JP2006093417A - Pattern forming method, and manufacturing method for solid image-capturing element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid image-capturing element which reduces dimensional errors at joints to enable highly precise and reliable pattern formation in manufacturing an element whose device area is larger than the exposure area of an exposure device. <P>SOLUTION: A method is provided for manufacturing the solid image-capturing element. The image-capturing element comprises a photoelectric converter, a charge transfer which has charge transfer electrodes for transferring charges generated at the photoelectric converter, and a wiring which is connected to the photoelectric converter or to the charge transfer. According to the method, an exposure process for forming the patterns on the same layer that compose the photoelectric converter, charge transfer, or wiring includes a first exposure process of exposing a first area, and a second exposure process of exposing a second area having an area overlapping the first area. The overlapping area is so formed as to build an synthetic image given by mask data used in both first and second exposure processes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pattern forming method and a method of manufacturing a solid-state imaging device using the pattern forming method, and more particularly to a method of performing divided exposure using a plurality of reticles when an area larger than an exposure area of an exposure apparatus is exposed.

  A solid-state imaging device using a CCD used for an area sensor or the like includes a photoelectric conversion unit including a photodiode and the like, a charge transfer unit including a charge transfer electrode for transferring a signal charge from the photoelectric conversion unit, and these And a wiring portion connected to the. A plurality of charge transfer electrodes are arranged adjacent to each other on a charge transfer path formed on the semiconductor substrate, and are sequentially driven.

In recent years, with the increase in the number of pixels of a CCD, the demand for higher resolution and higher sensitivity is increasing in solid-state imaging devices, and the number of imaging pixels is increasing to more than gigapixels.
In order to ensure high sensitivity in such a situation, it is difficult to reduce the light receiving area, and as a result, the area occupied by the charge transfer electrode must be reduced.

  Under such circumstances, with the progress of manufacturing technology, development for forming a large-area element on a large-area substrate has been advanced, and the device size is larger than the exposure range of the exposure apparatus. A solid-state image sensor has also been proposed.

  When forming such a large solid-state imaging device, as shown in FIG. 5, the entire exposure area is divided by using a plurality of reticles, and each divided area is sequentially exposed and connected to form an overall pattern. The method of obtaining is taken.

  However, such joint exposure causes misalignment due to an alignment error of the exposure apparatus at the joint, and a line width difference occurs between exposures due to exposure of a plurality of reticles separately. There is a problem that a manufacturing error becomes large with respect to a semiconductor device within the exposure range.

  Therefore, when a semiconductor device with a size exceeding the batch exposure range is exposed, if the entire pattern is simply divided and placed in separate reticles, and they are connected and exposed, the target characteristics of the semiconductor device are achieved. I couldn't do it.

  In view of this, a method has been proposed in which a plurality of regions are divided in advance and only an imaging unit that is a region having a large influence on image characteristics is collectively exposed (Patent Document 1).

JP 2003-249680 A

  However, with miniaturization and high integration, a situation has arisen in which even an image pickup unit, which is an area having high image characteristics, is divided according to function, and needs to be subjected to divided exposure. When divided exposure is performed in the imaging unit, the microlens, photodiode aperture size, transfer path size, etc. differ due to resist pattern dimension errors, etc., at the joint of the divided exposure. Differences in sensitivity and transfer efficiency may occur.

  In particular, since an optical system such as a microlens is mounted, the metal layer that doubles as the light shielding layer formed at a position as close as possible to the distance from the photoelectric conversion unit, that is, the height from the substrate surface to the uppermost layer, as much as possible. Often, it must be formed on an uneven surface. For this reason, a sensitivity difference and a transfer efficiency difference may be caused particularly when there is a joint between the divided exposures on the uneven surface. Further, in order to achieve surface flattening on the lower layer side, there may be a restriction on the layout.

  The present invention has been made in view of the above circumstances, and in manufacturing a solid-state imaging device having a device area larger than that of an exposure apparatus, it is possible to reduce a dimensional error of a joint and realize a highly accurate and reliable pattern formation. An object of the present invention is to provide a solid-state imaging device that can be used.

Therefore, the present invention is a pattern forming method for forming a desired pattern by exposing the wafer surface through a mask, wherein the exposure process for forming the pattern exposes a first region. And a second exposure step of exposing a second region having an overlap region between the first region and the first region, wherein the overlap region is in both the first and second exposure steps. A composite image of the mask data to be used is constructed.
According to this method, since the joint portion of the divided exposure portion is not made a simple joint, the joint data is overlapped, and the joint portion is composed of composite data. The difference and the transfer efficiency difference can be made unobtrusive.

