JPH05136115A - Method for preserving semiconductor substrate - Google Patents

Abstract

PURPOSE:To eliminate the contamination of semiconductor wafers due to a molecular organic matter by maintaining the wafers in the atmosphere of an organic solvent so that the surfaces of the wafers can hold hydrophilic properties until the wafers are fed to the succeeding process after the wafers are subjected to a substrate washing process. CONSTITUTION:This method for preserving semiconductor substrates is used for maintaining semiconductor wafers in the atmosphere of an organic solvent until the wafers are fed to the succeeding manufacturing process after the wafers are subjected to a substrate washing process. Namely, by immediately placing the semiconductor wafers which have been treated with H2SO4, H2O2 and HNO3 and washed with water in the atmosphere of an organic solvent or the vapor of the organic solvent, contamination of the wafers by the adhesion of a molecular organic matter is eliminated. Therefore, since the water repellency of the wafers caused by a molecular organic contaminant can be eliminated, the occurrence of hazes, water marks, etc., caused by the water repellency can be eliminated and the manufacturing yield of semiconductor elements can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for protecting a semiconductor substrate from molecular organic matter contamination. The integration of semiconductor integrated circuits has advanced, and LSI and VLSI have been put into practical use, but this was achieved by miniaturizing the semiconductor region, conductor lines, electrodes, etc. that make up the semiconductor element, and currently has the smallest pattern. It has been put to practical use up to a width of less than 1 μm (submicron).

Since the contamination of a semiconductor substrate (hereinafter referred to as a semiconductor wafer) greatly affects the manufacturing yield as the integration progresses in this way, this cleaning is an essential matter.

[0003]

2. Description of the Related Art Contamination factors for semiconductor substrates include
Contamination with dust particles, contamination with inorganic ions, contamination with molecular organic substances, etc.

Here, the contamination by dust has been solved by carrying out the work in a clean room, and the progress of filters has made it possible to remove fine particles of 0.1 μm or more at present.

[0005] As for the sodium ion (N
a ⁺⁾ and chlorine ions (Cl ^-) ions noticeable effect on characteristics of a semiconductor element such as generated from a human body in the form of perspiration, also the alkali ions or halogen ions adhering to the materials used Therefore, it is necessary to use a carefully selected material and use dustproof clothing to prevent the diffusion together with dust.

[0006] Regarding the above, in addition to the fact that it is released in the form of fat from the human body, the air supplied to the clean room through the filter contains various types. That is, phosphorus- and fluorine-based organic substances, siloxane, butyl acetate, toluene, xylene, etc. are suspended in the supply air in a molecular form.

Of these, solvents such as butyl acetate are used in the manufacturing process, so the solvent vapor diffuses and floats in the air. This is taken in from the air supply pipe and supplied to the clean room through the filter. ing.

That is, semiconductor elements are manufactured in a clean room, and dust in the air is filtered by a filter, and dust, fat, Na ⁺ , C generated by the human body when wearing dustproof clothing.
l ^- although treatment to prevent contamination is applied due special interrupt method for molecular organic substances suspended in the air is not taken.

When the molecular organic substance adheres to the semiconductor wafer, it becomes water repellent, which causes partial peeling of the resist spin-coated on the semiconductor wafer. Haze is generated in the material coated on the semiconductor wafer. Water marks on materials applied on semiconductor wafers
Produces a (Water-mark watermark). There are problems such as disconnection of wiring, defective conductivity, and breakdown voltage.

Therefore, as a means to prevent this, a semiconductor wafer sliced from an ingot to a thickness of about 500 μm and surface-polished and cleaned is stored in a nitrogen (N ₂ ) box until the manufacturing process. Although it prevents atmospheric pollution due to organic substances and alkali ions, it is not sufficient and water repellency cannot be avoided.

[0011]

Although semiconductor devices are manufactured in a clean room, the filter provided in this clean room can prevent the intrusion of dust. There is no such means.

Therefore, there is a problem that the semiconductor wafer becomes water repellent during storage. Therefore, the problem is to prevent water repellency.

[0013]

The above problem is to keep the surface of the substrate hydrophilic by keeping the semiconductor wafer after the substrate cleaning process in an organic solvent atmosphere until it is subjected to the subsequent manufacturing process. As a feature, it can be solved by configuring a method for storing a semiconductor substrate.

[0014]

The present invention eliminates the occurrence of water repellency due to the adhesion of molecular organic substances by immediately maintaining the surface of the obtained semiconductor wafer in an organic solvent or solvent vapor.

