JP2006294878A - Method and device for ion implantation for semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable ion implantation method and an ion implantation treatment device, and a semiconductor device manufactured by using the ion implantation treatment device, by restraining floating particles from breaking a resist pattern formed on the semiconductor substrate, and restraining floating particle stored on the semiconductor substrate from inhibiting the formation of a diffusion layer caused by the collision of the floating particle and an ion beam in a treatment chamber for treating a semiconductor device. <P>SOLUTION: When ion beam 3 is cast on a wafer 14 supported in a treatment chamber 12, the quantity of foreign matters in the treatment chamber 12 is calculated. When the calculated amount of foreign matters reaches a certain value or more, the irradiation of the ion beam 3 to the wafer 14 is stopped. When the calculated amount of foreign matters is less than a certain value, the irradiation of ion beam to the wafer 14 is started again. A control parameter for controlling the ion beam 3 is varied so that the amount of foreign matters in the treatment chamber 12 is less than a certain value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ion implantation method and apparatus for a semiconductor device, and more particularly to an ion implantation method and apparatus for a semiconductor device for forming an impurity diffusion layer in a semiconductor substrate when the semiconductor device is manufactured.

  Conventional ion implantation for forming a diffusion layer in a semiconductor substrate is performed by irradiating an ion beam to a semiconductor substrate on which a resist pattern is formed in a processing chamber in order to form the diffusion layer in a desired region. ing. However, when the ion beam is irradiated, a large amount of outgas is generated from the resist formed on the semiconductor substrate, and the pressure in the processing chamber in which the semiconductor substrate is processed increases. That is, the degree of vacuum deteriorates. When the pressure in the processing chamber increases due to the outgas from the resist, there is a high possibility that a part of the ion beam collides with gas molecules in the processing chamber. It adversely affects the formation of and causes various electrical characteristics to deteriorate and fluctuate.

  This phenomenon occurs as follows. That is, a part of the ion beam collides with gas molecules, and the ions in the ion beam lose electric charge and become electrically neutral. Although this is injected into the semiconductor substrate, the dose is measured by integrating the value of the current flowing through the semiconductor substrate by the ion beam, so that electrically neutral ion particles are implanted into the semiconductor substrate. Nevertheless, the appearance (measurement) is regarded as not being driven, and the dose cannot be measured correctly.

  This problem is significant when the current value of the ion beam is large as in a large current ion implantation apparatus, and is a problem related to ion implantation. Therefore, in order to solve this problem, conventionally, the pressure in the processing chamber is monitored, a certain threshold is set for the pressure, the processing is interrupted, and the measures disclosed in Patent Document 1 are taken. . That is, in Patent Document 1, a variable aperture is provided upstream of the ion beam processing chamber, the pupil size (opening) is linked with the pressure in the processing chamber, and the aperture is narrowed when the pressure decreases. The problem is solved by reducing the amount of ion beam entering the processing chamber to suppress an increase in pressure in the processing chamber and returning the aperture size to the original size when a desired pressure is reached.

  In addition, suspended particles in the processing chamber for processing the semiconductor substrate collide with the ion beam elastically, scatter in the processing chamber, and collide with the resist pattern formed on the semiconductor substrate, thereby destroying the resist pattern, The particles staying on the semiconductor substrate obstruct the formation of a diffusion layer in a desired region. Thus, although depending on the diffusion layer to be inhibited, there is a problem that various electrical characteristics of the semiconductor substrate are deteriorated and changed.

  The generation source of the floating particles in the processing chamber will be described. Although the floating particles are generated due to various factors, the largest generation cause is a beam line through which the ion beam passes. Usually, since the beam line is exposed to an ion beam, the location where the collision is considered and the location where the ion beam collides in the aperture for narrowing the beam shape are protected by graphite or the like. Although this graphite is stable, if it is used for a long time, the surface is deformed by the collision of the ion beam, or the graphite powder floats in the beam line, and the floating graphite powder is treated. Becomes floating particles in the room.

