TWI819432B - A double-baffle device for improving a uniformity of etching - Google Patents

Abstract

The present application discloses a double-baffle device for improving a uniformity of etching, including a first baffle and a second baffle both installed in an etching reaction chamber. The first baffle is a full-round plate fully being capable of covering ion beams generated by an ion source, under an action of a baffle driving device. A wafer is etched twice, wherein a first etching is an etching without covering by the baffle, and a second etching is an etching with covering by the second baffle. A structure of the second baffle is so selected according to etching conditions, to cover an area in a wafer surface having a higher etching rate during the first etching, under an action of a second baffle driving device, to keep etching rates in the wafer surface consistent. The etching conditions include a low energy condition, a medium energy condition and a high energy condition. The present application improves the overall etching uniformity of the wafer product by the cooperation of etching with two baffles, thereby increasing the utilization rate of the wafer.

Description

Dual baffle device to improve etching uniformity

The present invention relates to the field of ion beam etching, and in particular to a double baffle device for improving etching uniformity. Related applications

This application claims priority to the Chinese patent application filed with the China Patent Office on January 4, 2021, with application number 202110002167.1 and the application title "A double baffle device for improving etching uniformity", the entire content of which is incorporated by reference. in this application.

Ion beam etching uses the principle of glow discharge to decompose argon gas into argon ions. The argon ions are accelerated by the anode electric field and physically bombard the sample surface to achieve the etching effect. The etching process is to fill the inert gas such as argon (Ar) into the ion source discharge chamber, form a plasma through ionization, and transmit the plasma to the target substrate in the form of an ion beam through the gate, and shoot it to the solid surface to bombard the solid surface atoms, causing Material atoms are sputtered to achieve etching purposes. Ion beam etching can be widely used to etch various metals and their alloys, as well as non-metals, oxides, nitrides, carbides, semiconductors, polymers, ceramics, infrared and superconducting materials.

The uniformity of ion beam etching mainly depends on the performance of the ion source. Since the radio frequency (RF) ion source is cylindrical, when the radio frequency power supply is loaded on the radio frequency coil, the current mainly flows in the discharge cavity due to the skin effect of the current. It flows through the wall and gradually attenuates in the skin layer, so the plasma density in the discharge chamber generally shows a trend of being higher on both sides and lower in the middle. Affected by RF power and working pressure, the plasma density distribution in the discharge chamber will also show a saddle-shaped trend. Due to the uneven plasma density distribution, the etching rate will be uneven, affecting the etching uniformity. As shown in Figure 1a-1c, when the ion source operates under low energy conditions, the etching rate in the middle area of the wafer surface is greater than the edge area. As the gate loading voltage increases, the area with faster etching rate gradually moves outward. When Under high energy conditions, the etching rate is obviously greater in the edge area than in the center area. When calculating the etching uniformity of existing wafers, the wafer is generally calculated after trimming. How to save costs and increase the utilization rate of the wafer is an urgent problem that needs to be solved.

Each exemplary embodiment of the present application provides a double-baffle device that improves etching uniformity. The double-baffle device that improves etching uniformity is etched by the cooperation of two baffles, thereby improving the overall etching uniformity of the finished wafer and increasing the etching uniformity of the finished wafer. Wafer utilization.

Each exemplary embodiment of the present application provides a double baffle device for improving etching uniformity, including a first baffle and a second baffle both installed in an etching reaction chamber.

The first baffle is a full circular plate, which can completely block the ion beam generated by the ion source under the action of the first baffle driving device.

The wafer is etched twice. The first etching is etching without a baffle, and the second etching is etching with a second baffle.

The structure of the second baffle is selected according to the etching working conditions. Under the action of the second baffle driving device, the area of the wafer surface with a fast etching rate during the first etching can be blocked, so that the wafer surface has a high etching rate. The etch rate remains consistent.

In one embodiment, the etching conditions include low energy conditions, medium energy conditions and high energy conditions.

In one embodiment, when the etching working condition is a low-energy working condition, the second baffle includes a central circular plate and a plurality of first sector blocks evenly distributed along the circumferential direction of the central circular plate; wherein the central circular plate is used for shielding The low-energy central region of the wafer surface where the etching rate is fast.

