JP2002203881A - Method for evaluating reliability characteristics of oxide film of mos semiconductor device on semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating reliability characteristics of an oxide film of a MOS semiconductor device on a semiconductor wafer, by which quick accurate evaluation can be performed by utilizing a conventional oxide film reliability evaluation equipment for a small diameter wafer even if a semiconductor wafer diameter becomes larger than 300 mm. SOLUTION: The method is provided for evaluating the reliability characteristics of the oxide film of the MOS semiconductor device wherein an oxide film and a conductive film are formed on one another on the semiconductor wafer. The method comprises the evaluation after the process for reducing at least the diameter of the wafer in measuring the reliability characteristics of the oxide film by applying an electrical stress to the oxide film between the wafer of the MOS semiconductor device and the conductive film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to quality evaluation of large-diameter semiconductor wafers used for manufacturing semiconductor devices such as ICs and LSIs, and more particularly to MOS type semiconductor devices manufactured on large-diameter silicon wafers. And a method for detecting and evaluating a gate oxide film defect.

[0002]

2. Description of the Related Art MOS (Metal Oxide Se)
The purpose of measuring the reliability characteristics of an oxide film of a semiconductor device is to evaluate the quality of an oxide film formed on a semiconductor wafer. It is known that the quality of an oxide film, for example, an oxide film thermally oxidized on a silicon wafer reflects the quality of the oxide film forming conditions, the quality of the surface of the semiconductor wafer, and the like. Further, in order to miniaturize, increase the density, increase the speed, and increase the yield of the semiconductor integrated circuit, knowing the accurate oxide film reliability characteristics will be one of the more important factors in the future.

A MOS type semiconductor device is manufactured by, for example, a process shown in FIG. First, a P-type or N-type Si wafer having a conductivity type to be evaluated is prepared.
After cleaning to clean the surface of the i-wafer,
In step 2), a thermal oxide film (gate oxide film) is grown to form an insulating film. Thereafter, in step 3-1), polycrystals are deposited by a chemical vapor deposition (CVD) method to form electrodes.
Here, in the case where the conductive film is made of polycrystalline silicon, after introducing a dopant for lowering the resistivity, annealing is performed in step 3-2), and then photolithography is performed in step 3-3). An excess polycrystal is removed by dry etching to form an electrode. On the other hand, aluminum (A) is formed as a conductive film by a vacuum evaporation method as in step 4-1).
1) may be deposited using a metal mask to form an electrode. Next, in step 5), the back surface oxide film of the silicon wafer is removed by, for example, HF vapor, and a large number of MOS diodes are formed to obtain a MOS semiconductor device.

In measuring specific oxide film reliability characteristics, for example, a silicon wafer having a large number of MOS diodes formed thereon is placed on a stage in a light-shielding box, and a large number of oxide film reliability characteristics are measured. Is measured. Here, an electric circuit for measurement is shown in FIG. In this figure, 1 indicates an electrode, 2 indicates a gate oxide film, and 3 indicates a silicon wafer. The reliability characteristics are
A current is measured by applying a voltage between the semiconductor wafer and the conductive film, and a predetermined current value (determination current value), for example, 1
mA / cm ² (8 × 10 when the gate area is 8 mm ² )
^-5 Amp. ) Is defined by the electric field strength obtained by dividing the voltage value at the time of ()) by the thickness of the oxide film. Here, the applied voltage waveform includes, for example, a step-like (step) waveform shown in FIG. 7 and an inclined (ramp) waveform shown in FIG. 8 (T
ZDB: Time Zero Dielectric
Breakdown, dielectric breakdown voltage characteristics).

As another method, a constant voltage (FIG. 9) or a current value (FIG. 10) or a ramp-like voltage or current is applied to the MOS diode, and the time until the oxide film is destroyed is reduced. There is a method for evaluating oxide film reliability characteristics by measuring (TDDB: Time De)
pendent Dielectric Breakd
own, dielectric breakdown voltage characteristics over time).

