JP6851040B2 - Substrate processing method and substrate processing equipment - Google Patents

Description

The present invention relates to a substrate processing method and a substrate processing apparatus for forming a processing layer inside a crystal substrate to be processed by condensing laser light from the surface of the crystal substrate to be processed to the inside.

Conventionally, when manufacturing a semiconductor wafer typified by a single crystal silicon (Si) wafer, a cylindrical ingot solidified from a silicon melt melted in a quartz crucible is cut into blocks of an appropriate length. Then, the peripheral portion thereof is ground to a target diameter, and then the blocked ingot is sliced into a wafer shape by a wire saw to manufacture a semiconductor wafer (see, for example, Patent Document 1).

The semiconductor wafer manufactured in this way is subjected to various processes such as forming a circuit pattern in the pre-process and is subjected to the post-process, and the back surface is back-grinded in the post-process to be thinned. Thereby, the thickness is adjusted from about 750 μm to 100 μm or less, for example, about 75 μm or 50 μm.

Conventional semiconductor wafers are manufactured as described above, and the ingot is cut by a wire saw, and a cutting allowance larger than the thickness of the wire saw is required for cutting. Therefore, a thin semiconductor wafer having a thickness of 0.1 mm or less is required. It is very difficult to manufacture and the product rate does not improve.

Japanese Unexamined Patent Publication No. 2005-297156

By the way, when the size of the single crystal substrate is larger than the size to be used, it is efficient if the single crystal substrate can be reused in a good shape and small size. Further, this is often applicable not only to a single crystal substrate but also to other types of substrates.

On the other hand, a processing method has been proposed in which laser light is focused inside the wafer to form a modified region inside the wafer and the wafer is diced. Generally, this processing method utilizes the fact that the modified layer extends to the laser beam irradiation side due to heat absorption by the internally focused laser beam. This method is effective in shortening the processing time during dicing, but the growth of cracks in the modified layer causes deterioration of the cross-sectional shape and cracks that grow along the unexpected crystal orientation of the crystal substrate to be processed. .. Therefore, when the wafer is hollowed out, problems such as deterioration of the cross-sectional shape, deterioration of processing accuracy, and chipping of the wafer surface occur.

In view of the above problems, it is an object of the present invention to provide a substrate processing method and a substrate processing apparatus for processing a crystal substrate to be processed into a processed layer-containing substrate for obtaining a hollow crystal substrate without chips.

According to one aspect of the present invention for solving the above problems, a laser condensing means capable of condensing laser light and adjusting aberration correction is arranged non-contactly on the irradiated surface of the crystal substrate to be processed. In the first step, while condensing the laser light inside the crystal substrate to be processed by the laser condensing means, the condensing position of the laser light is changed in the peripheral direction and the thickness direction of the hollowed out target portion of the crystal substrate to be processed. A second step of forming a processed layer containing a processed layer by forming a processed layer having a reduced breaking strength on the outer peripheral side of the hollowed-out target portion is provided. Provided is a substrate processing method for adjusting the aberration correction of the laser condensing means so that the processing marks generated at the laser light condensing position near the surface of the crystal substrate to be processed do not extend along the crystal orientation of the crystal substrate to be processed. Light.

Further, according to another aspect of the present invention, the laser beam is directed toward the rotating stage that holds and rotates the mounted crystal substrate to be processed and the crystal substrate to be processed that is held on the rotating stage. Laser condensing means that can adjust the aberration correction of the laser light while condensing, irradiation axis direction distance changing means that changes the distance between the rotating stage and the laser condensing means, and the aberration correction according to the distance. The aberration correction control means includes an aberration correction control means for controlling adjustment, and the aberration correction control means produces a processing mark generated at a laser light condensing position inside the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface. Provided is a substrate processing apparatus that controls so as not to extend along the crystal orientation of the substrate.

According to the present invention, there is a substrate processing method and a substrate processing apparatus capable of providing a substrate processing method and a substrate processing apparatus for processing a crystal substrate to be processed into a processed layer-containing substrate for obtaining a hollow crystal substrate without chips. Can be provided.

