JP4927495B2 - Annealing apparatus management method and annealing method - Google Patents

Description

  The present invention relates to an annealing apparatus management method and an annealing method.

  In the semiconductor manufacturing process, annealing may be performed with the surface of the metal film exposed. For example, in a silicidation process in a MOS (Metal Oxide Semiconductor) transistor process, annealing is performed with the metal film exposed to prevent contact metal peeling.

  In such a process, if oxygen is mixed in the chamber of the annealing apparatus, there is a concern that the exposed metal may be oxidized by entraining the mixed oxygen (hereinafter also referred to as “entrained oxidation”). . For this reason, it is required to reliably grasp the oxygen concentration in the annealing atmosphere and to keep the oxygen concentration below a predetermined amount.

  Here, although the technical fields are different, non-patent documents 1 and 2 include techniques for detecting metal oxidation. Non-Patent Document 1 describes that the oxidation of the surface of a titanium-aluminum alloy is detected by XPS (X-ray Photoelectron Spectroscopy). Further, according to Non-Patent Document 2, it is said that oxidation of a metal surface can be detected also by AES (Auger Electron Spectroscopy) and SIMS (Secondary ion mass spectrometry).

  Moreover, although the technical field differs, there exists a thing of patent document 1 as a technique which determines the component density | concentration in a liquid. This document describes that it is confirmed whether the additive concentration in the Cu plating solution when forming the Cu plating layer on the silicon substrate satisfies the standard. In this document, the sheet resistance of the Cu silicide layer obtained by siliciding the Cu plating layer is measured, and the concentration of the additive in the Cu plating solution is determined from the measured value obtained. is doing.

Another technique for analyzing the composition of a silicide layer is disclosed in Patent Document 2. This document describes that the abundance ratio of titanium silicide in the titanium silicide layer is measured by fluorescent X-ray analysis.
JP 2005-294254 A JP 2004-214554 A DE Mencer, Jr. and 2 others, “Surface reactivity of titanium-aluminum alloys: Ti3Al, TiAl and TiAl3”, J. Vac. Sci. Technol, A9 (3), p. 1610 (1991) A. Benninghoven and two others, “Quasisimultaneous SIMS, AES, and XPS investigations of the oxidation of Mo, Ti, and Co in the monolayer range”, J. Vac. Sci. Technol, 15 (2), p. 506 (1978)

  Here, in Non-Patent Documents 1 and 2 described above, oxygen was measured for evaluation of the manufactured samples. For this reason, the manufactured sample was subjected to a physical analysis by being subjected to a predetermined measuring device.

  However, when such physical analysis is used to determine the oxygen concentration in the annealing apparatus, it is necessary to take a sample such as a wafer out of the line after annealing. For this reason, when wafer processing and measurement are included, it takes a lot of time, and during that time, the apparatus cannot be used, and there is a concern that productivity may be reduced. Furthermore, since the sample used for the determination cannot be reproduced, there is room for improvement in terms of manufacturing cost.

  For this reason, in order to suppress metal oxidation and to reduce the time during which the apparatus cannot be used (apparatus downtime) as much as possible, mixing oxygen exceeding the allowable amount in the annealing apparatus by a method different from the physical analysis described above. Is required to be detected.

  The present inventor has intensively studied in order to easily and surely determine whether the oxygen concentration in the annealing apparatus is equal to or lower than the reference concentration. As a result, when the Ti layer was heat-treated at a predetermined temperature, it was found that the resistance of the Ti layer changes depending on the presence or absence of oxygen in the annealing apparatus.

According to the present invention,
Preparing an evaluation substrate provided with a Ti layer on a silicon substrate via an oxide film;
Placing the evaluation substrate in an annealing apparatus;
Heat-treating the evaluation substrate disposed in the annealing apparatus at a predetermined temperature in an inert gas;
After the step of heat treatment, measuring the resistance of the Ti layer;
Comparing the resistance value measured in the step of measuring the resistance of the Ti layer with a reference value acquired in advance to determine whether the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration;
Including
There is provided a method for managing an annealing apparatus, wherein the highest temperature in the annealing apparatus in the step of performing the heat treatment is 650 ° C. or higher and 800 ° C. or lower.

