Method of controlling particle absorption on a wafer sample being inspected by a charged particle beam imaging system

1. Field of the Invention

The present invention relates to controlling particle absorption on a wafer sample, and more particularly to controlling particle absorption on a wafer sample being inspected by a charged particle beam imaging system.

2. Description of the Prior Art

As electronic devices become smaller in size, the processing technique thereof becomes more microscopic. Charged particle beam imaging will likely become one of the critical technologies in advanced semiconductor manufacture. Charged particle beam imaging tools, which include conventional scanning electron microscopes (SEMs) have a much higher resolution than optical tools and are able to detect smaller size defects.

Particles such as dust in atmosphere influence the characteristics or yield of manufactured electronic devices significantly. Due to this, elimination of particles during the manufacturing process is a very important factor. In a microscopic circuit, since the sizes of particles are as large as or even larger than the distance between metal wires, yield (ratio of source material to product) is degraded when particles are adhered to the wafer causing short circuits or other problems.

Conventional methods for removing particles from, for example, a wafer chuck in a testing apparatus include the use of an air gun or nozzle to blow particles away from the chuck. However, this method is only partially effective in removing the particles from the chuck, especially those carrying charges.

Hence, how to control particle absorption on a wafer sample within a charged particle beam imaging system is now urgently needed to target.

The present invention is directed to a method of controlling particle absorption on a wafer sample being inspected by a charged particle beam imaging system. The disclosed method prevents particle absorption by grounding the wafer sample to keep it electrically neutral during the transfer-in and transfer-out process of the wafer.

According to an aspect, a method of controlling particle absorption on a wafer sample within a charged particle beam imaging system in an embodiment includes performing a transfer-in process to transfer the wafer sample from a wafer sample storage onto a support member for a charged particle beam imaging, the wafer sample storage being configured for pre-imaging and post-imaging storage of the wafer sample, the support member being configured for supporting the wafer sample thereon during the charged particle beam imaging, the support member being equipped with a securing unit for securing and un-securing the wafer sample on the support member; performing the charged particle beam imaging of the wafer sample; and performing a transfer-out process to transfer the wafer sample from the support member to said wafer sample storage, wherein during the transfer-in and transfer-out process, the wafer sample is kept electrically neutral by grounding the wafer sample.

According to another aspect, a computer readable medium encoded with a computer program for controlling particle absorption on a wafer sample during charged particle beam imaging includes transferring, using a first sample handling member, the wafer sample from a wafer sample storage onto a surface of a pre-aligner, the wafer sample storage being configured for pre-imaging and post-imaging storage of the wafer sample, the pre-aligner being configured for adjusting an angle of the wafer sample; transferring, using the first sample handling member, the wafer sample from the pre-aligner onto a platform of a loading chamber, the loading chamber being configured for preparing the wafer sample for the charged particle beam imaging; picking the wafer sample within the loading chamber using a second sample handling member; transferring, using a third sample handling member, the wafer sample from the second sample handling member onto a surface of a support member disposed within an inspection chamber for supporting the wafer sample thereon during the charged particle beam imaging, the support member being equipped with a securing unit for securing and un-securing the wafer sample on the support member; securing the wafer sample on the support member using the securing unit; performing the charged particle beam imaging of the wafer sample; un-securing the wafer sample; picking the wafer sample from the support member using the third sample handling member; transferring, using the second sample handling member, the wafer sample from the third sample handling member onto the platform of the loading chamber; and transferring, using the first sample handling member, the wafer sample from the loading chamber into the wafer sample storage, wherein at any given time point other than the charged particle beam imaging step, the wafer sample is kept electrically neutral by grounding the first, second and third sample handling members, the pre-aligner, the loading chamber, the support member and the securing unit.