It is a schematic side view explaining the substrate processing apparatus which concerns on 1st Embodiment. (A) to (c) are schematic side views for explaining a process of manufacturing a processed layer-containing substrate by the substrate processing method according to the first embodiment, respectively. (A) and (b) are schematic side sectional views which show that the processed layer is formed by the substrate processing method which concerns on 1st Embodiment, respectively. It is a schematic perspective view explaining the hollowing out target part from the processed layer containing substrate in 1st Embodiment. It is a schematic side view for demonstrating the function as an aberration correction ring in the substrate processing apparatus which concerns on 1st Embodiment. It is a schematic explanatory drawing explaining that the processing mark is arranged in the processing layer formed by the substrate processing method which concerns on 1st Embodiment. FIG. 5 is a photographic view showing a side cross section of a processed layer-containing substrate obtained in Experimental Example 1 according to an example of the first embodiment (Example 1). FIG. 5 is a photographic view showing a side cross section of the processed layer-containing substrate obtained in Comparative Example 1 in Experimental Example 1. FIG. 5 is a schematic side view for explaining the focal position of the laser beam when one example (Example 2) of the first embodiment is performed in Experimental Example 2. FIG. 2 is a schematic side view for explaining that in Experimental Example 2, when the focal position of the laser beam is moved upward, the light collection becomes insufficient if the aberration correction is not performed. FIG. 2 is a schematic side view for explaining that in Experimental Example 2, when the focal position of the laser beam is moved upward, aberration correction is performed so that the laser beam is moved while being sufficiently focused at the focal position. FIG. 5 is a photographic view showing a side cross section of a processed layer-containing substrate obtained in Experimental Example 2 according to an example of the first embodiment (Example 2). FIG. 3 is a photographic view showing a partial side cross section of a processed layer-containing substrate obtained in Experimental Example 3 according to an example of the first embodiment (Example 3). It is a photographic figure explaining that the part to be hollowed out was hollowed out from the processed layer containing substrate obtained by the example of 1st Embodiment (Example 3) in Experimental Example 3. FIG. 3 is a photographic view showing a partial side cross section of the processed layer-containing substrate obtained in Comparative Example 2 in Experimental Example 3. It is a schematic side sectional view which shows the processed layer containing substrate manufactured by the substrate processing method which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, components that are the same as or similar to those already described are designated by the same or similar reference numerals, and detailed description thereof will be omitted as appropriate. Further, the embodiments shown below are examples for embodying the technical idea of the present invention, and the embodiments of the present invention describe the materials, shapes, structures, arrangements, etc. of the components as follows. It is not specific to. Embodiments of the present invention can be variously modified and implemented without departing from the gist.

[First Embodiment]
First, the first embodiment will be described. FIG. 1 is a schematic side view for explaining the substrate processing apparatus according to the present embodiment. 2A to 2C are schematic side views for explaining a process of manufacturing a processed layer-containing substrate by the substrate processing method according to the present embodiment, respectively. 3A and 3B are schematic side sectional views showing that a processed layer is formed by the substrate processing method according to the present embodiment, respectively. FIG. 4 is a schematic perspective view illustrating that the hollowed-out target portion is hollowed out from the processed layer-containing substrate in the present embodiment. FIG. 5 is a schematic side view for explaining the function of the substrate processing apparatus according to the present embodiment as an aberration correction ring. FIG. 6 is a schematic explanatory view for explaining that the processing marks are arranged in the processing layer formed by the substrate processing method according to the present embodiment.

(Substrate processing equipment)
As shown in FIGS. 1 and 2, the substrate processing apparatus 10 according to the present embodiment is placed on a rotating stage 11 that holds and rotates the mounted crystal substrate 20a to be processed, and on the stage surface Su of the rotating stage 11. A laser condensing means 12 (for example, a concentrator) that condenses the laser beam B toward the held crystal substrate 20a to be processed is provided. The laser condensing means 12 is adapted to receive the laser light emitted from the laser oscillator J. Further, the substrate processing apparatus 10 includes an irradiation axis direction distance changing means (not shown) that changes the distance L between the rotating stage 11 and the laser condensing means 12, and aberration correction of the laser condensing means 12 according to the distance L. The aberration correction control means 13 for controlling the adjustment state of the above is provided. Further, the substrate processing apparatus 10 includes radial distance changing means (not shown) for changing the distance r between the rotation center axis Cs of the rotation stage 11 and the irradiation center axis Cb of the laser condensing means 12.

The irradiation axis direction distance changing means may be a mechanism for moving the laser condensing means 12 in the perspective direction with respect to the rotating stage 11, or the rotating stage 11 may be moved in the perspective direction with respect to the laser condensing means 12. It may be a mechanism for causing (for example, an X stage or an XY stage).

The radial distance changing means may be a moving mechanism that moves the laser condensing means 12 in one direction parallel to the stage surface Su (for example, the X direction in FIGS. 1 and 2), or may be a moving mechanism that moves the rotating stage 11 to the stage. It may be a moving mechanism that moves in one direction parallel to the surface Su (for example, the X direction in FIGS. 1 and 2).

The aberration correction control means 13 transmits a control signal for adjusting the aberration correction (details will be described later) of the laser condensing means 12 according to the distance L. The aberration correction control means 13 is located inside the crystal substrate 20a to be processed and near the surface of at least one crystal substrate to be processed (near the front surface (near the upper surface) or near the back surface (near the lower surface)) at the condensing position Bf of the laser beam B. The aberration correction of the laser condensing means 12 is adjusted so that the generated processing marks 22c (see FIG. 6) do not extend along the crystal orientation of the crystal substrate 20a to be processed.

