JP2000077491A - Evaluation method for actual device by use of obic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an actual device to be evaluated and analyzed positively by a method, wherein a measurement position recipe and an OBIC image of a non-defective sample are prepared, and the OBIC images of a non-defective sample and a defective sample at the same position are compared with each other. SOLUTION: A sample 2 is fixed on a stage and aligned in position through an optical image, coordinates are set up for the sample 2, and a measurement position recipe is formed. Then, the OBIC image of a non-defective sample is introduced under a prescribed condition into a data base stored in an engineering work station 7. Then, the OBIC image of a defective sample is introduced under a prescribed condition into the data base. Similarly. Non-defective image data and defective image data are read out from the data base, and the images are compared with each other. At this point, when the image data read out are different in image state from those introduced into the data base, the images are adjusted in brightness threshold through a brightness conversion operation. With this setup, actual device can be evaluated and analyzed positively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating an actual device using an OBIC apparatus.

[0002]

2. Description of the Related Art As means for evaluating and analyzing a semiconductor device, there are an emission method for detecting a light emitting portion and an OBIC method utilizing a photovoltaic effect generated at a pn junction.
The OBIC method is a method for evaluating a sample by using light such as a laser instead of electrons or ions as a beam source for irradiating the sample. Since the image is an emission image (hereinafter, referred to as an EM image) or an OBIC image in which an abnormal point is expressed as a singular point, the position information cannot be determined from this image. Therefore, at present, a fault position is specified by superimposing an EM image or an OBIC image using an optical image as a basic screen.

[0003]

With this alone, when the observation position is moved, the position where the observation position is engaged with the previously acquired position information is not known, and it is difficult to perform evaluation and analysis.

FIG. 5 is an explanatory view of a problem of the conventional method.
When the observation position is moved to the position of (b) by moving the optical image + OBIC image shown in (a), the position of engagement with the previously acquired position information is lost. In the figure, ● indicates a failure point.

The present invention has been made in view of the above problems, and has as its object to provide a method for evaluating an actual device using an OBIC apparatus, which can perform reliable evaluation and analysis of an actual device. I have.

[0006]

The present invention for solving the above-mentioned problems is as follows. (1) A sample is fixed on a stage, alignment of the sample position is performed by an optical image, a coordinate system for the sample is determined, and a measurement position is determined. A step of creating a recipe, a step of taking in OBIC image data of a good sample under the measurement conditions, a step of fixing a defective sample to a stage, and the steps of
It is characterized by comprising a step of taking in BIC image data and a step of comparing non-defective OBIC image data with defective OBIC image data.

According to the configuration of the present invention, a recipe (measurement condition) at a measurement position and an OBIC image of a non-defective sample are prepared in advance, and the OBIC images at the same position as the defective sample are compared with each other. It is possible to reliably evaluate and analyze the actual device.

(2) In this case, the non-defective OBI
In comparing the C image data with the defective OBIC image data, the luminance conversion process is performed by adjusting the minus side luminance threshold value and the plus side luminance threshold value for each image.

According to the configuration of the present invention, when comparing the non-defective OBIC image with the defective OBIC image, the minus side luminance threshold value and the plus side luminance threshold value are adjusted for each image. Can be correctly compared.

(3) When the luminance conversion for each data is completed, the position of the image data is corrected based on the optical image of each data, and the OBIC images are superimposed to extract an abnormal part. Features.

According to the configuration of the present invention, after correcting the position of the image data based on the optical image of each data,
By performing the superposition comparison of the IC images, it is possible to perform the reliable evaluation and analysis of the actual device.

(4) If no abnormal part is extracted by the sequence, the coordinate position is moved according to the recipe and the comparison processing is repeated.

According to the structure of the present invention, according to the recipe,
By performing the comparison processing while sequentially moving the comparison position, it becomes possible to perform evaluation and analysis over the entire surface of the actual device.

(5) Further, in the brightness conversion processing, the minus brightness threshold and the plus brightness threshold are narrowed and adjusted, and the minus brightness threshold and the plus brightness threshold are broadened. The filter is characterized by performing a process of applying a filter to the defective sample side.

