Method of Sorting a Group of Integrated Circuit Devices for Those Devices Requiring Special Testing

The present application is related to: a co-pending application having Ser. No. 08/591,238, and now abandoned, entitled "METHOD AND APPARATUS [sic] FOR STORAGE OF TEST RESULTS WITHIN AN INTEGRATED CIRCUIT," and filed Jan. 17, 1996; a co-pending application having Ser. No. 08/664,109, Jun. 13, 1996 and now U.S. Pat. No. 5,895,962, entitled "A STRUCTURE AND A METHOD FOR STORING INFORMATION IN A SEMICONDUCTOR DEVICE," and filed Jun. 13, 1996; and an application having Ser. No. 08/785,353, and now U.S. Pat. No. 5,927,512, entitled "METHOD FOR SORTING INTEGRATED CIRCUIT DEVICES," and filed Jan. 17, 1997; a co-pending application having Ser. No. 08/822,731, and now U.S. Pat. No. 5,856,923, entitled "METHOD FOR CONTINUOUS, NON LOT-BASED INTEGRATED CIRCUIT MANUFACTURING," and filed Mar. 24, 1997; a co-pending application having Ser. No. 08/806,442, and now U.S. Pat. No. 5,915,231 entitled "METHOD IN AN INTEGRATED CIRCUIT (IC) MANUFACTURING PROCESS FOR IDENTIFYING AND RE-DIRECTING IC'S MIS-PROCESSED DURING THEIR MANUFACTURE," and filed Feb. 26, 1997; and a co-pending application having Ser. No. 08/871,015, and now U.S. Pat. No. 8,907,402 entitled "METHOD FOR USING DATA REGARDING MANUFACTURING PROCEDURES INTEGRATED CIRCUITS (IC'S) HAVE UNDERGONE, SUCH AS REPAIRS, TO SELECT PROCEDURES THE IC'S WILL UNDERGO, SUCH AS ADDITIONAL REPAIRS," and filed Jun. 6, 1997.

1. Field of the Invention

The present invention relates in general to integrated circuit (IC) manufacturing, and, more specifically, to methods in IC manufacturing processes for sorting IC devices using identification (ID) codes, such as fuse ID's, in the devices.

2. State of the Art

Integrated circuits (IC's) are small electronic circuits formed on the surface of a wafer of semiconductor material, such as silicon, in an IC manufacturing process referred to as "fabrication." Once fabricated, IC's are electronically probed to evaluate a variety of their electronic characteristics, cut from the wafer on which they were formed into discrete IC dice or "chips," and then assembled for customer use using various well-known IC packaging techniques, including lead frame packaging, Chip-On-Board (COB) packaging, and flip-chip packaging.

Before being shipped to customers, packaged IC's are generally tested to ensure they will function properly once shipped. Testing typically involves a variety of known test steps, such as pre-grade, burn-in, and final, which test IC's for defects and functionality and grade IC's for speed.

As shown in FIG. 1, a variety of data are collected as IC's proceed through an IC manufacturing process. For example, fabrication deviation data reflecting quality deviations, such as fabrication process errors, are collected during fabrication and summarized in one or more reports commonly referred to as "Quality Deviation Reports" (QDR's). Similarly, data are collected during probe which record the various electronic characteristics of the IC's tested during probe.

When any of the wafers in a wafer lot are deemed to be unreliable because they are low yielding wafers, as indicated by the collected probe data, or because they are misprocessed wafers, as indicated by the QDR's, all the IC's from the wafers in the wafer lot typically undergo special testing, such as enhanced reliability testing, that is more extensive and strict than standard testing. Since a wafer lot typically consists of fifty or more wafers, many IC's that undergo the special testing do not require it because they come from wafers that are not deemed unreliable. Performing special testing on IC's that do not need it is inefficient because such testing is typically more time-consuming and uses more resources than standard testing. Therefore, there is a need in the art for a method of identifying those IC's in a wafer lot that require special testing and sorting the IC's in the wafer lot into those that require special testing and those that do not.

