TW200300055A - Method and manufacture for wafer-level reliability electromigration and stress migration testing by isothermal heater - Google Patents

Abstract

Due to the test current and the test temperature of the wafer-level reliability depend on each other in those conventional arts, the result of electromigration etc is not sure cause of the test current or the test temperature and debases the reliability of the test result. In the present invention, the electromigration test and the stress migration test of the wafer-level reliability are independently controlled, respectively. Therefore, the cause of electromigration and the stress migration can be sure resulting from the test current or the test temperature respectively. Furthermore, the isothermal heater of the present invention not only can keep a whole test wafer at a more uniform test temperature, but also can offset the electromagnetism resulted from the current of the isothermal heater by the arrangement of circuits thereof for reducing the effect of the electromagnetism.

Description

200300055 V. Description of the invention α) 1. [Technical field to which the invention belongs] The present invention relates to the structure and method of electromigration and stress migration of wafer level reliability test, and particularly to the use of a constant temperature heater to achieve Structures and methods for wafer-level reliability testing of electromigration and stress migration independently of stress current and test temperature. 2. [Previous Technology] When purchasing electrical appliances such as home appliances or personal computer equipment, people often hear the term “warranty period”. However, if the warranty period is too long, the after-sales cost of the manufacturer will increase; if the warranty period is too short, consumers will reduce their willingness to purchase. So how do you know how long a reasonable product warranty period can ensure the profit and goodwill of the manufacturer? Therefore, manufacturers must evaluate the useful life of the products they produce. In addition to knowing the proper warranty period of the products, they can also be used as a reference for product improvements and amendments. Generally, this kind of evaluation is called "reliability evaluation". Reliability (Rel iabi 1 i ty) can be simply described as: "the life span of a product that can work smoothly under normal conditions of use." To learn about the service life of a product, an accelerated lifetime test is usually used to solve this problem. This kind of experiment uses a more severe working environment than normal working conditions, such as higher ambient temperature, voltage, and current. , Pressure, product life test, find the life under deteriorating conditions, and then use the life cycle model (L ifeti me

200300055 V. Description of the invention (2) M o d e 1) Calculate the life of the product under normal use conditions. In the wafer manufacturing process of a semiconductor factory, life test experiments can generally be divided into two categories, which are called product reliability and process reliability. Product reliability testing refers to testing the life of this product in harsh environments such as high temperature, high pressure, high humidity, etc. after the wafer manufacturing is completed and preliminary packaging is performed. The test items include the temperature seat bias test (T e in perature Humidity Bias Test (THB), High-Temperature Operation Lifetime (HTOL), Temperature Cycling Test (TC). The process reliability refers to the life test of the semiconductor component material when the wafer is initially produced in the factory to ensure that there are no doubts about reliability in the subsequent manufacturing process. These items include the gate of the front-end process (Front-end). Gate Oxide Integrity (GOI), Hot Carrier Injection (HCI), and back-end process metal wire electromigration (EM). The reliability test of a fab can be divided into wafer-level (WLR) and package-level reliability (PLR) according to its test method. The difference is that the former is to place the wafer directly into a test machine on a general production line for testing, while the latter must first cut and package the wafer into test wafers, and then insert these samples into the test board (Burn -in Board), again

Page 6 200300055 V. Description of the invention (3) Put it in a special high temperature furnace for testing. It is mentioned in U.S. Patent No. 5,6 2 5, 2 8 8 that the high-frequency reliability and fault test structure can be used in wafer-level and partially packaged test systems, and this test structure can provide thermal electrons (h 〇t -carriers), electromigration, and oxide breakdown. In addition, a method for measuring the lifetime of electromigration is mentioned in US Patent No. 6, 3, 50, 6, 26. The method is to first test the electromigration test at a temperature at which the crystal circle exceeds the critical temperature test temperature to obtain the first electromigration lifetime. When the true line width of the test wafer is greater than the critical line width, (1) when its use temperature is higher than the critical temperature, the use temperature, lattice diffusion activation energy, test temperature, and first electromigration Substitute the term of use into the equation to obtain the true electromigration term of use, or (2) When the use temperature is below the critical temperature, substitute the grain boundary diffusion activation energy into the equation to obtain the true Electromigration lifetime. 'Packaging-level reliability testing is mainly under normal operating conditions', but this is also one of the reasons, because the chip under the normal test time cannot be shipped in the package, cost. In addition, the advantages of using the necessary package level as the life test experiment are more disadvantageous than the reliability test of the package level for more than one month, and it is cut, so additional chips and cut packages are required. The reliability test is used as a regular spot test.

