Wafer natural oxide layer etching device and method

Abstract

The invention discloses a wafer natural oxide layer etching device, comprising a frame, a special gas cabinet component, an upper chamber component, a lower chamber component, a base lifting component, a plasma generator and a control component. The special gas cabinet component and the control component are both fixed on the frame, the lower chamber component is fixed on the frame by adjustable bolts, the upper chamber component is connected to the upper part of the lower chamber component by a rotating shaft, the base lifting component is connected to the lower part of the lower chamber component, and the plasma generator is installed on the upper part of the upper chamber component, thereby solving the problem that ordinary high-energy ion bombardment causes great damage to wafers and affects the quality of subsequent deposited films.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer oxide layer etching, and in particular to a wafer natural oxide layer etching device and method. Background Art

[0002] In the field of semiconductor production, before epitaxial thin film deposition on silicon wafers, the wafers need to be pre-cleaned because there will be a natural oxide layer on the surface of the wafer. The function of pre-cleaning is to etch the natural oxide layer on the surface of the wafer. The usual technical means is to form plasma with argon gas in the reaction chamber, and then bombard the surface of the wafer to remove the natural oxide layer. However, with the advancement of process technology, the conventional plasma pre-cleaning method will remove silicon oxide while the high-energy plasma will also damage the surface of the wafer, affecting the quality of the subsequent deposited film. To this end, the present invention provides a wafer natural oxide layer etching device and method with low damage to the wafer and high surface quality. Summary of the invention

[0003] The purpose of the present invention is to provide a wafer natural oxide layer etching device and method, which solves the problem that ordinary high-energy ion bombardment causes serious damage to the wafer and affects the quality of the subsequent deposited film.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions:

[0005] A wafer natural oxide layer etching device comprises a frame, a special gas cabinet assembly, an upper chamber assembly, a lower chamber assembly, a base lifting assembly, a plasma generator and a control assembly, wherein the special gas cabinet assembly and the control assembly are both fixed on the frame, the lower chamber assembly is fixed on the frame by an adjustable bolt, the upper chamber assembly is connected to the upper part of the lower chamber assembly by a rotating shaft, the base lifting assembly is connected to the lower part of the lower chamber assembly, and the plasma generator is installed on the upper part of the upper chamber assembly;

[0006] The upper chamber assembly includes a connecting channel, an upper cover, a first spray plate, a second spray plate, a heating ring, an upper hinge and a lower cover, the upper end of the connecting channel is connected to the plasma generator, the lower end of the connecting channel is connected to the upper cover, the first spray plate is arranged between the upper cover and the lower cover, the heating ring is arranged inside the second spray plate, the heating ring is an annular structure, the second spray plate is installed below the lower cover, and the upper hinge is installed on the side of the lower cover;

[0007] The lower chamber assembly includes a lower chamber, a lower hinge, an adjustment support, a gas pipeline, an exhaust manifold block, and an exhaust pipeline. The adjustment support is installed on the frame, and the lower end of the lower chamber is installed on the frame through the adjustment support. The lower hinge is installed on the lower chamber, and the lower hinge is connected to the upper hinge through a pin shaft. The gas pipeline is arranged inside the lower chamber, and the exhaust manifold block is installed below the lower chamber. Two mounting parts are provided at the lower end of the exhaust manifold block, one of which is connected to the exhaust pipeline, and the other is connected to the base lifting assembly.

[0008] Preferably, the base lifting assembly includes a base, a lifting mechanism, a connecting barrel, a mounting seat, a screw module, a stepper motor, a guide rail, a first movable seat, a second movable seat, a connecting block, a bellows and an adjusting bolt; the mounting seat includes a transverse portion and a longitudinal portion, the transverse portion of the mounting seat is mounted on the lower cavity through an adjusting bolt, the screw module is vertically mounted on the longitudinal portion of the mounting seat, the first movable seat is mounted on the longitudinal portion of the mounting seat through the guide rail, the stepper motor is mounted on the longitudinal portion of the mounting seat, the output shaft of the stepper motor is connected to the screw module, the second movable seat is fixed to the first movable seat through a connecting block, a ball head top column is arranged between the connecting block and the three sides of the second movable seat, the connecting barrel is mounted on the second movable seat, the base is mounted on the connecting barrel, and the lifting mechanism is arranged in the base for lifting and lowering the wafer on the base.