As described in U.S. Pat. Nos. 5,301,143, 5,294,812, and 5,103,166, some methods have been devised to electronically identify individual IC's. Such methods take place "off" the manufacturing line, and involve the use of electrically retrievable identification (ID) codes, such as so-called "fuse ID's," programmed into individual IC's to identify the IC's. The programming of a fuse ID typically involves selectively blowing an arrangement of fuses and anti-fuses in an IC so that when the fuses or anti-fuses are accessed, they output a selected ID code. Unfortunately, none of these methods addresses the problem of identifying and sorting IC's "on" a manufacturing line.

An inventive method in an integrated circuit (IC) manufacturing process for sorting IC devices of the type having an identification (ID) code, such as a fuse ID, into those devices requiring a first testing process, such as enhanced reliability testing, and those devices requiring a second testing process, such as standard testing, includes storing data in association with the ID code of each of the devices that indicates each of the devices requires the first or the second testing process. The data may include fabrication deviation data, such as a Quality Deviation Report (QDR), probe data, standard test data, or special test data, such as enhanced reliability testing data. Also, the data may, for example, indicate the need for the first or second testing process by indicating that one or more semiconductor wafers or wafer lots have been mis-processed, or have relatively low yields at probe or during testing. Further, the data may be generated by IC devices other than those devices to be sorted, and may be generated at a point in the manufacturing process before or after the point at which sorting will take place.

The ID code of each of the IC devices to be sorted is automatically read. This may be accomplished, for example, by electrically retrieving a unique fuse ID programmed into each of the devices, or by optically reading a unique laser fuse ID programmed into each of the devices. Also, the data stored in association with the automatically read ID code of each of the IC devices is accessed, and the devices are then sorted in accordance with the accessed data into those devices requiring the first testing process and those devices requiring the second testing process.

The present invention thus provides a method that directs those IC's needing enhanced reliability testing to such testing without the need for all IC's from the same wafer lot, including those from reliable wafers, to proceed through special testing.

In additional embodiments, the method described above is included in methods for manufacturing IC devices and Multi-Chip Modules (MCM's) from semiconductor wafers.

In a further embodiment, an inventive sorting method uses special test data generated by a first group of IC devices undergoing special testing to sort a second group of devices of the type having an identification (ID) code, such as a fuse ID, into those devices requiring the special testing and those requiring standard testing. Specifically, the method includes storing data in association with the ID code of some of the IC devices in the second group that indicates the devices require special testing. Special test data generated by the first group of devices is then stored in association with the ID codes of the previously mentioned devices in the second group, and the special test data indicates these devices in the second group that were previously indicated to require special testing instead require only standard testing. The ID codes of these devices in the second group are then automatically read, the data stored in association with the ID codes is accessed, and the second group of devices is sorted in accordance with the accessed data so the appropriate devices in the second group undergo standard testing.

FIG. 1 is a flow diagram illustrating a conventional procedure in an integrated circuit (IC) manufacturing process for directing IC's to special testing, such as enhanced reliability testing; and

FIG. 2 is a flow diagram illustrating a procedure in an IC manufacturing process for directing IC's to special testing, such as enhanced reliability testing, in accordance with a preferred embodiment of the present invention.

As shown in FIG. 2, an inventive method 10 for manufacturing integrated circuits (IC's) from a group of semiconductor wafers in a wafer lot 12 includes the step 14 of fabricating the IC's on the wafers. Any fabrication process errors occurring during the fabrication step 14 are noted in a Quality Deviation Report (QDR) 16. It will be understood by those having skill in the field of this invention that the present invention is applicable to any IC devices, including Dynamic Random Access Memory (DRAM) IC's, Static Random Access Memory (SRAM) IC's, Synchronous DRAM (SDRAM) IC's, processor IC's, Single In-line Memory Modules (SIMM's), Dual In-line Memory Modules (DIMM's), and other Multi-Chip Modules (MCM's).

After fabrication, the IC's are electronically probed in a probe step 18 to evaluate a variety of their electronic characteristics, and data from the probe step 18 are noted and stored as probe data 16. The probe data 16 may include, for example, data indicating that one or more wafers are providing a relatively low yield of IC's that are functional at probe, or data indicating that an abnormal number of problems are associated with wafers from a particular wafer lot, or with IC's from the same position on a series of wafers, or with IC's processed by a particular piece of fabrication equipment.

