JP3720007B2 - Film evaluation method, temperature measurement method, and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film evaluation method, a temperature measurement method, and a semiconductor device manufacturing method that can be used to manufacture semiconductor devices such as various types of transistors and semiconductor memories mounted on electronic devices.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the increase in integration and performance of semiconductor devices, fluorine-added silicon oxide films (hereinafter referred to as FSG films) having a low relative dielectric constant are used as interlayer insulating films for multilayer wiring. The FSG film is generally formed by an HDP-CVD (High Density Plasma-Chemical Vapor Deposition) apparatus suitable for embedding between fine wirings.
[0003]
However, since the HDP-CVD apparatus has a structure in which the wafer is held by an electrostatic chuck, there is a problem that it is impossible to monitor the film formation temperature. Furthermore, although the film formation temperature of the HDP-CVD apparatus is determined by the RF power at the time of film formation, it is difficult to measure the actual temperature using a silicon substrate with a thermocouple, etc., so the film formation temperature of the HDP-CVD apparatus is I don't know exactly.
[0004]
Therefore, the present applicant has measured the film formation temperature of the HDP-CVD apparatus using the temperature measurement technique based on the recovery rate of the amorphous silicon layer on the silicon substrate described in International Publication WO99 / 57146.
[0005]
In addition to the above international publications, the literature related to ellipsometry spectroscopy,
▲ 1 ▼ Nuclear Instruments and Methods in Physics Research B19 / 20 (1987) p.577-581
(2) Japanese Patent Application Laid-Open No. 06-077301
(3) Siemens Forsch.-u.Entwickl.-Ber.Bd.10 (1981) Nr.1, p.48-52
(4) Japanese Patent Laid-Open No. 05-249031
and so on.
[0006]
[Problems to be solved by the invention]
However, in the conventional method for measuring the film formation temperature based on the recovery rate of the amorphous silicon layer, advance preparation is necessary, for example, a step of forming the amorphous silicon layer on the silicon substrate in advance is necessary. Further, in order to measure the film formation temperature of the HDP-CVD apparatus, it is necessary to stop the operation of the HDP-CVD apparatus in the process and form the film under conditions dedicated to temperature measurement. That is, it is necessary to take the CVD apparatus offline.
[0007]
An object of the present invention is to easily measure the characteristics and temperature of a film formed by a film forming apparatus without taking the film forming apparatus offline, that is, without deteriorating the productivity of the film forming apparatus. It is in.
[0008]
[Means for Solving the Problems]
The film evaluation method of the present invention includes a step (a) of measuring an absorption spectrum of the electromagnetic wave by making an electromagnetic wave incident on the substrate on which the film is formed, and a specific shape corresponding to the film quality of the film from the shape of the absorption spectrum. And (b) calculating a value.
[0009]
By this method, the characteristics of the film can be detected using the absorption spectrum of electromagnetic waves, so that materials that can be used for controlling the film forming apparatus and determining the quality of a film such as a semiconductor device can be obtained.
[0010]
In the step (a), infrared light is incident as the electromagnetic wave, and in the step (b), the specific value can be calculated from the shape of the absorption spectrum of the infrared light.
[0011]
In that case, a plurality of reference infrared absorption spectra are prepared in advance corresponding to the film quality level of the film, and in the step (b), the reference infrared absorption spectrum and the infrared absorption of the film are prepared. The specific value can be easily obtained by comparing the spectrum and calculating the specific value.
[0012]
In the step (b), a multivariate analysis is performed on the basis of the infrared absorption spectrum for reference and the shape of the infrared absorption spectrum, and the specific value is calculated to obtain a PLS method (Partial Least Squres Regression) or the like. It is possible to calculate a specific value with high accuracy by using the method.
[0013]
In the step (a), it is preferable to obtain the infrared absorption spectrum of only the film by subtracting the infrared absorption spectrum of the substrate measured in advance from the infrared absorption spectrum of the film and the substrate.
[0014]
The temperature measurement method of the present invention includes a step (a) of measuring an absorption spectrum of the electromagnetic wave by making an electromagnetic wave incident on the substrate on which the film is formed, and a step of calculating a film formation temperature of the film from the shape of the absorption spectrum. (B).
[0015]
By this method, the film formation temperature of the film can be detected using the absorption spectrum of electromagnetic waves, so that materials that can be used for controlling the film formation apparatus and determining the quality of the film such as a semiconductor device can be obtained.
[0016]
In the step (a), infrared rays are incident as the electromagnetic wave, and in the step (b), the film formation temperature can be calculated from the shape of the absorption spectrum of the infrared rays.
[0017]
A plurality of reference infrared absorption spectra are prepared in advance corresponding to the film formation temperature, and in step (b), the reference infrared absorption spectrum is compared with the infrared absorption spectrum of the film. By calculating the film formation temperature, the film formation temperature can be calculated easily.
[0018]
In the step (b), a multivariate analysis is performed based on the shapes of the reference infrared absorption spectrum and the infrared absorption spectrum, and the film formation temperature is calculated by using a technique such as a PLS method. It becomes possible to calculate the deposition temperature with high accuracy.
[0019]
In the step (a), it is preferable to obtain the infrared absorption spectrum of only the film by subtracting the infrared absorption spectrum of the substrate measured in advance from the infrared absorption spectrum of the film and the substrate.
[0020]
In the step (a), the substrate is placed in the film forming apparatus in advance to form the film on the substrate. In the step (b), the film forming temperature of the film is set in the film forming apparatus. By calculating the temperature of the film, the temperature inside the film deposition system (chamber) can be measured quickly using a wafer flowing inline or a management wafer without taking steps such as attaching a sensor to the wafer. can do.
[0021]
A first method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device having a film as a constituent element, the step (a) of forming the film on a base wafer disposed in the film forming apparatus; (B) measuring infrared absorption spectrum by making infrared rays incident on the wafer on which the film is formed, and (c) calculating a specific value corresponding to the film quality of the film from the shape of the infrared absorption spectrum And a step (d) for controlling the setting conditions of the film forming apparatus according to the specific value calculated in the step (c).
