JP4869622B2 - Bonded wafer manufacturing method and peeling jig used therefor - Google Patents

Description

  The present invention relates to a method for manufacturing a bonded wafer by a so-called ion implantation separation method using two wafers such as a silicon wafer, and a separation jig used therefor.

  As a wafer for a high-performance device, a bonded wafer in which a semiconductor wafer is bonded to another wafer and bonded is used. The bonded wafer is manufactured by bonding a base wafer serving as a support substrate and a bond wafer on which a device is formed. For example, after an oxide film is formed on at least one of two mirror-polished silicon wafers, these wafers are bonded together. If necessary, heat treatment is performed at a temperature of 200 to 1200 ° C. to increase the bond strength, and the bond wafer is then thinned to a desired thickness by grinding and polishing. By such a method, a bonded SOI wafer in which an SOI (silicon on insulator) layer is formed can be manufactured.

  Another method for manufacturing a bonded wafer is a method called an ion implantation separation method. For example, an ion gas such as hydrogen ions is injected into a silicon wafer (bond wafer) on which an oxide film is formed to form an ion implantation layer (microbubble layer) inside, and then bonded to the base wafer. Note that silicon wafers may be bonded directly without using an oxide film, and an insulating wafer such as quartz, silicon carbide, or alumina may be used as a base wafer.

  After the bonding, the ion-implanted layer in the bond wafer is peeled off as a boundary. In this peeling step, a heat treatment (peeling heat treatment) of, for example, about 500 ° C. is performed on the bonded bond wafer and base wafer. By the peeling heat treatment, the ion-implanted layer is cracked at the atomic level, and is further peeled (separated) with the ion-implanted layer in the bond wafer as a boundary by applying a mechanical load. According to such an ion implantation separation method, it is possible to manufacture a bonded wafer in which a thinner SOI layer (active layer) having a uniform thickness is formed. In the manufactured bonded SOI wafer, a device is formed on the active layer.

When manufacturing a bonded wafer as described above, as a method for complete separation by an ion implantation layer or the like, a method of inserting a wedge into a portion to be separated such as an ion implantation layer or a method of injecting a fluid such as a gas Alternatively, a method has been proposed in which one wafer is adsorbed and held, the central portion of the other wafer is pressurized with a gas or the like, and a pressurized gas is supplied to a portion to be peeled off such as an ion implantation layer (Patent Literature). 1).
However, when the base wafer and the bond wafer are bonded together, an unbonded portion is formed on the outer periphery. However, when a wedge is inserted into the ion-implanted layer, the active layer is damaged by the wedge particularly when the unbonded portion is narrow. Very likely to give.
Further, since the ion implantation layer is an extremely thin layer, it is very difficult to insert a wedge or perform gas injection in that portion.

As another peeling method, a method has been proposed in which a wafer is slid and separated using a plate-like jig 30 as shown in FIGS. 8A and 8B (see Patent Document 2). After the peeling heat treatment, the wafer 38 supported by the heat treatment boat 35 is placed on the support surface 31 of the jig 30 and supported by the bowl-shaped portion 32 as shown in FIG. When the jig 30 is tilted as shown in FIG. 8B, the movement of the bonded wafer having the active layer formed on the base wafer, that is, the lower portion with the ion-implanted layer as a boundary is prevented by the stopper 33. On the other hand, the upper part, that is, the remaining part of the bond wafer (peeling wafer) slides down to the step part 34 by its own weight and is separated.
Such a slide-type jig 30 can perform the peeling operation relatively easily. However, since the peeling work is performed by its own weight, it does not peel off smoothly or on the surface (active layer) of the obtained bonded wafer. There are cases where particles are abnormally attached locally.

JP 2001-230393 A JP 2003-46070 A

  In view of the above points, when manufacturing a bonded wafer by an ion implantation separation method, the present invention can easily and reliably perform the separation without damaging the wafer or the active layer, and suppress the adhesion of particles. It is an object of the present invention to provide a technique for manufacturing a bonded wafer.

According to the present invention, at least a step of forming an ion-implanted layer inside by ion-implanting a wafer on which a device is formed, and a surface of the wafer on which the ion-implanted side is bonded to another wafer serving as a support substrate In the method for manufacturing a bonded wafer, including a step of combining, and a step of performing heat treatment on the bonded wafer and separating the wafer with the ion-implanted layer as a boundary. There is provided a method for producing a bonded wafer, characterized in that an implanted wafer and a wafer serving as a supporting substrate are each vacuum-sucked, and at least one of the wafers is separated and separated with the ion implanted layer as a boundary .

