JP2842898B2 - Foreign matter adhesion prevention method - Google Patents

Description

The present invention relates to a semiconductor device, a thin film device, a magnetic disk,
The present invention relates to a technology for cleaning electronic devices and components such as optical disks, and more particularly to a method for preventing foreign matter from adhering.

[Prior Art] With an increase in the density and integration of LSIs and the like, there has been a problem that element characteristics and yield are reduced due to minute foreign matter and the like.
Therefore, RCCA Review 31 (every 1970) No. 187
As described in p. 06 [RCA Review, 31 (1970), p. 187-206], a method of heating a mixture of aqueous ammonia and hydrogen peroxide to about 80 ° C. and immersing the wafer in the mixture may be used. In addition, minute foreign matter was removed by a method of applying ultrasonic waves in ultrapure water. Especially for the latter ultrasonic cleaning,
Instead of 50 kHz, Journal of Electronic Materials, Vol. 8 (1979), pages 855 to 864 [J. Elec. M
Aterials, 8 (1979) pp. 855-864], and a frequency of 850 kHz may be used.
The distance between the ultrasonic radiation surface and the liquid surface is changed as described in, and the frequency is modulated to the fundamental frequency as described in JP-A-61-101283. Was offered.

[Problems to be solved by the invention]

The above conventional technology is used for the manufacture of VLSI such as 4Mbit DRAM
Although it is effective for foreign matter with a particle size of about 0.08 μm which is a problem in the 0.8 μm process, the above-mentioned various measures are applied to ultrafine foreign matter with a particle size of 0.05 μm or less which is a problem after 16M. Even if it is performed, the removal effect is insufficient.

Therefore, the foreign matter removal method was considered to be limited, and the above problem was solved by a foreign matter adhesion prevention technique. In the semiconductor device manufacturing process, there are various opportunities for foreign matter to adhere to the wafer, but in many cases, foreign matter adheres to the wafer by immersion in a liquid. Therefore, as shown in FIG.
Is passed through the gas-liquid interface, and the area existing in the liquid 7a in the liquid tank 7 increases, for example, at "dipping" (FIG. 4 (a)).
"At the time of holding in liquid" held in liquid (FIG. 4 (b)), and "at the time of pulling" where the area of the wafer passing through the gas-liquid interface and existing in the liquid decreases (FIG. 4). Fig. 4 (a) shows the ease of attachment of foreign matter by examining (c)).
It was found that the particles easily adhered during "dipping" and "during liquid holding" in FIG. 4 (b).

Accordingly, an object of the present invention is to provide an improved foreign matter adhesion preventing method for preventing foreign matter adhesion during "immersion".

[Means for solving the problem]

The above object is achieved by increasing the wettability of a surface. The wettability refers to the wettability of the liquid on the surface of the substrate with respect to the liquid, and is quantitatively represented by the contact angle θ of the liquid droplet 8 generated when the liquid is dropped as shown in FIG. The smaller the contact angle, the greater the wettability. As will be described later, when the contact angle is about 40 ° or less, there is an effect of preventing adhesion of foreign matter, but this value varies depending on the type of the substrate, the environment, and the like, and is not limited to 40 ° or less.

Especially in the process of manufacturing electronic components such as semiconductor devices, thin film devices and disks, thermal oxide films,
Oxide films such as CVD oxide films are often exposed, and the surface of these oxide films usually has low wettability. That is, adhesion of foreign matter is likely to occur. Increasing the wettability can prevent foreign matter from adhering. Further, as described later, the oxygen content of the surface portion of the oxide film is related to the wettability, and the wettability increases as the content increases.

A method for increasing the wettability or increasing the oxygen content of the oxide film surface layer is to perform plasma treatment of a gas containing chlorine gas on the oxide film surface. The gas used
Cl ₂ gas alone or a mixed gas with an inert gas such as Ar can be used. The plasma processing apparatus generates plasma at a high frequency (preferably 10 kHz or more) as is usually performed, and removes a portion serving as a metal contamination source close to the substrate surface such as a chamber wall so as not to contaminate the wafer by sputtering. Those having a structure covered with a quartz plate are preferred. In addition, by incorporating the above-described plasma processing unit into an ion implantation apparatus, a chemical vapor deposition (CVD) apparatus, and a dry etching apparatus, if the apparatus can simultaneously perform foreign matter adhesion prevention processing, the throughput in a semiconductor manufacturing process and the like can be increased. be able to.