[0022]
By this method, using the absorption spectrum of electromagnetic waves, the characteristics of the film can be detected non-destructively in-line, and the result can be used for controlling the film forming apparatus, so that the productivity is not reduced. It is possible to control the conditions of the film forming apparatus by measuring specific values for all the film forming processes.
[0023]
A plurality of reference infrared absorption spectra are prepared in advance corresponding to the film quality level of the film, and in the step (c), the reference infrared absorption spectrum and the film measured in the step (b) are prepared. By comparing the above infrared absorption spectrum with the above and calculating the specific value, process control can be easily performed.
[0024]
In the step (c), the multivariate analysis is performed based on the shapes of the reference infrared absorption spectrum and the infrared absorption spectrum, and the specific value is calculated, whereby the process control can be performed accurately. .
[0025]
A second method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device having a film as a component, and the step (a) of forming the film on a base wafer arranged in the film forming apparatus; (B) measuring infrared absorption spectrum by making infrared rays incident on the wafer on which the film is formed; (c) calculating the film formation temperature of the film from the shape of the infrared absorption spectrum; And (d) controlling the set conditions of the film forming apparatus in accordance with the film forming temperature calculated in (c).
[0026]
By this method, the film formation temperature can be detected in-line in a non-destructive manner using the absorption spectrum of electromagnetic waves, and the result can be used to control the film formation apparatus, thereby reducing productivity. In addition, the temperature of the film forming apparatus can be controlled by measuring the film forming temperature for all the film forming processes.
[0027]
A plurality of reference infrared absorption spectra are prepared in advance corresponding to the film forming temperature, and in the step (c), the reference infrared absorption spectrum and the film measured in the step (b) are prepared. By comparing the above infrared absorption spectrum and calculating the film forming temperature, process control can be easily performed.
[0028]
In the step (c), the multivariate analysis is performed based on the shapes of the reference infrared absorption spectrum and the infrared absorption spectrum, and the film formation temperature is calculated, thereby enabling accurate process control. .
[0029]
DETAILED DESCRIPTION OF THE INVENTION
In the following embodiments, an infrared absorption spectrum of a substrate on which a film is formed is measured by an FT-IR method (Fourier-transform Infrared Spectroscopy), and pattern recognition is performed on the infrared absorption spectrum by a PLS method (Partial Least Squares Regression). Use a multivariate analysis based technique.
[0030]
-First embodiment-
1 (a) and 1 (b) show, in order, the infrared absorption spectrum of an FSG film (fluorine-containing silicon oxide film) by the FT-IR method and the vicinity of its peak, using the film formation temperature by the HDP-CVD apparatus as a parameter, respectively. It is a figure which expands and shows.
[0031]
The infrared absorption spectrum of the FSG film shown in FIGS. 1A and 1B is an infrared absorption spectrum of the FSG film formed on the silicon substrate, and is measured by the following procedure.
[0032]
In general, a silicon substrate has a property of transmitting infrared rays. Therefore, when infrared rays are incident on one surface of the silicon substrate, the infrared rays are absorbed by the silicon substrate in a certain proportion, and then the infrared rays that have passed through the silicon substrate are transmitted to the other side of the silicon substrate. Is output from the surface. Therefore, by the FT-IR method, for example, infrared interference light having a diameter of about 5 mm is incident on the back surface or front surface of the wafer from the vertical direction, and the interference light between the intensity of the infrared light transmitted through the wafer and the intensity of the incident infrared light is detected. A function for the wave number is calculated by Fourier transforming the function for the optical path difference of the intensity, and this is used as the first infrared absorption spectrum.
[0033]
Next, a silicon substrate is installed in the HDP-CVD apparatus, and an FSG film having a predetermined thickness is formed on the silicon substrate. Thereafter, by the FT-IR method, infrared rays are incident on the same part of the wafer under substantially the same conditions as described above, and the ratio of the intensity of the infrared rays incident on the FSG film and the silicon substrate and the intensity of the infrared rays transmitted through both are respectively It measures for every wavelength and makes this a 2nd infrared absorption spectrum. Then, the first infrared absorption spectrum is subtracted from the second infrared absorption spectrum to calculate the infrared absorption spectrum of only the FSG film. Thus, the infrared absorption spectrum of only the desired FSG film can be obtained by calculating the difference of the infrared absorption spectrum of the silicon substrate from the infrared absorption spectrum obtained by synthesizing the FSG film and the silicon substrate.
[0034]
Also in the following description, the infrared absorption spectrum of the FSG film is measured by the same procedure unless otherwise specified. However, the thin film to be measured for the infrared absorption spectrum in the present invention is not limited to the FSG film, and the manufacturing method of the thin semiconductor device is not limited to the HDP-CVD apparatus. Further, the substrate serving as the base of the thin film is not limited to the silicon substrate. Furthermore, the infrared absorption spectrum measurement method is not limited to the FT-IR method.
[0035]
Furthermore, if the thickness, phosphorus concentration, and oxygen concentration of the silicon substrate are the same, even when only the second infrared absorption spectrum is measured, the same result as when the first infrared absorption spectrum is subtracted from the second infrared absorption spectrum. Is obtained.
[0036]
In addition, the infrared absorption spectrum of the present invention is measured using a semiconductor infrared spectroscopic analyzer (IR-EPOCH 2000) manufactured by Newly Instruments Co., Ltd. as an FT-IR apparatus.
[0037]
Here, as can be seen from FIGS. 1A and 1B, when the film formation temperature of the FSG film is different, the shape of the infrared absorption spectrum is different, and in particular, the wavelength exhibiting the maximum absorption and the maximum absorption at the peak portion. Is different. The present inventor conducted various studies on whether there is a method for monitoring the film formation temperature of the HDP-CVD apparatus in addition to the conventional temperature measurement technique based on the recovery rate of the amorphous silicon film. It was found that in this embodiment, the infrared absorption spectrum (in this embodiment, the infrared absorption spectrum by the FT-IR method) differs depending on the film formation temperature of the HDP-CVD apparatus.
[0038]
Hereinafter, the reason why the infrared absorption spectrum of the FT-IR method differs depending on the film forming temperature of the HDP-CVD apparatus will be described.