[0009] Preferably, the lifting mechanism includes a lifting spindle, a sealing bellows, a lifting fork, a lifting cylinder and a lift pin; the lifting spindle is installed on the second movable seat through a linear bearing, the lift fork is installed on the upper end of the lifting spindle, the lower end of the sealing bellows is connected to the lifting spindle, the upper end of the sealing bellows is connected to the base, the movable end of the lifting cylinder is connected to the lifting spindle, the lifting cylinder is installed on the first movable seat, the lift pin is placed in the base, and the lift pin is located directly above the lift fork.

[0010] Preferably, a cooling water channel is provided inside the base, the interface of the cooling water channel is led out from the inside of the connecting barrel, the temperature setting range of the base is 24°C-45°C, and a ceramic protective shell is provided on the top surface of the base.

[0011] Preferably, the first spray plate and the second spray plate are both disc-shaped, both of which have fine holes, the thickness of the first spray plate is thicker in the middle and gradually thinner towards the edge, and the thickness of the second spray plate is uniform.

[0012] Preferably, the exhaust pipeline is provided with a butterfly valve, a gate valve, a vacuum gauge and a bypass valve for evacuating and controlling the pressure of the process gas in the cavity.

[0013] Preferably, the special gas cabinet assembly is used to provide process gas, and the process gas includes one or more of argon Ar, nitrogen N2, ammonia NH3, nitrogen trifluoride NF3, and hydrogen H2. The process gas is connected to the plasma generator through a pipeline.

[0014] A wafer natural oxide layer etching method,

[0015] S1 loading: the wafer enters the cavity, the lifting mechanism lifts up the ejector pin, and then places the wafer on the base, and the loading is completed;

[0016] S2 ionization: process gases including NH3, NF3, H2, N2, and Ar enter the chamber after being ionized by a plasma generator, and the ions include H+, NH4+, F-, and Ar+;

[0017] S3 reaction: The process gas falls after passing through the spray plate and reacts with the natural oxide layer SiO2 of the wafer to form an intermediate product (NH4)2SiF6; (NH4)2SiF6 is a solid product;

[0018] S4 gasification reaction: The stepper motor drives the base and the wafer to rise and approach the second spray plate. The second spray plate heats the wafer through thermal radiation, so that (NH4)2SiF6 is heated and volatilized, and the recovered product is discharged from the exhaust pipe;

[0019] S5 unloading: the base descends, the lifting mechanism lifts up the wafer, and the robot unloads the wafer.

[0020] Beneficial effect: The first spray plate and the second spray plate are set to perform two-stage diversion of the process gas. On the one hand, it can improve the uniformity of gas distribution. On the other hand, the plasma collides after passing through the fine holes, resulting in reduced energy. The first spray plate can make the energy of the plasma uniform when it falls on the wafer by setting the spray holes at different heights.

[0021] The height and level of the base can be adjusted by adjusting the bolts, and the center of the base can be adjusted by the ball head top column on the connecting block. The position of the base can be adjusted, and the installation accuracy is higher, thereby improving the uniformity of etching and the consistency of the equipment.

[0022] Using a lower process temperature can reduce damage to the chip and use a gentler method to etch the oxide layer, reducing defects and improving the quality of the wafer.

[0023] A wafer oxide layer etching method using separate etching and sublimation machines can improve wafer flow efficiency, reduce particle production and aggregation, and improve wafer quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a side sectional view of the present invention;

[0025] Figure 2 is a cross-sectional view of an embodiment for showing an upper chamber component;

[0026] Figure 3 It is a cross-sectional view of an embodiment for showing a lower chamber component;

[0027] Figure 4 The embodiment is used to show the schematic diagram of the structure of the lower cavity and the schematic diagram of the internal flow channel;

[0028] Figure 5 It is a cross-sectional view of an embodiment for showing a base lifting assembly;

[0029] Figure 6 The embodiment is used to show the relative position diagram of the second movable seat and the ball head top column;

[0030] Figure 7 The embodiment is used to show the structural schematic diagram of the jacking mechanism.

