TW201822289A - Method of thickness measurement - Google Patents

Abstract

The present invention provides a thickness measurement method. the method comprises providing a sample to be measured, wherein the sample has a first side and a second side; measuring the initial thickness dl of the sample; forming a first material layer on the first side, and forming a redundant layer on the second side, wherein the thickness of the redundant layer is smaller than 0.3 [mu]m; measuring the thickness d2 of the first material layer; measuring the final thickness d3 of the sample; and calculating the thickness of the redundant layer [Delta]d=d3-d2-d1. Compared with traditional method, the present invention can easily measure the thickness of the redundant layer, to save the time, manpower and cost, and therefore increase the throughput.

Description

   Measurement methods   

The present invention relates to the field of semiconductor technology processes, and in particular, to a measurement method.

For example, in the semiconductor processing and production process, the lithography process is a key factor that restricts product quality. Whether accurate lithography can be performed is very important.

However, the uniformity of the silicon wafer thickness directly affects the lithography process.

As shown in FIG. 1, an epitaxial layer is usually formed on the front surface of the silicon wafer 1. This process may be placing the silicon wafer 1 on the base 2. However, the silicon wafer 1 often slips and thus tilts. As a result, the reactive gas for the epitaxial layer can invade under the silicon wafer 1 from the staggered gap 3, and then an additional epitaxial layer 4 is formed on the back of the silicon wafer 1, and the epitaxial layer 4 is basically not Homogeneous, which can affect the lithography process.

In addition, there are other forms of redundant epitaxial layers with uneven thickness on the silicon wafer. For example, for polished silicon wafers, there is usually a thin layer of oxide film on the surface. When hydrogen treatment is performed on one side, pinholes are often formed on the other side, resulting in epitaxial growth in the pinholes, which will also affect the silicon wafer. Uniformity of thickness.

However, the thickness of these unwanted extra epitaxial layers is usually very thin, and it is difficult to directly detect their specific thickness.

Currently, there are multiple methods for detection. For example, U.S. Patent Publication No. US8409349B2 discloses the following method: 1. providing a silicon wafer; 2. forming an auxiliary layer on the back surface of the silicon wafer; 3. measuring the thickness of the auxiliary layer; 4. epitaxially forming on the front surface of the silicon wafer At this time, an additional extra epitaxial layer will be formed on the auxiliary layer; 5. The thickness of the auxiliary layer is measured again; 6. The thickness difference between the two measurements is the additional extra epitaxial layer thickness.

However, this process is cumbersome and requires the formation of a specialized auxiliary layer, which is costly.

In view of this, there is currently a need for a new measurement method to improve the above disadvantages.

An object of the present invention is to provide a measurement method that can simply and quickly measure the thickness of a film layer formed incidentally.

In order to solve the above technical problem, the present invention provides a measurement method, including: providing a product to be processed, the product to be processed having a first surface and a second surface opposite to each other; measuring an initial thickness d1 of the product to be processed; A first material layer is formed on the first surface, and a redundant material layer is formed on the second surface, and the thickness of the redundant material layer is less than 0.3 μm; the thickness d2 of the first material layer is measured; The final thickness d3 of the product to be processed; the thickness Δd = d3-d2-d1 of the redundant material layer is calculated.

Optionally, for the measurement method, the double-sided flatness detection method is used to obtain the initial thickness and the final thickness.

Optionally, for the measurement method, FTIR is used to obtain the thickness of the first material layer.

Optionally, for the measurement method, multiple points are selected on the product to be processed for each thickness measurement.

Optionally, for the measurement method, 13 points are selected and arranged in a cross.

Optionally, for the measurement method, the distance between adjacent points is the same.

Optionally, for the measurement method, the product to be processed is a silicon wafer.

Optionally, for the measurement method, the first material layer is an epitaxial layer.

The measurement method provided by the present invention includes providing a product to be processed, the product to be processed having first and second sides opposite to each other; measuring an initial thickness d1 of the product to be processed; and forming a first on the first surface Material layer, at the same time, a redundant material layer is formed on the second surface, and the thickness of the redundant material layer is less than 0.3 μm; the thickness d2 of the first material layer is measured; the final thickness of the product to be processed is measured d3; calculating the thickness of the redundant material layer Δd = d3-d2-d1. Therefore, compared with the prior art, the thickness of the excess material layer formed by simple and rapid measurement can be achieved, greatly optimizing the measurement process, saving time, manpower and material resources, and contributing to efficient production.

     Component label description     

1‧‧‧ silicon

2‧‧‧ base

3‧‧‧ gap

4‧‧‧ Super Yu Lei Crystal Layer

10‧‧‧ Products to be processed

11‧‧‧First material layer

12‧‧‧ redundant material layer

20‧‧‧Double-sided flatness detection device

FIG. 1 is a schematic diagram when an epitaxial layer is formed on a silicon wafer; FIG. 2 is a flowchart of a measurement method according to an embodiment of the present invention; and FIG. 3 is a schematic diagram of a product to be processed according to an embodiment of the present invention; FIG. 4 is a schematic diagram of a position for measuring an initial thickness of the product to be processed in an embodiment of the present invention; FIG. 5 is a schematic diagram of a first material layer formed in an embodiment of the present invention; and FIG. 6 is an embodiment of the present invention FIG. 7 to FIG. 8 are schematic diagrams of measuring the final thickness of the product to be processed in an embodiment of the present invention.

The measurement method of the present invention will be described in more detail below with reference to the schematic diagrams, which show the preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving the advantageous effects of the invention. Therefore, the following description should be understood as widely known to those skilled in the art, and not as a limitation on the present invention.

