A double baffle device for improving etching uniformity

Abstract

The present invention discloses a double baffle device for improving etching uniformity, comprising a first baffle and a second baffle both installed in an etching reaction chamber; the first baffle is a full-circular plate, which can fully shield the ion beam generated by an ion source under the action of a first baffle driving device; the wafer is etched twice, the first etching is etching without baffle shielding, and the second etching is etching shielded by a second baffle; the structure of the second baffle is selected according to the etching conditions, and can shield the area of ​​the wafer surface with a fast etching rate during the first etching under the action of the second baffle driving device, so that the etching rate of the wafer surface remains consistent. Etching conditions include low-energy conditions, medium-energy conditions and high-energy conditions. The present invention improves the overall etching uniformity of the finished wafer product and increases the utilization rate of the wafer by etching with the cooperation of two baffles.

Description

Technical Field

[0001] The invention relates to the field of ion beam etching, in particular to a double baffle device for improving etching uniformity. Background Art

[0002] 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 to physically bombard the sample surface to achieve the etching effect. The etching process is to fill the inert gas such as Ar into the ion source discharge chamber, form plasma after 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 atoms on the solid surface, causing the material atoms to sputter to achieve the purpose of etching. Ion beam etching can be widely used for etching and processing various metals and their alloys, as well as non-metals, oxides, nitrides, carbides, semiconductors, polymers, ceramics, infrared and superconducting materials.

[0003] The uniformity of ion beam etching mainly depends on the performance of the ion source. Since the RF ion source is cylindrical, when the RF power is loaded on the RF coil, due to the skin effect of the current, the current mainly flows through the wall of the discharge chamber and gradually decays in the skin layer. Therefore, the plasma density in the discharge chamber generally shows a trend of high on both sides and low in the middle. Affected by the RF power and working pressure, the plasma density distribution in the discharge chamber will also show a saddle-shaped trend. Due to the uneven distribution of plasma density, the etching rate is uneven, which affects the etching uniformity. Figure 1 As shown in the figure, when the ion source works under low energy conditions, the etching rate in the middle area of ​​the wafer surface is greater than that in the edge area. As the gate loading voltage increases, the area with faster etching rate gradually moves outward. When it is under high energy conditions, the etching rate in the edge area is obviously greater than that in the center area. When calculating the etching uniformity of existing wafers, the calculation is generally done after the wafer is trimmed. How to save costs and increase the utilization rate of wafers is a difficult problem that needs to be solved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a double baffle device for improving etching uniformity in view of the deficiencies of the above-mentioned prior art. The double baffle device for improving etching uniformity improves the overall etching uniformity of the finished wafer and increases the utilization rate of the wafer through the coordinated etching of two baffles.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A double baffle device for improving etching uniformity comprises a first baffle and a second baffle both installed in an etching reaction chamber.

[0007] The first baffle is a full-circular plate, which can completely shield the ion beam generated by the ion source under the action of the first baffle driving device.

[0008] The wafer is etched twice, the first etching is etching without shielding of a baffle, and the second etching is etching with shielding of a second baffle.

[0009] The structure of the second baffle is selected according to the etching conditions. Under the action of the second baffle driving device, the area on the wafer surface with a fast etching rate can be shielded during one etching, so that the etching rate on the wafer surface remains consistent.

[0010] Etching conditions include low energy conditions, medium energy conditions and high energy conditions.

[0011] When the etching condition is a low-energy condition, the second baffle includes a central circular plate and a plurality of fan-shaped blocks uniformly arranged along the circumference of the central circular plate; wherein the central circular plate is used to shield the low-energy central area of ​​the wafer surface with a fast etching rate.

[0012] A sector gap 1 is formed between two adjacent sector blocks 1. Assuming that at radius r, the arc length of sector block 1 is L1, and the arc length of sector gap 1 is L2, then L1<L2, and the ratio of L1 to L2 gradually decreases from inside to outside along the radial direction.

