JP3757828B2 - Evaluation method of semiconductor heat treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for evaluating a semiconductor heat treatment apparatus that does not have a gas supply line for forming an oxide film on a semiconductor wafer.
[0002]
[Prior art]
A CV evaluation method is known as a method for evaluating the quality of a thermal oxide film processed in a semiconductor manufacturing apparatus. In this CV evaluation, after pattern formation of the MIS structure (Metal-Insulator-Semiconductor), by applying a voltage between the electrode and the semiconductor wafer, the amount of charge in the film, the interface state, It is a technique for measuring mobile ion uptake, and is mainly used for contamination assessment. By such a CV evaluation technique, a contamination evaluation method for a thermal oxidation treatment apparatus has already been established. On the other hand, no contamination evaluation method has been established for semiconductor heat treatment apparatuses that do not have a gas supply line for forming an oxide film on a semiconductor wafer, such as a low pressure CVD apparatus or a diffusion heat treatment furnace.
[0003]
That is, at the time of CV evaluation of the MIS structure, it is necessary to form an electrode on the oxide film. However, when an electrode is formed on the oxide film and then the semiconductor wafer is put into the semiconductor heat treatment apparatus to be evaluated, metal contamination is caused by the electrode portion, making it impossible to evaluate the contamination of the semiconductor heat treatment apparatus. Referring to FIG. 5, as shown in FIG. 5A, when electrode formation and CV measurement are performed after the initial thermal oxidation treatment, the heat treatment apparatus (equipment to be evaluated) is different from the thermal oxidation treatment. Cannot be re-introduced.
[0004]
It is also conceivable that a semiconductor wafer with an oxide film before electrode formation is put into a semiconductor heat treatment apparatus to be evaluated for heat treatment, and then an electrode is formed on the oxide film and CV evaluation is performed. If it demonstrates using FIG. 5, as shown in (b), after initial thermal oxidation treatment, it will be thrown into evaluation object equipment, and non-oxidation heat processing will be implemented in the equipment. And after paying out a semiconductor wafer, the electrode pattern for CV measurement is formed, and CV measurement is carried out.
[0005]
However, in this case, even if it is evaluated that contamination is generated from the CV measurement result, it cannot be determined whether it is due to contamination in the facility to be evaluated or whether it has existed as the initial characteristics of the semiconductor wafer from the beginning. . In addition, it is conceivable that another factor causes contamination, such as additional contamination in the electrode forming process. From the above, there arises a problem that highly accurate CV evaluation cannot be performed.
[0006]
[Problems to be solved by the invention]
The present invention has been made paying attention to the above problems, and the object thereof is to have a gas supply line for forming an oxide film on a semiconductor wafer using a non-contact type CV measuring device. It is to carry out highly accurate contamination assessment of semiconductor heat treatment equipment.
[0007]
[Means for Solving the Problems]
The non-contact type CV measuring instrument measures CV characteristics, which are electrical characteristics of a semiconductor wafer, in a non-contact manner. When the CV measuring instrument is used, it is formed on an oxide film of a semiconductor wafer. The electrode to be used becomes unnecessary. Therefore, even for a semiconductor wafer with an oxide film that has been subjected to CV measurement, heat treatment can be performed thereafter. In the present invention, this non-contact type CV measuring device is used to evaluate contamination of a semiconductor heat treatment apparatus that does not have a gas supply line for forming an oxide film on a semiconductor wafer.
[0008]
In the evaluation method, a semiconductor wafer with an oxide film having an oxide film characteristic of 1E11 [ions / cm @ 2] or less in terms of the amount of charge in the film is prepared, and the semiconductor wafer is heat-treated in a semiconductor heat treatment apparatus to be evaluated. Is done. Thereafter, the characteristics of the oxide film of the semiconductor wafer after the heat treatment are measured by a non-contact type CV measuring device, and contamination of the semiconductor heat treatment apparatus is evaluated from the result of the measurement. [Ions / cm @ 2] is a unit indicating the number of ions in one centimeter square.
