JP2004022552A - Exposure deviation inspection method, exposure deviation inspection apparatus, exposure deviation inspection program, and computer-readable recording medium recording exposure deviation inspection program - Google Patents

Abstract

An object of the present invention is to perform a high-accuracy exposure overlay inspection with a limited number of measurement points.
The present invention includes a step of previously acquiring distortion matching data resulting from a difference between an exposure condition in a first exposure and an exposure condition in a second exposure at n points (n is a natural number) per one shot area. (Step S1) a step of obtaining m points (m is a natural number smaller than n) per shot area of a pattern displacement amount after the first exposure and the second exposure on the substrate to be inspected (Step S2) ), A step of calculating a linear component shift amount from the positional shift amount of the m point (step S3), and corresponding to the n point of one shot area of the substrate to be inspected from the distortion matching data of the n point and the linear component shift amount. The method includes a step of calculating a positional shift amount in exposure at each position (step S4).
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method, an apparatus, a program, and a computer-readable recording medium for inspecting a positional shift of a pattern formed by a first exposure of a substrate by an exposure apparatus and a second exposure performed thereafter.
[0002]
[Prior art]
In the manufacture of a semiconductor device in which a pattern is formed on a substrate such as a wafer by photolithography, the overlay accuracy is important as long as a method of patterning an upper surface in accordance with a base is used. Since the exposure apparatus that performs pattern exposure has fluctuations of the apparatus itself and fluctuations of each lot, it is necessary to measure the overlay accuracy after the lithography process to determine the quality of each lot.
[0003]
In particular, as the integration of devices has progressed, the margin for pattern formation has become smaller, and there is no room for the ability of overlay accuracy. There is a need to.
[0004]
Conventionally, in the overlay measurement method, since there are limitations on the mark arrangement area, inspection measurement time, and the like, only a part of the exposure area is sampled and measured to obtain the result of the lot.
[0005]
[Problems to be solved by the invention]
However, an error component remains in an unmeasured area in the exposure area, and there is a problem that a highly accurate result cannot be obtained by such a sampling measurement method.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve such a problem. That is, the present invention provides a method for inspecting a position shift of a pattern formed by a first exposure to a substrate and a second exposure to be performed thereafter, wherein an exposure condition in the first exposure and a second A step of obtaining n points (n is a natural number) per shot area of distortion matching data due to a difference from an exposure condition in exposure, and a step of obtaining a pattern after a first exposure and a second exposure on a substrate to be inspected. A step of obtaining a position shift amount of m points (m is a natural number smaller than n) per shot area; a step of calculating a linear component shift amount from the position shift amounts of the m points; a distortion matching data and a linear component shift amount of n points Calculating the amount of positional deviation in exposure at each position corresponding to n points in one shot area of the substrate to be inspected.
[0007]
Further, the present invention provides an apparatus for inspecting a position shift of a pattern formed by a first exposure to a substrate and a second exposure to be performed thereafter, wherein an exposure condition in the first exposure and an exposure condition in the second exposure A data input unit for acquiring n points (n is a natural number) per shot area for distortion matching data due to a difference from the exposure condition, and a first exposure and a second exposure pattern for a substrate to be inspected; A data acquisition unit for acquiring the position deviation amount at m points per shot area (m is a natural number smaller than n); a linear component deviation amount obtained from the position deviation amount of the m points acquired by the data acquisition unit; Based on the acquired n-point distortion matching data and the linear component shift amount, the positions at the exposures corresponding to the n-points in one shot area of the substrate to be inspected There is also one and a calculating means for calculating an amount is.
