TWI765786B - Method of increasing accuracy of signal acquisition in chip testing equipment - Google Patents

Abstract

A method of increasing accuracy of signal acquisition in chip test equipment includes: selecting ideal transiting point(s); selecting sampling point(s), performing scan test(s) on each sampling point and each ideal transiting point, and storing scan test results; repeatedly performing the previous one step; building a statistical data model; acquiring real transiting point(s); repeatedly performing the previous three steps; calculating overall offset time of the signal; and compensating the overall offset time to a signal input terminal.

Description

The method of improving the precision of the grasping signal in the chip tester

The invention relates to the technical field of chip testing machines, in particular to a method for improving the precision of grasping signals in a chip testing machine.

Due to the different paths of each channel of the chip tester, the time for the signal to reach the end of the channel will be different. Therefore, it is necessary to compensate for the slower transmission signal to ensure that the time of the signal reaching the end of the channel is consistent. The compensation needs to accurately capture the position of the signal change, but because of the uncertainty of the signal, the signal will be deviated every time it is captured. As shown in Figure 1, when the signal rises or falls, the ideal signal is a straight line. As for the actual signal, as shown in Figure 2, in practical applications, each time the signal changes, there will be deviations, which will cause accuracy problems when the repeatability is highly consistent. There are two main reasons for the deviation of the signal in the chip tester every time it changes. One is due to the limitation of the accuracy of the devices inside the programmable logic array (FPGA) of the chip tester and on the transmission line, so that the signal actually occurs in the Jitter within a range, this factor is circuit characteristics, it is difficult to eliminate. Second, since the minimum unit of the signal generated by the chip tester is a fixed value of 100 picoseconds (ps), the time for generating the signal is discontinuous. For example, ideally, 10 nanoseconds (ns), 10.1 ns, and 10.2 ns can generate rising or falling edges that are multiples of 100 ps, but cannot generate rising or falling edges such as 10.05 ns, 10.15 ns, and 10.25 ns. And due to the precision limitations of the hardware, 100ps itself is also a variable. The chip tester system clock is 2ns, the signal needs to take 20 steps in the 2ns period, these 20 steps are different for each step of the signal due to the uncertainty of the smallest unit.

At present, the traditional method is generally to obtain the average value, and the average value ignores the distribution of each signal, so the obtained signal is not optimal, and the position accuracy of the captured signal change is low.

When capturing a signal, if any measurement result is treated as the actual signal of the signal, it will inevitably cause deviation. Because this is only one measurement result, if it is measured at another location and time, it will be another result. If the compensation is processed by randomly grabbing the signal at any time without optimization, when repeating the inspection by changing different test points, the edge placement accuracy (hereinafter referred to as EPA) can only be within +/ -300Ps, and simple average processing, EPA can only reach +/-200ps, the signal stability is poor.

Therefore, a method for improving the accuracy of the grasping signal in the chip tester is designed. All points in a time period are taken, and the positions of several real points are obtained by multi-point and multi-scanning of all points, and then several real points are taken. The average is to cover the change of the signal at each position in a cycle, fully consider the distribution of the signal, and obtain the precise position of the signal change for compensation, thereby improving the signal capture accuracy.

In order to overcome the deficiencies of the prior art, the present invention provides a method for improving the precision of the grasping signal in a chip testing machine. All points are taken in a time period, and the positions of several real points are obtained by performing multi-point and multi-scan scanning on all points. Then take the average of several real points to cover the change of the signal at each position in a cycle, fully consider the distribution of the signal, and obtain the precise position of the signal change for compensation, thereby improving the signal capture accuracy.