Page 7 200300055 V. Description of the invention (4) The highest rate can only be once a month, and it is impossible to effectively detect sporadic defective products. For example, if a new process is initially developed in May, the traditional package-level reliability quality test will be performed immediately. If the test result does not meet the product design specifications, it will not be known until June; after improvement, Retesting, the experimental results still have to wait until August to determine, whether for good or bad in the end, has delayed the development of new processes. The wafer-level reliability quality test has a short test time, which can be completed within a few hours. In addition, during the manufacturing process, reliability tests are performed and they can still be shipped after testing. In addition, the frequency of regular spot testing can be tested several times a week, and reliability quality control can be included in wafer manufacturing and production. Therefore, compared to package-level reliability testing, wafer-level testing methods are faster and more straightforward. For all fabs that require timeliness, they are more important for their development. Using wafer-level test results, it is possible to determine whether there is any doubt about the reliability of the wafer in a relatively short period of time, so that subsequent processing can be performed, which will greatly help the fab to reduce manufacturing man-hours. . One of the basic reliability test items is the test of electromigration of metal wires. Metal wire electromigration means that when a metal wire (usually an aluminum wire) used to connect between transistors is passed through for a long time, the atom will be impacted by the electron wind force from the cathode to the anode. The physical mechanism that eventually causes the metal wire to break at the cathode end due to the lack of aluminum atoms or the short circuit caused by the accumulation of aluminum atoms at the anode end, this phenomenon will become more and more serious with time, and will eventually make the integrated body

200300055 V. Description of the invention (5) The circuit cannot work normally, so it is an important and basic reliability test item. Isothermal Electromigration is a wafer-level metal wire electromigration (WLR-EM) test method. Its principle is to apply a current density on the metal wire that is much higher than the normal working current (for example: dozens of Current to hundreds of times), which causes it to generate a relatively high Joule heating. In conjunction with its high current density, it measures the failure time of the metal wire and evaluates the reliability of the metal wire. However, some materials have poor mechanical strength and high thermal expansion coefficient. The thermal stress generated by different temperature processes on the metal interconnects may cause the material to diffuse or cause mechanical stress damage. Therefore, Stress Migration ° can Use the following formula to find the temperature coefficient of resistance of the metal wire TCRref (Temperature Coefficient of Resistance) (1) TCRref = AR / (Rref * AT) where 'TCRref is the temperature coefficient of the resistance value, △ τ is the measured temperature and ^ The temperature difference between the reference temperature Tref. Rref is the resistance value of the metal wire at the reference temperature. △ R is the resistance value difference between the resistance value Rtest and the reference resistance value Rref of the metal wire at the measurement temperature.

200300055 V. Description of the invention (6) So long as the TCRref of the metal wire is known, the temperature of the metal wire can be obtained from the resistance of the metal wire, or the resistance value of the metal wire can be obtained from the temperature of the metal wire. It can be expressed as the following formula: RTtest-RTref [1 + TCRref * (Ttest-Tref)] (2) As shown in the first figure, we first use a small current to measure the resistance value of the metal wire at different temperatures. After knowing the linear function relationship between resistance and temperature (because the measured current is small, Joule heat can be ignored at this time), and then use the resistance value measured at room temperature with a large current to match the resistance and temperature relationship previously obtained. The temperature of the metal wire under high current. The reason why it is called "constant temperature electromigration" is that during the test, the temperature of the metal wire can be maintained at a fixed value by a computer controlled program. Or you can also use a fixed current to make a constant current measurement, which cannot take into account the strange temperature control. "Ge, but the relative temperature or constant current electromigration test is still used in the industry. The main reason is that some controversies have not been clarified. The first is the problem of the Fai lure Mechanism. Melting due to temperature, rather than electromigration to be measured: ^ Constant temperature has been maintained during the test process, and fine temperature adjustment is required or the test process maintains strange currents that cause the temperature to rise. :Happening

