JP3744176B2 - Inspection method and apparatus for semiconductor wafer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer inspection method and apparatus, and more particularly to a semiconductor wafer inspection method and apparatus capable of simultaneously performing front and back surface quality inspection of a semiconductor wafer.
[0002]
[Prior art]
Although there are differences in the size and number of CZ silicon wafers that are shipped to the device factory after polishing and cleaning, there are usually wafer scratches and foreign matters. For example, slips on the wafer surface (wafer scratches) and particles (dust) such as metal impurities and organic substances. These foreign matters, scratches, protrusions, COP (Crystal Originated Particles), dirt, and the like greatly affect the product yield and reliability of the device as the device becomes finer and the chip area increases. This is because the appearance shape defects on the front and back surfaces of the wafer, particularly on the wafer surface, are the largest cause of a decrease in product yield. As a result, if the scratches or foreign matter on the wafer is above the reference value, it becomes a defective product, and the smaller the number, the higher the degree of non-defective product.
[0003]
Such foreign matters, scratches, protrusions, COPs, and dirt on the front and back surfaces of the wafer are usually inspected by various inspection apparatuses such as a total reflection fluorescent X-ray analyzer, a microscope such as an atomic force microscope, and a particle detector. For example, “SS6200”, “SS6420” manufactured by Tencor Co., Ltd. can be used as the particle detection device.
Conventionally, inspection of foreign matters, scratches, protrusions, COPs, dirt, etc. on the front and back surfaces of a silicon wafer has been carried out in order one by one using these inspection apparatuses. That is, for example, the wafer surface is inspected by the first inspection apparatus. Thereafter, the wafer is turned over, and the back surface of the wafer is inspected using the second inspection apparatus.
[0004]
[Problems to be solved by the invention]
However, inspecting foreign matters, scratches, protrusions, COPs, dirt, etc. on the front and back surfaces of the semiconductor wafer in this order one by one is time consuming and requires a long inspection time.
In addition, when the semiconductor wafer is transferred from the first inspection apparatus to the second inspection apparatus, there is a risk that new dust may be attached to or damaged on the front and back surfaces of the semiconductor wafer.
In addition, in such an inspection for each side of a wafer, a single inspection device for inspecting each surface must be provided in parallel on the inspection line. As a result, there is a problem in that an installation space for the inspection apparatus is increased.
In addition, since the installation space increases, it is necessary to design a clean room for inspecting the front and back surfaces of the wafer relatively widely. This clean room is usually set to a very high degree of cleanliness. For this reason, there existed a problem that it costs for equipment cost and maintenance of a clean environment.
[0005]
OBJECT OF THE INVENTION
Therefore, the present invention can simultaneously perform the quality inspection of the front and back surfaces of the semiconductor wafer. As a result, the inspection time can be shortened, and a new wafer foreign matter during transfer between the inspection devices for the front and back surfaces of the wafer , An object of the present invention is to provide a semiconductor wafer inspection method and apparatus capable of preventing the occurrence of scratches, protrusions, COPs, and dirt , and further reducing the size of a clean room for an inspection apparatus.
Another object of the present invention is to provide a semiconductor wafer inspection apparatus capable of accurately performing simultaneous inspection of the front and back surfaces of the wafer.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, after gripping the outer peripheral portion of a semiconductor wafer having a mirror-finished front surface and a relatively rough back surface, the held semiconductor wafer is held in a vertical state and a laser is applied to the surface. By irradiating light from the vertical direction and simultaneously irradiating laser light from a direction inclined at a predetermined angle with respect to the back surface, a semiconductor wafer for simultaneously inspecting foreign matter, scratches, protrusions, COP, and dirt existing on the front and back surfaces Inspection method.
The gripping of the outer peripheral portion of the semiconductor wafer is not limited to gripping in which the semiconductor wafer is annularly sandwiched by a gripping arm, or gripping a plurality of locations on the outer peripheral portion of the wafer with the tip of the clamp claw.
The gripped semiconductor wafer is placed in a vertical state.
The foreign matter, scratches, protrusions, COP, and dirt on the front and rear surfaces of the semiconductor wafer here refer to, for example, scratches or dust on the silicon wafer. Examples of garbage include metal impurities, organic substances, and particles.
