JP2002188912A - Flatness measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flatness measuring device measuring the flatness of a measuring object and outputting a measured result, capable of easily, surely grasping a shape within a site. SOLUTION: This flatness measuring device is equipped with a height measuring means measuring the height of a specified measuring point in the measuring object; an allocating means allocating the height value of the measuring point measured with the height measuring means to a plurality of sites of the corresponding measuring object; a displacement distribution map preparing means calculating the displacement amount from a reference plane in each site based on the height value in the measuring point allocated with the allocating means, and preparing a displacement distribution map of each site; and an output means outputting the displacement distribution map.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flatness measuring device for measuring the flatness of an object to be measured and outputting the result.

[0002]

2. Description of the Related Art Generally, a semiconductor wafer used for manufacturing an LSI is required to have high flatness in order to prevent a focusing defect in an exposure process at the time of manufacturing.
With the miniaturization of LSI patterns, it is becoming more and more severe. Therefore, when manufacturing a semiconductor wafer, the flatness of all the semiconductor wafers is measured and inspected.

The flatness of a semiconductor wafer is evaluated for each site corresponding to an exposure region in an exposure step, and the measurement result is indicated by a number as the width of the height distribution of each site, that is, a site flatness. Based on this, the quality of the semiconductor wafer is determined. Further, the width of the height distribution over the entire surface of the semiconductor wafer, that is, the global flatness is also indicated by a numeral.

[0004]

However, in the conventional flatness measuring apparatus, when the site flatness of a certain site is determined to be defective, the site flatness is simply displayed by a numerical value. There is a problem that it is difficult to accurately grasp the shape of the inside of the defective site.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a flatness measuring device capable of easily and reliably grasping the shape of a site.

[0006]

The flatness measuring device according to claim 1 is a height measuring means for measuring a height of a predetermined measuring point on a measuring object, and a measuring point measured by the height measuring means. Allocating means for allocating a height value to a plurality of sites of the measurement object corresponding thereto, and calculating a displacement amount from a reference plane at each site based on the height value of the measurement point allocated by the allocating means. It is characterized by having a displacement distribution map creating means for creating a displacement distribution map of a site, and an output means for outputting the displacement distribution map.

According to a second aspect of the present invention, there is provided a flatness measuring apparatus according to the first aspect, further comprising a site selecting means for selecting a specific site from a plurality of sites created by the displacement distribution map creating means. It is characterized by. A flatness measuring device according to a third aspect is the flatness measuring device according to the first or second aspect, wherein the site selecting unit automatically selects a specific site based on a displacement amount from the reference plane. Features.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the flatness measuring device of the present invention. In FIG. 1, reference numeral 10 denotes a Fizeau interferometer. This Fizeau interferometer 10
An apparatus for measuring the height of the entire surface of a semiconductor wafer, comprising a light source 11, a beam expander 12, and a half mirror 13.
, A Fizeau flat 14, a wafer holder 15, an imaging lens 16, and a TV camera 17.

As the light source 11, a laser (for example, He-
A light source having a long coherence distance such as a Ne laser is used.
As a result, the contrast of the obtained interference fringes becomes good, and high-precision measurement becomes possible. Beam expander 1
Reference numeral 2 includes a lens 12A and a collimator lens 12B. The wafer holder 15 holds the semiconductor wafer 20 fixedly. The imaging lens 16 and the TV camera 17 constitute an observation optical system 18.

The light from the light source 11 is expanded by a beam expander 12 and becomes a parallel light beam.
4 is incident. Part of the light incident on the Fizeau flat 14 is reflected by the reference plane 14a and becomes reference light. The light transmitted through the reference plane 14a is
reflected at a. This reflected light returns along the same optical path as the reference light, is reflected by the half mirror 13, and reaches the observation optical system 18. That is, the reflected light passes through the imaging lens 16 and T
The image reaches the imaging surface of the V camera 17.

When the light reflected by the reference plane 14a and the surface 20a of the semiconductor wafer 20 overlap on the imaging surface, they interfere with each other, and interference fringes are formed on the imaging surface. Reference plane 1
When 4a is a sufficiently accurate plane, the interference fringes can accurately indicate the surface shape of the semiconductor wafer 20, that is, the height distribution of the surface 20a of the semiconductor wafer 20.

The interference fringes are analyzed by a known automatic fringe analysis method using a computer 30, and the height distribution of the surface 20a of the semiconductor wafer 20 is measured. FIG.
It schematically shows the height distribution of the surface 20a of the semiconductor wafer 20, and a value corresponding to the height at a predetermined measurement point Pi is defined as a height value hi of the measurement point. The computer 30
As shown in FIG. 3, there are provided an assignment unit 31, a displacement distribution diagram creation unit 32, an output unit 33, and a site selection unit.

