A method for quickly determining yield and random yield of a wafer system

Abstract

The present application relates to a kind of methods for quickly determining wafer system yield and random yield, by the total number of wafers in the wafer system obtained based on judgment processing, once the total number of wafers is less than the first preset threshold, then determine the yield of wafer system is mainly determined by random yield, calculate the random yield and further calculate system yield;Once the total number of wafers is not less than the first preset threshold, determine the yield of wafer system is mainly determined by system yield, calculate the system yield and further calculate random yield, then based on the relationship between the recorded system yield and random yield and the number of measurements respectively determine that system yield set and random yield set are in compliance with normal distribution, then determine that wafer system process is stable, otherwise, determine that wafer system process is unstable, thereby improve the determination speed and precision of wafer system yield and random yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip wafer manufacturing, and more particularly to a method for rapidly determining wafer system yield and random yield. Background Technology

[0002] In the semiconductor chip wafer manufacturing process, determining the yield of the manufactured chips is beneficial for quickly diagnosing the chip manufacturing process, thereby shortening the yield improvement cycle. Because the semiconductor manufacturing process is extremely complex, its product yield has a high degree of uncertainty. Product yield not only affects cost but also the utilization rate of production resources.

[0003] Product yield includes system yield and random yield. System yield refers to yield loss caused by process factors, where defect distribution or causes are predictable and typically exhibit clear clustering characteristics, showing a specific distribution. On the other hand, random yield refers to yield loss caused by uncertain factors, where defects occur randomly and do not have a distributional pattern.

[0004] However, existing methods for determining wafer system yield and random yield have shortcomings: the determination speed for wafer system yield and random yield is slow, and it cannot quickly provide feedback on yield status. In addition, the process of determining wafer system yield and random yield requires a large number of wafers, and the accuracy of the determined yield is insufficient. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for rapidly determining wafer system yield and random yield with high speed and accuracy, which is in contrast to the above-mentioned prior art.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for rapidly determining wafer system yield and random yield, characterized by comprising the following steps:

[0007] Step 1: Obtain the total number of wafers on the wafer system and calculate the overall yield; whereby the total number of wafers on the wafer system is denoted as M, and the overall yield is denoted as Y. t ;

[0008] Step 2: Make a judgment based on the total number of wafers obtained:

[0009] When the total number of wafers M is less than the first preset threshold λ1, it is determined that the yield of the wafer system is mainly determined by the random yield, and the process proceeds to step 3; otherwise, it is determined that the yield of the wafer system is mainly determined by the system yield, and the process proceeds to step 4.

[0010] Step 3: Calculate the random yield of the wafer system, and based on this random yield, obtain the system yield of the wafer system, then proceed to step 5; wherein, the random yield Y of the wafer system... r and system yield Y s The calculation formulas are as follows:

[0011]

[0012] Where, N die Y represents the total number of chips on each wafer, and the quality of each chip is independent of the others; r It is the good yield of each chip, Y max This represents the maximum yield corresponding to all chips on each wafer;

[0013] Step 4: Calculate the system yield of the wafer system, and based on this system yield, obtain the random yield of the wafer system, then proceed to Step 5; wherein, the system yield Y of the wafer system... r and random yield Y s The calculation formulas are as follows:

[0014]

[0015] Where A represents the area of ​​each chip on the wafer, and D0 represents the defect density;

[0016] Step 5: Record the correspondence between the current number of measurements and the system yield and random yield corresponding to that number of measurements;

[0017] Step 6: Repeat steps 1 to 5 until the preset number of measurements is reached. Record the system yield and random yield corresponding to the preset number of measurements, forming a system yield set and a random yield set for all measurement counts. The preset number of measurements is denoted as n. TH The system yield corresponding to the nth measurement is denoted as Y. s,n The random yield corresponding to the nth measurement is labeled Y. r,n The resulting set of system yields for all measurement counts is denoted as {Y}. s,n The random yield set formed for all measurements is denoted as {Y, n}. r,n ,n};1≤n≤n TH ;

[0018] Step 7: Make a judgment based on whether the formed system yield set and random yield set satisfy a normal distribution:

[0019] If both the system yield set and the random yield set satisfy a normal distribution, proceed to step 8; otherwise, the chip process of the wafer system is determined to be unstable.