In one embodiment, a first sector-shaped gap is formed between two adjacent first sector-shaped blocks. At the radius r, the arc length of the first sector-shaped block is L1, and the arc length of the first sector-shaped gap is L2, where L1 <L2.

In one embodiment, the second stopper further includes a first connecting ring concentrically sleeved on the outer periphery of the central circular plate, and a plurality of first sector blocks are evenly arranged in the circumferential direction between the central circular plate and the first connecting ring.

In one embodiment, when the etching working condition is a medium-energy working condition, the second baffle includes a second connecting ring and a plurality of second sector blocks; the plurality of second sector blocks are evenly arranged on the second connecting ring along the circumferential direction. On the inside, each second sector-shaped block is connected to the inner wall surface of the second connecting ring directly or through connecting ribs; a second sector-shaped gap is formed between two adjacent second sector-shaped blocks.

In one embodiment, at the radius r, the arc length of the second sector block is L3, and the arc length of the second sector gap is L4, where L3>L4.

In one embodiment, the corners of each second segment block are arc chamfered.

In one embodiment, when the etching working condition is a high-energy working condition, the second baffle plate is a first annular plate.

In one embodiment, when the etching working condition is a high-energy working condition, the second baffle plate includes a second annular plate and an inverted fan-shaped gap evenly distributed along the circumferential direction of the second annular plate. The arc length end of the inverted fan-shaped gap faces toward The circular cavity of the second annular plate.

This application has the following beneficial effects: This application uses the first baffle to perform primary etching, selects second baffles with different structures according to different etching conditions, and uses the second baffle to perform secondary etching, thereby effectively improving the wafer finished product. Improve overall etching uniformity and increase wafer utilization.

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. The drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts. The embodiments described below are part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of this application.

It should be understood that the terms "comprise" and "include" used in the description and patent scope of this application indicate the presence of the described features, integers, steps, operations, elements and/or components, but do not exclude one or more other The presence or addition of features, integers, steps, operations, elements, components and/or collections thereof.

In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "left side", "right side", "upper part", "lower part", etc. are based on the orientation or positional relationship shown in the drawings, and are only for convenience The description of this application and the simplified description are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed and operate in a specific orientation, and "first", "second", etc. do not indicate the importance of the component. , therefore cannot be understood as a limitation on this application. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this application.

The meaning of "connection" in this application may be a direct connection between components or an indirect connection between components through other components. For the sake of simplicity, unless otherwise defined, when an element is described as being "connected to" another element in this application, it means that the element is electrically connected to the other element.

As shown in FIGS. 2 to 5 , each exemplary embodiment of the present application proposes a double baffle device for improving etching uniformity, including a first baffle 1 and a second baffle 2 both installed in the etching reaction chamber 8 .

As shown in FIG. 6 , the first baffle is a full circular plate, which can completely block the ion beam generated by the ion source under the action of the first baffle driving device 61 and the first baffle limiting device 71 .

In this application, the wafer is etched twice. The first etching is etching without a baffle, and the second etching is etching with a second baffle.

When the etching uniformity meets the requirements after one etching, the etching is ended. If the process requirements are not met, secondary etching is required.

When the wafer needs to be etched, plasma is generated in the ion source 5 and bombards the wafer 3 in the form of an ion beam. As shown in Figure 3, when the wafer 3 has not yet reached the process position, in order to avoid the ion beam damaging the wafer 3 and If the electrode 4 is damaged, the first baffle 1 blocks the ion beam generated by the ion source 5 under the action of the first baffle driving device 61 and the first baffle limiting device 71 . As shown in Figure 4, when the wafer 3 reaches the process position, the first baffle 1 falls, and the ion beam etches the surface of the wafer 3 until the first process is completed. At this time, because the ion beam generated by the ion source 5 is not Uniformity causes uneven etching of the entire wafer 3, and a second process is required to perform secondary etching on the uneven areas.