[0009]
In this case, since the initial characteristics of the oxide film are limited in advance, it is possible to evaluate the contamination of the semiconductor heat treatment apparatus to be evaluated based on the fluctuation amount of the characteristics of the oxide film. That is, the in-film charge amount measured as the CV characteristic of the oxide film is a charge amount including all of the movable charge Qm, the oxide film trap charge Qot, the fixed oxide film charge Qf, and the interface state Qit shown in FIG. . In this case, the movable charge Qm and the oxide trap charge Qot are caused by contamination, whereas the fixed oxide film charge Qf and the interface state Qit are not caused by contamination. Therefore, if the fixed oxide film charge Qf and the interface state Qit exist excessively before the heat treatment in the evaluation target apparatus, the contamination evaluation cannot be performed correctly. In the present invention, the above-described fixed oxide film charge Qf and interface state Qit are restricted to a very small amount by limiting the initial amount of charge in the film, and as a result, the accuracy of contamination evaluation is improved.
[0010]
In particular, a semiconductor wafer with an oxide film serving as an evaluation wafer has an in-film charge amount before heat treatment limited to 1E11 [ions / cm <2>] or less, so that it is possible to perform an appropriate evaluation excluding disturbance factors. That is, FIG. 4 shows experimental data obtained by the applicant of the present application regarding the relationship between the charge amount in the film and the oxide film variation. As can be seen from FIG. 4, when the charge amount in the film is larger than 1E11 [ions / cm 2], the variation in the oxide film is large and the reliability of the contamination evaluation is low. On the other hand, if the charge amount in the film is 1E11 [ions / cm 2] or less, the variation in the oxide film becomes minute and the reliability of the contamination evaluation is improved.
[0011]
Note that the smaller the initial value of the in-film charge amount, the better the amount of charge fluctuation can be monitored, and the more desirable initial value of the charge amount is 8E10 [ions / cm 2] or less.
[0012]
Further, as described in claim 2, it is preferable to perform the contamination evaluation from the difference between the initial characteristic in which the in-film charge amount of the oxide film is 1E11 [ions / cm 2] or less and the in-film charge amount measured after the heat treatment. . In this case, the contamination status can be correctly determined even if the initial value of the in-film charge amount varies.
[0013]
As an initial condition of the semiconductor wafer with an oxide film prepared in advance, as described in claim 3, the oxide film thickness is preferably 2.0 nm or more. However, more desirably, the oxide film thickness is 3.0 nm or more. Furthermore, as described in claim 4, it is preferable that the material is thermally oxidized at a temperature of 950 ° C. or higher.
[0014]
In the fifth aspect of the present invention, after the semiconductor wafer is thermally oxidized by the thermal oxidation processing apparatus, the charge in the oxide film is measured and the initial evaluation is performed. Then, on the condition that the measured value is 1E11 [ions / cm 2] or less, the semiconductor wafer after the thermal oxidation treatment is heat-treated in the evaluation target apparatus, and the apparatus is evaluated. In this case, the evaluation wafer used in the thermal oxidation processing apparatus can be used as it is, and the evaluation of the semiconductor heat treatment apparatus to be evaluated can be carried out. Therefore, the evaluation wafer can be shared and the cost can be reduced.
[0015]
In the invention described in claim 6, the CV characteristics are measured at the same point for the semiconductor wafer before the heat treatment by the evaluation object apparatus and the semiconductor wafer after the heat treatment by a non-contact type CV measuring device. Thereby, disturbance factors due to different measurement points are reduced, and the evaluation accuracy is further improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, it is assumed that a CV characteristic of a semiconductor wafer is measured in a non-contact manner using a non-contact type CV measuring instrument. First, an outline of non-contact CV measurement will be described with reference to the conceptual diagram of FIG.
[0017]
As shown in FIG. 1A, a semiconductor wafer 10 includes a semiconductor substrate 11 and an oxide film 12 formed on the surface thereof. Above the oxide film 12, a measurement electrode 13 is arranged with a minute air gap G therebetween. A voltage is applied between A and B in the figure by a measuring instrument (not shown), and the CV characteristic of the semiconductor wafer 10 is measured.
