JP2002048519A - Method and instrument for measuring difference in level, and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for measuring an etching depth capable of measuring precisely the depth of an etching groove usable for any wafer, even when the various kinds of wafers including a wafer narrow in a measuring objective surface area are measured, and provide a manufacturing method of a semiconductor device. SOLUTION: Irradiation positions of spot lights from light sources 25a, 25b...25n to a measured object (wafer 1) are specified by arrayed positions of arrayed lenses 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for irradiating a step on an object to be measured with measurement light and performing measurement based on the reflected light, and more particularly to a technique for measuring a step between a mask material and an etching groove by interference of reflected light. The present invention relates to a method and an apparatus for measuring a step measured by a change in intensity, and a method for manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art In a wiring process of a semiconductor substrate used in a manufacturing process of a semiconductor device, as the miniaturization progresses, in a conventional processing method of forming a wiring by etching a formed metal film, Because the aspect ratio has become too large, it has become difficult to obtain a desired good shape.

Therefore, a groove is formed in an insulator formed on a Si substrate in advance, and a metal layer for wiring including the inside of the groove is formed on the insulator.
This metal layer is uniformly polished to the surface of the insulator by CMP (Chemical Mechanical Polishing), thereby removing the wiring metal on the insulator and leaving the trench formed in the insulator by etching. Only the process of attaching metal (damascene process) is changing.

In this case, since the electrical resistance of the wiring metal is determined by the cross-sectional area of the wiring, it is necessary to control the depth of the groove formed by etching the insulator with high precision.

[0005] The principle of measuring the depth of the etching groove 56 during the etching process is as shown in FIG.
This is performed by detecting _two reflected lights R ₁ and R ₂ .

That is, the two reflected lights R ₁ and R ₂ are formed by the reflected light R ₁ from the bottom of the etching groove 56 during the etching and the reflected light R ₂ from the mask material 55 on the surface of the Si substrate 51. Then, interference light is generated by the interference phenomenon between the _two reflected lights R ₁ and R ₂ and detected by the optical sensor 57.
This interference light periodically changes in intensity as the etching groove 56 being processed becomes deeper. In addition, the amount of change in the depth when the interference light changes by a half cycle (or one cycle) between the poles is physically determined, and the ratio of the etching rate of the layer in which the etching groove 56 is formed to the etching rate of the mask 55 is determined. In the case where the etching selectivity is infinite, it means that the irradiated single wavelength light is １ ／ deeper. Thus, the depth of the etching groove 56 can be measured.

As described above, the depth of the etching groove 56 during the processing is measured, and as shown in FIG. 8B, the depth of the etching groove is compared with the calculated reference value to confirm the depth of the etching process. Controls the end point. In this confirmation, since the period of the intensity waveform of the interference light and the depth of the etching groove for each period are known, the depth of the etching groove for each unit time can also be calculated. Can be controlled.

One example of these dry etching apparatuses is
As disclosed in Japanese Patent Application Laid-Open No. Hei 10-27785, a semiconductor wafer 51 shown in FIG.
An RF plasma reactor of an RIE (reactive ion etching apparatus) for processing a wafer includes a reactor chamber 52 having side walls and sealing, a wafer pedestal 53 for supporting a semiconductor wafer 51 in the reactor chamber 52, and an RF power source 54. , A gas introducing device 55 for introducing a processing gas into the reactor chamber,
4 and a coil inductance 56 adjacent to the reactor chamber 52 connected to the reactor chamber 52.

Next, referring to the schematic diagram shown in FIG.
An example of an IE dry etching apparatus and a monitor apparatus will be described. The etching device 61 and the monitor device 62 are optically connected to each other. The etching device 61 is provided with an upper electrode 64 at an upper part in a processing chamber 63 which is a vacuum-sealed container. A lower electrode 66 serving as a mounting table for mounting a wafer 65 having a surface on which an insulating layer and a mask material are formed in order to form a cell portion, which is a work, is provided. Further, the lower electrode 66 is provided with a high-frequency power supply 67.
It is connected to the. The upper electrode 64 has a light passing portion 68 formed at the center thereof, and an observation window 69 is formed on a top plate of the processing chamber 63 above the light passing portion 68.

