JP2556996B2 - Sample preparation method for damage evaluation during semiconductor manufacturing process and its evaluation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to damages that occur on the surface of various materials such as semiconductors and metals during plasma processing such as dry etching and plasma vapor deposition. The present invention relates to a method for producing a sample for evaluating the above and a method for evaluating damage.

[Conventional technology]

On the surface exposed to plasma, crystal defects and impurities are mixed and damaged. Conventionally, in order to evaluate damage, there has been a method of analyzing a change in crystallinity and a change in composition of the surface. In addition, there is a method of forming a MOS, a diode, or the like, and evaluating the damage from the change in the electric characteristics.

[Problems to be Solved by the Invention]

Although electron diffraction method, electron microscope, etc. are used for the evaluation of crystallinity, there are drawbacks that it is difficult to prepare a sample and damage due to low energy ions of 100 eV or less cannot be detected. In the method of investigating changes in the composition of the surface, when corrosive gas is used or when iron, nickel, etc. are mixed in from the chamber of the manufacturing equipment, the distribution in the depth direction is measured to damage the low energy ions. However, the damage could not be evaluated when an inert gas was used or when the mixing of impurities was below the detection limit of the analyzer.

The method of estimating damage from changes in electrical characteristics is the most sensitive method, but has the drawback that new change factors may be introduced during the process of manufacturing the element for characteristic evaluation.

[Means for solving the problem]

In order to eliminate such defects, the damage evaluation sample preparation method in the semiconductor manufacturing process according to the present invention, in evaluating the damage generated in the semiconductor in the semiconductor manufacturing process, during the semiconductor manufacturing process and the evaluation sample manufacturing process. After adsorbing a substance that is not mixed in from the environment on the semiconductor surface, a step of performing a semiconductor manufacturing process and a step of vacuum-depositing a material of the same material as the evaluation sample on the semiconductor surface are included.

Further, the damage evaluation method during the semiconductor manufacturing process according to the present invention, the component of the substance adsorbed to the damage evaluation sample is analyzed from the surface in the depth direction, and the half-value width of the depth direction distribution is used in the semiconductor manufacturing process. It is designed to evaluate the amount of damage that occurs.

[Action]

In the present invention, a substance that is not mixed in the plasma treatment or the subsequent sample preparation process is adsorbed on the surface in advance, and the degree of damage is known from the depth distribution state of the adsorbed component,
Low or no damage process conditions can be determined.

〔Example〕

Crystal defects and impurities are mixed in the damage formed on the surface during the plasma process. The damage is formed by first forming a crystal defect and then accelerating diffusion of impurities through the crystal defect. This method makes use of the phenomenon that surface adsorbates penetrate into the interior depending on the damage during process treatment. That is, the degree of damage is evaluated from the depthwise distribution of impurities that have penetrated from the surface to the inside. In this method, unlike the conventional method, by using a component or isotope that is not mixed in during the sample preparation process, it is possible to clearly detect the magnitude of damage.

FIG. 1 is a diagram for explaining an example in which the present invention is applied to evaluation of damage due to dry etching, and is a case where deuterium is used as a substance that is not mixed into the surface by a subsequent process. In Fig. 1 (a), sample 2a was placed in heavy water 1.
Is immersed, a sample 2 is formed in which heavy water or deuterium is adsorbed on a part or all of the surface (Fig. 1 (b)). By such a treatment, deuterium having a higher isotope ratio can be adsorbed on the sample surface.

FIG. 2 is an example of a sample for examining dry etching damage on a Si wafer. When the Si wafer 2 as a sample on which heavy water or deuterium is adsorbed by the method of FIG. 1 is dry-etched, deuterium 3 diffuses inside. On this surface,
Amorphous Si4 is vacuum-deposited as a protective film for SIMS (Secondary Ion Spectrocopy) analysis. The vacuum deposition is performed here so that no new damage is formed when the amorphous Si4 film is formed.

