JP3895992B2 - Electron beam apparatus and semiconductor device manufacturing method using the apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron beam apparatus for performing shape observation and defect inspection of a wafer or mask having a high-density pattern having a minimum line width of 0.1 μm or less with high accuracy and high reliability, and the electron beam apparatus. The present invention relates to a device manufacturing method for performing pattern inspection of semiconductor devices during and after the process.
[0002]
[Prior art]
A pattern on the sample is obtained by irradiating a sample consisting of a semiconductor wafer or a mask for forming the wafer with a primary electron beam, processing an electrical signal obtained from secondary electrons emitted from the surface of the sample, An electron beam apparatus capable of obtaining the above is known. In such an electron beam apparatus, in order to improve the throughput, an apparatus that irradiates a sample with a plurality of primary electron beams using a single optical system (multi-beam method) has already been proposed. A system in which a plurality of primary electron beams are irradiated onto a sample by using systems in parallel has also been proposed.
[0003]
[Problems to be solved by the invention]
In the above-described conventional multi-beam type electron beam apparatus, a secondary electron image is formed when an energy filter effect is applied by applying a voltage lower than the sample surface to the sample-side electrode of the objective lens. The relationship is broken, and it is difficult to detect a secondary electron beam of a multi-beam without crosstalk. Therefore, high-accuracy image information cannot be obtained.
On the other hand, in the electron beam apparatus using a plurality of optical systems, the problem of crosstalk can be solved. However, since the plurality of optical systems are used, the larger the number of optical systems, the larger the apparatus. Further, the control system becomes complicated and expensive. Therefore, when these problems are taken into consideration, a relatively small number of optical systems must be provided, and ultimately the throughput cannot be significantly improved.
[0004]
The present invention is for solving the problems in the electron beam apparatus of the above-described conventional example, and the purpose thereof is to perform measurement and evaluation of the sample surface with high throughput, and further increase the size of the apparatus, An object of the present invention is to provide an electron beam apparatus capable of preventing complication and high price.
Another object of the present invention is to provide a semiconductor device manufacturing method including a step of evaluating a semiconductor wafer during or after the process using such an electron beam apparatus.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, in an electron beam apparatus according to the present invention, comprising a plurality of electron optical systems having at least one stage of electrostatic lens, and simultaneously evaluating a plurality of locations on a sample using these electron optical systems Is
One common control power source is provided for commonly controlling the electrostatic lenses of the plurality of electron optical systems.
[0006]
In the above-described electron beam apparatus according to the present invention, each electrostatic lens is composed of first to third electrodes, and the second electrode is the center of the first and third electrodes arranged vertically. And a voltage from a common control power source is applied, and the first or third electrode is configured to be applied with a voltage from an independently controllable power source provided for each electron optical system. It is preferable.
Further, at least one stage of electrostatic lens is configured as an objective lens, a voltage from an independent control power source is applied to the first electrode, and a third electrode which is the electrode facing the sample of the objective lens by the common control power source. By applying a voltage lower than the voltage applied to the sample to the electrode, it is preferable to have an energy filter effect of secondary electrons so that the potential contrast of the pattern on the sample can be evaluated.
[0007]
In an electron beam apparatus according to the present invention in another aspect, comprising a plurality of electron optical systems including an electron gun having an anode, a heat emission cathode and a Wehnelt, and simultaneously evaluating a plurality of locations on a sample.
One common control power source for controlling the cathodes in common by applying the same voltage to all the heat emitting cathodes of the plurality of electron guns in an adjustable manner;
An independent control power source provided for each electron optical system is provided, which individually adjusts the voltage to the Wehnelts of a plurality of electron guns and controls each Wehnelt independently.
The present invention further provides a semiconductor device manufacturing method including a step of inspecting a semiconductor device during or after the process using the electron beam apparatus according to the present invention.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory diagram for explaining a configuration of an electron beam apparatus according to an embodiment of the present invention, and the electron beam apparatus is of a system including a plurality of electron optical systems arranged in parallel. . In the figure, three sets of electron optical systems are shown as sectional views, but it is needless to say that two sets, or four sets or more can be provided. Each electron gun, L _a B ₆ cathode 1 constituting the heat emission cathode, and a Wehnelt 2, and the anode 3. A Wehnelt independent control power source 20 for supplying a voltage to the Wehnelt 2 is provided for each electron optical system, that is, for each electron gun, and these power sources 20 can individually adjust output voltages. The cathodes 1 of all the electron guns are commonly applied with the same voltage from one cathode common control power source 19 whose output voltage can be adjusted. Although not shown, the anodes 3 of all the electron guns are grounded. Has been.
