JPS62103503A - Wafer measuring instrument - Google Patents

Abstract

PURPOSE:To measure the patterns of wafers with a variety of widths by using a liquid crystal having a light transmitting region with a variable width and making the widths of the slit openings substantially continuously change. CONSTITUTION:A slit plate is constituted by a liquid crystal shutter 31 having a plurality of opposite pairs of stripe-shaped transparent electrodes 31a, 31a...31n, 31n arranged on the upper and lower surfaces of the shutter 31. The electrodes 31n are formed in a stripewise configuration with 12mum wide electrodes arranged at predetermined speaces, for example, at 3mum spaces while sandwiching a 3mum thick insulating layer 33. Since those electrodes 31n allow light to pass therethrough when a voltage is applied from a driving circuit, by sequentially increasing the number of electrodese to which the voltage is applied, the widths of the slit openings are accordingly increased. By sequentially stopping the applications of the voltage to the electrodes, the widths of the slit openings are accordingly decreased. The width of the openings in this case, when the arranging width of the electrodes are made, for example, 300mum, can be made continuous within the range of approximately 0mum-300mum. When the weidth of the insulating layer between the electrodes can not be reduced, two laminated liquid crystal shutters 35 and 37 can be used.

Description

[Detailed description of the invention] [Industrial use! I! F] The present invention relates to a wafer 4111 fixing device that measures patterns on a wafer by measuring 1° and 2 degrees, alignment accuracy, and the like.

[Prior Art] Generally, in a wafer measuring device, the X-Y stage mechanism on which the wafer is placed is manually operated while observing the screen of a monitor television, and the base point (
For example, the corner of the chip is positioned by the pattern detection optical system, the device reads the position coordinates of the X-Y stage at that time, and stores it in the internal memory. Based on this, the mark pattern of each chip to be measured is measured. Measurement is performed by sequentially moving the target pattern to the observation position of the pattern detection optical system in 11" strokes.

The actual measurement using the first method is performed by imaging the reflected light of the light irradiated onto the wafer surface on an image sensor through a slit, and analyzing the detection result.

Here, the patterns to be measured include narrow patterns such as memory cells, and wide wiring patterns such as power supply patterns, ground patterns, gate patterns, etc. In particular, a wiring pattern using AJl is a wide pattern.

[Problem to be solved] When observing such a wiring pattern and a pattern constituting a memory cell, etc. with a detection field of view of the same width, when measuring a narrow pattern such as a memory cell, etc. for,
Unless the detection field of view is correspondingly narrowed down, it will not be possible to accurately measure dimensions within one minute due to the influence of surrounding patterns and noise components from the surroundings. On the other hand, in the case of wide patterns, especially wiring patterns such as A and 11, when 411 is fixed with a narrowed detection field of view, noise components etc. are thick (and it is difficult to detect an accurate image). There is a problem.

[1] This invention solves the problems of the prior art, and provides a wafer measuring device that can more accurately and efficiently measure patterns of various widths. It is Ll's purpose to provide this.

[Means for Solving the Problems] This invention proposes that the strength of a wide pattern such as an AJl can be easily measured by observing its strength using an integral value, and that it is more appropriate to use such integral value measurement together. This method focuses on the fact that it also enables efficient measurement.

Therefore, it is conceivable to provide a wide slit to widen the detection field of view and enable integral observation. To achieve this, a wide slit and a narrow slit are prepared.

And the overall pattern's good foot, the AJl/dedicated pattern's /I11 constant, and the wide pattern's? l
It is conceivable to measure the 111 constant by performing integral value observation, and for narrow patterns such as memory cells, by performing differential local observation.

In order to achieve this, it is possible to prepare two slits, one wide and one narrow, and replace them.

However, this method is cumbersome to operate and poses the problem of lowering the actual measurement efficiency.Also, there are various widths of patterns, so it is difficult to make more accurate measurements. In this case, it is necessary to create several slits with a more appropriate width, which makes the management and operation complicated.

In addition, a mechanical actuator such as a solenoid can be used to open the slit [using an opening/closing plate for one part].

It is possible to control the opening width by combining a drive mechanism such as a voice coil motor or a stepping motor, but if a mechanical drive mechanism is used, dirt, dust, etc. will be generated and the width will be 4-1. This results in disadvantages of 1) having an adverse effect on wafers, etc.;

Therefore, by making the width of the same slit variable without using mechanical equipment, it is possible to make appropriate measurements on the spot.
It is something that has been learned.

Therefore, the means in the wafer measuring apparatus of the present invention for achieving the above object is to image the reflected light of the light irradiated on the surface of the wafer on an image sensor through a variable slit, and measure the wafer. The 1f5 variable slit uses a liquid crystal whose width of the light transmitting area can be changed.

[Function] By providing a liquid crystal slit with an aperture width of 1J in this way and using a mechanical drive mechanism,
By changing the opening width of the slit almost continuously, there is no generation of dust, ys dust, etc., the detection field of view can be controlled, and integral measurement and differential measurement can be used together.

