JPH04338666A - Evaluating apparatus for semiconductor device - Google Patents

Abstract

PURPOSE:To provide an apparatus for evaluating a semiconductor device, which can measure reliability of the device without applying an excess power source voltage in a short time and be applied from a single transistor to a super LSI as an object to be measured. CONSTITUTION:Initial characteristics of a semiconductor device 1 are measured by using a power source 2 and a current measuring unit 3. Then, the device 1 is irradiated with a light from a light source 4 for a predetermined time and characteristics of the device are deteriorated by an optical energy, electric characteristics of the device 1 are again measured by using the power source 2 and the unit 3, and variation amounts from the initial characteristics are calculated to evaluate reliability of the device.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device evaluation system, and more particularly to a semiconductor device failure analysis and reliability evaluation system.

0002

[Background Art] In recent years, with the miniaturization of semiconductor devices,
During device operation, hot carriers are generated due to the high electric field generated within the device, and these are injected into the gate oxide film.
Deterioration of device characteristics caused by capture is a major reliability issue.

Conventionally, the lifetime of characteristic deterioration of a semiconductor device due to hot carriers has been determined by actually applying a stress voltage to the semiconductor device and measuring the amount of change in the electrical characteristics of the device before and after the stress. An example of the conventional evaluation technique described above will be described below with reference to the drawings.

FIG. 6 shows a conventional evaluation technology measuring device. In FIG. 6, 1 is a semiconductor device, 2 is a power supply, and 3 is a current measuring device. Power supply 2 to semiconductor device 1
and connect the current measuring device 3.

The operation of the measuring device configured as described above will be explained below. First, the initial electrical characteristics of the semiconductor device 1 are measured using the power supply 2 and the current measuring device 3. Next, after applying a stress voltage to the semiconductor device 1 from the power supply 2 for a certain period of time, the electrical characteristics of the semiconductor device 1 are measured using the power supply 2 and the current measuring device 3,
Calculate the amount of variation from the initial characteristics. Application of the stress voltage and measurement of the electrical characteristics are repeated for several hours to several days until the amount of variation in the characteristics of the semiconductor device 1 reaches a certain reference amount, for example, 10% to 50% of the initial characteristics. When comparing hot carrier resistance between devices, after applying stress for the same time and voltage to each device, the amount of variation in the characteristics of each device is compared to determine superiority or inferiority. FIG. 7 and FIG. 8 show evaluation results using the above-mentioned conventional evaluation technique. The semiconductor device used for evaluation was N-ch
The MOS transistor has an oxide film thickness of 16 nm and a size of W/L=20 um/1 um. The amount of deterioration of the threshold voltage of the transistor characteristics, △Vt, is evaluated over time, and the upper limit of the amount of deterioration, that is, the lifetime, is △Vt = 50.
mV. FIG. 7 shows samples A and B with different production process conditions at the same stress voltage, Vd=7V, Vg=
The results of comparing the aging deterioration of ΔVt with 1.5V applied are shown. From FIG. 7, it can be seen that sample B has less ΔVt degradation than sample A, and therefore sample B has a longer reliability life. FIG. 8 shows the deterioration of ΔVt over time when the stress voltage applied to the device was changed. As can be seen from FIG. 8, the time it takes for ΔVt to exceed the 50 mV standard, that is, the lifetime, changes depending on the stress voltage applied to the device. The stress voltage is 2 times higher than the normal voltage to shorten the measurement time.
It is set high from 0% to about 50%. FIG. 9 shows the relationship between stress applied voltage and life. As shown in FIG. 9, the reciprocal of the applied voltage and the logarithm of the lifespan are in a proportional relationship, and from this graph the lifespan at the normally used voltage can be predicted. (For example, "Hot carrier effect" by Eiji Takeda, published by Nikkei McGraw-Hill)

[0006]

[Problem to be Solved by the Invention] However, with the above method, the time it takes to degrade a semiconductor device depends on the applied stress voltage, so when guaranteeing a 10-year lifespan with normal voltage, , in order to measure the life in a few hours, the stress voltage should be 50° higher than the normal voltage.
% or more, but if the stress voltage is too high, the electric field distribution inside the semiconductor device will be significantly different compared to normal operating conditions, which will change the deterioration mechanism and make accurate life prediction difficult. I become unable to do so. For example, in FIG. 9, Vd=9V
It can be seen that the lifespan deviates from the proportional line. Therefore, it is desirable that the stress voltage be as close to the normal voltage as possible, but if it is too low, it will take a very long time to determine the lifespan. For example, in FIG.
At Vd=6V, the lifetime of ΔVt=50mV is more than 10 days. As described above, the conventional method has had the problem that it is difficult to accurately determine the life span in a short period of time. Another problem is that the measurement target is limited to single transistors because it is necessary to apply a stress voltage to each individual device.

