JP3404979B2 - Etching equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching apparatus capable of accommodating semiconductor wafers individually and performing an etching process.

[0002]

2. Description of the Related Art S is excellent in strength and easy to form IC circuits.
A small pressure sensor is manufactured by thinning a part of the i substrate by etching to form a diaphragm, and an example thereof is shown in FIG. The figure shows the diaphragm forming surface (etching surface) 1b of the Si semiconductor wafer 1. Each rectangular chip C cut out by dicing has its inner peripheral portion etched to form a thin diaphragm C1.

By the way, in such an etching process, conventionally, as shown in FIG. 7, a mask M having a predetermined pattern opening M1 is deposited on the etching surface 1b, and a non-etching surface (circuit surface) opposite to the mask M is formed. Wax 91 is applied to 1a, and a bake plate 92 is attached on a heating plate 93, and masking is performed by separating from the treatment liquid.

That is, as shown in FIG. 8, the wafer 1 having the bake plate 92 attached thereto is filled with the processing liquid L in the processing tank 9 as shown in FIG.
4 is set in the jig 95. When immersed in the processing liquid L, the etching surface 1b of the wafer 1 is etched through the pattern opening M1 of the mask M (FIG. 7), and the bake plate 92 is formed.
The process liquid L is prevented from entering the circuit surface 1a attached with. After the processing is completed, the wafer 1 is removed from the bake plate 92 and washed with an organic solvent or the like.

When the etching of the wafer 1 is described in detail with reference to FIG. 9, the pattern opening M1 ((1) in the drawing) of the mask M is sized to form a diaphragm having a predetermined shape, and the processing liquid L is passed through the opening M1. Etched surface 1b in contact with
Is etched into a deep concave trapezoidal cross section as shown in FIG. 2B, and a diaphragm 11 having a predetermined thickness d is formed at this portion. Since the pressure sensor measures the deformation of the diaphragm 11 due to the pressure difference applied to both sides by the strain gauge formed on the circuit surface 1a, it is necessary to precisely control the thickness of the diaphragm 11.

Conventionally, this control is performed by measuring the thickness of the wafer 1 one by one with a micro gauge 96 as shown in FIG.
As a lot, etching processing is performed in lot units.

An apparatus in which a large number of wafers are held in a cylindrical space, a processing solution is supplied thereto, and the whole is rotated to improve etching efficiency (Japanese Patent Laid-Open No. 52-15).
6565), an apparatus for performing an etching process by sealing a container portion filled with a processing liquid with a lid portion holding a wafer (Japanese Patent Laid-Open No. 1-140631), and rotating the etched wafer in a horizontal plane, On the other hand, there is known an apparatus for injecting water from above to clean it (Japanese Utility Model Publication No. 59-117141), an apparatus for spraying a processing liquid and cleaning water onto a wafer by a nozzle (Japanese Patent Application Laid-Open No. 5-243202), and the like. Has been.

[0008]

By the way, the required etching amount is controlled on the basis of the relationship between the bath temperature and the etching rate shown in FIG. A change in concentration and contamination occur during common use with a lot, and the etching rate often changes.

Therefore, it is necessary to take out the sample wafer periodically during the etching process and measure the thickness of the diaphragm 11 with a micro gauge as shown in FIG. 12, which has been a bottleneck in automating the etching process. .

Further, even if the thickness of the sample wafer is accurately controlled, there is a problem that the variation in the thickness of each wafer in the lot remains as it is.

Further, in the lot processing, since the etching amount cannot be controlled for each wafer, the production efficiency is low for other types of small quantity products.

The present invention solves such a problem, and provides an etching apparatus capable of appropriately performing etching control for each semiconductor wafer, eliminating complicated manual work, and realizing process automation. With the goal.

[0013]

In the first structure of the present invention, the base bodies 2 and 7 having the receiving surface 2a for closely contacting the non-etching surface 1a of the wafer 1 and the outer periphery of the etching surface 1b of the wafer 1 are formed. A frame body 3 that forms a liquid storage space S having the lower opening 31 in close contact with the entire circumference and having the wafer 1 as a bottom wall,
A lid 4 in which the upper opening 32 of the frame 3 is liquid-tightly closed, and an opening 41 for supplying the processing liquid L to the liquid storage space S and an opening 42 for discharging the processing liquid L from the liquid storage space S are formed; It is provided with a holding means 5 which holds the frame body 3 from above and below in a reversible manner with the base bodies 2 and 7 and the lid body 4 mounted.