[0013] The second stopper also includes a connecting ring 1 which is concentrically sleeved on the outer periphery of the central circular plate, and a plurality of sector blocks 1 are evenly arranged between the central circular plate and the connecting ring 1 along the circumferential direction.

[0014] When the etching working condition is a medium energy working condition, the second baffle includes a connecting ring 2 and a plurality of fan-shaped blocks 2; the plurality of fan-shaped blocks 2 are evenly arranged on the inner side of the connecting ring 2 along the circumferential direction, and each fan-shaped block 2 is directly connected to the inner wall surface of the connecting ring 2 or through a connecting rib; a fan-shaped gap 2 is formed between two adjacent fan-shaped blocks 2.

[0015] Assuming that at radius r, the arc length of sector block 2 is L3, and the arc length of sector gap 2 is L4, then L3>L4.

[0016] The corners of each sector block 2 are all arc chamfered.

[0017] When the etching working condition is a high-energy working condition, the second baffle is the first circular ring plate.

[0018] When the etching condition is a high-energy condition, the second baffle includes an annular plate 2 and inverted fan-shaped gaps uniformly arranged along the circumference of the annular plate 2, and the arc length of the inverted fan-shaped gaps faces the circular cavity of the annular plate 2.

[0019] The present invention has the following beneficial effects: the present invention uses a first baffle to perform a first etching, selects a second baffle with a different structure according to different etching conditions, and uses the second baffle to perform a second etching, thereby effectively improving the overall etching uniformity of the finished wafer and increasing the utilization rate of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram showing the uniformity of etching rate on the wafer surface under different etching conditions; Figure 1 (a) Figure 1 (b) and Figure 1 (c) Schematic diagram of the uniformity of wafer surface etching rate under low energy conditions, medium energy conditions and high energy conditions respectively.

[0021] Figure 2 The overall structural schematic diagram of the ion etching system of the present invention is shown.

[0022] Figure 3 A schematic diagram showing the status of the two baffles when the wafer has not reached the etching position.

[0023] Figure 4 A schematic diagram showing the states of the two baffles during the first etching.

[0024] Figure 5 A schematic diagram showing the status of the two baffles during the second etching.

[0025] Figure 6 A schematic diagram of the structure of the first baffle is shown.

[0026] Figure 7 The schematic diagram of the structure of the second baffle is shown; wherein, Figure 7 (a) and Figure 7 (b) shows two examples of the second baffle under low energy conditions; Figure 7 (c) and Figure 7 (d) shows two examples of the second baffle under medium energy conditions; Figure 7 (e) and Figure 7 (f) shows two examples of the second baffle under high energy conditions.

[0027] Figure 8 A schematic diagram showing the state of two baffles cooperating to perform the second etching. Figure 8 (a) and Figure 8 (b) shows two examples of matching.

[0028] Fig. 9 A schematic diagram of the process of wafer etching using two baffles is shown.

[0029] Among them are:

[0030] 1. The first baffle;

[0031] 2. Second baffle; 21a. Center circular plate; 21b. Sector block 1; 21c. Sector gap 1; 21d. Connecting ring 1;

[0032] 22a. Connecting ring 2; 22b. Sector block 2; 22c. Sector gap 2; 22d. Connecting rib;

[0033] 23a. Circular ring plate 1; 23b. Circular ring plate 2; 23c. Inverted fan-shaped gap;

[0034] 3. Wafer;

[0035] 31a. Low energy central region; 31b. Low energy edge region; 32a. Medium energy central region; 32b. Medium energy intermediate region; 32c. Medium energy edge region; 33a. High energy central region; 33b. High energy edge region;

[0036] 4. Electrode; 5. Ion source; 6. Second baffle driving device; 61. First baffle driving device; 7. Second baffle limiting device; 71. First baffle limiting device; 8. Etching reaction chamber. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0038] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0039] like Figures 2 to 5 As shown, a double baffle device for improving etching uniformity includes a first baffle 1 and a second baffle 2 both installed in an etching reaction chamber 8.

[0040] like Figure 6 As shown, 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.

