JP6161365B2 - Workpiece etching method - Google Patents

Description

  The present invention relates to a method for etching a workpiece having an etched region and a non-etched region.

  A wafer such as a silicon wafer or a sapphire wafer formed on the surface by dividing a plurality of devices such as IC, LSI, LED, etc. by dividing lines is divided into individual devices by a processing apparatus, and the divided devices are mobile phones, Widely used in various electrical equipment such as personal computers.

  A dicing method using a cutting device called a dicer is widely used for dividing the wafer. In the dicing method, a wafer is cut by cutting a wafer into a wafer while rotating a cutting blade having a thickness of about 30 μm by solidifying abrasive grains such as diamond with a metal or a resin at a high speed of about 30000 rpm. Divide into

  In the dicing method using a cutting blade, if the device size is small and the number of division lines to be cut is large, it takes a considerable amount of time to cut all the division lines and the productivity is significantly reduced. There is.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 2006-114825 discloses that a resist film is coated on the surface of a wafer other than the planned division line, and plasma etching is performed from the surface to the rear surface of the region corresponding to the planned division line. A wafer dividing method for dividing a wafer into individual devices is disclosed.

  A photoresist made of a photosensitive resin is widely used as a resist film as a protective film. Usually, after a photoresist is spin-coated on the front surface of a wafer, light baking called pre-baking is performed, followed by baking after exposure ( A resist film is formed only in the non-etched region through post-baking) and development processing steps.

JP 2006-114825 A

  However, in the wafer dividing method disclosed in Patent Document 1 using a resist film, a coating device for applying a resist, a transfer device for transferring a mask pattern, an exposure mask, a developing device for performing development processing, and the like Since various facilities are required, there is a problem that the process is complicated.

  The present invention has been made in view of these points, and an object of the present invention is to provide an etching method for a workpiece that enables simpler etching.

According to the present invention, a mask for preparing a mask capable of covering a workpiece having an opening corresponding to the non-etched region of the workpiece, the etching method of the workpiece having an etched region and a non-etched region. The mask is placed on the work piece in a state where the opening of the mask and the non-etched area of the work piece coincide with each other, and the etched area of the work piece is covered with the mask. And a mask placing step for exposing the non-etched region, a protective film agent is applied to the workpiece on which the mask is placed via the mask, and a protective film is formed on the non-etched region of the workpiece. After performing the protective film forming step to be formed, the mask removing step for removing the mask from the workpiece on which the protective film is formed on the non-etched region, and the mask removing step Comprising an etching step of etching the etched region of the workpiece by etching the workpiece, and the mask is characterized by consisting of a material having the same thermal expansion coefficient and the workpiece A method for etching a workpiece is provided.

  Preferably, in the protective film forming step, the protective film agent is spray-coated on the workpiece on which the mask is placed via the mask.

  In the method for etching a workpiece according to the present invention, a protective film is formed in the non-etched region of the workpiece using a mask that covers the workpiece having an opening corresponding to the non-etched region. Therefore, simpler etching is possible as compared with the conventional method. In addition, since an equipment with an exposure device and a developing device is not required, the workpiece can be etched at a lower cost.

Furthermore , by selecting a material having the same thermal expansion coefficient as the workpiece as the mask, it is difficult for the mask opening and the non-etched region to shift when the mask is placed, and a protective film can be formed with high accuracy. .

According to the second aspect of the present invention, the amount of the protective film agent used can be reduced by spray coating the protective film agent in the protective film forming step.

It is a surface side perspective view of a semiconductor wafer. It is a perspective view of a mask. It is a perspective view which shows a mask mounting step. It is a perspective view which shows a protective film formation step. It is a perspective view which shows a mask removal step. It is a longitudinal cross-sectional view of a plasma etching apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a front side perspective view of a semiconductor wafer 11 as a workpiece is shown. A semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11 is made of, for example, a silicon wafer having a thickness of 100 μm, and a plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11a. At the same time, devices 15 such as ICs and LSIs are formed in each region partitioned by the plurality of division lines 13. Reference numeral 11 b denotes the back surface of the wafer 11.

  In the workpiece etching method of the present invention, first, as shown in FIG. 2, a mask 12 having a plurality of openings 14 corresponding to the non-etching region (device 15) of the wafer 11 and capable of covering the wafer 11 is formed. A mask preparation step is prepared.