The present invention also includes a photoelectric conversion unit, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and a wiring unit connected to the photoelectric conversion unit or the charge transfer unit. A method for manufacturing a solid-state imaging device comprising: an exposure step for forming a pattern constituting the photoelectric conversion unit, the charge transfer unit, or the wiring unit; and a first exposure step of exposing a first region And a second exposure step of exposing a second region having an overlapping region with the first region, wherein the overlapping region is a mask used in both the first and second exposure steps. A composite image of data is constructed.
According to this method, particularly in the formation of a photodiode of a photoelectric conversion part, the formation of a light-shielding layer for forming a light-receiving part of a photodiode or an opening in an insulating layer, the formation of a color filter layer, the formation of a microlens layer, etc. Since it is a repetitive pattern, it is particularly effective. According to the present invention, the joint portions of the divided exposure portions are not made simple joints, but the joint data are overlapped with each other, and the knot portion is composed of composite data. Therefore, it is possible to prevent the difference in sensitivity and transfer efficiency between the connected portions from being noticed. In the past, dimensional differences, pattern shape differences, positional deviations, etc. were caused by the effects of aberrations and distortions of the lens of the exposure light source, focus differences at the joints, exposure energy differences, reticle size differences, etc. According to the configuration, it is possible to avoid these problems and obtain a highly sensitive solid-state imaging device.

In the solid-state imaging device manufacturing method according to the present invention, the mask data may include a data retention rate that varies according to a distance from a center line of the overlapping region.
According to this method, depending on the distance from the joint portion, the density of the pixel data is changed and the mutual data is mixed, thereby eliminating or conspicuous the joint portion. When the divided exposure includes left and right or upper and lower joint exposure areas, a certain data area is overlapped (overlapped) from the joint. A normal pattern is formed by overlapping the data in the overlapped area on the left and right or top and bottom, and the data retention rate of each data area near the joint varies according to the distance from the overlap end. For example, in the case of stitching in upper and lower divided exposure, the upper area data retention rate at the upper end of the overlap is 0% lower area data retention rate 100%, and the upper area data retention rate is 50% lower area data at the regular joint portion. In the case of joining from the holding ratio 50%, the upper area data holding ratio at the lower end of the overlap is changed to 100% lower area data holding ratio 0%. In addition, the arrangement of the data in the overlap portion is alternated up and down by a certain unit according to the holding ratio. The same applies to a four-layer overlap that overlaps vertically and horizontally, and can be handled by changing the data storage ratio.

Moreover, the manufacturing method of the solid-state image sensor of this invention contains the said data retention rate changing continuously.
According to this method, since the data retention rate is continuously changed, the boundary can be made less noticeable.

In the method for manufacturing a solid-state imaging device according to the present invention, the data retention rate includes reciprocal numbers on equidistant lines with the center line as a center.
According to this method, it is easy to form data.

The solid-state imaging device manufacturing method of the present invention is characterized in that a boundary line between the first and second regions is in the charge transfer section.
According to this method, a high degree of pattern accuracy can be maintained without causing pattern deterioration even when the charge transfer unit is divided.

  According to this method, since the joint portion of the divided exposure portion is not made a simple joint, the joint data is overlapped, and the joint portion is composed of composite data. The difference and the transfer efficiency difference can be made unobtrusive.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
As shown in FIG. 1, the solid-state imaging device includes a photoelectric conversion unit, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and the photoelectric conversion unit or the charge transfer unit. A solid-state imaging device having a wiring portion connected to the substrate, wherein an exposure process for pattern formation of an amorphous silicon layer constituting the photoelectric conversion portion, the charge transfer portion, or the wiring portion is performed by divided exposure. It is realized.
This solid-state imaging device includes a light receiving region R including a photoelectric conversion unit, a vertical transfer path V formed in the light receiving region R and configured by a charge transfer unit, and a horizontal transfer path similarly configured by a charge transfer unit. FIG. 2 shows an active region T including H, an output circuit (peripheral circuit) O including an amplifier, and a pad p formed in the periphery, and including the light receiving region, the vertical transfer path, and the horizontal transfer path. The division exposure is performed using a reticle having various mask data.

As shown in FIG. 2, a first exposure step of exposing a first area including an overlapping area O _AB with an adjacent second area using the data of the data area A on the reticle, and the reticle A second region that exposes a second region that includes an overlap region _OAB with the first region and an overlap region _OBB with a third region adjacent on the other end side using the data in the upper data area B third including an exposure step, and the overlap area O _BB of the second area using the data of the data area B on the reticle, and the overlap region O _BB and the fourth area adjacent at the other end of the A third exposure step that exposes the second area, and an overlapping area _OBB that overlaps the third area with the third area by using the data in the data area B on the reticle and the fifth area that is adjacent on the other end side. _A fourth exposure step of exposing a fourth region including _BC ; And a fifth exposure step of exposing a fifth region including the data area C area O _BC overlaps with the fourth region data using the on the reticle, the overlapping area is used wherein in each exposure step A composite image of the mask data to be formed is constructed.

In this overlap area, as shown in an enlarged view in FIG. 3, the data in the data area A on the reticle used in the first exposure process for exposing the first area and the second area for exposing the second area are exposed. The data of the data area B on the reticle used in the exposure process is the center line C which is the original joint in the overlap area _OAB , and the area data retention ratio is A: B = 1: 1. Centering on the line C, the area data holding ratio at the upper end of the overlap is A: B = 100: 0, and the area data holding ratio at the lower end of the overlap is A: B = 0: 100, which is gradually continuous. Is changing. The data retention rate here refers to the data ratio between the mask data used in one exposure process and the mask data used in the exposure process following this exposure process, which occupies a certain area.

