JP2904642B2 - Detecting semiconductor element failure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a defective portion of a semiconductor device, and more particularly to a method for detecting a defective portion using an emission microscope.

[0002]

2. Description of the Related Art In a semiconductor device, semiconductor elements such as transistors are formed in an extremely fine pattern in a minute semiconductor substrate area, and these semiconductor elements are electrically connected to each other by wiring to perform a desired circuit function. obtain.

[0003] Although further miniaturization and lower current consumption have been attempted due to advances in semiconductor technology, detection of defects inside a semiconductor device has become extremely difficult with such high integration. I have. That is, the leak current caused by the defect is weakened by miniaturization and low current consumption, and the accuracy may be impaired due to noise or the like of the detection device. As a method for detecting such a leak current with high sensitivity, a method using an emission microscope for detecting minute light generated from a failure portion has been conventionally adopted.

[0004] First, a conventional method for specifying an unexpected portion of a semiconductor device will be described.

(1) A semiconductor element is set on a stage of an emission microscope to which an image processing apparatus is connected, in a state where power can be supplied from the outside.

(2) A lens with the lowest magnification is set.

(3) The semiconductor device pattern image is taken into a first memory built in the image processing apparatus.

(4) A voltage is applied to the semiconductor element so that the defect symptom is reproduced.

(5) The minute light emitted from the defective portion is detected by the emission microscope, and the light emission is integrated for a certain period of time and is taken into the second memory.

(6) The data in the first memory and the data in the second memory are read and superimposed by an image processing device and displayed on a monitor.

(7) If necessary, output the image on the monitor to a hard copy device and record it.

(8) The position where light emission is generated by the above operation is moved to the center of the screen.

(9) The objective lens of the microscope is changed to one having a high magnification.

(10) The above operations (3) to (9) are repeated up to a desired magnification.

(11) If there are a plurality of light emitting locations, the operations from (2) to (10) are repeated for all the light emitting locations.

The above operation makes it possible to detect a defective portion due to a leak current generated in the semiconductor element.

[0017]

In the above-described conventional defect detection method, the person who operates the operation of moving the light emitting portion of the semiconductor substrate to the center on the screen must be performed each time.
There is a problem that it takes a lot of trouble, and there is a possibility that the light emitting portion may be lost when the magnification is increased, so that the inspection requires time. In addition, when there are a plurality of light emitting portions on one semiconductor substrate, it is necessary to always return each of the portions to a low magnification to check the light emitting portions, and there is a problem that it takes a long time to specify a defective portion. Was.

Further, in the above-described conventional defect detection method, on a screen formed by accumulating light emission for a certain period of time, out of a plurality of bright spots, a light-emitting portion from the semiconductor substrate and a portion other than the light-emitting portion, that is, noise are determined. Recognition by distinction relies on the judgment and recognition of the measurer himself, and there is a risk of misidentifying the light emitting portion. In addition, differences in perception due to individual differences were also a problem. This is a major obstacle to the automation of failure analysis in the emission microscope, and the fatigue of the measurer due to the movement of the stage as described above, long-time measurement, and furthermore, the delicate test object. That is, it causes a secondary defect or the like in the semiconductor element.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a method capable of automatically detecting a defective portion of a semiconductor element using an emission microscope.

[0020]

This gun onset Ming semiconductor element defective portion detecting method Means for Solving the Problems] sets the semiconductor device to the emission microscope in order to solve the problems described above, the low magnification observation to emit the entire chip, etc. The position is stored, and based on this stored position information, one of the light emitting points is moved to the center of the stage to increase the magnification, and the magnification is automatically increased sequentially, and a light emission image is collected at a high magnification so that desired data can be obtained. A method for detecting a defective portion of a semiconductor element, in which the pre-stored position information is read, and a stage is moved from the light emission position information to a position of a next light emission image to start collecting next light emission.
When the detection intensity based on
Then, the center of gravity of the pixel is calculated as light emission position information .