As a result, narrow patterns such as memory cells and wide patterns, AJ! It is possible to separate and determine the pattern etc. at any time, and the overall quality of the pattern can be observed as needed using the integral value.

Therefore, more appropriate, 11Vilt and efficient measurement can be performed.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a wafer measuring device according to the present invention, FIG. 2(a) is an explanatory diagram of a liquid crystal shutter forming the slit, and FIG. FIG. 2(e) is a partially enlarged view of the structure of each of the two liquid crystal shutters.

In FIG. 1, ■ is a wafer measuring device, and 10
is its X-Y stage mechanism. A wafer 12 is carried into a chuck section 10 on the side of the two XY stays by a loader/unloader (not shown), and is positioned and held using the orientation flat 13 as a reference.

The negative side of the wafer 12 is exposed to a mirror 18 . by a halogen lamp 16 . Achromatic lens 20 and half mirror
22. Like this! ! (The local brightness and darkness images of the two sides of the wafer 12 that have been illuminated are viewed by the pattern detection optical system 24 and the monitor system 25.

The pattern detection optical system 24 includes an objective lens 26, the half mirrors 21 and 22, the half mirror 28, slind plates 30X and 30Y, and relay lenses 32X and 32Y.
, mirror 37, linear lens 36X, 36
CCD linear image sensors 38X and 38Y are one-dimensional image sensors.

Here, the contrast image in the circular view 1f of the wafer 1 determined by the objective lens 26 is the slit play 1-30X.

The field of view is further narrowed down through the CCD linear image sensor 30Y, and the image is captured by the CCD linear image sensors 38X and 38Y.

The opening 11 (aperture) of the slit plate 30X is
The image of the elongated field of view in the X direction passing through the center of the field of view of the objective lens 26 is the linear image sensor 38.
Focuses on X.

Similarly, the field of view of the other CCD linear image sensor 38X is narrowed down to an elongated region in the Y direction passing through the center of the field of view of the objective lens 26 by the slit play 1-30Y,
The wafer image within the field of view is the CCD linear image sensor 3
Imaged at 8X. And these slit plates 30
The width of the openings X and 30Y can be changed continuously as described later, and the detection angle of the CCI) linear image sensor 38° 38Y! l! F can be adjusted. In addition,
CC1) The linear image sensors 38X and 38Y separate the light and dark patterns formed into pixels into pixels and read them.
Outputs analog image signals serially.

On the other hand, the bright and dark images within the field of view of the objective lens 26 are also incident on the monitor system 25 side by the mirror 21, and
7 and a relay lens 29, the image is formed on the imaging surface of the television camera 23. The video signal output from the television camera 23 is sent to a CRT display device, and the corresponding information is displayed on the screen.

Here, the slit plates 30X and 30Y are each controlled to have one width between them in accordance with electricity No. 431 from the drive circuit 41. The drive circuit 41 is controlled in response to a signal from the processing device 40, and performs processing in accordance with a measurement pattern or a command signal manually input to the processing device 40 from the operation panel 42. The drive is controlled by a corresponding control signal from the device 40.

Now, the slit plates 30X and 30Y are shown in Fig. 2 (a).
), pairs of transparent electrodes 31 a, 31 al 3 l b+31 each have a stripe shape.
b+ *@*, 31n, and 31n are 1. This liquid crystal shutter 31 is composed of a liquid crystal shutter 31 having 31n and 31n corresponding to the lower surface.
mode), and polarizing plates (not shown) are provided on each of its front and back surfaces.

Here, striped electrodes 31 a + 31 a
+3 l b+ 3 l b+ * * *,
31 rL 3 i n is 12 μm at intervals of 3 μm across the insulating layer 33 at a predetermined interval 9, for example, 3 μrn.
Electrodes with a width of m are formed in a stripe shape.

These striped electrodes 31a, 31a, 31b, 3
1b, ea・, 31n, 3in are those that transmit light when a voltage from the drive circuit 41 is applied,
By sequentially increasing the number of striped electrodes to which a voltage is applied, the opening width of the slit is sequentially increased accordingly. , the width of the slit gradually decreases accordingly.

Here, in the initial state of the stripe electrode, a voltage is first applied to several electrodes in the center of the stripe electrode to bring it into a light transmitting state. The width of the opening is increased symmetrically by applying voltages from the central electrode to the electrodes located on both sides. On the other hand, when decreasing the opening am, the operation is the opposite.

By the way, in this case, the insulation gap between each stripe electrode is 3 μm, and this gap does not transmit light. However, even if a case r line that does not transmit light is formed in this way, if it is a linear line of about 3 μm, C
This has almost no effect on the images formed on the CD linear image sensors 38X and 38Y or the detection field of view.

Note that the narrower the width of this light-blocking grating, the better; however, if it cannot be made that narrow due to problems with the insulation between the electrodes,
As shown in Figure (b), two stacked liquid crystal shutters can be used.