  In addition, the beam profile (beam shape) is controlled so that the ion beam does not collide with the inner wall of the beam, but the fluctuation of plasma in the ion source, fluctuation of extraction voltage, fluctuation of steering voltage for orbit correction, lens for beam convergence The beam profile slightly varies even during the processing of the semiconductor substrate due to variations in voltage of the semiconductor substrate, that is, due to variations in various equipment parameters. Due to the fluctuation of the beam profile, a part of the beam collides with the inner wall of the beam line which does not normally collide, and the inner wall material is sputtered to become floating particles in the processing chamber.

  The former suspended particles due to graphite can be suppressed by regular replacement of parts such as graphite. However, the floating particles generated by the collision between the latter beam inner wall and the ion beam are caused by the state of the equipment parameters, and it is difficult to predict in advance and suppress the generation.

Regarding the above-described problem related to the pressure increase in the processing chamber, as shown in Patent Document 1, the pressure state of the processing chamber is monitored and the size of the variable aperture installed upstream of the processing chamber is set to the pressure value. It can be solved by controlling based on. However, the problem relating to floating particles cannot be solved by the technique described in Patent Document 1.
JP-A-7-296763

  If it repeats, although the method shown by the said patent document 1 can solve the error reduction of the dose amount resulting from the pressure fluctuation in a process chamber, it suppresses the floating particle in a process chamber and stabilizes the electrical property of a semiconductor device. It is not possible.

  On the other hand, by providing an ion beam line that is sufficiently larger than the ion beam profile, it is possible to completely avoid collision between the ion beam and the inner wall of the beam line. Because processing capacity is increased and power consumption is increased, it cannot be enlarged for various economic reasons. Even with the equipment currently in use, it is possible to avoid collisions with the inner walls of the beam line by processing the semiconductor substrate using an ion beam with a sufficiently small beam profile for the beam line. However, since the beam profile is small, it may be possible to process low doses, but processing high doses requires a long processing time, and the production capacity of the ion implantation facility is significantly reduced. . For this reason, it is actually difficult to reduce the beam profile, which is not practical.

  Accordingly, the present invention is based on the collision of floating particles and ion beams in a processing chamber for processing a semiconductor device, so that the floating particles destroy the resist pattern formed on the semiconductor substrate or are diffused by the floating particles remaining on the semiconductor substrate. An object of the present invention is to provide a stable ion implantation processing method, an ion implantation processing apparatus, and a semiconductor device manufactured by using the manufacturing apparatus while suppressing the formation of a layer.

  In order to achieve the above object, the ion implantation method of the present invention counts the number of floating particles as foreign matter in a processing chamber for performing ion beam irradiation processing on a wafer, and the amount of the counted foreign matter is a certain value or more. Then, the irradiation of the ion beam to the wafer is stopped. That is, if the number of floating particles increases, the electrical characteristics of the semiconductor device may be deteriorated. Therefore, the ion implantation process is temporarily stopped by stopping the irradiation of the ion beam onto the wafer. The quantity of floating particles can be counted by a particle counter.

According to the present invention, it is preferable to restart the ion implantation process when the number of floating particles decreases and becomes the desired number of particles or less.
The increase in the number of suspended particles occurs when the ion beam collides with the inner wall of the beam line. Therefore, according to the present invention, in order to prevent the ion beam from colliding with the inner wall of the beam line, the equipment profile is changed to change the beam profile shape. By changing the equipment parameters, the beam profile shape is changed, the collision with the inner wall of the beam line is eliminated, the suspended particles sputtered from the inner wall are eliminated, and the suspended particles in the processing chamber are also reduced. That is, the beam profile is controlled by changing the equipment parameters by counting the floating particles in the processing chamber.

  The floating particles in the processing chamber are discharged by an evacuation device provided to keep the pressure in the processing chamber constant. Therefore, if the generation of floating particles is eliminated, the number of floating particles in the processing chamber also decreases. Therefore, according to the present invention, the ion implantation process can be performed on the semiconductor substrate in such a state that the number of suspended particles in the processing chamber is suppressed.

