JP2011179998A - Method of inspecting crystal substrate - Google Patents

Abstract

The present invention relates to a method for inspecting a crystal substrate, and an object thereof is to shorten the time required for the crystal inspection process.
As a preparatory step, a first step of applying a resin solution to a crystal substrate, and as an inspection step, the crystal substrate on which the resin solution has been applied is fixed to an inspection device, and an inspection is performed. A crystal substrate comprising: a second step of removing from the inspection device; and a third step of removing the resin on the surface of the crystal substrate by immersing the crystal substrate removed from the inspection device in a resin removal solvent as a post-inspection step Inspection method.
[Selection] Figure 1

Description

  The present invention relates to a crystal substrate inspection method.

  Conventionally, crystal substrates have been inspected as follows.

  That is, as the inspection step, a second step of fixing the crystal substrate to the inspection device, inspecting the crystal substrate with the inspection device, and removing the crystal substrate from the inspection device, and a third step of polishing the removed crystal substrate, It was an inspection method with

  Prior literature on the substrate inspection method includes a method of fixing the conductive substrate to the inspection apparatus while monitoring the conductive state of the substrate so that an unnecessary stress is not applied to the substrate. (For example, a technique similar to this is described in Patent Document 1 below).

JP-A-2005-106606

  The problem in the conventional example is that the inspection takes time.

  That is, in the conventional example, the surface of the crystal substrate is often damaged when it is fixed to the inspection apparatus, and it is necessary to polish the surface of the crystal substrate as a post-process after removal from the inspection apparatus. This process takes a long time. For example, in a nitride crystal substrate, since one day is required, it takes time to perform a polishing process after inspection.

  Therefore, the object of the present invention is to shorten the inspection time.

  And in order to achieve this object, the present invention, as a preparatory step, a first step of applying a resin solution to the crystal substrate, and as an inspection step, the crystal substrate coated with the resin solution is fixed to an inspection device, A second step of performing inspection and then removing the crystal substrate from the inspection device, and a third step of removing the resin on the surface of the crystal substrate by immersing the crystal substrate removed from the inspection device in a resin removal solvent as a post-inspection step This process achieves the intended purpose.

  As described above, in the present invention, the first step of applying the resin solution to the crystal substrate as a preparation step, and the inspection step of fixing the crystal substrate to which the resin solution has been applied to the inspection apparatus, performing the inspection, A second step of removing the crystal substrate from the inspection device, and a third step of removing the resin on the surface of the crystal substrate by immersing the crystal substrate removed from the inspection device in a resin removal solvent as a post-inspection step. Since it is provided, the inspection time of the crystal substrate can be shortened.

  That is, in the present invention, before fixing to the inspection apparatus, the resin solution is applied to the surface of the crystal substrate to form a protective film, thereby preventing damage when fixing to the inspection apparatus, Since this protective film is later removed, a polishing process for removing scratches on the crystal substrate is not required after the inspection, and the inspection time can be greatly shortened.

Figure of single crystal substrate fixed to holder part of X-ray single crystal orientation measuring device Figure of resin application by spin coater Diagram showing the relationship between spin coater rotation speed and protective film thickness Diagram of X-ray single crystal orientation measuring device The figure which shows the holder part of a X-ray single crystal orientation measuring device Diagram showing the orientation evaluation part of a single crystal substrate The figure which shows the direction measurement result of the single crystal substrate

  Hereinafter, an embodiment in which an embodiment of the present invention is applied as a group III nitride crystal substrate inspection method as an example of a group III nitride crystal will be described with reference to the accompanying drawings.

  First, the first step of applying a resin solution to the crystal substrate will be described.

  A gallium nitride single crystal substrate is used as the crystal substrate 1, and this is fixed to the spin coater 3 by vacuum adsorption as shown in FIG. The resin solution 2 is dropped onto the fixed single crystal substrate 1 and rotated at a predetermined rotation speed, and the resin solution 2 is applied by a spin coating method. Further, the substrate was left on a heated hot plate, and the applied resin solution was dried and fixed.

  FIG. 3 shows the relationship between the rotation speed of the spin coater and the resin film thickness. As shown in FIG. 3, the spin coating method is an excellent method for forming a resin thin film on the substrate. However, the coating method is not limited to the spin coating method, and may be a vapor phase method such as a dip coating method, a spray coating method, or a vacuum deposition method. Among these, the dip coating method and the spray coating method are methods suitable for application to the orientation flat of the single crystal substrate 1, and are methods suitable for the embodiment of the present invention like the spin coating method.

