A WAT Automatic Retest Method

Abstract

The present invention discloses a WAT automatic retest method, belonging to the technical field of integrated circuit testing. Specifically, it includes the following steps: Step 1. The test equipment selects the retest settings and configuration information, and the configuration information includes the test-related data configuration file; selects and loads the wafer to be tested; Step 2. The test equipment executes the main test process to obtain the initial test results; Step 3. The test equipment automatically executes the retest analysis system according to the retest settings, analyzes the initial test results, and obtains the retest item list; Step 4. If the retest item list is empty, the retest process is not executed, and the main test process is continued; otherwise, the test equipment executes the retest process; retests the content of the retest item list, and continues to execute the main test process after the retest. The present invention can realize the automatic retest of the test items with unstable test results during the wafer electrical test process, greatly improving the test efficiency and test accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit testing, and particularly relates to an automatic retest method for WAT. Background Art

[0002] The integrated circuit manufacturing process is complex and lengthy. It often takes dozens or even hundreds of processes to complete a wafer from a semiconductor single crystal wafer. Any deviation in a process step or environmental change during the entire manufacturing process will affect the final product performance and yield of the integrated circuit chip. Therefore, the electrical testing of wafers runs through the entire integrated circuit production process and is an important part of chip manufacturing. Extracting and analyzing the effective information of test data to control the product yield, reliability, and production process is an irreplaceable and very effective means. Wafer electrical testing plays a very important role in aspects such as yield monitoring and process parameter extraction in the integrated circuit manufacturing process, especially in the development stage of advanced process manufacturing, where wafer electrical testing plays a crucial role.

[0003] During the manufacturing process, we are most concerned about two aspects: the WAT (Wafer Acceptance Test) and CP (Chip Probing) tests of integrated circuits. WAT is the data obtained by testing the electrical parameters of transistors on a wafer after the wafer is manufactured; the WAT test generally needs to use a probe card to connect the actual device and the test instrument to achieve the testing of devices with different sizes and shapes.

[0004] When the wafer / WAT test equipment performs WAT / electrical testing, the test process may show test failures. For example, it may be caused by unstable contact between the probes of the probe card and the pins of the chip, probe card manufacturing problems, problems with the test equipment itself, wafer design / production process problems, unreasonable clock setting of the test program, etc., or the test voltage or current value is not within the specified range. When such problems occur, some problems can obtain more stable test results through retesting, that is, repeating the test, to increase the accuracy of the test.

[0005] When current wafer test equipment encounters such problems, generally after the entire wafer test is completed and it is found through result analysis that the test results of some test items are unstable, the wafer is reloaded and tested. During this process, it is necessary to manually select the test items to be retested and re-run the entire test process to retest the test item. This method will incur a large amount of labor costs and there may also be missed retest items, thus greatly reducing the test efficiency. There is a need to provide a convenient and fast retest method to achieve high-efficiency wafer testing. Summary of the Invention

[0006] In view of all or part of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a WAT automatic retest method, which can realize the automatic retest of test items with unstable test results during the wafer electrical test process, greatly improving the test efficiency and test accuracy.

[0007] To achieve the above object of the invention, the present invention provides a WAT automatic retest method, which specifically includes the following steps:

[0008] Step 1. The test equipment selects the retest settings and configuration information, and the configuration information includes a test-related data configuration file; selects and loads the wafer to be tested;

[0009] Step 2. The test equipment executes the main test process to obtain the initial test results;

[0010] Step 3. The test equipment automatically executes the retest analysis system according to the retest settings, analyzes the initial test results, and obtains a list of retest items;

[0011] Step 4. If the list of retest items is empty, the retest process is not executed, and the main test process is continued; otherwise, the test equipment executes the retest process, retests the content of the list of retest items, and continues to execute the main test process after retesting.

[0012] The present invention analyzes the initial test results by setting up an automatic retest analysis system, and decides whether to perform a retest according to the obtained list of retest items, further determining which test items to retest, and using the retest process to retest the retest items. The retest analysis system is automatically executed according to the retest settings and analyzes the initial test results. When the list of retest items is not empty, the test equipment is controlled by the retest analysis system to automatically execute the retest process. It can realize the automatic retest of test items with unstable test results during the wafer electrical test process, replacing the manual selection of test items to be retested in the prior art. The automatic retest method provided by the present invention is more convenient and fast. It can also reduce the probability of missing test items to be retested, thus greatly improving the test efficiency and test accuracy.

[0013] In step 3, the retest analysis system adopts a scripted design, writes the limited conditions for test failure and retest required, and screens out the test items with test failure and the test items required for retest. The retest analysis system is independent of the control software of the test equipment; among them, the limited conditions for test failure and retest required are written according to the failure judgment criteria. Users can write the limited conditions for test failure and retest required according to their respective failure judgment criteria.

