JP2012042431A - Laminated wafer inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated wafer inspection method which is capable of detecting a poorly laminated portion with sufficiently high accuracy.SOLUTION: The laminated wafer inspection method for checking whether a laminated wafer has a poorly laminated portion or not includes: an ultrasonic inspection step of detecting a poorly laminated portion by using a reflected wave from the inside of the laminated wafer due to irradiation of an ultrasonic wave to the laminated wafer; and a peeling inspection step of pasting an adhesive tape to the laminated wafer after the execution of the ultrasonic inspection step and then peeling the adhesive tape to detect a poorly laminated portion.

Description

  The present invention relates to a method for inspecting a bonded wafer, and more particularly, to a method for inspecting the presence or absence of a defective bonding portion of a bonded wafer.

  Conventionally, in a bonded wafer, when a non-bonded portion such as a void (hereinafter referred to as “void defect”) exists at the bonding interface, the active layer is peeled and dropped during the device manufacturing process at the portion where the void defect exists. It is known that void defects cause device defects and dust generation.

  For this reason, various methods for inspecting the bonded wafer for the presence of void defects have been proposed for the purpose of improving the yield in the device manufacturing process.

  For example, infrared (IR) inspection, ultrasonic inspection, and peeling inspection have been proposed as methods for inspecting the bonded wafer for the presence of void defects (see, for example, Patent Document 1). In addition, as an inspection method combining infrared inspection and ultrasonic inspection, first, when bonding two wafers, the state of the bonding surface was inspected by infrared, and then no void defect was detected by infrared inspection. After heat-treating only the bonded wafer and strengthening the bonding of the bonded surface, the bonded surface with the bond strengthened is ultrasonically inspected to detect in advance the bonded wafer having void defects by infrared inspection before heat treatment Thus, a method has been proposed in which void defects are more reliably detected by ultrasonic inspection after heat treatment while the wafer is reused (see, for example, Patent Document 2).

  Here, in recent years, it has been required to detect void defects with higher accuracy from the viewpoint of further improving the yield of the semiconductor device manufacturing process.

JP 2010-21408 A JP-A-7-161596

  However, in the infrared inspection, a large void defect having a diameter of about 300 to 500 μm can be detected normally, but a minute void defect having a diameter of 100 μm or less cannot be detected. Similarly, in the peeling inspection, a minute void defect having a diameter of 100 μm or less could not be detected.

  On the other hand, although ultrasonic inspection takes time for inspection, minute void defects of about several tens to 100 μm can be detected. Therefore, if ultrasonic inspection is used, void defects can be detected with higher accuracy than infrared inspection and peeling inspection.

  However, according to the study by the present inventors, conventional inspection (only ultrasonic inspection or a combination of infrared inspection and ultrasonic inspection combined with ultrasonic inspection capable of detecting minute void defects) Even in the case of a bonded wafer in which no void defect was detected in (inspection), it was revealed that the active layer may be peeled off or dropped off in the device manufacturing process, resulting in a decrease in yield.

  Therefore, the present inventors have intensively investigated the cause of the active layer peeling / dropping in the device manufacturing process even in the bonded wafer in which no void defect was detected in the ultrasonic inspection. There are cases where there is a portion where the bonding strength of the bonding is weak, which is different from the void (void defect) that can be detected by ultrasonic inspection, and even in the portion where the bonding strength is weak in the device manufacturing process It has been found that the active layer is peeled off and dropped off (hereinafter, “void defect” and “part with weak bonding strength” are collectively referred to as “bonding defective part”). The present inventors have also found that a portion having a low bonding strength cannot be detected by ultrasonic inspection, but can be detected by using a peeling inspection.

  It should be noted that the ultrasonic inspection cannot detect the part where the bonding strength of the bonding is weak. The ultrasonic inspection transmits ultrasonic waves to the bonded wafer surface after bonding strengthening heat treatment and before thinning, using pure water as a medium. It is a technique to detect void defects by picking up reflection peaks at voids (void defects) that appear at the bonding interface that appear between reflection peaks on the front and back surfaces of the wafer. This is presumably because voids with a thickness cannot be recognized as void defects. On the other hand, the part where the bonding strength of the bonding is weak can be detected by the peeling inspection is an inspection performed after the active layer is thinned, and the active layer at the part where the bonding strength is low is forcibly peeled off. It is presumed that this is a technique that can be inspected.