In the substrate processing apparatus 10 of the present embodiment, the vicinity of the surface of the crystal substrate to be processed that controls such aberration correction is the vicinity of the irradiated surface 20u (surface) of the laser beam B, and the side opposite to the irradiated surface 20u. The aberration correction control means 13 does not perform such control in the vicinity of the surface, that is, the surface (back surface 20v) on the rotation stage side. Even in the vicinity of the back surface 20v, the device configuration may be such that such control is enabled by the aberration correction control means 13 by a changeover switch or the like.

In the present embodiment, the laser condensing means 12 includes a condensing lens 15 as shown in FIGS. 5 and 6, and has an aberration correction adjusting function, that is, a function as an aberration correction ring. Specifically, when the condenser lens 15 is focused in the air, the laser light that reaches the outer peripheral portion E of the condenser lens 15 is collected more than the laser light that reaches the central portion M of the condenser lens 15. The configuration is such that the light is focused on the optical lens side. That is, when condensing, the condensing point EP of the laser light that reaches the outer peripheral portion E of the condensing lens 15 is condensed as compared with the condensing point MP of the laser light that reaches the central portion M of the condensing lens 15. The configuration is such that the position is corrected so as to be close to the lens 15.

The condensing lens 15 is composed of a first lens 16 that condenses light in the air, and a second lens 18 that is arranged between the first lens 16 and the crystal substrate 20a to be processed. In the present embodiment, the first lens 16 and the second lens 18 are both lenses capable of condensing the laser beam in a conical shape. The lengths of the condensing point EP and the condensing point MP can be adjusted by adjusting the distance between the first lens 16 and the second lens 18, and the condensing lens 15 serves as a lens with a correction ring. It has a function.

As the first lens 16, in addition to a spherical or aspherical single lens, a group lens can be used to correct various aberrations and secure a working distance, and the NA is 0.3 to 0.7. Is preferable. As the second lens 18, a lens having an NA smaller than that of the first lens 16, for example, a convex glass lens having a radius of curvature of about 3 to 5 mm is preferable from the viewpoint of easy use.

In addition, instead of the second lens 18, it is also possible to arrange an aberration enhancing material (for example, an aberration enhancing glass plate) of the laser beam B.

(Substrate processing method)
Hereinafter, an example in which the crystal substrate 20a to be processed is a single crystal substrate will be given, and the substrate processing method according to the present embodiment will be described using the substrate processing apparatus 10 including its effect.

In the present embodiment, the first step of arranging the laser condensing means 12 on the irradiated surface 20u of the single crystal substrate 20am to be processed in a non-contact manner is performed. Then, while the laser light B is focused inside the processing target single crystal substrate 20am by the laser condensing means 12, the condensing position Bf of the laser light B is set in the peripheral direction of the hollowed-out target portion 20b of the processing target single crystal substrate 20am. A second processed layer-containing substrate 20c is formed by forming a processed layer 22 having a reduced breaking strength on the outer peripheral side of the hollowed-out target portion 20b by changing in the outer peripheral direction) and the thickness direction (Z direction in FIGS. 1 and 2). Perform the process. In the present embodiment, in this second step, the laser beam B is focused inside the crystal substrate 20a to be processed and near at least one surface of the crystal substrate to be processed (near the front surface (near the upper surface) or near the back surface (near the lower surface)). The aberration correction of the laser condensing means 12 is adjusted so that the processing mark 22c generated at the position Bf does not extend along the crystal orientation of the crystal substrate 20a to be processed.

Hereinafter, the procedure for forming the processed layer 22 in the second step will be described in detail. When irradiating the single crystal substrate 20am to be processed with the laser beam B, the single crystal substrate to be processed arranged on the rotating stage 11 so that the irradiation can be started from the surface (back surface 20v) opposite to the irradiated surface 20u. The Z-axis direction position of the condensing position Bf at 20 am is determined.

Then, first, the laser beam B is irradiated along the concentric circles while rotating the rotation stage 11 at least once. After that, the condensing position Bf is moved in the Z-axis direction of the substrate processing apparatus 10, and the laser beam B is similarly irradiated along the concentric circles. At this time, since the movement of the condensing position Bf in the Z-axis direction is in the same direction as the thickness direction of the single crystal substrate 20am to be processed, the processed layer 22 is formed into a short cylinder orthogonal to the irradiated surface 20u. Can be formed.

The processed layer 22 can be completed by performing this series of operations up to the vicinity of the irradiated surface 20u of the single crystal substrate 20am to be processed. In order to perform this movement of the focusing position Bf, at least one of the laser focusing means 12 and the rotating stage 11 may be moved.

In the present embodiment, in the second step, the output of the laser oscillator J is constant, that is, the output of the laser light incident on the laser condensing means 12 is constant. The output of the incident laser beam is preferably the lower limit output at which the machining marks 22c can be formed inside the substrate in order to suppress the elongation of the machining marks 22c.

This lower limit output is the substrate thickness of the processing mark 22c based on the correction ring adjustment amount (aberration correction adjustment amount) when the condensing position Bf is adjusted to the back surface 20v (bottom surface) side corresponding to the substrate thickness. The output can be formed with a longitudinal length K (see FIG. 6) of 10 μm or less, preferably 5 μm to 10 μm.