The present invention has been made to solve the above-mentioned problems, and it is possible to measure the characteristic deterioration of semiconductor devices in a short time, and the measurement target can be applied to semiconductor devices ranging from single transistors to very large scale integrated circuits. This provides an evaluation device.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the semiconductor device evaluation apparatus of the present invention includes a light source, a power source, and a current measuring device, and irradiates light onto the semiconductor device. The device is intended to evaluate the characteristics of devices.

[0009]

[Operation] With the above-described configuration, the present invention improves the reliability of semiconductor devices by irradiating light onto a semiconductor device, deteriorating device characteristics with the light energy, and evaluating changes in device characteristics before and after light irradiation. Since it can be measured in a short time and there is no need to apply a stress voltage to each individual device, it is a semiconductor device evaluation device that can be applied to everything from single transistors to very large scale integrated circuits.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device evaluation apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a semiconductor device evaluation apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a semiconductor device, 2 is a power supply, 3 is a current measuring device, and 4
is a light source. A power source 2 and a current measuring device 3 are connected to the semiconductor device 1 . The light source 4 is installed so that it can irradiate the semiconductor device 1 .

The operation of the measuring device constructed as described above will be explained below with reference to FIG.

First, using the power source 2 and current measuring device 3,
Initial characteristics of the semiconductor device 1 are measured. Next, light source 4
After irradiating the semiconductor device 1 with light for a certain period of time, the electrical characteristics of the semiconductor device 1 are measured again using the power source 2 and the current measuring device 3, and the amount of variation from the initial characteristics is calculated. FIG. 2 shows the measurement results according to this example. The semiconductor device is an N-ch MOS transistor with an oxide film thickness of 16 nm and a size of W/L=20 um/1 um.
The light source has an output wavelength range of 300 to 800
A nm halogen lamp was used. It can be seen from FIG. 2 that the characteristics are degraded by light as well as by conventional electrical stress. It is also possible to further accelerate the deterioration by changing the light source, shortening the output wavelength of the light source to increase the optical energy, or increasing the power consumption of the light source.

According to this embodiment, by irradiating the semiconductor device with light using the light source 4 to cause characteristic deterioration,
Device deterioration can be easily measured in a short time and without applying excessive power supply voltage. Furthermore, since there is no need to apply a stress voltage to each transistor, the measurement target can be applied to everything from single transistors to very large scale integrated circuits (VLSIs).

A second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram of a semiconductor device evaluation apparatus showing a second embodiment of the present invention.

In the figure, 1 is a semiconductor device, 2 is a power source, 3 is a current measuring device, and 4 is a light source, which is the same as the configuration shown in FIG.

The difference from FIG. 1 is that a wavelength filter 21 is provided in the light source 4. The operation of the semiconductor device evaluation apparatus of the second embodiment differs from the first embodiment in that a wavelength filter is used to specify the wavelength of light irradiated to the semiconductor device. FIG. 4 shows the measurement results according to this example. The semiconductor device is an N-ch MOS transistor with an oxide film thickness of 16 nm and a size of W/L=20.
um/1um, the light source has an output wavelength range of 300
~800 nm halogen lamps were used as wavelength filters, and the center wavelengths were 300, 400, and 50 nm, respectively.
A bandpass filter with a half width of 50 nm was used at 0, 600, and 700 nm. FIG. 4 shows the relationship between the wavelength of light irradiated to a transistor and the amount of deterioration of the characteristic parameters of the device caused by the irradiation. Threshold voltage, Vt, saturation current, and Ids are shown as characteristic parameters. As can be seen from FIG. 4, according to this embodiment, by specifying the wavelength of light, a specific characteristic parameter can be degraded, and how the degradation of a specific parameter in an LSI affects the operation of the LSI. can be measured. Furthermore, by limiting the energy range of the irradiated light, it is also possible to measure the dependence of the amount of deterioration on light energy.

Regarding the wavelength of the irradiated light, when examining the wavelength dependence of light emission by hot carriers observed from semiconductor devices in operation, it was found that there is a strong correlation between wavelengths around 200 nm and transfer conductance gm deterioration. Since it can be seen, it is also meaningful to use light around 200 nm. (See Japanese Patent Application No. 1-293523.) It is also considered effective to irradiate light with a wavelength around 1100 nm, which has an energy of 1.1 eV, which is the band gap width of silicon.