As shown in Figure 5, under the action of the second baffle driving device 6 and the second baffle limiting device 7, the second baffle 2 partially blocks the ion beam generated by the ion source 5 (that is, it blocks the crystal during one etching). Areas with a fast etching rate on the circular surface are blocked), and areas with a slow etching rate during the first process (one-time etching) are etched for a short period of time until the uniformity of the entire wafer meets the requirements.

In order to avoid contamination of the etching reaction chamber, the material of the first baffle 1 and the second baffle 2 is preferably graphite or molybdenum.

In order to ensure that the first baffle 1 can completely shield the ion beam when the wafer 3 has not reached the process position, the first baffle 1 can be an overall circular structure, and its diameter is at least larger than the grid component in the ion source 5 The beam diameter is increased by more than 30%. At the same time, it should be ensured that the first baffle 1 does not block the ion beam when it falls.

The structure of the second baffle is selected according to the etching working conditions.

The etching working conditions in the above embodiments include low-energy working conditions (Beamvoltage <300V), medium-energy working conditions (300V<Beamvoltage<600V) and high-energy working conditions (Beamvoltage>600V).

When the process conditions are under low energy conditions (low beam voltage, low beam voltage), as shown in Figure 1a, after the first process is completed, the etching rate on the wafer surface is that the low energy central area 31a is greater than the low energy edge area 31b, and along the The radial etch rate gradually decreases.

As shown in Figures 7a and 7b, during the second process, the second baffle 2 blocks the low-energy central region 31a to prevent the ion beam from over-etching the low-energy central region 31a of the wafer 3. For the low-energy edge region 31b. The blocking area of the second baffle should gradually decrease from the inside to the outside.

In the embodiment shown in Figure 7a, the second baffle includes a central circular plate 21a and a plurality of first sector blocks 21b evenly distributed along the circumferential direction of the central circular plate.

Among them, the central circular plate is used to block the low-energy central region 31a with a fast etching rate on the wafer surface. Therefore, the area of the central circular plate is 4/5~1 of the area of the low-energy central region 31a (taking into account the divergence angle).

A first sector gap 21c is formed between two adjacent first sector blocks 21b.

In this embodiment, the first sector blocks 21b may be three blocks.

Assume that at the radius r, the arc length of the first sector block is L1, the arc length of the first sector gap is L2, and L1 < L2.

The maximum outer diameter of the second baffle (that is, the outer diameter of the first sector block) is preferably more than 1.5 times the outer diameter of the wafer.

In the embodiment shown in Figure 7b, the second baffle includes a central circular plate 21a, a plurality of first sector blocks 21b and a first connecting ring 21d.

In this embodiment, the number of first sector blocks 21b may be three, but may also be other numbers.

The first connecting ring 21d is concentrically arranged on the outer periphery of the central circular plate 21a, and the area of the central circular plate and the area of the low-energy central region 31a are preferably the same.

A plurality of first sector blocks are evenly arranged in the circumferential direction between the central circular plate and the first connecting ring.

When the process conditions are under medium energy conditions (medium beam voltage), as shown in Figure 1b, after the first process is completed, the etching rate on the surface of wafer 3 is equal to the medium energy central area 32a and the medium energy edge area 32c. is lower, while the etch rate of the medium-energy middle region 32b is higher. Therefore, under medium-energy process conditions, the second baffle 2 should be etched twice for the medium-energy central area 32a and the medium-energy edge area 32c. The baffle can choose two preferred styles as shown in Figure 7c and Figure 7d.

In the embodiment shown in Figure 7c, the second baffle includes a second connecting ring 22a and a plurality of second sectors 22b.

The inner diameter of the second connecting ring is preferably larger than the outer diameter of the intermediate energy edge region 32c to avoid blocking the intermediate energy edge region 32c.

In this embodiment, the second sector block 22b may be three blocks. The second sector blocks are evenly arranged on the inside of the second connecting ring along the circumferential direction. Each second sector block is integrally arranged with the inner wall surface of the second connecting ring; a second sector gap 22c is formed between two adjacent second sector blocks. .

