Patent ID: 12191213

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described in detail below referring to the drawings. The present invention is not to be limited by the contents described in the following embodiment. In addition, the constituent elements described below include those which can easily be conceived by a person skilled in the art and those which are substantially the same. Further, the configurations described below can be combined appropriately. Besides, various kinds of omissions, replacement, or modifications of the configuration can be performed in such ranges as not to depart from the gist of the present invention.

An inspection method according to an embodiment of the present invention will be described on the basis of the drawings.FIG.1is a perspective view of a wafer divided into chips, the wafer being an object to be inspected by the inspection method according to the embodiment.FIG.2is a flow chart depicting the flow of the inspection method according to the embodiment.

(Wafer)

The inspection method according to the embodiment is an inspection method for the wafer1depicted inFIG.1. The wafer1as an object to be inspected by the inspection method according to the embodiment is, for example, a disk-shaped semiconductor wafer or optical device wafer using silicon, sapphire, gallium arsenide, silicon carbide (SiC), or the like as a substrate2. The wafer1is a disk-shaped wafer and has a front surface3and a back surface4positioned opposite the front surface3, the front surface3and the back surface4being parallel to each other. The wafer1has a plurality of intersecting streets5set on the front surface3, and devices6are formed in respective regions partitioned in grid form by the streets5.

In the embodiment, the device6is, for example, an integrated circuit such as an integrated circuit (IC) or a large scale integration (LSI) circuit, or any of various memories (semiconductor storage devices). In addition, in the embodiment, the device6has an electrode (not illustrated) for being electrically connected to an electrode of a substrate on which the device6is mounted, or to an electrode of another device6. The electrodes of the devices6are manufactured by the same manufacturing method as conductor patterns constituting the integrated circuits or various memories, and are formed to be flat.

In addition, the wafer1is divided along the streets5into chips7which are individual divided pieces. In other words, the wafer1has division grooves8which penetrate the wafer1itself and are formed between the chips7. Note that the chip7includes a part of the substrate2and the device6, and has the front surface3, the back surface4, and a plurality of side surfaces continuous with the front surface3and the back surface4. Note that parts of the wafer1and the chip7which are the same are denoted by the same reference character in description. The side surfaces of the chip7are also inner surfaces of the division grooves8.

In the embodiment, the wafer1is divided into the chips7by applying a laser beam to the wafer1along the streets5to form modified layers therein and breaking the wafer1with the modified layers as starting points. However, in the present invention, ablation processing may be conducted by applying a laser beam of such a wavelength as to be absorbed by the substrate2to the wafer1along the streets5, or cutting may be conducted by making a cutting blade cut into the wafer1along the streets5, and after grooves are formed along the streets5by the ablation processing or the cutting, grinding may be applied to the back surface4to divide the wafer1into individual chips7.

Note that the modified layer means a region in which density, a refractive index, mechanical strength, or other physical property is different from that in the surroundings, and examples of such a region include a melting treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and a region in which these regions are mixedly present. The modified layer is lower in mechanical strength than the other part in the substrate2.

The back surface4of the wafer1is attached to a disk-shaped tape21with an annular frame20attached to an outer edge part of the tape21, and the wafer1is supported in an opening22inside the annular frame20. Note that the outside diameter of the tape21and the inner diameter of the annular frame20are greater than the outside diameter of the wafer1. When the wafer1is divided into individual chips7, particles10(depicted inFIG.7and the like) are produced. Besides, the wafer1has a mark9indicating the crystal orientation. In the embodiment, the mark9is a notch formed by cutting out the outer edge of the wafer1in reverse V shape, but the mark9is not limited to the notch in the present invention.

In addition, in the embodiment, the wafer1is divided into the individual chips7, but the wafer may be divided into at least two pieces in the present invention. In this case, the wafer1may not be formed with the devices6on the front surface3thereof.

(Inspection Method)

The inspection method according to the embodiment is an inspection method for counting the number of particles adhering to the wafer1. The inspection method is used, for example, for selecting processing conditions where a reduced number of particles are produced, for example, at the time of selection of processing conditions for dividing the wafer1into individual chips7. As depicted inFIG.2, the inspection method according to the embodiment includes a wafer lamination step101, a particle transfer step102, and an inspection step103.

