JPH0542103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to semiconductor manufacturing equipment, and particularly to an ion implanter that can automatically control the ion beam profile during ion implantation to an appropriate state.

[Conventional technology]

FIG. 6 shows the structure of a conventional ion implanter.
This device consists of an ion source 4 that produces ions, and an extraction electrode 3 that extracts ions from the ion source 4.
The extracted ion beam 1a, the analyzer magnet 2 that performs mass analysis of this ion beam 1a, the analysis slit 5 that allows only the necessary ions to pass through, and the ions that have spread out more than necessary and have flown through. It is composed of a mask 6 that stops.

The ion beam 1a extracted from the ion source 4 by the extraction electrode 3 enters the analyzer magnet 2 while spreading due to the repulsive force between the positive charges forming the ion beam 1a. Among these, ions passing through the ion beam outer trajectory 1c have a longer distance to pass through the analyzer magnet 2 than ions passing through the ion beam inner trajectory 1b, and are therefore bent to a greater extent. Therefore, the ion beam 1a becomes focused. Among the extracted ions, ions other than the target ions are bent more or less than the ion beam 1a due to the difference in mass, and therefore do not pass through the focal point of the ion beam 1a. An analysis slit 5 is placed at the focal point 18 of this ion beam to extract only the necessary ions. Ion implantation is performed by irradiating the semiconductor wafer 7 with the highly pure ion beam 1a that has passed through the analysis slit 5. Further, the mask 6 is installed to prevent the ion beam 1a from spreading more than necessary.

[Problem that the invention seeks to solve]

Conventional ion implantation equipment is configured as described above, so when the charge density in the ion beam during ion implantation becomes high, the surface of the semiconductor wafer is The charge build-up causes transistor defects due to gate oxide film breakdown, and quality deterioration of semiconductor devices due to decreased implantation uniformity within the semiconductor wafer surface.

This invention was made to eliminate the above-mentioned problems, and aims to eliminate defective IC chips due to gate oxide film breakdown and improve the quality of semiconductor devices by improving the uniformity of ion implantation within the semiconductor wafer surface. shall be.

[Means for solving problems]

The semiconductor manufacturing apparatus according to the present invention has a maximum ion beam current density setting means that defines the maximum value of the ion beam current density in ion implantation, and the ion beam current density can measure the ion beam current density distribution in the radial direction of the ion beam. An ion device that has a density distribution measuring means and compares the maximum value in the measured ion beam current density distribution with the value set by the maximum ion beam current density setting means to determine whether or not to perform ion implantation. and probe position control means for controlling the probe position of the ion beam profile monitor in order to perform ion implantation based on the determination of the ion implantation determination means. The ion beam has an ion beam profile control means that changes the profile of the ion beam by moving a ball chip in the net section, and calculates where the focus of the ion beam will be based on the output of this ion beam profile control means. It has a beam focal position calculation means, and it has an analysis slit position control means that moves the analysis slit based on the calculation result to match the focal position of the ion beam, and automatically controls the ion beam current density in ion implantation. It has been made possible.

[Effect]

The maximum ion beam current density setting means in this invention sets the maximum current density of the ion beam in ion implantation, and the ion implantation determining means sets the maximum current density determined by the above set value and the ion beam current density distribution measuring means. The values are compared to determine whether or not to perform ion implantation. Based on this determination, when performing ion implantation, the ion implantation is performed by the probe position control means.
Change probe position. Also, based on this judgment,
When it becomes necessary to change the ion beam current density, the ion beam profile is changed by the ion beam profile control means. The ion beam focal position calculation means calculates the ion beam focal position from the exit angle of the ion beam changed by the ion beam profile control means, and causes the analysis slit position control means to place the analysis slit at this focal position. match. This feedback system suppresses the maximum charge density value to below the set value, eliminates the occurrence of defective semiconductor devices due to damage to the gate oxide film of MOS transistors due to charge up, and also prevents the uniformity of ion implantation due to charge up. To produce semiconductor devices of uniform quality by suppressing problems.

〔Example〕

FIG. 1 is an overall configuration diagram of an embodiment of a semiconductor manufacturing apparatus according to the present invention. In this example, the first
As is clear from the figure, the ion source 4 creates plasma of impurity ions, and the extraction electrode 3 extracts the ion beam 1a from the plasma. Analyzer magnet 2 converts the magnetic field into ion beam 1
The ion beam 1a is generated perpendicularly to a, thereby bending the traveling direction of the ion beam 1a. The pole chip 8 is configured to be able to change the emission angle A of the ion beam 1a about the pole chip rotation axis 24. Due to this change in the emission angle A, the position of the focal point 9 of the ion beam approaches or moves away from the analyzer magnet 2 side. The analysis slit 5 analyzes the ion beam 1a and increases the purity of the ion beam 1a. The mask 6 prevents the ion beam 1a from spreading more than necessary, and the probe 17
Before implanting ions into a semiconductor wafer 7 made of an IC or the like, the ion beam 1a is received and the ion beam current density distribution is measured by the ion beam current density distribution measuring means 10. A maximum ion beam current density value is set by the maximum ion beam current density setting means 13, and this value and the measured value are
If the ion implantation determining means 11 determines that the implantation can be performed, the probe position control means 12 controls the position of the probe 17. If the above judgment result indicates that implantation cannot be performed, the ion beam profile control means 16 moves the pole tip 8.