The inspection method for the front and back surfaces of the semiconductor wafer is performed by irradiating a laser beam.
[0007]
According to a second aspect of the present invention, there is provided a gripping means for gripping an outer peripheral portion of a semiconductor wafer , and a surface inspection means for inspecting foreign matter, scratches, protrusions, COP, and dirt existing on the surface of the semiconductor wafer gripped by the gripping means. And back surface inspection means for inspecting foreign matter, scratches, protrusions, and dirt existing on the back surface of the semiconductor wafer simultaneously with the inspection by the surface inspection means, and the surface inspection means is provided on the mirror-finished surface of the semiconductor wafer. On the other hand, it is a first particle detection apparatus that irradiates laser light from the vertical direction, and the back surface inspection means irradiates laser light from the inclined direction to the relatively rough back surface of the semiconductor wafer. In addition to being an apparatus, the gripping means is a semiconductor wafer inspection apparatus that grips a semiconductor wafer in a vertical state.
The gripping means for the outer periphery of the wafer may have any structure.
[0008]
The first particle detection device is not limited. For example, “SS6200” and “SP-1” manufactured by Tencor Corporation, “LS-6310” manufactured by Hitachi, Ltd., “WIS-CR80” manufactured by ADE, and the like can be given.
Further, the second particle detection device is not limited. An example is “SS6420” manufactured by Tencor Corporation.
[0009]
[0010]
[Action]
According to the present invention, only the outer peripheral portion of the semiconductor wafer is gripped and the semiconductor wafer is set at a predetermined inspection position. While maintaining this state, foreign matter, scratches, protrusions, COP, and dirt existing on the front and back surfaces of the wafer are simultaneously inspected. As a result, the inspection time can be shortened, and the generation of new wafer foreign matter, scratches, protrusions, COPs, and dirt during transfer between the front and back side inspection apparatuses can be prevented. It is also possible to reduce the size of the clean room that houses the front and back inspection devices.
[0011]
In particular, the mirror-finished surface of the semiconductor wafer is irradiated with laser light, for example, from the vertical direction to inspect foreign matter, scratches, protrusions, COPs, and dirt existing on the wafer surface. At the same time, the laser beam is irradiated from the inclined direction (the direction inclined at a predetermined angle rather than perpendicular to the wafer surface) to the relatively rough finished back surface of the semiconductor wafer , Inspect for scratches, protrusions, and dirt . Thereby, the simultaneous inspection of the front and back surfaces of the wafer can be accurately performed.
[0012]
Further, the semiconductor wafer gripped in the vertical state is set at a predetermined inspection position, and this state is maintained and the wafer front and back surfaces are simultaneously inspected. Since the semiconductor wafer stands vertically, the central portion of the wafer does not bend downward due to its own weight. As a result, the front and back surfaces of the wafer can be accurately inspected.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. First, a semiconductor wafer inspection method and apparatus according to a first embodiment of the present invention will be described.
FIG. 1 is an explanatory view of a silicon wafer inspection apparatus according to the first embodiment of the present invention. FIG. 2 is an explanatory view of a silicon wafer inspection apparatus according to another embodiment. FIG. 3 is a plan view of the gripping means.
In FIG. 1, reference numeral 10 denotes a silicon wafer inspection apparatus according to the first embodiment of the present invention. This silicon wafer inspection apparatus 10 is a gripping means for gripping an outer peripheral portion of a silicon wafer W which is an example of a semiconductor wafer. A robot hand 11 as an example, a first particle detection device 12 as a surface inspection means for inspecting foreign matter, scratches, protrusions, COPs and dirt existing on the surface w1 of the silicon wafer W, and a back surface w2 of the silicon wafer W And a second particle detection device 13 as a back surface inspection means for inspecting existing foreign matter, scratches, protrusions, and dirt .
[0014]
The silicon wafer W used here is a silicon wafer obtained by subjecting a silicon single crystal rod pulled up by the CZ method to block cutting, wafer cutting, chamfering, mechanical chemical polishing, and final cleaning by RCA cleaning. is there. In this silicon wafer W, the wafer front surface w1 is mirror-finished, and the wafer back surface w2 is a relatively rough finished surface.
