Image sensor having yellow filter units

The present disclosure relates to an image sensor, and in particular to an image sensor having yellow filter units.

In general, a digital camera utilizes an image sensor to sense light and generate an image signal, and thus a picture taken by the digital camera can be generated according to the image signal.

As digital cameras continue to develop, high-quality image signals are increasingly required. The image sensors using a backside illumination (BSI) technology have light pipe structures to guide light to photodiodes. The image sensors have greater sensitivity and image quality.

Although image sensors have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. Consequently, it is desirable to provide a solution for improving image sensors.

The present disclosure provides an image sensor having yellow filter units for improved sensitivity and image quality.

The present disclosure provides an image sensor including a sensing layer for sensing a light beam and a number of pixel groups. Each of the pixel groups includes a yellow filter unit allowing a green light component and a red light component of the light beam to pass through, a green filter unit allowing the green light component of the light beam to pass through, and a blue filter unit allowing a blue light component of the light beam to pass through.

The present disclosure provides an image sensor including a sensing layer for sensing a light beam and a number of pixel groups. Each of the pixel groups includes a first color group, a second color group, and a third color group. The first color group includes a yellow filter unit allowing a green light component and a red light component of the light beam to pass through, and a first clear filter unit allowing the red, green and blue components of the light beam to pass through.

The second color group includes a green filter unit allowing the green light component of the light beam to pass through, and a second clear filter unit allowing the red, green and blue components of the light beam to pass through. The third color group includes a blue filter unit allowing a blue light component of the light beam to pass through, and a third clear filter unit allowing the red, green and blue components of the light beam to pass through.

The present disclosure provides an image sensor including a sensing layer for sensing a light beam and a number of pixel groups. Each of the pixel groups includes a first color group, a second color group, and a third color group. The first color group includes a yellow filter unit allowing a green light component and a red light component of the light beam to pass through, and a number of first clear filter units allowing the red, green and blue components of the light beam to pass through. The yellow filter unit and the first clear filter units are arranged in a first filter array.

The second color group includes a green filter unit allowing the green light component of the light beam to pass through, and a number of second clear filter units allowing the red, green and blue components of the light beam to pass through. The green filter unit and the second clear filter units are arranged in a second filter array.

The third color group includes a blue filter unit allowing a blue light component of the light beam to pass through, and a number of third clear filter units allowing the red, green and blue components of the light beam to pass through. The blue filter unit and the third clear filter units are arranged in a third filter array. The pixel groups do not include a red filter unit allowing the red light component of the light beam to pass through, but block the green light component and the blue light component of the light beam.

In conclusion, the red filter units in a conventional image sensor are replaced by the yellow filter units. The yellow filter units allow green and red light components of light beams to pass through, and the yellow, green, and blue filter units match the human eye's cone spectrum. Therefore, the sensitivity and the image quality of the image sensor are improved.

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a schematic view of an image sensor in accordance with some embodiments of the present disclosure.

FIG. 2 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 3A is transmittance vs. wavelength diagrams of filter units in accordance with some embodiments of the present disclosure.

FIG. 3B is a human eye's response spectrum diagrams.

FIG. 4 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 5 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 6 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 7 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 8 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 9 is a top view of the filter units in accordance with some embodiments of the present disclosure.

FIG. 10 is a top view of the filter units in accordance with some embodiments of the present disclosure.

The following disclosure provides many different embodiments, or examples, for implementing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact.

In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Furthermore, the shape, size, and thickness in the drawings may not be drawn to scale or simplified for clarity of discussion; rather, these drawings are merely intended for illustration.

FIG. 1 is a schematic view of an image sensor 1 in accordance with some embodiments of the present disclosure. The image sensor 1 is configured to capture an image. The image sensor 1 can be applied to an imaging apparatus, such as a digital camera. In some embodiments, the image sensor 1 is a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. In some embodiments, the image sensor 1 may be a BSI (backside illumination) CMOS sensor.

The image sensor 1 includes a sensing layer 10 , filter units 20 , microlenses 30 , and a process module 40 . The sensing layer 10 extends along a reference plane P 1 . The sensing layer 10 is configured to detect incident light beams according to the light beams falling on the sensing layer 10 .

