JPH0381940A - Evaluation device for semiconductor device in semiconductor manufacturing process - Google Patents

Abstract

PURPOSE:To enhance the operating easiness by emitting one of electron beams having different energies selectively in conformity to a command, and thereby permitting a single unit of evaluating device to make evaluation of a semiconductor device about a process, in which insulation is exposed to the surface partially, and another process in which the insulation covers the whole surface. CONSTITUTION:An electron beam emitted from an electron gun 1 for emission of thermo electric field is focused on a target 15 upon passing through a capacitor lens 2, deflector coil 4, and objective lens 3. To observe the surface of the target 15 and make evaluation, electron beam with a low acceleration voltage is left incident to the target 15. To evaluate the condition of the pattern, etc., under the overlayer of the target 15, on the other hand, the acceleration voltage is raised, and sensing is made with a reflex electron sensor 6. Because signals from this sensor 6 also include surface information, information of the abovementioned secondary electron sensor 5 is subtracted per picture element from the information of the reflex electron sensor 6, followed by evaluation. This permits a single unit of evaluating device to make evaluation of the pattern, etc., under overlayer, which should enhance the operating easiness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for evaluating the line width, registration accuracy, etc. of a pattern of a semiconductor device during the manufacturing process of the semiconductor device.

(Prior Art) Conventionally, devices using electronics@mirrors are known as semiconductor device (wafer, etc.) evaluation devices in semiconductor manufacturing processes.

Semiconductor devices that are subject to evaluation equipment in this type of semiconductor manufacturing process are evaluated in processes in which the insulator is partially exposed on the surface, and in processes in which the insulator covers the entire surface. There are cases.

If a portion of the insulator is exposed on the surface, the surface of the target semiconductor device will be observed;
An electron microscope using a low acceleration electron beam is used. On the other hand, if the entire surface of the semiconductor device is covered with an insulator, the pattern underneath the insulator must be observed, so an electron microscope using a highly accelerated electron beam is used. .

(Problems to be Solved by the Invention) In the conventional techniques as described above, although it is necessary to evaluate the target semiconductor device at various stages of the semiconductor manufacturing process, It is necessary to use an electron microscope using a highly accelerated electron beam and an electron microscope using a low accelerated electron beam, which is not only difficult to operate but also uneconomical.

The present invention has been made in view of such conventional problems, and provides an easy-to-operate and economical evaluation device for semiconductor devices in the semiconductor manufacturing process when evaluating semiconductor devices at various stages of the semiconductor manufacturing process. The purpose is to obtain.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an electron beam generator that selectively emits electron beams of at least two different energies, and an electron beam generator that selectively emits electron beams with different energies. a condenser that focuses an electron beam; an objective lens that focuses the electron beam that has passed through the condenser onto a target; a deflection device that deflects and scans the electron beam on the target; a detection device that detects electrons from the target; A semiconductor device evaluation device in a semiconductor manufacturing process is characterized by comprising a command device that causes an electron beam generator to select which energy of electron beam is to be emitted.

(Function) In the device of the present invention, the electron beam generator can selectively emit electron beams of different energies based on the commands of the command device, so that the insulating material is partially exposed on the surface. It is possible to evaluate a semiconductor device in a process in which the entire surface is covered with an insulator, and to evaluate a semiconductor device in a process in which the entire surface is covered with an insulating material using a single device, which is easy to operate and is economical.

(Embodiment) FIG. 1 is a block diagram of an embodiment of the semiconductor manufacturing process evaluation apparatus of the present invention. The electron gun 1 is a thermal field emission electron gun. In the thermal field emission electron gun 1, the energy of the emitted electron beam changes depending on the voltage applied to the accelerating electrode. An electron beam emitted from an electron gun 1 is narrowly focused by a condenser lens 2 and an objective lens 3, and is imaged onto a target 15.