Further, outside the processing chamber 63 above the observation window 69, a condenser lens 71 and a reflection mirror 7 of a monitor device are provided.
2 is provided, and a monitoring optical system to which a plurality of optical fibers 73a and 73b are connected is provided in front of the reflected optical axis. A light source 74 or a sensor 75 is connected to the other end of each of the optical fibers 73a and 73b. Further, the sensor 75 is connected to a depth calculation unit 76.

In such a dry etching apparatus, since there is a restriction such as a relation between the horizontal components and their arrangement and exposure to a strong AC electric field, the monitoring optical system should be provided with a mechanical drive part. Instead, a fixed type is used. As a result, the measurement position by the spot for measurement is fixed.

On the other hand, as shown in FIGS. 11A and 11B, the cell portion on the wafer to be measured is measured for each type of wafer 71a, 71b (cell portion 72a, 72b).
Since the size and position of 72b) are different, it is possible to cope with various types by enlarging the measurement spot.

[0013]

However, in the above-described dry etching apparatus, the monitor optical system of the monitor apparatus is fixed due to structural magnetic influences and restrictions on arrangement.

In the system in which the monitor optical system is fixed, the position of the measurement spot cannot be changed. Therefore, in the case of a wide variety of wafers, the size and position of the measurement target (cell portion) vary, so By increasing the size of the measurement target, the measurement target enters the measurement spot. As a result, if the area of the measurement target is significantly smaller than the area of the measurement spot light, the amplitude of the interference light signal due to the measurement becomes very small.

When the amplitude of the interference light signal becomes very small,
It becomes difficult to detect the extreme point, and it becomes difficult to calculate the depth of the etching groove.

The present invention has been made on the basis of these circumstances. Even when measuring a wide variety of wafers including a wafer having a small area to be measured, the present invention can be applied to any of those wafers. It is an object of the present invention to provide a method and a device for measuring the etching depth, which can accurately calculate the depth of an etching groove, and a method for manufacturing a semiconductor device.

[0017]

According to the first aspect of the present invention, there is provided an irradiation step of irradiating light from a light source onto a step of a measured object as a plurality of spot lights, A step measuring method, comprising: a light receiving step of receiving reflected light of light; and a calculating step of calculating a depth of the step based on an interference waveform of the reflected light received in the light receiving step. .

According to the second aspect of the present invention,
The step of receiving a reflected light in the light receiving step may correspond to the spot light, respectively.

According to the third aspect of the present invention,
An irradiation step of irradiating light from a light source as a spot light whose position is movable on a step of the measured object, a light receiving step of receiving reflected light from the light irradiated by the irradiation step, and a light receiving step Calculating a depth of the step based on an interference waveform of the received reflected light.

Further, according to the means of the present invention,
Optical means for transmitting light from a light source to the step of the measured object as spot light, and transmitting reflected light from the measured object to light receiving means; and an interference waveform of the reflected light received by the light receiving means A step measuring apparatus having a calculating means for calculating a step based on the step, wherein the optical means defines an irradiation position of the spot light on the object to be measured by an array position of an array lens. It is a measuring device.

According to the fifth aspect of the present invention,
A step measuring device, wherein end portions of optical fibers are arranged corresponding to positions of the array of the array lens.

According to the means of the invention of claim 6,
A step measuring device, wherein an end of an optical fiber is movably provided by a moving means so as to correspond to an array position of the array lens.

According to the means of the invention of claim 7,
In a semiconductor device manufacturing method for manufacturing a semiconductor device by forming a chip on which an IC circuit is formed on a silicon wafer through an etching process, the above-described step measurement method is used for controlling the groove depth in the etching process. A method for manufacturing a semiconductor device, comprising:

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a method for measuring a step, an apparatus therefor, and a method for manufacturing a semiconductor device according to the present invention, which is applied to the case of measuring the depth of an etching groove, will be described with reference to the drawings. I do.

First, the principle of measuring the depth of the etching groove and the mathematical formula used therefor will be described. The measurement of the depth of the etching groove is performed as shown in FIG.
As the material to be etched, an insulating layer 2 and a mask material 3 are formed on the surface of a wafer 1, and light is irradiated from a light source (not shown) onto the wafer 1 to etch the insulating layer 2 according to the pattern of the mask material 3. While forming the groove 4, the level difference between the mask material 3 and the etching groove 4 is measured by a monitor device (not shown) based on a change in intensity due to light interference.