When the wafer 11 is formed from a silicon wafer, the mask 12 is preferably formed from a silicon wafer. The thermal expansion coefficient (linear expansion coefficient) of silicon is 2.6 μm. m ⁻¹ . K is ^-1, by forming a mask 12 from the silicon wafer 11 and the same material, the deviation occurs and the non-etched region of the opening 14 and the wafer 11 of the mask when placing the mask on the wafer 11 It becomes difficult.

  After preparing the mask 12, as shown in FIG. 3, the mask 12 is placed on the wafer 11 in a state where the opening 14 of the mask 12 and the non-etched region (device 15) of the wafer 11 coincide with each other. Then, a mask placement step of covering the 11 etching regions (division planned lines 13) with the mask 12 and exposing the non-etching regions (device 15) is performed.

  After performing the mask placement step, as shown in FIG. 4, a photoresist 18 as a protective film agent is applied to the wafer 11 on which the mask 12 is placed from the resist supply nozzle 16 via the mask 12. A protective film forming step for forming a protective film (resist film) 20 on the non-etched region (device 15) of the wafer 11 is performed.

  Preferably, the photoresist 18 is spray-coated by relatively moving the resist supply nozzle 16 and the wafer 11 on which the mask 12 is placed. The relative movement includes rotation of the wafer 11.

  After the photoresist 18 is spray-coated, the photoresist 18 is baked by heating to a predetermined temperature. Here, as the protective film agent, in addition to the photoresist 18, various resins having etching resistance to the etchant can be appropriately selected.

  In general, a photoresist, which is a photosensitive resin, is expensive, but by selecting a cheaper resin, etching can be performed at a lower cost than in the past. The baking temperature is appropriately set according to the organic solvent used for the resist composition (for example, 80 ° C. to 200 ° C.).

  After performing the protective film forming step, as shown in FIG. 5, a mask removing step for removing the mask 12 from the wafer 11 where the protective film 20 is formed on the non-etched region is performed.

  After performing the mask removal step, an etching step is performed in which the wafer 11 is etched to etch the wafer etching region (division planned line 13). Preferably, this etching step is performed by a plasma etching apparatus 22 as shown in FIG.

  The plasma etching apparatus 22 includes a housing 24 that forms a sealed space 25. The housing 24 includes a bottom wall 24a, an upper wall 24b, left and right side walls 24c and 24d, a rear side wall 24e, and a front side wall (not shown). The right side wall 24d is used for carrying a workpiece. An opening 27 is provided.

  A gate 26 for opening and closing the opening 27 is disposed outside the opening 27 so as to be movable in the vertical direction. The gate 26 is actuated by gate actuating means 28. The gate actuating means 28 includes an air cylinder 30 and a piston rod 30 a connected to a piston disposed in the air cylinder 30, and the air cylinder 30 is attached to the bottom wall 24 a of the housing 24 via a bracket 32. The tip of the piston rod 30 a is connected to the gate 26.

  When the gate 26 is opened by the gate operating means 28, the wafer 11 as a workpiece is carried into and out of the sealed space 25 through the opening 27. An exhaust port 29 is formed in the bottom wall 24 a of the housing 24, and the exhaust port 29 is connected to the gas discharge means 34.

  In the sealed space 25 formed by the housing 24, a lower electrode 36 and an upper electrode 38 are disposed to face each other. The lower electrode 36 is made of a conductive material, and includes a disk-shaped workpiece holding portion 40 and a columnar support portion 42 that protrudes from the center of the lower surface of the workpiece holding portion 40. ing.

  The lower electrode 36 composed of the workpiece holding part 40 and the columnar support part 42 is disposed by inserting the support part 42 through the hole 31 formed in the bottom wall 24 a of the housing 24, and the insulator 44. And is supported in a state of being sealed to the bottom wall 24a. The lower electrode 36 supported by the bottom wall 24 a of the housing 24 is electrically connected to the high frequency power supply 46 through the support portion 42.

  A circular fitting recess 40a having an open top is provided at the upper part of the work piece holding portion 40 constituting the lower electrode 36, and a disk-shaped disc formed by porous ceramics or the like in the fitting recess 40a. The suction holding part 48 is fitted.