200300055 V. Description of the invention (7) The density of each line on the circuit wiring will be uneven, which will cause the temperature of each part of the test wafer to be not equal. Therefore, 'how to make the metal wire of the test wafer pass current and temperature can be more stable, the temperature of the test wafer is more uniform, and the most important thing is how to ensure that the results obtained by the electromigration test are caused by electromigration. Caused by migration test phenomena or caused by high temperatures, which are all to be overcome by the present invention. 3. [Summary of the Invention] In view of the above background of the invention, the constant temperature electromigration test of the conventional technique may have doubts as to whether the electromigration is caused by high temperature. The invention provides a wafer level reliability test method and structure using a constant temperature heater. This test will independently control the temperature and current of electromigration, so that the measurable temperature and current can be used for electromigration or stress migration. To improve the accuracy and reliability of the test. Another object of the present invention is to provide a wafer-level reliability test method and structure using a constant temperature heater to achieve independent test temperature and stress current, so that the stress current and test temperature of the test wafer can be more stable. To improve the accuracy and reliability of test results. It is still another object of the present invention to provide a wafer-level reliability test method using a constant temperature heater and a structure thereof, so that the test wafer does not cause wiring to

Page 11 200300055 V. Description of the invention (8) The temperature unevenness caused by the uneven distribution of the roads, which reduces the error in the test results due to the unevenness in temperature. Another object of the present invention is to provide a wafer-level reliability test method for a constant temperature heater and a structure thereof, so that the electromagnetic fields caused by the currents of the strange temperature heaters can cancel each other out, thereby reducing constant temperature heating. Electromagnetic interference caused by the device current. According to the above-mentioned object, the present invention provides a structure and method of a constant temperature heater for wafer-level electromigration reliability testing. A constant temperature heater is used as a uniform single structure to contact a test wafer, and a strange temperature current is passed to the high temperature heater, so that the test wafer reaches and maintains a predetermined temperature to perform wafer leveling. Electromigration and stress migration (Stress M igrati ο η) reliability testing. A stress current is applied to the test wafer, and the stress current value is different from the temperature current value. In this way, the temperature and current that affect electromigration can be controlled independently, so that the effects of temperature and current on electromigration or stress migration can be measured, improving the accuracy and reliability of the test. In addition, the independent testing temperature and stress current can make the stress current and test temperature of the wafer more stable, so as to improve the accuracy and reliability of the test results. Furthermore, it can avoid that the test wafer does not cause temperature unevenness due to uneven distribution of the wiring circuit, and reduces errors in test results that may be caused by temperature unevenness. Furthermore, the electromagnetic field caused by the current of the constant temperature heater can be offset and reduced, so that the electromagnetic interference caused by the increased current of the constant temperature heater can be avoided.

Page 12 200300055 V. Description of the invention (9) IV. [Embodiments] Some embodiments of the present invention will be described in detail as follows. However, in addition to the detailed description, the present invention can also be widely implemented in other embodiments, and the scope of the present invention is not limited, which is subject to the scope of subsequent patents. Furthermore, in order to provide a clearer description and easier understanding of the present invention, the parts in the diagram are not drawn according to their relative sizes, and some dimensions have been exaggerated compared to other related scales; irrelevant details have not been completely drawn. Out for simplicity of illustration. It can be known from the second equation of the equation that the wafer level reliability test method is related to the temperature and current when measuring electromigration. That is, when the metal wire is set to a certain current value or a certain temperature to measure electromigration, the relative temperature or current will also have to be fixed to a certain value. In this way, electromigration is mainly caused by the influence of temperature or current, or the magnitude of their respective effects will be difficult to distinguish. Furthermore, when one of the variables of temperature or current is fixed (constant temperature or constant current), the other variable needs to be continuously fine-tuned, so that the two variables cannot be maintained at a fixed value at the same time. . Therefore, the main purpose of the present invention is to control these two variables independently. Therefore, in the embodiment of the present invention, the temperature and the electric current can be controlled independently by using a constant temperature heater to solve the disadvantages of the conventional art. And the heater's exterior structure