  In the present invention, the resistance after the heat treatment of the evaluation substrate provided with the Ti layer on the silicon substrate is measured, and the obtained resistance value is compared with the reference value to determine the oxygen concentration in the annealing apparatus. It is judged whether it is below the concentration of.

  Here, as will be described later in the section of the best mode for carrying out the invention, when the Ti layer is heat-treated at a predetermined temperature, the resistance of the Ti layer after the heat treatment depends on the presence or absence of oxygen in the annealing apparatus. In a system that fluctuates and oxygen is mixed, resistance increases compared to a system that does not contain oxygen. This is presumably because the Ti layer is oxidized due to the presence of oxygen in the heated atmosphere.

  In the present invention, the measured resistance value is compared with a reference value to determine the degree of variation in resistance value due to oxidation of the Ti layer. This makes it possible to reliably determine whether the oxygen concentration in the annealing apparatus is equal to or lower than the reference concentration.

  According to the study of the present inventor, the resistance measurement can be stably performed by setting the maximum temperature in the annealing apparatus to 650 ° C. or higher and 800 ° C. or lower. By setting the maximum temperature to 650 ° C. or higher, it is possible to reliably detect the variation in the resistance value of the Ti layer due to the mixing of oxygen. Moreover, the variation in resistance value can be suppressed by setting the maximum temperature to 800 ° C. or less.

  In the method of the present invention, the resistance of the Ti layer is measured using an evaluation substrate in which an oxide film is interposed between the silicon substrate and the Ti layer. For this reason, silicidation of Ti by heat treatment is suppressed. Therefore, it is possible to suppress a variation in resistance value due to silicidation of Ti and reliably detect a variation in resistance value caused by oxidation of the Ti layer due to oxygen mixed in the annealing apparatus.

  In addition, according to the present invention, since the resistance measurement of the Ti layer is used for the determination of the oxygen concentration, the measurement in the production line can be performed after the heat treatment in the annealing apparatus. In this case, after the heat treatment, it is not necessary to take the evaluation substrate out of the line and perform measurement using a measuring device or the like provided outside the line. Therefore, it is possible to quickly determine the oxygen concentration in the annealing apparatus within the line and manage the atmosphere state. Therefore, it is possible to suppress a decrease in productivity of the production line.

According to the present invention,
An annealing method using the above-described annealing apparatus management method of the present invention,
Prior to the step of heat treating, further comprising the step of placing a substrate in the annealing apparatus;
In the step of performing the heat treatment, the evaluation substrate and the substrate are heat-treated,
In the step of determining whether or not the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration, the post-process is performed on the heat-treated substrate on condition that the oxygen concentration is determined to be lower than or equal to the predetermined concentration. An annealing method is provided.

  According to the present invention, the substrate and the evaluation substrate are arranged in the annealing apparatus, and the heat treatment is performed by the method described above. Then, on the condition that the oxygen concentration is determined to be equal to or lower than the predetermined concentration, the heat-treated substrate is subjected to a subsequent process. In this way, only the substrate heat-treated in the annealing apparatus having an oxygen concentration equal to or lower than the predetermined concentration is surely provided for the post-process, and the substrate having the oxidized Ti film is not used for the post-process. Can do. Therefore, the manufacturing stability of the semiconductor device including the annealing step can be improved.

  It should be noted that any combination of these components, or a conversion of the expression of the present invention between a method, an apparatus, and the like is also effective as an aspect of the present invention.

  As described above, according to the present invention, it is possible to reliably determine the oxygen concentration in the annealing apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, common constituent elements are denoted by the same reference numerals, and description thereof is omitted as appropriate. In the following embodiments, the case where the annealing apparatus is an atmospheric pressure lamp annealing apparatus will be described as an example, but another annealing apparatus having a chamber may be used.

  FIG. 1 is a flowchart showing a method for managing an annealing apparatus in the present embodiment.

  In FIG. 1, first, an evaluation board is prepared (S11). The evaluation substrate is, for example, a wafer.

