JP2002340990A - Semiconductor device evaluation method and apparatus. - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable marking in an apparatus for analyzing a sample by irradiating a laser from the back surface. A laser light source, a laser scanning mechanism, and an objective that generate a laser beam having a wavelength capable of generating an OBIC phenomenon and transmitting through a silicon substrate serving as a base of a semiconductor device sample on a back surface of the sample. A first microscope 21 having a lens and the like is provided.
On the surface side of the sample 10, a marking laser light source 23,
A second microscope including a half mirror 24, a CCD camera 25, an objective lens, and the like for transmitting the laser beam from the first microscope 1 and reflecting the laser beam from the marking laser light source 23 toward the semiconductor device 10. 22 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for evaluating a semiconductor device provided with a laser light source for marking.

[0002]

2. Description of the Related Art Recently, for example, an OBIC method, an EBIC method, or the like has been used to find an abnormal portion such as a defect in a semiconductor device.

[0003] In the OBIC method, for example, a voltage is applied to a sample such as a semiconductor device so that carriers (for example, electrons) flow easily, and a laser beam is irradiated in that state, and different layers in the semiconductor device are separated. (For example, P
A carrier (for example, an electron) between the layer and the N layer),
In this method, the generation of the carrier is detected as an OBIC current, and a defective portion is found in the semiconductor device. Such a phenomenon in which carriers are excited by laser beam irradiation and carriers flow is referred to as an OBIC phenomenon. In each of the different layers forming a semiconductor device, a portion where the OBIC phenomenon is likely to occur, that is, a crystal defect or the like. The OBIC phenomenon appears at the part where the different layers where the abnormal phenomenon occurs
By displaying the image on the display device, it is possible to find a defective portion in the semiconductor device. The EBIC method uses an electron beam instead of the laser beam used in the OBIC method. It should be noted that the laser beam that causes the OBIC phenomenon is not limited to any type of laser beam.
The wavelength in which the BIC phenomenon can occur is approximately 1200 nm
These are:

FIG. 1 schematically shows a semiconductor device evaluation apparatus using the OBIC method, for example, and shows a system in which an OBIC apparatus is incorporated in a scanning laser microscope.

The scanning laser microscope includes a microscope (Microscope) 1, an AD converter / DA converter board (AD / DA Board) 2, an MPU 3, and an E
It comprises a WS (Engineering Workstation) 4, a keyboard 5, a mouse 6, and a color CRT 7. On the other hand, the OBIC device has an OBIC amplifier 8,
It comprises a power supply 9. Reference numeral 10 denotes a semiconductor device sample formed on a substrate such as a silicon wafer, which is supported by a sample holder 11, and the sample holder is mounted on a stage 12. The stage can be moved in a two-dimensional direction or the like by a stage drive mechanism 13 operated by a command from the MPU 3.

The microscope 1 includes a laser light source for generating a laser beam having a wavelength at which the OBIC phenomenon can occur, a two-dimensional laser scanning mechanism including an acousto-optic device, an objective lens, and the like.
The scanning control signal from the scanning controller 14 operated according to the command is sent to the laser scanning mechanism, thereby scanning the sample 10 in the horizontal and vertical directions with the focused laser beam. The light reflected from the sample by the scanning is taken in by a photodetector (not shown) and amplified by an amplifier (not shown), and the reflected light intensity signal at each scanning position is converted into an AD converter / DA converter board Sent to 2.

The AD converter of the AD converter / DA converter board 2 converts the reflected light intensity data sent in synchronization with the horizontal / vertical scanning into digital image data, and passes through the MPU 3 as reflected optical image data. Then, the image data is transferred to the EWS 4. The MPU 3 controls each of the microscopes 1 based on the control signals transferred from the EWS 4 (control of turning on the laser light source, scanning control of the laser scanning mechanism in the horizontal and vertical directions, control of the stage movement, control of the objective lens). Focusing control).

The EWS 4 displays the image data transferred from the MPU 3 on the color CRT 7, performs various types of image processing on the image data, and determines a signal input from the keyboard 5 and the mouse 6.

On the other hand, a voltage is applied to the sample 10 from the power supply 9, and in that state, carriers are generated by laser irradiation based on laser scanning on the sample 10. O
The BIC amplifier 8 captures the carrier as a current, performs current / voltage conversion / amplification, and sends the data to the AD converter / DA converter board 2. This data is OBI
The C image data is transferred to the EWS 4 via the MPU 3 and the OBIC image can be displayed on the color CRT 7 in the same manner as the reflected light image.

