JPH04282821A - Alignment evaluating pattern shape and evaluating method for alignment - Google Patents

Abstract

PURPOSE:To eliminate superposition of upper and lower alignment evaluation patterns so as to measured upto a critical limit of a scanning election microscope. CONSTITUTION:In a pattern shape for evaluating an alignment between a first pattern formed on an element 10 to be treated and a second pattern laminated on the first pattern, any one of a first alignment evaluating pattern 15 and a second alignment evaluating pattern made of photoresist is disposed in the other pattern to be disposed so that both the patterns 15, 17 are not superposed, and can be measured up to a capacity limit of a scanning electron microscope.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to alignment evaluation pattern shapes and alignment evaluation methods.

[Prior Art] Generally, in order to manufacture semiconductor devices, photolithography is used to place a
For example, a large number of silicon oxide film patterns or polysilicon patterns are stacked. In this case, it is ideal that there should be no misalignment between the patterns stacked above and below, but in reality it is impossible to prevent misalignment due to errors in the exposure equipment, etc. In order to minimize the misalignment of the laminated patterns, a photoresist pattern is formed directly on the underlying pattern on a trial basis, an alignment evaluation is performed to determine the misalignment between these patterns, and this result is used in actual device manufacturing. This is reflected in the process. To explain this specifically, as shown in FIG. 2, for example, a silicon oxide film (SiO2) is formed on a silicon wafer (Si) 1.
After forming a pattern, a photoresist 3 is directly applied using a spinner as shown in FIG. 3, and exposed using an exposure device while focusing on the alignment evaluation pattern 2, to finally form a pattern 4. At this time, ideally, the first alignment evaluation pattern 2 and the photoresist pattern 4 should match, but when applying the photoresist, the rotation speed and curing speed of the spinner must be adjusted to ensure a uniform thickness. Despite various operations being performed to coat the photoresist, the top 5 of the photoresist 3 is actually slightly misaligned with respect to the convex alignment evaluation pattern 2, as shown in FIG. is LS
Since the A laser is exposed while focusing on this topmost portion 5, the entire pattern shifts. Also, this top 5
The amount of deviation may vary slightly depending on the position from the wafer center of the alignment evaluation pattern provided on each IC chip and the alignment evaluation pattern for the wafer appropriately placed on the wafer, or due to warping of the wafer itself. different. In order to evaluate the above-mentioned alignment deviation, FIG.
As shown in Figure 2, the pitch of the first alignment evaluation pattern 2 and the pitch of the second photoresist pattern 4 are slightly changed, and the vernier principle of a caliper is applied, and the points where the scales match are visually checked using a metallurgical microscope. Evaluation was done by doing this. As another method, as shown in FIG. 5, the first alignment evaluation pattern 2 and the photoresist pattern 4 laminated thereon are overlapped in the same shape, and the alignment is performed by scanning this with a scanning electron microscope. We were evaluating the discrepancies.

0002

Problem to be Solved by the Invention In the method shown in FIG.
are formed in large numbers at a predetermined pitch, and a large number of second alignment evaluation patterns (photoresist) 4 are formed at pitches slightly different from the above predetermined pitch, and the positions where the scales of both patterns match according to the amount of alignment deviation are formed. Taking advantage of the fact that the
The amount of deviation was measured. However, the minimum readable range with a metallurgical microscope is at most 0.02 μm, and such a value is not sufficient, especially in today's world where the trend towards miniaturization has progressed. In addition, in the method shown in FIG. 6, the first alignment evaluation pattern (SiO2) 2 in the lower layer and the second alignment evaluation pattern (photoresist) 4 in the upper layer are made the same pattern, and the lengths X1 and X2 are By measuring the length, the amount of deviation a between the patterns is detected using a scanning electron microscope. However, due to the structure in which the first alignment evaluation pattern 2 is covered by the second evaluation pattern 4, the length measurement is difficult. There is an improvement point in that accurate alignment evaluation cannot be performed because interference sometimes occurs, including etching variations in the first evaluation pattern 2 and development variations in the second evaluation pattern 4. The present invention has been devised to address the above-mentioned problems and to effectively solve them.
An object of the present invention is to eliminate the overlap between upper and lower alignment evaluation patterns so that length measurements can be made up to the limit value of a scanning electron microscope.