In addition, the hardness (Hp) of the protective film such as resin used is lower than that of the single crystal substrate (H _S ) (Hp <H _S ). This is to prevent the substrate surface from being damaged by a protective film peeling piece or the like. The protective film is not limited to resin, and any low molecular or inorganic material can be used as long as it can protect the surface of the single crystal substrate 1.

  Next, as the inspection step, a second step will be described in which the crystal substrate coated with the resin solution is fixed to the inspection device, inspected, and then the crystal substrate is removed from the inspection device.

  FIG. 4 shows an X-ray single crystal orientation measuring apparatus. The apparatus in this embodiment includes a holder unit 7 that holds a single crystal substrate 1, an X generation unit 4 that irradiates the single crystal substrate 1 with X-rays, and an X-ray detection unit 5 that detects diffracted X-rays diffracted from the crystal. It has.

  Single crystal substrate 1 is sliced to a predetermined thickness after orientation flat is formed on a cylindrical gallium nitride ingot. The substrate is further subjected to a grinding process, a mechanical polishing process, and a CMP process, washed, and then coated with the resin.

  The holder portion 7 that holds the single crystal substrate 1 has a flat surface as shown in FIG. 5 and is made of a hard metal such as stainless steel in order to accurately measure the orientation of the single crystal. Further, a vacuum suction mechanism is provided on the surface of the board, and as shown in FIG. 1, the single crystal substrate 1 is fixed by this mechanism, and further, a substrate is applied by pressing a magnet or the like against the back surface of the single crystal substrate. Is fixed.

  Using the X-ray single crystal orientation measuring apparatus configured as described above, the deviation of crystal orientation in the plane direction (001) plane of the gallium nitride single crystal substrate with a protective film, that is, the off angle was evaluated.

  First, the (001) plane of the single crystal substrate 1 is fixed to the holder board surface 7 holding the single crystal substrate by vacuum suction. Further, a magnet was applied from the back surface of the single crystal substrate, and the single crystal substrate 1 was pressed against the holder portion to be firmly fixed.

  X-rays 6 irradiated from the X-ray generator 4 are incident on the (001) plane of the single crystal substrate 1, and the diffracted X-rays are detected by the X-ray detector 5. And the holder part 7 is rotated and the rotation angle when the intensity | strength of the diffraction X-ray detected by the X-ray detection part 5 becomes a peak is looked for. This was performed at a plurality of locations on the (001) plane of the single crystal substrate, and the in-plane distribution of off angles was evaluated.

  In order to investigate the influence of the protective film on the measured value, the off-angles when the protective film was provided on the single crystal substrate 1 (protective film thickness 5 μm) and without the protective film were evaluated. FIG. 7 shows the evaluation results. In addition, FIG. 6 is a figure which shows an evaluation site | part. As shown in FIG. 7, among the five measurement points, the angles are completely the same at (−15, 0) and (0, −15), and the difference between the measured values at the other three points is 0 to 0. A significant difference of 0.04 degrees was not observed, and it was confirmed that there was no influence on the measured value of the protective film.

  Conventionally, in the X-ray inspection for inspecting the surface of a substrate, the surface cannot be inspected unless the crystal material is exposed, or a measurement error occurs. The crystal surface was pressure bonded to perform measurement evaluation. If scratches occurred on the substrate surface during the process, the generated scratches were removed by repolishing. However, as described above, the protective film 10 is provided on the crystal surface with a resin or the like, and even when it is present, it is found that the X-ray inspection can be performed by controlling the protective film material and film thickness. It was possible to perform accurate X-ray inspection measurement as before while preventing the occurrence.

  In addition, this method is not only a gallium nitride substrate, and also does not require the conductivity of the substrate as in the conventional method (Japanese Patent Application Laid-Open No. 2005-106606). is there.

  Further, the protective film to be used is required to satisfy the following formula 1. This is to prevent X-ray absorption depending on the density and thickness of the protective film, so that it cannot be measured by being absorbed by the protective film. By satisfying the following formula 1, accurate X-ray evaluation is possible. It becomes.

0 <I ₀ exp (−μx / ρ) (Formula 1)
(Here, I ₀ is the X-ray initial intensity, μ is the linear absorption coefficient, x is the thickness of the protective film, and ρ is the density of the protective film.)
In the embodiment of the present invention, not only the planar direction such as the (001) plane but also a longitudinal section such as an orientation flat can be applied by applying the resin in the same manner.