In this case, a single wavelength is used as the wavelength of light used for measuring the depth of the light source. The wavelength of light used for measuring the lambda, also the incident light intensity of the entire set to A _0, when the reflected light intensity ratio of the mask material 3 and the etching groove and alpha, reflected light and the etching from the mask material 3 The light reflected from the groove is represented by the following equation.

(Equation 1) In this case, the actually observed light is the interference between the two reflected lights, and only the step D between the mask material 3 and the bottom of the etching groove 4 is used as a variable, that is, the etching of the mask material 3 or the like. , The complex amplitude reflectance γ of the mask material 3
_Assuming that the _mask does not change, the observed interference light is represented by the following equation.

(Equation 2) The last term indicates that the interference light changes periodically. That is, as shown in the graph of the interference light intensity in FIG. 2, the observed interference light signal has a wavelength 1 /
When the step between the mask material and the etching groove is deepened by two, 1
It becomes a periodic signal that changes its period.

The coefficient α of the last term indicating the period change
(1-α) means that when the area of the etching groove in the measurement spot is １ ／ or less of the area of the mask material, a decrease in the area of the etching groove causes a decrease in the amplitude of the interference light signal. I have.

This corresponds to this case when the area of the cell to be measured is small, as shown in the graph of FIG. 3 in comparison with the case of the present invention, and the area of the cell is reduced. This indicates that a small amount causes a decrease in the amplitude of the interference light signal. If the amplitude of the interference light signal becomes extremely small, it becomes difficult to detect the extreme point, and it becomes difficult to calculate the depth of the etching groove.

Next, a method of calculating the depth of the etching groove using the measurement result based on the above-described measurement principle will be described.

In principle, the step between the mask material and the etching groove is measured using the periodicity of the interference light signal from the depth of the etching groove. As shown in FIG. 2, in the section where the maximum / minimum point of the interference light signal is observed, the depth is calculated by counting the number of extreme values (section β in FIG. 2). Further, the etching rate is obtained from the time interval T from the observation of the pole to the observation of the next pole, and the depth of the section where no pole is observed is obtained by extrapolation (sections α,
γ). The step between the mask material and the etching groove is calculated by adding the depths calculated in these three sections to the combined cell portion.

Next, an example of the dry etching apparatus of the present invention and its monitoring apparatus will be described with reference to the schematic diagram shown in FIG.

An RIE (reactive ion etching apparatus) type etching apparatus 11 and a monitor apparatus 12 are optically connected. The etching apparatus 11 has an upper electrode 14 in an upper part of a processing chamber 13 which is a vacuum sealed container. Is provided,
A lower electrode 15 which also serves as a mounting table for mounting the wafer 1 having a surface on which the insulating layer 2 and the mask material 3 are formed is provided at a lower position opposed thereto. The lower electrode 15 is connected to a high-frequency power supply 16. Also,
The upper electrode 14 has a light passing portion 17 formed in the center thereof, and an observation window 18 made of quartz glass is formed on a top plate of the processing chamber 13 above the light passing portion 17.

Further, a condenser lens 19 and a reflection mirror 21 of the monitor device 12 are provided outside the processing chamber 13 above the observation window 18, and a plurality of optical fibers 22a are provided in front of the reflection optical axis. A monitoring optical system to which 22b... 22n are connected is provided. The monitor optical system includes an array lens 23 and a corresponding optical fiber connector 24a,
24b ... 24n etc., and each optical fiber connector 2
The optical axes of the arrays 4a, 24b... 24n and the respective arrays of the array lens 23 are set to coincide.

22n are connected to the other ends of the optical fibers 22a, 22b... 22n, respectively, to light sources 25a, 25b... 25n or sensors 26a, 26b. Also, sensors 26a, 26b... 2
6n is connected to a depth calculation unit 28 via a switching unit 27.

When the signal changes by a half cycle (or one cycle), the depth calculating section 28 determines the etching depth assuming that the depth has changed by the depth calculation reference value. As the depth calculation reference value, an output value from a depth calculation reference value correction unit (not shown) is used.