  That is, in the ion implantation delamination method, after the delamination heat treatment is performed on the bonded wafer, the wafers on both sides are vacuum-sucked to separate at least one wafer without damaging the wafer or the active layer. Can be peeled off. In addition, since the wafers on both sides are forcibly separated after being vacuum-sucked, it is possible to easily and surely peel off, and it is possible to produce a bonded wafer in which particle adhesion is extremely effectively suppressed after peeling. it can.

In this case, it is peeled off the ion-implanted layer the ion-implanted wafer as away from the wafer to be the support substrate as a boundary virtuous preferable.
If the ion-implanted wafer, that is, the bond wafer is separated from the base wafer and separated by the ion-implanted layer, damage to the bonded wafer or the like can be reliably prevented, and separation can be performed more easily. it can.

The ions implanted wafer, it is good preferable to vacuum suction third region to be the outside of the second radius from the center of the wafer.
That is, if the outer region of the bond wafer is vacuum-sucked, it can be more easily separated.

Further, the ion-implanted wafer, it is good preferable to adsorb the asymmetric center of the wafer as a reference.
If the bond wafer is adsorbed asymmetrically, it can be peeled off with a weaker force than when it is adsorbed symmetrically and peeled off.

A silicon wafer can be used as the ion-implanted wafer .
Bonded wafers using silicon wafers as bond wafers are in high demand, and by applying the present invention, for example, high-quality bonded SOI wafers in which the SOI layer is not damaged and particle adhesion is extremely suppressed are manufactured. be able to.

Furthermore, according to the present invention, after bonding the wafer having an ion implantation layer formed therein to a wafer serving as a support substrate, the jig is used to separate the ion implantation layer as a boundary. A stripping jig comprising a wafer suction stage having suction means for vacuum-sucking one of the wafers, and a wafer suction disk having a suction cup for vacuum-sucking the other wafer. Provided .

  In this way, if it is a peeling jig that vacuum-adsorbs the bonded wafer and base wafer after bonding, the wafers and the active layer are not damaged by separating the vacuum-adsorbed wafers from each other. The layer can be easily and reliably peeled off at the boundary.

In this case, the surface on the side of adsorbing the wafer of the wafer suction stage, it is good preferable to that pin for positioning the wafer to be adsorbed is provided.
That is, if the jig is provided with positioning pins on the wafer suction stage, the wafer before peeling can be reliably sucked at a predetermined position, and the peeling operation can be performed more easily. .

Further, the suction cup of the wafer suction cups are, it is good Mashiku provided in a position to adsorb 3 minutes region to be the outside of the second radius from the center of the wafer to be adsorbed, and the wafer to be adsorbed it is good preferable provided in a position to adsorb the asymmetric center of the wafer as a reference.
If a suction cup is provided at a position that adsorbs the outer region of the bond wafer or a position that adsorbs asymmetrically with respect to the center of the bond wafer, it can be easily separated with a small force.

Also, it is possible to prevent the wafer suction stage and the wafer suction disk from approaching a predetermined distance or less when performing the peeling on the wafer suction surface of at least one of the wafer suction stage and the wafer suction disk. it is good preferable that the protruding portions for are provided.
If such a protrusion is provided, the suction stage and the suction disk can be brought close to each other and the wafer can be reliably suctioned, and the wafer suction disk collides with the wafer and scratches it. Without this, the peeling operation can be performed more easily and reliably.

  According to the present invention, when a bonded wafer is manufactured by the ion implantation peeling method, after the two wafers bonded are subjected to a peeling heat treatment, the wafers on both sides are vacuum-sucked to separate at least one of the wafers. Thus, the ion-implanted layer can be peeled off at the boundary. Thereby, it can be made to peel, without damaging a wafer and an active layer. In addition, since both wafers are forcibly separated after being vacuum-adsorbed, it is possible to easily and reliably peel them off with an ion-implanted layer, and it is possible to manufacture a bonded wafer in which particle adhesion is extremely suppressed.

  Hereinafter, the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 schematically shows an example of a peeling jig according to the present invention. FIG. 2 schematically shows how the ion implantation layer is peeled off using the jig 1 after bonding the bond wafer and the base wafer. The peeling jig 1 mainly includes a wafer suction stage 2 and a wafer suction disk 3.

