KR20220053870A - Scan cell reordering method and scan cell reordering apparatus - Google Patents

Abstract

According to this embodiment of the present invention, a method for relocating scan cells included in a plurality of scan chains includes the steps of: analyzing a connection relationship of the scan cells; calculating a correlation between the scan cells; relocating the scan cells between scan chains according to the connection relationship in a scan chain; and relocating the scan cells in the scan chain. Thus, a failure can be detected with high accuracy and resolution.

Description

SCAN CELL REORDERING METHOD AND SCAN CELL REORDERING APPARATUS

The present technology relates to a scan chain fault diagnosis method and a scan cell relocation device.

As the density and complexity of the chip increase, the complexity of the test continues to increase in proportion. As an alternative to this, the scan test technique is widely used. If a failure occurs in the scan chain, the location of the failed chain can be found only with the flush test, but the location of the failed scan cell can be checked. there is no Therefore, various scan chain diagnosis methods have been proposed.

The scan chain diagnosis method is divided into three main directions. The first is a method of diagnosing the location of a failure using an Automatic Test Equipment (ATE) and a direct diagnosis device using a Physical Failure Analysis (PFA). This is very expensive, time consuming or otherwise destroying the sample by using special testing machines. The second method is to perform scan chain diagnosis by changing the hardware. By changing the structure of the scan cell to be more convenient for diagnosis, or by entering an additional hardware structure in the middle part of the scan chain, scan chain diagnosis can be performed efficiently. However, this method has a problem in that the performance of the chip can be reduced by increasing the size of the chip or causing a delay in the path due to the large hardware overhead. Finally, there is a way to use software. In this method, an input pattern that can output the same pattern as the failure pattern by generating an additional pattern for scan chain diagnosis or inputting a pattern for testing logic into the circuit and then checking the failure log is performed for failure simulation. It proceeds in a way that limits the range where the failure occurred by inferring through or using the failure log. However, this method has the advantage that there is no hardware overhead and only simulation is required for diagnosis, but it has disadvantages in that the failure simulation takes a lot of time and the resolution and accuracy are low.

In order to solve this problem, the accuracy and resolution of scan chain failure can be improved by learning the failure log formed by inputting the existing test pattern to various types of artificial intelligence (Artificial Neural Network) to diagnose scan chain failure. method was studied. However, in the case of this method, due to the nature of scan chain failure, when a failure occurring in SI is expressed in the failure chain after the capture operation, there is a disadvantage that the expressed failure is masked. There is a disadvantage in that it is difficult to predict a specific cell.

The present technology is intended to solve the above-mentioned difficulties of the prior art, and to provide a method of changing the arrangement of scan cells included in a scan chain so that a failure diagnosis and a failure location can be identified faster and more accurately than in the prior art.

A method of relocating scan cells included in a plurality of scan chains according to the present embodiment includes: analyzing a connection relationship between scan cells, calculating a correlation between scan cells, and according to a connection relationship in a scan chain relocating scan cells between scan chains and relocating scan cells within scan chains.

An apparatus for relocating scan cells included in a scan chain connected to a chip according to the present embodiment includes: at least one processor; and a memory storing one or more programs executed by the processor, wherein when the programs are executed by the one or more processors, analyzing, in the one or more processors, a connection relationship of scan cells included in the scan chain; to perform operations including calculating a correlation between cells, relocating a scan cell between scan chains, and relocating a scan cell within a scan chain.

According to the present embodiment, a failure can be detected with high accuracy and resolution by rearranging scan chain cells using cell connection relationships and correlations between cells.

1 is a flowchart showing an outline of a scan cell arrangement method according to the present embodiment.
2 is a block diagram schematically illustrating a scan cell relocation apparatus according to an embodiment of the present invention.
3 is a schematic diagram for explaining a step of analyzing the connection relationship between scan cells included in scan chain 1 and scan chain 2 (S2).
4 is a diagram schematically illustrating scan cells in which scan cells are rearranged between scan chains.
5 is a diagram illustrating detailed steps of a scan cell relocation step in a scan chain.
6 is a diagram schematically illustrating a scan cell arrangement process ( S410 ) according to the number of connected scan cells.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, preferred embodiments of the present invention will be described below, but the technical spirit of the present invention is not limited thereto and may be variously implemented by those skilled in the art without being limited thereto. Hereinafter, a scan chain fault diagnosis method using a filter proposed in the present invention and an apparatus therefor will be described in detail with reference to the drawings.