  And based on the above-mentioned new knowledge, the present inventors can compensate for the drawbacks of each other's inspection method by combining ultrasonic inspection and peeling inspection, and can detect defective bonding portions with sufficiently high accuracy. The headline and the present invention were completed.

  That is, the present invention aims to advantageously solve the above problems, and the bonded wafer inspection method of the present invention is a method for inspecting the presence or absence of a bonding failure portion of the bonded wafer. , An ultrasonic inspection step for detecting a defective bonding portion using a reflected wave from the inside of the bonded wafer when the bonded wafer is irradiated with ultrasonic waves, and a bonding after the ultrasonic inspection step is performed. And a peeling inspection step of peeling the pressure-sensitive adhesive tape and detecting a bonding failure portion after the pressure-sensitive adhesive tape is attached to the bonded wafer. As described above, if both the ultrasonic inspection and the peeling inspection are performed on the bonded wafer to detect the defective bonding portion, the presence or absence of the defective bonding portion can be inspected with sufficiently high accuracy.

  Here, in the bonded wafer inspection method of the present invention, in the ultrasonic inspection step, a defective bonding portion is detected in the outer peripheral portion of the bonded wafer, and in the peeling inspection step, the entire surface of the bonded wafer is detected. It is preferable to detect a defective bonding portion. In general, defective bonding portions such as void defects are likely to occur on the outer peripheral portion of the bonded wafer, particularly on the bonding end position side. Therefore, it is necessary to scan the ultrasonic irradiation position within the inspection target range, and the inspection takes time. In this ultrasonic inspection process, only the outer periphery of the bonded wafer, where bonding defects are likely to occur, is inspected, and the entire surface of the bonded wafer is inspected in a peeling inspection process that can inspect the entire bonded wafer in a short time. This is because the inspection can be performed in a short time while detecting a defective bonding portion with sufficiently high accuracy. In the present invention, the “outer peripheral portion” refers to a portion from the outermost periphery of the wafer to 5 mm toward the wafer center.

  In the bonded wafer inspection method of the present invention, the bonded wafer is obtained by bonding two wafers from the bonding start end position to the bonding end position, and in the ultrasonic inspection step, It is preferable that a bonding failure portion is detected on the bonding end position side of the bonded wafer, and the bonding failure portion is detected on the entire surface of the bonding wafer in the peeling inspection step. The bonding failure part is particularly likely to occur on the bonding end position side of the bonded wafer, so in the ultrasonic inspection process that takes a long time to inspect, only the bonding end position side where bonding defects are likely to occur is inspected for a short time. If the entire surface of the bonded wafer is inspected in a peeling inspection process that can inspect the entire surface of the bonded wafer, the inspection can be performed in a short time while detecting a defective bonding portion with sufficiently high accuracy. Because.

  In the bonded wafer inspection method of the present invention, before the ultrasonic inspection process and the peeling inspection process, and before the bonded wafer is heat-treated and strengthened, the bonded wafer is bonded to the bonded wafer. It is preferable that the method further includes an infrared inspection step of detecting a bonding failure portion using infrared rays that are irradiated with infrared rays and transmitted through the bonded wafer or reflected by the bonded wafer. This is because if the infrared inspection is performed before the bonded wafer is heat treated to strengthen the bonding, the bonded wafer having a defective bonding portion can be detected in advance and the wafer can be reused. In addition, if ultrasonic inspection and peeling inspection are performed after strengthening the bonding, poorly bonded portions such as minute void defects that could not be detected by infrared inspection can be detected with sufficiently high accuracy.

  According to the present invention, it is possible to provide a bonded wafer inspection method capable of detecting a defective bonding portion with sufficiently high accuracy.

