KR100664860B1 - Image sensor for defect pixel concealment - Google Patents

Abstract

According to the present invention, the address of a defective pixel is recorded inside a chip by an on / off method of a fuse through a laser blowing, and the compensation for the defective pixel is easily performed internally or externally using the recorded defective pixel address. The present invention provides an image sensor for compensating for defective pixels, which can be performed. To this end, the present invention is arranged in unit pixels of N (column number) × M (line number) to sense information about an image coming from the outside. An image sensor having a pixel array, the image sensor comprising: a fuse means for recording addresses of a plurality of defective pixels found in a wafer test of the image sensor in a laser melting method in the pixel array; In response to the recorded defective pixel address, a compensation operation for the defective pixel is performed.

Compensation for image sensor, defective pixel, laser blown, fuse block, defective pixel

Description

Image sensor for defective pixel compensation {IMAGE SENSOR FOR DEFECT PIXEL CONCEALMENT}             

1 conceptually illustrates a pixel array to illustrate the present invention.

2 is an internal block diagram of an image sensor according to an embodiment of the present invention;

3 is a view illustrating a unit fuse unit for recording an address 1 bit of a bad pixel of the fuse block of FIG. 2 according to an embodiment of the present invention;

Figure 4 is an internal block diagram of an image sensor according to another embodiment of the present invention.

FIG. 5 is an internal block diagram of a compensation circuit unit in the image sensor of FIG. 4 according to another embodiment of the present invention; FIG.

* Description of the main parts of the drawing

10, 100: pixel array 12, 120: ADC

14, 140: buffer memory 16, 160: digital block

18, 180: fuse block 200: compensation circuit

300: bad pixel address buffer                 

320: comparator 40, 380: multiplexer

360: reward block

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor, and in particular, location information (address) of defective pixels found during wafer testing due to a problem in the manufacturing process of the image sensor is recorded in a chip by a laser method The present invention relates to an image sensor for defective pixel compensation (hereinafter referred to as DPC), which makes it possible to easily compensate for a defective pixel using an address of a defective pixel recorded internally or externally.

In general, an image sensor is a device that captures an image by using a property of a semiconductor that reacts to light. Part of each subject in the natural world has different electrical values at each pixel of the sensing device due to different brightness and wavelength of light, which makes the image sensor a level capable of signal processing. Is what it does.

To this end, an image sensor consists of a pixel array consisting of hundreds of thousands to millions of pixels, a device that converts analog data sensed by the pixel into digital data, and hundreds to thousands of storage devices. Due to the large number of devices, the image sensor always has a process error.

On the other hand, the quality of the image sensor is a product grade is determined according to the number of defective pixels, the smaller the number of defective pixels is a good product. Errors caused by such defective pixels in the image sensor appear as small spots or lines on the screen. In this case, when all the image sensor chips having such partial errors are determined as defective chips, the yield is reduced.

Therefore, the problem of increasing the yield by DPC image sensor with a partial error due to defective pixels has been a great concern of chip developers and system developers.

Recently, image sensor developers divide image sensor chips according to the number of defective pixels and sell image sensor chips to system developers at different prices depending on the grade. When the chip is supplied, the board is retested with the pixels of the image sensor, and the defective pixels found are properly compensated for use in the system. More specifically, a system developer may test an image sensor including a plurality of defective pixels on a board, write an address of a defective pixel on an EEPROM, and separate data of defective pixels in response to an address recorded in the EEPROM. By compensating with, we use an image sensor with partial error in the same way as a normal image sensor.

In addition to the tests conducted during the chip manufacturing, the DPC by the system developer has to test the pixels for defects by taking the pixels of the image sensor on the system board one by one, and thus the system development period using the image sensor becomes longer. There is a problem in that the board configuration is complicated by requiring a separate EEPROM on the board.