The invention is described in more detail by way of example in the following paragraphs with reference to the drawings. The advantages and features of the invention will be apparent from the following description and claims. It should be noted that the drawings are in a very simplified form and all use inaccurate proportions, which are only used to facilitate and clearly assist the description of the embodiments of the present invention.

Referring to FIG. 2, FIG. 2 is a flowchart of a measurement method provided by the present invention. The measurement method of the present invention includes the following steps: Step S11, providing a product to be processed, the product to be processed has a first surface and a second surface opposite to each other. Step S12, the initial thickness d1 of the product to be processed is measured; Step S13, a first material layer is formed on the first surface, and a redundant material layer is formed on the second surface, and the redundant The thickness of the material layer is less than 0.3 μm; step S14, the thickness d2 of the first material layer is measured; step S15, the final thickness d3 of the product to be processed is measured; step S16, the thickness of the redundant material layer Δd is calculated = d3-d2-d1.

In order to explain the measurement method of FIG. 2 in more detail, please refer to FIGS. 3 to 8 for detailed description.

As shown in FIG. 3, step S11 is performed to provide a product 10 to be processed, which has a first surface and a second surface opposite to each other. In the embodiment of the present invention, the sub-processed product 10 may be silicon The wafer is, for example, a polished wafer. Of course, it can also be other wafers, or even other products, such as glass substrates and metal materials.

Please continue to refer to FIG. 3 and execute step S12 to measure the initial thickness d1 of the product 10 to be processed. In combination with FIG. 4, in order to obtain better measurement results, multi-point measurement may be performed on the product 10 to be processed. In an embodiment of the present invention, the number of selected points is 13, specifically, as shown in the distribution manner in FIG. 4, these 13 points are arranged in a cross, that is, they can be distributed in the XOY coordinate system and adjacent points The spacing between them is the same, for example, the spacing may be 30mm-50mm. The specific number of points and intervals, and the arrangement method can be determined by actual needs, for example, they can also be arranged in a "meter" shape. Appropriate number of points can ensure the accuracy of thickness measurement, and at the same time avoid too long measurement time. Considering that the subsequent redundant material layer is thin, in order to make the final result more accurate, the initial thickness d1 is obtained by using a double-sided flatness detection method.

Referring to FIG. 5, step S13 is performed to form a first material layer 11 on the first surface, and a redundant material layer 12 is formed on the second surface. The thickness of the redundant material layer 12 is less than 0.3 μm; taking the to-be-processed product 10 as a silicon wafer in the embodiment of the present invention as an example, the first material layer 11 may be an epitaxial layer and may be obtained by epitaxial growth, for example, the thickness may be 1 μm to 50 μm. As shown in FIG. 5, the formation of the redundant material layer 12 causes the thickness of the product 10 to be processed to be uneven. And because the thickness of the redundant material layer 12 is thin, it is not easy to measure.

Referring to FIG. 6, step S14 is performed to measure the thickness d2 of the first material layer 11. The thickness d2 of the first material layer 11 can be obtained by a Fourier Transform Infrared Spectroscopy (FTIR). Further, taking the selection of 13 points in the embodiment of the present invention as an example, the measurement in this step is still performed at the position of the previous 13 points.

Referring to FIG. 7 to FIG. 8, step S15 is performed to measure the final thickness d3 of the product 10 to be processed. In this embodiment, the double-sided flatness detection method is also used to obtain the final thickness d3. As shown in FIG. 8, the double-sided flatness detection device 20 obtains the final shape of the product 10 to be processed through interference, thereby further obtaining a final thickness d3. Further, taking the selection of 13 points in the embodiment of the present invention as an example, the measurement in this step is still performed at the position of the previous 13 points. Through this step, specific thickness data can be accurately obtained.

It can be understood that the order of step S14 and step S15 in the above steps can be reversed.

Finally, step S16 is executed to calculate the thickness Δd = d3-d2-d1 of the redundant material layer.

Through actual experimental verification, the thickness Δd of the redundant material layer obtained by the above method of the present invention is accurate and effective. After processing based on the obtained data, the accuracy of the lithography process can be effectively improved.

In summary, the measurement method provided by the present invention includes providing a product to be processed, the product to be processed having a first surface and a second surface opposite to each other; measuring an initial thickness d1 of the product to be processed; A first material layer is formed on the surface, and a redundant material layer is formed on the second surface, and the thickness of the redundant material layer is less than 0.3 μm; the thickness d2 of the first material layer is measured; The final thickness d3 of the processed product; the thickness Δd = d3-d2-d1 of the redundant material layer is calculated. Therefore, compared with the prior art, the thickness of the excess material layer formed by simple and rapid measurement can be achieved, greatly optimizing the measurement process, saving time, manpower and material resources, and contributing to efficient production.

Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (8)

    A measuring method includes: providing a product to be processed, the product to be processed having a first surface and a second surface opposite to each other; measuring an initial thickness d1 of the product to be processed; and forming a first material layer on the first surface At the same time, a redundant material layer is formed on the second surface, and the thickness of the redundant material layer is less than 0.3 μm; the thickness d2 of the first material layer is measured; the final thickness d3 of the product to be processed is measured; Calculate the thickness Δd = d3-d2-d1 of the redundant material layer.         The measurement method according to claim 1, wherein the initial thickness and the final thickness are obtained using a double-sided flatness detection method.         The measurement method according to claim 1, wherein the thickness of the first material layer is obtained by FTIR.         The measuring method according to claim 1, wherein a plurality of points are selected on the product to be processed for each thickness measurement.         The measuring method according to claim 4, wherein 13 points are selected for each thickness measurement, and the 13 points are arranged in a cross shape.         The measuring method according to claim 4, wherein a pitch between adjacent points is the same.         The measuring method according to claim 1, wherein the product to be processed is a silicon wafer.         The measuring method according to claim 7, wherein the first material layer is an epitaxial layer.