A hollow crystal substrate of good quality can be obtained by accurately connecting and forming processing marks 22c having a length K of 10 μm or less while gradually moving the light collecting position Bf to the surface side of the single crystal substrate 20 am to be processed. Can be done. Therefore, the spherical aberration is corrected by controlling the correction ring with respect to the focusing position Bf (controlling the distance between the first lens 16 and the second lens 18), and the length K is 10 μm or less at each focusing position Bf. 22c of processing marks can be formed. By forming the processing marks 22c to 10 μm or less in this way, it is possible to prevent the processing marks 22c from extending or cracking in the crystal orientation of the crystal substrate 20a to be processed.

At the first condensing position Bf of the single crystal substrate 20am to be processed toward the back surface 20v (bottom surface) side, the processing layer 22 formed by irradiation with the laser beam B has cracks or ablation on the back surface 20v of the single crystal substrate 20am to be processed. Set within a predetermined range that does not cause unnecessary damage (particularly damage to the hollowed-out target portion 20b).

On the processing layer 22, processing marks 22c formed by condensing the laser beam B are regularly arranged at regular intervals. Regarding the interval for forming the processing marks 22c, the relationship between the oscillation repetition frequency of the laser beam B and the rotation speed (that is, peripheral speed) of the rotation stage 11 in the plane direction of the substrate (direction parallel to the irradiated surface 20u and the back surface 20v). In the substrate height (depth) direction, it is determined by the amount of movement of the condensing position Bf in the Z-axis direction. The processed layer 22 is irradiated with the laser beam B at predetermined intervals as described above, and is obtained as a region where the processed marks 22c are intermittently formed. At this time, the laser beam B is composed of, for example, a pulsed laser beam having a pulse width of 1 μs or less, and a wavelength of 300 nm or more is selected. For example, when the single crystal substrate 20 am to be processed is a silicon wafer, a YAG laser having a wavelength of 1000 nm or more or the like is selected. Is preferably used.

Then, in the vicinity of the irradiated surface 20u, in order to prevent the hollow crystal substrate from being chipped or cracked, it is necessary to form the processing marks 22c in a state where the processing marks 22c are not exposed on the substrate surface, that is, the substrate surface is not ablated by the laser beam B. is there. Therefore, while keeping the output of the laser beam B constant, the correction ring is adjusted so as to defocus the laser beam B at the condensing position Bf (the distance between the first lens 16 and the second lens 18 is adjusted). ..

After that, the user bends the processed layer-containing substrate 20c so that the back surface side expands, cracks are generated from the processing marks 22c in the vicinity of the back surface 20v side, and the adjacent processing marks are sequentially made continuous by the cracks to be hollowed out. 20b is separated from the processed layer-containing substrate 20c to obtain a hollowed out single crystal substrate 20d.

Here, in the present embodiment, at the first condensing position Bf of the single crystal substrate 20am to be processed toward the back surface 20v (bottom surface) side, the processing layer 22 formed by irradiation with the laser beam B is the single crystal substrate 20am to be processed. The back surface 20v is set to a position that does not cause unnecessary damage (particularly damage to the hollowed-out target portion 20b) due to cracks or ablation. Therefore, when the user bends the processed layer-containing substrate 20c so that the back surface side expands, it is possible to effectively suppress the occurrence of unnecessary cracks from the processing marks 22c on the back surface side and damage to the hollowed-out target portion 20b. Can be done.

Then, in the present embodiment, the output of the laser oscillator J is made constant, and the correction ring is adjusted so that the closer to the irradiated surface 20u, the closer to the irradiated surface 20u, the more the laser beam B is out of focus at the condensing position Bf ( The distance between the first lens 16 and the second lens 18 is adjusted). As a result, it is possible to suppress the extension of the processing marks 22c in the vicinity of the irradiated surface 20u and obtain a state in which the processing marks 22c are not exposed on the substrate surface. The adjustment of the correction ring can be arbitrarily selected to set the laser beam B to be out of focus with respect to the substrate thickness.

Therefore, in the processed layer portion near the irradiated surface 20u, unintended damage (cracks) and strain generated around the processed mark 22c are relatively small as compared with the other processed layer portions. Therefore, when the user generates cracks from the machining marks 22c near the back surface side and sequentially continues the adjacent machining marks with the cracks to hollow out the hollowed-out target portion 20b, the machining marks 22c are formed near the irradiated surface 20u. It is possible to significantly suppress the occurrence of unnecessary cracks and damage to the hollowed out single crystal substrate 20d.

Therefore, according to this embodiment, a hollowed-out single crystal substrate 20d without chipping can be easily obtained from the processing target single crystal substrate 20am in a short time. The outer peripheral surface of the obtained hollowed-out single crystal substrate 20d is subjected to processing such as polishing as necessary.

