A method for judging open-circuit defects of through-holes

Abstract

The present invention relates to the field of integrated circuit technology, and in particular to a method for judging a through-hole open defect; the method comprises: defining a metal profile step length, and differentiating the metal profile to obtain a metal profile area; calculating the through-hole profile area, and replacing the through-hole profile with a square having the same area as the through-hole profile; calculating the overlapping area between the square and the metal profile; and calculating the potential open defect probability along the metal profile direction and the direction perpendicular to the metal profile based on the overlapping area, thereby judging whether the through-hole open defect is a through-hole open defect. Overlay error may cause the through-hole to fail to accurately fall at a predetermined design position, and eventually fall within a certain range. By calculating the open defect probability, it is judged whether an open circuit will occur within the range, thereby solving the problem that the prior art can only determine whether a predetermined position is open, but cannot determine the open risk under process fluctuations.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a method for judging a through-hole open circuit defect. Background Art

[0002] The calculation and judgment for optical proximity effect correction in the through-hole open circuit defect mainly includes the following steps:

[0003] (1) Calculate the overlapped area between the profile of the via after exposure / etching and the profile of the metal;

[0004] (2) Calculate the ratio of the overlap area to the area of ​​the original design via size, expressed as

[0005] Area ratio = overlapping area / area of ​​original design via

[0006] (3) Calculate based on the process variation range and eventually set a safety threshold for the area ratio;

[0007] (4) If the actual area ratio is greater than or equal to the safety threshold:

[0008] Area ratio ≥ safety threshold

[0009] The via can be judged as having no open circuit defect, because if the actual overlapping area between the via and the metal is sufficient, no open circuit phenomenon will occur.

[0010] (5) If the actual area ratio is lower than the safety threshold:

[0011] Area ratio < safety threshold

[0012] The via can be judged as having a possible open circuit defect, and the smaller the actual overlapping area between the via and the metal, and the smaller the area ratio, the smaller it will be below the safety threshold, and it will ultimately be more likely to cause an open circuit. Summary of the invention

[0013] The purpose of the present invention is to provide a method for determining an open circuit defect of a through hole, aiming to solve the problem that the prior art can only determine whether a predetermined position is open circuited, but cannot determine the open circuit risk under process fluctuations.

[0014] To achieve the above object, the present invention provides a method for judging a through hole open defect, comprising the following steps: defining a metal profile step length, and differentiating the metal profile to obtain a metal profile area;

[0015] Calculate the area of ​​the through hole outline and replace the through hole outline with a square with the same area as the through hole outline;

[0016] Calculating the overlapping area between the square and the metal outline;

[0017] The potential open circuit defect probability along the metal contour direction and the direction perpendicular to the metal contour direction is calculated based on the overlapping area, so as to determine whether the through hole open circuit is a defect.

[0018] The specific method of estimating the probability of an open circuit defect along the direction of the metal contour is: setting a probability safety threshold of a through-hole open circuit occurring in the same direction of the metal contour;

[0019] Calculate the overlapping area in the same direction by the moving distance of the square and the metal contour in the same direction;

[0020] Dividing the original area of ​​the through hole contour by the overlapping area in the same direction to obtain a same-direction safety threshold;

[0021] The probability of an open circuit defect along the direction of the metal contour is calculated based on the same-direction safety threshold.

[0022] The specific method of estimating the probability of an open circuit defect in a direction perpendicular to the metal contour is: setting a probability safety threshold of a through-hole open circuit in a direction perpendicular to the metal contour;

[0023] Calculate the vertical overlapping area by the distance the square moves vertically with the metal profile;

[0024] The vertical safety threshold is obtained by dividing the original area of ​​the through hole contour by the vertical overlap area.

[0025] The probability of an open circuit defect in a direction perpendicular to the metal contour line is calculated based on the vertical safety threshold.

[0026] The specific method of calculating the moving distance of the square and the metal contour in the same direction and the overlapping area in the same direction is:

[0027] Move the square in the horizontal positive direction and calculate the overlapping area after the movement;

[0028] The square is moved in the horizontal negative direction, and the overlapping area after the movement is calculated.

[0029] The specific method of calculating the vertical overlapping area of ​​the square and the metal contour is as follows:

[0030] Move the square up along a direction perpendicular to the metal contour, and calculate the overlapping area after the movement;

[0031] The square is moved downward in a direction perpendicular to the metal contour, and the overlapping area after the movement is calculated.