The corners of each second sector block are preferably provided with arc chamfers, so that the inner arc and the outer arc of each second sector block are basically equal, thereby enlarging the arc length of the outer arc of the second sector gap, so as to maximize the The occlusion of the centering energy edge area 32c is reduced to facilitate secondary etching.

Assume that at the radius r, the arc length of the second sector block is L3, and the arc length of the second sector gap is L4, then L3>L4.

The inner diameter of the second sector block 22b preferably corresponds to the inner diameter of the intermediate energy intermediate region 32b, and is used to shield the ion beam in the intermediate energy intermediate region 32b to the greatest extent.

The central cavity in the second sector block 22b preferably corresponds to the area of the medium-energy central region 32a, so that the medium-energy central region 32a is etched twice.

In the embodiment shown in Figure 7d, the second baffle includes a second connecting ring 22a and a plurality of second sectors 22b.

In this embodiment, the second sector block 22b is preferably three blocks. The second sector-shaped blocks are evenly arranged inside the second connecting ring along the circumferential direction, and each second sector-shaped block is preferably connected to the inner wall surface of the second connecting ring through a thin connecting rib 22d.

The radial position of the connecting rib preferably corresponds to the medium energy edge region 32c, and the radial length is preferably the same as the medium energy edge region 32c. The axial length of the connecting rib should be as small as possible, so that the annular gap where the connecting rib is located is as large as possible, the ion beam for secondary etching of the medium-energy edge area 32c is the largest, and the etching effect is good.

A second sector gap 22c is formed between two adjacent second sector blocks. For the arrangement of the second sector gap and the central cavity in the second sector block 22b, refer to the above embodiment.

When the process conditions are under high energy conditions (high beam voltage), as shown in Figure 1c, after the first process is completed, the etching rate on the surface of wafer 3 is the fastest in the high energy edge area 33b, from the high energy edge area to the high energy center area 33a gradually decrease. Therefore, the second baffle 2 can choose the style shown in Figure 7e and Figure 7f to perform a second etching on the central area.

As shown in Figure 7e, the second baffle plate includes a second annular plate 23b and an inverted fan-shaped gap 23c evenly distributed along the circumferential direction of the second annular plate. The arc length end of the inverted fan-shaped gap faces the circular shape of the second annular plate. Cavity.

In the embodiment shown in Figure 7f, the second baffle is a first annular plate.

When performing the second process, in addition to using the second baffle 2 alone, the present application can also combine the first baffle 1 and the second baffle 2 according to the situation to meet the etching uniformity requirements. By using two baffles for shielding, more situations can be etched to meet the overall etching uniformity requirements.

As shown in Figure 8a, when the etching rate in the edge area is slow, during the second process, the first baffle 1 can act alone to block the plasma density in other areas, and only etch the edge to meet the requirements. Overall etch uniformity.

As shown in Figure 8b, when the etching rate in the edge and center areas is fast and a ring-shaped area in the middle has a slow etching rate, two baffles can be used to etch the ring area twice (see the shaded area in the figure) ).

This application uses the second baffle 2 to perform secondary etching, which can improve the overall etching uniformity of the finished wafer and increase the utilization rate of the wafer.

The preferred embodiments of the present application have been described in detail above. However, the present application is not limited to the specific details in the above-mentioned embodiments. Within the scope of the technical concept of the present application, various equivalent transformations can be made to the technical solutions of the present application. These equivalent transformations are all It falls within the protection scope of this application.

1: First baffle 2:Second baffle 21a: Center circular plate 21b: First sector block 21c: First sector gap 21d: First connecting ring 22a: Second connecting ring 22b: Second sector block 22c: Second sector gap 22d: Connecting ribs 23a: First ring plate 23b: Second ring plate 23c: Inverted sector gap 3:wafer 31a: Low energy central area 31b: Low energy edge region 32a: Medium energy center area 32b: Middle energy intermediate region 32c: Medium energy edge area 33a: High energy center area 33b: High energy edge region 4:Electrode 5:Ion source 6: Second baffle driving device 61: First baffle driving device 7: Second baffle limiter 71: First baffle limiting device 8: Etching reaction chamber