[0009]
The primary electron beam emitted from each electron gun passes through the openings of the anode 3 and the aperture plate 4, travels along the trajectory indicated by reference numeral 31, and crosses over at the position 5. The crossover position 5 can be positioned at an appropriate position along the optical axis direction by individually adjusting the independent control power supply 20. At the crossover position 5, a circular opening for determining NA is arranged. The aperture of the aperture plate 4 has a square shape, whereby the trajectory 31 of the primary electron beam is shaped so that the cross-section is a square, and three cylindrical electrodes 6, 7 having an aperture at the center are provided. , 8 (upper electrode 6, central electrode 7, lower electrode 8) are reduced by a condenser lens comprising an electrostatic lens. Further, the primary electron beam is an objective composed of an electrostatic lens including three cylindrical electrodes 14, 15, 16 (upper electrode 14, central electrode 15, lower electrode 16) having an opening at the center. The sample 18 is irradiated through a lens to form a reduced image.
[0010]
All the central electrodes 7 of the condenser lens are electrically connected so as to have the same potential, and a voltage is applied from one common control power source 22 capable of adjusting the output voltage with high accuracy. The lower electrode 8 of each condenser lens is grounded, while the upper electrode 6 is applied with a voltage from an independent control power source 21 provided for each optical system and capable of individually adjusting the output voltage. By adjusting the output of each power supply 21 independently, each optical system can form a crossover image at an accurate position. As a result, crossover images of all optical systems can be formed at predetermined set positions.
[0011]
Similarly to the condenser lens, a voltage is applied to the central electrode 15 of the objective lens from one common control power supply 28 that is connected to have the same potential and can be adjusted with high accuracy. The accuracy R of the power source 28 is as _{follows. When} an electron gun using a La B ₆ cathode is used and the voltage to be supplied to the central electrode 15 is 20 kV,
R << ΔE / (20 × 10 ³ )
If ΔE ≒ 3V,
R << 1.5 × 10 ^-4
It becomes.
Therefore, the common control power supply 28 requires an adjustment accuracy of about 1 × 10 ⁻⁴ .
[0012]
A voltage is applied to the upper electrode 14 of the objective lens from an independent control power supply 27 that is provided for each electron optical system and can be individually adjusted. By adjusting the voltage individually, each electron optical system is adjusted. Control is performed so as to satisfy the set focusing condition, and a crossover image is formed at the position 17.
The deflectors 9 and 11 for scanning the primary electron beam in each electron optical system are scanned by scanning signals from the deflection power sources 24 and 25. An image plane generated during scanning by these deflectors 9 and 11 is used. It is necessary to correct the curvature. This curvature of field is corrected by adjusting the voltage applied to the upper electrode 14 from the independent control power supply 27 to adjust the in-focus state of the objective lens. In order to adjust the in-focus state, the power supply 27 needs to have a relatively high response speed, but if it can be corrected to ± 100 V or less, it does not require exceptionally high stability.
[0013]
The central electrodes 15 of all objective lenses are electrically connected so as to have the same potential, and are held at a voltage level from one common control power supply 28 whose output voltage can be adjusted. Similarly, the lower electrodes 16 of all objective lenses are electrically connected so as to have the same potential, and are held at a voltage level from one common control power source 29 whose output voltage can be adjusted. Depending on whether the output voltage of the power source 29 is higher or lower than the voltage applied to the sample 10 from the power source 30 (that is, depending on whether the potential of the lower electrode 16 is higher or lower than the potential of the sample 18), Part of the emitted secondary electrons can be turned back to the sample 18 side or passed through the objective lens.