[0039]
It is estimated that the FSG film formed by the HDP-CVD apparatus becomes a more complete silicon oxide film when the deposition temperature is increased. That is, when FSG films having the same film thickness and different film formation temperatures are analyzed by the FT-IR method, a change in peak height (αa) indicating the total absorption amount of Si—O bonds and the like by a complete silicon oxide film (FIG. 1). (A)) and a shift (αb) of the peak position of an Si—O bond or the like (see FIG. 1B) due to the difference in film quality based on the difference in film formation temperature.
[0040]
FIG. 2 is a table showing the wavelength indicating the maximum absorption at the peak portion and the maximum absorption value in the infrared absorption spectrum shown in FIGS. In the range shown in the figure, the maximum absorption increases as the film forming temperature increases, and the wave number indicating the maximum absorption increases as the film forming temperature increases.
[0041]
That is, when the present inventor forms an FSG film at different film formation temperatures, the present inventor pays attention to a point where the peak height and peak position of the Si—O bond or the like, that is, the shape of the absorption peak is different, and an FT-IR method that has not been conventionally used. It was found that the film formation temperature of the HDP-CVD apparatus can be detected by a new method using the above. The reason why the shape of the absorption spectrum is different at different film forming temperatures is presumed to be because the existence ratio of bonds such as Si—O, Si═O, and Si≡O in silicon oxide differs depending on the film forming temperature.
[0042]
Next, a procedure for analyzing the film forming temperature of the thin film with different infrared absorption spectra will be described. Here, in order to analyze the film formation temperature from different infrared absorption spectra, an analysis technique based on pattern recognition by the PLS method is used.
[0043]
3 (a) to 3 (c) are respectively an infrared absorption spectrum diagram for reference in a solution model of a multivariate analysis technique based on pattern recognition, and an infrared absorption spectrum diagram of a film to be measured (hereinafter referred to as the film to be measured). It is a figure which shows the film-forming temperature determination method by PLS method, and an infrared absorption spectrum figure. 3A and 3B, the peak O is SiO.₂ Etc., and peak F shows a peak due to absorption of SiF. As shown in the figure, the interval between the peaks O and F changes according to the film forming temperature.
[0044]
First, as shown in FIG. 3A, reference is made to a plurality of (three in this embodiment) FSG films formed in advance at different film formation temperatures (T1 <T2 <T3) by the FT-IR method. Infrared absorption spectrum pattern SPT₁ , SPT₂ , SPT_Three Is measured and stored in a storage device as a database.
[0045]
Next, as shown in FIG. 3B, the infrared absorption spectrum pattern SPT of the film to be measured._A Measure.
[0046]
4A to 4D are an infrared absorption spectrum diagram of an FSG film formed at 380 ° C., 430 ° C., and 480 ° C., respectively, and an infrared absorption spectrum diagram of an FSG film to be measured. That is, FIGS. 4A to 4C show infrared absorption spectrum patterns SPT of three FSG films having different film formation temperatures shown in FIG.₁ , SPT₂ , SPT_Three FIG. 4 (d) shows an infrared absorption spectrum pattern SPT of the film to be measured shown in FIG. 3 (b)._A This is a specific example.
[0047]
Next, three reference infrared absorption spectrum patterns SPT are obtained by pattern analysis.₁ , SPT₂ , SPT_Three And infrared absorption spectrum pattern SPT of the film to be measured_A The sum of squares of deviation from_i ²(1)
Χ_i ²= Σ (SPT_i -SPT_A )²                           (1)
Ask from. Σ (SPT on the right side of equation (1)_i -SPT_A )² Is the sum of squares of the difference in absorption at each wavelength between the infrared absorption spectrum pattern for reference and the infrared absorption spectrum pattern of the film to be measured, and is the sum of squares of each wavelength, the sum of the squares of the deviations. And Χ of formula (1)_i ²The difference between the maximum absorption value of the peak portion between the infrared absorption spectrum pattern for reference and the infrared absorption spectrum pattern of the film to be measured, the difference in wavelength indicating the maximum absorption value, and the peak O, A pattern shift caused by a difference in the F interval is included.
[0048]
As a result, as shown in FIG.₁ ², Χ₂ ², Χ_Three ²3 points are required.₁ ², Χ₂ ², Χ_Three ²Curve L passing through_A (In this example, a quadratic curve is used for simplicity). Therefore, this curve L_A The square sum of the deviation from² Temperature T that minimizes_A And this temperature is estimated as the film formation temperature of the FSG film. Hereinafter, this procedure will be specifically described with reference to examples.
[0049]
FIGS. 12A and 12B are a table showing an example of the setting contents of the constructed database and a diagram showing the calculation results, respectively. The solution in the PLS method is obtained by a numerical calculation method using a computer, and the accuracy of the temperature in a special database obtained by performing multiple regression analysis by the PLS method and the accuracy of the PLS model of the database approaches 1.0. This is a method of adjusting parameters. According to the result of numerical calculation performed by the inventor this time, the maximum wave number is 1600 cm.^-1Minimum wave number from 700cm^-1When the number of division points of the infrared absorption spectrum was set to 467 points, the accuracy (Correct Coefficient) was the highest, and an accuracy of 0.98 could be obtained.
[0050]
FIG. 13 is a table showing the verification results of the temperature in the constructed database and the analysis temperature. The figure shows the temperature in the database (spectrum pattern SPT shown in FIG. 3 (a))._i Deposition temperature T corresponding to_i Analysis temperature (deposition temperature T shown in FIG. 3C)_A ), Difference (difference between database temperature and analysis temperature), error rate (quotient obtained by dividing difference by database temperature, multiplied by 100), spectral residual (FIG. 3 (c)) Inner pot² And the reliability of the analysis value is displayed.
[0051]
In the figure, smaller values of spectral residuals and analysis values are preferable, and the reliability of analysis temperature is higher. As shown in the figure, since the numerical values indicating the reliability of the spectral residual and the analysis temperature are sufficiently small with respect to the set temperature in the database, it can be determined that there is no problem in practice. Furthermore, as a result of verification using the database created this time, an error rate of the film formation temperature of the FSG film is ± 1.0% or less. That is, a PLS model capable of estimating the temperature with an accuracy of ± 1.0% or less in the temperature range of 384.2 ° C. to 504.5 ° C. can be obtained from the present calculation result.
