JP3740079B2 - Apparatus and method for measuring etching groove depth distribution - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention can be applied to the surface of a substrate represented by a semiconductor wafer, a glass substrate for a liquid crystal display device, a glass substrate for a plasma display panel, etc. (the surface of these substrates themselves or a thin film formed on the substrate surface). The present invention relates to an apparatus and a method for measuring a distribution in an in-plane of an etching groove formed on a surface.
[0002]
[Prior art]
There is a damascene method as a technique for forming fine wiring on a semiconductor wafer. In the damascene method, an etching groove is formed in an insulating film formed on a wafer, a wiring metal such as copper is embedded in the etching groove, and then a surface is formed by a CMP (Chemical Mechanical Polishing) method. Grinding to remove the metal outside the grooves.
[0003]
[Problems to be solved by the invention]
In the etching process, a dry etcher capable of fine etching is used. However, the dry etcher is an apparatus that handles unstable plasma and magnetic fields, and has a feature that it is difficult to obtain a good in-plane distribution with respect to the etching depth due to the influence of gas flow. In addition, it is known that the in-plane distribution of the etching depth is not uniform, there is a significant difference between apparatuses, and a change with time that cannot be ignored occurs.
[0004]
Therefore, it is indispensable to measure the in-plane distribution of the etching depth in order to realize good processing at the time of starting up the apparatus and during maintenance. Therefore, at present, the in-plane distribution of the etching depth is measured by destructive inspection in which the wafer is broken and the fractured surface is observed with a scanning electron microscope (SEM).
However, in destructive inspection, the wafer must be wasted and labor for inspection is not small. Moreover, because it is a destructive inspection, it must be a sampling inspection, and not only a large number of sampling inspections but also a 100% inspection is impossible.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an etching depth distribution measuring apparatus and an etching distribution measuring method that can measure the etching depth distribution on the substrate surface in a nondestructive manner.
[0006]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the invention as set forth in claim 1 includes a substrate holding mechanism (2) for holding a substrate (W) having an etching groove formed in an integrated circuit formation region (FA), and the substrate holding An etching groove depth detection mechanism (4, 5, 15, 22) for detecting the depth of an etching groove formed on the surface of the substrate held by the mechanism, and the etching on the substrate held by the substrate holding mechanism The detection position changing mechanism (16, 21) for changing the detection position by the groove depth detection mechanism and the detection result of the groove depth by the etching groove depth detection mechanism are associated with the respective groove depth detection positions. look including the etching depth distribution calculating means (23) for obtaining the substrate in-plane distribution of etch depth formed on the substrate, the etching depth detection mechanism of incident infrared light on the substrate Means (4, 5), an infrared spectrometer (15) for generating a spectrum representing the intensity distribution of light in the infrared wavelength region reflected by the surface of the substrate, and the depth D of the etching groove as a parameter The theoretical value of the spectrum to be generated by the infrared spectrometer in a state where films having thicknesses corresponding to various depths D are formed on the substrate is obtained for each depth D, and a plurality of depths D are obtained. A plurality of mixed spectra obtained by mixing a plurality of theoretical values obtained and a spectrum generated by the infrared spectrometer with respect to an unetched substrate at a mixing ratio corresponding to an area ratio of etching grooves in the integrated circuit formation region. Patent that was created by matching the spectrum to which the plurality of mixing spectrum and the infrared spectrometer is produced, is intended to include the groove depth detection calculating unit for obtaining the etching depth data and (22) An etching depth distribution measuring device according to. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
[0007]
According to said structure, the depth of the etching groove | channel formed in the substrate surface is detected, changing the position on a board | substrate. Then, the in-plane distribution of the etching depth is obtained by associating the detected etching groove depth with the detected position. Thus, the in-plane distribution of the etching groove depth can be obtained without destroying the substrate. Moreover, in the conventional destructive inspection, the etching groove depth distribution is only required to be a one-dimensional distribution along the fracture surface. A two-dimensional distribution can also be obtained.
