JP2011103177A - Electron beam irradiation method and electron beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam irradiation method and device, capable of suppressing a partial effect by partial irradiation of a sample with electron beam. <P>SOLUTION: In the method and device, the electron beam is emitted to the whole surface of a semiconductor wafer between a semiconductor exposing step and an etching step. According to this structure, partial shrinkage of a pattern which is caused by the electron beam emitted for measurement or inspection can be suppressed to improve the overall accuracy of pattern formation in the semiconductor wafer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electron beam irradiation method and an electron beam irradiation apparatus, and more particularly to a method and apparatus capable of suppressing pattern shrinkage and / or pattern roughness based on beam irradiation.

  When an electron microscope is used to check the dimensions of the circuit pattern, the resist pattern on the wafer substrate may be shrunk by an electron beam (hereinafter also referred to as shrink). If the pattern shrinks, there is a possibility of affecting the subsequent manufacturing process. For example, in Patent Document 1, the distance between scanning lines of electron beams is expanded to reduce the amount of electron beam irradiation per unit area. A technique for suppressing the above is disclosed.

  Further, along with the recent miniaturization of devices, it has been confirmed that the linearity of the pattern shape is deteriorated, in particular, the uneven width seen in the line pattern. Such uneven portions (hereinafter sometimes referred to as roughness) may adversely affect the transistor gate that affects the performance of the device.

WO03 / 021186

  As described above, since an electron beam irradiated for measurement or inspection induces pattern shrinkage, measurement or inspection that irradiates the pattern with an electron beam as much as possible is required. According to the method disclosed in Patent Document 1, it is possible to suppress the irradiation amount per unit area without degrading the measurement accuracy, but the electron beam irradiation amount cannot be reduced to zero. The effects of local irradiation remain.

  Hereinafter, an electron beam irradiation method and apparatus aiming at suppressing a partial influence by partial irradiation of an electron beam on a sample will be described.

  In order to achieve the above object, a method and apparatus for irradiating an entire surface of a semiconductor wafer with an electron beam between a semiconductor exposure process and an etching process are proposed.

  According to the above configuration, it is possible to suppress partial pattern shrinkage caused by an electron beam performed for measurement or inspection, and to improve pattern formation accuracy in the entire semiconductor wafer.

The figure explaining the outline | summary of a scanning electron microscope for length measurement, and an example of the pattern formed on the semiconductor wafer. The figure explaining an example of the resist pattern in which resist shrinkage occurred partially by electron beam irradiation. The figure explaining the example with which several FOV for a measurement overlaps. The figure explaining an example of the apparatus which irradiates an electron beam to the wide range on a sample. The figure explaining a part of semiconductor manufacturing process. The figure explaining an example of the apparatus which attached the electron beam irradiation chamber to the dry etcher apparatus. The figure explaining an example of an electron beam irradiation chamber. The figure explaining an example of a semiconductor measurement and a test | inspection system.

  FIG. 8 is a diagram for explaining an example of a measurement / inspection system for measuring or inspecting a sample such as a semiconductor wafer. FIG. 8 illustrates a system in which a plurality of SEMs (Scanning Electron Microscopes) are connected around the data management device 801. Particularly in the case of this embodiment, the SEM 802 is mainly used for measuring and inspecting the pattern of a photomask and a reticle used in a semiconductor exposure process, and the SEM 803 is mainly used for the semiconductor by exposure using the photomask and the like. It is for measuring and inspecting the pattern transferred on the wafer. The SEM 802 and the SEM 803 have a structure corresponding to a difference in size between a semiconductor wafer and a photomask and a difference in resistance to charging, although there is no significant difference in the basic structure as an electron microscope.

  Respective control devices 804 and 805 are connected to the respective SEMs 802 and SEM 803, and control necessary for the SEM is performed. In each SEM, an electron beam emitted from an electron source is focused by a plurality of stages of lenses, and the focused electron beam is scanned one-dimensionally or two-dimensionally on a sample by a scanning deflector. . Each control device also functions as a control device that controls an electron beam irradiation device described later.

  Secondary electrons (SE) or backscattered electrons (BSE) emitted from the specimen by scanning with an electron beam are detected by a detector, and are synchronized with the scanning of the scanning deflector in a frame memory. Or the like. The image signals stored in the frame memory are integrated by an arithmetic device mounted in the control devices 804 and 805. Further, scanning by the scanning deflector can be performed in any size, position, and direction.