According to the configuration of the present invention, as the luminance conversion processing, a method of narrowing and adjusting the minus side luminance threshold value and the plus side luminance threshold value or the minus side luminance threshold value and the plus side luminance threshold are used. An accurate comparison process can be performed by adopting a method of adjusting the value by spreading the value or a method of filtering the defective sample.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to evaluate an actual device using an OBIC apparatus, it is necessary to combine the following four requirements. These requirements can be broadly classified into two categories. The first is the image processing procedure described in the following section, and the second is the measurement condition and method when using the OBIC apparatus in the following sections. Procedure for imaging the observed OBIC image and the OBIC image of the previously acquired non-defective sample Connection method of wiring to the sample Voltage condition applied to the sample (depending on device type and failure mode) Voltage balance with other power supply system in the sample The present invention relates to the image processing procedure described in the item. In order to carry out the present invention, it is necessary to provide a measurement method for assigning an address to the acquired data and recognizing which data in the chip is located.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a system for implementing the present invention. This embodiment shows a system in which an OBIC device is incorporated in a scanning laser microscope (including a resonance type and a non-resonance type). Scanning laser microscope (including resonance type and non-resonance type)
Is a microscope (Microscope) 1, A
/ D converter / D / A converter board (A / D / D / A B
old) 5, MPU6, EWS (Engineering
Workstation) 7, keyboard 8 and mouse 9,
It comprises a color CRT 10.

The OBIC device includes an OBIC amplifier 4 and a power supply (power supply) 3. 2
Is a sample to be irradiated with the microscope 1. The microscope 1 has a light source of 632.8 nmH
An e-Ne laser is mounted, scans horizontally and vertically, and irradiates the sample 2 with a laser. Next, light reflected from the sample 2 is captured by a photodetector (not shown), and the signal is sent to an A / D converter / D / A converter board 5.

The A / D converter / D / A converter board 5 includes:
The signal is converted into digital image data by an A / D converter in synchronization with horizontal and vertical scanning, and the data is transferred as optical image data to a data processing device EWS (engineering work station) 7 via an MPU 6. The MPU 6 is a unit for controlling the microscope 1 (for example, lighting control of a light source, horizontal and vertical scanning control, stage control, automatic focusing, and the like) by a control signal transferred from the EWS 7.

The EWS 7 displays the image data transferred from the MPU 6 on the CRT 10, processes the image data, and judges an input signal operated from the keyboard 8 or the mouse 9.

The OBIC amplifier 4 takes in the carrier induced in the sample 2 by the laser irradiation as a current (hereinafter referred to as OBIC current), performs current / voltage conversion, amplification, etc., and converts the signal into an A / D converter / D / A converter board 5
Send to The A / D converter / D / A converter board 5 converts the signal into digital image data in synchronization with horizontal and vertical scanning. This is an OBIC image of MPU6, EWS7
Is displayed on the CRT 10 via the.

The power supply 3 supplies a voltage to the sample 2.
The sample 2 is a semiconductor device, in which an optical image currently being observed is displayed by light reflected from the sample, and an OBIC image is observed by carriers generated by laser irradiation.
The optical image and the OBIC image are superimposed to specify a defect position in the sample.

FIG. 2 is a flowchart showing the operation of the present invention. In the figure, reference numeral 20 denotes a database for storing recipes (measurement conditions). As the database 20, for example, a hard disk device is used. The following control is performed by the EWS 7.

(Step S1) Measurement of non-defective sample The sample 2 is fixed on a stage, the position of the sample is aligned with an optical image, and a coordinate system for the sample 2 is constructed.
Create a recipe (measurement condition) for the measurement position. in this case,
With only the OBIC image, there is no positional information of the measurement point,
Positioning (reference origin) is performed on the sample to be measured by the optical image.

According to the procedure constructed above, an OBIC image of a non-defective sample serving as a database is taken in under the following conditions. (A) The voltage applied to the sample is set in a plurality of steps according to the sample. The connection condition with the OBIC device is as shown in FIG. A positive voltage is applied from the power supply 3 to the sample 2, one end of the sample is set to the ground potential, and the carrier current flowing out of the sample 2 is received by the OBIC amplifier 4.
However, depending on the failure mode, the measurement is performed by changing the wiring connection method.

At this time, on the OBIC device side, automatic gain adjustment is performed, and the gain is set to such an extent that the OBIC image is not saturated. In addition, the offset adjustment is set to an appropriate value while monitoring the offset monitor output. The above settings are performed, non-defective samples are measured, and the data is stored in the database 20.

(Step S2) Defective Sample Measurement Defective sample is fixed on the stage, and the sample position is aligned according to the coordinate system recipe determined above.

According to the measurement procedure constructed above, OBIC image data of a defective sample serving as a database is taken in under the following conditions. (A) Set the voltage applied to the sample 2 to the value set above.

