JP2019091065A - Projection exposure method - Google Patents

Abstract

SOLUTION: A rectile is actually put into a device when using a first rectile to perform oblique measurement and random measurement. A measurement spot size that is generally fixed is made variable and an incident angle is changed according to the measurement spot size.EFFECT: A partial sampling risk can be avoided even without increasing the number of samplings to catch a rectile transmittance of the entire rectile used as a population.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method of measuring transmittance of a reticle used for manufacturing a semiconductor device, and a projection exposure apparatus and a projection exposure method used for the measurement.

  When a first reticle is used in a projection exposure apparatus, for example, a stepper, the reticle is actually put into the apparatus, exposed by a mercury lamp of a light source, transmission / incident energy is calculated, and returned as reticle transmittance. At this time, the entire surface of the reticle pattern is exposed and sampled at equal intervals. When the entire reticle is viewed as a population, it is necessary to estimate the characteristics, but since it is practically difficult to recognize what pattern it is, there is often a possibility of biased sampling. For example, in a pattern repeated at the same pitch as sampling, the result returned as reticle transmittance deviates from the actual value. In the projection exposure apparatus, when the amount of light to be transmitted increases, a correction function works to cancel the influence of lens expansion caused by heat generation when the exposure load becomes large, but if it is not properly fed back, it leads to defocus and line width Variation of the resist profile, the resist profile can not maintain a rectangular shape, and it becomes difficult to form a desired pattern. In the wiring pattern, there is a problem that the short / open occurs and the quality is impaired.

  Therefore, by increasing the number of samplings, it is attempted to capture the entire reticle as a population. However, when measuring at equal intervals, the risk of biased sampling remains. Even if the measurement can be accurately performed, it takes a long time to perform the measurement, and the productivity of the projection exposure apparatus is impaired.

JP 2001-297961 A Japanese Patent Application Laid-Open No. 6-236838

  As described in the background art, in the case where there is a pattern repeated at the same pitch as sampling, the result obtained as the reticle transmittance sometimes causes a problem of divergence from the actual value. For example, in the case of obtaining the reticle transmittance in consideration of the feature of the pattern, when the area is different for each shot as in Patent Document 1, the total light quantity measurement of the entire reticle surface is performed to store data for the projected image. There is a method of obtaining the reticle transmittance by calculating the actual exposed portion of the reticle from the data and the opening and closing of the masking blade. In order to calculate the actual exposed portion of the reticle, it is a precondition that the total light amount measurement on the entire surface of the reticle can be accurately performed first. Even if an exposed portion is actually calculated by opening and closing the masking blade, if there is a pattern repeated at the same pitch as sampling, the result returned as reticle transmittance deviates from the actual, and the actual exposed portion of the reticle It will be difficult to calculate.

  Also, in order to accurately measure the reticle transmittance, it is attempted to capture the entire reticle as a population by increasing the sampling number. Further, as in Patent Document 2, the reticle is actually inserted into the apparatus, exposed with a mercury lamp as a light source, image data of a transferred image of the formed reticle pattern is taken in, and image data obtained by this is taken. Although there is a method of obtaining the reticle transmittance, in any case, it takes a lot of time for measurement because the huge number of sampling increases, and there is a problem that the productivity of the projection exposure apparatus is lost.

  The present invention has been made in view of such problems, and the problem is to calculate the load used for exposure load correction as a countermeasure for defocus due to lens expansion caused by an increase in exposure load in the projection exposure apparatus. Measurement method and reticle exposure apparatus for reticle transmittance measurement.

  In order to solve the above problems, the following means are used in the exposure method of the semiconductor device of the present invention.

  A process of creating design data of a reticle pattern using a standard CAD tool in order to obtain reticle transmittance in a short time without actually performing reticle transmittance measurement by diverting design data of a reticle pattern The process of converting this design data as a standard file format stream format (called GDSII) or data written in mask CAD such as cif format, and reticle transmittance from the converted design data And storing the obtained reticle transmittance. Further, the present invention provides a semiconductor exposure apparatus or an exposure method characterized in that reticle transmittance is directly obtained from data without measuring reticle transmittance using an actual reticle.

  According to the present invention, as a countermeasure for defocusing caused by lens expansion caused by an increase in exposure load in a projection exposure apparatus, a method of obtaining reticle transmittance with high accuracy and in a short time, regardless of a pattern having any features. That is, it is possible to provide a method of determining the correct reticle transmittance without losing productivity.