  Next, as a post-inspection step, a third step of immersing the crystal substrate removed from the inspection apparatus in a resin removal solvent to remove the resin on the crystal substrate surface will be described.

  The gallium nitride single crystal substrate 1 removed from the inspection apparatus was loaded on a wafer tray, placed in an ultrasonic cleaner filled with an organic solvent, and subjected to ultrasonic cleaning for 10 minutes. Ultrasonic cleaning was performed several times while appropriately changing the organic solvent, and then the wafer tray was taken out and blown with nitrogen to dry the single crystal substrate 1.

  Note that the cleaning method is not limited to ultrasonic cleaning, and a stirring cleaning method in which the solvent is stirred in a state of being immersed in a solvent, a method of wiping with a cloth moistened with a solvent, dry etching, or the like can be used. Further, the solvent is not limited to an organic solvent, and an acid or alkali solvent can be used as long as it is a good solvent capable of removing the resin.

  Next, the single crystal substrate 1 from which the resin was removed was subjected to visual inspection and visual inspection using a metal microscope. The visual inspection was performed under an illuminance of 2000 lux, and the metal microscope inspection was performed with an observation magnification of 100 times. For the substrate coated with the resin, there was no damage to the substrate such as scratches and chipping. On the other hand, as a comparison, the same evaluation was performed on 20 substrates not coated with resin, and as a result, 16 scratches or damages such as chipping were observed.

  Further, when the above 16 sheets in which damage was observed were re-polished, it took 7 hours at the shortest, 30 hours at the longest, and 17 hours on the average of all 16 sheets until the damage was removed and returned to the initial mirror state. It cost. On the other hand, according to the method of the present invention, the resin solution coating process is completed for 10 minutes, the drying process is 5 minutes, and the resin removing process is 10 minutes in total. Furthermore, the method according to the embodiment of the present invention makes process management very easy because there is almost no lot-to-lot variation in processing time as in re-polishing.

  As described above, in the present invention, the first step of applying the resin solution to the crystal substrate as a preparation step, and the inspection step of fixing the crystal substrate to which the resin solution has been applied to the inspection apparatus, performing the inspection, A second step of removing the crystal substrate from the inspection device, and a third step of removing the resin on the surface of the crystal substrate by immersing the crystal substrate removed from the inspection device in a resin removal solvent as a post-inspection step. Since it is provided, the inspection time of the crystal substrate can be shortened.

  That is, in the present invention, before fixing to the inspection apparatus, by applying a resin solution to the surface of the crystal substrate and forming a protective film, it prevents damage when fixing to the inspection apparatus, Since the protective film is removed after the inspection, a polishing step for removing the scratches on the crystal substrate is not necessary after the inspection, so that the inspection time can be shortened.

  Therefore, for example, it is expected to be widely used as an inspection method for not only nitride crystal substrates but also crystal substrates.

DESCRIPTION OF SYMBOLS 1 Single crystal substrate 2 Resin solution 3 Spin coater 4 X-ray generation part 5 X-ray detection part 6 X-ray 7 Holder part 8 Through-hole for X-ray passage 9 Through-hole for vacuum adsorption 10 Protective film

Claims (7)

As a preparatory step, a first step of applying a resin solution to a crystal substrate;
As the inspection step, the crystal substrate coated with the resin solution is fixed to the inspection device, the inspection is performed, and then the crystal substrate is removed from the inspection device;
As a post-inspection step, a third step of immersing the crystal substrate removed from the inspection apparatus in a resin removal solvent to remove the resin on the surface of the crystal substrate, and a crystal substrate inspection method. The crystal substrate inspection method according to claim 1, further comprising a step of drying and solidifying a resin solution on the crystal substrate between the first step and the second step. The crystal substrate inspection method according to claim 1, wherein the coating method in the first step is a spin coating method. The crystal substrate inspection method according to claim 1, wherein the coating method in the first step is a dip coating method. The crystal substrate inspection method according to claim 1, wherein the coating method in the first step is a spray coating method. The crystal substrate inspection method according to claim 1, wherein the inspection apparatus in the second step is an X-ray inspection apparatus. The crystal substrate inspection method according to claim 1, wherein the crystal substrate is a nitride crystal substrate.

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