GB2307779A

GB2307779A - Detecting contaminant particles during ion implantation

Info

Publication number: GB2307779A
Application number: GB9624313A
Authority: GB
Inventors: Jae-Sun Jeon; Won-Yeong Kim; Seung-Ki Chae; Chi-Seon Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1995-12-02
Filing date: 1996-11-22
Publication date: 1997-06-04
Also published as: GB9624313D0; DE19649640A1; JPH09180668A; KR970053215A; TW316292B

Description

2307779 APPARATUS AND METHOD FOR DETECTING PARTICLES IN PROCESS CHAMBER OF

ION IMPLANTER The present invention relates to a system for detecting particles in the process chamber of an ion-implanter. And more particularly, this invention relates to an apparatus and a method for detecting the number of particles and the size of each particle without the use of a separate test wafer.

During an ion-implantation, lots of micro-particles (hereinafter, referred to as "particles") occur in the process chamber of an ion implanter upon ions being implanted into the surface of a wafer. The contamination level of the process chamber caused by such particles serves as a very important factor in determining the quality of products.

So as to monitor the contamination level in the process chamber, a surfscan detecting method has widely been used which may detect the number of particles by using a bare wafer. Fig. 1 is a flow diagram showing process steps for detecting particles with the above described surfscan method.

As shown in Fig. 1, after detecting the number of particles on a bare wafer using a surf scan detector (step S1), the bare wafer is loaded in the chamber of an ion implanter and located on a disk in order (step S2). The ion implanter is then operated under usual operational conditions without the production of ions (step S3). If the implantation is completed, the wafer is unloaded from the chamber (step S4) and then a surface detecting process is carried out by the surfscan detector to detect again the number of particles included on the wafer (step S5). Then, by comparing the number of particles on the bare wafer with that of particles on the unloaded wafer, the contamination level in the chamber can be measured. As the result of this measure, if the number of particles in the chamber is below a predetermined value, the ion implanter can be operated, but, if not, the 1 a 0 operation of the ion implanter should be stopped to clean it.

However, since the above described method may detect a contamination level of the process chamber only in case that no ion beam exists therein, it is impossible to accurately detect a contamination level due to particles in case that ion beams exist in the chamber, i.e., during a normal operation of the ion implanter.

It is generally well known that many more particles occur during the normal operation of the ion implanter. For this reason, the conventional surfscan method is considerably lowered in reliability. Since the conventional surfscan method should be carried out while the operation of an ion implanter is stopped, the ion implanter is seriously lowered in both operation efficiency and yield rate.

Additionally, since the conventional surfscan method is periodically carried out, there arises a serious problem that it is impossible to detect a contamination level of the ion implanter during an interval between detecting time points.

It is an aim of certain embodiments of the present invention to provide an apparatus for detecting particles in a process chamber of an ion implanter during a normal operation of the ion implanter, and a method for detecting the particles.

It is a further aim of certain embodiments of the present invention to provide an apparatus for detecting particles by batches in a process chamber of an ion implanter without the use of a testing wafer, and a method for detecting the particles.

According to one embodiment of the present invention, an apparatus for detecting particles existing in a process chamber of an ion implanter, comprises means for generating a control signal by a control of a main controller for the ion implanter; means having a particle detector to be operated responsive to the 2 0 0! control signal, for radiating a laser beam toward particles existing in a process chamber of the ion implanter and converting a diffracted beam from the particles into an electrical signal indicative of a particle detection signal; and means for analysing the particle detection signal and outputting the pulse number and a voltage level of the particle detection signal, said pulse number being indicative of the number of the particles and said voltage level being indicative of each size of the particles.

In a preferred embodiment, said particle detector comprises an in-situ particle monitoring sensor, which comprises a laser diode for generating the laser beam and a detecting element for converting the diffracted beam into the electrical signal.

According to a further embodiment of the present invention, a method for detecting particles existing in a process chamber of an ion implanter, comprises the steps of loading wafers in the ion implanter; placing the wafers on a disk in the process chamber by a wafer handler; injecting ions into the wafers; detecting particles by using a particle detecting sensor during the ion injection step; and unloading the wafers from the ion implanter.

In a preferred embodiment, the step of detecting particles comprises the steps of radiating a laser beam toward the particles, receiving a diffracted beam from the particles and converting the diffracted beam into an electrical signal.

In a preferred embodiment, the method comprises the step of analyzing the electrical signal and outputting the pulse number thereof indicative of the number of particles and a voltage level thereof indicative of each size of the particles.

According to a still further embodiment of the present invention, a method for detecting particles existing in a process chamber of an ion implanter, comprises the steps of loading 3 wafers in the ion implanter; placing the wafers on a disk in the process chamber by a wafer handler; detecting particles to generate a first detection signal; injecting ions into the wafers; detecting particles to generate a second detection signal during the ion injection step; unloading the wafers from the ion implanter; detecting particles to generate a third detection signal; and comparing the detection signals with one another to check a contamination level of the process chamber.