In the second structure of the present invention, the base bodies 2 and 7 and the lid body 4 are integrally provided on the holding means 5.

In the third structure of the present invention, the holding means 5 is provided.
Has a pair of clampers 51, 52 for holding the frame body 3 therebetween, and these clampers 51, 52 are connected to the rotary shaft 52.
It is made to support on the support body 53 by 3.

In the fourth structure of the present invention, the receiving surface 2a is formed.
Heater member 71 for heating a wafer, the temperature distribution of which can be changed
Are further provided in the base bodies 2 and 7.

In the fifth structure of the present invention, a processing liquid supply means 652A for supplying the processing liquid by air blowing of compressed air is further provided to the opening 41 for supplying the processing liquid L.

In the sixth structure of the present invention, a cleaning liquid supply means 652B for supplying the cleaning liquid by air blowing of compressed air is further provided in the opening 41 for supplying the processing liquid.

[0019]

In the first structure, when the processing liquid L is supplied to the closed storage space S through the opening 41, only the etching surface 1b of the wafer 1 is exposed to the processing liquid L and the etching proceeds. After the etching is completed, when the sealed storage space S is inverted by the holding means 5, the treated processing liquid L is discharged from the opening 42. With this configuration, the wafers 1 can be processed one by one with the new processing liquid L.
It is possible to easily control the etching for each case, and it is possible to easily automate the masking of the non-etching surface 1a and the supply and discharge of the processing liquid.

In the second structure, at the same time when the holding means 5 holds the frame body 3, the base body 2, 7 and the lid body 4 form the liquid storage space S sealed in the frame body 3.

In the third structure, the holding means 5 is simply constructed.

In the fourth structure, the base body 2,
Wafer 1 by heater members 71A to 71D provided in
Is efficiently heated to the processing temperature. Further, even if the original thickness of the wafer is partially changed, the heater member 71 is correspondingly changed.
The etching rate can be adjusted in each part of the wafer by changing the temperature distribution of A to 71D.

In the fifth structure, the processing liquid L is rapidly supplied into the storage space S by the air blow of the processing liquid supply means 652A.

In the sixth structure, the opening 41 for supplying the processing liquid L is also used for supplying the cleaning liquid, which simplifies the structure.

[0025]

EXAMPLE FIG. 1 shows the appearance of an etching apparatus. In the figure, the etching apparatus comprises an operation panel unit 62, a handling unit 63, a clamp / reversing unit 5, a processing liquid measuring unit 64, and a processing liquid heating / supplying / discharging unit 65 which are integrally provided on a pedestal 61. Is operated by operating switches on the operation panel unit 62. Hereinafter, the entire configuration will be described centering on the clamp / reversing unit 5.

As shown in FIG. 2, the clamp / reversing unit 5 has upper and lower clampers 51 and 52, and the clamper 52 is composed of a horizontally extending box-shaped main body portion 521 and a base portion 522 extending upward at a right angle from one end thereof. Become. The center portion of the base portion 522 projects in a cylindrical shape to form a rotary shaft portion 523. A pedestal 61 (FIG. 1) is provided on the outer circumference of the rotary shaft portion 523.
The bearing 5 is provided between the support block 53 and the support block 53 fixed on the top.
4 is interposed and rotatably supported. The clamper 51 is a box-shaped main body 5 that extends to face the clamper 52.
11 and a base portion 512 extending downward at right angles from one end thereof, a slide piece 513 is provided on the base portion 512 and is slidably coupled to a slider 524 provided on the vertical wall of the clamper base portion 522. There is. Thus, the drive mechanism (not shown) causes the clamper 51 to move up and down and the clampers 51 and 52 to rotate in reverse.

Caps 4 and 7 are fixed to the opposing surfaces of the clampers 51 and 52, respectively. The cap 4 functions as a lid, and a space that expands downward is formed in the inner peripheral portion of the cylindrical body, and a liquid supply nozzle 41 and a liquid discharge port 42 are formed in the bottom wall, and the flexible tube 411 is formed in these. 421
Are connected. Further, a heater 43 is attached to the entire outer circumference of the cap 4. The cap 7 is formed with a space 72 that expands upward at the inner peripheral portion of the cylindrical body.
A heater 71 is housed inside, and a cylindrical wafer base 2 is airtightly fitted directly above the heater 71.