In order to solve the DPC problem caused by the system developer, the image sensor chip manufacturer records the address of the defective pixel found in the wafer test in a separate EEPROM, and packages the EEPROM and the image sensor chip together. System vendors can develop their systems without any pixel testing. However, in this case, there is another problem that a separate process step for the EEPROM is required in addition to the process step of the image sensor, and the entire process procedure is complicated.

The present invention has been made to solve the above problems, by recording the address of the defective pixel in the chip in the on / off method of the fuse through the laser blowing (blowing), the internal or by using the address of the recorded defective pixel It is an object of the present invention to provide an image sensor for compensating for defective pixels, which enables the external to easily compensate for a corresponding defective pixel.

According to an aspect of the present invention, there is provided an image sensor including a pixel array arranged in unit pixels of N (column number) × M (line number) to sense information about an image from outside. It provides an image sensor comprising a fuse means for recording the address for a plurality of defective pixels found in the wafer test of the image sensor in a laser melting method.

Preferably, the present invention provides an image sensor, comprising: a pixel array arranged in unit pixels of N (column number) x M (line number) to sense information about an image coming from the outside; Analog-digital conversion means for converting the analog data sensed by the unit pixel into digital data; A buffer memory for storing digital data output from the analog-digital converting means; Digital control means for controlling the interface with the outside and the operation of the image sensor; And fuse means for recording the addresses of the plurality of defective pixels found in the wafer test of the image sensor among the pixel arrays in a laser melting manner, and externally connected to the fuse means through the digital control means. It is configured to read the address of the recorded defective pixel and perform compensation for the defective pixel.

More preferably, the present invention provides an image sensor, comprising: a pixel array arranged in unit pixels of N (column number) x M (line number) to sense information about an image from outside; Analog-digital conversion means for converting the analog data sensed by the unit pixel into digital data; A buffer memory for storing digital data output from the analog-digital converting means; Digital control means for controlling the interface with the outside and the operation of the image sensor; Fuse means for recording addresses of a plurality of defective pixels found in a wafer test of the image sensor in the pixel array in a laser melting method; And digital data from the buffer memory when the digital data from the buffer memory is output from the bad pixel corresponding to the address of the bad pixel recorded in the fuse means. It comprises a compensation circuit unit for outputting.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

Unlike the memory, pixels arranged horizontally N and vertically M in the image sensor are sequentially scanned, and each position may be indicated by an address. The present invention contemplates this feature and includes a fuse block for writing the address of the defective pixels inside the image sensor chip. At this time, the fuse block includes a plurality of fuses, and the plurality of fuses are laser-melted in response to the address of the pixel determined as the defective pixel in the wafer test, thereby recording the address of the defective pixel.

FIG. 1 conceptually illustrates a pixel array for explaining the present invention, and illustrates an example of a pixel array of an image sensor having an 800 × 600 size. In the figure, an "X" indicates a pixel which is determined as a defective pixel in a wafer test.

Referring to FIG. 1, in order to display the position of each pixel in an 800 × 600 pixel array as an address, 10 bits for displaying a horizontal direction, 10 bits for displaying a vertical direction, and 20 bits in total may be represented as address bits. have.

If five pixels in the position shown in Fig. 1 were found to be defective when the image sensor was tested, the fuses in the fuse block were melted with a laser in response to the address (20 bits) for each defective pixel. This will be described in more detail below with reference to the internal block diagram of the image sensor.

FIG. 2 is an internal block diagram of an image sensor according to an embodiment of the present invention, and compensates for a corresponding defective pixel externally (ie, a system developer) by using address information of a defective pixel recorded in a fuse block of the present invention. This is the case when performing an operation.

