JP2009206143A - Alignment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that if a semiconductor substrate has nonlinear strain, a component thereof can not be corrected through alignment measurement before exposure in a step-and-repeat type alignment method, and misalignment is caused after the exposure. <P>SOLUTION: The state of nonlinear strain of the semiconductor substrate is previously measured, and information on the strain error is input to an exposure device. The input strain error is reflected on shot array coordinates of design to precisely align even the semiconductor device having the strain. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a step-and-repeat type exposure apparatus alignment method.

  In a process of reducing and exposing a reticle pattern to a resist applied on a semiconductor substrate by a step-and-repeat method, a first pattern transferred in a previous process to a semiconductor substrate and a second pattern transferred in a subsequent process This alignment needs to be performed with high accuracy.

  FIG. 3 is a flowchart showing a conventional alignment method.

  A step-and-repeat type exposure apparatus has a reference stage coordinate system. First, the position of the alignment mark is measured with several shots in the semiconductor substrate (STEP 31), and this measured value is statistically processed to determine the rotation component, magnification component, orthogonal component, and translation component of the shot. From this result, correction is performed as a coordinate system in consideration of the rotation component, magnification component, orthogonal component, and translation component of the shot on which the semiconductor substrate is arranged (STEP 32), and the calculated correction value is applied to the design position coordinate of each shot. In consideration, the arrangement coordinates of each shot are determined (STEP 33). Thereafter, each shot is exposed on the semiconductor substrate by a step-and-repeat method according to the arrangement coordinates (STEP 34).

  The types of errors that can be corrected by this method are shown in FIG. The alignment error components to be corrected are four error components: rotation error, magnification error, orthogonal error, and translation error.

Patent Document 1 discloses a method of correcting an alignment error caused by four alignment errors of a pattern position in each shot: a rotation error of a semiconductor substrate, an orthogonality error, a linear expansion / contraction, and a translational deviation. ing.
JP-A 61-44429

However, in a semiconductor manufacturing process that requires highly accurate alignment error correction, it is not sufficient to correct the four error components.
FIG. 6 is a diagram showing misalignment of each shot on the semiconductor substrate. An error component of misalignment will be described with reference to FIG. A plurality of shots 62 are arranged on the semiconductor substrate 61, and a vector 63 indicates the shift amount and direction of the shots. FIG. 6 (f) shows the total error before decomposing the measured misalignment amount. FIGS. 6 (b), (c), (d), and (e) are calculated from the total error shown in FIG. 6 (f). FIG. 6 (b) shows a rotation error, FIG. 6 (c) shows a magnification error, FIG. 6 (d) shows an orthogonal error, and FIG. 6 (e) shows a translation error. FIG. 6 (a) shows the total error components from FIG. 6 (f) to FIG. 6 (b) to FIG. 6 (e), that is, correctable rotation error, magnification error, orthogonal error, and translation error component. The error components (random components) remaining after the removal are shown. This random component is due to distortion of the semiconductor substrate. FIG. 5 is a schematic diagram showing distortion of a semiconductor substrate that has undergone a semiconductor manufacturing process. In the case of linear distortion as shown in FIGS. 5A and 5C, the distortion can be sufficiently corrected by the conventional alignment method, and exposure with high alignment accuracy is possible. In the case of nonlinear distortion as shown in (b) and FIG. 5 (d), it cannot be separated as a shift component that can be corrected by the conventional technique, and the alignment accuracy is deteriorated.

  That is, in the conventional alignment method, there is a limit to the improvement in alignment accuracy because the distortion of the semiconductor substrate itself is not taken into consideration.

  As described above, the conventional technique can achieve highly accurate alignment when the nonlinear distortion of the semiconductor substrate is negligibly small, but satisfies the required alignment accuracy when the nonlinear distortion is large. Can not do it.

  The present invention has been made to solve the above-described problems, and enables highly accurate alignment even with a semiconductor substrate having nonlinear distortion.

  In order to solve the above problems, the present invention uses the following alignment method.

  In a method of aligning each of a plurality of shots regularly arranged on a semiconductor substrate along design arrangement coordinates with a predetermined reference position by a step-and-repeat method, exposure is performed by the step-and-repeat method. Prior to the step, the distortion of the semiconductor substrate selected from within the lot is measured, and based on the distortion information of the semiconductor substrate, a correction is made to the design arrangement coordinates of the shot to create a new arrangement A step of generating coordinates, a step of measuring positions of alignment shots of several shots in a subsequent semiconductor substrate in the same lot, obtaining a deviation from the new arrangement coordinates, and a deviation from the new arrangement coordinates. Determining the placement coordinates of the shots to be placed on the semiconductor substrate, and step-and-repeat method according to the placement coordinates Was thus an alignment method characterized by and a step of exposing the shot.

  Further, the step of measuring the distortion of the semiconductor substrate is a method of measuring the positions of alignment marks of all shots in the selected semiconductor substrate and obtaining a deviation from the designed arrangement coordinates. It was set as the characteristic alignment method.

  The step of measuring the distortion of the semiconductor substrate may be performed using an apparatus used in the step of exposing.

  The step of measuring the distortion of the semiconductor substrate is performed using an apparatus different from the apparatus used in the exposing step.

  The alignment method is characterized in that a plurality of semiconductor substrates are selected from the lot.

  As described above, by using the exposure method and exposure apparatus for a semiconductor substrate according to the present invention, highly accurate alignment exposure can be performed even on a distorted semiconductor substrate, and the yield of a semiconductor manufacturing apparatus can be improved. it can.

  The present invention relates to a method for aligning shots formed on a semiconductor substrate by a step-and-repeat exposure apparatus, and an embodiment thereof will be described with reference to FIGS.