It is explanatory drawing which shows the process of manufacturing a bonded wafer by applying the inspection method of the typical bonded wafer according to this invention. It is explanatory drawing which shows a mode that an adhesive tape is affixed to the terrace part of a bonded wafer in the peeling test process which comprises the inspection method of the bonded wafer of this invention. It is explanatory drawing which shows the process of manufacturing a bonded wafer by applying the inspection method of another bonded wafer according to this invention. It is a figure which shows the bonding start end position and bonding end position of a bonding wafer, and (a) is a bonding starting end position and bonding when two wafers are bonded in one direction from one point near the outer periphery. (B) shows the bonding start end position and the bonding end position when two wafers are bonded from the wafer center toward the outer peripheral edge.

  Embodiments of the present invention will be described below with reference to the drawings. The method for inspecting a bonded wafer according to the present invention is used for inspecting the presence or absence of a bonding failure portion of a bonded wafer. The bonded wafer inspection method of the present invention is characterized by inspecting the presence or absence of a bonding defect portion by combining at least an ultrasonic inspection and a peeling inspection.

  Here, the process of manufacturing a bonded wafer by applying the first embodiment of the bonded wafer inspection method of the present invention is shown in FIG. In this bonded wafer manufacturing process, first, an active layer wafer 10 made of a silicon wafer having a silicon oxide film 10A on its surface and a support substrate wafer 20 made of a silicon wafer are bonded together to form a bonded wafer 30. (See FIGS. 1A and 1B). Next, before the bonded wafer 30 is heat treated to strengthen bonding at the bonded interface, an infrared inspection is performed to inspect the bonded wafer 30 for bonding defects (void defects) before the heat treatment (infrared rays). Inspection process). Then, the bonded wafer 30 in which the defective bonding portion is detected by the infrared inspection is reused without heat treatment. On the other hand, with respect to the bonded wafer 30 in which the defective bonding portion is not detected by the infrared inspection, the bonding at the bonding interface is strengthened by performing a heat treatment (see FIG. 1C), and the ultrasonic inspection is performed for the bonding. Inspect for defective parts (ultrasonic inspection process). Subsequently, after forming the terrace portion 30A by chamfering and etching the outer periphery of the active layer wafer 10 (see FIG. 1D), the surface of the active layer wafer 10 is ground to make the active layer wafer 10 thin. (See FIG. 1E). Finally, after performing a peeling inspection (peeling inspection step), the surface of the active layer wafer 10 is polished (see FIG. 1F). In the bonded wafer manufacturing process to which the bonded wafer inspection method of the present invention is applied, the active layer wafer and the support substrate wafer are not limited to the above-described wafers.

  In this example of the bonded wafer manufacturing process, only the wafers in which the bonding failure portion is not detected in the ultrasonic inspection are subjected to the peeling inspection, and only the wafer in which the bonding failure portion is not detected in the peeling inspection. It is sent to the subsequent device manufacturing process. Then, the wafer in which the bonding failure portion is detected in the ultrasonic inspection or the peeling inspection is excluded from the shipping line to the device manufacturing process and discarded or reused as Si resources.

  Here, the wafer 10 for active layer which has the silicon oxide film 10A on the surface, and the wafer 20 for support substrates can use what was manufactured by the known method. Further, the bonding of the active layer wafer 10 and the support substrate wafer 20 can be performed using a known technique. For example, as shown in FIG. 4A, the active layer wafer 10 and the support substrate From the state in which the wafer 20 is brought into contact with one point in the vicinity of the outer periphery (bonding start position S) toward the bonding end position F (position indicated by a thick line in FIG. 4A) (see FIG. In FIG. 4B, the active layer wafer 10 and the support substrate wafer 20 are brought into contact with each other at the center position (bonding start position S). The bonded state may be bonded toward the outer peripheral edge (bonding end position F).

  The infrared inspection is an inspection in which a void defect as a defective bonding portion is detected by irradiating the bonded wafer 30 with infrared light and using the infrared light transmitted through the bonded wafer 30 or the infrared light reflected by the bonded wafer 30. . In the infrared inspection, the void defect can be displayed as an image by photographing and detecting the transmitted or reflected infrared light with, for example, an infrared camera.

  The infrared inspection may be performed after the bonded wafer 30 is subjected to heat treatment to strengthen the bonding at the bonding interface. However, if the bonding inspection is performed before the bonding interface is strengthened, a defective bonding portion is detected. In addition, only the vicinity of the part where the bonding failure is detected is partially peeled and bonded again, or the two bonded wafers are completely peeled, and then polished, washed and reused. Can do. Therefore, in the bonded wafer inspection method of the present invention, it is preferable to perform infrared inspection before strengthening the bonding at the bonding interface.

