JPH09213675A - Fabrication of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fabricating a semiconductor device in which production of water mark can be prevented surely without requiring any special cleaning/drying equipment. SOLUTION: An oxide film 2 is deposited on a silicon substrate 1 arid a resist pattern 3 is formed thereon. Ashing is then performed using oxygen plasma within such range as the quantity of resist to be ashed will be 1-100nm and the surface of a resist pattern 7 is activated to provide hydrophilicity. Subsequently, wet etching is performed and a wafer is dried while turning by means of a spin drier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for preventing a watermark after immersion treatment such as wet etching and pure water cleaning.

[0002]

2. Description of the Related Art A conventional general semiconductor wafer cleaning process in a semiconductor device manufacturing process will be described with reference to FIGS. The cleaning process shown here is an example of a cleaning step after wet etching.

As shown in FIG. 3A, first, an oxide film 2 (SiO ₂ ) is formed on a silicon substrate 1, and a resist pattern 3 is formed thereon.

Next, as shown in FIG. 3B, a wet etching process using hydrofluoric acid (HF) is performed using the resist pattern 3 as a mask to form the resist pattern 3.
The oxide film 2 in the portion not covered with the is removed. On this occasion,
Since the surface of the resist is usually hydrophobic and the wettability of the etchant 4 (etching liquid) on the wafer surface is poor, in order to obtain sufficient wettability, ammonium fluoride (NH ₄ F) may be added to hydrofluoric acid. Depending on the case, a surfactant is further added. As a result, the etchant 4 and the material to be etched are in uniform contact with each other to proceed with etching, and the silicon substrate 1 is exposed in the portion where the resist pattern 3 does not exist.

After the etching is completed, the hydrofluoric acid (including additives) attached to the surface of the wafer is replaced with pure water.
Wash with pure water. FIG. 4C is a diagram showing a state in which the wafer is lifted from the water washing tank after cleaning. As shown in this figure, since the surface of the resist pattern 3 and the exposed surface of the silicon substrate 1 are both hydrophobic, hemispherical water droplets 5a and 5b are formed by surface tension. Then, by rotating the wafer using, for example, a spin dryer, the water drops 5a and 5b are removed by centrifugal force. However, although the water droplets 5a placed on the resist pattern are completely removed, the water droplets 5b attached to the sidewalls of the patterns or entering between the patterns cannot be completely removed.

[0006]

Therefore, as shown in FIG. 4C, when the subsequent processing is performed with the water droplet 5b remaining on the side portion of the oxide film 2 as shown in FIG. 4C, as shown in FIG. , Water drop 5b
The remaining part changes to hydroxide, or water drops 5
A so-called watermark is generated, which is a trace of precipitation of impurities contained in b. As a result, even if the subsequent processing is advanced, it will be a defective product as a semiconductor product.

Techniques for preventing this kind of watermark are disclosed in JP-A-6-196465 and JP-A-7-6616.
No. 8 publication and the like. JP-A-6-196465
The cleaning device described in Japanese Patent Publication is a combination of a conventional rotary spray cleaning device and a conventional immersion cleaning device. A plurality of processing chambers are connected in series to sequentially transfer wafers while spraying the chambers. Since cleaning is performed using a nozzle and the wafer is not pulled up into the air, no watermark is generated. In addition, Japanese Patent Application Laid-Open
The technique described in Japanese Patent No. 66168 is a method and an apparatus for performing drying by cleaning a pure water and then rotating the wafer in an IPA (isopropyl alcohol) gas atmosphere.

However, the former requires a plurality of processing chambers and a wafer transfer mechanism / rotation mechanism, and the latter requires an IPA gas supply mechanism / recovery mechanism.
In any case, the above-mentioned technique has a large defect that the device structure is complicated, the equipment cost is enormous, and a special device must be used for cleaning and drying.

The present invention has been made to solve the above problems, and provides a method for manufacturing a semiconductor device capable of reliably preventing the generation of a watermark without using a special cleaning / drying device. The purpose is to do.