[0018]
In this case, as shown in FIG. 1B, the capacitance between A and B is the capacitance Cd of the semiconductor substrate 11, the capacitance Cox of the oxide film 12, and the capacitance Cair of the air gap G. Are connected in series. Here, if the air gap length is known, the capacitance Cair of the air gap G can be easily obtained. Therefore, the capacitance of the semiconductor wafer 10 not including the air gap can be calculated by subtracting the capacitance Cair from the CV measurement result. This is a value equivalent to the CV measurement result when the contact type CV measuring device is used. In particular, in this embodiment, the charge amount in the oxide film 12 is measured as the CV characteristic.
[0019]
By the way, in the present embodiment, the above non-contact type CV measuring instrument is used to evaluate the contamination of a semiconductor heat treatment apparatus that does not have a gas supply line (for example, oxygen supply line) for forming an oxide film on a semiconductor wafer. The procedure will be described with reference to FIG. Incidentally, by using a non-contact type CV measuring device, it is not necessary to form an electrode on the oxide film, and the same semiconductor wafer (evaluation wafer) can be obtained even after initial CV measurement. It can be put into a semiconductor heat treatment apparatus to be evaluated.
[0020]
First, an initial thermal oxidation process is performed on a semiconductor wafer to produce a semiconductor wafer with an oxide film as an evaluation wafer (S1). At this time, the evaluation wafer is thermally oxidized at a temperature of 950 ° C. or higher, and its oxide film thickness is preferably 2.0 nm or more (more preferably 3.0 nm or more). That is, when the temperature of the thermal oxidation treatment is 950 ° C. or higher, the interface stress due to the viscous flow of the oxide film is relieved. In addition, when the oxide film thickness is 2.0 nm or more, distortion of the oxide film is prevented, and as a result, pseudo contamination due to an increase in charge due to the distortion is prevented.
[0021]
Next, the initial CV measurement by the non-contact type CV measuring device is performed on the semiconductor wafer after the thermal oxidation treatment, and the determination of the level free from contamination and pseudo contamination is performed (S2). At this time, it is determined that the charge amount in the film is 1E11 [ions / cm 2] or less, and if this criterion is not satisfied, the semiconductor wafer is disposed of. This is because if the in-film charge amount is larger than the criterion, the charge fluctuation amount after the heat treatment described later may be hidden in the initial CV characteristic and the difference evaluation of the CV characteristic may not be possible. is there.
[0022]
If the determination criterion that the in-film charge amount is 1E11 [ions / cm 2] or less is satisfied, the semiconductor wafer is put into an evaluation object facility which is a semiconductor heat treatment apparatus having no gas supply line for forming an oxide film (S3). ), Non-oxidizing heat treatment is performed in an inert gas atmosphere (S4). By this operation, impurities are taken into the oxide film of the semiconductor wafer. After the heat treatment, the semiconductor wafer is taken out from the equipment to be evaluated (S5).
[0023]
Thereafter, after CV measurement is performed by a non-contact type CV measuring device (S6). At this time, the CV characteristic is measured at the same point as the initial CV measurement. Finally, the contamination evaluation of the evaluation target facility is performed by differential analysis between the result of the after CV measurement and the result of the above-mentioned initial CV measurement (S7).
[0024]
According to the embodiment described in detail above, the following effects can be obtained.
Since the initial characteristics of the oxide film are limited in advance, it is possible to evaluate the contamination of the semiconductor heat treatment apparatus to be evaluated based on the characteristic fluctuation amount of the oxide film. In other words, by limiting the initial amount of charge in the film, the fixed oxide film charge Qf and the interface state Qit in FIG. 3 are regulated to a minute amount, and as a result, the accuracy of contamination evaluation is improved. In particular, a semiconductor wafer with an oxide film used as an evaluation wafer is limited to an initial in-film charge amount of 1E11 [ions / cm 2] or less, so that variations in the oxide film become minute (see FIG. 4), eliminating disturbance factors. Appropriate evaluation is possible.