[0032] The present invention provides a method for judging a through-hole open defect, which defines a metal contour step length and differentiates the metal contour to obtain a metal contour area; the metal contour has a large number of vertices, and in order to accelerate the calculation efficiency, the metal contour is differentiated / stepped to reduce the number of vertices of the metal contour, the through-hole contour area is calculated, and the through-hole contour is replaced with a square with the same area as the through-hole contour; the area of ​​the through-hole contour is calculated by software, the area of ​​the through-hole contour is replaced with a square with the same area, and the square replaces the through-hole contour area, and the overlapping area of ​​the square and the metal contour is calculated; the adjacent metal contour and the through-hole contour are differentiated, and the overlapping area of ​​the metal contour and the square is calculated. The overlapping area is calculated based on the overlapping area to estimate the potential open circuit defect probability along the direction of the metal contour and the direction perpendicular to the metal contour, so as to determine whether the through-hole open circuit is a defect. The overlay error will cause the through-hole to fail to accurately fall on the predetermined design position, and will eventually fall within a certain range. The present invention estimates the potential open circuit defect probability along the direction of the metal contour and the direction perpendicular to the metal contour to determine whether an open circuit will occur within the range, and uses the differentiated metal contour and the square to calculate the overlapping area. All edges are horizontal and vertical edges, the calculation speed is fast, and the area value is very close to the actual overlapping area, which solves the problem that the prior art can only determine whether the predetermined position is open circuit, but cannot determine the open circuit risk under process fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a schematic diagram of the metal profile of stepping / differentiation.

[0035] Figure 2 is a schematic diagram of an alternative through hole outline area.

[0036] Figure 3 It is a schematic diagram of the differentiated metal outline and the square overlapping area.

[0037] Figure 4 It is a schematic diagram of the movement and range of the through hole along the direction of the differential metal contour line.

[0038] Figure 5is the definition diagram of the differential outer angle of the metal profile.

[0039] Figure 6 A schematic diagram showing the edge of the through hole contour and the step line of the metal contour to which the overlapping area needs to be calculated.

[0040] Figure 7 It is a record data table.

[0041] Figure 8 It is the coordinate range map of the overlapping area ratio safety threshold.

[0042] Fig. 9 The present invention provides a method for determining a through-hole open defect.

[0043] Fig.10 The present invention provides a method for determining a through-hole open defect and a flow chart for estimating the probability of an open defect along the metal contour direction.

[0044] Fig.11 The present invention provides a method for judging through-hole open defects and a flow chart for estimating the probability of open defects in a direction perpendicular to the metal contour.

[0045] Fig.12 It is a flow chart of calculating the overlapping area in the same direction in a method for judging a through-hole open defect provided by the present invention.

[0046] Fig.13 It is a flow chart of calculating the vertical overlapping direction area in a method for judging a through-hole open circuit defect provided by the present invention. DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0048] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0049] See also Figures 1 to 13 The present invention provides a method for judging a through hole open defect, comprising the following steps:

[0050] S101 defines the step length of the metal profile, and differentiates the metal profile to obtain the metal profile area;

[0051] The metal contour has a large number of vertices. In order to increase the computational efficiency, the metal contour is differentiated / stepped to reduce the number of vertices of the metal contour.

[0052] S102 calculates the area of ​​the through hole outline and replaces the through hole outline with a square having the same area as the through hole outline;

[0053] The area of ​​the through-hole outline is calculated by software, the area of ​​the through-hole outline is replaced by a square of equal area, and the square replaces the area of ​​the through-hole outline.

[0054] S103 calculates the overlapping area between the square and the metal outline;

[0055] The adjacent metal contour and the through-hole contour are differentiated, and the overlapping area of ​​the metal contour and the square is calculated.

[0056] S104 calculates the probability of an open circuit defect along the direction of the metal contour and the direction perpendicular to the metal contour based on the overlapping area, thereby determining whether the through hole open circuit is a defect.

[0057] The specific method is as follows: S11 sets a probability safety threshold of a through-hole open circuit occurring in the same direction of the metal contour;

[0058] S12 calculates the overlapping area in the same direction by the moving distance of the square and the metal contour in the same direction;

[0059] The specific method of step S12 is as follows: S121 moves the square in a horizontal positive direction and calculates the overlapping area after the movement;

[0060] S122 moves the square in the horizontal negative direction and calculates the overlapping area after the movement.

