Does a ring homomorphism necessarily induce a map of their spectrums?

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As the text states, it is true.enter image description here However, the map $$\varphi:\mathbb Z \to \mathbb Z^2, n \mapsto (n, 0)$$ seems to be a counter example as $\varphi^{-1}(\mathbb Z\times\{0\})=\mathbb Z$.