  A groove 4 leading to a vacuum path 9 and a vacuum pump is formed at the center of the suction surface of the wafer suction stage 2 so that the entire surface of the wafer 8a to be sucked can be vacuum sucked evenly. Is provided with an O-ring 6. Further, a protrusion 5 is provided outside the O-ring 6 for avoiding the wafer suction stage 2 and the wafer suction disk 3 approaching a certain distance or less and colliding with the wafer when peeling. It has been.

The wafer suction disk 3 is provided with suction disks 7a and 7b for vacuum-sucking the wafer 8b. These suction cups 7a and 7b are provided at positions where the wafer 8b to be sucked is sucked asymmetrically with respect to the center of the wafer. In addition, each of the suction cups 7a and 7b is provided at a position that adsorbs a region outside the two-thirds of the radius from the center of the wafer. These suction cups 7 a and 7 b can vacuum-suck the wafer 8 (8 b) through the vacuum path 10. The suckers 7a and 7b can be made of a material that can be adsorbed without scratching or contaminating the wafer 8. For example, a sucker made of silicone rubber can be preferably used.
The material of each main body of the suction stage 2 and the suction disk 3 is not particularly limited as long as it does not contaminate the wafer 8 (8a, 8b), and plastic, ceramics, etc. can be used. For example, PEEK (polyether) A product made of ether ketone) can be preferably used.

FIG. 3 schematically shows another example of the peeling jig according to the present invention. FIG. 4 schematically shows how the jig 11 is peeled off.
The peeling jig 11 also includes a wafer suction stage 12 and a wafer suction disk 13. The suction surface of the suction stage 12 is provided with a groove (not shown) and an O-ring 6 for vacuum-sucking the wafer 8a. A pin 16 for positioning the wafer 8a to be attracted is provided outside the O-ring 6. The positioning pin 16 may also be used as the contact avoiding protrusion 5 shown in FIG.
1, the suction cups 17a and 17b are provided at positions where the suction cups 17a and 17b asymmetrically adsorb a region outside the two-thirds of the radius from the center of the wafer 8b to be sucked. ing.

Next, a method for manufacturing a bonded wafer using the peeling jig 1 will be described. FIG. 5 is a flowchart showing an example of a method for producing a bonded SOI wafer according to the present invention.
First, two mirror-finished silicon wafers are prepared as a base wafer 21 serving as a support substrate and a bond wafer 22 on which a device is formed (FIG. 5A).
Then, at least one of the wafers, here, the bond wafer 22 is thermally oxidized to form an oxide film 23 having a thickness of, for example, 0.1 μm to 2.0 μm on the surface (FIG. 5B).

  Hydrogen ions are implanted into one side of a bond wafer 22 having an insulating film (oxide film) 23 formed on the surface, thereby forming an ion implantation layer (microbubble layer) 24 parallel to the surface at an average ion penetration depth ( FIG. 5 (c)). The injection temperature at this time can be set to 25 to 450 ° C., for example. In addition to hydrogen ions, for example, rare gas ions or both of them can be implanted.

  The surface of the bond wafer 22 into which hydrogen ions have been implanted is bonded to the base wafer 21 (FIG. 5D). By bringing the surfaces of the two wafers 21 and 22 into contact with each other in a clean atmosphere at room temperature, the wafers are joined without using an adhesive or the like.

After bonding, peeling is performed using the ion implantation layer 24 in the bond wafer 22 as a boundary (FIG. 5E).
For example, the bonded base wafer 21 and bond wafer 22 are subjected to a heat treatment (peeling heat treatment) at about 500 ° C. in an inert gas atmosphere. Such peeling heat treatment causes cracks at the atomic level in the ion implantation layer 24. Therefore, the peeling jig 1 according to the present invention is used for complete peeling. For example, the base wafer 21 side is vacuum-sucked by the suction stage 2, and the bond wafer 22 side is vacuum-sucked by the suction plate 3. Next, the suction disk 3 is pulled up with the suction stage 2 fixed, and the bond wafer 22 is pulled away from the base wafer 21. As a result, the outer region of the bond wafer 22 adsorbed by the suction cups 7a and 7b can be warped, and the ion implantation layer 24 in the bond wafer 22 can be peeled off as a boundary.
At the time of peeling, the base wafer 21 may be separated from the bond wafer 22 or the wafers 21 and 22 may be separated from each other.

