JPH01302836A - Collection device of impurities on surface of semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain a collection device which does not require oxidation process before collecting impurities, requires only a small amount of liquid needed for collecting impurities, increases sensitivity for measuring the impurities, and improves analysis accuracy of the impurities and reliability of analyzed value by providing a specific stage, a magnetic floating mechanism, and a droplet retainer. CONSTITUTION:This device has a stage 1 for mounting a semiconductor substrate 2, where the surface oxide film is dissolved, in horizontal state, magnetic floating mechanism 3 and 4 for rotating or traveling the stage 1 within the horizontal plane while it is being floated, and a droplet retainer 9 for retaining a droplet 8 dripped on the surface of the above semiconductor substrate 2. For example, with the semiconductor substrate 2, an oxide film on the substrate surface is exposed into steam of hydrofluoric acid aqueous solution so that it is dissolved and the hydrofluoric acid solution droplet 8 is dripped on the surface of the substrate 2. Then, by traveling the droplet 8 to the radium direction of the substrate 2 by the droplet retainer 9 while allowing the rotary stage 1 to be floated, the droplet 8 can be dripped over the entire surface of the substrate 2 and the impurities on the substrate 2 are collected by the droplet 8.

Description

Detailed Description of the Invention [Objective of the Invention (Industrial Application Field) The present invention relates to a recovery device for recovering impurities on the surface of a semiconductor substrate in order to diffract the impurities on the surface of the substrate. The present invention relates to an apparatus in which a semiconductor substrate having an oxide film dissolved therein is suspended by a magnetic levitation structure and the surface of the substrate is scanned with droplets.

(Prior art) When impurities such as sodium (Na), potassium (K), iron (Fe), etc. are contained in a thin film such as an oxide film formed on a semiconductor substrate, even if the amount is extremely small, Even so,
It is well known that it has a great influence on the electrical characteristics of semiconductor devices. Therefore, the ninth step to improving the electrical characteristics of devices is to suppress the incorporation of impurities from the substrate as much as possible, and to do this, it is necessary to accurately measure impurities on the substrate surface. There is.

Conventionally, instrumental analysis using secondary ion mass spectrometers, Auger electron spectrometers, activation analyzers, etc. has been used to measure impurities on the substrate surface, but instead of these methods, it is possible to easily measure the entire substrate surface. The following two methods are mainly used for analysis. The first method is to generate an appropriate thermal oxide film on the surface of the substrate in advance, and then immerse the substrate in hydrofluoric acid vapor. This is a gas phase decomposition method in which impurities on the surface are collected together with the oxide film as a hydrofluoric acid solution, and the impurities are measured using a spectrometer. The second method is
In this method, the substrate is immersed in a hydrofluoric acid solution without oxidation treatment to dissolve the oxide film on the entire surface of the substrate, and the impurity-containing solution is measured.

However, since the first method involves an oxidation step, there is a risk that impurities may enter the substrate from the atmosphere in this step, evaporate impurities from the substrate surface, and diffuse impurities from inside the substrate to the substrate surface. There is. In addition, in the latter second method, the amount of hydrofluoric acid solution required for impurity recovery is too large compared to the amount of hydrofluoric acid solution required for analysis, so the impurity concentration in the recovered solution decreases significantly, and the impurity There is a problem that the accuracy of analysis data decreases.

(Problems to be Solved by the Invention) As mentioned above, the present invention solves the problems associated with having an oxidation process for generating a thermal oxide film on a substrate before recovering impurities, and the problems necessary for recovering impurities. This was developed to solve the problems associated with the large amount of hydrofluoric acid solution.It does not require an oxidation process before impurity recovery, only a small amount of liquid droplets are required for impurity recovery, and it can be used on substrates. A device for recovering impurities on the surface of semiconductor substrates that collects trace impurities on the surface, minimizes the decrease in the impurity concentration of droplets, and improves the sensitivity of impurity measurements, the accuracy of impurity analysis, and the reliability of analysis values. The purpose is to provide

[Structure of the Invention] (A Companion Means for Solving the Problems) The device for recovering impurities on the surface of a semiconductor substrate of the present invention includes a stage on which a semiconductor substrate whose surface oxide film has been dissolved is horizontally mounted, and a stage on which the stage is levitated. The present invention is characterized in that it is equipped with a magnetic levitation mechanism that rotates or moves within a horizontal plane in a horizontal plane, and a droplet holder that holds droplets for collecting impurities dropped on the surface of the semiconductor substrate.

(Operation) Impurities on the substrate can be collected with the droplets by driving the stage to rotate or move using the magnetic levitation mechanism so that the droplets scan the substrate. In this way, since only a small amount of liquid droplets are required to recover impurities, a decrease in the impurity concentration of the droplets that have recovered trace amounts of impurities on the substrate surface can be minimized. Furthermore, since the stage is driven in a floating state, there is no mechanical sliding part for driving the stage, and there is no fear that dust or the like generated by mechanical wear will be mixed in as impurities.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In the semiconductor substrate surface impurity recovery apparatus shown in FIG. 1, reference numeral 1 denotes a rotation stage which is levitated by a magnetic levitation mechanism and driven to rotate in a horizontal plane, and a semiconductor substrate (wafer) 2 is mounted on the upper surface of the rotation stage. installed and fixed. 3
is a magnet fixed to the rotary stage 2, and 4 is a magnet provided in the case 5 with the same polarity facing the magnet 3.