[0014] In step 1, the configuration information further includes a dependency configuration file. The dependency configuration file re-classifies the test items according to the mutual dependency relationships existing between the test items. The test items with mutual dependency relationships are mutually dependent items. Dependency means that there is a correlation between the test data of different test items before and after. For example, the test data output of test item A is the test input of test item B, which is recorded as a dependency relationship between test item A and test item B. During the test process, there may be dependency relationships between test items. When there is a problem with a retest item, that is, a certain retest item that needs to be retested, the test items with dependency relationships with it may not be analyzed as having problems with their test values. By reading the dependency configuration file, the test items with dependency relationships with this retest item can be automatically added to the retest item list, so that this retest item and the test items with dependency relationships with this retest item can all be retested, making the test results more accurate.

[0015] In step 3, in the retest item list, the test items that need to be retested, that is, the retest items, are grouped according to the test conditions. The retest items with the same test conditions are grouped in the same group; in step 4, when executing the retest process, the retest items in the same group are retested sequentially according to different groups. Under the same test condition, the retest items in the same group are retested sequentially. The test condition is the electrical condition required for each test item to be tested. A series of detections are completed under the same electrical condition, and then the electrical condition is adjusted to retest the retest items in other groups, which can greatly improve the test efficiency.

[0016] In step 1, the retest setting includes retest level setting, and the retest levels include test item level, Die level, and Wafer level. For the test item level, retest analysis is performed immediately after a test item is tested. For the Die level, retest analysis is performed immediately after a Die is tested. For the Wafer level, retest analysis is performed immediately after a Wafer is tested. The retest setting in step 1 can include three levels, and the retest setting can be selected according to the user's own needs. There are many Dies on a wafer, and there are countless test items on each Die. During the electrical test of the wafer, each test item on each Die on the wafer needs to be tested. When the retest level is the test item level, the test equipment runs the retest analysis system to perform retest analysis after a test item is tested, and outputs a list of retest items. The retest test program retests the test item according to the list of retest items. When the retest level is the Die level, the retest analysis system is run to perform retest analysis after all the test items in a Die are tested, and a list of retest items is output. The retest test program retests the Die according to the list of retest items. When the retest level is the Wafer level, the retest analysis system is run to perform retest analysis after all the test items on a wafer are tested, and a list of retest items is output. The retest test program retests the wafer according to the list of retest items.

[0017] In step 4, after retesting the content of the list of retest items, the output retest test result overwrites the initial test result.

[0018] In step 4, after retesting the content of the list of retest items, the output retest test result is marked as retest.

[0019] The retest analysis system includes a retest configuration file. According to the retest configuration file and the dependency configuration file, the test items that fail the test and the dependency items that have a dependency relationship with the test items that fail the test are screened to determine the retest items, and the final list of retest items is obtained. The dependency items that have a dependency relationship with the test items that fail the test can be another test item that fails the test or another test item that does not fail the test. The user can screen some test items that fail the test and their dependency items according to different test scenarios to obtain the final list of retest items.

[0020] The retest configuration file includes:

[0021] The lot type matching configuration file determines whether the current lot is in the configured lot types according to the lot ID of the current test. If not, the current lot is not subject to retest judgment, that is, it is not included in the list of retest items.

[0022] The test item type representation configuration file represents the type of test items using IDs or names.

[0023] The exclusion item configuration file determines whether the current test item is in the exclusion item configuration file based on the lot ID of the current test. If it is, the current lot will not be retested, that is, it will not be included in the retest item list.

[0024] The formula ID identification configuration file determines whether the formula ID of the current test item is in the formula ID identification configuration file based on the formula ID of the current test. If it is not, the current test will not be retested, that is, it will not be included in the retest item list.

[0025] The test item identification configuration file selects the test items to be retested based on the retest item identification.

[0026] The Spec configuration file defines the test data range limit of the test item and determines whether the current test item needs to be retested. When the test data of the test item is not within the limit range, it is recorded as needing to be retested, that is, it is included in the retest item list. The limit range is the valid range, and the test data within the valid range does not need to be retested. If the test data is not within the limit range, it is invalid and needs to be retested.

[0027] The associated item configuration file sets the test items that have mutual influence. All the set test items with mutual influence need to be retested, that is, they are included in the retest item list. That is, regardless of whether there is a mutual dependence relationship between the set test items with mutual influence, and regardless of whether there are problems with the test data of the set test items with mutual influence, they all need to be retested. Even if there is no mutual dependence relationship and the test data is also okay, they still need to be retested, that is, they are included in the retest item list. The specific setting method can be set manually by oneself.

[0028] The deletion item configuration file sets some fixed test items as non-retest items in the configuration and deletes the test items set as non-retest items in the retest item list.

