JP3333664B2 - Cleaning method and cleaning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cleaning method and a cleaning apparatus.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, particles on the surface of a semiconductor wafer (hereinafter referred to as "wafer"),
A cleaning apparatus is used to remove contamination such as organic contaminants and metal impurities. Among them, a wet cleaning apparatus can effectively remove the contamination, and can perform batch processing and has good throughput. Because of this, it is widely used.

In this type of cleaning apparatus, a wafer is subjected to a chemical treatment such as ammonia, hydrofluoric acid, or hydrochloric acid in a chemical tank, and then rinsed with pure water in a rinse tank. As for the apparatus configuration, a set of a chemical solution tank and a rinsing tank is arranged in series for each chemical solution, and a transfer system for sequentially transferring, for example, 50 wafers collectively to each tank is provided. FIG. 9 is a diagram showing a main part of a conventional cleaning apparatus. In this cleaning apparatus, for example, 50 wafers W are collectively transferred to a dedicated wafer holder 11 from a wafer cassette (not shown) in advance. First, the holder 11 is immersed in a chemical solution in the chemical solution tank 1A by a transport means (not shown), and a cleaning process such as etching is performed while circulating the chemical solution. Next, the wafer holder 11 is pulled up from the chemical solution tank 1A and is immersed in the rinse tank 1B, and the wafer W is rinsed while supplying, for example, pure water from the bottom of the rinse tank 1B.

[0004]

However, when the wafer is cleaned by the above-mentioned method, there is a problem that particles adhere (transfer) to the wafer surface. One of the main causes of the adhesion (transfer) of particles as described above is that particles adhering to the back surface of the wafer are transferred to the front surface of another wafer adjacent to and facing the wafer in a series of steps. It is mentioned. Although the mechanism of the transfer of the particles is not clear, according to the experiment of the present inventor, the particles adhering to the back surface of the wafer spread in the chemical solution tank, and the particles adhere to the holding member and are carried into the rinsing tank. When the wafer is put into the rinsing bath, it is considered that particles already spread in the rinsing liquid may adhere to the wafer surface. In any case, particles are attached to the surface of the wafer pulled up from the rinsing liquid, and the line width of the device tends to be finer and the allowable range of the particles tends to be narrower. There is a possibility that.

The present invention has been made under such circumstances, and an object of the present invention is to provide a cleaning method and a cleaning apparatus capable of reducing particle contamination.

[0006]

A cleaning method according to the present invention.
In the state where a plurality of substrates to be processed are
The bottom of the processing substrate and holds the holding groove of the holding member chemical tank
In the cleaning method including a step of pulling up from the chemical solution and then transporting the substrate into the rinsing tank, the substrate to be processed is kept until just before the upper end of the holding member is exposed from the liquid surface of the chemical solution.
Step of lifting the holding member at the first speed while holding
Then, the lower end of the holding member separates from the liquid surface of the chemical solution.
Until the holding member is slower than the first speed.
Droplets are visually observed on the outer surface of the holding member.
Lifting at a second speed, and then removing the holding member
A step of transferring into the rinsing tank at a speed higher than the second speed
And characterized in that:

[0007] The cleaning device according to the present invention contains a chemical solution.
A chemical tank, a rinsing tank containing a rinsing liquid,
The bottom of each substrate to be processed with the processing substrates arranged vertically and in parallel
For immersion in the chemical bath and the rinsing bath.
The holding member and the holding member are lifted up from the chemical solution tank, and
Conveying means for conveying to a storage tank, and an upper end of the holding member
Until the point immediately before the part is exposed from the liquid surface of the chemical solution.
Pulling up the holding member at the first speed while holding the substrate
Then, the lower end of the holding member separates from the liquid surface of the chemical solution.
Until the holding member is slower than the first speed.
Droplets are visually observed on the outer surface of the holding member.
Lifting at a second speed, and then holding the holding member at a second speed.
Transfer to the rinsing tank at a speed faster than
And a control unit for controlling the means .

[0008]

[0009]

[0010]

For example, a holder having a holding member for holding the bottom of a substrate to be processed is used. A plurality of substrates to be processed are held in parallel by the holder, and a cleaning processing liquid, for example, a chemical solution filled with a chemical solution is placed in the chemical tank. Immerse. Then, after the chemical treatment, the holder is pulled up at the first speed, and when a part of the holding member is exposed, the pulling speed is reduced, and the holding member is pulled up at a speed at which the droplets do not adhere to the holding member when visually observed. Particles in the chemical tank are taken into droplets adhering to the holding member and transported into the rinsing tank, so if the droplets do not adhere to the surface of the holding member, the number of particles brought into the rinsing tank is reduced. As a result, particle contamination of the substrate to be processed lifted from the rinsing bath can be reduced.

