JP3737585B2 - Semiconductor wafer surface inspection method and semiconductor device manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer surface inspection method and a semiconductor device manufacturing apparatus for inspecting the surface of a semiconductor wafer on which a circuit pattern is formed while polishing.
[0002]
[Prior art]
As the density of semiconductor devices increases, multilayer circuit patterns formed on semiconductor wafers are being studied. When the circuit pattern is multi-layered, the circuit pattern cannot be precisely formed unless the interlayer insulating film or the like is flattened.
[0003]
Chemical mechanical polishing called CMP is known as a technique for planarizing the interlayer insulating film and the like.
CMP mainly polishes the interlayer insulating film or the like using a slurry in which particles such as colloidal silical are dispersed in an aqueous solution of an alkali base such as KOH (potassium hydroxide) as an abrasive. Therefore, since a large amount of particles such as slurry and metal ions remain in the polished semiconductor wafer, it is required to sufficiently wash the semiconductor wafer after polishing.
[0004]
When the semiconductor wafer is cleaned, in order to perform cleaning evaluation, the particle remaining on the semiconductor wafer is measured by a particle counter. If the measured value is a predetermined value or less, It will be treated as a good product.
[0005]
By the way, it is inevitable that scratches are generated in the semiconductor wafer subjected to CMP before the cleaning process due to the influence of particles contained in the slurry. The particle counter irradiates laser light onto the measurement surface of the semiconductor wafer and counts the particles according to the profile of scattered light from the measurement surface.
[0006]
For this reason, when a scratch occurs on the measurement surface of the semiconductor wafer, the scratch profile is counted in the same manner as the particle, and therefore the counted number of particles includes the scratch. As a result, the number of particles on the measurement surface of the semiconductor wafer cannot be measured accurately.
[0007]
In other words, in a semiconductor device manufacturing process involving CMP, scratches occur during polishing. For this reason, when evaluating the cleaning of semiconductor wafers, it is impossible to determine whether the number counted in the particle is the actual number of particles or the number including scratches. Sometimes.
[0008]
[Problems to be solved by the invention]
Thus, conventionally, when a polished semiconductor wafer is cleaned and the cleaning state is measured by a particle counter and evaluated, the measured value is only the actual number of particles, or the polishing process is performed. In some cases, it was impossible to determine whether or not a scratch was generated.
[0009]
An object of the present invention is to provide a method for inspecting a surface of a semiconductor wafer in which it is possible to determine whether or not a measurement value by a particle counter includes a scratch generated during polishing.
[0010]
Another object of the present invention is to remove a semiconductor wafer from a semiconductor device including a polishing process if the measured value is equal to or greater than a predetermined value when the semiconductor wafer is measured by a particle counter. An object of the present invention is to provide a semiconductor device manufacturing apparatus that can reliably manufacture a semiconductor device by making it non-defective.
[0011]
[Means for Solving the Problems]
The invention of claim 1 is a surface inspection method for inspecting the surface of a polished semiconductor wafer.
A cleaning process for cleaning the polished semiconductor wafer;
A first measuring step of measuring the surface of the semiconductor wafer cleaned in this cleaning step with a particle counter;
An etching step of performing isotropic etching on the surface of the semiconductor wafer measured in the first measurement step;
A second measuring step of measuring the surface of the semiconductor wafer etched in this etching step with a particle counter;
From the difference between the measurement values of the first measurement step and the second measurement step, the degree of occurrence of scratches generated on the semiconductor wafer by polishing and the predetermined measurement measured by the first measurement step and the second measurement step. And a discrimination step for discriminating the degree of cleaning of the semiconductor wafer based on the difference in the number of particle sizes within the range of the above range .
[0012]
The invention of claim 2 is a manufacturing apparatus for manufacturing a semiconductor device by polishing a semiconductor wafer.
A polishing apparatus for polishing a semiconductor wafer;
A cleaning device for cleaning the polished semiconductor wafer;
A particle counter for measuring particles on the surface of the cleaned semiconductor wafer;
A sorting device for discriminating between the non-defective product and the defective product by determining the quality of the semiconductor wafer from the measurement result of the particle counter;
After measuring the surface of the semiconductor wafer determined to be poorly cleaned by this sorter with a particle counter, the surface of the semiconductor wafer is subjected to isotropic etching, and then the surface of the semiconductor wafer is measured again with the particle counter. The difference between the measurement values obtained by these two measurements and the difference in the degree of occurrence of scratches generated in the semiconductor wafer by polishing and the difference in the number of particle sizes having a predetermined range measured by the above two measurements. An inspection apparatus for determining the degree of cleaning of a wafer is provided.
