Device for rapidly measuring wafer roughness

Abstract

The utility model relates to a device for rapidly measuring wafer roughness. The device comprises a base, a tray, a light source and a CCD image sensor, the tray is installed on the base, the light source is installed on the tray, the CCD image sensor is located above the center of the tray, the light source is composed of a shell, a semiconductor laser and a cylindrical lens, the semiconductor laser is connected with the cylindrical lens, the shell wraps the semiconductor laser, and the cylindrical lens is connected with the semiconductor laser. The cylindrical lens is exposed on one side; the semiconductor laser adopts an edge-emitting semiconductor laser, the vertical direction is a fast axis, and the horizontal direction is a slow axis; the cylindrical lens can collimate the laser emitted by the fast axis, so that the divergence angle of the laser emitted by the fast axis of the semiconductor laser is reduced. Compared with the prior art, the beneficial effects of the utility model are that the measuring speed is fast and the measuring precision is high.

Description

Technical Field

[0001] The utility model relates to the technical field of optical element processing and detection, and in particular to a device for quickly measuring wafer roughness and a use method thereof. Background Art

[0002] During semiconductor chip manufacturing, the surface of semiconductor silicon wafers (wafers) becomes uneven and produces unwanted surface material during processes such as etching and ion implantation. To reduce the roughness and unevenness of the wafer surface, remove unwanted material, and efficiently proceed to the next processing step, the wafer is polished multiple times on specialized equipment using a polishing pad and polishing fluid. This process is called CMP, or Chemical Mechanical Polishing (CMP). CMP is a key process technology for flattening the wafer surface and is the most mainstream wafer polishing technology today. After polishing, the wafer surface still has a certain degree of roughness. Excessive roughness can affect subsequent micromachining processes such as bonding and photolithography. This roughness can be measured using a roughness tester.

[0003] Surface roughness measurement methods can be broadly categorized into contact and non-contact methods. Contact methods include comparison, impression, and stylus methods. Non-contact methods include light sectioning, real-time holography, speckle pattern analysis, astigmatism, optical heterodyning, AFM, and optical sensors.

[0004] Among the above methods, the optical scattering method has the advantages of being contactless, non-destructive, and highly accurate. References [1], [2], and many other papers have conducted detailed research on this technology. Optosurf's WaferMaster wafer roughness measurement instrument is a wafer inspection instrument based on this technology. However, due to the use of a point light source and a point detector, a single measurement takes 30 seconds, which is slow for large-scale wafer inspection.

[0005] The invention patent with application number 202322022482.8 proposes a surface roughness detection device for optical components based on regional scattering. It uses LED for illumination and a planar array detector for detection, which improves the measurement speed to a certain extent. However, due to the use of a wide-spectrum LED light source and the scattering intensity is related to the wavelength of light, the measurement accuracy is not high.

[0006] In summary, the wafer inspection instruments in the prior art cannot guarantee high measurement speed and high measurement accuracy at the same time.

[0007] [1] Bram van Ginneken, Marigo Stavridi, and Jan J. Koenderink, "Diffuse and Specular Reflectance from Rough Surfaces," Appl. Opt. 37, 130-139(1998).

[0008] [2] Zheng Jia, Surface roughness measuring instrument using laser scattering method, Master’s thesis, 2007. Summary of the Invention

[0009] The purpose of this utility model is to provide a device for rapidly measuring wafer roughness. The basic scheme employs a slightly grazing-incidence monochromatic laser light source for illumination, and employs a uniform illumination scheme using multiple light sources to surround the surface, thereby improving measurement accuracy.

[0010] To achieve the above technical objectives, the present invention adopts the following technical solution: a device for rapidly measuring wafer roughness, comprising a base, a tray, a light source, and a CCD image sensor, wherein the tray is mounted on the base, the light source is mounted on the tray, and the CCD image sensor is located above the center of the tray. The light source is composed of a housing, a semiconductor laser, and a cylindrical lens.