[0011]

FIG. 1 is a diagram showing an entire cleaning station including a cleaning apparatus for carrying out the cleaning method of the present invention. First, the overall configuration of this cleaning station will be briefly described.
The main part of the cleaning station is constituted by a cleaning processing section 100 and a loader section 200 and an unloader section 300 provided at both end portions of the cleaning processing section 100.

The loader 200 includes a loading section 21 for loading and loading a carrier C containing a predetermined number of unprocessed substrates, for example, 25 wafers, for example, 25 wafers. And a transfer device 23 for clamping the transferred carrier C and transferring it to the relay section 22.

The cleaning processing section 100 includes a transfer stage 20 for collectively transferring wafers in the carrier C placed on the relay section 22 to a dedicated wafer holder, and an n-th cleaning from the primary cleaning unit U1. A plurality of cleaning units up to the unit Un are provided. Transfer stage 20
Above is a wafer chuck that is not visible in the figure,
For example, 50 wafers in the carrier C are collectively transferred to a dedicated wafer holder, which will be described later, on the transfer stage 20. Each of the cleaning units U1 to Un includes, for example, a chemical solution tank 24, a primary water washing tank 25, and a secondary water washing tank 26. After the chemical solution cleaning in the chemical solution tank 24, the wafers are washed with pure water in the primary water washing tank 25 and the secondary water washing tank 26. After cleaning the chemical solution attached to the wafer, the wafer is transferred to a predetermined cleaning unit among the cleaning units U2 to Un further downstream and subjected to a predetermined process. The secondary washing tank 26 is located between adjacent cleaning units for cleaning with different kinds of chemicals, and has a function as a buffer for preventing mixing of both chemicals. Holder transfer means 27 for transferring a wafer holder holding a wafer is provided on the side of the cleaning units U1 to Un.

The unloader section 4 includes a mounting section 28 configured to mount a carrier C for storing a wafer that has been cleaned and dried by the above-described cleaning units U1 to Un. After the cleaning / drying process is completed, the wafer returned to the carrier C is carried out of the apparatus. The transfer stage 29 on the front side of the mounting section 28 is a stage for transferring the wafer in the wafer holder into the carrier C by a wafer chuck (not shown).

As described above, in each cleaning unit, a predetermined process is performed by a predetermined chemical solution, and the present invention is applied to such a cleaning unit, for example. Next, an embodiment in which the present invention is applied to a cleaning apparatus (corresponding to the above-described cleaning unit) in which a natural oxide film on the surface of a wafer is removed using a hydrofluoric acid solution and then rinsed with pure water will be described.

As shown in FIGS. 2 and 3, the cleaning apparatus according to the embodiment of the present invention comprises a chemical tank 3, a rinsing tank 4 (corresponding to a primary washing tank), and a wafer for holding a plurality of wafers. The holder 5, a holder transporter 6 having a pair of arms 61 for transporting the wafer holder 5 (corresponding to the holder transporter 27 in FIG. 1), and controls the holder transporter 6. And a control unit 60. The chemical solution tank 3 is formed into a rectangular shape, and has an inner tank 31 having a triangular cutout 30 for overflow formed at an upper edge thereof, and a liquid overflowing outside the upper edge of the inner tank 31. And an outer tank 32 provided to receive the water.

An outer tank is provided outside the inner tank 31 so as to supply the chemical solution in the outer tank 32 to the bottom of the inner tank 31, that is, to circulate the chemical solution overflowing from the inner tank 31 to the bottom of the inner tank 31. A chemical liquid circulation path 33 made of, for example, a resin tube is provided between the bottom of the inner tank 32 and the bottom of the inner tank 31. A pump P1 and a filter F
Is interposed. A rectifying means 3 is provided at the bottom of the inner tank 31.
The rectifying means 34 is opposed to a rectifying plate 36 in which a large number of small holes 35 are formed and a connection port (a supply port of the chemical solution) of the chemical solution circulation path 33 on the bottom surface of the inner tank 31. And a diffusing plate 37 arranged in the same direction.