The allocating means 31 allocates the height value h of the measurement point P existing on the entire surface of the semiconductor wafer 20 to the corresponding site S. In this embodiment, site S is L
A portion corresponding to an exposure area in an SI manufacturing process. The displacement distribution map creating means 32 calculates the amount of displacement of each site S from a reference plane based on the height value h of the measurement point P assigned by the assigning means 31, and creates a displacement distribution map of each site S. .

That is, the displacement distribution diagram creating means 32
Calculates a reference plane at each site S based on the height value h of the measurement point P assigned by the assigning means 31. FIG. 4 shows a reference plane KH at the site S at the left end of FIG. 2. The reference plane KH is based on a known least square method based on the height value hi of the measurement point Pi existing in the site S. Required by

In the site S, for example, the size of one pixel is ３ mm × １ ／ mm and the size of the site is 25 m corresponding to the number of pixels of the image sensor of the TV camera 17.
In the case of m × 25 mm, 25 × 3 × 25 × 3 measurement points P can be used, but without using all the measurement points P, a predetermined smaller number of measurement points P can be used. The reference plane KH may be obtained based on the height value h.

The displacement distribution diagram creating means 32 calculates the displacement amount Li from the reference plane KH to the surface 20a, that is, the distance in the direction perpendicular to the reference plane KH, and calculates the displacement distribution diagram of each site S described later. Create The site selecting means 34 determines a specific site S among the respective sites S, in particular, a site which exceeds the reference value and is determined to be defective, based on a predetermined reference value relating to the displacement L from the reference plane KH. Select S.

The flatness measuring apparatus is provided with a display device 35 which is created by the site displacement distribution map creating means 32 and shows the displacement distribution map of each site S outputted from the output means 33 to the operator. ing. In addition,
Not only the display device 35 but also an external output device such as a printer for printing and outputting can be provided.

FIG. 1 shows a Fizeau interferometer 1
Although the flatness measurement method according to 0 has been described, the present invention is not limited to this, and by using an optical distance sensor or a capacitance sensor and moving it relative to the semiconductor wafer 20, A method of measuring the height distribution of the entire surface of the semiconductor wafer 20 may be used. Next, an external output of a displacement distribution diagram based on the height distribution of the semiconductor wafer 20 measured by the above method will be described.

FIG. 5 is a flowchart for explaining from the measurement of the height distribution to the external output of the displacement distribution diagram. Steps S1 to S8 show the procedure. First, the height distribution of the entire surface of the semiconductor wafer 20 is measured (Step S1). Next, the height data of the entire surface of the semiconductor wafer 20 is assigned to each site S by the assigning means 31 (step S2).

Next, a reference plane KH in each site S is set based on the height data assigned to each site S (step S3). Next, the displacement amount L from the reference plane KH in the site S is calculated (step S4).

Next, a displacement distribution map of each site S is created (step S5). Next, a displacement distribution map of all sites S is output (step S6). FIG. 6 is a display screen showing an example of an external output of the displacement distribution map of all sites S. The semiconductor wafer 20 is divided into N pieces of sites 1 to N, and each site S displays a displacement distribution diagram of the site S.

The output result shown in FIG. 6 may be displayed on the display device 35 or printed by a printer or the like. Next, from the displacement distribution map of all sites S,
Based on a predetermined reference value relating to the maximum value of the displacement amount L from the reference plane KH, a specific site S, in particular, a site S to be determined to be defective beyond the reference value is automatically selected by the site selection means 34. (Step S
7).

This is because the operator wants to confirm the details by looking at the output result of FIG. 6, for example, n in FIG.
Manual operation is also possible, such as selecting. This selection is performed by the operator operating the site selection input means. Specifically, a specific site S may be selected by using a mouse or the like with respect to the displacement distribution map displayed on the display device 35, or by viewing the printed data and using a keyboard or the like. May be selected.

Finally, a displacement distribution map is output for the selected site S (step S8). This displacement distribution map may be displayed on the display device 35 or output to another external output device. When displayed on the display device 35, it may be displayed on the same screen side by side with the displacement distribution diagrams of all sites S, or may be displayed alone.

FIG. 7 is a display screen showing an example of a displacement distribution diagram in one selected site S. In this embodiment, the site n in FIG. 6 is selected, and the displacement distribution diagram F is displayed in black and white shading. Note that the displacement distribution diagram may use color-coded display according to the displacement amount L from the reference plane KH, may combine contour lines and color-coded,
A bird's eye view or a three-dimensional view may be used.