FIG. 2 is a cross-sectional view showing the configuration of the evaluation board.
In the evaluation substrate 110 shown in FIG. 2, a thermal oxide film 103 is formed on a silicon substrate 101, and a titanium layer 105 is formed on one surface of the silicon substrate 101 via the thermal oxide film 103. In FIG. 2, the configuration in which the thermal oxide film 103 is formed on the entire surface of the silicon substrate 101 is illustrated, but the thermal oxide film 103 is at least a lower layer (substrate side) of the titanium layer 105 in the formation region of the titanium layer 105. As long as it is provided.

  The film thickness of the thermal oxide film 103 is not limited as long as silicidation is suppressed, but is, for example, 100 nm or more. The upper limit of the thickness of the thermal oxide film 103 is not particularly limited, but is set to 300 nm or less, for example. Note that the wafer may be prepared with the thermal oxide film 103 formed.

  Titanium layer 105 is formed in contact with the upper portion of the thermal oxide film, for example, by sputtering. The film thickness of the titanium layer 105 should just be a grade which can measure the layer resistance (sheet resistance) mentioned later stably, for example, is 20 nm or more and 40 nm or less.

  Returning to FIG. 1, the wafer of the evaluation substrate 110 is placed in the annealing apparatus (S12). At this time, after the wafer is transferred, the chamber door of the annealing apparatus is opened to accept the evaluation substrate 110 and the product wafer.

  In this step 12, since the chamber is opened and closed, the atmosphere is involved in the chamber. For this reason, after the chamber door is closed, an inert gas may be introduced into the chamber as appropriate, and purge may be performed to expel oxygen trapped in the chamber. The purge time is, for example, about 10 to 60 seconds, more specifically about 25 seconds.

  Next, the annealing apparatus is set to a predetermined temperature, and the evaluation substrate 110 and the product wafer are simultaneously heated at a predetermined temperature in an inert gas (S13). For example, nitrogen, argon or helium or a mixture thereof is used as the inert gas. Step 13 is performed, for example, under normal pressure. The maximum temperature reached in the annealing apparatus in this step is 650 ° C. or higher. By doing so, a change in the layer resistance of the titanium layer 105 can be reliably detected with high sensitivity. Further, from the viewpoint of further improving the detection sensitivity of entrainment oxidation, the highest temperature reached in the annealing apparatus may be set to 720 ° C. or higher, for example. Further, the highest temperature reached in the annealing apparatus in step 13 is set to 800 ° C. or less, for example. By doing so, variation in the layer resistance of the titanium layer 105 can be more effectively suppressed, so that the oxygen concentration in the annealing apparatus can be more reliably managed.

  After the heat treatment in step 13, the evaluation substrate 110 is taken out from the annealing apparatus, and the resistance of the titanium layer 105 in the evaluation substrate 110 is measured using the apparatus in the line (S15). The resistance measured here is specifically the layer resistance of the titanium layer 105. Then, the measured resistance value is compared with a reference value acquired in advance to determine whether it is within the standard. Thus, it is determined whether or not the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration (S17).

  If the measured resistance value is within the specified range (Yes in S17), the annealing process is terminated, and the annealed product wafer is subjected to the subsequent processes.

  On the other hand, when the measured resistance value is out of specification (No in S17), oxygen may be mixed in the annealing apparatus at a concentration higher than the reference value. For this reason, an annealing apparatus is investigated (S19). In addition, maintenance of the apparatus is performed as necessary. Specifically, step 19 may be a re-pilot in a production line of semiconductor devices. After the investigation and maintenance of the annealing apparatus is completed, the process returns to step 11 and the subsequent processes are performed again. At this time, a process after the process of forming the titanium layer 105 on the wafer that has been prepared may be performed, or may be performed from the process of forming the thermal oxide film 103.

  As described above, in the present embodiment, the heat-treated product wafer is subjected to a post process on condition that the oxygen concentration is determined to be equal to or lower than the predetermined concentration in Step 17. As described above, the product wafer is placed in the annealing apparatus together with the evaluation substrate 110 in step 12.