[0052]
-Second Embodiment-
In the above-described example, in order to facilitate understanding, the method for estimating only the film formation temperature as a parameter has been described. However, in the actual process, the film thickness and impurity concentration (for example, fluorine concentration) of the thin film to be formed are not constant, and there are variations in these parameters between wafers and within wafers. Then, the estimation accuracy of the film formation temperature may be deteriorated due to variations in film thickness, impurity concentration, and the like. Therefore, in an actual process, it is necessary to perform multivariate analysis including parameters such as film thickness and impurity concentration even if the purpose is to estimate the film formation temperature.
[0053]
Next, a method for estimating multidimensional parameters including not only the film forming temperature of the thin film but also the film quality and film thickness will be described. Here, an infrared absorption spectrum pattern of an FSG film formed by an HDP-CVD apparatus will be described as an example.
[0054]
FIG. 5 is a diagram showing a database construction method comprising infrared absorption spectrum patterns of FSG films. First, as film formation conditions for determining the film quality of the FSG film, the film formation temperature of the HDP-CVD apparatus, the fluorine concentration contained in the FSG film, and the film thickness of the FSG film each have a plurality of conditions (for example, three types). Create a matrix of the set deposition conditions. An FSG film is formed under all conditions of the matrix, an infrared absorption spectrum is measured by the FT-IR method, and a database of infrared absorption spectrum patterns is constructed.
[0055]
In the example shown in FIG. 5, three types of film thicknesses of 300 nm, 600 nm, and 900 nm, three types of film forming temperatures of 370 ° C., 430 ° C., and 490 ° C., and three types of fluorine concentrations of 0.4%, 1.4%, A total of 27 infrared absorption spectrum patterns are stored in a database for 2.4%. Also, the figure shows an infrared absorption spectrum pattern for conditions k2 and k3 where the film thickness is 600 nm, the film formation temperature is about 370 ° C., and the fluorine concentrations are about 1.4% and 2.4%, respectively. ing.
[0056]
Next, the film thickness, film formation temperature, and fluorine concentration of the film to be measured are calculated from the infrared absorption pattern indicated by the film to be measured using a large number of databases as shown in FIG. At that time, by performing multivariate analysis in the same procedure as shown in FIGS. 3A and 3B, the sum of squares of the deviation as shown in FIG. 3C is finally obtained in the multidimensional space. Numerous dots to show_i ²Is obtained. In this case, since it is necessary to perform analysis in a multidimensional space, a graph display as shown in FIG. And these many points_i ²The film thickness, film formation temperature, and fluorine concentration at the point showing the minimum value in this multidimensional figure are determined as the film thickness, film formation temperature, and fluorine concentration of the film to be measured. Will be calculated.
[0057]
Instead of the above estimation method, three graphs are created with the horizontal axis representing the film formation temperature, film thickness, and fluorine concentration._i ²It is also possible to approximate the horizontal axis position indicating the minimum value of the quadratic curve passing through the film formation temperature, film thickness, and fluorine concentration of the film to be measured.
[0058]
As described above, using the solution model of multivariate analysis technology based on pattern recognition, the infrared absorption spectrum pattern of the film to be measured is estimated to be close to which infrared absorption spectrum pattern of the constructed database, and multivariate analysis is performed. The film formation temperature, fluorine concentration, and film thickness can be determined by technology.
[0059]
FIG. 6 is a flowchart showing a procedure for estimating the film formation temperature of the film to be measured (FSG film) by multivariate analysis.
[0060]
First, in step ST11, a reference infrared absorption spectrum pattern (for example, patterns for 27 conditions shown in FIG. 6) is created and stored in a storage device as a database.
[0061]
Next, in step ST12, the infrared absorption pattern of the film to be measured is measured by the FT-IR method. However, methods other than the FT-IR method can be used to measure the infrared absorption pattern in the present invention.
[0062]
Next, multivariate analysis is performed in step ST13. In the example shown in FIGS. 2A to 2C, three reference infrared absorption spectrum patterns SPT are used.₁ , SPT₂ , SPT_Three And infrared absorption spectrum pattern SPT of the film to be measured_A Χ equivalent to the sum of squared deviations_i ²However, in the present embodiment, an analysis is performed in which the squares of the deviations of the absorption values at the respective wavelengths of the 27 reference infrared absorption spectrum patterns and the infrared spectrum pattern of the film to be measured are integrated for each wavelength (multiple Variable analysis).
[0063]
Next, in step ST14, the film formation temperature and the like are calculated based on the pattern analysis result. In the first embodiment, the three dots shown in FIG.₁ ², Χ₂ ², Χ_Three ²Curve L passing through_A The square sum of the deviation from² Temperature T that minimizes_A This temperature is calculated as the film formation temperature of the FSG film. In this embodiment, in the multi-dimensional space, 27 dots indicating the sum of squares of deviation as shown in FIG._i ²Each point_i ²A multidimensional figure that is most likely to pass through is obtained, and the film formation temperature at the point indicating the minimum value of the multidimensional figure is calculated as the film formation temperature of the film to be measured.
[0064]
FIG. 7 shows the correlation between the film formation temperature of the HDP-CVD apparatus estimated by the method of the present embodiment and the film formation temperature measured by a method applying the method described in the above-mentioned International Publication WO99 / 57146. FIG. Here, when the method described in the above-mentioned WO99 / 57146 is used, it is difficult to grasp the recovery rate of the amorphous layer at 500 ° C. or lower, so another method using this method is used. As shown in FIG. 7, the film forming temperature of the present invention and the film forming temperature obtained by applying the conventional method have a substantially 1: 1 correlation, and the HDP-IR method by the FT-IR method is obtained. It can be seen that the measurement result of the film forming temperature of the CVD apparatus is good.