[0013]
According to the first aspect of the present invention, the surface of the semiconductor wafer is measured by a particle counter in the first measurement step after cleaning, and then the surface is subjected to isotropic etching. If scratches are generated, the scratches are enlarged, so that the measurement values in the second measurement process after the etching process include scratches, and the measurement values increase. Therefore, by comparing the measurement values of the first measurement process and the second measurement process, it is possible to determine whether or not a scratch has occurred on the semiconductor wafer in the polishing process.
[0014]
According to the second aspect of the present invention, when a semiconductor device is manufactured with a polishing process, a semiconductor wafer cleaned after the polishing process is measured with a particle counter, and a non-defective product and a defective product are determined based on the measured value. Can be selected.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a semiconductor device manufacturing apparatus 1, which has a film forming apparatus 2. In this film forming apparatus 2, a thermal oxide film 4 as an insulating film is formed on a semiconductor wafer 3 as shown in FIG.
[0016]
Since the surface of the thermal oxide film 4 formed on the semiconductor wafer 3 may become an uneven surface 5a as shown in FIG. 3A, in such a case, a circuit pattern is further formed on the upper surface. In this case, it is necessary to flatten the uneven surface 5a as shown in FIG.
[0017]
The semiconductor wafer 3 on which the thermal oxide film 4 is formed by the film forming apparatus 2 is polished by the polishing apparatus 6 of the manufacturing apparatus 1 in order to flatten the uneven surface 5a, as shown in FIG.
[0018]
As the polishing device 6, a device that performs chemical mechanical polishing (CMP) on the thermal oxide film 4 of the semiconductor wafer 3 is used. The polishing device 6 has a lapping machine 7 as shown in FIG. The board 7 is rotated by a lower drive shaft 8.
[0019]
An upper drive shaft 9 that is vertically driven and rotated by a drive mechanism (not shown) is provided above the lap board 7, and a holder 11 is attached to the lower end of the upper drive shaft 9. The semiconductor wafer 3 is held on the lower surface of the holder 11 by means such as adhesion or adsorption with the surface on which the thermal oxide film 4 is formed facing down.
[0020]
Slurry 13 is supplied from the supply nozzle 12 to the upper surface of the lapping machine 7. As this slurry 13, for example, a dispersion of particles such as colloidal silica in an aqueous solution of an alkali base such as KOH is used.
[0021]
Therefore, it causes contact with a predetermined pressure a semiconductor wafer 3 held on the upper surface of the lapping machine 7 in the holder 11, and supplies the slide Li on the upper surface of the lapping tool 7 is rotated and the holder 11 and the lapping tool 7 Thus, the thermal oxide film 4 of the semiconductor wafer 3 is polished from the uneven surface 5a shown in FIG. 3A to the flat surface 5b shown in FIG.
[0022]
The semiconductor wafer 3 polished by the polishing apparatus 6 is supplied to the cleaning apparatus 15 shown in FIG. For example, the cleaning device 15 performs a cleaning operation by spraying a cleaning liquid to which ultrasonic vibration is applied while rotating the semiconductor wafer 3, and rotating the semiconductor wafer 3 at a high speed without supplying the cleaning liquid after the cleaning. A so-called spin processing apparatus that can perform a drying operation for drying and removing the cleaning liquid is used.
[0023]
The semiconductor wafer 3 cleaned and dried by the cleaning device 15 is carried into the particle counter 16. As shown in FIG. 6, the particle counter 16 includes a laser oscillator 17 that outputs a laser beam L 1 and a laser beam L 1 that is output from the laser oscillator 17 irradiates the semiconductor wafer 3. The detector 18 for detecting the scattered light L2 generated by doing so is paired. In FIG. 6, for convenience of explanation, the laser oscillator 17 and the detector 18 are shown separately, but they are usually integrated.
[0024]
The semiconductor wafer 3 whose particle has been measured by the particle counter 16 is carried into the sorting device 21. This sorting device 21 judges the quality of the cleaning state of the semiconductor wafer 3 based on the value measured by the particle counter 16 and sorts the good product and the defective product. The non-defective product is conveyed to the next process, and the defective product is conveyed to the inspection device 23.
[0025]
In the manufacturing apparatus 1, a series of operations from film formation by the film formation apparatus 2 to selection by the selection apparatus 21 can be continuously and automatically performed.