  Bonding interface bonding strengthening using heat treatment can be performed by a known method. For example, bonding wafer 30 is heat-treated at a temperature of 800 ° C. or higher in an oxygen atmosphere to strengthen bonding interface bonding. can do. When heat treatment is performed in an oxygen atmosphere, a silicon oxide film 20A is also formed on the surface of the support substrate wafer 20 as shown in FIG.

  The ultrasonic inspection is an inspection for detecting a void defect as a defective bonding portion using a reflected wave from the inside of the bonded wafer 30 when the bonded wafer 30 is irradiated with ultrasonic waves. It is carried out in a state where the bonded wafer is immersed in a liquid such as. Therefore, from the viewpoint of preventing liquid from entering the bonding interface, it is necessary to perform the ultrasonic inspection after bonding strengthening (after heat treatment) at the bonding interface of the bonded wafer. From the viewpoint of securing the gate width required for ultrasonic inspection, the thickness of the active layer wafer of the bonded wafer is preferably 50 μm or more.

  Here, when the entire surface of the bonded wafer 30 is subjected to ultrasonic inspection, the ultrasonic irradiation position must be scanned so that the entire surface of the bonded wafer 30 is irradiated with ultrasonic waves. It takes. Therefore, in the bonded wafer inspection method of the present invention, it is preferable to ultrasonically inspect only a part of the bonded wafer, particularly a portion where a void defect that is a defective bonding portion detectable by ultrasonic inspection is likely to occur. In the bonded wafer inspection method of the present invention, a defective bonding portion is detected by using a peeling inspection in addition to an ultrasonic inspection. In the peeling inspection, a portion having a weak bonding strength and a void of a certain size or more are used. Since both the defect and the defect can be detected, only the peeling inspection is performed on the portion where the poor bonding portion is difficult to occur, and both the ultrasonic inspection and the peeling inspection are performed on the portion where the defective bonding portion is likely to occur. This is because a bonding failure portion can be detected with sufficiently high accuracy while reducing the inspection time by reducing the area for ultrasonic inspection.

  According to the studies by the present inventors, the portion where void defects are likely to occur is the outer peripheral portion of the bonded wafer 30, for example, the portion from the outermost periphery of the wafer to 5 mm toward the wafer center, or the bonded wafer 30. The bonding end position side of is mentioned.

  The chamfering of the outer periphery of the active layer wafer 10 is intended to remove a bonding failure region caused by the outer peripheral shape of the active layer wafer 10 and the support substrate wafer 20. The outer periphery of the active layer wafer 10 is chamfered to a depth that does not reach the bonding interface.

  The purpose of the alkali etching is to remove a portion left uncut during the chamfering process of the outer periphery of the active layer wafer 10 using an alkali etching solution such as KOH.

  Here, a terrace portion 30A is formed in the outer peripheral region of the supporting substrate wafer 20 of the bonded wafer 30 by chamfering and alkali etching of the outer periphery of the active layer wafer 10, and the terrace portion 30A has a chamfered portion. A silicon oxide film residue 10B that cannot be removed by processing and alkali etching remains. However, as will be described in detail later, the silicon oxide film residue 10B can be removed at the time of the peeling inspection by attaching the adhesive tape to the terrace portion 30A and performing the peeling inspection.

  The thinning of the active layer wafer 10 is achieved by grinding the surface of the active layer wafer 10 by a known method so that the thickness of the active layer wafer 10 is, for example, about 50 μm or less.

