JPH0289335A - Thermal-wave measuring device - Google Patents

Abstract

PURPOSE:To perform damage evaluation accurately also for the depth direction by providing a thermal-wave detection part for observing the difference of heat conduction on a wafer surface by irradiating laser beam to the wafer surface thereby to grasp the surface state, and an etching mechanism for performing etching on the wafer surface. CONSTITUTION:The title device consists substantially of an argon laser 2 for heating a wafer 1 with laser beam, a helium neon laser 3 for irradiating laser beam for monitor, a modulator 4, a photo-detector 9 etc., and it casts laser beam onto the wafer 1 through a quartz window 12. The photo detector 9 detects the difference in heat conduction on the surface of the wafer 1 as a TW value. Thus the surface of the wafer 1 is etched in sequence by an etching mechanism, and the TW value can be measured by a thermal-wave detection part 11. Therefore, the distribution of damage of the wafer 1 in depth direction may be exactly measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal wave measurement device, and more particularly to a thermal wave measurement device that makes it possible to measure damage distribution in the surface and depth directions of a wafer. .

[Summary of the Invention] The present invention is a thermal wave measurement device for detecting the state of a wafer, which enables the surface state to be determined by irradiating the wafer surface with a laser beam and observing the difference in thermal conductivity on the wafer surface. By providing a thermal wave detection section and an etching mechanism for etching the wafer surface, it is possible to accurately evaluate damage to the wafer in the depth direction.

[Prior Art] In recent years, with the progress of LSI processes, the occurrence of various types of damage such as damage to the lattice state of silicon substrates induced by these processes has become a problem. Thermal wave signal (hereinafter referred to as T
A thermal wave measurement device is known that evaluates the W value (referred to as W value).

This thermawave measuring device, as shown in Figure 3,
The surface of the wafer 1 is heated by an argon laser 2, the surface of the wafer 1 is monitored by a laser beam of a helium neon laser 3, and the difference in thermal conduction is evaluated as a TW value. In the figure, 4 indicates a modulator, 5 a lens, 7 a splitter, 8 a HeNe filter, and 9 a photodetector.

According to such a thermal wave measurement device, it is possible to directly detect disturbances in the crystal lattice on the surface of the wafer 1 by ion implantation, reactive ion etching (RIE), etc., and also to indirectly detect damage distribution within the wafer 1. You can guess.

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[Means for Solving the Problems] Therefore, the present invention provides a thermal wave detection section that makes it possible to grasp the surface state by irradiating the wafer surface with a laser beam and observing the difference in thermal conduction on the wafer surface; and an etching mechanism for etching the wafer surface.
This is the solution to this problem.

[Problem to be solved by the invention] However, such a thermawave measurement device has the following problems:
This is only a means of evaluating damage to the wafer surface, and there is a problem in that it cannot measure how the damage is distributed in the depth direction of the wafer.

The present invention has been devised by focusing on these conventional problems, and aims to provide a thermal wave measurement device that can accurately evaluate damage based on the TW value of a wafer even in the depth direction. [Operation] The wafer is gradually etched by the etching mechanism, and if the wafer surface condition is detected each time by the thermal wave detector, it becomes possible to grasp the damage condition of the wafer in the depth direction.

[Example] Hereinafter, details of the thermal wave measuring device according to the present invention will be described based on an example shown in the drawings.

First, FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

In the figure, A is the thermawave measuring device, which includes an etching mechanism IO and a thermawave detection section! It is roughly composed of l.

The etching mechanism 10 is constructed by communicating a vacuum chamber I3 provided with a quartz window 12 with a microwave discharge section 14 through a transport pipe 15. Decompression chamber! A wafer support stand 16 is provided inside the wafer 3 so that the surface of the wafer 1 faces the quartz window 12, as shown in FIG.

The microwave discharge section 14 produces active species for etching the silicon wafer l, and these active species are introduced into the vacuum chamber 13 through the transport pipe 15. Note that an exhaust pipe 17 is provided at the bottom of the decompression chamber (3).

Next, the thermawave detection unit 11 uses a mechanism similar to that of the conventional example, and uses an argon laser 2. It is generally composed of a helium-neon laser 3° modulator 4 for irradiating a monitoring laser beam, a photodetector 9, etc., and the laser beam is irradiated onto the wafer l through a quartz window 12.

Note that the photodetector 9 detects the difference in thermal conductivity on the surface of the wafer l as a TW value.

With this configuration, the surface of the wafer I can be gradually etched by the etching mechanism IO, and the TW value can be measured by the thermal wave detector 11 each time. Therefore, it is possible to accurately measure the damage distribution in the depth direction of the wafer 1.

Further, FIG. 2 is a schematic diagram showing a second embodiment of the present invention.

In this embodiment, an annular gas supply pipe 18 is disposed above the wafer l supported within the reduced pressure chamber 13. A plurality of supply ports 18a are opened at the bottom of this gas supply pipe 18. The gas supply pipe 18 is also connected to a gas supply source (not shown) outside the decompression chamber I3 via a gas transport pipe (not shown). In addition,
As the gas used for such etching, c(IFs) or other gases can be used. Note that the etching performed by the thermal wave measuring device A will not affect the subsequent measurement.

Note that FIG. 3 shows RIE using the apparatus according to this embodiment.
In order to evaluate the damage to silicon wafers whose surfaces were etched by ECR plasma etching and ECR plasma etching, changes in TW values were measured in the depth direction and plotted. In the figure, A is a value measured for a silicon wafer by ECR plasma etching, and B is a value measured for a silicon wafer by RIE.

As is clear from this graph, TW at the top surface of the wafer
Although the values are comparable for both RIE and ECR plasma etching, looking at the damage distribution in the depth direction clearly shows that ECR plasma etching has a shallower damage depth.

Although the embodiments have been described above, various other design changes are possible, and for example, etching means other than those used in the above embodiments may be used.

Further, in the above embodiment, an etching mechanism with good controllability under reduced pressure was used, but it is of course possible to use another etching mechanism.

[Effects of the Invention] As is clear from the above description, the thermal wave measuring device according to the present invention makes it possible to accurately evaluate damage to silicon wafers based on the TW value even in the depth direction. effective.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a Nth embodiment of the thermally wave measuring device according to the present invention, Fig. 2 is a schematic diagram showing the second embodiment of the same, and Fig. 3 is a diagram showing ECR plasma etching using this device. FIG. 4 is a graph showing the results of measuring the TW values of a silicon wafer subjected to RIE and a silicon wafer subjected to RIE, and FIG. 4 is a schematic diagram showing a conventional example. A...Thermawave measuring device, 卜...Wafer, lO...Etching mechanism, 11...
Damage detection section. Fig. 1 Ezuchinoku゛Yukai'sa (mu) Type A

Claims (1)

[Claims] (1) Equipped with a thermal wave detection section that makes it possible to grasp the surface condition by irradiating the wafer surface with a laser beam and observing the difference in thermal conduction on the wafer surface, and an etching mechanism that etches the wafer surface. A thermawave measurement device characterized by the following.