By peeling off at the ion implantation layer 24 in this way, the separation wafer 25 and the SOI wafer 26 (SOI layer 27 + buried oxide film 23 + base wafer 21) can be separated to obtain a bonded SOI wafer 26 (FIG. 5 (f)).
In the bonded wafer and the base wafer after bonding, an unbonded portion having a width of about 1 mm to 2 mm is generally generated in the outer peripheral portion. In the peeling jig 1 according to the present invention, ions are formed from the side surface of the bond wafer. Since no wedge or the like is inserted with the aim of the injection layer, the oxide film 23 and the SOI layer 27 formed on the base wafer 21 or the bonded wafer 26 is not damaged or scratched. Further, since both wafers are forcibly separated after being vacuum-adsorbed, the bonded wafer 26 can be manufactured, which can be easily and reliably peeled off by the ion-implanted layer and particle adhesion is extremely suppressed.

In addition, although the center part of the bond wafer 22 may be adsorbed, peeling can be performed with a weaker force when the outer region is adsorbed than when the center part of the bond wafer 22 is adsorbed. In particular, if an area outside the center of the bond wafer 22 that is outside of two-thirds of the radius is adsorbed by the suction cups 7a and 7b, the outer area of the bond wafer 22 can be reliably separated and easily separated. be able to.
In addition, the entire circumference may be adsorbed symmetrically with respect to the center of the bond wafer 22, but it is easier with a weaker force when adsorbing asymmetrically than when adsorbing symmetrically with respect to the center or the entire circumference. Can be peeled off.

  Alternatively, the bond wafer 22 may be vacuum-sucked by the suction stage 2, and the base wafer 21 may be vacuum-sucked by the suction plate 3 to perform peeling. However, if the outer region on the base wafer 21 side is attracted and separated from the bond wafer 22, the outer region of the bonded wafer 26 to be a product is warped, and the load may affect the SOI layer near the outer periphery. Therefore, it is preferable that the bond wafer 22 is vacuum-sucked by the suction disk 3 and separated from the base wafer 21 as described above.

  Furthermore, a series of operations from adsorption to peeling can be automated. For example, after the suction stage 2 vacuum-sucks the base wafer 21 side, the suction disk 3 automatically descends and vacuum-sucks the bond wafer 22 side. And if it comprises so that the suction disk 3 may raise automatically after adsorption | suction, it will become possible to perform a peeling process substantially automatically.

  After peeling, in order to further increase the bonding force between the base wafer 21 and the SOI layer, or to planarize the surface of the SOI layer 27, for example, in an inert gas, hydrogen gas, or mixed gas atmosphere thereof, 1000 to 1000 You may heat-process in the range of 1300 degreeC.

Examples of the present invention and comparative examples will be described below.
(Example)
Using a silicon wafer having a diameter of 200 mm, an SOI wafer was manufactured according to the flow shown in FIG.
Specifically, hydrogen ions were implanted into the bond wafer, bonded to the base wafer, and then subjected to a peeling heat treatment (argon gas atmosphere, about 500 ° C., 30 minutes). Next, using the peeling jig 1 as shown in FIG. 1, the base wafer side was vacuum-sucked by a suction stage, and a region within 10 mm from the outer edge of the bond wafer side was vacuum-sucked by a suction disk. Then, by pulling up the suction disk with the suction stage fixed, the bond wafer was separated from the base wafer, and the ion-implanted layer in the bond wafer was peeled off as a boundary.

Particles (0.5 μm or more) on the SOI layer of the obtained bonded wafer were counted using a particle counter (SP-1 manufactured by KLA Tencor).
FIG. 6A shows the number of particles and the frequency of 48 SOI wafers. As seen in FIG. 6A, the number of particles in 43 (about 90%) SOI wafers was 5 or less, and the maximum number of particles in the remaining 5 was 8. The average number of particles was 2.6.
FIG. 7A shows an example of the position of the suction cup and the state of generation of particles. There was no local abnormality of particles.

(Comparative example)
After bonding and peeling heat treatment using the same silicon wafer as in the example, peeling was performed using a slide-type jig 30 as shown in FIG. Particles (0.5 μm or more) on the SOI layer of the obtained bonded wafer were counted.
FIG. 6B shows the number of particles and the frequency of 132 SOI wafers. In 55 sheets (about 42%), the number of particles was 5 or less, but in 36 sheets (about 27%), 6 to 10 particles were counted, and the remaining wafers were counted 11 or more, and a maximum of 185 particles were counted. It was. The average number of particles was 13.3.
FIG. 7B shows an example of particle generation status. It can be seen that abnormal particles are occurring locally.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

For example, the peeling jig according to the present invention is not limited to the embodiment shown in FIGS. 1-4, for example, the shape, number, position, etc. of the suction cup of the suction cup, the shape of the vacuum groove of the suction stage, The arrangement and the like may be designed as appropriate. Further, a suction cup similar to the suction cup may be used as the suction means of the suction stage.
Moreover, you may perform adsorption | suction and peeling from a horizontal direction in the state which supported the bonding wafer after peeling heat processing perpendicularly | vertically.