Page 13 200300055 Five identical invention description (ίο) ^ ----, will also affect the problems of Junhu & 4 j / dish, etc. A preferred embodiment of the present invention. The test wafer 10 is placed at the value of the force current 20 ', and the value of w and w is heated by the / J3EL force to reach a predetermined value using the first equation to obtain the value of the second equation for reuse, so that the thermostat heater 丨The temperature of the tester 2 reaches the predetermined test temperature product greater than the test wafer 10, so that the test wafer 10 is 10, and the thermostatic heater 20 of the thermostatic heater 12 is opposite to the direction of the constant temperature electric wave. In this way, the constant temperature waves can cancel each other and reduce influences. The configuration example is, for example, the test temperature on the heater 12 and the constant temperature heating. A better test wafer can achieve a current of 22, a current of 22, and a small amount of electromagnetic waves. The resistance of the tester 12 is designed to be 10 to achieve uniform temperature and test. The stress resistance is reliable, which is '1'. The temperature of the test wafer is 22, and the relative value of the temperature of the test temperature and the resistance value can make the constant temperature heater fully contact the constant temperature. In addition, the test of the stress generated by the stress 10 of the wafer 10 may make the substrate junction 10 pass so that the constant temperature can be achieved by heating the surface of the resistance temperature 12 to < Another preferred embodiment of the present invention is as shown in the third diagram A and the third diagram B: == sandwich structure. The test wafer 10 is placed in a constant temperature heater 12 and the / JnL heater 12 is divided into two parts. One is the upper heater 14, the heating is 16, and the test wafer 10 is sandwiched. The test wafer 10 is passed through the stress current% $ value of the heater 12 and the upper heater 14 and the lower heater 16 are connected to the second heater 22, so that the constant temperature heater 12 reaches a predetermined test temperature. . This pre-testing and measuring temperature can be like the above-mentioned preferred embodiment.

200300055 V. Description of the invention (11) Corresponding resistance value of the test temperature ', and then making the strange temperature heater 12 reach this corresponding resistance value, the constant temperature heater 12 can reach the predetermined test temperature. With this sandwich structure, the overall temperature of the test wafer 10 can be made more uniform. Furthermore, the direction of the thermostatic current 22 of the upper heater 14 and the direction of the thermostatic current 22 of the lower heater 16 can be reversed. In this way, the electromagnetic waves generated by the upper and lower thermostatic currents 22 can offset each other, thereby reducing the electromagnetic waves. Possible impact on reliability testing. Still another preferred embodiment of the present invention is a spiral structure as shown in Figs. 4A and 4B. The test wafer 10 is placed on a spiral thermostatic heater 18. The test wafer 10 is passed through the stress current 20, and the thermostatic heater 18 is passed through the thermostatic current 22, so that the thermostatic heater 18 reaches a predetermined test temperature. The predetermined test temperature may be the same as the above-mentioned embodiment. First, the corresponding resistance value of the predetermined test temperature is known, and then the constant temperature heater 18 reaches this corresponding resistance value, so that the constant temperature heater 18 can reach the predetermined test. temperature. With this spiral structure, the overall temperature of the test wafer 10 can be made uniform. Furthermore, although the spiral structure does not need to have the double-layer structure as shown in Figures 4A and 4B, it can also achieve the effect of uniform temperature of the test wafer 10, but if the fourth A and fourth The double-layer structure shown in Figure B. The adjacent inner layer of the thermostatic heater 18 and the outer layer of the current 22 are in opposite directions. Therefore, the electromagnetic waves generated by the current 22 can offset each other, reducing the potential of electromagnetic waves for reliability testing. influences. In the above embodiment, the constant temperature heater may use a semiconductor manufacturing process