[0041] In the present invention, the wafer is etched twice, the first etching is etching without shielding of a baffle, and the second etching is etching with shielding of a second baffle.

[0042] After one etching, if the etching uniformity meets the requirements, the etching is terminated. If it does not meet the process requirements, a second etching is required.

[0043] 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. When the wafer 3 has not reached the process position, such as Figure 3 shown, to avoid damage to the wafer 3 and the electrode 4 by the ion beam, under the action of the first baffle driving device 61 and the first baffle limiting device 71, the first baffle 1 shields the ion beam generated by the ion source 5. When the wafer 3 reaches the process position, such as Figure 4 shown, the first baffle 1 drops, and the ion beam etches the surface of the wafer 3 until the first process is completed. At this time, due to the non-uniform ion beam generated by the ion source 5, the etching of the entire wafer 3 is non-uniform, and a second process is required to perform secondary etching on the non-uniform area.

[0044] Such as Figure 5 shown, under the action of the second baffle driving device 6 and the second baffle limiting device 7, the second baffle 2 locally shields the ion beam generated by the ion source 5 (that is, shields the area on the wafer surface with a fast etching rate during the first etching), and etches the area with a slower etching rate during the first process (primary etching) for a short time until the uniformity of the entire wafer meets the requirements.

[0045] To avoid contamination of the etching reaction chamber, the materials of the first baffle 1 and the second baffle 2 are preferably graphite or molybdenum, etc.

[0046] To ensure that when the wafer 3 has not reached the process position, the first baffle 1 can completely shield the ion beam, the first baffle 1 should be an integral circular structure, and its diameter should be at least 30% larger than the beam aperture of the Grid component in the ion source 5. At the same time, it should be ensured that the baffle does not block the ion beam when it drops.

[0047] The structure of the second baffle is selected according to the etching working conditions.

[0048] The above-mentioned etching working conditions include low-energy conditions (Beamvoltage < 300V), medium-energy conditions (300V < Beamvoltage < 600V), and high-energy conditions (Beamvoltage > 600V).

[0049] When the process conditions are under low-energy conditions (low beam voltage), such as Figure 1 shown in (a), when the first process is completed, the etching rate on the wafer surface is that the low-energy central region 31a is greater than the low-energy edge region 31b, and the etching rate gradually decreases along the radial direction.

[0050] At this time, during the second process, the second baffle 2 should shield the low-energy central region 31a to avoid over-etching of the low-energy central region 31a of the wafer 3 by the ion beam. For the low-energy edge region 31b, the shielding area of the second baffle should gradually decrease from the inside to the outside, such as Figure 7 shown in (a) and Figure 7 (b) shown.

[0051] Example 1

[0052] exist Figure 7 In (a), the second baffle includes a central circular plate 21a and a plurality of sector blocks 21b uniformly arranged along the circumference of the central circular plate.

[0053] The central circular plate is used to shield the low-energy central region 31 a with a fast etching rate on the wafer surface, so the area of ​​the central circular plate is 4 / 5 to 1 (taking into account the divergence angle) of the area of ​​the low-energy central region 31 a.

[0054] A sector-shaped gap 21c is formed between two adjacent sector-shaped blocks 21b.

[0055] In this embodiment, the number of sector blocks 21b is preferably three.

[0056] Assuming that at radius r, the arc length of sector block 1 is L1, and the arc length of sector gap 1 is L2, then L1<L2, and the ratio of L1 to L2 gradually decreases from inside to outside along the radial direction.

[0057] The maximum outer diameter of the second baffle (ie, the outer diameter of the first sector) is preferably at least 1.5 times the outer diameter of the wafer.

[0058] Example 2

[0059] exist Figure 7 In (b), the second baffle includes a central circular plate 21a, a plurality of sector blocks 21b and a connecting ring 21d.

[0060] In this embodiment, the number of sector blocks 21b is preferably three, but may be other numbers.

[0061] The connecting ring 21d is concentrically arranged on the outer periphery of the central circular plate 21a, and the area of ​​the central circular plate is preferably the same as the area of ​​the low-energy central region 31a.