  FIG. 1 is a flowchart showing the alignment method of the present invention. First, it is measured how much and in what direction the alignment marks already formed on the semiconductor substrate are shifted from the design arrangement coordinates of the shots regularly arranged on the semiconductor substrate. Thereby, the strain amount and strain direction of the semiconductor substrate can be known (STEP 11). The distortion of the semiconductor substrate must be measured in detail in order to know whether it is linear or non-linear, and the position coordinates of the alignment marks attached to all shots formed on the semiconductor substrate are measured. Is desirable. More detailed distortion information can be obtained by dividing each shot and obtaining position coordinates, but this should be determined in consideration of the manufacturing process through which the semiconductor substrate has passed.

  When a lot is composed of a plurality of semiconductor substrates and the lots flow in the same manner, the semiconductor substrates in the lot have almost the same strain. The position of the shot may be measured. However, if the strain information obtained from a single semiconductor substrate is not sufficient, it is possible to select a plurality of semiconductor substrates from a lot and measure the positions of all the shots, thereby achieving higher accuracy. Alignment is possible. For example, when five semiconductor substrates are selected from a lot composed of 25 semiconductor substrates, an average of the distortions of the five semiconductor substrates may be used as the representative value of the lot. Further, the distortion information obtained from the selected first substrate is applied to the first to fifth semiconductor substrates, and the distortion information obtained from the selected sixth substrate is applied to the sixth to tenth substrates. The distortion information obtained from the selected eleventh substrate is applied to the semiconductor substrate, and the distortion information obtained from the selected sixteenth substrate is applied to the eleventh to fifteenth semiconductor substrates. The strain information of the selected semiconductor substrate is applied to the 20th semiconductor substrate, and the strain information obtained from the 21st selected last substrate is applied to the 21st to 25th semiconductor substrate. May be used as a representative of distortion information of a plurality of subsequent semiconductor substrates. The measurement of STEP 11 is to measure how much the coordinate of the alignment mark formed on the semiconductor substrate is distorted in what direction with respect to the design arrangement coordinate. It can be measured if it is present, and may be an exposure apparatus, an overlay measuring machine or a reduction exposure apparatus.

  Next, the distortion information obtained here is input to the exposure apparatus (STEP 12). Next, based on the distortion information, correction is made to the design array coordinates of all shots so as to minimize the average deviation between the array coordinates and the alignment mark coordinates, thereby generating new array coordinates. (STEP 13). Then, the position of the alignment mark is measured with several shots in the semiconductor substrate, and the deviation from the new arrangement coordinates obtained in STEP 13 is obtained (STEP 14). This measured value is statistically processed to determine the rotation component, magnification component, orthogonal component, and translation component of the shot. From this result, correction is performed as a coordinate system taking into consideration the rotation component, magnification component, orthogonal component, and translation component of the shot on which the semiconductor substrate is arranged (STEP 15), and the arrangement coordinates of each shot are generated (STEP 16). Thereafter, each shot is exposed on the semiconductor substrate by a step-and-repeat method according to the arrangement coordinates (STEP 17).

  As described above, when the alignment method of the present invention is used, as shown in FIG. 2, in addition to the conventional rotation component, magnification component, orthogonal component, and translation component, correction can also be made for random components. Even with a semiconductor substrate that has undergone a large process with random components due to various distortions, highly accurate alignment is possible.

It is a flowchart figure which shows the alignment method of this invention. The correction error of the alignment method of this invention is shown. It is a flowchart figure which shows the alignment method of a prior art. The correction error of the alignment method of a prior art is shown. It is a schematic diagram which shows the distortion of the semiconductor substrate which passed through the semiconductor manufacturing process. (a) A semiconductor substrate with linear distortion is shown. (b) A cross-sectional view taken along line AB of FIG. 5 (a) is shown. (c) A semiconductor substrate having nonlinear distortion. (d) A sectional view taken along line A′-B ′ of FIG. It is the figure which showed the misalignment of each shot on a semiconductor substrate. (a) It is the figure which showed the random error by nonlinear distortion. (b) It is the figure which showed the rotation error. (c) It is the figure which showed the magnification error. (d) It is the figure which showed the orthogonal error. (e) It is the figure which showed the translation error. (f) It is the figure which showed the total error before decomposing | disassembling deviation | shift amount.

Explanation of symbols

61 Semiconductor substrate 62 Shot 63 Shot misalignment (arrow)

Claims (5)

A method of aligning each of a plurality of shots regularly arranged along design arrangement coordinates on a semiconductor substrate in a step-and-repeat manner with respect to a predetermined reference position,
Prior to performing exposure in the step-and-repeat method, measuring distortion of a semiconductor substrate selected from within a lot; and
Correcting the design arrangement coordinates of the shot based on the distortion information of the semiconductor substrate, and generating new arrangement coordinates;
Measuring the position of alignment marks of several shots in subsequent semiconductor substrates in the same lot, and determining a deviation from the new array coordinates;
Determining an arrangement coordinate of a shot to be arranged on the semiconductor substrate based on a shift with respect to the new arrangement coordinate;
Exposing the shot by a step-and-repeat method according to the arrangement coordinates;
An alignment method including:   2. The step of measuring the distortion of the semiconductor substrate includes measuring the positions of alignment marks of all shots in the selected semiconductor substrate and obtaining a deviation from the designed arrangement coordinates. Alignment method.   The alignment method according to claim 1, wherein the step of measuring distortion of the semiconductor substrate is performed using an apparatus used in the exposure step.   The alignment method according to claim 1, wherein the step of measuring distortion of the semiconductor substrate is performed using an apparatus different from the apparatus used in the exposing step.   The alignment method according to any one of claims 1 to 4, wherein a plurality of semiconductor substrates are selected from the lot.

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