Fig. 3 shows SI in the depth direction of deuterium concentration of sample 2 in Fig. 2.
This is the result of MS analysis. The horizontal axis is the depth and the vertical axis is the deuterium concentration, which shows the distribution of deuterium in the depth direction when dry etching is performed with Ar having different ion energies.
S1 is before etching, S2 is at an ion energy of 10 eV or less, and S3 is at an ion energy of 20 eV or more.
W1, W2, W3 are the half widths of the ion energy curves S1, S2, S3. When the ion energy is 20 eV or more (curve S
3), the amount of residual deuterium is large compared to the case of 10 and several eV, and
It can be seen that the full width at half maximum is wider than that before etching (curve S1) and when etching is performed at 10's eV.

In FIG. 4, the horizontal axis represents the Ar ion energy during dry etching, and the vertical axis represents the ratio of the half width of the deuterium profile after etching to the half width of the deuterium profile before etching (FWHM (Full Width at Ha
It is a graph which shows the result of having plotted (lf Maximum, half-width) ratio). As shown in the figure, the half-width ratio increases with 15 eV as the critical point. This indicates that the dry etching of Ar having an ion energy of 15 eV or more diffused the deuterium adsorbed on the surface to the inside, that is, formed damage in this region. Therefore, Ar
It can be seen that in order to perform dry etching so that the surface of the Si wafer is not damaged by ions, the surface should not be exposed to ions of 10 s eV or more.

Thus, using this method, it is possible to evaluate the damage to the surface caused by low energy ions. In addition to the above, by this method, the surface of semiconductors or metals other than Si, it is possible to evaluate the size of the damage of the surface that is received by low-energy dry etching, low etching or damage-free etching conditions It can be useful for decisions. Although the method for evaluating the damage of dry etching has been described here, the evaluation is difficult because there is a possibility that adsorbates such as deuterium will scatter during dry etching. On the other hand, when this method is used for thin film formation, the possibility is small, and damage can be evaluated more accurately.

In the example of the present method, the dry etching damage was evaluated on the sample in which heavy water was adsorbed on the Si wafer. There is no. For example,
When the semiconductor surface is etched with chlorine gas, a sample in which the surface is fluorinated by dipping it in a hydrofluoric acid solution is considered. Also, the analysis method need not be limited to SIMS. For example, in the depth direction analysis of fluorine on a fluorinated surface, the angle analysis
A non-destructive analysis method sensitive to changes in the depth direction of the surface, such as XPS (X-ray Photoelectron Spectroscopy), may be used to measure changes in the penetration depth of fluorine. In this case, it is not necessary to attach a surface protective film.

〔The invention's effect〕

As described above, the present invention, after adsorbing on the semiconductor surface a substance that is not mixed in from the environment during the semiconductor manufacturing process or the evaluation sample preparation process, the semiconductor manufacturing process is performed, and the semiconductor surface is made of the same material as the evaluation sample. The material for vacuum evaluation is prepared by vacuum evaporation of the material, and the components of the substance adsorbed to this sample for damage evaluation are analyzed in the depth direction from the surface, and the half-value width of the distribution in the depth direction causes it in the semiconductor manufacturing process. By evaluating the magnitude of the damage to be performed, there is an advantage that the damage can be easily evaluated by the low-energy ions and a process condition with low damage or no damage can be determined.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is a block diagram showing a sample whose surface is protected to analyze damage, and FIG. 3 is a Si which was subjected to dry etching with Ar after absorbing heavy water.
Graph showing SIMS depth distribution of deuterium on wafer, 4th
The figure is a graph showing the relationship between the ion energy of Ar used for dry etching and the penetration depth of deuterium.

Claims (2)

(57) [Claims] 1. When evaluating damage generated in a semiconductor in a semiconductor manufacturing process, a substance that is not mixed in from the environment is adsorbed on the semiconductor surface during the semiconductor manufacturing process or the evaluation sample preparation process, and then the semiconductor manufacturing process is performed. A method of preparing a sample for damage evaluation during a semiconductor manufacturing process, comprising: a step of performing a treatment; and a step of vacuum-depositing a material of the same material as the evaluation sample on the semiconductor surface. 2. A component of a substance adsorbed on a damage evaluation sample is analyzed in the depth direction from the surface, and the magnitude of damage generated in a semiconductor manufacturing process is evaluated from the half-value width of the distribution in the depth direction. A characteristic evaluation method during a semiconductor manufacturing process.