JPH02235337A - Treating method of semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent the attaching of fine particles and the contamination caused by inorganic impurity by treating a semiconductor substrate in chemical vapor and in steam, and drying it by using microwave. CONSTITUTION:A semiconductor substrate is treated in chemical vapor, followed by treating in steam. After the treatments, the semiconductor substrate is dried by using microwave. By treating the semiconductor substrate in vapor, the fine particles attaching to carrier and the like can be prevented from re- attaching on the semiconductor substrate surface, and further fine particles contained in chemicals become hard to mix with the vapor, so that the attaching of fine particles can be reduced. Further, by using vapor, the mixing of impurity can also be reduced, and the uniform treatment reaching fine parts is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for processing a semiconductor substrate, and more particularly to a method for cleaning and etching a semiconductor substrate and a thin film on a semiconductor substrate without being contaminated by particulates or impurities. Conventional technology Conventionally, this type of semiconductor substrate processing method involves performing a process called dipping, in which the semiconductor substrate is directly immersed in a processing solution, and then dried by centrifugal drying or steam drying. The treatment method was the mainstream. Problems to be Solved by the Invention However, in the conventional dip processing method described above, the semiconductor substrate is directly immersed in the processing solution. There is a problem with fine particles adhering to the substrate surface. In recent years, with the progress of miniaturization of semiconductor devices, the influence of fine particles attached on the surface of semiconductor substrates on device characteristics has become important. For example, it causes pattern defects in the lithography process, and it causes abnormal oxide film thickness in the oxidation process, leading to deterioration of gate oxide film breakdown voltage. In order to reduce particulates in the treatment solution, methods are used to circulate the treatment solution and filter it when the chemical solution is supplied. However, with conventional circulation filtration methods and methods in which filtration is performed during chemical supply, there is a problem in that fine particles brought in from carriers etc. diffuse into the processing solution and adhere to the surface of the semiconductor substrate. In addition, acid/alkali chemicals are more difficult to remove particles than pure or gas chemicals, and cannot completely prevent particles from adhering to the semiconductor substrate surface. On the other hand, the conventional dip-type treatment method also suffers from contamination due to impurities contained in the chemicals used. In the semiconductor device manufacturing process, so-called electronic industry chemicals with low particulates and low impurities are used, but even these chemicals contain a considerable amount of inorganic impurities. ing. These impurities also have an adverse effect on device characteristics; in particular, contaminants such as heavy metals increase junction leakage TIK, reduce carrier lifetime, and induce crystal defects. In order to eliminate the effects of impurities in chemicals, a method may be used in which the semiconductor substrate is treated in the vapor of the chemicals. However, in conventional processing methods, semiconductor substrates processed in steam are usually not rinsed, or even if they are rinsed, they are immersed in pure water. If rinsing is not performed, impurities brought into the semiconductor substrate surface from the previous process, for example, may form water-soluble fluorides or chlorides in hydrofluoric acid vapor or hydrochloric acid vapor. It is not completely removed from the semiconductor substrate surface. On the other hand, when rinsing is performed by immersing in pure water, water-soluble fluorides or chlorides are removed, but there is a possibility of contamination from silica, fine particles, etc. in the pure water. Furthermore, as the aspect ratio increases with the miniaturization of devices, in the conventional dip processing method, the processing liquid and pure water for rinsing cannot reach the fine details, resulting in uneven processing and rinsing effects. Met. Conventionally, centrifugal drying has been widely used as a method for drying semiconductor substrates due to its economic efficiency and high throughput.
However, with this method, splashing of water droplets and adhesion of fine particles are essentially unavoidable, and the semiconductor substrate is rotated at high speed, which causes the problem that the semiconductor substrate may crack. In addition, a steam drying method in which the semiconductor substrate is dried in IPA vapor has also been adopted, but although this method can prevent fine particles from adhering to the semiconductor substrate surface and cracking the semiconductor substrate, the surface of the semiconductor substrate after drying There are problems such as IPA being adsorbed on the surface and the use of organic solvents, which are highly dangerous and require careful handling. Furthermore, in conventional processing methods, the processing tank and dryer were separated, so semiconductor substrates that had been treated with chemicals and rinsed were transported in the air from the processing tank to the dryer. However, when semiconductor substrates are transported in the air, there are problems in that floating dust in the air adheres to them, and fine particles adhere to the surface of the semiconductor substrates due to dust generated from the drive unit of the transport machine. The present invention has been made in view of the above-mentioned conventional situation,
Therefore, an object of the present invention is to provide a novel method for processing semiconductor substrates that makes it possible to solve the above-mentioned problems inherent in the conventional techniques. Differences between the invention and the prior art In contrast to the conventional semiconductor substrate processing method described above, the present invention processes a semiconductor substrate in chemical vapor, and after processing the semiconductor substrate in water vapor, it is dried by microwaves. The difference is that all processes are carried out in one processing tank. By processing the semiconductor substrate in steam, it is possible to prevent particulates attached to the carrier etc. from re-adhering to the semiconductor substrate surface, and also to prevent particulates contained in the chemicals from getting mixed into the steam. This makes it difficult for particles to adhere to the surface, reducing the adhesion of fine particles. Also, by using steam, contamination with impurities can be reduced. Furthermore, by performing all processes in one processing tank, it is possible to prevent fine particles from adhering during transportation. Means for Solving the Problems In order to achieve the above object, a method for processing a semiconductor substrate according to the present invention includes a step of processing a semiconductor substrate in a chemical vapor;
It is characterized by comprising a step of processing the semiconductor substrate in water vapor and a step of drying the semiconductor substrate with microwaves, and all steps are performed in one processing tank. Hydrofluoric acid vapor, hydrochloric acid containing ozone, nitric acid, or ammonia vapor is used as the chemical vapor. Practical Directions D1 Next, preferred embodiments of the present invention will be specifically explained with reference to the drawings and compared with conventional methods. FIG. 1 is a diagram showing the measurement results of the number of particles attached to the surface of a semiconductor substrate when using the first embodiment of the present invention and the conventional processing method. Conventional methods include hydrochloric acid (IICLI), nitric acid (HNOi), and ammonia (NH40H) containing hydrogen peroxide, and dilute hydrofluoric acid (NH40H).
The semiconductor substrate was immersed in DIIF for 10 minutes, rinsed in pure water for 10 minutes, and then dried using the IPA vapor drying method. In the case of the present invention, the semiconductor substrate was exposed to hydrochloric acid, nitric acid, and ammonia vapor into which an ozone/oxygen mixed gas was introduced, or fluorine vapor for 10 minutes, and then exposed to water vapor for 10 minutes. After that, the semiconductor substrate was irradiated with the microfluid and dried. In the conventional method, the number of fine particles attached to the surface of a semiconductor substrate is about 100 per substrate when hydrochloric acid (HCL/H202/HzO) and nitric acid (HNO3/tl202) are used; (NH40H
/hOz/H. 0), the number was about 20. In addition, when DIIF was used, the number was about 200. On the other hand, when the treatment according to the present invention was performed, the number of fine particles was several or less in all cases.

