Inspection Apparatus and Inspection Method

Abstract

When performing an inspection using a charge control function in a SEM wafer inspection apparatus, acceleration voltage, control voltage and deceleration voltage are changed in conjunction so that incident energy determined by “acceleration voltage−deceleration voltage” and bias voltage determined by “deceleration voltage−control voltage” do not change. By this means, charge of a wafer can be controlled, while restraining electrostatic lens effect generated near a control electrode. As a result, an inspection using a charge control function at low incident energy and in a wide viewing field can be performed, and a highly sensitive inspection of semiconductor patterns subject to damages due to electron beam irradiation can be realized. Acceleration voltage, control voltage and deceleration voltage are changed in conjunction so that incident energy determined by “acceleration voltage−deceleration voltage” and bias voltage determined by “deceleration voltage−control voltage” do not change.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a schematic view of the inside structure of an apparatus according to one of preferred embodiment;

FIG. 2A is a diagram of the charge control principle;

FIG. 2B is a diagram of the charge control principle;

FIG. 3A is a diagram of the relation between bias voltage and optical characteristics;

FIG. 3B is a diagram of the relation between bias voltage and optical characteristics;

FIG. 4 is a diagram of the relation between bias voltage and deflection sensitivity;

FIG. 5 is a diagram of the relation between bias voltage and optical characteristics under an application of the embodiment;

FIG. 6 is a diagram for describing the characteristics of the bias voltage and the barrier potential;

FIG. 7 is a diagram for describing the correction method of barrier potential in the embodiment;

FIG. 8A is a diagram of the relation between bias voltage and optical characteristics under an application of the embodiment;

FIG. 8B is a diagram of the relation between bias voltage and optical characteristics under an application of the embodiment;

FIG. 8C is a diagram for describing the relation between bias voltage and optical characteristics under an application of the embodiment;

FIG. 9 is a diagram for describing the effect of the embodiment;

FIG. 10 is a flowchart showing the preparation procedure of recipe in the embodiment; and

FIG. 11 is a schematic view of an example of a GUI for the recipe preparation in the embodiment.

Claims

1. An inspection apparatus comprising: a sample stage on which a sample is mounted;an electron optical system which scans an electron beam on the sample, detects secondary electrons generated by the scan, and outputs them as secondary electron signals; andan information processor which processes the secondary electron signals, thereby inspecting the sample,wherein the electron optical system has an electron source, an extraction electrode which accelerates electrons generated in the electron source, a charge control electrode disposed above the sample, and a deceleration electrode which applies a deceleration voltage to the sample, andthe inspection apparatus further comprises electron optical system control means, which is provided with:a function to adjust voltage to be applied to the deceleration electrode,a function to adjust voltage to be applied to the control electrode, anda function to control the acceleration voltage, the deceleration voltage, and the control voltage in conjunction so that energy of the electron beam which enters the sample, a field formed on the sample, and probe current of the electron beam which enters the sample become almost constant.

2. The inspection apparatus according to claim 1, wherein a function to maintain the incident energy, the field on the sample, and the probe current constant and also adjust the acceleration voltage, the deceleration voltage, and the control voltage in conjunction so that a probe diameter of the electron beam becomes optimal is provided.

3. The inspection apparatus according to claim 1, wherein a value of the incident energy of the electron beam at which no damage occurs in an insulator sample and emission efficiency of secondary electrons becomes 1 or higher is stored in the information processor, andvoltages to be applied to the extraction electrode, the charge control electrode and the deceleration electrode are controlled on the basis of the stored value.

4. The inspection apparatus according to claim 3, wherein surface potential of the sample is controlled by difference between the control voltage and the deceleration voltage.

5. The inspection apparatus according to claim 1, further comprising: a display screen which displays a size of the probe diameter of the electron beam at the moment when the acceleration voltage, the deceleration voltage, and the control voltage are controlled in conjunction or a size of the probe diameter of the electron beam at a scan end at the moment when the electron beam is scanned.

6. The inspection apparatus according to claim 5, wherein the information processor is provided with a memory unit which stores the probe diameter.

7. The inspection apparatus according to claim 1, wherein the sample is a semiconductor wafer or a chip on which circuit patterns are formed, or a wafer piece obtained by dicing the wafer.

8. An inspection method in which electron beam is irradiated to a sample to be inspected and image signals obtained by detecting secondary electrons generated by the irradiation are processed, thereby performing an inspection of the sample to be inspected, wherein electrons emitted from an electron source are accelerated to an acceleration voltage,a deceleration voltage is applied to the sample to be inspected to adjust an incident energy of the electron beam, and a control voltage is applied to a control electrode disposed just above the sample, thereby forming an arbitrary field on the sample to be inspected, andthe acceleration voltage, the deceleration voltage, and the control voltage are controlled in conjunction so that the energy which enters the sample, the field formed on the sample, and probe current of the electron beam which enters the sample to be inspected become almost constant.

9. The inspection method according to claim 8, wherein, while the energy which enters the sample, the field formed on the sample, and the probe current of the electron beam which enters the sample to be inspected are maintained constant, the acceleration voltage, the deceleration voltage, and the control voltage are controlled in conjunction so that a probe diameter of the electron beam becomes optimal.

10. The inspection method according to claim 8, wherein the incident energy of the electron beam is controlled to a size at which an emission efficiency of secondary electrons becomes 1 or higher and no damage occurs in the sample to be inspected.

11. The inspection method according to claim 10, wherein surface potential of the sample to be inspected is controlled by difference between the control voltage and the deceleration voltage.

12. The inspection method according to claim 8, wherein the sample is a semiconductor device, and defective shapes and electric characteristic defects of patterns formed on the semiconductor device are detected.