Here, the vicinity of the irradiated surface 20u is a portion near the irradiated surface where the manual hollowing work after the formation of the processed layer 22 can be performed without causing unnecessary chipping by such laser light irradiation. Specifically, it refers to a range of up to 100 μm from the surface to be irradiated (the surface of the substrate) to the inside, and further to a range of up to 50 μm from the surface of the substrate. It is necessary to form processing marks without causing ablation by defocusing the laser beam B by adjusting the correction ring in this range.

When the size of the single crystal substrate is larger than the size to be used, the single crystal substrate is set as the processing target single crystal substrate 20am in this way, and the hollowed out single crystal substrate 20d having a size smaller than the processing target single crystal substrate 20am is used. By obtaining it, the single crystal substrate 20 am to be processed can be reused, and resources can be effectively utilized.

Further, in the present embodiment, when the laser condensing means 12 and the back surface 20v of the single crystal substrate 20am to be processed are moved away from each other, they are moved in the same direction as the thickness direction of the substrate. Therefore, since the processed layer 22 is formed in a short cylindrical shape, the outer circumference of the obtained hollowed-out single crystal substrate 20d has a cylindrical outer peripheral shape, which is convenient. Here, in the present embodiment, in the vicinity of the irradiated surface 20u of the processed layer-containing substrate 20c, the correction ring is provided so as to defocus the laser light B at the condensing position Bf while keeping the output of the laser light B constant. By adjusting (adjusting the distance between the first lens 16 and the second lens 18), the processing marks 22c generated at the condensing position Bf are not extended along the crystal orientation of the single crystal substrate 20am to be processed. Is formed.

In addition, the first light-collecting position Bf of the single crystal substrate 20am to be processed toward the back surface 20v is a substrate thickness position within a predetermined range from the back surface 20v so as not to cause unnecessary damage to the back surface 20v due to cracks or ablation. Is set to. Therefore, even if the shape of the processed layer 22 is not made into a shape that is unlikely to cause chipping (for example, a tapered shape that spreads to the back surface side) and is simply made into a short cylinder, unnecessary cracks are significantly suppressed from the processing marks 22c. ing.

Further, in the present embodiment, in the second step, the output of the laser oscillator J is constant, that is, the output of the laser light incident on the laser condensing means 12 is constant. Therefore, the parameter change according to the movement of the condensing position Bf in the Z-axis direction is limited to the adjustment of the correction ring (adjustment of the aberration correction of the condensing lens 15), and is controlled by the aberration correction control means 13. It is possible to obtain these effects by. The adjustment state of the aberration correction by the aberration correction control means 13 is set to an appropriate value in consideration of the difficulty of generating unnecessary cracks at the time of hollowing out, the ease of forming the processed layer 22 and the like.

Further, the substrate processing apparatus 10 is a radial distance changing means for changing the distance r between the rotation center axis Cs of the rotation stage 11 and the irradiation center axis Cb of the laser beam B on the single crystal substrate 20am to be processed by the laser condensing means 12. It has. Therefore, the formation position of the processed layer 22 can be easily changed according to the radius of the hollowed-out target portion 20b.

Further, in the second step, as shown in FIG. 6, the length K in the substrate thickness direction of the processing marks 22c formed on the processing layer 22 by condensing the laser beam B is set to 10 μm or less. As a result, it is easy to sufficiently prevent cracks from extending in the cleavage direction of the single crystal substrate 20 am to be processed and becoming uncontrollable.

The output of the laser light B may be changed while changing the distance adjustment between the first lens 16 and the second lens 18, that is, the adjustment of the laser light B by the function as an aberration correction ring. As a result, the dimensions of the machining marks 22c and the strain around the machining marks 22c can be controlled more accurately.

Further, the aberration correction control means 13 is inside the processing target crystal substrate 20a and in the vicinity of at least one processing target crystal substrate surface (near the front surface (near the upper surface) or near the back surface (near the lower surface)), and the focusing position Bf of the laser beam B. Not only is the aberration correction of the laser condensing means 12 adjusted so that the processing marks 22c (see FIG. 6) generated in the processing target crystal substrate 20a do not extend along the crystal orientation of the processing target crystal substrate 20a, but also the crystal orientation of the processing target crystal substrate 20a. The aberration correction of the laser condensing means 12 may be adjusted so as not to stretch even if the crystal orientation is different from the above.

Here, the fact that the processing marks extend along a crystal orientation different from the crystal orientation of the crystal substrate to be processed means that, for example, when a single crystal silicon wafer having a crystal orientation [100] is used as the substrate material, the processing marks extend along the crystal orientation [100]. It is necessary to form the machining marks in the thickness direction of the substrate, but in single crystal silicon, the opening is likely to occur in the [111] and [110] directions where the bonding force is weaker, and the machining marks propagate along these crystal orientations. Say that. As a result, the hollowed-out cross section becomes uneven, and chips and cracks occur.