[0031] Figure numerals: 1, rack; 2, special gas cabinet assembly; 3, upper chamber assembly; 31, connecting channel; 32, upper cover; 33, first spray plate; 34, second spray plate; 35, heating ring; 36, upper hinge; 37, lower cover; 4, lower chamber assembly; 41, lower chamber; 42, lower hinge; 43, adjustment support; 44, gas pipeline; 45, exhaust manifold; 46, exhaust pipeline; 47, butterfly valve; 48, gate valve; 49, vacuum gauge; 410, bypass valve; 5 , base lifting assembly; 51, base; 52, lifting mechanism; 521, lifting spindle; 522, sealing bellows; 523, lifting fork; 524, lifting cylinder; 525, ejector; 53, connecting barrel; 54, mounting seat; 55, screw module; 56, stepping motor; 57, guide rail; 58, first moving seat; 59, second moving seat; 510, connecting block; 511, bellows; 512, adjusting bolt; 6, plasma generator; 7, control assembly. DETAILED DESCRIPTION

[0032] The following is only a preferred embodiment of the present invention, and the protection scope is not limited to this embodiment. All technical solutions under the concept of the present invention should belong to the protection scope of the present invention. At the same time, it should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

[0033] like Figure 1As shown, a wafer natural oxide layer etching device includes a frame 1, a special gas cabinet assembly 2, an upper chamber assembly 3, a lower chamber assembly 4, a base lifting assembly 5, a plasma generator 6 and a control assembly 7. The special gas cabinet assembly 2 and the control assembly 7 are fixed to the frame 1, the lower chamber assembly 4 is fixed to the frame 1 by adjustable bolts, the upper chamber assembly 3 is connected to the lower chamber assembly 4 by a rotating shaft, the base lifting assembly 5 is connected under the lower chamber assembly 4, and the plasma generator 6 is installed on the upper chamber assembly 3.

[0034] The special gas cabinet assembly 2 provides process gas, which includes one or more of argon Ar, nitrogen N2, ammonia NH3, nitrogen trifluoride NF3, and hydrogen H2. The process gas is connected to the plasma generator 6 and ionized, and then flows evenly through the upper chamber assembly 3 to react with the wafer placed on the base lifting assembly 5. The exhaust gas after the reaction is extracted by the lower chamber assembly 4. The base lifting assembly 5 can lift or drop the wafer to adapt to different process operations of etching and loading and unloading.

[0035] like Figure 2 As shown, the upper chamber assembly 3 includes a connecting channel 31, an upper cover 32, a first spray plate 33, a second spray plate 34, a heating ring 35, an upper hinge 36 and a lower cover 37; the upper end of the connecting channel 31 is connected to the plasma generator 6, and the lower end of the connecting channel 31 is connected to the upper cover 32. The first spray plate 33 is arranged between the upper cover 32 and the lower cover 37, the heating ring 35 is annular, and the heating ring 35 is arranged inside the second spray plate 34, the second spray plate 34 is installed below the lower cover 37, and the upper hinge 36 is installed on the side of the lower cover 37. The first spray plate 33 and the second spray plate 34 are disc-shaped and have fine holes. The thickness of the first spray plate 33 is thickened in the middle and gradually becomes thinner toward the edge, and the thickness of the second spray plate 34 is consistent. The upper chamber component 3 performs two-stage diversion of the process gas by setting the first spray plate 33 and the second spray plate 34. On the one hand, it can improve the uniformity of gas distribution. On the other hand, the plasma collides after passing through the fine holes, resulting in reduced energy. The first spray plate 33 can make the energy of the plasma uniform when it falls on the wafer by setting the spray holes at different heights.