Hereinafter, this embodiment will be described with reference to the accompanying drawings. 1 is a flowchart showing an outline of a scan cell arrangement method according to the present embodiment. Referring to FIG. 1 , the scan arrangement method according to the present embodiment includes the steps of analyzing a connection relationship between scan cells ( S100 ), calculating a correlation between scan cells ( S200 ), and a scan chain and reordering inter-scan-chain scan cell (S300) and intra-scan-chain scan cell reordering (S400).

2 is a block diagram schematically illustrating a scan cell relocation apparatus according to an embodiment of the present invention. The scan cell relocation apparatus 100 for diagnosing scan chain failure according to the present embodiment includes an input unit 110 , an output unit 120 , a processor 130 , a memory 140 , and a database 150 . The scan cell relocation apparatus 100 of FIG. 2 is according to an exemplary embodiment, and not all blocks shown in FIG. 2 are essential components, and in another exemplary embodiment, some blocks included in the scan cell relocation apparatus 100 may be added. , may be changed or deleted. Meanwhile, the scan cell relocating apparatus 100 may be implemented as a computing device for relocating scan cells, and each component included in the scan cell relocating apparatus 100 may be implemented as a separate software device, or a software is combined. It may be implemented as a separate hardware device.

The scan cell relocation apparatus 100 analyzes a connection relationship between scan cells to calculate correlation between scan cells, rearranges scan cells between scan chains, and rearranges scan cells in scan chains. do.

The input unit 110 means a means for inputting or obtaining a signal or data for rearranging scan cells. The input unit 110 may input various types of signals or data in association with the processor 150 , or may directly acquire data in association with an external device and transmit the data to the processor 150 . The input unit 110 may be a device or a server for inputting or receiving a failure log information, various condition information or control signals, but is not necessarily limited thereto.

The output unit 120 may display failure log information, scan cell information, currently arranged scan cell information, and the like in conjunction with the processor 150 . The output unit 120 preferably displays various information through a display (not shown), a speaker, etc. provided in the scan cell relocation apparatus 100 in order to output predetermined information, but is not limited thereto.

The processor 150 performs a function of executing at least one instruction or program included in the memory 140 .

The processor 150 according to the present embodiment calculates a correlation between the scan cells by analyzing the connection relationship between the scan cells based on data obtained from the input unit 110 or the database 130, and the scan chain The scan cells are rearranged between each other, and the operation of rearranging the scan cells in the scan chain is performed.

The memory 140 includes at least one instruction or program executable by the processor 150 . The memory 140 may include instructions or programs for performing processing such as extracting a region of interest, determining a class, and determining a disease. The memory 140 may store a result of analyzing a connection relationship between the scan cells and correlation values calculated between the scan cells.

The database 130 refers to a general data structure implemented in the storage space (hard disk or memory) of a computer system using a database management program (DBMS), and performs data search (extraction), deletion, editing, addition, etc. Relational database management system (RDBMS) such as Oracle, Infomix, Sybase, DB2, Gemston, Orion ), an object-oriented database management system (OODBMS) such as O2, and an XML Native Database such as Excelon, Tamino, Sekaiju, etc. It can be implemented according to the requirements, and has appropriate fields or elements to achieve its function.

The database 130 according to the present embodiment may store failure log information for learning, failure log information, condition information, neural network model information, filter information, fault diagnosis result information, and the like, and provide the stored data. Meanwhile, although the database 140 is described as being implemented in the scan cell relocation apparatus 100, it is not necessarily limited thereto, and may be implemented as a separate data storage device.

3 is a schematic diagram for explaining a step of analyzing the connection relationship between scan cells included in scan chain 1 (S1) and scan chain 2 (S2). In the example illustrated by Fig. 3, scan chain 1 (S1) contains five scan cells 0, 1, 2, 3 and 4, and scan chain 2 (S2) contains 5, 6, 7, 8 and 9 scan cells. An example including five scan cells is illustrated. However, this is an example for concise and clear understanding, and is not intended to limit the scope of the present invention.

In the step of analyzing the connection relationship ( S100 ), cells that are connected to any one scan cell through system logic and thus affect the capture are identified. For example, when the connection relationship between scan cell 0 is analyzed, when scan cell 0 provides a signal during capture, scan cell 5, which is a scan cell affected by scan cell 0, is detected and stored. The analyzed connection relationship is illustrated by an arrow in FIG. 3 . In the step of analyzing the connection relationship ( S100 ), as illustrated in Table 1 below, the connection relationship between scan cells included in each scan chain is identified. The analyzed connection relationship may be stored in the memory 140 or the database 130 of the scan cell arrangement device in the form of a look-up table.

