JP2008124199A - Reliability test equipment and reliability test method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method to shorten a time required for performing reliability tests covering a plurality of temperature environments, which is capable of performing reliability tests under heating at a desired temperature for a wafer without mounting a semiconductor device in a package etc. <P>SOLUTION: Among semiconductor devices, power MOSFETs 15 incorporated into a wafer 16 arranged on a wafer prober, electricity is turned on polysilicon heaters which the selected semiconductor device, the power MOSFET 15 have for heating, a burn-in test of the semiconductor device, the power MOSFET 15 is performed for the wafer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reliability test apparatus and a reliability test method suitable for evaluating reliability by operating a semiconductor device under heating.

  Conventionally, reliability tests have been performed on manufactured semiconductor devices to evaluate operation reliability such as life that causes malfunction. In general, the reliability test is performed by cutting a semiconductor device formed on a wafer in advance into a chip and assembling it into a package, and assembling the package on an evaluation board to which wiring is further applied. It is carried out by placing it in a temperature-controlled room adjusted to a temperature of from about 0C to about 170C.

  Specifically, in the semiconductor device development process, as shown in FIG. 2- (b), after designing the device first, the device is prototyped and the reliability is evaluated, and there is a defect (NG). If there is a problem or the trial production process is improved, the trial production and the reliability test are repeated again after the improvement, and if the reliability test shows no problem (not NG), the product is manufactured. The At this time, the prototype semiconductor device is subjected to an operation test for about 1000 hours in a state where it is assembled as a chip as described above, and enormous time and cost are required for the test.

The success or failure of the reliability of the semiconductor device can be determined by testing whether or not the basic parameter of the semiconductor device is a characteristic variation within a desired range.
For example, the lifetime in which the reliability of the semiconductor device can be maintained can be evaluated by conducting a current test at a high temperature and testing the time until the electrical characteristics change to a certain value.

  The lifetime at this time generally shows Arrhenius-type dependence, and can be evaluated in a short time by raising the temperature based on the Arrhenius plot. Further, the lifetime at a desired temperature can be predicted by measuring the temperature dependence of the lifetime and obtaining the activation energy.

On the other hand, when trying to test the maximum temperature that can maintain the long-term reliability of the manufactured semiconductor device, it is necessary to operate in a plurality of temperature environments for a long time.
Therefore, when trying to operate for a long time by changing a plurality of temperatures, for example, if the evaluation time in one temperature environment is 1000 hours, it takes 1000 n hours in n temperature environments, and a huge amount of time is required for the test. become.

Further, as one method for heating a semiconductor device, a method in which a polysilicon heater is provided around the device region is disclosed (see Non-Patent Document 1). Here, it is described that the device region was operated for 1000 seconds at a temperature of 200 to 250 ° C.
“Bias temperature instability assessment of n- and p-channel MOS transistors using a polysilicon resistive heated scribe lane test structure” Microelectronics Reliability, Werner Muth and Wolfgang Walter, 44 (2004) p.1251-1262.

  As described above, the reliability test requires an enormous amount of time for evaluation by high-temperature heating and the like, and the semiconductor device to be evaluated needs to be assembled in a package as a chip. Therefore, by shortening the time required for the reliability test and simplifying the assembly work to the package, it is possible to expect a reduction in the process and cost reduction until the production of the semiconductor device.

  In addition, the reliability test requires an energization test at a high temperature, and the energization test can be evaluated in a shorter time as the temperature is higher. In recent years, for example, in an inferior high-temperature environment such as an in-vehicle semiconductor device. There is also a need to test reliability at higher temperatures than conventional (for example, temperatures exceeding 200 ° C. or 300 ° C.) assuming that they are used. Moreover, there is a need for a test over such a long time of 50 hours or more at such a high temperature.

  However, when the test is performed by heating in the wafer state, the semiconductor device is heated by raising the temperature of the stage on which the wafer is placed, but the limit of the temperature that can be heated in the wafer state is about 200 ° C.

  Furthermore, when conducting tests to evaluate the maximum temperature that guarantees long-term reliability, it is possible to shorten the test time by preparing multiple temperature-controlled rooms and changing the temperature to operate for a long time. Is unavoidable, and it is also disadvantageous in terms of cost.

