JP2021141107A - Wafer surface reformer and method - Google Patents

Abstract

To repair or modify surface defects and waviness of wafers that have undergone mechanical processing such as surface polishing, as uniformly as possible even at the edges.SOLUTION: A wafer surface reformer includes: a table 10 which modifies the surface of a silicon wafer W cut and formed from an ingot and on which the wafer is placed and held; an alignment device 110 including at least a measuring device 114 for measuring the surface state of a wafer before reforming; a laser unit 30 that irradiates the surface of the wafer with a pulsed laser; and an optical system 40 that guides a laser beam 36 emitted from the laser unit to the irradiation position on the wafer surface. The alignment device changes the pulse energy amount of the laser light emitted by the laser unit according to the crystal orientation at a position in a circumferential direction of the wafer which has reached the irradiation position by rotating the table at the time of repairing the edge portion of the wafer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wafer surface reforming apparatus and method, and particularly relates to a wafer surface reforming apparatus and method suitable for use after processing the peripheral portion of a wafer.

For example, a single crystal silicon ingod produced by pulling up is sliced and cut by a diamond plate or the like so as to form a wafer having a predetermined thickness. After that, the surface is polished to smooth the surface, and the peripheral edge portion is subjected to processing such as a predetermined notch and corner chamfering or R processing. In these series of machining, minute waviness and crystal defects may occur on the wafer surface. Conventionally, chemical treatment such as etching or mechanical treatment such as mechanical polishing has been carried out in order to repair the waviness and crystal defects. These processing processes are complicated, and in the case of etching, surface polishing is substantially added to the wafer, which may impair the flatness.

Therefore, in the "method for repairing surface defects of a single crystal wafer" described in Patent Document 1, the processed altered layer generated by machining is repaired to a crystal structure exactly similar to that of the substrate portion without removing the material on the single crystal surface. I'm trying to do it. Specifically, when repairing a surface defect which is a surface processing alteration layer of a single crystal wafer used for a semiconductor, MEMS or an optical lens, the single crystal surface is irradiated with a pulse laser once.

Japanese Unexamined Patent Publication No. 2008-147639

Mutsuko Hatano et al., "Melting Si thin films by laser annealing, real-time observation of crystallization process and quality improvement of crystals", Surface Science, vol. 24, No. 6, 375-382 pages, 2003

As described in Patent Document 1, the surface of a silicon wafer manufactured by cutting and polishing by machining has minute waviness and the like, which can be reduced by irradiating a laser. The laser irradiation method has an advantage that the processing time and the processing cost can be reduced, and can be greatly expected to reform the wafer. By the way, the peripheral edge of the silicon wafer also has roughness, swell, processing damage, etc. in machining from the silicon ingod, and these are also subjected to laser irradiation to remove the roughness and swell, repair the processing damage, or It is considered possible to cause dislocations to a certain depth.

In the peripheral portion (edge portion) of the single crystal silicon wafer, the crystal orientation changes according to the circumferential position, unlike the flat surface portion of the silicon wafer in which the crystal orientation is constant. Therefore, the state of damage after processing may differ depending on the location. Further, as described in detail below, different crystal orientations have different irradiation effects even with the same amount of laser irradiation. As a result, even if an attempt is made to uniformly irradiate the peripheral portion where the crystal orientation differs from place to place with the same amount of laser or laser pulse to repair or modify the wafer, the desired effect is obtained depending on the location at the peripheral portion of the wafer. May not be obtained.

For example, when irradiating a wafer after etching with a pulse laser, the etching intensity (or velocity) differs depending on the crystal orientation. Even if an attempt is made to modify the wafer surface by irradiating such a non-uniform surface with a laser under constant irradiation conditions, the wafer surface after laser irradiation is treated uniformly due to differences in absorption rates and the like. It is difficult to repair. In the above-mentioned prior art, consideration of this point is insufficient.

The present invention has been made in view of the above-mentioned defects of the prior art, and an object of the present invention is to repair surface defects and waviness of a wafer subjected to mechanical processing such as surface polishing as uniformly as possible even at an edge portion. To or modify. Another object of the present invention is, in addition to the above object, to reduce the damage of the wafer due to the edge portion and to improve the yield in semiconductor manufacturing.

