JP4208995B2 - Substrate temperature measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate temperature measuring method for measuring the temperature of a substrate such as a semiconductor wafer.
[0002]
[Prior art]
In the manufacturing process of a semiconductor device, there are various heat treatments such as annealing after implanting a predetermined impurity, and there are processes involving heat such as various film formation processes and etching processes. In these processes, since the temperature of the semiconductor wafer at that time has a great influence on the characteristics, temperature control of the semiconductor wafer is extremely important.
[0003]
However, since it is difficult to directly measure the temperature of the semiconductor wafer, conventionally, the temperature of the susceptor, which is a heated portion of the semiconductor wafer, and the ambient temperature in the chamber are monitored and indirectly based on the temperature. Since the wafer temperature is obtained and the actual wafer temperature itself is not directly grasped, the temperature during the process of the semiconductor wafer cannot be obtained with high accuracy. Although there is a method of directly measuring the specific resistance of the semiconductor wafer to grasp the uniformity of the in-plane temperature of the semiconductor wafer, it is difficult to obtain the absolute value of the temperature by this method.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for measuring a substrate temperature, in which the temperature can be grasped directly and accurately from the substrate itself.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a process for measuring an impurity distribution in a depth direction of a substrate when a predetermined heat treatment is performed on a substrate in which impurities are present, and a heat treatment condition including a heat treatment temperature and a holding time. Select the distribution that matches the impurity distribution obtained by the measurement from the process of calculating the impurity distribution in the depth direction of the substrate based on theory and the distribution of impurities determined by theoretical calculation for multiple cases with different A method for measuring a substrate temperature is provided, which includes grasping a thermal history that is a relationship between a substrate temperature and a time during heat treatment based on a calculation of a selected theoretical impurity distribution .
[0006]
The present invention also includes a step of measuring the impurity distribution in the depth direction of the substrate at a plurality of locations in the substrate surface when a predetermined heat treatment is performed on the substrate in which impurities are present, and a heat treatment including a heat treatment temperature and a holding time. For a plurality of cases with different conditions, a step of calculating the impurity distribution in the depth direction of the substrate based on the theory, and a distribution that matches the impurity distribution obtained by the above measurement from the plurality of distributions of the impurities obtained by the theoretical calculation. Substrate temperature characterized by grasping a thermal history that is a relation between substrate temperature and time at a plurality of locations in the substrate surface during the heat treatment based on calculation of the selected theoretical impurity distribution Provides a measurement method.
[0007]
Furthermore, the present invention measures the amount of impurities at a predetermined depth of a substrate when a predetermined heat treatment is performed on the substrate in which impurities are present when the temperature rising rate other than the heat treatment temperature and the holding time are constant , The measurement result is compared with the relationship between the substrate temperature within the holding time obtained by calculation based on theory and the amount of impurities at a predetermined depth , and the substrate temperature within the holding time during heat treatment is grasped. A method for measuring the substrate temperature is provided.
[0008]
Furthermore, the present invention relates to the amount of impurities at a predetermined depth of a substrate when a predetermined heat treatment is performed on a substrate in which impurities are present when a heating rate other than the heat treatment temperature and a holding time are constant . The measurement results are compared with the relationship between the substrate temperature within the holding time obtained by calculation based on theory and the amount of impurities at a predetermined depth, and within the holding time during the heat treatment . A method for measuring a substrate temperature characterized by grasping a temperature distribution in the substrate surface of the substrate is provided.
[0009]
In these inventions, impurities can be present in the substrate by doping the surface portion of the substrate before the heat treatment.
[0010]
In the present invention, the substrate temperature is grasped by utilizing the fact that when the substrate is heat-treated in the presence of impurities in the substrate, the diffusion of impurities according to the heat treatment temperature occurs. That is, for example, if the impurity distribution in the depth direction of the substrate at each temperature is grasped from a calculation result such as a theoretical simulation result, the impurity distribution in the substrate depth direction obtained by actual heat treatment can be obtained as described above. By comparing with the calculation result, the temperature of the substrate can be grasped. Thus, since the substrate temperature is grasped based on the state of the substrate itself, the temperature of the substrate can be measured with extremely high accuracy. If the actual impurity distribution is compared with the calculation results corresponding to various thermal histories, not only the temperature but also the thermal history can be grasped. If the heating rate and holding time are constant, instead of measuring the impurity distribution, measure the amount of impurities at a predetermined depth of the substrate and compare it with the relationship between the temperature based on the calculation results and the amount of impurities at the predetermined depth. Thus, the substrate temperature can be grasped more easily. Further, by measuring the impurity distribution in the depth direction of the substrate and the amount of impurities at a predetermined depth at a plurality of positions in the substrate surface, the temperature distribution in the substrate surface can be grasped with high accuracy.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. Here, a case where a semiconductor wafer is used as the substrate will be described.