In the displacement distribution diagram F of FIG. 7, the displacement L from the reference plane KH increases as the color changes from black to white. In the flatness measuring apparatus described above, the reference plane K is obtained by looking at the displacement distribution diagram F output from the output unit 33.
The shape inside the site S can be recognized as the displacement amount L from H, and the shape inside the site S can be grasped easily and reliably.

That is, for example, the site n shown in FIG.
8, it can be easily recognized that, as shown in FIG. 8, in the cross section taken along the diagonal line LL, the semiconductor wafer 20 has a shape that is curved on both sides around the portion a. it can. Therefore, information on the shape of the semiconductor wafer 20 can be fed back to the manufacturing process of the semiconductor wafer 20 quickly and easily, and the shape accuracy of the semiconductor wafer 20 can be improved.

Further, in the flatness measuring apparatus described above, a specific site S can be easily and reliably selected from the plurality of sites S created by the displacement distribution diagram creating means 32 by the site selecting means 34. Then, for example, the reference plane KH
Site S in which the maximum value of the displacement L from the target is larger than a predetermined value.
Can be automatically selected by the site selection means 34.

In the embodiment described above, each site S
Has been described using the least square method, the present invention is not limited to such an embodiment. For example, the reference plane KH may be located at the focal plane when the semiconductor wafer 20 is exposed by a stepper. A reference plane may be set using the same points as the plurality of measurement points.

That is, at the time of writing on the semiconductor wafer 20, for example, the optimum focal plane of each drawing area is detected by using a stepper AF sensor, and the focal plane is detected. By using the same points as the plurality of measurement points to set a reference plane by, for example, the least squares method, the shape of the semiconductor wafer 20 centered on the focal plane at the time of writing can be reliably grasped.

In the above-described embodiment, an example in which the flatness measuring apparatus of the present invention is applied to the measurement of the semiconductor wafer 20 has been described. However, the present invention is not limited to such an embodiment, Is divided into a plurality of sites, that is, a plurality of regions, and can be widely applied to a flatness measuring device that individually measures the shape of each region.

[0032]

As described above, the flatness measuring device according to the first aspect recognizes the shape in the site as the amount of displacement from the reference plane by looking at the displacement distribution diagram output from the output means. And the shape in the site can be easily and reliably grasped.

According to the flatness measuring device of the present invention, a specific site can be easily and reliably selected from a plurality of sites created by the displacement distribution diagram creating means. According to the flatness measuring device of the third aspect, for example, a site where the maximum value of the displacement L from the reference plane is larger than a predetermined value can be automatically selected.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a flatness measuring device according to the present invention.

FIG. 2 is an explanatory diagram showing a height distribution of a semiconductor wafer measured by the Fizeau interferometer of FIG. 1;

FIG. 3 is a block diagram showing the computer of FIG. 1;

FIG. 4 is an explanatory diagram showing a reference plane set for each site.

FIG. 5 is a flowchart showing an operation of the flatness measuring device of FIG. 1;

FIG. 6 is an explanatory diagram showing a displacement distribution map of all sites output from an output unit.

7 is an explanatory diagram showing a displacement distribution diagram of a lower left site in FIG. 6;

FIG. 8 is an explanatory diagram for explaining the displacement distribution diagram of FIG. 7;

[Explanation of symbols]

 Reference Signs List 10 Fizeau interferometer 20 Semiconductor wafer 31 Assigning means 32 Displacement distribution diagram creating means 33 Output means 34 Site selecting means P Measurement point S Site L Displacement KH Reference plane

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA24 AA47 AA51 BB01 CC19 FF52 FF61 GG05 LL00 LL04 LL09 SS01 SS06 SS13 2F069 AA42 AA54 BB15 CC07 GG04 GG06 GG07 HH09 HH30 QQ05 QQ10 4M106 DH01 BA01

Claims (3)

[Claims] 1. A height measuring means for measuring a height of a predetermined measuring point on a measuring object; and a plurality of measuring objects corresponding to height values of the measuring points measured by the height measuring means. Assigning means for allocating to the site, and a displacement distribution map creating means for calculating a displacement amount from a reference plane at each site based on the height value of the measurement point assigned by the assigning means and creating a displacement distribution map for each site. And an output means for outputting the displacement distribution map. 2. The flatness measuring device according to claim 1, further comprising: a site selecting unit that selects a specific site from the plurality of sites created by the displacement distribution diagram creating unit. . 3. The flatness measuring device according to claim 1, wherein said site selecting means automatically selects a specific site based on an amount of displacement from said reference plane. measuring device.