  The peeling inspection is an inspection in which after the adhesive tape is applied to the bonded wafer 30, the adhesive tape is peeled off to detect a portion having a low bonding strength as a defective bonding portion. For example, when there is a poorly bonded portion at the bonding interface, the wafer for active layer positioned above the poorly bonded portion adheres to the adhesive tape and is peeled off, so that the bonded wafer 30 after peeling the adhesive tape is removed. By observing the surface of the film or the peeled adhesive tape, it is possible to inspect the presence or absence of a bonding failure portion. In the peeling inspection, as described above, a void defect having a size of a certain size or more can be detected in addition to the portion having a low bonding strength. However, the ultrasonic inspection has a higher accuracy of detecting the void defect. Therefore, when the entire surface of the bonded wafer is inspected in the ultrasonic inspection process, all the bonded wafers having void defects are detected in the ultrasonic inspection process, excluded from the shipping line, and not subjected to the peeling inspection. In the peeling inspection, no void defect is detected (in the peeling inspection, only a portion having a low bonding strength is detected). On the other hand, when only a part of the bonded wafer is inspected in the ultrasonic inspection process, a void defect may be detected in a part where the ultrasonic inspection is not performed in the peeling inspection.

  Here, normally, in the peeling inspection, the adhesive tape may be attached to and peeled from the surface of the thinned active layer wafer. In this example of the bonded wafer manufacturing process, the terrace portion 30A In order to remove the remaining silicon oxide film residue 10B, the adhesive tape 40 is peeled off after the adhesive tape 40 is applied not only to the surface of the active layer wafer 10 but also to the terrace portion 30A.

  Specifically, as shown in FIG. 2, after the adhesive tape 40 is attached to the surface of the active layer wafer 10 constituting the bonded wafer 30, for example, the cross section is rotated 90 ° clockwise. By pressing the crank-shaped pressing member 41 provided with the pressing portion 41 </ b> A at the tip thereof near the outer peripheral edge of the active layer wafer 10 and the outer peripheral edge of the support substrate wafer 20 through the adhesive tape 40, Adhesive tape 40 is affixed not only to the surface of wafer 10 but also to terrace 30A. Then, by removing the adhesive tape 40 from the state where the adhesive tape 40 is also attached to the terrace portion 30A, the presence of a defective bonding portion is inspected, and the residue of the silicon oxide film remaining on the terrace portion 30A 10B is attached to the adhesive tape 40 and peeled off. In addition, when dust etc. have adhered to the terrace part 30A, the dust is also removed together with the residue 10B.

  As the adhesive tape 40, for example, an adhesive tape having an adhesive strength of 2 to 14 N / mm in which the tape substrate is a polyethylene substrate and the adhesive is an acrylic adhesive can be used.

  Note that, from the viewpoint of further improving the accuracy of detection of defective bonding in the peeling inspection, in the bonded wafer inspection method of the present invention, the adhesive tape bonding direction and the peeling direction are made different for the same bonded wafer. It is preferable to perform the peeling inspection a plurality of times.

  Polishing of the surface of the active layer wafer 10 after the peeling inspection can be performed using a known method.

  In the bonded wafer manufacturing process of this example, the first embodiment of the bonded wafer inspection method of the present invention is applied, and an infrared inspection is performed before the heat treatment of the bonded wafer 30, and a relatively large bonded wafer is obtained. Since a bonded wafer having a poorly aligned portion (void defect) can be detected and reused before heat treatment, the number of bonded wafers to be discarded can be reduced and the manufacturing cost can be reduced. In addition, since both ultrasonic inspection and peeling inspection are performed on the bonded wafer after heat treatment, it is possible to detect small void defects that are difficult to detect by infrared inspection, and the bonding strength is weak. Disadvantages of peeling inspection that cannot detect void defects as small as ultrasonic inspection while compensating for defects of ultrasonic inspection that cannot detect a part with peeling inspection that can detect a part with weak bonding strength Can be compensated by ultrasonic inspection, and defective bonding portions (both void defects and portions having low bonding strength) can be detected with high accuracy. Therefore, the yield in the device manufacturing process can be improved. Furthermore, since the residue of the silicon oxide film existing in the terrace portion is removed during the peeling inspection, it is not necessary to perform polishing or etching for removing the residue of the silicon oxide film. Note that, unlike the infrared inspection, the ultrasonic inspection and the peeling inspection do not reduce the inspection accuracy due to the attenuation of the infrared light in the bonded wafer. The present invention can also be applied to a bonded wafer having a resistance, for example, a bonded wafer having a resistance of 0.1 Ω · cm or less.