[0008]
According to the present invention, there is provided a program for inspecting a positional shift of a pattern formed by a first exposure to a substrate and a second exposure to be performed thereafter, the exposure condition in the first exposure and the exposure condition in the second exposure. A step of acquiring n points (n is a natural number) per one shot area for distortion matching data due to a difference from an exposure condition, and a positional displacement of a pattern after a first exposure and a second exposure on a substrate to be inspected A step of obtaining an amount of m points (m is a natural number smaller than n) per shot area; a step of obtaining a linear component deviation amount from the positional deviation amount of the m points; and a step of obtaining the n points of distortion matching data and the linear component deviation amount Calculating a displacement amount in exposure at each position corresponding to n points in one shot area of the substrate to be inspected. It is also a computer-readable recording medium recording this program.
[0009]
In the present invention, distortion matching data resulting from exposure deviation of the exposure apparatus itself is acquired in advance for n points (natural numbers) per one shot area, and the first exposure and the second exposure to the substrate to be inspected are performed. The position shift amount of the pattern after exposure is set to m points (a natural number smaller than n) per one shot area, and the linear component shift amount is calculated therefrom. The linear component shift amount is added to the distortion matching data of the previously obtained n points. In addition, the displacement amount for n points is calculated. As a result, the number of inspection points in one shot area of the substrate to be inspected can be m points, and an accurate positional deviation amount for n points can be calculated from the distortion matching data and the linear component deviation amount.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating an outline of the exposure shift inspection method according to the present embodiment. The exposure shift inspection method according to the present embodiment is a method for inspecting a position shift of a pattern to be formed by, for example, a first exposure in forming a pattern on a semiconductor wafer and a second exposure performed thereafter.
[0011]
First, as shown in step S1, distortion matching data resulting from the difference between the exposure condition in the first exposure using the exposure apparatus and the exposure condition in the second exposure is previously set to n points (n: (Natural number) and store it in the database.
[0012]
Next, as shown in step S2, using the substrate to be inspected which has been subjected to the exposure, the positional deviation amount of the pattern after the first exposure and the second exposure is set to m points per shot area (m is smaller than n). Natural number) to get.
[0013]
Next, as shown in step S3, a process is performed to obtain a linear component shift amount that can be corrected by the exposure apparatus from the previously obtained position shift amount of the m point. Then, as shown in step S4, from the distortion matching data of n points read from the database and the linear component shift amount, the position shift in the exposure of each position corresponding to the n point of one shot area of the substrate to be inspected is performed. A process for calculating the amount is performed.
[0014]
According to such a flow, accurate data for n points can be calculated by measuring only m points per one shot area on a substrate to be inspected, and a highly accurate exposure position shift can be verified in a limited time. become able to.
[0015]
Here, a mark for measuring a position shift of a pattern between the first exposure and the second exposure will be described. 2A and 2B are schematic views illustrating a measurement mark, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view. That is, the first mark P1 formed by the first exposure is formed, for example, of a substantially square shape in plan view, and is formed on the substrate S. The second mark P2 formed by the second exposure is formed, for example, of a substantially square shape in plan view smaller than the first mark P1, and is formed on the insulating layer I covering the first mark P1.
[0016]
In design, if the center of the first mark P1 and the center of the second mark P2 match, it means that there is no exposure shift between the first exposure and the second exposure. Therefore, by calculating the center position of the first mark P1 and the center position of the second mark P2, the shift amount (for example, the shift amount in the X direction and the Y direction) between the first exposure and the second exposure is calculated. Exposure shift amount.
[0017]
FIG. 3 is a schematic diagram illustrating the arrangement of the measurement marks. Several measurement marks (see the mark x in the figure) are arranged in one exposure (one shot) region on the substrate S such as a wafer. For example, they are provided at a total of five places at the center and four corners of one shot area. When measuring the exposure shift amount of the substrate S to be inspected, several shots (for example, shots indicated by oblique lines in the drawing) are selected from one substrate S, and the measurement marks in each shot are used. To calculate the exposure shift amount. Usually, a total of several hundred exposure shift amounts are calculated for one substrate S.
[0018]
In the present embodiment, in addition to the exposure deviation amounts actually measured and calculated in this way, the exposure deviation amount at the measurement point of the distortion matching data acquired in advance in one shot area is also calculated, and high accuracy is achieved in a short time. The feature is that the exposure deviation is verified.