  The present invention has been made in view of the above, and it is possible to perform a reliability test by heating to a desired temperature in a wafer state without assembling a semiconductor device in a package or the like, and performing a reliability test over a plurality of temperature environments in a short time. An object of the present invention is to provide a reliability test apparatus and a reliability test method that can be performed in the above-described manner, and to achieve the object.

  The present invention makes it possible to perform a heat test in a wafer state without providing an extra step by diverting a step in a semiconductor process when manufacturing a semiconductor device, and for a desired semiconductor device. The inventors have obtained knowledge that the operation test can be performed while selectively heating to a desired high temperature, and have been achieved based on such knowledge.

  In order to achieve the above object, a reliability test apparatus according to a first aspect of the present invention is at least a part selected from the heater of a wafer on which a semiconductor device having a heater manufactured by a semiconductor process is formed. Further, the semiconductor device is subjected to a reliability test by energizing the semiconductor device in a wafer state and selectively heating the semiconductor device having the energized heater.

In the reliability testing apparatus according to the first aspect of the invention, a part or all of desired semiconductor devices to be tested are selected from the semiconductor devices on the wafer, and the wafer state is selected with respect to the heater of the selected semiconductor device. By adopting a configuration that allows energization as it is, there is no need to assemble the semiconductor device as a chip as in the past, and the time required for the reliability test can be shortened and the assembly work to the package can be simplified. It is possible to shorten the process leading to production and reduce costs.
For example, as shown in FIG. 2- (a), the time required for the reliability test is shortened (period marked with *), and the total process time until the production of the semiconductor device is shown in FIG. 2- (b). The process time can be significantly shortened compared to the conventional process time.

  In addition, by locally energizing and heating the heater of the selected semiconductor device, there is no need to prepare a temperature-controlled room or the like and to increase the environmental temperature of the temperature-controlled room according to the test temperature, and the entire wafer Because it is possible to select the heating and heating temperature for each semiconductor device without heating the device, the test should be performed at a higher temperature (eg, 200 ° C. or higher) than in the past without providing extra equipment and processes. Therefore, it is possible to shorten the time required not only for a single test but also for testing by changing the environment to a plurality of temperatures. Furthermore, a test for evaluating a limit temperature that guarantees operation reliability is possible, and the reliability design of the semiconductor device is facilitated.

In the first invention, when the size of the heater is L (length) × W (width) and the size of the device operation area constituting the semiconductor device is Ld (length) × Wd (width), the device operation area The dimensional relationship between the heater and the heater is preferably in a range that satisfies the following relationships (1) and (2).
Wd ≦ 0.2W (1)
Ld ≦ 0.28L (2)

  The device operation region is a region where a semiconductor structure such as a bipolar transistor, a field effect transistor (FET), or a MOSFET is formed.

  The heater generates heat when energized, and the device operation region is heated by this heat generation. At this time, the limit electric power that keeps heating the heater for a long time (for example, 50 hours or more) is determined by the heat generation temperature of the heater, and this heat generation temperature is determined by the resistance when the heater is energized. And by using the ratio of the resistance value of the heater before energization and at the time of energization and satisfying the above dimensional relationship, it is possible to suppress degradation and destruction of the heater in a short time, so that the device operation area A reliability test over a long period of time, for example, 50 hours or more can be performed under (for example, 400 ° C.).

  According to a first aspect of the present invention, there is provided an energization means for energizing a heater of a semiconductor device having a heater manufactured by a semiconductor process, an energization means for energizing the semiconductor device, and energization for an initial value of a desired parameter of the semiconductor device. Determining means for determining whether or not the subsequent rate of change is equal to or less than a predetermined value; and when the determining means determines that the rate of change exceeds the predetermined value, energization of the heater and the semiconductor device is terminated. An energization control means for providing can be provided.

  When energizing the heater of the desired semiconductor device selected by the energizing means, the heater deteriorates or breaks as long as the dimensional relationship with the device operating area of the heater satisfies the relationship (1) and (2) above. Heater resistance and maximum power corresponding to the change can be applied within a range where no occurrence occurs, so heating at a high temperature (for example, 400 ° C) over a long period of time such as 50 hours or more is possible, and operation reliability is guaranteed. This is effective for tests that evaluate the critical temperature.