Therefore, the reflected light image and the OBIC image can be superimposed and displayed on the color CRT 7, and as a result,
It is possible to know where in the semiconductor device sample there is a defect. That is, the defect can be identified.

[0011] Recently, since the structure of a semiconductor device has been multi-layered and ultra-fine, the resolution required for determining a defect location has become about 0.1 μm. Decisions are often difficult.
Therefore, in place of observation from the surface, the semiconductor device is placed on the stage of the focused ion beam processing apparatus, and both sides sandwiching the defect part of the semiconductor device are scraped off by the focused ion beam, and then placed on the sample stage of the transmission electron microscope, A method has been considered in which an electron beam is irradiated to a defective portion from the cut side, and a defect factor is estimated and determined based on electrons transmitted through the defective portion.

The above-mentioned OBIC method is a method capable of identifying a defective portion with a position resolution of about 0.1 μm. However, even if such an OBIC method is used to identify a defective portion with a high resolution of about 0.1 μm, Defect factors could not be accurately grasped.

The reason is that in order to transmit electrons as described above with a transmission electron microscope, it is necessary to process at least a portion including a defect portion to a thickness of about 0.2 μm. This is because such processing was extremely difficult because the stage movement accuracy was about 0.5 μm.

Therefore, as shown in FIG. 1, a reflecting mirror 15 capable of switching the optical path is arranged between the microscope 1 and the semiconductor device sample 10, and a marking laser light source 16 is arranged right beside the reflecting mirror. By removing the mirror from the optical path of the laser beam from the laser light source for identification provided in the microscope 1 as shown in A,
By irradiating the identification laser beam to the semiconductor device sample 10 to identify a defect portion as described above, and crossing the reflecting mirror to the optical path of the laser beam from the identification laser light source as shown in B. The laser beam from the marking laser light source 16 is applied to the vicinity of the identified defect portion so as to make a mark by cutting off the irradiation of the semiconductor laser device 10 with the laser beam for identification. Then, the semiconductor device sample is placed on the stage of the focused ion beam processing apparatus, a mark is detected by scanning with the ion beam, and both side portions (for example, having a thickness of about 0.2 μm) sandwiching the defect with reference to the detected mark position ) Is scraped off (Japanese Patent Application Hei 5-
No. 164086).

[0015]

Recently, three-dimensional and high-density semiconductor devices have been increasingly used, and, for example, other wiring has been arranged on an element or the like directly provided on a silicon wafer. . In such a device, when observing an OBIC image of an element or the like directly provided on a silicon wafer, the laser beam cannot be applied to a portion to be observed because another wiring is disposed on the upper side. Therefore, a laser beam having a long wavelength of about 900 μm or more that transmits silicon is used, and this laser beam is irradiated from the back surface of the device, and transmitted through the silicon substrate to irradiate a target element portion or the like.

Now, attempts have been made to identify a defective portion of an element based on an OBIC image obtained by irradiating a laser beam from the back surface of a semiconductor device sample, and then to perform a laser beam marking near the identified defective portion. Not done.

As shown in FIG. 1, a reflecting mirror capable of switching the optical path is placed between the identification laser light source and the semiconductor device sample, and a marking laser light source is arranged right beside the reflecting mirror. When the laser beam from the light source is applied to the vicinity of the identified defective portion to form a mark, the following problem occurs.

Generally, a silicon substrate is significantly thicker than a layer of an element or the like formed thereon. Therefore, it is difficult to make a mark on a predetermined portion of the element layer through such a thick silicon substrate. If a laser light source with extremely high power is used, it is difficult to narrow the laser beam to a diameter suitable for marking, and a thick powerful beam will be irradiated, so a groove is formed in the laser irradiation part of the silicon substrate, Further, there is a possibility that a predetermined portion of the element layer may be destroyed, so that the marking itself is difficult.

The present invention has been made to solve such a problem, and has as its object to provide a novel semiconductor device evaluation method and apparatus.