[0006]

As described above, in order to evaluate the reliability of an oxide film, after cleaning for cleaning the surface of a silicon wafer, a thermal oxide film is grown to form an insulating film. To form Thereafter, for example, when polycrystal is deposited and formed as the conductive film, it is necessary to remove unnecessary polycrystal by wet or dry etching through a photolithography process to form an electrode. As wafer generation changes and wafer diameter increases, oxidation furnaces, CVD furnaces for polycrystalline deposition, photolithography equipment, measuring instruments, etc. must be updated to large sizes in accordance with the increase in wafer diameter. However, there is a problem that capital investment becomes very large. Also, even if these process devices are introduced, it takes a considerable time to start up.

In view of the above, the present invention has been made in view of the above problems, and has a silicon wafer having a diameter of 300 mm.
Oxide film reliability of a MOS type semiconductor device on a semiconductor wafer can be quickly and accurately evaluated using conventional oxide film reliability evaluation equipment for small diameter even if the diameter exceeds 12 inches. An object of the present invention is to provide a method for evaluating sexual characteristics.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and a method of evaluating the reliability of an oxide film of a MOS type semiconductor device on a semiconductor wafer according to the present invention is provided. And a conductive film are sequentially formed.
When applying an electrical stress to an oxide film between a semiconductor wafer and a conductive film of an OS-type semiconductor device to measure oxide film reliability characteristics, at least evaluate the semiconductor wafer after reducing the diameter of the semiconductor wafer. (Claim 1).

As described above, even when the diameter of the semiconductor wafer is reduced in diameter and the oxide film breakdown voltage characteristic is evaluated, the same highly reliable evaluation result as in the case of directly evaluating the wafer without diameter reduction can be obtained. . Therefore, for example, 300 mm in diameter
When evaluating oxide film breakdown voltage characteristics of large-diameter wafers exceeding that, even after evaluation after reducing the diameter to a small-diameter wafer, a highly reliable evaluation result equivalent to that when directly evaluating the original large-diameter wafer is obtained. be able to. Therefore, according to the evaluation method of the present invention, when evaluating the oxide withstand voltage characteristics of a large-diameter wafer, it is not necessary to update the electrical characteristic evaluation equipment to a large-sized equipment in accordance with the large-diameter wafer, and the evaluation is performed using existing equipment. This makes it possible to start an evaluation process for a next-generation large-diameter wafer in a short period of time and to reduce the evaluation cost.

In this case, the diameter reduction processing of the semiconductor wafer is performed by:
It is preferable to perform the eccentric diameter reduction so as to include the entire area of the radius of the wafer before the diameter reduction (claim 2). By doing so, at least the entire area from the outer peripheral edge to the center of the original wafer before diameter reduction is covered, so that an evaluation almost equivalent to the total surface area evaluation of the wafer before diameter reduction can be performed. it can.

Next, in order to protect the wafer from processing damage, the diameter reduction processing of the semiconductor wafer is preferably performed after attaching an organic resist film or a tape to one or both sides of the wafer. In this way, even if a method such as grinding, polishing, cutting with a laser beam, or cutting with a jet stream is used for the diameter reduction processing, the wafer is not subjected to the diameter reduction processing damage and highly reliable evaluation is performed. be able to.

An oxide film and a conductive film are sequentially formed on the wafer in advance before diameter reduction processing of the semiconductor wafer, and thereafter, the diameter of the wafer can be reduced to evaluate the MOS type semiconductor device. (Claim 4). As described above, before the diameter reduction of the semiconductor wafer, an oxide film and a conductive film are sequentially formed on the wafer in advance, and then the diameter reduction of the wafer is performed to manufacture and evaluate a MOS semiconductor device. It is very effective because it does not damage the oxide film and conductive film due to the diameter reduction processing, and can reduce the diameter of a large-diameter wafer and use the existing photolithography equipment and measuring device for oxide film breakdown voltage evaluation. And an appropriate method.