[0021]

[0022]

According to the present gun onset light detection method, if when observed at low magnification to the emission occurring in almost the entire area of the chip surface, for storing their positions in advance, for each emission only Instead, each light emission can be automatically and sequentially detected up to a high magnification, and the inspection time can be shortened. As described above, the defective portion can be automatically detected by sequentially changing the magnification from the low magnification to the high magnification while adjusting the light emitting portion to be at the center of the screen. Also, departure
When the light-based detection intensity spans neighboring pixels,
Calculate the center of gravity of these pixels and use it as light emission position information
Can be processed within the same field of view,
Need not be observed many times, and waste can be eliminated.

[0023]

[0024]

The present invention will be described in detail with reference to examples.

FIG. 8 is a view schematically showing an emission microscope system according to the first embodiment of the present invention. A computer 2 and peripheral devices such as a display and an operation tablet 3 are connected to a microscope main body 1 installed in a dark room. ing. The microscope body 1 includes an LSI chip 5 set on a stage 4.
Is irradiated with light from a light source to detect an image of the chip surface.
And outputs an image signal to the computer 2. Data of a chip surface image and an image in which light emission occurs due to energization are output from the detector 6 to the computer 2, and image signal processing described later is executed to detect a light emission position. A signal for controlling a relative position and the like is formed and output to the microscope 1.

FIGS. 1 (a), 1 (b) and 1 (c) show an LSI for collecting a luminescence image by increasing the microscope sequentially from a low magnification to a high magnification.
FIGS. 2 to 7 are flow charts showing the steps of a method for detecting a defective portion in a chip defective portion detecting operation. Next, a description will be given according to this flowchart.

In FIG. 2, the microscope 1 is set to an initial state in order to detect light emission occurring at a defective portion of the LSI chip. FIG. 5 shows the details of step S1 of this initial setup. In the initial setup, the optical system of the microscope 1 is set to the lowest magnification.

The LSI chip 5 is placed on the stage of the microscope 1 set in the initial state, and it is first determined in step S7 whether or not the entire chip image can be observed at a low magnification. If the entire chip cannot be displayed on the screen, the process proceeds to the LSI chip size storage routine shown in step S8 to correspond to the entire image by divided display. In this step S8, as shown in detail in FIG. 6, at least coordinates of corners at diagonal positions of the LSI chip are detected, and the number of screens required to observe one chip is calculated in step S9 based on this.

In order to measure the background intensity of each pixel (pixel) of the chip image projected on the screen, an LSI pattern in the field of view is photographed in step S11, and this image data is stored in the first memory in the computer 3. Store in

Next, as shown in the flowchart of FIG.
In step S12, the light source of the microscope is turned off, the LSI chip is energized, and light emission is generated at the defective portion as shown in FIG. 1 (a), an image is taken, and the intensity of each pixel is detected based on this image data. And store it in the second memory (step S
13). In step S14, the computer 2 calculates a difference from the background intensity for each pixel from the values in both memories, stores the subtraction result in the second memory, and determines "0" from the obtained value of each pixel. It is determined that a portion other than "" is a portion where light emission occurred.

Here, in determining whether or not the light emission is present, in order to determine whether the light emission location is from one point or from a plurality of light emission locations, the data in the second memory is read after step S18. , And the distribution is calculated, and in step S25, it is determined whether there is one light emitting point or plural light emitting points. If the distribution converges to one point, the process proceeds to step S26, and the light emission location is determined to be one point.

Result 1 determined from count value distribution calculation 1
If it is not possible to converge to a point, it is determined in step S27 whether or not there are a plurality of convergence points.
The following steps are executed as in the case of the point. If it is determined in step S27 that there are no convergence points, it is determined that there is no light-emitting point, and the operation is terminated.