[0065]
According to the present embodiment, it is possible to accurately measure the film forming temperature of the thin film by performing multivariate analysis using the FT-IR method with the film thickness, impurity concentration, film forming temperature and the like as parameters. . In particular, as described above, in the method described in International Publication No. WO99 / 57146, it is difficult to measure the film forming temperature in the range of 500 ° C. or lower, but in the method of the present invention, the range of 500 ° C. or lower. In addition, there is an advantage that the film forming temperature can be measured easily and quickly (specifically, about 2 to 3 minutes).
[0066]
However, the range of the film formation temperature that can be measured by the temperature measurement according to the present invention is not limited to 500 ° C. or less. The film formation temperature can be measured even in a lower temperature range including the temperature range almost the same as the method described in International Publication WO99 / 57146. The present invention has a remarkable effect that temperature measurement can be performed in a process temperature range of 350 ° C. to 500 ° C., which is performed in a wiring process of a semiconductor device, in recent years, as the temperature of a semiconductor process is decreasing. It can be demonstrated.
[0067]
In this method, the deposition temperature can be easily measured from the in-line conditions of the infrared absorption spectrum while using the deposition apparatus under the same conditions as the process. The film forming temperature can be measured for the film forming process.
[0068]
-Third embodiment-
Next, as an application example of the thin film evaluation method according to the present invention, a method for manufacturing a thin semiconductor device on a production line will be described.
[0069]
FIG. 8 is a cross-sectional view showing the structure of the semiconductor device formed in the third embodiment. The silicon substrate 11 is provided with a trench isolation region 12 for partitioning the active region, and a large number of MISFETs 13 are provided in the active region surrounded by the trench isolation region 12. Silicide layers 14a and 14b formed by a salicide process are respectively provided on source / drain regions (not shown) and gate electrodes of each MISFET 13.
[0070]
In the manufacturing method of this embodiment, first, a first interlayer insulating film 20 made of a BPSG film is deposited on a silicon substrate 11 on which a large number of MISFETs 13 are provided. The thickness of the first interlayer insulating film 20 is about 800 nm.
[0071]
Next, contact holes that penetrate through the first interlayer insulating film 20 and reach the silicide layers 14a and 14b of the source / drain regions and the gate electrodes are formed, and the contact holes are filled with tungsten (W) and plugged. 24 is formed. Although the plug on the gate electrode is not shown in FIG. 8, the plug connected to the gate electrode is provided on a cross section different from the cross section shown in FIG. Each plug 24 has a diameter of about 0.25 μm.
[0072]
Next, after depositing an Al film on the first interlayer insulating film 20, the Al film is patterned to form Al wirings 33 (first-layer wirings) connected to the plugs. The thickness of the Al wiring 33 is about 400 nm. Thereafter, a second interlayer insulating film 30 is deposited on the first interlayer insulating film 20 and the Al wiring 33. The second interlayer insulating film 30 includes a lower film 31 made of an FSG film and an upper film 32 made of a P-TEOS film (plasma TEOS film). The thickness of the lower film 31 is about 500 nm, and the thickness of the upper film 32 is about 300 nm.
[0073]
Here, in the present invention, before the lower film 31 of the second interlayer insulating film 30 is deposited, an infrared beam is incident on a region (measurement region) to be measured on the wafer, and the entire substrate serving as a base of the lower film 31 is formed. The infrared absorption spectrum of is measured. Then, the lower film 31 is deposited by HDP-CVD. At this time, the film forming conditions of the lower film 31 made of the FSG film are as follows: the chamber internal pressure of the film forming apparatus is 6 mTorr (about 0.8 Pa), the RF power of the plasma CVD apparatus is 900 W / 2300 W, the bias power is 2350 W, He pressure is 2 mTorr (about 0.27 Pa) on the IN side, the argon gas TOP flow rate is 9 (ml / min), the argon gas SIDE flow rate is 46 (ml / min), and the oxygen TOP flow rate is 53 (ml / min). min), SIDE flow rate of oxygen is 73 (ml / min), TOP flow rate of silane is 4 (ml / min), SIDE flow rate of silane is 40 (ml / min), and flow rate of tetrafluorosilane is 28 ml / min) It is.
[0074]
Then, after depositing the lower film 31, infrared rays are incident on the measurement area of the wafer, and the infrared absorption spectrum is measured. Then, the infrared absorption spectrum of the lower film 31 alone is measured from the difference between both infrared absorption spectra. Furthermore, using the infrared absorption spectrum pattern for reference (see FIG. 5) described in the second embodiment, multivariate analysis of the infrared absorption spectrum pattern of the lower film 31 using the film formation temperature, the film thickness, and the fluorine concentration as parameters. To do. As a result, the film formation temperature, film thickness, and fluorine concentration of the lower film 31 can be measured to determine whether or not the deposition conditions of the lower film 31 are appropriate.
[0075]
Next, after depositing the upper film 32 of the second interlayer insulating film 30, a via hole reaching the Al wiring 33 on the first interlayer insulating film 20 is formed in the second interlayer insulating film 30, and the via hole is made of tungsten. Filled with (W), the plug 34 is formed. The thickness of the upper film 32 of the second interlayer insulating film 30 is about 300 nm, and the diameter of the plug 34 is about 0.3 μm.
[0076]
Thereafter, an Al wiring 43 (second-layer wiring) and a third interlayer insulating film 40 are formed on the second interlayer insulating film 30 by the same procedure as described above. The third interlayer insulating film 40 includes a lower film 41 made of an FSG film and an upper film 42 made of a P-TEOS film. When the lower film 41 is formed, the third interlayer insulating film 40 uses multiple infrared absorption spectra. Perform variable analysis to manage film formation temperature, film thickness, fluorine concentration, etc.
[0077]
Thereafter, an Al wiring 53 (third layer wiring) and a fourth interlayer insulating film 50 are formed on the third interlayer insulating film 40 by the same procedure as described above. The fourth interlayer insulating film 50 has a lower film 51 made of an FSG film and an upper film 52 made of a P-TEOS film. When the lower film 51 is formed, the fourth interlayer insulating film 50 uses multiple infrared absorption spectra. Perform variable analysis to manage film formation temperature, film thickness, fluorine concentration, etc.
