Method for removing crystallites from silicon wafer surface

FIELD: semiconductor device manufacture; silicon-wafer surface post-oxidation etching, boron and phosphor sublimation.

SUBSTANCE: proposed method for removing crystallites from silicon wafer surface includes pre-oxidation of wafer surface in oxygen environment at temperature of 850 °C for 20 minutes followed by chemical treatment in hydrofluoric acid and ammonium fluoride solution, proportion of ingredients being 1 : 6.

EFFECT: provision for complete removal of crystallites from silicon wafer surface after heat treatment, reduced wafer treatment time.

1 cl

 

The invention relates to the technology of manufacturing semiconductor devices, in particular to the process of etching the surface of a silicon wafer after surgery: oxidation, distillation boron justify phosphorus. On the surface of the semiconductor wafer after the above operations are observed education in the form of a Mat on the appearance of dark spots and holes under a microscope. This type of defect is called crystallites, and they are caused by the formation of irregular shape crystals.

There are many solutions, acids, alkalis used in technologies for removal of various types of defects on the surfaces of semiconductor wafers. One is to provide the Etchant selective Circle [1], used to detect and remove various types of defects: dislocations, stacking faults, lemon slices.

Known to provide the Etchant another [1], which consists of the following components: hydrofluoric acid (HF), nitric acid (HNO3) and acetic acid (CH3COOH), used for the removal of the crystallites in the ratio 3:5:3. The removal time is 45 minutes. The total number of defects is equal to 300÷10000 units/cm2.

The main disadvantage of the used etching agents is that they do not provide complete removal of the crystallites with the surface of the wafer, does not give the possibility of obtaining exactly who, undisturbed surface and process for a long time.

The aim of the invention is the complete removal of the crystallites on the surface of the plate after carrying out thermal processes and reducing the time of processing plates.

This goal is achieved by conducting a preliminary low-temperature oxidation at a temperature of 850°From the surface of the silicon wafer and then etching in a chemical solution to remove the crystallites.

A chemical solution is picked up by experimental data and consists of the following components: hydrofluoric acid (HF) and ammonium fluoride (NH4F) in the ratio of 1:6, and optimal chemical process (20 minutes) to complete removal of the crystallites.

The essence of the method lies in the fact that a cassette of semiconductor wafers are loaded into a diffusion furnace and incubated in oxygen atmosphere with a flow rate of oxygen 15 l/H. Then after unloading conduct the process of chemical treatment. Next, a silicon wafer overload in a clean cassette and washed in deionized water and carry out the drying process in a nitrogen atmosphere. Control cleaning is performed under a focused beam of light. To do this, choose from the party control plate using vacuum tweezers and count the number of luminous points, and for whom adscita defects, which include the crystallites, choose the working magnification in the range of 100-400x.

Next, determine the diameter of the field of view of the microscope (D) for which:

1) set the object micrometer on the object table of the microscope and bring sharpness;

2) count the number of whole divisions of the scale, keeping in diameter;

3) multiply the number of divisions on the scale interval of the object micrometer 1×10-3cm;

4) determine the area (S cm2vision eyepiece according to the formula:

Then on the control plates count the number of defects.

EXAMPLE 1

Semiconductor wafer is loaded into a diffusion furnace and incubated in oxygen atmosphere with a flow rate of oxygen 15 l/h, at a temperature of 850°C for 20 minutes. Then after unloading was in the process of chemical treatment for 15 min in a solution of hydrofluoric acid and ammonium fluoride in a ratio of 1:6. Next, the silicon wafers were loaded into a clean cassette and washed in deionized water. The drying process was conducted in a nitrogen atmosphere. Control of cleaning was carried out under the focused beam of light. The number of defects on the test plate was 130 units/cm2.

The proposed method of removal of the crystallites with the application process preliminary low-temperature Oka the population and etching in selected chemical solution can reduce the time of carrying out the process. This way you can completely remove the crystallites with the surface of the wafer, enables to obtain a smooth, unbroken surface, which allows to increase the percentage of output devices, as well as to improve the quality of surface diffusion and epitaxial structures.

Literature

1. Suhotra. Technology microelectronic devices. Moscow, Radio I Svyaz, 1991, str.

Method of removing grains from the surface of a silicon wafer, including chemical processing, characterized in that the plate surface is pre-oxidized in oxygen atmosphere at a temperature of 850°C for 20 min, and then chemical processing is carried out in a solution of hydrofluoric acid and ammonium fluoride in a ratio of 1:6.



 

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