CN104034296A - Detection method for thickness of monocrystalline silicon surface scratch damaged layer - Google Patents

Abstract

A detection method for the thickness of a scratch damage layer on the surface of single crystal silicon, the steps are: A, cutting out a single crystal silicon sample on a single crystal silicon wafer polished by chemical mechanical polishing, scanning it with an atomic force microscope, Obtain the three-dimensional morphology of the surface of the single crystal silicon sample, and measure the depth of the depression; B. Place the single crystal silicon sample in an HF solution with a mass fraction of 15-25% and etch it for 20-40 minutes, and take out the single crystal silicon The sample is cleaned with acetone and alcohol in sequence, and then scanned with an atomic force microscope to obtain the three-dimensional surface morphology of the etched single crystal silicon sample, and measure the depth of the depression; C. The depression depth obtained in step B and the The depression depths at the corresponding positions are subtracted, and the increased value of the depression depth after etching is obtained, which is the thickness of the scratch damage layer on the surface of the single crystal silicon. The sample preparation and detection process of the method is simple, the detection time is short, the required sample material is small, the detection cost is low, and the detection result is accurate and intuitive.

Description

A detection method for the thickness of the scratch damage layer on the surface of single crystal silicon

technical field

The invention relates to a method for detecting the thickness of a scratch damage layer on the surface of single crystal silicon.

Background technique

Since the invention of semiconductor integrated circuits, monocrystalline silicon materials have become the main material for manufacturing micro-nano electromechanical systems due to their abundant resources, excellent physical and chemical properties, and good compatibility with microelectronic integrated circuit processes. Therefore, research on micro-nano-fabrication based on single crystal silicon has attracted much attention.

At present, due to the rapid development of high integration and high performance of semiconductor products, unprecedented requirements are placed on the quality of the processed surface of single crystal silicon. For example, as the line width of large-scale integrated circuits continues to decrease and develops towards three-dimensional structures and multilayer wiring, the surface of large-scale wafers is required to have nanometer-level surface accuracy and sub-nanometer surface roughness, and at the same time it is necessary to ensure Very high surface/subsurface integrity. Traditional surface planarization techniques, such as heat flow method, selective deposition, low pressure CVD, plasma enhanced CVD, etc., are local planarization techniques and cannot achieve global planarization. In 1990, IBM took the lead in proposing CMP (chemical mechanical polishing, chemical mechanical polishing) global planarization technology, and it was successfully applied in 64M DRAM production in 1991. After that, CMP developed rapidly. Current research shows that CMP polishing technology is the most effective method to ensure that the single crystal silicon wafer finally obtains a nano-scale ultra-smooth surface.

However, at present, in the process of wafer CMP polishing, due to the influence of many factors such as human operation, process, processing equipment, etc., damages such as micro scratches, micro cracks, dislocations, and surface defects on the material surface often occur. These damaged parts have different physical and chemical properties from other regions, and too thick a damaged layer will often increase the difficulty of subsequent processes and even directly lead to the scrapping of devices. Therefore, the detection and evaluation of the thickness of the surface/subsurface damage layer of single crystal silicon materials is a key problem that needs to be solved urgently in the process of practical application.

At present, the detection techniques for the surface/subsurface damage layer of single crystal silicon materials mainly include X-ray diffraction (XRD) and transmission electron microscopy (TEM).

X-ray diffraction (XRD): This method uses X-rays to irradiate the surface of the silicon wafer at a certain angle, and the diffraction phenomenon will occur. The position of the diffraction fringe will change due to the difference in the lattice spacing, and then compare whether there is residual stress or not. The change value of the lattice spacing can calculate the magnitude of the residual stress and calculate the thickness of the damaged layer. The X-ray diffraction method can only measure the comprehensive stress within a certain depth on the surface of the material, and there are great differences in the residual stress of the same sample and the same area measured by different types of X-rays. Therefore, the surface/subsurface of the single crystal silicon material measured by this method The thickness error of the damaged layer is large.