The reference value for calculating the depth by detecting a pole at the depth calculator 28 is obtained by calculating the average of the reference values obtained while the depth signal changes from the pole to the pole. Used.

With these configurations, the light sources 25a, 25b
The incident light from 25n passes through the array lens 23 to form a plurality of spot lights, is reflected by the reflection mirror 21, is collected by the condenser lens 19, and is collected by the observation window 1 of the processing chamber 13.
8 to form a plurality of measurement spot lights on the mask material 3 and the insulating layer 2 on the surface of the wafer 1 placed on the lower electrode 15 in the processing chamber 13. Interference light from each of the measurement spot lights passes through the condenser window 19, passes through the observation window 18, passes through the observation window 18, is reflected by the reflection mirror 21, passes through the array lens 23, and passes through the array lens 23 to the respective light receiving sections. An image is formed and each sensor 26 is transmitted through optical fibers 22a, 22b,.
a, 26b... 26n.

The sensors 26a, 26b... 26n measure the intensity of the incident interference light. The measurement result is transmitted to the depth calculation unit 28, which selects a signal from the optimum measurement spot where the amplitude of the interference light signal is large, and calculates the depth of the etching groove from the selected interference light signal. Is calculated.

For example, the graph of FIG. 5 (a) shows interference light obtained by measuring spots, spots A, B and C shown in FIG. 6 is a graph showing a result of signal strength. In this result, the amplitude of the interference light signal intensity of the spot A is the largest, and the amplitude of the interference light signal from the optimum measurement spot is used as the interference light signal waveform, and the depth of the etching groove is measured using this interference light signal waveform.

Next, a modification of the above embodiment will be described.

In the above-described embodiment, light sources and sensors are required for the number of measurement spots. For example, when the optimum measurement spot is known in advance from the product type, a schematic diagram shown in FIG. With a simple hardware configuration, the number of light sources and sensors can be reduced. This will be described below. The same functional portions as those in FIG. 4 are denoted by the same reference numerals with “′”, and the description thereof is omitted.

In this modification, the optical fiber connectors 24a 'and 24b' provided in front of the array lens 23 '.
.. 24n ′ are provided in parallel with the optical axis direction so as to coincide with the optical axis of each array of the array lens 23 ′. The optimum spot registration table 32 is connected to the positioning mechanism 31. Therefore,
At the time of processing, the type of product (wafer) is checked before etching, the optimum measurement spot position is searched from a registration table 32 registered in advance, the positioning mechanism 31 is operated, and the optical fiber connector 24a is operated. ´
24n 'are moved to predetermined corresponding array positions. At that position, measurement is performed by spot light while etching is started and processing is performed.

Therefore, in this case, simultaneous measurement of a plurality of spots cannot be performed, but an interference light signal waveform having a large amplitude can be obtained from an optimal measurement spot position registered in advance. The depth of the etching groove is measured using the interference light signal waveform.

As described above, conventionally, when an object to be measured for the depth of an etching groove (for example, a cell portion) is small,
Since the amplitude of the interference light signal thereafter was small and it was impossible to detect a pole, it was difficult to calculate the depth of the etching groove. However, according to the measurement of the etching groove depth of the present invention, the measurement target was Even if it is small, the amplitude of the interference light signal from it can be increased, and the depth of the etched groove can be measured with high accuracy.

In each of the above-described embodiments, the etching groove has been described. However, in the case where a step is formed in the object to be measured, such as in the case of a hole instead of forming the groove, the etching groove is added thereto. The step measurement method of the invention can be applied.

Further, a dry etching apparatus, which is a semiconductor manufacturing apparatus using the step measuring device of the present invention as an observation device, can perform groove processing by accurate etching.

An example will be described below. FIG.
7A and 7B are schematic cross-sectional views of a process for forming a groove in the insulator, wherein FIG. 7A shows a state before the groove is formed, and FIG. 7B shows a state after the groove is formed. That is, as shown in FIG. 7 (a), S placed in an etching chamber (not shown)
On the i-substrate 1a, an insulating layer 2a made of an insulator and a mask material 3a are formed. Thereby, as shown in FIG. 7B, an etching groove 4a corresponding to the mask pattern is formed in the insulating layer 254 at a predetermined depth.

