitching exposure has been described, actually, for example, only the exposure of the imaging unit may be performed, and such a case is also included in the present invention. Further, in the above-described example, both the formation of the marks 40A and 40B for the first image pickup unit and the exposure of the image pickup unit are simultaneously performed in the first exposure, but the marks 40A and 40 are formed in the first exposure.
A method of forming only B is also possible.

The elements included in the image pickup section 20 of the CCD type image pickup element are as described in the above-mentioned conventional example.
The photoelectric conversion element and the CCD vertical transfer unit may include the CCD horizontal transfer unit and the output unit.
Of these, for the output unit, the charge detection transistor up to the first stage is a factor that greatly affects the image quality, so this charge detection transistor is included in the image pickup unit.
The subsequent elements may be included in the peripheral circuit section.

That is, in this image pickup unit, a floating diffusion unit for receiving the signal charges from the CCD horizontal transfer unit, and a charge detection MO for detecting the potential fluctuation of the floating diffusion unit and converting it into an electric signal.
An S-transistor, an amplification circuit including a plurality of MOS transistors that amplifies the output of the charge detection transistor, and a reset MOS transistor that resets the potential of the charge detection transistor. A configuration may be adopted in which only the fusion part and the charge detection transistor are arranged in the image pickup part and the other parts are arranged in the peripheral circuit part.

Further, although the present invention is applied to the CCD type image pickup device in the above-mentioned example, it may be similarly applied to the CMOS type image pickup device. That is, the CMOS image sensor is a CCD
The signal charge of the photoelectric conversion element is not read out by the CCD transfer register like an image pickup device and converted into an electric signal all together at the output section at the subsequent stage, but each gate circuit is formed by various MOS transistors provided for each unit pixel. The photoelectric conversion element of a unit pixel is converted into an electric signal for each unit pixel and output to a signal line. Driving of each gate circuit is controlled by scanning circuits in the vertical direction and the horizontal direction, and an image of an arbitrary pixel area is captured. A signal can be output, and the method of the present invention can be applied to the case where such a CMOS type image pickup device is manufactured by divided exposure. The image pickup unit in this case includes a photoelectric conversion element for each unit pixel, a gate circuit, and vertical and horizontal scanning circuits.

Further, in the above-mentioned example, the wafer is rotated by 90 ° between the exposure of the image pickup section and the exposure of the peripheral circuit section, but the present invention is not limited to this. That is, in the above-described example, since the image capturing unit is exposed by making maximum use of the collective exposure range of the exposure device, it is possible to simply slide the exposure position in the longitudinal direction of the collective exposure range at the same angle. Since the dimension in the lateral direction of is not sufficient and divided exposure of the peripheral circuit part cannot be performed,
It was necessary to rotate the wafer. However, if the size of the imaging unit is made slightly smaller than the collective exposure range of the exposure apparatus so that the width of the peripheral circuit section in the lateral direction can be accommodated within the lateral dimension of the collective exposure range, the longitudinal position can be slid. Only by doing so, it is possible to perform the divided exposure of the peripheral circuit section, so that after the exposure of the imaging section, the peripheral circuit section can be exposed at the same angle.

That is, in this case, the maximum exposure range of the exposure apparatus is not utilized, but the wafer is rotated by 90 °.
No need to rotate. It should be noted that the exposure work including the operation of sliding the wafer and the exposure work including the operation of rotating the wafer have no advantages or disadvantages in the exposure work, but in the pattern design, when the wafer is rotated, Since the relationship between the x-coordinate and the y-coordinate is reversed, the work becomes a little complicated. Therefore, when there is a size margin between the required size of the imaging unit and the collective exposure range of the exposure apparatus, a method that does not include the rotation of the wafer is adopted to facilitate pattern design. It becomes possible.

Further, in the above example, the combination of the misalignment detection mark and the pattern alignment mark is used as the positioning mark, but various modifications can be made to the specific form of such mark. Further, the specific procedure of the exposure work is not limited to the above-described example, and the exposure order of the image pickup unit and the peripheral circuit unit after forming the alignment mark can be appropriately changed. Furthermore, the method for manufacturing a solid-state image sensor according to the present invention is not limited to the one described in the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0026]

As described above, according to the method for manufacturing a solid-state image pickup device of the present invention, when a solid-state image pickup device having an exposure area larger than the collective exposure range of the exposure apparatus used in the photoresist process is manufactured, In a divided exposure process in which the entire area of the solid-state image sensor is divided into a plurality of areas, and each divided area is exposed by an individual reticle, at least the entire image pickup section is collectively exposed to form a photoresist pattern. . Therefore, at least for the imaging unit that has a great influence on the image characteristics, by exposing the whole at once and forming a photoresist pattern,
Since it can be manufactured without exposure stitching in the image pickup section, a high-quality wide-angle-angle solid-state image pickup device can be obtained without degrading the image quality of the solid-state image pickup device and without using an expensive exposure device. There is an effect that it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing divided exposure regions of a solid-state image sensor used in an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing a collective exposure range of an exposure apparatus used for an exposure operation in the embodiment of the present invention.

FIG. 3 is a plan view showing a specific example of the exposure work in the embodiment of the present invention.