Referring to FIG. 2, the image sensor includes a pixel array 10, an analog-to-digital converter (ADC) 12 that converts analog data sensed by the pixel into digital data, and digital data output from the ADC 12. A buffer memory 14 for storing the data, a digital block 16 for controlling an interface to an external device, and an operation of an image sensor, and a pixel determined as a defective pixel during a wafer test among the pixels arranged in the pixel array 10. Comprising a fuse block 18 for recording the address of the pixel, and can read the address information of the defective pixel recorded in the fuse block 18 through the digital block 16 from the outside to compensate for the defective pixel. Make sure

Here, the size of the fuse block 18 may be arbitrarily determined by the designer in consideration of the yield of the chip. For example, if the image sensor having five or less defective pixels is more than a predetermined yield in the chip manufacturing, the fuse block ( 18 may be designed to be large enough to record the addresses of up to five defective pixels.

For reference, a connection relationship other than the fuse block 18 and the digital block 16 is not related to the core technical matters of the present invention and is not known in the drawings because it is a known technology.

FIG. 3 illustrates a unit fuse unit for recording an address 1 bit of a defective pixel of the fuse block of FIG. 2 according to an embodiment of the present invention, and includes a CMOS inverter and one fuse.

Referring to the configuration of the fuse block 18 with reference to FIGS. 2 and 3, the fuse block 18 of FIG. 2 includes a plurality of unit fuse units of FIG. 3 for recording an address 1 bit of a defective pixel. When the fuse block 18 is designed to be large enough to record an address of up to five defective pixels in the 800 × 600 pixel array of FIG. 18) requires 20 unit fuses to record one defective pixel, so that a total of 100 unit fuses are arranged in an array.

More specifically, the address of the defective pixel 1 ("0000000011" in the horizontal direction and "0000000010" in the vertical direction) shown in FIG. 1 is the 9th, 10th and 19th unit fuses of the fuse block 18. It is possible to record by melting the fuse.

Therefore, the system developer is provided with an image sensor chip that records the address of the defective pixel found in the wafer test in the fuse block 18 as described above, and the digital block 16 of the image sensor without separate testing of the defective pixel is performed. By reading the information of the defective pixel recorded in the fuse block 180 through) can perform a compensation operation for the corresponding defective pixel.                     

Meanwhile, a compensation circuit unit for a defective pixel may be further included in the image sensor, and as described above, a compensation operation for the defective pixel may be performed in the image sensor using the address of the defective pixel recorded in the fuse block.

4 is an internal block diagram of an image sensor according to another embodiment of the present invention, which performs compensation operation for a corresponding defective pixel in an image sensor using address information of a defective pixel recorded in a fuse block of the present invention. If it is.

Referring to FIG. 4, the image sensor includes a pixel array 100, an analog-to-digital converter (ADC) 120 that converts analog data sensed by the pixel into digital data, and digital data output from the ADC 120. A buffer memory 140 for storing the data, a digital block 160 for controlling an interface with an external device, and an operation of an image sensor, and a pixel determined as a defective pixel during a wafer test among the pixels arranged in the pixel array 100. The fuse block 180 for writing the address of the fuse and the address information of the defective pixel recorded in the fuse block 180 under the control of the digital block 160 are read out to compensate for the defective pixel, and then the final output is performed. Comprising a compensation circuit unit 200 for outputting data, the internal configuration of the compensation circuit unit 200 is shown in FIG.

FIG. 5 is an internal block diagram of a compensation circuit unit in the image sensor of FIG. 4 according to another embodiment of the present invention, and includes a bad pixel address buffer configured to read and store address information of a bad pixel recorded in the fuse block 180. 300, the address count signal (the signal input from the conventional image sensor to the buffer memory 140) for the pixel data output from the digital block 160 is compared with the bad pixel address from the bad pixel address buffer 300. A multiplexer for selectively outputting the pixel data from the buffer memory 140 or the disable signal output from the digital block 160 in response to the comparison result signal output from the comparator 320 and the comparator 320 ( When pixel data is output from the M1) 340 and the multiplexer 340, the pixel data is compensated through a predetermined compensation process and the multiplexer 34 The pixel data from the buffer memory 140 in response to the compensation block 360 and the comparison result signal output from the comparator 320 configured not to perform the compensation process when the disable signal from 0 is output. Or a multiplexer (M2) 380 for selectively outputting the compensated pixel data through the compensation block 360.