By adjusting the aberration correction of the laser condensing means 12 so that the processing marks 22c do not stretch even along a crystal orientation different from the crystal orientation of the crystal substrate 20a to be processed, defects such as chipping on the hollowed out single crystal substrate 20d occur. Can be more effectively prevented from occurring.

Further, in FIG. 4, the machined layer 22 is drawn so that the machined marks 22c are arranged in a single row, but in reality, the laser beam is applied so that the machined marks 22c are scattered over a plurality of rows in the machined layer 22. B may be irradiated. As a result, the work of hollowing out the hollowed-out target portion 20b from the processed layer-containing substrate 20c becomes easier.

Further, in the description of the substrate processing method according to the present embodiment, the example in which the single crystal substrate 20am to be processed is a single crystal substrate has been described, but the substrate processing method according to the present embodiment may be used even if the single crystal substrate is other than the single crystal substrate. Applicable.

Further, in the present embodiment, as a substrate processing method, an example of forming a processed layer-containing substrate 20c by using the substrate processing apparatus 10 of the present embodiment has been described, but another apparatus is used without using the substrate processing apparatus 10. Of course, it is also possible to manufacture the processed layer-containing substrate 20c.

<Experimental example 1>
According to one embodiment of the substrate processing method according to the above embodiment (hereinafter referred to as Example 1), the present inventor uses the substrate processing apparatus 10 of the above embodiment so that the length K in the substrate thickness direction is 10 μm or less. The aberration correction was adjusted so that the laser beam was focused on the single crystal substrate 20am to be processed to form the processing marks 22c.

Then, a cross section along the substrate thickness direction was imaged with an electron microscope. The image is shown in FIG. As can be seen from FIG. 7, it was found that in Example 1 in which the length of the machined mark 22c was 10 μm or less, the extending direction (advancing direction) of the machined mark 22c could be controlled.

Further, as an example for comparison (hereinafter referred to as Comparative Example 1), the present inventor focused the laser light on the single crystal substrate 20am to be processed without adjusting the aberration correction to form the processing marks 82c.

Then, a cross section along the substrate thickness direction was imaged with an electron microscope. The image is shown in FIG. As can be seen from FIG. 8, in Comparative Example 1, it was found that the extension direction (elongation direction) of the processing mark 82c could not be controlled, and the processing mark 82c was extended in a direction other than the substrate thickness direction.

<Experimental example 2>
The present inventor formed a processed layer 22 having a reduced breaking strength according to an embodiment of the substrate processing method according to the above embodiment (hereinafter referred to as Example 2) to obtain a processed layer-containing substrate 20c.

At that time, at the first condensing position Bf toward the back surface 20v (bottom surface) side of the processing target single crystal substrate 20am, the processing layer 22 formed by irradiation with the laser beam B cracks in the back surface 20v of the processing target single crystal substrate 20am. It was set within a predetermined range that does not cause unnecessary damage (particularly damage to the hollowed-out target portion 20b) due to ablation or the like, and was irradiated with the lower limit laser output at which the machining mark 22c is formed (see FIG. 9).

Then, by gradually moving the light collecting position Bf upward, the processed layer 22 having reduced breaking strength was formed on the outer peripheral side of the hollowed-out target portion 20b. Due to this movement, the distance from the irradiated surface 20u to the condensing position (distance in the substrate thickness direction) gradually becomes shorter, so that condensing becomes insufficient unless aberration correction is performed along with the movement (see FIG. 10). .. Therefore, by adjusting the aberration correction as in the above embodiment, the condensing position Bf is moved while sufficiently condensing the light, and the length K of the processing marks 22c in the substrate thickness direction is set to 10 μm or less and connected. Was irradiated with laser light (see FIG. 11).

Then, the hollowed-out target portion 20b was hollowed out, and the fracture surface was imaged with an electron microscope. The image is shown in FIG. As can be seen from FIG. 12, it was confirmed that the processing marks were well connected.

<Experimental example 3>
The present inventor has created a processed layer-containing substrate 20c by processing a single crystal substrate to be processed under the following conditions according to an embodiment of the substrate processing method according to the above embodiment (hereinafter referred to as Example 3). At that time, the condensing position Bf was set to a position from the irradiated surface 20u to 20 μm in the substrate thickness direction, and the laser beam was prevented from condensing at a position shallower than 20 μm from the irradiated surface 20u.
Objective lens: 100x single crystal substrate with correction ring function: single crystal silicon wafer, crystal orientation [100]
Laser oscillator: Wavelength 1064 nm, Fiber laser output (W): 0.6
Transmission frequency (kHz): 160
Pulse width (ns): 140
Dot pitch (μm): 2
Line pitch (μm): 2
Correction ring: 0.0 to 0.7

In this experimental example, the correction ring was adjusted as follows according to the focal position (processing position, the distance in the direction to the substrate pressure from the back surface 20v).
Focus position (μm) Correction ring
0-100 0.7
100-150 0.0
150-200 0.1
200-250 0.2
250-300 0.3
300-350 0.4
350-425 0.5
425-500 0.6
500-625 0.7

Then, the cross section in the vicinity of the processed layer 22 was imaged with an electron microscope. The image is shown in FIG. As can be seen from FIG. 13, in Example 3, no damage such as ablation occurred on the irradiated surface 20u near the processed layer 22. Therefore, when the hollowed-out target portion is hollowed out, it can be hollowed out without causing chipping.