[0010]

In order to achieve the above-mentioned object, a method of manufacturing a semiconductor device according to the present invention comprises a step of immersing a substrate on which a resist pattern is formed in a liquid and then pulling the substrate out of the liquid and drying it. In a method of manufacturing a semiconductor device having a step of performing a ashing process with oxygen plasma on a substrate having a resist pattern formed thereon before immersing the substrate in a liquid, the surface of the resist is activated to have hydrophilicity. It is characterized by keeping it.

More specifically, for example, when a resist pattern is formed on an oxide film on the surface of a silicon substrate and a wet etching process is performed using the resist pattern as a mask, the resist pattern is scraped after the resist pattern is formed. It is advisable to activate the surface of the resist to make it hydrophilic by performing ashing treatment with oxygen plasma to the extent that it does not affect the pattern accuracy, and then perform wet etching treatment, and then pull the substrate out of the etchant and dry it. . At that time, it is desirable to set the ashing amount of the resist in the range of 1 to 100 nm.

Generally, since the resist and the substrate are hydrophobic, when the resist is immersed in a liquid without any treatment and then pulled up, water drops adhere to the surface of the resist or the surface of the substrate. After that, even if the substrate is rotated for drying, for example, not all the water droplets can be removed, and some water droplets remain depending on the place. Then, the mechanism of water mark generation is that a hydroxylation reaction occurs at a place where water drops are present, impurities or dissolved substances contained in the water drops are deposited, and the traces thereof locally remain. Therefore,
The greater the amount of water remaining as water droplets, the more impurities and the like contained therein, and the more severe the watermark becomes.

On the other hand, in the present invention, since the surface of the resist is activated and made hydrophilic by performing the ashing treatment with oxygen plasma, when the resist is immersed in the liquid and pulled up, the resist surface is not exposed. A thin continuous layered water film is formed instead of water droplets. Therefore,
After that, even if the substrate is rotated for drying, the water film is removed while being continuously moved to the outside of the substrate by the centrifugal force, so that water is not locally left and the watermark is prevented. You can In addition, since the water content remains in a thin layer and the volume of the water is smaller than when it remains in the form of water droplets, the drying by evaporation is fast and the amount of impurities contained in the water is small. Contribute to the prevention of.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a method of manufacturing a semiconductor device according to the present embodiment, and is a process flow diagram showing a step of performing a wet etching process on an oxide film on a silicon substrate using a resist as a mask.

As shown in FIG. 1A, a silicon substrate 1
An oxide film 2 (SiO ₂ ) having an arbitrary thickness is formed on a (wafer), and a resist pattern 3 is formed thereon by a known method.
To form At this time, the film thickness of the deposited resist is, eg, about 1200 nm.

Next, as shown in FIG. 1 (b), a light ashing process using oxygen plasma is performed to change the surface of the resist pattern 7 to a moderately rough state, so-called active state, from hydrophobic to hydrophilic. Change. At this time, the conditions are set so that the resist ashing amount is 1 to 100 nm. Specifically, for example, a single-wafer plasma ashing device is used, and the condition is a pressure of 1.5 Tor.
r, O ₂ gas flow rate 150 sccm, RF power 400 W, 8
The ashing time is 5 seconds and the ashing time is 10 seconds.

When the ashing amount of the resist is less than 1 nm, the surface of the resist is not activated and remains hydrophobic. Then, as described as the conventional technique,
When the oxide film is wet-etched and washed with pure water, water remains in the form of water droplets, which causes water marks. The resist ashing amount is 100
If the thickness is not less than nm, the resist is excessively scraped and the pattern accuracy is affected, resulting in a large error in the finished dimension of the oxide film after etching. Therefore, it is necessary to set the ashing amount of the resist within the range of 1 to 100 nm.

Next, as shown in FIG. 1C, a wet etching process is performed using the resist pattern 7 as a mask and using a mixed solution of hydrofluoric acid (HF) and ammonium fluoride (NH ₄ F) as an etchant. Then, the oxide film 2 in the portion not covered with the resist pattern 7 is removed.