[0078]
Thereafter, an Al wiring 63 (fourth layer wiring) and a passivation film 60 made of a P-SiN film are formed on the fourth interlayer insulating film 50.
[0079]
In this embodiment, the first interlayer insulating film 20 made of a BPSG film, the upper films 32, 42, 52 of the second to fourth interlayer insulating films made of a P-TEOS film, and the P-SiN film When measuring the deposition temperature of the passivation film 60, the multivariate analysis using the infrared absorption spectrum is not performed. The reason is that the BPSG film, the P-TEOS film, and the P-SiN film use not a HDP-CVD apparatus that uses high-density plasma but a CVD apparatus that uses normal plasma or thermal reaction. Since there is no mechanism for electrostatic chucking and cleaning with He on the backside of the wafer like a CVD device, for example, by embedding a thermocouple in the lower electrode of a normal plasma CVD device and measuring the temperature of the lower electrode This is because the wafer temperature can be indirectly measured. However, when forming a BPSG film, a P-TEOS film, a P-SiN film, etc., by performing multivariate analysis using an infrared absorption spectrum, the impurity concentration (boron, phosphorus, etc. in the BPSG film) Since thickness can also be measured, process control can be performed strictly.
[0080]
Moreover, since the trench isolation region 12 may also be configured by USG (Undoped Silicate Glass) deposited using an HDP-CVD apparatus, multivariate analysis using an infrared absorption spectrum can be performed.
[0081]
FIG. 9 is a flowchart showing a processing procedure before and after the formation of the FSG film in the manufacturing process of the present embodiment.
[0082]
First, in step ST21, the infrared absorption spectrum of the base wafer is measured. This base wafer is a wafer in which the first interlayer insulating film 20 and the plug 24 are already formed when the lower film 31 of the second interlayer insulating film 30 is formed. When the lower film 41 is formed, the second interlayer insulating film 30 and the plug 34 are already formed on the wafer, and when the lower film 51 of the fourth interlayer insulating film 50 is formed, the third interlayer insulating film 30 and the plug 34 are formed. The interlayer insulating film 40 and the plug 44 are already formed on the wafer.
[0083]
Next, in step ST22, an FSG film (in this example, the lower films 31, 41, and 51) is deposited using the HDP-CVD apparatus under the above-described conditions.
[0084]
Next, in step ST23, the infrared absorption spectrum of the wafer after the FSG film is deposited is measured. That is, the absorption spectrum of infrared rays that have passed through the FSG film and the underlying wafer is measured.
[0085]
Next, in step ST24, the difference between the infrared absorption spectrum measured in step ST23 and the infrared absorption spectrum measured in step ST21 is calculated for each wavelength to create an infrared absorption spectrum pattern of the FSG film alone. .
[0086]
Next, in step ST25, by using a reference infrared absorption spectrum pattern (for example, a number of spectrum patterns having parameters such as film formation temperature, film thickness, and fluorine concentration as shown in FIG. 5) stored in the database in advance, Multivariate analysis is performed by the method described in the second embodiment. As a result, a graph or function in which the curve shown in FIG. 3C is replaced with a multidimensional figure or a multidimensional function is obtained.
[0087]
Next, in step ST26, from the multidimensional function or multidimensional figure obtained in step ST25, the film formation temperature, film thickness, fluorine concentration, etc. of the FSG film giving the minimum value are estimated.
[0088]
Next, in step ST27, it is determined whether or not the film formation temperature, film thickness, and fluorine concentration estimated in step ST26 are within appropriate ranges. If the deposition temperature is too low, the contact state (specifically, contact resistance) between the plug formed in the interlayer insulating film below the FSG film and the lower conductor layer in contact with the plug may be deteriorated. is there. Further, when the film forming temperature is too low, there are the following problems.
[0089]
FIG. 10 is a diagram showing the deposition temperature dependence of the etching rate of the FSG film. In the figure, the vertical axis represents the etching rate as the etching rate ratio with the thermal oxide film. As shown in the figure, if the film formation temperature is too low, the etching rate becomes high, so that it is difficult to manage the etching time and the like in the process. That is, when the etching rate of the thin film is increased, problems such as over-etching occur.
[0090]
In other words, the etching rate can be incorporated into the parameters of the multivariate analysis as the film quality of the FSG film or the like.
[0091]
On the other hand, if the deposition temperature is too high, the characteristics of the Al film already formed below the FSG film may be deteriorated. Therefore, there is an appropriate range for the film formation temperature of the FSG film. In this example, it is preferable that the FSG film is in the range of 380 ° C. to 480 ° C. If the film thickness is too large, it becomes difficult to form via holes and plugs. If the film thickness is too thin, the capacitance between the wirings sandwiching the interlayer insulating film increases or the insulating properties of the interlayer insulating film deteriorate. Since there is a possibility, there is an appropriate range for the film thickness. Furthermore, if the fluorine concentration is too low, the relative dielectric constant of the interlayer insulating film cannot be made sufficiently small, and if the fluorine concentration is too high, the Al film may peel off due to diffusion of F. There is a range.
[0092]
As a result, if the film formation temperature, film thickness, fluorine concentration, etc. are in the proper range, the process proceeds to the next step as it is, while if the film formation temperature, film thickness, fluorine concentration, etc. are not in the appropriate range, the process proceeds to step ST27. Then, after changing the conditions in HDP-CVD, the FSG film is removed by etching, and the FSG film is deposited again.
[0093]
In addition, after the condition change in step ST27, the process may proceed to the next process as it is. Even in this case, when the lower film 41 of the third interlayer insulating film 40 is formed after the lower film 31 of the second interlayer insulating film 30 is formed, the FSG film is deposited under appropriate conditions. Can do.
[0094]
As described above, in the process of the semiconductor device, it becomes easy to maintain parameters such as the film formation temperature, the film thickness, and the fluorine concentration of the FSG film within an appropriate range, so that the management of the manufacturing process of the semiconductor device can be strictly and easily performed. Can be done. In addition, the yield can be improved by re-forming the thin film.
