Method for detecting heavy boron doping defects

Abstract

The present application relates to a kind of methods for detecting heavy boron defect, the technical field of silicon wafer processing, comprising the following operating steps: first step: heavy boron monocrystalline silicon rod line cut silicon wafer according to every 50 in the middle extraction 1 is formed first piece.Pilot step two: to first piece double side grinding once chamfer and single side grinding is carried out second chamfer.Third step: second chamfer is carried out alkali etching.Fourth step: first piece is placed in the cleaning tank with HCL and H2O2 mixture and is cleaned.Fifth step: after drying, the surface defect of silicon wafer is checked using fluorescent lamp.Sixth step: the first piece of detection qualified is carried out double side polishing.Seventh step: after polishing, it is cleaned using tank washer.Eighth step: it is carried out single side polishing.Ninth step: the silicon wafer after single side polishing is again returned to alkali etching.Tenth step: after drying, the surface defect of silicon wafer is checked using fluorescent lamp.Exclude the scratch influence brought by mechanical processing, improve the accuracy of detection, avoid the problem of existing heavy boron defect detection method detection misjudgment.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer processing technology, and more specifically to a method for detecting heavily boron-doped defects. Background Technology

[0002] Heavy boron-doped Czochralski silicon single crystals are an important silicon material with advantages such as uniform resistivity distribution, strong gettering ability, and good mechanical properties. They are widely used in integrated circuit substrate materials and discrete device fields. Typically, a thin layer of material is epitaxially grown on a heavily doped substrate to form a P / P+ structure. When integrated circuit technology shrinks to the submicron and deep submicron level, even micro-defects close to the process linewidth can affect the yield and electrical performance of the device.

[0003] Heavy boron-doped single crystals have high doping concentrations and large lattice distortions, making them prone to dislocations and small-angle grain boundaries during crystal growth, especially when the impurity concentration is higher than 7 × 10⁻⁶. 19 cm -3 At that time, they are concentrated in a certain position on the crystal cross section in a certain form.

[0004] Currently, the detection of defects in 300mm heavily boron-doped single-crystal silicon wafers involves visually inspecting the surface condition of the sample under a fluorescent lamp after selective etching. This method can detect defects with high and relatively concentrated defect density, but it is difficult to detect defects such as dislocation arrays, small-angle grain boundaries, and slip lines. These defects are often mistaken for scratches after wire cutting on a macroscopic scale. Summary of the Invention

[0005] This invention primarily addresses the shortcomings of existing technologies by providing a method for detecting heavily boron-doped defects. It solves the problem of false detections of line defects, such as dislocation arrays, slip lines, and small-angle grain boundaries, in heavily boron-doped single-crystal silicon wafers. By employing a pre-wafer mode and a two-stage alkaline etching method, the influence of scratches from machining is effectively eliminated, improving detection accuracy and avoiding misjudgments in existing heavily boron-doped defect detection methods.

[0006] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions:

[0007] A method for detecting heavily boron-doped defects includes the following steps:

[0008] Step 1: After wire-cutting heavily boron-doped single crystal silicon rods, silicon wafers are randomly selected from every 50 rods to form pilot wafers.

[0009] Step 2: Perform a chamfer on the pre-cut sheet. The chamfering process is done by double-sided grinding with a 3000-grit grinding wheel. After double-sided grinding, a single-sided grinding is performed with an 8000-grit grinding wheel. The single-sided grinding is then used for a second chamfer.

[0010] Step 3: After secondary chamfering, alkali etching is carried out. The silicon wafer is placed in an alkali solution tank, and alkali etching is carried out using a KOH solution with a mass concentration of 45±5%.

[0011] Step 4: The preliminary wafer is put into a cleaning tank, and HCL with a mass concentration of 0.5-0.7% and H2O2 with a concentration of 0.3-0.8% are added to the tank for cleaning.

[0012] Step 5: After cleaning and drying, the surface defects of the silicon wafer are inspected with a fluorescent lamp. If obvious "well" defects are seen on the surface, it is directly judged as NG. If there are no "well" defects, it is normally transferred. Silicon wafers with defect aggregation can be detected well.

[0013] Step 6: The qualified preliminary wafers are polished on both sides.

[0014] Step 7: After polishing, a tank-type washing machine is used for cleaning.

[0015] Step 8: Single-sided polishing is carried out, and the removal amount of single-sided polishing is 1um.

[0016] Step 9: The silicon wafer after single-sided polishing returns to alkali etching again, and alkali etching is carried out using a KOH solution with a mass concentration of 45±5% for a thickness of 5um.

[0017] Step 10: After cleaning and drying, the surface defects of the silicon wafer are inspected with a fluorescent lamp. If there are filamentous fine lines on the surface, record the position and reconfirm with a laser microscope. If defects appear, the preliminary wafer is judged as scrapped. If there are no defects, it is judged as qualified.

[0018] For line defects with a small defect density, due to the influence of scratches generated by mechanical processing, they cannot be completely detected. After the silicon wafer is polished on both sides and single-sided, the scratches and grinding wheel marks on the surface of the silicon wafer are ground off by the polishing cloth. If there are still filamentous fine lines on the surface after re-alkali etching, it means that this defect is a through-hole defect, that is, a crystal defect generated during the growth of heavily boron-doped single-crystalline silicon. This situation can be confirmed with a laser microscope.

[0019] Preferably, the resistivity of the heavily boron-doped single-crystalline silicon rod is less than 0.003Ω.cm.

[0020] Preferably, during the alkali etching process, the temperature of the KOH solution is controlled at 75±5°C, the circulation flow rate is controlled at 10-15L / min, and the preliminary wafer is etched by 10um.