Further, when forming an oxide film and a conductive film on a semiconductor wafer, polycrystalline silicon is used as the conductive film, and when forming the polycrystalline silicon film, a dopant is doped simultaneously with the polycrystalline deposition. (Claim 5). Furthermore, when forming an oxide film and a conductive film on the semiconductor wafer, polycrystalline silicon may be used as the conductive film, and after forming the polycrystalline silicon film, a dopant may be doped into the polycrystalline film. 6). Thus, when forming an oxide film and a conductive film on a semiconductor wafer,
Polycrystalline silicon is used as the conductive film, and when forming a polycrystalline silicon film, a dopant that reduces the resistivity is deposited at the same time as the polycrystalline deposition, or the dopant is added to the polycrystalline film after the polycrystalline silicon film is formed. By doping, the actual M
The structure is the same as that of the OS type semiconductor device, and highly reliable evaluation can be performed.

When forming an oxide film and a conductive film on the semiconductor wafer, polycrystalline silicon is used as the conductive film. After forming the polycrystalline silicon film, the semiconductor wafer is reduced in diameter. The polycrystalline silicon film can be doped with a dopant. In this way, by performing the diameter reduction processing before doping the dopant and then doping the dopant, a highly reliable evaluation method can be obtained without further processing damage.

Further, when forming an oxide film and a conductive film on the semiconductor wafer, the conductive film may be made of Al or Al.
The conductive film may be formed by vapor deposition or sputtering using -Si. As described above, since the material of the conductive film is made of Al or Al-Si alloy and is formed by vapor deposition or sputtering, this method is also an effective evaluation method.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings, but the present invention is not limited thereto. FIGS. 1 and 2 are schematic flow charts showing a process for manufacturing a MOS semiconductor device in the method for evaluating the reliability of an oxide film of a MOS semiconductor device by reducing the diameter of a wafer according to the present invention.

FIG. 1 shows that a gate oxide film and polycrystalline silicon as an electrode material are deposited on a large-diameter wafer to be evaluated, the wafer is reduced in diameter to a small diameter, and a MOS type semiconductor device is manufactured through several steps. FIG. During this process, the polycrystal deposited as an electrode material
This is a polycrystal deposition step in which a dopant for reducing the resistivity of polycrystal used as an electrode material during deposition is introduced. However, the dopant may be separately doped after the polycrystal is deposited using POCl ₃ or the like.

The MOS type semiconductor device of the present invention is manufactured, for example, by the steps shown in FIG. First, a large-diameter silicon wafer whose conductivity type is P-type or N-type, which is to be evaluated symmetrically, is prepared, and a cleaning for cleaning the surface of the Si wafer is performed in step 1), and then a thermal oxide film ( A gate oxide film 4) is grown to form an insulating film (FIG. 1B)
reference). Thereafter, in step 3), a polycrystal is deposited by a CVD method to form a conductive film (electrode material). In this step, a dopant for reducing the resistivity of the polycrystal is introduced in advance.
Next, an annealing step of activating the dopant introduced to reduce the resistivity in step 4) is performed. Note that the oxide film and the conductive film can be formed after the diameter reduction processing described later. The effect can be reduced.

Thereafter, in step 5), a resist is applied to the wafer surface, and a dicing tape is pasted thereon to protect the wafer surface (see FIG. 1 (c)). It is preferable that the protective film is formed on both surfaces, but the back surface may be formed by simply attaching a dicing tape. These wafer surface protection steps are not necessarily required, but are preferably provided to avoid damage during diameter reduction processing. Further, baking after resist coating may or may not be performed. It is better to use a dicing tape that is slightly smaller than the target diameter of the dicing so as not to hinder the diameter reduction processing in the next step.

