JPS62190837A - Semiconductor manufacturing apparatus - Google Patents

Abstract

PURPOSE:To always give constant energy to resist even if it is set in any condition and improve size controllability of resist pattern by measuring reflectivity of reflection measuring mark having the same structure as the practical device and achieving exposure by changing amount of exposure to device depending on such measuring value. CONSTITUTION:The reflectivity measuring mark in the same structure as the practical device to be exposed is formed by alignment using the alignment mark and this reflectivity measuring mark 7 is moved to the region where the reflectivity measuring beam of reflectivity measuring means is applied. The beam is radiated, incident light intensity and reflected light intensity are measured respectively with measuring instruments 3, 4, reflectivity is calculated, this reflectivity is compared with that when amount of exposure is determined and such ratio is calculated into the existing amount of exposure. Amount of exposure is changed for every exposure processing so that energy stored in the resist 10 becomes constant. Thereby, size of resist pattern can always be kept constant and the wafer can be exposed with the wanted amount of exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor manufacturing apparatus, and more particularly to a semiconductor manufacturing apparatus that performs reduction projection type exposure to transfer a mask pattern.

[Conventional technology]

In the wafer process, it is important to apply resist on various materials and form a resist pattern according to the mask dimensions using an exposure machine. One of the major parameters controlling resist pattern formation is resist film thickness. This is particularly noticeable in reduction projection type exposure machines that use light of a single wavelength, so this case will be explained below.

FIG. 5 is a diagram explaining waveforms within the resist during exposure. In the figure, 21 is an incident wave, 22 is a reflected wave, 23 is a composite wave (standing wave), 24 is an air layer, and 25 is a resist waveform. ,2
6 is the base. When a resist 25 is applied on a certain base 26, within the resist 25, an incident wave 21 and a reflected wave 22 from the base 26 interfere with each other, as shown in FIG. 5, and a standing wave 23 is formed as a composite wave. occurs. In Figure 5, the base 2
The composite wave 23 is shown when the refractive index of the resist 25 is larger than the refractive index of the resist 25 and the base 26 has no electrical conductivity (σ), that is, when the phase is reversed by reflection.

Here, the composite wave 23 of the incident wave 21 and the reflected wave 22 at a certain time is calculated and shown. ''In other words, the position of the point where the electric field vector has the largest amplitude is constant over time. From this, the resist film thickness determines whether the composite wave forms a "node", "antinode", or an intermediate property on the resist surface.

Next, the proportion of optical energy applied to the resist when standing waves are generated within the resist will be explained with reference to FIG.

In the figure, 27 is the electric field vector of the incident wave, 28 is the electric field vector of the transmitted wave, 29 is the electric field vector of the reflected wave, and 30 is the electric field vector of the reflected wave.
is the electric field vector of the reflected wave from the substrate 26, 31 is the electric field vector of the composite wave of the incident wave and the reflected wave, and 32 is the electric field vector of the composite wave of the transmitted wave and the reflected wave from the substrate 26.

Since the electrical conductivity of air and resist is σ=O, the electromagnetic boundary condition is established, and IE resist=lE air. Here, IE is the electric field vector 1, and IE resist is the electric field vector 3 on the resist side at the interface between air and resist.
2. IE air is the air side electric field vector 31 at the interface between air and resist.

In addition, the electric field IE of an electromagnetic wave, which is a plane wave, is lE = l
It can be expressed as E 1sin ((1)t −λ χ+6). Here, IEI is the amplitude of the electric field ω is the angular frequency λ is the wavelength δ is the phase shift. Also, the flow of energy of electromagnetic waves is l IE l
This is the energy flow per time, and the time average of this is ω.

Then, the time-averaged energy flow of the reflected waves is calculated as follows.

Old air = lE resist IE air - IE incident wave + IE reflected wave Therefore, IE reflected wave - IE resist - IE incident wave This can be expressed mathematically as l E + 1 sin ((1) - λX + δ1) =
l Er 1sin ((J) t-λ7x+δ,)
+ l Eolsin (ωt−λX+δ.),
Here, the number of twists is 0.1. r represents the physical quantity of the incident wave, reflected wave, and electromagnetic wave at the resist interface, respectively.