0003

[Means for Solving the Problems] In order to solve the above-mentioned problems, the first invention includes a first pattern formed on an object to be processed, and a second pattern to be laminated on this pattern. In the alignment evaluation pattern shape for performing alignment evaluation between One alignment evaluation pattern is positioned within the other alignment evaluation pattern so that the alignment evaluation patterns do not overlap. In order to solve the above-mentioned problems, a second invention provides a method for evaluating alignment between a first pattern formed on an object to be processed and a second pattern to be laminated on this pattern. In,
Positioning either one of the alignment evaluation pattern of the first pattern and the alignment evaluation pattern made of a photoresist formed by a photomask for the second pattern within the other alignment evaluation pattern. The alignment evaluation patterns are arranged so that they do not overlap, and the distance between the end of the alignment evaluation pattern located on the inside and the end of the alignment evaluation pattern located on the outside is measured. It is configured to perform evaluation.

0004

[Operation] According to the first invention, the second pattern is placed on the alignment evaluation pattern of the first pattern formed on the object to be processed.
An alignment evaluation pattern is formed from a photoresist formed using a photomask for the pattern. At this time, the alignment evaluation pattern of the first pattern is formed as a square convex portion with small dimensions on each side, and the second alignment evaluation pattern made of photoresist is
A square recess is formed with the first alignment evaluation pattern in the center and each side having larger dimensions than the first alignment evaluation pattern. Then, the first alignment evaluation pattern is
Since it is located approximately at the center of the second alignment evaluation pattern, it is possible to eliminate overlap between the two patterns, which causes interference during length measurement. According to the second invention,
The two alignment evaluation patterns formed according to the first invention are scanned with a scanning electron microscope, and the end portions of the second alignment evaluation pattern located on the outside and the first alignment evaluation pattern located on the inside are By measuring the distance between the left and right sides, and performing this length measurement along both the X and Y directions, alignment deviation is evaluated.

[0005]

Embodiments Below, embodiments of alignment evaluation pattern shapes and alignment evaluation methods according to the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, a case will be described in which a pattern made of a silicon oxide film (SiO2) is formed as the first pattern of the first layer. First, as shown in FIGS. 1 and 7, a silicon oxide film 11 is formed on, for example, a silicon semiconductor wafer 10 as an object to be processed,
Further, after applying a photoresist 12 on top of the photoresist 12 using a spinner, an exposure device (for example) that performs 5:1 reduction projection is applied.
(not shown) and performs an etching process or the like to form a first pattern alignment evaluation pattern 15 as shown in FIG. In this embodiment, the first alignment evaluation pattern 15 has a side length L of 1, for example.
It is formed into a square shape of μm. Next, one semiconductor wafer 10 is taken out as a sampling out of a large number of wafers, for example, 25 wafers in one cassette, on which the first alignment evaluation pattern 15 is formed as described above, and as shown in FIG. A photoresist 16 is directly applied on top using a spinner. Then, using a photomask (not shown) for a second pattern to be laminated on the first pattern, the exposure device focuses the LSA laser on the first alignment evaluation pattern 15 and positions it. After alignment, exposure is performed as shown in FIG. The shape of the alignment evaluation pattern used at this time is larger than the first alignment evaluation pattern.
For example, the first alignment evaluation pattern 15 is set to have a square shape with a side length m of 5 μm, and therefore, when the pattern is extracted from the photoresist, as shown in FIGS. 1 and 11, the first alignment evaluation pattern 15 is made of the photoresist. Both patterns are positioned within the second alignment evaluation pattern 17 so as not to overlap.

An alignment evaluation method based on the alignment evaluation pattern constructed as described above will be described. First, using a scanning electron microscope, for example, the distance A1 between the end of the alignment evaluation pattern located on the inside, that is, the first alignment evaluation pattern 15, and the end of the alignment evaluation pattern 17 located on the outside, The lengths of A2, B1, and B2 are measured along the X direction and the Y direction. During this length measurement, both patterns 15 and 1
7 are completely separated without overlapping vertically, so there is no interference between the wavelength measurement waves, and each distance A1, A2, B
1. Accurate values of B2 can be measured up to the measurement limit of this scanning electron microscope, e.g. 0,002 μm, and are above the optical measurement limit of conventional alignment evaluation, e.g. 0,02 μm.
The measurement accuracy can be significantly improved compared to m.