[0020] Step 8: Calculate the average system yield within the system yield set and the average random yield within the random yield set, and make a judgment based on the obtained average system yield and average random yield.

[0021] When both the average system yield and the average random yield meet the preset requirements, the chip process of the wafer system is determined to be stable; otherwise, the chip process of the wafer system is determined to be unstable.

[0022] Improved in this invention, the method for rapidly determining wafer system yield and random yield further includes: after determining that the chip process of the wafer system is unstable, optimizing the chip process flow of the wafer system again, and then returning to step 1.

[0023] Improved, in the method for rapidly determining wafer system yield and random yield, the first preset threshold λ1∈[5,25].

[0024] Compared with the prior art, the advantages of the present invention are as follows: The invention makes a judgment based on the total number of wafers in the obtained wafer system. Once the total number of wafers is less than a first preset threshold, it is determined that the yield of the wafer system is mainly determined by the random yield. The random yield is calculated and the system yield is further calculated. Once the total number of wafers is not less than the first preset threshold, it is determined that the yield of the wafer system is mainly determined by the system yield. The system yield is calculated and the random yield is further calculated. Then, based on the relationship between the recorded system yield and random yield and the number of measurements, it is determined that when both the system yield set and the random yield set conform to a normal distribution, the wafer system process is determined to be stable. Otherwise, the wafer system process is determined to be unstable. This improves the speed and accuracy of determining the yield and random yield of the wafer system. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a method for rapidly determining wafer system yield and random yield in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] This embodiment provides a method for rapidly determining wafer system yield and random yield. Specifically, see [link to documentation]. Figure 1 As shown, the method for rapidly determining wafer system yield and random yield in this embodiment includes the following steps 1 to 7:

[0028] Step 1: Obtain the total number of wafers on the wafer system and calculate the overall yield; whereby the total number of wafers on the wafer system is denoted as M, and the overall yield is denoted as Y. t ;

[0029] Step 2: Make a judgment based on the total number of wafers obtained:

[0030] When the total number of wafers M is less than the first preset threshold λ1, it is determined that the yield of the wafer system is mainly determined by the random yield, and the process proceeds to step 3; otherwise, it is determined that the yield of the wafer system is mainly determined by the system yield, and the process proceeds to step 4; where the first preset threshold λ1 here is [5,25].

[0031] Step 3: Calculate the random yield of the wafer system, and based on this random yield, obtain the system yield of the wafer system, then proceed to step 5; wherein, the random yield Y of the wafer system... r and system yield Y s The calculation formulas are as follows:

[0032]

[0033] Where, N die Y represents the total number of chips on each wafer, and the quality of each chip is independent of the others; r It is the yield of each chip, Y max This represents the maximum yield corresponding to all chips on the wafer;

[0034] Where G represents the number of successes in n trials, then G follows a parameter (N) _die ,Y r The binomial random variable distribution of G:N(N) is given by G:N(N) die ,Y r The standard deviation of the binomial distribution can be obtained. So, Y r The following empirical formula can be used to obtain the yield (the difference between the maximum yield Ymax and the random yield of chips on the wafer is approximately 3 times the standard deviation σ):

[0035]

[0036] Step 4: Calculate the system yield of the wafer system, and based on this system yield, obtain the random yield of the wafer system, then proceed to Step 5; wherein, the system yield Y of the wafer system... r and random yield Y s The relevant calculation formulas are as follows:

[0037]

[0038] Where A represents the area of ​​each chip on the wafer, and D0 represents the defect density; specifically, lnY t -lnY s =-AD0,Y r =Y t / Y sThat is, Y r Determined by the chip area A and defect density D0, and obtained from the Poisson yield model. but:

[0039] Depend on We obtain lnY t -lnY s =-A·D0.

[0040] Y is calculated from this. s Y s Then, by Y r =Y t / Y s Y can be obtained r .

[0041] Step 5: Record the correspondence between the current number of measurements and the system yield and random yield corresponding to that number of measurements;

[0042] Step 6: Repeat steps 1 to 5 until the preset number of measurements is reached. Record the system yield and random yield corresponding to the preset number of measurements, forming a system yield set and a random yield set for all measurement counts. The preset number of measurements is denoted as n. TH The system yield corresponding to the nth measurement is denoted as Y. s,n The random yield corresponding to the nth measurement is labeled Y. r,n The resulting set of system yields for all measurement counts is denoted as {Y}. s,n The random yield set formed for all measurements is denoted as {Y, n}. r,n ,n};1≤n≤n TH ;

[0043] Step 7: Make a judgment based on whether the formed system yield set and random yield set satisfy a normal distribution:

[0044] If both the system yield set and the random yield set satisfy a normal distribution, proceed to step 8; otherwise, the chip process of the wafer system is determined to be unstable.