4 and 5, a process of performing a compensation operation on a defective pixel using the address information of the defective pixel recorded in the fuse block 180 in the image sensor will be described in detail.

First, as described above, the address of the defective pixel found during the wafer test through the laser melting is recorded in the fuse block 180, and the address of the defective pixel output through the reading unit of the fuse block 180 is the defective pixel address. It is stored in the buffer 300. Subsequently, the compensator 200 receiving the address count signal for the pixel data from the digital block 160 and the pixel data from the buffer memory 140 receives the address count signal and the bad pixel for the pixel data in the comparator 320. The addresses of the bad pixels stored in the address buffer 300 are compared. As a result of the comparison, if the two addresses match, the pixel data output from the current buffer memory 140 indicates error pixel data detected by the bad pixel, and the pixel data is compensated in the subsequent process. It indicates that the pixel data is outputted from, indicating that the compensation operation for the pixel data is not necessary in the subsequent process. Here, for convenience of explanation, it is assumed that the comparator 320 outputs "1" as a comparison result signal when the two addresses match, and outputs "0" as a comparison result signal when the two addresses do not match.

Subsequently, the multiplexer 340 outputs pixel data or a disable signal (Disable) according to the comparison result signal output from the comparator 320. When the comparison result signal of the comparator 320 is "1", the buffer is output. The pixel data from the memory 140 is selected, and when the comparison result signal of the comparator 320 is "0", the disable signal from the digital block 160 is selected and output. In this case, the disable signal Disable is a signal for disabling the compensation operation of the compensation block 360 that receives the output of the multiplexer 340.

Next, in the compensation block 360, the pixel data output from the multiplexer 340 is compensated using a predetermined compensation algorithm, and in the multiplexer 380, a comparison result signal (“1”) of the comparator 320 is performed. As a result, the compensated pixel data output from the compensation block 360 is exported as final output data.

Through this process, an image sensor chip manufacturer can improve chip yield by manufacturing a compensation sensor internally to operate normally even if an image sensor chip includes a defective pixel. The system may be developed by receiving the compensated output data of the defective pixel through the digital block 160 of the image sensor without testing.

Meanwhile, as another embodiment of the present invention, an image sensor chip may be configured to perform compensation for defective pixels in and outside the image sensor according to a user's (system development company) 's selection. Specifically, as shown in FIG. 4 and FIG. 5, the compensation operation for the defective pixel is basically performed inside the image sensor, but the user needs to perform the compensation for the defective pixel internally as needed when developing the system using the image sensor. Instead of using the image data output through the compensation operation, only the bad pixel address stored in the bad pixel address buffer 300 is read through the digital block 160, and the compensation operation for the bad pixel can be performed externally. It may be. As described above, the image sensor of the present invention for recording the address of the defective pixel through the laser melting may be configured in various ways depending on where the compensation operation for the defective pixel is performed.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

According to the present invention made as described above, the address of the defective pixel is written into the chip by the on / off method of the fuse through the laser melting, and the compensation for the defective pixel is performed internally or externally using the recorded defective pixel address. By easily configuring the controller, the yield of the image sensor chip can be increased, and the development time can be shortened when developing a system using the image sensor.

Claims (16)