Before, during, or after the probe step 18, IC's fabricated on the wafers are programmed in a program step 20 in the manner described above with a fuse identification (ID) unique to each IC. The fuse ID for each IC is then stored as data in association with the QDR/probe data 16 for that IC. The fuse ID may identify, for example, a wafer lot ID, the week the IC's were fabricated, a wafer ID, a die location on the wafer, and a fabrication facility ID. It will be understood, of course, that the present invention includes within its scope IC's having any ID code, including those having fuse ID's. It will also be understood that the ID code for each IC need not be unique, but instead may only specify the wafer the IC comes from, for example.

Once programmed, the IC's proceed through an assembly step 22 and then to a sort step 24. At this point in the manufacturing process, QDR/probe data 16 is available not only for those IC's presently at the sort step 24, but also for those IC's trailing the IC's presently at the sort step 24 which have completed the probe step 18. Therefore, sufficient QDR/probe data 16 may exist to determine that a particular wafer, for example, is unreliable as a result of low yields from the wafer at the probe step 18, or as a result of a processing error at the fabrication step 14. Similarly, sufficient QDR/probe data 16 may exist to determine that wafers from a particular wafer lot are unreliable, or that IC's from a particular location on a series of wafers are unreliable, or that IC's processed by a particular piece of fabrication equipment are unreliable.

As noted above, IC's that are deemed to be unreliable typically require some form of special testing, such as enhanced reliability testing, in which testing standards and methods are more strict than standard testing. Therefore, at the sort step 24, the fuse ID's of the IC's are automatically read so the QDR/probe data 16 (and test data 26, 28, and 30 as described below) stored in association with the fuse ID's may be accessed and used to sort the IC's into those IC's requiring special testing in a special test step 32, and those IC's requiring only standard testing in one or more test steps 34 and 36. It should be understood that although the fuse ID's are typically read electronically, they may also be read optically if the fuse ID consists of "blown" laser fuses that are optically accessible.

In general, the test data 26, 28, and 30 comprise data generated by IC's at one point in the IC manufacturing process which is used to sort IC's under test at a different point in the process. Thus, for example, test data 26 and 28 generated by IC's from a particular wafer may indicate that the wafer is unreliable because of low yields during the test steps 34 and 36. As a result, IC's from the same wafer that have yet to be tested may be diverted at the sort step 24 to the special test step 32.

Similarly, test data 26 and 28 generated by IC's from a particular wafer lot, or by IC's from a particular die location on a series of wafers, or by IC's that were processed by a particular piece of fabrication equipment at the fabrication step 14, may indicate that IC's respectively from the same wafer lot, or from the same die location, or that were processed by the same piece of fabrication equipment, are unreliable because of low yields or other problems at the test steps 34 and 36. As a result, IC's respectively from the same wafer lot, or from the same die location, or that were processed by the same piece of fabrication equipment, that have yet to be tested may be diverted at the sort step 24 to the special test step 32.

Likewise, test data 30 generated by IC's deemed unreliable and tested in the special test step 32 may indicate that similarly situated IC's that have yet to be tested are not, in fact, unreliable, and therefore need not be diverted to the special test step 32. The test data 26, 28, and 30 will be described in more detail below.

Thus, the present invention provides a method 10 that directs those IC's needing special testing to the special testing step 32 without the need for all IC's from the wafer lot 12, including those from reliable wafers, to proceed through the special testing step 32. In addition, because the method 10 takes advantage of test data 26 and 28 generated by already tested IC's to sort yet-to-be-tested IC's, the method 10 advantageously provides real-time feedback of data back up the manufacturing line. Further, because the method 10 takes advantage of QDR/probe data 16 generated by IC's trailing IC's presently at the sort step 24 to sort those IC's presently at the sort step 24, the method 10 advantageously provides real-time feedback of data down the manufacturing line.

Those IC's that proceed on to the standard test step 34 are tested in a variety of well-known ways so the test data 26 may be generated and stored for each IC in association with the fuse ID of the IC. It should be understood that the test step 34 may comprise many individual test procedures, or just one. It should also be understood that the test data 26 may include data such as the following: data identifying the testing equipment that tested the IC's, operating personnel who operated the testing equipment, and the set-up of the equipment when the IC's were tested; and data indicating the time and date the IC's were tested, the yield of shippable IC's through the test step 34, and test results for the IC's from the various stages of the test step 34.