The wiring connection with the OBIC device is shown in FIG.
Between the voltage and ground. However, depending on the failure mode, the measurement is performed by changing the wiring connection method. At this time, the OBIC device performs automatic gain adjustment,
The gain is set so that the OBIC image is not saturated. In addition, the offset adjustment is set to an appropriate value while monitoring the offset monitor output. The above setting is performed to measure a defective sample, and the data is stored in the database 20.

(Step S3) Image analysis processing The data fetched above and the data fetched above are called from the database 20, and the images are compared according to the measurement position recipe. At this time, if the captured data is not in the same image state, the luminance conversion process is performed by adjusting the minus luminance threshold and the plus luminance threshold for each image. A guide for the adjustment is that the average luminance values within an arbitrary range are the same.

FIG. 4 is an explanatory diagram of the image comparison of the present invention.
(A) is defective product data, and (b) is mass product data. First, a defective sample is divided into blocks of, for example, 512 × 512 pixels, and each block is read. At this time, the resolution of the OBIC image is, for example, 256 gradations in the depth direction. The OBIC image data of the defective product thus read out is represented in a histogram of the number of pixels. The vertical axis represents the number of pixels, and the horizontal axis represents luminance. In this case, the luminance conversion processing is performed by adjusting the plus side luminance threshold value and the minus side luminance threshold value. The characteristic A is the luminance conversion data obtained in this manner.

Similarly, a similar luminance conversion process is performed on the non-defective sample shown in FIG. As a result, as shown in B, luminance conversion data of a good sample is obtained. Then, the obtained luminance conversion data A and B are compared with each other (described later).

According to this embodiment, a recipe (measurement conditions) at a measurement position and an OBIC image of a non-defective sample are prepared in advance, and the OBIC images at the same position as the defective sample are compared. Thus, it is possible to reliably perform evaluation and analysis of the actual device.

Further, when comparing the non-defective OBIC image and the defective OBIC image, adjustment of the minus side luminance threshold value and the plus side luminance threshold value for each image allows comparison of both OBIC images. Can do it correctly.

When the luminance conversion for each data is completed, the position of the image data is corrected based on the optical image of each data, and the points which are not canceled by overlapping each OBIC image are extracted. The points that were not canceled are the defective spots of the defective sample. In this case, the comparison of the data is always made from the non-defective data at the coordinate position (x, y) at the applied voltage of 0.0 V and the defective data at the applied voltage of 0.0 V, and finally the non-defective product at the coordinate position (x, y) at the maximum applied voltage. Image processing is performed in a cycle for comparing data and defective product data.

According to this embodiment, the position of image data is corrected based on the optical image of each data, and then each O is corrected.
By performing the superposition comparison of the BIC images, it is possible to reliably evaluate and analyze the actual device.

By superimposing the OBIC images,
If no defective point is extracted, the coordinate position is moved according to the recipe, and the above processing is performed to extract an abnormal part.

According to this embodiment, by performing the comparison process while sequentially moving the comparison position in accordance with the recipe, it is possible to perform evaluation and analysis over the entire surface of the actual device.

If all the coordinate positions are scanned under the above-described luminance conversion conditions and an abnormal part cannot be extracted, the luminance conversion image processing is performed again on the data of good or defective products, and the above operation is performed. Repeat.

Since the brightness conversion processing differs depending on the failure mode of the sample, (1) the threshold value of the minus side and the threshold value of the plus side which are set above are adjusted by narrowing them.
(2) broadening and adjusting the minus luminance threshold and the plus luminance threshold set above; (3) processing the defective sample by applying various filters such as a median filter. It performs processing.

According to this embodiment, as the brightness conversion processing, a method of narrowing and adjusting the minus side brightness threshold value and the plus side brightness threshold value or a method of adjusting the minus side brightness threshold value and the plus side brightness value is used. How to spread and adjust the threshold,
By employing a method of performing a process of applying a filter to the defective sample side, an accurate comparison process can be performed.

(Step S4) Result Display After the failure location has been extracted as described above, the extracted sample coordinates are displayed on the screen (color CRT 10) or an image is displayed on the screen. In addition, assuming that the extracted information is large, the standard only displays the sample coordinate values on the screen.

(Step S5) Observation of Abnormal Location Image data is called up from the extracted information, and if necessary, the observation magnification is increased with respect to the abnormal location to observe it to confirm that it is a true failure location.

The above operation flow is for a sample whose failure mode is not specified. Therefore, for a sample whose failure mode is known in advance, the above-described OBIC
It is necessary to use the measurement method when using the device. The use of the measurement method simplifies the extraction of a fault location.