  With the above procedure, it is possible to easily and reliably determine whether the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration using the layer resistance of the titanium layer 105. Therefore, it can be surely checked whether or not the oxygen entrained in the chamber in Step 12 remains more than the allowable concentration. Also, when purging the chamber after step 12, whether or not oxygen has fallen to an allowable concentration or less can be reliably checked.

  This effect is remarkably exhibited in the case of an atmospheric pressure annealing apparatus. For example, when annealing using an atmospheric pressure process apparatus is performed with the titanium film 105 exposed as in the silicide process, it is reliably determined whether the oxygen concentration in the annealing apparatus is within an appropriate range. be able to. Therefore, it is possible to reliably prevent the product wafer including the titanium film 105 oxidized by oxygen entrainment from flowing out into the subsequent process.

  Further, in this method, annealing (S13) and resistance measurement (S15) can be performed in the same line in the annealing apparatus, and the oxygen concentration can be managed by the apparatus in the production line. Therefore, after annealing, the evaluation substrate 110 can be taken out of the line and subjected to measurement with another apparatus, and the oxygen concentration can be evaluated efficiently and quickly, and the down time of the annealing apparatus can be reduced. It is. For this reason, a decrease in productivity can be suppressed.

  By managing the annealing apparatus according to the above procedure, the entanglement oxidation of the titanium layer 105 can be reliably monitored, so that abnormal products of the product wafer can be reliably prevented from flowing out to the subsequent process.

  In addition, after the measurement, the evaluation substrate 110 whose layer resistance is measured can be regenerated by removing the titanium layer 105 and the thermal oxide film 103 by a predetermined method so that the surface of the silicon substrate 101 of the evaluation substrate 110 is exposed again. . For this reason, the cost increase of the whole manufacturing process can be suppressed.

  Further, when Ti is directly sputtered on the silicon substrate 101, annealing (S13) causes a silicidation reaction due to the effect of heat, and the layer resistance is lowered, while the surface is oxidized by entrained oxygen, and the layer resistance Can be expected to rise. For this reason, when the evaluation substrate 110 to be silicided is used, there is a concern that the oxygen concentration in the chamber cannot be accurately detected.

  Therefore, in this embodiment, the thermal oxide film 103 is formed on the silicon substrate 101 as a base. Thereby, the formation of silicide due to the reaction between the silicon in the silicon substrate 101 and the titanium in the titanium layer 105 at the time of annealing (S13) is suppressed. For this reason, the fluctuation | variation of the layer resistance of the titanium layer 105 resulting from silicidation can be suppressed. Therefore, the change in the layer resistance due to the oxidation of the titanium layer 105 can be reliably detected.

  In the present embodiment, the management device of the annealing device may be configured to be able to measure the layer resistance of the titanium layer 105. For example, it can be configured as follows.

  FIG. 3 is a diagram illustrating a configuration of the management apparatus according to the present embodiment. The management apparatus 100 illustrated in FIG. 3 includes a substrate holding unit 121, a resistance measurement unit 111, a display unit 113, and a control unit 123.

The substrate holding unit 121 holds the evaluation substrate 110 at a predetermined position.
The resistance measuring unit 111 measures the layer resistance of the evaluation substrate 110 disposed on the substrate holding unit 121. The layer resistance can be measured by any method as long as it can be performed in the same line as the annealing apparatus, for example, a four-end needle method. At this time, the resistance measuring unit 111 may include a probe for measuring the layer resistance by contacting the surface of the titanium layer 105.

The display unit 113 displays the value of the layer resistance of the titanium layer 105 measured by the resistance measurement unit 111, for example.
In addition, the control unit 123 controls operations of the substrate holding unit 121, the resistance measurement unit 111, and the display unit 113.

  In step 17 described above, the operator of the management apparatus 100 compares the measured value displayed on the display unit 113 with a preset threshold value of the resistance value. (Yes in S17) may be determined.

  Further, the management device 100 illustrated in FIG. 3 may include a determination unit that determines whether or not the measured value of the layer resistance of the titanium layer 105 is within a specified range. FIG. 4 is a diagram showing such a configuration.