Next, the protected wafer is subjected to diameter reduction in step 6) (see FIG. 1D). The diameter reduction processing is not particularly limited as long as the wafer can be cut, and grinding, polishing, cutting using a laser beam, cutting using a jet stream, or the like can be used. In the diameter reduction processing, it is preferable to reduce the diameter by eccentrically reducing the diameter of the original large-diameter wafer so as to include the entire radius area from the outer peripheral end of the original large-diameter wafer (in the radial direction of the large-diameter wafer). Distribution) can be more accurately evaluated. After reducing the diameter of the wafer to a small diameter, chamfering of the wafer edge is performed. This should preferably be performed to avoid troubles due to dust generation in the next step (see FIG. 1D).

After the diameter reduction processing, the dicing tape stuck on both surfaces of the wafer as a protective film in step 7) is peeled off, and then the resist is removed.
₍ Washing with a mixed solution of ₄ OH / H ₂ O ₂ / H ₂ O), a pattern is formed by a photolithography process, and excess polycrystal is removed by wet or dry etching to form an electrode. Next, in step 8), the backside oxide film of the silicon wafer is removed by HF vapor or the like, and a large number of MOS diodes are formed to complete a MOS type semiconductor device having a reduced diameter.

FIG. 2 is a flow chart showing another embodiment of the present invention. After depositing a gate oxide film and a polycrystal as an electrode material on a large diameter wafer to be evaluated, the diameter of the wafer is reduced to a small diameter. And then doping the polycrystal with a dopant
FIG. 3 is a schematic flow chart showing a step of manufacturing an OS type semiconductor device.

Steps 1) and 2) are the same as the steps shown in FIG. In step 3), polycrystal is deposited as an electrode material on the gate oxide film 7 of the large-diameter wafer, but in this step, a dopant is not doped. Next, in step 4), wafer protection before diameter reduction processing is performed. The protection method is the same as in step 5) in FIG. 1 (see FIG. 2C).

The protected wafer is then reduced in diameter in step 5) (see FIG. 2D). This method of reducing the diameter and the subsequent chamfering may be performed in the same manner as in step 6) of FIG.

After reducing the diameter, the dicing tape stuck on both surfaces of the wafer as a protective film is peeled off, the resist is removed, and the wafer is washed with SC-1. Then, in step 6), the resistivity of the polycrystal is reduced. A dopant is introduced using POCl ₃ or the like, and then an annealing step for activating the dopant is performed. Thereafter, the same steps 7) and 8) as in FIG. 1 are performed to complete the MOS type semiconductor device having a reduced diameter.

When the reliability of the oxide film is evaluated by the oxide film breakdown voltage measuring circuit for the MOS type semiconductor device having the reduced diameter manufactured by the above-described manufacturing process, the large-diameter wafer before the diameter reduction is directly evaluated. The same accurate evaluation information as the result of the above can be obtained. The method of measuring the oxide film reliability characteristic itself may be performed by the above-described conventional method.
Since the diameter is reduced, the apparatus itself can be performed using an existing apparatus.

Therefore, according to the evaluation method of the present invention, when evaluating the oxide film breakdown voltage characteristics of a large-diameter wafer, it is not necessary to update the electrical characteristic evaluation equipment to a large-scale equipment in accordance with the large-diameter wafer. This makes it possible to carry out the evaluation, and in a short time, it is possible to start the evaluation process for the next-generation large-diameter wafer and to reduce the evaluation cost.

[0028]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. (Example 1) A silicon wafer used as a sample has a p-type epitaxial layer having a normal resistivity (1 to 10 Ωcm) on a p-type low resistivity (0.01 Ωcm or less) substrate having a diameter of 200 mm. The formed p / p + epitaxial wafer (boron dope). A gate oxide film (having a thickness of about 25 nm) is formed on this silicon wafer, and a polycrystalline silicon film doped with a dopant is formed thereon for about 300 n.
m. At this time, the dopant was phosphorus. Then, after performing annealing for activating phosphorus as a dopant, a wafer having a diameter of 150 mm was subjected to diameter reduction processing, and a wafer having a diameter of 200 mm without performing diameter reduction processing was subjected to photolithography. By performing the following steps, a MOS type semiconductor device was manufactured, and evaluation of oxide film reliability characteristics was performed.

