JPH02118405A - Fine dimension measuring device - Google Patents

Abstract

PURPOSE:To improve the measuring accuracy of a pattern by providing a stage on which a semiconductor wafer is placed, a measuring part having an objective lens, an arithmetic processing part and a control part. CONSTITUTION:The dimension of the pattern on the same part of the wafer 4 is measured plural times at a focusing position whose height is H1. The measured value is processed in the arithmetic processing part 8 every time measurement is completed and the reproducing accuracy of the measurement which is repeated for the same focusing position is stored. Then, a driving signal is transmitted through a central control part 9 and a stage control part 10 and the stage 5 is moved by a stage driving part 6 to the focusing position whose height is H2, where the measurement is performed plural times and the reproducing accuracy of the repeated measurement is calculated and stored. Thereafter, the measurement is repeated n-times optionally in the same way. The arithmetic processing part 8 selects the focusing position which is the most excellent in reproducibility out of the reproducing accuracy of each focusing position. In order to get the selected focusing position, the signal is transmitted from the control part 9 to the driving part 6 and the measurement of the dimension of the respective points in the wafer 4 which is set at the optimum focusing position is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a minute dimension measuring device having an automatic focus positioning function used in the manufacturing process of semiconductor devices.

[Conventional technology]

Conventionally, when attempting to measure the width of wiring on a semiconductor wafer (hereinafter simply referred to as a wafer) using a micro-dimensional measuring device that has an automatic focus positioning function for this type of objective lens, the optimal focal position is: The height was set to match the average height of the unevenness on the surface of the wafer in the field of view centered on the wiring to be measured.

[Problem to be solved by the invention]

In the micro-dimensional measuring device using the conventional automatic optimal focus determination method described above, when measuring a pattern as an object on a wafer, the height of the wafer surface is microscopically
As shown in the figure, an interlayer insulating film 21 is formed on the semiconductor substrate 20.
Because the wires and wiring 22 are formed and are not uniform, the optimum focus position determined by the micro-dimensional measuring device may deviate from the target measurement point of the device pattern, and the accuracy of the obtained measurement value may deteriorate. There were always drawbacks when it was inferior.

[Means to solve the problem]

The micro-dimensional measuring device of the present invention includes a stage on which a semiconductor wafer is placed, a measuring section having an objective lens for measuring a pattern on the semiconductor wafer, and processing signals from the measuring section to calculate pattern dimensions. and a control section that controls the stage or objective lens to move stepwise in the optical axis direction based on signals from the arithmetic processing section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the invention.

In FIG. 1, a wafer 4 is placed on a stage 5 that can be moved stepwise in the optical axis direction, and an objective lens 1 that constitutes a measuring section together with an optical sensor 2 is placed above the wafer 4 in the optical axis direction. is provided. Information on patterns such as wiring to be measured on the wafer 4 is sent to the optical sensor 2 through the objective lens 1 and converted into an electrical signal. The pattern information converted into an electrical signal is sent to the arithmetic processing section 8, where statistical calculations such as the average value and dispersion of the measured values are performed. The results are transferred to the central control unit 9, where stage drive is determined. The results determined by the central control unit 9 are transferred to the stage control unit 10, which sends a signal to the stage drive unit 6 to drive the stage, and the stage drive unit 6 moves in the direction and amount of movement determined by the central control unit. Move the stage in the optical axis direction.

Next, the measurement operation will be explained. FIG. 2 is a side view of the objective lens and wafer for explaining the operation of the stage 5. A wafer 4 to be measured is placed on a stage 5.

First, the wafer 4 is placed at the focal point at the height Hl shown in FIG.
The pattern dimensions of the same portion of the pattern are measured multiple times. The measured values are transferred to the arithmetic processing unit 8 and processed each time one measurement is completed, and then the reproducibility accuracy of repeated measurements for the same focal position is stored. When the measurement at the focal position of H1 is completed, a drive signal is sent from the stage control unit 10 via the central control unit 9, and the stage driving unit 6 moves the stage 5 to the focal position at the height of H2. In H2, measurements are performed a plurality of times in the same way as the focal position of Hl, and the repeatability of the repeated measurements in H2 is calculated and stored. Thereafter, measurements are similarly performed at each focal position by repeating an arbitrary n number of times. Then, the arithmetic processing unit 8 selects the focal position with the best reproducibility from among the reproducibility of repeated measurements measured and stored at each focal position, and the focal position is determined. A signal is sent from the central control unit 9 to the stage drive unit 6 via the stage control unit 10 so that the focus position selected in this way is set, and the wafer 4 is set at the optimum focus position. Dimension measurements are started for each point.

As described above, according to the first embodiment, it is possible to select the focal position with the best measurement reproducibility of the pattern to be measured, so that the accuracy of the measured value is improved.

FIG. 3 is a block diagram of the second embodiment of the present invention. The difference from the first embodiment is that an objective lens drive section 7 is provided instead of the stage drive section, and the movement of the objective lens 1 causes the focus to be focused. It is located where the position is determined.

That is, the objective lens 1 is attached to an objective lens drive section 7 that moves the objective lens in the optical axis direction. 1st
Similarly to the embodiment, the objective lens control section 11 sends a control signal to the objective lens drive section 7 in response to a command from the central control section 9 to move the focal position of the objective lens stepwise.

In this second embodiment, since the driving section is provided on the objective lens side, there is an advantage that the mechanism on the stage side can be simplified.

〔Effect of the invention〕

As explained above, the present invention includes a micro-dimensional measuring device that includes a stage on which a semiconductor wafer is placed, a measuring section having an objective lens for measuring a pattern on the semiconductor wafer, and a signal from this measuring section. By comprising a calculation processing unit that calculates pattern dimensions and a control unit that controls the stage or objective lens to move stepwise in the optical axis direction based on signals from this calculation processing unit, it is possible to achieve maximum reproduction. Since the focal position can be determined with high precision, pattern measurement accuracy can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the first embodiment of the present invention, Fig. 2 is a side view of the objective lens and wafer for explaining the operation of the stage, and Fig. 3 is a block diagram of the second embodiment of the invention. FIG. 4 is a cross-sectional view of an example of a wafer. DESCRIPTION OF SYMBOLS 1... Objective lens, 2... Optical sensor, 4... Wafer, 5... Stage, 6... Stage drive unit,
7... Objective lens drive section, 8... Arithmetic processing section, 9.
... Central control section, 10... Stage control section, 11...
- Objective lens drive unit, 20... semiconductor substrate, 21...
- Interlayer insulating film, 22... wiring.

Claims (1)

[Claims] a stage on which a semiconductor wafer is placed; a measurement section having an objective lens for measuring a pattern on the semiconductor wafer; a calculation processing section that processes signals from the measurement section and calculates pattern dimensions; and the calculation processing. and a control section that controls the stage or objective lens to move stepwise in the optical axis direction based on signals from the micro-dimensional measuring device.