The robot hand 11 includes a fixed-side holding arm 14 and a movable-side holding arm 15 that holds the outer peripheral portion of the silicon wafer W from the side together with the fixed-side holding arm 14. Details will be described later with reference to FIG.
[0015]
Specifically, the first particle detection device 12 is “SS6200” manufactured by Tencor Corporation. That is, the apparatus detects the number of particles a having a minimum size of 0.10 μm existing on the surface w1 by irradiating the surface w1 of the silicon wafer W with laser light from the vertical direction.
This apparatus configuration includes a laser light source 16 arranged orthogonally to the wafer surface w1, and two channels (for bright field and dark field) radiating on the left and right of the light source 16 in the vertical plane. The photomultiplier 17 is provided. Laser light emitted at 90 ° from the upper light source 16 toward the wafer surface w1 strikes the particles a adhering to the mirror-finished wafer surface w1 and diffusely reflects. The reflected light spreads radially as shown by the arrows in FIG. An arbitrary photomultiplier 17 captures this to detect the number of particles a that are foreign matter, scratches, protrusions, COP, dirt, etc. on the surface of the silicon wafer W.
[0016]
Specifically, the second particle detection device 13 is “SS6420” manufactured by Tencor Corporation. That is, the laser beam is irradiated from the inclined direction to the wafer back surface w2 of the silicon wafer W, and particles a having a minimum size of 0.15 μm on the back surface w2 are counted. In addition to this count, classification by size and measurement of wafer surface characteristics can also be performed.
This apparatus configuration is arranged on one lower side of a silicon wafer W, and a light source 18 that irradiates laser light upward in parallel with the silicon wafer W, and a mirror 19 that bends the laser light upward to the silicon wafer W side. And a beam expander 20, a lens 21 for condensing the laser beam that has passed through it, and a large photomultiplier arranged on the other lower side of the silicon wafer W to capture the laser beam reflected from the wafer back surface w2. And a plier 22.
[0017]
The laser light emitted from the light source 18 is bent at an angle of 20 ° to 80 ° with respect to the back surface w2 of the wafer W by the mirror 19, and then processed into a relatively rough surface through the beam expander 20 and the lens 21. The irradiated wafer back surface w2 is irradiated. Among these, the reflected light reflected by the particle a is captured by the photomultiplier 22 of two channels (for bright field / dark field), whereby the particle a is detected.
[0018]
The scanning technique of SS6420 will be described. The focus mechanism moves the target silicon wafer W up and down with the wafer back surface w2 placed on the scan plane. The silicon wafer W moves in a high-speed telecentric scanning laser beam having a wavelength of 488 nm at a constant speed. The laser beam is focused so as to project a 75 μm diameter circle when traversing the substrate surface at an angle of 20 °. Further, the scanning beam crosses a straight path on the silicon wafer W back and forth, and reliably samples the entire silicon wafer W. When the laser beam illuminates the LPD (foreign matter) on the silicon wafer W, the light is scattered in all directions from the incident point. Part of this scattered light is collected and guided to a low noise photomultiplier tube for amplification. The analog signal output from the low noise photomultiplier tube PMT is digitized by a high-speed analog-to-digital converter. Data collection electronics periodically sample the digital converter to generate a raster image of the back surface w2 of the silicon wafer W. The raster image is then analyzed by a pipeline processor and a dedicated general purpose computer to create, display and manipulate surface measurement data.
[0019]
Moreover, you may change each assembly position of the 1st, 2nd particle | grain detection apparatuses 12 and 13 in the whole apparatus as shown, for example in FIG. That is, by maintaining the silicon wafer W in a vertical state by the robot hand 11, the first particle detection device 12 is arranged on one side of the silicon wafer W, and the second particle detection device 13 is placed on the other side of the wafer W. You may arrange in the direction. Thus, by holding the silicon wafer W in the vertical state, the concern that the silicon wafer W may be bent downward by its own weight, which is a concern when the silicon wafer W is held horizontally as shown in FIG. 1, is eliminated. . As a result, the wafer front and back surfaces w1, w2 can be accurately inspected.