By providing the rectifying means 34, the pure water introduced from the chemical liquid circulation path 33 first collides with the back surface of the diffusion plate 37, and the entire back surface of the rectification plate 36 is moved from the peripheral edge of the diffusion plate 37. Is supplied to the periphery of the wafer W held by the holder 5, so that the wafer W is wrapped at a uniform flow rate without generating a turbulent flow. It is possible to clean the entire wafer W evenly without unevenness. In addition, the chemical solution tank 3
A chemical solution supply unit 38 for supplying a chemical solution, for example, a hydrofluoric acid solution, into the chemical solution tank 3 is provided at a position where the transfer of the wafer holder described later is not hindered.

On the other hand, the wafer holder 5 has a pair of end plates 5.
Holding members 53, 54, and 55 for holding the lower end portion and the lower side of the wafer W, respectively, are provided between the holding members 53, 54, and 55. Groove 56 (for convenience, each holding member 53, 54, 55
, For example, 50 holding grooves are formed at a predetermined pitch. The pair of end plates 51, 5
The upper portions of the support portions 51 are each horizontally bent outwardly.
The substrates to be processed 51a, 51b are transported while being supported by the arm 61 of the holder transporting means 6 from below. The wafer holder 5 is made of, for example, Teflon (trade name) which is a fluororesin.

The rinsing tank 4 includes an inner tank 41, like the chemical tank 3, and an outer tank 42 for receiving the rinsing liquid overflowing from the inner tank 41. A pure water supply path 43 made of, for example, a resin tube for supplying a rinsing liquid, for example, pure water, into the inner tank 41 is connected to the bottom of the inner tank 41 and a valve VL1. Is connected to a drain pipe 44 for discharging pure water. A rectifying unit 45 similar to the rectifying unit 34 is provided at the bottom of the inner tank 41.

Next, an example of a cleaning method performed using the above-described cleaning apparatus will be described. First, a chemical solution, for example, a 0.5% hydrofluoric acid solution is supplied from the chemical solution supply unit 38 into the inner tank 31.
The chemical is circulated by the pump P1. Then, for example, the wafer holder 5 in which 50 wafers W are arranged and held in parallel is loaded into the inner tank 31 by the holder transporting means 6, and
The wafer W is immersed in a chemical solution to perform a cleaning process, for example, etching for a predetermined time.

Thereafter, the arm 61 is raised and
As shown in (a), the wafer holder 5 is pulled up at a first speed V1, for example, 200 millimeters per second, and the upper ends of the holding members 53, 54, and 55 of the wafer holder 5, in this example, the holding members located on the left and right sides. Immediately before the upper ends S1 (see FIGS. 3 and 4B) of the 54 and 55 are exposed from the liquid surface of the chemical solution, the lifting speed of the wafer holder 5 is set to a speed V lower than V1.
2. For example, drop to 70 millimeters per second, and FIG.
As shown in FIG. 7, the wafer holder 5 is pulled up at the speed V2 until the lower ends of the holding members 53, 54, 55, in this example, the lower end S2 of the holding member 53 located at the center are separated from the liquid surface of the chemical solution. The speed V2 is controlled by the holding members 53, 5
It is necessary that the speed is such that the droplets do not adhere to at least the side wall surfaces of the holding members 53, 54 and 55 due to the surface tension of the liquid if the speed is 70 millimeters per second as described above. No droplet adheres to the surface. However, that the droplet does not adhere means that the droplet is not confirmed when visually observed. Further, as will be understood from an experiment described later, if the speed V2 is too low, particles tend to adhere to the wafer W. Therefore, it is necessary that the speed V2 be not too low, for example, not lower than 16 mm per second.

Thereafter, as shown in FIG. 4 (d), the wafer holder 5 is returned to a speed higher than V2, for example, the original speed V1, and is raised. It is immersed in the rinsing liquid in the rinsing tank 4. When the wafer W is immersed in the rinsing liquid, it is preferable to immerse the wafer W at a speed as fast as possible, for example, at a rate of 200 mm per second. Such control of the transfer speed of the wafer holder 5 is performed according to a predetermined program stored in a memory in the control unit 60.

Then, while the valve V2 is opened to supply a rinsing liquid, for example, pure water into the inner tank 41 from the bottom of the inner tank 41, the pure water overflowing from the inner tank 41 is drained from the drain pipe 44 via the outer tank 42. Liquid. Thus, pure water is supplied into the inner tank 41 at a predetermined flow rate for a predetermined time or until the resistance value of the pure water in the inner tank 41 reaches a predetermined value, and a rinsing process is performed.

According to the above-described embodiment, particles adhering to the wafer W lifted from the rinsing bath 3 are reduced. The reason is as follows. First, the present inventor found that although the wafer W after the hydrofluoric acid treatment hardly had any particles attached thereto, as can be seen from an experiment described later, the wafer W after the rinsing treatment had a considerable amount of particles. Figured out the fact that was attached.