  According to the present invention, in a processing chamber in which ions are implanted into a wafer, processing is performed while the number of floating particles is constantly monitored during ion implantation, and processing is performed only when the number of particles is less than a certain number. When the number of floating particles increases above a certain value, the ion implantation process is temporarily stopped. Therefore, since the floating particles colliding with the ion beam do not collide with and destroy the resist pattern formed on the wafer, a diffusion layer can be formed in a predetermined region by ion implantation. It is possible to suppress the deterioration and fluctuation of the electrical characteristics. In addition, when suspended particles increase, the beam profile can be optimized by controlling equipment parameters so as to eliminate the collision between the ion beam and the inner wall of the ion beam line, which is the main cause of the generation. The number of floating particles can be reduced. As a result, the ion implantation process can be performed in a state where the number of floating particles in the processing chamber is kept below a certain value.

  FIG. 1 shows a schematic diagram of an example of an ion implantation apparatus according to the present invention. The illustrated ion implantation apparatus can be broadly classified into four types: a beam generation unit A, a mass analysis unit B, a beam transport unit C, and a processing unit D for wafers.

  The beam generation unit A is provided with an ion source 1 for generating ions that are the source of the ion beam and a vacuum pump 2 for keeping the inside of the ion source 1 in a vacuum, and is extracted from the ion source 1. The ion beam 3 passed through the electrostatic lens 4 for converging the ion beam 3 is introduced into the mass analyzer B. Each control parameter of the ion source 1 is controlled by the ion source control device 5. In order to generate ions, the source plasma is required, and the ion source control device 5 controls the material gas flow rate, plasma power, magnetic field for confining the plasma, ion beam from the ion source 1. It plays an important role in determining the beam profile and the amount of beam energy of the ion beam 3 by controlling the extraction voltage and the control of the electrostatic lens 4. Further, the beam profile of the ion beam 3 is determined by the energy of the ion beam 3 generated from the electrostatic lens 4 and the ion source 1.

  An entrance 7 made of graphite, for example, is provided at the entrance of the beam line 6 of the mass analyzer B, and the aperture 7 reduces the collision of the ion beam 3 with the inner wall of the beam line 6. In the mass analyzer B, the ion beam 3 is subjected to mass analysis by passing through an electromagnet for mass analysis, whereby an ion beam having a desired energy can be obtained.

  The ion beam 3 that has passed through the mass analysis section B is then introduced into the beam transport section C. The beam line 6 of the beam transport section C is provided with a vacuum pump 8 for keeping the inside of the ion source 1 in a vacuum like the ion source 1. Similarly to the beam generation unit A, an electrostatic lens 9 is provided to adjust the beam profile of the beam line 6. The electrostatic lens 9 is controlled by the ion source control device 5, and the control parameters are controlled so as to obtain a desired beam profile. After passing through the electrostatic lens 9, the ion beam 3 is introduced into the processing unit D through apertures 10 and 11 made of, for example, graphite for reducing the collision with the inner wall of the beam line 6.

  The processing unit D includes a processing chamber 12 for performing ion implantation on the semiconductor substrate, and a support base 15 that supports the wafer 14 is provided inside the processing chamber 12. Further, a vacuum pump 13 is provided for keeping the inside of the processing chamber 12 at a constant pressure. The illustrated apparatus is not an apparatus that performs an ion implantation process by scanning the ion beam 3 but performs an ion implantation process uniformly on the wafer 14 by operating a rotary support base 15. Therefore, a plurality of wafers 14 are arranged in the rotation direction on the support table 15, and in order to uniformly irradiate all the wafers 14 installed on the support table 15 with the ion beam 3, the support table 15. Is configured to rotate and move in a direction perpendicular to the ion beam 3, that is, in a radial direction of the rotation path. Thereby, the ion beam 3 can be uniformly irradiated to the wafer 14.

  The processing chamber 12 is provided with a Faraday cup 16 for measuring the dose of ions implanted into the wafer 14. The Faraday cup 16 measures the current value of the ion beam 3 and integrates it. The dose is measured by In the processing section D, the ion beam 3 is blocked by the support base 15, and it seems that the ion beam 3 does not go to the Faraday cup 16 installed on the downstream side, but a slit shape is formed in a part of the support base 15. There is no through-hole, and no wafer is installed in the through-hole. The pulsed ion beam 3 is incident on the Faraday cup 16, and the dose is measured by measuring it.