Page 15 200300055 V. Description of the invention (12) It is formed on the test wafer. The appropriate constant temperature heater is used to measure the wafer = wafer. After different test temperatures can be formed, the measurement can be used. Once the constant temperature heater is used, the wafer can be measured for parameters such as electrical properties. Use this spring. Set the temperature and wafer estimation of the test wafer, and evaluate its service life. P ^ is also used to perform reliability evaluation on wafers. The evaluation is modified to improve the structure of the present invention. The unevenness of the test can be made, and the constant temperature value that can be invented by electromagnetics can be avoided, and the constant temperature heater that can conduct electricity as a thermal conductivity effect tungsten, trioxide can achieve a constant temperature effect. The wafer-level wafer of the present invention 1 〇 Maintain the interference caused by the magnetic field caused by the current that is expected to cause the test result. A better material made of a material that does not have a heater, such as titanium barium UaTi〇3), etc. The structure is also the temperature of the reliability test. In addition to the error, you can offset the special requirements of the high test results. The structure can be polycrystalline seconds. Example The reduction of the constant temperature of the present invention is correct for different uses, as long as it is correct. Compared with the spirit of Shi Xi and Bronze Road, the heater is divided into the structural structure of temperature, so it is feasible. And this is a material with good resistance, aluminum, combined with the above, Taiji Jin # and stress migration reliability measurement continued, and a kind of wafer-level electromigration hair, which is said to be “0… The structure and method of the heater can be controlled by measuring the stress current 20 and ^ of the Japanese Yen 10 right, so that the temperature is 4 + 8 Japanese Yen 10 and the temperature of each other is high (you I ^ ΐ and electricity The effects of migration can be independent (for example, the temperature of the south stress current is low to exclude the effect of temperature, or ^ 200300055 V. Description of the invention (13) The temperature of the low stress current is high to exclude the effect of current), so the habit can be avoided. In the known constant temperature electromigration reliability test of wafer level, the problem of electromigration caused by temperature or current cannot be confirmed, which effectively improves the accuracy and reliability of wafer level reliability test. And the conventional wafer level The constant temperature electromigration reliability test can also avoid the problems of stress current oscillation caused by controlling the constant temperature, or the temperature drift up and down due to the constant current. Also, it can avoid testing the wafer without the wiring circuit. Minute The uneven temperature causes uneven temperature, which can reduce the error of the test results due to the uneven temperature. The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of patent application of the present invention; Other equivalent changes or modifications made without departing from the spirit disclosed by the present invention should be included in the scope of patent application described below.

Page 17 200300055 Brief description of the diagram V. [Simplified diagram of the diagram] The first diagram is a schematic diagram of the linear function relationship between the resistance and the temperature of the conductor; the second diagram is a diagram of a preferred embodiment of the present invention; the third A and Figure B is a schematic side and top view of another preferred embodiment of the invention; and Figures A and B are schematic top and side views of yet another preferred embodiment of the invention; Symbols of the main parts: 10 test wafers 12 base-shaped thermostatic heater 14 upper heater 16 lower heater 18 spiral thermostatic heater 20 stress current 2 2 丨 temperature current

Page 18

Claims (1)