  Next, a process of manufacturing a bonded wafer by applying the second embodiment of the bonded wafer inspection method of the present invention is shown in FIG. In FIG. 3, the same members as those shown in FIG.

  In this bonded wafer manufacturing process, first, the active layer wafer 10 and the support substrate wafer 20 are bonded to form a bonded wafer 30 (see FIGS. 3A and 3B). Next, before the bonded wafer 30 is heat-treated to strengthen bonding at the bonding interface, an infrared inspection is performed to inspect the bonded wafer 30 for a defective bonding portion (void defect) (infrared inspection process). . Then, the bonded wafer 30 in which the defective bonding portion is detected by the infrared inspection is reused without heat treatment. On the other hand, with respect to the bonded wafer 30 in which the defective bonding portion is not detected by the infrared inspection, the bonding at the bonding interface is strengthened by performing a heat treatment (see FIG. 3C), and the ultrasonic inspection is performed for the bonding. Inspect for defective parts (ultrasonic inspection process). Subsequently, the surface of the active layer wafer 10 is ground to thin the active layer wafer 10 (see FIG. 3D). Next, after performing a peeling inspection (peeling inspection step), the terrace portion 30A is formed by chamfering the outer periphery of the active layer wafer 10 and alkali etching, and then the surface of the active layer wafer 10 is polished (FIG. 3 (e)). In the case where an oxide film residue remains on the terrace portion 30A, the surface of the terrace portion 30A may be removed by performing a processing process such as polishing.

  Here, the bonding of the active layer wafer 10 and the support substrate wafer 20, infrared inspection, heat treatment of the bonded wafer 30, ultrasonic inspection, and processing of the bonded wafer in which bonding defects are detected are described above. It can carry out similarly to the manufacturing process to which 1st embodiment of the inspection method of the bonded wafer of invention is applied.

  The thinning of the active layer wafer 10 is achieved by grinding the surface of the active layer wafer 10 whose outer periphery is not chamfered by a known method so that the thickness of the active layer wafer 10 is, for example, about 50 μm or less. Achieved.

  In the peeling inspection, after sticking an adhesive tape on the surface of the thinned active layer wafer 10, the adhesive tape is peeled off, and the active layer wafer located on the upper part of the bonding failure is attached to the adhesive tape. This is done by peeling off. In addition, as an adhesive tape, the adhesive tape similar to the manufacturing process which applied previous 1st embodiment can be used.

  The chamfering of the outer periphery of the thinned active layer wafer 10 is caused by the outer peripheral shape of the thinned active layer wafer 10 and the support substrate wafer 20 as in the manufacturing process to which the first embodiment is applied. The purpose is to remove the poorly bonded region. Then, the outer periphery of the thinned active layer wafer 10 is chamfered to a depth that does not reach the bonding interface. In addition, in the alkaline etching, similarly to the manufacturing process to which the first embodiment is applied, a portion left uncut during the chamfering process on the outer periphery of the active layer wafer 10 is removed using an alkaline etching solution such as KOH. It is aimed at.

  Polishing of the surface of the active layer wafer 10 after the peeling inspection can be performed in the same manner as the manufacturing process to which the first embodiment of the bonded wafer inspection method of the present invention described above is applied.

  And in the manufacturing process of the bonded wafer of this other example, since the infrared inspection is performed before the heat treatment as in the manufacturing process to which the first embodiment of the bonded wafer inspection method of the present invention is applied, The manufacturing cost can be reduced by reducing the number of bonded wafers. In addition, since both the ultrasonic inspection and the peeling inspection are used, it is possible to detect a defective bonding portion (both void defect and weak bonding strength portion) with high accuracy. Therefore, a high-quality bonded wafer can be sent to the device manufacturing process to suppress the occurrence of peeling / dropping of the active layer in the device manufacturing process, thereby improving the yield.

  The bonded wafer inspection method of the present invention has been described above using the first embodiment and the second embodiment. However, the bonded wafer inspection method of the present invention is not limited to the above embodiment. The bonded wafer inspection method of the present invention can be modified as appropriate.