A feature of the present invention that achieves the above object is to modify the surface of a silicon wafer cut and formed from an ingot, and to measure the surface condition of the wafer on which the wafer is placed and held and the wafer before modification. Modification of the wafer surface including an alignment device including at least a measuring device, a laser unit that irradiates the surface of the wafer with a pulsed laser, and an optical system that guides the laser light emitted from the laser unit to the irradiation position on the wafer surface. In the apparatus, the alignment apparatus emits laser light from the laser unit according to the crystal orientation in the circumferential position of the wafer which has reached the irradiation position by rotating the table when the edge portion of the wafer is repaired. The purpose is to change the amount of pulse energy.

In this feature, the alignment device has the smallest pulse energy density at the position where the crystal orientation is (100) and the highest pulse energy density at the position where the crystal orientation is (110) in the circumferential position of the wafer that has reached the irradiation position. It is preferable to control the laser beam emitted from the laser unit. The pulse energy amount is a function of the pulse energy density, the pulse width, and the number of repetitions of the irradiation pulse.

In the above characteristics, the optical system has at least one of a laser spot diameter on the surface of the wafer when the laser is irradiated to the wafer, a pulse energy density, and a laser profile which is a time change of one pulse emitted by the pulse laser. It is desirable to control, and the laser unit controls at least one of the pulse energy, the pulse frequency of the pulsed laser to be repeatedly irradiated, and the number of times of irradiation of the pulse to be repeatedly irradiated to the same irradiation position.

Another feature of the present invention that achieves the above object is a method for surface-modifying a silicon wafer cut and formed from an ingot, from a step in which an alignment device measures the surface state of the wafer before reforming and a laser unit. The step of irradiating the irradiated surface of the wafer after surface polishing with the emitted pulsed laser to melt and modify the surface of the wafer is included, and the amount of energy of the pulsed laser irradiated on the surface of the wafer is calculated as described above. The purpose is to change the wafer according to the crystal orientation of the irradiation surface of the wafer.

In this feature, the amount of energy of the pulsed laser to be irradiated is preferably the maximum at the position where the crystal orientation is (110) and the minimum at the position where the crystal orientation is (100) in the same wafer, and is preferably the minimum in the same wafer. Further includes a step of irradiating the same crystal orientation position with a pulse laser having the same amount of energy and a step of measuring the surface texture of the wafer after the pulse laser irradiation, and the surface texture after the pulse laser irradiation at the same crystal orientation position. If there is a position that exceeds a predetermined permissible range, it is desirable to further include a step of performing feedback irradiation that irradiates the increased energy amount of the pulsed laser to the position exceeding the permissible range.

According to the present invention, the edge portion of the wafer is irradiated with a laser according to the crystal orientation at that location as well as the surface of the wafer that has been mechanically processed such as surface polishing. It becomes possible to repair or modify surface defects and waviness more uniformly. Further, since the chamfered or rounded edge portion is uniformly repaired or modified, the wafer damage caused by the edge portion can be reduced. Further, since the apparatus uses a laser irradiation apparatus, the restoration or reforming apparatus can be simplified as compared with the restoration or reforming apparatus used by a method such as etching or CMP without increasing the size of the restoration or reforming apparatus.

It is a figure explaining the crystal orientation of a semiconductor wafer. It is a front view of an example of the surface modification apparatus of the semiconductor wafer which concerns on this invention. It is a figure which shows an example of the optical system provided in the surface modification apparatus of FIG. It is a figure explaining a laser profile. It is a figure explaining the standard pulse laser light irradiation. It is a figure explaining the pulse laser light irradiation when the unacceptable result is obtained. It is a flowchart which shows an example of the surface modification method of a wafer.

Hereinafter, some examples of surface modification of the wafer W according to the present invention will be described with reference to the drawings. In the present invention, repairing the work-affected layer and internal damage by so-called laser annealing, smoothing the surface of the wafer W, and creating a dislocation layer on the surface layer of the wafer W are collectively referred to as surface modification. The original meaning of laser annealing is annealing using a laser. Applying laser annealing to the surface of the silicon wafer W means irradiating the surface of the silicon wafer W with a pulsed laser in the present invention, whereby the surface layer of the wafer W is melted. The cooling action after melting promotes the growth of epitaxial crystals toward the surface to achieve single crystallization, and the work-altered layer and internal damage are repaired. In surface smoothing, irradiating a silicon wafer W with a pulse laser to melt the surface layer of the wafer W is the same as repairing a work-affected layer and internal damage. However, when the surface layer is melted, the surface is smoothed by the action of surface tension to remove roughness and waviness, which is particularly referred to as surface smoothing. Further, in creating a dislocation layer on the surface layer of the wafer W, an event generated by continuously irradiating the same portion with a pulse laser is used. That is, by repeatedly irradiating the surface of the wafer W with a pulse laser and repeating heating and cooling on the surface of the wafer W, a smooth and constant-depth dislocation layer is created.