[0008]
According to a second aspect of the present invention, there is provided an etching groove depth detection step for detecting a depth of an etching groove formed on a surface of a substrate (W) having an etching groove formed in an integrated circuit formation region (FA), and the etching. The step of repeating the groove depth detection step a plurality of times by changing the detection position on the substrate, and by associating the detection result of the groove depth by the etching groove depth detection step with each groove depth detection position, look including the etching depth distribution calculating step of obtaining a substrate in-plane distribution of the substrate on the formed etched groove depth, the etching depth detecting step comprises the steps of incident infrared light on the substrate, Generating a spectrum representing an intensity distribution of light in an infrared wavelength region reflected by the surface of the substrate by an infrared spectrometer (15); Using the thickness D as a parameter, a theoretical value of a spectrum to be generated by the infrared spectrometer in a state where films having thicknesses corresponding to various depths D are formed on the substrate is obtained for each depth D, and a plurality of values are obtained. A plurality of theoretical values obtained for the depth D and a spectrum generated by the infrared spectrometer for the unetched substrate are mixed at a mixing ratio corresponding to the area ratio of the etching grooves in the integrated circuit formation region. Te create multiple mixed spectrum, by collating the spectrum the plurality of mixing spectrum and the infrared spectrometer generates, characterized in including Mukoto a groove depth calculation step of obtaining an etching depth data The etching groove depth distribution measurement method.
[0009]
By this method, an effect similar to the effect described in relation to claim 1 can be achieved. The detection position changing mechanism may include means (2, 16) for changing the relative position between the substrate holding mechanism and the etching groove depth detection mechanism. That is, for example, the detection position changing mechanism may include a mechanism for moving the optical system (4) of the etching groove depth detection mechanism relative to the substrate holding mechanism, or the optical system of the etching groove depth detection mechanism. In contrast, a mechanism (2, 16) for moving the substrate holding mechanism may be included.
[0010]
The etching groove may be a groove formed in a damascene process. Such an etching groove may be a groove in which a wiring metal is embedded. Furthermore, the etching grooves may be formed in a substantially uniform distribution in the substrate surface.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram for explaining the configuration of an etching groove depth distribution measuring apparatus according to an embodiment of the present invention. This apparatus is used, for example, in a so-called damascene process for embedding metal wiring in an insulating film formed on the surface of a semiconductor wafer W (hereinafter referred to as “wafer W”), and wiring metal formed in the insulating film. This is an apparatus for measuring the distribution in the plane of the wafer W with respect to the depth of the etching groove for filling.
[0012]
The etching grooves for embedding the wiring material are formed in a substantially uniform distribution in the surface of the wafer W, for example, by a dry etcher. The wafer W after the etching groove is formed is placed horizontally on the XY stage 2 disposed in the measurement chamber 1. An observation window 3 made of a transparent member such as glass is provided on the top surface of the measurement chamber 1. A lens unit 4 (optical system) used for observing the mirror surface of the wafer W is disposed at a position facing the observation window 3.
[0013]
Infrared light from an infrared lamp house 5 equipped with a halogen lamp or the like is incident on the lens unit 4 through a pinhole formed in the optical fiber 6 and the pinhole member 7. The lens unit 4 collects the infrared light on the surface of the wafer W.
On the other hand, two half mirrors 8 and 9 are arranged between the pinhole member 7 and the lens unit 4 in order from the pinhole 7 side. Visible light is guided to the half mirror 8 from the side of the optical axis of the lens unit 4 from the image processing lamp house 10 through the optical fiber 11. That is, the visible light guided from the image processing lamp house 10 through the optical fiber 11 is reflected by the half mirror 12 and guided to the half mirror 8, and further reflected by the half mirror 8 to be reflected by the lens unit 4. Then, the surface of the wafer W is illuminated.
[0014]
On the other hand, an imaging device 13 such as a CCD camera is disposed on the opposite side of the half mirror 12 from the half mirror 8. Visible light reflected on the surface of the wafer W, passing through the lens unit 4 and the half mirror 9, and further reflected by the half mirror 8 is detected by the imaging device 13. Therefore, the imaging device 13 outputs a video signal representing an image of the surface of the wafer W corresponding to a position near the optical axis of the lens unit 4.
[0015]
Part of the light passing through the lens unit 4 from the surface of the wafer W is reflected by the half mirror 9 and guided to the infrared spectrometer 15 through the optical fiber 14. The infrared spectrometer 15 generates and outputs an intensity distribution spectrum signal in the infrared wavelength region.
Coupled to the XY stage 2 is a stage drive mechanism 16 for driving the XY stage 2 along two orthogonal directions along the X and Y directions along the horizontal plane. By driving the stage driving mechanism 16, the relative position of the wafer W with respect to the optical axis of the lens unit 4 can be changed. Therefore, the etching groove depth is detected at a plurality of positions on the surface of the wafer W. Can do.
[0016]
The stage driving mechanism 16 is controlled by the computer processing system 20. The computer processing system 20 receives a video signal output from the imaging device 13 and a spectral signal output from the infrared spectrometer 15. The computer processing system 20 is connected to a display device 30 such as a CRT or a liquid crystal display device, a printer 40, and an operation unit 50 such as a keyboard.