(Wafer Lamination Step)

FIG.3is a perspective view schematically depicting the wafer lamination step of the inspection method depicted inFIG.2. The wafer lamination step101is a step of stacking a transfer wafer11on top of the wafer1that has been divided into a plurality of chips7.

In the wafer lamination step101, the transfer wafer11is stacked on the front surface3of the wafer1as depicted inFIG.3. Note that the transfer wafer11is a wafer for which the number of adhering particles is controlled, such as a prime wafer or a wafer having an oxide film formed thereon. In the embodiment, the transfer wafer11is a prime wafer which has a front surface13and a back surface14positioned opposite the front surface13and which is formed in a disk shape using silicon, sapphire, gallium arsenide, SiC, or the like as a substrate12.

In the embodiment, the outside diameter of the transfer wafer11is equal to the outside diameter of the wafer1. The transfer wafer11has a mark19indicating the crystal orientation. In the embodiment, the mark19is a notch formed by cutting out the outer edge of the transfer wafer11in reverse V shape; however, in the present invention, the mark19is not limited to the notch. In the embodiment, the mark19of the transfer wafer11is the same in shape as the mark9of the wafer1.

In the embodiment, in the wafer lamination step101, the front surface13of the transfer wafer11is placed on the front surface3of the wafer1, with the marks9and19of the wafer1and the transfer wafer11as references. In the embodiment, in the wafer lamination step101, the wafer1and the transfer wafer11are arranged to match the marks9and19with each other.

(Particle Transfer Step)

FIG.4is a side view schematically depicting, partly in section, the particle transfer step of the inspection method depicted inFIG.2.FIG.5is a side view schematically depicting, partly in section, a modification of the particle transfer step of the inspection method depicted inFIG.2. The particle transfer step102is a step of, after the wafer lamination step101is carried out, positioning the transfer wafer11on a lower side and the wafer1on an upper side and applying a vibration to the wafer1stacked on the transfer wafer11, to drop the particles adhering to the side surfaces of the chips7onto the transfer wafer11.

In the embodiment, in the particle transfer step102, the wafer1is mounted on a holding surface32of a chuck table31of a transfer device30through the transfer wafer11, as depicted inFIG.4. In other words, the transfer wafer11, which is stacked on top of the wafer1in the wafer lamination step101, is mounted on the holding surface32of the chuck table31of the transfer device30, and the wafer1is positioned on an upper side of the transfer wafer11.

In the particle transfer step102, the transfer device30holds the transfer wafer11under suction on the holding surface32of the chuck table31, and the annular frame20is clamped between clamp parts33in the periphery of the chuck table31. In the particle transfer step102, the transfer device30vibrates the chuck table31in a direction34parallel to the holding surface32for a predetermined period of time, and vibrates the chuck table31also in a direction35orthogonal to the holding surface32for a predetermined period of time. In the particle transfer step102, the transfer device30drops and transfers the particles10adhering to the front surface3of the wafer1onto the front surface13of the transfer wafer11, and also drops and transfers the particles10adhering to the side surfaces of the individually divided chips7of the wafer1onto the front surface13of the transfer wafer11.

In addition, in the present invention, in the particle transfer step102, the wafer1may be mounted on a holding surface32of a chuck table31of a transfer device30-1through the transfer wafer11, and the annular frame20may be mounted on a mount surface36flush with the holding surface32, as depicted inFIG.5. In this case, the transfer device30-1holds the transfer wafer11under suction on the holding surface32of the chuck table31.

In the present invention, in the particle transfer step102, the transfer device30-1lays a disk-shaped vibration applying member37, the diameter of which is greater than the outside diameter of the wafer1but smaller than the inside diameter of the annular frame20, on the back surface4of the wafer1through the tape21. In the present invention, in the particle transfer step102, the transfer device30-1applies electric power to an ultrasonic vibrator38inside the vibration applying member37for a predetermined period of time, thereby putting the ultrasonic vibrator38into an ultrasonic vibration (vibration at a frequency equivalent to the frequency of an ultrasonic wave). In the present invention, in the particle transfer step102, the transfer device30-1may drop and transfer the particles10adhering to the front surface3of the wafer1onto the front surface13of the transfer wafer11, and may also drop and transfer the particles10adhering to the side surfaces of the individually divided chips7of the wafer1onto the front surface13of the transfer wafer11.

