JP7507009B2 - Substrate Etching Equipment - Google Patents

Description

The present invention relates to a single-wafer substrate etching device that supplies a chemical solution to etch a substrate.

In the field of electronic component manufacturing, techniques for planarizing substrate surfaces include chemical mechanical polishing (CMP) and dry etching using gases, etc. Wet etching, in which an etching solution is supplied to etch the substrate surface through a chemical reaction, is also recognized as one of these techniques.
For example, Patent Document 1 describes a single-wafer etching apparatus in which a chemical solution for etching is supplied from above to the center of the substrate by a nozzle while the substrate is rotated around the center (axis of rotation) of the substrate.

In recent years, with the increase in integration in the electronic component manufacturing field, such as semiconductors, photomasks, and image panels, there has been a demand for a higher order of flatness for the substrate surface. In particular, there is now a demand for flatness adjustment to the order of a few nm, where the height difference on the substrate surface is counted in crystal structure units (also called crystal units).

Here, to help understand the crystal unit and numerical values on the order of several nm, an example is given in Table 1. For example, the crystals of a silicon wafer in Table 1 generally exhibit a diamond structure, with the crystal structure continuing in a chain to make up the material. Figure 5 shows a diamond structure. In Figure 5, "a" indicates the lattice constant. The interatomic distance in crystal units is 5.43 Å (0.543 nm). The level of flatness required in recent years is a high level, equivalent to several such crystal structure units.

JP 2013-065614 A

In the pursuit of a high degree of substrate flatness as described above, there were substrates in which partial irregularities occurred on the substrate surface, the number of which was counted in crystal structure units, and which could not be dealt with by conventional CMP, dry, or wet etching processes, and the peripheral region (particularly the outer periphery) of the substrate surface was concave and the central region of the substrate was convex. In the pursuit of even greater flatness, it was necessary to selectively etch the central region of the convexity of the substrate surface.
In the case of the single-wafer method, the chemical solution supplied to the center of the substrate inevitably spreads to the peripheral areas, such as the outer periphery of the substrate, due to the rotational movement of the substrate, and has an etching effect on the peripheral areas as well. Therefore, a mechanism was needed to efficiently supply a rinsing liquid to the peripheral area of the substrate to suppress etching.

The present invention aims to provide a substrate etching device that can be used in a process of etching a substrate by chemical reaction in a wet processing device, can easily etch a partial convex area in the center region of the substrate on the substrate surface, and can perform processing so that the height difference of the substrate surface is uniform.

In order to achieve the above object, the present invention provides a single-wafer processing substrate etching apparatus having a holding table which holds and rotates a substrate, a chemical liquid supply nozzle which supplies a chemical liquid for etching to a center of the substrate which is held and rotated on the holding table, and a cup which is disposed so as to surround the holding table and which prevents the chemical liquid supplied to the substrate from scattering,
The cup has a cup nozzle capable of supplying pure water toward a peripheral region of the substrate that is offset from the center of the substrate.

In the substrate etching apparatus of the present invention, the chemical supply nozzle can supply the chemical solution to the center of the rotating substrate, and the cup nozzle can supply pure water to the peripheral region of the substrate. This dilutes the chemical solution in the peripheral region, and the etching effect of the chemical solution can be suppressed compared to the central region. Therefore, the partial convex region in the central region can be easily and selectively etched, and the height difference at the crystal structure unit level can be adjusted. For example, in a substrate whose surface is convex in the central region and concave in the peripheral region (particularly the outer periphery), the central region can be selectively and efficiently etched, and a substrate with a uniform height difference on the surface can be obtained.
Furthermore, the cup can prevent the chemicals and the like from scattering due to the rotation of the substrate.

The cup has a plurality of the cup nozzles,
The plurality of cup nozzles may be arranged at equal intervals around the substrate in a plan view.

By arranging multiple cup nozzles in this way, pure water can be efficiently supplied to the peripheral region, and by arranging them at equal intervals, pure water can be evenly supplied to the peripheral region. As a result, the etching effect in the peripheral region can be more efficiently suppressed.