In order to achieve the above purpose, a method for improving the grasping signal accuracy in a chip tester is designed, including: S1, taking 21 points at 100 picosecond (ps) intervals as the 21 ideal change points of the signal change (for example, marking is P _n ); S2, taking the first ideal change point (for example, marked as P ₁ ) in the 21 ideal change points as the center, and taking 5 time points as the sample points at the time interval of 100ps in the time before and after, Each sample point and the _first ideal change point P1 are respectively detected and scanned, and the results of each detection scan are recorded. The detected signal change is recorded as the first value (for example, marked as P), and the undetected signal change is recorded as the first value. Binary value (for example, marked as F); S3, repeat the detection scan of step S2 for each sample point and the _first ideal change point P1 multiple times, and record the multiple detection scan results of the multiple detection scans; S4, A statistical data model is established according to the detection scan results, the column of the statistical data model is sorted according to the time sequence of each sample point and the _first ideal change point P1, and the horizontal column is sorted according to the sequence of the changes of the detected signals; S5, according to the position of the signal change in the statistical data model, obtain the first real change point of the signal change of the ideal change point P ₁ (for example, marked as V ₁ ); S6, repeat steps S2-S5 to obtain the 21 ideal changes The actual change point of the point P _n (for example, marked as V _n ); S7, according to the 21 ideal change points P _n and the 21 real change points V _n , calculate the overall deviation time of the signal (for example, marked as Δt) ; S8, the overall deviation time Δt is compensated at the signal input end of the chip tester; The method for obtaining the first real change point V ₁ of the signal change in the described step S5 is as follows: if multiple detection scans, If the positions of the signal change points are the same, take this point as the first real change point V ₁ of the signal change; if the signal change points appear in multiple positions in multiple detection scans, the point with the most occurrences is taken as the signal change The first real change point V ₁ of .

In the step S3, the number of repeated detection scans is 99 times.

，其中△t為該整體偏差時間，P_n為該21個理想變化點，且V_n為該21個真實變化點。 The calculation formula of the overall deviation time Δt in the step S7 is Δt=

, where Δt is the overall deviation time, P _{n is} the 21 ideal change points, and V _{n is} the 21 real change points.

Compared with the prior art, the present invention takes all points in a time period, performs multi-point and multi-scanning on all points to obtain the positions of several real points, and then averages the several real points to cover the signal in one period In the case of changes in various positions, the distribution of the signal is fully considered, and the precise position of the signal change is obtained to compensate, thereby improving the signal capture accuracy.

300: Statistical Modeling

P: first value

F: second value

[Figure 1] is a schematic diagram of the ideal signal change in the chip tester; [Fig. 2] is a schematic diagram of the actual signal change in the chip tester; [Fig. 3] is the statistical data model obtained in step S4 in the first embodiment of the present invention; and [ FIG. 4 ] is a schematic diagram of the ideal change point, the real change point and the difference thereof obtained in step S6 and step S7 according to the embodiment of the present invention.

Example 1:

The present embodiment is a method for improving the precision of a grasping signal in a chip testing machine, which specifically includes the following steps:

S1, take 21 points at 100 picosecond (ps) intervals as the ideal change points P _n for signal change, respectively P ₁ =10ns, P ₂ =10.1ns, P ₃ =10.2ns, P ₄ =10.3ns , _P5 = _10.4ns , P6= _10.5ns , P7= _10.6ns , _P8 = _10.7ns , P9= _10.8ns , P10=10.9ns, P11=11ns, _P12 = _11.1ns , P13 =11.2ns, P14= _11.3ns , P15= _11.4ns , P16= _11.5ns , P17= _11.6ns , _P18 = _11.7ns , P19= _11.8ns , P20= _11.9ns , P21=12ns ;

S2, with the ideal change point P ₁ (10ns) as the center, 5 time points are taken as the sample points at the time interval of 100ps before and after the time, respectively 9.5ns, 9.6ns, 9.7ns, 9.8ns, 9.9ns, 10.1 ns, 10.2ns, 10.3ns, 10.4ns, 10.5ns, respectively perform detection scans on each sample point and the ideal change point P ₁ (10ns), and record the detection scan results, and the detected signal changes are recorded as the first value (eg, marked as P), no signal change detected is recorded as the second value (eg, marked as F);

S3, perform 99 detection scans on the ideal change point P ₁ and 10 sample points, and obtain 11 scan results for each detection scan;

S4, a statistical data model is established according to the scanning results, the columns of the statistical data model are sorted according to the ideal change point P ₁ and the time sequence of the 10 sample points, and the horizontal columns are sorted according to the sequence of signal changes found in the scanning, and the obtained statistical data Model 300 is shown in FIG. 3 .

S5, in the obtained statistical data model, it can be seen that the signal has changed at a certain point. As can be seen from Figure 3, the signal change points appear in multiple positions, the point with the most occurrences is selected, and 10.1ns is the real change point V ₁ of the signal change.