[0020]

Means for Solving the Problems A semiconductor device evaluation method according to the present invention scans a semiconductor device sample from a back surface with a radiation beam, and scans a sample image based on a radiation beam obtained from the semiconductor device sample by the scanning. At the same time, an electric signal image is obtained based on an electric signal from a defective portion generated in the sample by the scanning, and a defective portion generated in the semiconductor device sample is obtained from the sample image and the electric signal image. After the identification, the laser beam is applied from the surface of the sample to the vicinity of the identified defect on the semiconductor device sample to perform marking.
A semiconductor device evaluation apparatus according to the present invention includes a scanning radiation beam generator for generating a radiation beam for scanning on the back surface of a semiconductor device sample, and a sample based on a radiation beam obtained from the semiconductor device sample by the scanning. A display device for displaying an image and an electric signal image based on an electric signal from a defective portion generated in the sample by the scanning, and irradiating from the surface of the semiconductor device sample to mark the vicinity of the defective portion And a marking laser light source for generating a laser beam.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a schematic example of a semiconductor device evaluation apparatus according to the present invention. In the figure, the same symbols as those used in FIG. 1 indicate the same components.

In the figure, reference numeral 21 denotes a first microscope, which is an OB.
A laser light source that generates a laser beam having a wavelength (a wavelength of approximately 1200 μm or less) at which an IC phenomenon can occur and a wavelength (a wavelength of approximately 900 μm or more) capable of transmitting through a silicon substrate serving as a base of the semiconductor device sample 10; A two-dimensional laser scanning mechanism including an acousto-optic element and the like, an objective lens, and the like are provided.

The laser scanning mechanism of the first microscope is controlled by a scanning control signal from a scanning controller 14 operated by a command from the MPU 3, and the light reflected from the sample by scanning the sample with the laser beam is a photodetector (not shown). After being captured by the amplifier and amplified by an amplifier (not shown), the reflected light intensity signal at each scanning position is sent to the AD converter / DA converter board 2.

Reference numeral 22 denotes a second microscope. A marking laser light source 23 is mounted on a side of the second microscope. Inside the laser microscope, a laser beam from the first microscope 1 is transmitted. A half mirror 24, a CCD camera 25, an objective lens, and the like for reflecting a laser beam from the semiconductor device 10 toward the semiconductor device 10 are provided. The marking laser light source 23 is turned on and off by a command from the MPU 3.
It is made to turn off.

Reference numeral 26 denotes a stage for moving the entire second microscope 22 in a two-dimensional direction, which can be moved by a stage drive mechanism 27 which is operated by a command from the MPU 3. Reference numeral 28 denotes a monitor cathode ray tube connected to the CCD camera 25.

The marking in the semiconductor device evaluation apparatus having such a configuration is performed as follows.

The optical axis of the laser beam from the laser light source of the first microscope 21 at the time of no deflection is made to coincide with the optical axis of the laser beam from the laser light source 23 for marking of the second microscope 22 in advance.

First, the back surface of the semiconductor device sample 10 is two-dimensionally scanned by a laser beam from the laser light source of the first microscope 21.

The light reflected from the sample 10 by the scanning is taken in by a photodetector (not shown) and is amplified by an amplifier (not shown).
After the amplification by the above, the reflected light intensity signal at each scanning position is A
The data is sent to the D / DA converter board 2.

The AD converter of the AD converter / DA converter board 2 converts the reflected light intensity data transmitted in synchronization with the horizontal / vertical scanning into digital image data, and passes through the MPU 3 as reflected optical image data. Then, the image data is transferred to the EWS 4.

The EWS 4 displays a reflected light image of the sample on the color CRT 7 based on the image data transferred from the MPU 3.

On the other hand, a voltage is applied to the sample 10 from the power supply 9, and in that state, carriers are generated by laser irradiation based on laser scanning on the sample 10. O
The BIC amplifier 8 captures the carrier as a current (OBIC current), performs current-voltage conversion / amplification, etc., and converts the data into the AD converter / DA converter board 2 and the MPU.
3 is transferred to the EWS 4 via the color CRT
An OBIC image is displayed on 7 in the same manner as in the case of the reflected light image. Therefore, the reflected light image and the OBIC image are displayed on the color CRT 7 in a superimposed manner, so that it is possible to know where the semiconductor device sample 10 has a defect.

The OBIC image data is stored in the MPU.
3 (for example, a frame memory). At this time, since the scan control signal from the scan controller 14 is sent to the AD converter / DA converter board 2 in synchronization with the supply to the laser scanning mechanism of the first microscope 21, it is stored in the memory of the MPU 3. The stored OBIC image data includes the position and OBIC
The current value corresponds to the digitized and stored value.

Next, the laser beam from the laser light source of the first microscope 21 is set in an undeflected state.