[0020]
Next, the robot hand 11 will be described in detail with reference to FIG.
As shown in FIG. 3, the robot hand 11 is attached to the tip of a robot arm 23 that is three-dimensionally movable in the XYZθ directions. The robot hand 11 slides on the base part 24 using a base part 24, a fixed-side gripping arm 14 for wafer clamping fixed to the base part 24, and a clamp opening / closing motor (not shown) as drive sources. A movable gripping arm 15 and a rotating means 27 for the silicon wafer W are provided.
[0021]
A plurality of guide rollers 28 having grooves on the outer peripheral surface for holding the outer peripheral portion of the silicon wafer W are disposed on the fixed and movable gripping arms 14 and 15.
The rotating means 27 is assembled from the base portion 24 to the base portion of the fixed gripping arm 14, and includes a small driving motor 29, a driving pulley 30, a driven pulley 31, a guide roller 32, and a power transmission belt. 33 and a wafer rotating roller 34. The drive pulley 30 is rotated by the drive motor 29, and the rotational force is transmitted to the wafer rotation roller 34 via the belt 33 via the driven pulley 31. As a result, the rotation of the roller 34 causes the silicon wafer W held by the fixed and movable holding arms 14 and 15 to rotate in the circumferential direction.
In FIG. 3, reference numeral 35 denotes a guide pin that protrudes from the side surface of the base portion 24 and guides the sliding of the movable gripping arm 15, and 36 is formed in the base portion of the movable gripping arm 15, A long hole 35 is inserted and 37 is a cushion spring.
[0022]
Next, a silicon wafer inspection method using the silicon wafer inspection apparatus 10 will be described.
As shown in FIG. 1, by operating the robot hand 11, the silicon wafer W held by the fixed and movable holding arms 14 and 15 is placed at an intermediate position between the first and second particle detectors 12 and 13. Place it horizontally.
Thereafter, the particles a existing on the front and back surfaces w1, w2 of the silicon wafer W are simultaneously inspected. That is, in the particle inspection of the wafer surface w1, laser light is irradiated at 90 ° from the light source 16 of the first particle detector 12 toward the wafer surface w1, and the reflected light is captured by the photomultiplier 17. Then, the particles a adhering to the surface w1 are detected. At the same time, the second particle detector 13 is used to irradiate the back surface w2 of the silicon wafer W, which is relatively rough, with laser light from the light source 18 in an inclined direction, thereby providing the wafer back surface w2. The particle a existing in the is detected. During the inspection, in order to move the inspection positions of the front and back surfaces w1, w2 of the silicon wafer W, the robot hand 11 is moved or the driving motor 29 of the rotating means 27 is driven to move the silicon wafer W in the XYZ directions. Or rotate in the θ direction.
[0023]
As described above, since the particles a adhering to the front and back surfaces w1, w2 of the silicon wafer W are simultaneously detected, the inspection time is shortened, and the conventional first and second particle detectors are installed upstream of the inspection line. As in the case of the arrangement from the downstream to the downstream, it is possible to prevent new particles a from adhering during the transfer between the two detection devices. In addition, the clean room that houses the first and second particle detectors 12 and 13 can be formed compactly.
In addition, as a particle detection device for the mirror-finished surface w1 of the silicon wafer W, an apparatus (herein “SS6200”) that irradiates laser light from the vertical direction with respect to the wafer surface w1 is used, while being relatively rough Since the apparatus (here, “SS6420”) that irradiates the finished wafer back surface w2 with a laser beam from an inclined direction is used, simultaneous inspection of the wafer front and back surfaces w1 and w2 can be performed more accurately. it can.
[0024]
Next, a silicon wafer inspection method and apparatus according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is an explanatory view of a silicon wafer inspection apparatus according to the second embodiment of the present invention.
In FIG. 4, reference numeral 40 denotes a second particle detection apparatus applied to the silicon wafer inspection apparatus according to the second embodiment of the present invention. The second particle detection device 40 performs image processing on the image captured from the CCD camera 41 by the image processing circuit 42 of the control unit of the silicon wafer inspection device 10 (not shown), and based on this, particles having a large particle size are processed. The number of scratches and protrusions a is detected.