  A chamber 40 b formed below the suction holding portion 48 in the circular recess 40 a is communicated with the suction means 50 through a communication path 33 formed in the workpiece holding portion 40 and the support portion 42. Accordingly, when the wafer 11 is placed on the suction holding portion 48 and the suction means 50 is operated, a negative pressure is applied to the chamber 40b via the communication path 33, and the wafer 11 placed on the suction holding portion 48 is moved. Suction hold. When the communication path 33 is opened to the atmosphere, the suction holding of the wafer 11 sucked and held on the suction holding portion 48 is released.

  A cooling passage 35 is formed in the lower part of the workpiece holding part 40 constituting the lower electrode 36. One end of the cooling passage 35 communicates with a refrigerant introduction passage 37 formed in the support portion 42, and the other end of the cooling passage 37 communicates with a refrigerant discharge passage 39 formed in the support portion 42.

  The refrigerant introduction passage 37 and the refrigerant discharge passage 39 are communicated with the refrigerant supply means 52. Therefore, when the refrigerant supply means 52 is operated, the refrigerant is circulated through the refrigerant introduction passage 37, the cooling passage 35 and the refrigerant discharge passage 39. As a result, since the lower electrode 36 is cooled by the circulating refrigerant, abnormal temperature rise of the lower electrode 36 due to heat generated during plasma processing, which will be described later, is prevented.

  The upper electrode 38 is formed of a conductive material, and includes a disk-shaped gas ejection portion 54 and a columnar support portion 56 formed to protrude from the center of the upper surface of the gas ejection portion 54.

  The upper electrode 38 composed of the gas ejection part 54 and the columnar support part 56 is disposed so that the gas ejection part 54 faces the workpiece holding part 40 constituting the lower electrode 36, and the support part 56 is a housing. The hole 41 formed in the upper wall 24b of the 24 is inserted through the hole 41 and supported by the seal member 58 mounted in the hole 41 so as to be movable in the vertical direction.

  An operation member 60 is attached to the upper end portion of the support portion 56, and the operation member 60 is connected to the elevation drive means 62. The upper electrode 38 is grounded through the support portion 56.

The disc-shaped gas ejection portion 54 constituting the upper electrode 38 is provided with a plurality of ejection ports 43 opened on the lower surface. The plurality of jet nozzles 43 are connected to the SF ₆ gas supply means 64 and the C ₄ F ₈ gas supply means 66 through the communication path 45 formed in the gas ejection section 54 and the communication path 47 formed in the support section 56. It is communicated.

The gate actuating means 28, the gas discharging means 34, the high frequency power supply 46, the suction means 50, the refrigerant supply means 52, the lift drive means 62, the SF ₆ gas supply means 64 and the C ₄ F ₈ gas supply means 68 are connected to the control means 68. And is controlled by the control means 68.

The control means 68 includes data relating to the pressure in the sealed space 25 formed by the housing 24 from the gas discharge means 34, and data relating to the refrigerant temperature (ie, electrode temperature) from the refrigerant supply means 52, the SF ₆ gas supply means 64 and Data relating to the gas flow rate is input from the C ₄ F ₈ gas supply means 66, and the control means 68 outputs a control signal based on these data.

  Hereinafter, the etching step by the plasma etching apparatus 22 configured as described above will be described. First, the gate actuating means 28 is actuated to move the gate 26 downward, and the opening 27 provided in the right side wall 24d of the housing 24 is opened.

  The wafer 11 in which the protective film 20 is formed on each device 15 by unillustrated loading / unloading means is conveyed into the sealed space 25 through the opening 27, and the suction holding portion of the workpiece holding portion 40 constituting the lower electrode 36. The wafer 11 is placed on 48.

  At this time, the raising / lowering drive means 62 is operated to raise the upper electrode 38. Then, by operating the suction means 50 to apply a negative pressure to the chamber 40 b of the lower electrode 36, the wafer 11 placed on the suction holding portion 48 is sucked and held by the lower electrode 36.

  If the wafer 11 is sucked and held on the suction holding portion 48 of the lower electrode 36, the gate means 28 is operated to move the gate 26 upward, and the opening 27 provided in the right side wall 24d of the housing 24 is closed. To do.

  Then, the upper and lower drive means 62 is operated to lower the upper electrode 38, and the lower surface of the gas ejection portion 54 constituting the upper electrode 38 and the upper surface of the wafer 11 held by the workpiece holding portion 40 constituting the lower electrode 36. Is positioned at a predetermined inter-electrode distance (for example, 10 mm) suitable for the plasma etching process.

