KR19980029062A - Wafer cleaning method - Google Patents

Abstract

The present invention provides a wafer cleaning method, which facilitates the development of a device having high reliability by removing particles and inorganic substances generated by side reactions when a nitride film is deposited on a silicon substrate by a sequential cleaning process using hydrofluoric acid and ammonia. However, there is an effect that can prevent the defocus phenomenon in the mask operation of the subsequent process.

Description

Wafer cleaning method

The present invention is suitable for a wafer cleaning method for removing particles generated by side reactions during nitride film deposition.

Generally, in order to develop a highly integrated memory device, a high density nitride film is essentially used. When the high density nitride film is deposited on a silicon substrate, powder (NH ₄ Cl) is also generated as a side reaction. In other words, the two gases used for depositing the nitride film are 3SiCl ₂ H ₂ and 4NH ₃ .

Formula 1 ₃ SiCl ₂ H ₂ + 4NH ₃ → Si ₃ N ₄ + 6HCl + 6H ₂

3 SiCl ₂ H ₂ + 10 NH ₃ → Si ₃ N ₄ + 6 NH ₄ Cl + 6 H ₂

It can be seen that in the above formula 1, 3SiCl ₂ H ₂ and 4NH ₃ gas react to form a nitride film as underlined. However, in addition to the reaction of Equation 1, it can be seen that another reaction as in Equation 2 occurs. 3SiCl ₂ H ₂ and 10NH ₃ gas react to generate powder (6NH ₄ Cl) in addition to the nitride film (Si ₃ N ₄ ). As described above, when the nitride film is formed, a large amount of bonds are contained on the nitride film due to particles such as unwanted powder. In order to remove the powder (NH ₄ Cl), a cleaning method using ultra pure water (DI Water) was conventionally performed. There is a problem that particles and inorganic matter remaining in the phase cannot be removed effectively.

It is an object of the present invention to provide a wafer cleaning method capable of removing particles and inorganic substances generated by side reactions during deposition of a nitride film by a hydrofluoric acid and ammonia cleaning process.

The cleaning method of the present invention for realizing the above object comprises the steps of forming a nitride film on a silicon substrate, and performing a hydrofluoric acid cleaning step to remove particles generated by side reactions when forming the nitride film from the step; Performing a first rinse treatment on the silicon substrate from the step, performing an ammonia washing process to remove inorganic substances caused by side reactions when forming the nitride film from the step, and performing a second rinse on the silicon substrate from the step The process is performed.

Referring to the wafer cleaning method according to the invention in detail as follows.

First, in order to form a nitride film, gases of 2SiCl ₂ H ₂ and 4NH ₃ are reacted according to the above formula (1). At this time, as a side reaction, particles such as powder (6NH ₄ Cl) and the like are formed on the entire surface of the silicon substrate according to the above-described formula 2, and the inorganic material also forms on the entire surface of the silicon substrate. In this way, the following cleaning process is performed to remove particles and inorganic substances formed on the silicon substrate.

First, using a mixed solution of HF: pure water (H ₂ O) in a silicon substrate at 1:45 to 55 days, perform a hydrofluoric acid washing process at room temperature (25 ° C) for 20 to 40 seconds, and then use ultra pure water (DI Water). The first rinse treatment is performed sequentially for 8 to 12 minutes. At this time, as the nitride film of the silicon substrate is etched with a thickness of approximately 5 to 10Å, particles such as powder remaining on the surface of the nitride film are removed.

Next, a temperature of 70 to 80 ° C. was obtained by using a mixed solution in which a ratio of ammonium hydroxide (NH ₄ OH): hydrogen peroxide (H ₂ O ₂ ): pure water (H ₂ O) was 1: 4: 15 to 25 on a silicon substrate. Under the conditions, the ammonia washing process is performed for 8 to 12 minutes, and then the second rinse treatment is sequentially performed for 8 to 12 minutes using ultrapure water. At this time, the inorganic material remaining on the nitride film surface of the silicon substrate is removed.

As described above, according to the present invention, it is easy to develop a device having high reliability by removing particles and inorganics generated by side reactions when depositing a nitride film on a silicon substrate by a sequential cleaning process using hydrofluoric acid and ammonia, as well as subsequent processes. There is a superb effect that can prevent the defocus phenomenon when working with the mask.

Claims (4)

A method of cleaning a wafer, comprising: forming a nitride film on a silicon substrate, and performing a hydrofluoric acid cleaning process to remove particles generated by side reactions when forming the nitride film from the step, and from the step to the silicon substrate. Performing a first rinse treatment, performing an ammonia washing process to remove inorganic substances generated by side reactions when forming the nitride film from the step, and performing a second rinse treatment on the silicon substrate from the step. Wafer cleaning method comprising a. The wafer cleaning method according to claim 1, wherein the hydrofluoric acid cleaning step is performed at room temperature for 20 to 40 seconds using a mixed solution having a ratio of HF: pure 1:45 to 55. The method of claim 1, wherein the first and second rinse treatments are performed for 8 to 12 minutes using ultrapure water. According to claim 1, wherein the ammonia washing step is carried out for 8 to 12 minutes at a temperature of 70 to 80 ℃ using a mixed solution of the ratio of ammonium hydroxide: hydrogen peroxide: pure water 1: 4: 15 to 25. Wafer cleaning method.