S6, repeating steps S2-S5 to obtain the real change points _{Vn corresponding to the 21 ideal change points Pn ,} respectively, V ₂ =9.9, V ₃ =10, V ₄ =9.7, V ₅ =10.2, V ₆ = 10.3, V7=10.4, V8=10.4, V9= _10.5 , _V10 =10.6, _V11 =10.7, _V12 = _10.8 , _V13 =10.9, _V14 = ₁₁ , _V15 =11.2, _V16 = 11.3, V ₁₇ =11.4, V ₁₈ =11.5, V ₁₉ =11.5, V ₂₀ =11.6, V ₂₁ =11.7, as shown in Figure 4.

； S7, calculate the overall deviation time Δt of the signal according to the ideal change point P _n and the real change point V _n ,

;

S8: Compensate the overall deviation time Δt at the signal input end of the chip tester.

In step S1, the minimum unit of the chip tester signal realization is 100ps, and the signal has a cycle of 2ns, so taking 21 points can cover the position where the signal appears in the whole cycle. In this embodiment, 21 points between 10-12ns are selected to cover all the positions where the signal appears in one signal period.

In step S2, the reason for taking 5 points on the left and right sides is that 10*100ps=1ns, which completely covers the possible variation range of the current signal. In this step, the comparison unit of the channel in the chip tester is used to detect whether the signal increases in 11 time points respectively.

In step S4 , the columns of the statistical data models are sorted according to the sequence of changes in the detected signals, rather than the chronological sequence of the detection scans. For example, in Figure 3, the first detection scan found that the level change position was 10.1ns, and the second detection scan found that the level change position was 9.9ns, then in the statistical data model, the result of the second detection scan should be Arranged in the previous row of the first inspection scan for easy modeling of statistical data.

In step S5, if the position of the signal change point is the same in the multiple detection scans, this point is taken as the actual change point V _n of the signal change.

In step S6, in the actual application process, the signal may appear at any time step position in a cycle, and the probability of appearing at any time step is equal. Therefore, in order to meet the requirement of the minimum position deviation of 21 steps, the time deviation of each point is averaged as the compensation value of the time signal deviation in the channel.

After compensating the overall deviation time Δt in step S8, the timing edge placement accuracy (EPA) of the channel of the chip tester is tested, and the measured EPA is +/-120ps. Compared with the simple average processing of the traditional method, the signal capture is improved. Take precision.

The present invention takes all points in a time period, performs multi-point and multi-scanning on all points to obtain the positions of several real points, and then averages the several real points to cover the situation that the signal changes at each position in a period, fully Considering the distribution of the signal, the precise position of the signal change is obtained to compensate, thereby improving the signal capture accuracy.

300: Statistical Modeling

P: first value

F: second value

Claims (3)

A method for improving the precision of a grasping signal in a chip testing machine, comprising the following steps: S1, taking 21 points at a time interval of 100 picoseconds as 21 ideal change points of signal change; S2, taking among the 21 ideal change points One of the first ideal change point is the center, and 5 time points are taken as sample points at a time interval of 100 picoseconds before and after, and each sample point and the first ideal change point are detected and scanned respectively, and the detection is recorded. As a result of scanning, the detected signal change is recorded as a first value, and the undetected signal change is recorded as a second value; S3, the detection scan of step S2 is repeated for each sample point and the first ideal change point multiple times , and record the multiple detection scan results of the multiple detection scans; S4, establish a statistical data model according to the detection scan results, and the column of the statistical data model is based on the relationship between each sample point and the first ideal change point. Sort the time sequence, and the rows are sorted according to the sequence of the signal change found by scanning; S5, according to the position of the signal change in the statistical data model, obtain a first real change point of the signal change of the first ideal change point; S6, Repeat the steps S2-S5 to obtain 21 real change points corresponding to the 21 ideal change points; S7, calculate the overall deviation time of the signal according to the 21 ideal change points and the 21 real change points; and S8, use the The overall deviation time compensation is performed at the signal input end of a chip tester, wherein the first real change point of the signal change obtained in the step S5 includes: If the position of the signal change point is the same in the multiple detection scans, the point is taken as the first real change point of the signal change; if the signal change point appears in multiple positions in the multiple detection scans, the most frequent occurrence is taken. The point is the first real change point of the signal change. As claimed in claim 1, for the method for improving the precision of the grasping signal in the chip testing machine, the number of times of repeated detection and scanning in the step S3 is 99 times. As claimed in claim 1, for the method for improving the precision of a grasping signal in a chip testing machine, wherein the calculation formula of the overall deviation time in the step S7 is:

, where Δt is the overall deviation time, P _{n is} the 21 ideal change points, and V _{n is} the 21 real change points.

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