[0014]
An image that clearly shows the difference between the shape and material of the pattern, such as when the pattern on the sample 18 is formed by a groove, or when it is formed by a plurality of different materials (for example, SiO ₂ and Al). When it is desired to obtain the voltage, a voltage higher than the potential of the sample 18 is applied from the power source 29 to the lower electrode 16.
On the other hand, in order to obtain a potential contrast image on the sample 18, a voltage lower than the output voltage of the power supply 30 is applied from the power supply 29 to the lower electrode 16. For example, when 0 V is applied from the power source 30 to the sample 18 and there are two regions of +2 V and −2 V on the sample 18, a voltage of −10 V is applied from the power source 29 to the lower electrode 16 of the objective lens. When applied, secondary electrons from the −2V region pass through the objective lens, and secondary electrons from the + 2V region are driven back to the sample 18 side by the objective lens. As a result, the -2V region in the obtained image becomes bright and the + 2V region becomes dark. Other areas have intermediate brightness. Therefore, potential contrast can be obtained.
[0015]
Secondary electrons that have passed through the objective lens are deflected by an E × B deflector (Wien filter) comprising an electrostatic deflector 11, an electromagnetic deflection coil 12, and a deflection core 13 for each electron optical system, and secondary electron detection is performed. And is processed by the SEM image forming circuit 23.
In the present embodiment, the electron gun uses a heat emission cathode. Then, by using this electron gun under space charge limiting conditions that reduce shot noise, shot noise is reduced, so that an image with a good S / N ratio can be obtained with a small beam current or high-speed scanning. Can be obtained at speed.
[0016]
Next, the semiconductor device manufacturing method of the present invention will be described. The semiconductor device manufacturing method of the present invention is executed in the semiconductor device manufacturing method described below with reference to FIGS. 2 and 3 using the above-described electron beam apparatus.
As shown in FIG. 2, the semiconductor device manufacturing method is roughly divided into a wafer manufacturing step S1 for manufacturing a wafer, a wafer processing step S2 for performing processing necessary for the wafer, and a mask required for exposure. A mask manufacturing process S3, a chip assembling process S4 for cutting out chips formed on the wafer one by one and making them operable, and a chip inspection process S5 for inspecting completed chips. Each of these steps includes several sub-steps.
[0017]
Among the processes described above, the process that has a decisive influence on the manufacturing of the semiconductor device is the wafer processing process S2. In this step, the designed circuit pattern is formed on the wafer, and a large number of chips that operate as a memory or MPU are formed.
Thus, it is important to evaluate the processing state of the wafer processed in the wafer processing step S2 that affects the manufacture of semiconductor devices, and the step S2 includes the following sub-steps.
[0018]
1. Thin film formation process (using CVD or sputtering) to form a dielectric thin film, wiring, or metal thin film that forms the electrode, which will be the insulating layer
2. 2. Oxidation process for oxidizing the thin film layer and the wafer substrate 3. Lithographic process for forming a resist pattern using a mask (reticle) for selectively processing a thin film layer, a wafer substrate or the like. Etching process that processes thin film layers and substrates according to resist pattern (eg, using dry etching technology)
5). 5. Ion / impurity implantation diffusion process Resist stripping step 7. Wafer inspection process for inspecting processed wafers.
Note that the sub-process of the wafer processing process S2 is repeatedly performed for the required number of layers, and a wafer before being separated for each chip in the chip assembly process S4 is formed.
[0019]
FIG. 3 is a flowchart showing a lithography process which is a sub-process of the wafer processing process of FIG. As shown in FIG. 3, the lithography process includes a resist coating process S21, an exposure process S22, a developing process S23, and an annealing process S24.
In the resist coating step S21, a resist is coated on the wafer on which the circuit pattern is formed by using CVD or sputtering, and in the exposure step S22, the coated resist is exposed. Then, in the developing step S23, the exposed resist is developed to obtain a resist pattern, and in the annealing step S24, the developed resist pattern is annealed and stabilized. These steps S21 to S24 are repeated for the required number of layers.
[0020]
In the semiconductor device manufacturing method of the present invention, the electron beam apparatus described with reference to FIG. 1 is used not only in the process in the middle of processing (wafer inspection process) but also in the chip inspection process S5 for inspecting the completed chip. As a result, even a semiconductor device having a fine pattern can obtain an image with reduced distortion, blur, etc., so that defects on the wafer can be reliably detected.