[Table 1]

A correlation is calculated with respect to the scan cells included in the scan chains (S200). Correlation indicates the degree to which the connection state of each scan cell is similar, and the correlation between the scan cells can be calculated as in Equation 1 below.

[Equation 1]

COR(A,B) : Correlation between A and B, N _AB : Number of scan cells connected equally between A and B, N _A : Number of scan cells connected to A

For example, when Cor(6,7) is calculated, scan cells connected to scan cell 6 are two scan cells 1 and 8, and scan cells 6 and 6 are commonly connected. The cell is one scan cell 1. Therefore, if Cor(6,7) is calculated, 1/2 = 0.5. As another example, when Cor(7,6) is calculated, scan cells connected to scan cell 7 are one scan cell 1, and scan cells 7 and 6 are commonly connected to scan cell 1 one Therefore, if Cor(7,6) is computed, 1/1 = 1. That is, Cor(x,y) and Cor(y,x) may not be equal to each other.

The step of calculating the correlation ( S200 ) is performed among all the scan cells, and the correlation values calculated between the scan cells are looked up in the memory 140 or the database 130 of the scan cell arrangement device. table) can be stored.

Inter-scan-chain scan cell reordering is performed (S300). 4 is a diagram schematically illustrating scan cells relocated between scan chains, and Table 2 is a scan chain connection before and after scan cell relocation between scan chains in scan chain 1 (S1) and scan chain 2 (S2) A table showing the number of relationships.

[Table 2]

3, 4, and Table 2, scan cells with a number of connection relationships equal to or greater than a threshold value are identified in the same chain in scan chain 1 (S1) and scan chain 2 (S2). In the illustrated example, when the threshold value is 2, the number of connections in the same chain of scan cell 4 in scan chain 1 ( S1 ) and scan cell 8 in scan chain 2 ( S2 ) is 2, which is the threshold value of 2 or more. In another embodiment, scan cell relocation between scan chains may be performed for a scan chain having the largest number of intra-chain connections within each scan chain.

In the process of relocating scan cells between scan chains, scan cell 4 of scan chain 1 (S1) and scan cell 8 of scan chain 2 (S2) are relocated. That is, scan cell 4 of scan chain 1 (S1) is replaced with scan cell 8 of scan chain 2 (S2), and similarly, scan cell 8 of scan chain 2 (S2) is scan cell 4 of scan chain 1 (S1) is replaced with However, the connection relationship between the relocated scan cell and the logic circuit and other scan cells is maintained during the scan cell relocation process between scan chains.

Scan cell relocation between scan chains may be performed among a plurality of scan chains. In the plurality of scan chains, a scan cell in which the number of connection relationships in the same chain is equal to or greater than a threshold value or a scan cell in the same chain having the largest number of connection relationships is identified.

The number of connections in the same chain is determined by sequentially replacing the target scan cell of the scan chain in which the scan cell relocation is to be performed between scan chains and the candidate scan cells of other scan chains. Scan cell rearrangement is performed between scan chains by replacing the target scan cell with the candidate scan cell having the smallest number of connections in the same chain obtained by sequentially replacing the target scan cell and the candidate scan cell. Scan cell relocation between such scan chains may be performed using a greedy algorithm.

The scan cell relocation process between scan chains is performed by exchanging cells between scan chains so that cells with multiple connections in the scan chain do not belong to the scan chain. If a plurality of scan cells connected to one scan cell are in the same scan chain, when a failure occurs in that cell, a failure exists in the chain even if a failure occurs during capture operation due to a failure close to scan-in. covered with By distributing scan cells with many connections in a scan chain to other chains, the characteristic of a failure can be changed to spread to other chains.

Accordingly, by relocating scan cells between scan chains, it is possible to form an accurate pattern according to a failure so that a failure can be recognized by a neural network or the like, as will be described later, and it is possible to reduce the number of failures hidden within the same scan chain.

Scan cell rearrangement in the scan chain is performed (S400). 5 is a diagram illustrating detailed steps of the scan cell arrangement step S400 in the scan chain. Referring to FIG. 5 , the scan cell relocation process (S400) in the scan chain may include a scan cell arrangement process (S410) according to the number of connected scan cells, and a scan cell arrangement process (S420) according to a correlation within a group. there is.