It is a block diagram of the stepper which concerns on embodiment of this invention. It is a block diagram of the conventional stepper. It is an explanatory view for explaining a method of obliquely measuring a reticle transmittance. It is explanatory drawing for demonstrating the method to measure the reticle transmittance | permeability at random. It is explanatory drawing for demonstrating the method to measure the inclination according to measurement spot size small. It is explanatory drawing for demonstrating the method to measure the inclination according to measurement spot size large. It is explanatory drawing for demonstrating the transmittance | permeability measurement method of one chip | tip area | region. It is explanatory drawing for demonstrating the transmittance | permeability measurement method of four chip | tip area | regions. It is explanatory drawing explaining the method to measure the transmittance | permeability of the area | region which narrowed down only to the arbitrary area | regions.

  FIG. 1 is a block diagram of a stepper which is one of the projection exposure apparatuses according to the embodiment of the present invention, and has a function of performing exposure load correction from design data. The stepper includes the illumination optical system 1, the reticle 2 which is an original plate for actually measuring the reticle transmittance, and a projection for reducing the reticle pattern to, for example, 1⁄5 and transferring the desired pattern by exposure. Optical system 3, stage 4 for moving the wafer to a predetermined measurement spot for measuring reticle transmittance, chuck 5 for supporting the wafer, photodetector 6 for measuring the amount of light passing through the projection optical system, and measured reticle transmittance The CPU 7 has a CPU 7 that performs exposure load correction, calculates reticle transmittance from design data to perform exposure load correction, and controls driving of the illumination optical system 1 and the stage 4.

  The reticle transmittance storage device 8 is a storage device for storing data of reticle transmittance measured actually and data of reticle transmittance calculated from the design data 9. The method of using the design data 9 will be described later.

  For reference, a block diagram of a conventional stepper is shown in FIG. The clear difference is that in the conventional stepper, there is no linkage with the design data, and the reticle transmittance storage unit 8 does not effectively utilize the reticle transmittance data calculated from the design data.

  Using the above configuration, it is possible to solve the conventional problem that the result returned as the reticle transmittance deviates from the actual value when there is a pattern repeated at the same pitch as sampling. The method of measuring the reticle transmittance will be specifically described below.

  In the first method, as shown in FIG. 3, for example, the light intensity measurement spots 10 are taken diagonally in the diagonal direction of the reticle, for example, in the conventional measurement with 0.2 mm pitch in the X and Y directions. .2 The measurement is performed at 2 mm pitch. Here, "diagonally diagonal" means to follow along a straight line that is a straight line that is diagonal to the four sides of the reticle and that is not generally coincident with the diagonal. At this time, sampling in the X and Y directions is set to have different intervals with respect to the repeated pattern of the reticle. Alternatively, the measurement spots 10 may be diagonally placed on the reticle and the transmittance may be measured at different pitches such as 0.2 mm, 0.3 mm, 0.2 mm and 0.3 mm. Also in this case, the sampling in the X and Y directions is set so as to overlap different patterns without overlapping the same pattern for repeated patterns of the reticle.

  The reticle transmittance, which is the characteristic of the entire reticle, is obtained from the above sampling and stored in the reticle transmittance storage unit 8. Based on the reticle transmittance thus determined, the CPU (exposure load correction device) 7 in FIG. 1 performs exposure load correction in the focus, lens distortion, and magnification as necessary in combination, and feeds it back to the projection optical system 3 in FIG. , Projection exposure.

  In the second method, as shown in FIG. 4, for example, in the conventional measurement in order of 0.2 mm pitch in the X and Y directions, for example, the pitch of the measurement spots 10 is 0.2 to 1.0 mm. And move them randomly in combination in the X and Y directions individually, and perform non-regular measurement, and do not overlap the same pattern for repeated patterns of the reticle. The sampling operation is set so as to overlap different patterns.

  In the third method, as shown in FIG. 5, the measurement spot conventionally fixed at 0.3 mmφ, for example, is made variable from 0.3 mmφ to 1.0 mmφ according to the size of the measurement spot, The inclination angle is changed. When the size of the measurement spot 11 viewed from the front is small, for example, 0.3 mmφ, the inclination angle θ1 (12) from the surface of the reticle 2 when viewed from the side is small with 10 to 30 degrees Measure the reticle transmittance. In this manner, even when the size of the measurement spot is small, a large effective measurement area can be secured. On the other hand, as shown in FIG. 6, when the size of the measurement spot 13 viewed from the front is large, for example, 1.0 mmφ, the inclination angle θ2 (14) from the surface of the reticle 2 viewed from the side is 70 to 90 degrees. The reticle transmission may be measured with a large slope between. When the size of the measurement spot is large, a large measurement area can be secured. By changing the size of the measurement spot in this manner, it is possible to prevent sampling by the same pattern.

