Measurement systems and measurement methods

A measurement system is provided to measure a hole of a target, including a light source generation unit, a capturing unit and a processing unit. The light source generation unit generates a light source and focuses the light source on a plurality of different height planes. The capturing unit captures a plurality of images scattered from the plurality of different height planes. The processing unit obtains boundaries of the hole on the plurality of different height planes according to the plurality of images, samples image intensities of different azimuth angles on the boundaries of the hole on each of the plurality of different height planes to generate a plurality of sampling values, and develops a sidewall image of the hole according to the plurality of sampling values, the plurality of different height planes and the different azimuth angles.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwan Patent Application No. 101134870, filed on Sep. 24, 2012, the entirety of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The disclosure relates to measurement systems and measurement methods, and relates to a measurement system for measuring the boundary of a hole.

2. Description of the Related Art

Fabrication of 3D ICs via stacking has increased due to development and demand for more advanced and complex ICs. One type of IC packaging staking method is through-silicon via. The yield rates of ICs are affected by the accuracy of measuring through-silicon vias.

However, through-silicon vias have a high depth-width ratio. Thus, depth and sidewalls thereof cannot be measured by an optical microscope. Therefore, a measurement system and a measurement method for measurement by an optical microscope are needed.

SUMMARY

An embodiment of a measurement system to measure a hole of a substrate is provided, and the measurement system comprises a light source generation unit, a capturing unit and a processing unit. The light source generation unit is used to generate a light source and focus the light source, respectively, on a plurality of different height planes of a hole, along a height axis direction of the hole. The capturing unit captures a plurality of images scattered by the plurality of different height planes. The processing unit obtains boundaries of the hole on the plurality of different height planes according to the plurality of images thereby sampling image intensities of different azimuth angles on the boundaries of the hole on each of the plurality of different height planes to generate a plurality of sampling values, and developing a sidewall image of the hole according to the plurality of sampling values, heights of the plurality of different height planes and the different azimuth angles.

An embodiment of a measurement method to measure a hole of a substrate is provided, the measurement method comprises focusing a light source, respectively, on a plurality of different height planes of a hole, along a height axis direction of the hole, capturing a plurality of images scattered by the plurality of different height planes, obtaining boundaries of the hole on the plurality of different height planes according to the plurality of images, sampling image intensities of different azimuth angles on the boundaries of the hole on each of the plurality of different height planes to generate a plurality of sampling values, and developing a sidewall image of the hole according to the plurality of sampling values, heights of the plurality of different height planes and the different azimuth angles.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims.

FIG. 1is the schematic diagram of a measurement system in accordance with an exemplary embodiment. Referring toFIG. 1, the measurement system100includes a light source generation unit110, a capturing unit120and a processing unit130. Specifically, each point of the sidewall of a hole can be expressed by the cylindrical system and written in the form of (R, θ, Z). The light source generation unit110is arranged to generate a light source, and to respectively focus the light source on a plurality different height of planes (such as planes PZ1˜PZ4) of a hole, along the height axis direction (also called z axis) of the hole HL. The capturing unit120captures a plurality of images (as shown inFIG. 2) scattered from the plurality of different height planes PZ1˜PZ4. The processing unit130is arranged to sample image intensities of different azimuth angles on boundaries of the hole on each of the plurality of different height planes, thereby generating a plurality of sampling values and developing a sidewall image of the hole HL according to the plurality of sampling values and heights of the plurality of different height planes and the different azimuth angles. In some embodiments, the capturing unit120and the processing unit130can be arranged within the light source generation unit110, but, the disclosure is not limited thereto.