[0019]
Next, a specific example of the exposure shift measuring method of the present embodiment will be described. First, a method for acquiring distortion matching data will be described with reference to FIG. That is, in order to obtain distortion matching data, exposure is performed using a dedicated mask in which a number of overlay inspection marks are arranged in an exposure area under an apparatus for processing the first exposure (1st step) under illumination conditions. .
[0020]
Next, an apparatus for processing the second exposure (2nd step), the wafer is superimposed and exposed under illumination conditions, and the amount of overlay deviation remaining in the first and second exposure areas is measured to obtain distortion matching (X, Y) = (A1, B1), (A2, B2),..., (An, Bn). Distortion matching data is acquired at n points per shot area.
[0021]
The distortion matching data represents the exposure deviation of the exposure apparatus itself, and the measurement is performed periodically to always calculate the latest matching result.
[0022]
Next, measurement of the exposure shift of the substrate to be inspected will be described with reference to FIG. Here, for the five shots at the top, bottom, left, and right in the drawing of the substrate S to be inspected, the results of the inspection of the overlay deviation of the patterns in the first exposure and the second exposure are obtained, and from this the deviation of the linear component is obtained. The quantities (P1, P2,..., Pm, Q1, Q2,..., Qm) are calculated.
[0023]
Here, the linear component shift amount is a shift amount that can be corrected on the exposure apparatus side. For example, offset X, Y, wafer magnification X, Y, wafer rotation, orthogonality, shot magnification X, Y, shot rotation X, Y And the like.
[0024]
Inspection of overlay displacement of the substrate S to be inspected is performed by measuring m points (4 points in the example shown in FIG. 5) per one shot area. m is a natural number smaller than n, whereby the measurement time can be shortened.
[0025]
Next, as shown in FIG. 6, for the n points of the latest distortion matching data (A1, B1) to (An, Bn) acquired in advance, the linear distortion is calculated using the linear component shift amount at the previously calculated m points. The correction is applied, and the exposure position shift amount at each of the n points is calculated.
[0026]
For example, if the coordinates of the (A1, B1) point are (C1, D1), the coordinates of (A2, B2) are (C2, D2), ..., the coordinates of (An, Bn) are (Cn, Dn), The exposure position shift values (E1, Fn) to (En, Fn) are represented by the following equations.
[0027]
E1 = A1 + h1 * C1 * P1 + ... + hm * C1 * Pm + k1 * D1 * P1 + ... + km * D1 * Pm
E2 = A2 + h1 * C2 * P1 + ... + hm * C2 * Pm + k1 * D2 * P1 + ... + km * D2 * Pm
・
・
・
En = An + h1 * Cn * P1 + ... + hm * Cn * Pm + k1 * Dn * P1 + ... + km * Dn * Pm
F1 = A1 + r1 * C1 * P1 + ... + rm * C1 * Pm + s1 * D1 * P1 + ... + sm * D1 * Pm
F2 = A2 + r1 * C2 * P1 + ... + rm * C2 * Pm + s1 * D2 * P1 + ... + sm * D2 * Pm
・
・
・
Fn = An + r1 * Cn * P1 + ... + rm * Cn * Pm + s1 * Dn * P1 + ... + sm * Dn * Pm
Here, h1 to hm, k1 to km, r1 to rm, and s1 to sm are coefficients.
[0028]
Using the results of (E1, Fn) to (En, Fn) obtained by the above calculation, the quality of the lot is determined.
[0029]
Next, as shown in FIG. 7, the linear component deviation amount of the actual lot is calculated again from the results of (E1, Fn) to (En, Fn). This result is defined as (U1, U2, ..., Um, V1, V2, ..., Vm). Then, this value is fed back to the next lot (overlay displacement correction).
[0030]
Assuming that the use correction values of the previous lot are (W1, W2,..., Wm, Z1, Z2,..., Zm), the new correction values (G1, G2,..., Gm, H1, H2,. Obtained by calculation.