In this state, the MPU 3 sends a drive signal corresponding to the position coordinates of the defect K1 measured in the previous step to the stage drive mechanism 13. Then, the stage 12 is moved two-dimensionally by the stage driving mechanism 13, and a defect K 1 comes on the optical axis of the laser beam from the laser light source of the first microscope 21.

At this time, the laser beam from the laser light source of the first microscope 21 passes through the defect K 1, passes through the half mirror 24 of the second microscope 22, is photographed by the CCD camera 25, and is monitored by the monitor cathode ray tube 28.
(Fig. 3).

In this state, the optical axis of the laser beam from the laser light source of the first microscope 21 and the optical axis of the marking laser light source 23 match. That is, there is a defect K1 on the optical axis of the marking laser light source 23.

In the case where marks for a defect are formed at, for example, four positions symmetrical to the left, right, up and down with respect to the defect, the X direction (right direction) and the -X direction (left direction) with respect to the defect position. The laser beam from the marking laser light source 23 is irradiated to each of the designated positions by designating four positions at a distance of Ya in the Xa and Y directions (upward) and in the -Y direction (downward), respectively. I do.

Therefore, the MPU 3 first sends an X-direction movement signal corresponding to Xa to the stage drive mechanism 27. Then, the stage 26 moves so that the optical axis of the laser beam from the marking laser light source 23 is located at a position Xa away from the defect K1 in the X direction. At this time, the MPU 3 sends a lighting command to the marking laser light source 23 to turn on the marking laser light source 23. As a result, a mark M1 is formed (FIG. 3). When the formation of M1 is completed, the marking laser light source 23 is turned off according to a command from the MPU3.

Next, the MPU 3 sets the X corresponding to -2Xa.
A direction movement signal is sent to the stage drive mechanism 27. Then
The stage 26 moves so that the optical axis of the laser beam from the marking laser light source 23 is located Xa away from the defect K1 in the -X direction. At this time, the MPU 3 sends a lighting command to the marking laser light source 23 to turn on the marking laser light source 23. as a result,
A mark M2 is formed (FIG. 3). When the formation of M2 is completed, the laser light source 2 for marking is instructed by MPU3.
3 is turned off.

Next, the MPU 3 sends an X, Y direction movement signal corresponding to (Xa, Ya) to the stage drive mechanism 27. Then, the stage 26 is moved such that the optical axis of the laser beam from the marking laser light source 23 is located at a position separated from the defect K1 by Ya in the Y direction. At this time, MP
U3 sends a lighting command to the marking laser light source 23 to turn the marking laser light source 23 on. As a result, a mark M3 is formed (FIG. 3). The M3
Is completed, the marking laser light source 23 is turned off in accordance with a command from the MPU 3.
Sends a Y-direction movement signal corresponding to -2Ya to the stage drive mechanism 27. Then, the marking laser light source 2
The stage 26 is moved so that the optical axis of the laser beam from No. 3 is located at a position away from the defect K1 by Ya in the -Y direction.
At this time, the MPU 3 sends a lighting command to the marking laser light source 23 to turn on the marking laser light source 23. As a result, a mark M4 is formed (FIG. 3). When the formation of M4 is completed, the marking laser light source 23 is turned off according to a command from the MPU3.

In this manner, marks M1, M2, M3, and M4 are formed at positions symmetrical to the left, right, up, and down of the defect K1. It should be noted that marking is performed similarly for other defects.

When a mark cannot be formed in the vicinity of a defect due to a semiconductor device sample, a process of shaving the periphery of the defect with a focused ion beam can be performed without forming a mark in the vicinity of the defect. That is, before the defect measurement based on the OBIC image detection, marking is performed on the sample at a place where marking is possible with a laser beam from a marking laser light source, and the marking position is set as a reference point. And
A defect in the sample is identified by irradiating a laser beam from a laser light source of the first microscope, and coordinates of the defect from the reference point are obtained. Next, the sample is placed on the stage of the focused ion beam processing apparatus, and the marked reference point is detected by scanning the sample with the focused ion beam. At this time, since it is known where the defect is located with respect to the reference point, the periphery of the defect can be machined based on the detected reference point.

In the above example, the marks are formed at positions (four places) symmetrical to the left, right, up and down of the defect. However, the present invention is not limited to this example. For example, they may be formed at positions (four places) symmetrical in the left and right directions with respect to the defect, or may be formed at positions (two places) symmetrical in one diagonal direction.

