JPH01217303A - Method of forming color filter - Google Patents

Abstract

PURPOSE:To improve the work efficiency, and the position accuracy of a filter by forming a pattern by applying a photoresist to the surface of a substrate, and subsequently, affixing a filter film to its surface by applying or printing a filter paint of an inorganic pigment and immersing the substrate into a solvent of the photoresist. CONSTITUTION:A photoresist is applied to a semiconductor substrate 1, and thereafter, a photoresist 4 on a light detecting element 2 for detecting a color is eliminated by mask exposure and development. Subsequently, an inorganic pigment 5 is applied onto a pattern of the photoresist by a printing method or a spin coating method. Next, by immersing the substrate into a solvent of the photoresist, the photoresist film is eliminated together with the inorganic pigment 5 which has been applied onto said film and a pattern of a color filter 6 is obtained. Since the inorganic pigment can be used, the filter film itself becomes stable chemically, as well, comparing with a dyed filter film. In such a way, a pattern of a stable filter film can be formed with high accuracy and efficiently on an image sensor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a color filter on the surface of a semiconductor wafer or a glass substrate, and is used for forming a filter for a color image sensor.

Traditional technique (hoi) Nowadays, small size products are available for industrial use, office use, and home use.

Demand for lightweight and highly reliable color image sensors is increasing. For example, high-resolution two-dimensional color image sensors are being used in television cameras, and high-resolution two-dimensional color image sensors are being used in digital color copying machines. These image sensors consist of an array of photodetecting elements formed on a semiconductor substrate ``2'', a scanning circuit, and a filter for color separation formed on the photodetecting element ``2''. Conventionally, methods for forming color filters include: (1) pasting a color filter plate previously formed on a glass plate in alignment with each pixel of the photodetector element of an image sensor;

■A dyeing medium such as a gelatin film containing a sensitizer is applied onto a conductive substrate to form an image sensor circuit.
There is a method in which this is subjected to mask exposure and development, and then dyed to form a predetermined color filter pattern. In method 0), as the resolution increases, the pixel size and pitch become smaller, making it difficult to align the filter position and the pixels. Since the method (2) uses mask exposure, the positional accuracy of the filter on each pixel is good, but since the filter material is a dyed organic material, it is susceptible to fading when used for a long time under high illuminance. It becomes a problem.

Problems to be Solved by the Invention With the method of bonding a color filter formed on a glass plate-F onto an image sensor chip, it becomes difficult to achieve the necessary positional accuracy as resolution increases. Further, in this method, it is necessary to attach the filter to each sensor vise, which increases the number of steps.

In the dyeing method, which consists of a gelatin film containing an aggravating agent, the pattern is formed using a photomask method, so the positioning accuracy is good, but it is necessary to use a photosensitive organic material for the filter material, which causes problems with fading. Color shift may occur under high illumination or long-term use.

This is a particular problem for image sensors in industrial cameras and image sensors in digital color copying machines.

Means for Solving the Problem First, a photoresist is spin-coded to a desired thickness on a semiconductor substrate on which elements and circuits necessary for an image sensor are formed, and each pixel-F is exposed through a photomask and developed. Remove the photoresist. Thereafter, a first color filter paint made of a non-alpha pigment is printed or spin-coated on this wafer, and after drying, it is immersed in a photoresist solvent to coat areas other than the pixel surface (;1 The deposited photoresist is removed together with the filter film covered by it.As a result, only the filter on each pixel remains, and the filter in other areas is removed to form a filter film in a predetermined pattern.After that, The filter film is dried and cured at a temperature of 100 to 200°C.The second color filter paint and the third color filter paint are also sequentially formed in the same manner.Substrates on which color filters are formed are not limited to semiconductor wafers. For example, a color filter can be formed on a glass substrate by a similar method.

Effect: According to this method, an inorganic pigment can be used as the filter material, so a filter film that is resistant to fading can be formed. Furthermore, since the pattern is formed using a photomask method, the positioning accuracy of the filter is good, and it can also be used to form filters for high-resolution image sensors. Furthermore, since the filter forming process can be performed on a wafer basis, work efficiency is improved.

Embodiment 2 Figures fal and bl respectively show examples of plan views of a one-dimensional and two-dimensional color image sensor formed on a Si crystal substrate. It can be seen in the configuration of three rows of colors.In the two-dimensional sensor, color filters 15 of three colors are attached in a mosaic pattern.

Note that 16 and 17 are scanning circuits formed on the same substrate.

FIG. 3 is a sectional view of the light detection section of the image sensor. The semiconductor substrate 1 has a photodetecting element 2. 7. 10 is formed in advance by a semiconductor process.