[0062] A plurality of sector blocks are evenly arranged between the central circular plate and the connecting ring along the circumferential direction.

[0063] When the process conditions are under medium beam voltage, such as Figure 1 As shown in (b), after the first process is completed, the etching rate of the surface of the wafer 3 is low in the medium energy center area 32a and the medium energy edge area 32c, while the etching rate of the medium energy middle area 32b is high. Therefore, under the medium energy process conditions, the second baffle 2 should perform secondary etching on the medium energy center area 32a and the medium energy edge area 32c. The baffle can be selected Figure 7 (c) and Figure 7 (d) Two preferred styles are shown.

[0064] Example 1

[0065] like Figure 7 As shown in (c), the second baffle includes a connecting ring 22a and a plurality of sector blocks 22b.

[0066] The inner diameter of the connecting ring 2 is preferably larger than the outer diameter of the middle energy edge region 32c to avoid blocking the middle energy edge region 32c.

[0067] In this embodiment, the number of the second sector blocks 22b is preferably three. The second sector blocks are evenly arranged on the inner side of the second connecting ring along the circumferential direction, and each second sector block is integrally arranged with the inner wall surface of the second connecting ring; and a second sector gap 22c is formed between two adjacent second sector blocks.

[0068] The corners of each sector block 2 are preferably provided with arc chamfers so that the inner arc and outer arc of each sector block 2 are substantially equal, thereby increasing the arc length of the outer arc of the sector gap 2, thereby minimizing the obstruction of the center energy edge region 32c and facilitating secondary etching.

[0069] Assuming that at radius r, the arc length of sector block 2 is L3, and the arc length of sector gap 2 is L4, then L3>L4.

[0070] The inner diameter of the second sector block 22b preferably corresponds to the inner diameter of the medium energy middle region 32b, so as to shield the ion beam in the medium energy middle region 32b to the greatest extent.

[0071] 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.

[0072] Example 2

[0073] like Figure 7 As shown in (d), the second baffle includes a connecting ring 22a and a plurality of sector blocks 22b.

[0074] In this embodiment, the number of the second sector blocks 22b is preferably three. The second sector blocks are evenly arranged on the inner side of the second connecting ring along the circumferential direction, and each second sector block is preferably connected to the inner wall surface of the second connecting ring through a thin strip-shaped connecting rib 22d.

[0075] The radial position of the connecting rib is preferably corresponding 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 is 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 region 32c is the largest, and the etching effect is good.

[0076] A second sector gap 22c is formed between two adjacent sector blocks 2. The arrangement of the second sector gap 2 and the inner center cavity of the second sector block 22b is similar to that of Example 1.

[0077] When the process conditions are under high energy conditions (high beam voltage), such as Figure 1 As shown in (c), after the first process is completed, the etching rate of the surface of the wafer 3 is the fastest in the high-energy edge area 33b, and gradually decreases from the high-energy edge area to the high-energy center area 33a. Therefore, the second baffle 2 can be selected Figure 7 (e) and Figure 7 (f) The style shown has a secondary etching of the central area.

[0078] like Figure 7 As shown in (e), the second baffle includes an annular plate 23b and inverted fan-shaped gaps 23c uniformly arranged along the circumference of the annular plate 2, and the arc length of the inverted fan-shaped gaps faces the circular cavity of the annular plate 2.

[0079] Example 2

[0080] like Figure 7 As shown in (f), the second baffle is an annular plate 1.

[0081] In the second process, in addition to using the second baffle 2 alone, the present invention can also combine the first baffle 1 and the second baffle 2 according to the situation to meet the etching uniformity requirements. Using two baffles for shielding can be used for etching in more situations to meet the overall etching uniformity requirements.

[0082] like Figure 8 As shown in (a), when the etching rate of the edge area is slow, in 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 overall etching uniformity.

[0083] like Figure 8 As shown in (b), when the etching rates of the edge and center areas are faster and a ring-shaped area with a slower etching rate appears in the middle, two baffles can be used to perform secondary etching on the ring-shaped area (see the shaded area in the figure).