[0021] Preferably, double-sided polishing uses a polishing cloth to remove 14.5um thickness of the preliminary wafer.

[0022] The present invention can achieve the following effects:

[0023] This invention provides a method for detecting defects in heavily boron-doped silicon wafers. Compared with existing technologies, it solves the problem of false detection of line defects such as dislocation arrays, slip lines, and small-angle grain boundaries in heavily boron-doped single-crystal silicon wafers. The method employs a pre-wafer mode and a two-stage alkaline etching process, which effectively eliminates the influence of scratches from machining, improves the accuracy of detection, and avoids the misjudgment problems of existing methods for detecting defects in heavily boron-doped silicon. Detailed Implementation

[0024] The technical solution of the invention will be further described in detail below through examples.

[0025] Example: A method for detecting heavily boron-doped defects, comprising the following steps:

[0026] Step 1: After wire-cutting heavily boron-doped monocrystalline silicon rods, one wafer is randomly selected from every 50 rods to form the lead wafer. The resistivity of the heavily boron-doped monocrystalline silicon rod is less than 0.003 Ω·cm.

[0027] Step 2: Perform a chamfer on the pre-cut sheet. The chamfering process is done by double-sided grinding with a 3000-grit grinding wheel. After double-sided grinding, a single-sided grinding is performed with an 8000-grit grinding wheel. The single-sided grinding is then used for a second chamfer.

[0028] Step 3: After the second chamfering, alkaline etching is performed. The silicon wafer is placed in an alkaline bath and etched with a 45% KOH solution. During the alkaline etching process, the KOH solution temperature is controlled at 75℃, the circulation flow rate is controlled at 12.5L / min, and the wafer is etched to a depth of 10µm.

[0029] Step 4: Place the pre-washed tablets into the cleaning tank, add 0.6% HCl and 0.55% H2O2 to the tank, and clean them.

[0030] Step 5: After cleaning and drying, use a fluorescent lamp to check for defects on the surface of the silicon wafer. If obvious "well" defects are seen on the surface, it is directly judged as NG. If there are no "well" defects, it can be processed normally.

[0031] Step 6: The qualified pre-coated wafers undergo double-sided polishing. Double-sided polishing uses a polishing cloth to remove 14.5µm of thickness from the pre-coated wafer.

[0032] Step 7: Clean with a trough-type cleaning machine after polishing.

[0033] Step 8: Perform single-sided polishing, removing 1µm of material.

[0034] Step 9: After single-sided polishing, the silicon wafer is returned to alkaline etching, and a thickness of 5µm is etched using a KOH solution with a mass concentration of 45±5%.

[0035] Step 10: After cleaning and drying, check the surface defects of the silicon wafer with a fluorescent lamp. If there are filamentous fine lines on the surface, record the position and reconfirm it with a laser microscope. If defects appear, determine that the pilot wafer is scrapped; if there are no defects, determine it as qualified.

[0036] In summary, the method for detecting heavy boron doping defects solves the problem of misdetection of line defects such as dislocation rows, slip lines, and small-angle grain boundaries in heavily boron-doped single-crystalline silicon wafers. By adopting the pilot wafer mode and the two-step alkali etching method, the influence of scratches caused by mechanical processing can be well eliminated, the detection accuracy is improved, and the problem of misjudgment in the existing heavy boron doping defect detection method is avoided.

[0037] The above are only specific embodiments of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for detecting heavily boron-doped defects, characterized in that... The operation steps are as follows: Step 1: After wire cutting the heavily boron-doped monocrystalline silicon rod, one silicon wafer is selected from every 50 wafers to form a preliminary wafer; Step 2: Perform a primary chamfer on the preliminary wafer. For chamfer processing, double-sided grinding is carried out using a 3000-mesh grinding wheel, followed by single-sided grinding using an 8000-mesh grinding wheel after double-sided grinding, and a secondary chamfer is performed during single-sided grinding; Step 3: After the secondary chamfer, perform alkali etching. The silicon wafer is placed in an alkali solution tank, and alkali etching is carried out using a KOH solution with a mass concentration of 45±5%; Step 4: Place the pre-washed tablets into the cleaning tank, and add 0.5-0.7% HCl and 0.3-0.8% H2O to the tank. 2, Perform cleaning; Step 5: After cleaning and drying, check the surface defects of the silicon wafer using a fluorescent lamp. If obvious "well" defects are seen on the surface, directly judge it as NG. If there are no "well" defects, it will flow normally; Step 6: Perform double-sided polishing on the qualified preliminary wafers; Step 7: After polishing, clean using a tank-type washing machine; Step 8: Perform single-sided polishing with a removal amount of 1um; Step 9: The silicon wafer after single-sided polishing returns to alkali etching again, and alkali etching is carried out using a KOH solution with a mass concentration of 45±5% for a thickness of 5um; Step 10: After cleaning and drying, check the surface defects of the silicon wafer using a fluorescent lamp. If there are filamentous fine lines on the surface, record the position and reconfirm it using a laser microscope. If defects appear, judge the preliminary wafer as scrapped. If there are no defects, judge it as qualified.

2. The method for detecting heavily boron-doped defects according to claim 1, characterized in that: The resistivity of the heavily boron-doped monocrystalline silicon rod is less than 0.003Ω.cm.

3. The method for detecting heavily boron-doped defects according to claim 1, characterized in that: During the alkali etching process after the secondary chamfer, the temperature of the KOH solution is controlled at 75±5℃, the circulation flow rate is controlled at 10 - 15L / min, and the preliminary wafer is etched by 10um.

4. The method for detecting heavily boron-doped defects according to claim 1, characterized in that: Double-sided polishing uses a polishing cloth to remove a thickness of 14.5um from the preliminary wafer.