FIG. 2 is a sectional view of the semiconductor manufacturing apparatus used in the embodiment of FIG. 1. The first step motor 26 moves the pole tip rotation shaft 24 via the belt 25 to move the pole tip 8 and change the emission angle A, and the second step motor 23 rotates the pole tip rotation shaft 24 via the belt 22 for moving the analysis slit. Axis 2
1 to change the position of analysis slit 5. The third step motor 19 moves the probe rotating shaft 18 via a belt 78. A control device 20 including a microcomputer etc. controls the first step motor 26 and the second step motor 2.
3. Control the third step motor 19. The display 26 shows the maximum value in the measured ion beam current density distribution, the maximum current density adjustment knob 27a determines the maximum value in the ion beam current density distribution, and the switch 28 turns on the input signal from the probe 17. and turn off the switch 29
is configured to turn ON and OFF the signal from the maximum current density adjustment knob 27a.

FIG. 3 is a circuit diagram showing the electrical connections of the embodiment of FIG. In the figure, the analog signal received by the probe 17 is passed through the multiplexer 60 to the A/D
The signal enters a converter 30 and is converted into a digital signal. This digital signal passes through the input circuit 34, enters the CPU 36, and is processed. switch 28
turns the input circuit 34 ON and OFF, and 32 is a resistor connected in series with the switch 28. Variable resistor 27b
can be changed using the maximum current density adjustment knob 27a in FIG.
Tell 5. Resistor 35 is a resistor in series with variable resistor 27b. The switch 29 is connected to the input circuit 35
This is a switch that turns ON and OFF, and 33 is a resistor in series with this switch. The memory 41 stores data and exchanges data with the CPU 36. The output circuit 37 is connected from the CPU 36 to the first step motor 2.
6 and transmits it to amplifiers 72a and 72b. The amplifier 72a is used to move the first step motor 26 closer to the pole tip. The amplifier 72b brings the first step motor closer to the semiconductor wafer 7. Amplifier 72a
The transistor 47 is turned on and off by a pulse signal from the output circuit 37, the resistor 42 is a base resistor, and the resistor 45 is a collector resistor. When the transistor 47 is turned on, the photocoupler 46
It is in the ON state, and voltage from the DC power supply 57 is supplied to the first step motor 26 to operate it. The internal configuration of the amplifier 27b is exactly the same as that of the amplifier 72b, but the first step motor 2
6 has been reversed by connecting the output cables in reverse. Amplifier 73a
The amplifier 74a has the same configuration as the amplifier 72a, and the amplifier 73b and the amplifier 74b have the same configuration as the amplifier 72b. The output circuit 38 receives a signal for operating the second step motor 23 and outputs it to the amplifiers 73a and 73b.
The output circuit 39 sends a signal for operating the third step motor 19 to the amplifier 74a and the amplifier 74.
Output to b. The output circuit 40 receives data of the set maximum current density value from the CPU 36, and
Output to the display 26.

Next, the operation of the above embodiment will be explained using FIGS. 1 to 5. FIG. 4 is a flowchart of a program stored in the memory 41 of the control device 20, and FIG. 5 is a front view of the probe 17.