The position information of the light emitting point is obtained in the above steps. Since the light emitting point obtained in steps S26 and S29 is usually composed of a plurality of pixels, the process proceeds to the flowchart shown in FIG. Determines if there is more than one pixel with a value. When the maximum count number appears in a plurality of pixels, these barycentric points are calculated, and these points are stored as emission positions in association with stage coordinates. If the pixel having the maximum count value is one as in step S34, the coordinates of that pixel are stored in step S33. Calculate the difference between the stored coordinates and the coordinates at the center of the screen, and calculate the moving distance of the stage required to move the light emitting point to the center of the screen from the calculation result,
In step S37, the microscope stage 4 is moved. In a state where the image is sent to the center of the screen, it is determined in step S38 whether the magnification of the objective lens is appropriate, for example, whether it is the highest magnification. If the result is the highest magnification, a necessary image is collected and the operation is terminated.

On the other hand, in a state where room for higher magnification is left, to continue working with an objective lens of higher magnification,
The process proceeds to step S40 to set a high magnification, performs focusing after turning on the microscope light source, and then proceeds to the previous step S11 shown in FIG. 2 to repeat the same operation at a high magnification.

If there are a plurality of light emitting points, the center of gravity of the light emitting point is calculated for each light emitting point, and the coordinates are stored in step S43. In the case where there are a plurality of light emitting points as described above, if a plurality of light emitting points are still included in one field of view due to an increase in magnification, the plurality of light emitting points are processed as one group. For this purpose, in step S44, as shown in FIG. 7, a range X displayed when the magnification is increased with respect to the currently displayed portion W is calculated, and how many regions are divided. The area where each of the plurality of light emitting points is located is calculated, and in step S47, the stage is moved to any of the areas where the light emitting points are present, and the process proceeds to step S38. By forming a plurality of light-emitting points into one group as described above, processing can be performed within the same field of view, and the same portion does not need to be observed many times, and waste can be reduced.

In the step of detecting a defective portion, not only the emission image obtained at the highest magnification but also the necessary drawing of the surface of the LSI chip is output from the computer 2 to the output device 3.
And outputs the image data as a hard copy.

FIG. 9 is a view schematically showing an emission microscope system according to the second embodiment of the present invention. The same components as those of the emission microscope system according to the first embodiment are denoted by the same reference numerals. And description thereof is omitted.

Referring to FIG. 9, the emission microscope system includes an emission microscope 101 and a computer 102. The emission microscope 101 is provided with a motor-driven spectral filter device 111 including a plurality of spectral filters having different transmission wavelength bands. Thus, by inserting a spectral filter into the optical system of the lens barrel, the emission wavelength can be analyzed by the computer 102 or the like. In particular, data that indicates which region has a large number of wavelengths
The data is useful for determining the cause of the defect and gives detailed information such as the shape of the defective portion. The spectral filter device 111 is configured so that the replacement of the spectral filter is automatically and sequentially switched by the motor 112 for driving the spectral filter. The band of the spectral filter is set according to the detection area.

The computer 102 is provided with first and second memories capable of sufficiently storing images, a memory containing a program indicating an analysis procedure, and a CPU image processing unit. The CPU image processing unit is configured to recognize the light emission point by recognizing and integrating the light emission, calculating the average μ and the variance σ in order to distinguish between noise and light emission, and further setting the value of μ + σ. Have been. In addition, computer 10
2 is an external device, for example, a CIDE system (Computer Integrated Design and
Evaluation system) and an extended data bus 114 for sending and receiving data that can send measurement data and obtain control data to EWS (Engineering Work Station). It is possible.

In the second embodiment, it is desirable to dispose the microscope 101 in a shielded dark room and to mount it on a vibration isolation table in order to improve the accuracy of automatic light emission recognition.

Here, the operation of detecting and analyzing a defective portion in the second embodiment configured as described above will be described with reference to FIG.
This will be described with reference to the flowchart of FIG.

In FIG. 10, the same steps as those in the first embodiment shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In the detection method of the second embodiment, step S114 is executed instead of step S14 of the first embodiment. Other steps are the same as in the first embodiment. Accordingly, by performing steps S1 to S13 shown in FIGS. 2 to 6, data on the light emission image is collected using the emission microscope and stored in the memory.

