NOVELTY - A mask ink containing a silicon compound is applied on a substrate (1), and a mask layer (2) is formed. The substrate comprising the mask layer is baked, and diffusion prevention mask is produced. The mask layer is analyzed planarly after baking, and a primary region (5b) located in center portion and a secondary region (5a) located in edge portion surrounding the primary region are observed. The mask layer is formed such that the thickness of layer in secondary region is more than primary region.    USE - Formation of diffusion prevention mask used for forming solar cell (claimed).    ADVANTAGE - The diffusion prevention mask is economically manufactured by a simple method, and has excellent diffusion prevention performance.    DETAILED DESCRIPTION - A mask ink containing a silicon compound is applied on a substrate by inkjet method, and a mask layer is formed. The substrate comprising the mask layer is baked, and mask is produced. The mask layer is analyzed planarly after baking, and a primary region located in center portion and a secondary region located in edge portion surrounding the primary region are observed. The thickness of mask layer in primary region is larger than masking-property-ensuring-minimum film thickness, which is the minimum film thickness required to function mask layer as mask for dopant diffusion prevention. The thickness of mask layer in secondary region is less than crack-proof film thickness, which is maximum film thickness at which cracks are not generated in mask layer. The mask layer is formed such that the thickness of layer in secondary region is more than primary region. An INDEPENDENT CLAIM is included for manufacture of solar cell. A primary diffusion prevention mask is formed on the surface of substrate. A n-type diffusion layer (4) is formed by diffusing n-dopant (3) on substrate surface portion, at which primary mask is not formed. The primary mask is removed, and a secondary diffusion prevention mask is formed on other region of substrate surface. A p-type diffusion layer is formed by diffusing p-dopant on substrate surface portion, at which secondary mask is not formed. The secondary mask is removed, and a passivation film having contact hole is formed. A back surface electrode consisting of p-type electrode electrically connected to n-type electrode, which is connected to n-type diffused layer is formed, and solar cell is manufactured.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view explaining formation of diffusion prevention mask.    Silicon substrate (1)    Mask layer (2)    Dopant (3)    Diffused layer (4)    Regions (5a,5b)