After the etching is completed, pure water cleaning is performed in order to replace the etchant adhering to the wafer surface with pure water so as to completely stop the etching. FIG.
(D) is a diagram showing a state in which the wafer is pulled out from the water washing tank after cleaning. Since the surface of the resist 7 is activated and hydrophilic due to the light ashing treatment,
As shown in this figure, a thin continuous layered water film 8 is formed on the surface of the resist 7. Further, since the oxide film 2 is also hydrophilic, the water film 8 attached on the surface of the resist 7 is continuously covered up to the side portion of the oxide film 2.

Then, as shown in FIG. 2E, the water film 8 is removed by centrifugal force by rotating the wafer using, for example, a spin dryer. At this time, since the water film 8 is adhered in a thin layer form from the surface of the resist 7 to the side of the oxide film 2 and the surface tension is not acting, the water film 8 is continuously moved to the outside of the wafer by the centrifugal force during rotation. As it is removed, water is completely removed without locally remaining.

According to the present embodiment, the light ashing treatment is applied to the resist to make it hydrophilic, so that the water content after the pure water cleaning is completely removed and the water content does not remain locally. Can be prevented. Also,
Water remains in a thin layer, and the volume of water is smaller than when it remains in the form of water droplets, so drying due to evaporation is fast and the amount of impurities contained in water is small, etc. Contribute. As described above, in the present method, since only the light ashing step is added before cleaning, it is possible to implement the watermark prevention measure without using a special cleaning / drying device which requires a high equipment cost. Furthermore, since the wettability is improved by making the surface of the resist hydrophilic, the wet etching process itself has good uniformity.

The technical scope of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the present invention is applied to the step of wet etching the oxide film on the silicon substrate, but the present invention can be applied to any step of immersing the wafer in the state where the resist pattern is attached. it can.

[0023]

As described above in detail, in the method for manufacturing a semiconductor device of the present invention, the substrate is immersed in the liquid by making the surface of the resist hydrophilic by using the ashing treatment with oxygen plasma. After that, the water content does not remain in the form of water drops, and the watermark can be prevented. Further, in this method, since only the ashing process is added before the immersion, it is possible to implement the watermark prevention measure without using a special cleaning / drying device which requires a high equipment cost.

[Brief description of drawings]

FIG. 1 is a process flow chart showing a step of performing wet etching processing on an oxide film on a silicon substrate according to an embodiment of the present invention.

FIG. 2 is a process flow diagram of the same.

FIG. 3 is a process flow diagram showing a step of performing wet etching processing on an oxide film on a silicon substrate in a conventional method.

FIG. 4 is a process flow diagram of the same.

[Explanation of symbols]

 1 Silicon Substrate 2 Oxide Film 3 Resist Pattern 4 Etchant 5a, 5b Water Drop 6 Watermark 7 Resist Pattern 8 Made Hydrophilic

Claims (3)

[Claims] 1. A method for manufacturing a semiconductor device, which comprises a step of immersing a substrate on which a resist pattern is formed in a liquid, and then pulling the substrate out of the liquid and drying the substrate, wherein the substrate on which the resist pattern is formed is immersed in the liquid. A method of manufacturing a semiconductor device, characterized in that the surface of the resist is activated to have hydrophilicity by subjecting the substrate to ashing treatment with oxygen plasma. 2. A method of manufacturing a semiconductor device, comprising the steps of forming an oxide film on a silicon substrate, forming a resist pattern on the oxide film, and then wet etching the oxide film using the resist pattern as a mask. In the above, after forming the resist pattern, the surface of the resist is activated to be hydrophilic by ashing treatment with oxygen plasma to such an extent that the abrasion of the resist pattern does not affect the pattern accuracy, and then wet etching is performed. After the treatment, the substrate is pulled out from the etching liquid and dried, which is a method for manufacturing a semiconductor device. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the ashing amount of the resist in the ashing process is set in the range of 1 to 100 nm.