For example, the time-averaged energy flow is determined. In other words, ・5in(ωt−λX+δ.)dL It is. Typically f’ sin” (ωt+Δ’) dt.

f sin (ωt+Δr) ・sin (
al t+Δ2 ) dt(Δ, Δ1.Δ2 is a constant) Since the calculated value is a constant determined only by ω, the time-averaged energy flow of the reflected wave is a+'1Erl'' +a2.l Eel ・l E,1 +3.・IEOI” (al, aZ* a2 is a constant).

From the above, if we consider a material with electrical conductivity σ = O as the base of the resist, the incident light energy flow is decomposed into the reflected light energy flow and the energy storage in the resist, and under a constant incident light energy flow, Energy storage in the resist is determined by the reflected light energy flow. Then, the reflected light energy flow is determined by IE, , l from the above equation, and IE, l is determined by the resist film thickness, so the energy storage in the resist is determined by the resist film thickness. Finally, since the resist pattern dimensions are determined by the energy storage in the resist,
Under certain underlying conditions, the resist pattern dimensions are determined by the resist film thickness.

[Problem that the invention seeks to solve]

Conventionally, in order to control the dimensions of the resist pattern, the performance of the coating equipment was improved and the resist film thickness was set to a film thickness with good dimensional controllability with an accuracy of 50 to 100 people. Due to this problem, it has become difficult to obtain a correct resist pattern no matter how much the film thickness is controlled on the coating side.

First, since actual devices have unevenness, the film thickness differs from the appropriate film thickness when coated on a flat wafer. Furthermore, since the change in film thickness due to unevenness depends on the density of the unevenness, coating conditions must be changed every time the device pattern changes in order to obtain an appropriate film thickness on an actual device.

Second, if the underlying material is a material such as an oxide film that has a refractive index almost equal to that of the resist, the reflectance from the resist surface (that is, equivalent to energy storage in the resist) is the difference between the oxide film and the resist. Determined by the sum of film thicknesses. However, when producing an oxide film, fluctuations in the thickness of the produced film and in-plane variations are often worse than the film thickness controllability of the coating machine (50 to 100 people), so the appropriate film thickness of the resist on the device is determined by the loft. It may change from time to time, or change from time to time for each shot of a reduction projection type exposure machine, and it is difficult to prevent this from happening in a coating machine.

Third, when the base has electrical conductivity σ such as polysilicon, there is no perfect correlation between the standing waves, the reflectance from the resist, and the energy storage in the resist.
Approximately, the discussion up to now holds true. And in this case,
Unlike a substance such as an oxide film where σ=0, the factor σ other than the film thickness affects the reflectance. In terms of process, it is called sheet resistance, and both the absolute value fluctuation and the in-plane distribution change in the same way as the film thickness.
Under heavy fluctuations, even if the film thickness is controlled by a coating machine, the reflectance on the actual device will fluctuate.

The present invention has been made in order to solve the above-mentioned problems, and provides a semiconductor manufacturing apparatus that performs reduction projection type exposure that can prevent variations in resist pattern dimensions due to variations in reflectance on an actual device. The purpose is to obtain.

[Means for solving problems]

A semiconductor manufacturing apparatus according to the present invention includes a reflectance measurement mark having the same structure as a device to be exposed, measures the reflectance of the mark, and changes the amount of exposure to the device according to the measured value to perform exposure. It is something to do.

[Effect]

In this invention, the reflectance of a reflectance measurement mark that has the same structure as the device to be exposed is measured, and the amount of exposure to the device is changed according to the measured value, so no matter what condition the wafer is in. can also impart a certain amount of energy to the resist.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the reflectance measuring means provided in the present embodiment apparatus for reduction projection exposure. In the figure, 1 is a light source with a known wavelength, 2 is a half mirror, 13 is an incident light intensity measuring device, and 4 is a reflection A light intensity measuring device, 5 a wafer stage, 6 a wafer,
7 is a reflectance measurement mark.