Here, the present inventors have found through experimental research that it is necessary to consider the crystal orientation when performing laser annealing on the surface of the wafer W. In particular, in a single crystal wafer, the surface portion or the flat portion on which the semiconductor circuit is formed has the same crystal orientation everywhere, but the crystal orientation does not show a single orientation at the peripheral portion (edge portion). When manufacturing a semiconductor from a wafer W, it is necessary to uniformly surface-modify the edge portion of the wafer W in order to prevent cleavage from occurring and progressing from the edge portion and reducing the yield of semiconductor manufacturing. For that purpose, it is necessary to grasp the crystal orientation of the edge portion.

The physical characteristics of the wafer W and the time required for surface treatment of the wafer W change depending on the crystal orientation. For example, when the crystal orientations (110), (100), and (111) are compared, in epitaxial growth, the crystal orientation (110) has the fastest growth, the orientation (100) is next, and the orientation (111) has the fastest growth. Slows down. In the case of the etching treatment, the progress of erosion is the same result, and the crystal orientation (110) is the most eroded, the orientation (100) is next, and the orientation (111) is the least eroded. Regarding the cleavage from each crystal orientation, unlike these cases, the crystal orientation (111) is the easiest to cleavage, the orientation (110) is next to this, and the orientation (100) is the most difficult to cleavage. As described above, since the wafer W has different characteristics depending on the crystal orientation, when laser annealing is applied to the silicon wafer W, the pulse laser takes into consideration the state of the irradiation surface, specifically, the crystal orientation, especially at the edge portion. It turned out that it had to be irradiated.

FIG. 1 shows an example of the semiconductor wafer W. FIG. 1A is a top view of a single crystal silicon wafer W in which a notch N, which is a reference point of a notch shape, is formed, and FIG. 1B is an enlarged front view of an edge portion. FIG. 1A also shows the crystal orientations at the main points. Since the wafer W is a single crystal silicon wafer, the crystal orientation is (100) on the flat circuit forming surface on which the semiconductor circuit is to be formed. At this time, for example, if the crystal orientation of the edge portion is (100) in the anti-notch portion AN on the opposite side of the notch portion N and the notch portion N by 180 °, the position orthogonal to the line connecting these positions, That is, the crystal orientation is (100) even when the circumferential angle φ with respect to the notch portion N is φ = 90 ° and 270 °. However, at the intermediate position, that is, at the positions of φ = 45 °, 135 °, 225 °, and 315 °, the crystal orientation changes to (110). From the above-mentioned characteristics of the crystal orientation, when the edge portion of the wafer W is uniformly irradiated with a laser over the entire circumference, for example, cleavage from an oblique direction (direction of the crystal orientation (110)) is likely to occur, or cleavage is likely to occur. Causes a decrease in yield in semiconductor manufacturing. As shown in FIG. 1B, in the wafer W in this embodiment, the outer diameter end portion of the wafer W, and the vicinity of the wafer end face 53, is oblique in order to suppress the occurrence of cracks and the like. A chamfered portion 52 is formed. In the processing of the end face 53 of the wafer W, in addition to the chamfer 52, R processing that avoids the formation of corners may be used. The end surface 53 substantially perpendicular to the circuit forming surface 51 of the wafer W and the chamfered surface 52 in the vicinity of the end surface 53 are collectively referred to as an edge portion 55.

Before forming a semiconductor circuit on the circuit forming surface 51 of the wafer W, and after mechanical processing such as surface polishing, the wafer W is irradiated with a laser in order to uniformly modify the edge portion 55 as well. At that time, the irradiation amount of the pulse laser used in the laser annealing and the like are changed according to the crystal orientation of each irradiation portion of the wafer W. An example of surface modification of the edge 55 of the wafer W will be described with reference to FIGS. 2 and 3.