As shown in FIG. 3, the heater 71 is actually divided into four parts 71A to 71D, which correspond to substantially quadrants of the wafer base, and each of the heaters 71A to 71A through the feeder line 711 (FIG. 2). By controlling the amount of electricity supplied to 71D, the temperature of these heaters 71A to 71D is set to, for example, 1
It can be independently changed between 20 ± 0.4 and ± 2 ° C. The heater 71 is divided into the semiconductor wafer 1 as described later.
The reason why the temperature distribution of the wafer base 2 on which is mounted can be changed is as follows. That is, as shown in FIG. 6, about a thousand diaphragms C1 are included in one wafer 1.
However, in order to make the pressure characteristics the same, it is necessary to make the thickness of each diaphragm uniform. Here, the etching rate E when potassium hydroxide (KOH) is used is represented by the following equation, and the etching temperature T substantially determines the etching rate E. On the other hand, since the original thickness of the wafer 1 usually has a variation of about several microns in the above-mentioned approximately quadrant, if the etching rate E is made constant in each part, the diaphragm thickness will be different. Therefore, by increasing the temperature of each of the heaters 71A to 71D as the original thickness of the wafer increases and increasing the etching rate in this portion, a constant diaphragm thickness can be obtained without being affected by the original thickness of the wafer. . If the original thickness of the wafer is constant and the temperatures of the heaters 71A to 71D are changed,
The diaphragm thickness can be positively changed in each part of the wafer 1. E = α ・ nk ・ noh ・ D ・ exp (-Q / RT) where E: etching rate α: constant nk: K hydrate ion concentration noh: OH ion concentration D: K hydrate ion diffusion coefficient Q: activity Energy R: gas constant
T: Etching temperature. Needless to say, the number of heaters installed is not limited to four.

A cylindrical frame-shaped carrier 3 is sandwiched between the upper and lower caps 4 and 7. The carrier 3 has slopes around the outer walls of the upper and lower openings 31 and 32, and the sealing members 33 and 34 disposed there are pressed against the inner peripheral surfaces of the caps 4 and 7 to ensure liquid tightness. ing. The wafer 1 is located on the wafer base 2 and its non-etched surface 1
"a" is in close contact with the upper surface 2a of the wafer base 2 which is a receiving surface, and shows a temperature distribution corresponding to the temperature distribution of the wafer base 2 (that is, the temperatures of the heaters 71A to 71D) with good responsiveness. The etching surface 1b of the wafer 1 faces the liquid storage space S formed by the carrier 3 and the cap 4, and the lower opening 3 of the carrier 3 is formed at the outer peripheral edge of the etching surface 1b.
The wafer packing 35 provided on the one-stepped portion is in liquid-tight contact. The wafer base 2 with the lower end of the carrier 3 facing
The surrounding space P is exhausted by an exhaust pipe (not shown) connected to the cap 7, and the non-etching surface 1a of the wafer 1 is surely brought into close contact with the wafer base 2 by the negative pressure of the space P, The wafer packing 35 and the seal member 33,
Good masking is done in combination with the presence of 34.

The wafer 1 is set on the clamp / reverse unit 5 as described above as follows. That is, the upper and lower positions of the clampers 51 and 52 are reversed from the state of FIG. 2 (state of FIG. 1), and the clamper 51 is lowered to the open state. In this state, the carrier 3 held by the handling unit 63 (FIG. 1) (upside down from that shown in FIG. 2) on the wafer packing 35 is aligned by the orientation flat 11 (FIG. 6). Place wafer 1
The handling unit 63 is advanced to put the carrier 3 on the cap 4. Then, the clamp 51 is raised to sandwich the carrier 3 with the cap 7, and the wafer 1 is pressed against the wafer base 2. Then, the upper and lower positions of the clamps 51 and 52 are inverted again to the state shown in FIG. The handling unit 63 also has a function of supplying and unloading the wafer 1 to and from the carrier 3.