In the above steps, when one position is set and one applied voltage condition is set,
The corresponding data may be automatically called out of the good image data, and the image comparison may be performed each time.

[0046]

As described in detail above, according to the present invention, (1) a sample is fixed to a stage, alignment of the sample position is performed by an optical image, a coordinate system for the sample is determined, and a measurement position is determined. A step of preparing OBIC image data of a non-defective sample under the above-mentioned measurement conditions, a step of fixing a defective sample on a stage, and
By including the step of taking in BIC image data and the step of comparing non-defective OBIC image data with defective OBIC image data, a recipe (measurement condition) at a measurement position and an OBIC image of a non-defective sample are prepared in advance. In addition, it is possible to compare the OBIC images at the same position with the defective sample and perform the reliable evaluation and analysis of the actual device.

(2) In this case, the non-defective OBI
When comparing the C image data with the defective OBIC image data, the negative luminance threshold and the positive luminance threshold are adjusted for each image, and the luminance conversion processing is performed. When comparing non-defective OBIC images, the minus side luminance threshold value and the plus side luminance threshold value are adjusted for each image, and both OBIC images can be correctly compared.

(3) When the luminance conversion for each data is completed, the position of the image data is corrected based on the optical image of each data, and each OBIC image is superimposed to extract an abnormal portion. Then, after correcting the position of the image data based on the optical image of each data, the superposition and comparison of each OBIC image are performed, and the reliable evaluation and analysis of the actual device can be performed.

(4) If no abnormal part is extracted by the above sequence, the coordinate position is moved according to the recipe and the comparison process is repeated, so that the comparison position is sequentially moved according to the recipe. By performing the processing, it is possible to perform evaluation and analysis over the entire surface of the actual device.

(5) Further, in the luminance conversion processing, the negative side luminance threshold value and the positive side luminance threshold value are narrowed and adjusted, and the negative side luminance threshold value and the positive side luminance threshold value are widened. By performing a process of applying a filter to the defective sample side, a method of narrowing and adjusting the minus side luminance threshold value and the plus side luminance threshold value as a luminance conversion process, Accurate comparison processing can be performed by adopting a method of spreading and adjusting the side luminance threshold value and the plus side luminance threshold value, or a method of performing a process of filtering a defective sample. .

As described above, according to the present invention, it is possible to provide a method for evaluating an actual device using an OBIC apparatus capable of performing reliable evaluation and analysis of an actual device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a system for implementing the present invention.

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a diagram showing a voltage application state according to the present invention.

FIG. 4 is an explanatory diagram of an image comparison of the present invention.

FIG. 5 is an explanatory diagram of a problem of the conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microscope 2 Sample 3 Power supply 4 OBIC amplifier 5 A / D converter / D / A converter board 6 MPU 7 EWS 8 Keyboard 9 Mouse 10 Color CRT

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G032 AB01 AC01 AE04 AE08 AE09 AL01 2H052 AA07 AC34 AF02 AF13 AF14 AF25 4M106 CB19 DB08 DH12 DH32 DH50 DJ18 DJ24

Claims (5)

[Claims] 1. A step of fixing a sample on a stage, performing alignment of the sample position with an optical image, determining a coordinate system for the sample, and creating a recipe of a measurement position, and OBIC image data of a good sample under the measurement conditions. OBIC apparatus comprising: a step of capturing defective data; a step of fixing a defective sample to a stage; and capturing OBIC image data under the same conditions as the measurement conditions; and a step of comparing non-defective OBIC image data with defective OBIC image data. Evaluation method of real device using. 2. The good OBIC image data and the defective OB.
2. The OBIC device according to claim 1, wherein, when comparing with the IC image data, a luminance conversion process is performed by adjusting a minus luminance threshold value and a plus luminance threshold value for each image. How to evaluate the actual device. 3. When the luminance conversion for each data is completed, the position of the image data is corrected based on the optical image of each data, and each OBIC image is superimposed to extract an abnormal portion. A method for evaluating an actual device using the OBIC apparatus according to claim 2. 4. The realization using an OBIC device according to claim 2, wherein, if no abnormal portion is extracted by the sequence, the coordinate position is moved according to a recipe and the comparison process is repeated. Device evaluation method. 5. The luminance conversion processing includes adjusting the negative luminance threshold and the positive luminance threshold by narrowing the luminance threshold.
5. The OBIC device according to claim 2, wherein a process of applying a filter to a defective sample side is performed to widen and adjust the minus side luminance threshold value and the plus side luminance threshold value. Evaluation method of the actual device used.