The inspection apparatus 23 reinspects the semiconductor wafer 3 that has been determined to be poorly cleaned. That is, the particle counter 16 (which is provided separately from the particle counter 16 of the manufacturing apparatus 1 but has the same configuration, and will be described using the same number) is used for the thermal oxide film 4 of the semiconductor wafer 3. When measuring the number of particles adhering to the surface and the particle size of the particles, the thermal oxide film 4 is polished and flattened by the polishing apparatus 6 so that the thermal oxide film 4 has a structure shown in FIG. As shown in (a), not only the particle 24 is adhered, but also a scratch 25 may occur.
[0026]
When the scratch 25 is generated, the particle counter 16 detects not only the scattered light L2 from the particle 24 but also the scattered light L2 from the scratch 25 as the same profile as the particle. The measurement value measured by the counter 16 does not match the number of particles 24 and includes the number of scratches 25. For this reason, it is impossible to determine how clean the semiconductor wafer 3 has been cleaned by the cleaning device 15 based on the measured value of the particle counter 16.
[0027]
Therefore, in the inspection apparatus 23, first, the particle counter 16 measures the surface of the semiconductor wafer 3 determined to be defective by the sorting apparatus 21 of the manufacturing apparatus 1 in the first measurement step S1. The measured value at that time is T1.
[0028]
Next, the surface of the semiconductor wafer 3 is isotropically etched in the etching step S2. This isotropic etching is performed on the thermal oxide film 4 with hydrofluoric acid (HF) for about 5 minutes. Since the surface of the semiconductor wafer 3, that is, the thermal oxide film 4 is isotropically etched, if there are many large and small scratches 25 as shown in FIG. 4A, the scratches 25 are also etched. As shown in FIG. 4B, a large scratch 25a is formed. That is, in the first measuring step S1, the scratch 25 measured as a small particle size is measured as a large particle size, and the scratch 25 that is too small to be measured as a particle is also enlarged to a measured size. .
[0029]
When the etching is completed, the surface is again measured by the particle counter 16. This is the second measuring step S3 as shown in FIG. The measured value in the second measuring step S3 is T2. In the second measurement step S3, among the scratches 25 generated on the semiconductor wafer 3, the small scratches 25 that were not measured as particles in the first measurement step S1 are enlarged. -It will be measured as a ticle.
[0030]
Then, in the determination step S4, the measurement value T1 in the first measurement step S1 is compared with the measurement value S2 in the second measurement step S3. As a result, when the measured value T2 is sufficiently larger than the measured value T1, it can be determined that the scratch 25 is generated in the thermal oxide film 4 of the semiconductor wafer 3 during the polishing process by the polishing apparatus 6. It can be determined that a polishing failure has occurred in the polishing apparatus 6. That is, the degree of occurrence of the scratch 25 in the polishing state in the polishing apparatus 6 can be determined by the value of (T2−T1).
[0031]
When the measured value T1 is substantially equal to the measured value T2, it is determined that the measured value T1 measured in the first measuring step S1 hardly includes the scratch 25 and only the particle 25 is counted. Therefore, the cleaning performance in the cleaning device 15 can be determined from the measured value T1.
[0032]
The number of particles can also be estimated from the change in particle size. For example, the number of particle sizes in a predetermined range that can be measured in the first measurement step S1 is compared with the number of particle sizes in a predetermined range that are measured in the second measurement step S2. Assuming that the number of particle sizes in the range increases, it can be determined that the increase in particle size in the size range is that the smaller scratch 25 has been expanded by etching. It can be estimated that the difference in the number is the particle 24 that has been attached to the semiconductor wafer 3 in advance.
[0033]
That is, according to the surface inspection method as described above, how much scratches 25 are generated in the thermal oxide film 4 formed on the semiconductor wafer 3 when the surface of the semiconductor wafer 3 is polished and then cleaned. No, that is, whether or not the polishing state of the semiconductor wafer 3 by the polishing apparatus 6 can be judged. If it can be judged that almost no scratch 25 is generated, the particle 24 adhered to the surface of the semiconductor wafer 3 is obtained. , That is, the cleaning performance of the cleaning device 15 can be determined.
[0034]
According to the experiment, when the semiconductor wafer 3 having the thermal oxide film 4 formed with a thickness of 10000 angstrom is cleaned without polishing and the particle is measured before the etching process, the measured value is 129 pieces. / 6 inch. When measured after the etching process, the value was 126 pieces / 6 inch. That is, when there is no polishing process, the scratch 25 does not occur, so there is almost no change in the measured value before and after the etching process.