6 is a diagram schematically illustrating a scan cell arrangement process ( S410 ) according to the number of connected scan cells, and Table 3 is a table showing the number of scan cells connected to each scan cell.

[Table 3]

6 and Table 3, in the step of arranging scan cells according to the number of scan cells, the scan cells with a larger number of connected scan cells are arranged toward a scan in side, and the scan cells with a smaller number of connected scan cells are arranged toward the scan in. It is performed by arranging it toward the scan out (scan out) side.

In scan chain 1 (S1), scan cells 3 and 8, which have the largest number of connected scan cells, are arranged closest to scan-in. Since scan cells 3 and 8 are both connected to scan cell 6, if they are placed adjacent to each other, the fault may be hidden and not detected. Accordingly, at least one scan cell is disposed to be spaced apart from each other.

In scan chain 2 ( S2 ), 4 having the largest number of connected scan cells is disposed closest to scan-in. Accordingly, in scan chain 2 ( S2 ), scan cell 4 is disposed closest to scan in.

The greater the number of connected scan cells, the more the failure propagates to other chains, which greatly affects the failure log. Therefore, if the location of such a cell is placed in a position where it is difficult to identify a failure in the scan chain, the failure can be predicted more easily by the influence of the failure.

In scan chain 1 (S1), scan cell 1 having the smallest number of connected scan cells is disposed closest to scan-out. In scan chain 2 (S2), scan cell 5, which has the smallest number of connected scan cells, is disposed closest to scan-out. Then, as described above, the remaining scan cells are rearranged according to the number of connected scan cells.

Next, scan cells are arranged according to the correlation within the group ( S420 ). A plurality of scan cells are sequentially grouped in a scan chain. For example, the number of scan cells belonging to one group may be 2 or more and less than 30.

Then, the positions of the scan cells are changed in the group, and the sum of the correlations between the scan cells is calculated to calculate the positions of the scan cells at which the sum of the correlations is the minimum. For example, the sum of correlations may be the sum of correlation values of scan cells included in the scan chain. As another example, the sum of correlation values may be the sum of correlation values between scan cells included in a group.

As described above, since the values of Cor(X, Y) and Cor(Y, X) are different from each other, the sum of the correlation values changes as the positions of the scan cells in the group are changed, and the sum of the correlation values changes. The position of the scan cell which becomes this minimum can be grasped|ascertained. In addition, correlation values for scan cells included in the scan chain are stored in the memory, so that scan cell rearrangement can be easily performed by using the correlation values.

As described above, by relocating the scan cells in the scan chain, it is possible to prevent a failure in the scan chain from being undetectable and to form a pattern for easily diagnosing a failure through artificial intelligence.

The above description is merely illustrative of the technical idea of the embodiment of the present invention, and those of ordinary skill in the art to which the embodiment of the present invention pertains may modify various modifications and transformation will be possible. Accordingly, the embodiments of the present invention are not intended to limit the technical spirit of the embodiment of the present invention, but to explain, and the scope of the technical spirit of the embodiment of the present invention is not limited by these embodiments. The protection scope of the embodiment of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

S100 to S400: each outline of the scan cell rearrangement method according to the present embodiment
S410~S420: Detailed steps of the scan cell relocation step in the scan chain
100: scan cell rearrangement device 110: input unit
120: output unit 140: memory
150: processor

Claims (20)

A method for relocating scan cells included in a plurality of scan chains, the method comprising:
analyzing the connection relationship of the scan cells;
calculating a correlation between the scan cells;
relocating scan cells between the scan chains according to the connection relationship in the scan chain;
and relocating the scan cells in the scan chain. According to claim 1,
The step of analyzing the connection relationship is
A method of relocating a scan cell in which the scan cell is connected through system logic to identify a scan cell that has an effect upon capture. According to claim 1,
The step of calculating the correlation comprises:
A scan cell rearrangement method for calculating each of the plurality of scan cells included in the plurality of scan chains. According to claim 1,
The step of calculating the correlation comprises:
formula