[0025]
Since the evaluation wafer used in the thermal oxidation processing apparatus is used as it is and the evaluation of the semiconductor heat treatment apparatus that is the evaluation target is performed, the evaluation wafer can be shared, and the cost can be reduced.
[0026]
In addition to the above, the present invention can be embodied in the following forms.
In the above embodiment, the contamination evaluation is performed by the difference analysis between the initial CV measurement result of the semiconductor wafer and the after CV measurement result. However, even if the contamination evaluation is performed only from the after CV measurement result. good. In other words, in the evaluation method of the present invention, the initial CV measurement result is regulated within a predetermined criterion. Therefore, if the amount of charge fluctuation due to contamination is large, it is reflected in the after CV measurement result. Appropriate contamination assessment can be conducted.
[0027]
As an initial characteristic of the in-film charge amount, the determination criterion may be changed within a range of 1E11 [ions / cm 2] or less, such as 8E10 [ions / cm 2] or less. In this case, as the initial value of the in-film charge amount is smaller, the charge fluctuation amount can be monitored with higher sensitivity.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an outline of non-contact CV measurement.
FIG. 2 is a flowchart showing a procedure for evaluating a semiconductor heat treatment apparatus.
FIG. 3 is a diagram showing charges on an oxide film and an interface in a SiO 2 —Si structure.
FIG. 4 is a diagram showing the relationship between the charge amount in the film and the oxide film variation.
FIG. 5 is a flowchart showing a CV evaluation procedure in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Semiconductor wafer, 11 ... Semiconductor substrate, 12 ... Oxide film, 13 ... Electrode for measurement.

Claims (6)

Semiconductor that performs contamination assessment of a semiconductor heat treatment apparatus that does not have a gas supply line for forming an oxide film on a semiconductor wafer using a non-contact type CV measuring device that measures CV characteristics of a semiconductor wafer in a non-contact manner An evaluation method for a heat treatment apparatus,
A step of preparing a semiconductor wafer with an oxide film in which the characteristic of the oxide film is 1E11 [ions / cm 2] or less in terms of in-film charge;
Heat treating the semiconductor wafer with a semiconductor heat treatment apparatus to be evaluated;
Measuring the characteristics of the oxide film on the semiconductor wafer after the heat treatment with the non-contact CV measuring device;
A step of evaluating contamination of the semiconductor heat treatment apparatus from the result of the measurement;
A method for evaluating a semiconductor heat treatment apparatus, comprising: 2. The evaluation method for a semiconductor heat treatment apparatus according to claim 1, wherein contamination evaluation is performed from a difference between an initial characteristic in which an in-film charge amount of the oxide film is 1E11 [ions / cm <2>] or less and an in-film charge amount measured after the heat treatment. The evaluation method for a semiconductor heat treatment apparatus according to claim 1, wherein the oxide film thickness of the semiconductor wafer with an oxide film prepared in advance is 2.0 nm or more. The evaluation method of a semiconductor heat treatment apparatus according to claim 1, wherein the semiconductor wafer with an oxide film prepared in advance is subjected to thermal oxidation at a temperature of 950 ° C. or higher. After the semiconductor wafer is thermally oxidized by a thermal oxidation processing apparatus, the amount of charge in the oxide film is measured and initial evaluation is performed. On the condition that the measured value is 1E11 [ions / cm 2] or less, The semiconductor heat treatment apparatus evaluation method according to claim 1, wherein the semiconductor wafer after the oxidation treatment is heat-treated with an evaluation target apparatus, and the apparatus is evaluated. 6. The semiconductor heat treatment according to claim 1, wherein the CV characteristics are measured at the same point by a non-contact type CV measuring device for the semiconductor wafer before the heat treatment and the semiconductor wafer after the heat treatment by the apparatus to be evaluated. Device evaluation method.

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