The wafer subjected to the diameter reduction processing was coated with a resist on the front surface, pasted with a dicing tape, and pasted with a dicing tape on the back surface to protect the wafer before processing. After diameter reduction, the wafer edge was chamfered. After the diameter reduction, the protective film was removed and a photolithography process was performed to produce a MOS semiconductor device, and its oxide film reliability characteristics were evaluated.

The results are shown in FIGS. FIG. 3 (a),
(B) shows a MOS type semiconductor device manufactured by reducing the diameter in the above-described process and a MOS type device having the same size without reducing the diameter, and showing the IV characteristics thereof. I can't see it. 4 (a) and 4 (b) show MOS semiconductor devices having the reduced diameter in the above-described process and those having the same size without reducing the diameter, respectively.
It shows DDB characteristics and shows no initial or accidental defects due to diameter reduction processing. The reduced diameter wafer can be sufficiently used for evaluating oxide film breakdown voltage characteristics.

Example 2 A silicon wafer used as a sample was a 300 mm diameter p / p + epitaxial wafer (boron doped). A gate oxide film (thickness: about 25 nm) was formed on this silicon wafer, and a polycrystalline silicon film doped with phosphorus as a dopant was deposited to a thickness of about 300 nm. Thereafter, annealing for activating phosphorus as a dopant is performed, and the diameter is 200 mm.
The MOS was manufactured under the same conditions as in Example 1 except that two types of wafers were prepared, ie, a wafer subjected to diameter reduction processing (eccentric diameter reduction) and a wafer having a diameter of 300 mm without performing diameter reduction processing.
A semiconductor device was fabricated, and the oxide film reliability characteristics were evaluated.

As a result, similar to the first embodiment, almost the same results as those shown in FIGS. 3 and 4 were obtained. In both the IV characteristic and the constant current TDDB characteristic, no defect due to the diameter reduction was observed. Therefore, the wafer whose diameter has been reduced can be sufficiently used for evaluating the withstand voltage characteristics of the oxide film.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same effect. Within the technical scope of

For example, the present invention is to evaluate the reliability of an oxide film after reducing the diameter of a large-diameter semiconductor wafer.
The diameter reduction processing is not limited to the method exemplified above. Where in the process the diameter reduction processing is to be performed, in what method, etc., may be arbitrarily selected as a matter of principle.

[0035]

As described above, according to the present invention, in evaluating the quality of a MOS type semiconductor device of a semiconductor wafer whose diameter is increasing more and more in the future, investment in the enlargement of evaluation equipment accompanying the increase in diameter is required. This is an extremely effective method for improving the quality of a semiconductor wafer having a large diameter because it can suppress the evaluation cost and reduce the evaluation cost, and can perform the evaluation quickly and accurately.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart showing a manufacturing process of a MOS semiconductor device in which a gate oxide film and a polycrystal doped with a dopant as an electrode material are deposited on a large-diameter wafer according to the present invention and the diameter of the wafer is reduced to a small diameter. FIG. (A) Flow diagram, (b) to (d) show the form of the wafer in each manufacturing process.

FIG. 2 shows a method of depositing a polycrystal as a gate oxide film and an electrode material on a large-diameter wafer according to the present invention, reducing the diameter of the wafer to a small diameter, and then doping the polycrystal with a dopant.
FIG. 3 is a schematic flowchart showing a manufacturing process of an OS type semiconductor device. (A) Flow diagram, (b) to (d) show the form of the wafer in each manufacturing process.

FIG. 3 shows a MOS type semiconductor device in which a large-diameter wafer is reduced to a small diameter after depositing polycrystalline as a gate oxide film and an electrode material, and a MOS type semiconductor device is produced in the same size without reducing the diameter. It is the comparison figure which compared IV characteristic. (A) Wafer with reduced diameter, (b) No diameter reduction processing.