[0017]
FIG. 2 is a block diagram for explaining the configuration of the computer processing system 20. The computer processing system 20 controls the stage driving mechanism 16 based on the video signal from the imaging device 13, thereby controlling at which position on the wafer W the etching groove depth should be detected. It has. The computer processing system 20 also includes a groove depth detection calculation unit 22 that calculates the etching groove depth based on the spectrum signal from the infrared spectrometer 15.
[0018]
The detection position control unit 21 provides the detection position data to the mapping processing unit 23, while the groove depth detection calculation unit 22 provides the calculated groove depth data to the mapping processing unit 23. The mapping processing unit 23 associates the detected position data with the groove depth data to generate mapping data as basic data representing the in-wafer surface distribution (mapping) of the depth of the etching groove formed on the wafer. . This mapping data is stored in the hard disk device 24 provided in the computer processing system 20.
[0019]
Based on the mapping data stored in the hard disk device 24, the etching groove depth distribution information on the surface of the wafer W can be displayed by the function of the display control unit 25. Further, by the operation of the print control unit 26, the etching groove depth distribution information on the surface of the wafer W can be printed out on the paper from the printer 40.
The functions of the detection position control unit 21, the groove depth detection calculation unit 22, the mapping processing unit 23, and the like are actually performed by software by program processing executed by a CPU as hardware provided in the computer processing system 20. Will be realized.
[0020]
FIG. 3 is a diagram for explaining the function of the detection position control unit 21. On the wafer W, a plurality of integrated circuit formation areas FA are set. For example, integrated circuits having the same design are built in a plurality of integrated circuit formation areas FA, and in the final stage of manufacturing a semiconductor device, the wafer W is diced and divided into individual integrated circuit formation areas FA. Thus, a plurality of pieces (chips) of integrated circuit elements are obtained. The detection position control unit 21 finds a predetermined groove depth detection point P (represented by a symbol “+” in FIG. 3) in each integrated circuit formation area FA based on the video signal from the imaging device 13, and the lens. The optical axis of the unit 4 is made to coincide with the groove depth detection point P.
[0021]
More specifically, since the infrared light generated from the infrared lamp house 5 includes light in the visible light region, the condensing spot LP formed on the surface of the wafer W by the light in the visible light region. And the stage drive mechanism 16 are controlled so as to match the groove depth detection point P. As a result, the reflected light from the vicinity of the groove depth detection point P in one integrated circuit formation area FA enters the infrared spectrometer 15 via the optical fiber 14. When the condensing spot LP and the groove depth detection point P in the integrated circuit formation area FA coincide with each other, the detection position control unit 21 sends the position data of the groove depth detection point P to the mapping processing unit 23. Output. This position data is combined with the groove depth detection data obtained based on the spectrum signal output from the infrared spectrometer 15 to generate mapping data.
[0022]
Such processing is repeatedly executed for a plurality of groove depth detection points P.
FIG. 4 is a diagram showing groove depth in-plane distribution data (data accumulated in the hard disk device 24) constituted by mapping data generated by the mapping processing unit 23. Based on the mapping data stored in the hard disk device 24, a plurality of contour lines EL are drawn in a circular area WA corresponding to the wafer W by connecting positions having the same groove depth with a curve or a straight line. Thus, the two-dimensional distribution of the groove depth on the surface of the wafer W can be illustrated.
[0023]
If the closed regions between adjacent contour lines EL or the closed regions surrounded by the contour lines EL are expressed by different colors, it is possible to display graphics more easily. On the display device 30 and the printer 40, the groove depth in-plane distribution may be illustrated in the manner shown in FIG. 4, or the groove depth in-plane distribution data accumulated in the hard disk device 24 is numerically displayed. Also good. Of course, the graphic display and the numerical display in the form shown in FIG. 4 may be used together.
5 and 6 are diagrams for explaining the principle of detecting the groove depth by the groove depth detection calculating unit 22.
[0024]
First, FIG. 5 is a diagram for explaining the principle of measuring the film thickness T of the insulating film I formed on the surface of the wafer W. In this case, as shown in FIG. 5A, the infrared light L irradiated from the air layer outside the insulating film I is reflected at the interface between the insulating film I and the wafer W. A part of the reflected light is emitted from the insulating film I to the air layer, but the remaining part is reflected at the interface between the air layer and the insulating film I and travels again to the surface of the wafer W.
