JPS61284927A - Method for washing semiconductor wafer - Google Patents

Abstract

PURPOSE:To enable uniform washing effect to be obtained by providing the flow-in and flow-out ports of the washing liquid at the symmetrical positions of a washing vessel, disposing semiconductor wafer surfaces along this direction, and providing a filter in the flow-in port. CONSTITUTION:A plurality of semiconductor wafer surfaces are disposed at a predetermined interval along between a flow-in port 11 and a flow-out port 12 of the washing liquid which are symmetrically formed on a hollow washing vessel 10, the semiconductor wafers 2 are washed with the circulating washing liquid from a filter 13 attached to the flow-in port 11. For instance, the filter 13 is made of Teflon, which is formed by binding fine pipes having a diameter of about 0.2mum. The flow-in port 11 provided with the filter 13 and the flow-out port 12 are connected by means of a pipe, and a pump is provided in the middle of the pipe, which enables the flow velocity to be controlled by the pump pressure as well as causes the washing liquid to be circulated. The fluid after washing is purified through the filter 13, and the washing liquid flows along the surfaces of the semiconductor wafers 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for cleaning a semiconductor wafer during a manufacturing process in which functional elements and circuits are built into the semiconductor wafer.

[Technical background of the invention]

The manufacturing of semiconductor products can be divided into a front-end process, in which elements and circuits are built onto wafers, and a back-end process, in which the elements are assembled into pellets. However, it has been considered difficult to automate the front-end process due to the complexity of the process and the work environment, which is extremely dust-averse.

On the other hand, in order to meet the increasing demand for semiconductor products, how to build a highly productive manufacturing line has become a major problem, and as a link to this problem, wafer sizes are trending toward larger diameters. Currently, diameters of 100 mφ, 125 nmφ and 150 mmφ are used, but it is already possible to pull single crystals up to 200 nmφ.

Recent semiconductor devices, as exemplified by VLSI, have made remarkable progress in becoming highly integrated and high-performance, and as a result, manufacturing processes have become more complex and diverse, and as a result, the cleanliness of the manufacturing line has become less and less clean. It has a big impact.

In addition to the cleanliness of this line, the removal of foreign matter that adheres to semiconductor wafers during the manufacturing process, that is, the cleaning process, is becoming increasingly important. As mentioned above, with the aim of improving production efficiency, the number of semiconductor wafers to be cleaned at one time is also increasing.

Incidentally, in this cleaning process, a carrier containing a plurality of semiconductor wafers, that is, 10 wafers, is immersed in a cleaning tank, but there are methods known to cause forced convection in the cleaning solution and methods to leave it for a certain period of time. It is being Specific methods for generating this forced convection include means for producing a stirring effect by heating the cleaning liquid, means for installing stirring blades in the cleaning container to forcefully produce a stirring effect, and methods for both. A method of using a combination of means is known. During this cleaning, the semiconductor wafer is accommodated in a carrier and immersed in a cleaning container filled with a cleaning solution.As shown in FIG. (21
) A connecting part (22) is provided at the center of the end to integrate and connect these parts, and a plurality of grooves (23) passing through the thickness of the plate are formed at a constant pitch. A common technique is to place a semiconductor wafer on the N.

[Problems with background technology]

As mentioned above, there is a tendency for semiconductor wafers, which are parts to be cleaned, to have larger diameters.
There may be considerable differences in level due to various processes.

In this cleaning step, the solution containing contaminants on the surface of the semiconductor wafer must be replaced with a clean cleaning solution as quickly as possible. However, even if one forced convection is formed, it is difficult to obtain a uniform cleaning effect over the entire surface of a semiconductor wafer whose surface has considerable irregularities.

This is because even when turbulent flow occurs due to forced convection, the circulation does not reach every corner of the cleaning container, resulting in a gradient in cleaning power depending on the location of the object to be cleaned. The cleaning effect near the carrier contact area and the central area becomes non-uniform, and similar differences occur between each semiconductor wafer.

In today's world where there is a demand for improved productivity efficiency, unevenness in cleaning efficiency is becoming serious due to the shrinking groove pitch of the carrier due to the increase in the number of wafers to be cleaned, and the increase in the area to be cleaned due to the larger diameter of semiconductor wafers. This has become a problem.

[Summary of invention□]

In order to achieve this object, in the method of the present invention, a cleaning liquid inlet and an outlet are provided at symmetrical positions in the cleaning container, and the semiconductor wafer surface is arranged along these directions. Furthermore, a method was adopted in which a filter was placed at the inlet, a pump was placed between the inlet and the outlet, and the flow rate of the cleaning liquid between the inlet and the outlet was adjusted by the pump pressure.

That is, by using a clean circulating cleaning solution and arranging the surface of the wafer to be cleaned in the direction in which the cleaning solution flows, consideration is given to keeping the conductance of the cleaning solution constant between the plurality of semiconductor wafers. Constant cleaning efficiency can be achieved continuously.