[0035]
As the next experiment, the thermal oxide film 4 was polished by CMP, washed, and the particles were measured. The number of particles was 413/6 inch. After the measurement, etching was performed and the measurement was performed again. As a result, the measured value was 2881/6 inches.
[0036]
From this, when the scratch 25 is generated by polishing the thermal oxide film 4, the scratch 25 is etched to reveal a size that can be measured by the particle counter 16. It was confirmed that the value increased rapidly.
[0037]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above embodiment, when a semiconductor wafer determined to be defective by the sorting device 21 is inspected by the inspection device 23, the particle is measured by the first measurement step S1 in the inspection step, and the value is measured. Although the value T1 is used, the first measurement step S1 in the inspection device 23 may be omitted by using the value measured by the particle counter 16 of the manufacturing apparatus 1 as T1.
[0038]
That is, when the particle counter 16 for determining the cleaning state is provided in the manufacturing apparatus 1, the first measuring step S1 of the inspection apparatus 23 can be omitted, but the particle counter 16 is not included in the manufacturing apparatus 1. Is not provided, and for example, a sampling inspection system that inspects the quality of the cleaning state for one semiconductor wafer 3 of one rod is employed, the first measurement process in the inspection apparatus 23 is performed. S1 is necessary.
[0039]
【The invention's effect】
According to the first aspect of the present invention, the polished semiconductor wafer is cleaned, and then the surface of the semiconductor wafer is measured with a particle counter in the first measurement step, and then the surface is subjected to isotropic etching. Then, measurement was performed with a particle counter in the second measurement step.
[0040]
Therefore, by performing isotropic etching on the semiconductor wafer, if scratches are generated during the polishing process, the scratches are enlarged and measured in the same manner as the particles in the second measurement process. By comparing the measurement values of the first measurement process and the second measurement process, it is possible to determine whether or not the semiconductor wafer is scratched in the polishing process.
[0041]
According to the second aspect of the present invention, when a semiconductor device is manufactured with a polishing process, a semiconductor wafer cleaned after the polishing process is measured with a particle counter, and a non-defective product and a defective product are determined based on the measured value. Can be selected. Therefore, it becomes possible to remove from the production line a semiconductor wafer that may have been scratched due to poor cleaning or polishing, so that it is possible to prevent the occurrence of defective manufacturing of the semiconductor device.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a semiconductor device manufacturing apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view of the inspection apparatus.
FIG. 3 is a cross-sectional view showing a state before and after polishing of a semiconductor wafer.
FIG. 4 is a cross-sectional view showing a state before and after isotropic etching.
FIG. 5 is also an explanatory view of a polishing apparatus.
FIG. 6 is also an explanatory diagram of a particle counter.
[Explanation of symbols]
3 ... Semiconductor wafer 6 ... Polishing device 15 ... Cleaning device 16 ... Particle counter 21 ... Sorting device 23 ... Inspection device

Claims (2)

In a surface inspection method for inspecting the surface of a polished semiconductor wafer,
A cleaning process for cleaning the polished semiconductor wafer;
A first measuring step of measuring the surface of the semiconductor wafer cleaned in this cleaning step with a particle counter;
An etching step of performing isotropic etching on the surface of the semiconductor wafer measured in the first measurement step;
A second measuring step of measuring the surface of the semiconductor wafer etched in this etching step with a particle counter;
From the difference between the measurement values of the first measurement step and the second measurement step, the degree of occurrence of scratches generated on the semiconductor wafer by polishing and the predetermined measurement measured by the first measurement step and the second measurement step. And a discrimination step of discriminating the degree of cleaning of the semiconductor wafer based on the difference in the number of particle sizes in the range of the range . In a manufacturing apparatus for manufacturing a semiconductor device by polishing a semiconductor wafer,
A polishing apparatus for polishing a semiconductor wafer;
A cleaning device for cleaning the polished semiconductor wafer;
A particle counter for measuring particles on the surface of the cleaned semiconductor wafer;
A sorting device for discriminating between the non-defective product and the defective product by determining the quality of the semiconductor wafer from the measurement result of the particle counter;
After measuring the surface of the semiconductor wafer determined to be poorly cleaned by this sorter with a particle counter, the surface of the semiconductor wafer is subjected to isotropic etching, and then the surface of the semiconductor wafer is measured again with the particle counter. The difference between the measurement values obtained by these two measurements and the difference in the degree of occurrence of scratches generated in the semiconductor wafer by polishing and the difference in the number of particle sizes having a predetermined range measured by the above two measurements. An apparatus for manufacturing a semiconductor device, comprising: an inspection device for determining a degree of cleaning of a wafer .

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