The present invention is effective for an oxide film, but is also applicable to a case where the wettability of a resist coating film or the like is poor.

(Operation)

Regarding the surface wettability and the easiness of adhesion of foreign matter, see, for example, IEICE Technical Report Vol. 89 (1989), No. 5
As stated on the page, it was known that it was very effective, but it was not specified whether it was `` dipping '' adhesion, `` holding in liquid '' adhesion or `` pulling up '' adhesion, and foreign matter is difficult to adhere It is not clear why.

As a result of detailed studies, the present invention has revealed for the first time that adhesion during "immersion" can be prevented by increasing the wettability of the surface. Further, the relationship between the wettability of the substrate surface and the adhesion during "immersion" can be estimated from FIG. That is, as shown in FIG. 6 (a), when the wettability of the surface of the substrate 6 is small, the foreign matter 9 receives the surface tension F _S from the liquid 10 as shown by a broken line, and the resultant force F as shown by a solid line. It is considered that a force approaching No. 6 is likely to be attached to the substrate. In contrast, the resultant force F is foreign matter 9 acts away from the substrate 6 when FIG. 6 (b) greater wettability shown in the surface tension F _S of the liquid 10 is considered less likely to adhere to the substrate 6 .

Next, the relationship between the magnitude of wettability (contact angle) and the adhesion of foreign matter was examined. Prepare Si wafers with different surface wettability, and place 1 × polystyrene standard particles in liquid tank 5 as shown in FIG.
After immersion in ultrapure water 5a in which 10 ⁸ particles / cm ^{3 were} dispersed, it was pulled up and dried, and the number of adhered particles was measured by an optical microscope. In the figure, (a) shows the state before immersion, (b) shows the state after immersion, and (c) shows the state after pulling up. Table 1 shows the obtained results. At a contact angle of about 40 ° or less, almost no extraneous matter was observed.
The range of the contact angle where almost no extraneous matter is seen is considered to vary depending on the type of substrate, environment, immersion speed, etc.
It is not limited to 40 mm or less.

It is considered that the resistance of the thermal oxide film, the CVD oxide film, and the like is determined by the oxygen content of the surface layer, that is, the ratio of Si to O, unless the surface is contaminated with an organic substance or the like.
The ratio of Si to O in the oxide film surface layer can be controlled by plasma treatment of a gas containing chlorine gas.

 The above points were confirmed by experimental data.

Samples shown in Table 2 were prepared, and a change in the ratio of Si to O in the oxide film surface layer was measured by an X-ray photoelectron spectroscopy (ESCA or XPS) apparatus using a Cl ₂ plasma treatment or an Ar sputtering apparatus. The contact angle, which is an index of wettability, was measured by a contact angle meter.

 Table 3 shows the obtained results.

The values of the content ratio of Si to O (O / Si) in the oxide film surface layer are all 2.0 or more (that is, the surface is more O-rich than SiO ₂ ). This is because it contains O ₂ adsorbed as a result. In Cl ₂ plasma treatment sample No.2 is estimated that Cl radical attacks the Si in Cl ₂ plasma treatment, the untreated sample No.1
As a result, the surface is O-rich as a result. The contact angle of this sample No.2 is 48 ° compared to the untreated sample No.1
It is 22 mm, greatly increasing wettability. That is, by increasing the oxygen content of the oxide film surface layer,
It can be said that the wettability increases.

In the Ar sputtering process, O has a higher sputtering efficiency than Si, and as a result, the oxide film surface is richer in Si in Ar sputtering sample No. 3 than in untreated sample No. 1. The contact angle of this sample No. 3 was 51 ° compared to 48 ° of the untreated sample No. 1, and the wettability was small. That is, it can be said that the wettability is reduced by decreasing the oxygen content of the oxide film surface layer.

From the above study, it has been clarified that the wettability changes depending on the ratio of Si and O in the surface layer, and that the wettability can be increased by increasing the oxygen content. Also. It was found that Cl ₂ plasma treatment was effective in increasing the oxygen content of the surface layer and increasing the wettability.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1 As shown in FIG. 1, a thermal oxide film 2 was formed on a Si substrate 1 and subjected to Cl ₂ plasma treatment a for 2 minutes. The Cl ₂ plasma treatment condition is a Cl ₂ flow rate of 3 to 10 sccm (standard cubic centimet).
er per minutes), Ar flow rate 100sccm, pressure 10 ~ 100mtor
r, RF power 15-300W (13.56MHz), substrate bias -70V
It is.