  Specifically, in the bonded wafer inspection method of the present invention, it is not necessary to perform infrared inspection. Further, the silicon oxide film residue may be removed by grinding or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

Example 1
Using a silicon wafer having a diameter of 200 mm, 719 bonded wafers subjected to bonding strengthening heat treatment were produced. An oxide film was formed on the active layer silicon wafer.
Then, ultrasonic inspection was performed on 719 manufactured bonded wafers under known conditions, and defective bonding portions (void defects) were detected on 28 bonded wafers.
Next, a peeling test was performed on the 691 bonded wafers in which no void defect was detected in the ultrasonic inspection after the thinning process. ) Is detected.
Then, when 688 bonded wafers in which a defective bonding portion was not detected by ultrasonic inspection and peeling inspection were sent to the device manufacturing process, no defect occurred.

(Example 2)
In the same manner as in Example 1, 131 bonded wafers subjected to bonding strengthening heat treatment were produced using a silicon wafer having a diameter of 200 mm.
And about 131 produced bonded wafers, when ultrasonic inspection was implemented on known conditions only on the half surface (left half surface in Fig.4 (a)) of the wafer bonding termination | terminus side of each wafer, A defective bonding portion (void defect) was detected on the bonded wafer. The time required for the ultrasonic inspection was half that of Example 1.
Next, a peeling test was performed on the 126 bonded wafers in which no void defect was detected in the ultrasonic inspection after the thinning process, and a defective bonding portion was detected in one bonded wafer. It was.
Then, when 125 bonded wafers in which bonding failure portions were not detected by ultrasonic inspection and peeling inspection were sent to the device manufacturing process, no defects occurred.

(Comparative Example 1)
In the same manner as in Example 1, 300 bonded wafers subjected to bonding strengthening heat treatment were produced using a silicon wafer having a diameter of 200 mm.
Next, an ultrasonic inspection was performed on 300 manufactured bonded wafers under known conditions, and defective bonding portions (void defects) were detected on the two bonded wafers.
Then, when 298 bonded wafers in which a defective bonding portion was not detected by ultrasonic inspection were sent to the device manufacturing process, a defect occurred.

  From Examples 1 and 2 and Comparative Example 1, it can be seen that if the inspection method of the present invention is applied, a defective bonding portion can be detected with high accuracy and the yield in the device manufacturing process can be improved. Further, it can be seen from Examples 1 and 2 that if the ultrasonic inspection is performed only on the bonding end side, the time required for the inspection can be shortened while detecting the bonding failure portion with high accuracy.

  According to the present invention, it is possible to provide a bonded wafer inspection method capable of detecting a defective bonding portion with sufficiently high accuracy.

DESCRIPTION OF SYMBOLS 10 Active layer wafer 10A Silicon oxide film 10B Residue 20 Support substrate wafer 20A Silicon oxide film 30 Bonded wafer 30A Terrace part 40 Adhesive tape 41 Press member 41A Press part

Claims (4)

A method for inspecting the presence or absence of a bonding failure portion of a bonded wafer,
An ultrasonic inspection step of detecting a bonding failure portion using a reflected wave from inside the bonded wafer when ultrasonic waves are applied to the bonded wafer;
After affixing the adhesive tape to the bonded wafer after performing the ultrasonic inspection step, a peeling inspection step of detecting the bonding failure part by peeling off the adhesive tape,
A method for inspecting a bonded wafer, comprising: In the ultrasonic inspection step, a defective bonding portion is detected for the outer peripheral portion of the bonded wafer,
The bonded wafer inspection method according to claim 1, wherein in the peeling inspection step, a defective bonding portion is detected on the entire surface of the bonded wafer. The bonded wafer is obtained by bonding two wafers from a bonding start end position toward a bonding end position,
In the ultrasonic inspection process, a bonding failure portion is detected for the bonding end position side of the bonded wafer,
The bonded wafer inspection method according to claim 1, wherein in the peeling inspection step, a defective bonding portion is detected on the entire surface of the bonded wafer. Before the ultrasonic inspection process and the peeling inspection process, and before the bonded wafer is heat-treated and strengthened by bonding, the bonded wafer is irradiated with infrared rays, and the infrared rays transmitted through the bonded wafer or The method for inspecting a bonded wafer according to any one of claims 1 to 3, further comprising an infrared inspection step of detecting a defective bonding portion using infrared light reflected by the bonded wafer.

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