According to yet another aspect, a charged particle beam imaging system of a wafer sample includes a charged particle beam generator, a condenser lens module, a probe forming objective lens module, a charged particle beam deflection module, a secondary charged particle detector module, an image forming module, and a particle contamination controller. The charged particle beam generator is configured for generating a primary charged particle beam; the probe forming objective lens module is configured for focusing condensed the primary charged particle beam into a charged particle beam probe; the charged particle beam deflection module for scanning the charged particle beam probe across a surface of the wafer sample; the secondary charged particle detector module is configured for detecting charged particles generated from the wafer sample surface when being bombarded by the charged particle beam probe, and whereby generating a secondary charged particle detection signal accordingly; and the image forming module electrically coupled with the secondary charged particle detector module for receiving the secondary charged particle detection signal from the secondary charged particle detector module and forming at least one charged particle microscopic image. The particle contamination controller is coupled with a first sample handling member, a second sample handling member and a third sample handling member for transferring the wafer sample, a wafer sample storage for pre-imaging and post-imaging storage of the wafer sample, a pre-aligner for adjusting an angle of the wafer sample, a loading chamber for preparing the wafer sample for the charged particle beam imaging, and a support member disposed within an inspection chamber for supporting the wafer sample thereon during the charged particle inspection, the support member being equipped with a securing unit for securing and un-securing the wafer sample on the support member. The particle contamination controller includes a computer readable medium encoded with a computer program for controlling particle absorption on a wafer sample during charged particle beam imaging. The computer program executes steps including transferring, using a first sample handling member, the wafer sample from a wafer sample storage onto a surface of a pre-aligner, the wafer sample storage being configured for pre-imaging and post-imaging storage of the wafer sample, the pre-aligner being configured for adjusting an angle of the wafer sample; transferring, using the first sample handling member, the wafer sample from the pre-aligner onto a platform of a loading chamber, the loading chamber being configured for preparing the wafer sample for the charged particle beam imaging; picking the wafer sample within the loading chamber using a second sample handling member; transferring, using a third sample handling member, the wafer sample from the second sample handling member onto a surface of a support member disposed within an inspection chamber for supporting the wafer sample thereon during the charged particle beam imaging, the support member being equipped with a securing unit for securing and un-securing the wafer sample on the support member; securing the wafer sample on the support member using the securing unit; performing the charged particle beam imaging of the wafer sample; un-securing the wafer sample; picking the wafer sample from the support member using the third sample handling member; transferring, using the second sample handling member, the wafer sample from the third sample handling member onto the platform of the loading chamber; and transferring, using the first sample handling member, the wafer sample from the loading chamber into the wafer sample storage, wherein at any given time point other than the charged particle beam imaging step, the wafer sample is kept electrically neutral by grounding the first, second and third sample handling members, the pre-aligner, the loading chamber, the support member and the securing unit.

Other advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present invention.

The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 to FIG. 3 are flow charts illustrating an embodiment of the present invention; and

FIG. 4 and FIG. 5 are schematic diagrams illustrating a charged particle beam imaging system of a wafer sample according to another embodiment of the present invention.

Refer to FIG. 1 in conjunction with FIG. 4 . FIG. 1 illustrates a flow chart of a method of controlling particle absorption on a wafer sample within a charged particle beam imaging system illustrated in FIG. 4 of an embodiment according to the present invention. FIG. 1 begins with performing a transfer-in process to transfer the wafer sample 100 from a wafer sample storage 10 onto a support member 70 for a charged particle beam imaging (S 11 ), in which the wafer sample storage 10 is configured for pre-imaging and post-imaging storage of the wafer sample 100 , the support member 70 is configured for supporting the wafer sample 100 thereon during the charged particle beam imaging, the support member 70 is equipped with a securing unit 80 for securing and un-securing the wafer sample 100 on the support member 70 . Next, perform a charged particle beam imaging of the wafer sample 100 (S 12 ). Lastly, perform a transfer-out process to transfer the wafer sample 100 from the support member 70 to the wafer sample storage 10 (S 13 ). It is noted that the wafer sample 100 is kept electrically neutral by grounding the wafer sample 100 during the transfer-in (S 11 ) and transfer-out process (S 13 ).

In one embodiment, the transfer-in process S 11 and the transfer-out process S 13 include transferring the wafer sample 100 between at least one work chamber using at least one sample handling device, in which the work chamber is configured for preparing the wafer sample 100 for the charged particle beam imaging, or for the charged particle beam imaging step S 12 to be performed therewithin. The sample handling device and at least one portion of the work chamber is in contact with the wafer sample 100 . This at least one portion of the work chamber is grounded anytime during the transfer-in process S 11 and the transfer-out process S 13 .

FIG. 2 is a flow chart illustrating the further detailed process of the transfer-in process S 11 illustrated in FIG. 1 . Referring to FIG. 2 and FIG. 4 , the transfer-in process S 11 begins with transferring, using a first sample handling member 20 , the wafer sample 100 from the wafer sample storage 10 onto the surface of a pre-aligner 30 , in which the pre-aligner 30 is configured for adjusting an angle of the wafer sample 100 (S 21 ). Next, transfer, using the first sample handling member 20 , the wafer sample 100 from the pre-aligner 30 onto a platform of a loading chamber 40 (S 22 ), in which the loading chamber 40 is configured for preparing the wafer sample 100 for the charged particle beam imaging. The wafer sample 100 is then grabbed by a second sample handling member 50 within the loading chamber 40 (S 23 ), and then picked and transferred from the second sample handling member 50 by a third sample handling member 60 onto the surface of the support member 70 disposed within an inspection chamber (S 24 ). Lastly, the wafer sample 100 on the support member 70 is secured by the securing unit 80 (S 25 ), so as for the charged particle beam imaging step to be performed subsequently. It is noted that the wafer sample 100 is kept electrically neutral by grounding the first, second and third sample handling members ( 20 , 50 , 60 ), the pre-aligner 30 , the platform of the loading chamber 40 , the support member 70 and the securing unit 80 anytime during the transfer-in process. In a preferred embodiment, any one of the first, second and third sample handling member ( 20 , 50 , 60 ), the pre-aligner 30 , the platform of the loading chamber 40 , the support member 70 and the securing unit 80 has an electrical resistivity of 10 5 to 10 9 ohms-cm, or less than 10 5 ohms-cm. In an embodiment, the securing unit 80 includes an electrostatic chuck (e-chuck).