  The above control and the like are performed by the control devices 804 and 805 of each SEM, and images and signals obtained as a result of scanning with the electron beam are sent to the data management device 801 via the communication lines 806 and 807. It is done. In this example, the control device that controls the SEM and the data management device that performs measurement based on the signal obtained by the SEM are described as separate units. However, the present invention is not limited to this. The data management apparatus may perform the apparatus control and the measurement process collectively, or each control apparatus may perform the SEM control and the measurement process together.

  The data management device or the control device stores a program for executing measurement processing, and measurement or calculation is performed according to the program. Furthermore, the design data management apparatus stores design data of photomasks (hereinafter sometimes simply referred to as masks) and wafers used in the semiconductor manufacturing process. This design data is expressed in, for example, the GDS format or the OASIS format, and is stored in a predetermined format. The design data can be of any type as long as the software that displays the design data can display the format and can handle the data as graphic data. The design data may be stored in a storage medium provided separately from the data management device.

  The data management device 801 has a function of creating a program (recipe) for controlling the operation of the SEM based on semiconductor design data, and functions as a recipe setting unit. Specifically, a position for performing processing necessary for the SEM such as a desired measurement point, auto focus, auto stigma, addressing point, etc. on design data, pattern outline data, or simulated design data And a program for automatically controlling the sample stage, deflector, etc. of the SEM is created based on the setting.

  FIG. 1 illustrates a specific configuration of the SEMs 802 and 803 illustrated in FIG. In a lithography process, which is one process of semiconductor manufacturing, the size of various patterns transferred onto a wafer by a scanning electron microscope for length measurement (hereinafter referred to as a CD-SEM (Critical Dimension-SEM)) 100 shown in FIG. Confirmation is in progress. In FIG. 1, a CD-SEM 100 scans a silicon wafer (sample) 105 by bending an electron beam, an electron beam source 101 emitting an electron beam (electron beam), a converging lens 102 for converging the electron beam. A deflector (deflection coil) 103, an objective lens 104 for irradiating the pattern 106 on the silicon wafer 105 with an electron beam, a detector 107 for detecting secondary electrons or reflected electrons from the pattern 106, It has.

  In the CD-SEM having such a configuration, the size of the fine pattern 106 transferred onto the silicon wafer 105 can be measured by scanning with an electron beam, and a recipe that manages length measurement points, wafer maps, and the like is executed. Automatic length measurement can be performed. These length measurement data are used for evaluation of device manufacturing conditions, process management, and the like, and in particular, in the evaluation of device manufacturing conditions, thousands of measurements are performed.

  On the other hand, a photoresist has a property that a portion irradiated with an electron beam contracts (hereinafter referred to as resist shrink). Therefore, it is considered that the size of the pattern used for the measurement as described above is changed compared with the portion where the measurement is not performed.

  FIG. 2 is a diagram for explaining an example of a resist pattern, in which a resist pattern 200, a resist pattern 201 in which an electron beam irradiation area 202 (Field Of View: FOV) of the SEM is set, and partial shrinkage are generated by electron beam irradiation. The resist pattern 203 is illustrated. As described above, when the beam is partially scanned for measurement or inspection, the pattern is contracted with respect to other regions.

  In recent years, the circuit pattern has been miniaturized and the degree of integration has been increased, so that not only the line width has been reduced, but also the distance between adjacent patterns has been reduced, and measurement can be performed without overlapping electron beam irradiation regions. It's getting harder. FIG. 3 shows a case where a field of view 301 for measuring the measurement point 1 and a field of view 302 for measuring the measurement point 2 are partially overlapped on a sample on which a plurality of patterns are arranged, so that electrons are doubled. An example in which a region 300 to be beam-scanned is described. Resist shrink is dependent on the electron dose to be irradiated, and the overlap of irradiated areas shown in the figure may increase resist shrink.

  The influence of resist shrink generated by electron beam irradiation varies depending on the importance of the process. Although the influence of resist shrink can be ignored if the process has a margin in the design rule, for example, in the gate formation process, a slight dimensional difference affects the performance of the transistor, so that the yield may be affected.