In FIG. 4, management device 100 further includes a determination unit 117, a notification unit 119, and a data storage unit 115.
The data storage unit 115 stores layer resistance threshold data of the titanium layer 105.

  The determination unit 117 acquires the measurement value in the resistance measurement unit 111 and the threshold value stored in the data storage unit 115, and compares these values. When the measured value is less than or equal to the threshold value, it is determined that the value is within the standard (Yes in S17), and when the measured value is greater than the threshold value, it is determined that the value is out of standard (No in S17).

  Further, the notification unit 119 acquires information on the determination result in the determination unit 117, and notifies the operator when it is determined that it is out of specification (No in S17).

  In this way, the procedure from the measurement of the layer resistance (S15) to the determination (S17) can be performed more efficiently.

  When managing the annealing apparatus, a step of measuring a layer resistance of the evaluation substrate 110 and obtaining a reference value is further provided after the installation (S12) of the evaluation substrate 110 and before the annealing (S13). The layer resistance value before annealing may be stored in the data storage unit 115 as a reference value. In step 17, the determination unit 117 may determine whether the measured layer resistance value before annealing and the layer resistance value after annealing are within the standard. Further, a standard value may be acquired in advance for the layer resistance before annealing, and it may be determined whether the measured value is within the standard.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  In this example, using the evaluation substrate 110 shown in FIG. 2, the layer resistance measurement, the annealing treatment, and the layer resistance measurement of the titanium layer 105 were continuously performed, and the layer resistance value after annealing was evaluated. The management procedure of the annealing apparatus in the present embodiment is shown in FIG.

  As shown in FIG. 5, first, a silicon substrate 101 (Bare-Si) was prepared (S21), and a thermal oxide film was formed to a thickness of 200 nm (S23). Thereafter, 30 nm of titanium was sputtered on the thermal oxide film 103 (S25). This evaluation substrate 110 was placed in an annealing apparatus. After performing a nitrogen purge for 30 seconds, the layer resistance of the titanium layer 105 immediately after sputtering was measured (S27).

  FIG. 6 is a diagram showing the measurement result of the sheet resistance of the titanium layer 105. The seven plots on the left side of FIG. 6 show the sheet resistance immediately after sputtering. These seven plots (day # 1 to 7) were measured on different days, respectively, and it can be seen that all the measured values are stable in the range of 23 to 30Ω / □. Further, the measured value of the sheet resistance hardly changed even after being annealed and left in the atmosphere for 4 days.

  Thus, since the layer resistance before annealing measured in step 27 was a value within the standard acquired in advance (Yes in S29), the process proceeds to the following annealing step. If the layer resistance before annealing is out of specification (No in S29), the process returns to step 21 or step 25 and the subsequent procedure is repeated.

Subsequently, the evaluation substrate 110 was annealed at 720 ° C. for 30 seconds in an N ₂ 100% atmosphere (S31). Then, the layer resistance of the annealed titanium layer 105 was measured (S15). The measurement results are shown in FIG. The seven plots on the right side of FIG. 6 show the sheet resistance after annealing. These seven plots (day # 1 to 7) were measured on different days, respectively, and it can be seen that all the measured values are stable in the range of 31 to 37 Ω / □.

  Thus, since the layer resistance after annealing measured in step 15 was a value within the standard acquired in advance (Yes in S17), it can be used for subsequent product operations (S33). If the layer resistance after annealing is out of specification (No in S17), the process proceeds to step 19 to investigate the device. Thereafter, the process may return to step 21 or step 25 to repeat the subsequent procedures.

  As a result of carrying out the entanglement oxidation monitoring from the above procedure, as described above with reference to FIG. 6, the resistance value is stable immediately after sputtering and after annealing, and the method of this embodiment is practical as an apparatus management method. It was shown that there is.

  Here, when the entanglement oxidation occurs due to some problem, the layer resistance value greatly exceeds the reference value after annealing.

  Therefore, in this example, the annealing atmosphere in step 31 was changed from 100% nitrogen to a flow of oxygen for a short time. Specifically, after supplying 100% nitrogen for 28 seconds, oxygen at the minimum flow rate was supplied together with nitrogen for 2 seconds. Then, annealing was performed at temperatures of 520 ° C., 620 ° C., and 720 ° C., the layer resistance of the annealed titanium layer 105 was measured, and compared with the value of the layer resistance in the case of 100% nitrogen.