200300055 6. Application Patent Scope 1. A wafer reliability test device, comprising: a constant temperature heater formed under a test wafer, and applying a current to the constant temperature heater to make the test wafer reach and maintain A test temperature; and a measuring device for measuring electrical parameters and temperature of the test wafer when the test wafer reaches the test temperature. 2. The constant temperature heater structure of item 1 of the scope of patent application, wherein the material of the above constant temperature heater is selected from the group consisting of polycrystalline stone, stone evening, copper, I Lu, crane and barium titanium oxide (B a T i 03). 3. For example, the structure of a constant temperature heater in the scope of application for patent No. 1 wherein the above-mentioned heating structure is a base structure. 4. For the constant temperature heater structure in the third item of the patent application, the current direction of the constant temperature heater is opposite to that of one of the test wafers. 5. For example, the constant temperature heater structure of the first patent application range, wherein the above-mentioned constant temperature heater structure is a sandwich structure, the constant temperature heater is divided into upper and lower heaters, which are respectively formed above and below the test wafer. side. 6. The constant temperature heater structure according to item 5 of the patent application scope, wherein the current direction of the heater above the constant temperature heater and the constant temperature heater Page 19 200300055 VI. The scope of patent application The current direction of the heater is opposite. 7. The constant temperature heater structure according to item 1 of the patent application scope, wherein the structure of the constant temperature heater is a spiral structure. 8. The constant temperature heater structure according to item 7 of the patent application scope, wherein the spiral structure of the above-mentioned constant temperature heater is a double-layer spiral structure. 9) The constant temperature heater structure according to item 8 of the patent application scope, wherein the double-layer spiral structure of the above-mentioned constant-temperature heater, the adjacent inner layer of the double-layer structure and the current direction of the outer layer are opposite. 1 (K) A wafer-level reliability test device that uses a measuring device to measure the electrical parameters and temperature of a test wafer when it reaches a test temperature, including: a constant temperature heater formed in Below the test wafer, an electric current is passed to the thermostatic heater, so that the test wafer reaches and maintains the test temperature. 1 1. The wafer level reliability test device according to item 10 of the patent application scope, wherein The structure of the above-mentioned constant temperature heater is a base structure. 12. As in the wafer level reliability test device for item 10 of the patent application scope, wherein the above-mentioned strange temperature heating structure is a two-Meiji structure, the ten The high temperature heater is divided into upper and lower heaters, which are respectively formed on the test wafer, Page 20 200300055 VI. Scope of patent application Setting, 1 ″ .: Λ · Please apply the wafer-level reliability test device No. 10 of the patent scope to the structure of the thermostatic heater α, which is a spiral structure. Method 14. Package—a device including a wafer-level electromigration and stress migration reliability test device; 2; temperature ;; device-under the test wafer, heat and electric μ to the strange temperature, so that the test crystal It reaches and maintains a test temperature; to measure the electrical parameters and temperature of the test wafer. When the test wafer reaches the test temperature, Deming Ding Tueshen patented the siege of the siege of 14 patents. Fang Zhiren and # Force Migration Reliability Test for Fang Zhiren's unjust migration and should be selected from the material of the above-mentioned constant temperature heaters (BaTiO, the group consisting of ~ ... Yu Yuxi) Said Shi Xi, Shi Xi, Copper, Ming, Crane and Barium Titanium Trioxide 16. As described in the method of force migration reliability test in item 14 of the patent application scope, the migration caused by the radio and television should be a base structure. The structure of the above-mentioned constant temperature heater in the eighth + s. For example, the method of the reliability test for the force migration of the wafer-level female mine M ^ 0 in the 16th patent application scope, one person is electromigrated and the above-mentioned constant temperature should be applied. The electricity of the heater Page 21 200300055 6. Scope of patent application The current direction is opposite to the current direction of one of the test wafers. 18. The method for reliability test of wafer level electromigration and stress migration according to item 14 of the scope of patent application, wherein the structure of the above-mentioned constant temperature heater is a sandwich structure, and the constant temperature heater is divided into upper and lower heaters Are respectively formed above and below the test wafer. 19. The method for reliability test of wafer level electromigration and stress migration according to item 18 of the scope of patent application, wherein the current direction of the heater above the constant temperature heater and the heater below the constant temperature heater The current direction is opposite. 20. The method for reliability test of wafer-level electromigration and stress migration according to item 14 of the scope of patent application, wherein the structure of the above-mentioned constant temperature heater is a spiral structure. 2 1. The method for reliability testing of wafer-level electromigration and stress migration according to item 20 of the patent application scope, wherein the spiral structure of the above-mentioned constant temperature heater is a double-layer spiral structure. 2 2. The method for reliability testing of wafer-level electromigration and stress migration according to item 21 of the scope of patent application, wherein the double-layer spiral structure of the above-mentioned thermostatic heater, and adjacent inner layers in the double-layer structure The current direction is opposite to that of the outer layer. Page 22