The orientation of the cup nozzle may be tilted from a direction toward the center of the substrate toward the direction of rotation of the substrate when viewed in a plan view.

When the cup nozzle is tilted in this way, pure water can be supplied more in the direction of rotation than if it were not tilted, so when the supplied pure water reaches the peripheral area of the substrate, it is possible to effectively suppress disturbances in the liquid flow and splashing caused by collisions with the rotating substrate or the chemical liquid that moves outward while rotating on the rotating substrate.

The substrate etching apparatus further includes a cup motor capable of driving the cup up and down,
The position where the pure water supplied from the cup nozzle reaches in the peripheral area of the substrate can be adjusted by controlling the vertical position of the cup with the cup motor.

With such a cup motor, it is easier to supply pure water to the desired location in the peripheral area of the substrate.

The cup may be made of any of the following materials: PTFE, PVDF, PFA, PCTFE, PEEK, PPS, PVC, PE, and PP.

Such materials are resistant to chemicals such as acids and will not contaminate the substrate, and the cups can be easily prepared.

The substrate may be any one of a photomask, a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, and a SiC wafer, or a substrate used in the manufacturing process of any one of a flat panel and a multilayer ceramic.

These substrates require high flatness through partial etching of the surface, and the present invention, which enables partial etching, is ideal.

The chemical solution may be any one of an inorganic acid solution, an inorganic alkaline solution, an organic acid solution, an organic alkaline solution, ozone water, and electrolytic water, or may be a mixture of two or more of these.

This allows for effective etching of the substrate.

As described above, with the substrate etching device of the present invention, even if a partial convex region at the crystal structure unit level exists in the central region of the substrate, the convex region can be easily and selectively etched, and in particular, a substrate with a uniform surface height difference can be obtained.

1 is a vertical sectional view showing an example of a substrate etching apparatus of the present invention. FIG. 2 is a top view showing an example of a cup and a cup nozzle and its periphery. FIG. 13 is a contour map of the etching amount in an example (when the rinsing position is a position 70 mm in the radial direction from the center of the substrate). FIG. 11 is a contour map of the etching amount in an example (when the rinsing position is a position 80 mm in the radial direction from the center of the substrate). FIG. 13 is a contour map of the etching amount in the example (when the rinsing position is a position 90 mm in the radial direction from the center of the substrate). 13 is a graph showing dispersion data of the etching amount versus position from the center of the substrate in the radial direction when the rinse position is 70 mm and 90 mm from the center of the substrate in the radial direction in an example. FIG. 1 is an explanatory diagram showing a diamond structure.

Hereinafter, the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments.
1 is a vertical cross-sectional view showing an example of a substrate etching apparatus of the present invention. The substrate etching apparatus 1 of the present invention is a single-wafer type, and mainly includes a holding table 2, a chemical supply nozzle 3, and a cup 5 having a cup nozzle 4.
The substrate W to be etched is held by a holding table 2 and may be, for example, a substrate used in the manufacturing process of a photomask, a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, or a SiC wafer, or a substrate used in the manufacturing process of a flat panel or multilayer ceramics. These require high flatness due to partial etching of the surface. For this reason, the apparatus of the present invention capable of partial etching as described below is suitable.
Each component of the substrate etching apparatus 1 of the present invention will now be described in detail.

The holding table 2 holds and rotates the substrate W (rotating about the center C of the substrate W). Pins 6 are provided on the upper end of the holding table 2, and the substrate W is held and fixed by these pins 6. Note that the number of pins 6 is four here, but is not limited to this. The holding table 2 is connected to a table rotation motor 8 via a table rotation shaft 7. With this configuration, by driving the table rotation motor 8, the table rotation shaft 7 can be rotated (axial rotation), and the holding table 2 connected to the table rotation shaft 7 can be rotated (axial rotation). Then, with the rotation of this holding table 2, the substrate W held by the pins 6 can be rotated (axial rotation).

