Gratings for metrology and process control 1: A simple parameter optimization problem

Mendes, Geraldo F.; Cescato, Lucila; Frejlich, Jaime

doi:10.1364/ao.23.000571

Cited by 10 publications

(16 citation statements)

References 9 publications

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“…The reflectance (R) of a multilayer stack is given by R = Irl s = (E1-/EI+) 2 [1] where E,-and E, + are, respectively, the amplitudes of the reflected and incident electric field vector at the first interface, r is the Fresnel reflection coefficient of the multilayer stack. With more multilayer stacks side by side on the same surface the reflectance is given by R = [EFiri exp (j~) [2 [2] where F~ is the surface fraction covered by layer stack i, r, is the Fresnel reflection coefficient of this stack, 5~ is equal to 4 7rhi/~, hi is the height difference between the surface of layer stack i and a reference level and ~ is the wavelength.…”

Section: Theorymentioning

confidence: 99%

“…Recently Weiss and Mainzer reported the passivation of Hgl-xCdxTe surfaces by growing anodic layers from fluoridic solutions (1,2). The use of anodic fluoridization or fluoro-oxidation is advantageous because the resulting interfaces are relatively thermally stable.…”

Section: Composition Growth Mechanism and Oxidation Of Anodicmentioning

confidence: 99%

“…An anodic fluoride, free of oxygen, is grown from nonaqueous solutions. Even low hydroxyl ion concentration in an aqueous bath causes the growth of an anodic fluoro-oxide, consisting of an oxide and small amounts of fluorides (1). An analysis, using a low-energy proton induced nuclear reaction, which is very sensitive to fluorine atoms, showed that in both cases fluorine is accumulated at the film-semiconductor interface and on the film surface (2).…”

Section: Composition Growth Mechanism and Oxidation Of Anodicmentioning

confidence: 99%

“…A grating has been successfully used in the past to monitor in situ the etch rate of, e.g., Si for dry trench etching (1)(2)(3).…”

mentioning

confidence: 99%

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In Situ Growth Rate Measurement of Selective LPCVD of Tungsten

Holleman

Hasper

Middelhoek

1991

J. Electrochem. Soc.

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The reflectance measurement during the selective deposition of W on Si covered with an insulator grating is proven to be a convenient method to monitor the W deposition. The reflectance change during deposition allows the in situ measurement of the deposition rate: The influence of surface roughening due to either the W growth or an etching pretreatment of the wafer is modeled, as well as the effect of selectivity loss and lateral overgrowth.

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Section: Theorymentioning

confidence: 99%

Section: Composition Growth Mechanism and Oxidation Of Anodicmentioning

confidence: 99%

Section: Composition Growth Mechanism and Oxidation Of Anodicmentioning

confidence: 99%

“…A grating has been successfully used in the past to monitor in situ the etch rate of, e.g., Si for dry trench etching (1)(2)(3).…”

mentioning

confidence: 99%

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In Situ Growth Rate Measurement of Selective LPCVD of Tungsten

Holleman

Hasper

Middelhoek

1991

J. Electrochem. Soc.

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“…Some optical parameters of the sample must be known in order to provide the data required by the mathematical model of the lamellar grating (Eq. [2]- [3]). …”

Section: Discussionmentioning

confidence: 99%

Continuous Optical Measurement of the Dry Etching of Silicon Using the Diffraction of a Lamellar Grating

Mendes

Cescato

Frejlich

et al. 1985

J. Electrochem. Soc.

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An optical method using the diffraction of a lamellar grating is described for continuously measuring the etching of a substrate through a masking layer. The finite selectivity of the process is accounted for. Automation and real-time measurement are possible. Some theoretical situations are analyzed, and the method is applied for the experimental plasma etching of silicon through a thermally grown silicon dioxide layer.Dry etching plays an important role in the manufacture of semiconductor devices requiring high resolution lithography. Many times, not only the end point detection for the process is desirable but also the measurement of the depth of incompletely etched areas is desirable. This is the case with etching silicon substrates for isolation purposes, when the etched depth should be carefully controlled in real time if a precise control of thickness is required.Kleinknecht and Meier (1) first proposed monitoring the plasma etching of dielectric films by measuring the diffraction of a lamellar grating adequately lithographed somewhere on the sample.Recently, Sternheim and van Gelder (2) used an interferometric system for monitoring the etching of a patterned silicon substrate. A laser beam is diffracted by the pattern being etched onto the substrate, and the zeroorder diffracted intensity is monitored. Its principal advantage is the fact that it uses the etched pattern itself for control purposes.Mendes et al. (3-6) further developed a method using lamellar gratings for thickness measurement and etching monitoring which permits one to measure the point-bypoint evolution of the depth of the layer being etched. In this paper, we shall profit from the previous developments, extending the method to monitor the etching of the substrate, and accounting for the selectivity of the process with respect to the mask layer. We illustrate its advantages in continuously measuring the evolution of the etched depth of a silicon substrate masked with silicon dioxide. Description of the MethodThe optical modulation of a lamellar grating recorded in the full depth of a layer may be used to monitor the etch rate of the layer by measuring the first-to-zero diffraction intensity orders ratio IJIo (4, 5). If a substrate is etched through a lamellar grating masking layer, the etched depth h may also be determined by measuring the I,/Io ratio, of the grating being formed in the process, as shown in Fig. 1. The I,/Io ratio may be written as ]r~ -rbl2(a/ d) 2 I~/Io = sin c2(a/ d) [1] Irb + (r~ -rb) a/dl ~ with sin c(x) =-sin vx/(~rx) and r, and rb being the complex amplitude reflectivities on bars and grooves of the grating, respectively. For normal laser beam incidence, it should be written (7) _ r, + r2e ~2~ L ra 1 + r~r2e i2~ [2] rb = r3e ~2~ 190 with and 2~ ~-4~r(T + h)nJX r, = ([3] where T is the thickness of the masking layer and h represents the etched depth of the substrate. In our experiment, we shall choose a/d = 0.5 for which value the IJIo ratio is less sensitive to a/d variations (4). In this case, Eq. [1] simplifies t...

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