JPH0469722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor wafer position detection method that can detect the position of a semiconductor wafer with high precision.

(Prior Art) When exposing semiconductor wafers in the manufacturing process of VLSIs and the like, it is required to detect the position of the semiconductor wafer with submicron accuracy.

Conventionally, when measuring the position of such a semiconductor wafer, for example, as shown in Fig. 6, He-Ne
The output beam of the laser oscillator 101 is transmitted to the X side and Y side of the stage 102 on which the semiconductor wafer is placed.
The beams irradiated onto plane mirrors 103 and 104 provided on the side surfaces and reflected by the respective plane mirrors 103 and 104 are transmitted to an X-interference lengthening device 105 and a Y-interference lengthening device 10.
6 and A-interferometer 107 are used to cause interference.

(Problems to be Solved by the Invention) However, according to this conventional method, the movement of the stage 102 rather than the semiconductor wafer itself was measured, so temperature changes and the movement of the stage 102 were measured.
The drawback was that measurement errors occurred due to pitching, yawing, vibration, etc.

The present invention was made in view of the above problems, and
The purpose is to realize a semiconductor wafer position detection method that can directly measure the movement of the semiconductor wafer itself with high precision.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is capable of measuring the movement of a semiconductor wafer by measuring the amount of movement of a scale formed on a part of the semiconductor wafer. It is characterized by the following.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an apparatus for use in an embodiment of the present invention. In FIG. 1, numeral 10 is a reflective scale, and as shown in FIG. is formed as a diffraction grating. 20 is a reading head, and 30 is a signal processing section. Scale 10 or reading head 2
0 moves in the direction of X-X' in the figure.

In the reading head 20, 21 is a coherent light source using a semiconductor laser or the like, 22 is a condenser lens that receives the emitted light from this light source, 23 and 24 are mirrors that receive the reflected diffracted light from the scale 10, and 25
26 is a light receiving element that receives the reflected light from these mirrors; 27 is the first half mirror 25;
This is a second half mirror that receives the transmitted light and mixes and interferes with it. As the second half mirror 27, an Inconel thin film is used. 2
Reference numerals 8 and 29 denote light receiving elements that receive interference light of different phases from the second half mirror 27 and convert it into an electrical signal.

In the signal processing section 30, 31 and 32 are amplifiers that amplify the outputs of the light receiving elements 28 and 29 in the reading head 20, and 33 receives the outputs of these amplifiers and performs arithmetic processing to calculate the moving distance of the reflective scale 10. 34 is a display circuit that displays the output of this signal processing circuit.

In an apparatus having such a configuration, when the output light of the coherent light source 21 focused by the lens 22 is projected onto the scale 10, the scale 10 is a diffraction grating with grooves formed at regular intervals.
The light projected onto 0 is diffracted. At this time, the diffraction angle θ
is the scale pitch of scale 10, d is the scale pitch of scale 10, and light source 2 is
Letting the wavelength of 1 be λ, it is expressed by the following equation.

sinθ=mλ/d (m; integer) However, -90°≦θ≦90° -1≦mλ/d≦+1 Here, for example, if λ=0.78μm and d=0.83μm, m=0, ±1 Therefore, θ=0° (0th-order diffracted light when m=0) θ=±70.0° (±1st-order diffracted light when m=±1). The ±1st-order diffracted light is mirrored by mirrors 23 and 2, respectively.
After being reflected by 4 and passing through the half mirror 25,
The second half mirror 27 mixes and interferes. This interfered light is transmitted to each light receiving element 2.
After being converted into an electrical signal at 8 and 29, the amplifier 3
1 and 32, the signal is processed by a signal processing circuit 33, and its output, the moving distance and moving direction of the reflective scale 10, is displayed on a display section 34.

Here, as described above, the second half mirror 2
7 is an Inconel half mirror that uses an Inconel thin film, but in the case of an Inconel half mirror that has both the reflective characteristics of a metal surface and the reflective characteristics of a glass surface, the light receiving elements 28 and 29 are
As shown in Figure 3, the phase difference α between
=90°. Therefore, the second half mirror 27
By setting the incident angle φ of the diffracted light to be approximately 75°, the moving direction of the scale 10 can be determined from the output of this half mirror. Furthermore, the phases of the ±1st-order diffracted lights that interfere with each other by the second half mirror 27 change as the scale 10 moves.
Therefore, the intensity of the interference light that reaches the light receiving elements 28 and 29 after interfering with the half mirror 27 is scale 1.
Since the amount of movement of 0 changes periodically by two pitches per pitch, by counting this in the signal processing section 30, the amount of movement of the scale 10 can be measured. Since the outputs of the light receiving elements 28 and 29 are sine waves with an accurate 90° phase difference, ultra-high resolution of 1/1000 μm can be obtained by analog interpolation. Incidentally, the first half mirror 25 and the light receiving element 26 in FIG. 1 are optical power monitors for the ±1st order diffracted light, and are used to generate a voltage for removing the bias component of the output sine wave of the light receiving elements 28 and 29.

With this configuration, the movement of the semiconductor wafer itself can be directly measured, thereby solving the inconvenience caused by measuring the movement of the stage as in the conventional method. In particular, since the thermal expansion of the semiconductor wafer and that of the scale 10 are the same, they are not affected by temperature changes.

In the above embodiment, an example was explained in which the scale 10 is formed on the same surface of the semiconductor wafer WF as the surface on which the chip CP is formed, but outside the chip, as shown in FIG. It may be formed on the back side. This allows more circuits to be incorporated into the semiconductor wafer WF.

Alternatively, as shown in FIG. 5, a scale may be formed for each chip CP of the semiconductor wafer WF to measure the movement of each chip CP.

Furthermore, the scale is not limited to a one-dimensional grid, but may be a two-dimensional scale on a Go board. In this case, it goes without saying that the reading head may be installed perpendicularly to the head, or may be integrated.

Furthermore, minute rotations of the wafer can be measured by forming one-dimensional scales on both ends of the wafer in the same direction and reading them with separate heads.

(Effects of the Invention) As described above, a semiconductor wafer position detection method that can directly measure the movement of the semiconductor wafer itself with high precision can be realized, and is suitable for a semiconductor wafer position detection device in a VLSI exposure apparatus.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an apparatus used in an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a semiconductor wafer to be measured in the present invention, and FIG. 3 is a configuration diagram showing an apparatus used in an embodiment of the present invention. A characteristic explanatory diagram of the half mirror used, FIG. 4 is a configuration diagram showing another embodiment of the present invention,
FIG. 5 is an explanatory diagram showing another example of a semiconductor wafer to be measured in the present invention, and FIG. 6 is a configuration diagram showing an example of a conventional apparatus. 10... Reflective scale, 20... Reading head, 30... Signal processing section, WF... Semiconductor wafer, CP... Chip.

Claims (1)

[Claims] 1. A reflective scale formed on a part of a semiconductor wafer is irradiated with light emitted from a coherent light source, and the reflected diffracted light is mixed and interfered with by a half mirror, and the incident light is adjusted to a specific angle of incidence. The phase difference between the interference lights emitted on both sides of the half mirror is 90°.
A method for detecting a position of a semiconductor wafer, characterized in that each of the interference lights is converted into an electric signal by a light receiving element and then subjected to arithmetic processing to measure the movement of the semiconductor wafer. 2. The semiconductor wafer position detection method according to claim 1, wherein an Inconel thin film is used as the half mirror and the incident angle is 75°. 3. Claim 1, characterized in that it is equipped with a half mirror for separating the obliquely incident coherent light source into two and irradiating the reflective scale.
The semiconductor wafer position detection method described in .