Method for cleaning parts, primarily semiconductor wafers

FIELD: semiconductor microelectronics; high-degree surface cleaning technologies.

SUBSTANCE: proposed method can be used in resource and energy conservation environmentally friendly and safe technology for integrated circuit manufacture, removal of positive photoresist from wafer surface, electrochemical etching of silicon, and degreasing of surfaces. Si surface is cleaned by detergent NH4HF2 of 0.1 - 4 M concentration activated by ozone at anode current density of 1 - 2 kA/m2, and waste solution is cleaned and activated by sequentially passing it through electrolyzer cathode and anode chamber.

EFFECT: enhanced quality and effectiveness of photoresist removal from semiconductor surface.

2 cl, 2 dwg

 

The invention relates to the production technology of semiconductor devices, in particular to a method of cleaning the surface of semiconductor wafers from the photoresist (AF), and may find application in the production processes of different classes of devices: discrete (diodes, transistors, varicaps are given, varactors etc), as well as integrated circuits (ICS) different classes and technology (MOS, CMOS, bipolar, and others).

Removal of photoresist from the surface of the PP is widely used various methods: physical (low-temperature oxygen plasma) and chemical degradation of polymers in mixtures of mineral acids) [1].

The essence of the physical method is the oxidation of FC in the atmosphere previously ionized gas at elevated temperature in plants under oxygen atmosphere at a pressure of 400-600 PA and in conditions of high-frequency electromagnetic fields power of about 1 kW. High-frequency electromagnetic field generated by the inductor, ionizes the gas in the chamber occurs glow discharge and plasma is formed is a mixture of ions. High-frequency field and the bombardment of the substrate with ions of oxygen are heated them up to 150-200°C. However, this method has some significant drawbacks. First, oxidation of the cleaned surface of PP, which necessitates removal of the formed oxide film. Secondly, the oxidation of the cleaned surface is ti causes the need for additional stages of purification. Thirdly, the emergence of a under the action of high-frequency fields and high voltage induction of charges in the oxide. Fourthly, it is expensive, precision equipment.

Typical chemical cleaning method PP includes the following operations:

1. Processing in a mixture of Karo H2SO4K. + H2O2K, at +120-150°

2. Rinsing in deionized water at room temperature

3. Processing in HF 0.5%

4. Processing in deionized water at room temperature

5. Processing in a mixture of NH4OH/O2H2/H2O in a ratio of 0.05:1:5 at 80°

6. Processing in deionized water

7. Steam treatment

8. Processing in deionized water

9. Processing in a mixture of HCl/H2O2/H2O in the ratio 1:1:6 at 80-90°

10. Processing in deionized water at room temperature

11. Processing in HF 0.5%

12. Processing in deionized water.

Major drawbacks are:

1. High aggressiveness of stain,

2. Their toxicity,

3. The difficulty neutralizing waste solutions

4. The difficulty of regeneration of etching solutions,

5. Large costs of the used reagents,

6. Instability in time of oxidizing ability of the mortar,

7. The need for heating pickling solution.

The closest t the political essence and the achieved result is a chemical method [2], which in return consistently applied two stages of purification in mixtures of Caro and peroxide-ammonia solutions offers cleaning detergents sulfuric acid concentration of from 3 M to 7 M, the electrochemically activated nadzornye acids in anodic current density of from 3 to 4.3 kA/m2and the voltage on the electrolytic cell 3 to 5 C. the Activated cleaning solution is supplied to the tub for processing PP, and the spent solution is sequentially sent to re-activate and clean the cell. In opposition to the method of cleaning the surface of the PP of the photoresist was performed at room temperature. Significant disadvantages of the opposable method are:

1. the destruction of the surface of the substrate, a drain that leads to the surface relief and the detection of hidden defects of the semiconductor, which has a negative effect on electrical parameters, which degrades the quality of the instruments,

2. oxidation cleared from the photoresist to the silicon surface, resulting in the need to remove akiskal film.

An object of the invention is to improve the quality and efficiency of removal of FP from the surface of the PP, the creation of resource-saving, environmentally friendly and safe technologies scrubbing PP of plates.

The technical result, which can be is obtained by implementing the invention, is that the cleaning of the surface of PP Si lead detergent solution NH4HF2activated by ozone in the anode current density 1-5 kA/m2exhaust solution is cleaned and activated by filing it in series across the cathode and anode chamber of the electrolyzer. Cleaning the surface of the PP Si concentrated detergent 6 m solution of NH4HF2activated by ozone leads to the destruction of the OP photoresistive polymer film and the oxide film. Cleaning the surface of the PP Si detergent diluted solutions (1-0 .1 M, preferably 0.1 M) NH4HF2removes FP and cures structural defects and compacts the oxide film.