Therefore, a mechanism as shown in FIG. 5 can be considered. That is, when the wafer W is immersed in the chemical solution tank 3, the particles PT attached to, for example, the back surface of the wafer W are separated and diffused into the hydrofluoric acid solution, and are held when the wafer W is pulled up from the chemical solution tank 3. Members 53, 54, 55
(In FIG. 5, 53 is representatively shown for convenience).
Adheres, the particles PT are taken into the droplet L, and these particles PT
It is carried into the rinsing tank 4 by 3, 54, 55.

When the wafer holder 5 is immersed in the rinsing bath 4, the particles adhering to the holding members 53, 54, and 55 diffuse into pure water, into which the wafer W is charged. Adhere to the wafer W. Thereafter, when the wafer W is pulled up from the pure water, the particles are pulled up while adhering to the wafer W, thus causing particle contamination. Although the relationship between the particles attached to the surface of the wafer W pulled up from pure water and the particles hardly attached to the surface of the wafer W after the hydrofluoric acid treatment is not clear, it is not clear. It is presumed that it is due to the difference in state.

Here, the following experiment was conducted to examine the relationship between the speed V when the wafer holder was pulled out of the chemical solution tank and the number of particles adhering to the wafer. That is, particles larger than 0.15 μm
00 contaminated wafers and clean wafers not adhering particles are alternately arranged and held on a wafer holder made of Teflon (trade name) at a pitch of 1/8 inch so that the mirror surfaces of both wafers face each other, Etching (removal of a natural oxide film) with 0.5% hydrofluoric acid was performed for 1 minute.

Next, the wafer holder is pulled up and put into a rinsing tank, and the wafer is rinsed with pure water and then dried.
0.15μ attached to the clean wafer surface (mirror surface)
The number of particles larger than m was determined. In such a cleaning step, the speed V at which the wafer holder is pulled up from the chemical solution tank is set to 16 mm / sec and 35 mm / sec.
c, 70mm / sec, 110mm / sec, 160m
When m / sec was set to 5 ways and the number of particles was checked in each case, the result shown in FIG. 6 was obtained.

When the wafer holder was pulled up at each of the above-mentioned speeds, the speed was reduced and the lower end surface of the holding member was visually observed. V was 110 mm / sec and 160 mm / sec.
In the case of c, the droplet was taken away and adhered to the lower end surface, but in the case of 70 mm / sec or less, the droplet was not adhered due to the surface tension of the liquid surface. Further, after the wafer was pulled up from the chemical solution tank, the particles on the wafer surface were separately examined without being put into the rinsing tank, and no adhesion of the particles was confirmed at any of the above-mentioned pulling speeds. Therefore, the carrier that carries the particles from the chemical tank to the rinsing tank is considered to be a holding member.

From the above, particles are mixed in the hydrofluoric acid solution droplets as shown in the mechanism of FIG.
When this adheres to the holding member, it is considered that the amount of particles adhered to the wafer increases as a result. However, as shown in FIG. 6, when V is reduced to 16 mm / sec, although the cause is unknown, the amount of particles attached to the wafer becomes extremely large.

As described above, when the wafer holder is lifted from the chemical solution tank, it is necessary that droplets do not adhere to the outer peripheral surface of the holding member. However, in the present invention, the wafer holder is necessarily pulled up at a constant speed. However, when the holding member does not pass through the liquid surface, the holding member may be pulled up at a high speed in order to increase the throughput. In the embodiment described above, the pulling speed is switched between V1 and V2 in accordance with the position of the holder for such a reason.

Further, the present invention is not limited to being applied to a cleaning apparatus for holding and transporting a wafer in a dedicated wafer holder, but also for holding a wafer with a wafer chuck and transferring the wafer to a wafer holder in a chemical solution tank. The present invention may be applied to a cleaning apparatus of a type in which a wafer in a chemical solution tank is transferred to a rinse tank by a wafer chuck after the chemical solution processing. 7 and 8 are views showing a wafer chuck of such a cleaning apparatus. The wafer chuck 7 is reciprocated by a driving mechanism 71 in a front-rear direction (Y direction), a vertical direction (Z direction), and as shown by arrows. A pair of right and left rotatable gripping members 72, 73, and a support 7 suspended downward from both ends of the gripping members 72, 73
4 and 75, and holding members 8a and 8b vertically extending between the support members 74 and 75, respectively.