The sensing layer 10 may include all of the following elements, but the sensing layer 10 does not necessarily include all of the following elements, as long as the object of the sensing layer 10 is achieved. The sensing layer 10 includes a substrate 11 , sensing units 12 , and a passivation layer 13 . In some embodiments, the sensing layer 10 further includes other optional layers (not shown in figures).

The sensing units 12 are disposed in the substrate 11 . The sensing units 12 are arranged in a sensing array at the reference plane P 1 . In some embodiments, the sensing units 12 are photodiodes. Each of the sensing units 12 is configured to sense light beams and generate an intensity signal according to the intensity of the light beams falling thereon. An image can be generated according to the intensity signals by the process module 40 .

The passivation layer 13 is disposed on the substrate 11 . The passivation layer 13 is to protect circuit (not shown in figures) underneath of the sensing units 12 . In some embodiments, the passivation layer 13 is parallel to the sensing layer 10 .

FIG. 2 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. As shown in FIGS. 1 and 2 , the filter units 20 are disposed on the passivation 13 of the sensing layer 10 . The filter units 20 are arranged in a filter array on a plane parallel to the reference plane P 1 . Each of the filter units 20 is disposed over one of the sensing units 12 . The filter units 20 are color filter units. Each of the filter units 20 allows a predetermined range of wavelengths of light beam to pass through.

In some embodiments, several filter units 20 belong to a pixel group E 1 . In other words, the pixel groups E 1 are disposed over the sensing units 12 , and arranged in a pixel array on a plane parallel to the reference plane P 1 . Each of the pixel groups E 1 corresponds to one pixel of the image captured by the image sensor 1 .

The number of filter units 20 included in one pixel group E 1 is not limited. Fore example, the pixel group E 1 includes at least two, three or four filter units 20 . In this embodiment, the filter units 20 in each of the pixel groups E 1 are arranged along a linear line.

The microlenses 30 are disposed on the pixel groups E 1 . Each of the microlenses 30 is disposed on one of the filter units 20 . The microlenses 30 are arranged in a microlens array on a plane parallel to the reference plane P 1 . The microlenses 30 are configured to focus light beams to the sensing units 12 .

The process module 40 is electrically connected to each of the sensing units 12 . The process module 40 is configured to receive the intensity signals from the filter units 20 .

As shown in FIG. 1 , when a light beam falls on the image sensor 1 , the light beam passes through the microlenses 30 and the filter units 20 to the sensing units 12 . The light beam is focused by the microlenses 30 . Each of the filter units 20 allows a predetermined range of wavelengths of light beam to pass. Each of the sensing units 12 generates an intensity signal according to the intensity of the light beam passing through the filter units 20 of pixel groups E 1 falling thereon. The process module 40 receives the intensity signals from the sensing units 12 and generates an image according to the intensity signals.

As shown in FIGS. 1 and 2 , the filter units 20 include yellow filter units 20 a , green filter units 20 b , and blue filter units 20 c . The yellow filter units 20 a , the green filter units 20 b , and the blue filter units 20 c are alternately arranged on the sensing layer 10 .

In this embodiment, one pixel group E 1 includes one yellow filter unit 20 a , one green filter unit 20 b , and one blue filter units 20 c . The yellow filter unit 20 a , the green filter unit 20 b , and the blue filter unit 20 c are arranged along a linear line. In some embodiments, the pixel group E 1 includes at least two yellow filter units 20 a , green filter units 20 b , and/or blue filter units 20 c.

FIG. 3A is a transmittance vs. wavelength diagrams of filter units 20 in accordance with some embodiments of the present disclosure. The yellow filter unit 20 a allows a green light component and a red light component of the light beam to pass through. In some embodiments, the yellow filter unit 20 a is a high-pass filter allowing wavelengths of the light beam longer than a specific wavelength to pass through, and the specific wavelength is defined as a 50% transmittance wavelength in a range from about 470 nm to 540 nm. In other words, at least 50% of the light beam with the wavelengths longer than the specific wavelength of visible light can pass through the yellow filter unit 20 a.