[0031]
G1 = W1-U1 H1 = Z1-V1
G2 = W2-U2 H2 = Z2-V2
・
・
・
Gm = Wm-Um Hm = Zm-Vm
[0032]
Although the above is the calculation result of the past one lot, it may be determined from the results of a plurality of lots. By performing exposure using this value, the next lot can be more accurately exposed. The quality of each lot can be determined based on the maximum (Worst) or average value of the calculated shift amounts and the standard deviation (ave + nσ).
[0033]
Next, an apparatus (exposure deviation inspection apparatus) that realizes the exposure deviation inspection method will be described. In this apparatus, all of the above-described exposure deviation inspection methods can be automatically performed. FIG. 8 is a configuration diagram illustrating an exposure deviation inspection apparatus according to the present embodiment.
[0034]
That is, this exposure deviation inspection apparatus is configured mainly with the host computer 1, and acquires data input means for acquiring distortion matching data from the database D / B, and acquires the exposure position deviation amount on the substrate to be inspected. Data acquisition means and calculation means for calculating the amount of positional deviation of each point within one shot area based on the acquired distortion matching data and the amount of exposure positional deviation. In this embodiment, the data input unit, the data acquisition unit, and the calculation unit are realized by a program executed by the host computer 1.
[0035]
First, the overlay displacement amount (distortion matching) of the 1st and 2nd is measured by the overlay measuring device 4, and the results (A1, B1), (A2, B2),..., (An, Bn) are periodically recorded. In the database D / B on the system. This result may be a fixed value or may be updated periodically.
[0036]
Next, the product lot is exposed by the exposure machine 2 and the overlay inspection is performed by the overlay measurement machine 3. The results (P1, P2,..., Pm, Q1, Q2,..., Qm) obtained at the end of the inspection are recorded in the host computer 1. At the same time, the host computer 1 automatically performs a correction calculation to calculate the exposure position deviation amounts (E1, Fn) to (En, Fn). Therefore, it is automatically determined whether or not the result is within a preset standard. (Lot Pass / Fail Automatic Determination) If it is within the specifications, the process proceeds to the next step.
[0037]
Next, the deviation amounts (U1, U2,..., Um, V1, V2,..., Vm) of the linear components of the actual lot are calculated from the results of (E1, Fn) to (En, Fn). The host holds the calculation result of each lot.
[0038]
Then, when the next lot starts the lithography process, new correction values (G1, G2,..., Gm, H1, H2,..., Hm) are calculated. The obtained new correction value is transmitted from the host at the time of lot processing, and the lot is processed based on the value. As a result, the linear component shift amount can be corrected with high accuracy, and the exposure shift of the next lot can be reduced.
[0039]
The above-described exposure position deviation measuring device may be configured as hardware in addition to the program executed by the host computer 1, or may be recorded on a recording medium such as a CD-ROM storing the program, or may be connected to a network. It may be configured to be distributed via the Internet.
[0040]
【The invention's effect】
As described above, the present invention has the following effects. That is, a highly accurate exposure position shift amount can be calculated even with a limited number of measurement points, and a highly accurate overlay inspection can be performed in a short time. As a result, the quality of the product can be accurately determined with a small number of measurement points, and the processing capability of the exposure position deviation measuring device can be improved and the cost can be reduced by simplifying the configuration.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating an outline of an exposure shift inspection method according to an embodiment.
FIG. 2 is a schematic diagram illustrating a measurement mark.
FIG. 3 is a schematic diagram illustrating the arrangement of measurement marks.
FIG. 4 is a diagram illustrating a method for acquiring distortion matching data.
FIG. 5 is a diagram illustrating measurement of exposure shift of a substrate to be inspected.
FIG. 6 is a diagram illustrating calculation of an exposure position shift at each position.
FIG. 7 is a diagram illustrating calculation of a new linear component deviation amount.