According to this method, the connecting portions of the divided exposure portions are not simply connected, but the connecting data are overlapped with each other, and the connecting portion is composed of synthesized data. The difference and the transfer efficiency difference can be made unobtrusive.
In this way, highly accurate exposure can be realized.

  When creating mask data, the layout should be such that the continuous pattern is not arranged at the joint as much as possible, and the joint is positioned in the area that is almost in the focal position in the exposure apparatus used by simulating the height level. It is desirable to create the joint data after adjusting the layout so that the pattern at the joint is reduced as much as possible and the fine pattern is not formed.

(Embodiment 2)
In this solid-state imaging device manufacturing method, as shown in FIG. 4A, a part of a mask for forming an amorphous silicon pattern constituting a signal line is shown in a first exposure step of exposing a first region. Data in the data area A on the used reticle and data in the data area B on the reticle used in the second exposure process for exposing the second area are the original junctions in the overlapping area O _AB . In the center line C, the area data retention rate is A: B = 1: 1. With this center line C as the center, the area data retention rate at the upper end of the overlap is A: B = 1: 0, A: B = 3: 1, A: B = 2: 1 and changes as the center line C is approached. The area data retention rate at the lower end of the overlap is A: B = 0: 1, and changes as the center line C approaches A: B = 1: 3 and A: B = 1: 2.
The composite pattern formed using the reticle thus obtained forms one line as shown in FIG. 4B, and the discontinuous portion is hardly conspicuous.
In this way, it is possible to obtain a pattern with no borderline even in divided exposure.

In the above-described embodiment, the data ratio is changed to a plurality of stages. However, it is better that the stage is finer, and a more natural line can be obtained by making it continuous.
However, the finer the variable rate of the data retention rate, the more complicated the data construction.
In the above embodiment, the pattern formation of the wiring layer has been described. However, the present invention can also be applied to a pattern of an insulating layer, a pattern of a light shielding film, and the like.

  In the above-described embodiment, the method for manufacturing the solid-state imaging device has been described. However, the present invention is not limited to the above-described embodiment, can be appropriately changed, and can be applied to pattern formation of other devices. Absent.

  As described above, according to the present invention, in the divided exposure, the data of the overlap portion is configured by changing the data retention rate step by step, and this is synthesized to combine the target pattern with the characteristics of the joint. Since the difference can be eliminated and high-precision pattern formation can be realized, it is applicable to formation of a large-sized solid-state imaging device.

Plane explanatory drawing of the solid-state image sensor formed with the method of Embodiment 1 of this invention Explanatory drawing of the reticle used at the exposure process in the manufacturing method of the solid-state image sensor of Embodiment 1 of this invention Explanatory drawing of the principal part of the reticle used in the exposure process in the method for manufacturing the solid-state imaging device according to the first embodiment of the present invention. Explanatory drawing of the reticle used at the exposure process in the manufacturing process of the solid-state image sensor of Embodiment 2 of this invention Explanatory drawing of the reticle used in the exposure process in the manufacturing process of the conventional solid-state imaging device

Explanation of symbols

A Data area B Data area C Data area O _AB overlapping area O _BB overlapping area O _BC overlapping area

Claims (6)

A pattern forming method for forming a desired pattern by exposing a wafer surface through a mask,
An exposure process for forming the pattern includes:
A first exposure step for exposing the first region;
A second exposure step of exposing a second region having an overlapping region between the first region and the first region,
The pattern forming method, wherein the overlapping region constitutes a composite image of mask data used in both the first and second exposure steps. A solid-state imaging device comprising: a photoelectric conversion unit; a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit; and a wiring unit connected to the photoelectric conversion unit or the charge transfer unit A method of manufacturing
An exposure process for forming a pattern constituting the photoelectric conversion unit, charge transfer unit or wiring unit,
A first exposure step for exposing the first region;
A second exposure step of exposing a second region having an overlapping region between the first region and the first region,
The method of manufacturing a solid-state imaging device, wherein the overlapping region constitutes a composite image of mask data used in both the first and second exposure steps. It is a manufacturing method of the solid-state image sensing device according to claim 2,
The method of manufacturing a solid-state imaging device, wherein the mask data is configured such that a data retention rate changes according to a distance from a center line of the overlapping region. It is a manufacturing method of the solid-state image sensing device according to claim 3,
The method for manufacturing a solid-state imaging device, wherein the data retention rate is continuously changed. It is a manufacturing method of the solid-state image sensing device according to claim 3 or 4,
The method of manufacturing a solid-state imaging device, wherein the data retention rates are reciprocal with each other on equidistant lines with the center line as a center. A method for manufacturing a solid-state imaging device according to any one of claims 2 to 5,
A solid-state imaging device manufacturing method, wherein a boundary line between the first and second regions is in the charge transfer section.

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