As described above, by using the processing method according to the present invention, it is possible to reduce the adhesion of fine particles to the surface of the semiconductor substrate, compared to the conventional processing method.

FIG. 2 is a diagram showing the distribution of dielectric breakdown field strength of the gate oxide film in a MOS diode when the second embodiment of the present invention and the conventional processing method are used. The gate oxide film thickness of the sample used for the measurement was approximately 100, and cleaning before and after forming the gate oxide film was performed using the processing methods of the present invention and the conventional method. In the conventional method, an aqueous ammonia/hydrogen peroxide mixture was used.

In the case of the conventional fK method, there were many initial failures, the breakdown electric field strength was distributed on the low electric field side, and there were almost no samples that showed a so-called intrinsic breakdown voltage of 8 MV/cm or more. On the other hand, in the case of the second example according to the present invention, no initial defects were observed, and almost all samples had a voltage of 9 MV/
It maintains an electric field strength of more than cm. If @ particles adhere to the surface of the semiconductor substrate during gate oxide film formation, bottle holes are likely to occur in the formed gate oxide film. Furthermore, if there is contamination with impurities such as heavy metals, the contaminants act as nuclei and induce crystal defects. Both of these bin poles and crystal defects cause deterioration of dielectric strength. This shows that the conventional method is significantly more contaminated by fine particles and inorganic impurities than the treatment method of the present invention. Figure 3 shows
The results of lifetime measurements of minority carriers in in-situ metallized semiconductor substrates using the present invention and conventional processing methods are shown. The measurements were carried out by treating contaminated semiconductor substrates according to the present invention and conventional methods, and after heat treatment in an oxidizing atmosphere.
This was done using the non-contact lifetime method. In the conventional method, heat treatment was performed without rinsing after exposure to hydrofluoric acid vapor for 5 minutes. In the present invention, the sample was treated in hydrofluoric acid vapor for 5 minutes and then in water vapor for 10 minutes. For comparison, the values for a clean semiconductor substrate and a semiconductor substrate without post-treatment after contamination are also shown. In the case of the conventional method, contaminants remain on the surface of the semiconductor substrate because rinsing with pure water is not performed.
The lifetime of minority carriers is almost the same as when no post-processing is performed. On the other hand, in the case of the present invention, contaminants converted into water-soluble fluoride by hydrofluoric acid vapor are removed from the semiconductor substrate surface by processing in water vapor, so minority carriers are removed from the surface of the semiconductor substrate. The lifetime is approximately the same as that of a clean semiconductor substrate. In addition, in the case of conventional treatment and rinsing in pure water for 10 minutes, the lifetime of minority carriers was almost the same as in the case of the present invention, but the number of particles attached to the semiconductor substrate surface was This was about one order of magnitude higher than that of the present invention. Effects of the Invention As explained above, according to the present invention, a semiconductor substrate is processed in chemical vapor, and after the semiconductor substrate is processed in water vapor, it is dried by microwave, and all steps are performed in one process. By performing the process in a bath, it is possible to prevent the adhesion of fine particles and contamination by inorganic impurities, and by using steam, it is possible to perform more uniform processing down to the smallest details, resulting in high quality and high yield semiconductor devices. This has the effect of making it possible to manufacture .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the measurement results of the number of fine particles adhering to the surface of a semiconductor substrate in a first embodiment according to the present invention and a conventional processing method, and FIG. 2 is a diagram showing a second embodiment according to the present invention. Figure 3 shows the distribution of dielectric breakdown field strength of the gate oxide film in a MOS diode when using the processing method of the present invention and the conventional method. It is a diagram showing the lifetime measurement results of minority carriers. Patent applicant: NEC Co., Ltd. Representative: Patent attorney: Yutaro Kumagai 1! Figure 1 Dielectric breakdown electric field strength (MV/song): 2 yen

Claims (1)

[Claims] A method for processing a semiconductor substrate, comprising the steps of exposing a semiconductor substrate to chemical vapor, exposing the semiconductor substrate to water vapor, and drying the semiconductor substrate using microwaves.