[Embodiments of the invention]

The present invention will be explained in detail with reference to FIGS. 1 to 4, in which FIG. 1 is a sectional view of a washing device according to the present invention, FIG. 2 is a top view thereof,
FIG. 3 is a perspective view of a carrier holding a semiconductor wafer.

As shown in FIG. 3, the carrier housed in the cleaning container according to the present invention is made of synthetic resin such as Teflon, but it is made of a beam frame with no walls around it so that the fluid, that is, the cleaning liquid, can freely flow. The main body seat can be separated into Mn and the main body seat for convenience in fixing the semiconductor wafer (2) to be further installed.

As shown in the figure, this carrier is almost square when viewed from the top, and the frame... is placed at the corner.
They are integrated by a support 0... that connects them.

On the other hand, the lid (2) is similarly composed of the frame (2)... and the support surface, and the opposing supports (20 and (C)) are provided with grooves (2) at the same pitch. Lock the semiconductor wafer ■ to the semiconductor.

On the other hand, the container (10) containing the cleaning liquid has an inlet (11).
) An outflow port (12) is provided, and a filter (13) is attached to this inflow port (11). This filter is made of Teflon and is formed by bundling thin tubes with a diameter of about 0.2 μs.The filter is attached to an inlet (11) and an outlet (
12) are connected by a pipe (not shown), and a pump (not shown) is installed between them to suppress the flow rate with pump pressure and to circulate the cleaning liquid.

Further, a heater (14) is provided at the bottom of the cleaning container (10), and the 0th surface of the semiconductor wafer is arranged along the plane connecting the inlet (11) and the outlet (12) as shown in FIG. As described above, since the method of the present invention is equipped with a circulation mechanism, the cleaned fluid is cleaned through the filter (13), and the cleaning liquid flows along the surface of the semiconductor wafer. become.

〔Effect of the invention〕

FIG. 4 shows the results of examining the cleaning effect of the method of the present invention using a mixed solution of hydrochloric acid and hydrogen peroxide. A semiconductor wafer contaminated under the same conditions was used as a sample, and the number of remaining fine particles (0.3- or more) was used as an index of the cleaning effect. Flow velocity (Oam/
The number of remaining fine particles at 5ec) corresponds to the case where the immersion method was adopted as a conventional means.

Curve 2 (A) is the case when the surface of the semiconductor wafer to be cleaned is smooth and round, curve (B) is the case when a groove with a depth of 0.4 μs and a width of 2 μs is formed on the surface of the semiconductor wafer, and curve (C) is the case when the semiconductor wafer surface is smooth. is a measured value of a semiconductor wafer in which a groove having a depth of 1 μs and a width of 2p was formed. In curve (A), the number of remaining fine particles and their dispersion begin to decrease around a flow rate of 10 (am/5ee), and reach the lower limit at 25 ((!l/116C)).

Also, the variation on a single wafer is similarly reduced.

On the other hand, curves (B) and (C) correspond to samples where medium and large degree of unevenness remain on the semiconductor surface.
In (b), the number of particles was about 37 at a flow rate of 0 (am/5ee), but it remained almost constant at a flow rate of 15 to 20 (CIl/86c), and the degree of decrease became larger from this N
(am/5ee) is disaturated. On the other hand, in (c), at flow rate 0 (a++/5ac), from 49 pieces to flow rate 2
It starts to decrease more from 0 to 25 (cm/5ac), and from 35 to
It is saturated at 4Q (am/5ee).

In the figure, the flow rate of 0 (am/5ac) indicates the value obtained when the immersion method was used as a conventional method.

In comparison, the method of the present invention shows an excellent value.

When the semiconductor wafer surface is very smooth, that is, curve (A), it is assumed that the cleaning liquid flows along the semiconductor wafer surface, that is, a laminar flow is formed, and the cleaning liquid conductance between each wafer is assumed to be constant. It will be done. On the other hand, in curves (b) and (c), the flow velocity at which the number of remaining fine particles begins to decrease considerably is faster than in curve l1A (a), and saturation is achieved at a higher flow velocity. In other words, if there are irregularities on the semiconductor surface,
This means that it is difficult to wash, and it is considered that turbulent flow occurs in these uneven parts, but the number of remaining fine particles after washing was improved by about 6 times compared to the conventional immersion method.

[Brief explanation of drawings]

Figure 1 is a sectional view of the apparatus used in the method of the present invention, Figure 2 is a side view of the apparatus, Figure 3 is a perspective view of the carrier, and Figure 4 shows the number of residual particles on the vertical axis and the flow rate on the horizontal axis. A curve diagram showing the relationship, and FIG. 5 is a perspective view of a conventional carrier.

Claims (1)

[Claims] A plurality of semiconductor wafer surfaces are arranged at predetermined intervals along the cleaning liquid inlet and outlet openings formed symmetrically in the hollow cleaning container, and the semiconductor wafers are cleaned by the circulating cleaning liquid from the filter attached to the inlet. A method for cleaning semiconductor wafers, the method comprising cleaning the semiconductor wafers.