[0025]
In other words, the laser light emitted from the light source 43 in parallel with the silicon wafer W is reflected toward the back surface w2 by the polarizing mirror 44 facing the wafer back surface w2. The reflected laser light passes through the condensing lens 45 and irradiates the back surface w2. The laser light regularly reflected by the back surface w2 passes through the polarization mirror 44 and enters the CCD camera 41 at the focal position of the convex lens 45. Thereafter, the image captured by the CCD camera 41 is processed by the image processing circuit 42 to detect particles, scratches, and protrusions a having a large particle diameter. As described above, by adopting the second particle detection device 40 using the CCD camera 41, it is possible to detect at the same level (macro) as the visual inspection, or more (micro) detection. can get.
[0026]
【The invention's effect】
As a result, according to the method and apparatus for inspecting a semiconductor wafer of the present invention, the outer periphery of the wafer is gripped to simultaneously inspect foreign matter, scratches, protrusions, COP, and dirt existing on the front and back surfaces of the semiconductor wafer. can do. As a result, the inspection time can be shortened, and the generation of new wafer foreign matter, scratches, protrusions, COPs, and dirt during transfer between the front and back side inspection apparatuses can be prevented. Furthermore, it is possible to reduce the size of the clean room for wafer front and back inspection.
[0027]
In particular, foreign matter, scratches, protrusions, COPs, and dirt on the surface (mirror finish surface) of a semiconductor wafer are inspected by a first particle detector that irradiates laser light from an arbitrary direction, and the back surface (rough finish surface) of a semiconductor wafer. ) Foreign matter, scratches, protrusions, and dirt are inspected by the second particle detector that irradiates laser light from the inclined direction, so that simultaneous inspection of the front and back surfaces of the wafer can be performed accurately.
Further, since the semiconductor wafer is placed in a vertical state and the front and back surfaces are simultaneously inspected, the center of the wafer is prevented from being bent downward due to the weight of the semiconductor wafer. As a result, the front and back surfaces of the wafer can be accurately inspected.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a semiconductor wafer inspection apparatus according to a first embodiment of the present invention.
FIG. 2 is an explanatory view of a semiconductor wafer inspection apparatus according to another aspect of the first embodiment of the present invention.
FIG. 3 is a plan view of the gripping means according to the first embodiment of the present invention.
FIG. 4 is an explanatory view of a semiconductor wafer inspection apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
10, 40 Silicon wafer inspection equipment (semiconductor wafer inspection equipment),
11 Robot hand (gripping means),
12 1st particle | grain detection apparatus (surface inspection means),
13 Second particle detection device (back surface inspection means),
W silicon wafer,
w1 surface,
w2 reverse side,
a Particles such as foreign matter, scratches, protrusions, and dirt.

Claims (2)

After gripping the outer periphery of a semiconductor wafer having a mirror-finished surface and a relatively rough back surface, hold the gripped semiconductor wafer in a vertical state and irradiate the surface with laser light from the vertical direction. A semiconductor wafer inspection method for simultaneously inspecting foreign matter, scratches, protrusions, COP, and dirt existing on the front and back surfaces by irradiating laser light from a direction inclined at a predetermined angle with respect to the back surface. Gripping means for gripping the outer periphery of the semiconductor wafer;
Surface inspection means for inspecting foreign matter, scratches, protrusions, COP, and dirt existing on the surface of the semiconductor wafer held by the holding means;
A back surface inspection means for inspecting foreign matter, scratches, protrusions, and dirt existing on the back surface of the semiconductor wafer simultaneously with the inspection by the surface inspection means,
The surface inspection means is a first particle detection device that irradiates laser light from a vertical direction on a mirror-finished surface of a semiconductor wafer,
The back surface inspection means is a second particle detecting device that irradiates a relatively rough back surface of a semiconductor wafer with laser light from an inclined direction,
The gripping means is a semiconductor wafer inspection apparatus for gripping a semiconductor wafer in a vertical state.

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