[0036] like Figure 3As shown, the lower chamber assembly 4 includes a lower chamber 41, a lower hinge 42, an adjustment support 43, a gas pipeline 44, an exhaust manifold 45, an exhaust pipeline 46, a butterfly valve 47, a gate valve 48, a vacuum gauge 49 and a bypass valve 410; the lower end of the lower chamber 41 is mounted on the frame 1 by setting an adjustment support 43, the lower hinge 42 is mounted on the lower chamber 41, and the lower hinge 42 is connected to the upper hinge 36 by a pin shaft, so that the upper chamber assembly 3 can be turned over. The gas pipeline 44 is arranged inside the lower chamber 41 to connect the process gas from the special gas cabinet assembly 2 to the upper chamber assembly 3. The exhaust manifold 45 is installed below the lower chamber 41, and the lower end of the exhaust manifold 45 has two mounting parts, one is connected to the exhaust pipeline 46 for exhaust, and the other is connected to the base lifting assembly 5. A butterfly valve 47, a gate valve 48, a vacuum gauge 49 and a bypass valve 410 are provided on the exhaust pipeline 46 to evacuate and control the pressure of the process gas in the chamber.

[0037] like Figure 4 As shown, a water channel is arranged inside the lower cavity 41, and the interface of the water channel is arranged on the outer wall of the lower cavity 41. The water channel flows through three sides of the lower cavity 41, and the fluid medium is introduced into the interface, so that the temperature of the cavity can be controlled at 60℃-90℃.

[0038] like Figure 5 and Figure 6 As shown, the base lifting assembly 5 includes a base 51, a lifting mechanism 52, a connecting barrel 53, a mounting seat 54, a screw module 55, a stepping motor 56, a guide rail 57, a first moving seat 58, a second moving seat 59, a connecting block 510, a bellows 511 and an adjusting bolt 512; the mounting seat 54 includes a transverse portion and a longitudinal portion, the transverse portion of the mounting seat 54 is mounted on the lower cavity 41 by means of an adjusting bolt 512, the number of the adjusting bolts 512 can be three or more, and the adjusting bolt 512 can adjust the height and level of the mounting seat 54; the screw module 55 is vertically mounted on the longitudinal portion of the mounting seat 54, the first moving seat 58 is connected to the longitudinal portion of the mounting seat 54 by means of a guide rail 57, and the screw module 55 drives the first moving seat 58 to move up and down. The stepping motor 56 is mounted on the longitudinal portion of the mounting seat 54, and the output shaft of the stepping motor 56 is connected to the screw module 55. The second movable seat 59 is fixed on the first movable seat 58 through the connecting block 510. A ball head top column 513 is arranged between the connecting block 510 and the three sides of the second movable seat 59. The ball head top column 513 can adjust the position of the second movable seat 59 relative to the first movable seat 58, thereby adjusting the center of the second movable seat 59. The connecting barrel 53 is installed on the second movable seat 59, and the base 51 is installed on the connecting barrel 53. A cooling water channel is opened inside the base 51, and the interface of the cooling water channel is led out from the inside of the connecting barrel 53. The temperature setting range of the base 51 is 25℃-45℃. A ceramic protective shell 514 is arranged on the top surface of the base 51. The lifting mechanism 52 is arranged in the base 51, and is used to lift and lower the wafer on the base 51.

[0039] like Figure 7 As shown, the lifting mechanism 52 includes a lifting spindle 521, a sealing bellows 522, a lifting fork 523, a lifting cylinder 524 and a pin 525; the lifting spindle 521 should be installed on the second moving seat 59 with a linear bearing and can move up and down, the pin 523 is installed on the upper end of the lifting spindle 521, the lower end of the sealing bellows 522 is connected to the lifting spindle 521, and the upper end of the sealing bellows 522 is connected to the base 51. The movable end of the lifting cylinder 524 is connected to the lifting spindle 521, and the lifting cylinder 524 is installed on the first moving seat 58. The pin 525 is placed in the base 51, and the pin 525 is located directly above the pin 523, so that the lifting spindle 521 is lifted when it moves.