(Inspection Step)

FIG.6is a plan view schematically depicting the inspection step of the inspection method depicted inFIG.2.FIG.7is a plan view schematically depicting the transfer wafer in the inspection step of the inspection method depicted inFIG.2. The inspection step103is a step of inspecting the particles10on the transfer wafer11, after the particle transfer step102is carried out.

In the embodiment, in the inspection step103, the wafer1and the transfer wafer11stacked on top of each other are separated into the wafer1depicted inFIG.6and the transfer wafer11depicted inFIG.7. In the transfer wafer11depicted inFIG.7, the particles10dropped from the side surfaces of each chip7, that is, the inner surfaces of the division grooves8, adhere to the front surface13, so that the particles10adhere to the front surface13at positions corresponding to the division grooves8.

In the embodiment, in the inspection step103, by use of a known particle counter, the position and size of each particle10on the front surface13of the transfer wafer11are detected, and the total number (corresponding to the number) of the particles10on the front surface13of the transfer wafer11is counted. Thus, in the embodiment, in the inspection step103, the positions, the total number, and the size of the particles10on the front surface13of the transfer wafer11are inspected; however, in the present invention, it may suffice to inspect any of the positions, the total number, and the size of the particles10.

In the embodiment, the position of the particle10detected in the inspection step103is defined by a distance in an X-axis direction and a distance in a Y-axis direction from the mark19of the transfer wafer11, with the mark19as a reference position. Note that, in the embodiment, the X-axis direction is a direction parallel to the streets5extending in one direction among the streets5in a grid pattern, and the Y-axis direction is a direction parallel to the streets5extending in the other direction.

In addition, inFIG.7, the particles10dropped from the side surfaces of each chip7, that is, the inner surfaces of the division grooves8, onto the front surface13of the transfer wafer11are illustrated, and other particles10are omitted. Thus, in the inspection step103, the position of the particle10is defined with the mark19of the transfer wafer11as a reference.

In the inspection method according to the embodiment described above, the transfer wafer11is stacked on top of the divided wafer1in the wafer lamination step101, and a vibration is applied to the divided wafer1in a state in which the transfer wafer11is positioned on a lower side in the particle transfer step102. Therefore, in the inspection method according to the embodiment, the particles10adhering to the side surfaces of the chips7can be dropped onto the transfer wafer11, so that the particles10on the divided wafer1can be transferred onto the transfer wafer11.

Therefore, the inspection method according to the embodiment can evaluate the particles10having been adhering to the side surfaces of the chips7, by inspecting the particles10on the front surface13of the transfer wafer11in the inspection step103. As a result, the inspection method according to the embodiment produces an effect that it is possible to inspect the side surfaces of the chips7of the divided wafer1.

Next, the inventor of the present invention checked the effect of the inspection method according to the embodiment.FIG.8is a plan view of the wafer for which the number of particles has been counted in checking the effect of the inspection method according to the embodiment.FIG.9is a plan view of the transfer wafer onto which the particles on the wafer depicted inFIG.8have been transferred by the inspection method according to the embodiment. Note that the marks9and19are omitted inFIGS.8and9.

In checking the effect, by use of a known particle counter, the position and size of each particle10on the front surface3of the wafer1divided into the chips7depicted inFIG.8were detected, and the total number (corresponding to the number) of the particles10on the front surface3of the wafer1was counted. Next, the wafer lamination step101and the particle transfer step102of the inspection method according to the embodiment were carried out, and the particles10on the wafer1depicted inFIG.8were transferred onto the front surface13of the transfer wafer11depicted inFIG.9. By use of a known particle counter, the position and size of each particle10on the front surface13of the transfer wafer11depicted inFIG.9were detected, and the total number (corresponding to the number) of the particles10on the front surface13of the transfer wafer11was counted.

On the front surface13of the transfer wafer11depicted inFIG.9, the particles10adhered along the division grooves8of the wafer1depicted inFIG.8. Therefore, according to the transfer wafer11depicted inFIG.9, it has been made clear that the particles10adhering to the inner surfaces of the division grooves8, that is, the side surfaces of the chips7, can be transferred onto the transfer wafer11by stacking the transfer wafer11on top of the divided wafer1in the wafer lamination step101and applying a vibration to the divided wafer1in a state in which the transfer wafer11is positioned on a lower side in the particle transfer step102. Thus, it has been made clear that the side surfaces of the chips7of the divided wafer1can be inspected.

The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.