FIG. 2 is a diagram showing an example of a reformer 100 that applies the laser annealing according to the present invention to the single crystal silicon wafer W, and is a front view thereof. The reformer 100 includes a 5-axis stage 20 having a turntable 10 on which and holds the wafer W. The wafer W is, for example, a 12-inch wafer, and its surface has already been polished. The turntable 10 has a degree of freedom of the θ axis and is used to rotate the wafer W and irradiate the laser. For example, in reforming the edge portion of the wafer W, the turntable 10 is rotated to continuously change the reforming position of the edge portion of the wafer W mounted on the turntable 10, and pulse laser light is irradiated to the modified position. .. The stage 20 is orthogonal to the X-axis that moves the wafer W in the left-right direction of the figure, the Y-axis that moves the wafer W in the direction that penetrates the paper surface, and is orthogonal to both the X-axis and the Y-axis. In addition to the three orthogonal axes of the Z axis that move the wafer W in the vertical direction, B and C that can be inclined according to the shape of the two chamfered portions 55 formed at the corners of both the front and back sides of the edge portion 55 of the wafer W. Equipped with a shaft. Since the stage 20 has an X-axis, a Y-axis, a Z-axis, a B-axis, a C-axis, and a θ-axis, the laser irradiator described later can be used regardless of the shape of the wafer W, particularly the shape of the edge portion 55. It can be arranged on the irradiation surface at an appropriate angle, and the laser beam 36 can be appropriately and continuously irradiated to the irradiation surface at a desired modification position.

The laser unit 30 is a device for irradiating the reformed position of the wafer W with a pulsed laser, and is a device for irradiating the modified position of the wafer W with a pulsed laser. Alternatively, it has a control unit 34 that controls at least one of the number of repetitions and the like. The laser light source 32 can emit pulsed laser light 36 having wavelengths of 355, 532, and 785 nm. These wavelengths used in the reformer 100 take into consideration the absorption rate of the silicon wafer W, and a wavelength having a high absorption rate is selected. The wavelength of the laser beam 36 is not limited to these, and can be changed according to the material of the wafer and the like. Further, only one or two of the above may be emitted.

The controlled pulsed laser beam 36 emitted from the laser unit 30 is irradiated to the wafer W to be irradiated via the optical system 40. The optical system 40 has a controllable axis between the pulsed laser light source 32 and the wafer W so that an appropriate focal length can be secured and adjusted. A typical example of the optical system 40 is shown in FIG.

FIG. 3 is a schematic layout diagram of the optical system 40. As shown in the figure, the optical system 40 has several prisms 42 and 43, a galvano mirror 44, and an f-θ lens 46 as a condenser lens. In the optical system 40, at least one of the laser spot diameter φd of the pulsed laser beam 36 at the modified position, the pulse energy density J, and the laser profile PL showing the time-varying shape of the pulse energy density J is controlled or adjusted.

An example of the laser profile PL is taken from Non-Patent Document 1 and shown in FIG. The vertical axis of FIG. 4 indicates the energy intensity, and is represented by the specific intensity which is the ratio of the energy intensity of the pulse laser to the reference amount. In the example of FIG. 4, one pulse is about 40 ns, and it rises rapidly with the passage of time, reaches a peak, and then gradually decreases. At the reforming position of the wafer W via the optical system 40, at least one of the pulse energy density J, the laser irradiation time, and the spot diameter φd becomes an appropriate irradiation laser beam 36, which is desired to be reformed. The area is illuminated.

The reformer 100 further includes an alignment device 110 for inspecting the surface of the wafer W before and / or after laser irradiation. The alignment device 110 uses a camera to measure the surface condition such as the waviness and roughness of the alignment unit 112, which arranges the wafer W to be reformed in the center of the stage 20, and / or the dedicated roughness. It is provided with a measuring unit 114 for measuring with a measuring machine or the like, and a control calculation unit 116 represented by a personal computer for controlling the alignment of the wafer W using a camera and controlling and calculating the surface texture measurement of the wafer W.