  Furthermore, in the above embodiment, the case where an SOI wafer is manufactured from two silicon wafers has been described. However, if a bonded wafer is manufactured by an ion implantation separation method, the material and size of the bond wafer and the base wafer are described. The present invention is not particularly limited. For example, the present invention is naturally applicable to a case where a compound semiconductor wafer such as GaAs is used as the bond wafer, and an insulating wafer such as silicon carbide or alumina is used as the base wafer.

It is the schematic which shows an example of the jig | tool for peeling which concerns on this invention. It is the schematic which shows the state which made the wafer for peeling of FIG. 1 adsorb | suck to a wafer. It is the schematic which shows the other example of the jig | tool for peeling which concerns on this invention. It is the schematic which shows the state which made the wafer for adsorption | suction of FIG. 3 adsorb | suck to a wafer. It is a flowchart which shows an example of the manufacturing method of the bonding wafer which concerns on this invention. It is a figure which shows the number of particles and frequency. (A) Examples (B) Comparative examples It is a figure which shows an example of the generation condition of a particle. (A) Examples (B) Comparative examples It is the schematic which shows an example of the conventional peeling jig | tool (slide type).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,11 ... Exfoliation jig | tool 2,12 ... Wafer adsorption | suction stage 3,13 ... Wafer adsorption board, 4 ... Vacuum groove, 5 ... Protrusion part for contact avoidance, 6 ... O-ring, 7a, 7b, 17a , 17b ... sucker, 8 ... bonded wafer (before peeling), 9, 10 ... vacuum path, 16 ... positioning pin, 21 ... base wafer, 22 ... bond wafer, 23 ... oxide film, 24 ... ion implantation layer, 25 ... Peeling wafer, 26 ... Laminated wafer, 27 ... SOI layer (active layer).

Claims (8)

At least a step of forming an ion implantation layer by ion implantation into a wafer on which a device is to be formed, a step of bonding an ion-implanted surface of the wafer to another wafer serving as a support substrate, and the bonding In a method for manufacturing a bonded wafer including a step of performing heat treatment on the combined wafer and separating the wafer from the ion-implanted layer as a boundary, the wafer is supported with the ion-implanted wafer after the heat treatment as the separation step. Each wafer serving as a substrate is vacuum-adsorbed, and at the time of the vacuum adsorption, the ion-implanted wafer is vacuum-adsorbed in a region outside the two-thirds of the radius from the center of the wafer , and at least one wafer is A bonded wafer characterized in that the ion-implanted layer is peeled off as a boundary so as to be separated. Production method.   2. The method for manufacturing a bonded wafer according to claim 1, wherein the ion-implanted wafer is separated from the wafer serving as the support substrate, and the ion-implanted layer is separated as a boundary. 3. The method for producing a bonded wafer according to claim 1, wherein the ion-implanted wafer is adsorbed asymmetrically with respect to the center of the wafer. The method for manufacturing a bonded wafer according to any one of claims 1 to 3 , wherein a silicon wafer is used as the wafer to be ion-implanted. A jig used to peel a wafer having an ion-implanted layer therein from a wafer serving as a support substrate, and then peel off the wafer using the ion-implanted layer as a boundary. At least one of the wafers is vacuumed A wafer suction stage having a suction means for suction, and a wafer suction disk having a suction cup for vacuum suction of the other wafer, and the suction cup of the wafer suction disk has a radius from the center of the wafer to be sucked A peeling jig characterized in that it is provided at a position to adsorb a region outside the two thirds of the above . 6. The peeling jig according to claim 5 , wherein a pin for positioning the wafer to be sucked is provided on a surface of the wafer suction stage on the side for sucking the wafer. The peeling jig according to claim 5 or 6 , wherein the suction cup of the wafer suction disk is provided at a position where the wafer to be sucked is sucked asymmetrically with reference to the center of the wafer. In order to prevent the wafer suction stage and the wafer suction disk from approaching a certain distance or less when performing the separation on the wafer suction surface of at least one of the wafer suction stage and the wafer suction disk. peeling jig according to to claim 5 any one of claims 7, characterized in that the projecting portion is provided in the.

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