[0029] The retest analysis system can analyze the initial test results, screen all test items to determine the test items that failed the test, and then screen the test items that failed the test and their dependencies according to all or part of the above retest configuration files and dependency configuration files to obtain the retest item list required by the end user.

[0030] When the format or content of the retest configuration file is incorrect and the retest items in the retest item list are empty, the test program of the test equipment will output the error information to the log file, will not retest, but will continue to execute the main test process.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects: A WAT automatic retest method provided by the present invention completes the automatic testing of the test items that need to be retested by setting up an automatic retest analysis system. Further, test items presenting interdependent relationships, artificially set associated items, etc. can be set for retesting. While greatly improving the testing efficiency, more accurate test data is also obtained, and the WAT testing of wafers is completed efficiently and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a flowchart of a WAT automatic retest method in an embodiment provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the specific embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] As Figure 1 shown is a flowchart of a WAT automatic retest method in an embodiment provided by the present invention. It should be noted that, in order to more specifically describe the technical solution, the steps described in this embodiment do not strictly correspond one by one to the steps described in the content of the invention.

[0036] This embodiment provides a WAT automatic retest method, which specifically includes the following steps:

[0037] Step 1. The test equipment, i.e., the wafer test equipment, selects the retest settings and configuration information, and the retest level is set to the Die level. The required wafer to be tested is selected and loaded. The configuration information includes test-related data configuration files and dependency configuration files. The dependency configuration files reclassify all test items according to the mutual dependencies existing between different test items. Test items with mutual dependencies are mutually dependent items. The dependency means that the test data of different items to be tested are related before and after. For example, the test data output of test item A is the test input of test item B, which is recorded as a dependency relationship between test item A and test item B. Of course, there can also be other dependency relationships. Specifically, according to the experience of those skilled in the art, if the test data of test items are considered related, the corresponding test items can be recorded as having a dependency relationship.

[0038] Step 2. The test equipment executes the main test process in the test process. When the test equipment finishes testing all test items of a Die, the initial test results of all test items of the Die are obtained. The test process of the test equipment includes the main test process, the retest process, etc. The main test process refers to the process of initially detecting the Die; the main test process is a conventional process of existing detection equipment, and initial detection is performed on each detection item.

[0039] Step 3. The test equipment automatically executes the retest analysis system according to the retest settings in Step 1. The retest analysis system is designed in a scripted manner, and the limiting conditions for test failure and retest are written to screen out the test items that fail the test and the test items that need to be retested. The retest analysis system is independent of the control software of the test equipment, and users can write the limiting conditions for test failure and retest according to their respective failure judgment criteria. The retest analysis system also includes a retest configuration file.

[0040] The retest analysis system analyzes the initial test results, screens all test items to determine the test items that fail the test, and then screens the test items that fail the test and their dependent items according to all or part of the retest configuration file and the dependency configuration file selected in Step 1, and groups the retest items according to the test conditions. The retest items with the same test conditions are grouped together to obtain the retest item list required by the end user.

[0041] Step 4. If the retest item list is empty, the retest process is not executed, and the main test process is continued to perform the test on the next Die or end the test of the wafer under test. If the retest item list is not empty, the test equipment executes the retest process in the test process. In the retest process, the items in the retest item list are retested in sequence for the items in the same group according to different groups. Under the same test conditions, the items in the same group are retested in sequence. The retest result is output, and the retest result will overwrite the initial test result and be marked as retest. After the test equipment retests, it continues to execute the main test process to perform the test on the next Die or end the test of the wafer under test.

[0042] When an error occurs in the format or content of the retest configuration file, resulting in the retest items in the retest item list being empty, the test program of the test equipment outputs the error information to the log file, does not perform retesting, but continues to execute the main test process.

[0043] The retest configuration file includes:

[0044] Lot type matching configuration file, which can determine whether the current lot is in the configured lot types according to the lot ID of the current test. If not, the current lot is not subject to retest judgment, that is, it is not included in the retest item list;

[0045] Test item type representation configuration file, which can represent the type of test items by ID or name;

[0046] Exclusion item configuration file, which can determine whether the current test item is in the exclusion item configuration file according to the lot ID of the current test. If so, the current lot is not subject to retest judgment, that is, it is not included in the retest item list;

[0047] Recipe ID identification configuration file, which can determine whether the recipe ID of the current test item is in the recipe ID identification configuration file according to the recipe ID of the current test. If not, the current test is not subject to retest judgment, that is, it is not included in the retest item list;

[0048] Test item identification configuration file, which can select the test items to be retested according to the retest item identification;

[0049] Spec configuration file, which can define the test data range limit of the test item to determine whether the current test item needs to be retested; when the test data of the test item is not within the limit range, it is recorded as needing retesting, that is, it is included in the retest item list;

[0050] The associated item configuration file allows for the artificial setting of test items that interact with each other. Regardless of whether there is a dependency relationship between the test items that interact with each other, and regardless of whether there are problems with the test data of the test items that interact with each other, retesting judgment needs to be performed, that is, they are included in the retest item list;

[0051] The deletion item configuration file sets some fixed test items in the configuration as non-retest items, that is, deletes the test items set as non-retest items in the retest item list.