In the first invention, the heater can be composed of a polysilicon heater.
When the polysilicon is energized, it self-heats, and the device operating region is heated by this heat generation. At this time, the limit power for continuously heating the polysilicon for a long time (for example, 50 hours or more) is determined by the self-heating temperature of the polysilicon, and this self-heating temperature is obtained by the resistance when the polysilicon is energized. Then, by utilizing the fact that the ratio of the resistance value of the polysilicon before and during energization is 1.5 and satisfying the dimensional relationship, it is possible to suppress degradation and destruction of the polysilicon in a short time. Therefore, it is possible to perform a reliability test over a long period of time, for example, 50 hours or more at a high temperature (for example, 400 ° C.) in the device operation region.

  A reliability test method according to a second aspect of the invention provides a wafer on which a semiconductor device having a heater manufactured by a semiconductor process is formed (preparation step), and at least a part of the heater on the wafer is in a wafer state. The reliability test of the semiconductor device is performed by energizing the semiconductor device and energizing the semiconductor device having the energized heater while selectively heating (heating process).

  In the second invention as well, as described above, a part or all of the desired semiconductor device to be tested is selected from the semiconductor devices on the wafer, and the heater of the selected semiconductor device is energized in the wafer state. This configuration eliminates the need to assemble semiconductor devices into chips as in the past, shortens the time required for reliability testing, and simplifies assembly work for packages. It is possible to shorten the process and reduce costs. Similarly to the above, for example, as shown in FIG. 2A, the time required for the reliability test (marked with *) is shortened.

  In addition, by locally energizing and heating the heater of the selected semiconductor device, there is no need to prepare a temperature-controlled room or the like and to increase the environmental temperature of the temperature-controlled room according to the test temperature, and the entire wafer. Because it is possible to select the heating and heating temperature for each semiconductor device without heating the device, the test should be performed at a higher temperature (eg, 200 ° C. or higher) than in the past without providing extra equipment and processes. Therefore, it is possible to shorten the time required not only for a single test but also for testing by changing the environment to a plurality of temperatures. Furthermore, a test for evaluating a limit temperature that guarantees operation reliability is possible, and the reliability design of the semiconductor device is facilitated.

Further, when the size of the heater of the second invention is L (length) × W (width), and the size of the device operation region constituting the semiconductor device is Ld (length) × Wd (width), device operation The dimensional relationship between the region and the polysilicon heater is preferably in a range that satisfies the following relationships (1) and (2). The device operation area is as described above.
Wd ≦ 0.2W (1)
Ld ≦ 0.28L (2)

  As in the case of the first invention, the second invention is configured so as to satisfy the dimensional relationship, so that deterioration and destruction of the heater in a short time can be suppressed. For example, a reliability test over a long time of 50 hours or more.

  In addition, energization of the heater and the semiconductor device can be performed by supplying power in a range where the rate of change after energization with respect to the initial value of a desired parameter of the semiconductor device is equal to or less than a predetermined value. In the range in which the dimensional relationship with the device operating area of the heater satisfies the relationship (1) and (2) above, the heater resistance and maximum power corresponding to the change are applied within a range where the heater does not deteriorate or break down. Therefore, heating at a high temperature (for example, 400 ° C.) over a long period of time, for example, 50 hours or more is possible, and it is effective for a test for evaluating a limit temperature that ensures operation reliability.

  In the second invention, similarly to the first invention, a polysilicon heater can be suitably used as the heater.

  The present invention, when testing the reliability of a manufactured semiconductor device, without any equipment investment such as preparation of a temperature-controlled room or board for evaluation and measures for heat resistance, any heating temperature, particularly 200 ° C. or more It is possible to construct a reliability test system capable of performing a severe operation test in a high temperature environment in a short time and at a low cost.

  According to the present invention, it is possible to perform a reliability test by heating to a desired temperature in a wafer state without assembling a semiconductor device in a package or the like, and to perform a reliability test over a plurality of temperature environments in a short time. A test apparatus and a reliability test method can be provided.