FIG. 4 shows that a large-diameter wafer is reduced to a small diameter after depositing a polycrystal as a gate oxide film and an electrode material, and a MOS type semiconductor device is produced in the same size without reducing the diameter. FIG. 9 is a comparison diagram comparing current TDDB characteristics. (A) Wafer with reduced diameter, (b) No diameter reduction processing.

FIG. 5 is a schematic flowchart showing a manufacturing process of a conventional MOS type semiconductor device.

FIG. 6 is a circuit diagram showing a configuration of an oxide film breakdown voltage measuring circuit of a MOS type semiconductor device.

FIG. 7 is a waveform diagram showing a waveform of a step voltage in an applied voltage.

FIG. 8 is a waveform diagram showing a waveform of a lamp voltage at an applied voltage.

FIG. 9 is a relationship diagram showing the relationship between voltage application and time in constant voltage TDDB evaluation.

FIG. 10 is a relationship diagram showing a relationship between voltage application and time in constant current TDDB evaluation.

[Explanation of symbols]

1. Polycrystalline silicon gate electrode 2. Gate oxide film
Reference numeral 3 denotes a silicon wafer, 4 denotes a gate oxide film, 5 denotes a protective tape attached to a large-diameter wafer, 6 denotes a wafer after diameter reduction, and 7 denotes a gate oxide film.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsushi Oka 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Inside the Semiconductor Isobe Laboratory F-term (reference) 2G003 AA02 AA10 AB01 AE01 AF01 AH00 AH04 4M106 AA01 AA07 AB02 BA14 BA20 CA14 CA27 CA56 DH04

Claims (8)

[Claims] 1. A method for evaluating an oxide film reliability characteristic of a MOS type semiconductor device in which an oxide film and a conductive film are sequentially formed on a semiconductor wafer, wherein the oxide film between the semiconductor wafer and the conductive film of the MOS type semiconductor device is provided. Measuring the oxide film reliability characteristics by applying an electric stress to the semiconductor wafer at least after reducing the diameter of the semiconductor wafer. Characteristic evaluation method. 2. The MOS type on a semiconductor wafer according to claim 1, wherein the diameter reduction of the semiconductor wafer is performed by eccentric diameter reduction so as to include the entire area of the radius of the wafer before diameter reduction. Method for evaluating oxide film reliability characteristics of semiconductor device. 3. The method according to claim 1, wherein the step of reducing the diameter of the semiconductor wafer is performed after attaching an organic resist film or a tape to one or both sides of the wafer in order to protect the wafer from processing damage. 3. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to claim 2. 4. An oxide film and a conductive film are sequentially formed on a wafer in advance before diameter reduction processing of the semiconductor wafer, and thereafter, the diameter of the wafer is reduced to evaluate a MOS type semiconductor device. Claims 1 to 3 characterized by the above-mentioned.
7. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to any one of the above items. 5. When forming an oxide film and a conductive film on said semiconductor wafer, polycrystalline silicon is used as said conductive film, and when forming said polycrystalline silicon film, a dopant is added simultaneously with polycrystalline deposition. 5. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to claim 1, wherein the method is performed by doping. 6. When forming an oxide film and a conductive film on the semiconductor wafer, polycrystalline silicon is used as the conductive film, and after forming the polycrystalline silicon film, a dopant is doped into the polycrystalline film. Claims 1 to 4 characterized by the above-mentioned.
7. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to any one of the above items. 7. When an oxide film and a conductive film are formed on the semiconductor wafer, polycrystalline silicon is used as the conductive film, and after forming the polycrystalline silicon film, the semiconductor wafer is subjected to diameter reduction processing. 5. The polycrystalline silicon film is doped with a dopant.
7. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to any one of the above items. 8. When forming an oxide film and a conductive film on the semiconductor wafer, the conductive film may be made of Al or Al-
5. The method according to claim 1, wherein said conductive film is formed by vapor deposition or sputtering using Si.
7. The method for evaluating the reliability of an oxide film of a MOS semiconductor device on a semiconductor wafer according to any one of the above items.