JP2015062946A - Marking method for monocrystal wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more efficient marking method, relating to a marking method for a monocrystal wafer which is transparent and does not absorb nitrogen visible light.SOLUTION: A marking method includes a step in which an ingot of a monocrystal semiconductor which is transparent to visible light is processed in cylindrical shape, a step in which marking is made with a constant interval along a direction running from an upper surface of the ingot toward a bottom surface, and a step in which the ingot is cut along a surface that faces the upper surface and the bottom surface, between the markings.

Description

  The present invention relates to a marking method for a single crystal wafer, and more particularly to a marking method for a transparent single crystal wafer that does not absorb visible light.

  Semiconductor wafers such as silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), and aluminum nitride (AlN) are marked with letters and symbols on part of the wafer to identify the crystal orientation and manufacturing lot. Marking may be performed.

  For example, for opaque wafers such as Si and GaAs, a YAG laser (λ = 1.06 μm) is used to mark characters and symbols on the wafer surface.

  However, in the case of a wafer transparent to visible light such as GaN and AlN, a YAG laser cannot be used. Therefore, in the marking method on the GaN wafer described in Patent Document 1, a 10 mm square, 420 μm thick GaN wafer is marked to a depth of 70 μm by irradiating a light beam having a wavelength of 400 nm or less or 5000 nm or more. .

JP 2003-209032 A

  However, in the method of marking for each wafer, it is very time-consuming because it is necessary to repeat the installation and removal of the wafer on the laser irradiation device while checking the crystal orientation and production lot of each wafer. .

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a marking method for marking a wafer more efficiently on a single crystal wafer transparent to visible light.

  The present invention relates to a method for marking a single crystal semiconductor wafer transparent to visible light, a step of processing an ingot of a single crystal semiconductor into a cylindrical shape, and a direction from the top surface to the bottom surface of the ingot processed into the cylindrical shape. The ingot is cut along a surface facing the top surface and the bottom surface between the marking of the marked ingot and the marking between the marking step and the marking of the marked ingot along the surface to form a wafer And a process.

  In the above invention, the marking may be to form a modified region using a femtosecond laser.

  In the above invention, a step of measuring a crystal orientation of the ingot may be further provided before the step of marking.

  The single crystal semiconductor may be an aluminum nitride single crystal.

  According to the present invention, since marking can be performed on a plurality of wafers at once by marking in an ingot state, the number of steps can be reduced compared to the case where marking is performed while placing each wafer on the apparatus. Marking can be performed. Thereby, marking on each wafer becomes more efficient.

It is a perspective view which shows an example of the single crystal semiconductor ingot processed into the column shape. It is the schematic of the apparatus which applies a femtosecond laser to the single crystal semiconductor ingot processed into the column shape, and performs marking. It is a side view which shows the state by which marking was given to the single crystal semiconductor ingot processed into the column shape. It is a top view which shows an example of the wafer to which marking was given.

  Hereinafter, an embodiment of a marking method according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a single crystal semiconductor ingot 1 processed into a cylindrical shape according to the present invention, FIG. 2 shows an apparatus 10 for marking the single crystal semiconductor ingot 1, and FIG. 3 shows a single crystal semiconductor to which marking has been applied. An ingot 1 is shown, and FIG. 4 shows a single crystal semiconductor wafer 4.

  The manufacturing method of the single crystal semiconductor ingot 1 shown in FIG. 1 is not particularly limited. First, a known method such as a Czochralski method or a sublimation recrystallization method (improved Rayleigh method) may be used for manufacturing a single crystal semiconductor. For example, if it is an AlN single crystal, it is preferable to prepare by a sublimation recrystallization method.

  Next, the single crystal semiconductor produced as described above is cut, polished, and processed into a cylindrical shape to obtain a single crystal semiconductor ingot 1. At this time, the top surface 1a (S1 surface) and the bottom surface 1b (S2 surface) of the columnar single crystal semiconductor ingot 1 are preferably processed in parallel and flat with each other in order to facilitate subsequent processes.

  FIG. 2 shows an apparatus 10 for marking a single crystal semiconductor ingot 1. The single crystal semiconductor ingot 1 processed into a cylindrical shape as described above is installed in the X-ray diffractometer while being fixed to the stage 14 with a goniometer. Next, X-ray diffraction is performed to detect the crystal orientation <0001> plane, and the goniometer-equipped stage 14 is driven so that the crystal orientation <0001> plane faces a specified direction. Further, the single crystal semiconductor ingot 1 is placed on the marking device 10 while being fixed to the stage 14 with a goniometer, and marking indicating the crystal orientation <0001> is performed.

  The marking device 10 includes a femtosecond laser generator 11 and an objective lens 13 that condenses the femtosecond laser 12 irradiated from the femtosecond laser generator 11 inside the single crystal semiconductor ingot 1. A stage 14 with a goniometer to which is fixed is installed in the apparatus.