  Hereinafter, an example of an embodiment of the reliability test apparatus of the present invention will be described in detail with reference to FIGS. 1 to 10, and details of the reliability test method of the present invention will also be described through the description. However, the present invention is not limited to these embodiments.

  As shown in FIG. 1, the reliability test apparatus of this embodiment includes a power supply 11 for energization testing for operating a semiconductor device on a wafer (semiconductor substrate), and a heater for energizing a polysilicon heater of the semiconductor device. A semiconductor device on a wafer, which is provided on a wafer prober, includes a power source 12 and a controller 13 which is an energization control means for controlling the operation of the semiconductor device necessary for the reliability test and energizing control of the polysilicon heater. In the wafer state, an inspection needle (probe) connected to the tester is set up and energized to perform a reliability test.

  The wafer prober performs inspection by setting an inspection needle (probe) on a semiconductor device on the wafer. As shown in FIG. 1, the wafer 16 in which the semiconductor device 15 to be tested is fabricated can be placed on the wafer prober for testing.

The semiconductor device 15 on the wafer 16 is configured in the structure shown in FIG. 3 and remains in a state of being formed on the wafer by a semiconductor process before being cut into chips.
As shown in FIG. 3, a device structure portion 21 which is a device operation region having a MOSFET structure is provided at the central portion of the semiconductor device 15, and a polysilicon heater 22 is provided so that the device structure portion 21 can be heated. It has been.

  As shown in FIG. 3, the device structure portion 21 is an operation region in which a MOSFET having a size of Ld (length) 39 μm and Wd (width) 28.8 μm is fabricated, and size L (length) × W (width) ) At the center of the polysilicon heater 22 (leaving the equal distance Lp in the length L direction and the equal distance Wp in the width W direction).

  The polysilicon heater 22 is formed by depositing polysilicon in a process in which the device structure portion 21 is manufactured by a semiconductor process. The resistance value is L (length) 140 μm, W (width) 144 μm, and thickness 0.4 μm. This is a 46Ω heater. The polysilicon heater is connected to the heater electrodes 23 and 24 at both ends in the length L direction. The polysilicon heater 22 generates heat when current flows between the heater electrodes 23 and 24, and the device generates heat. The structural part 21 can be heated.

In the present embodiment, the device structure portion 21 and the polysilicon heater 22 have a dimensional relationship of Wd = 0.2W and Ld = 0.28L.
In the present invention, the device operation region (here, the device structure portion 21) and the polysilicon heater 22 are configured to satisfy the dimensional relationship of Wd ≦ 0.2W and Ld ≦ 0.28L. When Wd and W and Ld and L are in the above relationship, the deterioration of the polysilicon can be prevented from being accelerated, and destruction in a short time can be suppressed. As a result, it is possible to perform a reliability test over a long period of time of 50 hours or more particularly at a temperature up to 400 ° C. in the device operating region.

  Further, it is desirable that the dimensional relationship is satisfied and the device operation region is disposed at a substantially central position of the heater (here, the polysilicon heater). By disposing at a substantially central position, the device operating region can be heated uniformly.

  The heater may be any heater that can be manufactured together with the device structure by a semiconductor process. Examples of the heater include a diffusion layer resistor and a metal wiring layer in addition to the polysilicon heater.

  Since the heater is provided by a semiconductor process, that is, by partially diverting the manufacturing process of the device structure part, it is not necessary to provide a separate process for the heater manufacturing or to invest in facilities, and within a series of manufacturing processes of semiconductor devices. A heater can be precisely manufactured for each device structure portion without cost.

  Here, the semiconductor process for producing the heater is a process for depositing metal or polysilicon to form a film. For example, a semiconductor silicon process for forming a polysilicon film having a semiconductor structure, a CMOS process, and a nonvolatile memory process. There are means such as a bipolar process and a BiCMOS process.

  Each semiconductor device provided on the wafer is formed with an electrode pad (not shown), and one end of each of the device energization lead wire 17 and the heater energization lead wire 18 is connected through the electrode pad. Yes.