[0095]
In addition, although the infrared absorption spectrum of the FT-IR method shown in FIG. 1 showed the data of the infrared absorption spectrum of only the FSG film formed with the HDP-CVD apparatus, the infrared absorption obtained by synthesizing the FSG film and the silicon substrate. Even in the case of the spectrum, it has been confirmed that the film formation temperature of the HDP-CVD apparatus can be measured as in FIG.
[0096]
Furthermore, according to this method, only the infrared absorption spectrum component of the thin film can be detected by calculating the difference, so that not only the in-line monitor but also the deposition temperature of an actual device having a complicated back surface structure of the substrate can be accurately determined. Can be measured.
[0097]
In each of the above embodiments, the FSG film formed by the HDP-CVD apparatus has been described. However, other silicon oxide films such as a phosphorus-added silicon oxide film (PSG film) or a boron / phosphorus-added silicon oxide film are used. (BPSG film), silicon nitride film, etc. can also be applied. Further, although the HDP-CVD apparatus has been described for forming the silicon oxide film such as the FSG film, other film forming apparatuses such as a normal plasma CVD apparatus (P-CVD) and a low pressure CVD apparatus (LP-CVD) are used. It can also be applied to the case where a film is formed using the above.
[0098]
-Fourth Embodiment-
In the present embodiment, a method for measuring the temperature in the chamber using measurement of the film formation temperature will be described.
[0099]
As described above, since the film formation temperature can be measured using an infrared absorption spectrum of an FSG film or the like, the temperature of the chamber can be measured. If the temperature of the chamber is known, it can be used not only for CVD but also for various processes in the manufacturing process of the semiconductor device.
[0100]
Conventional temperature measurement in a chamber has been performed by a temperature sensor attached to the back surface of a wafer with a thermocouple. However, even if a wafer with a thermocouple is used, the temperature on the back surface of the wafer can be determined, but the temperature on the surface of the wafer, that is, the actual temperature at which the amorphous region is subjected to heat treatment cannot be measured. Also, there is a limit to the temperature measurement range, and it becomes difficult to measure at a certain high temperature.
[0101]
Moreover, in the case of the technique described in the above-mentioned conventional international publication WO99 / 57146, when it becomes 500 degrees C or less, the recovery rate from an amorphous state will become unknown. This is because at a low temperature, recovery from the amorphous state ends at an extremely early stage, and recovery does not proceed even if more time is spent.
[0102]
On the other hand, in the case of the method using the infrared absorption spectrum of the present invention, there is an advantage that measurement can be performed at any temperature within the temperature range where CVD is possible. In particular, it can be said that the effect is large in the range of 500 ° C. or less, which is difficult to measure with the technique described in International Publication WO99 / 57146.
[0103]
FIG. 11 is data showing the temperature distribution in the wafer surface obtained for the FSG film formed using the HDP-CVD apparatus. Since the infrared beam has a diameter of about 5 mm, infrared absorption spectra can be measured at a number of locations in the wafer. In that case, it is necessary that the location where the infrared absorption spectrum is measured for the wafer before forming the film and the location where the infrared absorption spectrum is measured after forming the film are almost the same, but the current infrared The positioning accuracy of the measuring device has been greatly improved, so there were no practical problems.
[0104]
As shown in the figure, the temperature distribution in the wafer surface can be measured by performing multivariate analysis using the infrared absorption spectrum of the present invention. Temperature distribution can be measured. The wafer used for this temperature measurement may be a product wafer flowing in a production line or a management wafer used for process management.
[0105]
-Other embodiments-
In each of the above embodiments, the film to be measured was evaluated by injecting infrared light into the film to be measured and measuring the infrared absorption spectrum by the FT-IR method. The present invention can also be applied when measuring an absorption spectrum for observing a bonding state between atoms constituting a thin film by using infrared spectroscopy, laser Raman spectroscopy, X-ray photoelectron spectroscopy, or the like.
[0106]
【The invention's effect】
According to the present invention, since the film formation temperature and film characteristics can be measured from the in-line monitor of the film formation apparatus, the film formation temperature can be measured for all film formation processes without reducing productivity. Become.
[Brief description of the drawings]
FIGS. 1A and 1B are an infrared absorption spectrum diagram of an FSG film by an FT-IR method and an enlarged view of the vicinity of a peak portion, respectively.
FIG. 2 is a table showing the wavelength and the maximum absorption value showing the maximum absorption at the peak in the infrared absorption spectrum shown in FIGS. 1 (a) and 1 (b).
FIGS. 3A to 3C are diagrams showing a reference infrared absorption spectrum diagram, an infrared absorption spectrum diagram of a film to be measured, and a film formation temperature determination method by a PLS method, respectively.
FIGS. 4A to 4D are an infrared absorption spectrum diagram of an FSG film formed at 380 ° C., 430 ° C., and 480 ° C., respectively, and an infrared absorption spectrum diagram of an FSG film to be measured. .
FIG. 5 is a diagram showing a database construction method composed of infrared absorption spectrum patterns of FSG films.
FIG. 6 is a flowchart showing a procedure for estimating a film formation temperature of a film to be measured (FSG film) by multivariate analysis.
FIG. 7 is a diagram showing a correlation between the film formation temperature of the HDP-CVD apparatus estimated by the method of the second embodiment and the film formation temperature measured by a method using a conventional method.
FIG. 8 is a cross-sectional view showing a structure of a semiconductor device formed in a third embodiment.
FIG. 9 is a flowchart showing a processing procedure before and after forming an FSG film in the manufacturing process of the third embodiment.
FIG. 10 is a diagram showing the dependence of the etching rate of the FSG film on the deposition temperature.
FIG. 11 is data showing a temperature distribution in a wafer surface obtained for an FSG film formed using an HDP-CVD apparatus.
FIGS. 12A and 12B are a diagram illustrating an example of setting contents of a constructed database in a table and a diagram illustrating calculation results, respectively.
FIG. 13 is a table showing the verification results of the temperature in the constructed database and the analysis temperature.