[0052] In other embodiments, the retest level setting of the retest can also be at the test item level. After a test item test is completed, the test equipment runs the retest analysis system for retest analysis and outputs the retest item list. The retest program retests the test item according to this retest item list.

[0053] In other embodiments, the retest level setting of the retest equipment can also be at the wafer level. After all test items of a wafer are tested, the test equipment runs the retest analysis system for retest analysis and outputs the retest item list. The retest program retests the wafer according to this retest item list.

[0054] The description of the above embodiments is only used to help understand the method and core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A WAT automatic retest method, characterized in that, Specifically, it includes the following steps: Step 1. The test equipment selects the retest settings and configuration information, and the configuration information includes a test-related data configuration file; select and load the wafer to be tested; Step 2. The test equipment executes the main test process to obtain an initial test result; Step 3. The test equipment automatically executes the retest analysis system according to the retest settings, analyzes the initial test result, and obtains a list of retest items; Step 4. If the list of retest items is empty, the retest process is not executed, and the main test process continues to be executed; Otherwise, the test equipment executes the retest process, retests the content of the list of retest items, and continues to execute the main test process after retesting; In Step 1, the configuration information further includes a dependency configuration file, and the dependency configuration file re-classifies the test items according to the mutual dependency relationship existing between the test items. The test items with a mutual dependency relationship are dependent items on each other; The retest analysis system is independent of the control software of the test equipment. The retest analysis system includes a retest configuration file, and filters the test items that fail the test and the dependent items that have a dependency relationship with the test items that fail the test according to the retest configuration file and the dependency configuration file to determine the retest items and obtain the final list of retest items.

2. The WAT automatic retest method according to claim 1, wherein In Step 3, the retest analysis system adopts a scripted design, writes the limiting conditions for test failure and retest required, and filters out the test items that fail the test and the test items that need to be retested.

3. The WAT automatic retest method according to claim 1, wherein In Step 3, in the list of retest items, the test items that need to be retested, that is, the retest items, are grouped according to the test conditions, and the retest items with the same test conditions are grouped in the same group; in Step 4, when executing the retest process, the retest items in the same group are retested in sequence according to different groups.

4. A WAT automatic retest method according to claim 1, characterized in that, In Step 1, the retest settings include retest level settings, and the retest levels include test item level, Die level, and Wafer level; for the test item level, retest analysis is performed immediately after a test item is tested, for the Die level, retest analysis is performed immediately after a Die is tested, and for the Wafer level, retest analysis is performed immediately after a Wafer is tested.

5. A WAT automatic retest method according to claim 1, characterized in that, In Step 4, after retesting the content of the list of retest items, the output retest result overwrites the initial test result.

6. The WAT automatic retest method according to claim 1, characterized in that, In Step 4, after retesting the content of the list of retest items, the output retest result is marked as retest.

7. A WAT automatic retest method according to claim 1, characterized in that The retest configuration file includes: The lot type matching configuration file determines whether the current lot is in the configured lot types according to the lot ID of the current test. If not, the current lot is not subject to retest judgment, that is, it is not included in the list of retest items; The test item type representation configuration file represents the type of test item by using an ID or a name; The exclusion item configuration file determines whether the current test item is in the exclusion item configuration file according to the lot ID of the current test. If so, the current lot is not subject to retest judgment, that is, it is not included in the list of retest items; The formula ID identification configuration file determines whether the formula ID of the current test item is in the formula ID identification configuration file according to the formula ID of the current test. If it is not, the current test will not be retested, that is, it will not be included in the retest item list; The test item identification configuration file selects the test items that need to be retested according to the retest item identification; The Spec configuration file defines the test data range limit of the test item and determines whether the current test item needs to be retested; When the test data of the test item is not within the limit range, it is recorded as needing to be retested, that is, it is included in the retest item list; The associated item configuration file sets the test items that have mutual influence. All the set test items that have mutual influence need to be retested, that is, they are included in the retest item list; The deletion item configuration file sets some fixed test items as non-retest items in the configuration and deletes the test items set as non-retest items in the retest item list.

8. A WAT automatic retest method according to claim 1, characterized in that When the format or content of the retest configuration file is incorrect and the retest items in the retest item list are empty, the test program of the test equipment will output the error information to the log file, will not perform retesting, but will continue to execute the main test process.

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