First, during ion implantation, determine the maximum current density value of the ion beam 1a that does not cause the problem of gate oxide film breakdown of MOS transistors in the semiconductor wafer using the maximum current density adjustment knob 2 in FIG.
7a in the maximum ion beam current density setting step 61 in FIG.
1, becomes a digital quantity, and input circuit 35
This value is stored in memory 4 through CPU 36.
1 and displayed on the display 26 through the output circuit 40. Next, in the ion beam current density distribution measurement step 63 in FIG. 4, the measurement points 71 arranged in a matrix in the probe 17 shown in FIG. 5 measure the ion beam current density at each point. Of the measurement points filled in black, the x direction and y direction
Regarding the direction, the measured values are shown in Figures 5b and 5c, respectively. The values measured by each measurement point 71 pass through the multiplexer 60 in FIG.
4 and enters the CPU 36. Next, in a step 64 of searching for the maximum ion beam current density Im, the individual digitized measurements are compared to find the maximum value Im of the ion beam current density value, and a step 65 of comparing the next Io and Im. Then, if Im is greater than or equal to Io, in the process 66 of moving the first step motor 26 in FIG. 4, a pulse is output from the CPU 36 in FIG. 3 via the output circuit 37, turning on the transistor 47. , the output of photocoupler 46 is ON
to move the first step motor 26 and the second step motor 26.
The pole tip rotating shaft 24 is moved via the belt 25 in the figure to increase the exit angle A of the ion beam and move the ion beam focus 9 to the pole tip 8.
The probe 17 is brought closer to the probe 17 to spread the ion beam irradiated to the probe 17 and lower the ion beam current density.
Next, a step 67 of calculating the ion beam focal position
In the CPU 3, the position of the ion beam focus 9 that has changed due to the increase in the emission angle A is
6, and sends the result through the output circuit 38 to a pulse corresponding to the change in the ion beam focal position, and this pulse operates the amplification circuit 73a in the same manner as when the first step motor 26 is operated. It is moved by the second step motor 23 to move the analysis slit 5 in FIG. Next, the ion beam current density distribution measurement process 63 in FIG. 4, the maximum ion beam current density
The process of searching for Im 64 moves on to the process of comparing Io and Im. Next, when Im becomes smaller than Io, the process proceeds to step 69 for operating the third step motor, in which the CPU 36 in FIG. Operate the first step motor 26 in the same manner as when operating the third step motor 19,
In FIG. 2, the probe 17 is rotated 90 degrees to the left about the probe rotation axis 18, and ion implantation is performed in step 70 of performing ion implantation. Step 7 of moving the third step motor 19 after ion implantation
5, the output circuit 39 from the CPU 36 in FIG.
through the amplifier 74b to move the third step motor 19 to return the probe 17 to the position shown in FIG. Next, in the process 76 of moving the first step motor 26, the CPU 36,
The first step motor 26 is moved through the output circuit 37 and the amplifier 72b to move the pole piece 8 and set the output angle A to 0°. Next, in the process 77 of moving the second step motor 23, the CPU 36,
The second step motor 23 is operated through the output circuit 38 and the amplifier 73b to bring the analysis slit 5 closest to the probe side in preparation for the next ion implantation.

Note that although the above embodiment is for manufacturing a semiconductor device including a MOS transistor,
It can also be used in the manufacture of semiconductor devices having other structures.

〔Effect of the invention〕

As described above, according to the present invention, a means is provided to automatically control the maximum value of the ion beam current density during ion implantation, so that it can be adjusted according to the type of semiconductor device, changes in ion implantation conditions during the semiconductor process, etc. Since the maximum current density can be set, problems such as damage to the gate oxide film of the transistor due to charge up and deterioration of uniformity of ion implantation can be eliminated.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a semiconductor manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a configuration diagram embodying FIG. 1 using actual equipment, and FIG. 3 mainly shows the inside of a control device 20. FIG. 4 is a flowchart of an embodiment of the present invention, and FIG. 5 is a front view and an explanatory view showing the probe of FIG. 2.
FIG. 6 is a block diagram of a conventional device. 1a is an ion beam, 7 is a semiconductor wafer, 1
7 is a probe, 8 is a pole chip, 5 is an analysis slit, 6 is a mask, 10 is an ion beam current density measuring means, 11 is an ion implantation determining means, 12 is a probe position control means, 13 is a maximum ion beam current density setting means, 14 is an analysis slit, 15 is an ion beam focal position calculation means, and 16 is an ion beam profile control means. In addition, in each figure,
The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Ion beam current density distribution measuring means for determining the current density distribution of the ion beam before performing ion implantation, and maximum ion beam current density setting that defines the maximum value in the ion beam current density distribution. and the specified maximum ion beam current density value and the maximum ion beam current value in the ion beam current density distribution measured by the ion beam current density measuring means, and determine whether or not to perform ion implantation. ion implantation determining means for determining the probe position of the ion beam profile monitor based on the determination by the ion implantation determining means; and probe position control means for determining the probe position of the ion beam profile monitor based on the determination by the ion implantation determining means; Based on the ion beam profile control means to be adjusted and the output of this ion beam profile control means,
A semiconductor manufacturing device comprising an ion beam focal position calculation means for calculating the focal position of an ion beam, and an analysis slit position control means for positioning an analysis slit at the ion beam focal position determined by the ion beam position calculation means. . 2. The semiconductor manufacturing apparatus according to claim 1, wherein the ion beam current density measuring means measures the current density distribution of an ion beam cross section parallel to the surface of the semiconductor wafer where ion implantation is performed. 3. The semiconductor manufacturing apparatus according to claim 1 or 2, wherein the ion implantation determining means and the ion beam focal position calculating means are realized by a microcomputer.