  Next, the gas discharge means 34 is operated to evacuate the sealed space 25. If the sealed space 25 is evacuated, an etching step for etching the etching region (division planned line 13) of the wafer 11 is performed.

  In this etching step, the wafer 11 may be fully cut along the planned division line 13 or an etching groove along the planned division line 13 may be formed. When the etching groove is formed, the wafer 11 is divided into device chips 15 by cleaving or back grinding, for example.

In the etching step, the SF ₆ gas supply means 64 and the C ₄ F ₈ gas supply means 66 are alternately operated to supply SF ₆ gas and C ₄ F ₈ gas for generating plasma to the upper electrode 38. SF _{6 C} 4 _{F 8} gas formed from SF ₆ gas and _C 4 _{F 8} gas supply means 66 which is supplied from the gas supply means 64, formed in the communication passage 47 and the gas ejection portion 54 formed in the support portion 56 The plurality of jet nozzles 43 are alternately jetted toward the wafer 11 sucked and held by the suction holding portion 48 of the lower electrode 36 through the communication passage 45 thus formed.

At this time, the inside of the sealed space 25 is maintained at a predetermined gas pressure (for example, 20 Pa). In this manner, in the state where SF ₆ gas and C ₄ F ₈ gas for plasma generation are alternately supplied, a high frequency power of 50 W, for example, is applied from the high frequency power source 46 to the lower electrode 36, and a high frequency of 3000 W, for example, is applied to the upper electrode 38. Apply power.

As a result, a plasma having anisotropy composed of SF ₆ gas and C ₄ F ₈ gas is generated in the space between the lower electrode 36 and the upper electrode 38, and this plasma-converted active material is a line to be divided into the wafer 11. Therefore, depending on the degree of etching, an etching groove along the planned dividing line 13 is formed in the wafer 11 or the wafer 11 is completely cut along the planned dividing line 13 to obtain individual device chips. It is divided into 15.

  This etching process is performed, for example, under the following conditions.

Pressure in the sealed space 25: 20Pa
High frequency power: Lower electrode: 50W
Upper electrode: 3000 W
SF ₆ gas supply rate: 1.0 liter / min C ₄ F ₈ gas supply rate: 0.7 liter / min SF ₆ gas supply interval: 1 second supply at 2 second intervals C ₄ F ₈ gas supply interval: 1 second interval Supply for 2 seconds

  After the etching is completed, the wafer 11 is taken out from the sealed container 25, and the protective film 20 is removed by ashing or washing. The protective film deposited on the mask 12 is similarly removed. Ashing uses photo-excited ashing or plasma ashing, which is performed by irradiating ultraviolet rays or the like in a processing chamber filled with a gas such as ozone and using a chemical reaction between the protective film 20 and the gas.

11 Semiconductor wafer 12 Mask 13 Scheduled division line (etching area)
14 opening 15 device (non-etched region)
16 Resist supply nozzle 18 Photoresist 20 Protective film (resist film)
22 Plasma etching apparatus 24 Housing 25 Sealed space 36 Lower electrode 38 Upper electrode 46 High frequency power supply 64 SF ₆ gas supply means 66 C ₄ F ₈ gas supply means

Claims (3)

A method of etching a workpiece having an etched region and a non-etched region,
A mask preparation step of preparing a mask capable of covering a workpiece having an opening corresponding to a non-etched region of the workpiece;
The mask is placed on the workpiece in a state in which the opening of the mask and the non-etched region of the workpiece are aligned, and the etched region of the workpiece is covered with the mask and the non-etched region A mask placement step to expose;
A protective film forming step of applying a protective film agent on the workpiece on which the mask is placed through the mask and forming a protective film on the non-etched region of the workpiece;
A mask removing step of removing the mask from a workpiece on which the protective film is formed on the non-etched region;
An etching step of performing etching on the workpiece and etching the etching region of the workpiece after performing the mask removing step,
The method for etching a workpiece , wherein the mask is made of a material having the same thermal expansion coefficient as the workpiece.   The method for etching a workpiece according to claim 1, wherein in the protective film forming step, the protective film agent is spray-coated on the workpiece on which the mask is placed via the mask.   The method for etching a workpiece according to claim 1, wherein the etching includes plasma etching.

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