  In the fourth method, as shown in FIG. 7, only one chip area is sampled and transmittance measurement is performed on a polyhedral reticle composed of a plurality of identical chips, and the reticle transmittance is obtained from the result. It is a method to calculate. Here, one chip region 15 refers to, for example, a region which is a unit surrounded by an operation region of a semiconductor device and a region to the center (middle) of a scribe line to be ground by dicing outside the region. In addition, the entire area of the polyhedron refers to the entire surface of the reticle including all of these unit areas. As these, the parameters are input to the apparatus as the area to be sampled in advance and the entire area of poly-imposition. The reticle transmittance of the entire surface of the reticle is calculated from the area ratio of one chip region 15 to the entire region of polyhedralization, and is stored in the reticle transmittance storage unit 8. Based on the reticle transmittance thus determined, the CPU (exposure load correction device) 7 in FIG. 1 performs exposure load correction in the focus, lens distortion, and magnification as necessary in combination, and feeds it back to the projection optical system 3 in FIG. , Projection exposure.

  In the fifth method, as shown in FIG. 8, in a multi-faceted reticle composed of a plurality of identical chips, only four chip areas 16 are sampled to measure the transmittance, and the result shows that the reticle transmittance Is a method of calculating The exposure load correction similar to the fourth method can be performed by calculating the transmittance of the entire surface of the reticle, which is calculated from the area ratio of the four chip areas 16 and the entire area of polyhedra.

  In the sixth method, as shown in FIG. 9, transmittance measurement is performed by sampling only a region 17 narrowed down to 1⁄4 of the entire reticle, in a multi-faceted reticle composed of a plurality of identical chips, It is a method of calculating the reticle transmittance from the result. The reticle transmittance of the entire surface of the reticle is calculated from the area ratio of the area 17 narrowed to 1/4 of the entire reticle and the entire area of polyhedra, thereby shortening the required time to 1/4 of the usual time. Exposure load correction similar to the fourth and fifth methods is possible.

  The seventh method is a method of determining the reticle transmittance without actually performing the transmittance measurement, unlike the above method. In order to obtain the design data 9 of FIG. 1, first, design data of the reticle is created by CAD for all layers. Next, the design data is converted into a standard file format stream format (called GDSII) or cif format. Then, the reticle transmittance is obtained from the converted data from the occupied area of the light shielding film on the reticle, and data is stored as reticle transmittance in the reticle transmittance storage device 8 of FIG. 1 via the LAN network. Based on the stored reticle transmittance, the CPU (exposure load correction device) 7 of FIG. 1 performs exposure load correction as needed in focusing, lens distortion, and magnification in combination, and the projection optical system 3 of FIG. give feedback. By doing this, it is possible to obtain reticle transmittance in a short time without measuring transmittance with an actual reticle. In this way, the reticle transmittance determined without performing the measurement is compared with the reticle transmittance determined by the above first to sixth methods to increase the accuracy of obtaining the reticle transmittance from CAD data, or to measure It is possible to optimize the sampling in the above, and it is possible to further improve the accuracy.

  It is possible to use for manufacture of an apparatus which needs micro processing which has a process of using a photolithographic technique using a reticle in a semiconductor substrate and a projection exposure apparatus such as MEMS.

1 Illumination optical system 2 Reticle (original)
Reference Signs List 3 projection optical system 4 moving stage 5 chuck 6 photodetector 7 CPU (exposure load correction device)
8 Reticle transmittance storage unit 9 Design data 10 Light quantity measurement spot (point to measure light quantity)
11 Measurement spot (small size, for example, 0.3 mmφ) as viewed from the front
12 Tilt angle θ1 from reticle surface
13 Measurement spot (in the case of large size, for example, 1.0 mmφ) viewed from the front
14 Tilt angle θ2 from reticle surface
15 One chip area 16 for measuring the transmittance Four chip areas 17 for measuring the transmittance 17 Area reduced to 1/4 of the whole reticle for measuring the transmittance

Claims (2)

A projection exposure method using design data of a reticle
Creating reticle design data;
Converting the design data into stream format or cif format;
Determining reticle transmittance from the data converted design data;
Storing the reticle transmittance in a reticle transmittance storage device of a projection exposure apparatus;
Performing exposure load correction based on the reticle transmittance;
A projection exposure method characterized by comprising:   The projection exposure method according to claim 1, wherein the exposure load correction is at least one of focus correction, lens distortion correction, and magnification correction.

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