JPH05149780A - Balance for measuring plate-like sample - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a balance capable of always accurately measuring the mass of a plate-shaped sample such as a wafer without being affected by airflow or the like. [Structure] In a balance in which a frame having supporting members is provided at two upper and lower positions in a load-sensitive portion of the balance, and a supporting device for loading and unloading a sample is arranged in the vicinity of each supporting device, Shielding plates are provided on the top and bottom so as not to contact them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balance for accurately measuring the mass of a plate-shaped sample such as a silicon wafer.

[0002]

2. Description of the Related Art In order to measure the mass of a plate-shaped sample such as a silicon wafer, a frame having upper and lower supports for horizontally supporting the plate-shaped sample is engaged with a weighing hook or weighing pan of a balance, Place the standard or reference sample on the side support and the sample requiring measurement on the other side, and weigh the masses of both individually to obtain the mass information of the sample to be measured from the difference. There is a balance that I have made.

That is, for example, the average film thickness and the average etching depth can be known by obtaining the change in the mass of the silicon wafer before and after the film formation or etching process. The change in mass at is extremely small, and the influence of buoyancy on the wafer from the atmosphere, that is, the influence of change in buoyancy due to atmospheric pressure and temperature cannot be ignored. For example, regarding the silicon film thickness on the entire surface of an 8-inch wafer, the mass of the wafer changes by 0.1 mg due to the change of the film thickness of 13 angstrom, but there is no error on the balance side due to the change of atmospheric pressure by 10 mbar. Even in the state, the measured value is 0.3
Changes in mg occur. If there are such changes in atmospheric pressure and temperature before and after the processing such as film formation, a large error will occur in the data such as the film thickness obtained from the mass change before and after the processing.

Therefore, as described above, the reference wafer is placed on one of the upper and lower supports, its mass is measured and lowered, and then the wafer to be measured is placed on the other support to determine its mass. By measuring and calculating the difference between the two, the reference and measured wafers are equally affected by the measurement environment such as atmospheric pressure and temperature at that time. The effect will be canceled. Therefore, if the difference between the two is calculated using the same reference wafer before and after the process, even if the atmospheric pressure change occurs before and after the process, the difference between the reference wafer before and after the process causes It is possible to accurately know the change in mass of, and the data such as the film thickness obtained from this will be accurate.

Such a balance is often installed, for example, in-line in a wafer processing step, and there is a balance in which the difference in mass before and after the processing is automatically measured in one cycle operation. It has already been put to practical use.

For this purpose, the frame body having the upper and lower supports for mounting the reference wafer and the wafer to be measured as described above is attached to the load sensitive portion, that is, the weighing hook or the weighing pan of the balance. One of them is used for mounting the reference wafer and the other is used for mounting the wafer to be measured. By separately arranging the load-sensitive part of the balance and non-contact supports for this frame, and mounting the loading and unloading supports in a mechanism that operates upside down, The wafer is placed on only one of the upper and lower supports,
In that state, other wafers are supported by the support tool for loading and unloading,
After that, by moving the support for loading and unloading,
It is possible to put into practical use a method in which the wafers loaded on the frame are alternately measured.

[0007]

By the way, the balance used for measuring the film thickness of the wafer as described above has a very small reading limit, for example, about 0.1 mg to 0.01 mg. For such a balance,
As described above, the frame is provided with the upper and lower two support tools, and the sample loading / unloading and replacement mechanism is provided correspondingly to the above, so that the measurement conditions such as temperature change due to the approach of a person when the sample is reloaded. Disturbance is prevented, and highly sensitive measurement is possible.

However, in the case of a plate-shaped sample such as a wafer, even a slight air flow such as convection in a room is affected, and it takes time until the measured value becomes stable, or the measured value is not stable. Occurs, which also causes a measurement error.

The present invention has been made in view of the above circumstances, and provides a balance for plate-like sample measurement, which is not affected by airflow or the like and can always accurately measure the mass of a plate-like sample such as a wafer. It is intended to be provided.

[0010]

In order to achieve the above object, in a plate sample measuring balance of the present invention, a frame body that engages with a load sensitive portion of the balance is provided with two upper and lower supports as described above. Tools (first and second support tools) are provided, and support tools (third and fourth support tools) for loading and unloading the sample are arranged in a non-contact manner with respect to the respective support tools. By vertically moving the lowering support tool up and down in opposite directions by the vertical movement mechanism, one of the upper and lower two objects to be measured is loaded on the frame, and the other is supported on the supporting tool side for loading and unloading. In the balance in which the object to be measured on the side of loading on the frame is alternately turned upside down, the frame and the first and second supports above and below the first and second supports, respectively. Is characterized by providing a shield plate in a non-contact manner.