  The device energization lead wire 17 is a wiring for energizing and operating the semiconductor device when performing a reliability test of the semiconductor device, and the other end is connected to the energization test power source 11. The heater energization lead 18 is a wiring for selectively energizing a polysilicon heater of a desired semiconductor device and heating the desired semiconductor device when performing a reliability test of the semiconductor device. The end is connected to the heater power source 12.

  Note that the inspection probe (probe) of the wafer prober is connected to a tester. This tester exchanges electrical signals with the semiconductor device 15 fabricated on the wafer 16 and measures the electrical characteristics of the semiconductor device.

  The power supply 11 for energization test is a power supply for supplying power for operating the semiconductor device 15 built on the wafer 16. The energization test power supply 11 is electrically connected to the control device 13 so that at least power supply control is possible, and receives power from the control device 13 to supply power to the semiconductor device. It has become.

  The heater power source 12 is a power source for supplying power for energizing the polysilicon heater of the semiconductor device to be heated. The heater power supply is electrically connected to the control device 13 so that at least power supply control is possible, and power is supplied to the selected polysilicon heater in response to a signal from the control device 13. It is like that.

  The energization test power source 11, the heater power source 12, and the like described above are electrically connected to the control device 13. The control device 13 selects the semiconductor device when performing the reliability test, switches the polysilicon heater ON / OFF, turns the semiconductor device operation ON / OFF, controls the temperature of the polysilicon heater, monitors the test time, and the like. It is responsible for operation control during testing.

Next, an example of a reliability test method for performing a reliability test of a semiconductor device will be described.
First, as described above, the wafer 16 in which the semiconductor device 15 having the polysilicon heater 22 is previously formed is placed on the wafer prober. Under the room temperature environment, the polysilicon heater 22 of the semiconductor device 15 is energized from the heater power source 12 to heat the semiconductor device, and the semiconductor device 15 is energized from the energization test power source 11 to operate the semiconductor device. . By doing so, it is possible to conduct an energization test on a semiconductor device heated to a desired temperature at room temperature.

  In the heating by the polysilicon heater 22, the control device 13 controls the heater power source 12 to cause a current to flow between the heater electrodes 23 and 24, whereby the polysilicon heater 22 generates heat, and the semiconductor device 15 is heated to the heat generation temperature. Is done.

  At this time, the energization test of the semiconductor device 15 selects a semiconductor device or a set of a plurality of semiconductor devices so that the heating temperature varies as desired from among the semiconductor devices fabricated on the wafer in the wafer state. Specifically, an energization test can be performed at 150 ° C., 200 ° C., and 250 ° C., for example. Under a room temperature environment, for example, when 1.5 W, 2.0 W, and 2.5 W are respectively applied to the polysilicon heater 22, the temperature of the semiconductor device 15 can be increased to 150 ° C., 200 ° C., and 250 ° C.

Note that the temperature of the semiconductor device 15 can be measured by, for example, a pn junction diode of the semiconductor device.
Here, the temperature dependence of the current-voltage characteristics of the diode is shown in FIG. As shown in FIG. 4, when the current is constant, the voltage VF changes with increasing temperature. FIG. 5 is a graph showing the relationship between the forward voltage and the temperature of the pn junction diode. As shown in FIG. 5, the forward voltage changes linearly with respect to temperature, and the following relationship is obtained.
VF / VF ₀ = 1−β · (T−T ₀ )
[T: temperature of pn junction diode, T ₀ : ambient temperature, VF: forward voltage, VF ₀ : VF at ambient temperature T ₀ , β: temperature coefficient]
Therefore, from the above equation, the temperature of the semiconductor device is
T = (1−VF / VF ₀ ) / β + T ₀
Thus, by measuring VF when power is supplied to the polysilicon heater, the relationship between power and temperature can be obtained.