Figures 1a-1c show schematic diagrams of wafer surface etching rate uniformity under different etching conditions in the prior art. Figures 1a, 1b and 1c respectively show the wafer surface etching rate uniformity under low energy conditions, medium energy conditions and high energy conditions. Schematic diagram of wafer surface etch rate uniformity. Figure 2 shows a schematic diagram of the overall structure of an ion etching system according to an embodiment of the present application. FIG. 3 shows a schematic diagram of the state of two baffles when the wafer has not reached the etching position according to an embodiment of the present application. Figure 4 shows a schematic diagram of the state of two baffles during the first etching according to an embodiment of the present application. Figure 5 shows a schematic diagram of the state of two baffles during the second etching according to an embodiment of the present application. Figure 6 shows a schematic structural diagram of the first baffle according to an embodiment of the present application. Figures 7a-7f show a schematic structural diagram of the second baffle according to an embodiment of the present application. Figures 7a and 7b show two example diagrams of the second baffle under low energy conditions; Figures 7c and 7d show Two example diagrams of the second baffle under medium-energy working conditions; Figure 7e and Figure 7f show two example diagrams of the second baffle under high-energy working conditions. Figures 8a-8b show a schematic diagram of the state in which two baffles cooperate for the second etching according to an embodiment of the present application. Figures 8a and 8b respectively show two examples of cooperation. Figure 9 shows a schematic flow diagram of two baffles cooperating for wafer etching.

1: First baffle

2:Second baffle

5:Ion source

6: Second baffle driving device

61: First baffle driving device

7: Second baffle limiter

71: First baffle limiting device

8: Etching reaction chamber

Claims (8)

A double baffle device for improving etching uniformity, including a first baffle and a second baffle installed in an etching reaction chamber; wherein the first baffle is a full circular plate that can be driven by the first baffle driving device Under the action of ; The structure of the second baffle is selected according to the etching working conditions, and under the action of the second baffle driving device, the area of the surface of the wafer with a fast etching rate during the first etching can be Shield, so that the etching rate of the surface of the wafer remains consistent, wherein the etching working conditions include low energy working conditions, medium energy working conditions and high energy working conditions, and when the etching working conditions are high energy working conditions When, the second baffle is a first annular plate. The double baffle device according to claim 1, wherein when the etching working condition is the low energy working condition, the second baffle includes a central circular plate and is evenly arranged along the circumferential direction of the central circular plate. A plurality of first sector blocks, wherein the central circular plate is used to block the low-energy central area of the surface of the wafer where the etching rate is fast. The double baffle device according to claim 2, wherein a first sector gap is formed between two adjacent first sector blocks, and at the radius r, the arc length of the first sector block is L1, and the arc length of the first sector block is L1, and the arc length of the first sector block is L1. The arc length of a sector gap is L2, where L1<L2. The double baffle device according to claim 2, wherein the second baffle further includes a first connecting ring concentrically sleeved on the outer periphery of the central circular plate, and the plurality of The first sector block is evenly arranged between the central circular plate and the first connecting ring along the circumferential direction. The double baffle device according to claim 1, wherein when the etching working condition is a medium energy working condition, the second baffle plate includes a second connecting ring and a plurality of second sector blocks; The second sector-shaped blocks are evenly arranged inside the second connecting ring along the circumferential direction, and each second sector-shaped block is connected to the inner wall surface of the second connecting ring directly or through connecting ribs; two adjacent second sector-shaped blocks are connected to the inner wall of the second connecting ring directly or through connecting ribs. A second sector-shaped gap is formed between the two sector-shaped blocks. The double baffle device according to claim 5, wherein at the radius r, the arc length of the second sector block is L3, and the arc length of the second sector gap is L4, where L3>L4. The double baffle device according to claim 5, wherein the corners of each second sector block are arc chamfered. The double baffle device according to claim 1, wherein when the etching working condition is a high-energy working condition, the second baffle plate includes a second annular plate and a second baffle plate along the circumferential direction of the second annular plate. Inverted fan-shaped gaps are evenly arranged, and the long arc end of the inverted fan-shaped gaps faces the circular cavity of the second annular plate.

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