[0011]

By providing shield plates above and below each of the first and second supports for supporting a plate-shaped object to be measured such as a wafer, convection that occurs when the object to be measured is replaced or from the outside world The air flow of does not act on the object to be measured and does not affect the measurement results.

[0012]

Embodiment FIG. 1 is a block diagram of the essential parts of an embodiment of the present invention.
Is the A-A arrow view. The frame body 2 hung on the weighing hook 1 of the balance is provided with first and second sample support tools 3 and 4 at two upper and lower positions. The first and second sample supports 3 and 4 each have protrusions e equally distributed at three or more locations, for example, four locations on a predetermined circumference, and a plate-shaped sample such as a wafer is provided on the top thereof. W ₀ or W ₁ can be supported horizontally.

Third and fourth sample supports 5 and 6 are arranged in proximity to the first and second sample supports 3 and 4, respectively. The third and fourth sample supports 5 and 6 are
And a protrusion e for loading and unloading the sample to and from the second sample supporters 3 and 4, and similarly having four protrusions e equally arranged on the circumference.
A plate-like sample can be supported horizontally by the top of the arm and is connected to a vertical movement mechanism 9 via arms 7 and 8, respectively. The third and fourth sample supports 5 and 6 and the arms 7 and 8 are moved so as not to contact the frame 2 and the first and second sample supports 3 and 4, respectively. Is becoming

The vertical movement mechanism 9 has sliders 9a and 9b fixed to the arms 7 and 8, a guide 9c for restricting the movement direction of the sliders 9a and 9b only in the vertical direction, and one end of each of the sliders 9a and 9b. Of the rod 9 and the other end of which are pin-joined to the disc 9d, respectively.
e and 9f, and a motor 9g for rotating the disc 9d
In the so-called slider-crank mechanism, the rods 9e and 9f are joined to the opposite side of the disk 9d with the center of rotation interposed therebetween. With this configuration, the third and fourth sample holders 5 and 6 are vertically displaced in synchronization with each other by driving the motor 9g in opposite directions.

A first shielding plate 11 extending in the horizontal direction with a certain gap is provided above the first sample support 3, and below the first sample support 3, Third
A second shielding plate 12 that also extends in the horizontal direction is arranged at a position that does not hinder the vertical movement of the sample supporter 5.

Similarly, above the second sample support 4, the third shield plate 1 in the horizontal direction is also provided with a gap.
3 is arranged, and further below the second sample support 4, a horizontal fourth shielding plate 14 is arranged at a position where the vertical movement of the fourth sample support is not hindered. ..

Of the above shielding plates, the first to third shielding plates 11 to 13 are formed with holes h..h through which the frame body 2 passes, and the fourth lowermost portion is formed. Neither the shield plate 14 nor the frame body 2 and the first and second sample supports 3 and 4 are in contact with each other.

Here, the frame 2, the first to fourth sample supports 3 to 6, the arms 7 and 8, and the first to fourth shield plates 11 to 14 as a whole have an opening / closing door. It is housed in the weighing chamber, and the vertical movement mechanism 9 is housed in a case behind the weighing chamber.

The embodiment of the present invention having the above structure is
Controlled by a microcomputer, FIG. 3 is a flow chart showing the operation. Before starting the measurement, plate-shaped samples are placed on the first and fourth sample supports 3 and 6, respectively. In this example, the reference wafer W ₀ is placed on the first sample support 3. Wafer W on which to mount and actually measure
₁ is placed on the fourth sample support 6. The loading and unloading of the wafer to and from the first to fourth sample supports 3 to 6 is performed from the outside by a wafer handling device, but this may be done manually.

With each sample placed, for example, the third sample support 5 is initially lowered, and at the same time, the fourth sample support 6 is raised. In this state, as shown in FIG.
₀ rides on the first sample support 3 and the lower wafer W ₁
Is on the fourth sample support 6 and is in non-contact with the frame 1.

The motor 9g is temporarily stopped in this state, and the weighing data D ₀ of the balance is read in this state. After that, the motor 9g rotates in the opposite direction. This makes the third
The first lift the wafer W ₀ sample support 5 is increased
At the same time as not contacting the sample support 3 or the frame 1, the fourth sample support 6 descends and the wafer W ₁ is placed on the second sample support 4. The motor 9g is temporarily stopped even in this state, and the weighing data D ₁ of the balance in that state is read.