After that, the hollowed-out target portion was hollowed out. FIG. 14 is a photographic diagram illustrating that the hollowed-out target portion is hollowed out from the processed layer-containing substrate obtained in Example 3. It was possible to hollow out the hollowed-out target part without chipping.

Further, as an example for comparison (hereinafter referred to as Comparative Example 2), the present inventor processed the substrate by moving the focusing position of the laser beam to the irradiated surface 20u. Then, the cross section near the processed layer was imaged with an electron microscope. The image is shown in FIG. As can be seen from FIG. 15, in Comparative Example 2, ablation occurred on the irradiated surface 20u near the processed layer. Therefore, chipping occurs when the hollowed-out target portion is hollowed out.

[Second Embodiment]
Next, the second embodiment will be described. FIG. 16 is a schematic side sectional view showing a processed layer-containing substrate manufactured by the substrate processing method according to the present embodiment. In the present embodiment, as in the first embodiment, an example in which the crystal substrate 20a to be processed is a single crystal substrate will be described.

In the present embodiment, as compared with the first embodiment, when the processing layer 22 is formed on the processing target single crystal substrate 20am in the second step, the back surface (bottom surface) side of the processing target single crystal substrate 20am is configured in the processing layer 22. In the processed layer back surface 22v, the distance r between the rotation center axis Cs of the rotating stage 11 and the irradiation central axis Cb of the laser condensing means 12 is gradually increased as the distance from the back surface 20v increases, and the distance r is gradually increased from the processing layer back surface 22v. This distance is constant on the irradiated surface 20u side (surface side) (see FIG. 16). Then, by gradually expanding in this way, the outer peripheral side of the back surface portion 22v of the processing layer is formed into an R-plane shape (cross-sectional arc shape) in which the diameter gradually increases as the distance from the back surface 20v of the single crystal substrate 20am to be processed increases. are doing. As a result, the processed layer back surface portion 22v has a chamfered shape having a radius N (that is, the portion of the hollowed out target portion 20b located on the inner peripheral side of the processed layer back surface portion 22v is also R-plane). The hollowed-out target portion 20b has a structure that can be easily broken from the back surface portion 22v of the processed layer.

As the substrate processing apparatus used in this embodiment, for example, the substrate processing apparatus 10 described in the first embodiment is used, and the distance r is gradually increased by the radial distance changing means (not shown). In this case, it is preferable that the control program for moving the rotary stage 11 in this way is input to the control means (CPU or the like) of the substrate processing apparatus in order to ensure accuracy and ease of processing.

In the present embodiment, by hollowing out the hollowed-out target portion 20b from the processed layer-containing substrate 20c, a hollowed-out single crystal substrate 20d having a radius N on the back surface side of the substrate can be easily obtained. Therefore, the chamfering work of the hollowed out single crystal substrate 20d can be eliminated or significantly reduced, and the handling of the hollowed out single crystal substrate 20d (wafer) becomes easy.

Further, when irradiating the laser beam in the second step, such a processed layer 22 is formed by connecting the processing marks one by one, so that the time required for forming the processed layer 22 is the first. The time can be suppressed to the same extent as that of the embodiment.

Further, as in the first embodiment, the aberration correction control means 13 has a processing mark 22c (FIG. 6) generated at the condensing position Bf of the laser beam B inside the crystal substrate 20a to be processed and near the surface of at least one crystal substrate to be processed. (See), but not only the aberration correction of the laser condensing means 12 is adjusted so as not to extend along the crystal orientation of the crystal substrate 20a to be processed, but also along a crystal orientation different from the crystal orientation of the crystal substrate 20a to be processed. The aberration correction of the laser condensing means 12 may be adjusted so as not to stretch. As a result, it is possible to more effectively prevent problems such as chipping from occurring in the hollowed out single crystal substrate 20d.

From the viewpoint of satisfactorily hollowing out the hollowed-out target portion 20b on the back surface portion 22v of the processed layer, it is important to connect the machining marks 22c in the radial direction of the hollowed-out target portion 20b (wafer) closer to the back surface 20v. As it approaches the irradiated surface side (surface side), it is important to gradually connect the processing marks 22c in the substrate thickness direction. Therefore, the line pitch of the processing mark 22c is narrowed toward the position closer to the back surface 20v, and the line pitch is gradually widened as it approaches the irradiated surface side (front surface side), so that the hollowed-out target portion 20b is further improved. It becomes possible to hollow out.