  Therefore, as a method for reducing the influence of resist shrink by CD-SEM, a method of irradiating an entire surface of the wafer after exposure and development with an electron beam is proposed. This method suppresses partial shrinkage caused by beam irradiation for measurement and inspection by generating shrinkage uniformly on all resist patterns on the sample by irradiation of the entire surface with the electron beam to the sample. Is possible. By irradiating the entire surface of the wafer with the electron beam, a difference in the degree of shrinkage between the region irradiated with the measurement beam and the other regions can be suppressed. In the place where the measurement beam is irradiated, the electron beam irradiation and the measurement beam irradiation are superimposed on the entire wafer surface. The difference in the amount of shrinkage between the regions can be suppressed.

  This technique is a slimming process performed after an exposure process and after a resist pattern is formed before the etching process, and is particularly effective for a pattern having a size of about 30 nm or less after etching by a microfabrication technique. It does not depend on size. In addition, electron beam irradiation reduces the line width non-uniformity (hereinafter referred to as LINE (Line Edge Roughness) or LWR (Line Width Roughness)) seen in the line pattern, and thus the influence of shrinkage. Combined with reduction, it is synergistically effective in improving pattern formation accuracy. The CD-SEM measurement has no problem either before or after the entire surface irradiation.

  FIG. 5 is a diagram for explaining an example of a semiconductor process having a slimming process by irradiation with an entire surface of an electron beam. A resist film is applied on the multilayer substrate, and the exposed resist pattern 500 is irradiated with the entire surface of the electron beam. By irradiating the entire surface with an electron beam, the resist pattern contracts, and a resist pattern 501 having a reduced line width is formed. Then, the reflective film is processed (pattern 502), and further a lower layer film is formed, thereby creating a pattern 503. 500 is a resist pattern on a wafer substrate having a multilayer structure, 501 is a resist pattern shrunk by electron beam irradiation, 502 is a resist pattern after slimming, and 503 is a pattern after etching.

  The description so far relates to a method of performing the entire irradiation of the electron beam by scanning the electron beam. For example, the entire irradiation can be performed by mounting an electron gun capable of large-diameter beam irradiation on the SEM. It is also possible to do this. As a specific example, an electron gun that can irradiate an electron beam with a large aperture as shown in FIG. 4 is mounted on a CD-SEM, or an electron beam is irradiated to an electron beam on a wafer after exposure and development processing. To do. The irradiation dose at this time is increased or decreased depending on the type of resist and the process with 3000 pA as a guide. When the effect of shrinking is mainly desired to be reduced, the effect is effective even at 1000 pA or less, and when the main purpose is LER reduction, 4000 pA is the most effective.

  In order to make it possible to set the current amount of the electron beam as described above, it is desirable to design the electron beam irradiation apparatus so that the current amount can be controlled, for example, to about 500 pA to 5000 pA.

  An electron beam irradiation mechanism 400 illustrated in FIG. 5 includes an electron beam source 401, a converging lens 402, and a deflector 403, as in a general SEM, and forms a beam with a larger diameter than a normal SEM. Designed to be able to. By scanning a large-diameter beam with the deflector 403, the entire surface can be irradiated. Such an electron beam irradiation mechanism may be provided separately from the normal SEM optical system, or may be incorporated in the SEM.

  Further, as a method for irradiating the entire surface of the electron beam, there is a method performed by an etching apparatus in addition to the above-described method. 6 and 7 illustrate the outline of the etching apparatus. FIG. 6 illustrates the outline of the etching apparatus, and FIG. 7 illustrates the electron beam irradiation chamber connected to the etching apparatus. 6 is provided between the electron beam irradiation chamber 601, the dry etcher chamber 602, the wafer transfer unit 604, the preliminary exhaust chamber 604, and the electron beam irradiation chamber 601 whose details are illustrated in FIG. A gate valve 603 and a wafer cassette installation unit 605 are provided. The etching apparatus illustrated in FIG. 6 has a structure in which two chambers are coupled via a transfer unit 604, and each can be evacuated.