In the above series of operations, the wafers W ₀ and W ₁ are shielded from the top and bottom by the first and second shield plates 11 and 12 and the third and fourth shield plates 13 and 14, respectively. Therefore, the air flow caused by convection or the like does not act, and therefore the respective measurement data D ₀ and D ₁ are accurate.

Now, in the computer, the difference (D) between the weighing data of the wafers W ₀ and W ₁ read as described above is calculated.
₀ −D ₁ ) is calculated and the value δ ₀ is stored in the memory.
In this case, when measuring the weight data D ₀ of W _0, the value of the D ₀ and zero display, displaying the weighing data D ₁ of the W ₁ directly the value D ₁ represents (D ₀ -D ₁₎ Therefore, such a method can be adopted.

Then, the wafer W ₀ is left as it is on the third sample support 5, and the wafer W ₁ is removed and subjected to a processing step such as film formation. After this process is completed, the wafer W ₁ is placed on the fourth sample support 6 again, and its mass is measured together with the reference wafer W _{0 in the same} manner as above. Then, the computer similarly calculates the difference δ ₁ between the two measurement data, and further calculates the difference δ ₀ −δ ₁ before and after the processing and displays it on the display. This display value δ ₀ −δ ₁ represents the amount of change in the mass of the wafer W ₁ before and after the processing. For example, if the processing is film forming processing, the display value and the film area and the density of the film material are used. You can know the thickness of the film.

[0025] Here, even the change, such as, for example, atmospheric pressure and temperature in the process before and after the wafer W ₁ is, the wafer W ₁ is not to calculate the change in the absolute weight, the same reference wafer W ₀ Since the difference in the measured value before and after the process is compared, the measurement is, so to speak, a null method, and is not affected by the change in the measurement environment as described above. Since the measurement is performed without being affected by convection due to the presence of the shielding plates 11 to 14, the obtained value is extremely accurate.

The motor 9g in the vertical movement mechanism 9
Alternatively, the disc 9d may be rotated by a manual handle, and its mechanism is not limited to that of the above-described embodiment, and any mechanism capable of achieving a similar function may be used. Any mechanism can be adopted.

Further, the number of the protrusions e of each of the sample supporters 3 to 6 is not limited to 4, and any number of protrusions of 3 or more may be provided as long as the plate-shaped sample can be supported horizontally. Is.

[0028]

As described above, according to the present invention, a plate-shaped sample such as a wafer is used for reference and for measurement.
Each piece is individually measured by the support tools provided at two locations,
In balances that measure the mass of the sample to be measured from the difference between the two with high sensitivity, the upper and lower parts of the upper and lower sample supports are configured to be shielded by the shielding plates, so that convection in the weighing chamber and external environment The air flow caused by the inflow of air does not act on the plate-like sample, and the measured values are not affected by the air flow, and it is possible to always perform accurate measurement. In particular, in applications such as calculating the thickness and etching amount of the film formed by the processing from the mass change before and after various processing of the wafer, the mass change due to the processing is extremely small, and measurement by slight convection etc. Although the change of the value has a great influence on the calculation result, the application of the present invention has a great effect on such an application.

[Brief description of drawings]

FIG. 1 is a configuration diagram of main parts of an embodiment of the present invention.

FIG. 2 is a view taken along arrow AA.

FIG. 3 is a flowchart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

 1 ...- Measuring hook 2 ...- Frame body 3-6 ...- First to fourth sample support tools 7,8 ... ···Shield

Claims (1)

[Claims] 1. A frame having upper and lower first and second supporting members for horizontally supporting a plate-shaped object to be measured is suspended from a measuring hook or placed on a measuring pan. , The first and second corresponding to the first and second supports.
Are placed in non-contact with the support and the frame of
Further, it has third and fourth support tools for horizontally supporting the object to be measured, and the third and fourth support tools move up and down in synchronization with each other in opposite directions by an up-and-down movement mechanism to move up and down. One of the two objects to be measured is supported by the corresponding one of the first and second support tools, and the other is supported by the corresponding one of the third and fourth support tools. Then, only one of the upper and lower objects to be measured is loaded on the frame body,
In addition, in a balance configured such that these are alternately loaded, a shield plate is provided above and below each of the first and second support tools without contacting the frame body and the first and second support tools. A balance for plate-shaped sample measurement, characterized by being provided with.