The chemical liquid supply nozzle 3 discharges and supplies chemical liquid 9 for etching to the center C of the substrate W which is held and rotated on the holding table 2. The chemical liquid supply nozzle 3 is connected to a chemical liquid supply pipe 10, and is capable of supplying the chemical liquid 9 through the chemical liquid supply pipe 10. In addition, an arm 11 is disposed so as to extend above the holding table 2, and the chemical liquid supply nozzle 3 is supported by this arm 11. With this configuration, the chemical liquid 9 can be supplied from the chemical liquid supply nozzle 3 toward the center C of the substrate W on the holding table 2.

The chemical solution 9 may be, for example, any one of an inorganic acid solution, an inorganic alkaline solution, an organic acid solution, an organic alkaline solution, ozone water, and electrolytic water, or a mixture of two or more of these solutions. These can effectively etch the substrate W.

The cup 5 is disposed so as to surround the periphery of the holding table 2. The shape of the cup 5 is not particularly limited as long as it has a shape that can prevent the chemical solution 9, etc., that is thrown by the rotation of the substrate W on the holding table 2 from scattering outside the substrate etching apparatus 1.
1, the device comprises a cylinder, a portion (top plate) that protrudes horizontally inward from the upper end of the cylinder, and a portion (bottom plate) that protrudes horizontally outward from the lower end, and can effectively prevent the scattering of chemicals 9 and the like from the substrate W positioned inside the cylinder. A cup nozzle 4 is disposed in this inward protruding portion. In addition, a portion that protrudes outward is provided at a position midway through the cylinder, and is connected to the upper end of a cup shaft 12.

A plurality of cup shafts 12 are provided around the cup 5, and pass through the device base 13. The lower ends of the plurality of cup shafts 12 are supported by a plate-shaped shaft base 14. A cup motor 15 is also provided on the shaft base 14. With this configuration, the shaft base 14 can be moved up and down by driving the cup motor 15, and accordingly the cup shafts 12, and further the cup 5 and cup nozzle 4 can be moved up and down integrally.
A linear bush 16 of a ring mechanism is provided in the hole through which the cup shaft 12 penetrates the device base 13, allowing the cup shaft 12 to move smoothly up and down. The cup shaft 12 is also covered and protected by a shaft bellows cover 17 with an expandable bellows structure.

The cup nozzle 4 supplies pure water 18 toward the peripheral area P that is off center C of the substrate W on the holding table 2. The cup 5 and cup nozzle 4 can be moved up and down by driving the cup motor 15 described above, and this mechanism that can move up and down can be used to adjust the pure water 18 to reach a desired position within the peripheral area P of the substrate W. This adjustment is easy because it is made by a relatively simple mechanism that moves the cup 5 and cup nozzle 4 up and down.

1, as described above, the cup nozzle 4 is provided at a portion of the cup 5 that protrudes inward. A pure water supply joint 19 is connected to the protruding portion, and a pure water passage 20 is provided so as to connect to the pure water supply joint 19 and pass through the protruding portion. Pure water supplied from a pure water supply pipe 21 that connects to the pure water supply joint 19 from the outside is discharged toward the substrate W through the pure water passage 20.
The pure water passage 20 extends horizontally from the pure water supply joint 19 side and then slopes downward midway, so that the pure water is discharged in an obliquely downward direction. Because the pure water passage 20 has such a shape, it is easier to supply the pure water 18 to a targeted position on the surface of the substrate W than if the pure water passage 20 were to extend horizontally and discharge the pure water horizontally.

Here, the peripheral region P, which is the position where the deionized water is supplied to the substrate W, will be described.
1, the position where the pure water actually reaches can be determined appropriately as long as it is within a region outside the center C of the substrate W. It can be determined depending on how far from the center C of the substrate W it is desired to selectively and intensively etch (conversely, whether it is desired to suppress the etching effect in the other outer region).
The position at which the pure water reaches can be adjusted by the mechanism for vertically moving the cup 5 and the cup nozzle 4 using the cup motor 15 described above, the shape and direction of the pure water passage 20 of the cup nozzle 4, or the flow velocity, flow rate, water pressure, etc.