The camera is also used to determine the crystal orientation of each point on the edge portion 55 of the wafer W. For example, when the notch N is formed on the wafer W, if the positional deviation of the reference crystal orientation (for example, the orientation (100)) from the notch N is known in advance, the notch N is used as a reference (for example, a circumferential angle). Using the angular coordinates φ with φ = 0 °), the crystal orientation at each circumferential position φ is determined from the position of the notch N in the image captured by the camera. Here, it is not always necessary to use a camera to determine the crystal orientation, and an X-ray crystal orientation measuring device dedicated to crystal orientation measurement may be included inside or outside the reforming device 100. After the crystal orientation is specified using the measuring device for measuring the crystal orientation or the camera of the measuring unit 114, the wafer W is irradiated with the pulse laser based on the result of specifying the crystal orientation, so that the alignment unit 112 is on the wafer W. It has the ability to identify the laser irradiation position of the wafer with sufficient accuracy.

In the alignment device 110, before and after irradiating the pulse laser on the W surface of the wafer, the measuring unit 114 measures, observes, and analyzes the surface state, and feeds back to the laser irradiation conditions based on the analysis result. At that time, optimization is performed for each phase, and the pulse intensity, irradiation time, and irradiation laser profile PL according to the crystal orientation are reconstructed.

A specific example of reforming at the edge portion of the wafer W using the reformer 100 shown in FIG. 2 will be described below with reference to FIG. FIG. 5 shows an example of pulse irradiation with a pulse energy J set in advance according to the crystal orientation. The distribution of the crystal orientation in the circumferential direction of each wafer W has already been measured using the alignment device 110 or in a pretreatment step. In this example, the crystal orientation of the notch N (φ = 0 °), which is the reference of the position of the wafer W, is (100), and the positions of φ = 90 °, 180 °, and 270 ° clockwise from the notch N are also crystallized. The orientation is (100). Further, the crystal orientation is (110) at the positions of φ = 45 °, 135 °, 225 °, and 315 ° clockwise from the notch N. As described above, in the crystal orientation (110), erosion is larger due to etching than in the crystal orientation (100), surface defects are expected to be large, and it is easy to open the crystal orientation. The energy intensity is increased to Jmax at 110), the energy intensity is decreased to Jmin at the crystal orientation (100), and the pulse energy intensity of the laser beam 36 is changed by a curve distribution connected by a sine curve during that time.

With such a setting, the edge portion 55 of the wafer W is pulsed with the laser beam 36. The influence of the pulse laser irradiation on the modification is influenced not only by the pulse energy density J but also by the pulse width, the number of repetitions of the irradiation pulse, the repetition frequency, the spot diameter, and the like. Therefore, in this embodiment, only the pulse energy density irradiates the pulse laser in the circumferential direction of the wafer W with the pulse energy density distribution shown in FIG. 5, but the pulse width, the repetition frequency of the irradiation pulse, and the spot diameter are kept constant. .. With this setting, the irradiation position of the edge portion of the wafer W is a function of the amount of pulse energy (pulse energy density, pulse width, and number of repetitions) that changes according to the circumferential position φ of the wafer W. Will be the product of) is added. Of course, it is also possible to change the pulse width and the number of repetitions or the repetition frequency.

The vicinity of the surface of the wafer W is thermally affected by the repeated cooling and heat transfer to the inside of the wafer W, which occurs during the time when the laser beam 36 is not irradiated due to the heating by the laser beam 36 and the intermittent irradiation. In consideration of these relationships, the pulse width and the number of repetitions or the repetition frequency are set to be constant or variable.

After that, whether or not the desired annealing (surface modification) has been applied to the irradiation position is measured using the alignment device 110. The measurement items are waviness and roughness of the irradiated surface of the wafer W, surface defects, and the like. If the waviness and roughness of the surface of the wafer W are within a predetermined range, the same treatment is performed on the other wafer W. If the surface roughness and waviness of the wafer W are not within a predetermined allowable range, the pulse energy intensity is corrected and laser irradiation is performed again.

In the measurement using the alignment device 110, the roughness and waviness at each irradiation position in the circumferential direction are measured by a camera or a dedicated measuring device. Of course, the measurement may be performed continuously with respect to the circumferential position of the wafer W, or only the position φ having a crystal orientation whose crystal orientation is significantly different from the reference orientation, for example (100), may be measured. It is also possible to improve the throughput of measurement. As can be seen from the pulse energy intensity change diagram shown in FIG. 5, since the approximate value of the pulse energy amount to be changed depending on the crystal orientation is obtained by actual measurement in advance, it is approximated from the measurement results at the positions φ of a plurality of different crystal orientations. The change in irradiation conditions can be determined by referring to the value.