The magnet 4 is fixed on a rotary table 7 which is rotated in a horizontal plane by a motor 6 on a base 10. Therefore, the magnet 4 on the case side and the magnet 3 on the rotating stage side
are magnetically repelled and the rotary stage 1 levitates, and as the magnet 4 on the case side rotates, the rotary stage 1 and the magnet 3
begins to rotate.

On the other hand, in the semiconductor substrate 1, the oxide film on the surface of the substrate is exposed to vapor of a highly purified aqueous hydrofluoric acid solution (in a hydrofluoric acid atmosphere) and dissolved. A droplet 8 of the hydrofluoric acid solution is dropped onto the surface of the substrate 2 and comes into contact with the surface of the substrate 2. A droplet holder 9 made of Teflon and having a recess for holding the droplet 8 is provided. It is being

Therefore, in the above impurity recovery device, the rotation stage 1
By moving the droplet 8 in the radial direction of the substrate 2 using the droplet holder 9 while rotating it in a floating state, the droplet 8 can be scanned over the entire surface of the substrate. It becomes possible to collect impurities with the droplets 8.

In this way, since only a small amount of liquid droplets are necessary for recovering impurities, a decrease in the impurity concentration of the droplets that have recovered trace impurities on the substrate surface is prevented.

Further, since the rotary stage 1 is driven in a floating state, there is no mechanical sliding part for driving the stage, and there is no fear that dust or the like generated by mechanical wear will be mixed in as impurities. Therefore, it is possible to improve the sensitivity of impurity measurement, the accuracy of impurity analysis, and the reliability of analytical values.

In addition, in the second son method explained in the conventional example, the detection limit of impurities was on the order of 1010 to 1011, whereas in the method using the above-mentioned apparatus, the detection limit was lowered to the order of 108 to 109.

In addition, when using the above device, the impurity recovery work becomes easier, and the damage rate of the substrate during the recovery work becomes almost zero, compared to about 5% with the conventional method, and the work is significantly reduced. stability was obtained.

FIG. 2 shows another embodiment, in which 2, 8 and 9 are the same semiconductor substrates, droplets and droplet holders as in the previous embodiment, and 21 is suspended in a horizontal plane by magnetic force. It is a movable stage that can be moved freely, and magnets 22... are fixed. Reference numeral 23 denotes a magnetic rail provided and fixed horizontally on the base 24, and magnets 25... are arranged in the length direction of the rail. 26 is the above magnetic rail 23
It is an intermediate stage which is levitated by a magnetic force above the rail and is movable in a horizontal plane in the length direction of the rail, and has magnets 27 with the same polarity facing the magnets 25 of the magnetic rail 23 and which are orthogonal to the direction of movement. Magnets 28... arranged in the direction are provided. The magnets 28 and the magnets 22 of the moving stage 21 are provided so that the rims thereof face each other.

In the impurity recovery device described above, the intermediate stage 26 moves in the X direction in the horizontal plane, and the moving stage 21 moves in the Y direction in the horizontal plane, so that the substrate 2 can be moved to any position in the horizontal plane, By holding the droplet holder 9 in a fixed position, the droplet 8 can be scanned over the entire surface of the substrate. Therefore, impurities can be recovered in the same manner as in the embodiment described above, and the same effects as described above can be obtained.

Note that the magnetic levitation mechanism is not limited to the above-mentioned embodiments, and various modifications are possible.

[Effects of the Invention] As mentioned above, according to the device for recovering impurities on the surface of a semiconductor substrate of the present invention, it is possible to prevent a drop in the impurity concentration of droplets that collect trace impurities on the substrate surface, and to improve the sensitivity of impurity measurement. Furthermore, it is possible to improve the accuracy of impurity analysis and the reliability of analytical values.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram schematically showing one embodiment of a semiconductor substrate surface impurity recovery apparatus according to the present invention, and FIG. 2 is a water quantity structural diagram of another embodiment. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Rotating stator, 3, 4 degrees 22.25, 27.28... Magnet, 7... Rotating table, 8... Droplet, 9... Droplet Holder, 2 pieces...
Moving stage, 23... Magnetic rail, 26... Intermediate stage. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A stage on which a semiconductor substrate with an oxide film on the surface thereof has been dissolved is mounted in a horizontal state, a magnetic levitation mechanism that rotates or moves this stage in a horizontal plane while floating, and a droplet dropped on the surface of the semiconductor substrate. A device for recovering impurities on the surface of a semiconductor substrate, comprising: a droplet holder for holding a droplet holder;