A method of rearranging scan cells that is performed by calculating
(COR(A,B) : Correlation between A and B, N _AB : Number of scan cells connected equally between A and B, N _A : Number of scan cells connected to A) According to claim 1,
Relocating the scan cells between the scan chains comprises:
(a) identifying a scan cell in which the number of connection relationships is greater than or equal to a threshold value in each scan chain;
(b) identifying a target scan cell and one or more candidate scan cells from the result of step (a);
(c) counting the number of interconnection relationships in the scan chain by replacing the target scan cell with the candidate scan cell; and
and (d) replacing the target cell with a candidate scan cell having the smallest result of counting in step (c). According to claim 1,
Relocating the scan cells between the scan chains comprises:
(a) identifying a scan cell having the largest number of connection relationships in each scan chain;
(b) identifying a target scan cell and one or more candidate scan cells from the result of step (a);
(c) counting the number of interconnection relationships in the scan chain by replacing the target scan cell with the candidate scan cell; and
and (d) replacing the target cell with a candidate scan cell having the smallest result of counting in step (c). According to claim 1,
Relocating the scan cells in the scan chain comprises:
(a) placing scan cells according to the number of connected scan cells; and
(b) a scan cell rearrangement method performed including the step of arranging scan cells in a scan cell group according to a correlation. 8. The method of claim 7,
The step (a) is,
A scan cell rearrangement method in which a scan cell having a larger number of connected scan cells is arranged toward a scan in side. 8. The method of claim 7,
The step (a) is,
When the scan cells having the same number of connected scan cells are connected to the same scan cell, the scan cell rearrangement method is arranged to be spaced apart from each other by one or more scan cell intervals. 8. The method of claim 7,
The step (b) is,
(b1) dividing the scan chain into a plurality of scan cell groups;
(b2) calculating a correlation between the scan cells included in the scan chain while changing positions of the scan cells included in the plurality of scan cell groups;
(b3) arranging the scan cells such that a sum of correlation values of the scan cells in the scan chain is minimized. A device for relocating scan cells included in a scan chain associated with a chip, the device comprising:
at least one processor; and
a memory storing one or more programs executed by the processor, wherein the programs, when executed by the one or more processors, in the one or more processors;
analyzing a connection relationship between scan cells included in the scan chain;
calculating a correlation between the scan cells;
relocating scan cells between the scan chains; and
A scan cell relocation apparatus for performing operations including relocating a scan cell in the scan chain. 12. The method of claim 11,
The step of analyzing the connection relationship is
A scan cell rearrangement device for relocating the scan cells by recognizing the scan cells that are connected through system logic and affecting the capture. 12. The method of claim 11,
The step of calculating the correlation comprises:
A scan cell relocation apparatus for calculating each of the plurality of scan cells included in the plurality of scan chains. 12. The method of claim 11,
The step of calculating the correlation comprises:
formula

A scan cell relocation device that calculates
(COR(A,B) : Correlation between A and B, N _AB : Number of scan cells connected equally between A and B, N _A : Number of scan cells connected to A) 12. The method of claim 11,
Relocating the scan cells between the scan chains comprises:
(a) identifying a scan cell in which the number of connection relationships is greater than or equal to a threshold value in each scan chain;
(b) identifying a target scan cell and one or more candidate scan cells from the result of step (a);
(c) counting the number of interconnection relationships in the scan chain by replacing the target scan cell with the candidate scan cell; and
(d) replacing the target cell with a candidate scan cell having the smallest result of the counting in step (c). 12. The method of claim 11,
Relocating the scan cells between the scan chains comprises:
(a) identifying a scan cell having the largest number of connection relationships in each scan chain;
(b) identifying a target scan cell and one or more candidate scan cells from the result of step (a);
(c) counting the number of interconnection relationships in the scan chain by replacing the target scan cell with the candidate scan cell; and
(d) replacing the target cell with a candidate scan cell having the smallest result of the counting in step (c). 12. The method of claim 11,
Relocating the scan cells in the scan chain comprises:
(a) placing scan cells according to the number of connected scan cells; and
(b) a scan cell rearrangement apparatus performed including the step of arranging scan cells in a scan cell group according to a correlation. 18. The method of claim 17,
The step (a) is,
A scan cell rearrangement device that performs a scan in which the number of connected scan cells increases by arranging the scan cells toward the scan in side. 18. The method of claim 17,
The step (a) is,
When the scan cells having the same number of connected scan cells are connected to the same scan cells, the scan cell rearrangement apparatus is arranged to be spaced apart from each other by one or more scan cell intervals. 18. The method of claim 17,
The step (b) is,
(b1) dividing the scan chain into a plurality of scan cell groups;
(b2) calculating a correlation between the scan cells included in the scan chain while changing positions of the scan cells included in the plurality of scan cell groups;
(b3) arranging the scan cells such that a sum of correlation values of the scan cells in the scan chain is minimized.

Images