A third embodiment of the present invention will be described with reference to the drawings. As the evaluation device, the same device as in the first embodiment is used. In the operation of the semiconductor device evaluation apparatus of the third embodiment, the difference from the first embodiment is that a stress voltage is applied at the same time as the semiconductor device is irradiated with light. Its operation will be explained using FIG.

First, using the power source 2 and current measuring device 3,
Initial characteristics of the semiconductor device 1 are measured. Next, light source 4
At the same time, the semiconductor device 1 is irradiated with light for a certain period of time, and at the same time, a stress voltage is applied using the power source 2. Thereafter, the electrical characteristics of the semiconductor device 1 are measured again using the power supply 2 and the current measuring device 3, and the amount of variation from the initial characteristics is calculated. This light irradiation, stress voltage application, and electrical characteristic measurement are repeated to determine the relationship between the stress time and the amount of characteristic variation. According to this embodiment, by causing characteristic deterioration of the semiconductor device by both light irradiation using the light source 4 and stress voltage using the power source 2, Device deterioration can be measured without applying excessive power supply voltage.

A fourth embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows a semiconductor device evaluation apparatus showing a fourth embodiment of the present invention.

In the figure, 1 is a semiconductor device, 2 is a power supply, 3 is a current measuring device, and 4 is a light source, which is the same as the configuration shown in FIG.

The difference from FIG. 1 is that a dark room 41, a microscope 42, a photomultiplier 43, a video camera 44, a controller 45, and a display 46 are provided as a weak light measuring device for measuring light emitted from a semiconductor device. be. For details of the weak light measuring device, see Japanese Patent Application No. 1-29352.
It is described in 3. The difference in the operation of the semiconductor device evaluation apparatus of the fourth embodiment from that of the first embodiment is that the two-dimensional luminescence distribution of the semiconductor device is measured by a weak light measurement device, and the deterioration of the device is measured by luminescence. It is. The operation will be explained below using FIG.

First, the operation of the weak light measuring device will be explained. In a dark room 41, the semiconductor device 1 to be evaluated is set on a microscope 42, and an external image of the semiconductor device 1 is magnified under light from the light source 4 and inputted to a photomultiplier 43 and a video camera 44, and then displayed on a display. 46. Controller 45 controls these devices and stores images from video camera 44 in internal memory. Next, the light source 4 and external light are shut off, the semiconductor device 1 is operated by applying the necessary voltage from the power supply 2, and the emitted light is magnified with a microscope and inputted to the photomultiplier 43, where it is highly amplified. The multiplied luminescence image is captured by a video camera 44, displayed on a display 46, and stored in an internal memory of a controller 45 for a certain period of time. First, by superimposing and displaying the external image of the semiconductor device stored in the controller 45 with the accumulated image of the light emission, the location of the light emission and the distribution of the amount of light emission can be detected.

As described above, the emission distribution of a semiconductor device in an operating state can be measured. Light emission from a semiconductor device in an operating state depends on the location of hot carrier generation, insulation film breakdown,
This can be seen at locations where PN junction breakdown has occurred. Therefore, when observing the light emission distribution of a semiconductor device in an operating state, defective areas of the device appear to be glowing, and this can be used to detect defective areas of the semiconductor device.

Next, a fourth embodiment of the present invention using this weak light measuring device will be explained. First, the luminescence distribution of the semiconductor device 1 is measured using the procedure described above. Next, the semiconductor device 1 is irradiated with light from the light source 4 for a certain period of time. After that, using the weak light measurement device again, the semiconductor device 1 is measured.
It is possible to measure the luminescence distribution of the device, examine changes from the initial characteristics, and find out where the device has deteriorated due to light irradiation. According to this embodiment, by irradiating a semiconductor device with light to cause characteristic deterioration, it is possible to easily find a location where the characteristic deterioration of the device is less likely to occur in a short time and without applying an excessive power supply voltage. In semiconductor devices such as VLSIs, which are composed of a large number of transistors, in order to examine deterioration using only electrical stress, it is necessary to create and apply a complex operation pattern that causes all transistors to operate. Light irradiation makes it very easy to degrade all transistors simultaneously under the same stress conditions. Furthermore, by examining the luminescence distribution of a device, it is possible to easily identify transistors whose characteristics tend to deteriorate due to circuit design or process defects, which are extremely difficult to detect using electrical measurements alone. . As described above, by combining the deterioration of device characteristics due to light irradiation and the detection of defective locations in the device using light emission, this embodiment greatly simplifies the detection of transistors that are prone to deterioration in LSIs, which was previously extremely difficult. This makes it possible to implement

In the first embodiment, the light source 4 was a halogen lamp, but the light source 4 was a tungsten lamp,
Can be used with any type of mercury lamp.