[0040] A wafer natural oxide layer etching method:

[0041] S1 loading: the wafer enters the cavity, the lifting mechanism 52 lifts the ejector pin 525, and then places the wafer on the base 51, and the loading is completed;

[0042] S2 ionization: process gases including NH3, NF3, H2, N2, and Ar enter the chamber after being ionized by the plasma generator 6, and the ions include H+, NH4+, F-, and Ar+;

[0043] S3 reaction: The process gas falls after passing through the spray plate and reacts with the natural oxide layer SiO2 of the wafer to form an intermediate product (NH4)2SiF6; (NH4)2SiF6 is a solid product;

[0044] S4 gasification reaction: the stepper motor 56 drives the base 51 and the wafer to rise and approach the second spray plate 34. The second spray plate 34 heats the wafer by heat radiation, so that the (NH4)2SiF6 is heated and volatilized, and the recovered product is discharged from the exhaust pipe 46;

[0045] S5 unloading: the base 51 descends, the lifting mechanism 52 lifts up the wafer, and the robot unloads the wafer.

[0046] In the actual production of the above method, the first step is to form (NH4)2SiF6, and the second step is to sublimate it into a gaseous state. The wet etching of the prior art uses chemical solvents for reaction, and the disadvantage is that it is difficult to control the morphology; conventional dry etching is that ions and neutral particles (such as free radicals) in the plasma are accelerated to the surface of the target material to undergo a chemical reaction. Usually, silicon oxide reacts with the chemical substances in the plasma to form gaseous compounds, which are then extracted to achieve the etching effect. The presence of high-energy ions and electrons in this direct etching can cause damage to certain materials or existing patterns. The method of the present invention adopts two steps, firstly, (NH4)2SiF6 is formed by plasma and silicon oxide, and then (NH4)2SiF6 is heated and sublimated, and then extracted after becoming a gaseous product. The ionized gas will have a greater reaction activity with SiO2, so that the etching efficiency of silicon oxide is the highest, the etching of other materials is reduced, and the morphology is maintained. SiO2 is etched in two steps to form a (NH4)2SiF6 layer, which can also protect the wafer substrate. This method reduces damage to the chip on the wafer and can improve chip quality.

Claims

1. A wafer natural oxide layer etching device, comprising a frame (1), a special gas cabinet assembly (2), an upper chamber assembly (3), a lower chamber assembly (4), a base lifting assembly (5), a plasma generator (6) and a control assembly (7), characterized in that: The special gas cabinet assembly (2) and the control assembly (7) are both fixed on the frame (1), the lower chamber assembly (4) is fixed on the frame (1) by means of adjustable bolts, the upper chamber assembly (3) is connected to the upper part of the lower chamber assembly (4) by means of a rotating shaft, the base lifting assembly (5) is connected to the lower part of the lower chamber assembly (4), and the plasma generator (6) is installed on the upper part of the upper chamber assembly (3); The upper chamber assembly (3) comprises a connecting channel (31), an upper cover (32), a first spray plate (33), a second spray plate (34), a heating ring (35), an upper hinge (36) and a lower cover (37); the upper end of the connecting channel (31) is connected to the plasma generator (6); the lower end of the connecting channel (31) is connected to the upper cover (32); the first spray plate (33) is arranged between the upper cover (32) and the lower cover (37); the heating ring (35) is arranged between the second spray plate (34) and the upper hinge (36); Inside the plate (34), the heating ring (35) is an annular structure, the second spray plate (34) is installed below the lower cover (37), the upper hinge (36) is installed on the side of the lower cover (37), the first spray plate (33) and the second spray plate (34) are both disc-shaped, and the first spray plate (33) and the second spray plate (34) are both provided with fine holes, the thickness of the first spray plate (33) is thickened in the middle and gradually becomes thinner towards the edge, and the thickness of the second spray plate (34) is consistent; The lower chamber assembly (4) comprises a lower chamber (41), a lower hinge (42), an adjustment support (43), a gas pipeline (44), an exhaust manifold (45), and an exhaust pipeline (46). The adjustment support (43) is mounted on the frame (1). The lower end of the lower chamber (41) is mounted on the frame (1) through the adjustment support (43). The lower hinge (42) is mounted on the lower chamber (41). The lower hinge (42) is connected to the upper hinge (36) through a pin shaft. The gas pipeline (44) is arranged inside the lower chamber (41). The exhaust manifold (45) is mounted below the lower chamber (41). Two mounting parts are arranged at the lower end of the exhaust manifold (45), one of which is connected to the exhaust pipeline (46), and the other is connected to the base lifting assembly (5).