Example 1.

A semiconductor silicon wafer with photoresist was placed in a working bath PTFE. Here comes the cleaning solution 30-40% of NH4HF2activated by ozone in the anode chamber of the electrolytic cell with an anode current density of 1-5 kA/m2. The cleaning process is carried out at room temperature for 20 minutes.

Analysis of the surface quality PP silicon was carried out by the following methods: IR, AUGER spectroscopy, as well as visually under a microscope by successive observations of the bright and dark fields with 200x magnification. Graph 1 shows the IR spectrum of the silicon surface: curve - with photoresist before processing, curve O after processing, as the prototype curve X after processing of the proposed method.

Conclusively shows that the OP is completely removed after the treatment by the proposed method, namely in the washing solutions of NH4HF2activated by ozone. Important distinctive features of the prototype, a sign is the fact that the cleaning solution NH4HF2activated ozone, removes not only the photoresist, and silicon oxides. The IR spectrum of the Si surface after the treatment by the proposed method there are no absorption bands at frequencies 1100 cm-1- SiO and the absorption band at a frequency of 3400 cm-1- stretching vibrations of hydroxyl groups Si and water.

Thus, the processing of PP Si photoresist proposed method, namely detergent solution NH4HF2activated ozone, allows you to combine the stage of removal of the photoresist and the stage of removal of the oxide in a single phase.

Example 2.

Semiconductor wafer Si photoresist is placed in the working bath PTFE. Here comes the cleaning solution NH4HF2(c concentration from 1 to 0.1 N), activated by ozone in the anode chamber of the electrolytic cell with an anode current density of 1-5 kA/m2. The cleaning process was performed at room temperature.

Figure 2 Dan IR spectrum of the surface of the wafer with the PT and SiO2courtesy of "Angstrom", when you have washed the given curve About - 1 M NH4HF2curve X 0.1 M NH4HF2curve - original sample. The time of washing - 15 minutes. See that in dilute solutions of NH4HF2activated by ozone, not only removed photoresistive polymer film, but there is a growth of the oxide film, which is indicated by the increase in the intensity of absorption bands with the frequency of stretching vibrations 1030-1040 cm-1. Note that the half-width of the absorption of Si-O links is equal to Δω1/2=80 cm-1that is typical of quite dense and relatively perfect thermally grown oxide. Processing Si PP with AF in solutions of NH4HF2+O3leads to reduction of porosity, as Δω1/2=72 cm-1because the line is narrowed due to the sealing of the oxide film, and healing of structural defects.

Obviously, active oxygen (radical) penetrates through the pores, chemically associated with broken bonds Si-O.

Thus, the wet cleaning in diluted solutions of NH4HF2+O3does not result in surface topography and the detection of hidden defects PP, adversely affect the electrical parameters of the devices.

Thus, the use of this together: a solution of NH4HF2activated ozone is the main distinctive feature of predlagaemoj the invention and a significant advantage over the known technology of wet cleaning Si PP from the photoresist.

SOURCES of INFORMATION

1. Ugoltsev, Ashkenazi. The surface treatment technology in microelectronics. Kiev, Technology, 1990.

2. Higaonna, Leschyshyn and other Method of cleaning products, mainly semiconductor wafers. Patent RU 2024993, H 01 L 21/312.

3. Senri Ojima, Kazuki Kubo, Masayuki Kato, Masayuki Toda, Tadahiro Ohmi. Megasonic Excited Ozonated Water for the Cleaning of Silicon Surfaces. J. Eiectrochem. Soc., V.144, No4, P.1482-1487.

1. The method of cleaning products, mainly semiconductor wafers, including the effect on the surface of Si pre-activated solutions, cleaning and activation of the cell by successive feed it through the cathode and anode chamber of the electrolytic cell, characterized in that on the Si surface with the exposed photoresist with a solution of NH4HF2concentrations from 0.1 M to 4 M, activated ozone at an anode current density of 1-2 kA/m2, clearing and activating the spent solution NH4HF2carried out in the electrolytic cell by successive flows through the cathode and anode chambers.

2. The method according to claim 1, characterized in that on the Si surface with the exposed photoresist diluted from 1 M to 0.1 M NH4HF2(preferably, 0.1 M).



 

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