FIG. 1 is a process diagram illustrating an embodiment of the method of the present invention. When measuring the semiconductor wafer temperature according to the present invention, as shown in FIG. 1, first, a predetermined heat treatment is performed on the semiconductor wafer in which impurities are present (step 1). Next, the impurity distribution in the depth direction of the semiconductor wafer is measured (step 2). Further, curve fitting is performed using an impurity distribution curve under each condition obtained in advance by simulation (step 3). That is, a simulation curve that matches the impurity distribution curve obtained in step 2 is selected. Then, the temperature of the semiconductor wafer during heat treatment is specified from the selected simulation curve (step 4).
[0012]
As the impurity used in the step 1, a trivalent or pentavalent element, typically B or As, which is usually used as an impurity element of a semiconductor wafer can be used. These impurity elements can be present in the surface portion by doping using ordinary ion implantation.
[0013]
The heat treatment to which the present invention is applied is not particularly limited, but an annealing treatment in a high temperature region of about 600 to 1200 ° C. after doping with impurities is suitable. In the heat treatment in such a temperature range, the impurity distribution easily changes due to the temperature change, and the wafer temperature can be grasped with high accuracy.
[0014]
For such annealing treatment, rapid annealing (RTA; Rapid Thermal Annealing) with good controllability is frequently used, and therefore an RTP (Rapid Thermal Processor) as shown in FIG. 2 is used. In FIG. 2, reference numeral 1 denotes a process chamber. The process chamber 1 can be separated into an upper chamber 1a and a lower chamber 1b. A quartz window 2 is provided between the upper chamber 1a and the lower chamber 1b. A heating unit 3 is detachably provided above the chamber 1. The heat generating unit 3 includes a water cooling jacket 4 and a plurality of tungsten lamps 5 arranged on the lower surface thereof. A water-cooled platen 6 that holds the semiconductor wafer W is detachably provided below the process chamber 1. Wafer support pins 7 are provided on the upper surface of the platen 6, and the semiconductor wafer W is supported by the support pins 7. A seal member S is provided between the jacket 4 of the heat generating part 3 and the upper chamber 1a, between the upper chamber 1a and the quartz window 2, between the quartz window 2 and the lower chamber 1b, and between the lower chamber 1b and the platen 6. The process chamber 1 is in an airtight state. The chamber 1 can be depressurized by an exhaust device (not shown).
[0015]
In such a heat treatment apparatus, the semiconductor wafer W is set in the process chamber 1, an airtight space is formed therein, the air is exhausted by an exhaust device, and the inside is evacuated. Next, when the tungsten lamp 5 of the heat generating unit 3 is turned on, the heat generated by the tungsten lamp 5 passes through the quartz window 2 and reaches the semiconductor wafer W, and the semiconductor wafer W is rapidly heated. After the heating is completed, the inside of the process chamber 1 is returned to the atmospheric pressure, the heat generating part 3 is retracted, and the platen 6 is lowered to rapidly cool the semiconductor wafer W. In this way, the desired rapid heating process is realized.
[0016]
Impurities doped in the surface portion of the semiconductor wafer diffuse into the interior by such heat treatment, and form a predetermined distribution in the depth direction. In step 2, such a distribution of impurities in the depth direction is obtained by analysis. Although the analysis method in this case is not particularly limited, it can be suitably obtained by secondary ion mass spectrometry (SIMS).
[0017]
In step 3, a simulation curve of the impurity distribution in the depth direction is input to a computer in advance for each condition by theoretical calculation, and curve fitting using these simulation curves is performed on the impurity distribution curve actually obtained by SIMS. I do. Creation of the simulation curve and curve fitting at this time can be performed using appropriate software, for example, using a T-CAD process simulator.
[0018]
FIG. 3 is a diagram comparing a simulation curve of impurity distribution of a silicon wafer based on a theoretical calculation result and a curve of impurity distribution actually obtained by SIMS, and (a) shows an RTA for 1 minute at 1000 ° C. (B): RTA at 1000 ° C. for 1 minute followed by deactivation annealing at 750 ° C. for 160 minutes, (c): Annealing at 750 ° C. for 10 minutes , (D) shows the result of annealing at 750 ° C. for 160 minutes (Source: Chang et al. IEDM97).
[0019]
As shown in FIG. 3, the simulation curve of the impurity distribution drawn based on the theoretical calculation result almost coincides with the actual analysis value, and the temperature of the semiconductor wafer is grasped based on such a simulation result. The effectiveness of doing is understood. As shown in this figure, the impurity distribution varies depending on the processing temperature, so if simulation data at various heat treatment temperatures is input, the analysis results after heat treatment can be compared with these simulation data. Thus, the temperature of the semiconductor wafer during the heat treatment can be specified.
[0020]
In this way, curve fitting is performed based on high-precision simulation data, and the temperature is grasped based on the state of the semiconductor wafer itself, which is the impurity distribution of the semiconductor wafer. Compared to conventional indirect temperature measurement. Thus, temperature measurement with extremely high accuracy can be performed.
[0021]
Further, as is apparent from FIG. 3, the impurity distribution differs depending not only on the heat treatment temperature but also on other heat treatment conditions such as the holding time. Therefore, by inputting the simulation results of the impurity distribution when various heat histories are added, it is possible to grasp not only the heat treatment temperature when performing heat treatment on the semiconductor wafer but also the heat history. is there.