An image sensor having a pixel array arranged in unit pixels of N (column number) × M (line number) and sensing information about an image coming from the outside, And fuse means for recording addresses of a plurality of defective pixels found in a wafer test of the image sensor in the pixel array in a laser melting manner. According to claim 1, wherein the size of the fuse means, An image sensor arbitrarily determined by a chip designer in response to a chip yield of the image sensor. The method according to claim 1 or 2, wherein the fuse means, And a unit fuse unit having a minimum number of bits capable of displaying the number N of columns of the pixel array + a minimum number of bits capable of displaying a number M of lines. An image sensor that records the address for one bad pixel. The method of claim 3, wherein the unit fuse unit, A fuse blown in response to the defective pixel address; And Reading means connected to the fuse for reading a signal responsive to on or off of the fuse; Image sensor comprising a. In the image sensor, A pixel array arranged in unit pixels of N (number of columns) × M (number of lines) to sense information about an image coming from the outside; Analog-digital conversion means for converting the analog data sensed by the unit pixel into digital data; A buffer memory for storing digital data output from the analog-digital converting means; Digital control means for controlling the interface with the outside and the operation of the image sensor; And And fuse means for recording the addresses of a plurality of defective pixels found in the wafer test of the image sensor among the pixel arrays in a laser melting method. And externally read an address of the defective pixel recorded in the fuse means through the digital control means to compensate for the defective pixel. The method of claim 5, wherein the size of the fuse means, An image sensor arbitrarily determined by a chip designer in response to a chip yield of the image sensor. The method of claim 5 or 6, wherein the fuse means, And a unit fuse unit having a minimum number of bits capable of displaying the number N of columns of the pixel array + a minimum number of bits capable of displaying a number M of lines. An image sensor that records the address for one bad pixel. The method of claim 7, wherein the unit fuse unit, A fuse blown in response to the defective pixel address; And Reading means connected to the fuse for reading a signal responsive to on or off of the fuse; Image sensor comprising a. In the image sensor, A pixel array arranged in unit pixels of N (number of columns) × M (number of lines) to sense information about an image coming from the outside; Analog-digital conversion means for converting the analog data sensed by the unit pixel into digital data; A buffer memory for storing digital data output from the analog-digital converting means; Digital control means for controlling the interface with the outside and the operation of the image sensor; Fuse means for recording addresses of a plurality of defective pixels found in a wafer test of the image sensor in the pixel array in a laser melting method; And Under the control of the digital control means, when the digital data from the buffer memory is output from the bad pixel corresponding to the address of the bad pixel recorded in the fuse means, the digital data from the buffer memory is compensated for the final output. Compensation circuit Image sensor comprising a. The method of claim 9, wherein the compensation circuit unit, Defective pixel address storage means for reading and storing address information of the defective pixel recorded in the fuse means; Comparison means for comparing an address count signal output from the digital control means to the buffer memory and a bad pixel address from the bad pixel address storage means; First selecting means for selectively outputting digital data from the buffer memory or disable signal output from the digital control means in response to a comparison result signal output from the comparing means; Compensation means for compensating digital data in the buffer memory using a predetermined compensation algorithm in response to an output result of the first selection means; And Second selection means for selectively outputting digital data from the buffer memory or data compensated through the compensation means in response to a comparison result signal output from the comparison means Image sensor comprising a. The method of claim 10, wherein the first selection means, Selecting and outputting digital data from the buffer memory when an address count signal input into the buffer memory and a bad pixel address from the bad pixel address storage means match in response to a comparison result signal output from the comparing means; Image sensor. The method of claim 10, wherein the second selection means, Selecting and outputting compensated data through the compensating means when an address count signal input to the buffer memory and a bad pixel address from the bad pixel address storage means match in response to a comparison result signal output from the comparing means; Image sensor. The method of claim 10, wherein the compensation means, Compensating the digital data of the buffer memory using a predetermined compensation algorithm when the digital data of the buffer memory is output from the first selecting means, and performing a compensation process when the disable signal is output from the first selecting means. An image sensor configured to not perform. The method of claim 9, wherein the size of the fuse means, An image sensor arbitrarily determined by a chip designer in response to a chip yield of the image sensor. The method according to claim 9 or 14, wherein the fuse means, And a unit fuse unit having a minimum number of bits capable of displaying the number N of columns of the pixel array + a minimum number of bits capable of displaying a number M of lines. An image sensor that records the address for one bad pixel. The method of claim 15, wherein the unit fuse unit, A fuse blown in response to the defective pixel address; And Reading means connected to the fuse for reading a signal responsive to on or off of the fuse; Image sensor comprising a.

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