[0061] S13 divides the original area of ​​the through hole contour by the overlapping area in the same direction to obtain a same-direction safety threshold;

[0062] S14: calculating the probability of an open circuit defect along the direction of the metal contour based on the same-direction safety threshold,

[0063] S21 sets a probability safety threshold of a through hole open circuit occurring in a direction perpendicular to the metal contour;

[0064] S22 calculates the vertical overlap area by the distance that the square moves vertically with the metal profile;

[0065] The specific method of step S22 is as follows: S221 moves the square up along a direction perpendicular to the metal contour, and calculates the overlapping area after the movement;

[0066] S222: moving the square downward in a direction perpendicular to the metal contour, and calculating the overlapping area after the movement.

[0067] S23 divides the original area of ​​the through hole contour by the vertical overlap area to obtain a vertical safety threshold;

[0068] S24 calculates the probability of an open circuit defect in a direction perpendicular to the metal contour line based on the vertical safety threshold.

[0069] Overlay error will cause the through hole to not fall accurately at the predetermined design position, and will eventually fall within a certain range. By calculating the potential probability of open circuit defects along the metal contour direction and perpendicular to the metal contour direction, it is determined whether an open circuit will occur within the range.

[0070] Example:

[0071] S111 defines the metal profile step length and differentiates the metal profile to obtain the metal profile area;

[0072] The metal contour has a lot of vertices. To speed up the calculation efficiency, the metal contour is differentiated / stepped to reduce the number of vertices of the metal contour. Figure 1 .

[0073] S112 calculates the area of ​​the through hole outline and replaces the through hole outline with a square having the same area as the through hole outline;

[0074] The area of ​​the through hole outline is calculated by software, the area of ​​the through hole outline is replaced by a square of equal area, and the square replaces the area of ​​the through hole outline, Figure 2 The left side is the through hole outline, and its area can be calculated by software. The area is recorded as S. Figure 2 The right side shows the area and Figure 2 For the square with the same through hole contour area on the left, calculate the length of the positive side of the equal through hole contour area, and the side length is

[0075] S113 calculates the overlapping area between the square and the metal outline;

[0076] Differentiate the adjacent metal contours from the through-hole contours (e.g. Figure 3 Left side), calculate the overlapping area of ​​the metal contour and the square (such as Figure 3on the right side).

[0077] S114 estimates the potential open defect probability in the direction along the metal contour and perpendicular to the metal contour based on the overlapping area, so as to determine whether there is a defect in the via opening.

[0078] It is assumed that the process fluctuation distribution of the lithography error along the metal line direction is a normal distribution, with an expected value of mean and a standard deviation of σ overlay_x ; that is, the probability Px of the via opening in this lithography error distribution can be calculated by combining all coordinate intervals smaller than the same-direction safety threshold. Therefore, (1 - Px) is the probability that no open circuit will occur in this case. Set the probability safety threshold Psafe for the occurrence of the via opening. When 1 - Px < Psafe, it is necessary to observe the post-lithography / etching contour of the layout according to the root cause of the actual occurrence of this defect, and increase the layout design of the via in the metal layout design to reduce the probability Px of the open circuit, so as to increase the final probability (1 - Px) of the occurrence of the open circuit, making it greater than or equal to the probability safety threshold Psafe of the via opening. Set the probability safety threshold for the potential occurrence of the via opening in the same direction as the metal contour; calculate the overlapping area in the same direction through the moving distance of the square in the same direction as the metal contour; specifically, move the square along the positive horizontal direction and calculate the overlapping area after the movement; move the square along the negative horizontal direction and calculate the overlapping area after the movement. First, calculate the result of moving the square along the positive horizontal direction by +3σ overlay_x Then calculate the result of moving the square along the negative horizontal direction by -3σ overlay_x The results are as follows Figure 4 、 Figure 5 、 Figure 6 as shown (where 3σ overlay_x is the 3sigma fluctuation range of the lithography error along the x direction); at each position where the overlapping area is calculated when the square moves along the horizontal direction, it is necessary to correspond and record the overlapping area value with the coordinate of the position moved from the origin in the horizontal direction, forming a record data table such as Figure 7 Divide the original area of the via contour by the overlapping area in the same direction to obtain the same-direction safety threshold; use the same-direction safety threshold to compare with the data in the third row of the above table, and calculate all coordinate intervals smaller than the same-direction safety threshold, such as Figure 8As shown, based on the same-direction safety threshold, the probability of open circuit defects along the direction of the metal contour is inferred, and the probability safety threshold of the through-hole open circuit in the direction perpendicular to the metal contour is set; the vertical overlapping area is calculated by the distance that the square moves in the vertical direction with the metal contour; specifically, the square is moved up in the direction perpendicular to the metal contour, and the overlapping area after the movement is calculated; the square is moved down in the direction perpendicular to the metal contour, and the overlapping area after the movement is calculated. The original area of ​​the through-hole contour is divided by the vertical overlapping area to obtain the vertical safety threshold; similarly, the process fluctuation distribution of the overlay error perpendicular to the metal contour is assumed to be a normal distribution, and its expected value is mean and the standard deviation is σ overlay_y ; The probability Py of an open circuit in the through hole under the overlay error distribution can be calculated by combining all coordinate intervals less than the safety threshold, so (1-Py) is the probability that an open circuit will not occur when perpendicular to the metal line. The probability of an open circuit defect perpendicular to the direction of the metal contour is calculated in combination with the vertical safety threshold, and the probability of an open circuit defect perpendicular to the direction of the metal contour line is calculated based on the vertical safety threshold to determine whether an open circuit will occur within the range.