Similarly, multiple reflection occurs at the interface between the wafer W and the insulating film I and at the interface between the insulating film I and the air layer. As a result, due to the difference in the optical path length corresponding to the film thickness T, the specific wavelength Light will intensify, and light of other specific wavelengths will weaken.
[0025]
That is, when the intensity distribution with respect to the wavelength of the infrared light L is examined, as shown in FIG. 5B, the intensity of light of a specific wavelength is strong and the intensity of light of another specific wavelength is weak. Since the spectrum (wavelength vs. intensity characteristic) thus obtained depends on the film thickness T, the film thickness T can be specified based on this spectrum.
Next, FIG. 6 is a diagram for explaining a method of detecting the depth D when the etching groove IT having a depth D is formed in the insulating film I on the wafer W (FIG. 6A). It is. If the etching grooves IT having a depth D are formed in the integrated circuit formation region FA (see FIG. 3) at a constant area ratio, the surface state of the integrated circuit formation region FA (FIG. 6A) is: When viewed macroscopically, it can be said that it is a mixed state of the state of FIG. 6 (b) and the state of FIG. 6 (c). That is, it is a mixed state of the state in which the insulating film I having the film thickness T is formed (FIG. 6B) and the state in which the insulating film I having the film thickness TD is formed (FIG. 6C). If the mixing ratio is determined based on the area ratio of the etching grooves IT in the integrated circuit formation region FA, the state shown in FIG. 6A is obtained. The area ratio of the etching grooves IT in the integrated circuit formation region FA can be determined based on the design of the integrated circuit.
[0026]
When the insulating film I having a film thickness T is formed on the surface of the wafer W (that is, when it is in an unetched state) , the spectrum signal output from the infrared spectrometer 15 is as shown in FIG. Assume that the spectrum signal output from the infrared spectrometer 15 when the insulating film I having the film thickness TD is formed on the surface of the wafer W is as shown in FIG. In this case, the output of the infrared spectrometer 15 corresponding to the surface state of FIG. 6 (a) is the result of mixing the spectra of FIGS. 6 (e) and (f) at the above mixing ratio as shown in FIG. 6 (d). become.
[0027]
Therefore, the groove depth detection calculation unit 22 can specify the depth D of the etching groove IT based on the spectrum signal output from the infrared spectrometer 15. More specifically, the groove depth detection calculation unit 22 changes the depth D as a parameter in various ways, and the spectrum corresponding to the value of each D (in the case of the surface state of FIG. 15 is a theoretical value of the spectrum to be output . A plurality of theoretical value I to obtained this and the spectrum shown in FIG. 6 (e) were mixed by the mixing ratio, the mixed spectrum corresponding to the value of the D (spectrum as shown in FIG. 6 (d)) Ask. Then, the spectral signal output from the infrared spectrometer 15 is collated with the plurality of mixed spectra obtained by the above calculation, and the value of the parameter D corresponding to the mixed spectrum having the highest degree of coincidence is determined as the etching groove. Output as depth data.
[0028]
As described above, according to this embodiment, the etching depth at the etching groove depth detection point P set for each integrated circuit formation area FA on the surface of the wafer W is detected, and based on this, the wafer is detected. The groove depth in-plane distribution data on the W surface is stored in the hard disk device 24. Therefore, the in-plane distribution of the etching groove depth can be obtained without destroying the wafer W.
Further, in the destructive inspection performed by rupturing the wafer W, only the etching groove depth distribution in the fracture surface can be detected, so that it is possible to measure only the one-dimensional groove depth distribution. On the other hand, according to this embodiment, as shown in FIG. 4, the two-dimensional etching groove depth in-plane distribution can be measured.
[0029]
Furthermore, the in-plane distribution of the etching groove depth can be quickly measured as compared to the destructive inspection for breaking the wafer W.
Deriving from these effects, it is possible to quickly start up and maintain the dry etcher, and to efficiently manage a plurality of dry etchers.
Furthermore, since the in-plane distribution of the etching groove depth can be measured nondestructively, it is possible to perform 100% inspection for inspecting all wafers W, thereby manufacturing a more reliable semiconductor device. It becomes possible to do.
[0030]
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the etching groove depth detection point P is set for each integrated circuit formation area FA, but it is necessary to set the etching groove depth detection position in all the integrated circuit formation areas FA. There is no. That is, for example, rough etching groove depth in-plane distribution in the surface of the wafer W may be obtained by setting four to five etching groove depth detection positions on the surface of the wafer W. Further, more detailed groove depth in-plane distribution may be measured by setting two or more etching groove depth detection positions in each integrated circuit forming area FA.