FIG. 4 shows a piping system of the treatment liquid metering unit 64 and the treatment liquid heating / supply / discharge liquid unit 65. In the figure, heating tanks 651A and 651B provided with heaters 652A and 652B on the outer circumference are provided, and a processing liquid (KOH) is stored in one side and a cleaning liquid (pure water) is stored in the other side. The processing liquid and the cleaning liquid are supplied from the storage tanks 642A and 642B in a predetermined amount necessary for processing one wafer by the measuring pumps 641A and 641B having a measuring function, and the temperatures suitable for the etching processing in the heating tanks 651A and 651B. It is heated to (for example, 120 ° C.). Each heating tank 651A, 651B has a pressure valve 653A,
653B and flow rate adjusting valves 654A and 654B are connected to an air source 655, and a pipe 657 provided with a blow valve 656 leads from the air source 655 to the liquid supply nozzle 41 (FIG. 2) of the cap 4. This pipe 657
In the clamp / reversing unit 5, the flexible tube 411 is formed as described above. The heating tanks 651A and 651B are provided with liquid supply valves 658A and 658B.
Is connected to the pipe 657 via the flow rate adjusting valves 654A and 654B and the pressurizing valves 653A and 653.
Pressure gauges 659A and 659B are provided between 53B.

Prior to the start of etching, the heaters 43 and 71 of the caps 4 and 7 are energized to heat the caps 4 and 7, the carrier 3 and the wafer base 2 to a temperature suitable for the etching process. . In particular, the temperature of the wafer 1 can be realized in the temperature range described above by the heater 71 so as to realize an arbitrary temperature distribution according to the change in the original thickness of the wafer.
Since the wafer 1 is in close contact with the receiving surface 2a of the wafer base 2 due to the negative pressure of the space P, the heat transfer from the heater 71 is performed well. Pressurization valve 653 at the start of etching
A is opened to increase the pressure inside the heating tank 651A. When the liquid supply valve 658A is opened in this state, the processing liquid L is supplied to the pipe 657.
The liquid is pressure-fed and supplied from the liquid supply nozzle 41 into the liquid storage space S (see FIG. 2). As a result, the etching surface 1b of the wafer 1 comes into contact with the processing liquid L and the etching processing is started. The change in the air blow pressure at this time measured by the pressure gauge 659A is shown in FIG.

In FIG. 5, the blow pressure is maintained at a high constant pressure while the processing liquid is being pumped. When air begins to mix with the processing liquid near the end of the pressure feeding, the blow pressure gradually decreases, and when only air is supplied, it becomes constant again at a low pressure. This is due to the difference in viscosity between gas and liquid. Then, when the blow pressure decreases by ΔP, it is considered that the liquid supply has ended, and the air blow is stopped, and this is set as the etching start time. By detecting the end of the liquid supply in this way, it is possible to prevent the temperature drop and the concentration change of the processing liquid due to excessive blowing, and it is possible to control the etching start timing with high accuracy. Further, by supplying by air blow, it is possible to supply a small amount of high-temperature, high-concentration highly corrosive processing liquid with high accuracy and at high speed without causing chemical liquid contamination. By the way, blow pressure 0.2MPa, pipe diameter φ4mm, KOH ・ 120 ℃ ・
It takes 4.14 hours to supply 40 wt% 100cc
Dispersion of liquid supply speed 26 cc / second and liquid supply time ±
It was 0.12 seconds. The etching process is performed based on the etching time calculated from the wafer thickness and the etching rate measured in advance, and the wafer 71 being processed is kept at a constant temperature by the heater 71.

After the etching is completed, the carrier 3 is inverted from the state shown in FIG. 2 so that the etching surface 1b of the wafer 1 faces downward, and the pressurizing valve 653B and the liquid supply valve 658B.
Open and open the heating tank 651B with pure water.
Send to 1. As a result, the etching surface 1b is cleaned and the etching liquid L is discharged from the liquid discharge port 42. After washing with water, the blow valve 656 is opened to blow dry air for a certain period of time to dry the etching surface 1b. After that, the clamper 51 is lowered to be in the open state, and the carrier 3 is taken out by the handling unit 63.

As described above, according to the etching apparatus of the present embodiment, the etching process for each wafer can be automatically performed, and the etching process is performed for each wafer. The etching amount can be controlled according to the degree. Therefore, the diaphragm thickness t of each wafer can be made uniform as compared with the conventional etching in the lot processing. Further, since etchings having different etching amounts can be processed by the same apparatus, it is possible to efficiently perform a large amount of small quantity etching.

Further, etching is performed in a processing tank having a size equal to the size of one wafer, and the non-etched surface of the wafer is directly heated by a heater with a variable temperature distribution adjusted according to the variation in the original thickness of the wafer. The etching conditions can be controlled uniformly and stably, and the fluctuation of the etching amount of the wafer can be made highly accurate from 2% in the past to 1% or less.

