JPH0321803A - Measuring method for opposite surface interval and shape - Google Patents

Abstract

PURPOSE:To measure the interval or surface shape of opposite flanks formed of a recessed part provided in a conductor without destructing nor bringing into contact by applying a voltage between a probe and an object, and putting the probe in scanning operation while detecting a tunnel current generated when putting the probe close to the measured surface. CONSTITUTION:A conductive measuring element 2 which has two needlelike tips 2a and 2b is interposed between the opposite surfaces 1a and 1b provided to the conductor 1 so that the tips 2a and 2b face the opposite surfaces 1a and 1b. The voltage E is applied between the measuring element 2 and conductor 1. Then the measuring element 2 is moved in three dimensions between the opposite surfaces 1a and 1b to detect the tunnel current between one of the opposite surfaces 1a and 1b and the opposite tip 2a or 2b. Then the gap size between the tip 2a or 2b and surface 1a or 1b, the movement size of the measuring element 2, and the size between the tips 2a and 2b at the time of detecting the tunnel current are used to find the gap or surface shape of the opposite surfaces 1a and 1b.

Description

[Detailed Description of the Invention] [Summary] Opposing side surfaces formed by recesses formed in a conductor such as a semiconductor (
The purpose of the present invention is to provide a method for three-dimensionally measuring the distance or surface shape of opposing surfaces (opposed surfaces) in a non-destructive, non-contact manner. , insert a conductive probe having two needle-like tips with the tip branching laterally to the left and right so that each of the tips faces each of the opposing surfaces, and connect the probe to the conductive probe. A voltage is applied between the body and the probe is moved three-dimensionally to detect a tunnel current between one of the opposing surfaces and the tip facing it on both sides of the opposing surface. The distance or surface shape of the opposing surfaces is determined from the gap between the tip of the object to be detected and the surface, the movement dimension of the probe, and the dimension between the two tips when detecting the tunnel current.

[Industrial application field]

The present invention relates to a method for measuring the shape of the distance between opposing surfaces, and particularly to a method of measuring the distance or surface shape of opposing side surfaces (opposing surfaces) formed by recesses provided in a conductor such as a semiconductor.

In recent years, semiconductor devices have continued to become smaller. This trend is particularly noticeable in semiconductor memory devices, where the structure of capacitance, which is the main structure of devices, is changing from two-dimensional to three-dimensional. In the trench structure, which represents the three-dimensional structure of a capacitor, the spacing or surface shape of the opposing sides formed by the recess is important for capacitive formation, and the spacing or surface shape can be changed non-destructively, non-contact, and three-dimensionally. need to be measured.

[Conventional technology]

Conventionally, methods for measuring the distance or surface shape of opposing side surfaces of a recess include a method using a scanning electron microscope and a method using a contact probe. However, the former method can only be measured from a cut cross section, and only two-dimensional information can be obtained.

In the latter case, when observing the shape of the side surface of a recess, the probe must be made thinner, but it cannot be made too thin because it will not come into contact with the tip. Also, this method is not sensitive to vertical changes.

[Problem to be solved by the invention]

Therefore, in the conventional method described above, when measuring the distance or surface shape of the opposing side surfaces of a recess, the object must be destroyed or brought into contact with the object. However, the information available is not sufficient.

Therefore, an object of the present invention is to provide a method for three-dimensionally measuring the distance or surface shape of opposing side surfaces (opposing surfaces) formed by recesses provided in a conductor such as a semiconductor in a non-destructive and non-contact manner.

[Means to solve the problem]

FIG. 1 is a perspective view illustrating the present invention.

Referring to the same figure, the above object is to provide a conductive conductor having two needle-shaped tips 2a and 2b whose tips are branched laterally to the left and right between the opposing surfaces 1a and 1b provided on the conductor l. Insert the measuring tip 2 such that the tips 2a and 2b face each of the facing surfaces 1a and 1b, apply the voltage E between the measuring tip 2 and the conductor 2, and measure. The child 2 is moved three-dimensionally to face the opposing surface 1a or 1.
The opposing surfaces 1a and 1b are configured to detect a tunnel current between one of the ends 2a and 2b facing the tip 2a or 2b.
from the gap dimension between the tip 2a or 2b of the object to be detected and the surface 1a or 1b, the movement dimension of the probe 2, and the dimension between the two tips 2a and 2b when detecting the tunnel current. , can be achieved by the measuring method of the present invention for determining the distance or surface shape of the opposing surfaces 1a and 1b.