Since the centers of both patterns are the same, the alignment shift in the X direction is given by the following equation. Absolute value A1 - Absolute value A2 = alignment deviation (X direction)
Further, the alignment shift in the Y direction is given by the following equation. Absolute value B1 - Absolute value B2 = Alignment deviation (Y direction)
Therefore, if no misalignment occurs, A
1=A2, B1=B2. The alignment evaluation obtained in this way is reflected as a correction value when the second pattern is actually exposed by the exposure device, and proper positioning is performed. When forming the second pattern, the actual process is to form, for example, a polysilicon film 20 on the first alignment evaluation pattern as shown in FIG. The exposure is performed using a photomask for the second pattern as shown in FIG.
The thickness n3 of the top layer photoresist 22 is, for example, 1.
On the other hand, the thickness n2 of the intermediate layer polysilicon film 20 is very small, for example, 2000 to 3000 angstroms, and therefore, even without this intermediate layer, the accuracy of alignment evaluation is hardly affected. The previously obtained alignment evaluation can be directly applied to the actual second pattern manufacturing process.

The alignment evaluation described above is performed on all the chips of the sampled semiconductor wafer, resulting in a comprehensive alignment evaluation. In addition, the semiconductor wafers sampled for alignment evaluation were not discarded after ashing and cleaning, but were
Of course, it is incorporated into the C manufacturing process. Further, in the above embodiment, the first alignment evaluation pattern was formed small and the second alignment evaluation pattern made of photoresist was formed large, but by reversing this size, the first alignment evaluation pattern may be formed large, and the second alignment evaluation pattern may be formed small within this. Furthermore, if the alignment evaluation pattern is provided at the center of the photomask, deviations due to aberrations of the exposure device can be minimized, and alignment evaluation can be performed more accurately. Further, in the above embodiment, both pattern shapes are squares of different sizes, but the shape is not limited to this, for example, they may be circles of different sizes, rectangles of different sizes, or a combination of a square and a rectangle. As long as the two patterns do not overlap, the shape does not matter. Furthermore, in the above embodiments, the explanation has been made regarding the patterns of the first layer and the second layer, but it goes without saying that the same applies to each pattern stacked one above the other.

[0009]

As described above, according to the present invention, the following excellent effects can be achieved. Since it is possible to eliminate the overlap between the first alignment evaluation pattern and the second alignment evaluation pattern, it is possible to measure the alignment deviation with high precision using, for example, a scanning electron microscope. Therefore, it is possible to increase the limit accuracy of alignment evaluation and form a pattern with less deviation, so that it is possible to respond to the trend toward higher integration.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the shape of an alignment evaluation pattern according to the present invention.

FIG. 2 is an explanatory diagram illustrating a conventional alignment evaluation pattern.

FIG. 3 is an explanatory diagram illustrating a conventional alignment evaluation pattern.

FIG. 4 is an explanatory diagram illustrating the cause of misalignment.

FIG. 5 is a plan view showing a conventional alignment evaluation pattern.

FIG. 6 is a diagram showing a conventional alignment evaluation pattern.

FIG. 7 is a process diagram showing a process of forming an alignment evaluation pattern according to the present invention.

FIG. 8 is a process diagram showing a process of forming an alignment evaluation pattern according to the present invention.

FIG. 9 is a process diagram showing a process of forming an alignment evaluation pattern according to the present invention.

FIG. 10 is a process diagram showing a process of forming an alignment evaluation pattern according to the present invention.

FIG. 11 is a process diagram showing a process of forming an alignment evaluation pattern according to the present invention.

FIG. 12 is a process diagram showing an actual process when forming a second pattern.

[Explanation of symbols]

10 Semiconductor wafer (object to be processed) 11 Silicon oxide film

Claims (2)

[Claims] 1. In an alignment evaluation pattern shape for performing alignment evaluation between a first pattern formed on an object to be processed and a second pattern to be laminated on this pattern, the first and an alignment evaluation pattern made of a photoresist formed by the photomask for the second pattern, one of which is positioned within the other alignment evaluation pattern, and the alignment is performed. An alignment evaluation pattern shape characterized in that the evaluation patterns are configured so that they do not overlap. 2. A method for evaluating alignment between a first pattern formed on an object to be processed and a second pattern to be laminated on this pattern, comprising: and an alignment evaluation pattern made of a photoresist formed by the photomask for the second pattern, and one of the alignment evaluation patterns is positioned within the other alignment evaluation pattern so that the alignment evaluation patterns do not overlap. The alignment evaluation pattern is arranged as shown in FIG. An alignment evaluation method characterized by: