JP4124437B2 - Ion implantation apparatus and ion implantation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ion implantation apparatus and an ion implantation method for implanting ions into a semiconductor substrate or a glass substrate through a mask member in which an opening for defining an ion implantation region is formed on a chip basis, for example.
[0002]
[Prior art]
As is well known, the ion implantation method (ion implantation method) is used in the impurity element doping step in the semiconductor manufacturing process, and has features such as precise control of the implantation amount and implantation depth. It has become an indispensable technology.
[0003]
In the ion implantation method, an ion beam composed of ions of impurity elements to be implanted, such as B, P, As, etc., is accelerated to a predetermined energy and irradiated onto a wafer. At this time, since the ion beam has linearity, ions can be implanted only into a target region (ion implantation region) using a mask.
[0004]
Conventionally, a resist mask formed on a wafer has been used as the mask. The resist mask is formed by applying a material mainly composed of a photosensitive resin to a uniform thickness on a wafer using a known spin coater or the like, and then printing an exposure pattern corresponding to the ion implantation region on the resist film, By performing development processing, only the ion implantation region is formed as a resist pattern exposed to the outside. Then, after the ion implantation is performed, the resist mask is removed by performing a plasma ashing (ashing) treatment and a wet treatment using sulfuric acid / hydrogen peroxide solution, etc., and in preparation for the next ion implantation step, A resist mask having a different pattern is formed by the above-described process.
[0005]
As described above, in ion implantation using a resist mask, there are many steps required for resist processing in the pre-processing and post-processing of the ion implantation process. Therefore, the processes related to the resist processing are complicated and high in the semiconductor process. There was the problem of bringing about costing.
[0006]
Therefore, for example, as shown in FIG. 5, a conductive mask member M having an opening Ma that defines an ion implantation region is disposed above the wafer W via a gap d, and the wafer W is interposed via the mask member M. There is a technique of irradiating an ion beam L onto the surface of the substrate and implanting ions into the ion implantation layer A (see, for example, Patent Document 1 below). According to this, when ion implantation is performed, it is possible to form a necessary ion implantation layer using a dedicated mask member for each ion implantation.
[0007]
Therefore, by preparing a plurality of types of the mask members, a resist mask forming step which has been conventionally required is unnecessary, and a desired ion implantation process can be performed only by replacing the mask members. Simplification and cost reduction.
[0008]
On the other hand, in the ion implantation step, positive ions are implanted into an ion implantation region on a substrate to be processed such as a wafer, and thus a phenomenon occurs in which the substrate to be processed is positively charged due to accumulation of positive ions. This charge-up phenomenon has a problem of having an electrical influence (for example, a reduction in gate breakdown voltage or dielectric breakdown) on a manufactured semiconductor element such as a transistor.
[0009]
For this reason, in the conventional ion implantation apparatus, when the wafer W is irradiated with the ion beam L, for example, as shown in FIG. 6, an electron generation source G that generates electrons e is provided and supplied from the electron generation source G. A technique for electrically neutralizing the wafer W with electrons e is known.
[0010]
For example, in Patent Document 2 below, two electron generation sources are provided in the beam transport path, and the electron current for neutralization is equalized in both apparatuses so that the electron distribution in the sample plane is uniform. A configuration for achieving equalization is disclosed. In Patent Document 3 below, an electroflood gun as an electron generation source is provided with a scan magnet for scanning electrons in the direction of the semiconductor substrate, and scanning is performed in the same direction and at the same speed as the ion beam. A technique for improving the in-plane uniformity of the summing action is disclosed.
[0011]
However, Patent Documents 2 and 3 do not mention any method for supplying electrons from an electron source when ion implantation is performed through a mask member in which an opening for defining an ion implantation region is formed.
[0012]
[Patent Document 1]
JP 2002-176005 A [Patent Document 2]
Japanese Patent Laid-Open No. 10-12181 [Patent Document 3]
Japanese Patent Laid-Open No. 8-96744 [0013]
[Problems to be solved by the invention]
When ion implantation is performed through a mask member in which an opening for defining an ion implantation region is formed, secondary electrons generated from the mask member and the substrate to be processed due to collision with ions between the mask member and the substrate to be processed. Thus, the substrate to be processed that has been charged up can be neutralized.
[0014]
However, there are cases where positive charge-up in the ion implantation region cannot be eliminated only by secondary electrons generated between the mask member and the substrate to be processed. For example, in the ion implantation process, since the mask member is also irradiated with an ion beam, the mask member 21 is also positively charged up, which makes it difficult for secondary electrons to be generated. Insufficient supply of electrons. Therefore, in this case, there arises a problem that the gate breakdown voltage of a semiconductor element on the substrate to be processed, for example, a transistor is lowered or the gate insulating film is destroyed.
[0015]
The present invention has been made in view of the above problems, and in the case where ions are implanted into a substrate to be processed through a mask member in which an opening for defining an ion implantation region is formed, adverse effects on the elements on the substrate to be processed due to charge-up. It is an object to provide an ion implantation apparatus and an ion implantation method that can be eliminated.
[0016]
[Means for Solving the Problems]
The above-described problems include a stage that supports a substrate to be processed , a mask member that is disposed opposite to the substrate to be processed and that has an opening that defines an ion implantation region, and is connected to a ground potential. wherein an ion implantation device for implanting ions into the substrate to be processed, an electron source for supplying electrons to the mask than member is disposed on the upstream side on the substrate to be treated with respect to the traveling direction of the ion beam, the electron generation A mask potential detecting means for detecting the potential of the mask member irradiated with electrons generated from a source, a substrate potential detecting means for detecting the potential of the substrate to be processed, the mask potential detecting means, and the substrate potential detecting means ; based on the output, the potential of the mask member is set to the ground potential, and to generate the amount of electrons potential of the substrate to be processed is equal to or less than a predetermined value from said generating source Ion implantation apparatus is characterized in that a control unit is solved by.
[0017]
Further, the above problem, an ion implantation mask member having an opening formed to define a region is disposed to face the target substrate, ions are implanted into the mask member through the target substrate, said mask member The potential of the substrate to be processed and the potential of the substrate to be processed are detected, respectively, and at the time of ion implantation, the potential of the mask member becomes the ground potential, and the amount of electrons that causes the potential of the substrate to be processed to be a predetermined value or less This is solved by an ion implantation method characterized by supplying the substrate to be processed from an electron generation source through a member .
[0018]
The present invention aims to electrically neutralize a substrate to be processed which has been positively charged by ion implantation by supplying electrons from the electron generation source onto the substrate to be processed. At this time, will be trapped electrons from positively charged up to the electron source by irradiation of the mask member also ion beam positioned above the target substrate, the output of the mask potential detection means and the substrate potential detecting means The electron generating source is controlled by the receiving control means so that a sufficient amount of electrons are generated to cancel the potential of the mask member.
[0019]
Thereby, although a part of the electrons generated from the electron generation source are trapped by the mask member, the remaining electrons are supplied onto the substrate to be processed. As described above, in the ion implantation apparatus provided with the mask member, electrons can always be supplied onto the substrate to be processed at the time of ion implantation. It is possible to eliminate an adverse electrical effect on the element such as destruction.
[0020]
Here, “a sufficient amount of electrons to cancel the potential of the mask member” means that the total potential of electrons generated from the electron generation source is larger (higher) than the mask potential detected by the mask potential detecting means. More specifically, in the present invention, it means an amount of electrons in which the potential of the mask member becomes the ground potential and the potential of the substrate to be processed is a predetermined value or less .
[0021]
Note that when the amount of electrons supplied from the electron generation source onto the substrate to be processed is large, the substrate to be processed is negatively (negatively) charged, which may cause element destruction. In this case, a substrate potential detecting means for detecting the potential of the substrate to be processed is separately provided, and the output is supplied to the control means, and the amount of electrons generated from the electron generation source is controlled so that the potential of the substrate to be processed does not become more negative than a predetermined value. Adjust it.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0023]
1 to 3 show the configuration of an ion implantation apparatus according to an embodiment of the present invention. Referring to FIG. 1, an ion implantation apparatus 10 includes a vacuum system including a high voltage terminal 10A, a beam line 10B, and an end station 10E. The high voltage terminal 10A located in the shield box S accommodates the ion source 1, the mass separator 2 and the beam blocker 3 located between the slits 3a and 3b having a known configuration. The beam blocker 3 jumps up the ion beam L when a voltage is applied, and temporarily blocks the ion beam L toward the slit 3b.
[0024]
An acceleration tube 4 having a known configuration is attached between the high voltage terminal 3A and the shield box S, and a focusing lens 5a and an ion beam L are electromagnetically moved in the X and Y directions on the beam line 10B at the subsequent stage. In addition, an octopole scanner 6 that scans a minute angle, a beam collimating magnet 7 that also removes contamination particles, and a focusing lens 5b are provided. And the non-contact beam ammeter 8 which electromagnetically measures the electric current of the ion beam L with the coil provided in the outer periphery is attached to the terminal part of the beam line 10B.
As described above, the “ion implantation means” of the present invention is configured.
[0025]
For scanning the ion beam L, an electromagnetic deflection scanner other than the octopole scanner 6 may be used, or an X, Y electrostatic deflection scanner may be used. The magnet 7 acts to remove ions and neutral particles whose charge has changed by colliding with the residual gas in the beam path.
[0026]
The end station 10E is provided with a mask portion 9 that determines an irradiation region of the ion beam L on the wafer W. As shown in FIG. 2, the mask portion 9 is a conductive material having an opening 21 a that defines an ion implantation region in units of one chip with respect to a semiconductor wafer (hereinafter referred to as “wafer”) W as a substrate to be processed. The mask member 21, a holder 23 that holds the mask member 21 via the chuck member 22, and a drive unit 24 that can mechanically drive the holder 23 in the X, Y, and Z directions for a predetermined distance. The drive unit 24 has, for example, a pulse motor as a drive source, and mainly operates when the mask member 21 is replaced.
[0027]
Referring to FIG. 1, a Faraday cup 12 for measuring the current of the ion beam L is disposed below the mask portion 9, and a non-contact beam ammeter 8 is formed with reference to a measurement value by the Faraday cup 12. It is calibrated.
[0028]
As shown in FIG. 1, either a beam density distribution monitor 11 or a stage (platen) 13 that supports the wafer W can be inserted immediately below the mask portion 9. The beam density distribution monitor 11 has a measurement head in which minute Faraday cups are two-dimensionally arranged, but may be configured by other methods. The beam density distribution monitor 11 is used to measure the consistency between the scan region of the ion beam L and the mask portion 9 and the density distribution of the beam current in the mask portion 9 before ion implantation. Is inappropriate, the amplitude of the scan by the octopole scanner 6 is adjusted, and when the current density distribution is not uniform, the beam scan speed adjustment or the excitation current of the focusing lens 5a is adjusted.
[0029]
A rotation mechanism 14 that adjusts the twist angle of the wafer W is attached to the stage 13. The stage 13 and the rotation mechanism 14 are mechanically fast in the X direction (left and right direction in the figure) via the support pillar 15. A movable X-direction drive mechanism 16 is attached. The X-direction drive mechanism 16 is attached to a Y-direction drive mechanism 17 that can be mechanically moved in the Y direction (direction perpendicular to the paper surface). The rotation mechanism 14 has the piezoelectric body 2, and the X and Y direction drive mechanisms 16 and 17 each have a pulse motor as a drive source. The wafer W is transported and the wafer W is aligned with the mask member 21. Driven.
[0030]
Now, as shown in FIG. 2, electrons for supplying electrons to the wafer W on the stage 13 above the mask portion 9, that is, upstream of the mask portion 9 with respect to the traveling direction of the ion beam L. A source 28 is arranged. In the present embodiment, the electron generation source 28 is constituted by a hot filament, but other than this, it may be constituted by, for example, an electron gun.
[0031]
The amount of electrons generated from the electron generation source 28 is controlled by the control unit 29. The controller 29 is supplied with the output of a mask potential sensor 30 that detects the potential of the mask member 21. The control unit 29 controls the output of the electron generation source 28 based on the output of the mask potential sensor 30 so as to generate a sufficient amount of electrons to cancel the potential of the mask member 21. .
[0032]
As shown in FIGS. 2 and 3, the mask member 21 tends to be charged up positively by being irradiated with the ion beam L at the time of ion implantation into the wafer W. The mask potential sensor 30 detects this mask potential and supplies the output to the control unit 29. The control unit 29 receives the output of the mask potential sensor 30 and controls the amount of generated electrons by adjusting the voltage applied to the hot filament (not shown) in the electron generation source 28 and the electron extraction voltage. As a control method, on / off control of the electron generation operation, increase / decrease control of the amount of generated electrons, and the like are applied.
[0033]
In this embodiment, a wafer potential sensor 31 for detecting the potential of the wafer W at the time of ion implantation is provided, and this output is supplied to the control unit 29. Based on the output of the mask potential sensor 31, the controller 29 complementarily prevents the wafer W from being negatively charged more than the predetermined value V0 (so that the wafer potential Vw does not become lower than the predetermined value V0). The amount of electrons generated from the is controlled.
[0034]
Next, the operation of the ion implantation apparatus 10 of the present embodiment configured as described above will be described.
[0035]
As shown in FIG. 2, the wafer W placed on the stage 13 is held by the wafer holding member 26, and is moved directly below the mask member 21 by the X and Y direction driving mechanisms 16 and 17. Then, based on a preset control sequence, the chip region to be ion-implanted first is aligned with the mask member 21.
[0036]
Subsequently, ion implantation is started. An ion beam L made of desired ions selected from the ion species generated by the ion source 1 by the mass separator 2 is accelerated to a predetermined energy by the accelerating tube 4, and then the focusing lens 5 a, octopole, The wafer W is irradiated through the scanner 6, the magnet 7, and the focusing lens 5b. The ion implantation area A (FIG. 3) on the wafer W is regulated by the opening 21 a of the mask member 21. That is, the mask member 21 functions as a conventional resist mask.
[0037]
When the ion implantation process is started, the mask member 21 is irradiated with the ion beam L to generate secondary electrons as shown in FIG. Further, secondary ions are also generated from the wafer W along with ion implantation into the wafer W. By supplying these secondary electrons to the wafer W, the positive charge-up of the wafer is suppressed. However, the mask member 21 is gradually charged up in the positive direction due to the irradiation of the ion beam and the emission of secondary electrons, which makes it difficult for the electrons to jump out of the mask member and the generation of secondary electrons from the mask member 21. The amount decreases. On the other hand, since the secondary electrons generated from the wafer W are trapped by the mask member 21, the amount of electrons existing between the mask member 21 and the wafer W is reduced. This causes a shortage of electrons. This causes the charge up of the wafer W in the positive direction.
[0038]
Therefore, in the present embodiment, supply control of electrons from the electron generation source 28 to the wafer W is performed according to the control flow shown in FIG.
[0039]
That is, first, the potential Vm of the mask member 21 is detected by the mask potential sensor 30 (step S1), and the control unit 29 receiving the output determines whether or not the mask member 21 is charged up (step S2). Although the mask member 21 is connected to the ground potential from the beginning, the potential rises over a range of several mV to several volts due to the ground resistance. The mask potential sensor 30 detects the increased potential.
[0040]
If charge-up of the mask member 21 is recognized, next, the potential Vw of the wafer W is detected by the wafer potential sensor 31 (step S3). If this is higher than the predetermined value V0 (<0), the electron generation source 28 is detected. To generate electrons (steps S4 and S5). This step is to detect the degree of charge up of the wafer W, and electrons are generated from the electron source 28 only when charge up of the wafer W is recognized.
[0041]
Here, as described above, the amount of electrons generated from the electron generation source 28 is an amount of electrons having a potential sufficient to cancel the potential of the mask member 21, and the value can be set freely. In addition, the amount of generated electrons may be fixed or variable. The reference for setting the predetermined value V0 of the wafer potential is the magnitude of the negative potential allowed as the wafer potential, and this value is naturally determined by the type of element to be protected. Also, setting the predetermined value V0 to less than 0 leads to preventing an unexpected positive charge-up of the wafer W due to erroneous detection of the wafer potential.
[0042]
Among all the electrons generated from the electron generation source 28, some are trapped by the mask member 21, but the remaining electrons are supplied to the wafer W and contribute to electrical neutralization of the wafer W. The supply of electrons from the electron generation source 28 is continued until the mask potential Vm becomes the ground potential (Vm = 0) and the wafer potential Vw becomes a predetermined value V0 or less. In the case of Vw ≦ V0, supply of more electrons induces charge-up of the wafer W to a predetermined negative potential or higher, so that supply of electrons from the electron generation source 28 is stopped (step S6). .