As seen in FIG. 2(b), the slit plate 30X,
30Y is the 1st. It is constructed by stacking second liquid crystal shutters 35 and 37. Then, as shown in Figure 2 (C),
These first. The second liquid crystal shutter 35.37 includes a pair of striped transparent electrodes 35a, 35ar 35b, each having a width of 15 μm, arranged at predetermined intervals, for example, every 10 μm.
35b.

... + 35n, 35n, 37a, 37a, 37
b+ 37b, @ 41 'h #, 37n+ 3
7n. Here, each pair of striped electrodes 37a, 37a, 37bt3 of the second liquid crystal shutter 37
7b, * * e e, 37nv 37n is a pair of striped electrodes 35a, 3 of the first liquid crystal shutter 35.
5a, 35b, 35b, Bandai*Fist, 35n.

The 35n electrodes are stacked so as to be arranged correspondingly between each electrode.

Therefore, the spacing between the electrodes (10 μm) is equal to the width of the electrodes (
15 μm), so when stacked according to the spacing position between the electrodes as described above, each striped electrode 37a, 3 of the second liquid crystal shutter 37 located on the lower side
7 at 37 be 37 b.

..., 37n, 37n are respective striped electrodes 35a of the first liquid crystal shutter 35 located on the 1- side,
35a, 35b, 35b, **
Fist e, 35n, 35n and some of them will form a ball. This allows the opening width to be adjusted continuously.

Next, open the slit plates 30X and 30Y by 1-" 1
The width adjustment operation will be explained.

Drive circuit 4 is connected to the selected stripe electrode of the liquid crystal shutter.
When a voltage is applied from 1, the striped portion to which that voltage is applied becomes light-transmissive with the width of the stripe.

As a result, the slit width increases or decreases in accordance with this stripe width. In this case, the width of the opening [1] is approximately 0 μm to 300 μm, for example, if the stripe array width is 30,071 m at maximum.
It can be continuous in the range of tt m.

In the case of a two-layer liquid crystal shutter, the electrodes of the liquid crystals at the top are selected to be crossed.

By selecting the stripe electrodes in the liquid crystal in this manner and changing the width of the slit, the detection field of view can be freely set accordingly.

In this embodiment, the liquid crystal shutter is FEM, but DSA (dynamic scattering) may also be used. In this case, the striped electrode portion becomes a reflective portion and does not transmit light. The rest becomes a light-transmitting part. Therefore, the driving of the electrodes is also controlled in a manner opposite to that described above.

1. As explained above, in the embodiment, the slit width is controlled by striped electrodes provided on the liquid crystal, but the electrode structure is not necessarily limited to linear stripes. The shape can be changed freely. Moreover, the numerical values in the examples are - examples and are not limited thereto.

[Effects of the Invention - 1] As explained above, according to the present invention, the reflected light of the light irradiated on the surface of the wafer is imaged on the image sensor through the iI-shaped slit, and measurements regarding the Ueno bird can be carried out. A wafer measuring device that performs! Since the 11-variable slit uses a liquid crystal that can change the width of the light transmission area, the opening width of the slit can be changed almost continuously without using a mechanical drive mechanism. rubbish,
There is no generation of dust, etc., and integral measurement and differential measurement can be used together by controlling the detection vessel.

As a result, there are narrow patterns such as memory cells and wide patterns, A, I! II) It is possible to separate and measure the pattern at any time, and to measure the overall height of the pattern using an integral value. ! Can be measured.

Therefore, more appropriate, accurate and efficient measurements can be made.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the wafer measuring device according to the present invention, FIG. 2(a) is an explanatory diagram of the liquid crystal display forming the slots, and FIG. 2 is an explanatory diagram of the case where two liquid crystal shutters are stacked, and FIG. 2(C) is a partially enlarged view of the structure of each of the two liquid crystal shutters. 10...X-Y stage mechanism, 12... Wafer, 2
4... Pattern detection optical system, 26... Objective lens 3
0X, 30Y...Slit plate, 31.35.3
7...Liquid crystal shutter, 31a, 31b, 31n, 35
a, 35b, 35n, 37a, 37b, 37n-...Transparent electrode, 33...Insulating layer, 38X, 38Y...CC
l) Linear image sensor.

Claims (3)

[Claims] (1) A wafer measuring device that measures the wafer by imaging the reflected light of the light irradiated onto the surface of the wafer on an image sensor via a variable slit, the variable slit having a width of a light transmission area. A wafer measuring device characterized by using a changeable liquid crystal. (2) The variable slit is composed of a liquid crystal shutter,
2. The wafer measuring device according to claim 1, wherein the liquid crystal shutter has stripe-shaped electrodes arranged at predetermined intervals. (3) The variable slit is composed of a liquid crystal shutter,
This liquid crystal shutter consists of first and second liquid crystal shutter sections having striped transparent electrodes arranged at predetermined intervals, and the electrodes of the second liquid crystal shutter are arranged between the electrodes of the first liquid crystal shutter. the first, second so that the parts are arranged
2. The wafer measuring device according to claim 1, wherein the liquid crystal shutter portions are stacked.