The green filter unit 20 allows the green light component of the light beam to pass through. In some embodiments, the green filter unit 20 is a band-pass filter allowing a green waveband of the light beam pass through. In some embodiments, the green waveband in a range from about 470 nm to about 600 nm of 50% transmittance wavelength. In other words, at least 50% of the light beam in the green waveband can pass through the green filter unit 20 . A short 50% transmittance wavelength, such as 470 nm, of the green waveband is equal to or shorter than the specific wavelength of yellow filter units 20 .

The blue filter unit 20 allows a blue light component of the light beam to pass through. In some embodiments, the filter units 20 and the pixel groups E 1 do not include any red filter unit 20 allowing the red light component of the light beam, but block the green light component and the blue light component of the light beam.

Accordingly, the yellow filter units 20 a allow more of the light beam to pass than the red filter units, and so the sensitivity of the image sensor 1 is improved. Moreover, the yellow, green, and blue filter units match the human eye's cone spectrum as shown in FIG. 3B . Therefore, the sensitivity and the image quality of the image sensor are improved.

In some embodiments, the sensing units 12 include sensing units 20 a , sensing units 12 b , and sensing units 12 c . The sensing units 12 a are disposed under the yellow filter units 20 a , and configured to generate yellow intensity signals according to the intensity of the light beam passing through the yellow filter units 20 falling thereon.

The sensing units 12 b are disposed under the green filter units 20 b , and configured to generate green intensity signals according to the intensity of the light beam passing through the green filter units 20 b falling thereon.

The sensing units 12 c are disposed under the blue filter units 20 c , and configured to generate blue intensity signals according to the intensity of the light beam passing through the blue filter units 20 c falling thereon.

The process module 40 is configured to receive the yellow intensity signal, the green intensity signal, and the blue intensity signal of each of the pixel groups E 1 . The process module 40 generates a yellow pixel value according the yellow intensity signal, a green pixel value according the green intensity signal, a blue pixel value according to the blue intensity signal, and a red pixel value according to the yellow intensity signal and the green intensity signal.

In some embodiments, the process module 40 generates the red pixel value by the yellow intensity value minus the green intensity value. In some embodiments, the red intensity value, the green intensity value, and the blue intensity value are integers in a range from 0 to 1023.

The red pixel value corresponds to a red color, the green pixel value corresponds to a green color, and the blue pixel value corresponds to a blue color. The process module 40 generates pixel values according to the green, blue, and red pixel values of each of the pixel groups E 1 . Therefore, an image can be generated according to the pixel values of the pixel groups E 1 by the process module 40 .

FIG. 4 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. In some embodiments, the filter units 20 are arranged in an N×M array. The N and M are integers. In some embodiments, the N and M are in a range from 2 to 10. For example, the filter units 20 are arranged in a 2×2, 2×3, 2×4, 3×3, 3×4, or 4×4 array.

The pixel groups E 1 are arranged in a pixel array. In this embodiment, the pixel group E 1 includes four filter units 20 . The filter units 20 are arranged in a 2×2 array. In some embodiments, the pixel group E 1 includes two green filter units 20 b , one yellow filter unit 20 a and one blue filter unit 20 c . The green filter units 20 b are arranged at two opposite corners of the pixel group E 1 . The yellow filter unit 20 a and the blue filter unit 20 c are arranged at other opposite corners of the pixel group E 1 .

Since the human eye is sensitive to the color green, the number of green filter units 20 b is greater than the number of yellow filter units 20 a and/or the number of blue filter units 20 c . Therefore, the green colors of the image generated by the image sensor 1 have more details, and the image quality of the image sensor 1 is improved.

FIG. 5 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. In this embodiment, the pixel group E 1 includes two yellow filter units 20 a . The yellow filter units 20 a are arranged at two opposite corners of the pixel group E 1 , and the green filter unit 20 b and the blue filter unit 20 c are arranged at other opposite corners of the pixel group E 1 .

Accordingly, the red and green colors of the image are improved since the number of yellow filter units 20 a is greater than the number of green filter units 20 b and/or the number of blue filter units 20 c.