[0011] Wherein: the semiconductor laser is connected to the cylindrical lens, the housing wraps the semiconductor laser, and the cylindrical lens is exposed on one side;

[0012] The semiconductor laser is an edge-emitting semiconductor laser, with the vertical direction being the fast axis and the horizontal direction being the slow axis;

[0013] The cylindrical lens can collimate the laser light diverging on the fast axis, so that the divergence angle of the laser light on the fast axis of the semiconductor laser is reduced;

[0014] Furthermore, the semiconductor laser has an emission cross-section of 0.1 mm×10 mm and emits laser light of a single wavelength of 405 nm, 450 nm, 532 nm, 650 nm, 660 nm, 1064 nm, 1330 nm, or 1550 nm.

[0015] Furthermore, after being collimated by the cylindrical lens (3-3), the laser light emitted by the semiconductor laser (3-2) has a divergence angle of 30 degrees on the fast axis and a divergence angle of 15 degrees on the slow axis.

[0016] Furthermore, the number of the light sources is greater than 3, and they are distributed at equal intervals around the center of the tray, and the light emitted by each light source can cover the entire wafer being inspected.

[0017] Furthermore, the light source is installed at an angle such that the incident light is incident in a grazing incidence manner.

[0018] Furthermore, the CCD image sensor is a visible light CCD image sensor or a near-infrared CCD image sensor.

[0019] Furthermore, the dynamic range of the CCD image sensor is 60–70 dB.

[0020] Furthermore, the material of the tray is metal, plastic, resin or carbon fiber whose reflectivity is reduced through surface processing.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] First, the present invention replaces a point light source with a parallel light-emitting semiconductor laser shaped by a cylindrical lens, and replaces a point detector with a CCD, significantly increasing detection speed. Detection with a point light source requires scanning the entire surface. For example, a single point detection takes 10 seconds. However, detecting the entire wafer requires 10 single point scans, which takes 100 seconds. The present invention can obtain results for the entire wafer in a single scan. For example, if a single scan takes 10 seconds, then detecting the entire wafer takes 10 seconds.

[0023] Second, the present invention uses multiple light sources for illumination, which is different from the single illumination of a point light source. Multiple light sources are necessary for surface light roughness detection, because if only one light source is used, it can only illuminate from a single direction, which can easily cause uneven illumination, different light intensities due to different distances, and surface topography affecting the measurement results. Using multiple light sources, similar to the uniform illumination result of a shadowless lamp, the illumination is uniform, and the surface topography has no obstruction to the illumination, which can improve the measurement accuracy.

[0024] Third, the emission form of the light source of the present invention is grazing incidence emission. The larger incident angle enhances scattering, making it easier to image defects and scratches on the wafer surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a three-dimensional structural diagram of a device for rapidly measuring wafer roughness according to Example 1;

[0026] Figure 2 for Figure 1 A side view of a device for rapidly measuring wafer roughness;

[0027] Figure 3 is a three-dimensional schematic diagram of a light source;

[0028] Figure 4 is a cross-sectional view of the light source;

[0029] Figure 5 This is the basic principle diagram of the utility model;

[0030] Among them, there are 1 base, 2 trays, 3 light sources, 4 CCD image sensors, 5 wafers, 3-1 light source housing, 3-2 cylindrical lenses, and 3-3 semiconductor lasers. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure. Example

[0032] refer to Figure 1 and Figure 2 , a device for quickly measuring wafer roughness of the present invention, includes a base 1, a tray 2, a light source 3 and a CCD image sensor 4, the tray 2 is mounted on the base 1, and the light source 3 is mounted on the tray 2; there are a total of 6 light sources 3, which are evenly spaced around the center of the tray in a circle, and the light emitted by each light source 3 can cover the entire wafer 5 to be inspected; the CCD image sensor 4 is located above the center of the tray 2 and is connected to the base 1 through a support arm.