The femtosecond laser 12 is a laser having a pulse width on the order of 10 ⁻¹³ seconds. When the femtosecond laser 12 is condensed inside a material transparent to the femtosecond laser 12 using the objective lens 13, Multiphoton absorption is caused only at the condensing point, which is the condensing position where the laser is condensed. Thereby, the transparent material is modified at the condensing point, and a modified region 2a is generated. The modified region 2a is a polycrystal and has a reduced transmittance. This modified region 2 a becomes the marking 2.

  As described above, the femtosecond laser 12 can freely move the condensing point by using the objective lens 13. Therefore, it is possible to mark any position of the single crystal semiconductor ingot 1.

For example, in FIG. 2, a femtosecond laser generator 11 is disposed at a position facing the S1 surface of a cylindrical single crystal semiconductor ingot 1, and an objective lens 13 is disposed therebetween. In such an arrangement, the marking 2 is applied while moving the condensing point of the femtosecond laser 12 from the S1 surface along the S2 surface direction. The markings 2 are preferably applied at equal intervals.
Further, the modified surface 3 a may be formed by condensing a laser also on a cut surface 3 to be described later and modifying the single crystal along the cut surface 3. By using the modified surface 3a, accurate cutting along the cut surface 3 is facilitated.

  FIG. 3 shows a cylindrical single crystal semiconductor ingot 1 provided with a marking 2. A surface facing the S1 surface and the S2 surface between the markings 2 of the single crystal semiconductor ingot 1 is a cut surface 3. The single crystal semiconductor ingot 1 is cut along the cut surface 3 at a constant interval, and becomes a single crystal semiconductor wafer 4 with the marking 2.

  The position of the marking 2 is provided in the center of the single crystal semiconductor wafer 4 with respect to the thickness direction. For example, the marking 2 may be marked on the surface.

  FIG. 4 shows a single crystal semiconductor wafer 4 provided with the marking 2. The position of the marking 2 may be an arbitrary position with respect to the surface direction. However, since the marking portion cannot be used as a product, it is preferable to mark the end of the wafer from the viewpoint of improving the yield of the product.

  Hereinafter, the present invention will be specifically described.

  First, an AlN single crystal prepared by a known technique such as a sublimation method is processed into a cylindrical single crystal semiconductor ingot 1 having a diameter of 100 mm and a thickness of 4 mm by cylindrical grinding.

  Next, the ingot 1 is installed in an X-ray diffractometer and the crystal orientation <0001> is detected.

  Furthermore, the said ingot 1 was installed in the marking apparatus 10, and the modified surface 3a was given along the marking 2 which shows a crystal orientation, and the cut surface 3. FIG. The femtosecond laser 12 used at this time is a titanium sapphire laser.

  As shown in FIG. 3, the marking 2 is a modified region 2a having a diameter of 20 μm, which is provided at a distance a of 250 μm in depth from the S1 surface of the single crystal semiconductor ingot 1. After the next marking 2, marking was performed in the same manner while moving the condensing point in the direction from the S1 surface toward the S2 surface so that the distance A between the markings 2 was 500 μm.

  As shown in FIG. 3, the modified surface 3a is a modified layer having a thickness of 10 μm applied to the surface facing the S1 surface and the S2 surface at a distance b of 250 μm from the marking 2. After the next modified surface 3a, the condensing point was moved in the direction from the S1 surface to the S2 surface so that the distance B between the modified layers was 500 μm. As described above, the modified surface 3 a is also the cut surface 3.

  Finally, the single crystal semiconductor ingot 1 is cut along the cut surface 3 to complete the single crystal semiconductor wafer 4 provided with the marking 2. A known technique can be used for cutting the single crystal semiconductor ingot 1. For example, there is a method of cutting using a diamond grindstone.

  The present invention relates to a method for producing a transparent single crystal wafer that does not absorb visible light, and it is possible to efficiently mark individual wafers with a crystal orientation mark.

  1 single crystal semiconductor ingot, 1a top surface (S1 surface), 1b bottom surface (S2 surface), 2 marking, 2a modified region, 3 cut surface, 3a modified surface, 4 single crystal semiconductor wafer, 10 marking device, 11 femtoseconds Laser generator, 12 femtosecond laser, 13 objective lens, 14 stage with goniometer.

Claims (4)

Processing a single crystal semiconductor ingot transparent to visible light into a cylindrical shape;
Marking at regular intervals along the direction from the top surface to the bottom surface of the ingot processed into the cylindrical shape;
Cutting the ingot between the marking of the marked ingot and the marking along a surface facing the top surface and the bottom surface to form a wafer;
A marking method for a single crystal semiconductor wafer, comprising:   The single-crystal semiconductor wafer marking method according to claim 1, wherein the marking is to form a modified region using a femtosecond laser.   3. The method for marking a single crystal semiconductor wafer according to claim 1, further comprising a step of measuring a crystal orientation of the ingot before the step of marking.   4. The marking method for a single crystal semiconductor wafer according to claim 1, wherein the single crystal semiconductor is an aluminum nitride single crystal.

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