By the way, even if the laser beam 36 having the same pulse energy amount is irradiated to different circumferential positions having the same crystal orientation for the same time, there may be a position where the restoration is sufficient and a point where the restoration is insufficient. In such a case, it is necessary to change the irradiation amount of the pulse laser to the position where the repair is insufficient. Such an example will be described with reference to FIG.

FIG. 6 is a diagram for explaining a method of changing the pulse energy intensity by feeding back the measurement result, and FIG. 6A shows the laser beam 36 according to the circumferential position φ of the wafer W similar to FIG. It is a figure of the pulse energy distribution, and FIG. 6B is a schematic diagram which shows the state of measuring the reforming state of each part of a wafer W.

As shown in FIG. 6B, the camera is irradiated with a pulse laser at points A (φ = 45 °) and B (φ = 135 °) in the circumferential direction of the wafer W having both crystal orientations (110). or signals _S a to measure the surface state in a dedicated measuring instrument 114, _{S B} is obtained and sent to the alignment device 110. In FIG. 6B, two cameras are drawn for easy understanding, but in reality, the wafer W is rotated to take an image when the laser irradiation position comes to the camera position, so only one camera is required. It is enough. Results of the determination of the alignment apparatus 110, but the signal S _A is within the tolerable range, the signal S _B was greater than the allowable range. In this case, with respect to the position B where the signal S _B outside the permissible range is obtained, a correction to change the intensity. Since the relationship between the pulse energy intensity and the change in the laser irradiation surface of the wafer W has been obtained in advance, the required correction amount is determined using this relationship. In this embodiment, the modification was insufficient at the position B where the crystal orientation (110) is φ = 135 °, so the energy intensity is corrected and laser irradiation is performed on this portion.

That is, in the surface modification of the wafer W rotated around the θ-axis using the turntable 10, the pulse energy amount of the laser beam 36 is synchronized with the arrival of the position B exceeding the permissible range at the laser irradiation position. Is increased from the pulse energy amount Jmax assigned to the crystal orientation (110) to Jfb. Here, the irradiation of the pulsed laser with the corrected energy intensity is not limited to the point of φ = 135 °, which is the crystal orientation (110), but also the time before and after that in the rotating wafer W, and the circumferential direction in the wafer W. A pulse laser with an irradiation energy increased by a correction amount according to the position is also irradiated to both side portions. The irradiation range of this increased pulse laser is represented by Zfb in FIG. 6 (b). On the other hand, even if the crystal orientation is the same (110), the pulse energy remains Jmax at the position A and the position φ = 225 ° other positions where the measurement result satisfies the predetermined reference, and at the other positions φ, the pulse energy remains Jmax. The reference irradiation pattern shown in FIG. 5 is repeated.

By changing the irradiation energy of the laser beam 36 according to the circumferential position φ of the wafer W in addition to the crystal orientation in this way, more uniform modification of the surface of the wafer W can be realized. The change diagram of the pulse energy density shown in FIGS. 5 and 6A is a diagram showing the relationship between the circumferential angular position φ of the wafer W and the irradiation energy, and the laser beam 36 actually irradiated is a pulse laser. Therefore, it is irradiated at time intervals. The time change of the output of the laser irradiation light 36 intermittently traces the curve shown in FIG.

A flowchart of the surface modification method for the wafer W is shown in FIG. The waviness and roughness of each part of the surface of the wafer W are measured in advance with a dedicated measuring machine or a camera or the like provided in the alignment device 110 of the surface reforming device 100, and the circumferential position φ and crystal orientation of the wafer W are measured. And their data are associated (step S710). With reference to the relationship between the crystal orientation of the wafer W obtained in advance and the amount of energy of the pulsed laser to be irradiated, the pulse energy corresponding to the circumferential position φ of the wafer W at which the turntable 10 rotates to reach the irradiation position. Find the amount. At the same time, the frequency of the laser beam to be used and the like are also determined (step S720). The control unit 34 of the laser unit 30 irradiates the irradiation surface of the wafer W from the laser light source 32 via the optical system 40 with the irradiation amount required for the irradiation position (step S730). The surface of the wafer W after pulse laser irradiation is measured and inspected by using a measuring device including a camera or the like included in the alignment device 110 or a dedicated measuring machine (step S740). The measurement result is determined (step S750). If the measured values at all the circumferential positions of the wafer W are within the permissible range, the reforming of the wafer W is completed (step S760). Then, the next measurement of the wafer W is started. When a measurement value outside the permissible range is obtained at the measurement position φ in the circumferential direction of the wafer W, the process returns to step S720, and the energy amount of the pulsed laser to be irradiated is based on the previously obtained data at the place where the energy amount is out of the permissible range. Perform pulsed laser irradiation with varying feedback. Hereinafter, the same procedure is repeated.