FIG. 4 is a front view showing an appearance of a conventional CCD type image pickup device.

5A and 5B are explanatory diagrams showing divided exposure areas when division and joint exposure is performed on the CCD type image pickup device shown in FIG.

[Explanation of symbols]

10 ... Element chip, 20 ... Imaging section, 30 ... Peripheral circuit section, 40A, 40B ... Positioning mark, 100 ...
… Image formation range, 110 …… Batch exposure range, 120 ……
Both side arc portions, 210, 310, 320 ... Batch exposure area.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomohiro Shiiba             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Yasuaki Arai             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 2H097 AA12 JA02 KA03 KA12 LA20                 4M118 BA09 EA01 EA14 EA20 FA06                 5F046 AA25 CB17 CC13

Claims (17)

[Claims] 1. An image pickup unit including a plurality of photoelectric conversion elements for generating at least a signal charge according to an amount of incident light, and a peripheral circuit unit provided around the image pickup unit and processing a signal from the image pickup unit. In a method of manufacturing a solid-state image sensor, when a solid-state image sensor having an exposure area larger than a collective exposure range of an exposure apparatus used in a photoresist process is manufactured, the entire area of the solid-state image sensor is divided into a plurality of areas, A divided exposure step of exposing the area by individual reticle, the divided exposure step including a first exposure step of exposing at least the entire image pickup section at once to form a photoresist pattern. And a method for manufacturing a solid-state image sensor. 2. The divided exposure step includes a second exposure step in which the peripheral circuit section is divided into a plurality of pieces and each divided area is exposed by an individual reticle.
A method for manufacturing the solid-state imaging device according to claim 1. 3. The method for manufacturing a solid-state image sensor according to claim 2, further comprising a step of changing an angle of the semiconductor substrate by 90 ° between the first exposure step and the second exposure step. 4. The method for manufacturing a solid-state image pickup device according to claim 1, further comprising the step of forming positioning marks at a plurality of predetermined positions of the image pickup section at the time of the first exposure of the divided exposure step. . 5. The alignment mark is composed of a misalignment detection mark and a pattern alignment mark, the exposure position is determined with the pattern alignment mark as a target at the next exposure, and the alignment error is detected by the alignment error detection mark. The method for manufacturing a solid-state imaging device according to claim 4, wherein the correction is performed. 6. The first exposure step is the first exposure step of the divided exposure step, and the positioning mark is formed when the entire image pickup section is collectively exposed. Of manufacturing the solid-state image sensor of. 7. The exposure mark is formed at the first exposure of the divided exposure process, and then the first exposure process is performed in a subsequent process to collectively expose the entire imaging unit. Item 5. A method for manufacturing a solid-state image sensor according to Item 4. 8. The divided exposure step includes a second exposure step in which the peripheral circuit section is divided into a plurality of portions, and each divided area is exposed by an individual reticle, and the peripheral circuit is exposed during the exposure in the second exposure step. The method for manufacturing a solid-state image pickup device according to claim 4, further comprising the step of forming positioning marks at a plurality of predetermined positions of the section. 9. The method for manufacturing a solid-state image pickup device according to claim 4, wherein the exposure operation of the plurality of solid-state image pickup devices is sequentially performed on the semiconductor wafer. 10. The method for manufacturing a solid-state imaging device according to claim 9, wherein the positioning mark formed on the solid-state imaging device exposed first is used for positioning the solid-state imaging device to be subsequently exposed. 11. The solid-state image pickup device is a CCD type image pickup device, and the image pickup section is provided with a plurality of photoelectric conversion devices that generate signal charges corresponding to an amount of incident light and signal charges generated by the photoelectric conversion devices. The solid-state imaging device manufacturing method according to claim 1, further comprising a CCD transfer unit for transferring. 12. The method according to claim 11, wherein the peripheral circuit section includes a protection transistor, a bus line, and an electrode pad. 13. The image pickup section further converts the signal charge transferred by the CCD transfer section into an electric signal,
13. The method for manufacturing a solid-state image pickup device according to claim 12, further comprising an output unit that outputs the image pickup signal. 14. The image pickup section further converts the signal charge transferred by the CCD transfer section into an electric signal,
Of the output section that outputs as an image pickup signal, a floating diffusion section that receives the signal charge from the CCD transfer section and a charge detection transistor that detects a potential fluctuation of the floating diffusion section and converts it into an electric signal are included. 13. The method for manufacturing a solid-state image pickup device according to claim 12, wherein. 15. The method of manufacturing a solid-state image sensor according to claim 14, wherein the peripheral circuit section further includes an amplifier circuit that amplifies an output of the charge detection transistor in the output section. 16. The solid-state image pickup device is a CMOS type image pickup device, and the image pickup section is provided with a plurality of photoelectric conversion devices that generate signal charges according to an amount of incident light and signal charges generated by the photoelectric conversion devices. 2. The solid-state imaging device according to claim 1, further comprising: a plurality of gate circuits that convert into electric signals and output as pixel signals; and a scanning circuit that controls the gate circuits to select pixel signals to be read. Method. 17. The method according to claim 16, wherein the peripheral circuit section includes a protection transistor, a bus line, and an electrode pad.