  The processing chamber 12 is further provided with a particle measuring device 17 using, for example, laser scattered light in order to count the floating particles inside the processing chamber 12. Reference numeral 18 denotes a particle measurement control device. The particle measuring instrument 17 and the particle measurement control device 18 constantly measure and monitor floating particles in the processing chamber 12.

  If the measurement value (for example, N) of the particle measuring instrument exceeds a desired value (for example, nt) during the processing of the wafer 14, the particle measurement control device 18 determines that it is abnormal. Then, in order to interrupt the implantation process, the beam stopper 19 provided in the beam transport section C operates to stop the ion beam 3, thereby interrupting the beam irradiation to the wafer 14.

  Alternatively, as shown in FIG. 2, the support 14 that supports the wafer 14 moves in a direction perpendicular to the ion beam 3, so that the wafer 14 moves out of the trajectory of the ion beam 3, and the ion beam 3 is removed. Make it impossible to irradiate.

  When the process is continued on the wafer 14 in a state where the suspended particles in the processing chamber 12 are increased, the suspended particles collide with the ions constituting the ion beam 3 and are combined with the ion beam 3 to be irradiated onto the wafer 14. The Then, a resist pattern is formed on the wafer 14 in order to form a diffusion layer, and floating particles colliding with the ion beam 3 collide with the resist pattern to destroy the resist pattern. The floating particles are generated, for example, when the ion beam 3 collides with the inner wall of the beam line 6 and performs sputtering, floats in the beam line 6, and part of the particles flows into the processing chamber 12.

  This will be described with reference to FIG. FIG. 3A shows the ion beam 3 in the processing chamber 12, and in this ion beam 3, there are countless particles 31 that are implanted into the wafer in order to form a diffusion layer. The number of particles 31 present in the ion beam 3 varies depending on the current value of the ion beam. In FIG. 3A, the floating particles 32 in the processing chamber 12 are in the state of floating in the vicinity of the ion beam 3. When this floating particle 32 further approaches the ion beam 3, it collides with the particle 31 as shown in FIG. 5B, and the floating particle 32 moves in the direction of the flow of the ion beam 3 as shown in FIG. To do. At this time, the particles 31 and the floating particles 32 are scattered in all directions, but this figure shows only the case where the particles 31 and the suspended particles 32 are scattered in the direction of the flow of the ion beam 3 in question. The floating particles 32 colliding with the particles 31 move toward the resist pattern 34 formed on the wafer 33 together with the ion beam 3 and collide with the resist pattern 34 as shown in FIG. As a result, as shown in FIG. 5E, the resist pattern 34 falls or is lost on the wafer 33, so that a diffusion layer can be formed in accordance with the resist pattern created to form a desired diffusion region. Absent. For this reason, the characteristics of the semiconductor device deteriorate or the semiconductor device becomes inoperable.

  In order to avoid the occurrence of such a situation, the ion implantation apparatus of the present invention shown in FIG. 1 and FIG. A mechanism is provided to stop processing immediately. That is, as described above, the generation of floating particles is caused by the collision of the ion beam 3 with the inner wall of the beam line 6. A command is sent to the control device 5 to change the equipment parameter in order to change the beam profile. For example, the ion source controller 5 uses an algorithm for changing the beam profile shape, such as reducing the ion beam current value in order to reduce the cross-sectional shape of the ion beam or to suppress the spread of the beam. Be prepared. In this case, it is preferable to determine an algorithm in advance for each ion species and control the ion beam 3 according to the ion species of the ion beam 3.

  By changing the profile of the ion beam 3 in this way, the number of floating particles 32 in the processing chamber 12 is reduced, and the operation of the beam stopper 19 that has stopped the ion beam 3 is canceled, or the wafer 14 is removed. The supporting stage 15 that is supported is returned to the trajectory of the beam line 6 and the processing on the wafer 14 is resumed.