[For production]

A scanning tunneling microscope (STM) is a device that non-destructively and non-contactly measures the shape of a surface with an open top. This method applies a voltage between the probe and the object, detects the tunnel current that occurs when the probe approaches the measurement surface, and then scans the probe to bring the probe into contact with the object. It measures the surface shape without causing any damage.

The present invention utilizes this STM principle, and uses the measuring element 2 described above, which has two needle-shaped tips 2a and 2b whose tips are branched laterally to the left and right, instead of a probe, to carry out measurements. By moving the child 2 three-dimensionally, the distance or surface shape of the opposing surfaces 1a and 1b provided on the conductor 1 can be determined.

As shown in the tunnel current characteristic diagram in FIG. 2, the tunnel current at that time depends on the gap size between the tip 2a or 2b of the probe 2 and the surface 1a or 1b under a constant applied voltage E. It increases as the gap size becomes smaller, and with an applied voltage of several V and a gap size of about inn, n
Indicates the size of A order.

These quantitative relationships can be clarified in advance regardless of the object.

Further, the dimension between the two tips 2a and 2b of the measuring stylus 2 is known, and the movement dimension of the measuring stylus 2 can be determined at the time of measurement.

Therefore, by performing simple calculations from the above dimensions, it is possible to determine three-dimensionally, non-destructively and non-contact, the spacing or surface shape of the opposing side surfaces (opposing surfaces) where the recess is formed in a conductor such as a semiconductor. becomes possible.

〔Example〕

Examples of measurement according to the present invention will be described below with reference to FIGS. 3 to 5. Fig. 3 is a schematic diagram of the main parts of the measuring device used in the example, Fig. 4 is a diagram of probe movement during STM scanning in the example, and Fig. 5 is a diagram showing the state of the probe during measurement of the opposing surface in the example. , and the same reference numerals indicate the same objects throughout the figures.

In FIG. 3, reference numeral 3 denotes a probe drive unit that moves the probe 2 three-dimensionally, 4 a probe drive control circuit that controls the drive unit 3, and 5 a tunnel formed at the tip 2a or 2b of the probe 2. 1 is a tunnel current detection circuit that detects the current and sends the output to circuit 4; 6 is a movement dimension memory circuit that stores the movement dimension of the probe 2 as data; Used for three-dimensional measurement of surface shape. In addition, in order to know the position of the recess that defines the opposing surfaces 1a and 1b of the conductor l, which is the object to be measured,
It is equipped with an STM consisting of a probe 7, a probe drive unit 8, and the like.

The measuring tip 2 is rod-shaped and made of metal such as tungsten, and its tips 2a and 2b are formed by branching the tip of the measuring tip 2 laterally to the left and right, and are needle-shaped with sharp points in the left-right direction.
The dimensions from the tip 2a to the tip 2b are the opposing surfaces 1a and 1b.
The spacing is smaller than that of .

The measuring element driving section 3 uses a piezoelectric element or the like as a driving source for the measuring element 2, and can move the measuring element 2 with extremely high accuracy.

The above measurements of the opposing surfaces 1a and 1b are performed as follows.

First, the conductor l is set so that the direction of the perpendicular line erected on the opposing surfaces 1a and 1b matches the direction (X direction) of the line connecting the tips 2a and 2b of the probe 2, and the probe 2 is placed at the tip of the probe 2. is positioned so that it is higher than the tip of the probe 7,
The probe 7 scans the top surface of the conductor 1 in the X direction. The progress of the movement of the probe 7 is as shown in FIG. 4, and the position of the recess in the conductor 1 can be determined from the falling and rising points of the progress.