The holding members 8a and 8b are provided with, for example, 50 holding grooves 81 at a constant pitch along the longitudinal direction.
When the gripping members 72 and 73 are inserted into the holding grooves 81 of the holding rods 8a and 8b of the gripping members 72 and 73, the gripping members 72 and 73 are rotated in directions approaching each other so as to be gripped by the wafer chuck 12. It has become.

When such a wafer chuck 7 is used, the wafer W which has been subjected to the chemical treatment in the chemical solution tank 4 and is held on a wafer holder (not shown) is held by the wafer chuck, and the upper end of the upper holding member 8a is held. During the period from immediately before the portion is exposed to the liquid surface of the chemical solution until the lower end of the lower holding member 8b separates from the liquid surface, the lifting speed of the holding members 8a and 8b is increased by applying the liquid to the outer peripheral surfaces of the holding members 8a and 8b. The speed V2 at which the drops do not adhere is set. However, after the lower end of the holding member 8a separates from the liquid surface, until the time immediately before the upper end of the holding member 8b is exposed from the liquid surface, the speed is faster than the speed V2. The rate of attachment may be used.

In the above, the present invention is not limited to the case where an oxide film is etched with a hydrofluoric acid solution, but the case where a nitride film is etched with a phosphoric acid solution or aluminum is etched with a mixed solution of phosphoric acid, acetic acid and nitric acid. Also applicable to In addition, A
When removing particles with a PM solution (ammonia + hydrogen peroxide + pure water) When cleaning metal contamination with an HPM solution (hydrochloric acid + hydrogen peroxide + pure water), or using an SPM solution (sulfuric acid + hydrogen peroxide) For example, the organic matter in the resist film may be removed with water. The substrate to be processed may be a liquid crystal substrate, a printed circuit board, or the like.

[0037]

According to the cleaning method of the present invention, particle contamination (transfer) on the substrate to be processed can be reduced, and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a cleaning station including a cleaning apparatus for performing the method of the present invention.

FIG. 2 is a vertical sectional front view showing an example of a cleaning apparatus for performing the method of the present invention.

FIG. 3 is a perspective view showing a chemical solution tank and a wafer holder used in the cleaning apparatus.

FIG. 4 is a process chart showing one embodiment of the method of the present invention.

FIG. 5 is an explanatory diagram showing an estimated mechanism of particle contamination of a wafer.

FIG. 6 is a graph showing the relationship between the wafer pulling speed and the number of particles.

FIG. 7 is a perspective view showing an example of a wafer chuck.

FIG. 8 is a perspective view showing a holding member of the wafer chuck.

FIG. 9 is an explanatory view showing a conventional cleaning method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Placement part 22 Relay part U1-Un cleaning unit 27 Holder conveyance means 3 Chemical tank 33 Chemical liquid circulation path 4 Rinse tank 5 Wafer holder 53,54,55 Holding member 56 Holding groove 6 Holder conveyor 7 Wafer chuck 8a , 8b Holding member 81 Holding groove

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/304

Claims (2)

(57) [Claims] 1. A plurality of substrates to be processed are vertically arranged in parallel.
And hold the holding groove of the holding member bottom of the substrate to be processed in a state lifted from the chemical liquid in the chemical tank and then in the cleaning method comprising the step of conveying in the rinsing tank, the upper end portion of the holding member of the chemical A step of pulling up a holding member at a first speed while holding the substrate to be processed until immediately before being exposed from a liquid surface; and holding the holding member until the lower end of the holding member is separated from the liquid surface of the chemical solution. Holding the member at a speed lower than the first speed ;
A step of lifting the holding member at a second speed at which adhesion of droplets to the outer surface of the holding member is not visually observed , and then rinsing the holding member at a speed higher than the second speed
And a step of transporting the cleaning solution into the inside . Wherein each of the process and the chemical bath containing a chemical liquid, a rinsing tank containing a rinsing liquid, in a state arranged in parallel a plurality of the substrate in a vertical
A holding member for holding the bottom of the substrate and immersing the substrate in the chemical solution bath and the rinsing bath, a transporting unit for lifting the holding member from the chemical bath and transporting the substrate to the rinsing bath, and an upper end of the holding member. The holding member is pulled up at a first speed while holding the substrate to be processed until immediately before the liquid is exposed from the liquid surface of the chemical, and the holding is performed until the lower end of the holding member is separated from the liquid surface of the chemical. The member is the first
Droplets on the outer surface of the holding member
Pull up at a second speed not visible , then hold
A cleaning device, comprising: a control unit that controls the transfer unit to transfer the member to the rinsing tank at a speed higher than the second speed .