A deflection coil 4 is provided between the condenser lens 2 and the objective lens 3 to deflect the electron beam. When the accelerating voltage applied to the accelerating electrode is low, the condenser lens 2
A partial crossover image is formed at a position 13 between the target lens 3 and the objective lens 3, and this crossover image is further formed on the target 15 by the objective lens 3. The working distance of the objective lens 3 is as short as 3 tm, and a lens current corresponding to strong excitation can be applied to focus at a low accelerating voltage. When the accelerating voltage of the electron beam becomes high, the excitation current for the objective lens 3 is insufficient, and the focal length cannot be made very short.

In this case, the crossover image by the condenser lens 2 is not formed between the condenser lens 2 and the objective lens 3, but the condenser is used so that the image is formed at a position 14 behind the target 15 without the objective lens 3. Controls the excitation current of the lens 2. Since the electron beam focused at the position 14 can be focused on the target 15 by bending it very slightly by the objective lens 3, the excitation of the objective lens 3 does not require much excitation, and even a high accelerating voltage can achieve sufficient focusing. can be done.

A scanning coil 4 is used to scan the focused electron beam onto the target. As the accelerating voltage V increases, the deflection sensitivity of the scanning coil 4 deteriorates in inverse proportion to Ima, so for example, if the accelerating voltage increases by four times, the scanning field of view size becomes 1/2.

In most semiconductor manufacturing processes, some type of insulator is placed on the surface of a semiconductor device. Therefore, if an electron beam is applied to the target 15 while the sample chamber 18 housing the target 15 is kept in a vacuum, the surface of the target 15 will be charged.
) Gas etc. are introduced into the sample chamber 18. The sample chamber 18 is connected to the inside of the liner tube through a pressure limiting aperture (not shown) at the tip of the liner tube that forms a path for the electron beam. Secondary electrons generated from the target 15 are detected by a secondary electron detector 5 to which a voltage of several hundred V is applied to the target 15. When observing and evaluating the surface of the target 15, an electron beam with a low acceleration voltage is made incident on the target 15, and a signal from the secondary electron detector 5 is used. The state under the overlayer of target 15! I4
(patterns, etc.), the accelerating voltage is increased and the backscattered electron detector 6 is used.The signal from the backscattered electron detector 6 contains information not only on the surface but also on the surface of the overlayer. Therefore, it is necessary to select only the information below the overlayer by referring to the information from the secondary electron detector 5 that includes only surface information.

Amplifiers 9 and 10 are connected to the secondary electron detector 5 and the backscattered electron detector 6, respectively, and the secondary electron detection signals and backscattered electron detection signals amplified by the amplifiers 9 and 1O are sent to A/D converters lla and llb. After being converted into a digital signal,
The information is taken into an arithmetic and control unit 12 configured by a computer.

The arithmetic and control unit W12 receives commands from the input device 17 manually, performs operations based on the flowchart shown in FIG.
Control power supply 8a of electron gun l, control of condenser lens 2? I
It controls the power source 8b, the control power source 8c for the deflection coil 4, the control power source 8d for the objective lens 3, and the monitor 16.

That is, the arithmetic control unit W12 is configured to set the acceleration voltage of the electron gun 1 to a relatively high first voltage or to a second voltage that is lower than the first voltage according to a command from the human power device 17. If the first voltage is commanded, a control signal is sent to the control power source 8a to set the acceleration voltage of the electron gun 1 to the first voltage (step 21). .

Then, the control current of condenser lens 2 is set to target 1.
A control signal is sent to the control power source 8b so that the crossover image resides at the position 14 behind the electron beam 5 (step 22), and the current of the objective lens 3 is controlled by an amount so that the electron beam is focused on the target 15. A control signal is sent to tA8d (step 23).

Next, the current flowing through the deflection coil 4 is changed and a control signal is sent to the control power source 8c so as to scan the electron beam on the target 15 (step 24). The output signals of the secondary electron detector 5 and the backscattered electron detector 6 are synchronized with the scanning of the electron beam and stored as two-dimensional image data in an image memory (not shown).
Step 25).