Transmission Electron Microscope (TEM): Utilize the high-resolution characteristics of TEM (up to 0.2nm) to directly image the lattice structure. This method is suitable for analyzing lattice defects, and can directly observe the morphology of defects and analyze the composition of defects, etc. However, the electron beam is used as the light source in the transmission electron microscope, and the penetrating power of the electron beam is very weak, so the sample needs to be made into an ultra-thin section with a thickness of about 50 nanometers. This makes the sample making process very complicated and lengthy.

In summary, the existing detection methods for the damage thickness of the surface/subsurface of single crystal silicon materials have defects such as poor detection accuracy and difficulty in sample preparation to varying degrees. It is urgent to develop a high-precision damage detection method that is easy to operate.

Contents of the invention

The purpose of the present invention is to provide a detection method for the thickness of the scratch damage layer on the surface of single crystal silicon, the method can easily detect the thickness of the damage layer on the surface/subsurface of single crystal silicon after chemical mechanical polishing, and its sample preparation detection process Simple, short detection time, small sample material required, low detection cost and accurate and intuitive results.

The technical scheme adopted by the present invention to realize the purpose of the invention is: cut out a 2 mm × 2 mm to 5 mm × 5 mm single crystal silicon sample on the single crystal silicon wafer polished by the chemical mechanical polishing method, and use an atomic force microscope to analyze the single crystal silicon sample Scan to obtain the three-dimensional topography of the surface of the single crystal silicon sample, and measure the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample;

B. Place the monocrystalline silicon sample in an HF solution with a mass fraction of 15-25% and etch for 20-40 minutes, take out the monocrystalline silicon sample and wash it with acetone and alcohol in sequence, then scan it with an atomic force microscope to obtain an etched The three-dimensional topography of the surface of the single crystal silicon sample, and measure the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample;

C. Subtract the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step B from the depth of depression at the corresponding position in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step A to obtain the depth of depression after etching Increased value; the increased value of the depth of the depression is the thickness of the scratch damage layer on the surface of the single crystal silicon.

The process and mechanism of the present invention are: cut the sample piece from the wafer polished by the chemical mechanical polishing method, and scan it with an atomic force microscope to obtain the three-dimensional topography of the surface of the single crystal silicon sample, and measure the depth of the depression therein. The depth is the scratch depth of single crystal silicon during polishing. Then use HF solution to etch the single crystal silicon sample for 20-40 minutes, the scratched damaged part will be completely etched away, and then use the atomic force microscope to scan to obtain the three-dimensional morphology and etching of the surface of the single crystal silicon sample after etching The depth of the depression after etching; the depth of depression after etching minus the corresponding depression depth before etching is the thickness of the damaged layer of single crystal silicon during polishing.

Compared with prior art, the beneficial effect of the present invention is:

1. It only needs to cut a small piece of 2mm×2mm to 5mm×5mm from the single crystal silicon wafer polished by chemical mechanical polishing method as a test sample. The sample preparation is simple and the required sample material is small.

2. Use the atomic force microscope to scan the single crystal silicon sample before and after etching respectively to obtain the recess depth and its difference of the single crystal silicon sample before and after etching, so as to conveniently detect the surface/sub-surface of the single crystal silicon during the polishing process. Surface scratch damage layer thickness. The whole detection process is simple, all carried out under normal temperature and normal pressure environment, without special environment such as vacuum, constant temperature, constant humidity, etc., and the detection cost is low; there are no obvious interference and error factors in the detection process, and the detection results are accurate and reliable; The surface morphology and its depressions can be directly obtained by scanning with an atomic force microscope. The detection results are intuitive and the accuracy is as high as 0.01nm.

3. Short detection time, 20-40 minutes of etching time plus a very short scanning time can complete the entire detection; it will not cause delays to the subsequent process progress of monocrystalline silicon.