[0033] CCD image sensor 4 is a visible light or near-infrared CCD image sensor with a dynamic range of 60–70 dB. Tray 2 is made of carbon fiber with surface processing to reduce reflectivity. The base is made of stainless steel to maintain stability with a low center of gravity. Tray 2 has an 8-inch diameter and accommodates 8-inch wafers.

[0034] refer to Figure 3 and Figure 4 The light source 3 is composed of a shell 3-1, a semiconductor laser 3-2 and a cylindrical lens 3-3. The semiconductor laser 3-2 is connected to the cylindrical lens 3-3. The shell 3-1 wraps the semiconductor laser 3-2, and the cylindrical lens 3-3 is exposed on one side. The semiconductor laser 3-2 adopts an edge-emitting semiconductor laser, with the vertical direction as the fast axis and the horizontal direction as the slow axis. The cylindrical lens 3-3 can collimate the laser light diverging along the fast axis, so that the laser light emitted by the semiconductor laser 3-2 has a divergence angle of 30 degrees on the fast axis and a divergence angle of 15 degrees on the slow axis. The emission cross-section of the semiconductor laser 3-3 is 0.1 mm × 10 mm, and a 650 nm red semiconductor laser is adopted. The divergent light emitted by the laser is collimated by the cylindrical lens, irradiated on the sample surface and collected by the CCD image sensor.

[0035] refer to Figure 5The light source (3) is installed at an angle such that the incident light is incident in a grazing incidence manner.

Claims

1. A device for rapidly measuring wafer roughness, comprising a base (1), a tray (2), a light source (3) and a CCD image sensor (4), wherein the tray (2) is mounted on the base (1), the light source (3) is mounted on the tray (2), and the CCD image sensor (4) is located above the center of the tray (2), characterized in that: The light source (3) is composed of a housing (3-1), a semiconductor laser (3-3) and a cylindrical lens (3-2). Wherein: the semiconductor laser (3-3) is connected to the cylindrical lens (3-2), the housing (3-1) wraps the semiconductor laser (3-3), and the cylindrical lens (3-2) is exposed on one side; The semiconductor laser (3-3) is an edge-emitting semiconductor laser, with the vertical direction being the fast axis and the horizontal direction being the slow axis; The cylindrical lens (3-2) can collimate the laser light diverging on the fast axis, thereby reducing the divergence angle of the laser light on the fast axis of the semiconductor laser (3-3).

2. The device for rapidly measuring wafer roughness according to claim 1, characterized in that: The semiconductor laser (3-3) has an emission cross-section of 0.1 mm×10 mm and emits laser light of a single wavelength, the wavelength of which is 405 nm, 450 nm, 532 nm, 650 nm, 660 nm, 1064 nm, 1330 nm, or 1550 nm.

3. The device for rapidly measuring wafer roughness according to claim 1, wherein: After being collimated by the cylindrical lens (3-2), the laser light emitted by the semiconductor laser (3-3) has a divergence angle of 30 degrees on the fast axis and a divergence angle of 15 degrees on the slow axis.

4. The device for rapidly measuring wafer roughness according to claim 1, wherein: The number of the light sources (3) is greater than 3 and they are distributed at equal intervals around the center of the tray. The light emitted by each light source (3) can cover the entire wafer (5) being inspected.

5. The device for rapidly measuring wafer roughness according to claim 1, wherein: The light source (3) is installed at an angle such that the incident light is incident in a grazing incidence manner.

6. The device for rapidly measuring wafer roughness according to claim 1, characterized in that: The CCD image sensor (4) is a visible light CCD image sensor or a near infrared CCD image sensor.

7. The device for rapidly measuring wafer roughness according to claim 5, characterized in that: The dynamic range of the CCD image sensor (4) is 60–70 dB.

8. The device for rapidly measuring wafer roughness according to claim 1, characterized in that: The material of the tray (2) is metal, plastic, resin or carbon fiber whose reflectivity is reduced through surface processing.

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