Further, in the present embodiment, the example in which the outer peripheral surface of the back surface portion 22v of the processed layer is formed in an R-plane shape has been described, but the portion to be hollowed out from the processed layer-containing substrate 20c is not limited to the R-plane shape but also has a curved convex surface shape. It is possible to easily hollow out 20b.

Further, the back surface portion 22v of the processed layer does not have such a shape, and the front surface portion of the processed layer forming the irradiated surface side (front surface side) of the single crystal substrate 20 am to be processed is formed on the back surface side of the processed layer. By forming the shape like the portion 22v, it is possible to obtain a hollow single crystal substrate 20d in which the surface side of the substrate has an R-plane shape with a radius N.

Further, in the description of the substrate processing method according to the present embodiment, the example in which the single crystal substrate 20am to be processed is a single crystal substrate has been described, but the substrate processing method according to the present embodiment may be used even if the single crystal substrate is other than the single crystal substrate. Applicable.

Since the present invention makes it possible to obtain a substrate having a size smaller than that from the crystal substrate to be processed, the thinly cut substrate is, for example, a single crystal substrate and a Si substrate (silicon substrate). It can be applied to solar cells, sapphire substrates such as GaN-based semiconductor devices can be applied to light-emitting diodes, laser diodes, etc., and SiC can be applied to SiC-based power devices, etc. , Transparent electronics field, lighting field, hybrid / electric vehicle field, etc.

10 Substrate processing device 11 Rotating stage 12 Laser condensing means 13 Aberration correction control means 15 Condensing lens 16 First lens 18 Second lens 20a Processing target single crystal substrate 20am Processing target single crystal substrate 20b Hollow target part 20c Processing layer-containing substrate 20d Hollowed single crystal substrate 20u Irradiated surface 20v Back surface (back surface of substrate)
22 Machining layer 22c Machining marks 22v Machining layer back surface (machining layer on one side of substrate)
B Laser light Bf Condensing position Cb Irradiation center axis Cs Rotation center axis E Outer circumference EP Condensing point K Substrate thickness direction Length L Distance M Central part MP Condensing point Su Stage surface r Distance

Claims (9)

The first step of arranging the laser condensing means capable of condensing the laser light and adjusting the aberration correction on the irradiated surface of the crystal substrate to be processed in a non-contact manner.
While condensing the laser light inside the crystal substrate to be processed by the laser condensing means, the condensing position of the laser light is changed in the peripheral direction and the thickness direction of the hollowed-out target portion of the crystal substrate to be processed, and the breaking strength is lowered. A second step of forming a processed layer on the outer peripheral side of the hollowed-out target portion to form a processed layer-containing substrate is provided.
In the second step, the processing marks generated at the condensing position of the laser beam are not stretched along the crystal orientation of the processing target crystal substrate inside the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface. Adjust the aberration correction of the laser focusing means ,
In the second step, the substrate processing method is characterized in that the closer the laser beam condensing position is to the irradiated surface, the larger the adjustment amount of the aberration correction of the laser condensing means. The substrate processing method according to claim 1, wherein the vicinity of the crystal substrate surface to be processed is the vicinity of the irradiated surface. In the second step,
Focus the laser beam on the substrate thickness position within a predetermined range from the back surface of the substrate, which is the surface opposite to the irradiated surface.
The substrate processing method according to claim 2, wherein the processed layer is formed by irradiating a laser beam while moving the laser condensing means away from the back surface of the substrate. The substrate processing method according to any one of claims 1 to 3 , wherein in the second step, the processed layer is formed into a short cylindrical shape. The substrate processing according to any one of claims 1 to 4 , wherein in the second step, the length of the processing marks formed by condensing laser light in the substrate thickness direction is 10 μm or less. Method. The substrate processing method according to any one of claims 1 to 5, wherein in the second step, the output of the laser light incident on the laser condensing means is kept constant. Of the processed layers, the outer peripheral side of the one side of the processed layer forming the single crystal substrate surface side to be processed is a curved convex surface whose diameter gradually increases as the distance from the one processed single crystal substrate surface increases. The substrate processing method according to any one of claims 1 to 6 , wherein the substrate is formed in a shape. A rotating stage that holds and rotates the placed crystal substrate to be processed,
A laser condensing means capable of condensing laser light toward the crystal substrate to be processed held on the rotating stage and adjusting the aberration correction of the laser light.
An irradiation axis direction distance changing means for changing the distance between the rotating stage and the laser condensing means,
Aberration correction control means that controls the adjustment of the aberration correction according to the distance, and
With
The aberration correction control means controls so that the processing marks generated at the laser light condensing position do not extend along the crystal orientation of the processing target crystal substrate inside the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface. And
The aberration correction control means is characterized in that the closer the laser light condensing position is to the irradiated surface of the crystal substrate to be processed, the larger the adjustment amount of the aberration correction of the laser condensing means is. Processing equipment. The substrate processing apparatus according to claim 8 , further comprising a radial distance changing means for changing the distance between the rotation center axis of the rotation stage and the irradiation center axis of the laser condensing means.

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