[0045] Step 8: Calculate the average system yield within the system yield set and the average random yield within the random yield set, and make a judgment based on the obtained average system yield and average random yield.

[0046] When both the average system yield and the average random yield meet the preset requirements, the chip process of the wafer system is determined to be stable; otherwise, the chip process of the wafer system is determined to be unstable.

[0047] To ensure the stability of the chip process of the wafer system, this embodiment will further optimize the chip process flow of the wafer system after determining that the chip process of the wafer system is unstable, and then return to step 1 again.

[0048] The method for rapidly determining wafer system yield and random yield in this embodiment can obtain relatively accurate system yield and random yield with a relatively small number of wafers, and the feedback speed is fast, enabling rapid diagnosis of chip manufacturing processes and shortening the chip yield improvement cycle. If the system yield is too low, the focus of process optimization is on optimizing equipment and process flow; if the random yield is too low, the focus of process optimization is on the production environment and operators. In this way, the efficiency of process optimization for wafer systems and product yield can be effectively improved.

[0049] Although preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for rapidly determining wafer system yield and random yield, characterized in that, Includes the following steps: Step 1: Obtain the total number of wafers on the wafer system and calculate the overall yield; whereby the total number of wafers on the wafer system is denoted as M, and the overall yield is denoted as Y. t ; Step 2: Make a judgment based on the total number of wafers obtained: When the total number of wafers M is less than the first preset threshold λ1, it is determined that the yield of the wafer system is mainly determined by the random yield, and the process proceeds to step 3; otherwise, it is determined that the yield of the wafer system is mainly determined by the system yield, and the process proceeds to step 4. Step 3: Calculate the random yield of the wafer system, and based on this random yield, obtain the system yield of the wafer system, then proceed to step 5; wherein, the random yield Y of the wafer system... r and system yield Y s The calculation formulas are as follows: Where, N die Y represents the total number of chips on each wafer, and the quality of each chip is independent of the others; r It represents the good yield of each chip, Y max This represents the maximum yield corresponding to all chips on each wafer; Step 4: Calculate the system yield of the wafer system, and based on this system yield, obtain the random yield of the wafer system, then proceed to Step 5; wherein, the system yield Y of the wafer system... r and random yield Y s The calculation formulas are as follows: Where A represents the area of ​​each chip on the wafer, and D0 represents the defect density; Step 5: Record the correspondence between the current number of measurements and the system yield and random yield corresponding to that number of measurements; Step 6: Repeat steps 1 to 5 until the preset number of measurements is reached. Record the system yield and random yield corresponding to the preset number of measurements, forming a system yield set and a random yield set for all measurement counts. The preset number of measurements is denoted as n. TH The system yield corresponding to the nth measurement is denoted as Y. s,n The random yield corresponding to the nth measurement is labeled Y. r,n The resulting set of system yields for all measurement counts is denoted as {Y}. s,n The random yield set formed for all measurements is denoted as {Y, n}. r,n ,n};1≤n≤n TH ; Step 7: Make a judgment based on whether the formed system yield set and random yield set satisfy a normal distribution: If both the system yield set and the random yield set satisfy a normal distribution, proceed to step 8; otherwise, the chip process of the wafer system is determined to be unstable. Step 8: Calculate the average system yield within the system yield set and the average random yield within the random yield set, and make a judgment based on the obtained average system yield and average random yield. When both the average system yield and the average random yield meet the preset requirements, the chip process of the wafer system is determined to be stable; otherwise, the chip process of the wafer system is determined to be unstable.

2. The method for rapidly determining wafer system yield and random yield according to claim 1, characterized in that, Also includes: After determining that the chip process of the wafer system is unstable, the chip process flow of the wafer system is optimized again, and the process returns to step 1.

3. The method for rapidly determining wafer system yield and random yield according to claim 1, characterized in that, The first preset threshold λ1∈[5,25].

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