An example of this is shown in FIG. FIG. 6 is a diagram showing the relationship between the input power to the polysilicon heater and the temperature. The temperature Ts (° C) of the device when power is applied to the polysilicon heater is
Ts = Rth · P + T ₀
[Rth: resistance, P: input power (Power; W)]
It is represented by
Therefore, if the input power P is made constant, the device temperature becomes constant if the environment has a constant ambient temperature. Therefore, by keeping the input power of the polysilicon heater constant, the temperature of the device region can be kept constant. In order to make the power supplied to the polysilicon heater constant, in general, the applied voltage or current may be made constant. However, the resistance of the polysilicon itself changes due to the heat generated by the polysilicon. Therefore, in order to make the input power constant, it is preferable to continuously monitor the power value and perform feedback control of voltage or current so that the power becomes constant.

  In this embodiment, the characteristic variation of the semiconductor device is measured by setting an inspection needle (probe) on the semiconductor device on the wafer in the wafer state at room temperature before and during or after the test. Find the desired parameter change.

  Of the control routine by the control device 13 of the present embodiment, a control routine for testing the long-term reliability of a semiconductor device in a room temperature environment will be described in detail. FIG. 7 shows a test control routine for automatically controlling the heater heating and energization operations. The temperature change of the semiconductor device 15 during the test will be described with reference to FIG. 8 showing the temperature change of the device structure portion 21 (here, the case where the semiconductor device is energized at 400 ° C.) is described.

  When this routine is executed, first, in step 100, an inspection needle (probe) is set up on the semiconductor device 15 built in the wafer 16, and the operating characteristic (initial characteristic) of the semiconductor device 15 before heating is measured. The The temperature of the semiconductor device at this time is 50 ° C.

  After measuring the initial characteristics, in step 120, one of the semiconductor devices 15 on the wafer 16 to be tested at a target temperature (here, 400 ° C.) is selected, and the selected semiconductor device poly is selected. Electric power is supplied from the heater power source 12 to the silicon heater 22 and heated until a desired power of 3.7 W (temperature of 400 ° C.) is reached. The temperature of the semiconductor device is increased as shown in FIG.

  Here, the semiconductor device is controlled so that the input power is controlled by the control device 13 and is stably heated to 400 ° C. in a 50 ° C. environment. That is, in step 140, it is determined whether or not the power is stabilized by monitoring the input power to the polysilicon heater. In this case, the power (temperature) when the semiconductor device is in the state shown in FIG.

  When it is determined in step 140 that the electric power is stabilized, the energization test at a desired heating temperature is possible, so that the process proceeds to the next step 160, and when it is determined that the electric power is not stabilized, the step At 180, voltage or current feedback control is applied so that the power is constant, and the process returns to step 120 again to repeat the same control.

  In step 160, the semiconductor device is operated by supplying power from the power supply 11 for energization test while being heated to 400 ° C., and the energization test is started. After starting the energization test, the semiconductor device continues to be energized for an arbitrary period as shown in FIG. Then, in the next step 200, it is determined whether the energization time from the start of operation has reached the set time.

  In step 180, if it is determined in step 200 that the energization time has not yet reached the set time, the energization test is continued until the predetermined set time elapses in a predetermined stable power state. While monitoring the input power to the polysilicon heater, voltage or current feedback control is performed so that the power becomes constant, and the process returns to step 120 again to repeat the same control.

  Conversely, when it is determined in step 200 that the energization time has reached the set time, the intended high-temperature operation has been completed, so in step 220 the heating state is maintained (d in FIG. 8). The power supply (energization operation) from the power supply 11 is stopped. At this time, the temperature of the semiconductor device is maintained at a desired temperature (here, 400 ° C.) as shown in FIG.

  In step 240, the energization of the polysilicon heater is turned off. The temperature of the semiconductor device 15 drops from the desired temperature (here, 400 ° C.) to around 50 ° C. as shown in e of FIG.

  In step 260, the semiconductor device 15 waits until the temperature of the semiconductor device becomes stable. After that, in step 280, the operating characteristic (endurance characteristic) of the semiconductor device 15 after the energization test at high temperature heating is the same as in step 100. Measured.

  Then, in step 300, it is determined whether or not the integrated value of the energization time of the energization test in step 200 has reached the preset total set time of the reliability test.

  If it is determined in step 300 that the integrated value of the energization time has reached the entire set time (for example, 50 hours), the intended reliability test has been completed, and this routine is immediately terminated.