The IC's tested in the test step 34 then proceed on to an intra-test sort step 38, where the fuse ID's of the tested IC's are again automatically read so the IC's can be sorted in accordance with the QDR/probe data 16, the test data 26, and the test data 28 and 30 of other previously tested IC's, into those IC's requiring special testing in the special test step 32, and those IC's eligible to continue with standard testing in the test step 36.

At the intra-test sort step 38, the QDR/probe data 16 and test data 26, 28, and 30 may identify those IC's in need of special testing in the same manner as described above with respect to the sort step 24. In addition, the test data 26 and 28 may indicate that IC's that were tested by a particular piece of test equipment at the test step 34 are unreliable because of low yields or other problems at the test steps 34 and 36. As a result, IC's that were processed by the same piece of test equipment may be diverted at the sort step 38 to the special test step 32.

Of course, it should be understood that the special test procedures conducted on IC's sorted out in the intra-test sort step 38 may differ from those conducted on IC's sorted out in the sort step 24. Also, it should be understood that the present invention includes within its scope those methods which include only a pre-test sort step, such as the sort step 24, or only an intra-test sort step, such as the sort step 38, or any combination thereof.

Those IC's that continue on to the standard test step 36 are also tested in a variety of well-known ways so the test data 28 may be generated and stored for each IC in association with the fuse ID of the IC. It should be understood that the test step 36 may comprise many individual test procedures, or just one. It should also be understood that the test data 28 may include data such as the following: data identifying the testing equipment that tested the IC's, operating personnel who operated the testing equipment, and the set-up of the equipment when the IC's were tested; and data indicating the time and date the IC's were tested, the yield of shippable IC's through the test step 36, and test results for the IC's from the various stages of the test step 36.

The IC's tested in the test step 36 then proceed on to a post-test sort step 40, where the fuse ID's of the tested IC's are yet again automatically read so the IC's can be sorted in accordance with the QDR/probe data 16, the test data 26 and 28, and the test data 30 of other previously tested IC's, into those IC's requiring special testing in the special test step 32, and those IC's eligible to be shipped (the disposition of non-shippable IC's is not shown).

At the post-test sort step 40, the QDR/probe data 16 and test data 26, 28, and 30 may identify those IC's in need of special testing in the same manner as described above with respect to the sort steps 24 and 38. In addition, the test data 28 may indicate that IC's that were tested by a particular piece of test equipment at the test step 36 are unreliable because of low yields or other problems at the test step 36. As a result, IC's that were processed by the same piece of test equipment may be diverted at the sort step 40 to the special test step 32.

Of course, it should be understood that the special test procedures conducted on IC's sorted out in the post-test sort step 40 may differ from those conducted on IC's sorted out in the sort step 24 and the intra-test sort step 38. Also, it should be understood that the present invention includes within its scope those methods which include only a pre-test sort step, such as the sort step 24, only an intra-test sort step, such as the sort step 38, or only a post-test sort step, such as the sort step 40, or any combination thereof.

Those IC's that proceed on to the special test step 32 are subjected to a variety of special tests, such as enhanced reliability tests, so the test data 30 may be generated and stored for each IC in association with the fuse ID of the IC. It should be understood that the special test step 32 may comprise many individual test procedures, or just one. It should also be understood that the test data 30 may include data such as the following: data identifying the testing equipment that tested the IC's, operating personnel who operated the testing equipment, and the set-up of the equipment when the IC's were tested; and data indicating the time and date the IC's were tested, the yield of shippable IC's through the test step 32, and test results for the IC's from the various stages of the test step 32. Of course, those IC's that pass the special test step 32 are generally allowed to ship.

The present invention thus provides an inventive method for identifying those IC's in a wafer lot that require special testing through the use of ID codes, such as fuse ID's, and for sorting the IC's in the wafer lot into those that require special testing and those that do not using the ID codes of the IC's. The invention also advantageously provides real-time feedback of data up and down the IC manufacturing line by using probe and test data generated by already probed or tested IC's to sort yet-to-be-tested IC's.

Although the present invention has been described with reference to a preferred embodiment, the invention is not limited to this embodiment. For example, while the various steps of the preferred embodiment have been described as occurring in a particular order, it will be understood that these steps need not necessarily occur in the described order to fall within the scope of the present invention. Thus, the invention is limited only by the appended claims, which include within their scope all equivalent methods that operate according to the principles of the invention as described.