Further, in the second embodiment, the wavelength filter 11 is used to specify the wavelength output of the light source,
A spectrometer may be used instead of the wavelength filter 11.

[0029] Furthermore, in the third and fourth embodiments, the second
It is also possible to specify the wavelength of the irradiated light using a wavelength filter or a spectroscope as in the embodiment.

Further, in the fourth embodiment, the semiconductor device was deteriorated by only light irradiation, but electric stress may be applied simultaneously with light irradiation as in the third embodiment.

[0031]

As described above, the present invention improves the reliability of semiconductor devices by irradiating light onto a semiconductor device, deteriorating the device characteristics with the light energy, and evaluating the amount of deterioration of the device characteristics before and after the light irradiation. It is possible to easily measure the stress in a very short time, and since it is not necessary to apply stress voltage to each individual device, it can be applied to everything from single transistors to VLSIs. .

[Brief explanation of the drawing]

FIG. 1 is a diagram of a semiconductor device evaluation apparatus in a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the light irradiation time and the amount of characteristic deterioration ΔVt of the N-ch MOS transistor according to the same example.

FIG. 3 is a diagram of a semiconductor device evaluation apparatus in a second embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the wavelength of light irradiated to the N-ch MOS transistor and the amount of deterioration of characteristic parameters caused by the irradiation.

FIG. 5 is a diagram of a semiconductor device evaluation apparatus in a fourth embodiment of the present invention.

FIG. 6 is a diagram of a conventional semiconductor device evaluation apparatus.

[Fig. 7] A, B, and two types of N using a conventional evaluation device
FIG. 3 is a diagram showing the relationship between stress voltage application time and characteristic deterioration amount ΔVt of a -ch MOS transistor.

FIG. 8 is a diagram showing the relationship between stress voltage application time and characteristic deterioration amount ΔVt of an N-ch MOS transistor when the applied voltage is changed using a conventional evaluation device.

FIG. 9 is a diagram showing the relationship between the applied voltage of an N-ch MOS transistor and the life of ΔVt=50 mV, measured by a conventional evaluation device.

[Explanation of symbols]

1 Semiconductor device 2 Power supply 3 Current measuring device 4 Light source 21 Wavelength filter 41 Darkroom 42 Microscope 43 Photomultiplier 44 Video camera 45 Controller 46 Display

Claims (5)

[Claims] [Claim 1] Comprising a light source, a power source, and a current measuring device,
The semiconductor device is irradiated with light for a certain period of time from the light source to deteriorate the characteristics of the device with light energy, and the electrical characteristics of the semiconductor device before and after deterioration are measured using the power source and the current measuring device, and the initial A semiconductor device evaluation apparatus that calculates the amount of variation from characteristics and evaluates the reliability of the semiconductor device. Claim 2: The output range of the light source is set from 200 nm to 1
2. The semiconductor device evaluation apparatus according to claim 1, wherein the semiconductor device evaluation apparatus includes at least a part of a range of 100 nm. [Claim 3] Comprising a light source, a power source, and a current measuring device,
The semiconductor device is irradiated with light from the light source for a certain period of time, and at the same time a voltage is applied to degrade the characteristics of the device with both light energy and voltage. 1. A semiconductor device evaluation apparatus, characterized in that the reliability of the semiconductor device is evaluated by measuring the electrical characteristics of the device, calculating the amount of variation from the initial characteristics. 4. A method comprising: a light source, a power supply, and a weak light measuring device; the semiconductor device is irradiated with light from the light source for a certain period of time to degrade the characteristics of the device with light energy; A semiconductor device evaluation apparatus characterized in that the reliability of the semiconductor device is evaluated by measuring the light emitting characteristics of the semiconductor device before and after deterioration using the semiconductor device. 5. The light source is from 200 nm to 1100 nm.
5. The semiconductor device evaluation apparatus according to claim 4, wherein the semiconductor device evaluation apparatus is capable of outputting in a specific wavelength range that includes at least a portion of the range.