Furthermore, since the liquid storage space is sealed, there is no change in concentration due to evaporation of the etching liquid. Further, since etching is always performed using a new solution, there is no deterioration of the solution or mixing of foreign matters and harmful substances that occurs when processing a large number of wafers with the same etching solution as in the conventional apparatus. Therefore, the relationship between the etching rate and the treatment liquid temperature / concentration shown in FIG. 11 is stable.

Further, by automatically supplying and discharging the treatment liquid and pure water by air blow, the supply and discharge can be performed quickly and with good reproducibility. That is, since the accuracy of the liquid supply time and the amount of liquid supply is improved, the variation in the etching start time due to the variation in the etching liquid supply time and the variation in the etching end time due to the variation in the pure water supply time are reduced, and the etching The relationship between the etching amount at the start and end portions and the processing time is stable. Therefore, the etching amount can be controlled with high accuracy by the processing time. As a result, it is possible to save the troublesome work of performing etching while frequently measuring the diaphragm thickness as in the conventional case.

In this embodiment, since the masking of the non-etched surface is performed mechanically by the packing, the complicated masking process as in the conventional case can be simplified.

Although the cap is fixed to the clamper in the above embodiment, the clamper may be separated.

[0041]

As described above, according to the etching apparatus of the present invention, it is possible to appropriately perform etching control for each semiconductor wafer, eliminate complicated manual work, and realize automation of the process. it can.

[Brief description of drawings]

FIG. 1 is a partially transparent perspective view of an etching apparatus showing an embodiment of the present invention.

FIG. 2 is an overall vertical sectional view of a clamp / inversion unit.

FIG. 3 is a plan view of the wafer base as seen from above.

FIG. 4 is a piping system diagram of a processing liquid metering unit and a processing liquid heating / supply / discharge liquid unit.

FIG. 5 is a graph showing the change over time of the blow pressure.

FIG. 6 is a plan view of a semiconductor wafer and a perspective view of a chip.

FIG. 7 is an overall cross-sectional view of a semiconductor wafer in a conventional etching process.

FIG. 8 is a sectional view of an etching treatment tank.

FIG. 9 is a partially enlarged sectional view of a semiconductor wafer showing an etching process.

FIG. 10 is an explanatory diagram showing measurement of the thickness of a semiconductor wafer.

FIG. 11 is a graph showing the relationship between bath temperature and etching rate.

FIG. 12 is an explanatory diagram showing the measurement of the thickness of the diaphragm.

[Explanation of symbols]

1 wafer 1a Non-etched surface 1b Etched surface 2 Wafer base (base body) 2a Receiving surface 3 carrier (frame) 31 Lower opening 32 Upper opening 4 Cap (cover) 41 Liquid supply nozzle (opening) 42 Drainage port (opening) 5 Clamp / reversing unit (holding means) 51,52 clamper 523 Rotating shaft (rotating shaft) 53 Support block (support) 652A heating tank (processing liquid supply means) 652B heating tank (cleaning liquid supply means) 7 Cap (base body) 71 Heater (heater member) L treatment liquid S storage space

Continuation of front page (56) Reference JP-A-8-255780 (JP, A) JP-A-5-283394 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21 / 304,21 / 306,21 / 308

Claims (6)

(57) [Claims] 1. A base body having a receiving surface for closely contacting a non-etching surface of a wafer, and a liquid storage space in which a lower opening end surface is in close contact with the entire outer circumference of the etching surface of the wafer and the wafer serves as a bottom wall. A frame body to be formed, a lid body in which an upper opening of the frame body is closed in a liquid-tight manner, and an opening for supplying the processing liquid to the storage space and an opening for discharging the processing liquid from the storage space are formed, and the base body. An etching apparatus comprising: a holding means for holding the frame body from above and below and holding the lid body in a reversible manner. 2. The etching apparatus according to claim 1, wherein the base body and the lid body are integrally provided on a holding means. 3. The etching apparatus according to claim 1, wherein the holding means has a pair of clampers for holding the frame body, and the clampers are supported by a support body by a rotating shaft. 4. The etching apparatus according to claim 1, further comprising a heater member for heating a wafer, the heater member being capable of changing the temperature distribution of the receiving surface. 5. The etching apparatus according to claim 1, further comprising processing liquid supply means for supplying the processing liquid to the opening for supplying the processing liquid by blowing air of compressed air. 6. The etching apparatus according to claim 1, further comprising a cleaning liquid supply means for supplying a cleaning liquid to the opening for supplying the processing liquid by blowing air of compressed air.