[0022]
On the contrary, when the heating rate other than the heat treatment temperature, the holding time, etc. are constant, instead of measuring the impurity distribution as described above, the impurity amount at a predetermined depth of the wafer is measured, and the heat treatment temperature and the predetermined depth are measured. If the comparison is made with the simulation data of the relationship with the impurity amount, the substrate temperature can be grasped more easily.
[0023]
The temperature of the semiconductor wafer can be grasped by the procedure as described above. However, when the temperature distribution in the semiconductor wafer surface is grasped, the impurity distribution in the depth direction and the measurement of the impurity amount at the predetermined depth are measured. It is only necessary to measure at a plurality of positions and compare it with simulation data. Thereby, the temperature distribution in the wafer surface can be grasped with high accuracy.
[0024]
The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the temperature measurement of the semiconductor wafer has been described in the above embodiment, but the present invention is not limited to this, and any substrate can be used as long as impurity diffusion is assumed. The target heat treatment is not limited to the above-described annealing, and can be applied to a process involving other various heats.
[0025]
【The invention's effect】
As described above, according to the present invention, the impurity distribution in the depth direction of the substrate when a predetermined heat treatment is performed on the substrate in which the impurity is present is measured, and the measurement result is expressed as a temperature based on the calculation result. Compared with the relationship with the impurity distribution, the substrate temperature at the time of heat treatment is grasped, so the substrate temperature can be grasped directly based on the actual substrate state, and the substrate temperature is measured with extremely high accuracy. be able to. In addition, when the heating rate and holding time are constant, instead of measuring the impurity distribution, the amount of impurities at a predetermined depth of the substrate is measured, and the relationship between the temperature based on the calculation result and the amount of impurities at the predetermined depth is In comparison, the substrate temperature can be grasped more easily. Furthermore, by measuring the impurity distribution in the depth direction of the substrate and the amount of impurities at a predetermined depth at multiple positions in the substrate surface and comparing these with the calculation results, the temperature distribution in the substrate surface can be accurately measured. Can be grasped.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an embodiment of the method of the present invention.
FIG. 2 is a cross-sectional view showing an example of an apparatus for performing a heat treatment to which the present invention is applied.
FIG. 3 is a diagram showing a comparison between a simulation curve of impurity distribution of a silicon wafer based on theoretical calculation results and a curve of impurity distribution actually obtained by secondary ion mass spectrometry.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Chamber 2; Quartz window 3; Heat generating part 4; Water cooling jacket 5; Tungsten lamp 6; Platen 7; Wafer support pin S;

Claims (5)

Measuring the impurity distribution in the depth direction of the substrate when a predetermined heat treatment is performed on the substrate in which the impurities are present ; and
For a plurality of cases where the heat treatment conditions including the heat treatment temperature and the holding time are different, the step of calculating the impurity distribution in the depth direction of the substrate based on the theory,
Selecting a distribution that matches the impurity distribution obtained by the measurement from a plurality of distributions of impurities determined by theoretical calculation;
A substrate temperature measurement method characterized by grasping a thermal history which is a relation between a substrate temperature and a time during heat treatment based on calculation of a selected theoretical impurity distribution . A step of measuring the impurity distribution in the depth direction of the substrate when a predetermined heat treatment is performed on the substrate in which the impurities are present at a plurality of locations in the substrate surface ;
For a plurality of cases where the heat treatment conditions including the heat treatment temperature and the holding time are different, the step of calculating the impurity distribution in the depth direction of the substrate based on the theory,
Selecting a distribution that matches the impurity distribution obtained by the measurement from a plurality of distributions of impurities determined by theoretical calculation;
A method for measuring a substrate temperature, characterized in that a thermal history that is a relationship between a substrate temperature and time at a plurality of locations in a substrate surface during heat treatment is grasped based on a calculation of a selected theoretical impurity distribution . When the heating rate and holding time other than the heat treatment temperature are constant,
The amount of impurities at a predetermined depth of the substrate when a predetermined heat treatment is performed on the substrate in which impurities are present is measured, and the measurement result is obtained by calculating the substrate temperature and the predetermined depth within the holding time obtained by calculation based on theory. A substrate temperature measurement method characterized in that the substrate temperature within the holding time during heat treatment is ascertained in comparison with the relationship with the amount of impurities. When the heating rate and holding time other than the heat treatment temperature are constant,
The amount of impurities at a predetermined depth of the substrate when a predetermined heat treatment is performed on the substrate in which impurities are present is measured at a plurality of locations in the substrate surface, and the measurement results are obtained by calculation based on theory. A method for measuring a substrate temperature, characterized in that the temperature distribution in the substrate surface within the holding time during the heat treatment is grasped by comparing the relationship between the substrate temperature within the time and the amount of impurities at a predetermined depth.   5. The substrate temperature measuring method according to claim 1, wherein the impurity is doped in a surface portion of the substrate before the heat treatment.

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