On the other hand, when it is determined in step 300 that the integrated value of the energization time has not yet reached the entire set time (for example, 50 hours), the change rate r of the parameter of the semiconductor device is equal to or less than the predetermined value R in step 320. It is determined whether or not.
A threshold voltage, a current amplification factor, etc. can be applied to the parameter.

  If it is determined in step 320 that the rate of change r is equal to or less than the predetermined value R, it is possible to continue heating the polysilicon heater and energize the semiconductor device, so the process returns to step 120 and the same operation is repeated. Conversely, when it is determined that the rate of change r exceeds the predetermined value R, this routine is terminated as it is.

In the present invention, as shown in the above embodiment, as shown in FIG. 2- (a), the time required for the reliability test is shortened (period marked with *), and all the processes until the production of the semiconductor device are completed. The time can be significantly shortened compared to the conventional process time shown in FIG.
In addition, as described above, a test for evaluating the operation reliability of a semiconductor device under high-temperature heating is selectively performed on a desired semiconductor device at a temperature equal to or higher than the ambient temperature, and 200 has been difficult in the past. The temperature can be raised to a temperature higher than or equal to 0 ° C. (for example, 250 ° C., 300 ° C., 350 ° C., etc.), and a plurality of reliability tests can be performed in different temperatures.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

  In this embodiment, a wafer prober, an energization test power supply 11 that operates by supplying (energizing) power to a semiconductor device, a heater power supply 12 that can energize a polysilicon heater of the semiconductor device, and an energization operation of the semiconductor device A control device 13 responsible for control necessary for reliability tests such as energization control for the polysilicon heater is arranged, and a reliability test device configured in the same manner as in FIG. 1 is prepared. As shown in FIG. 3, a wafer 16 in which a power MOSFET 15 which is a semiconductor device having a polysilicon heater 22 is formed is disposed.

  The power MOSFET 15 was manufactured by a composite process in which a bipolar transistor, a diode, and a CMOSFET were simultaneously manufactured on a wafer.

  The dimensional relationship between the power MOSFET device structure portion 21 and the polysilicon heater 22 is Wd = 0.30W and Ld = 0.44L. The device structure portion 21 is located at the center of the polysilicon heater 22 as shown in FIG. It is arranged in the part.

  Then, one power MOSFET on the wafer is selected and the test control routine shown in FIG. 7 is executed, and in a 50 ° C. environment, the power input to the polysilicon heater 22 is initially 2.6 W, and the heating temperature of the power MOSFET is increased. The test was conducted while controlling the temperature to 250 ° C., and thereafter, the input power was changed to 2.0 W and 1.4 W, thereby sequentially controlling the power to 200 ° C. and 150 ° C. and repeating Step 100 to Step 320 in the same manner.

FIG. 9 shows the temperature dependence of the threshold voltage over time when a current is applied to the power MOSFET as described above.
As shown in FIG. 9, it can be seen that the time change of the threshold voltage changes in a shorter time as the device temperature during the energization test is higher. Also, the activation energy can be obtained by plotting the time (time: ΔVth = 10 mV) when the change amount of the threshold voltage is 10 mV against the reciprocal of the temperature. This is shown in FIG. The activation energy was 0.79 eV. By using this value, it is possible to estimate the lifetime of the semiconductor device at a low temperature.
Here, the test time required to obtain this value was 100 seconds at 250 ° C., 1000 seconds at 200 ° C., and 10,000 seconds at 150 ° C., and the total time was about 3 hours.

  Further, in this example, the reliability test at a plurality of heating temperatures was possible by one setup, and the reliability test could be performed efficiently in a short time.

  As a comparison with the above embodiment, a reliability test apparatus having the structure shown in FIG. 1 was prepared in the same manner as in the above embodiment, except that the heater power source 12 was not provided, and the wafer having the power MOSFET in the same manner as described above. A reliability test was attempted. In this reliability test apparatus, it is inevitable to raise the environmental temperature using a thermostatic bath so that the temperature of the power MOSFET becomes a desired temperature, and it is difficult to raise the environmental temperature to 200 ° C. and 250 ° C. It was.