  As shown in FIG. 2, when the particle measurement control device 18 recognizes an abnormality and moves the support base 15 to temporarily stop the processing on the wafer 14, the ion beam 3 is moved by the beam stopper 19. Unlike the case where the ion beam 3 is stopped, the ion beam 3 reaches the inside of the processing chamber 12 where floating particles exist. Therefore, in a state where the ion source control device 5 is not controlling, the particle measuring device 17 continues to show an abnormal value. Under such circumstances, the ion for changing the beam profile so that the particle measurement control device 18 and the ion source control device 5 are connected and all control parameters controlled by the ion source control device 5 are changed. The algorithm of the source control device 5 is created in advance.

  As a result, when processing is performed using the ion implantation apparatus of FIGS. 1 and 2, it is possible to perform processing in a state where the floating particles in the processing chamber 12 are always controlled to a desired quantity or less. The problem at the time of forming the diffusion layer of the semiconductor substrate can be solved.

  The ion implantation method and apparatus according to the present invention constantly monitors the number of suspended particles in the implantation process chamber and changes the ion beam profile to reduce suspended particles when a desired number or more of suspended particles are generated. Therefore, it is useful as an ion implantation apparatus for a semiconductor substrate, and can also be applied to applications such as ion implantation for forming a plasma display. Furthermore, the manufacturing process of a semiconductor substrate or the like that changes the processing conditions for the object to be processed by constantly monitoring the environment in which the object to be processed such as a semiconductor substrate is installed and catching the change in the state. Also can be applied.

Configuration diagram of ion implantation apparatus according to the present invention Configuration diagram of ion implantation apparatus according to the present invention in a state different from FIG. Schematic diagram showing the behavior of airborne particles in the ion implantation chamber

Explanation of symbols

A Beam generation unit B Mass analysis unit C Beam transport unit D Processing unit to semiconductor substrate 3 Ion beam 5 Ion source control device 6 Beam line 12 Processing chamber 14 Wafer 17 Particle measuring device 18 Particle measurement control device 19 Beam stopper

Claims (10)

  When irradiating a wafer supported in the processing chamber with an ion beam, the number of foreign particles in the processing chamber is counted, and when the counted amount of foreign particles exceeds a certain value, the irradiation of the ion beam to the wafer is stopped. An ion implantation method for a semiconductor device.   2. The ion for a semiconductor device according to claim 1, wherein after the irradiation of the ion beam to the wafer is stopped, the ion beam irradiation to the wafer is resumed when the counted amount of foreign matter becomes less than a certain value. Injection method.   3. The control parameter for controlling the ion beam is varied by an algorithm for varying the control parameter for controlling the ion beam so that the number of foreign matters in the processing chamber is less than a predetermined value. An ion implantation method for the described semiconductor device.   4. The ion implantation method for a semiconductor device according to claim 3, wherein the ion beam is controlled in accordance with the ion species by a predetermined algorithm corresponding to each ion species.   An ion implantation apparatus for irradiating a wafer supported in a processing chamber with an ion beam, and a measuring instrument for measuring the number of foreign substances in the processing chamber, and the amount of foreign substances counted by the measuring instrument exceeds a certain value An ion implantation apparatus for a semiconductor device, comprising: means for stopping irradiation of an ion beam to the wafer.   6. The ion implantation apparatus for a semiconductor device according to claim 5, further comprising means for resuming irradiation of the ion beam onto the wafer when the amount of foreign matter counted by the measuring instrument becomes less than a predetermined value.   A control device capable of controlling a control parameter for controlling the shape of the ion beam, a measuring device, a means for stopping irradiation of the ion beam to the wafer, a means for restarting irradiation of the ion beam to the wafer, and the control device, 7. The ion implantation apparatus for a semiconductor device according to claim 6, wherein the ion implantation apparatus is configured so as to be ion-implanted in a state in which the number of foreign substances in the processing chamber is equal to or less than a predetermined number by being configured to cooperate with each other.   The means for stopping the irradiation of the ion beam onto the wafer is a stopper provided on the upstream side of the processing chamber and capable of physically stopping the ion beam. An ion implantation apparatus for a semiconductor device according to claim 1.   8. The means for stopping the irradiation of the ion beam onto the wafer is a means for moving the support table supporting the wafer from the ion beam trajectory and retracting it. Implanter for semiconductor devices. A semiconductor device manufactured using the ion implantation apparatus for a semiconductor device according to claim 5.

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