2. The wafer natural oxide layer etching device according to claim 1, characterized in that: The base lifting assembly (5) comprises a base (51), a lifting mechanism (52), a connecting barrel (53), a mounting seat (54), a screw module (55), a stepping motor (56), a guide rail (57), a first movable seat (58), a second movable seat (59), a connecting block (510), a bellows (511) and an adjusting bolt (512); the mounting seat (54) comprises a transverse portion and a longitudinal portion, the transverse portion of the mounting seat (54) is mounted on the lower cavity (41) by means of the adjusting bolt (512), the screw module (55) is vertically mounted on the longitudinal portion of the mounting seat (54), the first movable seat (58) is mounted by means of the guide rail (57) Mounted on the longitudinal part of the mounting seat (54), the stepper motor (56) is mounted on the longitudinal part of the mounting seat (54), the output shaft of the stepper motor (56) is connected to the lead screw module (55), the second movable seat (59) is fixed on the first movable seat (58) through a connecting block (510), a ball head top column is arranged between the three side surfaces of the connecting block (510) and the second movable seat (59), the connecting barrel (53) is mounted on the second movable seat (59), the base (51) is mounted on the connecting barrel (53), and the lifting mechanism (52) is arranged in the base (51) for lifting and lowering the wafer on the base (51).

3. The wafer natural oxide layer etching device according to claim 2, characterized in that: The lifting mechanism (52) comprises a lifting spindle (521), a sealing bellows (522), a lifting fork (523), a lifting cylinder (524) and a lifting pin (525); the lifting spindle (521) is mounted on a second movable seat (59) via a linear bearing, the lifting fork (523) is mounted on the upper end of the lifting spindle (521), the lower end of the sealing bellows (522) is connected to the lifting spindle (521), the upper end of the sealing bellows (522) is connected to the base (51), the movable end of the lifting cylinder (524) is connected to the lifting spindle (521), the lifting cylinder (524) is mounted on a first movable seat (58), the lifting pin (525) is placed in the base (51), and the lifting pin (525) is located directly above the lifting fork (523).

4. The wafer natural oxide layer etching device according to claim 2, characterized in that: A cooling water channel is provided inside the base (51), and an interface of the cooling water channel is led out from the inside of the connecting barrel (53). The temperature setting range of the base (51) is 24° C.-45° C., and a ceramic protective shell is provided on the top surface of the base (51).

5. The wafer natural oxide layer etching device according to claim 1, characterized in that: The exhaust pipeline (46) is provided with a butterfly valve (47), a gate valve (48), a vacuum gauge (49) and a bypass valve (410) for exhausting and controlling the pressure of the process gas in the chamber.

6. The wafer natural oxide layer etching device according to claim 1, characterized in that: The special gas cabinet assembly (2) is used to provide process gas, which includes one or more of argon Ar, nitrogen N2, ammonia NH3, nitrogen trifluoride NF3, and hydrogen H2. The process gas is connected to the plasma generator (6) through a pipeline.

7. A method for etching a natural oxide layer of a wafer, applied to the etching equipment according to any one of claims 1 to 6, characterized in that: S1 loading: the wafer enters the cavity, the lifting mechanism (52) lifts the ejector pin (525), and then the wafer is placed on the base (51), and the loading is completed; S2 ionization: process gases include NH3, NF3, H2, N2, Ar, which enter the chamber after being ionized by the plasma generator (6), and the ions include H+, NH4+, F-, Ar+; S3 reaction: The process gas falls after passing through the spray plate and reacts with the natural oxide layer SiO2 of the wafer to form an intermediate product (NH4)2SiF6; (NH4)2SiF6 is a solid product; S4 gasification reaction: the stepper motor (56) drives the base (51) and the wafer to rise and approach the second spray plate (34). The second spray plate (34) heats the wafer through thermal radiation, so that (NH4)2SiF6 is heated and volatilized, and the recovered product is discharged through the exhaust pipe (46); S5 unloading: the base (51) descends, the lifting mechanism (52) lifts up the wafer, and the robot unloads the wafer.

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