In this way, when two-dimensional image data is obtained, the output signal of the secondary electron detector is subtracted from the output signal of the backscattered electron detector between the corresponding picture elements from each image data, and each picture The subtracted signal obtained for each element is stored as new image data (step 26). As a result, a signal with information only on the underside of the insulator from which the influence of secondary electrons from the surface of the target 15 has been removed is created. can be obtained as a subtracted signal. It goes without saying that this image can be displayed on the monitor 16.

Processing such as line width measurement is then performed from the image data stored in step 26 (step 27), and the results are displayed on the monitor 16 (step 28).

On the other hand, if it is determined in step 20 that the second voltage is commanded, a control signal is sent to the control g5 power supply 8a to set the acceleration voltage of the electron gun 1 to a second voltage lower than the first voltage (step 20).・P29).

Then, the control current of the condenser lens 2 is changed to the objective lens 3.
A control signal is sent to the control power source 8b so that a crossover image is generated at a position 13 in front of A control signal is sent to (step 31).

Then, by changing the current flowing through the deflection coil 4,
At the same time, a control signal is sent to the control power source 8c to cause the electron beam to scan on the electron beam 15 (step 32), and at the same time, the output signal of the secondary electron detector 5 obtained from the A/D converter 9 is synchronized with the scanning of the electron beam. The image data is then stored in an image memory (not shown) as two-dimensional image data (step 33).

Once the two-dimensional image data is obtained in this way, steps 27 and 28 are reached.

According to the embodiments of the present invention, it is possible to evaluate, observe, and measure not only the surface condition of a semiconductor device in the process of manufacturing, but also the condition of the underlying layer of an overlayer. Because of its functionality, it is possible to use only one device instead of multiple conventional devices, helping to reduce the floor space required for clean rooms.

Since the lens at high accelerating voltage is operated with sufficient lens current for low accelerating voltage, there is no need to increase the lens current too much, and the stability of the lens current is relatively improved at low accelerating voltage. Chromatic aberration is reduced and high resolution can be obtained. Since the objective lens only needs to be designed for low acceleration voltage, it is possible to achieve sufficiently strong excitation and to sufficiently reduce the spherical aberration coefficient.

Since a voltage of several hundred volts is always applied to the secondary electron detector and the sample chamber is filled with low-pressure gas, the sample surface will not be charged no matter what the acceleration voltage is.

Note that the above embodiment is a device that can select electron beams with two different energies, but the voltage applied to the accelerating electrode of the electron gun 1 can be changed so as to select electron beams with two or more energies. You can.

This makes it possible to vary the accelerating voltage depending on the thickness of the overlayer, for example. At this time, the position of the crossover image formed by the condenser lens 2 is set at an appropriate position between positions 14 and 15, for example, if position 14 in FIG. 1 is an electron beam with the maximum energy that can be assumed. Set.

(Effects of the Invention) As described above, according to the present invention, it is possible to evaluate, observe, and measure not only the surface condition of a semiconductor device during manufacture, but also the condition of the underlying layer of an overlayer (insulator) using a single device. Since this can be carried out using simple commands, it is possible to obtain a semiconductor device evaluation device that is easy to operate and is economical.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an electron optical system and an electric block showing an evaluation apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart of the arithmetic and control unit 12 used in FIG. 1. (Explanation of symbols of main parts) 1... Electron gun, 2... Condenser lens, 3...
...Objective lens, 4...Deflection coil, 5...Secondary electron detection 2L6...
... Backscattered electron detector, 8a, 8b, 8c, 8d...
......Control power supply, 12......Arithmetic control device.

Claims (1)

[Scope of Claims] An electron beam generator that selectively emits electron beams of at least two different energies; a capacitor that focuses the electron beams generated by the electron beam generator; and an electron beam that has passed through the capacitor. An objective lens that focuses the electron beam on the target, a deflection device that deflects and scans the electron beam on the target, a detection device that detects the electrons from the target, and an electron beam of which energy is applied to the electron beam generator. 1. An evaluation device for a semiconductor device in a semiconductor manufacturing process, comprising a command device for selecting whether to eject or not.