For example, if the arrival position (supply position) of the pure water 18 is at point P1, which is inside (inner periphery) of the position of 1/2 the radius of the substrate W, the centrifugal force caused by the rotation of the substrate W will cause the pure water 18 to spread from point P1 to the outer region, where the chemical solution 9 is diluted by the pure water 18 and the etching action is suppressed. On the other hand, the supplied chemical solution 9 effectively etches the region inside point P1.
Moreover, the pure water 18 can be adjusted so as to reach not only point P1 but also point P2, which is outside (outer periphery) of the position of 1/2 the radius of the substrate W. In this case as well, the etching action is suppressed in the region outside point P2, while effective etching is possible in the region inside point P2.
In this way, depending on the extent of the convex area of the substrate W, it is possible to intentionally control the areas to be etched and the areas to be inhibited from etching.

2 is a top view showing an example of the periphery of the cup 5 and the cup nozzle 4 in the substrate etching apparatus 1. Here, six cup nozzles 4 are arranged. As shown in FIG. 2, in a plan view, they are arranged at equal intervals around the substrate W (in this case, with respect to the circumference of the circular substrate W). That is, they are arranged at 60° angles around the center C of the substrate W. Of course, it is possible to arrange only one cup nozzle 4, but by arranging two or more nozzles evenly in this manner, it is easy to efficiently and evenly supply the pure water 18 to the peripheral region P of the substrate W. The region to be selectively etched and the region to be inhibited from etching can be more clearly separated.
Although the example has been described assuming that the substrate W is circular, even if the substrate is rectangular, the electrodes can be arranged at equal intervals around the substrate (for example, at a constant central angle relative to the substrate center).

It is also preferable that the orientation of the cup nozzle 4 is inclined from the direction toward the center C of the substrate W in a plan view to the direction of rotation of the substrate W. In the example of FIG. 2, the substrate W rotates clockwise (right rotation). Here, the pure water supply joint 19 of each cup nozzle 4 faces the center C of the substrate W, but from the middle of the pure water passage 20, it is inclined to face slightly leftward (i.e., the direction of rotation of the substrate W) toward the center C of the substrate W. This inclination toward the rotation direction makes it possible to effectively suppress the disturbance of the liquid flow and the liquid splash caused by the collision between the chemical solution 9 flowing on the substrate W or its surface and the pure water 18, compared to the case where there is no inclination or the case where it is inclined in a direction against the direction of rotation of the substrate W. Therefore, it is possible to further suppress the disturbance of the boundary between the area to be selectively etched and the area to be inhibited from etching.

Adjusting the range of these etching regions and etching inhibition regions and clarifying their boundaries affects whether or not only the desired regions can be effectively etched, and thus affects the quality of the substrate after etching, such as its flatness.

The cup 5 may be made of any one of the following materials: PTFE, PVDF, PFA, PCTFE, PEEK, PPS, PVC, PE, and PP.
Such a material is resistant to the chemical solution 9 such as acid, and can suppress contamination of the substrate W being processed, while allowing the cup 5 to be easily prepared.

With the substrate etching apparatus 1 of the present invention as described above, for example, if a partial convex region exists in the central region on the center C side of the substrate W, it is possible to easily selectively and intensively etch only that convex region on the surface of the substrate W. At the same time, etching of the outer regions can be suppressed. Therefore, minute height differences such as those at the crystal structure unit level can be adjusted by partial etching to obtain a flat substrate W.

The present invention will be described in more detail below by showing examples of the present invention, but the present invention is not limited to these.
(Example)
Using the substrate etching apparatus 1 of the present invention shown in FIG. 1-2, partial etching of the Si layer (SOI layer) which is the surface layer of an SOI wafer was performed in the following steps (1) to (10), and the amount of etching was measured.
(1) An SOI wafer (also simply referred to as a substrate) having a diameter of 200 mm and having a cross section consisting of a Si substrate, a _SiO2 layer, and a Si layer (SOI layer) from the bottom was prepared, and the thickness distribution within the substrate surface of the Si layer in the surface layer was measured using an optical interference sensor.
(2) The substrate for which distribution measurement was to be performed was placed horizontally on the holding table 2 of the substrate etching apparatus 1 .
(3) The substrate was rotated at 200 rpm, and pure water 18 (rinsing solution) was supplied from six cup nozzles 4 toward the peripheral region of the substrate.
(4) A HF solution was supplied as the chemical solution 9 from the chemical solution supply nozzle 3 .
(5) After the HF solution was supplied for a predetermined time, the supply was stopped, and ozone water was supplied toward the substrate to form a thin oxide film on the surface.
(6) The supply of ozone water was stopped.
(7) The steps (4) to (6) were repeated five times to slightly etch the surface layer of the substrate.
(8) (7) After the operation, a rinsing solution was supplied and the substrate was then dried.
(9) The in-plane thickness distribution after the treatment was confirmed using an optical interference sensor.
(10) The film thickness before and after the treatment was subtracted to calculate the amount of etching within the surface.