[0084] The present invention utilizes the second baffle plate 2 to perform secondary etching, which can improve the overall etching uniformity of the finished wafer and increase the utilization rate of the wafer.

[0085] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A double baffle device for improving etching uniformity, characterized in that: It includes a first baffle and a second baffle both installed in the 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 shielding of a baffle, and the second etching is etching with shielding of a second baffle; The structure of the second baffle is selected according to the etching conditions, and under the action of the second baffle driving device, the area on the wafer surface with a fast etching rate during the first etching can be shielded, so that the etching rate on the wafer surface remains consistent; Etching conditions include low energy conditions, medium energy conditions and high energy conditions; When the etching condition is a low-energy condition, the etching rate of the low-energy center area of ​​the wafer surface is greater than that of the low-energy edge area, and the etching rate gradually decreases along the radial direction; at this time, the second baffle can shield the low-energy center area to prevent the ion beam from over-etching the low-energy center area of ​​the wafer, and for the low-energy edge area, the shielding area of ​​the second baffle gradually decreases from the inside to the outside; When the etching condition is a medium energy condition, the etching rate of the medium energy center area and the medium energy edge area of ​​the wafer surface is low, while the etching rate of the medium energy middle area is high; at this time, the second baffle can shield the medium energy middle area, making it convenient to perform secondary etching on the medium energy center area and the medium energy edge area; When the etching condition is a high-energy condition, the etching rate of the wafer surface is fastest in the high-energy edge area and gradually decreases from the high-energy edge area to the high-energy center area; at this time, by setting a second baffle structure, the center area is etched for the second time.

2. The double baffle device for improving etching uniformity according to claim 1, characterized in that: When the etching condition is a low-energy condition, the second baffle includes a central circular plate and a plurality of fan-shaped blocks uniformly arranged along the circumference of the central circular plate; wherein the central circular plate is used to shield the low-energy central area of ​​the wafer surface with a fast etching rate.

3. The double baffle device for improving etching uniformity according to claim 2, characterized in that: A sector gap 1 is formed between two adjacent sector blocks 1. Assuming that at radius r, the arc length of sector block 1 is L1, and the arc length of sector gap 1 is L2, then L1<L2, and the ratio of L1 to L2 gradually decreases from inside to outside along the radial direction.

4. The double baffle device for improving etching uniformity according to claim 3, characterized in that: The second stopper also includes a connecting ring 1 which is concentrically sleeved on the outer periphery of the central circular plate, and a plurality of sector blocks 1 are evenly arranged between the central circular plate and the connecting ring 1 along the circumferential direction.

5. The double baffle device for improving etching uniformity according to claim 1, characterized in that: When the etching working condition is a medium energy working condition, the second baffle includes a connecting ring 2 and a plurality of fan-shaped blocks 2; the plurality of fan-shaped blocks 2 are evenly arranged on the inner side of the connecting ring 2 along the circumferential direction, and each fan-shaped block 2 is directly connected to the inner wall surface of the connecting ring 2 or through a connecting rib; a fan-shaped gap 2 is formed between two adjacent fan-shaped blocks 2.

6. The double baffle device for improving etching uniformity according to claim 5, characterized in that: Assuming that at radius r, the arc length of sector block 2 is L3, and the arc length of sector gap 2 is L4, then L3>L4.

7. The double baffle device for improving etching uniformity according to claim 5, characterized in that: The corners of each sector block 2 are all arc chamfered.

8. The double baffle device for improving etching uniformity according to claim 1, characterized in that: When the etching working condition is a high-energy working condition, the second baffle is the first circular ring plate.

9. The double baffle device for improving etching uniformity according to claim 1, characterized in that: When the etching condition is a high-energy condition, the second baffle includes an annular plate 2 and inverted fan-shaped gaps uniformly arranged along the circumference of the annular plate 2, and the arc length of the inverted fan-shaped gaps faces the circular cavity of the annular plate 2.

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