As mentioned above, the apparatus and the method of detecting particles in accordance with the present invention makes it possible to take an accurate measurement of contamination in the process chamber and to monitor particles in the process chamber by batch even during the ion implanting process.

Preferred embodiments of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a f low diagram showing the process steps of a conventional method for detecting particles in the process chamber of an ion implanter; Fig. 2 is a plan view illustrating the overall structure of an ion implanter in which a particle detecting apparatus according to the present invention is located; Fig. 3 is a side view illustrating a schematic structure of the process chamber in which a particle detector of the particle detecting apparatus is installed; Fig. 4 is a schematic block diagram illustrating the particle detecting apparatus of Fig. 2; Fig. SA is a diagram explaining a principle of detecting particles by ISPM (In-Situ Particle Monitoring) sensor used as 4 0 - ' %! the particle detector in the particle detecting apparatus of the invention; Fig. 5B is a waveform diagram showing the relationship between the pulse number and the voltage level of a particle detection signal in accordance with a predetermined time; and Fig. 6 is a f low diagram showing the process steps of a novel method for detecting particles in the process chamber of an ion implanter.

Fig. 2 illustrates an ion implanter with which a preferred embodiment of the invention may be implemented. A novel particle detecting apparatus in accordance with this embodiment has a detector 50 for detecting the number and each size of particles in the process chamber 40 of an ion implanter during a normal operation thereof. By using the detector 50, it is possible to check a more accurate measurement of the contamination level in the process chamber.

In the ion implanter, impurity ions produced by an ion source portion 31 are accelerated with an energy produced by an ion beam line 32 and radiated toward wafers 100, which are placed on a disk 21 in the process chamber 40. As a result, the ions are injected on the surface of the respective wafer 100.

As the result of checking particles in the process chamber 40, it can be seen that the number of particles occurring during the presence of beam ions is proportional to the amount of the beam ions and the magnitude of the energy, and that the number thereof is from several times to several hundreds times as many as the number of particles, which exist in the absence of beam ions. In order to accurately detect particles in the process chamber, therefore, it is necessary to detect the particles during the ion injection process.

As shown again in Fig. 2, the ion implanter is broadly constituted with a loading part 10 which is provided for loading wafers 100 into the process chamber 40, a driver part 20 for driving the disk 21 with the loaded wafers placed thereon in order that impurity ions can be implanted toward the wafers, and an ion injecting part 100 for producing and radiating the impurity ions into the wafers. The implanter further has a vacuum pump for pumping the air in the process chamber 40 and maintaining the process chamber 40 in a high vacuum state.

If wafers stored in a wafer cassette 12 are loaded the loading part 10 through an elevator 11, they are placed one by one on the disk 21 by means of a waf er handler 14. Thirteen wafers are normally placed on the disk 21 at one ion-implanting process, and they are called one batch.

The ion injecting part 30 has a beam source portion 31 for producing ion beam, an ion line portion 32 for transferring the produced ion beam, and a beam gate 33 installed at an outlet of the ion injecting part 30, for radiating the transferred ion beam toward the wafers 100 on the disk 21. This disk 21 is controlled from a horizontal position (shown in a broken line) to a vertical position (shown in a solid line), as shown in Fig. 3, and then rotated by a driving motor 23 at a high speed. At the same time, ion beam is radiated from the beam gate 33 into the wafers on the disk 21.

Fig. 4 illustrates the particle detecting apparatus, which comprises a detector 50 secured to the inside of the process chamber 40, a controller 70 for controlling the detection operation of the detector 50, and an output portion 60 for analyzing the detected signals and providing analyzed results from the detector 50 to the outside of the process chamber 40. Specifically, the detector 50 is fixed to a frame 22 for supporting the disk 21 and placed at an upper side of the disk 21 regardless of the rotation thereof. The detector 50 is provided with an ISPM (In-Situ Particle Monitoring) sensor which is capable of detecting particles. The operating time of the 6 0 controller 70 is determined by the control of a main controller (not shown) which is used to monitor overall operations of the ion implanter.

Fig. SA illustrates a principle of detecting particles by an ISPM sensor of the detector 50. In this figure, if a laser beam is radiated from a laser diode 51 during the ion injecting process, the beam collides with particles to be diffracted by them. The diffracted beam is provided to a detecting element 52 and converted into an electrical signal of pulse type. The pulse signals from the detecting element 52 is then provided, as a particle detection signal, to the output portion 60 and monitored by the output portion 60. The pulse signals may be represented as waveforms shown in Fig. 5B. The number of the pulse signals during a predetermined time period indicates the number of detected particles and each voltage level of the pulse signals indicates the size of each particle. As a result, if an operator analyzes the detection signal in the pulse number thereof and a voltage level of respective pulse, and the number and each size of particles existing the process chamber during the ion injecting process can be checked by the particle detecting apparatus.