That is, most of the organic solvents utilize the characteristic that they have a dissolving action for molecular organic substances and do not react with the semiconductor wafer. In addition, most organic solvents have a low boiling point, so that they have the advantage that they are easier to dry than when washed with water.

Conventionally, the thickness is 500 μ than the ingot.
Sulfurized wafers are sliced to about m and polished.
(H ₂ SO ₄ ) dipping and hydrogen peroxide (H ₂ O ₂ ) dipping are sequentially performed to remove organic substances adhering to the surface, and then nitric acid (HNO ₃ )
The metal components adhering to the surface are removed by immersion.

After washing with water and storing in a N ₂ box, it was unavoidable that water repellency would occur over time. The inventor is H ₂ SO ₄
As a result of observing the state of occurrence of water repellency on the Si wafer after the —H ₂ O ₂ —HNO ₃ treatment, the following facts were found. When a Si wafer is left in a clean room, it exhibits water repellency in about one day, and the contact angle when water drops are 40.8 °. This contact angle remains in the range of 41 ° to 45 ° even if left for one week. There is.

Here, the contact angle θ is θ = 2 × tan ⁻¹ (when the water drop radius is dmm and the height from the center of the water drop surface to the apex is hmm when the water drop is dropped on the substrate. h / d) ····· It can be obtained from the relational expression of (1). If the Si wafer is immersed in an organic solvent such as butyl acetate, acetone, benzene, ethyl ether, heptane, and acetophenone, it does not exhibit water repellency and can maintain a clean surface state. The same applies to the case of holding the Si wafer in the vapor of the Si wafer, which does not exhibit water repellency and can maintain a clean surface state. When a Si wafer is dipped in alcohol, for example, isopropyl alcohol, it is hydrophilic and does not show water repellency for about one full day, but when left for more than one day, it shows a contact angle of about 8.5 °.

However, by washing with pure water, the original hydrophilic state can be immediately returned. The same applies when the Si wafer is left in alcohol vapor, for example, isopropyl alcohol vapor. Placed in a clean room to show water repellency
The Si wafer does not become hydrophilic even if it is washed with pure water. (
The Si wafer that has become water-repellent can be returned to the hydrophilic state by acid cleaning (eg H ₂ SO ₄ ) or alkali (eg NH ₄ OH).

Here, it is not clear why the contact angle of about 8.5 ° is exhibited when immersed in alcohol and allowed to stand for one day or more.
It is thought that the chemical adsorption occurs due to orientation on the Si wafer surface.

From the above, the present invention provides H ₂ SO ₄ --H ₂ O ₂ --HN
By subjecting the semiconductor wafer, which has been subjected to O ₃ treatment and washed with water, to an atmosphere of an organic solvent or an organic solvent vapor immediately, the contamination due to the adhesion of molecular organic substances is eliminated.

Although the above is performed for the Si wafer,
The same applies to a wafer of a single semiconductor such as Ge or a compound semiconductor such as GaAs or InP.

[0023]

[Examples] Example 1: After the H ₂ SO ₄ —H ₂ O ₂ —HNO ₃ treatment and the washing with water, a Si wafer with a thickness of about 500 μm was dipped in a benzene solution for the device formation process. I left it until I called it.

As a result of examining the pulled-up wafer, it was hydrophilic, it was impossible to measure the contact angle, and no contamination of molecular organic matter was observed. Example 2: After the H ₂ SO ₄ —H ₂ O ₂ —HNO ₃ treatment and the washing with water, the Si wafer having a thickness of about 500 μm was kept on acetone kept at 50 ° C. to form an acetone atmosphere. Keep it
It was left to stand until the device formation process.

Since the pulled wafer was hydrophilic, it was impossible to measure the contact angle, and no contamination of molecular organic matter was observed. Example 3: H ₂ SO ₄ —H ₂ O ₂ —HNO ₃ treatment, washing with water, washing a Si wafer with a thickness of about 500 μm was dipped in isopropyl alcohol and allowed to stand until the device formation process. I saved it.

As a result of measuring the contact angle of this wafer, the contact angle was 8.5 °, but as a result of washing with pure water, it returned to its original hydrophilicity and the contact angle could not be measured. It was

[0027]

By implementing the present invention, the water repellency due to the contamination of molecular organic substances can be eliminated, so that the generation of haze, watermark, etc. due to the water repellency is eliminated, and the manufacturing yield of semiconductor elements is improved. Is achieved.

Claims (1)

[Claims] 1. A method for preserving a semiconductor substrate, characterized in that the substrate surface is made hydrophilic by keeping the semiconductor wafer after the substrate cleaning treatment in an organic solvent atmosphere until it is subjected to the subsequent manufacturing process. ..