FIG. 3 is a flow chart illustrating the further detailed process of the transfer-out process S 13 illustrated in FIG. 1 . In transfer-out process S 13 , the wafer sample 100 on the support member 70 is released or un-secured from the securing unit 80 after the step of the charged particle beam imaging (S 31 ). Next, the wafer sample 100 is picked by the third sample handling member 60 from the support member 70 (S 32 ), transferred to the second sample handling member 50 , and then put onto the platform of the loading chamber 40 (S 33 ) by the second sample handling member 50 . Lastly, transfer, using the first sample handling member 20 , the wafer sample 100 from the loading chamber 40 into the wafer sample storage 10 (S 34 ). It is noted that in the entire transfer-out process the wafer sample 100 is kept electrically neutral all the time by grounding the first, second and third sample handling members ( 20 , 50 , 60 ), the platform of the loading chamber 40 , the support member 70 and the securing unit 80 . In a preferred embodiment, the first, second and third sample handling members ( 20 , 50 , 60 ), the pre-aligner 30 , the platform of the loading chamber 40 , the support member 70 and the securing unit 80 have an electrical resistivity of 10 5 to 10 9 ohms-cm, or less than 10 5 ohms-cm. In an embodiment, the securing unit 80 includes an electrostatic chuck (e-chuck).

In an embodiment, the wafer sample storage 10 includes one selected from a group consisting of the following, or any combination thereof: cassette, standard mechanical interface (SMIF), front opening unified pod (FOUP); the first sample handling member 20 includes a robot end effecter; the second sample handling member includes a vacuum arm; the third sample handling member 60 includes at least one projections arranged on the support member 70 and upon which the wafer sample 100 is seated; and the loading chamber 40 includes a load lock.

Referring to FIG. 4 and FIG. 5 , a charged particle beam imaging system of a wafer sample according to an embodiment of the present invention is illustrated. As shown in FIG. 5 , a charged particle beam imaging system includes a charged particle beam generator 110 , a condenser lens module 120 , a probe forming objective lens module 130 , a charged particle beam deflection module 150 , a secondary charged particle detector module 170 , an image forming module 180 , and a particle contamination controller 220 .

The charged particle beam generator 110 is configured for generating a primary charged particle beam; the condenser lens module 120 for condensing said primary charged particle beam; the probe forming objective lens module 130 is configured for focusing condensed the primary charged particle beam into a charged particle beam probe 140 ; the charged particle beam deflection module 150 is configured for scanning the charged particle beam probe 140 across a surface of the wafer sample 100 ; the secondary charged particle detector module 170 is configured for detecting charged particles 160 generated from the surface of wafer sample 100 when being bombarded by the charged particle beam probe 140 , and whereby generating a secondary charged particle detection signal accordingly; and the image forming module 180 electrically coupled with the secondary charged particle detector module 170 is configured for receiving the secondary charged particle detection signal from the secondary charged particle detector module 170 and forming at least one charged particle microscope image.

As shown in FIG. 4 , the particle contamination controller 220 is coupled with the first sample handling member 20 , the second sample handling member 50 and the third sample handling member 60 for transferring the wafer sample 100 , the wafer sample storage 10 for pre-imaging and post-imaging storage of the wafer sample 100 , the pre-aligner 30 for adjusting an angle of the wafer sample 100 , the loading chamber 40 for preparing the wafer sample 100 for the charged particle beam imaging, and the support member 70 disposed within an inspection chamber for supporting the wafer sample 100 thereon during the charged particle inspection, the support member 70 being equipped with a securing unit 80 for securing and un-securing the wafer sample 100 on the support member 70 .

The particle contamination controller 220 includes a computer readable medium encoded with a computer program for controlling particle absorption on the wafer sample 100 during charged particle beam imaging. Referring to FIG. 1 to FIG. 3 , the computer program performs the same steps in the above-mentioned embodiment, including steps S 21 ˜ 25 , S 12 , and S 31 ˜ 34 .

It is noted that at any given time point other than the charged particle beam imaging step S 12 , the wafer sample 100 is kept electrically neutral by grounding the first, second and third sample handling members ( 20 , 50 , 60 ), the pre-aligner 30 , the loading chamber 40 , the support member 70 and the securing unit 80 . In a preferred embodiment, the first, second and third sample handling members ( 20 , 50 , 60 ), the pre-aligner 30 , the platform of the loading chamber 40 , the support member 70 and the securing unit 80 have an electrical resistivity of 10 5 to 10 9 ohms-cm, or less than 10 5 ohms-cm.

In an embodiment, the wafer sample storage 10 includes one selected from a group consisting of the following, or any combination thereof: cassette, standard mechanical interface (SMIF), front opening unified pod (FOUP); the first sample handling member 20 includes a robot end effecter; the second sample handling member 50 includes a vacuum arm; the third sample handling member 60 includes at least one projections upon the wafer sample is seated; and the loading chamber 40 includes a load lock.

To sum up the foregoing descriptions, the present invention controls particle absorption on a wafer sample within a charged particle beam imaging system and is achieved by keeping the wafer sample electrically neutral by grounding the wafer sample all the time except for during the actual inspection.

While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.