A Cl ₂ plasma-treated substrate and an untreated substrate (a substrate that has not been subjected to plasma treatment after forming a thermal oxide film) are
As shown in the figure, 1 × 10 ⁸ polystyrene standard particles / cm ³
It was immersed in the dispersed ultrapure water 5a. The polystyrene standard particles used had a particle size of 2 μm, 1 μm, 0.5 μm, 0.1 μm.
m, 0.05 μm. However, in the case of 0.05 μm, an appropriate amount of sodium dodecyl sulfate was added as a surfactant so that the particles did not aggregate. After immersion, spinner drying was performed, and the number of adhered polystyrene standard particles was measured with an optical microscope or an electron microscope. In the untreated substrate as a comparative example, there was not much difference in the number of adhesions depending on the particle diameter, and as shown in Table ^4, adhesion was about 1.6 × 10 ⁴ / cm ² (average value of data at each particle diameter). In contrast, the sample No. 1
10 Most deposited by Cl ₂ plasma treatment substrates was observed.

The number of foreign substances adhered to the untreated substrate did not change even when the immersion time in the liquid was changed. In other words, it is considered that the foreign matter adhered not at the time of holding in the liquid but at the time of immersion.
Also, after adding hydrochloric acid to ultrapure water in which polystyrene particles are dispersed so as to have a pH of about ₂ , the Cl ₂ plasma-treated substrate was immersed and the number of foreign particles adhered was measured. Was found to increase. That is, it is shown that the adhesion during "holding in the liquid" occurs even when the wettability is high, and it is concluded that the high wettability is effective in preventing the adhesion during "dipping".

In the range of the plasma processing conditions studied in this example, as shown in Table 4, the contact angle was 21 to 29 °, and the effect of preventing foreign matter adhesion was sufficient. Therefore, the range of effective plasma processing conditions of the present invention is considered to be wider.

Example 2 As shown in FIG. 2, a thermal oxide film 2 was formed on a Si wafer 1, and a hole 3 was formed by lithography. Cl ₂ plasma treatment a was performed under the same conditions as in Example 1. A Cl ₂ plasma-treated substrate and an untreated substrate as a comparative example were immersed in ultrapure water in which polystyrene standard particles were dispersed in the same manner as in Example 1, dried with a spinner, and adhered using an optical microscope or an electron microscope. The number of polystyrene standard particles was measured. Table 5 shows the results. As can be seen from this table, 1 × 10 ⁴ /
While the adhesion of about ² cm ² was observed, the sample N of the present example
Almost no adhesion was observed on the Cl ₂ plasma treated substrates of o.

[Effects of the Invention] According to the present invention, adhesion of minute foreign matter can be prevented, and thus there is an effect of improving the yield in the manufacturing process of semiconductor devices, thin film devices, disks, and the like.

[Brief description of the drawings]

1 and 2 show one embodiment of the present invention, respectively, and are cross-sectional views showing a substrate processing state, and FIG. 3 is a process diagram showing an experimental method for confirming the effect of the present invention. 4, 5, and 6 illustrate the principle of the present invention, respectively, and show a process diagram of a fine particle adhesion process, a schematic diagram of a contact angle for explaining wettability, a wettability of a substrate, and a foreign matter in a liquid. FIG. 4 is a schematic diagram for explaining a mechanism of adhering. DESCRIPTION OF SYMBOLS 1 ... Si substrate, 2 ... Thermal oxide film 3 ... Pore, 4 ... Si wafer 5 ... Liquid tank 5a ... Ultra pure water in which polystyrene particles are dispersed 6 ... Si wafer semiconductor device, thin film device , Electronic substrate such as disk 7... Liquid containing foreign matter, 8... Droplet 9... Foreign matter, 10... Liquid a... Plasma treatment, θ.

────────────────────────────────────────────────── (5) References JP-A-62-250645 (JP, A) JP-A-62-117330 (JP, A) JP-A-63-133534 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 21/304 H01L 21/302

Claims (2)

(57) [Claims] In the process of manufacturing an electronic component, an oxygen content of a surface layer portion of an oxide film formed on a substrate constituting a part of the component is increased to increase wettability of the substrate surface. A method for preventing foreign matter from adhering to the substrate. 2. The method according to claim 1, further comprising a step of performing a Cl ₂ plasma treatment as a method for increasing the oxygen content of the surface layer of the oxide film formed on the substrate.