Thereby, the measuring element 2 can be inserted between the opposed surfaces 1a and 1b defined by the recessed portion without contacting the conductor 1. This state is shown in FIG. 5 and FIG. 1 mentioned above.

After that, measurement of the distance or surface shape of the opposing surfaces 1a and 1b begins.

That is, referring to FIG. 5, move the probe 2 in the X direction to bring the tip 2a (or 2b) of the probe 2 closer to the opposing surface 1a (or 1b) as shown by the broken line, and create a tunnel between the two. A detection circuit 5 detects the current. Further, the probe 2 is moved in the opposite direction to bring the tip 2b (or 2a) of the probe 2 closer to the opposing surface 1b (or 1a), and the detection circuit 5 detects the tunnel current between the two. At that time, the memory circuit 6
The movement dimension of the probe 2 is stored as data.

By doing so, the gap size when detecting the tunnel current, the measuring point 2
From the movement dimension and the known dimension between the tips 2a and 2b, the distance at a certain point between the opposing surfaces 1a and 1b can be determined by simple calculation. The spacing at other points may be measured in the same manner as described above by appropriately shifting the position of the measuring element 2 in the Y and Z directions (the Y direction is a direction perpendicular to the plane of the paper).

For tunnel current detection by the detection circuit 5 described above, it is practical to set the magnitude of the tunnel current to a certain constant value, and to set the detection point at the time when the tip 2a or 2b approaches the current value. be.

The surface shape is such that the tip 2a (or 2b) of the probe 2 inserted between the opposing surfaces 1a and 1b is moved in the X direction and the tip 2a (or 2b) of the probe 2 is inserted between the opposing surfaces 1a (or
b), and the detection circuit 5 detects the tunnel current between the two.
When detected, the probe 2 is moved appropriately in the Y, Z, and X directions while keeping the tunnel current constant, and the dimensions of the movement locus are stored in the memory circuit 6 as data.
, and can be determined three-dimensionally from the movement locus of the tracing stylus 2.

〔Effect of the invention〕

As explained above, according to the structure of the present invention, regarding the method of measuring the distance or surface shape of the opposing side surfaces (opposing surfaces) formed by a recess provided in a conductor such as a semiconductor, the distance or surface shape can be measured in a non-conductive manner. A non-destructive, non-contact three-dimensional measurement method is provided, which has the effect of ensuring, for example, the manufacturing evaluation of the capacitance of a trench structure of a highly integrated semiconductor memory element.

[Brief explanation of drawings]

Fig. 1 is a perspective view explaining the present invention, Fig. 2 is a tunnel current characteristic diagram, Fig. 3 is a schematic diagram of the main parts of the measuring device used in the embodiment, and Fig. 4 is a probe for STM scanning in the embodiment. FIG. 5 is a diagram showing the state of the probe during measurement of the opposing surface of the embodiment. In the figure, 1 is a conductor, 1a and 1b are opposing surfaces, 2 is a probe, 2a and 2b are tips of the probe, 3 is a probe drive unit, 4 is a probe drive control circuit, and 5 is a tunnel current detection 6 is a measuring stylus movement dimension memory circuit, and E is an applied voltage. 20 Shisa 2b is also tsuki! Conductor water brightness left explanation 5 Perspective view Go straw 7i! ! I1's STM flea running probe Shoudo 2 Ashi 4 Figure

Claims (1)

[Claims] Between the opposing surfaces (1a, 1b) provided on the conductor (1), there are two needle-shaped tips (1a, 1b) with the tips branching laterally to the left and right.
2a, 2b) is inserted so that each of the tips (2a, 2b) faces each of the opposing surfaces (1a, 1b), and A voltage (E) is applied between the conductor (1) and the probe (2) is moved three-dimensionally to form the opposite surface (1a,
1b) and the opposing tip (2a or 2)
b) to detect the tunnel current between the opposing surface (1
a, 1b), and the tip (2a or 2b) of the detection target during tunnel current detection and the surface (1
a or 1b), the movement dimension of the probe (2), and the dimension between the two tips (2a, 2b),
A method for measuring the spacing between opposing surfaces (1a, 1b) or the surface shape of the opposing surfaces (1a, 1b).