  In the electron beam irradiation chamber 700 illustrated in FIG. 7, electromagnetic waves emitted from the plasma power source 701 are emitted from the antenna 702 into the vacuum chamber 704 through a window 703 that transmits electromagnetic waves such as quartz. A rare gas such as argon or an inert gas such as nitrogen is held in the chamber 704 at a constant pressure, and plasma 705 is generated by electromagnetic waves. Between the plasma 705 and the wafer 708, mesh grids 706 and 707 for extracting electrons are installed. 706 is a ground potential, and a power source 707 is connected to 707 to become a positive potential to accelerate electrons. Electrons extracted from the plasma are irradiated onto the wafer 708 on the sample stage 709. The sample stage is maintained at a positive potential by a power source 710 as necessary.

  Before the dry etching, the entire surface of the wafer is irradiated with an electron beam at the electron beam irradiation unit shown in FIG. 7, and the effects of reducing the influence of the resist shrink and the line edge roughness can be expected. In addition, after the electron beam irradiation treatment, the wafer is transferred to the dry etching chamber and the processing is started, so that efficient wafer processing is possible.

  According to the above-described method, it is possible to reduce the influence of resist shrink and reduce the line edge roughness in a pattern with a post-process dimension of 30 nm or less, thereby improving the pattern creation accuracy.

  It is also possible to control the overall irradiation amount according to the measurement result of the pattern width by SEM. For example, if the measurement is performed by SEM and the measurement result is a predetermined value or less, the entire surface irradiation is selectively performed, or the current amount of the entire surface irradiation beam is relatively increased. It becomes possible to suppress a general shrink. In the case of this example, by providing a function or table indicating the relationship between the measured value (or shrink amount) and the beam current for the entire surface irradiation, it is possible to perform appropriate entire surface irradiation according to the measured value. good.

  Furthermore, by providing a function or table indicating the relationship between the optical conditions such as the measurement magnification, beam current, and the number of frames and the beam current for the entire surface irradiation, it is possible to perform appropriate entire surface irradiation according to the optical conditions. May be.

  Further, a function or a table indicating the relationship between the two may be provided so that the optical condition can be determined according to the current amount of the beam for whole surface irradiation. Further, when the allowable amount of shrinkage is determined in advance, a function or a table showing the relationship between the allowable amount and the measurement beam condition and / or the whole-surface irradiation beam condition is prepared. May be automatically determined.

  Further, in order to set the measurement beam condition and the full-surface irradiation beam condition according to the design rule registered as the design data, a function or a table indicating the relationship between the two may be provided. More specifically, for example, when there is a pattern having a design value whose line width is equal to or less than a predetermined value, the entire surface irradiation may be selectively performed. Such setting may be performed by the data management apparatus 801 illustrated in FIG. 8 or may be performed by the control apparatus 805.

  In addition, since the degree of shrinkage changes depending on whether or not a plurality of FOVs for measurement overlap, if the FOV is determined to overlap based on the position of the FOV set on the design data, it is selectively You may make it perform whole surface irradiation.

DESCRIPTION OF SYMBOLS 100 Scanning electron microscope for length measurement 101 Electron beam source 102 Converging lens 103 Deflector 104 Objective lens 105 Silicon wafer 106 Pattern 107 Detector

Claims (5)

In an electron beam irradiation method for irradiating a semiconductor wafer with an electron beam,
After the exposure process of irradiating the resist coated on the semiconductor wafer with light to expose the pattern, the entire surface of the semiconductor wafer coated with the resist is irradiated with the electron beam, and the electron beam irradiation is performed. An electron beam irradiation method, comprising: etching a semiconductor wafer after being performed. In claim 1,
The electron beam irradiation method according to claim 1, wherein the electron beam on the entire surface of the semiconductor wafer has a current amount between 500 pA and 5000 pA. In claim 1,
An electron beam irradiation method comprising performing pattern dimension measurement by electron beam scanning before or after electron beam irradiation on the entire surface of the semiconductor wafer. In claim 1,
An electron beam irradiation method, comprising: performing electron beam irradiation on the entire surface of the semiconductor wafer, shrinking a resist pattern on the semiconductor wafer, and then etching the semiconductor wafer. In a scanning electron microscope that detects electrons emitted from the semiconductor wafer by scanning an electron beam with respect to the semiconductor wafer and measures a pattern formed on the semiconductor wafer,
A scanning electron microscope comprising an electron beam irradiation mechanism for irradiating an entire surface of the semiconductor wafer with an electron beam.

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