The present invention will be described in further detail below in conjunction with accompanying drawing and specific embodiment

Description of drawings

Fig. 1a is a three-dimensional topography diagram of the single crystal silicon sample in Example 1 before etching.

Fig. 1b is a three-dimensional topography diagram of the monocrystalline silicon sample in Example 1 after etching.

Fig. 1c is a surface contour map obtained from the three-dimensional topography map in Fig. 1a.

Fig. 1d is a surface contour map obtained from the three-dimensional topography map in Fig. 1b.

Fig. 2a is a three-dimensional topography diagram of the single crystal silicon sample in Example 2 before etching.

Fig. 2b is a three-dimensional topography diagram of the monocrystalline silicon sample in Example 2 after etching.

Fig. 2c is a surface profile diagram obtained from the three-dimensional topography diagram in Fig. 2a.

Fig. 2d is a surface contour map obtained from the three-dimensional topography map in Fig. 2b.

Fig. 3a is a three-dimensional topography diagram of the single crystal silicon sample in Example 3 before etching.

Fig. 3b is a three-dimensional topography diagram of the monocrystalline silicon sample of the third embodiment after etching.

Fig. 3c is a surface profile diagram obtained from the three-dimensional topography diagram in Fig. 3a.

Fig. 3d is a surface profile diagram obtained from the three-dimensional topography diagram in Fig. 3b.

Fig. 4a is a three-dimensional topography diagram of the single crystal silicon sample in Example 4 before etching.

Fig. 4b is a three-dimensional topography diagram of the monocrystalline silicon sample of the fourth embodiment after etching.

Fig. 4c is a surface profile diagram obtained from the three-dimensional topography diagram in Fig. 4a.

Fig. 4d is a surface contour map obtained from the three-dimensional topography map in Fig. 4b.

Detailed ways

Embodiment one

A detection method for the thickness of a scratch damage layer on a single crystal silicon surface, the steps are:

A. Cut out a 3mm×3mm monocrystalline silicon sample from a monocrystalline silicon wafer polished by chemical mechanical polishing, scan the monocrystalline silicon sample with an atomic force microscope, and obtain the three-dimensional morphology of the surface of the monocrystalline silicon sample, see Figure 1a; and the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of depression was measured to be 2nm, as shown in Figure 1c.

B. Place the monocrystalline silicon sample in HF solution with a mass fraction of 20% for etching for 30 minutes, take out the monocrystalline silicon sample and wash it with acetone and alcohol in sequence, and then scan it with an atomic force microscope to obtain the etched single crystal The three-dimensional topography of the surface of the silicon sample is shown in Figure 1b; the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the measured depth of the depression was 32nm, as shown in Figure 1d.

C. Subtract the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step B from the depth of depression at the corresponding position in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step A to obtain the depth of depression after etching Increased value; the increased value of the depth of the depression is the thickness of the scratch damage layer on the surface of the single crystal silicon. The measured thickness of the damaged layer = 30(32-2) nm, which belongs to moderate damage.

Embodiment two

A detection method for the thickness of a scratch damage layer on a single crystal silicon surface, the steps are:

A. Cut out a 4mm×4mm monocrystalline silicon sample from a monocrystalline silicon wafer polished by chemical mechanical polishing, scan the monocrystalline silicon sample with an atomic force microscope, and obtain the three-dimensional morphology of the surface of the monocrystalline silicon sample, see Figure 2a; and the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 58nm, as shown in Figure 2c.

B. Place the monocrystalline silicon sample in HF solution with a mass fraction of 25% for etching for 25 minutes, take out the monocrystalline silicon sample and wash it with acetone and alcohol in sequence, and then scan it with an atomic force microscope to obtain the etched single crystal The three-dimensional topography of the surface of the silicon sample is shown in Figure 2b; the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 96nm, as shown in Figure 2d.