[0043]
By performing the above control repeatedly, the desired ion implantation process can be performed while suppressing the charge-up of the wafer W. Therefore, according to the present embodiment, it is possible to suppress the charge-up of the wafer W and eliminate electrical adverse effects on the elements such as a decrease in breakdown voltage and dielectric breakdown.
[0044]
In changing the chip region where ions are to be implanted, the ion beam L is temporarily interrupted by the beam interrupter 3, and the relative position between the wafer W and the mask member 21 is adjusted by the X and Y direction driving mechanisms 16, 17 and the like. This is realized by changing, and finally, ions are implanted into the entire chip region on the wafer W by the same operation as described above.
[0045]
The embodiment of the present invention has been described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.
[0046]
For example, in the above embodiment, the amount of electrons generated from the electron generation source 28 is constant regardless of the magnitude of the mask potential Vm. Instead, the amount of electrons corresponding to the magnitude of the mask potential Vm is changed to an electron. It may be generated from the generation source 28.
[0047]
In the above embodiment, the amount of electrons supplied to the wafer W is adjusted by controlling the on / off of the electron generation source 28. Instead, the amount of electrons decreases (or increases) step by step. It is also possible to control the operation of the electron generation source 28.
[0048]
Furthermore, in the above embodiment, the semiconductor wafer W is applied as the substrate to be processed. However, the present invention is not limited to this, and the present invention can also be applied to an ion implantation process for a ceramic substrate such as a glass substrate.
[0049]
【The invention's effect】
As described above, according to the present invention, during ion implantation, a sufficient amount of electrons are generated from an electron generation source to cancel the potential of the charged-up mask member, thereby electrically neutralizing the substrate to be processed. Therefore, when ion implantation is performed on a substrate to be processed using a mask member in which an opening for defining an ion implantation region is formed, charge-up of the substrate to be processed can be suppressed. Deterioration and destruction of the element due to charge-up can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an ion implantation apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a configuration of a main part in an end station of the ion implantation apparatus.
FIG. 3 is a side sectional view showing the relationship between a mask member and a wafer during ion implantation.
FIG. 4 is a control flow illustrating an example of an ion implantation method according to an embodiment of the present invention.
FIG. 5 is a schematic diagram illustrating a conventional example in which ion implantation is performed through a mask member.
FIG. 6 is a schematic diagram for explaining a conventional example including an electron generation source for preventing charge-up of a wafer during ion implantation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ion implantation apparatus 13 Stage 21 Mask member 21a Opening part 28 Electron generation source 29 Control part 30 Mask potential sensor 31 Wafer potential sensor Vm Mask potential Vw Wafer potential W Wafer

Claims (4)

A stage for supporting the substrate to be processed;
A mask member connected to the ground potential, which is disposed opposite to the substrate to be processed and has an opening for defining an ion implantation region;
Ion implantation means for implanting ions into the substrate to be processed through the mask member ;
An electron generating source arranged on the upstream side of the mask member with respect to the traveling direction of the ion beam to supply electrons onto the substrate to be processed;
Mask potential detection means for detecting the potential of the mask member irradiated with electrons generated from the electron generation source ;
Substrate potential detection means for detecting the potential of the substrate to be processed;
Based on the outputs of the mask potential detecting means and the substrate potential detecting means , the electron generating source generates electrons in an amount such that the potential of the mask member becomes a ground potential and the potential of the substrate to be processed is a predetermined value or less. And an ion implantation apparatus characterized by comprising: The ion implantation apparatus according to claim 1,
The control means adjusts the amount of electrons generated from the electron generation source based on the output of the substrate potential detection means so that the potential of the substrate to be processed does not become more negative than a predetermined value. apparatus. A mask member in which an opening for defining an ion implantation region is formed is disposed oppositely on the substrate to be processed .
Ions are implanted onto the substrate to be processed through the mask member ,
Detecting the potential of the mask member and the potential of the substrate to be processed,
At the time of ion implantation, the mask member has a ground potential, and an amount of electrons that causes the potential of the substrate to be processed to be a predetermined value or less is supplied from the electron generation source to the substrate to be processed through the mask member. An ion implantation method characterized by: The ion implantation method according to claim 3,
The step of supplying electrons from the electron generation source to the substrate to be processed controls the amount of electrons supplied from the electron generation source so that the substrate to be processed is not negatively charged more than a predetermined amount. Ion implantation method.

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