As described above, according to each embodiment of the present invention, in the modification of the edge portion of the single crystal wafer W, the intensity and the amount of energy of the pulse laser used for the modification are determined according to the crystal orientation of each point of the edge portion. Since it is changed, it is possible to deal with different surface textures depending on the crystal orientation. In addition, since the amount of energy is applied according to different surface textures, it is possible to sufficiently modify the point where cleavage is likely to occur, and it is possible to reduce the growth of cleavage and cracks from the edge portion due to the difference in crystal orientation.

10 ... turntable, 20 ... stage, 30 ... laser unit, 32 ... laser light source, 34 ... control unit, 36 ... laser light, 40 ... optical system, 42, 43 ... prism, 44 ... galvano mirror, 46 ... f-θ Lens, 51 ... Circuit forming surface, 52 ... Chamfered part, 53 ... End face, 55 ... Edge part or edge, 100 ... (Surface) modifier, 110 ... Alignment device, 112 ... Alignment part, 114 ... Measuring part, 116 ... Control computing device (personal computer), AN ... anti-notch part, N ... notch part, W ... wafer, φ ... (wafer) circumferential angle

Claims (8)

An alignment device that modifies the surface of a silicon wafer cut and formed from an ingot, including at least a table on which the wafer is placed and held, and a measuring device that measures the surface condition of the wafer before reforming, and a wafer. In a wafer surface reforming device provided with a laser unit that irradiates the surface of the wafer with a pulsed laser and an optical system that guides the laser light emitted from the laser unit to the irradiation position on the wafer surface.
The alignment device rotates the table and reaches the irradiation position at the time of repairing the edge portion of the wafer. A wafer surface reforming device characterized by changing the number of wafers. In the alignment device, the laser unit irradiates the lowest pulse energy density at the position where the crystal orientation is (100) and the highest pulse energy density at the position where the crystal orientation is (110) in the circumferential position of the wafer that has reached the irradiation position. The wafer surface reforming apparatus according to claim 1, wherein the laser beam is controlled. The wafer surface reforming apparatus according to claim 1 or 2, wherein the pulse energy amount is a function of the pulse energy density, the pulse width, and the number of repetitions of the irradiation pulse. The optical system is characterized by controlling at least one of a laser spot diameter, a pulse energy density, and a laser profile, which is a time change of one pulse emitted by the pulse laser, when irradiating the wafer with the laser. The wafer surface reforming apparatus according to any one of claims 1 to 3. The laser unit according to any one of claims 1 to 4, wherein the laser unit controls at least one of the pulse energy, the pulse frequency of the pulsed laser to be repeatedly irradiated, and the number of times of irradiation of the pulse to be repeatedly irradiated to the same irradiation position. The wafer surface reformer according to. A method for surface modification of silicon wafers cut and formed from ingots.
The step of measuring the surface condition of the wafer before reforming by the alignment device and the step of irradiating the irradiated surface of the wafer after surface polishing with a pulse laser emitted from the laser unit to melt and reform the surface of the wafer. A method for modifying a wafer surface, which comprises changing the amount of energy of a pulsed laser irradiated on the surface of a wafer according to the crystal orientation of the irradiated surface of the wafer. The method for modifying a wafer surface according to claim 6, wherein the amount of energy of the pulsed laser to be irradiated is large at the position where the crystal orientation is (110) and small at the position where the crystal orientation is (100) in the same wafer. .. A step of irradiating the same wafer with a pulse laser having the same amount of energy at the same crystal orientation position and a step of measuring the surface texture of the wafer after the pulse laser irradiation are further included, and the pulse laser irradiation at the same crystal orientation position is further included. When there is a position where the surface texture later exceeds a predetermined allowable range, it is characterized by adding a step of executing feedback irradiation for irradiating the increased energy amount of the pulsed laser to the position exceeding the allowable range. The method for modifying a wafer surface according to claim 7.

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