C. Subtract the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step B from the depth of depression at the corresponding position in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step A to obtain the depth of depression after etching Increased value; the increased value of the depth of the depression is the thickness of the scratch damage layer on the surface of the single crystal silicon. The measured thickness of the damaged layer = 38 (96-58) nm, which belongs to moderate damage.

Embodiment Three

A detection method for the thickness of a scratch damage layer on a single crystal silicon surface, the steps are:

A. Cut out a 5mm×5mm monocrystalline silicon sample from a monocrystalline silicon wafer polished by chemical mechanical polishing, scan the monocrystalline silicon sample with an atomic force microscope, and obtain the three-dimensional morphology of the surface of the monocrystalline silicon sample, see Figure 3a; and the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 126nm, as shown in Figure 3c.

B. Place the monocrystalline silicon sample in HF solution with a mass fraction of 15% for etching for 40 minutes, take out the monocrystalline silicon sample and wash it with acetone and alcohol in sequence, and then scan it with an atomic force microscope to obtain the etched single crystal The three-dimensional topography of the surface of the silicon sample is shown in Figure 3b; the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 156nm, as shown in Figure 3d.

C. Subtract the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step B from the depth of depression at the corresponding position in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step A to obtain the depth of depression after etching Increased value; the increased value of the depth of the depression is the thickness of the scratch damage layer on the surface of the single crystal silicon. The measured thickness of the damaged layer = 30 (156-126) nm, which belongs to moderate damage.

Embodiment Four

A detection method for the thickness of a scratch damage layer on a single crystal silicon surface, the steps are:

A. Cut out a 2mm×2mm monocrystalline silicon sample from a monocrystalline silicon wafer polished by chemical mechanical polishing, scan the monocrystalline silicon sample with an atomic force microscope, and obtain the three-dimensional morphology of the surface of the monocrystalline silicon sample, see Figure 4a; and the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 133nm, as shown in Figure 4c.

B. Place the monocrystalline silicon sample in HF solution with a mass fraction of 20% for etching for 20 minutes, take out the monocrystalline silicon sample and wash it with acetone and alcohol in sequence, and then scan it with an atomic force microscope to obtain the etched single crystal The three-dimensional topography of the surface of the silicon sample is shown in Figure 4b; the depth of the depression in the three-dimensional topography of the surface of the single crystal silicon sample was measured, and the depth of the depression was measured to be 303nm, as shown in Figure 4d.

C. Subtract the depth of depression in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step B from the depth of depression at the corresponding position in the three-dimensional topography of the surface of the single crystal silicon sample obtained in step A to obtain the depth of depression after etching Increased value; the increased value of the depth of the depression is the thickness of the scratch damage layer on the surface of the single crystal silicon. The measured thickness of the damaged layer = 170 (303-133) nm, which belongs to severe damage.

Claims (1)

1. a detection method for monocrystalline silicon surface scratch damage layer thickness, the steps include:

On A, monocrystalline silicon wafer crystal after chemical mechanical polishing method polishing, cut out the monocrystal silicon sample of 2mm × 2mm to 5mm × 5mm, use atomic force microscope to scan monocrystal silicon sample, obtain the three-dimensional appearance on monocrystal silicon sample surface, and measure the cup depth in the three-dimensional appearance on monocrystal silicon sample surface;

B, monocrystal silicon sample is positioned over to etching 20-40 minute in the HF solution that massfraction is 15-25%, after taking-up monocrystal silicon sample also cleans successively with acetone, alcohol, re-using atomic force microscope scans, obtain the three-dimensional appearance on the monocrystal silicon sample surface after etching, measure the cup depth in the three-dimensional appearance on this monocrystal silicon sample surface;

C, the cup depth that B is walked to corresponding position in the three-dimensional appearance that cup depth in the three-dimensional appearance on the monocrystal silicon sample surface obtaining and A walk the monocrystal silicon sample surface obtaining subtract each other, and obtain cup depth added value after etching; This cup depth added value is monocrystalline silicon surface scratch damage layer thickness.