[Explanation of symbols]
11 Silicon substrate
12 Trench isolation region
13 MISFET
14 Silicide layer
20 First interlayer insulating film
24 plug
30 Second interlayer insulating film
31 Lower membrane
32 Upper membrane
33 Al wiring
34 plug
40 Third interlayer insulating film
41 Lower membrane
42 Upper membrane
43 Al wiring
44 plug
50 Fourth interlayer insulating film
51 Lower membrane
52 Upper membrane
53 Al wiring
54 plug
60 Passivation film
63 Al wiring

Claims (15)

(A) measuring an absorption spectrum of the electromagnetic wave by making the electromagnetic wave incident on the substrate on which the film is formed;
(B) calculating a film forming temperature of the film from the shape of the absorption spectrum ,
In the step (b), the film forming temperature is calculated from the change in the peak height of the absorption peak and the shift of the peak position in the absorption spectrum .   (A) measuring an absorption spectrum of the electromagnetic wave by making the electromagnetic wave incident on the substrate on which the film is formed;
  (B) calculating a film forming temperature of the film from the shape of the absorption spectrum,
  The film is a fluorine-added silicon oxide film,
  In step (b), silicon oxide (SiO ₂ The film formation temperature is calculated from the change in the interval between the absorption peak of) and the absorption peak of silicon fluoride (SiF). In the temperature measuring method according to claim 1 or 2 ,
In the step (a), infrared light is incident as the electromagnetic wave,
In the step (b), the film forming temperature is calculated from the shape of the infrared absorption spectrum. The temperature measuring method according to claim 3 , wherein
Prepare in advance a plurality of reference infrared absorption spectra corresponding to the film formation temperature,
In the step (b), the film forming temperature is calculated by comparing the reference infrared absorption spectrum with the infrared absorption spectrum of the film. The temperature measuring method according to claim 4 , wherein
In the step (b), a multivariate analysis is performed based on the shapes of the reference infrared absorption spectrum and the infrared absorption spectrum to calculate the film formation temperature.   Step (a) of measuring the infrared absorption spectrum by making infrared rays incident on the substrate on which the film is formed;
  (B) calculating a film formation temperature of the film from the shape of the infrared absorption spectrum,
  The film is a fluorine-added silicon oxide film,
  Prepare in advance a plurality of reference infrared absorption spectra corresponding to the film formation temperature,
  In the step (b), the difference in peak maximum absorption value between the reference infrared absorption spectrum and the infrared absorption spectrum of the film, the difference in wavelength indicating the maximum absorption value, and silicon oxide (SiO 2) ₂ ) And the difference in spacing between the absorption peak of silicon fluoride (SiF) and the difference in pattern due to the difference between the absorption peaks of silicon fluoride (SiF), the film formation temperature is calculated.   The temperature measuring method according to claim 6, wherein
  In the step (b), the film evaluation method is characterized in that the film formation temperature is calculated by performing multivariate analysis based on the shift of the pattern. In the temperature measuring method according to any one of claims 3 to 7 ,
In the step (a), the infrared absorption spectrum of only the film is obtained by subtracting the infrared absorption spectrum of the substrate measured in advance from the infrared absorption spectrum of the film and the substrate. . In the temperature measuring method according to any one of claims 1 to 8 ,
In the step (a), the substrate is previously placed in a film forming apparatus, and the film is formed on the substrate.
In the step (b), the temperature measuring method is characterized in that a film forming temperature of the film is calculated as a temperature in the film forming apparatus. A method of manufacturing a semiconductor device having a film as a component,
A step (a) of forming the film on a base wafer disposed in a film forming apparatus;
Step (b) of measuring infrared absorption spectrum by making infrared rays incident on the wafer on which the film is formed;
Calculating the film formation temperature of the film from the shape of the infrared absorption spectrum; and
(D) controlling the setting conditions of the film forming apparatus according to the film forming temperature calculated in the step (c) ,
In the step (c), the film formation temperature is calculated from the change in the peak height of the absorption peak and the shift of the peak position in the infrared absorption spectrum .   A method of manufacturing a semiconductor device having a film as a component,
  A step (a) of forming the film on a base wafer disposed in a film forming apparatus;
  Step (b) of measuring infrared absorption spectrum by making infrared rays incident on the wafer on which the film is formed;
  Calculating the film formation temperature of the film from the shape of the infrared absorption spectrum; and
  (D) controlling the setting conditions of the film forming apparatus according to the film forming temperature calculated in the step (c),
  The film is a fluorine-added silicon oxide film,
  In the step (c), silicon oxide (SiO2) in the infrared absorption spectrum is used. ₂ The film formation temperature is calculated from the change in the interval between the absorption peak of) and the absorption peak of silicon fluoride (SiF). In the manufacturing method of the semiconductor device according to claim 10 or 11 ,
Prepare in advance a plurality of reference infrared absorption spectra corresponding to the film formation temperature,
In the step (c), the film formation temperature is calculated by comparing the infrared absorption spectrum for reference with the infrared absorption spectrum of the film measured in the step (b). Device manufacturing method. In the manufacturing method of the semiconductor device according to claim 12 ,
In the step (c), a multivariate analysis is performed based on the shapes of the reference infrared absorption spectrum and the infrared absorption spectrum, and the film formation temperature is calculated.   A method of manufacturing a semiconductor device having a film as a component,
  A step (a) of forming the film on a base wafer disposed in a film forming apparatus;
  Step (b) of measuring infrared absorption spectrum by making infrared rays incident on the wafer on which the film is formed;
  Calculating the film formation temperature of the film from the shape of the infrared absorption spectrum; and
  (D) controlling the setting conditions of the film forming apparatus according to the film forming temperature calculated in the step (c),
  The film is a fluorine-added silicon oxide film,
  Prepare in advance a plurality of reference infrared absorption spectra corresponding to the film formation temperature,
  In the step (c), the difference between the maximum absorption value of the peak portion between the infrared absorption spectrum for reference and the infrared absorption spectrum of the film measured in the step (b), and the difference in wavelength indicating the maximum absorption value. And silicon oxide (SiO ₂ ) And the difference in spacing between the absorption peaks of silicon fluoride (SiF) and the difference in pattern caused by the difference between the patterns, the film formation temperature is calculated.   15. The method of manufacturing a semiconductor device according to claim 14,
  In the step (c), a multivariate analysis is performed based on the shift of the pattern, and the film formation temperature is calculated.

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