Here, the reflectance measurement mark 7 has the same underlying structure, cross-sectional structure, and the same density as the unevenness of the pattern of the device to be exposed (hereinafter referred to as the actual device), and forms the pattern of the actual device. It is created to have the same reflectance as the location where it is created.

2 and 3 show reflectance measurement marks used in the process of manufacturing a polysilicon gate of a MOS transistor according to an embodiment of the present invention, FIG. 2 is a view seen from the top of the wafer, and FIG. shows. This has almost the same structure as an example of a polysilicon transistor in an actual device as shown in FIG.
9.9a is the edge of LOGO3, 10 is the resist, 11
is polysilicon, 12 is an oxide film of LOGO3, 13 is an incident beam for measuring reflectance, 14 is a reflected beam for measuring reflectance, and lla is a polysilicon gate.

In addition, the reflectance measurement beam is collimated and irradiated onto the reflectance measurement mark 7 on the wafer, but since various reflectance measurement marks are possible, the beam diameter is 1μ.
It shall be limited to a certain extent.

Further, as the wavelength, an exposure wavelength may be used, or a non-exposure wavelength such as a laser may be used, and the measured reflectance may be converted to reflectance at the exposure wavelength.

Next, the operation of the apparatus of this embodiment will be explained. A reflectance measuring mark 7 having the same structure as the actual device to be exposed is created by aligning it using an alignment mark, and this reflectance measuring mark 7 is used as the reflectance measuring beam of the reflectance measuring means shown in FIG. Move it to the position where it hits. Then, the beam is irradiated, the incident light intensity and the reflected light intensity are measured by respective measuring devices 3.4, and the reflectance is calculated. Next, compare the reflectance with the reflectance when determining the exposure amount,
The ratio is calculated to the existing exposure amount. In this way, by changing the exposure amount for each exposure process so that the energy stored in the resist remains constant, the dimensions of the resist pattern can always be kept constant. Then, the wafer is exposed with the determined exposure amount. Here, an item for inputting the reflectance for each process must be added to the program of the apparatus of this embodiment, but this may be input automatically or manually.

In general, the resist film thickness tends to vary in the radial direction of the wafer, and the underlying film thickness and sheet resistance also have in-plane distribution.If the wafer is exposed with the same amount of light under these conditions, the resist pattern size will change. However, by having a reflectance measurement function like the device of this embodiment, it is possible to measure the reflectance for each shot and apply a constant energy to the resist for each shot. Exposure can be performed with the given exposure amount, and dimensional controllability within the wafer plane can be improved.

〔Effect of the invention〕

As described above, according to the present invention, the reflectance of a reflection measurement mark that has the same structure as the actual device is measured, and the amount of exposure to the device is changed according to the measured value. Even if the wafer is in such a state, constant energy can always be applied to the resist, which has the effect of improving the dimensional controllability of the resist pattern.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a reflectance measuring means provided in a semiconductor manufacturing apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 show reflectance measuring means provided in a semiconductor manufacturing apparatus according to an embodiment of the present invention. A plan view and a cross-sectional view showing a reflectance measurement mark, FIG. 4 is a plan view showing a polysilicon transistor having almost the same structure as the reflectance measurement mark, and FIG. 5 explains the waveform in the resist during exposure. FIG. 6 is a diagram for explaining the ratio of light energy within the resist during exposure. In the figure, 1 is a light source, 2 is a half mirror, 13 is an incident light intensity measurement device, 4 is a reflected light intensity measurement device, 5 is a wafer stage, 6 is a wafer, 7 is a reflectance measurement mark, and 8 is a reflectance measurement beam 9 is the edge of LOGO3, 10
11 is a resist, 11 is polysilicon, 12 is an oxide film of LOGO3, 13 is an incident beam for measuring reflectance, and 14 is a reflected beam for measuring reflectance. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a semiconductor manufacturing apparatus that performs exposure to transfer a mask pattern to a resist, the following equipment is provided: a reflectance measurement mark having the same structure as the device to be exposed, a reflectance measurement means for measuring the reflectance of the mark, and the measurement means. 1. A semiconductor manufacturing apparatus comprising: an exposure amount control means for changing an exposure amount in accordance with a measured value obtained by the method.