FIG. 2is the schematic diagram of an image of a hole received by the measurement system in accordance with an exemplary embodiment. Referring toFIG. 2, when the light source is focused on planes PZ1, PZ2, PZ3and PZ4of the plurality of different heights Z1, Z2, Z3and Z4, the plurality of images I1, I2, I3and I4are respectively obtained. To further explain, circle B1, B2, B3and B4are boundaries of the hole on the plurality of different height planes PZ1, PZ2, PZ3and PZ4. The magnification ratio of the plurality of different height planes PZ1˜PZ4are

Therefore, when the light source is focused on the plurality of different height planes PZ1, the change in image intensity of the circle B1increases in sensitivity. For example, the image intensity outside of the circle B1is very weak, but the image intensity within the circle B1is strong. Therefore, the boundary of the hole can be determined by the variations of the image intensity of the radical coordinate. Similarly, when the light source is focused on the plane PZ2, circle B2can be determined as the boundary of the hole of the plane PZ2from the image I2. When the light source is focused on the plane PZ3, circle B3can be determined as the boundary of the hole of the plane PZ3from the image I3. When the light source is focused on the plane PZ4, circle B4can be determined as the boundary of the hole of the plane PZ4from the image I4.

FIG. 4is a schematic diagram of the relation between the image intensity and radial in accordance with an exemplary embodiment. As shown inFIG. 4, an intensity curve is along the radial coordinate r at a predetermined azimuth angle θ1. The intensity curve CV1is differentiated by the radial coordinate to obtain the differential curve CV2. The processing unit130obtains a radial point R1according to the maximum limit value of the differential curve CV2and obtains the mean value VA1of the image intensity in the region between R1+δ and R1−δ, and regards the mean value VA1of the radial point R1as the plurality of sampling values (image intensity) of the coordinate (R1, θ1, Z2). Referring toFIG. 2again, in other words, the closed curve composed of the radial points at the azimuth angles can be regarded as the boundary of the hole in accordance with the plane PZ2.

FIG. 5is a measurement system in accordance with another exemplary embodiment. Referring toFIG. 5, the measurement system500includes a light source generation unit510, a capturing unit520, a processing unit530and a platform540. In the embodiment of the present disclosure, the light source generation unit510can be a dark field optical microscope. A light source is transmitted through a ring mirror511to a ring condenser lens512, and through the ring condenser512to a target550. The light scattered by the target550is transmitted through the objectives513to the capturing unit520, but the light transmitted to the capturing unit520doesn't include the mirror reflected light transmitted to the target550. The dark field device is different from the bright field device. Instead of observing illuminated light directly, the dark field device observes the scattered light from the target. Therefore, the viewing field is a dark background, but the target displays a bright image. The dark microscope is suitable for observing a figure and profile of tiny structures which can not be observed by the bright microscope. In the embodiment of the present disclosure, the target550is placed on the platform540. By fixing the focal length and moving the platform540along the height axis direction of a hole, the light source can focus on the plurality of different heights of the hole.

FIG. 6is a schematic diagram of the relation between the image intensity and height in accordance with an exemplary embodiment. Referring toFIG. 6, the horizontal axis is the height Z, and the vertical axis is the standardized image intensity. When fixing the azimuth angle and the radial length, the image intensity changes corresponding to the focus positions (height). By observation, it can be realized that there are periodical notches and bumps on the boundary of the hole.

FIG. 7is the sidewall image of a hole in accordance with an exemplary embodiment.FIG. 8AandFIG. 8Bare sidewall images of a hole obtained by a scanning electron microscope. Referring toFIG. 7, the horizontal axis is the azimuth angle θ, and the vertical axis is the height Z. The sidewall image of the hole HL inFIG. 7is developed according to the plurality of sampling values and the corresponding height Z and the azimuth angle θ. By observation, it can be realized that the sidewall of the hole has a scallop-type structure which is the same as that shown inFIGS. 8A and 8B.

FIG. 9is a flowchart of a measurement method in accordance with an exemplary embodiment. Referring toFIG. 9, the measurement method includes the following steps.

In step S91, the light source is focused, respectively, on a plurality of different height planes (such as planes PZ1˜PZ4) of a hole, along the height axis direction (also called z axis) of the hole HL. In step S92, a plurality of images scattered by the plurality of different height planes are captured. In step S93, boundaries of the hole on the plurality of different height planes are obtained according to the plurality of images. In step S94, image intensities of different azimuth angles on boundaries of the hole on each of the plurality of different height planes are sampled to generate a plurality of sampling values. In step S95, a sidewall image of the hole HL is developed according to the plurality of sampling values and heights of the plurality of different height and the different azimuth angles.