A red filter 6 is placed on the surface of the photodetecting element 2 for red detection, a green filter 9 is placed on the surface of the photodetecting element 7 for green detection, and a blue filter is placed on the surface of the photodetecting element 10 for blue detection. A filter 12 is attached, and the color-separated light is incident on each photodetector element. In recent years, high resolution has progressed, and one-dimensional image sensors with a resolution of 16 tof)/m2 have a pixel pitch of 62.5 μm and a photodetector element size (pixel size) of approximately 55 x 55 μM, making it possible to produce two-dimensional images at the level of 250,000 pixels. In the sensor, pixel pinch 10μm 1 pixel size 7×
It is also 7μM. Therefore, techniques for forming fine color filter patterns at predetermined positions are becoming increasingly important.

FIG. 1 shows the process of forming a color filter according to the present invention. FIG. 1(a) does not show the state in which a photoresist is coated on a semiconductor substrate 1 on which a photodetection element and a scanning circuit have been formed in advance, and then a photoresist is applied to a photodetection element for detecting red color. 3 is a protective film made of SiO2 or SiN film, and 4 is a resist. Figure 1(b)
The red inorganic pigment 5 was applied to the Tsume I/Resos I pattern by the printing method or spin-to method. In FIG. 1 tc), the photoresist film is removed together with the inorganic pigment 5 coated thereon by drying and curing the coating film made of the inorganic pigment and then immersing it in a photoresist solvent. This is a pattern of a filter formed on a photodetecting element for red color by 6G and 1 steps.

Figure 1(d) shows a photodetector element for red color.A red filter pattern is formed on the photodetector element for red color.A photoresist layer 1~ is applied to the semi-iron substrate. 7) shows the state in which the resist has been removed by mask exposure and development. FIG. 1te) shows a state in which a green inorganic pigment 8 is applied to the surface of this substrate by a printing method or a Subinko method. Figure 1) shows the coating film made of inorganic pigment, which is dried and cured.
By applying the 4-layer coating, the Folresist 11 was removed along with the 1-column face F) 8 that was applied to the 10th area. 9 is a filter pattern formed on the photodetector element 2 for green color through this process.

Figure 1 (b) shows a photo-detecting element for red. Second, a red filter pattern is formed on the photo-detecting element for green, and a green filter pattern is formed on the semiconductor substrate. After coating photoresist on the semiconductor substrate. , photodetector for blue color] The photoresist on [0] is shown removed by mask exposure and development. Printing method or spin coat I on the surface of this substrate.
・The state in which the blue inorganic pigment 11 is applied by the method is shown in FIG. 1 (hl). FIG.

After curing, the photoresist I film is coated with the inorganic pigment 1 by dipping it in a photoresist solvent.
It was removed along with 1. 12 A pattern of filters formed on the photodetecting element for blue color by the tobacco process.

FIG. 1(j) shows the final form of the filter forming method according to the present invention, in which each filter is coated with a transparent filter protective film 13.

In the above steps, filters are formed in the order of red, green, and blue, but this order may be changed. Also, I use red, green, and blue as filters, but the complementary colors are yellow and cyan.

You can also use green.

In this method, since an inorganic pigment can be used, it is chemically more effective than the filter membrane itself or a dyed filter membrane.
It is also optically stable. The accuracy of the filter pattern is high because it is based on the fumetomask method.

Therefore, both stability and positional accuracy of the filter membrane can be achieved.

Effects of the Invention As described above, according to the present invention, a stable filter film pattern can be formed on an image sensor substrate with high precision and efficiency. Therefore, it is extremely useful as a method for forming various color image sensors, and has extremely large industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing the process of forming a color filter according to the present invention, Fig. 2 is a plan view of one-dimensional and two-dimensional color image sensors formed on a crystal substrate, and Fig. 3 is a light detection of the image sensor. FIG. 1... Semiconductor substrate, 2.7.10...
Photodetecting element, 3... Semiconductor protective film, 6, 9.
12... Color filter, 13... Filter protective film.

Claims (2)

[Claims] (1) After coating the surface of the substrate on which the color filter is to be formed with photoresist, exposing it to light through a photomask,
A process of forming a predetermined pattern by developing, followed by a process of attaching a filter film by applying or printing a filter paint made of an inorganic pigment on the surface, and then a process of forming a filter by immersing it in a photoresist solvent. A method for forming a color filter, comprising the step of selectively removing a film according to a pattern of a photoresist. (2) The method for forming a color filter according to claim 1, wherein the substrate on which the color filter is formed is a semiconductor substrate on which a circuit necessary for an image sensor or an optical sensor has been formed in advance.