  FIG. 7 is a graph showing the dependency of the layer resistance on the heat treatment temperature. As shown in FIG. 7, the layer resistance value is uniform in the case where oxygen is flowed for a short time (“Δ” in the figure) compared to the case where annealing is performed in an atmosphere containing only nitrogen (“●” in the figure). It is rising. This is presumably because a small amount of flowing oxygen oxidizes the titanium surface, which is detected as an increase in the layer resistance value.

In particular, a material subjected to annealing treatment at 720 ° C. by mixing a trace amount of oxygen shows a 7-fold increase in layer resistance as compared with a material in which oxygen is not mixed (N ₂ 100%). Thus, the presence or absence of entanglement oxidation can be detected with high sensitivity by monitoring the layer resistance value of the annealed titanium.

  In addition, as shown in FIG. 7, at least when the annealing temperature is 650 ° C. or higher and 800 ° C. or lower, it is possible to stably detect the change in resistance value of the titanium layer 105 after annealing due to the mixing of oxygen in the chamber.

  As described above, according to the present example, even when oxygen trapped in the chamber of the annealing apparatus cannot be completely removed by purge, the sheet resistance of the titanium layer 105 before and after annealing is measured by the above-described procedure. By doing this, it was possible to reliably detect this with a device in the line.

It is a flowchart which shows the management method of the annealing apparatus in embodiment. It is sectional drawing which shows the structure of the evaluation board | substrate in embodiment. It is a figure which shows the structure of the management apparatus in embodiment. It is a figure which shows the structure of the management apparatus in embodiment. It is a flowchart which shows the management method of the annealing apparatus in an Example. It is a figure which shows the measurement result of the layer resistance of the evaluation board | substrate in an Example. It is a figure which shows the relationship between the heat processing temperature of an evaluation board | substrate in an Example, and a layer resistance value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Management apparatus 101 Silicon substrate 103 Thermal oxide film 105 Titanium layer 110 Evaluation board 111 Resistance measurement part 113 Display part 115 Data storage part 117 Judgment part 119 Notification part 121 Substrate holding part 123 Control part

Claims (5)

Preparing an evaluation substrate provided with a Ti layer on a silicon substrate via an oxide film;
Placing the evaluation substrate in an annealing apparatus;
Heat-treating the evaluation substrate disposed in the annealing apparatus at a predetermined temperature in an inert gas;
After the step of heat treatment, measuring the resistance of the Ti layer;
Comparing the resistance value measured in the step of measuring the resistance of the Ti layer with a reference value acquired in advance to determine whether the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration;
Including
The annealing apparatus management method, wherein the highest temperature in the annealing apparatus in the step of performing the heat treatment is 650 ° C. or higher and 800 ° C. or lower. In the management method of the annealing apparatus according to claim 1,
A method for managing an annealing apparatus, wherein the heat treatment is performed under normal pressure. In the management method of the annealing apparatus according to claim 1 or 2,
An annealing apparatus management method, wherein the oxide film is a thermal oxide film of the silicon substrate. In the management method of the annealing apparatus in any one of Claims 1 thru | or 3,
The step of preparing the evaluation board includes
Forming the Ti layer in contact with the upper portion of the oxide film by sputtering,
An annealing apparatus management method, further comprising the step of measuring the resistance of the Ti layer and obtaining the reference value after the step of forming the Ti layer and before the step of heat-treating. An annealing method using the annealing apparatus management method according to claim 1,
Prior to the step of heat treating, further comprising the step of placing a substrate in the annealing apparatus;
In the step of performing the heat treatment, the evaluation substrate and the substrate are heat-treated,
In the step of determining whether or not the oxygen concentration in the annealing apparatus is equal to or lower than a predetermined concentration, the post-process is performed on the heat-treated substrate on condition that the oxygen concentration is determined to be lower than or equal to the predetermined concentration. An annealing method to be used.

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