[0079] The present invention provides a method for judging the open circuit defect of a through hole. The traditional method for judging whether a through hole will be open circuited with the connected metal in the optical proximity effect correction has many vertices, is irregular, and is slow. However, because the present invention differentiates the metal contour and uses the square through hole with the same through hole contour area as a substitute, the overlapping area calculation is fast and the accuracy error is not large; it can be predicted that due to the existence of the overlay error, the through hole will be connected to the metal within a certain range, which can reflect the possibility of the through hole being open circuited within a certain range; the probability of the through hole being open circuited with the connected metal within the process fluctuation range of this overlay error can be calculated.

[0080] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for judging a through hole open defect, characterized in that: The following steps are involved: Define the step length of the metal profile, and differentiate the metal profile to obtain the metal profile area; Calculate the area of ​​the through hole outline and replace the through hole outline with a square with the same area as the through hole outline; Calculating the overlapping area between the square and the metal outline; Based on the overlapping area, the probability of potential open circuit defects along the direction of the metal contour and perpendicular to the metal contour is calculated, so as to determine whether the through hole open circuit is a defect; The specific method of estimating the probability of an open circuit defect along the direction of the metal contour is: setting a probability safety threshold of a through-hole open circuit occurring in the same direction of the metal contour; Calculate the overlapping area in the same direction by the moving distance of the square and the metal contour in the same direction; Dividing the original area of ​​the through hole contour by the overlapping area in the same direction to obtain a same-direction safety threshold; Calculating the probability of an open circuit defect along the direction of the metal contour based on the same-direction safety threshold; The specific method of estimating the probability of an open circuit defect in a direction perpendicular to the metal contour is: setting a probability safety threshold of a through-hole open circuit occurring in a direction perpendicular to the metal contour; Calculate the vertical overlapping area by the distance the square moves vertically with the metal profile; The vertical safety threshold is obtained by dividing the original area of ​​the through hole contour by the vertical overlap area. The probability of an open circuit defect in a direction perpendicular to the metal contour line is calculated based on the vertical safety threshold.

2. A method for judging a through hole open defect as claimed in claim 1, characterized in that: The moving distance of the square and the metal contour in the same direction, and the specific method of calculating the overlapping area in the same direction are: Move the square in the horizontal positive direction and calculate the overlapping area after the movement; The square is moved in the horizontal negative direction, and the overlapping area after the movement is calculated.

3. A method for judging a through hole open defect as claimed in claim 1, characterized in that: The specific method of calculating the vertical overlapping area between the square and the metal contour is as follows: Move the square up along a direction perpendicular to the metal outline, and calculate the overlapping area after the movement; move the square down along a direction perpendicular to the metal outline, and calculate the overlapping area after the movement.

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