FIG. 6 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. In some embodiments, each of the pixel groups E 1 further includes one or more enhancing filter units 20 . In this embodiment, the enhancing filter unit 20 d allows an infrared ray component of the light beam to pass through. The yellow filter unit 20 a , the green filter unit 20 b , the blue filter unit 20 c , and the enhancing filter unit 20 d are arranged in a filter array. Therefore, the image sensor 1 can be a spectrum-inspection device. The infrared ray can be displayed in the image by the enhancing filter units 20 d.

FIG. 7 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. In some embodiments, the enhancing filter unit 20 d is a clear filter unit. In some embodiments, the clear filter unit 20 d is made from a transparent material, such as organic transparent materials or transparent photoresists. The clear filter unit 20 d allows the light beam to pass through. In some embodiments, the clear filter unit 20 d does not filter the light beam.

Since the red, green, and blue components of the light beam can pass through the clear filter unit 20 d , the quantity of the of light beam sensed by the sensing unit 12 , which under the clear filter unit 20 d , is increased. Moreover, the sensitivity of the sensing unit 12 , which under the clear filter unit 20 d , is increased. Therefore, the intensity of the yellow, green and blue intensity signals relative to the yellow, green, blue filter units 20 a , 20 b and 20 c can be adjusted by the process module 40 (as shown in FIG. 1 ) according to the intensity signals relative to the clear filter unit 20 d . Therefore, the sensitivity of the image sensor is improved.

FIG. 8 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. In FIG. 8 , there is only one pixel group E 1 is illustrated for clarity. Each of the pixel groups E 1 includes color groups E 2 . In some embodiments, the color groups E 2 are arranged in a color array. In this embodiment, the color array is a 2×2 array.

The color group E 2 includes the color groups E 21 , E 22 and E 23 . The color group E 21 includes at least one yellow filter unit 20 a and at least one clear filter unit 20 d . In this embodiment, the color group E 21 includes two yellow filter units 20 a and two clear filter units 20 arranged in a 2×2 array. Therefore, the sensitivity of the image sensor 1 relative to the yellow components of the light beam is improved.

The color group E 22 includes at least one green filter unit 20 b and at least one clear filter unit 20 d . In this embodiment, the color group E 22 includes two green filter units 20 b and two clear filter units 20 arranged in a 2×2 array. Therefore, the sensitivity of the image sensor 1 relative to the green components of the light beam is improved. In addition, since the pixel group E 1 includes at least two color groups E 22 , the sensitivity of the image sensor 1 to the green components is further improved.

The color group E 23 includes at least one blue filter unit 20 c and at least one clear filter unit 20 d . In this embodiment, the color group E 23 includes two blue filter units 20 and two clear filter units 20 arranged in a 2×2 array. Therefore, the sensitivity of the image sensor 1 relative to the blue components of the light beam is improved.

FIG. 9 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. The color group E 2 includes color groups E 22 and E 24 . The color group E 24 includes at least one yellow filter unit 20 a , at least one blue filter unit 20 c and at least two clear filter units 20 d . In this embodiment, the color group E 24 includes one yellow filter unit 20 a , one blue filter unit 20 c and two clear filter units 20 d.

FIG. 10 is a top view of the filter units 20 in accordance with some embodiments of the present disclosure. The color group E 2 includes color groups E 25 and E 26 . The color group E 25 includes at least one yellow filter unit 20 a , at least one green filter unit 20 b and at least one clear filter unit 20 d . In this embodiment, the color group E 25 includes one yellow filter unit 20 a , one green filter unit 20 b and two clear filter units 20 d.

The color group E 26 includes at least one blue filter unit 20 c , at least one green filter unit 20 b and at least one clear filter unit 20 d . In this embodiment, the color group E 25 includes one blue filter unit 20 c , one green filter unit 20 b and two clear filter units 20 .

In conclusion, the red filter units in a conventional image sensor are replaced by the yellow filter units. The yellow filter units allow green and red light components of light beams to pass through, and the yellow, green, and blue filter units match the human eye's cone spectrum. Therefore, the sensitivity and the image quality of the image sensor are improved.

While the invention has been described by way of example and in terms of preferred embodiment, it should be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.