FIG. 8 is a configuration diagram illustrating an exposure deviation inspection apparatus according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Host computer, 2 ... Exposure machine, 3 ... Overlay measuring machine, 4 ... Overlay measuring machine, P1: 1st mark, P2 ... 2nd mark, S ... Substrate

Claims (8)

In a method for inspecting a position shift of a pattern formed by a first exposure to a substrate and a second exposure performed thereafter,
Previously acquiring n points (n is a natural number) per shot area of distortion matching data resulting from a difference between the exposure conditions in the first exposure and the exposure conditions in the second exposure;
Obtaining m points (m is a natural number smaller than n) per shot area of a displacement amount of the pattern after the first exposure and the second exposure on the substrate to be inspected;
Obtaining a linear component shift amount from the position shift amount of the m point;
Calculating a displacement amount of the exposure at each position corresponding to the n point in the one-shot area of the substrate to be inspected from the distortion matching data of the n points and the displacement amount of the linear component. Characteristic exposure deviation inspection method. 2. The exposure shift inspection method according to claim 1, wherein after calculating a shift amount in exposure at each position corresponding to the n points, a new shift amount of a linear component is obtained based on the shift amount. In an apparatus for inspecting a position shift of a pattern formed by a first exposure on a substrate and a second exposure performed thereafter,
Data input means for acquiring n points (n is a natural number) per shot area of distortion matching data resulting from a difference between the exposure condition in the first exposure and the exposure condition in the second exposure;
Data acquisition means for acquiring the position deviation amount of the pattern after the first exposure and the second exposure on the substrate to be inspected per point m per shot area (m is a natural number smaller than n);
The linear component shift amount is obtained from the positional shift amount of the m points obtained by the data obtaining means, and the distortion matching data of the n points obtained by the data input means and the linear component shift amount are used to obtain the linear component shift amount. An exposure shift inspection apparatus, comprising: a calculating unit that calculates a shift amount in exposure at each position corresponding to the n points in one shot area. 4. The exposure deviation inspection apparatus according to claim 3, wherein the calculation unit calculates a new linear component deviation amount from the positional deviation amount in exposure at each position corresponding to the n points. In a program for inspecting a position shift of a pattern formed by a first exposure on a substrate and a second exposure performed thereafter,
Acquiring n points (n is a natural number) per shot area of distortion matching data resulting from a difference between the exposure condition in the first exposure and the exposure condition in the second exposure;
Acquiring m points (m is a natural number smaller than n) per shot area of the amount of positional shift of the pattern after the first exposure and the second exposure on the substrate to be inspected;
Obtaining a linear component shift amount from the position shift amount of the m point;
Calculating a displacement amount in exposure at each position corresponding to the n point in one shot area of the substrate to be inspected from the distortion matching data at the n points and the displacement amount of the linear component. Characteristic exposure deviation inspection program. 6. The exposure deviation inspection program according to claim 5, wherein, after calculating a deviation amount in exposure at each position corresponding to the n points, a new linear component deviation amount is obtained based on the deviation amount. In a computer-readable recording medium recording a program for inspecting a positional shift of a pattern formed by a first exposure on a substrate and a second exposure performed thereafter,
Acquiring n points (n is a natural number) per shot area of distortion matching data resulting from a difference between the exposure condition in the first exposure and the exposure condition in the second exposure;
Acquiring m points (m is a natural number smaller than n) per shot area of the amount of positional shift of the pattern after the first exposure and the second exposure on the substrate to be inspected;
Obtaining a linear component shift amount from the position shift amount of the m point;
Calculating a displacement amount in exposure at each position corresponding to the n point in one shot area of the substrate to be inspected from the distortion matching data at the n points and the linear component displacement amount. A computer-readable recording medium on which an inspection program is recorded. 8. The exposure deviation inspection program according to claim 7, wherein after calculating a deviation amount in exposure of each position corresponding to the n point, a new linear component deviation amount is obtained based on the deviation amount. A recorded computer-readable recording medium.

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