In these etching processes, the depth is measured and monitored during the process so that the etching groove 4a to be formed has a predetermined depth, and the end of the etching process is controlled.

In the manufacture of a semiconductor device, a "pre-process" for forming an IC circuit on a silicon through an exposure process, a development process, an etching process, etc., After cutting the wafer, placing non-defective chips on the lead frame, electrically bonding the electrodes on the chip and the electrodes on the lead frame, sealing with mold resin, and completing the product Is manufactured, and the step measurement method of the present invention is used for the depth measurement control during the above-described etching process.

[0050]

According to the present invention, it is possible to accurately measure the depth of an etching groove even when the object to be measured is small.

Further, the measurement results in a method of manufacturing a semiconductor device capable of performing precise etching.

[Brief description of the drawings]

FIG. 1 is a model diagram of a measurement target for explaining a step measurement method.

FIG. 2 is a graph of interference light intensity.

FIG. 3 is a graph of interference light intensity corresponding to the area of a cell part.

FIG. 4 is a schematic diagram of a dry etching apparatus of the present invention and a monitor thereof.

5A is a graph for each measurement location, and FIG. 5B is an explanatory diagram of the measurement location.

FIG. 6 is a schematic view of a modified example of the dry etching apparatus and the monitor apparatus of the present invention.

FIGS. 7A and 7B are schematic cross-sectional views of a process for forming a groove in an insulator.

8 (a) and (b) are explanatory diagrams of a measurement principle.

FIG. 9 is a side sectional view of a conventional dry etching apparatus.

FIG. 10 is a schematic view of a conventional dry etching apparatus and a modification of the monitoring apparatus.

FIGS. 11A and 11B are diagrams showing the relationship between a measurement spot and an object to be measured.

[Explanation of symbols]

1, 1a wafer, 2, 2a insulating layer, 3, 3a mask material, 4 etching groove, 11, 11 'etching device, 12, 12' monitoring device, 13, 13 'processing chamber, 14 , 14 ': upper electrode, 15, 15': lower electrode, 22a, 22b to 22n: optical fiber, 23, 2
3 ': array lens, 25a, 25b to 25n: light source,
26a, 26b to 26n: sensor, 28, 28 ': depth calculator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F064 AA09 FF00 GG02 GG47 HH02 HH07 2F065 AA25 BB02 BB18 CC20 EE00 FF51 HH04 HH13 JJ02 JJ09 JJ25 LL03 LL04 LL10 LL12 QQ42 5F004 FB04 FB18 FB18

Claims (7)

[Claims] An irradiation step of irradiating light from a light source onto a step of a measured object as a plurality of spot lights; a light receiving step of receiving reflected light of the light irradiated by the irradiation step;
Calculating a depth of the step based on an interference waveform of the reflected light received in the light receiving step. 2. Receiving the reflected light in the light receiving step,
The step measurement method according to claim 1, wherein the method corresponds to each of the spot lights. An irradiation step of irradiating light from a light source onto a step of the measured object as spot light whose position is movable;
A light receiving step of receiving reflected light from the light irradiated by the irradiation step; and an arithmetic step of calculating a depth of the step based on an interference waveform of the reflected light received by the light receiving step. A step measuring method characterized by the above-mentioned. 4. An optical unit for transmitting light from a light source to a step of a measured object as spot light, and transmitting reflected light from the measured object to a light receiving unit, and receiving the light received by the light receiving unit. In a step measuring apparatus having a calculating unit that calculates a step based on an interference waveform of reflected light, the optical unit defines an irradiation position of the spot light on the measured object by an array position of an array lens. A step measuring device characterized by the above-mentioned. 5. The step measuring device according to claim 4, wherein ends of the optical fibers are arranged corresponding to the positions of the array of the array lens. 6. An optical fiber according to claim 4, wherein an end of the optical fiber is movably provided by a moving means so as to correspond to the position of the array of the array lens.
The step measuring device according to the above. 7. A method for manufacturing a semiconductor device by manufacturing a semiconductor device by forming a chip on which an IC circuit is formed on a silicon wafer through an etching process, wherein the groove depth control in the etching process is performed. A method for manufacturing a semiconductor device, comprising using the step measurement method according to claim 3.