[0021]
【The invention's effect】
Since this invention is comprised as mentioned above, there can exist the following effects.
1. Since a plurality of electron optical systems are arranged in parallel, the crosstalk is reduced and the throughput is improved as compared with the case of the multi-beam method in which a plurality of primary electron beams are formed using one electron gun. Can do.
2. The potential of the electron gun cathode, condenser lens center electrode, and objective lens center electrode and lower electrode that need to be adjusted with high precision is adjusted and controlled by a common power source for multiple electron optical systems. The configuration of the electric control system can be simplified.
3. Since the Wehnelt potential of the electron gun can be controlled by a separate power supply provided for each electron optical system, the crossover position created by the electron gun is adjusted to the designed position even if there is a difference in the electron gun. be able to.
4). Since focusing is controlled by the electrode (that is, electrode 14) that is originally grounded of the condenser lens and the objective lens, correction for each electron optical system can be performed by an independent power source.
5). Since the lens of the electron optical system has two stages of the condenser lens and the objective lens and is small, the structure and the control system can be simplified. Thereby, for example, ten or more optical systems can be arranged on a 12-inch wafer, and the throughput can be improved about 10 times.
6). By operating the electron gun under a space charge limiting condition that reduces shot noise, a high-quality image can be obtained even with a small beam current or high-speed scanning.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an electron beam apparatus according to the present invention.
FIG. 2 is a flowchart showing an example of a semiconductor device manufacturing method.
FIG. 3 is a flowchart showing a lithography process that forms the core of the wafer processing process shown in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cathode 2 ... Wehnelt 3 ... Anode 4 ... Aperture plate 5, 17 ... Crossover position 6-8 ... Condenser lens 9 ... Deflector 10 ... Secondary electron detector 11-13 ... ExB deflector 14-16 ... Objective lens 18 ... Samples 19, 22, 28, 29 ... Common control power source 20, 21, 27 ... Independent control power source 23 ... Image processing device 24, 25, 30 ... Power source

Claims (3)

The anode, the thermal emission cathode and an electron gun having a Wehnelt, each having a plurality of electron-optical system having a first and second electrostatic lens which is constituted by three electrodes, these electron optical system In an electron beam apparatus that simultaneously evaluates multiple locations on a sample,
A common control power source for commonly controlling a plurality of first electrostatic lenses, a first common control power source for commonly applying a voltage to an intermediate electrode of the first electrostatic lens;
A common control power source for commonly controlling a plurality of second electrostatic lenses, a second common control power source for commonly applying a voltage to an intermediate electrode of the second electrostatic lens;
A third common control power source for tunably applying the same voltage to all the heat emitting cathodes of the plurality of electron guns to control the cathodes in common;
A plurality of first independent control power supplies for independently applying a voltage to one of both end electrodes of the plurality of first electrostatic lenses;
A plurality of second independent control power sources for independently applying a voltage to one of both end electrodes of the plurality of second electrostatic lenses;
In order to locate the crossover position of the electron beam from these electron guns in a circular opening by independently applying an adjustable voltage to the Wehnelts of a plurality of electron guns and controlling each Wehnelt independently. An electron beam apparatus comprising: a plurality of third independent control power supplies provided for each electron optical system . The electron beam apparatus according to claim 1 ,
The first electrostatic lens is an objective lens,
The voltage from the first independent control power source is applied to the electrode on the side that does not face the sample among the two end electrodes of the objective lens ,
The electron beam apparatus further includes a common control electrode for controlling a plurality of objective lenses in common, and a voltage applied to the sample to an electrode on the side opposite to the sample among both end electrodes of the objective lens. A fourth common control electrode for applying a lower voltage ,
Thus, to have an energy filtering effect of the secondary electron, electron beam apparatus is characterized in that to be able to assess the potential contrast of a pattern on the sample. A method of manufacturing a semiconductor device, using the electron beam apparatus according to claim 1 or 2, the semiconductor device manufacturing method comprising the step of examining the semiconductor device after the process during or complete.

Images