Here, in the second embodiment, in step S114 of FIG. 10, the computer 102 calculates the average μ and the variance σ of the normal distribution from the values in the second memory, obtains the value of μ + σ, and obtains the value of μ + σ The value of a pixel with a value less than or equal to
Then, in step S15, the values of all the pixels are stored again in the second memory. From the values of the pixels thus obtained, it is determined that a portion that is not “0” is a portion where light emission has occurred, and the following steps S16, S17,... Are executed.

As a result, according to the second embodiment, it is possible to recognize a light emitting portion by distinguishing noise from light emission.

The data on the defective portion obtained as a light emitting portion in this way is transferred to an analysis system via a bus and integrated with the analysis results of a simulation, an LSI tester, an electronic beam tester, and the like. Processed as data. As a result, the cause of the defective portion can be clarified, and a response method (change of a layout to be produced next) can be quickly dealt with. For example, data accumulated by measurement can be used as CAD design rules and device process simulation data.

By analyzing the light emission characteristics in detail, it is possible to use the reliability of the device, for example, to find the cause of the failure between the activation energy of the Arrhenius plot and the light emission phenomenon.

As described above, according to the second embodiment, the light-emitting portion is recognized and distinguished from noise, and the light-emitting portion is sequentially adjusted from the low magnification while adjusting the light-emitting portion to be at the center of the screen based on the information. This is extremely convenient because a defective portion can be detected by automatically changing the magnification to a high magnification.

[0049]

According to this gun onset bright as described [Effect Invention above in detail, the low magnification overall view of the semiconductor device surface to store the information of the photographed by defective portion, the raised successively magnification on the basis of the information While detecting the defective part, the work can be automated, and when increasing the magnification, it does not require the trouble of searching for an image out of the field of view unlike the conventional method, and it can be used for semiconductor element failure analysis. The time required can be greatly reduced. In addition, the detection intensity based on the emission
Calculate the centroid of these pixels over a few pixels
By using the light emission position information, processing can be performed within the same field of view.
Without having to observe the same spot many times.
The waste can be eliminated.

[0050]

As described above, the present invention has tremendous industrial value in analyzing defective parts in the most advanced industries.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an operation of a first embodiment of the present invention;
It is a figure showing the surface of an SI chip.

FIG. 2 is a flowchart for explaining a background intensity detection step in the first embodiment.

FIG. 3 is a flowchart for explaining a light emitting point detecting step in the first embodiment.

FIG. 4 is a flowchart for explaining a stage moving stage in the first embodiment.

FIG. 5 is a flowchart showing detailed steps of an initial setup S1 of FIG. 2;

FIG. 6 is a flowchart showing detailed steps of an LSI chip size storage routine of FIG. 2;

FIG. 7 is a diagram for explaining the relationship between display areas before and after increasing the magnification of the microscope.

FIG. 8 is a schematic configuration diagram of an emission microscope system according to the first embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an emission microscope system according to a second embodiment of the present invention.

FIG. 10 is a flowchart for explaining a light emitting point detecting step in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Emission microscope 2, 102 Computer 3 I / O unit 4 Stage 5 Semiconductor element (LSI chip) 6 Detector 111 Spectral filter device 112 Driving motor 113 CIDE system network 114 Data bus S1-S47, S114 Step

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/66 G01N 21/66 G01N 21/88 G02B 21/00 G02B 21/06-21/36

Claims (1)

(57) [Claims] 1. A semiconductor device is set on an emission microscope, the entire chip is observed at a low magnification, the position of light emission is stored, and one of the light-emitting portions is moved to the center of the stage based on the stored position information. The light emission image is collected at a high magnification at which desired data can be obtained by sequentially increasing the magnification automatically, and the position information stored in advance is read out from the light emission position information to the position of the next light emission image. Defective semiconductor element where stage is moved to start collecting next emission
A detection method, wherein the detection intensity based on the light emission is
When spanning pixels, calculate the center of gravity of these pixels and issue
A method for detecting a defective portion of a semiconductor element, wherein the method is used as optical position information .