[0031]
In the above embodiment, the example of measuring the in-plane distribution of the etching groove depth of the insulating film formed on the semiconductor wafer W has been described. However, when multiple layers of wiring are formed on the wafer W, Can measure the in-plane distribution of the etching groove depth of the insulating layer corresponding to the wiring of each layer. In addition to semiconductor wafers, when a film such as an insulating film is formed on the surface of a glass substrate for a liquid crystal display device or a glass substrate for a plasma display, and the in-plane distribution of groove depth formed on this thin film is measured. Also, the present invention can be applied.
[0032]
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining a configuration of an etching groove depth distribution measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining a configuration of a computer processing system.
FIG. 3 is a diagram for explaining the function of a detection position control unit;
FIG. 4 is a diagram illustrating groove depth in-plane distribution data configured by mapping data generated by a mapping processing unit.
FIG. 5 is a diagram for explaining the principle of measuring the thickness of an insulating film formed on the surface of a wafer.
FIG. 6 is a diagram for explaining the principle of detecting the depth of an etching groove formed in an insulating film on a wafer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measurement chamber 2 XY stage 3 Observation window 4 Lens unit 5 Infrared lamp house 6 Optical fiber 7 Pinhole member 8 Half mirror 9 Half mirror 10 Image processing lamp house 11 Optical fiber 12 Half mirror 13 Imaging device 14 Optical fiber 15 Red External spectroscope 16 Stage drive mechanism 20 Computer processing system 21 Detection position control unit 22 Groove depth detection calculation unit 23 Mapping processing unit 24 Hard disk device 25 Display control unit 26 Print control unit 30 Display device 40 Printer 50 Operation unit D Depth EL Contour line FA Integrated circuit formation region I Insulating film IT Etching groove L Infrared light LP Condensing spot P Groove depth detection point P Measurement position P
T film thickness TD film thickness W wafer WA circular area

Claims (2)

A substrate holding mechanism for holding a substrate having an etching groove formed in an integrated circuit formation region ;
An etching groove depth detection mechanism for detecting the depth of the etching groove formed on the surface of the substrate held by the substrate holding mechanism;
A detection position changing mechanism for changing a detection position by the etching groove depth detection mechanism on the substrate held by the substrate holding mechanism;
Etching groove depth distribution for obtaining the distribution of the etching groove depth formed on the substrate in the substrate plane by associating the groove depth detection result by the etching groove depth detecting mechanism with each groove depth detection position. and an arithmetic means only including,
The etching groove depth detection mechanism is
Means for making infrared light incident on the substrate;
An infrared spectrometer that generates a spectrum representing the intensity distribution of light in the infrared wavelength region reflected by the surface of the substrate;
Using the depth D of the etching groove as a parameter, the theoretical value of the spectrum to be generated by the infrared spectrometer in the state in which films having thicknesses corresponding to various depths D are formed on the substrate is given for each depth D. A plurality of theoretical values obtained for a plurality of depths D and a spectrum generated by the infrared spectrometer for an unetched substrate, and a mixing ratio corresponding to an area ratio of etching grooves in the integrated circuit formation region A groove depth detection calculation unit for obtaining etching groove depth data by comparing each of the plurality of mixed spectra with the spectrum generated by the infrared spectrometer, and An etching groove depth distribution measuring apparatus characterized by comprising: An etching groove depth detection step for detecting the depth of the etching groove formed on the surface of the substrate in which the etching groove is formed in the integrated circuit formation region ;
This etching groove depth detection step is repeated a plurality of times by changing the detection position on the substrate,
Etch groove depth distribution for obtaining the in-plane distribution of the etching groove depth formed on the substrate by associating the detection result of the groove depth in the etching groove depth detection step with each groove depth detection position and an arithmetic step seen including,
The etching groove depth detection step includes
Making infrared light incident on the substrate;
Generating a spectrum representing an intensity distribution of light in the infrared wavelength region reflected by the surface of the substrate by an infrared spectrometer;
Using the depth D of the etching groove as a parameter, the theoretical value of the spectrum to be generated by the infrared spectrometer in the state in which films having thicknesses corresponding to various depths D are formed on the substrate is given for each depth D. A plurality of theoretical values obtained for a plurality of depths D and a spectrum generated by the infrared spectrometer for an unetched substrate, and a mixing ratio corresponding to an area ratio of etching grooves in the integrated circuit formation region A plurality of mixed spectra to create a plurality of mixed spectra, and a groove depth calculation step for obtaining etching groove depth data by collating the plurality of mixed spectra with the spectrum generated by the infrared spectrometer. An etching groove depth distribution measuring method characterized by comprising:

Images