In (3), the supply position (rinsing position) of the pure water 18 was changed to a 140 mm diameter position (70 mm radially from the center C), a 160 mm diameter position (80 mm radially from the center C), and a 180 mm diameter position (90 mm radially from the center C) on a 200 mm diameter substrate, and a comparison was made for each.

The etching amount was compared for each of the above pure water supply positions. The results are shown in Figures 3A-3C and 4. Figures 3A-3C are contour maps of the etching amount (when the rinsing position is 70 mm, 80 mm, and 90 mm in the radial direction from the center C of the substrate, respectively). Figure 4 is a graph of dispersion data of the etching amount versus the position from the center of the substrate in the radial direction when the rinsing position is 70 mm and 90 mm in the radial direction from the center C of the substrate. The average value was obtained for each 10 mm.
In both cases, it was confirmed that etching was suppressed outside the pure water supply position, and etching occurred inside the pure water supply position. This shows that by adjusting the pure water supply position, it is possible to effectively etch only the desired central region of the substrate surface.

The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

1... Substrate etching apparatus of the present invention, 2... Holding table, 3... Chemical liquid supply nozzle,
4...cup nozzle; 5...cup; 6...pin; 7...table rotation axis;
8...table rotation motor; 9...chemical solution; 10...chemical solution supply pipe;
11: arm; 12: cup shaft; 13: device base;
14... shaft base, 15... cup motor, 16... linear bush,
17... shaft bellows cover, 18... pure water, 19... pure water supply joint,
20: pure water passage; 21: pure water supply pipe;
C: center of the substrate; P: peripheral region of the substrate; P1, P2: points in the peripheral region of the substrate;
W... Circuit board.

Claims (6)

A single-wafer type substrate etching apparatus having a holding table which holds and rotates a substrate, a chemical liquid supply nozzle which supplies a chemical liquid for etching to a center of the substrate which is held and rotated on the holding table, and a cup which is disposed so as to surround the holding table and which prevents the chemical liquid supplied to the substrate from scattering,
the cup has a plurality of cup nozzles capable of supplying pure water toward a peripheral region of the substrate that is off the center of the substrate;
A substrate etching apparatus , wherein each of the plurality of cup nozzles is disposed at equal intervals around the substrate in a plan view . 2. The substrate etching apparatus according to claim 1 , wherein the cup nozzle is oriented in a direction inclined from a direction toward the center of the substrate to a direction along a rotation direction of the substrate in a plan view. the substrate etching apparatus has a cup motor capable of driving the cup up and down;
3. The substrate etching apparatus according to claim 1, wherein the position at which the pure water supplied from the cup nozzle reaches within the peripheral area of the substrate can be adjusted by controlling the vertical position of the cup using the cup motor. 4. The substrate etching apparatus according to claim 1, wherein the cup is made of any one of the materials selected from the group consisting of PTFE, PVDF, PFA, PCTFE, PEEK, PPS, PVC, PE, and PP. 5. The substrate etching apparatus according to claim 1, wherein the substrate is any one of a photomask, a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, and a SiC wafer, or a substrate used in a manufacturing process of any one of a flat panel and a multilayer ceramic. 6. The substrate etching apparatus according to claim 1, wherein the chemical solution is any one of an inorganic acid solution, an inorganic alkaline solution, an organic acid solution, an organic alkaline solution, ozone water, and electrolytic water, or a mixture of two or more of these solutions .

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