In the above example, after the defect point and the optical axis of the marking laser are matched, the stage is moved to move the optical axis of the marking laser to the marking position. First,
A laser beam deflecting mechanism may be attached to the microscope 22 and the scanning mechanism may deflect and move the irradiation position of the marking laser beam to the marking position.

In the above example, after the defect is identified, the stage 12 is once moved so that the defect position is located on the optical axis of the laser light source, but the identified defect is not moved without moving the stage. The laser beam optical axis of the marking laser light source 23 may be moved according to the position of the marking laser light source, or the marking laser beam may be deflected and moved by a separately provided deflection mechanism for marking.

In the above example, the defect of the semiconductor device sample is measured based on the OBIC phenomenon. However, the defect may be measured based on other phenomena such as an internal photoelectron effect.

In the above example, a laser beam is used as a beam for measuring defects, but an electron beam may be used instead of the laser beam.

[Brief description of the drawings]

FIG. 1 shows an example of a conventional semiconductor device evaluation apparatus.

FIG. 2 shows an example of a semiconductor device evaluation apparatus according to the present invention.

FIG. 3 shows an example of a marking.

[Description of Signs] 1 ... Microscope 2 ... AD converter / DA converter board 3 ... MPU 4 ... EWS 5 ... Keyboard 6 ... Mouse 7 ... Color CRT 8 ... OBIC amplifier 9 ... Power supply 10 ... Semiconductor device sample 11 ... Sample Holder 12 Stage 13 Stage drive mechanism 14 Scan controller 15 Reflector mirror 16 Laser light source for marking 21 First microscope 22 Second microscope 23 Laser light source for marking 24 Half mirror 25 CCD camera 26 ... Stage 27 ... Stage drive mechanism 28 ... Cathode tube for monitor K1 ... Defect M1, M2, M3, M4 ... Mark

Claims (14)

[Claims] 1. A semiconductor device sample is scanned from the back side with a radiation beam, and a sample image is obtained based on the radiation beam obtained from the semiconductor device sample by the scanning.
An electrical signal image is obtained based on an electrical signal from a defect location occurring in the sample by the scanning, and a defect location occurring in the semiconductor device sample is identified from the sample image and the electrical signal image. And a method for evaluating a semiconductor device in which a laser beam is irradiated from the surface of the sample to the vicinity of the identified defective portion on the semiconductor device sample to perform marking. 2. The method according to claim 1, wherein the radiation beam is a laser beam. 3. The method according to claim 1, wherein the radiation beam is an electron beam. 4. An electric signal from the defective portion is an OBIC
The method for evaluating a semiconductor device according to claim 1, wherein the electrical signal is an electrical signal based on: 5. The semiconductor according to claim 1, wherein the radiation beam is a laser beam having a wavelength which transmits through a substrate of a semiconductor device sample and has a wavelength capable of generating an electric signal from a defective portion generated in the sample. Device evaluation method. 6. The laser beam is approximately 900 μm.
6. The semiconductor device evaluation method according to claim 5, having a wavelength of from about 1200 [mu] m. 7. A scanning radiation beam generator for generating a radiation beam for scanning a back surface of a semiconductor device sample, a sample image based on a radiation beam obtained from the semiconductor device sample by the scanning, and the scanning A display device for displaying an electric signal image based on an electric signal from a defect portion generated in the sample, a laser beam for irradiating from the surface of the semiconductor device sample and marking the vicinity of the defect portion with a laser beam A semiconductor device evaluation device equipped with a laser light source for marking that is generated. 8. The semiconductor device evaluation apparatus according to claim 7, wherein said radiation beam is a laser beam. 9. The semiconductor device evaluation apparatus according to claim 7, wherein said radiation beam is an electron beam. 10. An electric signal from the defective portion is an OBI signal.
8. The semiconductor device evaluation device according to claim 7, wherein the semiconductor device evaluation device is an electric signal based on C. 11. The semiconductor according to claim 7, wherein the radiation beam is a laser beam having a wavelength that transmits through a substrate of a semiconductor device sample and has a wavelength capable of generating an electric signal from a defect generated in the sample. Device evaluation equipment. 12. The laser beam is approximately 900 μm.
The semiconductor device evaluation apparatus according to claim 11, having a wavelength of m to 1200 m. 13. The semiconductor device evaluation apparatus according to claim 1, further comprising means for monitoring an irradiation point of the radiation beam on the sample. 14. The semiconductor device evaluation apparatus according to claim 1, further comprising means for two-dimensionally moving the laser light source for marking on a plane perpendicular to the optical axis.