Hereinafter, the operation of detecting particles in accordance with a novel method of the present invention will be described with reference to Fig. 6.

As shown in Fig. 6, if wafers are loaded in an ion implanter (step S11) and placed on a disk of the process chamber in order by a wafer handler (step S12), the process proceeds to step S13, wherein the disk is controlled from a horizontal position to a vertical position and rotated by a driving motor at a high speed. From this time, the particle detecting apparatus of the present invention starts to detect particles in the process chamber by the control of the controller 70 (shown in Fig. 4). The process proceeds to step S14, wherein ion implantation is carried out to inject impurity ions into each surface of the wafers placed on 7 0 the disk. If the implantation is completed, the disk is controlled from the vertical position to the horizontal position (step S15) and unloaded from the disk to the wafer cassette by means of the wafer handler (step S16). The particle detecting apparatus continues to detect the particles until the disk is completely placed in the vertical position to the implanter so as to unload the wafers placed thereon.

As described immediately above, the particle detecting apparatus can check particles existing in the process chamber without the use of a bare wafer for testing. As the results of detecting particles every process step, it can be seen that many more particles are detected during a time between the process steps S13 and S15. So as to accurately check the number of particles existing in the process chamber, thus, the detecting operation should be continuously performed during the steps S13, S14 and S15.

Also in order to effectively monitor particles in the process chamber, the detecting operations should be performed at the step S12, during the steps S13 and S14, and at the step S15. Namely, detection signals are generated from the particle detector at the respective steps S12 through S15, and compared with one another. As comparing the detection signals and outputting the compared result by the output portion 60 such as, a monitor and/or a pen oscillograph, an operator can easily monitor the contamination level of the process chamber.

In addition, the particle detecting apparatus can check the number and each size of particles existing in the process chamber even while an ion injecting process is performed, and can check the particles every batch.

Moreover, the particle detecting apparatus further comprises an alarm portion (not shown) for generating an alarm signal in case that the number of detected particles exceeds a limited range.

8 0.! According to the particle detecting apparatus, the consumption of wafers can be reduced because testing wafers are not used in detecting particles. The detecting operation can be also carried without interruption of the operation of an ion implanter.

9 0 000

Claims

CLAIMS:

1. An apparatus for detecting particles existing in a process chamber of an ion implanter, comprising: means for generating a control signal by a control of a main controller for the ion implanter; means having a particle detector to be operated responsive to the control signal, for radiating a laser beam toward particles existing in a process chamber of the ion implanter and converting a diffracted beam from the particles into an electrical signal indicative of a particle detection signal; and means for analyzing the particle detection signal and outputting the pulse number thereof and a voltage level thereof the pulse number being indicative of the number of the particles and the voltage level being indicative of each size of the particles.

2. The apparatus for detecting particles as defined in claim 1, wherein said particle detector comprises an in-situ particle monitoring sensor.

3. The apparatus for detecting particles as defined in claim 2, said sensor comprises a laser diode for generating the laser beam and a detecting element for converting the diffracted beam into the electrical signal.

4. The apparatus for detecting particles as defined in claim 1, wherein said outputting means comprises a monitor for displaying the particle detection signal and/or an oscillograph for printing it.

5. A method for detecting particles existing in a process chamber of an ion implanter, comprising the steps of: loading wafers in the ion implanter; placing the wafers on a disk in the process chamber by a h 0 wafer handler:

injecting ions into the wafers; detecting particles by using a particle detecting sensor during the ion injection step; and unloading the wafers from the ion implanter.

6. The method for detecting particles as defined in claim 5; wherein the step of detecting particles comprises the steps of radiating a laser beam toward the particles, receiving a diffracted beam from the particles and converting the diffracted beam into an electrical signal.

7. The method for detecting particles as defined in claim 6, further comprising the step of analyzing the electrical signal and outputting the pulse number thereof indicative of the number of particles and a voltage level thereof indicative of each size of the particles.

8. A method for detecting particles existing in a process chamber of an ion implanter, comprising the steps of: loading wafers in the ion implanter; placing the wafers on a disk in the process chamber by a wafer handler; detecting particles to generate a first detection signal; injecting ions into the wafers; detecting particles to generate a second detection signal during the ion injection step; unloading the wafers from the ion implanter; detecting particles to generate a third detection signal; and comparing the detection signals with one another to check a contamination level of the process chamber.

9. Apparatus for detecting particles in the process chamber of an ionimplanter substantially as hereinbefore described with reference to the accompanying drawings.

10. A method for detecting particles in the process chamber of 11 an ion-implanter substantially as hereinbefore described with reference to the accompanying drawings.

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