As a reliability test apparatus, as shown in FIG. 11, a constant temperature bath 31 in which an evaluation board is installed, an energization test power supply 32 that operates by supplying (energizing) power to the semiconductor device, and energization control of the semiconductor device. A device in which the control device 33 is arranged is prepared, and an evaluation board 34 in which a power MOSFET, which is a semiconductor device similar to that of the first embodiment, is cut into a chip and assembled in a package in the thermostatic chamber 11. installed.
As described above, in the reliability test performed using the evaluation board, the test time required about 1000 hours. That is, in this example, the evaluation could be performed with a test time of 1/100 or less as compared with the conventional test time.
In addition, the heat resistance of the evaluation board could not be maintained, and an energization test for a long time could not be performed at 200 ° C. or higher.

It is the schematic which shows the structural example of the reliability test apparatus which concerns on embodiment of this invention. (A) is a general | schematic process figure which shows the total process time required to produce a semiconductor device in this invention, (b) is a schematic process which shows the total process time required until the production of a conventional semiconductor device. FIG. It is a top view which shows an example of a structure of the semiconductor device which has a polysilicon heater. It is a graph which shows the temperature dependence of the electric current-voltage characteristic of the pn junction diode of the semiconductor device in embodiment of this invention. It is a graph which shows the relationship between the forward voltage of the pn junction diode of FIG. 4, and temperature. It is a graph which shows the relationship between the input electric power to a polysilicon heater, and temperature. 5 is a flowchart showing a test control routine for automatically controlling heater heating and energization operation in the embodiment of the present invention. It is a schematic explanatory drawing for demonstrating the temperature change of the device structure site | part at the time of a test. It is a graph which shows the temperature dependence with respect to the time change of the threshold voltage at the time of carrying out the electricity test of the power MOSFET of an Example. It is a graph which shows the temperature dependence of time when the variation | change_quantity of a threshold voltage becomes 10 mV, when conducting the electricity test of the power MOSFET of an Example. It is the schematic for demonstrating the structure of the conventional reliability test apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Current supply for energization test 12 ... Power supply for heater power 13 ... Control device 15 ... Semiconductor device, power MOSFET
16 ... Wafer 21 ... Device structure part,
22 ... Polysilicon heater

Claims (8)

  At least a part selected from the heaters of a wafer on which a semiconductor device having a heater manufactured by a semiconductor process is formed is energized in the wafer state, and the semiconductor device having the energized heater is selectively heated. By doing so, a reliability tester that performs a reliability test of semiconductor devices. The reliability test apparatus according to claim 1, wherein the heater and a device operation region of the semiconductor device satisfy the following relationships (1) and (2).
Wd ≦ 0.2W (1)
Ld ≦ 0.28L (2)
[L: length of heater, W: width of heater, Ld: length of device operating area, Wd: width of device operating area] Energizing means for energizing the heater;
Energizing means for energizing the semiconductor device;
Determining means for determining whether a rate of change after energization with respect to an initial value of a desired parameter of the semiconductor device is equal to or less than a predetermined value;
Energization control means for ending energization of the heater and the semiconductor device when it is determined by the determination means that the rate of change exceeds a predetermined value;
The reliability test apparatus according to claim 2, further comprising:   The reliability test apparatus according to claim 1, wherein the heater is a polysilicon heater.   Prepare a wafer on which a semiconductor device having a heater manufactured by a semiconductor process is formed, energize at least a part of the heater on the wafer in a wafer state, and select the semiconductor device having the energized heater. A reliability test method in which a semiconductor device is subjected to a reliability test by energizing it with heating. The reliability test method according to claim 5, wherein the heater and a device operation region of the semiconductor device satisfy the following relationships (1) and (2).
Wd ≦ 0.2W (1)
Ld ≦ 0.28L (2)
[L: length of heater, W: width of heater, Ld: length of device operating area, Wd: width of device operating area]   7. The energization of the heater and the semiconductor device is performed by supplying power in a range where a change rate after energization with respect to an initial value of a desired parameter of the semiconductor device is equal to or less than a predetermined value. Reliability test method described in 1.   The reliability test method according to claim 5, wherein the heater is a polysilicon heater.

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